From 44678e5476db5b0d46a03bb4625c03a6ea7e49c8 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 5 Mar 2021 14:45:57 -0800
Subject: [PATCH 001/638] Shuffling code in test_multiple_inheritance.cpp to
 separate struct/class definitions from bindings code. (#2890)

---
 tests/test_multiple_inheritance.cpp | 46 ++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index e67200809d..ad801fe198 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -11,6 +11,8 @@
 #include "pybind11_tests.h"
 #include "constructor_stats.h"
 
+namespace {
+
 // Many bases for testing that multiple inheritance from many classes (i.e. requiring extra
 // space for holder constructed flags) works.
 template <int N> struct BaseN {
@@ -43,7 +45,34 @@ int WithStatic2::static_value2 = 2;
 int VanillaStaticMix1::static_value = 12;
 int VanillaStaticMix2::static_value = 12;
 
+// test_multiple_inheritance_virtbase
+struct Base1a {
+    Base1a(int i) : i(i) { }
+    int foo() { return i; }
+    int i;
+};
+struct Base2a {
+    Base2a(int i) : i(i) { }
+    int bar() { return i; }
+    int i;
+};
+struct Base12a : Base1a, Base2a {
+    Base12a(int i, int j) : Base1a(i), Base2a(j) { }
+};
+
+// test_mi_unaligned_base
+// test_mi_base_return
+struct I801B1 { int a = 1; I801B1() = default; I801B1(const I801B1 &) = default; virtual ~I801B1() = default; };
+struct I801B2 { int b = 2; I801B2() = default; I801B2(const I801B2 &) = default; virtual ~I801B2() = default; };
+struct I801C : I801B1, I801B2 {};
+struct I801D : I801C {}; // Indirect MI
+
+} // namespace
+
 TEST_SUBMODULE(multiple_inheritance, m) {
+    // Please do not interleave `struct` and `class` definitions with bindings code,
+    // but implement `struct`s and `class`es in the anonymous namespace above.
+    // This helps keeping the smart_holder branch in sync with master.
 
     // test_multiple_inheritance_mix1
     // test_multiple_inheritance_mix2
@@ -99,27 +128,14 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_multiple_inheritance_virtbase
     // Test the case where not all base classes are specified, and where pybind11 requires the
     // py::multiple_inheritance flag to perform proper casting between types.
-    struct Base1a {
-        Base1a(int i) : i(i) { }
-        int foo() { return i; }
-        int i;
-    };
     py::class_<Base1a, std::shared_ptr<Base1a>>(m, "Base1a")
         .def(py::init<int>())
         .def("foo", &Base1a::foo);
 
-    struct Base2a {
-        Base2a(int i) : i(i) { }
-        int bar() { return i; }
-        int i;
-    };
     py::class_<Base2a, std::shared_ptr<Base2a>>(m, "Base2a")
         .def(py::init<int>())
         .def("bar", &Base2a::bar);
 
-    struct Base12a : Base1a, Base2a {
-        Base12a(int i, int j) : Base1a(i), Base2a(j) { }
-    };
     py::class_<Base12a, /* Base1 missing */ Base2a,
                std::shared_ptr<Base12a>>(m, "Base12a", py::multiple_inheritance())
         .def(py::init<int, int>());
@@ -130,10 +146,6 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_mi_unaligned_base
     // test_mi_base_return
     // Issue #801: invalid casting to derived type with MI bases
-    struct I801B1 { int a = 1; I801B1() = default; I801B1(const I801B1 &) = default; virtual ~I801B1() = default; };
-    struct I801B2 { int b = 2; I801B2() = default; I801B2(const I801B2 &) = default; virtual ~I801B2() = default; };
-    struct I801C : I801B1, I801B2 {};
-    struct I801D : I801C {}; // Indirect MI
     // Unregistered classes:
     struct I801B3 { int c = 3; virtual ~I801B3() = default; };
     struct I801E : I801B3, I801D {};

From f110889dde14da15dab08d431791a2080f9a9357 Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Mon, 8 Mar 2021 08:42:01 +0100
Subject: [PATCH 002/638] Use correct duration representation when casting from
 datetime.timdelta to std::chrono::duration (#2870)

* Use correct duration representation when casting from datetime.timdelta to std::chrono::duration

* When asserting datetime/timedelta/date/time we can equality-compare whole objects
---
 include/pybind11/chrono.h |  2 +-
 tests/test_chrono.py      | 35 +++++++++++++----------------------
 2 files changed, 14 insertions(+), 23 deletions(-)

diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index 551a802ad3..317afd1837 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -35,7 +35,7 @@ template <typename type> class duration_caster {
     using rep = typename type::rep;
     using period = typename type::period;
 
-    using days = std::chrono::duration<uint_fast32_t, std::ratio<86400>>;
+    using days = std::chrono::duration<int_least32_t, std::ratio<86400>>; // signed 25 bits required by the standard.
 
     bool load(handle src, bool) {
         using namespace std::chrono;
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index e9e24e0826..12312c7207 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -39,9 +39,7 @@ def test_chrono_system_clock_roundtrip():
 
     # They should be identical (no information lost on roundtrip)
     diff = abs(date1 - date2)
-    assert diff.days == 0
-    assert diff.seconds == 0
-    assert diff.microseconds == 0
+    assert diff == datetime.timedelta(0)
 
 
 def test_chrono_system_clock_roundtrip_date():
@@ -64,9 +62,7 @@ def test_chrono_system_clock_roundtrip_date():
     assert diff.microseconds == 0
 
     # Year, Month & Day should be the same after the round trip
-    assert date1.year == date2.year
-    assert date1.month == date2.month
-    assert date1.day == date2.day
+    assert date1 == date2
 
     # There should be no time information
     assert time2.hour == 0
@@ -117,10 +113,7 @@ def test_chrono_system_clock_roundtrip_time(time1, tz, monkeypatch):
     assert isinstance(time2, datetime.time)
 
     # Hour, Minute, Second & Microsecond should be the same after the round trip
-    assert time1.hour == time2.hour
-    assert time1.minute == time2.minute
-    assert time1.second == time2.second
-    assert time1.microsecond == time2.microsecond
+    assert time1 == time2
 
     # There should be no date information (i.e. date = python base date)
     assert date2.year == 1970
@@ -140,9 +133,13 @@ def test_chrono_duration_roundtrip():
 
     cpp_diff = m.test_chrono3(diff)
 
-    assert cpp_diff.days == diff.days
-    assert cpp_diff.seconds == diff.seconds
-    assert cpp_diff.microseconds == diff.microseconds
+    assert cpp_diff == diff
+
+    # Negative timedelta roundtrip
+    diff = datetime.timedelta(microseconds=-1)
+    cpp_diff = m.test_chrono3(diff)
+
+    assert cpp_diff == diff
 
 
 def test_chrono_duration_subtraction_equivalence():
@@ -153,9 +150,7 @@ def test_chrono_duration_subtraction_equivalence():
     diff = date2 - date1
     cpp_diff = m.test_chrono4(date2, date1)
 
-    assert cpp_diff.days == diff.days
-    assert cpp_diff.seconds == diff.seconds
-    assert cpp_diff.microseconds == diff.microseconds
+    assert cpp_diff == diff
 
 
 def test_chrono_duration_subtraction_equivalence_date():
@@ -166,9 +161,7 @@ def test_chrono_duration_subtraction_equivalence_date():
     diff = date2 - date1
     cpp_diff = m.test_chrono4(date2, date1)
 
-    assert cpp_diff.days == diff.days
-    assert cpp_diff.seconds == diff.seconds
-    assert cpp_diff.microseconds == diff.microseconds
+    assert cpp_diff == diff
 
 
 def test_chrono_steady_clock():
@@ -183,9 +176,7 @@ def test_chrono_steady_clock_roundtrip():
     assert isinstance(time2, datetime.timedelta)
 
     # They should be identical (no information lost on roundtrip)
-    assert time1.days == time2.days
-    assert time1.seconds == time2.seconds
-    assert time1.microseconds == time2.microseconds
+    assert time1 == time2
 
 
 def test_floating_point_duration():

From 0e01c243c7ffae3a2e52f998bacfe82f56aa96d9 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 9 Mar 2021 15:07:44 -0800
Subject: [PATCH 003/638] Generalizing suppression for pypocketfft. (#2896)

* Adding suppression for pypocketfft.

* Generalize existing pypocketfft Valgrind suppression

Co-authored-by: Yannick Jadoul <yannick.jadoul@belgacom.net>
---
 tests/valgrind-numpy-scipy.supp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/valgrind-numpy-scipy.supp b/tests/valgrind-numpy-scipy.supp
index e8ff680dd3..fea9bcb4a6 100644
--- a/tests/valgrind-numpy-scipy.supp
+++ b/tests/valgrind-numpy-scipy.supp
@@ -111,7 +111,7 @@
    fun:_Znwm
    fun:PyInit_pypocketfft
    fun:_PyImport_LoadDynamicModuleWithSpec
-   fun:_imp_create_dynamic_impl.constprop.3
+   fun:_imp_create_dynamic_impl.constprop.*
    fun:_imp_create_dynamic
    fun:cfunction_vectorcall_FASTCALL
    fun:PyVectorcall_Call

From 3df0ee6fe36f85786477fb1d15dc68ea9087b073 Mon Sep 17 00:00:00 2001
From: JYX <1449843302@qq.com>
Date: Fri, 2 Apr 2021 23:46:43 +0800
Subject: [PATCH 004/638] docs: typo in classes.rst (#2926)

---
 docs/advanced/classes.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 4927902069..3dfc0c935b 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -259,7 +259,7 @@ override the ``name()`` method):
 
 .. note::
 
-    Note the trailing commas in the ``PYBIND11_OVERIDE`` calls to ``name()``
+    Note the trailing commas in the ``PYBIND11_OVERRIDE`` calls to ``name()``
     and ``bark()``. These are needed to portably implement a trampoline for a
     function that does not take any arguments. For functions that take
     a nonzero number of arguments, the trailing comma must be omitted.

From c2db53da56af7bce1dabf1b3c71913385111f49b Mon Sep 17 00:00:00 2001
From: Robert Haschke <rhaschke@users.noreply.github.com>
Date: Fri, 2 Apr 2021 19:13:44 +0200
Subject: [PATCH 005/638] fix: catch missing self argument in overloads
 constructor (#2914)

---
 include/pybind11/pybind11.h        |  4 ++--
 tests/test_factory_constructors.py | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 648300eef2..eff40a8495 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -555,8 +555,8 @@ class cpp_function : public function {
 
         auto self_value_and_holder = value_and_holder();
         if (overloads->is_constructor) {
-            if (!PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
-                PyErr_SetString(PyExc_TypeError, "__init__(self, ...) called with invalid `self` argument");
+            if (!parent || !PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
+                PyErr_SetString(PyExc_TypeError, "__init__(self, ...) called with invalid or missing `self` argument");
                 return nullptr;
             }
 
diff --git a/tests/test_factory_constructors.py b/tests/test_factory_constructors.py
index ffcce6fd4d..8c6ca173ac 100644
--- a/tests/test_factory_constructors.py
+++ b/tests/test_factory_constructors.py
@@ -486,7 +486,9 @@ def __init__(self, bad):
     # Same as above, but for a class with an alias:
     class BrokenTF6(m.TestFactory6):
         def __init__(self, bad):
-            if bad == 1:
+            if bad == 0:
+                m.TestFactory6.__init__()
+            elif bad == 1:
                 a = m.TestFactory2(tag.pointer, 1)
                 m.TestFactory6.__init__(a, tag.base, 1)
             elif bad == 2:
@@ -506,13 +508,13 @@ def __init__(self, bad):
             BrokenTF1(arg)
         assert (
             str(excinfo.value)
-            == "__init__(self, ...) called with invalid `self` argument"
+            == "__init__(self, ...) called with invalid or missing `self` argument"
         )
 
-    for arg in (1, 2, 3, 4):
+    for arg in (0, 1, 2, 3, 4):
         with pytest.raises(TypeError) as excinfo:
             BrokenTF6(arg)
         assert (
             str(excinfo.value)
-            == "__init__(self, ...) called with invalid `self` argument"
+            == "__init__(self, ...) called with invalid or missing `self` argument"
         )

From 1259db6fd99bc60228ef0e4af2e379f8e86abc1d Mon Sep 17 00:00:00 2001
From: Jerome Robert <jeromerobert@gmx.com>
Date: Fri, 2 Apr 2021 19:26:17 +0200
Subject: [PATCH 006/638] Fix Pybind11Extension on mingw64 (#2921)

* Pybind11Extension add the "/EHsc /bigobj /std:c++14" flags on Windows.
  This is good for Visual C++ but not for Mingw.
* According
  https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-python2/0410-MINGW-build-extensions-with-GCC.patch
  sysconfig.get_platform() is the way to check for a Mingw64
---
 pybind11/setup_helpers.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index c69064ca50..84a4584c5d 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -47,6 +47,7 @@
 import threading
 import platform
 import warnings
+import sysconfig
 
 try:
     from setuptools.command.build_ext import build_ext as _build_ext
@@ -59,7 +60,7 @@
 import distutils.ccompiler
 
 
-WIN = sys.platform.startswith("win32")
+WIN = sys.platform.startswith("win32") and sysconfig.get_platform() != "mingw"
 PY2 = sys.version_info[0] < 3
 MACOS = sys.platform.startswith("darwin")
 STD_TMPL = "/std:c++{}" if WIN else "-std=c++{}"

From f676782becc5bcd30c56b4da1ff1026db61bcce3 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Fri, 2 Apr 2021 14:34:09 -0400
Subject: [PATCH 007/638] env: Add surrogate for pytest.deprecated_call for
 ptyest<3.9 (#2923)

env: Add surrogate for pytest.deprecated_call for ptyest<3.9
---
 tests/env.py                  | 19 +++++++++++++++++++
 tests/test_builtin_casters.py |  4 ++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/tests/env.py b/tests/env.py
index 5cded44127..6172b451b3 100644
--- a/tests/env.py
+++ b/tests/env.py
@@ -2,6 +2,8 @@
 import platform
 import sys
 
+import pytest
+
 LINUX = sys.platform.startswith("linux")
 MACOS = sys.platform.startswith("darwin")
 WIN = sys.platform.startswith("win32") or sys.platform.startswith("cygwin")
@@ -12,3 +14,20 @@
 PY2 = sys.version_info.major == 2
 
 PY = sys.version_info
+
+
+def deprecated_call():
+    """
+    pytest.deprecated_call() seems broken in pytest<3.9.x; concretely, it
+    doesn't work on CPython 3.8.0 with pytest==3.3.2 on Ubuntu 18.04 (#2922).
+
+    This is a narrowed reimplementation of the following PR :(
+    https://github.com/pytest-dev/pytest/pull/4104
+    """
+    # TODO: Remove this when testing requires pytest>=3.9.
+    pieces = pytest.__version__.split(".")
+    pytest_major_minor = (int(pieces[0]), int(pieces[1]))
+    if pytest_major_minor < (3, 9):
+        return pytest.warns((DeprecationWarning, PendingDeprecationWarning))
+    else:
+        return pytest.deprecated_call()
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index fda0384333..5ee8603a6b 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -301,7 +301,7 @@ def cant_convert(v):
     cant_convert(3.14159)
     # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
     if (3, 8) <= env.PY < (3, 10):
-        with pytest.deprecated_call():
+        with env.deprecated_call():
             assert convert(Int()) == 42
     else:
         assert convert(Int()) == 42
@@ -336,7 +336,7 @@ def require_implicit(v):
     # The implicit conversion from np.float32 is undesirable but currently accepted.
     # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
     if (3, 8) <= env.PY < (3, 10):
-        with pytest.deprecated_call():
+        with env.deprecated_call():
             assert convert(np.float32(3.14159)) == 3
     else:
         assert convert(np.float32(3.14159)) == 3

From ad6bf5cd39ca64b4a9bf846b84b11c4c8df1c8e1 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 2 Apr 2021 18:17:12 -0700
Subject: [PATCH 008/638] Adding PyGILState_Check() in
 object_api<>::operator(). (#2919)

* Adding PyGILState_Check() in object_api<>::operator().

* Enabling PyGILState_Check() for Python >= 3.6 only.

Possibly, this explains why PyGILState_Check() cannot safely be used with Python 3.4 and 3.5:

https://github.com/python/cpython/pull/10267#issuecomment-434881587

* Adding simple micro benchmark.

* Reducing test time to minimum (purely for coverage, not for accurate results).

* Fixing silly oversight.

* Minor code organization improvement in test.

* Adding example runtimes.

* Removing capsys (just run with `-k test_callback_num_times -s` and using `.format()`.
---
 include/pybind11/cast.h  |  5 +++++
 tests/test_callbacks.cpp |  6 ++++++
 tests/test_callbacks.py  | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 0ad10e9a93..f68a35bfa4 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1348,6 +1348,11 @@ unpacking_collector<policy> collect_arguments(Args &&...args) {
 template <typename Derived>
 template <return_value_policy policy, typename... Args>
 object object_api<Derived>::operator()(Args &&...args) const {
+#if !defined(NDEBUG) && PY_VERSION_HEX >= 0x03060000
+    if (!PyGILState_Check()) {
+        pybind11_fail("pybind11::object_api<>::operator() PyGILState_Check() failure.");
+    }
+#endif
     return detail::collect_arguments<policy>(std::forward<Args>(args)...).call(derived().ptr());
 }
 
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index dffe538fc5..61bc3a8f06 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -172,4 +172,10 @@ TEST_SUBMODULE(callbacks, m) {
         for (auto i : work)
             start_f(py::cast<int>(i));
     });
+
+    m.def("callback_num_times", [](py::function f, std::size_t num) {
+        for (std::size_t i = 0; i < num; i++) {
+            f();
+        }
+    });
 }
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 039b877ced..cec68bda5c 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -2,6 +2,7 @@
 import pytest
 from pybind11_tests import callbacks as m
 from threading import Thread
+import time
 
 
 def test_callbacks():
@@ -146,3 +147,34 @@ def test_async_async_callbacks():
     t = Thread(target=test_async_callbacks)
     t.start()
     t.join()
+
+
+def test_callback_num_times():
+    # Super-simple micro-benchmarking related to PR #2919.
+    # Example runtimes (Intel Xeon 2.2GHz, fully optimized):
+    #   num_millions  1, repeats  2:  0.1 secs
+    #   num_millions 20, repeats 10: 11.5 secs
+    one_million = 1000000
+    num_millions = 1  # Try 20 for actual micro-benchmarking.
+    repeats = 2  # Try 10.
+    rates = []
+    for rep in range(repeats):
+        t0 = time.time()
+        m.callback_num_times(lambda: None, num_millions * one_million)
+        td = time.time() - t0
+        rate = num_millions / td if td else 0
+        rates.append(rate)
+        if not rep:
+            print()
+        print(
+            "callback_num_times: {:d} million / {:.3f} seconds = {:.3f} million / second".format(
+                num_millions, td, rate
+            )
+        )
+    if len(rates) > 1:
+        print("Min    Mean   Max")
+        print(
+            "{:6.3f} {:6.3f} {:6.3f}".format(
+                min(rates), sum(rates) / len(rates), max(rates)
+            )
+        )

From 16c23fef312bcb98c951b71170a49508e1de4eb7 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 5 Apr 2021 22:53:59 -0400
Subject: [PATCH 009/638] chore(deps): bump pre-commit/action from v2.0.0 to
 v2.0.2 (#2935)

---
 .github/workflows/format.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 5cebed17da..c1d576e13b 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -19,7 +19,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-python@v2
-    - uses: pre-commit/action@v2.0.0
+    - uses: pre-commit/action@v2.0.2
       with:
         # Slow hooks are marked with manual - slow is okay here, run them too
         extra_args: --hook-stage manual --all-files

From 4f0727f2804f96b896155f1a680ea6da23cd4407 Mon Sep 17 00:00:00 2001
From: Weiming Zhao <wmzhao.code@gmail.com>
Date: Mon, 5 Apr 2021 20:50:50 -0700
Subject: [PATCH 010/638] Fix the enabling of default extension handling
 (#2938)

---
 tools/pybind11NewTools.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 18da8be170..a20803bc74 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -230,7 +230,7 @@ function(pybind11_add_module target_name)
   endif()
 
   # If we don't pass a WITH_SOABI or WITHOUT_SOABI, use our own default handling of extensions
-  if(NOT ARG_WITHOUT_SOABI OR NOT "WITH_SOABI" IN_LIST ARG_UNPARSED_ARGUMENTS)
+  if(NOT ARG_WITHOUT_SOABI AND NOT "WITH_SOABI" IN_LIST ARG_UNPARSED_ARGUMENTS)
     pybind11_extension(${target_name})
   endif()
 

From e0c1dadb757296c8bc91760a62bfb48b48c39530 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sat, 10 Apr 2021 11:12:56 -0400
Subject: [PATCH 011/638] chore: add myself to CODEOWNERS (#2940)

* chore: add myself to CODEOWNERS

This will ensure I get notified about pull requests where these files change.

* Update .github/CODEOWNERS
---
 .github/CODEOWNERS | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 .github/CODEOWNERS

diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
new file mode 100644
index 0000000000..60af5e7971
--- /dev/null
+++ b/.github/CODEOWNERS
@@ -0,0 +1,6 @@
+*.cmake @henryiii
+CMakeLists.txt @henryiii
+*.yml @henryiii
+*.yaml @henryiii
+/tools/ @henryiii
+/pybind11/ @henryiii

From 6709abba934e968d31c24f20c132c67a6f424a6a Mon Sep 17 00:00:00 2001
From: Tamaki Nishino <otamachan@gmail.com>
Date: Wed, 14 Apr 2021 08:53:56 +0900
Subject: [PATCH 012/638] Allow function pointer extraction from overloaded
 functions (#2944)

* Add a failure test for overloaded functions

* Allow function pointer extraction from overloaded functions
---
 include/pybind11/functional.h | 16 +++++++++++-----
 tests/test_callbacks.cpp      |  2 ++
 tests/test_callbacks.py       |  4 ++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 92c17dc225..aee9be4e45 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -46,11 +46,17 @@ struct type_caster<std::function<Return(Args...)>> {
             auto c = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(cfunc.ptr()));
             auto rec = (function_record *) c;
 
-            if (rec && rec->is_stateless &&
-                    same_type(typeid(function_type), *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
-                struct capture { function_type f; };
-                value = ((capture *) &rec->data)->f;
-                return true;
+            while (rec != nullptr) {
+                if (rec->is_stateless
+                    && same_type(typeid(function_type),
+                                 *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
+                    struct capture {
+                        function_type f;
+                    };
+                    value = ((capture *) &rec->data)->f;
+                    return true;
+                }
+                rec = rec->next;
             }
         }
 
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 61bc3a8f06..33927f5c38 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -97,6 +97,8 @@ TEST_SUBMODULE(callbacks, m) {
     // test_cpp_function_roundtrip
     /* Test if passing a function pointer from C++ -> Python -> C++ yields the original pointer */
     m.def("dummy_function", &dummy_function);
+    m.def("dummy_function_overloaded", [](int i, int j) { return i + j; });
+    m.def("dummy_function_overloaded", &dummy_function);
     m.def("dummy_function2", [](int i, int j) { return i + j; });
     m.def("roundtrip", [](std::function<int(int)> f, bool expect_none = false) {
         if (expect_none && f)
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index cec68bda5c..3526614304 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -93,6 +93,10 @@ def test_cpp_function_roundtrip():
         m.test_dummy_function(m.roundtrip(m.dummy_function))
         == "matches dummy_function: eval(1) = 2"
     )
+    assert (
+        m.test_dummy_function(m.dummy_function_overloaded)
+        == "matches dummy_function: eval(1) = 2"
+    )
     assert m.roundtrip(None, expect_none=True) is None
     assert (
         m.test_dummy_function(lambda x: x + 2)

From 62976cfcb8ccc76a79849028d7f5a3f8c7019007 Mon Sep 17 00:00:00 2001
From: Philipp Bucher <philipp.bucher@tum.de>
Date: Wed, 14 Apr 2021 20:01:27 +0200
Subject: [PATCH 013/638] fix: using -Werror-all for Intel (#2948)

* correcting Werror for Intel

* adding ward for Intel

* adding wards for intel

* another ward for Intel

* missed one intel ward

* exact match for intel compiler

* removing inline limits

* disable warnings about inline limits

* formatter suggestion

* more indent

* hopefully make formatter happy

* addressed review

* fix &&

* Update tests/CMakeLists.txt

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 include/pybind11/pybind11.h            | 6 +++---
 tests/CMakeLists.txt                   | 9 ++++++++-
 tests/test_constants_and_functions.cpp | 8 ++++----
 tests/test_operator_overloading.cpp    | 6 +++---
 4 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index eff40a8495..754c875cda 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -143,12 +143,12 @@ class cpp_function : public function {
             /* Without these pragmas, GCC warns that there might not be
                enough space to use the placement new operator. However, the
                'if' statement above ensures that this is the case. */
-#if defined(__GNUG__) && !defined(__clang__) && __GNUC__ >= 6
+#if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wplacement-new"
 #endif
             new ((capture *) &rec->data) capture { std::forward<Func>(f) };
-#if defined(__GNUG__) && !defined(__clang__) && __GNUC__ >= 6
+#if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
             if (!std::is_trivially_destructible<Func>::value)
@@ -2283,6 +2283,6 @@ PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 #if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(pop)
-#elif defined(__GNUG__) && !defined(__clang__)
+#elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9ff6c0dd9a..3d89404911 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -268,8 +268,15 @@ function(pybind11_enable_warnings target_name)
       target_compile_options(${target_name} PRIVATE /WX)
     elseif(PYBIND11_CUDA_TESTS)
       target_compile_options(${target_name} PRIVATE "SHELL:-Werror all-warnings")
-    elseif(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Intel|Clang)")
+    elseif(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang|IntelLLVM)")
       target_compile_options(${target_name} PRIVATE -Werror)
+    elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+      target_compile_options(
+        ${target_name}
+        PRIVATE
+          -Werror-all
+          # "Inlining inhibited by limit max-size", "Inlining inhibited by limit max-total-size"
+          -diag-disable 11074,11076)
     endif()
   endif()
 
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 8855dd7d7c..5bbbd0c70b 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -56,12 +56,12 @@ int f1(int x) noexcept { return x+1; }
 #endif
 int f2(int x) noexcept(true) { return x+2; }
 int f3(int x) noexcept(false) { return x+3; }
-#if defined(__GNUG__)
+#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
 int f4(int x) throw() { return x+4; } // Deprecated equivalent to noexcept(true)
-#if defined(__GNUG__)
+#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
 struct C {
@@ -71,13 +71,13 @@ struct C {
     int m4(int x) const noexcept(true) { return x-4; }
     int m5(int x) noexcept(false) { return x-5; }
     int m6(int x) const noexcept(false) { return x-6; }
-#if defined(__GNUG__)
+#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
     int m7(int x) throw() { return x-7; }
     int m8(int x) const throw() { return x-8; }
-#if defined(__GNUG__)
+#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
 };
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index 0a27bfd57b..eb3167dc08 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -80,8 +80,8 @@ std::string abs(const Vector2&) {
     return "abs(Vector2)";
 }
 
-// MSVC warns about unknown pragmas, and warnings are errors.
-#ifndef _MSC_VER
+// MSVC & Intel warns about unknown pragmas, and warnings are errors.
+#if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
   #pragma GCC diagnostic push
   // clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
   // `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
@@ -221,6 +221,6 @@ TEST_SUBMODULE(operators, m) {
         .def(py::self == py::self);
 }
 
-#ifndef _MSC_VER
+#if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
   #pragma GCC diagnostic pop
 #endif

From 114be7f4ade0ad798cd4c7f5d65ebe4ba8bd892d Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 15 Apr 2021 18:27:16 -0400
Subject: [PATCH 014/638] docs: remove recommonmark (#2955)

---
 docs/requirements.txt | 2 --
 1 file changed, 2 deletions(-)

diff --git a/docs/requirements.txt b/docs/requirements.txt
index a1276a65d9..671dc4b3f3 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,6 +1,4 @@
 breathe==4.26.1
-commonmark==0.9.1
-recommonmark==0.7.1
 sphinx==3.3.1
 sphinx_rtd_theme==0.5.0
 sphinxcontrib-moderncmakedomain==3.17

From e08a58111dbea38d667b209f7543864d51a3b185 Mon Sep 17 00:00:00 2001
From: mvoelkle-cern <54059203+mvoelkle-cern@users.noreply.github.com>
Date: Mon, 19 Apr 2021 19:53:57 +0200
Subject: [PATCH 015/638] Fix compilation with gcc < 5 (#2956)

When the user defines _GLIBCXX_USE_CXX11_ABI=0 to force the pre-c++11 ABI, numpy.h assumes that is_trivially_copyable is available.
It is not necessarily the case. This patch uses clang's feature detection instead.
The workaround is for certain libstdc++ versions, so the test should target these particular versions.
---
 include/pybind11/numpy.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index d1ddc4a9db..dd7f43d16a 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -319,14 +319,13 @@ template <typename T> using remove_all_extents_t = typename array_info<T>::type;
 
 template <typename T> using is_pod_struct = all_of<
     std::is_standard_layout<T>,     // since we're accessing directly in memory we need a standard layout type
-#if !defined(__GNUG__) || defined(_LIBCPP_VERSION) || defined(_GLIBCXX_USE_CXX11_ABI)
-    // _GLIBCXX_USE_CXX11_ABI indicates that we're using libstdc++ from GCC 5 or newer, independent
-    // of the actual compiler (Clang can also use libstdc++, but it always defines __GNUC__ == 4).
-    std::is_trivially_copyable<T>,
-#else
-    // GCC 4 doesn't implement is_trivially_copyable, so approximate it
+#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150623 || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
+    // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after 5)
+    // don't implement is_trivially_copyable, so approximate it
     std::is_trivially_destructible<T>,
     satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
+#else
+    std::is_trivially_copyable<T>,
 #endif
     satisfies_none_of<T, std::is_reference, std::is_array, is_std_array, std::is_arithmetic, is_complex, std::is_enum>
 >;

From 5e4804bb66e7d1915558adca1803db0815398fce Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 21 Apr 2021 13:30:01 -0400
Subject: [PATCH 016/638] tests: use master commit for pytest on 3.10 (#2967)

---
 tests/requirements.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/requirements.txt b/tests/requirements.txt
index 257d8d85fb..00cb5f119f 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -5,7 +5,8 @@ numpy==1.19.3; (platform_python_implementation!="PyPy" or sys_platform=="linux")
 numpy==1.20.0; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
 pytest==4.6.9; python_version<"3.5"
 pytest==6.1.2; python_version=="3.5"
-pytest==6.2.1; python_version>="3.6"
+pytest==6.2.1; python_version>="3.6" and python_version<="3.9"
+pytest @ git+https://github.com/pytest-dev/pytest@c117bc350ec1e570672fda3b2ad234fd52e72b53; python_version>="3.10"
 pytest-timeout
 scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version<"3.6"
 scipy==1.5.4; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.10"

From bca4b36ba75957b463463a35ad7dc98b8326b04c Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 21 Apr 2021 15:00:00 -0400
Subject: [PATCH 017/638] chore(deps): bump pre-commit/action from v2.0.2 to
 v2.0.3 (#2964)

Bumps [pre-commit/action](https://github.com/pre-commit/action) from v2.0.2 to v2.0.3.
- [Release notes](https://github.com/pre-commit/action/releases)
- [Commits](https://github.com/pre-commit/action/compare/v2.0.2...9b88afc9cd57fd75b655d5c71bd38146d07135fe)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/format.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index c1d576e13b..6550acccdb 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -19,7 +19,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-python@v2
-    - uses: pre-commit/action@v2.0.2
+    - uses: pre-commit/action@v2.0.3
       with:
         # Slow hooks are marked with manual - slow is okay here, run them too
         extra_args: --hook-stage manual --all-files

From 54430436fee2afc4f8443691075a6208f9ea8eba Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 22 Apr 2021 00:03:07 -0400
Subject: [PATCH 018/638] ci: install Boost for boost checks (#2968)

---
 .github/workflows/ci.yml | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a1bdec7bd7..19e1030d82 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -66,9 +66,13 @@ jobs:
       with:
         python-version: ${{ matrix.python }}
 
-    - name: Setup Boost (Windows / Linux latest)
-      shell: bash
-      run: echo "BOOST_ROOT=$BOOST_ROOT_1_72_0" >> $GITHUB_ENV
+    - name: Setup Boost (Linux)
+      if: runner.os == 'Linux'
+      run: sudo apt-get install libboost-dev
+
+    - name: Setup Boost (macOS)
+      if: runner.os == 'macOS'
+      run: brew install boost
 
     - name: Update CMake
       uses: jwlawson/actions-setup-cmake@v1.8

From 0c93a0f3fcf6bf26be584558d7426564720cea6f Mon Sep 17 00:00:00 2001
From: Pieter P <pieter.pas@outlook.com>
Date: Tue, 4 May 2021 07:04:38 +0200
Subject: [PATCH 019/638] Fix Unicode support for ostream redirects (#2982)

* Crash when printing Unicode to redirected cout
Add failing tests

* Fix Unicode crashes redirected cout

* pythonbuf::utf8_remainder check end iterator

* Remove trailing whitespace and formatting iostream

* Avoid buffer overflow if ostream redirect races
This doesn't solve the actual race, but at least it now has a much lower
probability of reading past the end of the buffer even when data races
do occur.
---
 include/pybind11/iostream.h | 75 ++++++++++++++++++++++++++-----
 tests/test_iostream.py      | 90 +++++++++++++++++++++++++++++++++++++
 2 files changed, 153 insertions(+), 12 deletions(-)

diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 9dee755431..7c1c718b02 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -16,6 +16,9 @@
 #include <string>
 #include <memory>
 #include <iostream>
+#include <cstring>
+#include <iterator>
+#include <algorithm>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -38,25 +41,73 @@ class pythonbuf : public std::streambuf {
         return sync() == 0 ? traits_type::not_eof(c) : traits_type::eof();
     }
 
+    // Computes how many bytes at the end of the buffer are part of an
+    // incomplete sequence of UTF-8 bytes.
+    // Precondition: pbase() < pptr()
+    size_t utf8_remainder() const {
+        const auto rbase = std::reverse_iterator<char *>(pbase());
+        const auto rpptr = std::reverse_iterator<char *>(pptr());
+        auto is_ascii = [](char c) {
+            return (static_cast<unsigned char>(c) & 0x80) == 0x00;
+        };
+        auto is_leading = [](char c) {
+            return (static_cast<unsigned char>(c) & 0xC0) == 0xC0;
+        };
+        auto is_leading_2b = [](char c) {
+            return static_cast<unsigned char>(c) <= 0xDF;
+        };
+        auto is_leading_3b = [](char c) {
+            return static_cast<unsigned char>(c) <= 0xEF;
+        };
+        // If the last character is ASCII, there are no incomplete code points
+        if (is_ascii(*rpptr))
+            return 0;
+        // Otherwise, work back from the end of the buffer and find the first
+        // UTF-8 leading byte
+        const auto rpend   = rbase - rpptr >= 3 ? rpptr + 3 : rbase;
+        const auto leading = std::find_if(rpptr, rpend, is_leading);
+        if (leading == rbase)
+            return 0;
+        const auto dist    = static_cast<size_t>(leading - rpptr);
+        size_t remainder   = 0;
+
+        if (dist == 0)
+            remainder = 1; // 1-byte code point is impossible
+        else if (dist == 1)
+            remainder = is_leading_2b(*leading) ? 0 : dist + 1;
+        else if (dist == 2)
+            remainder = is_leading_3b(*leading) ? 0 : dist + 1;
+        // else if (dist >= 3), at least 4 bytes before encountering an UTF-8
+        // leading byte, either no remainder or invalid UTF-8.
+        // Invalid UTF-8 will cause an exception later when converting
+        // to a Python string, so that's not handled here.
+        return remainder;
+    }
+
     // This function must be non-virtual to be called in a destructor. If the
     // rare MSVC test failure shows up with this version, then this should be
     // simplified to a fully qualified call.
     int _sync() {
-        if (pbase() != pptr()) {
-
-            {
-                gil_scoped_acquire tmp;
-
+        if (pbase() != pptr()) { // If buffer is not empty
+            gil_scoped_acquire tmp;
+            // Placed inside gil_scoped_acquire as a mutex to avoid a race.
+            if (pbase() != pptr()) { // Check again under the lock
                 // This subtraction cannot be negative, so dropping the sign.
-                str line(pbase(), static_cast<size_t>(pptr() - pbase()));
-
-                pywrite(line);
-                pyflush();
-
-                // Placed inside gil_scoped_aquire as a mutex to avoid a race
+                auto size        = static_cast<size_t>(pptr() - pbase());
+                size_t remainder = utf8_remainder();
+
+                if (size > remainder) {
+                    str line(pbase(), size - remainder);
+                    pywrite(line);
+                    pyflush();
+                }
+
+                // Copy the remainder at the end of the buffer to the beginning:
+                if (remainder > 0)
+                    std::memmove(pbase(), pptr() - remainder, remainder);
                 setp(pbase(), epptr());
+                pbump(static_cast<int>(remainder));
             }
-
         }
         return 0;
     }
diff --git a/tests/test_iostream.py b/tests/test_iostream.py
index 6d493beda3..e2b74d01cb 100644
--- a/tests/test_iostream.py
+++ b/tests/test_iostream.py
@@ -69,6 +69,96 @@ def test_captured_large_string(capsys):
     assert stderr == ""
 
 
+def test_captured_utf8_2byte_offset0(capsys):
+    msg = "\u07FF"
+    msg = "" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_2byte_offset1(capsys):
+    msg = "\u07FF"
+    msg = "1" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_3byte_offset0(capsys):
+    msg = "\uFFFF"
+    msg = "" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_3byte_offset1(capsys):
+    msg = "\uFFFF"
+    msg = "1" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_3byte_offset2(capsys):
+    msg = "\uFFFF"
+    msg = "12" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_4byte_offset0(capsys):
+    msg = "\U0010FFFF"
+    msg = "" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_4byte_offset1(capsys):
+    msg = "\U0010FFFF"
+    msg = "1" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_4byte_offset2(capsys):
+    msg = "\U0010FFFF"
+    msg = "12" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
+def test_captured_utf8_4byte_offset3(capsys):
+    msg = "\U0010FFFF"
+    msg = "123" + msg * (1024 // len(msg) + 1)
+
+    m.captured_output_default(msg)
+    stdout, stderr = capsys.readouterr()
+    assert stdout == msg
+    assert stderr == ""
+
+
 def test_guard_capture(capsys):
     msg = "I've been redirected to Python, I hope!"
     m.guard_output(msg)

From 417fd120ccd6a40294058a4d9cc3c6c6038fbb26 Mon Sep 17 00:00:00 2001
From: Akira Kawata <akawashiro@users.noreply.github.com>
Date: Thu, 6 May 2021 16:19:05 +0900
Subject: [PATCH 020/638] Fix: fix typo of WITHOUT_SOABI (#2992)

---
 tools/pybind11Config.cmake.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 9921aeb355..0f136005b7 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -139,7 +139,7 @@ This module defines the following commands to assist with creating Python module
 
   pybind11_add_module(<target>
     [STATIC|SHARED|MODULE]
-    [THIN_LTO] [OPT_SIZE] [NO_EXTRAS] [WITHOUT_SOBAI]
+    [THIN_LTO] [OPT_SIZE] [NO_EXTRAS] [WITHOUT_SOABI]
     <files>...
     )
 

From b6ec0e950c4a12d25cadf492f193ced94f681d6c Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 6 May 2021 10:13:30 -0400
Subject: [PATCH 021/638] functions: Add doc on incorrect argument index
 (#2979)

test_call_policies: Explicitly check free-functions and static methods
---
 docs/advanced/functions.rst  |  3 +++
 tests/test_call_policies.cpp |  8 +++++++-
 tests/test_call_policies.py  | 30 ++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index 6a93ab9da8..f6061ffbe6 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -182,6 +182,9 @@ relies on the ability to create a *weak reference* to the nurse object. When
 the nurse object is not a pybind11-registered type and does not support weak
 references, an exception will be thrown.
 
+If you use an incorrect argument index, you will get a ``RuntimeError`` saying
+``Could not activate keep_alive!``. You should review the indices you're using.
+
 Consider the following example: here, the binding code for a list append
 operation ties the lifetime of the newly added element to the underlying
 container:
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index 26c83f81b0..7cb98d0d86 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -51,6 +51,7 @@ TEST_SUBMODULE(call_policies, m) {
         void addChild(Child *) { }
         Child *returnChild() { return new Child(); }
         Child *returnNullChild() { return nullptr; }
+        static Child *staticFunction(Parent*) { return new Child(); }
     };
     py::class_<Parent>(m, "Parent")
         .def(py::init<>())
@@ -60,7 +61,12 @@ TEST_SUBMODULE(call_policies, m) {
         .def("returnChild", &Parent::returnChild)
         .def("returnChildKeepAlive", &Parent::returnChild, py::keep_alive<1, 0>())
         .def("returnNullChildKeepAliveChild", &Parent::returnNullChild, py::keep_alive<1, 0>())
-        .def("returnNullChildKeepAliveParent", &Parent::returnNullChild, py::keep_alive<0, 1>());
+        .def("returnNullChildKeepAliveParent", &Parent::returnNullChild, py::keep_alive<0, 1>())
+        .def_static(
+            "staticFunction", &Parent::staticFunction, py::keep_alive<1, 0>());
+
+    m.def("free_function", [](Parent*, Child*) {}, py::keep_alive<1, 2>());
+    m.def("invalid_arg_index", []{}, py::keep_alive<0, 1>());
 
 #if !defined(PYPY_VERSION)
     // test_alive_gc
diff --git a/tests/test_call_policies.py b/tests/test_call_policies.py
index e0413d1451..af017e9d0c 100644
--- a/tests/test_call_policies.py
+++ b/tests/test_call_policies.py
@@ -46,6 +46,19 @@ def test_keep_alive_argument(capture):
     """
     )
 
+    p = m.Parent()
+    c = m.Child()
+    assert ConstructorStats.detail_reg_inst() == n_inst + 2
+    m.free_function(p, c)
+    del c
+    assert ConstructorStats.detail_reg_inst() == n_inst + 2
+    del p
+    assert ConstructorStats.detail_reg_inst() == n_inst
+
+    with pytest.raises(RuntimeError) as excinfo:
+        m.invalid_arg_index()
+    assert str(excinfo.value) == "Could not activate keep_alive!"
+
 
 def test_keep_alive_return_value(capture):
     n_inst = ConstructorStats.detail_reg_inst()
@@ -85,6 +98,23 @@ def test_keep_alive_return_value(capture):
     """
     )
 
+    p = m.Parent()
+    assert ConstructorStats.detail_reg_inst() == n_inst + 1
+    with capture:
+        m.Parent.staticFunction(p)
+        assert ConstructorStats.detail_reg_inst() == n_inst + 2
+    assert capture == "Allocating child."
+    with capture:
+        del p
+        assert ConstructorStats.detail_reg_inst() == n_inst
+    assert (
+        capture
+        == """
+        Releasing parent.
+        Releasing child.
+    """
+    )
+
 
 # https://foss.heptapod.net/pypy/pypy/-/issues/2447
 @pytest.mark.xfail("env.PYPY", reason="_PyObject_GetDictPtr is unimplemented")

From bc7cf6ef17031393d300acb30b8526345e6465a7 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 13 May 2021 23:19:51 -0400
Subject: [PATCH 022/638] chore(deps): bump jwlawson/actions-setup-cmake from
 1.8 to 1.9 (#3000)

---
 .github/workflows/ci.yml        | 12 ++++++------
 .github/workflows/configure.yml |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 19e1030d82..8adb0743b7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -75,7 +75,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -193,7 +193,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -445,7 +445,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Configure
       shell: bash
@@ -727,7 +727,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1
@@ -773,7 +773,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1
@@ -827,7 +827,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt --prefer-binary
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 0f3117be99..abcff1dde5 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -55,7 +55,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.8
+      uses: jwlawson/actions-setup-cmake@v1.9
       with:
         cmake-version: ${{ matrix.cmake }}
 

From f61855b9d8821e2576960109a2a67379a6c2366f Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 13 May 2021 23:21:13 -0400
Subject: [PATCH 023/638] chore(deps): bump ilammy/msvc-dev-cmd from 1 to 1.8.0
 (#3001)

---
 .github/workflows/ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8adb0743b7..ac797181cb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -151,7 +151,7 @@ jobs:
     # MSVC, but for now, this action works:
     - name: Prepare compiler environment for Windows 🐍 2.7
       if: matrix.python == 2.7 && runner.os == 'Windows'
-      uses: ilammy/msvc-dev-cmd@v1
+      uses: ilammy/msvc-dev-cmd@v1.8.0
       with:
         arch: x64
 
@@ -730,7 +730,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1
+      uses: ilammy/msvc-dev-cmd@v1.8.0
       with:
         arch: x86
 
@@ -776,7 +776,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1
+      uses: ilammy/msvc-dev-cmd@v1.8.0
       with:
         toolset: 14.0
 

From 14023c9cda70215ccef7fd92ebb4c42197e98e1f Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 27 May 2021 06:10:28 +0000
Subject: [PATCH 024/638] chore(deps): bump ilammy/msvc-dev-cmd from 1.8.0 to
 1.8.1 (#3021)

---
 .github/workflows/ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ac797181cb..de7aeeb00b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -151,7 +151,7 @@ jobs:
     # MSVC, but for now, this action works:
     - name: Prepare compiler environment for Windows 🐍 2.7
       if: matrix.python == 2.7 && runner.os == 'Windows'
-      uses: ilammy/msvc-dev-cmd@v1.8.0
+      uses: ilammy/msvc-dev-cmd@v1.8.1
       with:
         arch: x64
 
@@ -730,7 +730,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.8.0
+      uses: ilammy/msvc-dev-cmd@v1.8.1
       with:
         arch: x86
 
@@ -776,7 +776,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.8.0
+      uses: ilammy/msvc-dev-cmd@v1.8.1
       with:
         toolset: 14.0
 

From 3ac690b88be00a44c1988afc209a395d87a57051 Mon Sep 17 00:00:00 2001
From: Yichen <oraluben@outlook.com>
Date: Thu, 27 May 2021 23:00:18 +0800
Subject: [PATCH 025/638] Explicitly export exception types. (#2999)

* Set visibility of exceptions to default.

Co-authored-by: XZiar <czktc2007@gmail.com>

* add test

* update docs

* Skip failed test.
---
 docs/advanced/exceptions.rst          |  4 ++++
 include/pybind11/detail/common.h      | 11 +++++++++--
 include/pybind11/detail/internals.h   |  2 ++
 include/pybind11/pytypes.h            |  9 ++++++++-
 tests/pybind11_cross_module_tests.cpp |  8 ++++++++
 tests/test_exceptions.cpp             |  2 ++
 tests/test_exceptions.h               | 12 ++++++++++++
 tests/test_exceptions.py              | 14 ++++++++++++++
 8 files changed, 59 insertions(+), 3 deletions(-)
 create mode 100644 tests/test_exceptions.h

diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index 7a4d6cbc6e..f70c202fd5 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -164,6 +164,10 @@ section.
     may be explicitly (re-)thrown to delegate it to the other,
     previously-declared existing exception translators.
 
+    Note that ``libc++`` and ``libstdc++`` `behave differently <https://stackoverflow.com/questions/19496643/using-clang-fvisibility-hidden-and-typeinfo-and-type-erasure/28827430>`_
+    with ``-fvisibility=hidden``. Therefore exceptions that are used across ABI boundaries need to be explicitly exported, as exercised in ``tests/test_exceptions.h``.
+    See also: "Problems with C++ exceptions" under `GCC Wiki <https://gcc.gnu.org/wiki/Visibility>`_.
+
 .. _handling_python_exceptions_cpp:
 
 Handling exceptions from Python in C++
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 5560198a05..987f0badf9 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -723,16 +723,23 @@ using expand_side_effects = bool[];
 
 PYBIND11_NAMESPACE_END(detail)
 
+#if defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable: 4275) // warning C4275: An exported class was derived from a class that wasn't exported. Can be ignored when derived from a STL class.
+#endif
 /// C++ bindings of builtin Python exceptions
-class builtin_exception : public std::runtime_error {
+class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
 public:
     using std::runtime_error::runtime_error;
     /// Set the error using the Python C API
     virtual void set_error() const = 0;
 };
+#if defined(_MSC_VER)
+#  pragma warning(pop)
+#endif
 
 #define PYBIND11_RUNTIME_EXCEPTION(name, type) \
-    class name : public builtin_exception { public: \
+    class PYBIND11_EXPORT name : public builtin_exception { public: \
         using builtin_exception::builtin_exception; \
         name() : name("") { } \
         void set_error() const override { PyErr_SetString(type, what()); } \
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 75fcd3c208..5578c65160 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -276,6 +276,8 @@ PYBIND11_NOINLINE inline internals &get_internals() {
         // initial exception translator, below, so add another for our local exception classes.
         //
         // libstdc++ doesn't require this (types there are identified only by name)
+        // libc++ with CPython doesn't require this (types are explicitly exported)
+        // libc++ with PyPy still need it, awaiting further investigation
 #if !defined(__GLIBCXX__)
         (*internals_pp)->registered_exception_translators.push_front(&translate_local_exception);
 #endif
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 6f0e6067ef..6a1d8356a5 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -319,11 +319,15 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 inline std::string error_string();
 PYBIND11_NAMESPACE_END(detail)
 
+#if defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable: 4275 4251) // warning C4275: An exported class was derived from a class that wasn't exported. Can be ignored when derived from a STL class.
+#endif
 /// Fetch and hold an error which was already set in Python.  An instance of this is typically
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
 /// else falls back to the function dispatcher (which then raises the captured error back to
 /// python).
-class error_already_set : public std::runtime_error {
+class PYBIND11_EXPORT error_already_set : public std::runtime_error {
 public:
     /// Constructs a new exception from the current Python error indicator, if any.  The current
     /// Python error indicator will be cleared.
@@ -371,6 +375,9 @@ class error_already_set : public std::runtime_error {
 private:
     object m_type, m_value, m_trace;
 };
+#if defined(_MSC_VER)
+#  pragma warning(pop)
+#endif
 
 /** \defgroup python_builtins _
     Unless stated otherwise, the following C++ functions behave the same
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index f705e31061..944d085597 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -9,6 +9,7 @@
 
 #include "pybind11_tests.h"
 #include "local_bindings.h"
+#include "test_exceptions.h"
 #include <pybind11/stl_bind.h>
 #include <numeric>
 
@@ -30,6 +31,13 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("throw_pybind_value_error", []() { throw py::value_error("pybind11 value error"); });
     m.def("throw_pybind_type_error", []() { throw py::type_error("pybind11 type error"); });
     m.def("throw_stop_iteration", []() { throw py::stop_iteration(); });
+    py::register_exception_translator([](std::exception_ptr p) {
+      try {
+          if (p) std::rethrow_exception(p);
+      } catch (const shared_exception &e) {
+          PyErr_SetString(PyExc_KeyError, e.what());
+      }
+    });
 
     // test_local_bindings.py
     // Local to both:
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index e27c16dfef..4c5e10dbe0 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -7,6 +7,7 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include "test_exceptions.h"
 #include "pybind11_tests.h"
 
 // A type that should be raised as an exception in Python
@@ -228,4 +229,5 @@ TEST_SUBMODULE(exceptions, m) {
     // Test repr that cannot be displayed
     m.def("simple_bool_passthrough", [](bool x) {return x;});
 
+    m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
 }
diff --git a/tests/test_exceptions.h b/tests/test_exceptions.h
new file mode 100644
index 0000000000..5d02d1b35b
--- /dev/null
+++ b/tests/test_exceptions.h
@@ -0,0 +1,12 @@
+#pragma once
+#include "pybind11_tests.h"
+#include <stdexcept>
+
+// shared exceptions for cross_module_tests
+
+class PYBIND11_EXPORT shared_exception : public pybind11::builtin_exception {
+public:
+    using builtin_exception::builtin_exception;
+    explicit shared_exception() : shared_exception("") {}
+    void set_error() const override { PyErr_SetString(PyExc_RuntimeError, what()); }
+};
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index c6cb65299e..b9fc269381 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -3,6 +3,8 @@
 
 import pytest
 
+import env  # noqa: F401
+
 from pybind11_tests import exceptions as m
 import pybind11_cross_module_tests as cm
 
@@ -44,6 +46,18 @@ def test_cross_module_exceptions():
         cm.throw_stop_iteration()
 
 
+# TODO: FIXME
+@pytest.mark.xfail(
+    "env.PYPY and env.MACOS",
+    raises=RuntimeError,
+    reason="Expected failure with PyPy and libc++ (Issue #2847 & PR #2999)",
+)
+def test_cross_module_exception_translator():
+    with pytest.raises(KeyError):
+        # translator registered in cross_module_tests
+        m.throw_should_be_translated_to_key_error()
+
+
 def test_python_call_in_catch():
     d = {}
     assert m.python_call_in_destructor(d) is True

From e25b1505dbca042289c4076141092cff49b0b96b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 27 May 2021 12:51:46 -0700
Subject: [PATCH 026/638] Adjusting valgrind suppression for pypocketfft to
 resolve systematic failures that started to appear on 2020-05-27. (#3022)

---
 tests/valgrind-numpy-scipy.supp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/valgrind-numpy-scipy.supp b/tests/valgrind-numpy-scipy.supp
index fea9bcb4a6..001b6c717a 100644
--- a/tests/valgrind-numpy-scipy.supp
+++ b/tests/valgrind-numpy-scipy.supp
@@ -111,7 +111,7 @@
    fun:_Znwm
    fun:PyInit_pypocketfft
    fun:_PyImport_LoadDynamicModuleWithSpec
-   fun:_imp_create_dynamic_impl.constprop.*
+   fun:_imp_create_dynamic_impl*
    fun:_imp_create_dynamic
    fun:cfunction_vectorcall_FASTCALL
    fun:PyVectorcall_Call

From 4c7697dbe973ed01ae6fbec37d186ebd05982e1f Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Tue, 8 Jun 2021 20:56:45 +0200
Subject: [PATCH 027/638] Add const T to docstring generation. (#3020)

* Add const T to docstring generation.

* Change order.

* See if existing test triggers for a const type.

* Add tests.

* Fix test.

* Remove experiment.

* Reformat.

* More tests, checks run.

* Adding `test_fmt_desc_` prefix to new test functions.

* Using pytest.mark.parametrize to 1. condense test; 2. exercise all functions even if one fails; 3. be less platform-specific (e.g. C++ float is not necessarily float32).

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/numpy.h   |  9 +++++++--
 tests/test_numpy_array.cpp |  6 ++++++
 tests/test_numpy_array.py  | 13 +++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index dd7f43d16a..ec4c53b430 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1029,7 +1029,10 @@ struct npy_format_descriptor_name<T, enable_if_t<std::is_integral<T>::value>> {
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::value>> {
-    static constexpr auto name = _<std::is_same<T, float>::value || std::is_same<T, double>::value>(
+    static constexpr auto name = _<std::is_same<T, float>::value
+                                   || std::is_same<T, const float>::value
+                                   || std::is_same<T, double>::value
+                                   || std::is_same<T, const double>::value>(
         _("numpy.float") + _<sizeof(T)*8>(), _("numpy.longdouble")
     );
 };
@@ -1037,7 +1040,9 @@ struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::valu
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<is_complex<T>::value>> {
     static constexpr auto name = _<std::is_same<typename T::value_type, float>::value
-                                   || std::is_same<typename T::value_type, double>::value>(
+                                   || std::is_same<typename T::value_type, const float>::value
+                                   || std::is_same<typename T::value_type, double>::value
+                                   || std::is_same<typename T::value_type, const double>::value>(
         _("numpy.complex") + _<sizeof(typename T::value_type)*16>(), _("numpy.longcomplex")
     );
 };
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index dca7145f9d..204ea8367e 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -437,4 +437,10 @@ TEST_SUBMODULE(numpy_array, sm) {
     sm.def("accept_double_f_style_forcecast_noconvert",
            [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
            "a"_a.noconvert());
+
+    // Check that types returns correct npy format descriptor
+    sm.def("test_fmt_desc_float", [](py::array_t<float>) {});
+    sm.def("test_fmt_desc_double", [](py::array_t<double>) {});
+    sm.def("test_fmt_desc_const_float", [](py::array_t<const float>) {});
+    sm.def("test_fmt_desc_const_double", [](py::array_t<const double>) {});
 }
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 02f3ecfc0e..548c84bab1 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -482,6 +482,19 @@ def test_index_using_ellipsis():
     assert a.shape == (6,)
 
 
+@pytest.mark.parametrize(
+    "test_func",
+    [
+        m.test_fmt_desc_float,
+        m.test_fmt_desc_double,
+        m.test_fmt_desc_const_float,
+        m.test_fmt_desc_const_double,
+    ],
+)
+def test_format_descriptors_for_floating_point_types(test_func):
+    assert "numpy.ndarray[numpy.float" in test_func.__doc__
+
+
 @pytest.mark.parametrize("forcecast", [False, True])
 @pytest.mark.parametrize("contiguity", [None, "C", "F"])
 @pytest.mark.parametrize("noconvert", [False, True])

From cd4b49a2c8c659d3933cf902bb10e34931dbd1e7 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 17 Jun 2021 16:20:17 -0400
Subject: [PATCH 028/638] Update py::kwargs examples to pass by reference
 (#3038)

---
 docs/advanced/functions.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index f6061ffbe6..d880008b0f 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -254,7 +254,7 @@ For instance, the following statement iterates over a Python ``dict``:
 
 .. code-block:: cpp
 
-    void print_dict(py::dict dict) {
+    void print_dict(const py::dict& dict) {
         /* Easily interact with Python types */
         for (auto item : dict)
             std::cout << "key=" << std::string(py::str(item.first)) << ", "
@@ -292,7 +292,7 @@ Such functions can also be created using pybind11:
 
 .. code-block:: cpp
 
-   void generic(py::args args, py::kwargs kwargs) {
+   void generic(py::args args, const py::kwargs& kwargs) {
        /// .. do something with args
        if (kwargs)
            /// .. do something with kwargs

From b4b67f026bc2aa1a1ae17e9858a9e61210c77c31 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 17 Jun 2021 16:39:59 -0400
Subject: [PATCH 029/638] Fix typos (#3044)

---
 docs/advanced/pycpp/numpy.rst | 2 +-
 docs/compiling.rst            | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index 0a81aa8fd5..53ec8c1a3c 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -390,7 +390,7 @@ operation on the C++ side:
    py::array b = a[py::make_tuple(0, py::ellipsis(), 0)];
 
 .. versionchanged:: 2.6
-   ``py::ellipsis()`` is now also avaliable in Python 2.
+   ``py::ellipsis()`` is now also available in Python 2.
 
 Memory view
 ===========
diff --git a/docs/compiling.rst b/docs/compiling.rst
index 3a8a270d58..27f30e5a06 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -149,7 +149,7 @@ Your ``pyproject.toml`` file will likely look something like this:
     and ``pyproject.toml`` are not even contained in the wheel, so this high
     Pip requirement is only for source builds, and will not affect users of
     your binary wheels. If you are building SDists and wheels, then
-    `pypa-build`_ is the recommended offical tool.
+    `pypa-build`_ is the recommended official tool.
 
 .. _PEP 517: https://www.python.org/dev/peps/pep-0517/
 .. _cibuildwheel: https://cibuildwheel.readthedocs.io
@@ -411,7 +411,7 @@ existing targets instead:
 
 .. code-block:: cmake
 
-    cmake_minumum_required(VERSION 3.15...3.19)
+    cmake_minimum_required(VERSION 3.15...3.19)
     project(example LANGUAGES CXX)
 
     find_package(Python COMPONENTS Interpreter Development REQUIRED)
@@ -516,7 +516,7 @@ Instead of setting properties, you can set ``CMAKE_*`` variables to initialize t
     compiler flags are provided to ensure high quality code generation. In
     contrast to the ``pybind11_add_module()`` command, the CMake interface
     provides a *composable* set of targets to ensure that you retain flexibility.
-    It can be expecially important to provide or set these properties; the
+    It can be especially important to provide or set these properties; the
     :ref:`FAQ <faq:symhidden>` contains an explanation on why these are needed.
 
 .. versionadded:: 2.6

From 19d99a87fedc7272ec48bd90e91a00eff8e57b68 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 18 Jun 2021 01:35:36 -0700
Subject: [PATCH 030/638] Working around Centos 8 failure. (#3030)

* Experiment using -DCMAKE_BUILD_TYPE=Debug for Centos 8.

* Moving comment because the current placement seems to mess up the cmake command.

* Using `echo > VAR_XXX` and `$(cat VAR_XXX)` trick to emulate using variables (https://github.com/actions/starter-workflows/issues/68#issuecomment-524937002).
---
 .github/workflows/ci.yml | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index de7aeeb00b..2ed1da5c5e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -592,10 +592,21 @@ jobs:
     - name: Install dependencies
       run: python3 -m pip install cmake -r tests/requirements.txt --prefer-binary
 
+    - name: VAR_BUILD_TYPE 7
+      if: matrix.centos == 7
+      run: echo Release > VAR_BUILD_TYPE
+
+    # Using Debug to avoid segfault that appeared around 2021-06-04,
+    # apparently when the gcc version changed from 8.3 to 8.4.
+    - name: VAR_BUILD_TYPE 8
+      if: matrix.centos == 8
+      run: echo Debug > VAR_BUILD_TYPE
+
     - name: Configure
       shell: bash
       run: >
         cmake -S . -B build
+        -DCMAKE_BUILD_TYPE=$(cat VAR_BUILD_TYPE)
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON

From 79178e713d8f3ac3ae5b77017eb57f1bc67f336f Mon Sep 17 00:00:00 2001
From: jbarlow83 <jbarlow83@users.noreply.github.com>
Date: Fri, 18 Jun 2021 07:17:34 -0700
Subject: [PATCH 031/638] fix(setup_helpers): try import
 multiprocessing.synchronize too (#3043)

---
 pybind11/setup_helpers.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 84a4584c5d..1050f61253 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -410,7 +410,9 @@ def _single_compile(obj):
                     compiler._compile(obj, src, ext, cc_args, extra_postargs, pp_opts)
 
             try:
-                import multiprocessing
+                # Importing .synchronize checks for platforms that have some multiprocessing
+                # capabilities but lack semaphores, such as AWS Lambda and Android Termux.
+                import multiprocessing.synchronize
                 from multiprocessing.pool import ThreadPool
             except ImportError:
                 threads = 1

From af6218ff78d480c5e93237174ee6f02ec36853cc Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sat, 19 Jun 2021 13:53:27 -0400
Subject: [PATCH 032/638] fix(clang-tidy): Apply performance fixes from
 clang-tidy (#3046)

* Apply performance fixes from clang-tidy

* 2nd Round of Perf Optimizations

* 3rd round of fixes & handle false-positive

* Apply missing fix and clang-format

* Apply reviewer comment
---
 .clang-tidy                    |  4 +++
 include/pybind11/buffer_info.h |  6 ++--
 include/pybind11/cast.h        | 11 +++---
 include/pybind11/eval.h        |  8 +++--
 include/pybind11/iostream.h    | 39 ++++++++++-----------
 include/pybind11/numpy.h       |  4 +--
 include/pybind11/pybind11.h    | 62 +++++++++++++++++++---------------
 include/pybind11/pytypes.h     |  4 +--
 include/pybind11/stl.h         | 11 +++---
 include/pybind11/stl_bind.h    | 49 ++++++++++++++-------------
 10 files changed, 106 insertions(+), 92 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index e29d929897..3079b3b3c0 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -10,4 +10,8 @@ modernize-use-auto,
 modernize-use-emplace,
 '
 
+CheckOptions:
+- key:             performance-unnecessary-value-param.AllowedTypes
+  value:           'exception_ptr$;'
+
 HeaderFilterRegex: 'pybind11/.*h'
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index d803004a10..47dc39d4ea 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -91,11 +91,9 @@ struct buffer_info {
     buffer_info(const buffer_info &) = delete;
     buffer_info& operator=(const buffer_info &) = delete;
 
-    buffer_info(buffer_info &&other) {
-        (*this) = std::move(other);
-    }
+    buffer_info(buffer_info &&other) noexcept { (*this) = std::move(other); }
 
-    buffer_info& operator=(buffer_info &&rhs) {
+    buffer_info &operator=(buffer_info &&rhs) noexcept {
         ptr = rhs.ptr;
         itemsize = rhs.itemsize;
         size = rhs.size;
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index f68a35bfa4..1ef1a9ce9b 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1064,7 +1064,9 @@ struct kw_only {};
 struct pos_only {};
 
 template <typename T>
-arg_v arg::operator=(T &&value) const { return {std::move(*this), std::forward<T>(value)}; }
+arg_v arg::operator=(T &&value) const {
+    return {*this, std::forward<T>(value)};
+}
 
 /// Alias for backward compatibility -- to be removed in version 2.0
 template <typename /*unused*/> using arg_t = arg_v;
@@ -1286,7 +1288,7 @@ class unpacking_collector {
                          "may be passed via py::arg() to a python function call. "
                          "(compile in debug mode for details)");
     }
-    [[noreturn]] static void nameless_argument_error(std::string type) {
+    [[noreturn]] static void nameless_argument_error(const std::string &type) {
         throw type_error("Got kwargs without a name of type '" + type + "'; only named "
                          "arguments may be passed via py::arg() to a python function call. ");
     }
@@ -1295,7 +1297,7 @@ class unpacking_collector {
                          "(compile in debug mode for details)");
     }
 
-    [[noreturn]] static void multiple_values_error(std::string name) {
+    [[noreturn]] static void multiple_values_error(const std::string &name) {
         throw type_error("Got multiple values for keyword argument '" + name + "'");
     }
 
@@ -1304,7 +1306,8 @@ class unpacking_collector {
                          "(compile in debug mode for details)");
     }
 
-    [[noreturn]] static void argument_cast_error(std::string name, std::string type) {
+    [[noreturn]] static void argument_cast_error(const std::string &name,
+                                                 const std::string &type) {
         throw cast_error("Unable to convert call argument '" + name
                          + "' of type '" + type + "' to Python object");
     }
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index fa6b8af479..bf06504a33 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -11,6 +11,8 @@
 
 #pragma once
 
+#include <utility>
+
 #include "pybind11.h"
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -43,7 +45,7 @@ enum eval_mode {
 };
 
 template <eval_mode mode = eval_expr>
-object eval(str expr, object global = globals(), object local = object()) {
+object eval(const str &expr, object global = globals(), object local = object()) {
     if (!local)
         local = global;
 
@@ -75,8 +77,8 @@ object eval(const char (&s)[N], object global = globals(), object local = object
     return eval<mode>(expr, global, local);
 }
 
-inline void exec(str expr, object global = globals(), object local = object()) {
-    eval<eval_statements>(expr, global, local);
+inline void exec(const str &expr, object global = globals(), object local = object()) {
+    eval<eval_statements>(expr, std::move(global), std::move(local));
 }
 
 template <size_t N>
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 7c1c718b02..6a793eadca 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -11,14 +11,15 @@
 
 #include "pybind11.h"
 
-#include <streambuf>
-#include <ostream>
-#include <string>
-#include <memory>
-#include <iostream>
+#include <algorithm>
 #include <cstring>
+#include <iostream>
 #include <iterator>
-#include <algorithm>
+#include <memory>
+#include <ostream>
+#include <streambuf>
+#include <string>
+#include <utility>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -117,11 +118,8 @@ class pythonbuf : public std::streambuf {
     }
 
 public:
-
-    pythonbuf(object pyostream, size_t buffer_size = 1024)
-        : buf_size(buffer_size),
-          d_buffer(new char[buf_size]),
-          pywrite(pyostream.attr("write")),
+    pythonbuf(const object &pyostream, size_t buffer_size = 1024)
+        : buf_size(buffer_size), d_buffer(new char[buf_size]), pywrite(pyostream.attr("write")),
           pyflush(pyostream.attr("flush")) {
         setp(d_buffer.get(), d_buffer.get() + buf_size - 1);
     }
@@ -168,9 +166,8 @@ class scoped_ostream_redirect {
     detail::pythonbuf buffer;
 
 public:
-    scoped_ostream_redirect(
-            std::ostream &costream = std::cout,
-            object pyostream = module_::import("sys").attr("stdout"))
+    scoped_ostream_redirect(std::ostream &costream  = std::cout,
+                            const object &pyostream = module_::import("sys").attr("stdout"))
         : costream(costream), buffer(pyostream) {
         old = costream.rdbuf(&buffer);
     }
@@ -199,10 +196,9 @@ class scoped_ostream_redirect {
 \endrst */
 class scoped_estream_redirect : public scoped_ostream_redirect {
 public:
-    scoped_estream_redirect(
-            std::ostream &costream = std::cerr,
-            object pyostream = module_::import("sys").attr("stderr"))
-        : scoped_ostream_redirect(costream,pyostream) {}
+    scoped_estream_redirect(std::ostream &costream  = std::cerr,
+                            const object &pyostream = module_::import("sys").attr("stderr"))
+        : scoped_ostream_redirect(costream, pyostream) {}
 };
 
 
@@ -261,9 +257,10 @@ PYBIND11_NAMESPACE_END(detail)
             m.noisy_function_with_error_printing()
 
  \endrst */
-inline class_<detail::OstreamRedirect> add_ostream_redirect(module_ m, std::string name = "ostream_redirect") {
-    return class_<detail::OstreamRedirect>(m, name.c_str(), module_local())
-        .def(init<bool,bool>(), arg("stdout")=true, arg("stderr")=true)
+inline class_<detail::OstreamRedirect>
+add_ostream_redirect(module_ m, const std::string &name = "ostream_redirect") {
+    return class_<detail::OstreamRedirect>(std::move(m), name.c_str(), module_local())
+        .def(init<bool, bool>(), arg("stdout") = true, arg("stderr") = true)
         .def("__enter__", &detail::OstreamRedirect::enter)
         .def("__exit__", [](detail::OstreamRedirect &self_, args) { self_.exit(); });
 }
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index ec4c53b430..9287842460 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -164,10 +164,10 @@ struct npy_api {
             NPY_ULONG_, NPY_ULONGLONG_, NPY_UINT_),
     };
 
-    typedef struct {
+    struct PyArray_Dims {
         Py_intptr_t *ptr;
         int len;
-    } PyArray_Dims;
+    };
 
     static npy_api& get() {
         static npy_api api = lookup();
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 754c875cda..2ff88dbf5b 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1412,15 +1412,15 @@ class class_ : public detail::generic_type {
 
     template <typename D, typename... Extra>
     class_ &def_readwrite_static(const char *name, D *pm, const Extra& ...extra) {
-        cpp_function fget([pm](object) -> const D &{ return *pm; }, scope(*this)),
-                     fset([pm](object, const D &value) { *pm = value; }, scope(*this));
+        cpp_function fget([pm](const object &) -> const D & { return *pm; }, scope(*this)),
+            fset([pm](const object &, const D &value) { *pm = value; }, scope(*this));
         def_property_static(name, fget, fset, return_value_policy::reference, extra...);
         return *this;
     }
 
     template <typename D, typename... Extra>
     class_ &def_readonly_static(const char *name, const D *pm, const Extra& ...extra) {
-        cpp_function fget([pm](object) -> const D &{ return *pm; }, scope(*this));
+        cpp_function fget([pm](const object &) -> const D & { return *pm; }, scope(*this));
         def_property_readonly_static(name, fget, return_value_policy::reference, extra...);
         return *this;
     }
@@ -1671,30 +1671,36 @@ struct enum_base {
             }, name("__members__")), none(), none(), ""
         );
 
-        #define PYBIND11_ENUM_OP_STRICT(op, expr, strict_behavior)                     \
-            m_base.attr(op) = cpp_function(                                            \
-                [](object a, object b) {                                               \
-                    if (!type::handle_of(a).is(type::handle_of(b)))                    \
-                        strict_behavior;                                               \
-                    return expr;                                                       \
-                },                                                                     \
-                name(op), is_method(m_base), arg("other"))
-
-        #define PYBIND11_ENUM_OP_CONV(op, expr)                                        \
-            m_base.attr(op) = cpp_function(                                            \
-                [](object a_, object b_) {                                             \
-                    int_ a(a_), b(b_);                                                 \
-                    return expr;                                                       \
-                },                                                                     \
-                name(op), is_method(m_base), arg("other"))
-
-        #define PYBIND11_ENUM_OP_CONV_LHS(op, expr)                                    \
-            m_base.attr(op) = cpp_function(                                            \
-                [](object a_, object b) {                                              \
-                    int_ a(a_);                                                        \
-                    return expr;                                                       \
-                },                                                                     \
-                name(op), is_method(m_base), arg("other"))
+#define PYBIND11_ENUM_OP_STRICT(op, expr, strict_behavior)                                        \
+    m_base.attr(op) = cpp_function(                                                               \
+        [](const object &a, const object &b) {                                                    \
+            if (!type::handle_of(a).is(type::handle_of(b)))                                       \
+                strict_behavior;                                                                  \
+            return expr;                                                                          \
+        },                                                                                        \
+        name(op),                                                                                 \
+        is_method(m_base),                                                                        \
+        arg("other"))
+
+#define PYBIND11_ENUM_OP_CONV(op, expr)                                                           \
+    m_base.attr(op) = cpp_function(                                                               \
+        [](const object &a_, const object &b_) {                                                  \
+            int_ a(a_), b(b_);                                                                    \
+            return expr;                                                                          \
+        },                                                                                        \
+        name(op),                                                                                 \
+        is_method(m_base),                                                                        \
+        arg("other"))
+
+#define PYBIND11_ENUM_OP_CONV_LHS(op, expr)                                                       \
+    m_base.attr(op) = cpp_function(                                                               \
+        [](const object &a_, const object &b) {                                                   \
+            int_ a(a_);                                                                           \
+            return expr;                                                                          \
+        },                                                                                        \
+        name(op),                                                                                 \
+        is_method(m_base),                                                                        \
+        arg("other"))
 
         if (is_convertible) {
             PYBIND11_ENUM_OP_CONV_LHS("__eq__", !b.is_none() &&  a.equal(b));
@@ -2054,7 +2060,7 @@ exception<CppException> &register_exception(handle scope,
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-PYBIND11_NOINLINE inline void print(tuple args, dict kwargs) {
+PYBIND11_NOINLINE inline void print(const tuple &args, const dict &kwargs) {
     auto strings = tuple(args.size());
     for (size_t i = 0; i < args.size(); ++i) {
         strings[i] = str(args[i]);
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 6a1d8356a5..d1d92af6ad 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -503,7 +503,7 @@ class accessor : public object_api<accessor<Policy>> {
 public:
     accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) { }
     accessor(const accessor &) = default;
-    accessor(accessor &&) = default;
+    accessor(accessor &&) noexcept = default;
 
     // accessor overload required to override default assignment operator (templates are not allowed
     // to replace default compiler-generated assignments).
@@ -1508,7 +1508,7 @@ class memoryview : public object {
         detail::any_container<ssize_t> shape,
         detail::any_container<ssize_t> strides) {
         return memoryview::from_buffer(
-            const_cast<void*>(ptr), itemsize, format, shape, strides, true);
+            const_cast<void *>(ptr), itemsize, format, std::move(shape), std::move(strides), true);
     }
 
     template<typename T>
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 18fbafb1e2..61d3fba61e 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -159,10 +159,13 @@ template <typename Type, typename Value> struct list_caster {
     }
 
 private:
-    template <typename T = Type,
-              enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
-    void reserve_maybe(sequence s, Type *) { value.reserve(s.size()); }
-    void reserve_maybe(sequence, void *) { }
+    template <
+        typename T                                                                          = Type,
+        enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
+    void reserve_maybe(const sequence &s, Type *) {
+        value.reserve(s.size());
+    }
+    void reserve_maybe(const sequence &, void *) {}
 
 public:
     template <typename T>
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 83195ee496..b78bd27ced 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -128,11 +128,11 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
            arg("x"),
            "Add an item to the end of the list");
 
-    cl.def(init([](iterable it) {
+    cl.def(init([](const iterable &it) {
         auto v = std::unique_ptr<Vector>(new Vector());
         v->reserve(len_hint(it));
         for (handle h : it)
-           v->push_back(h.cast<T>());
+            v->push_back(h.cast<T>());
         return v.release();
     }));
 
@@ -151,27 +151,28 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
        "Extend the list by appending all the items in the given list"
     );
 
-    cl.def("extend",
-       [](Vector &v, iterable it) {
-           const size_t old_size = v.size();
-           v.reserve(old_size + len_hint(it));
-           try {
-               for (handle h : it) {
-                   v.push_back(h.cast<T>());
-               }
-           } catch (const cast_error &) {
-               v.erase(v.begin() + static_cast<typename Vector::difference_type>(old_size), v.end());
-               try {
-                   v.shrink_to_fit();
-               } catch (const std::exception &) {
-                   // Do nothing
-               }
-               throw;
-           }
-       },
-       arg("L"),
-       "Extend the list by appending all the items in the given list"
-    );
+    cl.def(
+        "extend",
+        [](Vector &v, const iterable &it) {
+            const size_t old_size = v.size();
+            v.reserve(old_size + len_hint(it));
+            try {
+                for (handle h : it) {
+                    v.push_back(h.cast<T>());
+                }
+            } catch (const cast_error &) {
+                v.erase(v.begin() + static_cast<typename Vector::difference_type>(old_size),
+                        v.end());
+                try {
+                    v.shrink_to_fit();
+                } catch (const std::exception &) {
+                    // Do nothing
+                }
+                throw;
+            }
+        },
+        arg("L"),
+        "Extend the list by appending all the items in the given list");
 
     cl.def("insert",
         [](Vector &v, DiffType i, const T &x) {
@@ -400,7 +401,7 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
         return buffer_info(v.data(), static_cast<ssize_t>(sizeof(T)), format_descriptor<T>::format(), 1, {v.size()}, {sizeof(T)});
     });
 
-    cl.def(init([](buffer buf) {
+    cl.def(init([](const buffer &buf) {
         auto info = buf.request();
         if (info.ndim != 1 || info.strides[0] % static_cast<ssize_t>(sizeof(T)))
             throw type_error("Only valid 1D buffers can be copied to a vector");

From e0b5cbd4c6503a96747ca184621e242818fa2ef4 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sat, 19 Jun 2021 18:38:56 -0400
Subject: [PATCH 033/638] chore(clang-tidy): add more modernize clang-tidy
 checks (#3049)

* Add more modernize clang-tidy checks

* Enable a few more
---
 .clang-tidy                         | 15 +++++++++++----
 tests/test_factory_constructors.cpp |  4 ++--
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 3079b3b3c0..9098e77ff2 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -2,12 +2,17 @@ FormatStyle: file
 
 Checks: '
 llvm-namespace-comment,
-modernize-use-override,
-readability-container-size-empty,
-modernize-use-using,
-modernize-use-equals-default,
+modernize-avoid-bind,
+modernize-replace-auto-ptr,
+modernize-replace-disallow-copy-and-assign-macro,
+modernize-shrink-to-fit,
 modernize-use-auto,
+modernize-use-equals-default,
+modernize-use-equals-delete,
 modernize-use-emplace,
+modernize-use-override,
+modernize-use-using,
+readability-container-size-empty,
 '
 
 CheckOptions:
@@ -15,3 +20,5 @@ CheckOptions:
   value:           'exception_ptr$;'
 
 HeaderFilterRegex: 'pybind11/.*h'
+
+WarningsAsErrors: '*'
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 7ff7e7b52c..6832ac4943 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -20,12 +20,12 @@ class TestFactory1 {
     TestFactory1() : value("(empty)") { print_default_created(this); }
     TestFactory1(int v) : value(std::to_string(v)) { print_created(this, value); }
     TestFactory1(std::string v) : value(std::move(v)) { print_created(this, value); }
+public:
+    std::string value;
     TestFactory1(TestFactory1 &&) = delete;
     TestFactory1(const TestFactory1 &) = delete;
     TestFactory1 &operator=(TestFactory1 &&) = delete;
     TestFactory1 &operator=(const TestFactory1 &) = delete;
-public:
-    std::string value;
     ~TestFactory1() { print_destroyed(this); }
 };
 // Non-public construction, but moveable:

From 9b3b35770650832a70c4829b1dcbcd2ab62ae09e Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sat, 19 Jun 2021 18:39:54 -0400
Subject: [PATCH 034/638] chore(deps): bump ilammy/msvc-dev-cmd from 1.8.1 to
 1.9.0 (#3027)

---
 .github/workflows/ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2ed1da5c5e..e00745df7e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -151,7 +151,7 @@ jobs:
     # MSVC, but for now, this action works:
     - name: Prepare compiler environment for Windows 🐍 2.7
       if: matrix.python == 2.7 && runner.os == 'Windows'
-      uses: ilammy/msvc-dev-cmd@v1.8.1
+      uses: ilammy/msvc-dev-cmd@v1.9.0
       with:
         arch: x64
 
@@ -741,7 +741,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.8.1
+      uses: ilammy/msvc-dev-cmd@v1.9.0
       with:
         arch: x86
 
@@ -787,7 +787,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.9
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.8.1
+      uses: ilammy/msvc-dev-cmd@v1.9.0
       with:
         toolset: 14.0
 

From d00fc62931bde0f2899940f4d487c979a0110422 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert=20Sch=C3=BCtz?= <rschuetz17@gmail.com>
Date: Sun, 20 Jun 2021 00:45:53 +0200
Subject: [PATCH 035/638] use CMAKE_INSTALL_FULL_INCLUDEDIR (#3005)

---
 tools/pybind11Config.cmake.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 0f136005b7..6fa03a0f24 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -201,7 +201,7 @@ Using ``find_package`` with version info is not recommended except for release v
 @PACKAGE_INIT@
 
 # Location of pybind11/pybind11.h
-set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_INCLUDEDIR@")
+set(pybind11_INCLUDE_DIR "@CMAKE_INSTALL_FULL_INCLUDEDIR@")
 
 set(pybind11_LIBRARY "")
 set(pybind11_DEFINITIONS USING_pybind11)

From 3b30b0a51e48a3273918f30dfb222db604cea5e9 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 21 Jun 2021 10:37:48 -0400
Subject: [PATCH 036/638] fix(clang-tidy): clang-tidy readability and misc
 fixes, like adding const (#3052)

* Enable and apply clang-tidy readability and misc fixes.

* Revert deprecated tester

* add space to tests/test_constants_and_functions.cpp
---
 .clang-tidy                                | 13 +++++++++++++
 include/pybind11/detail/common.h           |  2 +-
 include/pybind11/detail/descr.h            |  4 ++--
 include/pybind11/detail/type_caster_base.h |  6 +++---
 include/pybind11/numpy.h                   |  4 ++--
 include/pybind11/pybind11.h                |  3 ++-
 tests/local_bindings.h                     |  2 +-
 tests/test_constants_and_functions.cpp     | 10 +++++++---
 tests/test_factory_constructors.cpp        |  4 ++--
 tests/test_iostream.cpp                    |  6 +++---
 tests/test_methods_and_attributes.cpp      | 12 +++++-------
 tests/test_modules.cpp                     |  3 ++-
 tests/test_multiple_inheritance.cpp        |  8 ++++----
 tests/test_numpy_vectorize.cpp             |  2 +-
 tests/test_smart_ptr.cpp                   |  2 +-
 tests/test_stl_binders.cpp                 |  4 +++-
 16 files changed, 52 insertions(+), 33 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 9098e77ff2..60531abe05 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -2,17 +2,30 @@ FormatStyle: file
 
 Checks: '
 llvm-namespace-comment,
+misc-misplaced-const,
+misc-static-assert,
+misc-uniqueptr-reset-release,
 modernize-avoid-bind,
 modernize-replace-auto-ptr,
 modernize-replace-disallow-copy-and-assign-macro,
 modernize-shrink-to-fit,
 modernize-use-auto,
+modernize-use-bool-literals,
 modernize-use-equals-default,
 modernize-use-equals-delete,
+modernize-use-default-member-init,
+modernize-use-noexcept,
 modernize-use-emplace,
 modernize-use-override,
 modernize-use-using,
 readability-container-size-empty,
+readability-make-member-function-const,
+readability-redundant-function-ptr-dereference,
+readability-redundant-smartptr-get,
+readability-redundant-string-cstr,
+readability-simplify-subscript-expr,
+readability-string-compare,
+readability-uniqueptr-delete-release,
 '
 
 CheckOptions:
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 987f0badf9..1f7446103e 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -480,7 +480,7 @@ struct instance {
     void allocate_layout();
 
     /// Destroys/deallocates all of the above
-    void deallocate_layout();
+    void deallocate_layout() const;
 
     /// Returns the value_and_holder wrapper for the given type (or the first, if `find_type`
     /// omitted).  Returns a default-constructed (with `.inst = nullptr`) object on failure if
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 92720cd562..7cb8350e7b 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -23,9 +23,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /* Concatenate type signatures at compile time */
 template <size_t N, typename... Ts>
 struct descr {
-    char text[N + 1];
+    char text[N + 1]{'\0'};
 
-    constexpr descr() : text{'\0'} { }
+    constexpr descr() = default;
     constexpr descr(char const (&s)[N+1]) : descr(s, make_index_sequence<N>()) { }
 
     template <size_t... Is>
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 8ebe39879a..0dd9d48e55 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -241,7 +241,7 @@ struct value_and_holder {
             ? inst->simple_holder_constructed
             : inst->nonsimple.status[index] & instance::status_holder_constructed;
     }
-    void set_holder_constructed(bool v = true) {
+    void set_holder_constructed(bool v = true) const {
         if (inst->simple_layout)
             inst->simple_holder_constructed = v;
         else if (v)
@@ -254,7 +254,7 @@ struct value_and_holder {
             ? inst->simple_instance_registered
             : inst->nonsimple.status[index] & instance::status_instance_registered;
     }
-    void set_instance_registered(bool v = true) {
+    void set_instance_registered(bool v = true) const {
         if (inst->simple_layout)
             inst->simple_instance_registered = v;
         else if (v)
@@ -397,7 +397,7 @@ PYBIND11_NOINLINE inline void instance::allocate_layout() {
     owned = true;
 }
 
-PYBIND11_NOINLINE inline void instance::deallocate_layout() {
+PYBIND11_NOINLINE inline void instance::deallocate_layout() const {
     if (!simple_layout)
         PyMem_Free(nonsimple.values_and_holders);
 }
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 9287842460..fdb7a9794b 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1291,7 +1291,7 @@ class common_iterator {
     using value_type = container_type::value_type;
     using size_type = container_type::size_type;
 
-    common_iterator() : p_ptr(0), m_strides() {}
+    common_iterator() : m_strides() {}
 
     common_iterator(void* ptr, const container_type& strides, const container_type& shape)
         : p_ptr(reinterpret_cast<char*>(ptr)), m_strides(strides.size()) {
@@ -1312,7 +1312,7 @@ class common_iterator {
     }
 
 private:
-    char* p_ptr;
+    char *p_ptr{0};
     container_type m_strides;
 };
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 2ff88dbf5b..4979236050 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -395,7 +395,8 @@ class cpp_function : public function {
             rec->def = new PyMethodDef();
             std::memset(rec->def, 0, sizeof(PyMethodDef));
             rec->def->ml_name = rec->name;
-            rec->def->ml_meth = reinterpret_cast<PyCFunction>(reinterpret_cast<void (*) (void)>(*dispatcher));
+            rec->def->ml_meth
+                = reinterpret_cast<PyCFunction>(reinterpret_cast<void (*)(void)>(dispatcher));
             rec->def->ml_flags = METH_VARARGS | METH_KEYWORDS;
 
             capsule rec_capsule(unique_rec.release(), [](void *ptr) {
diff --git a/tests/local_bindings.h b/tests/local_bindings.h
index 22537b13ad..91c23fe594 100644
--- a/tests/local_bindings.h
+++ b/tests/local_bindings.h
@@ -56,7 +56,7 @@ class Pet {
 public:
     Pet(std::string name) : name_(name) {}
     std::string name_;
-    const std::string &name() { return name_; }
+    const std::string &name() const { return name_; }
 };
 } // namespace pets
 
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 5bbbd0c70b..04830d8d2d 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -1,5 +1,6 @@
 /*
-    tests/test_constants_and_functions.cpp -- global constants and functions, enumerations, raw byte strings
+    tests/test_constants_and_functions.cpp -- global constants and functions, enumerations, raw
+    byte strings
 
     Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
 
@@ -60,6 +61,7 @@ int f3(int x) noexcept(false) { return x+3; }
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
+// NOLINTNEXTLINE(modernize-use-noexcept)
 int f4(int x) throw() { return x+4; } // Deprecated equivalent to noexcept(true)
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
@@ -75,8 +77,10 @@ struct C {
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
-    int m7(int x) throw() { return x-7; }
-    int m8(int x) const throw() { return x-8; }
+    // NOLINTNEXTLINE(modernize-use-noexcept)
+    int m7(int x) throw() { return x - 7; }
+    // NOLINTNEXTLINE(modernize-use-noexcept)
+    int m8(int x) const throw() { return x - 8; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 6832ac4943..7308ad5fc1 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -77,7 +77,7 @@ class TestFactory6 {
     TestFactory6(const TestFactory6 &f) { print_copy_created(this); value = f.value; alias = f.alias; }
     virtual ~TestFactory6() { print_destroyed(this); }
     virtual int get() { return value; }
-    bool has_alias() { return alias; }
+    bool has_alias() const { return alias; }
 };
 class PyTF6 : public TestFactory6 {
 public:
@@ -102,7 +102,7 @@ class TestFactory7 {
     TestFactory7(const TestFactory7 &f) { print_copy_created(this); value = f.value; alias = f.alias; }
     virtual ~TestFactory7() { print_destroyed(this); }
     virtual int get() { return value; }
-    bool has_alias() { return alias; }
+    bool has_alias() const { return alias; }
 };
 class PyTF7 : public TestFactory7 {
 public:
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index 1be0655dfb..f21fed5465 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -34,7 +34,7 @@ void noisy_funct_dual(std::string msg, std::string emsg) {
 // simply repeatedly write to std::cerr until stopped
 // redirect is called at some point to test the safety of scoped_estream_redirect
 struct TestThread {
-    TestThread() : t_{nullptr}, stop_{false} {
+    TestThread() : stop_{false} {
         auto thread_f = [this] {
             while (!stop_) {
                 std::cout << "x" << std::flush;
@@ -49,7 +49,7 @@ struct TestThread {
 
     void stop() { stop_ = true; }
 
-    void join() {
+    void join() const {
         py::gil_scoped_release gil_lock;
         t_->join();
     }
@@ -59,7 +59,7 @@ struct TestThread {
         std::this_thread::sleep_for(std::chrono::milliseconds(50));
     }
 
-    std::thread * t_;
+    std::thread *t_{nullptr};
     std::atomic<bool> stop_;
 };
 
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index f99909bda7..1f855ef354 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -25,9 +25,7 @@ class ExampleMandA {
     ExampleMandA(ExampleMandA &&e) : value(e.value) { print_move_created(this); }
     ~ExampleMandA() { print_destroyed(this); }
 
-    std::string toString() {
-        return "ExampleMandA[value=" + std::to_string(value) + "]";
-    }
+    std::string toString() const { return "ExampleMandA[value=" + std::to_string(value) + "]"; }
 
     void operator=(const ExampleMandA &e) { print_copy_assigned(this); value = e.value; }
     void operator=(ExampleMandA &&e) { print_move_assigned(this); value = e.value; }
@@ -48,13 +46,13 @@ class ExampleMandA {
 
     ExampleMandA self1() { return *this; }                          // return by value
     ExampleMandA &self2() { return *this; }                         // return by reference
-    const ExampleMandA &self3() { return *this; }                   // return by const reference
+    const ExampleMandA &self3() const { return *this; }             // return by const reference
     ExampleMandA *self4() { return this; }                          // return by pointer
-    const ExampleMandA *self5() { return this; }                    // return by const pointer
+    const ExampleMandA *self5() const { return this; }              // return by const pointer
 
-    int internal1() { return value; }                               // return by value
+    int internal1() const { return value; }                         // return by value
     int &internal2() { return value; }                              // return by reference
-    const int &internal3() { return value; }                        // return by const reference
+    const int &internal3() const { return value; }                  // return by const reference
     int *internal4() { return &value; }                             // return by pointer
     const int *internal5() { return &value; }                       // return by const pointer
 
diff --git a/tests/test_modules.cpp b/tests/test_modules.cpp
index 67387e809b..5867135404 100644
--- a/tests/test_modules.cpp
+++ b/tests/test_modules.cpp
@@ -24,7 +24,8 @@ TEST_SUBMODULE(modules, m) {
         ~A() { print_destroyed(this); }
         A(const A&) { print_copy_created(this); }
         A& operator=(const A &copy) { print_copy_assigned(this); v = copy.v; return *this; }
-        std::string toString() { return "A[" + std::to_string(v) + "]"; }
+        std::string toString() const { return "A[" + std::to_string(v) + "]"; }
+
     private:
         int v;
     };
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index ad801fe198..daecb9564f 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -48,12 +48,12 @@ int VanillaStaticMix2::static_value = 12;
 // test_multiple_inheritance_virtbase
 struct Base1a {
     Base1a(int i) : i(i) { }
-    int foo() { return i; }
+    int foo() const { return i; }
     int i;
 };
 struct Base2a {
     Base2a(int i) : i(i) { }
-    int bar() { return i; }
+    int bar() const { return i; }
     int i;
 };
 struct Base12a : Base1a, Base2a {
@@ -78,7 +78,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_multiple_inheritance_mix2
     struct Base1 {
         Base1(int i) : i(i) { }
-        int foo() { return i; }
+        int foo() const { return i; }
         int i;
     };
     py::class_<Base1> b1(m, "Base1");
@@ -87,7 +87,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
 
     struct Base2 {
         Base2(int i) : i(i) { }
-        int bar() { return i; }
+        int bar() const { return i; }
         int i;
     };
     py::class_<Base2> b2(m, "Base2");
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index 274b7558a9..8ed9b27e1b 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -62,7 +62,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     // test_method_vectorization
     struct VectorizeTestClass {
         VectorizeTestClass(int v) : value{v} {};
-        float method(int x, float y) { return y + (float) (x + value); }
+        float method(int x, float y) const { return y + (float) (x + value); }
         int value = 0;
     };
     py::class_<VectorizeTestClass> vtc(m, "VectorizeTestClass");
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index e0af249790..2ece3bf0c9 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -240,7 +240,7 @@ struct ElementBase {
 
 struct ElementA : ElementBase {
     ElementA(int v) : v(v) { }
-    int value() { return v; }
+    int value() const { return v; }
     int v;
 };
 
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index c791477e3e..22847eb7a1 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -125,5 +125,7 @@ TEST_SUBMODULE(stl_binders, m) {
     PYBIND11_NUMPY_DTYPE(VStruct, w, x, y, z);
     py::class_<VStruct>(m, "VStruct").def_readwrite("x", &VStruct::x);
     py::bind_vector<std::vector<VStruct>>(m, "VectorStruct", py::buffer_protocol());
-    m.def("get_vectorstruct", [] {return std::vector<VStruct> {{0, 5, 3.0, 1}, {1, 30, -1e4, 0}};});
+    m.def("get_vectorstruct", [] {
+        return std::vector<VStruct>{{false, 5, 3.0, true}, {true, 30, -1e4, false}};
+    });
 }

From dac74ebdf5d64cb30a4492003a87d7455ad00144 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 22 Jun 2021 12:11:54 -0400
Subject: [PATCH 037/638] fix(clang-tidy): performance fixes applied in tests
 and CI (#3051)

* Initial fixes

* Whoops

* Finish clang-tidy manual fixes

* Add two missing fixes

* Revert

* Update clang-tidy

* Try to fix unreachable code error

* Move nolint comment

* Apply missing fix

* Don't override clang-tidy config

* Does this fix clang-tidy?

* Make all clang-tidy errors visible

* Add comments about NOLINTs and remove a few

* Fix typo
---
 .clang-tidy                            |   1 +
 .github/workflows/format.yml           |   6 +-
 include/pybind11/iostream.h            |   2 +-
 include/pybind11/pybind11.h            |  17 +--
 tests/local_bindings.h                 |   4 +-
 tests/object.h                         |   4 +-
 tests/pybind11_cross_module_tests.cpp  |   3 +
 tests/test_buffers.cpp                 |  43 ++++----
 tests/test_builtin_casters.cpp         |  12 +-
 tests/test_callbacks.cpp               |  42 ++++---
 tests/test_class.cpp                   |  22 ++--
 tests/test_constants_and_functions.cpp |  13 ++-
 tests/test_copy_move.cpp               |  31 ++++--
 tests/test_custom_type_casters.cpp     |  23 +++-
 tests/test_eigen.cpp                   |  21 +++-
 tests/test_embed/test_interpreter.cpp  |   5 +-
 tests/test_eval.cpp                    |   4 +-
 tests/test_exceptions.cpp              |  26 +++--
 tests/test_factory_constructors.cpp    | 126 ++++++++++++---------
 tests/test_gil_scoped.cpp              |  27 ++---
 tests/test_iostream.cpp                |  21 ++--
 tests/test_kwargs_and_defaults.cpp     |  24 ++--
 tests/test_local_bindings.cpp          |   2 +
 tests/test_methods_and_attributes.cpp  |  61 +++++++----
 tests/test_multiple_inheritance.cpp    |   1 +
 tests/test_numpy_array.cpp             | 136 +++++++++++++++--------
 tests/test_numpy_dtypes.cpp            |   9 +-
 tests/test_numpy_vectorize.cpp         |  54 +++++----
 tests/test_opaque_types.cpp            |   2 +-
 tests/test_operator_overloading.cpp    |  13 ++-
 tests/test_pickling.cpp                |  63 +++++------
 tests/test_pytypes.cpp                 |  64 ++++++-----
 tests/test_sequences_and_iterators.cpp | 146 ++++++++++++++-----------
 tests/test_smart_ptr.cpp               |  50 ++++++---
 tests/test_stl.cpp                     |   8 +-
 tests/test_virtual_functions.cpp       |  15 ++-
 36 files changed, 667 insertions(+), 434 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 60531abe05..22a736208c 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -18,6 +18,7 @@ modernize-use-noexcept,
 modernize-use-emplace,
 modernize-use-override,
 modernize-use-using,
+*performance*,
 readability-container-size-empty,
 readability-make-member-function-const,
 readability-redundant-function-ptr-dereference,
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 6550acccdb..27f52932b7 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -27,7 +27,7 @@ jobs:
   clang-tidy:
     name: Clang-Tidy
     runs-on: ubuntu-latest
-    container: silkeh/clang:10
+    container: silkeh/clang:12
     steps:
     - uses: actions/checkout@v2
 
@@ -37,10 +37,10 @@ jobs:
     - name: Configure
       run: >
         cmake -S . -B build
-        -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);--warnings-as-errors=*"
+        -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy)"
         -DDOWNLOAD_EIGEN=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=17
 
     - name: Build
-      run: cmake --build build -j 2
+      run: cmake --build build -j 2 -- --keep-going
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 6a793eadca..89d1813ba8 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -262,7 +262,7 @@ add_ostream_redirect(module_ m, const std::string &name = "ostream_redirect") {
     return class_<detail::OstreamRedirect>(std::move(m), name.c_str(), module_local())
         .def(init<bool, bool>(), arg("stdout") = true, arg("stderr") = true)
         .def("__enter__", &detail::OstreamRedirect::enter)
-        .def("__exit__", [](detail::OstreamRedirect &self_, args) { self_.exit(); });
+        .def("__exit__", [](detail::OstreamRedirect &self_, const args &) { self_.exit(); });
 }
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 4979236050..1fb0d1fa18 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1629,12 +1629,13 @@ struct enum_base {
         auto static_property = handle((PyObject *) get_internals().static_property_type);
 
         m_base.attr("__repr__") = cpp_function(
-            [](object arg) -> str {
+            [](const object &arg) -> str {
                 handle type = type::handle_of(arg);
                 object type_name = type.attr("__name__");
                 return pybind11::str("<{}.{}: {}>").format(type_name, enum_name(arg), int_(arg));
-            }, name("__repr__"), is_method(m_base)
-        );
+            },
+            name("__repr__"),
+            is_method(m_base));
 
         m_base.attr("name") = property(cpp_function(&enum_name, name("name"), is_method(m_base)));
 
@@ -1718,8 +1719,10 @@ struct enum_base {
                 PYBIND11_ENUM_OP_CONV("__ror__",  a |  b);
                 PYBIND11_ENUM_OP_CONV("__xor__",  a ^  b);
                 PYBIND11_ENUM_OP_CONV("__rxor__", a ^  b);
-                m_base.attr("__invert__") = cpp_function(
-                    [](object arg) { return ~(int_(arg)); }, name("__invert__"), is_method(m_base));
+                m_base.attr("__invert__")
+                    = cpp_function([](const object &arg) { return ~(int_(arg)); },
+                                   name("__invert__"),
+                                   is_method(m_base));
             }
         } else {
             PYBIND11_ENUM_OP_STRICT("__eq__",  int_(a).equal(int_(b)), return false);
@@ -1740,10 +1743,10 @@ struct enum_base {
         #undef PYBIND11_ENUM_OP_STRICT
 
         m_base.attr("__getstate__") = cpp_function(
-            [](object arg) { return int_(arg); }, name("__getstate__"), is_method(m_base));
+            [](const object &arg) { return int_(arg); }, name("__getstate__"), is_method(m_base));
 
         m_base.attr("__hash__") = cpp_function(
-            [](object arg) { return int_(arg); }, name("__hash__"), is_method(m_base));
+            [](const object &arg) { return int_(arg); }, name("__hash__"), is_method(m_base));
     }
 
     PYBIND11_NOINLINE void value(char const* name_, object value, const char *doc = nullptr) {
diff --git a/tests/local_bindings.h b/tests/local_bindings.h
index 91c23fe594..8629ed7784 100644
--- a/tests/local_bindings.h
+++ b/tests/local_bindings.h
@@ -1,4 +1,6 @@
 #pragma once
+#include <utility>
+
 #include "pybind11_tests.h"
 
 /// Simple class used to test py::local:
@@ -54,7 +56,7 @@ py::class_<T> bind_local(Args && ...args) {
 namespace pets {
 class Pet {
 public:
-    Pet(std::string name) : name_(name) {}
+    Pet(std::string name) : name_(std::move(name)) {}
     std::string name_;
     const std::string &name() const { return name_; }
 };
diff --git a/tests/object.h b/tests/object.h
index 9235f19c20..865a9beae8 100644
--- a/tests/object.h
+++ b/tests/object.h
@@ -81,7 +81,7 @@ template <typename T> class ref {
     }
 
     /// Move constructor
-    ref(ref &&r) : m_ptr(r.m_ptr) {
+    ref(ref &&r) noexcept : m_ptr(r.m_ptr) {
         r.m_ptr = nullptr;
 
         print_move_created(this, "with pointer", m_ptr); track_move_created((ref_tag*) this);
@@ -96,7 +96,7 @@ template <typename T> class ref {
     }
 
     /// Move another reference into the current one
-    ref& operator=(ref&& r) {
+    ref &operator=(ref &&r) noexcept {
         print_move_assigned(this, "pointer", r.m_ptr); track_move_assigned((ref_tag*) this);
 
         if (*this == r)
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index 944d085597..f238ddb042 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -104,6 +104,8 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("return_self", [](LocalVec *v) { return v; });
     m.def("return_copy", [](const LocalVec &v) { return LocalVec(v); });
 
+    // Changing this broke things with pygrep. TODO fix
+    // NOLINTNEXTLINE
     class Dog : public pets::Pet { public: Dog(std::string name) : Pet(name) {}; };
     py::class_<pets::Pet>(m, "Pet", py::module_local())
         .def("name", &pets::Pet::name);
@@ -126,6 +128,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_missing_header_message
     // The main module already includes stl.h, but we need to test the error message
     // which appears when this header is missing.
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("missing_header_arg", [](std::vector<float>) { });
     m.def("missing_header_return", []() { return std::vector<float>(); });
 }
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 46eabf3963..9902c1084e 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -27,7 +27,7 @@ TEST_SUBMODULE(buffers, m) {
             memcpy(m_data, s.m_data, sizeof(float) * (size_t) (m_rows * m_cols));
         }
 
-        Matrix(Matrix &&s) : m_rows(s.m_rows), m_cols(s.m_cols), m_data(s.m_data) {
+        Matrix(Matrix &&s) noexcept : m_rows(s.m_rows), m_cols(s.m_cols), m_data(s.m_data) {
             print_move_created(this);
             s.m_rows = 0;
             s.m_cols = 0;
@@ -49,7 +49,7 @@ TEST_SUBMODULE(buffers, m) {
             return *this;
         }
 
-        Matrix &operator=(Matrix &&s) {
+        Matrix &operator=(Matrix &&s) noexcept {
             print_move_assigned(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             if (&s != this) {
                 delete[] m_data;
@@ -79,6 +79,7 @@ TEST_SUBMODULE(buffers, m) {
     py::class_<Matrix>(m, "Matrix", py::buffer_protocol())
         .def(py::init<py::ssize_t, py::ssize_t>())
         /// Construct from a buffer
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def(py::init([](py::buffer const b) {
             py::buffer_info info = b.request();
             if (info.format != py::format_descriptor<float>::format() || info.ndim != 2)
@@ -89,31 +90,31 @@ TEST_SUBMODULE(buffers, m) {
             return v;
         }))
 
-       .def("rows", &Matrix::rows)
-       .def("cols", &Matrix::cols)
+        .def("rows", &Matrix::rows)
+        .def("cols", &Matrix::cols)
 
         /// Bare bones interface
-       .def("__getitem__", [](const Matrix &m, std::pair<py::ssize_t, py::ssize_t> i) {
-            if (i.first >= m.rows() || i.second >= m.cols())
-                throw py::index_error();
-            return m(i.first, i.second);
-        })
-       .def("__setitem__", [](Matrix &m, std::pair<py::ssize_t, py::ssize_t> i, float v) {
-            if (i.first >= m.rows() || i.second >= m.cols())
-                throw py::index_error();
-            m(i.first, i.second) = v;
-        })
-       /// Provide buffer access
-       .def_buffer([](Matrix &m) -> py::buffer_info {
+        .def("__getitem__",
+             [](const Matrix &m, std::pair<py::ssize_t, py::ssize_t> i) {
+                 if (i.first >= m.rows() || i.second >= m.cols())
+                     throw py::index_error();
+                 return m(i.first, i.second);
+             })
+        .def("__setitem__",
+             [](Matrix &m, std::pair<py::ssize_t, py::ssize_t> i, float v) {
+                 if (i.first >= m.rows() || i.second >= m.cols())
+                     throw py::index_error();
+                 m(i.first, i.second) = v;
+             })
+        /// Provide buffer access
+        .def_buffer([](Matrix &m) -> py::buffer_info {
             return py::buffer_info(
                 m.data(),                               /* Pointer to buffer */
                 { m.rows(), m.cols() },                 /* Buffer dimensions */
                 { sizeof(float) * size_t(m.cols()),     /* Strides (in bytes) for each index */
                   sizeof(float) }
             );
-        })
-        ;
-
+        });
 
     // test_inherited_protocol
     class SquareMatrix : public Matrix {
@@ -208,7 +209,5 @@ TEST_SUBMODULE(buffers, m) {
         })
         ;
 
-    m.def("get_buffer_info", [](py::buffer buffer) {
-        return buffer.request();
-    });
+    m.def("get_buffer_info", [](const py::buffer &buffer) { return buffer.request(); });
 }
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index f4e775676d..a98b67bdbd 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -30,7 +30,11 @@ class type_caster<ConstRefCasted> {
   // cast operator.
   bool load(handle, bool) { return true; }
 
-  operator ConstRefCasted&&() { value = {1}; return std::move(value); }
+  operator ConstRefCasted &&() {
+      value = {1};
+      // NOLINTNEXTLINE(performance-move-const-arg)
+      return std::move(value);
+  }
   operator ConstRefCasted&() { value = {2}; return value; }
   operator ConstRefCasted*() { value = {3}; return &value; }
 
@@ -101,6 +105,7 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_bytes_to_string
     m.def("strlen", [](char *s) { return strlen(s); });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("string_length", [](std::string s) { return s.length(); });
 
 #ifdef PYBIND11_HAS_U8STRING
@@ -146,6 +151,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("int_passthrough_noconvert", [](int arg) { return arg; }, py::arg{}.noconvert());
 
     // test_tuple
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("pair_passthrough", [](std::pair<bool, std::string> input) {
         return std::make_pair(input.second, input.first);
     }, "Return a pair in reversed order");
@@ -177,10 +183,13 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_none_deferred
     m.def("defer_none_cstring", [](char *) { return false; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("defer_none_cstring", [](py::none) { return true; });
     m.def("defer_none_custom", [](UserType *) { return false; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("defer_none_custom", [](py::none) { return true; });
     m.def("nodefer_none_void", [](void *) { return true; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("nodefer_none_void", [](py::none) { return false; });
 
     // test_void_caster
@@ -231,6 +240,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     }, "copy"_a);
 
     m.def("refwrap_iiw", [](const IncType &w) { return w.value(); });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("refwrap_call_iiw", [](IncType &w, py::function f) {
         py::list l;
         l.append(f(std::ref(w)));
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 33927f5c38..908d5743e7 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -17,8 +17,8 @@ int dummy_function(int i) { return i + 1; }
 
 TEST_SUBMODULE(callbacks, m) {
     // test_callbacks, test_function_signatures
-    m.def("test_callback1", [](py::object func) { return func(); });
-    m.def("test_callback2", [](py::object func) { return func("Hello", 'x', true, 5); });
+    m.def("test_callback1", [](const py::object &func) { return func(); });
+    m.def("test_callback2", [](const py::object &func) { return func("Hello", 'x', true, 5); });
     m.def("test_callback3", [](const std::function<int(int)> &func) {
         return "func(43) = " + std::to_string(func(43)); });
     m.def("test_callback4", []() -> std::function<int(int)> { return [](int i) { return i+1; }; });
@@ -27,51 +27,48 @@ TEST_SUBMODULE(callbacks, m) {
     });
 
     // test_keyword_args_and_generalized_unpacking
-    m.def("test_tuple_unpacking", [](py::function f) {
+    m.def("test_tuple_unpacking", [](const py::function &f) {
         auto t1 = py::make_tuple(2, 3);
         auto t2 = py::make_tuple(5, 6);
         return f("positional", 1, *t1, 4, *t2);
     });
 
-    m.def("test_dict_unpacking", [](py::function f) {
+    m.def("test_dict_unpacking", [](const py::function &f) {
         auto d1 = py::dict("key"_a="value", "a"_a=1);
         auto d2 = py::dict();
         auto d3 = py::dict("b"_a=2);
         return f("positional", 1, **d1, **d2, **d3);
     });
 
-    m.def("test_keyword_args", [](py::function f) {
-        return f("x"_a=10, "y"_a=20);
-    });
+    m.def("test_keyword_args", [](const py::function &f) { return f("x"_a = 10, "y"_a = 20); });
 
-    m.def("test_unpacking_and_keywords1", [](py::function f) {
+    m.def("test_unpacking_and_keywords1", [](const py::function &f) {
         auto args = py::make_tuple(2);
         auto kwargs = py::dict("d"_a=4);
         return f(1, *args, "c"_a=3, **kwargs);
     });
 
-    m.def("test_unpacking_and_keywords2", [](py::function f) {
+    m.def("test_unpacking_and_keywords2", [](const py::function &f) {
         auto kwargs1 = py::dict("a"_a=1);
         auto kwargs2 = py::dict("c"_a=3, "d"_a=4);
         return f("positional", *py::make_tuple(1), 2, *py::make_tuple(3, 4), 5,
                  "key"_a="value", **kwargs1, "b"_a=2, **kwargs2, "e"_a=5);
     });
 
-    m.def("test_unpacking_error1", [](py::function f) {
+    m.def("test_unpacking_error1", [](const py::function &f) {
         auto kwargs = py::dict("x"_a=3);
         return f("x"_a=1, "y"_a=2, **kwargs); // duplicate ** after keyword
     });
 
-    m.def("test_unpacking_error2", [](py::function f) {
+    m.def("test_unpacking_error2", [](const py::function &f) {
         auto kwargs = py::dict("x"_a=3);
         return f(**kwargs, "x"_a=1); // duplicate keyword after **
     });
 
-    m.def("test_arg_conversion_error1", [](py::function f) {
-        f(234, UnregisteredType(), "kw"_a=567);
-    });
+    m.def("test_arg_conversion_error1",
+          [](const py::function &f) { f(234, UnregisteredType(), "kw"_a = 567); });
 
-    m.def("test_arg_conversion_error2", [](py::function f) {
+    m.def("test_arg_conversion_error2", [](const py::function &f) {
         f(234, "expected_name"_a=UnregisteredType(), "kw"_a=567);
     });
 
@@ -80,7 +77,7 @@ TEST_SUBMODULE(callbacks, m) {
         Payload() { print_default_created(this); }
         ~Payload() { print_destroyed(this); }
         Payload(const Payload &) { print_copy_created(this); }
-        Payload(Payload &&) { print_move_created(this); }
+        Payload(Payload &&) noexcept { print_move_created(this); }
     };
     // Export the payload constructor statistics for testing purposes:
     m.def("payload_cstats", &ConstructorStats::get<Payload>);
@@ -127,7 +124,8 @@ TEST_SUBMODULE(callbacks, m) {
         virtual ~AbstractBase() {};  // NOLINT(modernize-use-equals-default)
         virtual unsigned int func() = 0;
     };
-    m.def("func_accepting_func_accepting_base", [](std::function<double(AbstractBase&)>) { });
+    m.def("func_accepting_func_accepting_base",
+          [](const std::function<double(AbstractBase &)> &) {});
 
     struct MovableObject {
         bool valid = true;
@@ -135,8 +133,8 @@ TEST_SUBMODULE(callbacks, m) {
         MovableObject() = default;
         MovableObject(const MovableObject &) = default;
         MovableObject &operator=(const MovableObject &) = default;
-        MovableObject(MovableObject &&o) : valid(o.valid) { o.valid = false; }
-        MovableObject &operator=(MovableObject &&o) {
+        MovableObject(MovableObject &&o) noexcept : valid(o.valid) { o.valid = false; }
+        MovableObject &operator=(MovableObject &&o) noexcept {
             valid = o.valid;
             o.valid = false;
             return *this;
@@ -145,7 +143,7 @@ TEST_SUBMODULE(callbacks, m) {
     py::class_<MovableObject>(m, "MovableObject");
 
     // test_movable_object
-    m.def("callback_with_movable", [](std::function<void(MovableObject &)> f) {
+    m.def("callback_with_movable", [](const std::function<void(MovableObject &)> &f) {
         auto x = MovableObject();
         f(x); // lvalue reference shouldn't move out object
         return x.valid; // must still return `true`
@@ -159,7 +157,7 @@ TEST_SUBMODULE(callbacks, m) {
 
     // test async Python callbacks
     using callback_f = std::function<void(int)>;
-    m.def("test_async_callback", [](callback_f f, py::list work) {
+    m.def("test_async_callback", [](const callback_f &f, const py::list &work) {
         // make detached thread that calls `f` with piece of work after a little delay
         auto start_f = [f](int j) {
             auto invoke_f = [f, j] {
@@ -175,7 +173,7 @@ TEST_SUBMODULE(callbacks, m) {
             start_f(py::cast<int>(i));
     });
 
-    m.def("callback_num_times", [](py::function f, std::size_t num) {
+    m.def("callback_num_times", [](const py::function &f, std::size_t num) {
         for (std::size_t i = 0; i < num; i++) {
             f();
         }
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index bd545e8c68..a26c59c1ce 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -19,6 +19,8 @@
 #include "local_bindings.h"
 #include <pybind11/stl.h>
 
+#include <utility>
+
 #if defined(_MSC_VER)
 #  pragma warning(disable: 4324) // warning C4324: structure was padded due to alignment specifier
 #endif
@@ -129,6 +131,7 @@ TEST_SUBMODULE(class_, m) {
     m.def("return_none", []() -> BaseClass* { return nullptr; });
 
     // test_isinstance
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("check_instances", [](py::list l) {
         return py::make_tuple(
             py::isinstance<py::tuple>(l[0]),
@@ -155,17 +158,13 @@ TEST_SUBMODULE(class_, m) {
             return py::type::of<Invalid>();
     });
 
-    m.def("get_type_of", [](py::object ob) {
-        return py::type::of(ob);
-    });
+    m.def("get_type_of", [](py::object ob) { return py::type::of(std::move(ob)); });
 
     m.def("get_type_classic", [](py::handle h) {
         return h.get_type();
     });
 
-    m.def("as_type", [](py::object ob) {
-        return py::type(ob);
-    });
+    m.def("as_type", [](const py::object &ob) { return py::type(ob); });
 
     // test_mismatched_holder
     struct MismatchBase1 { };
@@ -219,6 +218,7 @@ TEST_SUBMODULE(class_, m) {
     py::implicitly_convertible<UserType, ConvertibleFromUserType>();
 
     m.def("implicitly_convert_argument", [](const ConvertibleFromUserType &r) { return r.i; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("implicitly_convert_variable", [](py::object o) {
         // `o` is `UserType` and `r` is a reference to a temporary created by implicit
         // conversion. This is valid when called inside a bound function because the temp
@@ -397,6 +397,7 @@ TEST_SUBMODULE(class_, m) {
     struct StringWrapper { std::string str; };
     m.def("test_error_after_conversions", [](int) {});
     m.def("test_error_after_conversions",
+          // NOLINTNEXTLINE(performance-unnecessary-value-param)
           [](StringWrapper) -> NotRegistered { return {}; });
     py::class_<StringWrapper>(m, "StringWrapper").def(py::init<std::string>());
     py::implicitly_convertible<std::string, StringWrapper>();
@@ -461,19 +462,20 @@ TEST_SUBMODULE(class_, m) {
     struct OtherDuplicate {};
     struct DuplicateNested {};
     struct OtherDuplicateNested {};
-    m.def("register_duplicate_class_name", [](py::module_ m) {
+
+    m.def("register_duplicate_class_name", [](const py::module_ &m) {
         py::class_<Duplicate>(m, "Duplicate");
         py::class_<OtherDuplicate>(m, "Duplicate");
     });
-    m.def("register_duplicate_class_type", [](py::module_ m) {
+    m.def("register_duplicate_class_type", [](const py::module_ &m) {
         py::class_<OtherDuplicate>(m, "OtherDuplicate");
         py::class_<OtherDuplicate>(m, "YetAnotherDuplicate");
     });
-    m.def("register_duplicate_nested_class_name", [](py::object gt) {
+    m.def("register_duplicate_nested_class_name", [](const py::object &gt) {
         py::class_<DuplicateNested>(gt, "DuplicateNested");
         py::class_<OtherDuplicateNested>(gt, "DuplicateNested");
     });
-    m.def("register_duplicate_nested_class_type", [](py::object gt) {
+    m.def("register_duplicate_nested_class_type", [](const py::object &gt) {
         py::class_<OtherDuplicateNested>(gt, "OtherDuplicateNested");
         py::class_<OtherDuplicateNested>(gt, "YetAnotherDuplicateNested");
     });
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 04830d8d2d..e7f018540c 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -34,7 +34,7 @@ py::bytes return_bytes() {
     return std::string(data, 4);
 }
 
-std::string print_bytes(py::bytes bytes) {
+std::string print_bytes(const py::bytes &bytes) {
     std::string ret = "bytes[";
     const auto value = static_cast<std::string>(bytes);
     for (size_t i = 0; i < value.length(); ++i) {
@@ -146,8 +146,13 @@ TEST_SUBMODULE(constants_and_functions, m) {
         LargeCapture capture;  // VS 2015's MSVC is acting up if we create the array here
         m.def("should_raise", [capture](int) { return capture.zeros[9] + 33; }, py::kw_only(), py::arg());
     });
-    m.def("register_with_raising_repr", [](py::module_ m, py::object default_value) {
-        m.def("should_raise", [](int, int, py::object) { return 42; }, "some docstring",
-              py::arg_v("x", 42), py::arg_v("y", 42, "<the answer>"), py::arg_v("z", default_value));
+    m.def("register_with_raising_repr", [](py::module_ m, const py::object &default_value) {
+        m.def(
+            "should_raise",
+            [](int, int, const py::object &) { return 42; },
+            "some docstring",
+            py::arg_v("x", 42),
+            py::arg_v("y", 42, "<the answer>"),
+            py::arg_v("z", default_value));
     });
 }
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 322e9bb85d..08f4dd7497 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -37,9 +37,16 @@ template <> lacking_move_ctor empty<lacking_move_ctor>::instance_ = {};
 class MoveOnlyInt {
 public:
     MoveOnlyInt() { print_default_created(this); }
-    MoveOnlyInt(int v) : value{std::move(v)} { print_created(this, value); }
-    MoveOnlyInt(MoveOnlyInt &&m) { print_move_created(this, m.value); std::swap(value, m.value); }
-    MoveOnlyInt &operator=(MoveOnlyInt &&m) { print_move_assigned(this, m.value); std::swap(value, m.value); return *this; }
+    MoveOnlyInt(int v) : value{v} { print_created(this, value); }
+    MoveOnlyInt(MoveOnlyInt &&m) noexcept {
+        print_move_created(this, m.value);
+        std::swap(value, m.value);
+    }
+    MoveOnlyInt &operator=(MoveOnlyInt &&m) noexcept {
+        print_move_assigned(this, m.value);
+        std::swap(value, m.value);
+        return *this;
+    }
     MoveOnlyInt(const MoveOnlyInt &) = delete;
     MoveOnlyInt &operator=(const MoveOnlyInt &) = delete;
     ~MoveOnlyInt() { print_destroyed(this); }
@@ -49,9 +56,16 @@ class MoveOnlyInt {
 class MoveOrCopyInt {
 public:
     MoveOrCopyInt() { print_default_created(this); }
-    MoveOrCopyInt(int v) : value{std::move(v)} { print_created(this, value); }
-    MoveOrCopyInt(MoveOrCopyInt &&m) { print_move_created(this, m.value); std::swap(value, m.value); }
-    MoveOrCopyInt &operator=(MoveOrCopyInt &&m) { print_move_assigned(this, m.value); std::swap(value, m.value); return *this; }
+    MoveOrCopyInt(int v) : value{v} { print_created(this, value); }
+    MoveOrCopyInt(MoveOrCopyInt &&m) noexcept {
+        print_move_created(this, m.value);
+        std::swap(value, m.value);
+    }
+    MoveOrCopyInt &operator=(MoveOrCopyInt &&m) noexcept {
+        print_move_assigned(this, m.value);
+        std::swap(value, m.value);
+        return *this;
+    }
     MoveOrCopyInt(const MoveOrCopyInt &c) { print_copy_created(this, c.value); value = c.value; }
     MoveOrCopyInt &operator=(const MoveOrCopyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
     ~MoveOrCopyInt() { print_destroyed(this); }
@@ -61,7 +75,7 @@ class MoveOrCopyInt {
 class CopyOnlyInt {
 public:
     CopyOnlyInt() { print_default_created(this); }
-    CopyOnlyInt(int v) : value{std::move(v)} { print_created(this, value); }
+    CopyOnlyInt(int v) : value{v} { print_created(this, value); }
     CopyOnlyInt(const CopyOnlyInt &c) { print_copy_created(this, c.value); value = c.value; }
     CopyOnlyInt &operator=(const CopyOnlyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
     ~CopyOnlyInt() { print_destroyed(this); }
@@ -111,6 +125,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
                     py::return_value_policy::move);
 
     // test_move_and_copy_casts
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("move_and_copy_casts", [](py::object o) {
         int r = 0;
         r += py::cast<MoveOrCopyInt>(o).value; /* moves */
@@ -126,7 +141,9 @@ TEST_SUBMODULE(copy_move_policies, m) {
 
     // test_move_and_copy_loads
     m.def("move_only", [](MoveOnlyInt m) { return m.value; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("move_or_copy", [](MoveOrCopyInt m) { return m.value; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("copy_only", [](CopyOnlyInt m) { return m.value; });
     m.def("move_pair", [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) {
         return p.first.value + p.second.value;
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 3fe910d491..076777d6f1 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -67,9 +67,12 @@ class DestructionTester {
     DestructionTester() { print_default_created(this); }
     ~DestructionTester() { print_destroyed(this); }
     DestructionTester(const DestructionTester &) { print_copy_created(this); }
-    DestructionTester(DestructionTester &&) { print_move_created(this); }
+    DestructionTester(DestructionTester &&) noexcept { print_move_created(this); }
     DestructionTester &operator=(const DestructionTester &) { print_copy_assigned(this); return *this; }
-    DestructionTester &operator=(DestructionTester &&) { print_move_assigned(this); return *this; }
+    DestructionTester &operator=(DestructionTester &&) noexcept {
+        print_move_assigned(this);
+        return *this;
+    }
 };
 namespace pybind11 { namespace detail {
 template <> struct type_caster<DestructionTester> {
@@ -94,7 +97,11 @@ TEST_SUBMODULE(custom_type_casters, m) {
     class ArgInspector {
     public:
         ArgInspector1 f(ArgInspector1 a, ArgAlwaysConverts) { return a; }
-        std::string g(ArgInspector1 a, const ArgInspector1 &b, int c, ArgInspector2 *d, ArgAlwaysConverts) {
+        std::string g(const ArgInspector1 &a,
+                      const ArgInspector1 &b,
+                      int c,
+                      ArgInspector2 *d,
+                      ArgAlwaysConverts) {
             return a.arg + "\n" + b.arg + "\n" + std::to_string(c) + "\n" + d->arg;
         }
         static ArgInspector2 h(ArgInspector2 a, ArgAlwaysConverts) { return a; }
@@ -106,8 +113,14 @@ TEST_SUBMODULE(custom_type_casters, m) {
         .def("g", &ArgInspector::g, "a"_a.noconvert(), "b"_a, "c"_a.noconvert()=13, "d"_a=ArgInspector2(), py::arg() = ArgAlwaysConverts())
         .def_static("h", &ArgInspector::h, py::arg{}.noconvert(), py::arg() = ArgAlwaysConverts())
         ;
-    m.def("arg_inspect_func", [](ArgInspector2 a, ArgInspector1 b, ArgAlwaysConverts) { return a.arg + "\n" + b.arg; },
-            py::arg{}.noconvert(false), py::arg_v(nullptr, ArgInspector1()).noconvert(true), py::arg() = ArgAlwaysConverts());
+    m.def(
+        "arg_inspect_func",
+        [](const ArgInspector2 &a, const ArgInspector1 &b, ArgAlwaysConverts) {
+            return a.arg + "\n" + b.arg;
+        },
+        py::arg{}.noconvert(false),
+        py::arg_v(nullptr, ArgInspector1()).noconvert(true),
+        py::arg() = ArgAlwaysConverts());
 
     m.def("floats_preferred", [](double f) { return 0.5 * f; }, "f"_a);
     m.def("floats_only", [](double f) { return 0.5 * f; }, "f"_a.noconvert());
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index 8432547439..a24bf273d2 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -54,8 +54,7 @@ void reset_refs() {
 }
 
 // Returns element 2,1 from a matrix (used to test copy/nocopy)
-double get_elem(Eigen::Ref<const Eigen::MatrixXd> m) { return m(2, 1); };
-
+double get_elem(const Eigen::Ref<const Eigen::MatrixXd> &m) { return m(2, 1); };
 
 // Returns a matrix with 10*r + 100*c added to each matrix element (to help test that the matrix
 // reference is referencing rows/columns correctly).
@@ -94,14 +93,16 @@ TEST_SUBMODULE(eigen, m) {
     m.def("double_complex", [](const Eigen::VectorXcf &x) -> Eigen::VectorXcf { return 2.0f * x; });
     m.def("double_threec", [](py::EigenDRef<Eigen::Vector3f> x) { x *= 2; });
     m.def("double_threer", [](py::EigenDRef<Eigen::RowVector3f> x) { x *= 2; });
-    m.def("double_mat_cm", [](Eigen::MatrixXf x) -> Eigen::MatrixXf { return 2.0f * x; });
-    m.def("double_mat_rm", [](DenseMatrixR x) -> DenseMatrixR { return 2.0f * x; });
+    m.def("double_mat_cm", [](const Eigen::MatrixXf &x) -> Eigen::MatrixXf { return 2.0f * x; });
+    m.def("double_mat_rm", [](const DenseMatrixR &x) -> DenseMatrixR { return 2.0f * x; });
 
     // test_eigen_ref_to_python
     // Different ways of passing via Eigen::Ref; the first and second are the Eigen-recommended
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("cholesky1", [](Eigen::Ref<MatrixXdR> x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky3", [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("cholesky4", [](Eigen::Ref<const MatrixXdR> x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
 
     // test_eigen_ref_mutators
@@ -247,8 +248,11 @@ TEST_SUBMODULE(eigen, m) {
     m.def("fixed_copy_r", [](const FixedMatrixR &m) -> FixedMatrixR { return m; });
     m.def("fixed_copy_c", [](const FixedMatrixC &m) -> FixedMatrixC { return m; });
     // test_mutator_descriptors
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("fixed_mutator_r", [](Eigen::Ref<FixedMatrixR>) {});
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("fixed_mutator_c", [](Eigen::Ref<FixedMatrixC>) {});
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("fixed_mutator_a", [](py::EigenDRef<FixedMatrixC>) {});
     // test_dense
     m.def("dense_r", [mat]() -> DenseMatrixR { return DenseMatrixR(mat); });
@@ -280,6 +284,7 @@ TEST_SUBMODULE(eigen, m) {
     // that would allow copying (if types or strides don't match) for comparison:
     m.def("get_elem", &get_elem);
     // Now this alternative that calls the tells pybind to fail rather than copy:
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("get_elem_nocopy", [](Eigen::Ref<const Eigen::MatrixXd> m) -> double { return get_elem(m); },
             py::arg{}.noconvert());
     // Also test a row-major-only no-copy const ref:
@@ -295,13 +300,16 @@ TEST_SUBMODULE(eigen, m) {
 
     // test_issue1105
     // Issue #1105: when converting from a numpy two-dimensional (Nx1) or (1xN) value into a dense
-    // eigen Vector or RowVector, the argument would fail to load because the numpy copy would fail:
-    // numpy won't broadcast a Nx1 into a 1-dimensional vector.
+    // eigen Vector or RowVector, the argument would fail to load because the numpy copy would
+    // fail: numpy won't broadcast a Nx1 into a 1-dimensional vector. NOLINTNEXTLINE
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("iss1105_col", [](Eigen::VectorXd) { return true; });
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("iss1105_row", [](Eigen::RowVectorXd) { return true; });
 
     // test_named_arguments
     // Make sure named arguments are working properly:
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("matrix_multiply", [](const py::EigenDRef<const Eigen::MatrixXd> A, const py::EigenDRef<const Eigen::MatrixXd> B)
             -> Eigen::MatrixXd {
         if (A.cols() != B.rows()) throw std::domain_error("Nonconformable matrices!");
@@ -318,6 +326,7 @@ TEST_SUBMODULE(eigen, m) {
     // In case of a failure (the caster's temp array does not live long enough), creating
     // a new array (np.ones(10)) increases the chances that the temp array will be garbage
     // collected and/or that its memory will be overridden with different values.
+    // NOLINTNEXTLINE (performance-unnecessary-value-param)
     m.def("get_elem_direct", [](Eigen::Ref<const Eigen::VectorXd> v) {
         py::module_::import("numpy").attr("ones")(10);
         return v(5);
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 944334ce66..6925ee9782 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -8,16 +8,17 @@
 
 #include <catch.hpp>
 
-#include <thread>
 #include <fstream>
 #include <functional>
+#include <thread>
+#include <utility>
 
 namespace py = pybind11;
 using namespace py::literals;
 
 class Widget {
 public:
-    Widget(std::string message) : message(message) { }
+    Widget(std::string message) : message(std::move(message)) {}
     virtual ~Widget() = default;
 
     std::string the_message() const { return message; }
diff --git a/tests/test_eval.cpp b/tests/test_eval.cpp
index 5416c2ec4d..66cdf71051 100644
--- a/tests/test_eval.cpp
+++ b/tests/test_eval.cpp
@@ -9,7 +9,9 @@
 
 
 #include <pybind11/eval.h>
+
 #include "pybind11_tests.h"
+#include <utility>
 
 TEST_SUBMODULE(eval_, m) {
     // test_evals
@@ -67,7 +69,7 @@ TEST_SUBMODULE(eval_, m) {
         int val_out;
         local["call_test2"] = py::cpp_function([&](int value) { val_out = value; });
 
-        auto result = py::eval_file(filename, global, local);
+        auto result = py::eval_file(std::move(filename), global, local);
         return val_out == 43 && result.is_none();
     });
 
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 4c5e10dbe0..d34f1a94e1 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -8,7 +8,9 @@
 */
 
 #include "test_exceptions.h"
+
 #include "pybind11_tests.h"
+#include <utility>
 
 // A type that should be raised as an exception in Python
 class MyException : public std::exception {
@@ -199,6 +201,8 @@ TEST_SUBMODULE(exceptions, m) {
         throw py::error_already_set();
     });
 
+    // Changing this broke things. Don't know why
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("python_call_in_destructor", [](py::dict d) {
         try {
             PythonCallInDestructor set_dict_in_destructor(d);
@@ -210,21 +214,23 @@ TEST_SUBMODULE(exceptions, m) {
         return false;
     });
 
-    m.def("python_alreadyset_in_destructor", [](py::str s) {
+    m.def("python_alreadyset_in_destructor", [](const py::str &s) {
         PythonAlreadySetInDestructor alreadyset_in_destructor(s);
         return true;
     });
 
     // test_nested_throws
-    m.def("try_catch", [m](py::object exc_type, py::function f, py::args args) {
-        try { f(*args); }
-        catch (py::error_already_set &ex) {
-            if (ex.matches(exc_type))
-                py::print(ex.what());
-            else
-                throw;
-        }
-    });
+    m.def("try_catch",
+          [m](const py::object &exc_type, const py::function &f, const py::args &args) {
+              try {
+                  f(*args);
+              } catch (py::error_already_set &ex) {
+                  if (ex.matches(exc_type))
+                      py::print(ex.what());
+                  else
+                      throw;
+              }
+          });
 
     // Test repr that cannot be displayed
     m.def("simple_bool_passthrough", [](bool x) {return x;});
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 7308ad5fc1..235ec4dca6 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -8,10 +8,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 #include <cmath>
 #include <new>
+#include <utility>
 
 // Classes for testing python construction via C++ factory function:
 // Not publicly constructible, copyable, or movable:
@@ -35,8 +36,15 @@ class TestFactory2 {
     TestFactory2(int v) : value(std::to_string(v)) { print_created(this, value); }
     TestFactory2(std::string v) : value(std::move(v)) { print_created(this, value); }
 public:
-    TestFactory2(TestFactory2 &&m) { value = std::move(m.value); print_move_created(this); }
-    TestFactory2 &operator=(TestFactory2 &&m) { value = std::move(m.value); print_move_assigned(this); return *this; }
+    TestFactory2(TestFactory2 &&m) noexcept {
+        value = std::move(m.value);
+        print_move_created(this);
+    }
+    TestFactory2 &operator=(TestFactory2 &&m) noexcept {
+        value = std::move(m.value);
+        print_move_assigned(this);
+        return *this;
+    }
     std::string value;
     ~TestFactory2() { print_destroyed(this); }
 };
@@ -48,8 +56,15 @@ class TestFactory3 {
     TestFactory3(int v) : value(std::to_string(v)) { print_created(this, value); }
 public:
     TestFactory3(std::string v) : value(std::move(v)) { print_created(this, value); }
-    TestFactory3(TestFactory3 &&m) { value = std::move(m.value); print_move_created(this); }
-    TestFactory3 &operator=(TestFactory3 &&m) { value = std::move(m.value); print_move_assigned(this); return *this; }
+    TestFactory3(TestFactory3 &&m) noexcept {
+        value = std::move(m.value);
+        print_move_created(this);
+    }
+    TestFactory3 &operator=(TestFactory3 &&m) noexcept {
+        value = std::move(m.value);
+        print_move_assigned(this);
+        return *this;
+    }
     std::string value;
     virtual ~TestFactory3() { print_destroyed(this); }
 };
@@ -73,7 +88,11 @@ class TestFactory6 {
     bool alias = false;
 public:
     TestFactory6(int i) : value{i} { print_created(this, i); }
-    TestFactory6(TestFactory6 &&f) { print_move_created(this); value = f.value; alias = f.alias; }
+    TestFactory6(TestFactory6 &&f) noexcept {
+        print_move_created(this);
+        value = f.value;
+        alias = f.alias;
+    }
     TestFactory6(const TestFactory6 &f) { print_copy_created(this); value = f.value; alias = f.alias; }
     virtual ~TestFactory6() { print_destroyed(this); }
     virtual int get() { return value; }
@@ -85,7 +104,7 @@ class PyTF6 : public TestFactory6 {
     // when an alias is needed:
     PyTF6(TestFactory6 &&base) : TestFactory6(std::move(base)) { alias = true; print_created(this, "move", value); }
     PyTF6(int i) : TestFactory6(i) { alias = true; print_created(this, i); }
-    PyTF6(PyTF6 &&f) : TestFactory6(std::move(f)) { print_move_created(this); }
+    PyTF6(PyTF6 &&f) noexcept : TestFactory6(std::move(f)) { print_move_created(this); }
     PyTF6(const PyTF6 &f) : TestFactory6(f) { print_copy_created(this); }
     PyTF6(std::string s) : TestFactory6((int) s.size()) { alias = true; print_created(this, s); }
     ~PyTF6() override { print_destroyed(this); }
@@ -98,7 +117,11 @@ class TestFactory7 {
     bool alias = false;
 public:
     TestFactory7(int i) : value{i} { print_created(this, i); }
-    TestFactory7(TestFactory7 &&f) { print_move_created(this); value = f.value; alias = f.alias; }
+    TestFactory7(TestFactory7 &&f) noexcept {
+        print_move_created(this);
+        value = f.value;
+        alias = f.alias;
+    }
     TestFactory7(const TestFactory7 &f) { print_copy_created(this); value = f.value; alias = f.alias; }
     virtual ~TestFactory7() { print_destroyed(this); }
     virtual int get() { return value; }
@@ -107,7 +130,7 @@ class TestFactory7 {
 class PyTF7 : public TestFactory7 {
 public:
     PyTF7(int i) : TestFactory7(i) { alias = true; print_created(this, i); }
-    PyTF7(PyTF7 &&f) : TestFactory7(std::move(f)) { print_move_created(this); }
+    PyTF7(PyTF7 &&f) noexcept : TestFactory7(std::move(f)) { print_move_created(this); }
     PyTF7(const PyTF7 &f) : TestFactory7(f) { print_copy_created(this); }
     ~PyTF7() override { print_destroyed(this); }
     int get() override { PYBIND11_OVERRIDE(int, TestFactory7, get, /*no args*/); }
@@ -122,7 +145,9 @@ class TestFactoryHelper {
     // Holder:
     static std::unique_ptr<TestFactory1> construct1(int a) { return std::unique_ptr<TestFactory1>(new TestFactory1(a)); }
     // pointer again
-    static TestFactory1 *construct1_string(std::string a) { return new TestFactory1(a); }
+    static TestFactory1 *construct1_string(std::string a) {
+        return new TestFactory1(std::move(a));
+    }
 
     // Moveable type:
     // pointer:
@@ -130,7 +155,7 @@ class TestFactoryHelper {
     // holder:
     static std::unique_ptr<TestFactory2> construct2(int a) { return std::unique_ptr<TestFactory2>(new TestFactory2(a)); }
     // by value moving:
-    static TestFactory2 construct2(std::string a) { return TestFactory2(a); }
+    static TestFactory2 construct2(std::string a) { return TestFactory2(std::move(a)); }
 
     // shared_ptr holder type:
     // pointer:
@@ -173,10 +198,11 @@ TEST_SUBMODULE(factory_constructors, m) {
         ;
     py::class_<TestFactory2>(m, "TestFactory2")
         .def(py::init([](pointer_tag, int v) { return TestFactoryHelper::construct2(v); }))
-        .def(py::init([](unique_ptr_tag, std::string v) { return TestFactoryHelper::construct2(v); }))
+        .def(py::init([](unique_ptr_tag, std::string v) {
+            return TestFactoryHelper::construct2(std::move(v));
+        }))
         .def(py::init([](move_tag) { return TestFactoryHelper::construct2(); }))
-        .def_readwrite("value", &TestFactory2::value)
-        ;
+        .def_readwrite("value", &TestFactory2::value);
 
     // Stateful & reused:
     int c = 1;
@@ -188,7 +214,9 @@ TEST_SUBMODULE(factory_constructors, m) {
         .def(py::init([](pointer_tag, int v) { return TestFactoryHelper::construct3(v); }))
         .def(py::init([](shared_ptr_tag) { return TestFactoryHelper::construct3(); }));
     ignoreOldStyleInitWarnings([&pyTestFactory3]() {
-        pyTestFactory3.def("__init__", [](TestFactory3 &self, std::string v) { new (&self) TestFactory3(v); }); // placement-new ctor
+        pyTestFactory3.def("__init__", [](TestFactory3 &self, std::string v) {
+            new (&self) TestFactory3(std::move(v));
+        }); // placement-new ctor
     });
     pyTestFactory3
         // factories returning a derived type:
@@ -219,52 +247,54 @@ TEST_SUBMODULE(factory_constructors, m) {
     py::class_<TestFactory6, PyTF6>(m, "TestFactory6")
         .def(py::init([](base_tag, int i) { return TestFactory6(i); }))
         .def(py::init([](alias_tag, int i) { return PyTF6(i); }))
-        .def(py::init([](alias_tag, std::string s) { return PyTF6(s); }))
+        .def(py::init([](alias_tag, std::string s) { return PyTF6(std::move(s)); }))
         .def(py::init([](alias_tag, pointer_tag, int i) { return new PyTF6(i); }))
         .def(py::init([](base_tag, pointer_tag, int i) { return new TestFactory6(i); }))
-        .def(py::init([](base_tag, alias_tag, pointer_tag, int i) { return (TestFactory6 *) new PyTF6(i); }))
+        .def(py::init(
+            [](base_tag, alias_tag, pointer_tag, int i) { return (TestFactory6 *) new PyTF6(i); }))
 
         .def("get", &TestFactory6::get)
         .def("has_alias", &TestFactory6::has_alias)
 
-        .def_static("get_cstats", &ConstructorStats::get<TestFactory6>, py::return_value_policy::reference)
-        .def_static("get_alias_cstats", &ConstructorStats::get<PyTF6>, py::return_value_policy::reference)
-        ;
+        .def_static(
+            "get_cstats", &ConstructorStats::get<TestFactory6>, py::return_value_policy::reference)
+        .def_static(
+            "get_alias_cstats", &ConstructorStats::get<PyTF6>, py::return_value_policy::reference);
 
     // test_init_factory_dual
     // Separate alias constructor testing
     py::class_<TestFactory7, PyTF7, std::shared_ptr<TestFactory7>>(m, "TestFactory7")
-        .def(py::init(
-            [](int i) { return TestFactory7(i); },
-            [](int i) { return PyTF7(i); }))
-        .def(py::init(
-            [](pointer_tag, int i) { return new TestFactory7(i); },
-            [](pointer_tag, int i) { return new PyTF7(i); }))
-        .def(py::init(
-            [](mixed_tag, int i) { return new TestFactory7(i); },
-            [](mixed_tag, int i) { return PyTF7(i); }))
-        .def(py::init(
-            [](mixed_tag, std::string s) { return TestFactory7((int) s.size()); },
-            [](mixed_tag, std::string s) { return new PyTF7((int) s.size()); }))
-        .def(py::init(
-            [](base_tag, pointer_tag, int i) { return new TestFactory7(i); },
-            [](base_tag, pointer_tag, int i) { return (TestFactory7 *) new PyTF7(i); }))
-        .def(py::init(
-            [](alias_tag, pointer_tag, int i) { return new PyTF7(i); },
-            [](alias_tag, pointer_tag, int i) { return new PyTF7(10*i); }))
+        .def(py::init([](int i) { return TestFactory7(i); }, [](int i) { return PyTF7(i); }))
+        .def(py::init([](pointer_tag, int i) { return new TestFactory7(i); },
+                      [](pointer_tag, int i) { return new PyTF7(i); }))
+        .def(py::init([](mixed_tag, int i) { return new TestFactory7(i); },
+                      [](mixed_tag, int i) { return PyTF7(i); }))
+        .def(py::init([](mixed_tag, const std::string &s) { return TestFactory7((int) s.size()); },
+                      [](mixed_tag, const std::string &s) { return new PyTF7((int) s.size()); }))
+        .def(py::init([](base_tag, pointer_tag, int i) { return new TestFactory7(i); },
+                      [](base_tag, pointer_tag, int i) { return (TestFactory7 *) new PyTF7(i); }))
+        .def(py::init([](alias_tag, pointer_tag, int i) { return new PyTF7(i); },
+                      [](alias_tag, pointer_tag, int i) { return new PyTF7(10 * i); }))
         .def(py::init(
             [](shared_ptr_tag, base_tag, int i) { return std::make_shared<TestFactory7>(i); },
-            [](shared_ptr_tag, base_tag, int i) { auto *p = new PyTF7(i); return std::shared_ptr<TestFactory7>(p); }))
-        .def(py::init(
-            [](shared_ptr_tag, invalid_base_tag, int i) { return std::make_shared<TestFactory7>(i); },
-            [](shared_ptr_tag, invalid_base_tag, int i) { return std::make_shared<TestFactory7>(i); })) // <-- invalid alias factory
+            [](shared_ptr_tag, base_tag, int i) {
+                auto *p = new PyTF7(i);
+                return std::shared_ptr<TestFactory7>(p);
+            }))
+        .def(py::init([](shared_ptr_tag,
+                         invalid_base_tag,
+                         int i) { return std::make_shared<TestFactory7>(i); },
+                      [](shared_ptr_tag, invalid_base_tag, int i) {
+                          return std::make_shared<TestFactory7>(i);
+                      })) // <-- invalid alias factory
 
         .def("get", &TestFactory7::get)
         .def("has_alias", &TestFactory7::has_alias)
 
-        .def_static("get_cstats", &ConstructorStats::get<TestFactory7>, py::return_value_policy::reference)
-        .def_static("get_alias_cstats", &ConstructorStats::get<PyTF7>, py::return_value_policy::reference)
-        ;
+        .def_static(
+            "get_cstats", &ConstructorStats::get<TestFactory7>, py::return_value_policy::reference)
+        .def_static(
+            "get_alias_cstats", &ConstructorStats::get<PyTF7>, py::return_value_policy::reference);
 
     // test_placement_new_alternative
     // Class with a custom new operator but *without* a placement new operator (issue #948)
@@ -331,12 +361,10 @@ TEST_SUBMODULE(factory_constructors, m) {
     pyNoisyAlloc.def(py::init([](int i, double) { return new NoisyAlloc(i); }));
     // Regular again: requires yet another preallocation
     ignoreOldStyleInitWarnings([&pyNoisyAlloc]() {
-        pyNoisyAlloc.def("__init__", [](NoisyAlloc &a, int i, std::string) { new (&a) NoisyAlloc(i); });
+        pyNoisyAlloc.def(
+            "__init__", [](NoisyAlloc &a, int i, const std::string &) { new (&a) NoisyAlloc(i); });
     });
 
-
-
-
     // static_assert testing (the following def's should all fail with appropriate compilation errors):
 #if 0
     struct BadF1Base {};
diff --git a/tests/test_gil_scoped.cpp b/tests/test_gil_scoped.cpp
index b6a45a5f03..b261085c88 100644
--- a/tests/test_gil_scoped.cpp
+++ b/tests/test_gil_scoped.cpp
@@ -35,20 +35,15 @@ TEST_SUBMODULE(gil_scoped, m) {
       .def("virtual_func", &VirtClass::virtual_func)
       .def("pure_virtual_func", &VirtClass::pure_virtual_func);
 
-    m.def("test_callback_py_obj",
-          [](py::object func) { func(); });
-    m.def("test_callback_std_func",
-          [](const std::function<void()> &func) { func(); });
-    m.def("test_callback_virtual_func",
-          [](VirtClass &virt) { virt.virtual_func(); });
-    m.def("test_callback_pure_virtual_func",
-          [](VirtClass &virt) { virt.pure_virtual_func(); });
-    m.def("test_cross_module_gil",
-          []() {
-              auto cm = py::module_::import("cross_module_gil_utils");
-              auto gil_acquire = reinterpret_cast<void (*)()>(
-                  PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
-              py::gil_scoped_release gil_release;
-              gil_acquire();
-          });
+  m.def("test_callback_py_obj", [](py::object &func) { func(); });
+  m.def("test_callback_std_func", [](const std::function<void()> &func) { func(); });
+  m.def("test_callback_virtual_func", [](VirtClass &virt) { virt.virtual_func(); });
+  m.def("test_callback_pure_virtual_func", [](VirtClass &virt) { virt.pure_virtual_func(); });
+  m.def("test_cross_module_gil", []() {
+      auto cm = py::module_::import("cross_module_gil_utils");
+      auto gil_acquire
+          = reinterpret_cast<void (*)()>(PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
+      py::gil_scoped_release gil_release;
+      gil_acquire();
+  });
 }
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index f21fed5465..908788007f 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -17,15 +17,14 @@
 #include <iostream>
 #include <thread>
 
-
-void noisy_function(std::string msg, bool flush) {
+void noisy_function(const std::string &msg, bool flush) {
 
     std::cout << msg;
     if (flush)
         std::cout << std::flush;
 }
 
-void noisy_funct_dual(std::string msg, std::string emsg) {
+void noisy_funct_dual(const std::string &msg, const std::string &emsg) {
     std::cout << msg;
     std::cerr << emsg;
 }
@@ -70,12 +69,12 @@ TEST_SUBMODULE(iostream, m) {
 
     // test_evals
 
-    m.def("captured_output_default", [](std::string msg) {
+    m.def("captured_output_default", [](const std::string &msg) {
         py::scoped_ostream_redirect redir;
         std::cout << msg << std::flush;
     });
 
-    m.def("captured_output", [](std::string msg) {
+    m.def("captured_output", [](const std::string &msg) {
         py::scoped_ostream_redirect redir(std::cout, py::module_::import("sys").attr("stdout"));
         std::cout << msg << std::flush;
     });
@@ -84,7 +83,7 @@ TEST_SUBMODULE(iostream, m) {
             py::call_guard<py::scoped_ostream_redirect>(),
             py::arg("msg"), py::arg("flush")=true);
 
-    m.def("captured_err", [](std::string msg) {
+    m.def("captured_err", [](const std::string &msg) {
         py::scoped_ostream_redirect redir(std::cerr, py::module_::import("sys").attr("stderr"));
         std::cerr << msg << std::flush;
     });
@@ -95,15 +94,11 @@ TEST_SUBMODULE(iostream, m) {
             py::call_guard<py::scoped_ostream_redirect, py::scoped_estream_redirect>(),
             py::arg("msg"), py::arg("emsg"));
 
-    m.def("raw_output", [](std::string msg) {
-        std::cout << msg << std::flush;
-    });
+    m.def("raw_output", [](const std::string &msg) { std::cout << msg << std::flush; });
 
-    m.def("raw_err", [](std::string msg) {
-        std::cerr << msg << std::flush;
-    });
+    m.def("raw_err", [](const std::string &msg) { std::cerr << msg << std::flush; });
 
-    m.def("captured_dual", [](std::string msg, std::string emsg) {
+    m.def("captured_dual", [](const std::string &msg, const std::string &emsg) {
         py::scoped_ostream_redirect redirout(std::cout, py::module_::import("sys").attr("stdout"));
         py::scoped_ostream_redirect redirerr(std::cerr, py::module_::import("sys").attr("stderr"));
         std::cout << msg << std::flush;
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 627a79690e..ab1c94c914 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -11,6 +11,8 @@
 #include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include <utility>
+
 TEST_SUBMODULE(kwargs_and_defaults, m) {
     auto kw_func = [](int x, int y) { return "x=" + std::to_string(x) + ", y=" + std::to_string(y); };
 
@@ -37,18 +39,16 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     m.def("args_function", [](py::args args) -> py::tuple {
         return std::move(args);
     });
-    m.def("args_kwargs_function", [](py::args args, py::kwargs kwargs) {
+    m.def("args_kwargs_function", [](const py::args &args, const py::kwargs &kwargs) {
         return py::make_tuple(args, kwargs);
     });
 
     // test_mixed_args_and_kwargs
-    m.def("mixed_plus_args", [](int i, double j, py::args args) {
-        return py::make_tuple(i, j, args);
-    });
-    m.def("mixed_plus_kwargs", [](int i, double j, py::kwargs kwargs) {
-        return py::make_tuple(i, j, kwargs);
-    });
-    auto mixed_plus_both = [](int i, double j, py::args args, py::kwargs kwargs) {
+    m.def("mixed_plus_args",
+          [](int i, double j, const py::args &args) { return py::make_tuple(i, j, args); });
+    m.def("mixed_plus_kwargs",
+          [](int i, double j, const py::kwargs &kwargs) { return py::make_tuple(i, j, kwargs); });
+    auto mixed_plus_both = [](int i, double j, const py::args &args, const py::kwargs &kwargs) {
         return py::make_tuple(i, j, args, kwargs);
     };
     m.def("mixed_plus_args_kwargs", mixed_plus_both);
@@ -65,6 +65,8 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     #endif
     m.def("arg_refcount_h", [](py::handle h) { GC_IF_NEEDED; return h.ref_count(); });
     m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) { GC_IF_NEEDED; return h.ref_count(); });
+    // TODO replace the following nolints as appropiate
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("arg_refcount_o", [](py::object o) { GC_IF_NEEDED; return o.ref_count(); });
     m.def("args_refcount", [](py::args a) {
         GC_IF_NEEDED;
@@ -74,6 +76,7 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
             t[i] = (int) Py_REFCNT(PyTuple_GET_ITEM(a.ptr(), static_cast<py::ssize_t>(i)));
         return t;
     });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("mixed_args_refcount", [](py::object o, py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size() + 1);
@@ -103,6 +106,7 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
             py::arg() = 3, "j"_a = 4, py::kw_only(), "k"_a = 5, "z"_a);
     m.def("kw_only_mixed", [](int i, int j) { return py::make_tuple(i, j); },
             "i"_a, py::kw_only(), "j"_a);
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("kw_only_plus_more", [](int i, int j, int k, py::kwargs kwargs) {
             return py::make_tuple(i, j, k, kwargs); },
             py::arg() /* positional */, py::arg("j") = -1 /* both */, py::kw_only(), py::arg("k") /* kw-only */);
@@ -137,6 +141,8 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
 
     // Make sure a class (not an instance) can be used as a default argument.
     // The return value doesn't matter, only that the module is importable.
-    m.def("class_default_argument", [](py::object a) { return py::repr(a); },
+    m.def(
+        "class_default_argument",
+        [](py::object a) { return py::repr(std::move(a)); },
         "a"_a = py::module_::import("decimal").attr("Decimal"));
 }
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index c61e388833..2ac77b143b 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -86,6 +86,8 @@ TEST_SUBMODULE(local_bindings, m) {
     m.def("return_self", [](LocalVec *v) { return v; });
     m.def("return_copy", [](const LocalVec &v) { return LocalVec(v); });
 
+    // Reformatting this class broke pygrep checks
+    // NOLINTNEXTLINE
     class Cat : public pets::Pet { public: Cat(std::string name) : Pet(name) {}; };
     py::class_<pets::Pet>(m, "Pet", py::module_local())
         .def("get_name", &pets::Pet::name);
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 1f855ef354..3eb22b4a37 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -22,14 +22,18 @@ class ExampleMandA {
     ExampleMandA(int value) : value(value) { print_created(this, value); }
     ExampleMandA(const ExampleMandA &e) : value(e.value) { print_copy_created(this); }
     ExampleMandA(std::string&&) {}
-    ExampleMandA(ExampleMandA &&e) : value(e.value) { print_move_created(this); }
+    ExampleMandA(ExampleMandA &&e) noexcept : value(e.value) { print_move_created(this); }
     ~ExampleMandA() { print_destroyed(this); }
 
     std::string toString() const { return "ExampleMandA[value=" + std::to_string(value) + "]"; }
 
     void operator=(const ExampleMandA &e) { print_copy_assigned(this); value = e.value; }
-    void operator=(ExampleMandA &&e) { print_move_assigned(this); value = e.value; }
+    void operator=(ExampleMandA &&e) noexcept {
+        print_move_assigned(this);
+        value = e.value;
+    }
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     void add1(ExampleMandA other) { value += other.value; }         // passing by value
     void add2(ExampleMandA &other) { value += other.value; }        // passing by reference
     void add3(const ExampleMandA &other) { value += other.value; }  // passing by const reference
@@ -112,7 +116,7 @@ int none1(const NoneTester &obj) { return obj.answer; }
 int none2(NoneTester *obj) { return obj ? obj->answer : -1; }
 int none3(std::shared_ptr<NoneTester> &obj) { return obj ? obj->answer : -1; }
 int none4(std::shared_ptr<NoneTester> *obj) { return obj && *obj ? (*obj)->answer : -1; }
-int none5(std::shared_ptr<NoneTester> obj) { return obj ? obj->answer : -1; }
+int none5(const std::shared_ptr<NoneTester> &obj) { return obj ? obj->answer : -1; }
 
 struct StrIssue {
     int val = -1;
@@ -226,36 +230,41 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def(py::init<>())
         .def_readonly("def_readonly", &TestProperties::value)
         .def_readwrite("def_readwrite", &TestProperties::value)
-        .def_property("def_writeonly", nullptr,
-                      [](TestProperties& s,int v) { s.value = v; } )
+        .def_property("def_writeonly", nullptr, [](TestProperties &s, int v) { s.value = v; })
         .def_property("def_property_writeonly", nullptr, &TestProperties::set)
         .def_property_readonly("def_property_readonly", &TestProperties::get)
         .def_property("def_property", &TestProperties::get, &TestProperties::set)
         .def_property("def_property_impossible", nullptr, nullptr)
         .def_readonly_static("def_readonly_static", &TestProperties::static_value)
         .def_readwrite_static("def_readwrite_static", &TestProperties::static_value)
-        .def_property_static("def_writeonly_static", nullptr,
-                             [](py::object, int v) { TestProperties::static_value = v; })
-        .def_property_readonly_static("def_property_readonly_static",
-                                      [](py::object) { return TestProperties::static_get(); })
-        .def_property_static("def_property_writeonly_static", nullptr,
-                             [](py::object, int v) { return TestProperties::static_set(v); })
-        .def_property_static("def_property_static",
-                             [](py::object) { return TestProperties::static_get(); },
-                             [](py::object, int v) { TestProperties::static_set(v); })
-        .def_property_static("static_cls",
-                             [](py::object cls) { return cls; },
-                             [](py::object cls, py::function f) { f(cls); });
+        .def_property_static("def_writeonly_static",
+                             nullptr,
+                             [](const py::object &, int v) { TestProperties::static_value = v; })
+        .def_property_readonly_static(
+            "def_property_readonly_static",
+            [](const py::object &) { return TestProperties::static_get(); })
+        .def_property_static(
+            "def_property_writeonly_static",
+            nullptr,
+            [](const py::object &, int v) { return TestProperties::static_set(v); })
+        .def_property_static(
+            "def_property_static",
+            [](const py::object &) { return TestProperties::static_get(); },
+            [](const py::object &, int v) { TestProperties::static_set(v); })
+        .def_property_static(
+            "static_cls",
+            [](py::object cls) { return cls; },
+            [](const py::object &cls, const py::function &f) { f(cls); });
 
     py::class_<TestPropertiesOverride, TestProperties>(m, "TestPropertiesOverride")
         .def(py::init<>())
         .def_readonly("def_readonly", &TestPropertiesOverride::value)
         .def_readonly_static("def_readonly_static", &TestPropertiesOverride::static_value);
 
-    auto static_get1 = [](py::object) -> const UserType & { return TestPropRVP::sv1; };
-    auto static_get2 = [](py::object) -> const UserType & { return TestPropRVP::sv2; };
-    auto static_set1 = [](py::object, int v) { TestPropRVP::sv1.set(v); };
-    auto static_set2 = [](py::object, int v) { TestPropRVP::sv2.set(v); };
+    auto static_get1 = [](const py::object &) -> const UserType & { return TestPropRVP::sv1; };
+    auto static_get2 = [](const py::object &) -> const UserType & { return TestPropRVP::sv2; };
+    auto static_set1 = [](const py::object &, int v) { TestPropRVP::sv1.set(v); };
+    auto static_set2 = [](const py::object &, int v) { TestPropRVP::sv2.set(v); };
     auto rvp_copy = py::return_value_policy::copy;
 
     // test_property_return_value_policies
@@ -266,24 +275,30 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def_property_readonly("ro_func", py::cpp_function(&TestPropRVP::get2, rvp_copy))
         .def_property("rw_ref", &TestPropRVP::get1, &TestPropRVP::set1)
         .def_property("rw_copy", &TestPropRVP::get2, &TestPropRVP::set2, rvp_copy)
-        .def_property("rw_func", py::cpp_function(&TestPropRVP::get2, rvp_copy), &TestPropRVP::set2)
+        .def_property(
+            "rw_func", py::cpp_function(&TestPropRVP::get2, rvp_copy), &TestPropRVP::set2)
         .def_property_readonly_static("static_ro_ref", static_get1)
         .def_property_readonly_static("static_ro_copy", static_get2, rvp_copy)
         .def_property_readonly_static("static_ro_func", py::cpp_function(static_get2, rvp_copy))
         .def_property_static("static_rw_ref", static_get1, static_set1)
         .def_property_static("static_rw_copy", static_get2, static_set2, rvp_copy)
-        .def_property_static("static_rw_func", py::cpp_function(static_get2, rvp_copy), static_set2)
+        .def_property_static(
+            "static_rw_func", py::cpp_function(static_get2, rvp_copy), static_set2)
         // test_property_rvalue_policy
         .def_property_readonly("rvalue", &TestPropRVP::get_rvalue)
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def_property_readonly_static("static_rvalue", [](py::object) { return UserType(1); });
 
     // test_metaclass_override
     struct MetaclassOverride { };
     py::class_<MetaclassOverride>(m, "MetaclassOverride", py::metaclass((PyObject *) &PyType_Type))
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def_property_readonly_static("readonly", [](py::object) { return 1; });
 
     // test_overload_ordering
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("overload_order", [](std::string) { return 1; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("overload_order", [](std::string) { return 2; });
     m.def("overload_order", [](int) { return 3; });
     m.def("overload_order", [](int) { return 4; }, py::prepend{});
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index daecb9564f..f4acf7861e 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -141,6 +141,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def(py::init<int, int>());
 
     m.def("bar_base2a", [](Base2a *b) { return b->bar(); });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("bar_base2a_sharedptr", [](std::shared_ptr<Base2a> b) { return b->bar(); });
 
     // test_mi_unaligned_base
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 204ea8367e..a6c7ae8d74 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -13,6 +13,7 @@
 #include <pybind11/stl.h>
 
 #include <cstdint>
+#include <utility>
 
 // Size / dtype checks.
 struct DtypeCheck {
@@ -192,7 +193,7 @@ TEST_SUBMODULE(numpy_array, sm) {
     sm.def("scalar_int", []() { return py::array(py::dtype("i"), {}, {}, &data_i); });
 
     // test_wrap
-    sm.def("wrap", [](py::array a) {
+    sm.def("wrap", [](const py::array &a) {
         return py::array(
             a.dtype(),
             {a.shape(), a.shape() + a.ndim()},
@@ -222,8 +223,10 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_isinstance
     sm.def("isinstance_untyped", [](py::object yes, py::object no) {
-        return py::isinstance<py::array>(yes) && !py::isinstance<py::array>(no);
+        return py::isinstance<py::array>(std::move(yes))
+               && !py::isinstance<py::array>(std::move(no));
     });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("isinstance_typed", [](py::object o) {
         return py::isinstance<py::array_t<double>>(o) && !py::isinstance<py::array_t<int>>(o);
     });
@@ -236,7 +239,7 @@ TEST_SUBMODULE(numpy_array, sm) {
             "array_t<double>"_a=py::array_t<double>()
         );
     });
-    sm.def("converting_constructors", [](py::object o) {
+    sm.def("converting_constructors", [](const py::object &o) {
         return py::dict(
             "array"_a=py::array(o),
             "array_t<int32>"_a=py::array_t<std::int32_t>(o),
@@ -245,39 +248,59 @@ TEST_SUBMODULE(numpy_array, sm) {
     });
 
     // test_overload_resolution
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<double>) { return "double"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<float>) { return "float"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<int>) { return "int"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<unsigned short>) { return "unsigned short"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<long long>) { return "long long"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<std::complex<double>>) { return "double complex"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded", [](py::array_t<std::complex<float>>) { return "float complex"; });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded2", [](py::array_t<std::complex<double>>) { return "double complex"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded2", [](py::array_t<double>) { return "double"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded2", [](py::array_t<std::complex<float>>) { return "float complex"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded2", [](py::array_t<float>) { return "float"; });
 
     // [workaround(intel)] ICC 20/21 breaks with py::arg().stuff, using py::arg{}.stuff works.
 
     // Only accept the exact types:
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded3", [](py::array_t<int>) { return "int"; }, py::arg{}.noconvert());
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded3", [](py::array_t<double>) { return "double"; }, py::arg{}.noconvert());
 
     // Make sure we don't do unsafe coercion (e.g. float to int) when not using forcecast, but
     // rather that float gets converted via the safe (conversion to double) overload:
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded4", [](py::array_t<long long, 0>) { return "long long"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded4", [](py::array_t<double, 0>) { return "double"; });
 
     // But we do allow conversion to int if forcecast is enabled (but only if no overload matches
     // without conversion)
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded5", [](py::array_t<unsigned int>) { return "unsigned int"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("overloaded5", [](py::array_t<double>) { return "double"; });
 
     // test_greedy_string_overload
     // Issue 685: ndarray shouldn't go to std::string overload
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("issue685", [](std::string) { return "string"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("issue685", [](py::array) { return "array"; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("issue685", [](py::object) { return "other"; });
 
     // test_array_unchecked_fixed_dims
@@ -306,7 +329,7 @@ TEST_SUBMODULE(numpy_array, sm) {
             r(i, j, k) = start++;
         return a;
     });
-    sm.def("proxy_squared_L2_norm", [](py::array_t<double> a) {
+    sm.def("proxy_squared_L2_norm", [](const py::array_t<double> &a) {
         auto r = a.unchecked<1>();
         double sumsq = 0;
         for (py::ssize_t i = 0; i < r.shape(0); i++)
@@ -396,51 +419,78 @@ TEST_SUBMODULE(numpy_array, sm) {
         return a;
     });
 
-    sm.def("index_using_ellipsis", [](py::array a) {
-        return a[py::make_tuple(0, py::ellipsis(), 0)];
-    });
+    sm.def("index_using_ellipsis",
+           [](const py::array &a) { return a[py::make_tuple(0, py::ellipsis(), 0)]; });
 
     // test_argument_conversions
-    sm.def("accept_double",
-           [](py::array_t<double, 0>) {},
-           py::arg("a"));
-    sm.def("accept_double_forcecast",
-           [](py::array_t<double, py::array::forcecast>) {},
-           py::arg("a"));
-    sm.def("accept_double_c_style",
-           [](py::array_t<double, py::array::c_style>) {},
-           py::arg("a"));
-    sm.def("accept_double_c_style_forcecast",
-           [](py::array_t<double, py::array::forcecast | py::array::c_style>) {},
-           py::arg("a"));
-    sm.def("accept_double_f_style",
-           [](py::array_t<double, py::array::f_style>) {},
-           py::arg("a"));
-    sm.def("accept_double_f_style_forcecast",
-           [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
-           py::arg("a"));
-    sm.def("accept_double_noconvert",
-           [](py::array_t<double, 0>) {},
-           "a"_a.noconvert());
-    sm.def("accept_double_forcecast_noconvert",
-           [](py::array_t<double, py::array::forcecast>) {},
-           "a"_a.noconvert());
-    sm.def("accept_double_c_style_noconvert",
-           [](py::array_t<double, py::array::c_style>) {},
-           "a"_a.noconvert());
-    sm.def("accept_double_c_style_forcecast_noconvert",
-           [](py::array_t<double, py::array::forcecast | py::array::c_style>) {},
-           "a"_a.noconvert());
-    sm.def("accept_double_f_style_noconvert",
-           [](py::array_t<double, py::array::f_style>) {},
-           "a"_a.noconvert());
-    sm.def("accept_double_f_style_forcecast_noconvert",
-           [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
-           "a"_a.noconvert());
+    sm.def(
+        "accept_double",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, 0>) {},
+        py::arg("a"));
+    sm.def(
+        "accept_double_forcecast",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::forcecast>) {},
+        py::arg("a"));
+    sm.def(
+        "accept_double_c_style",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::c_style>) {},
+        py::arg("a"));
+    sm.def(
+        "accept_double_c_style_forcecast",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::forcecast | py::array::c_style>) {},
+        py::arg("a"));
+    sm.def(
+        "accept_double_f_style",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::f_style>) {},
+        py::arg("a"));
+    sm.def(
+        "accept_double_f_style_forcecast",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
+        py::arg("a"));
+    sm.def(
+        "accept_double_noconvert",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, 0>) {},
+        "a"_a.noconvert());
+    sm.def(
+        "accept_double_forcecast_noconvert",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::forcecast>) {},
+        "a"_a.noconvert());
+    sm.def(
+        "accept_double_c_style_noconvert",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::c_style>) {},
+        "a"_a.noconvert());
+    sm.def(
+        "accept_double_c_style_forcecast_noconvert",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::forcecast | py::array::c_style>) {},
+        "a"_a.noconvert());
+    sm.def(
+        "accept_double_f_style_noconvert",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::f_style>) {},
+        "a"_a.noconvert());
+    sm.def(
+        "accept_double_f_style_forcecast_noconvert",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
+        "a"_a.noconvert());
 
     // Check that types returns correct npy format descriptor
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("test_fmt_desc_float", [](py::array_t<float>) {});
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("test_fmt_desc_double", [](py::array_t<double>) {});
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("test_fmt_desc_const_float", [](py::array_t<const float>) {});
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     sm.def("test_fmt_desc_const_double", [](py::array_t<const double>) {});
 }
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index 9dece73ec3..edf9cf200f 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -266,10 +266,11 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         .def_readwrite("uint_", &SimpleStruct::uint_)
         .def_readwrite("float_", &SimpleStruct::float_)
         .def_readwrite("ldbl_", &SimpleStruct::ldbl_)
-        .def("astuple", [](const SimpleStruct& self) {
-            return py::make_tuple(self.bool_, self.uint_, self.float_, self.ldbl_);
-        })
-        .def_static("fromtuple", [](const py::tuple tup) {
+        .def("astuple",
+             [](const SimpleStruct &self) {
+                 return py::make_tuple(self.bool_, self.uint_, self.float_, self.ldbl_);
+             })
+        .def_static("fromtuple", [](const py::tuple &tup) {
             if (py::len(tup) != 4) {
                 throw py::cast_error("Invalid size");
             }
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index 8ed9b27e1b..77e281bbdc 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -11,6 +11,8 @@
 #include "pybind11_tests.h"
 #include <pybind11/numpy.h>
 
+#include <utility>
+
 double my_func(int x, float y, double z) {
     py::print("my_func(x:int={}, y:float={:.0f}, z:float={:.0f})"_s.format(x, y, z));
     return (float) x*y*z;
@@ -25,11 +27,10 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     m.def("vectorized_func", py::vectorize(my_func));
 
     // Vectorize a lambda function with a capture object (e.g. to exclude some arguments from the vectorization)
-    m.def("vectorized_func2",
-        [](py::array_t<int> x, py::array_t<float> y, float z) {
-            return py::vectorize([z](int x, float y) { return my_func(x, y, z); })(x, y);
-        }
-    );
+    m.def("vectorized_func2", [](py::array_t<int> x, py::array_t<float> y, float z) {
+        return py::vectorize([z](int x, float y) { return my_func(x, y, z); })(std::move(x),
+                                                                               std::move(y));
+    });
 
     // Vectorize a complex-valued function
     m.def("vectorized_func3", py::vectorize(
@@ -38,8 +39,12 @@ TEST_SUBMODULE(numpy_vectorize, m) {
 
     // test_type_selection
     // NumPy function which only accepts specific data types
+    // Alot of these no lints could be replaced with const refs, and probably should at some point.
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("selective_func", [](py::array_t<int, py::array::c_style>) { return "Int branch taken."; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("selective_func", [](py::array_t<float, py::array::c_style>) { return "Float branch taken."; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("selective_func", [](py::array_t<std::complex<float>, py::array::c_style>) { return "Complex float branch taken."; });
 
 
@@ -53,11 +58,16 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     py::class_<NonPODClass>(m, "NonPODClass")
         .def(py::init<int>())
         .def_readwrite("value", &NonPODClass::value);
-    m.def("vec_passthrough", py::vectorize(
-        [](double *a, double b, py::array_t<double> c, const int &d, int &e, NonPODClass f, const double g) {
-            return *a + b + c.at(0) + d + e + f.value + g;
-        }
-    ));
+    m.def("vec_passthrough",
+          py::vectorize([](double *a,
+                           double b,
+                           // Changing this broke things
+                           // NOLINTNEXTLINE(performance-unnecessary-value-param)
+                           py::array_t<double> c,
+                           const int &d,
+                           int &e,
+                           NonPODClass f,
+                           const double g) { return *a + b + c.at(0) + d + e + f.value + g; }));
 
     // test_method_vectorization
     struct VectorizeTestClass {
@@ -78,16 +88,20 @@ TEST_SUBMODULE(numpy_vectorize, m) {
         .value("f_trivial", py::detail::broadcast_trivial::f_trivial)
         .value("c_trivial", py::detail::broadcast_trivial::c_trivial)
         .value("non_trivial", py::detail::broadcast_trivial::non_trivial);
-    m.def("vectorized_is_trivial", [](
-                py::array_t<int, py::array::forcecast> arg1,
-                py::array_t<float, py::array::forcecast> arg2,
-                py::array_t<double, py::array::forcecast> arg3
-                ) {
-        py::ssize_t ndim;
-        std::vector<py::ssize_t> shape;
-        std::array<py::buffer_info, 3> buffers {{ arg1.request(), arg2.request(), arg3.request() }};
-        return py::detail::broadcast(buffers, ndim, shape);
-    });
+    m.def("vectorized_is_trivial",
+          [](
+              // NOLINTNEXTLINE(performance-unnecessary-value-param)
+              py::array_t<int, py::array::forcecast> arg1,
+              // NOLINTNEXTLINE(performance-unnecessary-value-param)
+              py::array_t<float, py::array::forcecast> arg2,
+              // NOLINTNEXTLINE(performance-unnecessary-value-param)
+              py::array_t<double, py::array::forcecast> arg3) {
+              py::ssize_t ndim;
+              std::vector<py::ssize_t> shape;
+              std::array<py::buffer_info, 3> buffers{
+                  {arg1.request(), arg2.request(), arg3.request()}};
+              return py::detail::broadcast(buffers, ndim, shape);
+          });
 
     m.def("add_to", py::vectorize([](NonPODClass& x, int a) { x.value += a; }));
 }
diff --git a/tests/test_opaque_types.cpp b/tests/test_opaque_types.cpp
index 5a23431635..804de6d4ff 100644
--- a/tests/test_opaque_types.cpp
+++ b/tests/test_opaque_types.cpp
@@ -44,7 +44,7 @@ TEST_SUBMODULE(opaque_types, m) {
     m.def("print_opaque_list", [](const StringList &l) {
         std::string ret = "Opaque list: [";
         bool first = true;
-        for (auto entry : l) {
+        for (const auto &entry : l) {
             if (!first)
                 ret += ", ";
             ret += entry;
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index eb3167dc08..0b6c496cf2 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -16,9 +16,18 @@ class Vector2 {
 public:
     Vector2(float x, float y) : x(x), y(y) { print_created(this, toString()); }
     Vector2(const Vector2 &v) : x(v.x), y(v.y) { print_copy_created(this); }
-    Vector2(Vector2 &&v) : x(v.x), y(v.y) { print_move_created(this); v.x = v.y = 0; }
+    Vector2(Vector2 &&v) noexcept : x(v.x), y(v.y) {
+        print_move_created(this);
+        v.x = v.y = 0;
+    }
     Vector2 &operator=(const Vector2 &v) { x = v.x; y = v.y; print_copy_assigned(this); return *this; }
-    Vector2 &operator=(Vector2 &&v) { x = v.x; y = v.y; v.x = v.y = 0; print_move_assigned(this); return *this; }
+    Vector2 &operator=(Vector2 &&v) noexcept {
+        x   = v.x;
+        y   = v.y;
+        v.x = v.y = 0;
+        print_move_assigned(this);
+        return *this;
+    }
     ~Vector2() { print_destroyed(this); }
 
     std::string toString() const { return "[" + std::to_string(x) + ", " + std::to_string(y) + "]"; }
diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index 1a48595af6..c2cee6c3c7 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -46,17 +46,16 @@ TEST_SUBMODULE(pickling, m) {
             return py::make_tuple(p.value(), p.extra1(), p.extra2());
         });
     ignoreOldStyleInitWarnings([&pyPickleable]() {
-        pyPickleable
-            .def("__setstate__", [](Pickleable &p, py::tuple t) {
-                if (t.size() != 3)
-                    throw std::runtime_error("Invalid state!");
-                /* Invoke the constructor (need to use in-place version) */
-                new (&p) Pickleable(t[0].cast<std::string>());
-
-                /* Assign any additional state */
-                p.setExtra1(t[1].cast<int>());
-                p.setExtra2(t[2].cast<int>());
-            });
+        pyPickleable.def("__setstate__", [](Pickleable &p, const py::tuple &t) {
+            if (t.size() != 3)
+                throw std::runtime_error("Invalid state!");
+            /* Invoke the constructor (need to use in-place version) */
+            new (&p) Pickleable(t[0].cast<std::string>());
+
+            /* Assign any additional state */
+            p.setExtra1(t[1].cast<int>());
+            p.setExtra2(t[2].cast<int>());
+        });
     });
 
     py::class_<PickleableNew, Pickleable>(m, "PickleableNew")
@@ -65,7 +64,7 @@ TEST_SUBMODULE(pickling, m) {
             [](const PickleableNew &p) {
                 return py::make_tuple(p.value(), p.extra1(), p.extra2());
             },
-            [](py::tuple t) {
+            [](const py::tuple &t) {
                 if (t.size() != 3)
                     throw std::runtime_error("Invalid state!");
                 auto p = PickleableNew(t[0].cast<std::string>());
@@ -73,8 +72,7 @@ TEST_SUBMODULE(pickling, m) {
                 p.setExtra1(t[1].cast<int>());
                 p.setExtra2(t[2].cast<int>());
                 return p;
-            }
-        ));
+            }));
 
 #if !defined(PYPY_VERSION)
     // test_roundtrip_with_dict
@@ -92,35 +90,33 @@ TEST_SUBMODULE(pickling, m) {
     };
 
     py::class_<PickleableWithDict> pyPickleableWithDict(m, "PickleableWithDict", py::dynamic_attr());
-    pyPickleableWithDict
-        .def(py::init<std::string>())
+    pyPickleableWithDict.def(py::init<std::string>())
         .def_readwrite("value", &PickleableWithDict::value)
         .def_readwrite("extra", &PickleableWithDict::extra)
-        .def("__getstate__", [](py::object self) {
+        .def("__getstate__", [](const py::object &self) {
             /* Also include __dict__ in state */
             return py::make_tuple(self.attr("value"), self.attr("extra"), self.attr("__dict__"));
         });
     ignoreOldStyleInitWarnings([&pyPickleableWithDict]() {
-        pyPickleableWithDict
-            .def("__setstate__", [](py::object self, py::tuple t) {
-                if (t.size() != 3)
-                    throw std::runtime_error("Invalid state!");
-                /* Cast and construct */
-                auto& p = self.cast<PickleableWithDict&>();
-                new (&p) PickleableWithDict(t[0].cast<std::string>());
-
-                /* Assign C++ state */
-                p.extra = t[1].cast<int>();
-
-                /* Assign Python state */
-                self.attr("__dict__") = t[2];
-            });
+        pyPickleableWithDict.def("__setstate__", [](const py::object &self, const py::tuple &t) {
+            if (t.size() != 3)
+                throw std::runtime_error("Invalid state!");
+            /* Cast and construct */
+            auto &p = self.cast<PickleableWithDict &>();
+            new (&p) PickleableWithDict(t[0].cast<std::string>());
+
+            /* Assign C++ state */
+            p.extra = t[1].cast<int>();
+
+            /* Assign Python state */
+            self.attr("__dict__") = t[2];
+        });
     });
 
     py::class_<PickleableWithDictNew, PickleableWithDict>(m, "PickleableWithDictNew")
         .def(py::init<std::string>())
         .def(py::pickle(
-            [](py::object self) {
+            [](const py::object &self) {
                 return py::make_tuple(self.attr("value"), self.attr("extra"), self.attr("__dict__"));
             },
             [](const py::tuple &t) {
@@ -132,7 +128,6 @@ TEST_SUBMODULE(pickling, m) {
 
                 auto py_state = t[2].cast<py::dict>();
                 return std::make_pair(cpp_state, py_state);
-            }
-        ));
+            }));
 #endif
 }
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 6921796aa0..9e0ebc206f 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -7,6 +7,8 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <utility>
+
 #include "pybind11_tests.h"
 
 
@@ -27,16 +29,14 @@ TEST_SUBMODULE(pytypes, m) {
         list.insert(2, "inserted-2");
         return list;
     });
-    m.def("print_list", [](py::list list) {
+    m.def("print_list", [](const py::list &list) {
         int index = 0;
         for (auto item : list)
             py::print("list item {}: {}"_s.format(index++, item));
     });
     // test_none
     m.def("get_none", []{return py::none();});
-    m.def("print_none", [](py::none none) {
-        py::print("none: {}"_s.format(none));
-    });
+    m.def("print_none", [](const py::none &none) { py::print("none: {}"_s.format(none)); });
 
     // test_set
     m.def("get_set", []() {
@@ -46,20 +46,17 @@ TEST_SUBMODULE(pytypes, m) {
         set.add(std::string("key3"));
         return set;
     });
-    m.def("print_set", [](py::set set) {
+    m.def("print_set", [](const py::set &set) {
         for (auto item : set)
             py::print("key:", item);
     });
-    m.def("set_contains", [](py::set set, py::object key) {
-        return set.contains(key);
-    });
-    m.def("set_contains", [](py::set set, const char* key) {
-        return set.contains(key);
-    });
+    m.def("set_contains",
+          [](const py::set &set, const py::object &key) { return set.contains(key); });
+    m.def("set_contains", [](const py::set &set, const char *key) { return set.contains(key); });
 
     // test_dict
     m.def("get_dict", []() { return py::dict("key"_a="value"); });
-    m.def("print_dict", [](py::dict dict) {
+    m.def("print_dict", [](const py::dict &dict) {
         for (auto item : dict)
             py::print("key: {}, value={}"_s.format(item.first, item.second));
     });
@@ -68,12 +65,10 @@ TEST_SUBMODULE(pytypes, m) {
         auto d2 = py::dict("z"_a=3, **d1);
         return d2;
     });
-    m.def("dict_contains", [](py::dict dict, py::object val) {
-        return dict.contains(val);
-    });
-    m.def("dict_contains", [](py::dict dict, const char* val) {
-        return dict.contains(val);
-    });
+    m.def("dict_contains",
+          [](const py::dict &dict, py::object val) { return dict.contains(val); });
+    m.def("dict_contains",
+          [](const py::dict &dict, const char *val) { return dict.contains(val); });
 
     // test_str
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
@@ -137,7 +132,7 @@ TEST_SUBMODULE(pytypes, m) {
     });
 
     // test_accessors
-    m.def("accessor_api", [](py::object o) {
+    m.def("accessor_api", [](const py::object &o) {
         auto d = py::dict();
 
         d["basic_attr"] = o.attr("basic_attr");
@@ -178,7 +173,7 @@ TEST_SUBMODULE(pytypes, m) {
         return d;
     });
 
-    m.def("tuple_accessor", [](py::tuple existing_t) {
+    m.def("tuple_accessor", [](const py::tuple &existing_t) {
         try {
             existing_t[0] = 1;
         } catch (const py::error_already_set &) {
@@ -226,7 +221,7 @@ TEST_SUBMODULE(pytypes, m) {
         );
     });
 
-    m.def("converting_constructors", [](py::dict d) {
+    m.def("converting_constructors", [](const py::dict &d) {
         return py::dict(
             "bytes"_a=py::bytes(d["bytes"]),
             "bytearray"_a=py::bytearray(d["bytearray"]),
@@ -242,6 +237,7 @@ TEST_SUBMODULE(pytypes, m) {
         );
     });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("cast_functions", [](py::dict d) {
         // When converting between Python types, obj.cast<T>() should be the same as T(obj)
         return py::dict(
@@ -259,8 +255,10 @@ TEST_SUBMODULE(pytypes, m) {
         );
     });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("convert_to_pybind11_str", [](py::object o) { return py::str(o); });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("nonconverting_constructor", [](std::string type, py::object value, bool move) -> py::object {
         if (type == "bytes") {
             return move ? py::bytes(std::move(value)) : py::bytes(value);
@@ -333,8 +331,9 @@ TEST_SUBMODULE(pytypes, m) {
 
     m.def("print_failure", []() { py::print(42, UnregisteredType()); });
 
-    m.def("hash_function", [](py::object obj) { return py::hash(obj); });
+    m.def("hash_function", [](py::object obj) { return py::hash(std::move(obj)); });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("test_number_protocol", [](py::object a, py::object b) {
         py::list l;
         l.append(a.equal(b));
@@ -355,6 +354,7 @@ TEST_SUBMODULE(pytypes, m) {
         return l;
     });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("test_list_slicing", [](py::list a) {
         return a[py::slice(0, -1, 2)];
     });
@@ -369,10 +369,12 @@ TEST_SUBMODULE(pytypes, m) {
         return is_this_none;
     });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("test_memoryview_object", [](py::buffer b) {
         return py::memoryview(b);
     });
 
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("test_memoryview_buffer_info", [](py::buffer b) {
         return py::memoryview(b.request());
     });
@@ -425,20 +427,22 @@ TEST_SUBMODULE(pytypes, m) {
     m.attr("PYBIND11_STR_LEGACY_PERMISSIVE") = true;
 #endif
 
-    m.def("isinstance_pybind11_bytes", [](py::object o) { return py::isinstance<py::bytes>(o); });
-    m.def("isinstance_pybind11_str", [](py::object o) { return py::isinstance<py::str>(o); });
+    m.def("isinstance_pybind11_bytes",
+          [](py::object o) { return py::isinstance<py::bytes>(std::move(o)); });
+    m.def("isinstance_pybind11_str",
+          [](py::object o) { return py::isinstance<py::str>(std::move(o)); });
 
-    m.def("pass_to_pybind11_bytes", [](py::bytes b) { return py::len(b); });
-    m.def("pass_to_pybind11_str", [](py::str s) { return py::len(s); });
+    m.def("pass_to_pybind11_bytes", [](py::bytes b) { return py::len(std::move(b)); });
+    m.def("pass_to_pybind11_str", [](py::str s) { return py::len(std::move(s)); });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("pass_to_std_string", [](std::string s) { return s.size(); });
 
     // test_weakref
     m.def("weakref_from_handle",
           [](py::handle h) { return py::weakref(h); });
     m.def("weakref_from_handle_and_function",
-          [](py::handle h, py::function f) { return py::weakref(h, f); });
-    m.def("weakref_from_object",
-          [](py::object o) { return py::weakref(o); });
+          [](py::handle h, py::function f) { return py::weakref(h, std::move(f)); });
+    m.def("weakref_from_object", [](const py::object &o) { return py::weakref(o); });
     m.def("weakref_from_object_and_function",
-          [](py::object o, py::function f) { return py::weakref(o, f); });
+          [](py::object o, py::function f) { return py::weakref(std::move(o), std::move(f)); });
 }
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index d318052a48..c39798229f 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -14,6 +14,7 @@
 #include <pybind11/stl.h>
 
 #include <algorithm>
+#include <utility>
 
 template<typename T>
 class NonZeroIterator {
@@ -80,18 +81,17 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
       int start,stop,step;
       int size;
     };
-    py::class_<Sliceable>(m,"Sliceable")
+    py::class_<Sliceable>(m, "Sliceable")
         .def(py::init<int>())
-        .def("__getitem__",[](const Sliceable &s, py::slice slice) {
-          py::ssize_t start, stop, step, slicelength;
-          if (!slice.compute(s.size, &start, &stop, &step, &slicelength))
-              throw py::error_already_set();
-          int istart = static_cast<int>(start);
-          int istop =  static_cast<int>(stop);
-          int istep =  static_cast<int>(step);
-          return std::make_tuple(istart,istop,istep);
-        })
-        ;
+        .def("__getitem__", [](const Sliceable &s, const py::slice &slice) {
+            py::ssize_t start, stop, step, slicelength;
+            if (!slice.compute(s.size, &start, &stop, &step, &slicelength))
+                throw py::error_already_set();
+            int istart = static_cast<int>(start);
+            int istop  = static_cast<int>(stop);
+            int istep  = static_cast<int>(step);
+            return std::make_tuple(istart, istop, istep);
+        });
 
     // test_sequence
     class Sequence {
@@ -111,7 +111,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             m_data = new float[m_size];
             memcpy(m_data, s.m_data, sizeof(float)*m_size);
         }
-        Sequence(Sequence &&s) : m_size(s.m_size), m_data(s.m_data) {
+        Sequence(Sequence &&s) noexcept : m_size(s.m_size), m_data(s.m_data) {
             print_move_created(this);
             s.m_size = 0;
             s.m_data = nullptr;
@@ -130,7 +130,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             return *this;
         }
 
-        Sequence &operator=(Sequence &&s) {
+        Sequence &operator=(Sequence &&s) noexcept {
             if (&s != this) {
                 delete[] m_data;
                 m_size = s.m_size;
@@ -179,43 +179,54 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     };
     py::class_<Sequence>(m, "Sequence")
         .def(py::init<size_t>())
-        .def(py::init<const std::vector<float>&>())
+        .def(py::init<const std::vector<float> &>())
         /// Bare bones interface
-        .def("__getitem__", [](const Sequence &s, size_t i) {
-            if (i >= s.size()) throw py::index_error();
-            return s[i];
-        })
-        .def("__setitem__", [](Sequence &s, size_t i, float v) {
-            if (i >= s.size()) throw py::index_error();
-            s[i] = v;
-        })
+        .def("__getitem__",
+             [](const Sequence &s, size_t i) {
+                 if (i >= s.size())
+                     throw py::index_error();
+                 return s[i];
+             })
+        .def("__setitem__",
+             [](Sequence &s, size_t i, float v) {
+                 if (i >= s.size())
+                     throw py::index_error();
+                 s[i] = v;
+             })
         .def("__len__", &Sequence::size)
         /// Optional sequence protocol operations
-        .def("__iter__", [](const Sequence &s) { return py::make_iterator(s.begin(), s.end()); },
-                         py::keep_alive<0, 1>() /* Essential: keep object alive while iterator exists */)
+        .def(
+            "__iter__",
+            [](const Sequence &s) { return py::make_iterator(s.begin(), s.end()); },
+            py::keep_alive<0, 1>() /* Essential: keep object alive while iterator exists */)
         .def("__contains__", [](const Sequence &s, float v) { return s.contains(v); })
         .def("__reversed__", [](const Sequence &s) -> Sequence { return s.reversed(); })
         /// Slicing protocol (optional)
-        .def("__getitem__", [](const Sequence &s, py::slice slice) -> Sequence* {
-            size_t start, stop, step, slicelength;
-            if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
-                throw py::error_already_set();
-            auto *seq = new Sequence(slicelength);
-            for (size_t i = 0; i < slicelength; ++i) {
-                (*seq)[i] = s[start]; start += step;
-            }
-            return seq;
-        })
-        .def("__setitem__", [](Sequence &s, py::slice slice, const Sequence &value) {
-            size_t start, stop, step, slicelength;
-            if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
-                throw py::error_already_set();
-            if (slicelength != value.size())
-                throw std::runtime_error("Left and right hand size of slice assignment have different sizes!");
-            for (size_t i = 0; i < slicelength; ++i) {
-                s[start] = value[i]; start += step;
-            }
-        })
+        .def("__getitem__",
+             [](const Sequence &s, const py::slice &slice) -> Sequence * {
+                 size_t start, stop, step, slicelength;
+                 if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
+                     throw py::error_already_set();
+                 auto *seq = new Sequence(slicelength);
+                 for (size_t i = 0; i < slicelength; ++i) {
+                     (*seq)[i] = s[start];
+                     start += step;
+                 }
+                 return seq;
+             })
+        .def("__setitem__",
+             [](Sequence &s, const py::slice &slice, const Sequence &value) {
+                 size_t start, stop, step, slicelength;
+                 if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
+                     throw py::error_already_set();
+                 if (slicelength != value.size())
+                     throw std::runtime_error(
+                         "Left and right hand size of slice assignment have different sizes!");
+                 for (size_t i = 0; i < slicelength; ++i) {
+                     s[start] = value[i];
+                     start += step;
+                 }
+             })
         /// Comparisons
         .def(py::self == py::self)
         .def(py::self != py::self)
@@ -231,8 +242,8 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         StringMap(std::unordered_map<std::string, std::string> init)
             : map(std::move(init)) {}
 
-        void set(std::string key, std::string val) { map[key] = val; }
-        std::string get(std::string key) const { return map.at(key); }
+        void set(const std::string &key, std::string val) { map[key] = std::move(val); }
+        std::string get(const std::string &key) const { return map.at(key); }
         size_t size() const { return map.size(); }
     private:
         std::unordered_map<std::string, std::string> map;
@@ -243,19 +254,24 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     py::class_<StringMap>(m, "StringMap")
         .def(py::init<>())
         .def(py::init<std::unordered_map<std::string, std::string>>())
-        .def("__getitem__", [](const StringMap &map, std::string key) {
-                try { return map.get(key); }
-                catch (const std::out_of_range&) {
-                    throw py::key_error("key '" + key + "' does not exist");
-                }
-        })
+        .def("__getitem__",
+             [](const StringMap &map, const std::string &key) {
+                 try {
+                     return map.get(key);
+                 } catch (const std::out_of_range &) {
+                     throw py::key_error("key '" + key + "' does not exist");
+                 }
+             })
         .def("__setitem__", &StringMap::set)
         .def("__len__", &StringMap::size)
-        .def("__iter__", [](const StringMap &map) { return py::make_key_iterator(map.begin(), map.end()); },
-                py::keep_alive<0, 1>())
-        .def("items", [](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
-                py::keep_alive<0, 1>())
-        ;
+        .def(
+            "__iter__",
+            [](const StringMap &map) { return py::make_key_iterator(map.begin(), map.end()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "items",
+            [](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
+            py::keep_alive<0, 1>());
 
     // test_generalized_iterators
     class IntPairs {
@@ -304,7 +320,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
 #endif
 
     // test_python_iterator_in_cpp
-    m.def("object_to_list", [](py::object o) {
+    m.def("object_to_list", [](const py::object &o) {
         auto l = py::list();
         for (auto item : o) {
             l.append(item);
@@ -322,22 +338,22 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     });
 
     // test_sequence_length: check that Python sequences can be converted to py::sequence.
-    m.def("sequence_length", [](py::sequence seq) { return seq.size(); });
+    m.def("sequence_length", [](const py::sequence &seq) { return seq.size(); });
 
     // Make sure that py::iterator works with std algorithms
-    m.def("count_none", [](py::object o) {
+    m.def("count_none", [](const py::object &o) {
         return std::count_if(o.begin(), o.end(), [](py::handle h) { return h.is_none(); });
     });
 
-    m.def("find_none", [](py::object o) {
+    m.def("find_none", [](const py::object &o) {
         auto it = std::find_if(o.begin(), o.end(), [](py::handle h) { return h.is_none(); });
         return it->is_none();
     });
 
-    m.def("count_nonzeros", [](py::dict d) {
-       return std::count_if(d.begin(), d.end(), [](std::pair<py::handle, py::handle> p) {
-           return p.second.cast<int>() != 0;
-       });
+    m.def("count_nonzeros", [](const py::dict &d) {
+        return std::count_if(d.begin(), d.end(), [](std::pair<py::handle, py::handle> p) {
+            return p.second.cast<int>() != 0;
+        });
     });
 
     m.def("tuple_iterator", &test_random_access_iterator<py::tuple>);
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 2ece3bf0c9..534dec0be4 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -170,7 +170,7 @@ struct SharedPtrRef {
     struct A {
         A() { print_created(this); }
         A(const A &) { print_copy_created(this); }
-        A(A &&) { print_move_created(this); }
+        A(A &&) noexcept { print_move_created(this); }
         ~A() { print_destroyed(this); }
     };
 
@@ -183,7 +183,7 @@ struct SharedFromThisRef {
     struct B : std::enable_shared_from_this<B> {
         B() { print_created(this); }
         B(const B &) : std::enable_shared_from_this<B>() { print_copy_created(this); }
-        B(B &&) : std::enable_shared_from_this<B>() { print_move_created(this); }
+        B(B &&) noexcept : std::enable_shared_from_this<B>() { print_move_created(this); }
         ~B() { print_destroyed(this); }
     };
 
@@ -209,7 +209,9 @@ struct C {
 struct TypeForHolderWithAddressOf {
     TypeForHolderWithAddressOf() { print_created(this); }
     TypeForHolderWithAddressOf(const TypeForHolderWithAddressOf &) { print_copy_created(this); }
-    TypeForHolderWithAddressOf(TypeForHolderWithAddressOf &&) { print_move_created(this); }
+    TypeForHolderWithAddressOf(TypeForHolderWithAddressOf &&) noexcept {
+        print_move_created(this);
+    }
     ~TypeForHolderWithAddressOf() { print_destroyed(this); }
     std::string toString() const {
         return "TypeForHolderWithAddressOf[" + std::to_string(value) + "]";
@@ -245,7 +247,7 @@ struct ElementA : ElementBase {
 };
 
 struct ElementList {
-    void add(std::shared_ptr<ElementBase> e) { l.push_back(e); }
+    void add(const std::shared_ptr<ElementBase> &e) { l.push_back(e); }
     std::vector<std::shared_ptr<ElementBase>> l;
 };
 
@@ -308,6 +310,7 @@ TEST_SUBMODULE(smart_ptr, m) {
     m.def("make_myobject2_1", []() { return new MyObject2(6); });
     m.def("make_myobject2_2", []() { return std::make_shared<MyObject2>(7); });
     m.def("print_myobject2_1", [](const MyObject2 *obj) { py::print(obj->toString()); });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("print_myobject2_2", [](std::shared_ptr<MyObject2> obj) { py::print(obj->toString()); });
     m.def("print_myobject2_3", [](const std::shared_ptr<MyObject2> &obj) { py::print(obj->toString()); });
     m.def("print_myobject2_4", [](const std::shared_ptr<MyObject2> *obj) { py::print((*obj)->toString()); });
@@ -317,6 +320,7 @@ TEST_SUBMODULE(smart_ptr, m) {
     m.def("make_myobject3_1", []() { return new MyObject3(8); });
     m.def("make_myobject3_2", []() { return std::make_shared<MyObject3>(9); });
     m.def("print_myobject3_1", [](const MyObject3 *obj) { py::print(obj->toString()); });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("print_myobject3_2", [](std::shared_ptr<MyObject3> obj) { py::print(obj->toString()); });
     m.def("print_myobject3_3", [](const std::shared_ptr<MyObject3> &obj) { py::print(obj->toString()); });
     m.def("print_myobject3_4", [](const std::shared_ptr<MyObject3> *obj) { py::print((*obj)->toString()); });
@@ -358,12 +362,15 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::class_<SharedPtrRef, std::unique_ptr<SharedPtrRef>>(m, "SharedPtrRef")
         .def(py::init<>())
         .def_readonly("ref", &SharedPtrRef::value)
-        .def_property_readonly("copy", [](const SharedPtrRef &s) { return s.value; },
-                               py::return_value_policy::copy)
+        .def_property_readonly(
+            "copy", [](const SharedPtrRef &s) { return s.value; }, py::return_value_policy::copy)
         .def_readonly("holder_ref", &SharedPtrRef::shared)
-        .def_property_readonly("holder_copy", [](const SharedPtrRef &s) { return s.shared; },
-                               py::return_value_policy::copy)
+        .def_property_readonly(
+            "holder_copy",
+            [](const SharedPtrRef &s) { return s.shared; },
+            py::return_value_policy::copy)
         .def("set_ref", [](SharedPtrRef &, const A &) { return true; })
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def("set_holder", [](SharedPtrRef &, std::shared_ptr<A>) { return true; });
 
     // test_shared_ptr_from_this_and_references
@@ -372,13 +379,19 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::class_<SharedFromThisRef, std::unique_ptr<SharedFromThisRef>>(m, "SharedFromThisRef")
         .def(py::init<>())
         .def_readonly("bad_wp", &SharedFromThisRef::value)
-        .def_property_readonly("ref", [](const SharedFromThisRef &s) -> const B & { return *s.shared; })
-        .def_property_readonly("copy", [](const SharedFromThisRef &s) { return s.value; },
-                               py::return_value_policy::copy)
+        .def_property_readonly("ref",
+                               [](const SharedFromThisRef &s) -> const B & { return *s.shared; })
+        .def_property_readonly(
+            "copy",
+            [](const SharedFromThisRef &s) { return s.value; },
+            py::return_value_policy::copy)
         .def_readonly("holder_ref", &SharedFromThisRef::shared)
-        .def_property_readonly("holder_copy", [](const SharedFromThisRef &s) { return s.shared; },
-                               py::return_value_policy::copy)
+        .def_property_readonly(
+            "holder_copy",
+            [](const SharedFromThisRef &s) { return s.shared; },
+            py::return_value_policy::copy)
         .def("set_ref", [](SharedFromThisRef &, const B &) { return true; })
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def("set_holder", [](SharedFromThisRef &, std::shared_ptr<B>) { return true; });
 
     // Issue #865: shared_from_this doesn't work with virtual inheritance
@@ -396,10 +409,14 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::class_<TypeForHolderWithAddressOf, HolderWithAddressOf>(m, "TypeForHolderWithAddressOf")
         .def_static("make", []() { return HolderWithAddressOf(new TypeForHolderWithAddressOf); })
         .def("get", [](const HolderWithAddressOf &self) { return self.get(); })
-        .def("print_object_1", [](const TypeForHolderWithAddressOf *obj) { py::print(obj->toString()); })
+        .def("print_object_1",
+             [](const TypeForHolderWithAddressOf *obj) { py::print(obj->toString()); })
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def("print_object_2", [](HolderWithAddressOf obj) { py::print(obj.get()->toString()); })
-        .def("print_object_3", [](const HolderWithAddressOf &obj) { py::print(obj.get()->toString()); })
-        .def("print_object_4", [](const HolderWithAddressOf *obj) { py::print((*obj).get()->toString()); });
+        .def("print_object_3",
+             [](const HolderWithAddressOf &obj) { py::print(obj.get()->toString()); })
+        .def("print_object_4",
+             [](const HolderWithAddressOf *obj) { py::print((*obj).get()->toString()); });
 
     // test_move_only_holder_with_addressof_operator
     using MoveOnlyHolderWithAddressOf = unique_ptr_with_addressof_operator<TypeForMoveOnlyHolderWithAddressOf>;
@@ -411,6 +428,7 @@ TEST_SUBMODULE(smart_ptr, m) {
     // test_smart_ptr_from_default
     py::class_<HeldByDefaultHolder, std::unique_ptr<HeldByDefaultHolder>>(m, "HeldByDefaultHolder")
         .def(py::init<>())
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
         .def_static("load_shared_ptr", [](std::shared_ptr<HeldByDefaultHolder>) {});
 
     // test_shared_ptr_gc
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 0590162770..07899b84e0 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -202,6 +202,7 @@ TEST_SUBMODULE(stl, m) {
     }, py::arg_v("x", std::nullopt, "None"));
 
     m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("nodefer_none_optional", [](py::none) { return false; });
 
     using opt_holder = OptionalHolder<std::optional, MoveOutDetector>;
@@ -245,13 +246,13 @@ TEST_SUBMODULE(stl, m) {
         using result_type = const char *;
 
         result_type operator()(int) { return "int"; }
-        result_type operator()(std::string) { return "std::string"; }
+        result_type operator()(const std::string &) { return "std::string"; }
         result_type operator()(double) { return "double"; }
         result_type operator()(std::nullptr_t) { return "std::nullptr_t"; }
     };
 
     // test_variant
-    m.def("load_variant", [](variant<int, std::string, double, std::nullptr_t> v) {
+    m.def("load_variant", [](const variant<int, std::string, double, std::nullptr_t> &v) {
         return py::detail::visit_helper<variant>::call(visitor(), v);
     });
     m.def("load_variant_2pass", [](variant<double, int> v) {
@@ -287,8 +288,11 @@ TEST_SUBMODULE(stl, m) {
     m.def("stl_pass_by_pointer", [](std::vector<int>* v) { return *v; }, "v"_a=nullptr);
 
     // #1258: pybind11/stl.h converts string to vector<string>
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("func_with_string_or_vector_string_arg_overload", [](std::vector<std::string>) { return 1; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("func_with_string_or_vector_string_arg_overload", [](std::list<std::string>) { return 2; });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("func_with_string_or_vector_string_arg_overload", [](std::string) { return 3; });
 
     class Placeholder {
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 685d64a7ca..51068f6380 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -17,7 +17,10 @@ class ExampleVirt  {
 public:
     ExampleVirt(int state) : state(state) { print_created(this, state); }
     ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
-    ExampleVirt(ExampleVirt &&e) : state(e.state) { print_move_created(this); e.state = 0; }
+    ExampleVirt(ExampleVirt &&e) noexcept : state(e.state) {
+        print_move_created(this);
+        e.state = 0;
+    }
     virtual ~ExampleVirt() { print_destroyed(this); }
 
     virtual int run(int value) {
@@ -100,7 +103,10 @@ class PyExampleVirt : public ExampleVirt {
 class NonCopyable {
 public:
     NonCopyable(int a, int b) : value{new int(a*b)} { print_created(this, a, b); }
-    NonCopyable(NonCopyable &&o) { value = std::move(o.value); print_move_created(this); }
+    NonCopyable(NonCopyable &&o) noexcept {
+        value = std::move(o.value);
+        print_move_created(this);
+    }
     NonCopyable(const NonCopyable &) = delete;
     NonCopyable() = delete;
     void operator=(const NonCopyable &) = delete;
@@ -120,7 +126,10 @@ class Movable {
 public:
     Movable(int a, int b) : value{a+b} { print_created(this, a, b); }
     Movable(const Movable &m) { value = m.value; print_copy_created(this); }
-    Movable(Movable &&m) { value = std::move(m.value); print_move_created(this); }
+    Movable(Movable &&m) noexcept {
+        value = m.value;
+        print_move_created(this);
+    }
     std::string get_value() const { return std::to_string(value); }
     ~Movable() { print_destroyed(this); }
 private:

From 484b0f04332fff15543d4c2a49c355d6942455fa Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 22 Jun 2021 15:12:58 -0700
Subject: [PATCH 038/638] Updating and slightly enhancing instructions for
 running clang-tidy. (#3055)

* Updating and slightly enhancing instructions for running clang-tidy.

* Making documented commands identical to workflow commands. Adding comment in workflow file pointing to documentation.
---
 .github/CONTRIBUTING.md      | 13 +++++++------
 .github/workflows/format.yml |  2 ++
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 08d9e7cb93..6f9ebf21f1 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -203,14 +203,15 @@ of the pybind11 repo.
 [`clang-tidy`][clang-tidy] performs deeper static code analyses and is
 more complex to run, compared to `clang-format`, but support for `clang-tidy`
 is built into the pybind11 CMake configuration. To run `clang-tidy`, the
-following recipe should work. Files will be modified in place, so you can
-use git to monitor the changes.
+following recipe should work. Run the `docker` command from the top-level
+directory inside your pybind11 git clone. Files will be modified in place,
+so you can use git to monitor the changes.
 
 ```bash
-docker run --rm -v $PWD:/pybind11 -it silkeh/clang:10
-apt-get update && apt-get install python3-dev python3-pytest
-cmake -S pybind11/ -B build -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);-fix"
-cmake --build build
+docker run --rm -v $PWD:/mounted_pybind11 -it silkeh/clang:12
+apt-get update && apt-get install -y python3-dev python3-pytest
+cmake -S /mounted_pybind11/ -B build -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);-fix" -DDOWNLOAD_EIGEN=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=17
+cmake --build build -j 2 -- --keep-going
 ```
 
 ### Include what you use
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 27f52932b7..ab7b40503a 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -25,6 +25,8 @@ jobs:
         extra_args: --hook-stage manual --all-files
 
   clang-tidy:
+    # When making changes here, please also review the "Clang-Tidy" section
+    # in .github/CONTRIBUTING.md and update as needed.
     name: Clang-Tidy
     runs-on: ubuntu-latest
     container: silkeh/clang:12

From 93e69191c1ad81ccde1b3dfd46bb69dccd8e45ce Mon Sep 17 00:00:00 2001
From: Cris Luengo <crisluengo@users.noreply.github.com>
Date: Fri, 25 Jun 2021 18:56:17 -0600
Subject: [PATCH 039/638] fix: enable py::implicitly_convertible<py::none, ...>
 for py::class_-wrapped types (#3059)

* Allow casting from None to a custom object, closes #2778

* ci.yml patch from the smart_holder branch for full CI coverage.
---
 .github/workflows/ci.yml                   | 26 +++++++++++-----------
 include/pybind11/detail/type_caster_base.h | 20 +++++++++++------
 tests/test_methods_and_attributes.cpp      | 18 +++++++++++++++
 tests/test_methods_and_attributes.py       | 11 +++++++++
 4 files changed, 55 insertions(+), 20 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e00745df7e..df7441b9e6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -100,7 +100,7 @@ jobs:
       run: >
         cmake -S . -B .
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_CATCH=OFF
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
         ${{ matrix.args }}
@@ -111,10 +111,10 @@ jobs:
     - name: Python tests C++11
       run: cmake --build . --target pytest -j 2
 
-    - name: C++11 tests
-      # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
-      run: cmake --build .  --target cpptest -j 2
+    #- name: C++11 tests
+    #  # TODO: Figure out how to load the DLL on Python 3.8+
+    #  if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
+    #  run: cmake --build .  --target cpptest -j 2
 
     - name: Interface test C++11
       run: cmake --build . --target test_cmake_build
@@ -127,7 +127,7 @@ jobs:
       run: >
         cmake -S . -B build2
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_CATCH=OFF
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         ${{ matrix.args }}
@@ -139,10 +139,10 @@ jobs:
     - name: Python tests
       run: cmake --build build2 --target pytest
 
-    - name: C++ tests
-      # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
-      run: cmake --build build2 --target cpptest
+    #- name: C++ tests
+    #  # TODO: Figure out how to load the DLL on Python 3.8+
+    #  if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
+    #  run: cmake --build build2 --target cpptest
 
     - name: Interface test
       run: cmake --build build2 --target test_cmake_build
@@ -754,7 +754,7 @@ jobs:
         cmake -S . -B build
         -G "Visual Studio 16 2019" -A Win32
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_CATCH=OFF
         -DDOWNLOAD_EIGEN=ON
         ${{ matrix.args }}
     - name: Build C++11
@@ -800,7 +800,7 @@ jobs:
         cmake -S . -B build
         -G "Visual Studio 14 2015" -A x64
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_CATCH=OFF
         -DDOWNLOAD_EIGEN=ON
 
     - name: Build C++14
@@ -849,7 +849,7 @@ jobs:
         cmake -S . -B build
         -G "Visual Studio 15 2017" -A x64
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_CATCH=OFF
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
         ${{ matrix.args }}
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 0dd9d48e55..a8d3938c7c 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -657,12 +657,6 @@ class type_caster_generic {
     PYBIND11_NOINLINE bool load_impl(handle src, bool convert) {
         if (!src) return false;
         if (!typeinfo) return try_load_foreign_module_local(src);
-        if (src.is_none()) {
-            // Defer accepting None to other overloads (if we aren't in convert mode):
-            if (!convert) return false;
-            value = nullptr;
-            return true;
-        }
 
         auto &this_ = static_cast<ThisT &>(*this);
         this_.check_holder_compat();
@@ -731,7 +725,19 @@ class type_caster_generic {
         }
 
         // Global typeinfo has precedence over foreign module_local
-        return try_load_foreign_module_local(src);
+        if (try_load_foreign_module_local(src)) {
+           return true;
+        }
+
+        // Custom converters didn't take None, now we convert None to nullptr.
+        if (src.is_none()) {
+           // Defer accepting None to other overloads (if we aren't in convert mode):
+           if (!convert) return false;
+           value = nullptr;
+           return true;
+        }
+
+        return false;
     }
 
 
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 3eb22b4a37..67ee117c6c 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -118,6 +118,14 @@ int none3(std::shared_ptr<NoneTester> &obj) { return obj ? obj->answer : -1; }
 int none4(std::shared_ptr<NoneTester> *obj) { return obj && *obj ? (*obj)->answer : -1; }
 int none5(const std::shared_ptr<NoneTester> &obj) { return obj ? obj->answer : -1; }
 
+// Issue #2778: implicit casting from None to object (not pointer)
+class NoneCastTester {
+public:
+    int answer = -1;
+    NoneCastTester() = default;
+    NoneCastTester(int v) : answer(v) {};
+};
+
 struct StrIssue {
     int val = -1;
 
@@ -354,6 +362,16 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     m.def("no_none_kwarg", &none2, "a"_a.none(false));
     m.def("no_none_kwarg_kw_only", &none2, py::kw_only(), "a"_a.none(false));
 
+    // test_casts_none
+    // Issue #2778: implicit casting from None to object (not pointer)
+    py::class_<NoneCastTester>(m, "NoneCastTester")
+          .def(py::init<>())
+          .def(py::init<int>())
+          .def(py::init([](py::none const&) { return NoneCastTester{}; }));
+    py::implicitly_convertible<py::none, NoneCastTester>();
+    m.def("ok_obj_or_none", [](NoneCastTester const& foo) { return foo.answer; });
+
+
     // test_str_issue
     // Issue #283: __str__ called on uninitialized instance when constructor arguments invalid
     py::class_<StrIssue>(m, "StrIssue")
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 2aaf9331fd..89b7225a97 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -431,6 +431,17 @@ def test_accepts_none(msg):
     assert "incompatible function arguments" in str(excinfo.value)
 
 
+def test_casts_none(msg):
+    """#2778: implicit casting from None to object (not pointer)"""
+    a = m.NoneCastTester()
+    assert m.ok_obj_or_none(a) == -1
+    a = m.NoneCastTester(4)
+    assert m.ok_obj_or_none(a) == 4
+    a = m.NoneCastTester(None)
+    assert m.ok_obj_or_none(a) == -1
+    assert m.ok_obj_or_none(None) == -1
+
+
 def test_str_issue(msg):
     """#283: __str__ called on uninitialized instance when constructor arguments invalid"""
 

From fbae8f313be887e0bf4b702fe551966efdc8cbc2 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 30 Jun 2021 12:34:32 -0700
Subject: [PATCH 040/638] pickle setstate: setattr __dict__ only if not empty
 (#2972)

* pickle setstate: setattr __dict__ only if not empty, to not force use of py::dynamic_attr() unnecessarily.

* Adding unit test.

* Clang 3.6 & 3.7 compatibility.

* PyPy compatibility.

* Minor iwyu fix, additional comment.

* Addressing reviewer requests.

* Applying clang-tidy suggested fixes.

* Adding check_dynamic_cast_SimpleCppDerived, related to issue #3062.
---
 include/pybind11/detail/init.h |  8 ++++-
 tests/test_pickling.cpp        | 56 ++++++++++++++++++++++++++++++++++
 tests/test_pickling.py         | 36 ++++++++++++++++++++++
 3 files changed, 99 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 3ef78c1179..3269e04254 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -293,7 +293,13 @@ template <typename Class, typename T, typename O,
           enable_if_t<std::is_convertible<O, handle>::value, int> = 0>
 void setstate(value_and_holder &v_h, std::pair<T, O> &&result, bool need_alias) {
     construct<Class>(v_h, std::move(result.first), need_alias);
-    setattr((PyObject *) v_h.inst, "__dict__", result.second);
+    auto d = handle(result.second);
+    if (PyDict_Check(d.ptr()) && PyDict_Size(d.ptr()) == 0) {
+        // Skipping setattr below, to not force use of py::dynamic_attr() for Class unnecessarily.
+        // See PR #2972 for details.
+        return;
+    }
+    setattr((PyObject *) v_h.inst, "__dict__", d);
 }
 
 /// Implementation for py::pickle(GetState, SetState)
diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index c2cee6c3c7..0d5827315f 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -1,7 +1,9 @@
+// clang-format off
 /*
     tests/test_pickling.cpp -- pickle support
 
     Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+    Copyright (c) 2021 The Pybind Development Team.
 
     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
@@ -9,6 +11,58 @@
 
 #include "pybind11_tests.h"
 
+// clang-format on
+
+#include <memory>
+#include <stdexcept>
+#include <utility>
+
+namespace exercise_trampoline {
+
+struct SimpleBase {
+    int num               = 0;
+    virtual ~SimpleBase() = default;
+
+    // For compatibility with old clang versions:
+    SimpleBase()                   = default;
+    SimpleBase(const SimpleBase &) = default;
+};
+
+struct SimpleBaseTrampoline : SimpleBase {};
+
+struct SimpleCppDerived : SimpleBase {};
+
+void wrap(py::module m) {
+    py::class_<SimpleBase, SimpleBaseTrampoline>(m, "SimpleBase")
+        .def(py::init<>())
+        .def_readwrite("num", &SimpleBase::num)
+        .def(py::pickle(
+            [](const py::object &self) {
+                py::dict d;
+                if (py::hasattr(self, "__dict__"))
+                    d = self.attr("__dict__");
+                return py::make_tuple(self.attr("num"), d);
+            },
+            [](const py::tuple &t) {
+                if (t.size() != 2)
+                    throw std::runtime_error("Invalid state!");
+                auto cpp_state = std::unique_ptr<SimpleBase>(new SimpleBaseTrampoline);
+                cpp_state->num = t[0].cast<int>();
+                auto py_state  = t[1].cast<py::dict>();
+                return std::make_pair(std::move(cpp_state), py_state);
+            }));
+
+    m.def("make_SimpleCppDerivedAsBase",
+          []() { return std::unique_ptr<SimpleBase>(new SimpleCppDerived); });
+    m.def("check_dynamic_cast_SimpleCppDerived", [](const SimpleBase *base_ptr) {
+        return dynamic_cast<const SimpleCppDerived *>(base_ptr) != nullptr;
+    });
+}
+
+} // namespace exercise_trampoline
+
+// clang-format off
+
 TEST_SUBMODULE(pickling, m) {
     // test_roundtrip
     class Pickleable {
@@ -130,4 +184,6 @@ TEST_SUBMODULE(pickling, m) {
                 return std::make_pair(cpp_state, py_state);
             }));
 #endif
+
+    exercise_trampoline::wrap(m);
 }
diff --git a/tests/test_pickling.py b/tests/test_pickling.py
index 6b27a73a57..303213068d 100644
--- a/tests/test_pickling.py
+++ b/tests/test_pickling.py
@@ -45,3 +45,39 @@ def test_enum_pickle():
 
     data = pickle.dumps(e.EOne, 2)
     assert e.EOne == pickle.loads(data)
+
+
+#
+# exercise_trampoline
+#
+class SimplePyDerived(m.SimpleBase):
+    pass
+
+
+def test_roundtrip_simple_py_derived():
+    p = SimplePyDerived()
+    p.num = 202
+    p.stored_in_dict = 303
+    data = pickle.dumps(p, pickle.HIGHEST_PROTOCOL)
+    p2 = pickle.loads(data)
+    assert isinstance(p2, SimplePyDerived)
+    assert p2.num == 202
+    assert p2.stored_in_dict == 303
+
+
+def test_roundtrip_simple_cpp_derived():
+    p = m.make_SimpleCppDerivedAsBase()
+    assert m.check_dynamic_cast_SimpleCppDerived(p)
+    p.num = 404
+    if not env.PYPY:
+        # To ensure that this unit test is not accidentally invalidated.
+        with pytest.raises(AttributeError):
+            # Mimics the `setstate` C++ implementation.
+            setattr(p, "__dict__", {})  # noqa: B010
+    data = pickle.dumps(p, pickle.HIGHEST_PROTOCOL)
+    p2 = pickle.loads(data)
+    assert isinstance(p2, m.SimpleBase)
+    assert p2.num == 404
+    # Issue #3062: pickleable base C++ classes can incur object slicing
+    #              if derived typeid is not registered with pybind11
+    assert not m.check_dynamic_cast_SimpleCppDerived(p2)

From cad79c1146c64ece40a9513dbffb4bb8ba93d561 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 30 Jun 2021 14:30:26 -0700
Subject: [PATCH 041/638] tests: remove very minor oversight in PR #3059.
 (#3066)

---
 tests/test_methods_and_attributes.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 89b7225a97..750ec02f89 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -431,7 +431,7 @@ def test_accepts_none(msg):
     assert "incompatible function arguments" in str(excinfo.value)
 
 
-def test_casts_none(msg):
+def test_casts_none():
     """#2778: implicit casting from None to object (not pointer)"""
     a = m.NoneCastTester()
     assert m.ok_obj_or_none(a) == -1

From 733f8de24feed964f96b639a0a44247f46bed868 Mon Sep 17 00:00:00 2001
From: jonathan-conder-sm
 <63538679+jonathan-conder-sm@users.noreply.github.com>
Date: Thu, 1 Jul 2021 17:19:14 +1200
Subject: [PATCH 042/638] Avoid string copy if possible when passing a Python
 object to std::ostream (#3042)

---
 include/pybind11/stl.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 61d3fba61e..ca20b7483b 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -380,7 +380,11 @@ struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> {
 PYBIND11_NAMESPACE_END(detail)
 
 inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
+#ifdef PYBIND11_HAS_STRING_VIEW
+    os << str(obj).cast<std::string_view>();
+#else
     os << (std::string) str(obj);
+#endif
     return os;
 }
 

From f067deb563d1073a7193b87d058fce37838ea5aa Mon Sep 17 00:00:00 2001
From: cyy <cyyever@outlook.com>
Date: Thu, 1 Jul 2021 14:35:25 +0800
Subject: [PATCH 043/638] avoid unnecessary strlen (#3058)

---
 include/pybind11/attr.h     | 2 +-
 include/pybind11/pybind11.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 50efdc7cec..97147904ce 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -377,7 +377,7 @@ template <> struct process_attribute<is_new_style_constructor> : process_attribu
 };
 
 inline void process_kw_only_arg(const arg &a, function_record *r) {
-    if (!a.name || strlen(a.name) == 0)
+    if (!a.name || a.name[0] == '\0')
         pybind11_fail("arg(): cannot specify an unnamed argument after an kw_only() annotation");
     ++r->nargs_kw_only;
 }
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 1fb0d1fa18..9938b0b716 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -470,7 +470,7 @@ class cpp_function : public function {
                 signatures += it->signature;
                 signatures += "\n";
             }
-            if (it->doc && strlen(it->doc) > 0 && options::show_user_defined_docstrings()) {
+            if (it->doc && it->doc[0] != '\0' && options::show_user_defined_docstrings()) {
                 // If we're appending another docstring, and aren't printing function signatures, we
                 // need to append a newline first:
                 if (!options::show_function_signatures()) {

From 5bcaaa0423c6757ca1c2738d0a54947dacdb03a1 Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Fri, 2 Jul 2021 16:00:50 +0200
Subject: [PATCH 044/638] Add a std::filesystem::path <-> os.PathLike caster.
 (#2730)

---
 docs/advanced/cast/overview.rst |  6 +++
 include/pybind11/stl.h          | 81 +++++++++++++++++++++++++++++++++
 tests/CMakeLists.txt            | 37 +++++++++++++++
 tests/test_stl.cpp              |  6 +++
 tests/test_stl.py               | 19 ++++++++
 5 files changed, 149 insertions(+)

diff --git a/docs/advanced/cast/overview.rst b/docs/advanced/cast/overview.rst
index b0e32a52f9..6341fce6d4 100644
--- a/docs/advanced/cast/overview.rst
+++ b/docs/advanced/cast/overview.rst
@@ -151,6 +151,8 @@ as arguments and return values, refer to the section on binding :ref:`classes`.
 +------------------------------------+---------------------------+-------------------------------+
 | ``std::variant<...>``              | Type-safe union (C++17)   | :file:`pybind11/stl.h`        |
 +------------------------------------+---------------------------+-------------------------------+
+| ``std::filesystem::path<T>``       | STL path (C++17) [#]_     | :file:`pybind11/stl.h`        |
++------------------------------------+---------------------------+-------------------------------+
 | ``std::function<...>``             | STL polymorphic function  | :file:`pybind11/functional.h` |
 +------------------------------------+---------------------------+-------------------------------+
 | ``std::chrono::duration<...>``     | STL time duration         | :file:`pybind11/chrono.h`     |
@@ -163,3 +165,7 @@ as arguments and return values, refer to the section on binding :ref:`classes`.
 +------------------------------------+---------------------------+-------------------------------+
 | ``Eigen::SparseMatrix<...>``       | Eigen: sparse matrix      | :file:`pybind11/eigen.h`      |
 +------------------------------------+---------------------------+-------------------------------+
+
+.. [#] ``std::filesystem::path`` is converted to ``pathlib.Path`` and
+   ``os.PathLike`` is converted to ``std::filesystem::path``, but this requires
+   Python 3.6 (for ``__fspath__`` support).
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index ca20b7483b..2350a5247f 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -41,11 +41,21 @@
 #    include <variant>
 #    define PYBIND11_HAS_VARIANT 1
 #  endif
+// std::filesystem::path
+#  if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
+      PY_VERSION_HEX >= 0x03060000
+#    include <filesystem>
+#    define PYBIND11_HAS_FILESYSTEM 1
+#  endif
 #elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
 #  include <optional>
 #  include <variant>
 #  define PYBIND11_HAS_OPTIONAL 1
 #  define PYBIND11_HAS_VARIANT 1
+#  if PY_VERSION_HEX >= 0x03060000
+#    include <filesystem>
+#    define PYBIND11_HAS_FILESYSTEM 1
+#  endif
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -377,6 +387,77 @@ template <typename... Ts>
 struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> { };
 #endif
 
+#if defined(PYBIND11_HAS_FILESYSTEM)
+template<typename T> struct path_caster {
+
+private:
+    static PyObject* unicode_from_fs_native(const std::string& w) {
+#if !defined(PYPY_VERSION)
+        return PyUnicode_DecodeFSDefaultAndSize(w.c_str(), ssize_t(w.size()));
+#else
+        // PyPy mistakenly declares the first parameter as non-const.
+        return PyUnicode_DecodeFSDefaultAndSize(
+            const_cast<char*>(w.c_str()), ssize_t(w.size()));
+#endif
+    }
+
+    static PyObject* unicode_from_fs_native(const std::wstring& w) {
+        return PyUnicode_FromWideChar(w.c_str(), ssize_t(w.size()));
+    }
+
+public:
+    static handle cast(const T& path, return_value_policy, handle) {
+        if (auto py_str = unicode_from_fs_native(path.native())) {
+            return module::import("pathlib").attr("Path")(reinterpret_steal<object>(py_str))
+                   .release();
+        }
+        return nullptr;
+    }
+
+    bool load(handle handle, bool) {
+        // PyUnicode_FSConverter and PyUnicode_FSDecoder normally take care of
+        // calling PyOS_FSPath themselves, but that's broken on PyPy (PyPy
+        // issue #3168) so we do it ourselves instead.
+        PyObject* buf = PyOS_FSPath(handle.ptr());
+        if (!buf) {
+            PyErr_Clear();
+            return false;
+        }
+        PyObject* native = nullptr;
+        if constexpr (std::is_same_v<typename T::value_type, char>) {
+            if (PyUnicode_FSConverter(buf, &native)) {
+                if (auto c_str = PyBytes_AsString(native)) {
+                    // AsString returns a pointer to the internal buffer, which
+                    // must not be free'd.
+                    value = c_str;
+                }
+            }
+        } else if constexpr (std::is_same_v<typename T::value_type, wchar_t>) {
+            if (PyUnicode_FSDecoder(buf, &native)) {
+                if (auto c_str = PyUnicode_AsWideCharString(native, nullptr)) {
+                    // AsWideCharString returns a new string that must be free'd.
+                    value = c_str;  // Copies the string.
+                    PyMem_Free(c_str);
+                }
+            }
+        }
+        Py_XDECREF(native);
+        Py_DECREF(buf);
+        if (PyErr_Occurred()) {
+            PyErr_Clear();
+            return false;
+        } else {
+            return true;
+        }
+    }
+
+    PYBIND11_TYPE_CASTER(T, _("os.PathLike"));
+};
+
+template<> struct type_caster<std::filesystem::path>
+    : public path_caster<std::filesystem::path> {};
+#endif
+
 PYBIND11_NAMESPACE_END(detail)
 
 inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 3d89404911..3729b5c7df 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -247,6 +247,41 @@ if(Boost_FOUND)
   endif()
 endif()
 
+# Check if we need to add -lstdc++fs or -lc++fs or nothing
+if(MSVC)
+  set(STD_FS_NO_LIB_NEEDED TRUE)
+else()
+  file(
+    WRITE ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
+    "#include <filesystem>\nint main(int argc, char ** argv) {\n  std::filesystem::path p(argv[0]);\n  return p.string().length();\n}"
+  )
+  try_compile(
+    STD_FS_NO_LIB_NEEDED ${CMAKE_CURRENT_BINARY_DIR}
+    SOURCES ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
+    COMPILE_DEFINITIONS -std=c++17)
+  try_compile(
+    STD_FS_NEEDS_STDCXXFS ${CMAKE_CURRENT_BINARY_DIR}
+    SOURCES ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
+    COMPILE_DEFINITIONS -std=c++17
+    LINK_LIBRARIES stdc++fs)
+  try_compile(
+    STD_FS_NEEDS_CXXFS ${CMAKE_CURRENT_BINARY_DIR}
+    SOURCES ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
+    COMPILE_DEFINITIONS -std=c++17
+    LINK_LIBRARIES c++fs)
+endif()
+
+if(${STD_FS_NEEDS_STDCXXFS})
+  set(STD_FS_LIB stdc++fs)
+elseif(${STD_FS_NEEDS_CXXFS})
+  set(STD_FS_LIB c++fs)
+elseif(${STD_FS_NO_LIB_NEEDED})
+  set(STD_FS_LIB "")
+else()
+  message(WARNING "Unknown compiler - not passing -lstdc++fs")
+  set(STD_FS_LIB "")
+endif()
+
 # Compile with compiler warnings turned on
 function(pybind11_enable_warnings target_name)
   if(MSVC)
@@ -357,6 +392,8 @@ foreach(target ${test_targets})
     target_compile_definitions(${target} PRIVATE -DPYBIND11_TEST_BOOST)
   endif()
 
+  target_link_libraries(${target} PRIVATE ${STD_FS_LIB})
+
   # Always write the output file directly into the 'tests' directory (even on MSVC)
   if(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
     set_target_properties(${target} PROPERTIES LIBRARY_OUTPUT_DIRECTORY
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 07899b84e0..7183c56b7a 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -238,6 +238,12 @@ TEST_SUBMODULE(stl, m) {
         .def("member_initialized", &opt_exp_holder::member_initialized);
 #endif
 
+#ifdef PYBIND11_HAS_FILESYSTEM
+    // test_fs_path
+    m.attr("has_filesystem") = true;
+    m.def("parent_path", [](const std::filesystem::path& p) { return p.parent_path(); });
+#endif
+
 #ifdef PYBIND11_HAS_VARIANT
     static_assert(std::is_same<py::detail::variant_caster_visitor::result_type, py::handle>::value,
                   "visitor::result_type is required by boost::variant in C++11 mode");
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 330017544d..96939257cf 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -162,6 +162,25 @@ def test_exp_optional():
     assert holder.member_initialized()
 
 
+@pytest.mark.skipif(not hasattr(m, "has_filesystem"), reason="no <filesystem>")
+def test_fs_path():
+    from pathlib import Path
+
+    class PseudoStrPath:
+        def __fspath__(self):
+            return "foo/bar"
+
+    class PseudoBytesPath:
+        def __fspath__(self):
+            return b"foo/bar"
+
+    assert m.parent_path(Path("foo/bar")) == Path("foo")
+    assert m.parent_path("foo/bar") == Path("foo")
+    assert m.parent_path(b"foo/bar") == Path("foo")
+    assert m.parent_path(PseudoStrPath()) == Path("foo")
+    assert m.parent_path(PseudoBytesPath()) == Path("foo")
+
+
 @pytest.mark.skipif(not hasattr(m, "load_variant"), reason="no <variant>")
 def test_variant(doc):
     assert m.load_variant(1) == "int"

From 6d4409466b6c7e6fa53e7b93cb05d78647c26313 Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Fri, 2 Jul 2021 10:02:33 -0400
Subject: [PATCH 045/638] Check dict item accesses where it isn't already
 checked (#2863)

* Convert PyDict_GetXXX to internal error checking variant

* Check unlikely error return from PyDict_DelItemString
---
 include/pybind11/pybind11.h | 10 ++++++----
 include/pybind11/pytypes.h  | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 9938b0b716..4d7bc5c73e 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -636,7 +636,7 @@ class cpp_function : public function {
                 bool bad_arg = false;
                 for (; args_copied < args_to_copy; ++args_copied) {
                     const argument_record *arg_rec = args_copied < func.args.size() ? &func.args[args_copied] : nullptr;
-                    if (kwargs_in && arg_rec && arg_rec->name && PyDict_GetItemString(kwargs_in, arg_rec->name)) {
+                    if (kwargs_in && arg_rec && arg_rec->name && dict_getitemstring(kwargs_in, arg_rec->name)) {
                         bad_arg = true;
                         break;
                     }
@@ -684,7 +684,7 @@ class cpp_function : public function {
 
                         handle value;
                         if (kwargs_in && arg_rec.name)
-                            value = PyDict_GetItemString(kwargs.ptr(), arg_rec.name);
+                            value = dict_getitemstring(kwargs.ptr(), arg_rec.name);
 
                         if (value) {
                             // Consume a kwargs value
@@ -692,7 +692,9 @@ class cpp_function : public function {
                                 kwargs = reinterpret_steal<dict>(PyDict_Copy(kwargs.ptr()));
                                 copied_kwargs = true;
                             }
-                            PyDict_DelItemString(kwargs.ptr(), arg_rec.name);
+                            if (PyDict_DelItemString(kwargs.ptr(), arg_rec.name) == -1) {
+                                throw error_already_set();
+                            }
                         } else if (arg_rec.value) {
                             value = arg_rec.value;
                         }
@@ -2139,7 +2141,7 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
     if (frame && (std::string) str(frame->f_code->co_name) == name &&
         frame->f_code->co_argcount > 0) {
         PyFrame_FastToLocals(frame);
-        PyObject *self_caller = PyDict_GetItem(
+        PyObject *self_caller = dict_getitem(
             frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
         if (self_caller == self.ptr())
             return function();
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index d1d92af6ad..80637fb980 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -485,6 +485,43 @@ inline handle get_function(handle value) {
     return value;
 }
 
+// Reimplementation of python's dict helper functions to ensure that exceptions
+// aren't swallowed (see #2862)
+
+// copied from cpython _PyDict_GetItemStringWithError
+inline PyObject * dict_getitemstring(PyObject *v, const char *key)
+{
+#if PY_MAJOR_VERSION >= 3
+    PyObject *kv, *rv;
+    kv = PyUnicode_FromString(key);
+    if (kv == NULL) {
+        throw error_already_set();
+    }
+
+    rv = PyDict_GetItemWithError(v, kv);
+    Py_DECREF(kv);
+    if (rv == NULL && PyErr_Occurred()) {
+        throw error_already_set();
+    }
+    return rv;
+#else
+    return PyDict_GetItemString(v, key);
+#endif
+}
+
+inline PyObject * dict_getitem(PyObject *v, PyObject *key)
+{
+#if PY_MAJOR_VERSION >= 3
+    PyObject *rv = PyDict_GetItemWithError(v, key);
+    if (rv == NULL && PyErr_Occurred()) {
+        throw error_already_set();
+    }
+    return rv;
+#else
+    return PyDict_GetItem(v, key);
+#endif
+}
+
 // Helper aliases/functions to support implicit casting of values given to python accessors/methods.
 // When given a pyobject, this simply returns the pyobject as-is; for other C++ type, the value goes
 // through pybind11::cast(obj) to convert it to an `object`.

From 795e3c4ce11dea3df7ef164c3faeef01026cb6c5 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 2 Jul 2021 14:14:18 -0700
Subject: [PATCH 046/638] Removing `AlignConsecutiveAssignments: true`. (#3067)

Also removing a commented-out line.
---
 .clang-format | 2 --
 1 file changed, 2 deletions(-)

diff --git a/.clang-format b/.clang-format
index 8700fca84d..8e0fd8b014 100644
--- a/.clang-format
+++ b/.clang-format
@@ -3,7 +3,6 @@
 # clang-format --style=llvm --dump-config
 BasedOnStyle: LLVM
 AccessModifierOffset: -4
-AlignConsecutiveAssignments: true
 AlwaysBreakTemplateDeclarations: Yes
 BinPackArguments: false
 BinPackParameters: false
@@ -15,7 +14,6 @@ IndentPPDirectives: AfterHash
 IndentWidth: 4
 Language: Cpp
 SpaceAfterCStyleCast: true
-# SpaceInEmptyBlock: true # too new
 Standard: Cpp11
 TabWidth: 4
 ...

From 8bee61b645da98c833166e85113f55a114319ceb Mon Sep 17 00:00:00 2001
From: luzpaz <luzpaz@users.noreply.github.com>
Date: Sun, 4 Jul 2021 19:58:35 -0400
Subject: [PATCH 047/638] docs: fix various typos (#3075)

Found via `codespell -q 3 -L nd,ot,thist`
---
 .github/workflows/ci.yml           | 2 +-
 docs/changelog.rst                 | 2 +-
 docs/compiling.rst                 | 2 +-
 docs/faq.rst                       | 2 +-
 docs/upgrade.rst                   | 2 +-
 include/pybind11/detail/class.h    | 2 +-
 pybind11/setup_helpers.py          | 2 +-
 tests/test_builtin_casters.py      | 2 +-
 tests/test_kwargs_and_defaults.cpp | 2 +-
 tests/test_numpy_vectorize.cpp     | 2 +-
 tests/valgrind-numpy-scipy.supp    | 2 +-
 11 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index df7441b9e6..2fa4303d9b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -384,7 +384,7 @@ jobs:
       run:  yum -y install https://developer.download.nvidia.com/hpc-sdk/20.9/nvhpc-20-9-20.9-1.x86_64.rpm https://developer.download.nvidia.com/hpc-sdk/20.9/nvhpc-2020-20.9-1.x86_64.rpm
 
     # On CentOS 7, we have to filter a few tests (compiler internal error)
-    # and allow deeper templete recursion (not needed on CentOS 8 with a newer
+    # and allow deeper template recursion (not needed on CentOS 8 with a newer
     # standard library). On some systems, you many need further workarounds:
     # https://github.com/pybind/pybind11/pull/2475
     - name: Configure
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 84f1352fb9..6787349e53 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -504,7 +504,7 @@ v2.4.0 (Sep 19, 2019)
   `#1888 <https://github.com/pybind/pybind11/pull/1888>`_.
 
 * ``py::details::overload_cast_impl`` is available in C++11 mode, can be used
-  like ``overload_cast`` with an additional set of parantheses.
+  like ``overload_cast`` with an additional set of parentheses.
   `#1581 <https://github.com/pybind/pybind11/pull/1581>`_.
 
 * Fixed ``get_include()`` on Conda.
diff --git a/docs/compiling.rst b/docs/compiling.rst
index 27f30e5a06..5d02727bad 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -93,7 +93,7 @@ to a memory dependent number.
 If you are developing rapidly and have a lot of C++ files, you may want to
 avoid rebuilding files that have not changed. For simple cases were you are
 using ``pip install -e .`` and do not have local headers, you can skip the
-rebuild if a object file is newer than it's source (headers are not checked!)
+rebuild if an object file is newer than its source (headers are not checked!)
 with the following:
 
 .. code-block:: python
diff --git a/docs/faq.rst b/docs/faq.rst
index 8c0b0f9fc2..56ded0329a 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -180,7 +180,7 @@ How can I create smaller binaries?
 
 To do its job, pybind11 extensively relies on a programming technique known as
 *template metaprogramming*, which is a way of performing computation at compile
-time using type information. Template metaprogamming usually instantiates code
+time using type information. Template metaprogramming usually instantiates code
 involving significant numbers of deeply nested types that are either completely
 removed or reduced to just a few instructions during the compiler's optimization
 phase. However, due to the nested nature of these types, the resulting symbol
diff --git a/docs/upgrade.rst b/docs/upgrade.rst
index 5691879c85..b2b6b12456 100644
--- a/docs/upgrade.rst
+++ b/docs/upgrade.rst
@@ -281,7 +281,7 @@ Within pybind11's CMake build system, ``pybind11_add_module`` has always been
 setting the ``-fvisibility=hidden`` flag in release mode. From now on, it's
 being applied unconditionally, even in debug mode and it can no longer be opted
 out of with the ``NO_EXTRAS`` option. The ``pybind11::module`` target now also
-adds this flag to it's interface. The ``pybind11::embed`` target is unchanged.
+adds this flag to its interface. The ``pybind11::embed`` target is unchanged.
 
 The most significant change here is for the ``pybind11::module`` target. If you
 were previously relying on default visibility, i.e. if your Python module was
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 2f414e5c7c..ca6854e7bf 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -329,7 +329,7 @@ inline bool deregister_instance(instance *self, void *valptr, const type_info *t
 inline PyObject *make_new_instance(PyTypeObject *type) {
 #if defined(PYPY_VERSION)
     // PyPy gets tp_basicsize wrong (issue 2482) under multiple inheritance when the first inherited
-    // object is a a plain Python type (i.e. not derived from an extension type).  Fix it.
+    // object is a plain Python type (i.e. not derived from an extension type).  Fix it.
     ssize_t instance_size = static_cast<ssize_t>(sizeof(instance));
     if (type->tp_basicsize < instance_size) {
         type->tp_basicsize = instance_size;
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 1050f61253..ec553d1669 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -85,7 +85,7 @@ class Pybind11Extension(_Extension):
     * ``stdlib=libc++`` on macOS
     * ``visibility=hidden`` and ``-g0`` on Unix
 
-    Finally, you can set ``cxx_std`` via constructor or afterwords to enable
+    Finally, you can set ``cxx_std`` via constructor or afterwards to enable
     flags for C++ std, and a few extra helper flags related to the C++ standard
     level. It is _highly_ recommended you either set this, or use the provided
     ``build_ext``, which will search for the highest supported extension for
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 5ee8603a6b..99c400c308 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -521,7 +521,7 @@ def test_void_caster_2():
 
 def test_const_ref_caster():
     """Verifies that const-ref is propagated through type_caster cast_op.
-    The returned ConstRefCasted type is a mimimal type that is constructed to
+    The returned ConstRefCasted type is a minimal type that is constructed to
     reference the casting mode used.
     """
     x = False
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index ab1c94c914..a349d43184 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -65,7 +65,7 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     #endif
     m.def("arg_refcount_h", [](py::handle h) { GC_IF_NEEDED; return h.ref_count(); });
     m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) { GC_IF_NEEDED; return h.ref_count(); });
-    // TODO replace the following nolints as appropiate
+    // TODO replace the following nolints as appropriate
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("arg_refcount_o", [](py::object o) { GC_IF_NEEDED; return o.ref_count(); });
     m.def("args_refcount", [](py::args a) {
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index 77e281bbdc..0be30d8e88 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -39,7 +39,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
 
     // test_type_selection
     // NumPy function which only accepts specific data types
-    // Alot of these no lints could be replaced with const refs, and probably should at some point.
+    // A lot of these no lints could be replaced with const refs, and probably should at some point.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("selective_func", [](py::array_t<int, py::array::c_style>) { return "Int branch taken."; });
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
diff --git a/tests/valgrind-numpy-scipy.supp b/tests/valgrind-numpy-scipy.supp
index 001b6c717a..16db302c17 100644
--- a/tests/valgrind-numpy-scipy.supp
+++ b/tests/valgrind-numpy-scipy.supp
@@ -2,7 +2,7 @@
 #
 # On updating a dependency, to get a list of "default" leaks in e.g. NumPy, run
 # `PYTHONMALLOC=malloc valgrind --leak-check=full --show-leak-kinds=definite,indirect python3.9-dbg -c "import numpy"`
-# To use theses suppression files, add e.g. `--suppressions=valgrind-numpy-scipy.supp`
+# To use these suppression files, add e.g. `--suppressions=valgrind-numpy-scipy.supp`
 
 {
    Leaks when importing NumPy

From 0ad116d3717a3a39b837b9053a6f9b051784454a Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 6 Jul 2021 14:10:35 -0700
Subject: [PATCH 048/638] Adding codespell to .pre-commit-config.yaml
 (follow-on to PR #3075). (#3076)

---
 .pre-commit-config.yaml | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 6781ac4f11..85d575464f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -81,6 +81,17 @@ repos:
     stages: [manual]
     additional_dependencies: [cmake, ninja]
 
+- repo: https://github.com/codespell-project/codespell
+  rev: v2.1.0
+  hooks:
+  - id: codespell
+    name: codespell
+    description: Checks for common misspellings in text files.
+    entry: codespell
+    language: python
+    types: [text]
+    args: ["-q", "3", "--skip", "*.supp", "-L", "nd,ot,thist,readded"]
+
 # The original pybind11 checks for a few C++ style items
 - repo: local
   hooks:

From c090c8c409feb6f7f89657b0677a46b3e2192493 Mon Sep 17 00:00:00 2001
From: Robert Haschke <rhaschke@users.noreply.github.com>
Date: Wed, 7 Jul 2021 00:13:13 +0200
Subject: [PATCH 049/638] Unify cast_error message thrown by
 [simple|unpacking]_collector (#3013)

* Unify cast_error message thrown by [simple|unpacking]_collector

simple_collector and unpacking_collector throw different error messages
when the casting of an argument failed: While the former mentions make_tuple(),
the latter emphasises the call argument (and its name/position).

* Consolidating "Unable to convert call argument" error reporting code to guarantee uniformity.

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/cast.h | 40 ++++++++++++++++++++++------------------
 tests/test_pytypes.py   |  6 +++---
 2 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 1ef1a9ce9b..4a219e2df3 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -958,6 +958,21 @@ template <> inline void cast_safe<void>(object &&) {}
 
 PYBIND11_NAMESPACE_END(detail)
 
+// The overloads could coexist, i.e. the #if is not strictly speaking needed,
+// but it is an easy minor optimization.
+#if defined(NDEBUG)
+inline cast_error cast_error_unable_to_convert_call_arg() {
+    return cast_error(
+        "Unable to convert call argument to Python object (compile in debug mode for details)");
+}
+#else
+inline cast_error cast_error_unable_to_convert_call_arg(const std::string &name,
+                                                        const std::string &type) {
+    return cast_error("Unable to convert call argument '" + name + "' of type '" + type
+                      + "' to Python object");
+}
+#endif
+
 template <return_value_policy policy = return_value_policy::automatic_reference>
 tuple make_tuple() { return tuple(0); }
 
@@ -971,11 +986,10 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
     for (size_t i = 0; i < args.size(); i++) {
         if (!args[i]) {
 #if defined(NDEBUG)
-            throw cast_error("make_tuple(): unable to convert arguments to Python object (compile in debug mode for details)");
+            throw cast_error_unable_to_convert_call_arg();
 #else
             std::array<std::string, size> argtypes { {type_id<Args>()...} };
-            throw cast_error("make_tuple(): unable to convert argument of type '" +
-                argtypes[i] + "' to Python object");
+            throw cast_error_unable_to_convert_call_arg(std::to_string(i), argtypes[i]);
 #endif
         }
     }
@@ -1230,9 +1244,10 @@ class unpacking_collector {
         auto o = reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
         if (!o) {
 #if defined(NDEBUG)
-            argument_cast_error();
+            throw cast_error_unable_to_convert_call_arg();
 #else
-            argument_cast_error(std::to_string(args_list.size()), type_id<T>());
+            throw cast_error_unable_to_convert_call_arg(
+                std::to_string(args_list.size()), type_id<T>());
 #endif
         }
         args_list.append(o);
@@ -1260,9 +1275,9 @@ class unpacking_collector {
         }
         if (!a.value) {
 #if defined(NDEBUG)
-            argument_cast_error();
+            throw cast_error_unable_to_convert_call_arg();
 #else
-            argument_cast_error(a.name, a.type);
+            throw cast_error_unable_to_convert_call_arg(a.name, a.type);
 #endif
         }
         m_kwargs[a.name] = a.value;
@@ -1301,17 +1316,6 @@ class unpacking_collector {
         throw type_error("Got multiple values for keyword argument '" + name + "'");
     }
 
-    [[noreturn]] static void argument_cast_error() {
-        throw cast_error("Unable to convert call argument to Python object "
-                         "(compile in debug mode for details)");
-    }
-
-    [[noreturn]] static void argument_cast_error(const std::string &name,
-                                                 const std::string &type) {
-        throw cast_error("Unable to convert call argument '" + name
-                         + "' of type '" + type + "' to Python object");
-    }
-
 private:
     tuple m_args;
     dict m_kwargs;
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index f17bf76b77..f234c77315 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -372,10 +372,10 @@ def test_print(capture):
 
     with pytest.raises(RuntimeError) as excinfo:
         m.print_failure()
-    assert str(excinfo.value) == "make_tuple(): unable to convert " + (
-        "argument of type 'UnregisteredType' to Python object"
+    assert str(excinfo.value) == "Unable to convert call argument " + (
+        "'1' of type 'UnregisteredType' to Python object"
         if debug_enabled
-        else "arguments to Python object (compile in debug mode for details)"
+        else "to Python object (compile in debug mode for details)"
     )
 
 

From 6d1b197b4669c70da94c8efb516374e1935d3ea3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 8 Jul 2021 09:02:48 -0700
Subject: [PATCH 050/638] Splitting out pybind11/stl/filesystem.h. (#3077)

* Splitting out pybind11/stl/filesystem.h.

To solve breakages like: https://github.com/deepmind/open_spiel/runs/2999582108

Mostly following the suggestion here: https://github.com/pybind/pybind11/pull/2730#issuecomment-750507575

Except using pybind11/stl/filesystem.h instead of pybind11/stlfs.h, as decided via chat.

stl.h restored to the exact state before merging PR #2730 via:
```
git checkout 733f8de24feed964f96b639a0a44247f46bed868 stl.h
```

* Properly including new stl subdirectory in pip wheel config.

This now passes interactively:
```
pytest tests/extra_python_package/
```

* iwyu cleanup.

iwyuh.py -c -std=c++17 -DPYBIND11_TEST_BOOST -Ipybind11/include -I/usr/include/python3.9 -I/usr/include/eigen3 include/pybind11/stl/filesystem.h

* Adding PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL.

* Eliminating else after return.
---
 CMakeLists.txt                           |   3 +-
 include/pybind11/stl.h                   |  81 ------------------
 include/pybind11/stl/filesystem.h        | 103 +++++++++++++++++++++++
 tests/extra_python_package/test_files.py |   7 +-
 tests/test_stl.cpp                       |   5 ++
 tools/setup_global.py.in                 |   4 +-
 tools/setup_main.py.in                   |   2 +
 7 files changed, 121 insertions(+), 84 deletions(-)
 create mode 100644 include/pybind11/stl/filesystem.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 152763eb42..c988ea0b50 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -125,7 +125,8 @@ set(PYBIND11_HEADERS
     include/pybind11/pybind11.h
     include/pybind11/pytypes.h
     include/pybind11/stl.h
-    include/pybind11/stl_bind.h)
+    include/pybind11/stl_bind.h
+    include/pybind11/stl/filesystem.h)
 
 # Compare with grep and warn if mismatched
 if(PYBIND11_MASTER_PROJECT AND NOT CMAKE_VERSION VERSION_LESS 3.12)
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 2350a5247f..ca20b7483b 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -41,21 +41,11 @@
 #    include <variant>
 #    define PYBIND11_HAS_VARIANT 1
 #  endif
-// std::filesystem::path
-#  if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
-      PY_VERSION_HEX >= 0x03060000
-#    include <filesystem>
-#    define PYBIND11_HAS_FILESYSTEM 1
-#  endif
 #elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
 #  include <optional>
 #  include <variant>
 #  define PYBIND11_HAS_OPTIONAL 1
 #  define PYBIND11_HAS_VARIANT 1
-#  if PY_VERSION_HEX >= 0x03060000
-#    include <filesystem>
-#    define PYBIND11_HAS_FILESYSTEM 1
-#  endif
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -387,77 +377,6 @@ template <typename... Ts>
 struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> { };
 #endif
 
-#if defined(PYBIND11_HAS_FILESYSTEM)
-template<typename T> struct path_caster {
-
-private:
-    static PyObject* unicode_from_fs_native(const std::string& w) {
-#if !defined(PYPY_VERSION)
-        return PyUnicode_DecodeFSDefaultAndSize(w.c_str(), ssize_t(w.size()));
-#else
-        // PyPy mistakenly declares the first parameter as non-const.
-        return PyUnicode_DecodeFSDefaultAndSize(
-            const_cast<char*>(w.c_str()), ssize_t(w.size()));
-#endif
-    }
-
-    static PyObject* unicode_from_fs_native(const std::wstring& w) {
-        return PyUnicode_FromWideChar(w.c_str(), ssize_t(w.size()));
-    }
-
-public:
-    static handle cast(const T& path, return_value_policy, handle) {
-        if (auto py_str = unicode_from_fs_native(path.native())) {
-            return module::import("pathlib").attr("Path")(reinterpret_steal<object>(py_str))
-                   .release();
-        }
-        return nullptr;
-    }
-
-    bool load(handle handle, bool) {
-        // PyUnicode_FSConverter and PyUnicode_FSDecoder normally take care of
-        // calling PyOS_FSPath themselves, but that's broken on PyPy (PyPy
-        // issue #3168) so we do it ourselves instead.
-        PyObject* buf = PyOS_FSPath(handle.ptr());
-        if (!buf) {
-            PyErr_Clear();
-            return false;
-        }
-        PyObject* native = nullptr;
-        if constexpr (std::is_same_v<typename T::value_type, char>) {
-            if (PyUnicode_FSConverter(buf, &native)) {
-                if (auto c_str = PyBytes_AsString(native)) {
-                    // AsString returns a pointer to the internal buffer, which
-                    // must not be free'd.
-                    value = c_str;
-                }
-            }
-        } else if constexpr (std::is_same_v<typename T::value_type, wchar_t>) {
-            if (PyUnicode_FSDecoder(buf, &native)) {
-                if (auto c_str = PyUnicode_AsWideCharString(native, nullptr)) {
-                    // AsWideCharString returns a new string that must be free'd.
-                    value = c_str;  // Copies the string.
-                    PyMem_Free(c_str);
-                }
-            }
-        }
-        Py_XDECREF(native);
-        Py_DECREF(buf);
-        if (PyErr_Occurred()) {
-            PyErr_Clear();
-            return false;
-        } else {
-            return true;
-        }
-    }
-
-    PYBIND11_TYPE_CASTER(T, _("os.PathLike"));
-};
-
-template<> struct type_caster<std::filesystem::path>
-    : public path_caster<std::filesystem::path> {};
-#endif
-
 PYBIND11_NAMESPACE_END(detail)
 
 inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
new file mode 100644
index 0000000000..7a8acdb60b
--- /dev/null
+++ b/include/pybind11/stl/filesystem.h
@@ -0,0 +1,103 @@
+// Copyright (c) 2021 The Pybind Development Team.
+// All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#pragma once
+
+#include "../cast.h"
+#include "../pybind11.h"
+#include "../pytypes.h"
+
+#include "../detail/common.h"
+#include "../detail/descr.h"
+
+#include <string>
+
+#ifdef __has_include
+#  if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
+      PY_VERSION_HEX >= 0x03060000
+#    include <filesystem>
+#    define PYBIND11_HAS_FILESYSTEM 1
+#  endif
+#endif
+
+#if !defined(PYBIND11_HAS_FILESYSTEM) && !defined(PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL)
+#    error                                                                                        \
+        "#include <filesystem> is not available. (Use -DPYBIND11_HAS_FILESYSTEM_IS_OPTIONAL to ignore.)"
+#endif
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+#if defined(PYBIND11_HAS_FILESYSTEM)
+template<typename T> struct path_caster {
+
+private:
+    static PyObject* unicode_from_fs_native(const std::string& w) {
+#if !defined(PYPY_VERSION)
+        return PyUnicode_DecodeFSDefaultAndSize(w.c_str(), ssize_t(w.size()));
+#else
+        // PyPy mistakenly declares the first parameter as non-const.
+        return PyUnicode_DecodeFSDefaultAndSize(
+            const_cast<char*>(w.c_str()), ssize_t(w.size()));
+#endif
+    }
+
+    static PyObject* unicode_from_fs_native(const std::wstring& w) {
+        return PyUnicode_FromWideChar(w.c_str(), ssize_t(w.size()));
+    }
+
+public:
+    static handle cast(const T& path, return_value_policy, handle) {
+        if (auto py_str = unicode_from_fs_native(path.native())) {
+            return module_::import("pathlib").attr("Path")(reinterpret_steal<object>(py_str))
+                   .release();
+        }
+        return nullptr;
+    }
+
+    bool load(handle handle, bool) {
+        // PyUnicode_FSConverter and PyUnicode_FSDecoder normally take care of
+        // calling PyOS_FSPath themselves, but that's broken on PyPy (PyPy
+        // issue #3168) so we do it ourselves instead.
+        PyObject* buf = PyOS_FSPath(handle.ptr());
+        if (!buf) {
+            PyErr_Clear();
+            return false;
+        }
+        PyObject* native = nullptr;
+        if constexpr (std::is_same_v<typename T::value_type, char>) {
+            if (PyUnicode_FSConverter(buf, &native)) {
+                if (auto c_str = PyBytes_AsString(native)) {
+                    // AsString returns a pointer to the internal buffer, which
+                    // must not be free'd.
+                    value = c_str;
+                }
+            }
+        } else if constexpr (std::is_same_v<typename T::value_type, wchar_t>) {
+            if (PyUnicode_FSDecoder(buf, &native)) {
+                if (auto c_str = PyUnicode_AsWideCharString(native, nullptr)) {
+                    // AsWideCharString returns a new string that must be free'd.
+                    value = c_str;  // Copies the string.
+                    PyMem_Free(c_str);
+                }
+            }
+        }
+        Py_XDECREF(native);
+        Py_DECREF(buf);
+        if (PyErr_Occurred()) {
+            PyErr_Clear();
+            return false;
+        }
+        return true;
+    }
+
+    PYBIND11_TYPE_CASTER(T, _("os.PathLike"));
+};
+
+template<> struct type_caster<std::filesystem::path>
+    : public path_caster<std::filesystem::path> {};
+#endif // PYBIND11_HAS_FILESYSTEM
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 064a3e12fe..c1d12ed76b 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -46,6 +46,10 @@
     "include/pybind11/detail/typeid.h",
 }
 
+stl_headers = {
+    "include/pybind11/stl/filesystem.h",
+}
+
 cmake_files = {
     "share/cmake/pybind11/FindPythonLibsNew.cmake",
     "share/cmake/pybind11/pybind11Common.cmake",
@@ -67,7 +71,7 @@
     "setup_helpers.pyi",
 }
 
-headers = main_headers | detail_headers
+headers = main_headers | detail_headers | stl_headers
 src_files = headers | cmake_files
 all_files = src_files | py_files
 
@@ -77,6 +81,7 @@
     "pybind11/include",
     "pybind11/include/pybind11",
     "pybind11/include/pybind11/detail",
+    "pybind11/include/pybind11/stl",
     "pybind11/share",
     "pybind11/share/cmake",
     "pybind11/share/cmake/pybind11",
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 7183c56b7a..dc75762e85 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -11,6 +11,11 @@
 #include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#ifndef PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
+#define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
+#endif
+#include <pybind11/stl/filesystem.h>
+
 #include <vector>
 #include <string>
 
diff --git a/tools/setup_global.py.in b/tools/setup_global.py.in
index 4cf040b2d8..8b7e538714 100644
--- a/tools/setup_global.py.in
+++ b/tools/setup_global.py.in
@@ -33,8 +33,9 @@ class InstallHeadersNested(install_headers):
 
 main_headers = glob.glob("pybind11/include/pybind11/*.h")
 detail_headers = glob.glob("pybind11/include/pybind11/detail/*.h")
+stl_headers = glob.glob("pybind11/include/pybind11/stl/*.h")
 cmake_files = glob.glob("pybind11/share/cmake/pybind11/*.cmake")
-headers = main_headers + detail_headers
+headers = main_headers + detail_headers + stl_headers
 
 cmdclass = {"install_headers": InstallHeadersNested}
 $extra_cmd
@@ -58,6 +59,7 @@ setup(
         (base + "share/cmake/pybind11", cmake_files),
         (base + "include/pybind11", main_headers),
         (base + "include/pybind11/detail", detail_headers),
+        (base + "include/pybind11/stl", stl_headers),
     ],
     cmdclass=cmdclass,
 )
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index 2231a08fdc..bcd4ef4aeb 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -16,12 +16,14 @@ setup(
         "pybind11",
         "pybind11.include.pybind11",
         "pybind11.include.pybind11.detail",
+        "pybind11.include.pybind11.stl",
         "pybind11.share.cmake.pybind11",
     ],
     package_data={
         "pybind11": ["py.typed", "*.pyi"],
         "pybind11.include.pybind11": ["*.h"],
         "pybind11.include.pybind11.detail": ["*.h"],
+        "pybind11.include.pybind11.stl": ["*.h"],
         "pybind11.share.cmake.pybind11": ["*.cmake"],
     },
     extras_require={

From b5357d1fa8e91ddbfbc2ad057b9a1ccb74becbba Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 9 Jul 2021 09:45:53 -0400
Subject: [PATCH 051/638] fix(clang-tidy): Enable clang-tidy else-after-return
 and redundant void checks (#3080)

* Enable clang-tidy else-after-return and redundant void checks

* Fix remaining else-after

* Address reviewer comments

* Fix indentation

* Rerun clang-tidy post merge
---
 .clang-tidy                                |  3 +
 include/pybind11/cast.h                    | 85 ++++++++++++----------
 include/pybind11/chrono.h                  |  4 +-
 include/pybind11/detail/class.h            |  4 +-
 include/pybind11/detail/type_caster_base.h |  4 +-
 include/pybind11/eigen.h                   |  9 +--
 include/pybind11/functional.h              |  3 +-
 include/pybind11/numpy.h                   |  6 +-
 include/pybind11/pybind11.h                | 45 ++++++------
 include/pybind11/pytypes.h                 | 21 ++----
 include/pybind11/stl.h                     |  3 +-
 include/pybind11/stl_bind.h                | 13 ++--
 tests/test_callbacks.cpp                   |  9 ++-
 tests/test_class.cpp                       |  3 +-
 tests/test_copy_move.cpp                   |  3 +-
 tests/test_pytypes.cpp                     | 10 +--
 tests/test_virtual_functions.cpp           |  4 +-
 17 files changed, 114 insertions(+), 115 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 22a736208c..ea50bf39bc 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,11 +1,13 @@
 FormatStyle: file
 
 Checks: '
+clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,
 misc-static-assert,
 misc-uniqueptr-reset-release,
 modernize-avoid-bind,
+modernize-redundant-void-arg,
 modernize-replace-auto-ptr,
 modernize-replace-disallow-copy-and-assign-macro,
 modernize-shrink-to-fit,
@@ -20,6 +22,7 @@ modernize-use-override,
 modernize-use-using,
 *performance*,
 readability-container-size-empty,
+readability-else-after-return,
 readability-make-member-function-const,
 readability-redundant-function-ptr-dereference,
 readability-redundant-smartptr-get,
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 4a219e2df3..a748c77c0f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -85,25 +85,28 @@ template <typename type> class type_caster<std::reference_wrapper<type>> {
     operator std::reference_wrapper<type>() { return cast_op<type &>(subcaster); }
 };
 
-#define PYBIND11_TYPE_CASTER(type, py_name) \
-    protected: \
-        type value; \
-    public: \
-        static constexpr auto name = py_name; \
-        template <typename T_, enable_if_t<std::is_same<type, remove_cv_t<T_>>::value, int> = 0> \
-        static handle cast(T_ *src, return_value_policy policy, handle parent) { \
-            if (!src) return none().release(); \
-            if (policy == return_value_policy::take_ownership) { \
-                auto h = cast(std::move(*src), policy, parent); delete src; return h; \
-            } else { \
-                return cast(*src, policy, parent); \
-            } \
-        } \
-        operator type*() { return &value; } \
-        operator type&() { return value; } \
-        operator type&&() && { return std::move(value); } \
-        template <typename T_> using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
-
+#define PYBIND11_TYPE_CASTER(type, py_name)                                                       \
+protected:                                                                                        \
+    type value;                                                                                   \
+                                                                                                  \
+public:                                                                                           \
+    static constexpr auto name = py_name;                                                         \
+    template <typename T_, enable_if_t<std::is_same<type, remove_cv_t<T_>>::value, int> = 0>      \
+    static handle cast(T_ *src, return_value_policy policy, handle parent) {                      \
+        if (!src)                                                                                 \
+            return none().release();                                                              \
+        if (policy == return_value_policy::take_ownership) {                                      \
+            auto h = cast(std::move(*src), policy, parent);                                       \
+            delete src;                                                                           \
+            return h;                                                                             \
+        }                                                                                         \
+        return cast(*src, policy, parent);                                                        \
+    }                                                                                             \
+    operator type *() { return &value; }                                                          \
+    operator type &() { return value; }                                                           \
+    operator type &&() && { return std::move(value); }                                            \
+    template <typename T_>                                                                        \
+    using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
 
 template <typename CharT> using is_std_char_type = any_of<
     std::is_same<CharT, char>, /* std::string */
@@ -247,7 +250,8 @@ template <> class type_caster<void> : public type_caster<void_type> {
     bool load(handle h, bool) {
         if (!h) {
             return false;
-        } else if (h.is_none()) {
+        }
+        if (h.is_none()) {
             value = nullptr;
             return true;
         }
@@ -272,8 +276,7 @@ template <> class type_caster<void> : public type_caster<void_type> {
     static handle cast(const void *ptr, return_value_policy /* policy */, handle /* parent */) {
         if (ptr)
             return capsule(ptr).release();
-        else
-            return none().inc_ref();
+        return none().inc_ref();
     }
 
     template <typename T> using cast_op_type = void*&;
@@ -289,9 +292,15 @@ template <> class type_caster<bool> {
 public:
     bool load(handle src, bool convert) {
         if (!src) return false;
-        else if (src.ptr() == Py_True) { value = true; return true; }
-        else if (src.ptr() == Py_False) { value = false; return true; }
-        else if (convert || !std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name)) {
+        if (src.ptr() == Py_True) {
+            value = true;
+            return true;
+        }
+        if (src.ptr() == Py_False) {
+            value = false;
+            return true;
+        }
+        if (convert || !std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name)) {
             // (allow non-implicit conversion for numpy booleans)
 
             Py_ssize_t res = -1;
@@ -315,9 +324,8 @@ template <> class type_caster<bool> {
             if (res == 0 || res == 1) {
                 value = (bool) res;
                 return true;
-            } else {
-                PyErr_Clear();
             }
+            PyErr_Clear();
         }
         return false;
     }
@@ -351,7 +359,8 @@ template <typename StringType, bool IsView = false> struct string_caster {
         handle load_src = src;
         if (!src) {
             return false;
-        } else if (!PyUnicode_Check(load_src.ptr())) {
+        }
+        if (!PyUnicode_Check(load_src.ptr())) {
 #if PY_MAJOR_VERSION >= 3
             return load_bytes(load_src);
 #else
@@ -554,10 +563,11 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     static handle cast(T *src, return_value_policy policy, handle parent) {
         if (!src) return none().release();
         if (policy == return_value_policy::take_ownership) {
-            auto h = cast(std::move(*src), policy, parent); delete src; return h;
-        } else {
-            return cast(*src, policy, parent);
+            auto h = cast(std::move(*src), policy, parent);
+            delete src;
+            return h;
         }
+        return cast(*src, policy, parent);
     }
 
     static constexpr auto name = _("Tuple[") + concat(make_caster<Ts>::name...) + _("]");
@@ -664,14 +674,14 @@ struct copyable_holder_caster : public type_caster_base<type> {
             value = v_h.value_ptr();
             holder = v_h.template holder<holder_type>();
             return true;
-        } else {
-            throw cast_error("Unable to cast from non-held to held instance (T& to Holder<T>) "
+        }
+        throw cast_error("Unable to cast from non-held to held instance (T& to Holder<T>) "
 #if defined(NDEBUG)
-                             "(compile in debug mode for type information)");
+                         "(compile in debug mode for type information)");
 #else
-                             "of type '" + type_id<holder_type>() + "''");
+                         "of type '"
+                         + type_id<holder_type>() + "''");
 #endif
-        }
     }
 
     template <typename T = holder_type, detail::enable_if_t<!std::is_constructible<T, const T &, type*>::value, int> = 0>
@@ -917,8 +927,7 @@ template <typename T> detail::enable_if_t<detail::move_always<T>::value, T> cast
 template <typename T> detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
     if (object.ref_count() > 1)
         return cast<T>(object);
-    else
-        return move<T>(std::move(object));
+    return move<T>(std::move(object));
 }
 template <typename T> detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
     return cast<T>(object);
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index 317afd1837..d32b5b0569 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -53,11 +53,11 @@ template <typename type> class duration_caster {
             return true;
         }
         // If invoked with a float we assume it is seconds and convert
-        else if (PyFloat_Check(src.ptr())) {
+        if (PyFloat_Check(src.ptr())) {
             value = type(duration_cast<duration<rep, period>>(duration<double>(PyFloat_AsDouble(src.ptr()))));
             return true;
         }
-        else return false;
+        return false;
     }
 
     // If this is a duration just return it back
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index ca6854e7bf..5fee3318b0 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -162,9 +162,7 @@ extern "C" inline PyObject *pybind11_meta_getattro(PyObject *obj, PyObject *name
         Py_INCREF(descr);
         return descr;
     }
-    else {
-        return PyType_Type.tp_getattro(obj, name);
-    }
+    return PyType_Type.tp_getattro(obj, name);
 }
 #endif
 
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a8d3938c7c..451690dc73 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -670,7 +670,7 @@ class type_caster_generic {
             return true;
         }
         // Case 2: We have a derived class
-        else if (PyType_IsSubtype(srctype, typeinfo->type)) {
+        if (PyType_IsSubtype(srctype, typeinfo->type)) {
             auto &bases = all_type_info(srctype);
             bool no_cpp_mi = typeinfo->simple_type;
 
@@ -687,7 +687,7 @@ class type_caster_generic {
             // Case 2b: the python type inherits from multiple C++ bases.  Check the bases to see if
             // we can find an exact match (or, for a simple C++ type, an inherited match); if so, we
             // can safely reinterpret_cast to the relevant pointer.
-            else if (bases.size() > 1) {
+            if (bases.size() > 1) {
                 for (auto base : bases) {
                     if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type) : base->type == typeinfo->type) {
                         this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base));
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index e8c6f63391..218fe27034 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -169,21 +169,18 @@ template <typename Type_> struct EigenProps {
                 return false; // Vector size mismatch
             return {rows == 1 ? 1 : n, cols == 1 ? 1 : n, stride};
         }
-        else if (fixed) {
+        if (fixed) {
             // The type has a fixed size, but is not a vector: abort
             return false;
         }
-        else if (fixed_cols) {
+        if (fixed_cols) {
             // Since this isn't a vector, cols must be != 1.  We allow this only if it exactly
             // equals the number of elements (rows is Dynamic, and so 1 row is allowed).
             if (cols != n) return false;
             return {1, n, stride};
-        }
-        else {
-            // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
+        } // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
             if (fixed_rows && rows != n) return false;
             return {n, 1, stride};
-        }
     }
 
     static constexpr bool show_writeable = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index aee9be4e45..cc7099c6a3 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -98,8 +98,7 @@ struct type_caster<std::function<Return(Args...)>> {
         auto result = f_.template target<function_type>();
         if (result)
             return cpp_function(*result, policy).release();
-        else
-            return cpp_function(std::forward<Func>(f_), policy).release();
+        return cpp_function(std::forward<Func>(f_), policy).release();
     }
 
     PYBIND11_TYPE_CASTER(type, _("Callable[[") + concat(make_caster<Args>::name...) + _("], ")
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index fdb7a9794b..edba8bac92 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1340,9 +1340,8 @@ template <size_t N> class multi_array_iterator {
             if (++m_index[i] != m_shape[i]) {
                 increment_common_iterator(i);
                 break;
-            } else {
-                m_index[i] = 0;
             }
+            m_index[i] = 0;
         }
         return *this;
     }
@@ -1493,8 +1492,7 @@ struct vectorize_returned_array {
     static Type create(broadcast_trivial trivial, const std::vector<ssize_t> &shape) {
         if (trivial == broadcast_trivial::f_trivial)
             return array_t<Return, array::f_style>(shape);
-        else
-            return array_t<Return>(shape);
+        return array_t<Return>(shape);
     }
 
     static Return *mutable_data(Type &array) {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 4d7bc5c73e..616fa70255 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -396,7 +396,7 @@ class cpp_function : public function {
             std::memset(rec->def, 0, sizeof(PyMethodDef));
             rec->def->ml_name = rec->name;
             rec->def->ml_meth
-                = reinterpret_cast<PyCFunction>(reinterpret_cast<void (*)(void)>(dispatcher));
+                = reinterpret_cast<PyCFunction>(reinterpret_cast<void (*)()>(dispatcher));
             rec->def->ml_flags = METH_VARARGS | METH_KEYWORDS;
 
             capsule rec_capsule(unique_rec.release(), [](void *ptr) {
@@ -924,20 +924,20 @@ class cpp_function : public function {
             append_note_if_missing_header_is_suspected(msg);
             PyErr_SetString(PyExc_TypeError, msg.c_str());
             return nullptr;
-        } else if (!result) {
+        }
+        if (!result) {
             std::string msg = "Unable to convert function return value to a "
                               "Python type! The signature was\n\t";
             msg += it->signature;
             append_note_if_missing_header_is_suspected(msg);
             PyErr_SetString(PyExc_TypeError, msg.c_str());
             return nullptr;
-        } else {
-            if (overloads->is_constructor && !self_value_and_holder.holder_constructed()) {
-                auto *pi = reinterpret_cast<instance *>(parent.ptr());
-                self_value_and_holder.type->init_instance(pi, nullptr);
-            }
-            return result.ptr();
         }
+        if (overloads->is_constructor && !self_value_and_holder.holder_constructed()) {
+            auto *pi = reinterpret_cast<instance *>(parent.ptr());
+            self_value_and_holder.type->init_instance(pi, nullptr);
+        }
+        return result.ptr();
     }
 };
 
@@ -1860,9 +1860,9 @@ PYBIND11_NOINLINE inline void keep_alive_impl(size_t Nurse, size_t Patient, func
     auto get_arg = [&](size_t n) {
         if (n == 0)
             return ret;
-        else if (n == 1 && call.init_self)
+        if (n == 1 && call.init_self)
             return call.init_self;
-        else if (n <= call.args.size())
+        if (n <= call.args.size())
             return call.args[n - 1];
         return handle();
     };
@@ -2186,18 +2186,19 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
     return tinfo ? detail::get_type_override(this_ptr, tinfo, name) : function();
 }
 
-#define PYBIND11_OVERRIDE_IMPL(ret_type, cname, name, ...) \
-    do { \
-        pybind11::gil_scoped_acquire gil; \
-        pybind11::function override = pybind11::get_override(static_cast<const cname *>(this), name); \
-        if (override) { \
-            auto o = override(__VA_ARGS__); \
-            if (pybind11::detail::cast_is_temporary_value_reference<ret_type>::value) { \
-                static pybind11::detail::override_caster_t<ret_type> caster; \
-                return pybind11::detail::cast_ref<ret_type>(std::move(o), caster); \
-            } \
-            else return pybind11::detail::cast_safe<ret_type>(std::move(o)); \
-        } \
+#define PYBIND11_OVERRIDE_IMPL(ret_type, cname, name, ...)                                        \
+    do {                                                                                          \
+        pybind11::gil_scoped_acquire gil;                                                         \
+        pybind11::function override                                                               \
+            = pybind11::get_override(static_cast<const cname *>(this), name);                     \
+        if (override) {                                                                           \
+            auto o = override(__VA_ARGS__);                                                       \
+            if (pybind11::detail::cast_is_temporary_value_reference<ret_type>::value) {           \
+                static pybind11::detail::override_caster_t<ret_type> caster;                      \
+                return pybind11::detail::cast_ref<ret_type>(std::move(o), caster);                \
+            }                                                                                     \
+            return pybind11::detail::cast_safe<ret_type>(std::move(o));                           \
+        }                                                                                         \
     } while (false)
 
 /** \rst
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 80637fb980..fb9680dfa1 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -440,19 +440,17 @@ inline object getattr(handle obj, const char *name) {
 inline object getattr(handle obj, handle name, handle default_) {
     if (PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr())) {
         return reinterpret_steal<object>(result);
-    } else {
-        PyErr_Clear();
-        return reinterpret_borrow<object>(default_);
     }
+    PyErr_Clear();
+    return reinterpret_borrow<object>(default_);
 }
 
 inline object getattr(handle obj, const char *name, handle default_) {
     if (PyObject *result = PyObject_GetAttrString(obj.ptr(), name)) {
         return reinterpret_steal<object>(result);
-    } else {
-        PyErr_Clear();
-        return reinterpret_borrow<object>(default_);
     }
+    PyErr_Clear();
+    return reinterpret_borrow<object>(default_);
 }
 
 inline void setattr(handle obj, handle name, handle value) {
@@ -791,10 +789,9 @@ inline bool PyIterable_Check(PyObject *obj) {
     if (iter) {
         Py_DECREF(iter);
         return true;
-    } else {
-        PyErr_Clear();
-        return false;
     }
+    PyErr_Clear();
+    return false;
 }
 
 inline bool PyNone_Check(PyObject *o) { return o == Py_None; }
@@ -1188,10 +1185,8 @@ Unsigned as_unsigned(PyObject *o) {
         unsigned long v = PyLong_AsUnsignedLong(o);
         return v == (unsigned long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
     }
-    else {
-        unsigned long long v = PyLong_AsUnsignedLongLong(o);
-        return v == (unsigned long long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
-    }
+    unsigned long long v = PyLong_AsUnsignedLongLong(o);
+    return v == (unsigned long long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
 }
 PYBIND11_NAMESPACE_END(detail)
 
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index ca20b7483b..51994c656b 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -278,7 +278,8 @@ template<typename T> struct optional_caster {
     bool load(handle src, bool convert) {
         if (!src) {
             return false;
-        } else if (src.is_none()) {
+        }
+        if (src.is_none()) {
             return true;  // default-constructed value is already empty
         }
         value_conv inner_caster;
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index b78bd27ced..76700763fe 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -414,13 +414,12 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
         if (step == 1) {
             return Vector(p, end);
         }
-        else {
-            Vector vec;
-            vec.reserve((size_t) info.shape[0]);
-            for (; p != end; p += step)
-                vec.push_back(*p);
-            return vec;
-        }
+        Vector vec;
+        vec.reserve((size_t) info.shape[0]);
+        for (; p != end; p += step)
+            vec.push_back(*p);
+        return vec;
+
     }));
 
     return;
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 908d5743e7..7e79217a3d 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -82,7 +82,7 @@ TEST_SUBMODULE(callbacks, m) {
     // Export the payload constructor statistics for testing purposes:
     m.def("payload_cstats", &ConstructorStats::get<Payload>);
     /* Test cleanup of lambda closure */
-    m.def("test_cleanup", []() -> std::function<void(void)> {
+    m.def("test_cleanup", []() -> std::function<void()> {
         Payload p;
 
         return [p]() {
@@ -108,12 +108,13 @@ TEST_SUBMODULE(callbacks, m) {
         if (!result) {
             auto r = f(1);
             return "can't convert to function pointer: eval(1) = " + std::to_string(r);
-        } else if (*result == dummy_function) {
+        }
+        if (*result == dummy_function) {
             auto r = (*result)(1);
             return "matches dummy_function: eval(1) = " + std::to_string(r);
-        } else {
-            return "argument does NOT match dummy_function. This should never happen!";
         }
+        return "argument does NOT match dummy_function. This should never happen!";
+
     });
 
     class AbstractBase {
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index a26c59c1ce..bcc73ef0b8 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -154,8 +154,7 @@ TEST_SUBMODULE(class_, m) {
         //     return py::type::of<int>();
         if (category == 1)
             return py::type::of<DerivedClass1>();
-        else
-            return py::type::of<Invalid>();
+        return py::type::of<Invalid>();
     });
 
     m.def("get_type_of", [](py::object ob) { return py::type::of(std::move(ob)); });
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 08f4dd7497..05caf28ff1 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -203,8 +203,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
             void *ptr = std::malloc(bytes);
             if (ptr)
                 return ptr;
-            else
-                throw std::bad_alloc{};
+            throw std::bad_alloc{};
         }
     };
     py::class_<PrivateOpNew>(m, "PrivateOpNew").def_readonly("value", &PrivateOpNew::value);
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 9e0ebc206f..2b91af37b0 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -263,13 +263,13 @@ TEST_SUBMODULE(pytypes, m) {
         if (type == "bytes") {
             return move ? py::bytes(std::move(value)) : py::bytes(value);
         }
-        else if (type == "none") {
+        if (type == "none") {
             return move ? py::none(std::move(value)) : py::none(value);
         }
-        else if (type == "ellipsis") {
+        if (type == "ellipsis") {
             return move ? py::ellipsis(std::move(value)) : py::ellipsis(value);
         }
-        else if (type == "type") {
+        if (type == "type") {
             return move ? py::type(std::move(value)) : py::type(value);
         }
         throw std::runtime_error("Invalid type");
@@ -385,9 +385,7 @@ TEST_SUBMODULE(pytypes, m) {
         if (is_unsigned)
             return py::memoryview::from_buffer(
                 ui16, { 4 }, { sizeof(uint16_t) });
-        else
-            return py::memoryview::from_buffer(
-                si16, { 5 }, { sizeof(int16_t) });
+        return py::memoryview::from_buffer(si16, {5}, {sizeof(int16_t)});
     });
 
     m.def("test_memoryview_from_buffer_nativeformat", []() {
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 51068f6380..5280af8eb6 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -112,7 +112,9 @@ class NonCopyable {
     void operator=(const NonCopyable &) = delete;
     void operator=(NonCopyable &&) = delete;
     std::string get_value() const {
-        if (value) return std::to_string(*value); else return "(null)";
+        if (value)
+            return std::to_string(*value);
+        return "(null)";
     }
     ~NonCopyable() { print_destroyed(this); }
 

From bac5a0c3700f1ee7b4fcc98659f3c924e915322f Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 9 Jul 2021 14:09:56 -0700
Subject: [PATCH 052/638] Go all the way fixing clang-tidy issues to avoid the
 NOLINTNEXTLINE clutter and clang-format issues. This was really meant to be
 part of PR #3051 but was held back either out of an abundance of caution, or
 because of confusion caused by stray semicolons. (#3086)

---
 tests/pybind11_cross_module_tests.cpp | 10 +++++++---
 tests/test_builtin_casters.cpp        | 10 ++++++----
 tests/test_kwargs_and_defaults.cpp    | 13 +++++++++----
 tests/test_local_bindings.cpp         | 10 +++++++---
 4 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index f238ddb042..27a349d231 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -10,8 +10,11 @@
 #include "pybind11_tests.h"
 #include "local_bindings.h"
 #include "test_exceptions.h"
+
 #include <pybind11/stl_bind.h>
+
 #include <numeric>
+#include <utility>
 
 PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.doc() = "pybind11 cross-module test module";
@@ -104,9 +107,10 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("return_self", [](LocalVec *v) { return v; });
     m.def("return_copy", [](const LocalVec &v) { return LocalVec(v); });
 
-    // Changing this broke things with pygrep. TODO fix
-    // NOLINTNEXTLINE
-    class Dog : public pets::Pet { public: Dog(std::string name) : Pet(name) {}; };
+    class Dog : public pets::Pet {
+    public:
+        Dog(std::string name) : Pet(std::move(name)) {}
+    };
     py::class_<pets::Pet>(m, "Pet", py::module_local())
         .def("name", &pets::Pet::name);
     // Binding for local extending class:
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index a98b67bdbd..caafb06314 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -151,10 +151,12 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("int_passthrough_noconvert", [](int arg) { return arg; }, py::arg{}.noconvert());
 
     // test_tuple
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("pair_passthrough", [](std::pair<bool, std::string> input) {
-        return std::make_pair(input.second, input.first);
-    }, "Return a pair in reversed order");
+    m.def(
+        "pair_passthrough",
+        [](const std::pair<bool, std::string> &input) {
+            return std::make_pair(input.second, input.first);
+        },
+        "Return a pair in reversed order");
     m.def("tuple_passthrough", [](std::tuple<bool, std::string, int> input) {
         return std::make_tuple(std::get<2>(input), std::get<1>(input), std::get<0>(input));
     }, "Return a triple in reversed order");
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index a349d43184..3e078bd9ba 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -106,10 +106,15 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
             py::arg() = 3, "j"_a = 4, py::kw_only(), "k"_a = 5, "z"_a);
     m.def("kw_only_mixed", [](int i, int j) { return py::make_tuple(i, j); },
             "i"_a, py::kw_only(), "j"_a);
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("kw_only_plus_more", [](int i, int j, int k, py::kwargs kwargs) {
-            return py::make_tuple(i, j, k, kwargs); },
-            py::arg() /* positional */, py::arg("j") = -1 /* both */, py::kw_only(), py::arg("k") /* kw-only */);
+    m.def(
+        "kw_only_plus_more",
+        [](int i, int j, int k, const py::kwargs &kwargs) {
+            return py::make_tuple(i, j, k, kwargs);
+        },
+        py::arg() /* positional */,
+        py::arg("j") = -1 /* both */,
+        py::kw_only(),
+        py::arg("k") /* kw-only */);
 
     m.def("register_invalid_kw_only", [](py::module_ m) {
         m.def("bad_kw_only", [](int i, int j) { return py::make_tuple(i, j); },
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index 2ac77b143b..bfbab3ed3b 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -10,9 +10,12 @@
 
 #include "pybind11_tests.h"
 #include "local_bindings.h"
+
 #include <pybind11/stl.h>
 #include <pybind11/stl_bind.h>
+
 #include <numeric>
+#include <utility>
 
 TEST_SUBMODULE(local_bindings, m) {
     // test_load_external
@@ -86,9 +89,10 @@ TEST_SUBMODULE(local_bindings, m) {
     m.def("return_self", [](LocalVec *v) { return v; });
     m.def("return_copy", [](const LocalVec &v) { return LocalVec(v); });
 
-    // Reformatting this class broke pygrep checks
-    // NOLINTNEXTLINE
-    class Cat : public pets::Pet { public: Cat(std::string name) : Pet(name) {}; };
+    class Cat : public pets::Pet {
+    public:
+        Cat(std::string name) : Pet(std::move(name)) {}
+    };
     py::class_<pets::Pet>(m, "Pet", py::module_local())
         .def("get_name", &pets::Pet::name);
     // Binding for local extending class:

From cf006af2f06810b10e2ff0fa8281eb25642e9122 Mon Sep 17 00:00:00 2001
From: Jan Iwaszkiewicz <jan.iwaszkiewicz@intel.com>
Date: Sat, 10 Jul 2021 20:16:07 +0200
Subject: [PATCH 053/638] Fix typos and docs style (#3088)

* py::pickle typo

* correct dots and parentheses
---
 docs/advanced/classes.rst | 2 +-
 docs/faq.rst              | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 3dfc0c935b..9d1b1f0d9b 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -804,7 +804,7 @@ to bind these two functions:
             }
         ));
 
-The ``__setstate__`` part of the ``py::picke()`` definition follows the same
+The ``__setstate__`` part of the ``py::pickle()`` definition follows the same
 rules as the single-argument version of ``py::init()``. The return type can be
 a value, pointer or holder type. See :ref:`custom_constructors` for details.
 
diff --git a/docs/faq.rst b/docs/faq.rst
index 56ded0329a..d6a048b06f 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -5,7 +5,7 @@ Frequently asked questions
 ===========================================================
 
 1. Make sure that the name specified in PYBIND11_MODULE is identical to the
-filename of the extension library (without suffixes such as .so)
+filename of the extension library (without suffixes such as ``.so``).
 
 2. If the above did not fix the issue, you are likely using an incompatible
 version of Python (for instance, the extension library was compiled against
@@ -170,7 +170,7 @@ complete independence of the symbols involved when not using
 ``-fvisibility=hidden``.
 
 Additionally, ``-fvisibility=hidden`` can deliver considerably binary size
-savings.  (See the following section for more details).
+savings. (See the following section for more details.)
 
 
 .. _`faq:symhidden`:

From 0f4761b44ae2a9b7caf2f95e26dfc62178a2a776 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 11 Jul 2021 00:40:38 -0700
Subject: [PATCH 054/638] Rollback of DOWNLOAD_CATCH=OFF change merged via PR
 #3059. (#3092)

---
 .github/workflows/ci.yml | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2fa4303d9b..03c9225c12 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -100,7 +100,7 @@ jobs:
       run: >
         cmake -S . -B .
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=OFF
+        -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
         ${{ matrix.args }}
@@ -111,10 +111,10 @@ jobs:
     - name: Python tests C++11
       run: cmake --build . --target pytest -j 2
 
-    #- name: C++11 tests
-    #  # TODO: Figure out how to load the DLL on Python 3.8+
-    #  if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
-    #  run: cmake --build .  --target cpptest -j 2
+    - name: C++11 tests
+      # TODO: Figure out how to load the DLL on Python 3.8+
+      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
+      run: cmake --build .  --target cpptest -j 2
 
     - name: Interface test C++11
       run: cmake --build . --target test_cmake_build
@@ -127,7 +127,7 @@ jobs:
       run: >
         cmake -S . -B build2
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=OFF
+        -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         ${{ matrix.args }}
@@ -139,10 +139,10 @@ jobs:
     - name: Python tests
       run: cmake --build build2 --target pytest
 
-    #- name: C++ tests
-    #  # TODO: Figure out how to load the DLL on Python 3.8+
-    #  if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
-    #  run: cmake --build build2 --target cpptest
+    - name: C++ tests
+      # TODO: Figure out how to load the DLL on Python 3.8+
+      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
+      run: cmake --build build2 --target cpptest
 
     - name: Interface test
       run: cmake --build build2 --target test_cmake_build
@@ -754,7 +754,7 @@ jobs:
         cmake -S . -B build
         -G "Visual Studio 16 2019" -A Win32
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=OFF
+        -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         ${{ matrix.args }}
     - name: Build C++11
@@ -800,7 +800,7 @@ jobs:
         cmake -S . -B build
         -G "Visual Studio 14 2015" -A x64
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=OFF
+        -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
 
     - name: Build C++14
@@ -849,7 +849,7 @@ jobs:
         cmake -S . -B build
         -G "Visual Studio 15 2017" -A x64
         -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=OFF
+        -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
         ${{ matrix.args }}

From 7a64b8adcc7d74b7f6ce601db8b47a00e4cf107c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 12 Jul 2021 14:10:46 -0400
Subject: [PATCH 055/638] docs: fix script issues for changelog compilation
 (#3100)

[skip ci]
---
 tools/make_changelog.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/make_changelog.py b/tools/make_changelog.py
index 609ce2f194..4e8fbf5b00 100755
--- a/tools/make_changelog.py
+++ b/tools/make_changelog.py
@@ -27,7 +27,10 @@
 
 api = ghapi.all.GhApi(owner="pybind", repo="pybind11")
 
-issues = api.issues.list_for_repo(labels="needs changelog", state="closed")
+issues_pages = ghapi.page.paged(
+    api.issues.list_for_repo, labels="needs changelog", state="closed"
+)
+issues = (issue for page in issues_pages for issue in page)
 missing = []
 
 for issue in issues:
@@ -41,7 +44,7 @@
 
         msg += f"\n  `#{issue.number} <{issue.html_url}>`_"
 
-        print(Syntax(msg, "rst", theme="ansi_light"))
+        print(Syntax(msg, "rst", theme="ansi_light", word_wrap=True))
         print()
 
     else:

From 2d468697d9c1a6209c2ccf13f3b57ba548230655 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 12 Jul 2021 13:10:28 -0700
Subject: [PATCH 056/638] NOLINT reduction (#3096)

* Copying from prework_no_rst branch (PR #3087): test_numpy_array.cpp, test_stl.cpp

* Manual changes reducing NOLINTs.

* clang-format-diff.py

* Minor adjustment to avoid MSVC warning C4702: unreachable code
---
 tests/pybind11_cross_module_tests.cpp |   3 +-
 tests/test_buffers.cpp                |   3 +-
 tests/test_builtin_casters.cpp        |  15 ++--
 tests/test_class.cpp                  |   9 +-
 tests/test_copy_move.cpp              |   4 +-
 tests/test_eigen.cpp                  |  52 +++++------
 tests/test_exceptions.cpp             |   9 +-
 tests/test_kwargs_and_defaults.cpp    |  10 +--
 tests/test_methods_and_attributes.cpp |  13 ++-
 tests/test_multiple_inheritance.cpp   |   3 +-
 tests/test_numpy_array.cpp            | 124 ++++++++++----------------
 tests/test_numpy_vectorize.cpp        |  24 +++--
 tests/test_pytypes.cpp                |  62 ++++++-------
 tests/test_stl.cpp                    |  14 ++-
 14 files changed, 140 insertions(+), 205 deletions(-)

diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index 27a349d231..e79701c6c6 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -132,7 +132,6 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_missing_header_message
     // The main module already includes stl.h, but we need to test the error message
     // which appears when this header is missing.
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("missing_header_arg", [](std::vector<float>) { });
+    m.def("missing_header_arg", [](const std::vector<float> &) {});
     m.def("missing_header_return", []() { return std::vector<float>(); });
 }
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 9902c1084e..15dd4f1c74 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -79,8 +79,7 @@ TEST_SUBMODULE(buffers, m) {
     py::class_<Matrix>(m, "Matrix", py::buffer_protocol())
         .def(py::init<py::ssize_t, py::ssize_t>())
         /// Construct from a buffer
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        .def(py::init([](py::buffer const b) {
+        .def(py::init([](const py::buffer &b) {
             py::buffer_info info = b.request();
             if (info.format != py::format_descriptor<float>::format() || info.ndim != 2)
                 throw std::runtime_error("Incompatible buffer format!");
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index caafb06314..51e410cadd 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -105,8 +105,7 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_bytes_to_string
     m.def("strlen", [](char *s) { return strlen(s); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("string_length", [](std::string s) { return s.length(); });
+    m.def("string_length", [](const std::string &s) { return s.length(); });
 
 #ifdef PYBIND11_HAS_U8STRING
     m.attr("has_u8string") = true;
@@ -185,14 +184,11 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_none_deferred
     m.def("defer_none_cstring", [](char *) { return false; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("defer_none_cstring", [](py::none) { return true; });
+    m.def("defer_none_cstring", [](const py::none &) { return true; });
     m.def("defer_none_custom", [](UserType *) { return false; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("defer_none_custom", [](py::none) { return true; });
+    m.def("defer_none_custom", [](const py::none &) { return true; });
     m.def("nodefer_none_void", [](void *) { return true; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("nodefer_none_void", [](py::none) { return false; });
+    m.def("nodefer_none_void", [](const py::none &) { return false; });
 
     // test_void_caster
     m.def("load_nullptr_t", [](std::nullptr_t) {}); // not useful, but it should still compile
@@ -242,8 +238,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     }, "copy"_a);
 
     m.def("refwrap_iiw", [](const IncType &w) { return w.value(); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("refwrap_call_iiw", [](IncType &w, py::function f) {
+    m.def("refwrap_call_iiw", [](IncType &w, const py::function &f) {
         py::list l;
         l.append(f(std::ref(w)));
         l.append(f(std::cref(w)));
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index bcc73ef0b8..73de2a61aa 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -131,8 +131,7 @@ TEST_SUBMODULE(class_, m) {
     m.def("return_none", []() -> BaseClass* { return nullptr; });
 
     // test_isinstance
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("check_instances", [](py::list l) {
+    m.def("check_instances", [](const py::list &l) {
         return py::make_tuple(
             py::isinstance<py::tuple>(l[0]),
             py::isinstance<py::dict>(l[1]),
@@ -217,8 +216,7 @@ TEST_SUBMODULE(class_, m) {
     py::implicitly_convertible<UserType, ConvertibleFromUserType>();
 
     m.def("implicitly_convert_argument", [](const ConvertibleFromUserType &r) { return r.i; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("implicitly_convert_variable", [](py::object o) {
+    m.def("implicitly_convert_variable", [](const py::object &o) {
         // `o` is `UserType` and `r` is a reference to a temporary created by implicit
         // conversion. This is valid when called inside a bound function because the temp
         // object is attached to the same life support system as the arguments.
@@ -396,8 +394,7 @@ TEST_SUBMODULE(class_, m) {
     struct StringWrapper { std::string str; };
     m.def("test_error_after_conversions", [](int) {});
     m.def("test_error_after_conversions",
-          // NOLINTNEXTLINE(performance-unnecessary-value-param)
-          [](StringWrapper) -> NotRegistered { return {}; });
+          [](const StringWrapper &) -> NotRegistered { return {}; });
     py::class_<StringWrapper>(m, "StringWrapper").def(py::init<std::string>());
     py::implicitly_convertible<std::string, StringWrapper>();
 
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 05caf28ff1..859da9df7e 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -126,7 +126,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
 
     // test_move_and_copy_casts
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("move_and_copy_casts", [](py::object o) {
+    m.def("move_and_copy_casts", [](const py::object &o) {
         int r = 0;
         r += py::cast<MoveOrCopyInt>(o).value; /* moves */
         r += py::cast<MoveOnlyInt>(o).value; /* moves */
@@ -141,8 +141,10 @@ TEST_SUBMODULE(copy_move_policies, m) {
 
     // test_move_and_copy_loads
     m.def("move_only", [](MoveOnlyInt m) { return m.value; });
+    // Changing this breaks the existing test: needs careful review.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("move_or_copy", [](MoveOrCopyInt m) { return m.value; });
+    // Changing this breaks the existing test: needs careful review.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("copy_only", [](CopyOnlyInt m) { return m.value; });
     m.def("move_pair", [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) {
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index a24bf273d2..ba74f58156 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -98,12 +98,13 @@ TEST_SUBMODULE(eigen, m) {
 
     // test_eigen_ref_to_python
     // Different ways of passing via Eigen::Ref; the first and second are the Eigen-recommended
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("cholesky1", [](Eigen::Ref<MatrixXdR> x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    m.def("cholesky1",
+          [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky3", [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("cholesky4", [](Eigen::Ref<const MatrixXdR> x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    m.def("cholesky4", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd {
+        return x.llt().matrixL();
+    });
 
     // test_eigen_ref_mutators
     // Mutators: these add some value to the given element using Eigen, but Eigen should be mapping into
@@ -248,12 +249,9 @@ TEST_SUBMODULE(eigen, m) {
     m.def("fixed_copy_r", [](const FixedMatrixR &m) -> FixedMatrixR { return m; });
     m.def("fixed_copy_c", [](const FixedMatrixC &m) -> FixedMatrixC { return m; });
     // test_mutator_descriptors
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("fixed_mutator_r", [](Eigen::Ref<FixedMatrixR>) {});
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("fixed_mutator_c", [](Eigen::Ref<FixedMatrixC>) {});
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("fixed_mutator_a", [](py::EigenDRef<FixedMatrixC>) {});
+    m.def("fixed_mutator_r", [](const Eigen::Ref<FixedMatrixR> &) {});
+    m.def("fixed_mutator_c", [](const Eigen::Ref<FixedMatrixC> &) {});
+    m.def("fixed_mutator_a", [](const py::EigenDRef<FixedMatrixC> &) {});
     // test_dense
     m.def("dense_r", [mat]() -> DenseMatrixR { return DenseMatrixR(mat); });
     m.def("dense_c", [mat]() -> DenseMatrixC { return DenseMatrixC(mat); });
@@ -284,9 +282,10 @@ TEST_SUBMODULE(eigen, m) {
     // that would allow copying (if types or strides don't match) for comparison:
     m.def("get_elem", &get_elem);
     // Now this alternative that calls the tells pybind to fail rather than copy:
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("get_elem_nocopy", [](Eigen::Ref<const Eigen::MatrixXd> m) -> double { return get_elem(m); },
-            py::arg{}.noconvert());
+    m.def(
+        "get_elem_nocopy",
+        [](const Eigen::Ref<const Eigen::MatrixXd> &m) -> double { return get_elem(m); },
+        py::arg{}.noconvert());
     // Also test a row-major-only no-copy const ref:
     m.def("get_elem_rm_nocopy", [](Eigen::Ref<const Eigen::Matrix<long, -1, -1, Eigen::RowMajor>> &m) -> long { return m(2, 1); },
             py::arg{}.noconvert());
@@ -301,20 +300,22 @@ TEST_SUBMODULE(eigen, m) {
     // test_issue1105
     // Issue #1105: when converting from a numpy two-dimensional (Nx1) or (1xN) value into a dense
     // eigen Vector or RowVector, the argument would fail to load because the numpy copy would
-    // fail: numpy won't broadcast a Nx1 into a 1-dimensional vector. NOLINTNEXTLINE
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("iss1105_col", [](Eigen::VectorXd) { return true; });
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("iss1105_row", [](Eigen::RowVectorXd) { return true; });
+    // fail: numpy won't broadcast a Nx1 into a 1-dimensional vector.
+    m.def("iss1105_col", [](const Eigen::VectorXd &) { return true; });
+    m.def("iss1105_row", [](const Eigen::RowVectorXd &) { return true; });
 
     // test_named_arguments
     // Make sure named arguments are working properly:
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("matrix_multiply", [](const py::EigenDRef<const Eigen::MatrixXd> A, const py::EigenDRef<const Eigen::MatrixXd> B)
-            -> Eigen::MatrixXd {
-        if (A.cols() != B.rows()) throw std::domain_error("Nonconformable matrices!");
-        return A * B;
-    }, py::arg("A"), py::arg("B"));
+    m.def(
+        "matrix_multiply",
+        [](const py::EigenDRef<const Eigen::MatrixXd> &A,
+           const py::EigenDRef<const Eigen::MatrixXd> &B) -> Eigen::MatrixXd {
+            if (A.cols() != B.rows())
+                throw std::domain_error("Nonconformable matrices!");
+            return A * B;
+        },
+        py::arg("A"),
+        py::arg("B"));
 
     // test_custom_operator_new
     py::class_<CustomOperatorNew>(m, "CustomOperatorNew")
@@ -326,8 +327,7 @@ TEST_SUBMODULE(eigen, m) {
     // In case of a failure (the caster's temp array does not live long enough), creating
     // a new array (np.ones(10)) increases the chances that the temp array will be garbage
     // collected and/or that its memory will be overridden with different values.
-    // NOLINTNEXTLINE (performance-unnecessary-value-param)
-    m.def("get_elem_direct", [](Eigen::Ref<const Eigen::VectorXd> v) {
+    m.def("get_elem_direct", [](const Eigen::Ref<const Eigen::VectorXd> &v) {
         py::module_::import("numpy").attr("ones")(10);
         return v(5);
     });
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index d34f1a94e1..f7bacd07e4 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -201,17 +201,16 @@ TEST_SUBMODULE(exceptions, m) {
         throw py::error_already_set();
     });
 
-    // Changing this broke things. Don't know why
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("python_call_in_destructor", [](py::dict d) {
+    m.def("python_call_in_destructor", [](const py::dict &d) {
+        bool retval = false;
         try {
             PythonCallInDestructor set_dict_in_destructor(d);
             PyErr_SetString(PyExc_ValueError, "foo");
             throw py::error_already_set();
         } catch (const py::error_already_set&) {
-            return true;
+            retval = true;
         }
-        return false;
+        return retval;
     });
 
     m.def("python_alreadyset_in_destructor", [](const py::str &s) {
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 3e078bd9ba..63332d32ea 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -65,9 +65,10 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     #endif
     m.def("arg_refcount_h", [](py::handle h) { GC_IF_NEEDED; return h.ref_count(); });
     m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) { GC_IF_NEEDED; return h.ref_count(); });
-    // TODO replace the following nolints as appropriate
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("arg_refcount_o", [](py::object o) { GC_IF_NEEDED; return o.ref_count(); });
+    m.def("arg_refcount_o", [](const py::object &o) {
+        GC_IF_NEEDED;
+        return o.ref_count();
+    });
     m.def("args_refcount", [](py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size());
@@ -76,8 +77,7 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
             t[i] = (int) Py_REFCNT(PyTuple_GET_ITEM(a.ptr(), static_cast<py::ssize_t>(i)));
         return t;
     });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("mixed_args_refcount", [](py::object o, py::args a) {
+    m.def("mixed_args_refcount", [](const py::object &o, py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size() + 1);
         t[0] = o.ref_count();
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 67ee117c6c..6e5999f0c4 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -294,20 +294,17 @@ TEST_SUBMODULE(methods_and_attributes, m) {
             "static_rw_func", py::cpp_function(static_get2, rvp_copy), static_set2)
         // test_property_rvalue_policy
         .def_property_readonly("rvalue", &TestPropRVP::get_rvalue)
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        .def_property_readonly_static("static_rvalue", [](py::object) { return UserType(1); });
+        .def_property_readonly_static("static_rvalue",
+                                      [](const py::object &) { return UserType(1); });
 
     // test_metaclass_override
     struct MetaclassOverride { };
     py::class_<MetaclassOverride>(m, "MetaclassOverride", py::metaclass((PyObject *) &PyType_Type))
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        .def_property_readonly_static("readonly", [](py::object) { return 1; });
+        .def_property_readonly_static("readonly", [](const py::object &) { return 1; });
 
     // test_overload_ordering
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("overload_order", [](std::string) { return 1; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("overload_order", [](std::string) { return 2; });
+    m.def("overload_order", [](const std::string &) { return 1; });
+    m.def("overload_order", [](const std::string &) { return 2; });
     m.def("overload_order", [](int) { return 3; });
     m.def("overload_order", [](int) { return 4; }, py::prepend{});
 
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index f4acf7861e..d6b24d34da 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -141,8 +141,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def(py::init<int, int>());
 
     m.def("bar_base2a", [](Base2a *b) { return b->bar(); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("bar_base2a_sharedptr", [](std::shared_ptr<Base2a> b) { return b->bar(); });
+    m.def("bar_base2a_sharedptr", [](const std::shared_ptr<Base2a> &b) { return b->bar(); });
 
     // test_mi_unaligned_base
     // test_mi_base_return
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index a6c7ae8d74..5c22a3d25b 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -226,8 +226,7 @@ TEST_SUBMODULE(numpy_array, sm) {
         return py::isinstance<py::array>(std::move(yes))
                && !py::isinstance<py::array>(std::move(no));
     });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("isinstance_typed", [](py::object o) {
+    sm.def("isinstance_typed", [](const py::object &o) {
         return py::isinstance<py::array_t<double>>(o) && !py::isinstance<py::array_t<int>>(o);
     });
 
@@ -248,60 +247,47 @@ TEST_SUBMODULE(numpy_array, sm) {
     });
 
     // test_overload_resolution
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<double>) { return "double"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<float>) { return "float"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<int>) { return "int"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<unsigned short>) { return "unsigned short"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<long long>) { return "long long"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<std::complex<double>>) { return "double complex"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded", [](py::array_t<std::complex<float>>) { return "float complex"; });
-
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded2", [](py::array_t<std::complex<double>>) { return "double complex"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded2", [](py::array_t<double>) { return "double"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded2", [](py::array_t<std::complex<float>>) { return "float complex"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded2", [](py::array_t<float>) { return "float"; });
+    sm.def("overloaded", [](const py::array_t<double> &) { return "double"; });
+    sm.def("overloaded", [](const py::array_t<float> &) { return "float"; });
+    sm.def("overloaded", [](const py::array_t<int> &) { return "int"; });
+    sm.def("overloaded", [](const py::array_t<unsigned short> &) { return "unsigned short"; });
+    sm.def("overloaded", [](const py::array_t<long long> &) { return "long long"; });
+    sm.def("overloaded",
+           [](const py::array_t<std::complex<double>> &) { return "double complex"; });
+    sm.def("overloaded", [](const py::array_t<std::complex<float>> &) { return "float complex"; });
+
+    sm.def("overloaded2",
+           [](const py::array_t<std::complex<double>> &) { return "double complex"; });
+    sm.def("overloaded2", [](const py::array_t<double> &) { return "double"; });
+    sm.def("overloaded2",
+           [](const py::array_t<std::complex<float>> &) { return "float complex"; });
+    sm.def("overloaded2", [](const py::array_t<float> &) { return "float"; });
 
     // [workaround(intel)] ICC 20/21 breaks with py::arg().stuff, using py::arg{}.stuff works.
 
     // Only accept the exact types:
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded3", [](py::array_t<int>) { return "int"; }, py::arg{}.noconvert());
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded3", [](py::array_t<double>) { return "double"; }, py::arg{}.noconvert());
+    sm.def(
+        "overloaded3", [](const py::array_t<int> &) { return "int"; }, py::arg{}.noconvert());
+    sm.def(
+        "overloaded3",
+        [](const py::array_t<double> &) { return "double"; },
+        py::arg{}.noconvert());
 
     // Make sure we don't do unsafe coercion (e.g. float to int) when not using forcecast, but
     // rather that float gets converted via the safe (conversion to double) overload:
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded4", [](py::array_t<long long, 0>) { return "long long"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded4", [](py::array_t<double, 0>) { return "double"; });
+    sm.def("overloaded4", [](const py::array_t<long long, 0> &) { return "long long"; });
+    sm.def("overloaded4", [](const py::array_t<double, 0> &) { return "double"; });
 
     // But we do allow conversion to int if forcecast is enabled (but only if no overload matches
     // without conversion)
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded5", [](py::array_t<unsigned int>) { return "unsigned int"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("overloaded5", [](py::array_t<double>) { return "double"; });
+    sm.def("overloaded5", [](const py::array_t<unsigned int> &) { return "unsigned int"; });
+    sm.def("overloaded5", [](const py::array_t<double> &) { return "double"; });
 
     // test_greedy_string_overload
     // Issue 685: ndarray shouldn't go to std::string overload
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("issue685", [](std::string) { return "string"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("issue685", [](py::array) { return "array"; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("issue685", [](py::object) { return "other"; });
+    sm.def("issue685", [](const std::string &) { return "string"; });
+    sm.def("issue685", [](const py::array &) { return "array"; });
+    sm.def("issue685", [](const py::object &) { return "other"; });
 
     // test_array_unchecked_fixed_dims
     sm.def("proxy_add2", [](py::array_t<double> a, double v) {
@@ -424,73 +410,53 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_argument_conversions
     sm.def(
-        "accept_double",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, 0>) {},
-        py::arg("a"));
+        "accept_double", [](const py::array_t<double, 0> &) {}, py::arg("a"));
     sm.def(
         "accept_double_forcecast",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::forcecast>) {},
+        [](const py::array_t<double, py::array::forcecast> &) {},
         py::arg("a"));
     sm.def(
         "accept_double_c_style",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::c_style>) {},
+        [](const py::array_t<double, py::array::c_style> &) {},
         py::arg("a"));
     sm.def(
         "accept_double_c_style_forcecast",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::forcecast | py::array::c_style>) {},
+        [](const py::array_t<double, py::array::forcecast | py::array::c_style> &) {},
         py::arg("a"));
     sm.def(
         "accept_double_f_style",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::f_style>) {},
+        [](const py::array_t<double, py::array::f_style> &) {},
         py::arg("a"));
     sm.def(
         "accept_double_f_style_forcecast",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
+        [](const py::array_t<double, py::array::forcecast | py::array::f_style> &) {},
         py::arg("a"));
     sm.def(
-        "accept_double_noconvert",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, 0>) {},
-        "a"_a.noconvert());
+        "accept_double_noconvert", [](const py::array_t<double, 0> &) {}, "a"_a.noconvert());
     sm.def(
         "accept_double_forcecast_noconvert",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::forcecast>) {},
+        [](const py::array_t<double, py::array::forcecast> &) {},
         "a"_a.noconvert());
     sm.def(
         "accept_double_c_style_noconvert",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::c_style>) {},
+        [](const py::array_t<double, py::array::c_style> &) {},
         "a"_a.noconvert());
     sm.def(
         "accept_double_c_style_forcecast_noconvert",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::forcecast | py::array::c_style>) {},
+        [](const py::array_t<double, py::array::forcecast | py::array::c_style> &) {},
         "a"_a.noconvert());
     sm.def(
         "accept_double_f_style_noconvert",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::f_style>) {},
+        [](const py::array_t<double, py::array::f_style> &) {},
         "a"_a.noconvert());
     sm.def(
         "accept_double_f_style_forcecast_noconvert",
-        // NOLINTNEXTLINE(performance-unnecessary-value-param)
-        [](py::array_t<double, py::array::forcecast | py::array::f_style>) {},
+        [](const py::array_t<double, py::array::forcecast | py::array::f_style> &) {},
         "a"_a.noconvert());
 
     // Check that types returns correct npy format descriptor
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("test_fmt_desc_float", [](py::array_t<float>) {});
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("test_fmt_desc_double", [](py::array_t<double>) {});
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("test_fmt_desc_const_float", [](py::array_t<const float>) {});
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    sm.def("test_fmt_desc_const_double", [](py::array_t<const double>) {});
+    sm.def("test_fmt_desc_float", [](const py::array_t<float> &) {});
+    sm.def("test_fmt_desc_double", [](const py::array_t<double> &) {});
+    sm.def("test_fmt_desc_const_float", [](const py::array_t<const float> &) {});
+    sm.def("test_fmt_desc_const_double", [](const py::array_t<const double> &) {});
 }
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index 0be30d8e88..42fb2002ec 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -40,13 +40,13 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     // test_type_selection
     // NumPy function which only accepts specific data types
     // A lot of these no lints could be replaced with const refs, and probably should at some point.
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("selective_func", [](py::array_t<int, py::array::c_style>) { return "Int branch taken."; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("selective_func", [](py::array_t<float, py::array::c_style>) { return "Float branch taken."; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("selective_func", [](py::array_t<std::complex<float>, py::array::c_style>) { return "Complex float branch taken."; });
-
+    m.def("selective_func",
+          [](const py::array_t<int, py::array::c_style> &) { return "Int branch taken."; });
+    m.def("selective_func",
+          [](const py::array_t<float, py::array::c_style> &) { return "Float branch taken."; });
+    m.def("selective_func", [](const py::array_t<std::complex<float>, py::array::c_style> &) {
+        return "Complex float branch taken.";
+    });
 
     // test_passthrough_arguments
     // Passthrough test: references and non-pod types should be automatically passed through (in the
@@ -89,13 +89,9 @@ TEST_SUBMODULE(numpy_vectorize, m) {
         .value("c_trivial", py::detail::broadcast_trivial::c_trivial)
         .value("non_trivial", py::detail::broadcast_trivial::non_trivial);
     m.def("vectorized_is_trivial",
-          [](
-              // NOLINTNEXTLINE(performance-unnecessary-value-param)
-              py::array_t<int, py::array::forcecast> arg1,
-              // NOLINTNEXTLINE(performance-unnecessary-value-param)
-              py::array_t<float, py::array::forcecast> arg2,
-              // NOLINTNEXTLINE(performance-unnecessary-value-param)
-              py::array_t<double, py::array::forcecast> arg3) {
+          [](const py::array_t<int, py::array::forcecast> &arg1,
+             const py::array_t<float, py::array::forcecast> &arg2,
+             const py::array_t<double, py::array::forcecast> &arg3) {
               py::ssize_t ndim;
               std::vector<py::ssize_t> shape;
               std::array<py::buffer_info, 3> buffers{
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 2b91af37b0..6ed59aad21 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -237,8 +237,7 @@ TEST_SUBMODULE(pytypes, m) {
         );
     });
 
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("cast_functions", [](py::dict d) {
+    m.def("cast_functions", [](const py::dict &d) {
         // When converting between Python types, obj.cast<T>() should be the same as T(obj)
         return py::dict(
             "bytes"_a=d["bytes"].cast<py::bytes>(),
@@ -255,25 +254,24 @@ TEST_SUBMODULE(pytypes, m) {
         );
     });
 
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("convert_to_pybind11_str", [](py::object o) { return py::str(o); });
-
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("nonconverting_constructor", [](std::string type, py::object value, bool move) -> py::object {
-        if (type == "bytes") {
-            return move ? py::bytes(std::move(value)) : py::bytes(value);
-        }
-        if (type == "none") {
-            return move ? py::none(std::move(value)) : py::none(value);
-        }
-        if (type == "ellipsis") {
-            return move ? py::ellipsis(std::move(value)) : py::ellipsis(value);
-        }
-        if (type == "type") {
-            return move ? py::type(std::move(value)) : py::type(value);
-        }
-        throw std::runtime_error("Invalid type");
-    });
+    m.def("convert_to_pybind11_str", [](const py::object &o) { return py::str(o); });
+
+    m.def("nonconverting_constructor",
+          [](const std::string &type, py::object value, bool move) -> py::object {
+              if (type == "bytes") {
+                  return move ? py::bytes(std::move(value)) : py::bytes(value);
+              }
+              if (type == "none") {
+                  return move ? py::none(std::move(value)) : py::none(value);
+              }
+              if (type == "ellipsis") {
+                  return move ? py::ellipsis(std::move(value)) : py::ellipsis(value);
+              }
+              if (type == "type") {
+                  return move ? py::type(std::move(value)) : py::type(value);
+              }
+              throw std::runtime_error("Invalid type");
+          });
 
     m.def("get_implicit_casting", []() {
         py::dict d;
@@ -333,8 +331,7 @@ TEST_SUBMODULE(pytypes, m) {
 
     m.def("hash_function", [](py::object obj) { return py::hash(std::move(obj)); });
 
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("test_number_protocol", [](py::object a, py::object b) {
+    m.def("test_number_protocol", [](const py::object &a, const py::object &b) {
         py::list l;
         l.append(a.equal(b));
         l.append(a.not_equal(b));
@@ -354,10 +351,7 @@ TEST_SUBMODULE(pytypes, m) {
         return l;
     });
 
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("test_list_slicing", [](py::list a) {
-        return a[py::slice(0, -1, 2)];
-    });
+    m.def("test_list_slicing", [](const py::list &a) { return a[py::slice(0, -1, 2)]; });
 
     // See #2361
     m.def("issue2361_str_implicit_copy_none", []() {
@@ -369,15 +363,10 @@ TEST_SUBMODULE(pytypes, m) {
         return is_this_none;
     });
 
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("test_memoryview_object", [](py::buffer b) {
-        return py::memoryview(b);
-    });
+    m.def("test_memoryview_object", [](const py::buffer &b) { return py::memoryview(b); });
 
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("test_memoryview_buffer_info", [](py::buffer b) {
-        return py::memoryview(b.request());
-    });
+    m.def("test_memoryview_buffer_info",
+          [](const py::buffer &b) { return py::memoryview(b.request()); });
 
     m.def("test_memoryview_from_buffer", [](bool is_unsigned) {
         static const int16_t si16[] = { 3, 1, 4, 1, 5 };
@@ -432,8 +421,7 @@ TEST_SUBMODULE(pytypes, m) {
 
     m.def("pass_to_pybind11_bytes", [](py::bytes b) { return py::len(std::move(b)); });
     m.def("pass_to_pybind11_str", [](py::str s) { return py::len(std::move(s)); });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("pass_to_std_string", [](std::string s) { return s.size(); });
+    m.def("pass_to_std_string", [](const std::string &s) { return s.size(); });
 
     // test_weakref
     m.def("weakref_from_handle",
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index dc75762e85..1f308e1393 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -207,8 +207,7 @@ TEST_SUBMODULE(stl, m) {
     }, py::arg_v("x", std::nullopt, "None"));
 
     m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("nodefer_none_optional", [](py::none) { return false; });
+    m.def("nodefer_none_optional", [](const py::none &) { return false; });
 
     using opt_holder = OptionalHolder<std::optional, MoveOutDetector>;
     py::class_<opt_holder>(m, "OptionalHolder", "Class with optional member")
@@ -299,12 +298,11 @@ TEST_SUBMODULE(stl, m) {
     m.def("stl_pass_by_pointer", [](std::vector<int>* v) { return *v; }, "v"_a=nullptr);
 
     // #1258: pybind11/stl.h converts string to vector<string>
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("func_with_string_or_vector_string_arg_overload", [](std::vector<std::string>) { return 1; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("func_with_string_or_vector_string_arg_overload", [](std::list<std::string>) { return 2; });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("func_with_string_or_vector_string_arg_overload", [](std::string) { return 3; });
+    m.def("func_with_string_or_vector_string_arg_overload",
+          [](const std::vector<std::string> &) { return 1; });
+    m.def("func_with_string_or_vector_string_arg_overload",
+          [](const std::list<std::string> &) { return 2; });
+    m.def("func_with_string_or_vector_string_arg_overload", [](const std::string &) { return 3; });
 
     class Placeholder {
     public:

From 7472d37a93514dd22bf27da4123ff7b7f2a1545a Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 12 Jul 2021 13:39:06 -0700
Subject: [PATCH 057/638] Adding iostream.h thread-safety documentation.
 (#2995)

* Adding iostream.h thread-safety documentation.

* Restoring `TestThread` code with added `std::lock_guard<std::mutex>`.

* Updating new comments to reflect new information.

* Fixing up `git rebase -X theirs` accidents.
---
 docs/advanced/pycpp/utilities.rst | 11 ++++++++
 include/pybind11/iostream.h       | 45 +++++++++++++++++--------------
 tests/test_iostream.cpp           | 14 +++++++++-
 3 files changed, 49 insertions(+), 21 deletions(-)

diff --git a/docs/advanced/pycpp/utilities.rst b/docs/advanced/pycpp/utilities.rst
index c15051fb96..8b8e5196af 100644
--- a/docs/advanced/pycpp/utilities.rst
+++ b/docs/advanced/pycpp/utilities.rst
@@ -47,6 +47,17 @@ redirects output to the corresponding Python streams:
         call_noisy_func();
     });
 
+.. warning::
+
+    The implementation in ``pybind11/iostream.h`` is NOT thread safe. Multiple
+    threads writing to a redirected ostream concurrently cause data races
+    and potentially buffer overflows. Therefore it is currrently a requirement
+    that all (possibly) concurrent redirected ostream writes are protected by
+    a mutex. #HelpAppreciated: Work on iostream.h thread safety. For more
+    background see the discussions under
+    `PR #2982 <https://github.com/pybind/pybind11/pull/2982>`_ and
+    `PR #2995 <https://github.com/pybind/pybind11/pull/2995>`_.
+
 This method respects flushes on the output streams and will flush if needed
 when the scoped guard is destroyed. This allows the output to be redirected in
 real time, such as to a Jupyter notebook. The two arguments, the C++ stream and
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 89d1813ba8..c98067ad8a 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -5,6 +5,16 @@
 
     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
+
+    WARNING: The implementation in this file is NOT thread safe. Multiple
+    threads writing to a redirected ostream concurrently cause data races
+    and potentially buffer overflows. Therefore it is currrently a requirement
+    that all (possibly) concurrent redirected ostream writes are protected by
+    a mutex.
+    #HelpAppreciated: Work on iostream.h thread safety.
+    For more background see the discussions under
+    https://github.com/pybind/pybind11/pull/2982 and
+    https://github.com/pybind/pybind11/pull/2995.
 */
 
 #pragma once
@@ -85,30 +95,25 @@ class pythonbuf : public std::streambuf {
         return remainder;
     }
 
-    // This function must be non-virtual to be called in a destructor. If the
-    // rare MSVC test failure shows up with this version, then this should be
-    // simplified to a fully qualified call.
+    // This function must be non-virtual to be called in a destructor.
     int _sync() {
         if (pbase() != pptr()) { // If buffer is not empty
             gil_scoped_acquire tmp;
-            // Placed inside gil_scoped_acquire as a mutex to avoid a race.
-            if (pbase() != pptr()) { // Check again under the lock
-                // This subtraction cannot be negative, so dropping the sign.
-                auto size        = static_cast<size_t>(pptr() - pbase());
-                size_t remainder = utf8_remainder();
-
-                if (size > remainder) {
-                    str line(pbase(), size - remainder);
-                    pywrite(line);
-                    pyflush();
-                }
-
-                // Copy the remainder at the end of the buffer to the beginning:
-                if (remainder > 0)
-                    std::memmove(pbase(), pptr() - remainder, remainder);
-                setp(pbase(), epptr());
-                pbump(static_cast<int>(remainder));
+            // This subtraction cannot be negative, so dropping the sign.
+            auto size        = static_cast<size_t>(pptr() - pbase());
+            size_t remainder = utf8_remainder();
+
+            if (size > remainder) {
+                str line(pbase(), size - remainder);
+                pywrite(line);
+                pyflush();
             }
+
+            // Copy the remainder at the end of the buffer to the beginning:
+            if (remainder > 0)
+                std::memmove(pbase(), pptr() - remainder, remainder);
+            setp(pbase(), epptr());
+            pbump(static_cast<int>(remainder));
         }
         return 0;
     }
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index 908788007f..c620b59493 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -15,6 +15,8 @@
 #include "pybind11_tests.h"
 #include <atomic>
 #include <iostream>
+#include <mutex>
+#include <string>
 #include <thread>
 
 void noisy_function(const std::string &msg, bool flush) {
@@ -35,8 +37,18 @@ void noisy_funct_dual(const std::string &msg, const std::string &emsg) {
 struct TestThread {
     TestThread() : stop_{false} {
         auto thread_f = [this] {
+            static std::mutex cout_mutex;
             while (!stop_) {
-                std::cout << "x" << std::flush;
+                {
+                    // #HelpAppreciated: Work on iostream.h thread safety.
+                    // Without this lock, the clang ThreadSanitizer (tsan) reliably reports a
+                    // data race, and this test is predictably flakey on Windows.
+                    // For more background see the discussion under
+                    // https://github.com/pybind/pybind11/pull/2982 and
+                    // https://github.com/pybind/pybind11/pull/2995.
+                    const std::lock_guard<std::mutex> lock(cout_mutex);
+                    std::cout << "x" << std::flush;
+                }
                 std::this_thread::sleep_for(std::chrono::microseconds(50));
             } };
         t_ = new std::thread(std::move(thread_f));

From f0a65c899c7245f1dbaabad73330b4120ed6f2d4 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 12 Jul 2021 16:57:28 -0400
Subject: [PATCH 058/638] docs(fix): spelling mistake in recent commit

---
 docs/advanced/pycpp/utilities.rst | 2 +-
 include/pybind11/iostream.h       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/advanced/pycpp/utilities.rst b/docs/advanced/pycpp/utilities.rst
index 8b8e5196af..30429e84d7 100644
--- a/docs/advanced/pycpp/utilities.rst
+++ b/docs/advanced/pycpp/utilities.rst
@@ -51,7 +51,7 @@ redirects output to the corresponding Python streams:
 
     The implementation in ``pybind11/iostream.h`` is NOT thread safe. Multiple
     threads writing to a redirected ostream concurrently cause data races
-    and potentially buffer overflows. Therefore it is currrently a requirement
+    and potentially buffer overflows. Therefore it is currently a requirement
     that all (possibly) concurrent redirected ostream writes are protected by
     a mutex. #HelpAppreciated: Work on iostream.h thread safety. For more
     background see the discussions under
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index c98067ad8a..e4d2095857 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -8,7 +8,7 @@
 
     WARNING: The implementation in this file is NOT thread safe. Multiple
     threads writing to a redirected ostream concurrently cause data races
-    and potentially buffer overflows. Therefore it is currrently a requirement
+    and potentially buffer overflows. Therefore it is currently a requirement
     that all (possibly) concurrent redirected ostream writes are protected by
     a mutex.
     #HelpAppreciated: Work on iostream.h thread safety.

From 9f11951b5beee10c86eaeba56707da22d913bdbd Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 12 Jul 2021 14:00:48 -0700
Subject: [PATCH 059/638] Fixing spelling errors that went undetected because
 the pre-commit spell check was added after the CI for PR #2995 last ran.
 (#3103)


From ddf0efb9905770399eea765b4aaca09446155f04 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 12 Jul 2021 17:45:40 -0400
Subject: [PATCH 060/638] chore: add nox support (#3101)

* chore: add nox support

* chore: add more lines to CODEOWNERS
---
 .github/CODEOWNERS      |  3 ++
 .github/CONTRIBUTING.md | 27 ++++++++++++++
 .pre-commit-config.yaml |  1 +
 noxfile.py              | 83 +++++++++++++++++++++++++++++++++++++++++
 setup.cfg               |  1 +
 5 files changed, 115 insertions(+)
 create mode 100644 noxfile.py

diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 60af5e7971..4e2c66902e 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -4,3 +4,6 @@ CMakeLists.txt @henryiii
 *.yaml @henryiii
 /tools/ @henryiii
 /pybind11/ @henryiii
+noxfile.py @henryiii
+.clang-format @henryiii
+.clang-tidy @henryiii
diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 6f9ebf21f1..ff1997f989 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -53,6 +53,33 @@ derivative works thereof, in binary and source code form.
 
 ## Development of pybind11
 
+### Quick setup
+
+To setup a quick development environment, use [`nox`](https://nox.thea.codes).
+This will allow you to do some common tasks with minimal setup effort, but will
+take more time to run and be less flexible than a full development environment.
+If you use [`pipx run nox`](https://pipx.pypa.io), you don't even need to
+install `nox`. Examples:
+
+```bash
+# List all available sessions
+nox -l
+
+# Run linters
+nox -s lint
+
+# Run tests
+nox -s tests
+
+# Build and preview docs
+nox -s docs -- serve
+
+# Build SDists and wheels
+nox -s build
+```
+
+### Full setup
+
 To setup an ideal development environment, run the following commands on a
 system with CMake 3.14+:
 
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 85d575464f..3f5a5723c4 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -28,6 +28,7 @@ repos:
   - id: requirements-txt-fixer
   - id: trailing-whitespace
   - id: fix-encoding-pragma
+    exclude: ^noxfile.py$
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
diff --git a/noxfile.py b/noxfile.py
new file mode 100644
index 0000000000..3bc61273ff
--- /dev/null
+++ b/noxfile.py
@@ -0,0 +1,83 @@
+import nox
+
+
+nox.options.sessions = ["lint", "tests", "tests_packaging"]
+
+
+@nox.session(reuse_venv=True)
+def lint(session: nox.Session) -> None:
+    """
+    Lint the codebase (except for clang-format/tidy).
+    """
+    session.install("pre-commit")
+    session.run("pre-commit", "run", "-a")
+
+
+@nox.session
+def tests(session: nox.Session) -> None:
+    """
+    Run the tests (requires a compiler).
+    """
+    tmpdir = session.create_tmp()
+    session.install("pytest", "cmake")
+    session.run(
+        "cmake",
+        "-S",
+        ".",
+        "-B",
+        tmpdir,
+        "-DPYBIND11_WERROR=ON",
+        "-DDOWNLOAD_CATCH=ON",
+        "-DDOWNLOAD_EIGEN=ON",
+        *session.posargs
+    )
+    session.run("cmake", "--build", tmpdir)
+    session.run("cmake", "--build", tmpdir, "--config=Release", "--target", "check")
+
+
+@nox.session
+def tests_packaging(session: nox.Session) -> None:
+    """
+    Run the packaging tests.
+    """
+
+    session.install("-r", "tests/requirements.txt", "--prefer-binary")
+    session.run("pytest", "tests/extra_python_package")
+
+
+@nox.session(reuse_venv=True)
+def docs(session: nox.Session) -> None:
+    """
+    Build the docs. Pass "serve" to serve.
+    """
+
+    session.install("-r", "docs/requirements.txt")
+    session.chdir("docs")
+    session.run("sphinx-build", "-M", "html", ".", "_build")
+
+    if session.posargs:
+        if "serve" in session.posargs:
+            print("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")
+            session.run("python", "-m", "http.server", "8000", "-d", "_build/html")
+        else:
+            print("Unsupported argument to docs")
+
+
+@nox.session(reuse_venv=True)
+def make_changelog(session: nox.Session) -> None:
+    """
+    Inspect the closed issues and make entries for a changelog.
+    """
+    session.install("ghapi", "rich")
+    session.run("python", "tools/make_changelog.py")
+
+
+@nox.session(reuse_venv=True)
+def build(session: nox.Session) -> None:
+    """
+    Build SDists and wheels.
+    """
+
+    session.install("build")
+    session.run("python", "-m", "build")
+    session.run("python", "-m", "build", env={"PYBIND11_GLOBAL_SDIST": "1"})
diff --git a/setup.cfg b/setup.cfg
index 041e62dae6..527d18aacf 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -47,6 +47,7 @@ ignore =
     pybind11/include/**
     pybind11/share/**
     CMakeLists.txt
+    noxfile.py
 
 
 [flake8]

From 75090647cea463e4e43914e404674cb1b8b47a13 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 12 Jul 2021 16:56:10 -0700
Subject: [PATCH 061/638] More precise return_value_policy::automatic
 documentation. (#2920)

* Adding test_return_vector_bool_raw_ptr to test_stl.py.

* First attempt to make the documentation more accurate, but not trying to be comprehensive, to not bloat the reference table with too many details.

* Fixing minor oversights.

* Applying reviewer suggestion.
---
 docs/advanced/functions.rst | 7 ++++---
 tests/test_stl.cpp          | 6 ++++++
 tests/test_stl.py           | 7 +++++++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index d880008b0f..a537cb65ee 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -90,17 +90,18 @@ The following table provides an overview of available policies:
 |                                                  | return value is referenced by Python. This is the default policy for       |
 |                                                  | property getters created via ``def_property``, ``def_readwrite``, etc.     |
 +--------------------------------------------------+----------------------------------------------------------------------------+
-| :enum:`return_value_policy::automatic`           | **Default policy.** This policy falls back to the policy                   |
+| :enum:`return_value_policy::automatic`           | This policy falls back to the policy                                       |
 |                                                  | :enum:`return_value_policy::take_ownership` when the return value is a     |
 |                                                  | pointer. Otherwise, it uses :enum:`return_value_policy::move` or           |
 |                                                  | :enum:`return_value_policy::copy` for rvalue and lvalue references,        |
 |                                                  | respectively. See above for a description of what all of these different   |
-|                                                  | policies do.                                                               |
+|                                                  | policies do. This is the default policy for ``py::class_``-wrapped types.  |
 +--------------------------------------------------+----------------------------------------------------------------------------+
 | :enum:`return_value_policy::automatic_reference` | As above, but use policy :enum:`return_value_policy::reference` when the   |
 |                                                  | return value is a pointer. This is the default conversion policy for       |
 |                                                  | function arguments when calling Python functions manually from C++ code    |
-|                                                  | (i.e. via handle::operator()). You probably won't need to use this.        |
+|                                                  | (i.e. via ``handle::operator()``) and the casters in ``pybind11/stl.h``.   |
+|                                                  | You probably won't need to use this explicitly.                            |
 +--------------------------------------------------+----------------------------------------------------------------------------+
 
 Return value policies can also be applied to properties:
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 1f308e1393..eb8cdab7b5 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -334,4 +334,10 @@ TEST_SUBMODULE(stl, m) {
     py::class_<Issue1561Outer>(m, "Issue1561Outer")
         .def(py::init<>())
         .def_readwrite("list", &Issue1561Outer::list);
+
+    m.def(
+        "return_vector_bool_raw_ptr",
+        []() { return new std::vector<bool>(4513); },
+        // Without explicitly specifying `take_ownership`, this function leaks.
+        py::return_value_policy::take_ownership);
 }
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 96939257cf..5fd3570fae 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -283,3 +283,10 @@ def test_issue_1561():
     bar.list = [m.Issue1561Inner("bar")]
     bar.list
     assert bar.list[0].data == "bar"
+
+
+def test_return_vector_bool_raw_ptr():
+    # Add `while True:` for manual leak checking.
+    v = m.return_vector_bool_raw_ptr()
+    assert isinstance(v, list)
+    assert len(v) == 4513

From 84fdadfbcc50d3eaa9f8a64a83505eae17e81560 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 12 Jul 2021 14:56:06 -0400
Subject: [PATCH 062/638] chore: update pre-commit hooks

---
 .pre-commit-config.yaml               | 11 ++++++-----
 tests/test_class.py                   |  2 +-
 tests/test_sequences_and_iterators.py |  4 ++--
 tests/test_stl.py                     |  2 +-
 4 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3f5a5723c4..4ce9cff57d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,7 +15,7 @@
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: v3.4.0
+  rev: v4.0.1
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
@@ -32,7 +32,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 20.8b1
+  rev: 21.6b0
   hooks:
   - id: black
     # By default, this ignores pyi files, though black supports them
@@ -41,13 +41,13 @@ repos:
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: v1.1.9
+  rev: v1.1.10
   hooks:
   - id: remove-tabs
 
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://gitlab.com/pycqa/flake8
-  rev: 3.8.4
+  rev: 3.9.2
   hooks:
   - id: flake8
     additional_dependencies: [flake8-bugbear, pep8-naming]
@@ -64,7 +64,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.800
+  rev: v0.910
   hooks:
   - id: mypy
     # The default Python type ignores .pyi files, so let's rerun if detected
@@ -72,6 +72,7 @@ repos:
     files: ^pybind11.*\.pyi?$
     # Running per-file misbehaves a bit, so just run on all files, it's fast
     pass_filenames: false
+    additional_dependencies: [typed_ast]
 
 # Checks the manifest for missing files (native support)
 - repo: https://github.com/mgedmin/check-manifest
diff --git a/tests/test_class.py b/tests/test_class.py
index bdcced9643..1ff60fe214 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -321,7 +321,7 @@ def foo(self):
 
 
 def test_brace_initialization():
-    """ Tests that simple POD classes can be constructed using C++11 brace initialization """
+    """Tests that simple POD classes can be constructed using C++11 brace initialization"""
     a = m.BraceInitialization(123, "test")
     assert a.field1 == 123
     assert a.field2 == "test"
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index c3b608c436..70fb697f95 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -104,7 +104,7 @@ def test_sequence():
 
 
 def test_sequence_length():
-    """#2076: Exception raised by len(arg) should be propagated """
+    """#2076: Exception raised by len(arg) should be propagated"""
 
     class BadLen(RuntimeError):
         pass
@@ -187,7 +187,7 @@ def test_iterator_passthrough():
 
 
 def test_iterator_rvp():
-    """#388: Can't make iterators via make_iterator() with different r/v policies """
+    """#388: Can't make iterators via make_iterator() with different r/v policies"""
     import pybind11_tests.sequences_and_iterators as m
 
     assert list(m.make_iterator_1()) == [1, 2, 3]
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 5fd3570fae..6f08459043 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -278,7 +278,7 @@ def test_array_cast_sequence():
 
 
 def test_issue_1561():
-    """ check fix for issue #1561 """
+    """check fix for issue #1561"""
     bar = m.Issue1561Outer()
     bar.list = [m.Issue1561Inner("bar")]
     bar.list

From 11e12fe455831cae33b138a0ce4d4df5da9ace96 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 12 Jul 2021 14:58:59 -0400
Subject: [PATCH 063/638] chore: move some config to pyproject.toml

---
 pyproject.toml | 32 ++++++++++++++++++++++++++++++++
 setup.cfg      | 31 -------------------------------
 2 files changed, 32 insertions(+), 31 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 5c9d153541..f86470eef8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,35 @@
 [build-system]
 requires = ["setuptools>=42", "wheel", "cmake>=3.18", "ninja"]
 build-backend = "setuptools.build_meta"
+
+[tool.check-manifest]
+ignore = [
+    "tests/**",
+    "docs/**",
+    "tools/**",
+    "include/**",
+    ".*",
+    "pybind11/include/**",
+    "pybind11/share/**",
+    "CMakeLists.txt",
+    "noxfile.py",
+]
+
+[tool.mypy]
+files = "pybind11"
+python_version = "2.7"
+warn_unused_configs = true
+
+disallow_any_generics = true
+disallow_subclassing_any = true
+disallow_untyped_calls = true
+disallow_untyped_defs = true
+disallow_incomplete_defs = true
+check_untyped_defs = true
+disallow_untyped_decorators = true
+no_implicit_optional = true
+warn_redundant_casts = true
+warn_unused_ignores = true
+warn_return_any = true
+no_implicit_reexport = true
+strict_equality = true
diff --git a/setup.cfg b/setup.cfg
index 527d18aacf..31038eb026 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -37,18 +37,6 @@ zip_safe = False
 [bdist_wheel]
 universal=1
 
-[check-manifest]
-ignore =
-    tests/**
-    docs/**
-    tools/**
-    include/**
-    .*
-    pybind11/include/**
-    pybind11/share/**
-    CMakeLists.txt
-    noxfile.py
-
 
 [flake8]
 max-line-length = 99
@@ -62,25 +50,6 @@ ignore =
     # Black conflict
     W503, E203
 
-[mypy]
-files = pybind11
-python_version = 2.7
-warn_unused_configs = True
-
-# Currently (0.800) identical to --strict
-disallow_any_generics = True
-disallow_subclassing_any = True
-disallow_untyped_calls = True
-disallow_untyped_defs = True
-disallow_incomplete_defs = True
-check_untyped_defs = True
-disallow_untyped_decorators = True
-no_implicit_optional = True
-warn_redundant_casts = True
-warn_unused_ignores = True
-warn_return_any = True
-no_implicit_reexport = True
-strict_equality = True
 
 [tool:pytest]
 timeout = 300

From 0e2e003508ab0dfbea8a0f825d3d001b5f4be2cd Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 12 Jul 2021 15:01:19 -0400
Subject: [PATCH 064/638] style: add pyupgrade check, 2.7+

---
 .pre-commit-config.yaml                  |  5 +++++
 tests/extra_python_package/test_files.py | 26 ++++++++++++------------
 tests/test_builtin_casters.py            |  2 +-
 tests/test_callbacks.py                  |  2 +-
 tests/test_pytypes.py                    |  4 ++--
 5 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4ce9cff57d..133eb6df4e 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -30,6 +30,11 @@ repos:
   - id: fix-encoding-pragma
     exclude: ^noxfile.py$
 
+- repo: https://github.com/asottile/pyupgrade
+  rev: v2.21.0
+  hooks:
+  - id: pyupgrade
+
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
   rev: 21.6b0
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index c1d12ed76b..43e93c2633 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -126,7 +126,7 @@ def test_build_sdist(monkeypatch, tmpdir):
     with tarfile.open(str(sdist)) as tar:
         start = tar.getnames()[0] + "/"
         version = start[9:-1]
-        simpler = set(n.split("/", 1)[-1] for n in tar.getnames()[1:])
+        simpler = {n.split("/", 1)[-1] for n in tar.getnames()[1:]}
 
         with contextlib.closing(
             tar.extractfile(tar.getmember(start + "setup.py"))
@@ -138,9 +138,9 @@ def test_build_sdist(monkeypatch, tmpdir):
         ) as f:
             pyproject_toml = f.read()
 
-    files = set("pybind11/{}".format(n) for n in all_files)
+    files = {"pybind11/{}".format(n) for n in all_files}
     files |= sdist_files
-    files |= set("pybind11{}".format(n) for n in local_sdist_files)
+    files |= {"pybind11{}".format(n) for n in local_sdist_files}
     files.add("pybind11.egg-info/entry_points.txt")
     files.add("pybind11.egg-info/requires.txt")
     assert simpler == files
@@ -181,7 +181,7 @@ def test_build_global_dist(monkeypatch, tmpdir):
     with tarfile.open(str(sdist)) as tar:
         start = tar.getnames()[0] + "/"
         version = start[16:-1]
-        simpler = set(n.split("/", 1)[-1] for n in tar.getnames()[1:])
+        simpler = {n.split("/", 1)[-1] for n in tar.getnames()[1:]}
 
         with contextlib.closing(
             tar.extractfile(tar.getmember(start + "setup.py"))
@@ -193,9 +193,9 @@ def test_build_global_dist(monkeypatch, tmpdir):
         ) as f:
             pyproject_toml = f.read()
 
-    files = set("pybind11/{}".format(n) for n in all_files)
+    files = {"pybind11/{}".format(n) for n in all_files}
     files |= sdist_files
-    files |= set("pybind11_global{}".format(n) for n in local_sdist_files)
+    files |= {"pybind11_global{}".format(n) for n in local_sdist_files}
     assert simpler == files
 
     with open(os.path.join(MAIN_DIR, "tools", "setup_global.py.in"), "rb") as f:
@@ -220,7 +220,7 @@ def tests_build_wheel(monkeypatch, tmpdir):
 
     (wheel,) = tmpdir.visit("*.whl")
 
-    files = set("pybind11/{}".format(n) for n in all_files)
+    files = {"pybind11/{}".format(n) for n in all_files}
     files |= {
         "dist-info/LICENSE",
         "dist-info/METADATA",
@@ -233,10 +233,10 @@ def tests_build_wheel(monkeypatch, tmpdir):
     with zipfile.ZipFile(str(wheel)) as z:
         names = z.namelist()
 
-    trimmed = set(n for n in names if "dist-info" not in n)
-    trimmed |= set(
+    trimmed = {n for n in names if "dist-info" not in n}
+    trimmed |= {
         "dist-info/{}".format(n.split("/", 1)[-1]) for n in names if "dist-info" in n
-    )
+    }
     assert files == trimmed
 
 
@@ -250,8 +250,8 @@ def tests_build_global_wheel(monkeypatch, tmpdir):
 
     (wheel,) = tmpdir.visit("*.whl")
 
-    files = set("data/data/{}".format(n) for n in src_files)
-    files |= set("data/headers/{}".format(n[8:]) for n in headers)
+    files = {"data/data/{}".format(n) for n in src_files}
+    files |= {"data/headers/{}".format(n[8:]) for n in headers}
     files |= {
         "dist-info/LICENSE",
         "dist-info/METADATA",
@@ -264,6 +264,6 @@ def tests_build_global_wheel(monkeypatch, tmpdir):
         names = z.namelist()
 
     beginning = names[0].split("/", 1)[0].rsplit(".", 1)[0]
-    trimmed = set(n[len(beginning) + 1 :] for n in names)
+    trimmed = {n[len(beginning) + 1 :] for n in names}
 
     assert files == trimmed
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 99c400c308..1b9dbb2b40 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -50,7 +50,7 @@ def test_single_char_arguments():
     """Tests failures for passing invalid inputs to char-accepting functions"""
 
     def toobig_message(r):
-        return "Character code point not in range({0:#x})".format(r)
+        return "Character code point not in range({:#x})".format(r)
 
     toolong_message = "Expected a character, but multi-character string found"
 
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 3526614304..397bf63d24 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -144,7 +144,7 @@ def gen_f():
     from time import sleep
 
     sleep(0.5)
-    assert sum(res) == sum([x + 3 for x in work])
+    assert sum(res) == sum(x + 3 for x in work)
 
 
 def test_async_async_callbacks():
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index f234c77315..25e9f6dffc 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -65,7 +65,7 @@ def test_set(capture, doc):
     """
     )
 
-    assert not m.set_contains(set([]), 42)
+    assert not m.set_contains(set(), 42)
     assert m.set_contains({42}, 42)
     assert m.set_contains({"foo"}, "foo")
 
@@ -448,7 +448,7 @@ def test_memoryview(method, args, fmt, expected_view):
         view_as_list = list(view)
     else:
         # Using max to pick non-zero byte (big-endian vs little-endian).
-        view_as_list = [max([ord(c) for c in s]) for s in view]
+        view_as_list = [max(ord(c) for c in s) for s in view]
     assert view_as_list == list(expected_view)
 
 

From 6a644c8f0472ba4a23517a22e30aff9e5eff1dea Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 13 Jul 2021 00:08:29 -0400
Subject: [PATCH 065/638] docs: update changelog (#3099)

* docs: update changelog

* docs: add one more and merge tidy
---
 docs/changelog.rst | 131 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 6787349e53..d71fccc251 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -9,12 +9,143 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 v2.7.0 (TBA, not yet released)
 ------------------------------
 
+New features:
+
+* Enable ``py::implicitly_convertible<py::none, ...>`` for
+  ``py::class_``-wrapped types.
+  `#3059 <https://github.com/pybind/pybind11/pull/3059>`_
+
+* Allow function pointer extraction from overloaded functions.
+  `#2944 <https://github.com/pybind/pybind11/pull/2944>`_
+
+* NumPy: added ``.char_()`` to type which gives the NumPy public ``char``
+  result, which also distinguishes types by bit length (unlike ``.kind()``).
+  `#2864 <https://github.com/pybind/pybind11/pull/2864>`_
+
+* Add ``pybind11::bytearray`` to manipulate ``bytearray`` similar to ``bytes``.
+  `#2799 <https://github.com/pybind/pybind11/pull/2799>`_
+
+* ``pybind11/stl/filesystem.h`` registers a type caster that, on C++17/Python
+  3.6+, converts ``std::filesystem::path`` to ``pathlib.Path`` and any
+  ``os.PathLike`` to ``std::filesystem::path``.
+  `#2730 <https://github.com/pybind/pybind11/pull/2730>`_
+
+
+Changes:
+
 * ``py::str`` changed to exclusively hold `PyUnicodeObject`. Previously
   ``py::str`` could also hold `bytes`, which is probably surprising, was
   never documented, and can mask bugs (e.g. accidental use of ``py::str``
   instead of ``py::bytes``).
   `#2409 <https://github.com/pybind/pybind11/pull/2409>`_
 
+* Add a safety guard to ensure that the Python GIL is held when C++ calls back
+  into Python via ``object_api<>::operator()`` (e.g. ``py::function``
+  ``__call__``).  (This feature is available for Python 3.6+ only.)
+  `#2919 <https://github.com/pybind/pybind11/pull/2919>`_
+
+* Catch a missing ``self`` argument in calls to ``__init__()``.
+  `#2914 <https://github.com/pybind/pybind11/pull/2914>`_
+
+* Use ``std::string_view`` if available to avoid a copy when passing an object
+  to a ``std::ostream``.
+  `#3042 <https://github.com/pybind/pybind11/pull/3042>`_
+
+* An important warning about thread safety was added to the ``iostream.h``
+  documentation; attempts to make ``py::scoped_ostream_redirect`` thread safe
+  have been removed, as it was only partially effective.
+  `#2995 <https://github.com/pybind/pybind11/pull/2995>`_
+
+
+Fixes:
+
+* Performance: avoid unnecessary strlen calls.
+  `#3058 <https://github.com/pybind/pybind11/pull/3058>`_
+
+* Fix auto-generated documentation string when using ``const T`` in
+  ``pyarray_t``.
+  `#3020 <https://github.com/pybind/pybind11/pull/3020>`_
+
+* Unify error messages thrown by ``simple_collector``/``unpacking_collector``.
+  `#3013 <https://github.com/pybind/pybind11/pull/3013>`_
+
+* ``pybind11::builtin_exception`` is now explicitly exported, which means the
+  types included/defined in different modules are identical, and exceptions
+  raised in different modules can be caught correctly. The documentation was
+  updated to explain that custom exceptions that are used across module
+  boundaries need to be explicitly exported as well.
+  `#2999 <https://github.com/pybind/pybind11/pull/2999>`_
+
+* Fixed exception when printing UTF-8 to a ``scoped_ostream_redirect``.
+  `#2982 <https://github.com/pybind/pybind11/pull/2982>`_
+
+* Pickle support enhancement: ``setstate`` implementation will attempt to
+  ``setattr`` ``__dict__`` only if the unpickled ``dict`` object is not empty,
+  to not force use of ``py::dynamic_attr()`` unnecessarily.
+  `#2972 <https://github.com/pybind/pybind11/pull/2972>`_
+
+* Allow negative timedelta values to roundtrip.
+  `#2870 <https://github.com/pybind/pybind11/pull/2870>`_
+
+* Fix unchecked errors could potentially swallow signals/other exceptions.
+  `#2863 <https://github.com/pybind/pybind11/pull/2863>`_
+
+* Add null pointer check with ``std::localtime``.
+  `#2846 <https://github.com/pybind/pybind11/pull/2846>`_
+
+* Fix the ``weakref`` constructor from ``py::object`` to create a new
+  ``weakref`` on conversion.
+  `#2832 <https://github.com/pybind/pybind11/pull/2832>`_
+
+* Avoid relying on exceptions in C++17 when getting a ``shared_ptr`` holder
+  from a ``shared_from_this`` class.
+  `#2819 <https://github.com/pybind/pybind11/pull/2819>`_
+
+
+Build system improvements:
+
+* In ``setup_helpers.py``, test for platforms that have some multiprocessing
+  features but lack semaphores, which ``ParallelCompile`` requires.
+  `#3043 <https://github.com/pybind/pybind11/pull/3043>`_
+
+* Fix ``pybind11_INCLUDE_DIR`` in case ``CMAKE_INSTALL_INCLUDEDIR`` is
+  absolute.
+  `#3005 <https://github.com/pybind/pybind11/pull/3005>`_
+
+* Fix bug not respecting ``WITH_SOABI`` or ``WITHOUT_SOABI`` to CMake.
+  `#2938 <https://github.com/pybind/pybind11/pull/2938>`_
+
+* Fix the default ``Pybind11Extension`` compilation flags with a Mingw64 python.
+  `#2921 <https://github.com/pybind/pybind11/pull/2921>`_
+
+* Clang on Windows: do not pass ``/MP`` (ignored flag).
+  `#2824 <https://github.com/pybind/pybind11/pull/2824>`_
+
+
+Backend and tidying up:
+
+* Enable clang-tidy performance, readability, and modernization checks
+  throughout the codebase to enforce best coding practices.
+  `#3046 <https://github.com/pybind/pybind11/pull/3046>`_,
+  `#3049 <https://github.com/pybind/pybind11/pull/3049>`_,
+  `#3051 <https://github.com/pybind/pybind11/pull/3051>`_,
+  `#3052 <https://github.com/pybind/pybind11/pull/3052>`_, and
+  `#3080 <https://github.com/pybind/pybind11/pull/3080>`_
+
+* Checks for common misspellings were added to the pre-commit hooks.
+  `#3076 <https://github.com/pybind/pybind11/pull/3076>`_
+
+* Changed ``Werror`` to stricter ``Werror-all`` for Intel compiler and fixed
+  minor issues.
+  `#2948 <https://github.com/pybind/pybind11/pull/2948>`_
+
+* Fixed compilation with GCC < 5 when the user defines ``_GLIBCXX_USE_CXX11_ABI``.
+  `#2956 <https://github.com/pybind/pybind11/pull/2956>`_
+
+* Added nox support for easier local testing and linting of contributions.
+  `#3101 <https://github.com/pybind/pybind11/pull/3101>`_
+
+
 
 v2.6.2 (Jan 26, 2021)
 ---------------------

From 25e470c57d6a5df00c7a4010ecfb9f2c991bca14 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 13 Jul 2021 09:54:32 -0400
Subject: [PATCH 066/638] fix(clang-tidy): Add
 cppcoreguidelines-init-vars,slicing, and throw-by-value-catch-by-reference
 checks (#3094)

* clang-tidy: guard against more UB behavior

* Remove slicing check for now
---
 .clang-tidy                            |  4 ++++
 include/pybind11/eval.h                |  4 ++--
 include/pybind11/pytypes.h             | 18 ++++++++---------
 include/pybind11/stl_bind.h            | 27 +++++++++++++-------------
 tests/test_eval.cpp                    |  2 +-
 tests/test_numpy_vectorize.cpp         |  2 +-
 tests/test_sequences_and_iterators.cpp |  6 +++---
 7 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index ea50bf39bc..72304528a5 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,10 +1,12 @@
 FormatStyle: file
 
 Checks: '
+cppcoreguidelines-init-variables,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,
 misc-static-assert,
+misc-throw-by-value-catch-by-reference,
 misc-uniqueptr-reset-release,
 modernize-avoid-bind,
 modernize-redundant-void-arg,
@@ -33,6 +35,8 @@ readability-uniqueptr-delete-release,
 '
 
 CheckOptions:
+- key:             performance-for-range-copy.WarnOnAllAutoCopies
+  value:           true
 - key:             performance-unnecessary-value-param.AllowedTypes
   value:           'exception_ptr$;'
 
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index bf06504a33..33fcdc09d1 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -55,7 +55,7 @@ object eval(const str &expr, object global = globals(), object local = object())
        this seems to be the only alternative */
     std::string buffer = "# -*- coding: utf-8 -*-\n" + (std::string) expr;
 
-    int start;
+    int start = 0;
     switch (mode) {
         case eval_expr:             start = Py_eval_input;   break;
         case eval_single_statement: start = Py_single_input; break;
@@ -107,7 +107,7 @@ object eval_file(str fname, object global = globals(), object local = object())
 
     detail::ensure_builtins_in_globals(global);
 
-    int start;
+    int start = 0;
     switch (mode) {
         case eval_expr:             start = Py_eval_input;   break;
         case eval_single_statement: start = Py_single_input; break;
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index fb9680dfa1..32386a44d0 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -490,7 +490,7 @@ inline handle get_function(handle value) {
 inline PyObject * dict_getitemstring(PyObject *v, const char *key)
 {
 #if PY_MAJOR_VERSION >= 3
-    PyObject *kv, *rv;
+    PyObject *kv = nullptr, *rv = nullptr;
     kv = PyUnicode_FromString(key);
     if (kv == NULL) {
         throw error_already_set();
@@ -1016,8 +1016,8 @@ class str : public object {
             if (!temp)
                 pybind11_fail("Unable to extract string contents! (encoding issue)");
         }
-        char *buffer;
-        ssize_t length;
+        char *buffer = nullptr;
+        ssize_t length = 0;
         if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length))
             pybind11_fail("Unable to extract string contents! (invalid type)");
         return std::string(buffer, (size_t) length);
@@ -1072,8 +1072,8 @@ class bytes : public object {
     explicit bytes(const pybind11::str &s);
 
     operator std::string() const {
-        char *buffer;
-        ssize_t length;
+        char *buffer = nullptr;
+        ssize_t length = 0;
         if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length))
             pybind11_fail("Unable to extract bytes contents!");
         return std::string(buffer, (size_t) length);
@@ -1090,8 +1090,8 @@ inline bytes::bytes(const pybind11::str &s) {
         if (!temp)
             pybind11_fail("Unable to extract string contents! (encoding issue)");
     }
-    char *buffer;
-    ssize_t length;
+    char *buffer = nullptr;
+    ssize_t length = 0;
     if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length))
         pybind11_fail("Unable to extract string contents! (invalid type)");
     auto obj = reinterpret_steal<object>(PYBIND11_BYTES_FROM_STRING_AND_SIZE(buffer, length));
@@ -1101,8 +1101,8 @@ inline bytes::bytes(const pybind11::str &s) {
 }
 
 inline str::str(const bytes& b) {
-    char *buffer;
-    ssize_t length;
+    char *buffer = nullptr;
+    ssize_t length = 0;
     if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length))
         pybind11_fail("Unable to extract bytes contents!");
     auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, (ssize_t) length));
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 76700763fe..effac0b931 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -217,9 +217,10 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
     );
 
     /// Slicing protocol
-    cl.def("__getitem__",
+    cl.def(
+        "__getitem__",
         [](const Vector &v, slice slice) -> Vector * {
-            size_t start, stop, step, slicelength;
+            size_t start = 0, stop = 0, step = 0, slicelength = 0;
 
             if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
                 throw error_already_set();
@@ -234,12 +235,12 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             return seq;
         },
         arg("s"),
-        "Retrieve list elements using a slice object"
-    );
+        "Retrieve list elements using a slice object");
 
-    cl.def("__setitem__",
-        [](Vector &v, slice slice,  const Vector &value) {
-            size_t start, stop, step, slicelength;
+    cl.def(
+        "__setitem__",
+        [](Vector &v, slice slice, const Vector &value) {
+            size_t start = 0, stop = 0, step = 0, slicelength = 0;
             if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
                 throw error_already_set();
 
@@ -251,8 +252,7 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
                 start += step;
             }
         },
-        "Assign list elements using a slice object"
-    );
+        "Assign list elements using a slice object");
 
     cl.def("__delitem__",
         [wrap_i](Vector &v, DiffType i) {
@@ -262,9 +262,10 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         "Delete the list elements at index ``i``"
     );
 
-    cl.def("__delitem__",
+    cl.def(
+        "__delitem__",
         [](Vector &v, slice slice) {
-            size_t start, stop, step, slicelength;
+            size_t start = 0, stop = 0, step = 0, slicelength = 0;
 
             if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
                 throw error_already_set();
@@ -278,9 +279,7 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
                 }
             }
         },
-        "Delete list elements using a slice object"
-    );
-
+        "Delete list elements using a slice object");
 }
 
 // If the type has an operator[] that doesn't return a reference (most notably std::vector<bool>),
diff --git a/tests/test_eval.cpp b/tests/test_eval.cpp
index 66cdf71051..16cdf17f22 100644
--- a/tests/test_eval.cpp
+++ b/tests/test_eval.cpp
@@ -66,7 +66,7 @@ TEST_SUBMODULE(eval_, m) {
         auto local = py::dict();
         local["y"] = py::int_(43);
 
-        int val_out;
+        int val_out = 0;
         local["call_test2"] = py::cpp_function([&](int value) { val_out = value; });
 
         auto result = py::eval_file(std::move(filename), global, local);
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index 42fb2002ec..ed08a42bef 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -92,7 +92,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
           [](const py::array_t<int, py::array::forcecast> &arg1,
              const py::array_t<float, py::array::forcecast> &arg2,
              const py::array_t<double, py::array::forcecast> &arg3) {
-              py::ssize_t ndim;
+              py::ssize_t ndim = 0;
               std::vector<py::ssize_t> shape;
               std::array<py::buffer_info, 3> buffers{
                   {arg1.request(), arg2.request(), arg3.request()}};
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index c39798229f..d49fb1f459 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -84,7 +84,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     py::class_<Sliceable>(m, "Sliceable")
         .def(py::init<int>())
         .def("__getitem__", [](const Sliceable &s, const py::slice &slice) {
-            py::ssize_t start, stop, step, slicelength;
+            py::ssize_t start = 0, stop = 0, step = 0, slicelength = 0;
             if (!slice.compute(s.size, &start, &stop, &step, &slicelength))
                 throw py::error_already_set();
             int istart = static_cast<int>(start);
@@ -204,7 +204,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         /// Slicing protocol (optional)
         .def("__getitem__",
              [](const Sequence &s, const py::slice &slice) -> Sequence * {
-                 size_t start, stop, step, slicelength;
+                 size_t start = 0, stop = 0, step = 0, slicelength = 0;
                  if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
                      throw py::error_already_set();
                  auto *seq = new Sequence(slicelength);
@@ -216,7 +216,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
              })
         .def("__setitem__",
              [](Sequence &s, const py::slice &slice, const Sequence &value) {
-                 size_t start, stop, step, slicelength;
+                 size_t start = 0, stop = 0, step = 0, slicelength = 0;
                  if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
                      throw py::error_already_set();
                  if (slicelength != value.size())

From 2b7985e548ee7fb551528384ae864f8b175ffbe9 Mon Sep 17 00:00:00 2001
From: jbarlow83 <jbarlow83@users.noreply.github.com>
Date: Tue, 13 Jul 2021 12:32:56 -0700
Subject: [PATCH 067/638] Improve documentation of discard_as_unraisable() API
 (#2697)

* Improve documentation of discard_as_unraisable() API

* Update pytypes.h

Remove "the above"

* Update pytypes.h

Fix precommit error

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/pytypes.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 32386a44d0..0fca32a4e9 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -345,16 +345,17 @@ class PYBIND11_EXPORT error_already_set : public std::runtime_error {
     /// error variables (but the `.what()` string is still available).
     void restore() { PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr()); }
 
-    /// If it is impossible to raise the currently-held error, such as in destructor, we can write
-    /// it out using Python's unraisable hook (sys.unraisablehook). The error context should be
-    /// some object whose repr() helps identify the location of the error. Python already knows the
-    /// type and value of the error, so there is no need to repeat that. For example, __func__ could
-    /// be helpful. After this call, the current object no longer stores the error variables,
-    /// and neither does Python.
+    /// If it is impossible to raise the currently-held error, such as in a destructor, we can write
+    /// it out using Python's unraisable hook (`sys.unraisablehook`). The error context should be
+    /// some object whose `repr()` helps identify the location of the error. Python already knows the
+    /// type and value of the error, so there is no need to repeat that. After this call, the current
+    /// object no longer stores the error variables, and neither does Python.
     void discard_as_unraisable(object err_context) {
         restore();
         PyErr_WriteUnraisable(err_context.ptr());
     }
+    /// An alternate version of `discard_as_unraisable()`, where a string provides information on the
+    /// location of the error. For example, `__func__` could be helpful.
     void discard_as_unraisable(const char *err_context) {
         discard_as_unraisable(reinterpret_steal<object>(PYBIND11_FROM_STRING(err_context)));
     }

From 1be0a0a6107478d8523191a053c24f47ebeda1ad Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Tue, 13 Jul 2021 23:21:55 +0200
Subject: [PATCH 068/638] Add helper to build in-tree extensions. (#2831)

For single-file extensions, a convenient pattern offered by cython
is to place the source files directly in the python source tree
(`foo/__init__.py`, `foo/ext.pyx`), deriving the package names from
their filesystem location.  Adapt this pattern for pybind11, using an
`intree_extensions` helper, which should be thought of as the moral
equivalent to `cythonize`.

Differences with cythonize: I chose not to include globbing support
(`intree_extensions(glob.glob("**/*.cpp"))` seems sufficient), nor to
provide extension-customization kwargs (directly setting the attributes
on the resulting Pybind11Extension objects seems sufficient).

We could choose to have `intree_extension` (singular instead) and make
users write `[*map(intree_extension, glob.glob("**/*.cpp"))]`; no strong
opinion here.

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 docs/compiling.rst                         | 13 +++++++
 pybind11/setup_helpers.py                  | 36 +++++++++++++++++++
 pybind11/setup_helpers.pyi                 |  5 ++-
 tests/extra_setuptools/test_setuphelper.py | 42 ++++++++++++++++++++++
 4 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/docs/compiling.rst b/docs/compiling.rst
index 5d02727bad..bf7acfc808 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -70,6 +70,19 @@ that is supported via a ``build_ext`` command override; it will only affect
         ext_modules=ext_modules
     )
 
+If you have single-file extension modules that are directly stored in the
+Python source tree (``foo.cpp`` in the same directory as where a ``foo.py``
+would be located), you can also generate ``Pybind11Extensions`` using
+``setup_helpers.intree_extensions``: ``intree_extensions(["path/to/foo.cpp",
+...])`` returns a list of ``Pybind11Extensions`` which can be passed to
+``ext_modules``, possibly after further customizing their attributes
+(``libraries``, ``include_dirs``, etc.).  By doing so, a ``foo.*.so`` extension
+module will be generated and made available upon installation.
+
+``intree_extension`` will automatically detect if you are using a ``src``-style
+layout (as long as no namespace packages are involved), but you can also
+explicitly pass ``package_dir`` to it (as in ``setuptools.setup``).
+
 Since pybind11 does not require NumPy when building, a light-weight replacement
 for NumPy's parallel compilation distutils tool is included. Use it like this:
 
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index ec553d1669..2b27f1f5ad 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -303,6 +303,42 @@ def build_extensions(self):
         _build_ext.build_extensions(self)
 
 
+def intree_extensions(paths, package_dir=None):
+    """
+    Generate Pybind11Extensions from source files directly located in a Python
+    source tree.
+
+    ``package_dir`` behaves as in ``setuptools.setup``.  If unset, the Python
+    package root parent is determined as the first parent directory that does
+    not contain an ``__init__.py`` file.
+    """
+    exts = []
+    for path in paths:
+        if package_dir is None:
+            parent, _ = os.path.split(path)
+            while os.path.exists(os.path.join(parent, "__init__.py")):
+                parent, _ = os.path.split(parent)
+            relname, _ = os.path.splitext(os.path.relpath(path, parent))
+            qualified_name = relname.replace(os.path.sep, ".")
+            exts.append(Pybind11Extension(qualified_name, [path]))
+        else:
+            found = False
+            for prefix, parent in package_dir.items():
+                if path.startswith(parent):
+                    found = True
+                    relname, _ = os.path.splitext(os.path.relpath(path, parent))
+                    qualified_name = relname.replace(os.path.sep, ".")
+                    if prefix:
+                        qualified_name = prefix + "." + qualified_name
+                    exts.append(Pybind11Extension(qualified_name, [path]))
+            if not found:
+                raise ValueError(
+                    "path {} is not a child of any of the directories listed "
+                    "in 'package_dir' ({})".format(path, package_dir)
+                )
+    return exts
+
+
 def naive_recompile(obj, src):
     """
     This will recompile only if the source file changes. It does not check
diff --git a/pybind11/setup_helpers.pyi b/pybind11/setup_helpers.pyi
index 23232e1fda..8b16c0a137 100644
--- a/pybind11/setup_helpers.pyi
+++ b/pybind11/setup_helpers.pyi
@@ -1,7 +1,7 @@
 # IMPORTANT: Should stay in sync with setup_helpers.py (mostly checked by CI /
 # pre-commit).
 
-from typing import Any, Callable, Iterator, Optional, Type, TypeVar, Union
+from typing import Any, Callable, Dict, Iterator, List, Optional, Type, TypeVar, Union
 from types import TracebackType
 
 from distutils.command.build_ext import build_ext as _build_ext  # type: ignore
@@ -33,6 +33,9 @@ def auto_cpp_level(compiler: distutils.ccompiler.CCompiler) -> Union[int, str]:
 class build_ext(_build_ext):  # type: ignore
     def build_extensions(self) -> None: ...
 
+def intree_extensions(
+    paths: Iterator[str], package_dir: Optional[Dict[str, str]] = None
+) -> List[Pybind11Extension]: ...
 def no_recompile(obj: str, src: str) -> bool: ...
 def naive_recompile(obj: str, src: str) -> bool: ...
 
diff --git a/tests/extra_setuptools/test_setuphelper.py b/tests/extra_setuptools/test_setuphelper.py
index 0d8bd0e4d6..fb2d342086 100644
--- a/tests/extra_setuptools/test_setuphelper.py
+++ b/tests/extra_setuptools/test_setuphelper.py
@@ -99,3 +99,45 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
     subprocess.check_call(
         [sys.executable, "test.py"], stdout=sys.stdout, stderr=sys.stderr
     )
+
+
+def test_intree_extensions(monkeypatch, tmpdir):
+    monkeypatch.syspath_prepend(MAIN_DIR)
+
+    from pybind11.setup_helpers import intree_extensions
+
+    monkeypatch.chdir(tmpdir)
+    root = tmpdir
+    root.ensure_dir()
+    subdir = root / "dir"
+    subdir.ensure_dir()
+    src = subdir / "ext.cpp"
+    src.ensure()
+    (ext,) = intree_extensions([src.relto(tmpdir)])
+    assert ext.name == "ext"
+    subdir.ensure("__init__.py")
+    (ext,) = intree_extensions([src.relto(tmpdir)])
+    assert ext.name == "dir.ext"
+
+
+def test_intree_extensions_package_dir(monkeypatch, tmpdir):
+    monkeypatch.syspath_prepend(MAIN_DIR)
+
+    from pybind11.setup_helpers import intree_extensions
+
+    monkeypatch.chdir(tmpdir)
+    root = tmpdir / "src"
+    root.ensure_dir()
+    subdir = root / "dir"
+    subdir.ensure_dir()
+    src = subdir / "ext.cpp"
+    src.ensure()
+    (ext,) = intree_extensions([src.relto(tmpdir)], package_dir={"": "src"})
+    assert ext.name == "dir.ext"
+    (ext,) = intree_extensions([src.relto(tmpdir)], package_dir={"foo": "src"})
+    assert ext.name == "foo.dir.ext"
+    subdir.ensure("__init__.py")
+    (ext,) = intree_extensions([src.relto(tmpdir)], package_dir={"": "src"})
+    assert ext.name == "dir.ext"
+    (ext,) = intree_extensions([src.relto(tmpdir)], package_dir={"foo": "src"})
+    assert ext.name == "foo.dir.ext"

From aca6c3ba37ca8f0855dfe60370b407abca4cb994 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 13 Jul 2021 18:14:58 -0700
Subject: [PATCH 069/638] * Removing stray semicolons (discovered by running
 clang-format v12 followed by tools/check-style.sh). (#3087)

* Manually moving `// NOLINT` comments so that clang-format does not move them to the wrong places.

* Manually reformatting comments related to `static_assert`s so that clang-format does not need two passes.

* Empty lines between #includes, to prevent clang-format from shuffling the order and thereby confusing MSVC 2015.

* git diff -U0 --no-color HEAD^ | python3 $HOME/clone/llvm-project/clang/tools/clang-format/clang-format-diff.py -p1 -style=file -i
---
 include/pybind11/attr.h               |  3 ++-
 include/pybind11/detail/common.h      |  3 ++-
 tests/pybind11_tests.h                |  7 ++++++-
 tests/test_buffers.cpp                |  2 +-
 tests/test_callbacks.cpp              |  2 +-
 tests/test_eigen.cpp                  |  5 ++++-
 tests/test_methods_and_attributes.cpp | 12 ++++++------
 tests/test_smart_ptr.cpp              |  2 +-
 8 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 97147904ce..60ed9fd90e 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -62,7 +62,8 @@ struct metaclass {
     handle value;
 
     PYBIND11_DEPRECATED("py::metaclass() is no longer required. It's turned on by default now.")
-    metaclass() { } // NOLINT(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
+    // NOLINTNEXTLINE(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
+    metaclass() {}
 
     /// Override pybind11's default metaclass
     explicit metaclass(handle value) : value(value) { }
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1f7446103e..f804e7c85a 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -801,7 +801,8 @@ struct nodelete { template <typename T> void operator()(T*) { } };
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename... Args>
 struct overload_cast_impl {
-    constexpr overload_cast_impl() {}; // NOLINT(modernize-use-equals-default):  MSVC 2015 needs this
+    // NOLINTNEXTLINE(modernize-use-equals-default):  MSVC 2015 needs this
+    constexpr overload_cast_impl() {}
 
     template <typename Return>
     constexpr auto operator()(Return (*pf)(Args...)) const noexcept
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index ccb0529787..d970ba8bd4 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -1,10 +1,15 @@
 #pragma once
+
+// This must be kept first for MSVC 2015.
+// Do not remove the empty line between the #includes.
 #include <pybind11/pybind11.h>
+
 #include <pybind11/eval.h>
 
 #if defined(_MSC_VER) && _MSC_VER < 1910
 // We get some really long type names here which causes MSVC 2015 to emit warnings
-#  pragma warning(disable: 4503) // warning C4503: decorated name length exceeded, name was truncated
+#    pragma warning(                                                                              \
+        disable : 4503) // warning C4503: decorated name length exceeded, name was truncated
 #endif
 
 namespace py = pybind11;
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 15dd4f1c74..e77c626f87 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -154,7 +154,7 @@ TEST_SUBMODULE(buffers, m) {
                                    py::format_descriptor<int32_t>::format(), 1);
         }
 
-        ConstBuffer() : value(new int32_t{0}) { };
+        ConstBuffer() : value(new int32_t{0}) {}
     };
     py::class_<ConstBuffer>(m, "ConstBuffer", py::buffer_protocol())
         .def(py::init<>())
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 7e79217a3d..a208b44d04 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -122,7 +122,7 @@ TEST_SUBMODULE(callbacks, m) {
         // [workaround(intel)] = default does not work here
         // Defaulting this destructor results in linking errors with the Intel compiler
         // (in Debug builds only, tested with icpc (ICC) 2021.1 Beta 20200827)
-        virtual ~AbstractBase() {};  // NOLINT(modernize-use-equals-default)
+        virtual ~AbstractBase() {} // NOLINT(modernize-use-equals-default)
         virtual unsigned int func() = 0;
     };
     m.def("func_accepting_func_accepting_base",
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index ba74f58156..651be0575f 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -258,7 +258,10 @@ TEST_SUBMODULE(eigen, m) {
     m.def("dense_copy_r", [](const DenseMatrixR &m) -> DenseMatrixR { return m; });
     m.def("dense_copy_c", [](const DenseMatrixC &m) -> DenseMatrixC { return m; });
     // test_sparse, test_sparse_signature
-    m.def("sparse_r", [mat]() -> SparseMatrixR { return Eigen::SparseView<Eigen::MatrixXf>(mat); }); //NOLINT(clang-analyzer-core.uninitialized.UndefReturn)
+    m.def("sparse_r", [mat]() -> SparseMatrixR {
+        // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+        return Eigen::SparseView<Eigen::MatrixXf>(mat);
+    });
     m.def("sparse_c", [mat]() -> SparseMatrixC { return Eigen::SparseView<Eigen::MatrixXf>(mat); });
     m.def("sparse_copy_r", [](const SparseMatrixR &m) -> SparseMatrixR { return m; });
     m.def("sparse_copy_c", [](const SparseMatrixC &m) -> SparseMatrixC { return m; });
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 6e5999f0c4..9db31a0b82 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -123,7 +123,7 @@ class NoneCastTester {
 public:
     int answer = -1;
     NoneCastTester() = default;
-    NoneCastTester(int v) : answer(v) {};
+    NoneCastTester(int v) : answer(v) {}
 };
 
 struct StrIssue {
@@ -390,14 +390,14 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def("increase_value", &RegisteredDerived::increase_value)
         .def_readwrite("rw_value", &RegisteredDerived::rw_value)
         .def_readonly("ro_value", &RegisteredDerived::ro_value)
-        // These should trigger a static_assert if uncommented
-        //.def_readwrite("fails", &UserType::value) // should trigger a static_assert if uncommented
-        //.def_readonly("fails", &UserType::value) // should trigger a static_assert if uncommented
+        // Uncommenting the next line should trigger a static_assert:
+        // .def_readwrite("fails", &UserType::value)
+        // Uncommenting the next line should trigger a static_assert:
+        // .def_readonly("fails", &UserType::value)
         .def_property("rw_value_prop", &RegisteredDerived::get_int, &RegisteredDerived::set_int)
         .def_property_readonly("ro_value_prop", &RegisteredDerived::get_double)
         // This one is in the registered class:
-        .def("sum", &RegisteredDerived::sum)
-        ;
+        .def("sum", &RegisteredDerived::sum);
 
     using Adapted = decltype(py::method_adaptor<RegisteredDerived>(&RegisteredDerived::do_nothing));
     static_assert(std::is_same<Adapted, void (RegisteredDerived::*)() const>::value, "");
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 534dec0be4..7fd5a9b36e 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -24,7 +24,7 @@ template <typename T> class huge_unique_ptr {
     std::unique_ptr<T> ptr;
     uint64_t padding[10];
 public:
-    huge_unique_ptr(T *p) : ptr(p) {};
+    huge_unique_ptr(T *p) : ptr(p) {}
     T *get() { return ptr.get(); }
 };
 

From 7331d381af4639f385fa07b5cb07d6c5dbacba71 Mon Sep 17 00:00:00 2001
From: Shane Loretz <shane.loretz@gmail.com>
Date: Tue, 13 Jul 2021 21:21:55 -0700
Subject: [PATCH 070/638] Raise codec errors when casting to std::string
 (#2903)

* Raise codec errors when casting to std::string

Allow the codec's exception to be raised instead of RuntimeError when
casting from py::str to std::string.

PY2 allows ucs surrogates in UTF-8 conversion

Signed-off-by: Shane Loretz <sloretz@openrobotics.org>
Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

* Attempt to fix py2 error

* Revert all unicode literals

* Fixed

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/pytypes.h | 2 +-
 tests/test_pytypes.cpp     | 3 +++
 tests/test_pytypes.py      | 8 ++++++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 0fca32a4e9..b483fb323c 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1015,7 +1015,7 @@ class str : public object {
         if (PyUnicode_Check(m_ptr)) {
             temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(m_ptr));
             if (!temp)
-                pybind11_fail("Unable to extract string contents! (encoding issue)");
+                throw error_already_set();
         }
         char *buffer = nullptr;
         ssize_t length = 0;
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 6ed59aad21..d70536d3f0 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -76,6 +76,9 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("str_from_object", [](const py::object& obj) { return py::str(obj); });
     m.def("repr_from_object", [](const py::object& obj) { return py::repr(obj); });
     m.def("str_from_handle", [](py::handle h) { return py::str(h); });
+    m.def("str_from_string_from_str", [](const py::str& obj) {
+        return py::str(static_cast<std::string>(obj));
+    });
 
     m.def("str_format", []() {
         auto s1 = "{} + {} = {}"_s.format(1, 2, 3);
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 25e9f6dffc..66d6d30a0c 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -133,6 +133,14 @@ def __repr__(self):
     else:
         assert m.str_from_handle(malformed_utf8) == "b'\\x80'"
 
+    assert m.str_from_string_from_str("this is a str") == "this is a str"
+    ucs_surrogates_str = u"\udcc3"
+    if env.PY2:
+        assert u"\udcc3" == m.str_from_string_from_str(ucs_surrogates_str)
+    else:
+        with pytest.raises(UnicodeEncodeError):
+            m.str_from_string_from_str(ucs_surrogates_str)
+
 
 def test_bytes(doc):
     assert m.bytes_from_string().decode() == "foo"

From cd061aeef164b380ba7a4b7699679a38f87cb111 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 14 Jul 2021 16:49:13 -0400
Subject: [PATCH 071/638] style: pre-commit cleanup (#3111)

* style: disallow PyTest (should be pytest)

* style: cleanup spell checking a bit

* style: add a few items to the .gitignore
---
 .gitignore              |  2 ++
 .pre-commit-config.yaml | 10 +++-------
 docs/changelog.rst      |  2 +-
 tests/CMakeLists.txt    |  2 +-
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/.gitignore b/.gitignore
index 3f36b89e0c..3cf4fbbda0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,3 +41,5 @@ pybind11Targets.cmake
 /.vscode
 /pybind11/include/*
 /pybind11/share/*
+/docs/_build/*
+.ipynb_checkpoints/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 133eb6df4e..4b0a349165 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -92,12 +92,8 @@ repos:
   rev: v2.1.0
   hooks:
   - id: codespell
-    name: codespell
-    description: Checks for common misspellings in text files.
-    entry: codespell
-    language: python
-    types: [text]
-    args: ["-q", "3", "--skip", "*.supp", "-L", "nd,ot,thist,readded"]
+    exclude: ".supp$"
+    args: ["-L", "nd,ot,thist"]
 
 # The original pybind11 checks for a few C++ style items
 - repo: local
@@ -105,7 +101,7 @@ repos:
   - id: disallow-caps
     name: Disallow improper capitalization
     language: pygrep
-    entry: PyBind|Numpy|Cmake|CCache
+    entry: PyBind|Numpy|Cmake|CCache|PyTest
     exclude: .pre-commit-config.yaml
 
 - repo: local
diff --git a/docs/changelog.rst b/docs/changelog.rst
index d71fccc251..698b78c1a0 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -226,7 +226,7 @@ Bug fixes:
 * Fix ``py::gil_scoped_acquire`` assert with CPython 3.9 debug build.
   `#2683 <https://github.com/pybind/pybind11/pull/2683>`_
 
-* Fix issue with a test failing on PyTest 6.2.
+* Fix issue with a test failing on pytest 6.2.
   `#2741 <https://github.com/pybind/pybind11/pull/2741>`_
 
 Warning fixes:
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 3729b5c7df..dc70038dba 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -315,7 +315,7 @@ function(pybind11_enable_warnings target_name)
     endif()
   endif()
 
-  # Needs to be readded since the ordering requires these to be after the ones above
+  # Needs to be re-added since the ordering requires these to be after the ones above
   if(CMAKE_CXX_STANDARD
      AND CMAKE_CXX_COMPILER_ID MATCHES "Clang"
      AND PYTHON_VERSION VERSION_LESS 3.0)

From c4b0dc7cdd9cd70acce65940305d039ef336fc23 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 14 Jul 2021 16:52:13 -0400
Subject: [PATCH 072/638] Add shellcheck style checking (#3114)

---
 .pre-commit-config.yaml | 5 +++++
 tools/check-style.sh    | 6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4b0a349165..c6f31b280b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -95,6 +95,11 @@ repos:
     exclude: ".supp$"
     args: ["-L", "nd,ot,thist"]
 
+-   repo: https://github.com/shellcheck-py/shellcheck-py
+    rev: v0.7.2.1
+    hooks:
+    -   id: shellcheck
+
 # The original pybind11 checks for a few C++ style items
 - repo: local
   hooks:
diff --git a/tools/check-style.sh b/tools/check-style.sh
index f7af2a4169..6d832523a7 100755
--- a/tools/check-style.sh
+++ b/tools/check-style.sh
@@ -16,11 +16,11 @@ check_style_errors=0
 IFS=$'\n'
 
 
-found="$(grep '\<\(if\|for\|while\|catch\)(\|){' $@ -rn --color=always)"
+found="$(grep '\<\(if\|for\|while\|catch\)(\|){' "$@" -rn --color=always)"
 if [ -n "$found" ]; then
     echo -e '\033[31;01mError: found the following coding style problems:\033[0m'
     check_style_errors=1
-    echo "$found" | sed -e 's/^/    /'
+    echo "${found//^/    /}"
 fi
 
 found="$(awk '
@@ -34,7 +34,7 @@ last && /^\s*{/ {
     last=""
 }
 { last = /(if|for|while|catch|switch)\s*\(.*\)\s*$/ ? $0 : "" }
-' $(find include -type f) $@)"
+' "$(find include -type f)" "$@")"
 if [ -n "$found" ]; then
     check_style_errors=1
     echo -e '\033[31;01mError: braces should occur on the same line as the if/while/.. statement. Found issues in the following files:\033[0m'

From 5cd37507572db8a849309340de9b64645c9094f0 Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@protonmail.com>
Date: Thu, 15 Jul 2021 16:38:52 +0000
Subject: [PATCH 073/638] Enable -Wstrict-aliasing warning (#2816)

* Enable -Wstrict-aliasing warning

* Narrow down the scope of -Wstrict-aliasing

* Go home, MSVC, you're drunk

* Make sure "pragma GCC" is not executed on ICC

Co-authored-by: Yannick Jadoul <yannick.jadoul@belgacom.net>
---
 include/pybind11/pybind11.h | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 616fa70255..b4aab51a7c 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -35,7 +35,6 @@
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wunused-but-set-variable"
 #  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
-#  pragma GCC diagnostic ignored "-Wstrict-aliasing"
 #  pragma GCC diagnostic ignored "-Wattributes"
 #  if __GNUC__ >= 7
 #    pragma GCC diagnostic ignored "-Wnoexcept-type"
@@ -49,10 +48,18 @@
 #include "detail/init.h"
 
 #include <memory>
+#include <new>
 #include <vector>
 #include <string>
 #include <utility>
 
+#if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
+#  define PYBIND11_STD_LAUNDER std::launder
+#  define PYBIND11_HAS_STD_LAUNDER 1
+#else
+#  define PYBIND11_STD_LAUNDER
+#  define PYBIND11_HAS_STD_LAUNDER 0
+#endif
 #if defined(__GNUG__) && !defined(__clang__)
 #  include <cxxabi.h>
 #endif
@@ -151,8 +158,21 @@ class cpp_function : public function {
 #if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
+#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+            // UB without std::launder, but without breaking ABI and/or
+            // a significant refactoring it's "impossible" to solve.
             if (!std::is_trivially_destructible<Func>::value)
-                rec->free_data = [](function_record *r) { ((capture *) &r->data)->~capture(); };
+                rec->free_data = [](function_record *r) {
+                    auto data = PYBIND11_STD_LAUNDER((capture *) &r->data);
+                    (void) data;
+                    data->~capture();
+                };
+#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
+#  pragma GCC diagnostic pop
+#endif
         } else {
             rec->data[0] = new capture { std::forward<Func>(f) };
             rec->free_data = [](function_record *r) { delete ((capture *) r->data[0]); };

From 31843d455dd347ce9ccb27dd5b51822fe2b561c5 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 15 Jul 2021 15:01:13 -0400
Subject: [PATCH 074/638] docs: reduce visibility of 3.9.0 warning (#3105)

---
 README.rst           | 15 +--------------
 docs/limitations.rst | 20 ++++++++++----------
 2 files changed, 11 insertions(+), 24 deletions(-)

diff --git a/README.rst b/README.rst
index 6c2a255109..69a7797e83 100644
--- a/README.rst
+++ b/README.rst
@@ -13,19 +13,6 @@
 
 .. start
 
-.. warning::
-
-   Combining older versions of pybind11 (< 2.6.0) with Python 3.9.0 will
-   trigger undefined behavior that typically manifests as crashes during
-   interpreter shutdown (but could also destroy your data. **You have been
-   warned.**)
-
-   We recommend that you update to the latest patch release of Python (3.9.1),
-   which includes a `fix <https://github.com/python/cpython/pull/22670>`_
-   that resolves this problem. If you do use Python 3.9.0, please update to
-   the latest version of pybind11 (2.6.0 or newer), which includes a temporary
-   workaround specifically when Python 3.9.0 is detected at runtime.
-
 
 **pybind11** is a lightweight header-only library that exposes C++ types
 in Python and vice versa, mainly to create Python bindings of existing
@@ -110,7 +97,7 @@ goodies:
   transparently applied to all entries of one or more NumPy array
   arguments.
 
-- Python’s slice-based access and assignment operations can be
+- Python's slice-based access and assignment operations can be
   supported with just a few lines of code.
 
 - Everything is contained in just a few header files; there is no need
diff --git a/docs/limitations.rst b/docs/limitations.rst
index be7300cdb6..def5ad659c 100644
--- a/docs/limitations.rst
+++ b/docs/limitations.rst
@@ -57,16 +57,16 @@ clean, well written patch would likely be accepted to solve them.
 Python 3.9.0 warning
 ^^^^^^^^^^^^^^^^^^^^
 
-Combining older versions of pybind11 (< 2.6.0) with Python on 3.9.0 will
-trigger undefined behavior that typically manifests as crashes during
+Combining older versions of pybind11 (< 2.6.0) with Python on exactly 3.9.0
+will trigger undefined behavior that typically manifests as crashes during
 interpreter shutdown (but could also destroy your data. **You have been
 warned**).
 
-This issue has been
-`fixed in Python <https://github.com/python/cpython/pull/22670>`_.  As a
-mitigation until 3.9.1 is released and commonly used, pybind11 (2.6.0 or newer)
-includes a temporary workaround specifically when Python 3.9.0 is detected at
-runtime, leaking about 50 bytes of memory when a callback function is garbage
-collected. For reference; the pybind11 test suite has about 2,000 such
-callbacks, but only 49 are garbage collected before the end-of-process. Wheels
-built with Python 3.9.0 will correctly avoid the leak when run in Python 3.9.1.
+This issue was `fixed in Python <https://github.com/python/cpython/pull/22670>`_.
+As a mitigation for this bug, pybind11 2.6.0 or newer includes a workaround
+specifically when Python 3.9.0 is detected at runtime, leaking about 50 bytes
+of memory when a callback function is garbage collected.  For reference, the
+pybind11 test suite has about 2,000 such callbacks, but only 49 are garbage
+collected before the end-of-process. Wheels (even if built with Python 3.9.0)
+will correctly avoid the leak when run in Python 3.9.1, and this does not
+affect other 3.X versions.

From 2415c09459efb0c6ab33d9dfe2a555237577dc6e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 15 Jul 2021 15:01:29 -0400
Subject: [PATCH 075/638] feat(package): support pipx run (#3117)

---
 tools/setup_main.py.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index bcd4ef4aeb..533a75ae71 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -32,6 +32,9 @@ setup(
     entry_points={
         "console_scripts": [
              "pybind11-config = pybind11.__main__:main",
+        ],
+        "pipx.run": [
+             "pybind11 = pybind11.__main__:main",
         ]
     },
     cmdclass=cmdclass

From 55f6f6e9bf7f0848a1c1415f90120be9076e8add Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Thu, 15 Jul 2021 12:41:36 -0700
Subject: [PATCH 076/638] Fix: RTD Docutils Build (#3119)

The docutils 0.17+ release uses more semantic HTML5 tags, which
the RTD theme does not (yet) know.

This breaks side bar, lists and other elements.
---
 docs/requirements.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/docs/requirements.txt b/docs/requirements.txt
index 671dc4b3f3..8f293b5d34 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,4 +1,7 @@
 breathe==4.26.1
+# docutils 0.17 breaks HTML tags & RTD theme
+# https://github.com/sphinx-doc/sphinx/issues/9001
+docutils==0.16
 sphinx==3.3.1
 sphinx_rtd_theme==0.5.0
 sphinxcontrib-moderncmakedomain==3.17

From 1b10292c0597a497cdee43dcba731bcdd1ce0c49 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 15 Jul 2021 16:54:40 -0400
Subject: [PATCH 077/638] chore: support PDF from nox (#3121)

---
 noxfile.py | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/noxfile.py b/noxfile.py
index 3bc61273ff..f0f6680159 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -53,14 +53,18 @@ def docs(session: nox.Session) -> None:
 
     session.install("-r", "docs/requirements.txt")
     session.chdir("docs")
+
+    if "pdf" in session.posargs:
+        session.run("sphinx-build", "-M", "latexpdf", ".", "_build")
+        return
+
     session.run("sphinx-build", "-M", "html", ".", "_build")
 
-    if session.posargs:
-        if "serve" in session.posargs:
-            print("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")
-            session.run("python", "-m", "http.server", "8000", "-d", "_build/html")
-        else:
-            print("Unsupported argument to docs")
+    if "serve" in session.posargs:
+        session.log("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")
+        session.run("python", "-m", "http.server", "8000", "-d", "_build/html")
+    elif session.posargs:
+        session.error("Unsupported argument to docs")
 
 
 @nox.session(reuse_venv=True)

From 4359e00b97154c663b5710a5aef1c961d48753d5 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 15 Jul 2021 15:00:57 -0700
Subject: [PATCH 078/638] Introducing PYBIND11_VERSION_HEX (#3120)

* Introducing PYBIND11_VERSION_HEX (better late than never!)

* PYBIND11_VERSION_HEX consistency check in setup.py
---
 include/pybind11/detail/common.h |  4 ++++
 setup.py                         | 39 ++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index f804e7c85a..f036269afd 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -13,6 +13,10 @@
 #define PYBIND11_VERSION_MINOR 6
 #define PYBIND11_VERSION_PATCH 3.dev1
 
+// Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
+// Additional convention: 0xD = dev
+#define PYBIND11_VERSION_HEX 0x020603D1
+
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
 
diff --git a/setup.py b/setup.py
index 3a0327982a..ced3d69581 100644
--- a/setup.py
+++ b/setup.py
@@ -19,6 +19,36 @@
     r"^\s*#\s*define\s+PYBIND11_VERSION_([A-Z]+)\s+(.*)$", re.MULTILINE
 )
 
+
+def build_expected_version_hex(matches):
+    patch_level_serial = matches["PATCH"]
+    serial = None
+    try:
+        major = int(matches["MAJOR"])
+        minor = int(matches["MINOR"])
+        flds = patch_level_serial.split(".")
+        if flds:
+            patch = int(flds[0])
+            level = None
+            if len(flds) == 1:
+                level = "0"
+                serial = 0
+            elif len(flds) == 2:
+                level_serial = flds[1]
+                for level in ("a", "b", "c", "dev"):
+                    if level_serial.startswith(level):
+                        serial = int(level_serial[len(level) :])
+                        break
+    except ValueError:
+        pass
+    if serial is None:
+        msg = 'Invalid PYBIND11_VERSION_PATCH: "{}"'.format(patch_level_serial)
+        raise RuntimeError(msg)
+    return "0x{:02x}{:02x}{:02x}{}{:x}".format(
+        major, minor, patch, level[:1].upper(), serial
+    )
+
+
 # PYBIND11_GLOBAL_SDIST will build a different sdist, with the python-headers
 # files, and the sys.prefix files (CMake and headers).
 
@@ -49,6 +79,15 @@
     )
     raise RuntimeError(msg)
 
+version_hex = matches.get("HEX", "MISSING")
+expected_version_hex = build_expected_version_hex(matches)
+if version_hex != expected_version_hex:
+    msg = "PYBIND11_VERSION_HEX {} does not match expected value {}!".format(
+        version_hex,
+        expected_version_hex,
+    )
+    raise RuntimeError(msg)
+
 
 def get_and_replace(filename, binary=False, **opts):
     with open(filename, "rb" if binary else "r") as f:

From 6642f389dc5b7b05b5682ba5db8460817649791d Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 15 Jul 2021 20:00:07 -0400
Subject: [PATCH 079/638] docs: update changelog (#3122)

---
 docs/changelog.rst | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 698b78c1a0..31dcae2069 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -30,6 +30,10 @@ New features:
   ``os.PathLike`` to ``std::filesystem::path``.
   `#2730 <https://github.com/pybind/pybind11/pull/2730>`_
 
+* A ``PYBIND11_VERSION_HEX`` define was added, similar to ``PY_VERSION_HEX``.
+  `#3120 <https://github.com/pybind/pybind11/pull/3120>`_
+
+
 
 Changes:
 
@@ -101,6 +105,10 @@ Fixes:
   from a ``shared_from_this`` class.
   `#2819 <https://github.com/pybind/pybind11/pull/2819>`_
 
+* Allow the codec's exception to be raised instead of :code:`RuntimeError` when
+  casting from :code:`py::str` to :code:`std::string`.
+  `#2903 <https://github.com/pybind/pybind11/pull/2903>`_
+
 
 Build system improvements:
 
@@ -121,6 +129,10 @@ Build system improvements:
 * Clang on Windows: do not pass ``/MP`` (ignored flag).
   `#2824 <https://github.com/pybind/pybind11/pull/2824>`_
 
+* ``pybind11.setup_helpers.intree_extensions`` can be used to generate
+  ``Pybind11Extension`` instances from cpp files placed in the Python package
+  source tree.
+  `#2831 <https://github.com/pybind/pybind11/pull/2831>`_
 
 Backend and tidying up:
 
@@ -129,8 +141,10 @@ Backend and tidying up:
   `#3046 <https://github.com/pybind/pybind11/pull/3046>`_,
   `#3049 <https://github.com/pybind/pybind11/pull/3049>`_,
   `#3051 <https://github.com/pybind/pybind11/pull/3051>`_,
-  `#3052 <https://github.com/pybind/pybind11/pull/3052>`_, and
-  `#3080 <https://github.com/pybind/pybind11/pull/3080>`_
+  `#3052 <https://github.com/pybind/pybind11/pull/3052>`_,
+  `#3080 <https://github.com/pybind/pybind11/pull/3080>`_, and
+  `#3094 <https://github.com/pybind/pybind11/pull/3094>`_
+
 
 * Checks for common misspellings were added to the pre-commit hooks.
   `#3076 <https://github.com/pybind/pybind11/pull/3076>`_
@@ -143,7 +157,14 @@ Backend and tidying up:
   `#2956 <https://github.com/pybind/pybind11/pull/2956>`_
 
 * Added nox support for easier local testing and linting of contributions.
-  `#3101 <https://github.com/pybind/pybind11/pull/3101>`_
+  `#3101 <https://github.com/pybind/pybind11/pull/3101>`_ and
+  `#3121 <https://github.com/pybind/pybind11/pull/3121>`_
+
+* Avoid RTD style issue with docutils 0.17+.
+  `#3119 <https://github.com/pybind/pybind11/pull/3119>`_
+
+* Support pipx run, such as ``pipx run pybind11 --include`` for a quick compile.
+  `#3117 <https://github.com/pybind/pybind11/pull/3117>`_
 
 
 

From 65e95ea8675ea34bdd566d6461330f25c651e5a8 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 16 Jul 2021 09:27:47 -0400
Subject: [PATCH 080/638] chore: bump to 2.7.0 (#3123)

---
 docs/changelog.rst               | 4 ++--
 docs/release.rst                 | 2 +-
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 31dcae2069..293e9fb7ff 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,8 +6,8 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
-v2.7.0 (TBA, not yet released)
-------------------------------
+v2.7.0 (Jul 16, 2021)
+---------------------
 
 New features:
 
diff --git a/docs/release.rst b/docs/release.rst
index 9dbff03838..2c64e64ab8 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -53,7 +53,7 @@ To release a new version of pybind11:
     name like "Version X.Y.Z", and optionally copy-and-paste the changelog into
     the description (processed as markdown by Pandoc). Check "pre-release" if
     this is a beta/RC. You can get partway there with
-    ``cat docs/changelog.rst | pandsoc -f rst -t markdown``.
+    ``cat docs/changelog.rst | pandoc -f rst -t markdown``.
   - CLI method: with ``gh`` installed, run ``gh release create vX.Y.Z -t "Version X.Y.Z"``
     If this is a pre-release, add ``-p``.
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index f036269afd..cf20e4a2eb 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 6
-#define PYBIND11_VERSION_PATCH 3.dev1
+#define PYBIND11_VERSION_MINOR 7
+#define PYBIND11_VERSION_PATCH 0
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020603D1
+#define PYBIND11_VERSION_HEX 0x02070000
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index ffadcca5a8..5c0fa0b44f 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.6.3.dev1"
+__version__ = "2.7.0"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 74935f8d675a308244a7cdcf92aa97f41f496124 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sat, 17 Jul 2021 11:50:42 -0400
Subject: [PATCH 081/638] chore: post-release (#3128)

---
 docs/changelog.rst               |  5 +++
 docs/release.rst                 | 64 ++++++++++++++++----------------
 include/pybind11/detail/common.h |  4 +-
 pybind11/_version.py             |  2 +-
 4 files changed, 41 insertions(+), 34 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 293e9fb7ff..5e8a63258f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,6 +6,11 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
+Next version (WIP)
+------------------
+
+
+
 v2.7.0 (Jul 16, 2021)
 ---------------------
 
diff --git a/docs/release.rst b/docs/release.rst
index 2c64e64ab8..e4f3d1902a 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -15,31 +15,33 @@ For example:
 
 For beta, ``PYBIND11_VERSION_PATCH`` should be ``Z.b1``. RC's can be ``Z.rc1``.
 Always include the dot (even though PEP 440 allows it to be dropped). For a
-final release, this must be a simple integer.
+final release, this must be a simple integer. There is also a HEX version of
+the version just below.
 
 
 To release a new version of pybind11:
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 - Update the version number
-  - Update ``PYBIND11_VERSION_MAJOR`` etc. in
-    ``include/pybind11/detail/common.h``. PATCH should be a simple integer.
-  - Update ``pybind11/_version.py`` (match above)
-  - Ensure that all the information in ``setup.cfg`` is up-to-date, like
-    supported Python versions.
-  - Add release date in ``docs/changelog.rst``.
-      - Check to make sure
-        `needs-changelog <https://github.com/pybind/pybind11/pulls?q=is%3Apr+is%3Aclosed+label%3A%22needs+changelog%22>`_
-        issues are entered in the changelog (clear the label when done).
-  - ``git add`` and ``git commit``, ``git push``. **Ensure CI passes**. (If it
-    fails due to a known flake issue, either ignore or restart CI.)
+    - Update ``PYBIND11_VERSION_MAJOR`` etc. in
+      ``include/pybind11/detail/common.h``. PATCH should be a simple integer.
+    - Update the version HEX just below, as well.
+    - Update ``pybind11/_version.py`` (match above)
+    - Ensure that all the information in ``setup.cfg`` is up-to-date, like
+      supported Python versions.
+    - Add release date in ``docs/changelog.rst``.
+          - Check to make sure
+            `needs-changelog <https://github.com/pybind/pybind11/pulls?q=is%3Apr+is%3Aclosed+label%3A%22needs+changelog%22>`_
+            issues are entered in the changelog (clear the label when done).
+    - ``git add`` and ``git commit``, ``git push``. **Ensure CI passes**. (If it
+      fails due to a known flake issue, either ignore or restart CI.)
 - Add a release branch if this is a new minor version, or update the existing release branch if it is a patch version
-  - New branch: ``git checkout -b vX.Y``, ``git push -u origin vX.Y``
-  - Update branch: ``git checkout vX.Y``, ``git merge <release branch>``, ``git push``
+    - New branch: ``git checkout -b vX.Y``, ``git push -u origin vX.Y``
+    - Update branch: ``git checkout vX.Y``, ``git merge <release branch>``, ``git push``
 - Update tags (optional; if you skip this, the GitHub release makes a
-  non-annotated tag for you)
-  - ``git tag -a vX.Y.Z -m 'vX.Y.Z release'``.
-  - ``git push --tags``.
+    non-annotated tag for you)
+    - ``git tag -a vX.Y.Z -m 'vX.Y.Z release'``.
+    - ``git push --tags``.
 - Update stable
     - ``git checkout stable``
     - ``git merge master``
@@ -48,22 +50,22 @@ To release a new version of pybind11:
   notifications to users watching releases, and also uploads PyPI packages).
   (Note: if you do not use an existing tag, this creates a new lightweight tag
   for you, so you could skip the above step).
-  - GUI method: click "Create a new release" on the far right, fill in the tag
-    name (if you didn't tag above, it will be made here), fill in a release
-    name like "Version X.Y.Z", and optionally copy-and-paste the changelog into
-    the description (processed as markdown by Pandoc). Check "pre-release" if
-    this is a beta/RC. You can get partway there with
-    ``cat docs/changelog.rst | pandoc -f rst -t markdown``.
-  - CLI method: with ``gh`` installed, run ``gh release create vX.Y.Z -t "Version X.Y.Z"``
-    If this is a pre-release, add ``-p``.
+    - GUI method: click "Create a new release" on the far right, fill in the tag
+      name (if you didn't tag above, it will be made here), fill in a release
+      name like "Version X.Y.Z", and optionally copy-and-paste the changelog into
+      the description (processed as markdown by Pandoc). Check "pre-release" if
+      this is a beta/RC. You can get partway there with
+      ``cat docs/changelog.rst | pandoc -f rst -t gfm``.
+    - CLI method: with ``gh`` installed, run ``gh release create vX.Y.Z -t "Version X.Y.Z"``
+      If this is a pre-release, add ``-p``.
 
 - Get back to work
-  - Make sure you are on master, not somewhere else: ``git checkout master``
-  - Update version macros in ``include/pybind11/detail/common.h`` (set PATCH to
-    ``0.dev1`` and increment MINOR).
-  - Update ``_version.py`` to match
-  - Add a spot for in-development updates in ``docs/changelog.rst``.
-  - ``git add``, ``git commit``, ``git push``
+    - Make sure you are on master, not somewhere else: ``git checkout master``
+    - Update version macros in ``include/pybind11/detail/common.h`` (set PATCH to
+      ``0.dev1`` and increment MINOR).
+    - Update ``_version.py`` to match
+    - Add a spot for in-development updates in ``docs/changelog.rst``.
+    - ``git add``, ``git commit``, ``git push``
 
 If a version branch is updated, remember to set PATCH to ``1.dev1``.
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index cf20e4a2eb..52b0193350 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 7
-#define PYBIND11_VERSION_PATCH 0
+#define PYBIND11_VERSION_PATCH 1.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x02070000
+#define PYBIND11_VERSION_HEX 0x020701D1
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 5c0fa0b44f..2bb14b963d 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.7.0"
+__version__ = "2.7.1.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 34f587dd2398efb933b5b8d97b73791ddcb4b87b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 17 Jul 2021 08:54:31 -0700
Subject: [PATCH 082/638] Removing all warning pragmas that have not effect.
 (#3127)

---
 include/pybind11/pybind11.h | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b4aab51a7c..af8e730d3f 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -12,29 +12,19 @@
 
 #if defined(__INTEL_COMPILER)
 #  pragma warning push
-#  pragma warning disable 68    // integer conversion resulted in a change of sign
-#  pragma warning disable 186   // pointless comparison of unsigned integer with zero
 #  pragma warning disable 878   // incompatible exception specifications
-#  pragma warning disable 1334  // the "template" keyword used for syntactic disambiguation may only be used within a template
-#  pragma warning disable 1682  // implicit conversion of a 64-bit integral type to a smaller integral type (potential portability problem)
-#  pragma warning disable 1786  // function "strdup" was declared deprecated
-#  pragma warning disable 1875  // offsetof applied to non-POD (Plain Old Data) types is nonstandard
 #  pragma warning disable 2196  // warning #2196: routine is both "inline" and "noinline"
 #elif defined(_MSC_VER)
 #  pragma warning(push)
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#  pragma warning(disable: 4512) // warning C4512: Assignment operator was implicitly defined as deleted
 #  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
 #  pragma warning(disable: 4996) // warning C4996: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name
-#  pragma warning(disable: 4702) // warning C4702: unreachable code
 #  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
-#  pragma GCC diagnostic ignored "-Wunused-but-set-variable"
-#  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
 #  pragma GCC diagnostic ignored "-Wattributes"
 #  if __GNUC__ >= 7
 #    pragma GCC diagnostic ignored "-Wnoexcept-type"

From 9626483cdfb1e9d22275d7bd059822e08bdf55c2 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 20 Jul 2021 11:29:42 -0400
Subject: [PATCH 083/638] [pre-commit.ci] pre-commit autoupdate (#3134)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.21.0 → v2.21.2](https://github.com/asottile/pyupgrade/compare/v2.21.0...v2.21.2)
- [github.com/psf/black: 21.6b0 → 21.7b0](https://github.com/psf/black/compare/21.6b0...21.7b0)
- https://gitlab.com/pycqa/flake8 → https://github.com/PyCQA/flake8
---
 .pre-commit-config.yaml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c6f31b280b..aa7b4774e3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,13 +31,13 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.21.0
+  rev: v2.21.2
   hooks:
   - id: pyupgrade
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.6b0
+  rev: 21.7b0
   hooks:
   - id: black
     # By default, this ignores pyi files, though black supports them
@@ -51,7 +51,7 @@ repos:
   - id: remove-tabs
 
 # Flake8 also supports pre-commit natively (same author)
-- repo: https://gitlab.com/pycqa/flake8
+- repo: https://github.com/PyCQA/flake8
   rev: 3.9.2
   hooks:
   - id: flake8

From 6d5d4e738caad61152427f2b3b0c3fa09b52ce03 Mon Sep 17 00:00:00 2001
From: blacktea <42189825+blacktea@users.noreply.github.com>
Date: Tue, 20 Jul 2021 18:48:09 +0300
Subject: [PATCH 084/638] Move object in pop method of List. (#3116)

* Move item instead of copy.

* Make Clang 3.6 happy.

Co-authored-by: c99 <email@dummy.com>
---
 include/pybind11/stl_bind.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index effac0b931..82317b3791 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -191,7 +191,7 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         [](Vector &v) {
             if (v.empty())
                 throw index_error();
-            T t = v.back();
+            T t = std::move(v.back());
             v.pop_back();
             return t;
         },
@@ -201,8 +201,8 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
     cl.def("pop",
         [wrap_i](Vector &v, DiffType i) {
             i = wrap_i(i, v.size());
-            T t = v[(SizeType) i];
-            v.erase(v.begin() + i);
+            T t = std::move(v[(SizeType) i]);
+            v.erase(std::next(v.begin(), i));
             return t;
         },
         arg("i"),

From d65edfb0243c9bc24b748c52d2983ef4dd627004 Mon Sep 17 00:00:00 2001
From: jesse-sony <50677487+jesse-sony@users.noreply.github.com>
Date: Wed, 21 Jul 2021 08:22:18 -0400
Subject: [PATCH 085/638] Feature/local exception translator (#2650)

* Create a module_internals struct

Since we now have two things that are going to be module local, it felt
correct to add a struct to manage them.

* Add local exception translators

These are added via the  register_local_exception_translator function
and are then applied before the global translators

* Add unit tests to show the local exception translator works

* Fix a bug in the unit test with the string value of KeyError

* Fix a formatting issue

* Rename registered_local_types_cpp()

Rename it to get_registered_local_types_cpp() to disambiguate from the
new member of module_internals

* Add additional comments to new local exception code path

* Add a register_local_exception function

* Add additional unit tests for register_local_exception

* Use get_local_internals like get_internals

* Update documentation for new local exception feature

* Add back a missing space

* Clean-up some issues in the docs

* Remove the code duplication when translating exceptions

Separated out the exception processing into a standalone function in the
details namespace.

Clean-up some comments as per PR notes as well

* Remove the code duplication in register_exception

* Cleanup some formatting things caught by clang-format

* Remove the templates from exception translators

But I added a using declaration to alias the type.

* Remove the extra local from local_internals variable names

* Add an extra explanatory comment to local_internals

* Fix a typo in the code
---
 docs/advanced/exceptions.rst               |  72 +++++++++++--
 include/pybind11/detail/class.h            |   2 +-
 include/pybind11/detail/internals.h        |  27 ++++-
 include/pybind11/detail/type_caster_base.h |   2 +-
 include/pybind11/pybind11.h                | 119 ++++++++++++++++-----
 tests/local_bindings.h                     |  19 ++++
 tests/pybind11_cross_module_tests.cpp      |  16 ++-
 tests/test_exceptions.cpp                  |  31 +++++-
 tests/test_exceptions.py                   |  29 ++++-
 tests/test_local_bindings.cpp              |   2 +-
 10 files changed, 274 insertions(+), 45 deletions(-)

diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index f70c202fd5..738fb0ba9c 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -75,9 +75,10 @@ Registering custom translators
 
 If the default exception conversion policy described above is insufficient,
 pybind11 also provides support for registering custom exception translators.
-To register a simple exception conversion that translates a C++ exception into
-a new Python exception using the C++ exception's ``what()`` method, a helper
-function is available:
+Similar to pybind11 classes, exception translators can be local to the module
+they are defined in or global to the entire python session.  To register a simple
+exception conversion that translates a C++ exception into a new Python exception
+using the C++ exception's ``what()`` method, a helper function is available:
 
 .. code-block:: cpp
 
@@ -87,12 +88,20 @@ This call creates a Python exception class with the name ``PyExp`` in the given
 module and automatically converts any encountered exceptions of type ``CppExp``
 into Python exceptions of type ``PyExp``.
 
+A matching function is available for registering a local exception translator:
+
+.. code-block:: cpp
+
+    py::register_local_exception<CppExp>(module, "PyExp");
+
+
 It is possible to specify base class for the exception using the third
 parameter, a `handle`:
 
 .. code-block:: cpp
 
     py::register_exception<CppExp>(module, "PyExp", PyExc_RuntimeError);
+    py::register_local_exception<CppExp>(module, "PyExp", PyExc_RuntimeError);
 
 Then `PyExp` can be caught both as `PyExp` and `RuntimeError`.
 
@@ -100,16 +109,18 @@ The class objects of the built-in Python exceptions are listed in the Python
 documentation on `Standard Exceptions <https://docs.python.org/3/c-api/exceptions.html#standard-exceptions>`_.
 The default base class is `PyExc_Exception`.
 
-When more advanced exception translation is needed, the function
-``py::register_exception_translator(translator)`` can be used to register
+When more advanced exception translation is needed, the functions
+``py::register_exception_translator(translator)`` and
+``py::register_local_exception_translator(translator)`` can be used to register
 functions that can translate arbitrary exception types (and which may include
-additional logic to do so).  The function takes a stateless callable (e.g.  a
+additional logic to do so).  The functions takes a stateless callable (e.g. a
 function pointer or a lambda function without captured variables) with the call
 signature ``void(std::exception_ptr)``.
 
 When a C++ exception is thrown, the registered exception translators are tried
 in reverse order of registration (i.e. the last registered translator gets the
-first shot at handling the exception).
+first shot at handling the exception). All local translators will be tried
+before a global translator is tried.
 
 Inside the translator, ``std::rethrow_exception`` should be used within
 a try block to re-throw the exception.  One or more catch clauses to catch
@@ -168,6 +179,53 @@ section.
     with ``-fvisibility=hidden``. Therefore exceptions that are used across ABI boundaries need to be explicitly exported, as exercised in ``tests/test_exceptions.h``.
     See also: "Problems with C++ exceptions" under `GCC Wiki <https://gcc.gnu.org/wiki/Visibility>`_.
 
+
+Local vs Global Exception Translators
+=====================================
+
+When a global exception translator is registered, it will be applied across all
+modules in the reverse order of registration. This can create behavior where the
+order of module import influences how exceptions are translated.
+
+If module1 has the following translator:
+
+.. code-block:: cpp
+
+      py::register_exception_translator([](std::exception_ptr p) {
+        try {
+            if (p) std::rethrow_exception(p);
+        } catch (const std::invalid_argument &e) {
+            PyErr_SetString("module1 handled this")
+        }
+      }
+
+and module2 has the following similar translator:
+
+.. code-block:: cpp
+
+      py::register_exception_translator([](std::exception_ptr p) {
+        try {
+            if (p) std::rethrow_exception(p);
+        } catch (const std::invalid_argument &e) {
+            PyErr_SetString("module2 handled this")
+        }
+      }
+
+then which translator handles the invalid_argument will be determined by the
+order that module1 and module2 are imported. Since exception translators are
+applied in the reverse order of registration, which ever module was imported
+last will "win" and that translator will be applied.
+
+If there are multiple pybind11 modules that share exception types (either
+standard built-in or custom) loaded into a single python instance and
+consistent error handling behavior is needed, then local translators should be
+used.
+
+Changing the previous example to use ``register_local_exception_translator``
+would mean that when invalid_argument is thrown in the module2 code, the
+module2 translator will always handle it, while in module1, the module1
+translator will do the same.
+
 .. _handling_python_exceptions_cpp:
 
 Handling exceptions from Python in C++
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 5fee3318b0..15e09165de 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -209,7 +209,7 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
         internals.direct_conversions.erase(tindex);
 
         if (tinfo->module_local)
-            registered_local_types_cpp().erase(tindex);
+            get_local_internals().registered_types_cpp.erase(tindex);
         else
             internals.registered_types_cpp.erase(tindex);
         internals.registered_types_py.erase(tinfo->type);
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 5578c65160..a621aed2a6 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -12,7 +12,11 @@
 #include "../pytypes.h"
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+using ExceptionTranslator = void (*)(std::exception_ptr);
+
 PYBIND11_NAMESPACE_BEGIN(detail)
+
 // Forward declarations
 inline PyTypeObject *make_static_property_type();
 inline PyTypeObject *make_default_metaclass();
@@ -100,7 +104,7 @@ struct internals {
     std::unordered_set<std::pair<const PyObject *, const char *>, override_hash> inactive_override_cache;
     type_map<std::vector<bool (*)(PyObject *, void *&)>> direct_conversions;
     std::unordered_map<const PyObject *, std::vector<PyObject *>> patients;
-    std::forward_list<void (*) (std::exception_ptr)> registered_exception_translators;
+    std::forward_list<ExceptionTranslator> registered_exception_translators;
     std::unordered_map<std::string, void *> shared_data; // Custom data to be shared across extensions
     std::vector<PyObject *> loader_patient_stack; // Used by `loader_life_support`
     std::forward_list<std::string> static_strings; // Stores the std::strings backing detail::c_str()
@@ -313,12 +317,25 @@ PYBIND11_NOINLINE inline internals &get_internals() {
     return **internals_pp;
 }
 
-/// Works like `internals.registered_types_cpp`, but for module-local registered types:
-inline type_map<type_info *> &registered_local_types_cpp() {
-    static type_map<type_info *> locals{};
-    return locals;
+
+// the internals struct (above) is shared between all the modules. local_internals are only
+// for a single module. Any changes made to internals may require an update to
+// PYBIND11_INTERNALS_VERSION, breaking backwards compatibility. local_internals is, by design,
+// restricted to a single module. Whether a module has local internals or not should not
+// impact any other modules, because the only things accessing the local internals is the
+// module that contains them.
+struct local_internals {
+  type_map<type_info *> registered_types_cpp;
+  std::forward_list<ExceptionTranslator> registered_exception_translators;
+};
+
+/// Works like `get_internals`, but for things which are locally registered.
+inline local_internals &get_local_internals() {
+  static local_internals locals;
+  return locals;
 }
 
+
 /// Constructs a std::string with the given arguments, stores it in `internals`, and returns its
 /// `c_str()`.  Such strings objects have a long storage duration -- the internal strings are only
 /// cleared when the program exits or after interpreter shutdown (when embedding), and so are
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 451690dc73..bdf3a39822 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -160,7 +160,7 @@ PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type) {
 }
 
 inline detail::type_info *get_local_type_info(const std::type_index &tp) {
-    auto &locals = registered_local_types_cpp();
+    auto &locals = get_local_internals().registered_types_cpp;
     auto it = locals.find(tp);
     if (it != locals.end())
         return it->second;
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index af8e730d3f..0c25ca1a23 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -56,6 +56,29 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+// Apply all the extensions translators from a list
+// Return true if one of the translators completed without raising an exception
+// itself. Return of false indicates that if there are other translators
+// available, they should be tried.
+inline bool apply_exception_translators(std::forward_list<ExceptionTranslator>& translators) {
+    auto last_exception = std::current_exception();
+
+    for (auto &translator : translators) {
+        try {
+            translator(last_exception);
+            return true;
+        } catch (...) {
+            last_exception = std::current_exception();
+        }
+    }
+    return false;
+}
+
+PYBIND11_NAMESPACE_END(detail)
+
+
 /// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object
 class cpp_function : public function {
 public:
@@ -550,6 +573,7 @@ class cpp_function : public function {
         }
     }
 
+
     /// Main dispatch logic for calls to functions bound using pybind11
     static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) {
         using namespace detail;
@@ -830,8 +854,12 @@ class cpp_function : public function {
 #endif
         } catch (...) {
             /* When an exception is caught, give each registered exception
-               translator a chance to translate it to a Python exception
-               in reverse order of registration.
+               translator a chance to translate it to a Python exception. First
+               all module-local translators will be tried in reverse order of
+               registration. If none of the module-locale translators handle
+               the exception (or there are no module-locale translators) then
+               the global translators will be tried, also in reverse order of
+               registration.
 
                A translator may choose to do one of the following:
 
@@ -840,17 +868,15 @@ class cpp_function : public function {
                 - do nothing and let the exception fall through to the next translator, or
                 - delegate translation to the next translator by throwing a new type of exception. */
 
-            auto last_exception = std::current_exception();
-            auto &registered_exception_translators = get_internals().registered_exception_translators;
-            for (auto& translator : registered_exception_translators) {
-                try {
-                    translator(last_exception);
-                } catch (...) {
-                    last_exception = std::current_exception();
-                    continue;
-                }
+            auto &local_exception_translators = get_local_internals().registered_exception_translators;
+            if (detail::apply_exception_translators(local_exception_translators)) {
+                return nullptr;
+            }
+            auto &exception_translators = get_internals().registered_exception_translators;
+            if (detail::apply_exception_translators(exception_translators)) {
                 return nullptr;
             }
+
             PyErr_SetString(PyExc_SystemError, "Exception escaped from default exception translator!");
             return nullptr;
         }
@@ -951,6 +977,7 @@ class cpp_function : public function {
     }
 };
 
+
 /// Wrapper for Python extension modules
 class module_ : public object {
 public:
@@ -1124,7 +1151,7 @@ class generic_type : public object {
         auto tindex = std::type_index(*rec.type);
         tinfo->direct_conversions = &internals.direct_conversions[tindex];
         if (rec.module_local)
-            registered_local_types_cpp()[tindex] = tinfo;
+            get_local_internals().registered_types_cpp[tindex] = tinfo;
         else
             internals.registered_types_cpp[tindex] = tinfo;
         internals.registered_types_py[(PyTypeObject *) m_ptr] = { tinfo };
@@ -1310,7 +1337,7 @@ class class_ : public detail::generic_type {
         generic_type::initialize(record);
 
         if (has_alias) {
-            auto &instances = record.module_local ? registered_local_types_cpp() : get_internals().registered_types_cpp;
+            auto &instances = record.module_local ? get_local_internals().registered_types_cpp : get_internals().registered_types_cpp;
             instances[std::type_index(typeid(type_alias))] = instances[std::type_index(typeid(type))];
         }
     }
@@ -2010,12 +2037,24 @@ template <typename InputType, typename OutputType> void implicitly_convertible()
         pybind11_fail("implicitly_convertible: Unable to find type " + type_id<OutputType>());
 }
 
-template <typename ExceptionTranslator>
-void register_exception_translator(ExceptionTranslator&& translator) {
+
+inline void register_exception_translator(ExceptionTranslator &&translator) {
     detail::get_internals().registered_exception_translators.push_front(
         std::forward<ExceptionTranslator>(translator));
 }
 
+
+/**
+  * Add a new module-local exception translator. Locally registered functions
+  * will be tried before any globally registered exception translators, which
+  * will only be invoked if the module-local handlers do not deal with
+  * the exception.
+  */
+inline void register_local_exception_translator(ExceptionTranslator &&translator) {
+    detail::get_local_internals().registered_exception_translators.push_front(
+        std::forward<ExceptionTranslator>(translator));
+}
+
 /**
  * Wrapper to generate a new Python exception type.
  *
@@ -2049,22 +2088,20 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // directly in register_exception, but that makes clang <3.5 segfault - issue #1349).
 template <typename CppException>
 exception<CppException> &get_exception_object() { static exception<CppException> ex; return ex; }
-PYBIND11_NAMESPACE_END(detail)
 
-/**
- * Registers a Python exception in `m` of the given `name` and installs an exception translator to
- * translate the C++ exception to the created Python exception using the exceptions what() method.
- * This is intended for simple exception translations; for more complex translation, register the
- * exception object and translator directly.
- */
+// Helper function for register_exception and register_local_exception
 template <typename CppException>
-exception<CppException> &register_exception(handle scope,
-                                            const char *name,
-                                            handle base = PyExc_Exception) {
+exception<CppException> &register_exception_impl(handle scope,
+                                                const char *name,
+                                                handle base,
+                                                bool isLocal) {
     auto &ex = detail::get_exception_object<CppException>();
     if (!ex) ex = exception<CppException>(scope, name, base);
 
-    register_exception_translator([](std::exception_ptr p) {
+    auto register_func = isLocal ? &register_local_exception_translator
+                                 : &register_exception_translator;
+
+    register_func([](std::exception_ptr p) {
         if (!p) return;
         try {
             std::rethrow_exception(p);
@@ -2075,6 +2112,36 @@ exception<CppException> &register_exception(handle scope,
     return ex;
 }
 
+PYBIND11_NAMESPACE_END(detail)
+
+/**
+ * Registers a Python exception in `m` of the given `name` and installs a translator to
+ * translate the C++ exception to the created Python exception using the what() method.
+ * This is intended for simple exception translations; for more complex translation, register the
+ * exception object and translator directly.
+ */
+template <typename CppException>
+exception<CppException> &register_exception(handle scope,
+                                            const char *name,
+                                            handle base = PyExc_Exception) {
+    return detail::register_exception_impl<CppException>(scope, name, base, false /* isLocal */);
+}
+
+/**
+ * Registers a Python exception in `m` of the given `name` and installs a translator to
+ * translate the C++ exception to the created Python exception using the what() method.
+ * This translator will only be used for exceptions that are thrown in this module and will be
+ * tried before global exception translators, including those registered with register_exception.
+ * This is intended for simple exception translations; for more complex translation, register the
+ * exception object and translator directly.
+ */
+template <typename CppException>
+exception<CppException> &register_local_exception(handle scope,
+                                                  const char *name,
+                                                  handle base = PyExc_Exception) {
+    return detail::register_exception_impl<CppException>(scope, name, base, true /* isLocal */);
+}
+
 PYBIND11_NAMESPACE_BEGIN(detail)
 PYBIND11_NOINLINE inline void print(const tuple &args, const dict &kwargs) {
     auto strings = tuple(args.size());
diff --git a/tests/local_bindings.h b/tests/local_bindings.h
index 8629ed7784..f11c08e616 100644
--- a/tests/local_bindings.h
+++ b/tests/local_bindings.h
@@ -35,6 +35,25 @@ using NonLocalVec2 = std::vector<NonLocal2>;
 using NonLocalMap = std::unordered_map<std::string, NonLocalType>;
 using NonLocalMap2 = std::unordered_map<std::string, uint8_t>;
 
+
+// Exception that will be caught via the module local translator.
+class LocalException : public std::exception {
+public:
+    explicit LocalException(const char * m) : message{m} {}
+    const char * what() const noexcept override {return message.c_str();}
+private:
+    std::string message = "";
+};
+
+// Exception that will be registered with register_local_exception_translator
+class LocalSimpleException : public std::exception {
+public:
+    explicit LocalSimpleException(const char * m) : message{m} {}
+    const char * what() const noexcept override {return message.c_str();}
+private:
+    std::string message = "";
+};
+
 PYBIND11_MAKE_OPAQUE(LocalVec);
 PYBIND11_MAKE_OPAQUE(LocalVec2);
 PYBIND11_MAKE_OPAQUE(LocalMap);
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index e79701c6c6..4bfd5302d5 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -29,11 +29,14 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     bind_local<ExternalType2>(m, "ExternalType2", py::module_local());
 
     // test_exceptions.py
+    py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException");
     m.def("raise_runtime_error", []() { PyErr_SetString(PyExc_RuntimeError, "My runtime error"); throw py::error_already_set(); });
     m.def("raise_value_error", []() { PyErr_SetString(PyExc_ValueError, "My value error"); throw py::error_already_set(); });
     m.def("throw_pybind_value_error", []() { throw py::value_error("pybind11 value error"); });
     m.def("throw_pybind_type_error", []() { throw py::type_error("pybind11 type error"); });
     m.def("throw_stop_iteration", []() { throw py::stop_iteration(); });
+    m.def("throw_local_error", []() { throw LocalException("just local"); });
+    m.def("throw_local_simple_error", []() { throw LocalSimpleException("external mod"); });
     py::register_exception_translator([](std::exception_ptr p) {
       try {
           if (p) std::rethrow_exception(p);
@@ -42,6 +45,17 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
       }
     });
 
+    // translate the local exception into a key error but only in this module
+    py::register_local_exception_translator([](std::exception_ptr p) {
+      try {
+          if (p) {
+            std::rethrow_exception(p);
+          }
+      } catch (const LocalException &e) {
+        PyErr_SetString(PyExc_KeyError, e.what());
+      }
+    });
+
     // test_local_bindings.py
     // Local to both:
     bind_local<LocalType, 1>(m, "LocalType", py::module_local())
@@ -94,7 +108,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); });
 
     // test_internal_locals_differ
-    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::registered_local_types_cpp(); });
+    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
 
     // test_stl_caster_vs_stl_bind
     py::bind_vector<std::vector<int>>(m, "VectorInt");
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index f7bacd07e4..e28f0bb798 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -6,9 +6,10 @@
     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
 */
-
 #include "test_exceptions.h"
 
+#include "local_bindings.h"
+
 #include "pybind11_tests.h"
 #include <utility>
 
@@ -68,6 +69,17 @@ class MyException5_1 : public MyException5 {
     using MyException5::MyException5;
 };
 
+
+// Exception that will be caught via the module local translator.
+class MyException6 : public std::exception {
+public:
+    explicit MyException6(const char * m) : message{m} {}
+    const char * what() const noexcept override {return message.c_str();}
+private:
+    std::string message = "";
+};
+
+
 struct PythonCallInDestructor {
     PythonCallInDestructor(const py::dict &d) : d(d) {}
     ~PythonCallInDestructor() { d["good"] = true; }
@@ -138,14 +150,29 @@ TEST_SUBMODULE(exceptions, m) {
     // A slightly more complicated one that declares MyException5_1 as a subclass of MyException5
     py::register_exception<MyException5_1>(m, "MyException5_1", ex5.ptr());
 
+    //py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException")
+
+    py::register_local_exception_translator([](std::exception_ptr p) {
+      try {
+          if (p) {
+            std::rethrow_exception(p);
+          }
+      } catch (const MyException6 &e) {
+        PyErr_SetString(PyExc_RuntimeError, e.what());
+      }
+    });
+
     m.def("throws1", []() { throw MyException("this error should go to a custom type"); });
     m.def("throws2", []() { throw MyException2("this error should go to a standard Python exception"); });
     m.def("throws3", []() { throw MyException3("this error cannot be translated"); });
     m.def("throws4", []() { throw MyException4("this error is rethrown"); });
     m.def("throws5", []() { throw MyException5("this is a helper-defined translated exception"); });
     m.def("throws5_1", []() { throw MyException5_1("MyException5 subclass"); });
+    m.def("throws6", []() { throw MyException6("MyException6 only handled in this module"); });
     m.def("throws_logic_error", []() { throw std::logic_error("this error should fall through to the standard handler"); });
-    m.def("throws_overflow_error", []() {throw std::overflow_error(""); });
+    m.def("throws_overflow_error", []() { throw std::overflow_error(""); });
+    m.def("throws_local_error", []() { throw LocalException("never caught"); });
+    m.def("throws_local_simple_error", []() { throw LocalSimpleException("this mod"); });
     m.def("exception_matches", []() {
         py::dict foo;
         try {
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index b9fc269381..966ae07fc0 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -25,7 +25,7 @@ def test_error_already_set(msg):
     assert msg(excinfo.value) == "foo"
 
 
-def test_cross_module_exceptions():
+def test_cross_module_exceptions(msg):
     with pytest.raises(RuntimeError) as excinfo:
         cm.raise_runtime_error()
     assert str(excinfo.value) == "My runtime error"
@@ -45,6 +45,15 @@ def test_cross_module_exceptions():
     with pytest.raises(StopIteration) as excinfo:
         cm.throw_stop_iteration()
 
+    with pytest.raises(cm.LocalSimpleException) as excinfo:
+        cm.throw_local_simple_error()
+    assert msg(excinfo.value) == "external mod"
+
+    with pytest.raises(KeyError) as excinfo:
+        cm.throw_local_error()
+    # KeyError is a repr of the key, so it has an extra set of quotes
+    assert str(excinfo.value) == "'just local'"
+
 
 # TODO: FIXME
 @pytest.mark.xfail(
@@ -221,3 +230,21 @@ def __repr__(self):
 
     with pytest.raises(TypeError):
         m.simple_bool_passthrough(MyRepr())
+
+
+def test_local_translator(msg):
+    """Tests that a local translator works and that the local translator from
+    the cross module is not applied"""
+    with pytest.raises(RuntimeError) as excinfo:
+        m.throws6()
+    assert msg(excinfo.value) == "MyException6 only handled in this module"
+
+    with pytest.raises(RuntimeError) as excinfo:
+        m.throws_local_error()
+    assert not isinstance(excinfo.value, KeyError)
+    assert msg(excinfo.value) == "never caught"
+
+    with pytest.raises(Exception) as excinfo:
+        m.throws_local_simple_error()
+    assert not isinstance(excinfo.value, cm.LocalSimpleException)
+    assert msg(excinfo.value) == "this mod"
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index bfbab3ed3b..8d6e33f790 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -78,7 +78,7 @@ TEST_SUBMODULE(local_bindings, m) {
     m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); });
 
     // test_internal_locals_differ
-    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::registered_local_types_cpp(); });
+    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
 
     // test_stl_caster_vs_stl_bind
     m.def("load_vector_via_caster", [](std::vector<int> v) {

From e58c6897cc7b77b92e1c49df82a3504f777b97c9 Mon Sep 17 00:00:00 2001
From: ka-bo <55587089+ka-bo@users.noreply.github.com>
Date: Wed, 21 Jul 2021 18:00:57 +0200
Subject: [PATCH 086/638] Specified encoding in setup.py calls of open()
 (#3137)

* Specified encoding in setup.py calls of open()

* Fix for Python2

Co-authored-by: Karsten Bock <karsten.bock@dlr.de>
---
 setup.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/setup.py b/setup.py
index ced3d69581..7aa151c01b 100644
--- a/setup.py
+++ b/setup.py
@@ -11,6 +11,7 @@
 import subprocess
 import sys
 import tempfile
+import io
 
 import setuptools.command.sdist
 
@@ -70,7 +71,7 @@ def build_expected_version_hex(matches):
 version = loc["__version__"]
 
 # Verify that the version matches the one in C++
-with open("include/pybind11/detail/common.h") as f:
+with io.open("include/pybind11/detail/common.h", encoding="utf8") as f:
     matches = dict(VERSION_REGEX.findall(f.read()))
 cpp_version = "{MAJOR}.{MINOR}.{PATCH}".format(**matches)
 if version != cpp_version:

From ff97f101d96cc780ce348ac6b4b4464982578929 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 26 Jul 2021 11:28:36 -0700
Subject: [PATCH 087/638] Removing MSVC C4996 from pragma block at the top of
 pybind11.h (#3129)

* Removing MSVC C4996 from pragma block at the top of pybind11.h

* localtime_thread_safe, PYBIND11_COMPAT_STRDUP

* Adding #include <ctime> (attempt to fix MSVC 2015, 2017 errors).
---
 include/pybind11/chrono.h        | 33 +++++++++++++++++++++++---------
 include/pybind11/detail/common.h |  5 +++++
 include/pybind11/pybind11.h      | 19 ++++++++++++------
 3 files changed, 42 insertions(+), 15 deletions(-)

diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index d32b5b0569..c4e81f5720 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -11,9 +11,14 @@
 #pragma once
 
 #include "pybind11.h"
+
+#include <chrono>
 #include <cmath>
 #include <ctime>
-#include <chrono>
+#include <mutex>
+
+#include <time.h>
+
 #include <datetime.h>
 
 // Backport the PyDateTime_DELTA functions from Python3.3 if required
@@ -95,6 +100,22 @@ template <typename type> class duration_caster {
     PYBIND11_TYPE_CASTER(type, _("datetime.timedelta"));
 };
 
+inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
+#if defined(__STDC_WANT_LIB_EXT1__) || defined(_MSC_VER)
+    if (localtime_s(buf, time))
+        return nullptr;
+    return buf;
+#else
+    static std::mutex mtx;
+    std::lock_guard<std::mutex> lock(mtx);
+    std::tm *tm_ptr = localtime(time);
+    if (tm_ptr != nullptr) {
+        *buf = *tm_ptr;
+    }
+    return tm_ptr;
+#endif
+}
+
 // This is for casting times on the system clock into datetime.datetime instances
 template <typename Duration> class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
 public:
@@ -162,16 +183,10 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         // (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
         std::time_t tt = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
 
-        // std::localtime returns a pointer to a static internal std::tm object on success,
-        // or null pointer otherwise
-        std::tm *localtime_ptr = std::localtime(&tt);
+        std::tm localtime;
+        std::tm *localtime_ptr = localtime_thread_safe(&tt, &localtime);
         if (!localtime_ptr)
             throw cast_error("Unable to represent system_clock in local time");
-
-        // this function uses static memory so it's best to copy it out asap just in case
-        // otherwise other code that is using localtime may break this (not just python code)
-        std::tm localtime = *localtime_ptr;
-
         return PyDateTime_FromDateAndTime(localtime.tm_year + 1900,
                                           localtime.tm_mon + 1,
                                           localtime.tm_mday,
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 52b0193350..3faf3ea327 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -125,6 +125,11 @@
 #  endif
 #endif
 
+// https://en.cppreference.com/w/c/chrono/localtime
+#if defined(__STDC_LIB_EXT1__) && !defined(__STDC_WANT_LIB_EXT1__)
+#    define __STDC_WANT_LIB_EXT1__
+#endif
+
 #include <Python.h>
 #include <frameobject.h>
 #include <pythread.h>
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 0c25ca1a23..696e7cd377 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -19,7 +19,6 @@
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
-#  pragma warning(disable: 4996) // warning C4996: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name
 #  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
@@ -43,6 +42,8 @@
 #include <string>
 #include <utility>
 
+#include <string.h>
+
 #if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
 #  define PYBIND11_STD_LAUNDER std::launder
 #  define PYBIND11_HAS_STD_LAUNDER 1
@@ -76,8 +77,13 @@ inline bool apply_exception_translators(std::forward_list<ExceptionTranslator>&
     return false;
 }
 
-PYBIND11_NAMESPACE_END(detail)
+#if defined(_MSC_VER)
+#    define PYBIND11_COMPAT_STRDUP _strdup
+#else
+#    define PYBIND11_COMPAT_STRDUP strdup
+#endif
 
+PYBIND11_NAMESPACE_END(detail)
 
 /// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object
 class cpp_function : public function {
@@ -276,7 +282,7 @@ class cpp_function : public function {
                 std::free(s);
         }
         char *operator()(const char *s) {
-            auto t = strdup(s);
+            auto t = PYBIND11_COMPAT_STRDUP(s);
             strings.push_back(t);
             return t;
         }
@@ -520,7 +526,8 @@ class cpp_function : public function {
         auto *func = (PyCFunctionObject *) m_ptr;
         std::free(const_cast<char *>(func->m_ml->ml_doc));
         // Install docstring if it's non-empty (when at least one option is enabled)
-        func->m_ml->ml_doc = signatures.empty() ? nullptr : strdup(signatures.c_str());
+        func->m_ml->ml_doc
+            = signatures.empty() ? nullptr : PYBIND11_COMPAT_STRDUP(signatures.c_str());
 
         if (rec->is_method) {
             m_ptr = PYBIND11_INSTANCE_METHOD_NEW(m_ptr, rec->scope.ptr());
@@ -1525,7 +1532,7 @@ class class_ : public detail::generic_type {
            detail::process_attributes<Extra...>::init(extra..., rec_fget);
            if (rec_fget->doc && rec_fget->doc != doc_prev) {
               free(doc_prev);
-              rec_fget->doc = strdup(rec_fget->doc);
+              rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
            }
         }
         if (rec_fset) {
@@ -1533,7 +1540,7 @@ class class_ : public detail::generic_type {
             detail::process_attributes<Extra...>::init(extra..., rec_fset);
             if (rec_fset->doc && rec_fset->doc != doc_prev) {
                 free(doc_prev);
-                rec_fset->doc = strdup(rec_fset->doc);
+                rec_fset->doc = PYBIND11_COMPAT_STRDUP(rec_fset->doc);
             }
             if (! rec_active) rec_active = rec_fset;
         }

From 7904ba1a5c600ea8455b16c1010a1d46181d3148 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 26 Jul 2021 12:02:50 -0700
Subject: [PATCH 088/638] Adding pragma warning(disable: 4522) for MSVC <=
 2017. (#3142)

---
 include/pybind11/pybind11.h | 1 -
 include/pybind11/pytypes.h  | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 696e7cd377..9c0b723839 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -19,7 +19,6 @@
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
-#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
 #  pragma GCC diagnostic push
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index b483fb323c..3329982777 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -532,6 +532,10 @@ object object_or_cast(T &&o);
 // Match a PyObject*, which we want to convert directly to handle via its converting constructor
 inline handle object_or_cast(PyObject *ptr) { return ptr; }
 
+#if defined(_MSC_VER) && _MSC_VER < 1920
+#  pragma warning(push)
+#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
+#endif
 template <typename Policy>
 class accessor : public object_api<accessor<Policy>> {
     using key_type = typename Policy::key_type;
@@ -580,6 +584,9 @@ class accessor : public object_api<accessor<Policy>> {
     key_type key;
     mutable object cache;
 };
+#if defined(_MSC_VER) && _MSC_VER < 1920
+#  pragma warning(pop)
+#endif
 
 PYBIND11_NAMESPACE_BEGIN(accessor_policies)
 struct obj_attr {

From 7f76d79508475ef2e8f17941e350b1dfa8d828b4 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 26 Jul 2021 15:05:58 -0400
Subject: [PATCH 089/638] [pre-commit.ci] pre-commit autoupdate (#3143)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.21.2 → v2.23.0](https://github.com/asottile/pyupgrade/compare/v2.21.2...v2.23.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index aa7b4774e3..510b841260 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.21.2
+  rev: v2.23.0
   hooks:
   - id: pyupgrade
 

From a0f862d428acd11dacb344ce9690e420d98cde53 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 26 Jul 2021 13:26:36 -0700
Subject: [PATCH 090/638] Removing MSVC C4800 from pragma block at the top of
 pybind11.h (#3141)

* Adding PYBIND11_COMPAT_BOOL_CAST to appease MSVC 2015 warning C4800.

* Replacing PYBIND11_COMPAT_BOOL_CAST with simpler != 0

* Extra parentheses (almost all compilers failed without these).
---
 include/pybind11/buffer_info.h             | 2 +-
 include/pybind11/cast.h                    | 2 +-
 include/pybind11/detail/type_caster_base.h | 4 ++--
 include/pybind11/pybind11.h                | 1 -
 include/pybind11/pytypes.h                 | 6 ++++--
 5 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 47dc39d4ea..eba68d1aa1 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -83,7 +83,7 @@ struct buffer_info {
             view->strides
             ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
             : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
-            view->readonly) {
+            (view->readonly != 0)) {
         this->m_view = view;
         this->ownview = ownview;
     }
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index a748c77c0f..1da432358f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -322,7 +322,7 @@ template <> class type_caster<bool> {
             }
             #endif
             if (res == 0 || res == 1) {
-                value = (bool) res;
+                value = (res != 0);
                 return true;
             }
             PyErr_Clear();
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index bdf3a39822..a6b6bea6a3 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -231,7 +231,7 @@ struct value_and_holder {
         return reinterpret_cast<V *&>(vh[0]);
     }
     // True if this `value_and_holder` has a non-null value pointer
-    explicit operator bool() const { return value_ptr(); }
+    explicit operator bool() const { return value_ptr() != nullptr; }
 
     template <typename H> H &holder() const {
         return reinterpret_cast<H &>(vh[1]);
@@ -252,7 +252,7 @@ struct value_and_holder {
     bool instance_registered() const {
         return inst->simple_layout
             ? inst->simple_instance_registered
-            : inst->nonsimple.status[index] & instance::status_instance_registered;
+            : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
     }
     void set_instance_registered(bool v = true) const {
         if (inst->simple_layout)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 9c0b723839..93b920d852 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -18,7 +18,6 @@
 #  pragma warning(push)
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
 #  pragma GCC diagnostic push
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 3329982777..cea4e7eb01 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -367,7 +367,9 @@ class PYBIND11_EXPORT error_already_set : public std::runtime_error {
     /// Check if the currently trapped error type matches the given Python exception class (or a
     /// subclass thereof).  May also be passed a tuple to search for any exception class matches in
     /// the given tuple.
-    bool matches(handle exc) const { return PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()); }
+    bool matches(handle exc) const {
+        return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
+    }
 
     const object& type() const { return m_type; }
     const object& value() const { return m_value; }
@@ -853,7 +855,7 @@ PYBIND11_NAMESPACE_END(detail)
         Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) { } \
         Name(handle h, stolen_t) : Parent(h, stolen_t{}) { } \
         PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead") \
-        bool check() const { return m_ptr != nullptr && (bool) CheckFun(m_ptr); } \
+        bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); } \
         static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); } \
         template <typename Policy_> \
         Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }

From a0b975965fe5df66f20a1d29193055f8538ac94e Mon Sep 17 00:00:00 2001
From: David Hewitt <1939362+davidhewitt@users.noreply.github.com>
Date: Tue, 27 Jul 2021 19:16:28 +0100
Subject: [PATCH 091/638] Allow python builtins to be used as callbacks (#1413)

* Allow python builtins to be used as callbacks

* Try to fix pypy segfault

* Add expected fail for PyPy

* Fix typo

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add more info to xfail

* Add env

* Try returning false

* Try removing the move for pypy

* Fix bugs

* Try removing move

* Just keep ignoring for PyPy

* Add back xfail

* Fix ctors

* Revert change of std::move

* Change to skip

* Fix bug and edit comments

* Remove clang-tidy bugprone fix skip bug

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/functional.h | 36 ++++++++++++++++++++---------------
 tests/test_callbacks.cpp      |  6 ++++++
 tests/test_callbacks.py       | 11 +++++++++++
 3 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index cc7099c6a3..b9bf38919c 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -43,27 +43,33 @@ struct type_caster<std::function<Return(Args...)>> {
            captured variables), in which case the roundtrip can be avoided.
          */
         if (auto cfunc = func.cpp_function()) {
-            auto c = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(cfunc.ptr()));
-            auto rec = (function_record *) c;
-
-            while (rec != nullptr) {
-                if (rec->is_stateless
-                    && same_type(typeid(function_type),
-                                 *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
-                    struct capture {
-                        function_type f;
-                    };
-                    value = ((capture *) &rec->data)->f;
-                    return true;
+            auto cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
+            if (isinstance<capsule>(cfunc_self)) {
+                auto c = reinterpret_borrow<capsule>(cfunc_self);
+                auto rec = (function_record *) c;
+
+                while (rec != nullptr) {
+                    if (rec->is_stateless
+                        && same_type(typeid(function_type),
+                                     *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
+                        struct capture {
+                            function_type f;
+                        };
+                        value = ((capture *) &rec->data)->f;
+                        return true;
+                    }
+                    rec = rec->next;
                 }
-                rec = rec->next;
             }
+            // PYPY segfaults here when passing builtin function like sum.
+            // Raising an fail exception here works to prevent the segfault, but only on gcc.
+            // See PR #1413 for full details
         }
 
         // ensure GIL is held during functor destruction
         struct func_handle {
             function f;
-            func_handle(function&& f_) : f(std::move(f_)) {}
+            func_handle(function &&f_) noexcept : f(std::move(f_)) {}
             func_handle(const func_handle& f_) {
                 gil_scoped_acquire acq;
                 f = f_.f;
@@ -77,7 +83,7 @@ struct type_caster<std::function<Return(Args...)>> {
         // to emulate 'move initialization capture' in C++11
         struct func_wrapper {
             func_handle hfunc;
-            func_wrapper(func_handle&& hf): hfunc(std::move(hf)) {}
+            func_wrapper(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
                 object retval(hfunc.f(std::forward<Args>(args)...));
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index a208b44d04..a50771038b 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -156,6 +156,12 @@ TEST_SUBMODULE(callbacks, m) {
         .def(py::init<>())
         .def("triple", [](CppBoundMethodTest &, int val) { return 3 * val; });
 
+    // This checks that builtin functions can be passed as callbacks
+    // rather than throwing RuntimeError due to trying to extract as capsule
+    m.def("test_sum_builtin", [](const std::function<double(py::iterable)> &sum_builtin, const py::iterable &i) {
+      return sum_builtin(i);
+    });
+
     // test async Python callbacks
     using callback_f = std::function<void(int)>;
     m.def("test_async_callback", [](const callback_f &f, const py::list &work) {
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 397bf63d24..5bc4d1773d 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -3,6 +3,7 @@
 from pybind11_tests import callbacks as m
 from threading import Thread
 import time
+import env  # NOQA: F401
 
 
 def test_callbacks():
@@ -124,6 +125,16 @@ def test_movable_object():
     assert m.callback_with_movable(lambda _: None) is True
 
 
+@pytest.mark.skipif(
+    "env.PYPY",
+    reason="PyPy segfaults on here. See discussion on #1413.",
+)
+def test_python_builtins():
+    """Test if python builtins like sum() can be used as callbacks"""
+    assert m.test_sum_builtin(sum, [1, 2, 3]) == 6
+    assert m.test_sum_builtin(sum, []) == 0
+
+
 def test_async_callbacks():
     # serves as state for async callback
     class Item:

From 7cc0ebb4753770ace452d118bb327cdd9e76dcbb Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 27 Jul 2021 14:23:52 -0700
Subject: [PATCH 092/638] fix: the CMake config in Python package had a hard
 coded path (#3144)

---
 CMakeLists.txt                           |  6 ++++++
 tests/extra_python_package/test_files.py | 14 ++++++++++++--
 tools/pybind11Config.cmake.in            |  3 ++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c988ea0b50..b04311fd85 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -203,6 +203,12 @@ if(PYBIND11_INSTALL)
       "${CMAKE_INSTALL_DATAROOTDIR}/cmake/${PROJECT_NAME}"
       CACHE STRING "install path for pybind11Config.cmake")
 
+  if(IS_ABSOLUTE "${CMAKE_INSTALL_INCLUDEDIR}")
+    set(pybind11_INCLUDEDIR "${CMAKE_INSTALL_FULL_INCLUDEDIR}")
+  else()
+    set(pybind11_INCLUDEDIR "\$\{PACKAGE_PREFIX_DIR\}/${CMAKE_INSTALL_INCLUDEDIR}")
+  endif()
+
   configure_package_config_file(
     tools/${PROJECT_NAME}Config.cmake.in "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
     INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 43e93c2633..337a72dfea 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -138,6 +138,16 @@ def test_build_sdist(monkeypatch, tmpdir):
         ) as f:
             pyproject_toml = f.read()
 
+        with contextlib.closing(
+            tar.extractfile(
+                tar.getmember(
+                    start + "pybind11/share/cmake/pybind11/pybind11Config.cmake"
+                )
+            )
+        ) as f:
+            contents = f.read().decode("utf8")
+        assert 'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")' in contents
+
     files = {"pybind11/{}".format(n) for n in all_files}
     files |= sdist_files
     files |= {"pybind11{}".format(n) for n in local_sdist_files}
@@ -151,11 +161,11 @@ def test_build_sdist(monkeypatch, tmpdir):
             .substitute(version=version, extra_cmd="")
             .encode()
         )
-        assert setup_py == contents
+    assert setup_py == contents
 
     with open(os.path.join(MAIN_DIR, "tools", "pyproject.toml"), "rb") as f:
         contents = f.read()
-        assert pyproject_toml == contents
+    assert pyproject_toml == contents
 
 
 def test_build_global_dist(monkeypatch, tmpdir):
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 6fa03a0f24..73ec104a0e 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -201,7 +201,8 @@ Using ``find_package`` with version info is not recommended except for release v
 @PACKAGE_INIT@
 
 # Location of pybind11/pybind11.h
-set(pybind11_INCLUDE_DIR "@CMAKE_INSTALL_FULL_INCLUDEDIR@")
+# This will be relative unless explicitly set as absolute
+set(pybind11_INCLUDE_DIR "@pybind11_INCLUDEDIR@")
 
 set(pybind11_LIBRARY "")
 set(pybind11_DEFINITIONS USING_pybind11)

From 9beaa925db49cf4751642a1529d34bef4a3682ce Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 27 Jul 2021 18:32:26 -0400
Subject: [PATCH 093/638] maint(clang-tidy): Improve code readability with
 explicit boolean casts (#3148)

* maint(clang-tidy) Improve code readability

* Fix minor typos

* Revert optimization that removed test case

* Fix comment formatting

* Revert another optimization to repro an issue

* Remove make_unique since it C++14 and newer only

* eformat comments

* Fix unsignedness of comparison

* Update comment
---
 .clang-tidy                                | 13 +++++++++++++
 include/pybind11/cast.h                    | 16 ++++++++++------
 include/pybind11/detail/class.h            |  7 ++++---
 include/pybind11/detail/internals.h        |  2 +-
 include/pybind11/detail/type_caster_base.h |  4 ++--
 include/pybind11/embed.h                   |  4 ++--
 include/pybind11/numpy.h                   | 19 +++++++++++--------
 include/pybind11/pybind11.h                | 15 +++++++++------
 include/pybind11/pytypes.h                 | 12 ++++++++----
 include/pybind11/stl/filesystem.h          |  4 ++--
 tests/test_embed/test_interpreter.cpp      |  2 +-
 tests/test_methods_and_attributes.cpp      |  1 +
 tests/test_numpy_dtypes.cpp                |  6 ++++--
 tests/test_numpy_vectorize.cpp             |  2 +-
 tests/test_smart_ptr.cpp                   |  4 ++--
 tests/test_stl.cpp                         |  6 ++----
 16 files changed, 73 insertions(+), 44 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 72304528a5..db5077c227 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -5,13 +5,17 @@ cppcoreguidelines-init-variables,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,
+misc-non-copyable-objects,
 misc-static-assert,
 misc-throw-by-value-catch-by-reference,
 misc-uniqueptr-reset-release,
+misc-unused-parameters,
 modernize-avoid-bind,
+modernize-make-shared,
 modernize-redundant-void-arg,
 modernize-replace-auto-ptr,
 modernize-replace-disallow-copy-and-assign-macro,
+modernize-replace-random-shuffle,
 modernize-shrink-to-fit,
 modernize-use-auto,
 modernize-use-bool-literals,
@@ -23,13 +27,20 @@ modernize-use-emplace,
 modernize-use-override,
 modernize-use-using,
 *performance*,
+readability-avoid-const-params-in-decls,
 readability-container-size-empty,
 readability-else-after-return,
+readability-delete-null-pointer,
+readability-implicit-bool-conversion,
 readability-make-member-function-const,
+readability-misplaced-array-index,
+readability-non-const-parameter,
 readability-redundant-function-ptr-dereference,
 readability-redundant-smartptr-get,
 readability-redundant-string-cstr,
 readability-simplify-subscript-expr,
+readability-static-accessed-through-instance,
+readability-static-definition-in-anonymous-namespace,
 readability-string-compare,
 readability-uniqueptr-delete-release,
 '
@@ -39,6 +50,8 @@ CheckOptions:
   value:           true
 - key:             performance-unnecessary-value-param.AllowedTypes
   value:           'exception_ptr$;'
+- key:             readability-implicit-bool-conversion.AllowPointerConditions
+  value:           true
 
 HeaderFilterRegex: 'pybind11/.*h'
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 1da432358f..898047b304 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -181,7 +181,7 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
         // Signed/unsigned checks happen elsewhere
         if (py_err || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T) && py_value != (py_type) (T) py_value)) {
             PyErr_Clear();
-            if (py_err && convert && PyNumber_Check(src.ptr())) {
+            if (py_err && convert && (PyNumber_Check(src.ptr()) != 0)) {
                 auto tmp = reinterpret_steal<object>(std::is_floating_point<T>::value
                                                      ? PyNumber_Float(src.ptr())
                                                      : PyNumber_Long(src.ptr()));
@@ -300,7 +300,7 @@ template <> class type_caster<bool> {
             value = false;
             return true;
         }
-        if (convert || !std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name)) {
+        if (convert || (std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name) == 0)) {
             // (allow non-implicit conversion for numpy booleans)
 
             Py_ssize_t res = -1;
@@ -501,10 +501,14 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         // can fit into a single char value.
         if (StringCaster::UTF_N == 8 && str_len > 1 && str_len <= 4) {
             auto v0 = static_cast<unsigned char>(value[0]);
-            size_t char0_bytes = !(v0 & 0x80) ? 1 : // low bits only: 0-127
-                (v0 & 0xE0) == 0xC0 ? 2 : // 0b110xxxxx - start of 2-byte sequence
-                (v0 & 0xF0) == 0xE0 ? 3 : // 0b1110xxxx - start of 3-byte sequence
-                4; // 0b11110xxx - start of 4-byte sequence
+            // low bits only: 0-127
+            // 0b110xxxxx - start of 2-byte sequence
+            // 0b1110xxxx - start of 3-byte sequence
+            // 0b11110xxx - start of 4-byte sequence
+            size_t char0_bytes = (v0 & 0x80) == 0      ? 1
+                                 : (v0 & 0xE0) == 0xC0 ? 2
+                                 : (v0 & 0xF0) == 0xE0 ? 3
+                                                       : 4;
 
             if (char0_bytes == str_len) {
                 // If we have a 128-255 value, we can decode it into a single char:
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 15e09165de..f9822c7b35 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -129,8 +129,9 @@ extern "C" inline int pybind11_meta_setattro(PyObject* obj, PyObject* name, PyOb
     //   2. `Type.static_prop = other_static_prop` --> setattro:  replace existing `static_prop`
     //   3. `Type.regular_attribute = value`       --> setattro:  regular attribute assignment
     const auto static_prop = (PyObject *) get_internals().static_property_type;
-    const auto call_descr_set = descr && value && PyObject_IsInstance(descr, static_prop)
-                                && !PyObject_IsInstance(value, static_prop);
+    const auto call_descr_set = (descr != nullptr) && (value != nullptr)
+                                && (PyObject_IsInstance(descr, static_prop) != 0)
+                                && (PyObject_IsInstance(value, static_prop) == 0);
     if (call_descr_set) {
         // Call `static_property.__set__()` instead of replacing the `static_property`.
 #if !defined(PYPY_VERSION)
@@ -562,7 +563,7 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
     view->len = view->itemsize;
     for (auto s : info->shape)
         view->len *= s;
-    view->readonly = info->readonly;
+    view->readonly = static_cast<int>(info->readonly);
     if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT)
         view->format = const_cast<char *>(info->format.c_str());
     if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES) {
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index a621aed2a6..a93a83e268 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -297,7 +297,7 @@ PYBIND11_NOINLINE inline internals &get_internals() {
         PyThreadState *tstate = PyThreadState_Get();
         #if PY_VERSION_HEX >= 0x03070000
             internals_ptr->tstate = PyThread_tss_alloc();
-            if (!internals_ptr->tstate || PyThread_tss_create(internals_ptr->tstate))
+            if (!internals_ptr->tstate || (PyThread_tss_create(internals_ptr->tstate) != 0))
                 pybind11_fail("get_internals: could not successfully initialize the TSS key!");
             PyThread_tss_set(internals_ptr->tstate, tstate);
         #else
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a6b6bea6a3..2a675418a7 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -238,8 +238,8 @@ struct value_and_holder {
     }
     bool holder_constructed() const {
         return inst->simple_layout
-            ? inst->simple_holder_constructed
-            : inst->nonsimple.status[index] & instance::status_holder_constructed;
+                   ? inst->simple_holder_constructed
+                   : (inst->nonsimple.status[index] & instance::status_holder_constructed) != 0u;
     }
     void set_holder_constructed(bool v = true) const {
         if (inst->simple_layout)
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 204aaf989f..abb1cd3cca 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -76,7 +76,7 @@ struct embedded_module {
     using init_t = void (*)();
 #endif
     embedded_module(const char *name, init_t init) {
-        if (Py_IsInitialized())
+        if (Py_IsInitialized() != 0)
             pybind11_fail("Can't add new modules after the interpreter has been initialized");
 
         auto result = PyImport_AppendInittab(name, init);
@@ -101,7 +101,7 @@ PYBIND11_NAMESPACE_END(detail)
     .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
  \endrst */
 inline void initialize_interpreter(bool init_signal_handlers = true) {
-    if (Py_IsInitialized())
+    if (Py_IsInitialized() != 0)
         pybind11_fail("The interpreter is already running");
 
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index edba8bac92..7313897fe1 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -465,7 +465,9 @@ class dtype : public object {
     explicit dtype(const buffer_info &info) {
         dtype descr(_dtype_from_pep3118()(PYBIND11_STR_TYPE(info.format)));
         // If info.itemsize == 0, use the value calculated from the format string
-        m_ptr = descr.strip_padding(info.itemsize ? info.itemsize : descr.itemsize()).release().ptr();
+        m_ptr = descr.strip_padding(info.itemsize != 0 ? info.itemsize : descr.itemsize())
+                    .release()
+                    .ptr();
     }
 
     explicit dtype(const std::string &format) {
@@ -486,7 +488,7 @@ class dtype : public object {
     /// This is essentially the same as calling numpy.dtype(args) in Python.
     static dtype from_args(object args) {
         PyObject *ptr = nullptr;
-        if (!detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) || !ptr)
+        if ((detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) == 0) || !ptr)
             throw error_already_set();
         return reinterpret_steal<dtype>(ptr);
     }
@@ -542,7 +544,7 @@ class dtype : public object {
             auto name = spec[0].cast<pybind11::str>();
             auto format = spec[1].cast<tuple>()[0].cast<dtype>();
             auto offset = spec[1].cast<tuple>()[1].cast<pybind11::int_>();
-            if (!len(name) && format.kind() == 'V')
+            if ((len(name) == 0u) && format.kind() == 'V')
                 continue;
             field_descriptors.push_back({(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
         }
@@ -872,11 +874,12 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
         : array(std::move(shape), std::move(strides), ptr, base) { }
 
     explicit array_t(ShapeContainer shape, const T *ptr = nullptr, handle base = handle())
-        : array_t(private_ctor{}, std::move(shape),
-                ExtraFlags & f_style
-                ? detail::f_strides(*shape, itemsize())
-                : detail::c_strides(*shape, itemsize()),
-                ptr, base) { }
+        : array_t(private_ctor{},
+                  std::move(shape),
+                  (ExtraFlags & f_style) != 0 ? detail::f_strides(*shape, itemsize())
+                                              : detail::c_strides(*shape, itemsize()),
+                  ptr,
+                  base) {}
 
     explicit array_t(ssize_t count, const T *ptr = nullptr, handle base = handle())
         : array({count}, {}, ptr, base) { }
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 93b920d852..e2cbb54493 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -318,7 +318,8 @@ class cpp_function : public function {
                 a.descr = guarded_strdup(repr(a.value).cast<std::string>().c_str());
         }
 
-        rec->is_constructor = !strcmp(rec->name, "__init__") || !strcmp(rec->name, "__setstate__");
+        rec->is_constructor
+            = (strcmp(rec->name, "__init__") == 0) || (strcmp(rec->name, "__setstate__") == 0);
 
 #if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
@@ -1131,7 +1132,8 @@ class generic_type : public object {
             pybind11_fail("generic_type: cannot initialize type \"" + std::string(rec.name) +
                           "\": an object with that name is already defined");
 
-        if (rec.module_local ? get_local_type_info(*rec.type) : get_global_type_info(*rec.type))
+        if ((rec.module_local ? get_local_type_info(*rec.type) : get_global_type_info(*rec.type))
+            != nullptr)
             pybind11_fail("generic_type: type \"" + std::string(rec.name) +
                           "\" is already registered!");
 
@@ -1209,8 +1211,9 @@ class generic_type : public object {
     void def_property_static_impl(const char *name,
                                   handle fget, handle fset,
                                   detail::function_record *rec_func) {
-        const auto is_static = rec_func && !(rec_func->is_method && rec_func->scope);
-        const auto has_doc = rec_func && rec_func->doc && pybind11::options::show_user_defined_docstrings();
+        const auto is_static = (rec_func != nullptr) && !(rec_func->is_method && rec_func->scope);
+        const auto has_doc = (rec_func != nullptr) && (rec_func->doc != nullptr)
+                             && pybind11::options::show_user_defined_docstrings();
         auto property = handle((PyObject *) (is_static ? get_internals().static_property_type
                                                        : &PyProperty_Type));
         attr(name) = property(fget.ptr() ? fget : none(),
@@ -2220,8 +2223,8 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
        Unfortunately this doesn't work on PyPy. */
 #if !defined(PYPY_VERSION)
     PyFrameObject *frame = PyThreadState_Get()->frame;
-    if (frame && (std::string) str(frame->f_code->co_name) == name &&
-        frame->f_code->co_argcount > 0) {
+    if (frame != nullptr && (std::string) str(frame->f_code->co_name) == name
+        && frame->f_code->co_argcount > 0) {
         PyFrame_FastToLocals(frame);
         PyObject *self_caller = dict_getitem(
             frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index cea4e7eb01..161aed06f4 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -773,7 +773,11 @@ class dict_readonly {
     dict_readonly(handle obj, ssize_t pos) : obj(obj), pos(pos) { increment(); }
 
     reference dereference() const { return {key, value}; }
-    void increment() { if (!PyDict_Next(obj.ptr(), &pos, &key, &value)) { pos = -1; } }
+    void increment() {
+        if (PyDict_Next(obj.ptr(), &pos, &key, &value) == 0) {
+            pos = -1;
+        }
+    }
     bool equal(const dict_readonly &b) const { return pos == b.pos; }
 
 private:
@@ -1169,14 +1173,14 @@ class bool_ : public object {
     bool_() : object(Py_False, borrowed_t{}) { }
     // Allow implicit conversion from and to `bool`:
     bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) { }
-    operator bool() const { return m_ptr && PyLong_AsLong(m_ptr) != 0; }
+    operator bool() const { return (m_ptr != nullptr) && PyLong_AsLong(m_ptr) != 0; }
 
 private:
     /// Return the truth value of an object -- always returns a new reference
     static PyObject *raw_bool(PyObject *op) {
         const auto value = PyObject_IsTrue(op);
         if (value == -1) return nullptr;
-        return handle(value ? Py_True : Py_False).inc_ref().ptr();
+        return handle(value != 0 ? Py_True : Py_False).inc_ref().ptr();
     }
 };
 
@@ -1607,7 +1611,7 @@ inline memoryview memoryview::from_buffer(
     size_t ndim = shape->size();
     if (ndim != strides->size())
         pybind11_fail("memoryview: shape length doesn't match strides length");
-    ssize_t size = ndim ? 1 : 0;
+    ssize_t size = ndim != 0u ? 1 : 0;
     for (size_t i = 0; i < ndim; ++i)
         size *= (*shape)[i];
     Py_buffer view;
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 7a8acdb60b..431b94b4f7 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -67,7 +67,7 @@ template<typename T> struct path_caster {
         }
         PyObject* native = nullptr;
         if constexpr (std::is_same_v<typename T::value_type, char>) {
-            if (PyUnicode_FSConverter(buf, &native)) {
+            if (PyUnicode_FSConverter(buf, &native) != 0) {
                 if (auto c_str = PyBytes_AsString(native)) {
                     // AsString returns a pointer to the internal buffer, which
                     // must not be free'd.
@@ -75,7 +75,7 @@ template<typename T> struct path_caster {
                 }
             }
         } else if constexpr (std::is_same_v<typename T::value_type, wchar_t>) {
-            if (PyUnicode_FSDecoder(buf, &native)) {
+            if (PyUnicode_FSDecoder(buf, &native) != 0) {
                 if (auto c_str = PyUnicode_AsWideCharString(native, nullptr)) {
                     // AsWideCharString returns a new string that must be free'd.
                     value = c_str;  // Copies the string.
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 6925ee9782..cd50e952f6 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -103,7 +103,7 @@ bool has_pybind11_internals_builtin() {
 
 bool has_pybind11_internals_static() {
     auto **&ipp = py::detail::get_internals_pp();
-    return ipp && *ipp;
+    return (ipp != nullptr) && (*ipp != nullptr);
 }
 
 TEST_CASE("Restart the interpreter") {
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 9db31a0b82..4cf6f08b85 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -43,6 +43,7 @@ class ExampleMandA {
     void add6(int other) { value += other; }                        // passing by value
     void add7(int &other) { value += other; }                       // passing by reference
     void add8(const int &other) { value += other; }                 // passing by const reference
+    // NOLINTNEXTLINE(readability-non-const-parameter) Deliberately non-const for testing
     void add9(int *other) { value += *other; }                      // passing by pointer
     void add10(const int *other) { value += *other; }               // passing by const pointer
 
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index edf9cf200f..340c972db2 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -108,9 +108,11 @@ PYBIND11_PACKED(struct EnumStruct {
 
 std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
     os << "a='";
-    for (size_t i = 0; i < 3 && v.a[i]; i++) os << v.a[i];
+    for (size_t i = 0; i < 3 && (v.a[i] != 0); i++)
+        os << v.a[i];
     os << "',b='";
-    for (size_t i = 0; i < 3 && v.b[i]; i++) os << v.b[i];
+    for (size_t i = 0; i < 3 && (v.b[i] != 0); i++)
+        os << v.b[i];
     return os << "'";
 }
 
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index ed08a42bef..b08a9f7edd 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -59,7 +59,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
         .def(py::init<int>())
         .def_readwrite("value", &NonPODClass::value);
     m.def("vec_passthrough",
-          py::vectorize([](double *a,
+          py::vectorize([](const double *a,
                            double b,
                            // Changing this broke things
                            // NOLINTNEXTLINE(performance-unnecessary-value-param)
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 7fd5a9b36e..57b2d894e2 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -101,7 +101,7 @@ class MyObject3 : public std::enable_shared_from_this<MyObject3> {
 // test_unique_nodelete
 // Object with a private destructor
 class MyObject4;
-static std::unordered_set<MyObject4 *> myobject4_instances;
+std::unordered_set<MyObject4 *> myobject4_instances;
 class MyObject4 {
 public:
     MyObject4(int value) : value{value} {
@@ -127,7 +127,7 @@ class MyObject4 {
 // Object with std::unique_ptr<T, D> where D is not matching the base class
 // Object with a protected destructor
 class MyObject4a;
-static std::unordered_set<MyObject4a *> myobject4a_instances;
+std::unordered_set<MyObject4a *> myobject4a_instances;
 class MyObject4a {
 public:
     MyObject4a(int i) {
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index eb8cdab7b5..23e2c07b32 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -102,7 +102,7 @@ TEST_SUBMODULE(stl, m) {
     // test_set
     m.def("cast_set", []() { return std::set<std::string>{"key1", "key2"}; });
     m.def("load_set", [](const std::set<std::string> &set) {
-        return set.count("key1") && set.count("key2") && set.count("key3");
+        return (set.count("key1") != 0u) && (set.count("key2") != 0u) && (set.count("key3") != 0u);
     });
 
     // test_recursive_casting
@@ -196,9 +196,7 @@ TEST_SUBMODULE(stl, m) {
     m.def("double_or_zero", [](const opt_int& x) -> int {
         return x.value_or(0) * 2;
     });
-    m.def("half_or_none", [](int x) -> opt_int {
-        return x ? opt_int(x / 2) : opt_int();
-    });
+    m.def("half_or_none", [](int x) -> opt_int { return x != 0 ? opt_int(x / 2) : opt_int(); });
     m.def("test_nullopt", [](opt_int x) {
         return x.value_or(42);
     }, py::arg_v("x", std::nullopt, "None"));

From 2164c2e0e78ca4bf12123f98349722907732581b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 27 Jul 2021 15:33:31 -0700
Subject: [PATCH 094/638] Removing __INTEL_COMPILER section from pragma block
 at the top of pybind11.h (#3135)

* Fixing `pragma warning pop` for `__INTEL_COMPILER`.

* Adding push/pop to 3 tests. Removing #878 from top of pybind11.h (it was/is only needed for 1 test).

* Trying again after CI failure, moving the push to the top of 2 tests.

* Trying more after CI failure, adding push/pop to pybind11_tests.h, constructor_stats.h.

* Moving ICC #2196 suppression to CMakeLists.txt

* Fixing condition for `pragma GCC diagnostic push` in pybind11.h

* Moving `pragma warning disable 2196` to common.h

* Revising #ifdef to be more conservative.

* Undoing insertion of notes that will hopefully soon be completely obsolete anyway.
---
 include/pybind11/detail/common.h       | 3 +++
 include/pybind11/pybind11.h            | 8 ++------
 tests/test_constants_and_functions.cpp | 7 +++++++
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 3faf3ea327..0b4e30c18b 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -56,6 +56,9 @@
 #  elif __INTEL_COMPILER < 1900 && defined(PYBIND11_CPP14)
 #    error pybind11 supports only C++11 with Intel C++ compiler v18. Use v19 or newer for C++14.
 #  endif
+/* The following pragma cannot be pop'ed:
+   https://community.intel.com/t5/Intel-C-Compiler/Inline-and-no-inline-warning/td-p/1216764 */
+#  pragma warning disable 2196 // warning #2196: routine is both "inline" and "noinline"
 #elif defined(__clang__) && !defined(__apple_build_version__)
 #  if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
 #    error pybind11 requires clang 3.3 or newer
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index e2cbb54493..b14aff58a2 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,16 +10,12 @@
 
 #pragma once
 
-#if defined(__INTEL_COMPILER)
-#  pragma warning push
-#  pragma warning disable 878   // incompatible exception specifications
-#  pragma warning disable 2196  // warning #2196: routine is both "inline" and "noinline"
-#elif defined(_MSC_VER)
+#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(push)
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
-#elif defined(__GNUG__) && !defined(__clang__)
+#elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wattributes"
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index e7f018540c..c0554503fa 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -133,7 +133,14 @@ TEST_SUBMODULE(constants_and_functions, m) {
         ;
     m.def("f1", f1);
     m.def("f2", f2);
+#if defined(__INTEL_COMPILER)
+#    pragma warning push
+#    pragma warning disable 878 // incompatible exception specifications
+#endif
     m.def("f3", f3);
+#if defined(__INTEL_COMPILER)
+#    pragma warning pop
+#endif
     m.def("f4", f4);
 
     // test_function_record_leaks

From f4721a7b44e5513df3681ccb2c08eca50132b4bd Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 28 Jul 2021 08:58:36 -0700
Subject: [PATCH 095/638] Accommodating environments that define
 __STDC_WANT_LIB_EXT1__ even if __STDC_LIB_EXT1__ is not defined by the
 implementation. (#3151)

Follow-on to PR #3129.
---
 include/pybind11/chrono.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index c4e81f5720..61bbcbc540 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -101,7 +101,7 @@ template <typename type> class duration_caster {
 };
 
 inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
-#if defined(__STDC_WANT_LIB_EXT1__) || defined(_MSC_VER)
+#if (defined(__STDC_LIB_EXT1__) && defined(__STDC_WANT_LIB_EXT1__)) || defined(_MSC_VER)
     if (localtime_s(buf, time))
         return nullptr;
     return buf;

From b72ca7d1bd8d07470b5094017c790f6c763f9b0f Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 28 Jul 2021 17:01:21 -0700
Subject: [PATCH 096/638] Removing MSVC C4100 from pragma block at the top of
 pybind11.h (#3150)

* Removing pragma for 4100 (to see what is still broken with the latest code).

* Adding --keep-going

* Revert "Adding --keep-going"

This reverts commit 1c844c6ffd07a6111b644811e7e3b0a50b9d44bb.

* Introducing PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100.

* _MSC_VER <= 1916

* Replacing simple variadic function with variadic template (attempt to resolve MSVC 2017 failures).

* Preserving existing comment (moved from pybind11.h to detail/common.h).

* Adding blank lines for readability.
---
 include/pybind11/attr.h                    |  5 +++++
 include/pybind11/cast.h                    |  1 +
 include/pybind11/detail/common.h           | 13 +++++++++++++
 include/pybind11/detail/descr.h            |  1 +
 include/pybind11/detail/init.h             |  3 +++
 include/pybind11/detail/type_caster_base.h |  2 ++
 include/pybind11/pybind11.h                |  3 ++-
 7 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 60ed9fd90e..20d119f0ff 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -516,18 +516,22 @@ template <size_t Nurse, size_t Patient> struct process_attribute<keep_alive<Nurs
 /// Recursively iterate over variadic template arguments
 template <typename... Args> struct process_attributes {
     static void init(const Args&... args, function_record *r) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::init(args, r), 0) ... };
         ignore_unused(unused);
     }
     static void init(const Args&... args, type_record *r) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::init(args, r), 0) ... };
         ignore_unused(unused);
     }
     static void precall(function_call &call) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call);
         int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::precall(call), 0) ... };
         ignore_unused(unused);
     }
     static void postcall(function_call &call, handle fn_ret) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call, fn_ret);
         int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::postcall(call, fn_ret), 0) ... };
         ignore_unused(unused);
     }
@@ -545,6 +549,7 @@ template <typename... Extra,
           size_t named = constexpr_sum(std::is_base_of<arg, Extra>::value...),
           size_t self  = constexpr_sum(std::is_same<is_method, Extra>::value...)>
 constexpr bool expected_num_args(size_t nargs, bool has_args, bool has_kwargs) {
+    PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(nargs, has_args, has_kwargs);
     return named == 0 || (self + named + size_t(has_args) + size_t(has_kwargs)) == nargs;
 }
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 898047b304..5ff0355a6f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -605,6 +605,7 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     /* Implementation: Convert a C++ tuple into a Python tuple */
     template <typename T, size_t... Is>
     static handle cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(src, policy, parent);
         std::array<object, size> entries{{
             reinterpret_steal<object>(make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...
         }};
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 0b4e30c18b..0add6272f5 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -913,5 +913,18 @@ inline static std::shared_ptr<T> try_get_shared_from_this(std::enable_shared_fro
 #endif
 }
 
+#if defined(_MSC_VER) && _MSC_VER <= 1916
+
+// warning C4100: Unreferenced formal parameter
+template <typename... Args>
+inline constexpr void workaround_incorrect_msvc_c4100(Args &&...) {}
+
+#    define PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(...)                                         \
+        detail::workaround_incorrect_msvc_c4100(__VA_ARGS__)
+
+#else
+#    define PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(...)
+#endif
+
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 7cb8350e7b..0acfc7db37 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -42,6 +42,7 @@ struct descr {
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2, size_t... Is1, size_t... Is2>
 constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b,
                                                    index_sequence<Is1...>, index_sequence<Is2...>) {
+    PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(b);
     return {a.text[Is1]..., b.text[Is2]...};
 }
 
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 3269e04254..3ebec041f0 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -94,6 +94,7 @@ void construct(...) {
 // construct an Alias from the returned base instance.
 template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> *ptr, bool need_alias) {
+    PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     no_nullptr(ptr);
     if (Class::has_alias && need_alias && !is_alias<Class>(ptr)) {
         // We're going to try to construct an alias by moving the cpp type.  Whether or not
@@ -131,6 +132,7 @@ void construct(value_and_holder &v_h, Alias<Class> *alias_ptr, bool) {
 // derived type (through those holder's implicit conversion from derived class holder constructors).
 template <typename Class>
 void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
+    PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     auto *ptr = holder_helper<Holder<Class>>::get(holder);
     no_nullptr(ptr);
     // If we need an alias, check that the held pointer is actually an alias instance
@@ -148,6 +150,7 @@ void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
 // need it, we simply move-construct the cpp value into a new instance.
 template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
+    PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
         "pybind11::init() return-by-value factory function requires a movable class");
     if (Class::has_alias && need_alias)
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 2a675418a7..e2d1bcb8cc 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -930,6 +930,7 @@ template <typename type> class type_caster_base : public type_caster_generic {
        does not have a private operator new implementation. */
     template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
     static auto make_copy_constructor(const T *x) -> decltype(new T(*x), Constructor{}) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
         return [](const void *arg) -> void * {
             return new T(*reinterpret_cast<const T *>(arg));
         };
@@ -937,6 +938,7 @@ template <typename type> class type_caster_base : public type_caster_generic {
 
     template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
     static auto make_move_constructor(const T *x) -> decltype(new T(std::move(*const_cast<T *>(x))), Constructor{}) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
         return [](const void *arg) -> void * {
             return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
         };
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b14aff58a2..139a4111e9 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -12,7 +12,6 @@
 
 #if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(push)
-#  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
@@ -1388,12 +1387,14 @@ class class_ : public detail::generic_type {
 
     template <typename... Args, typename... Extra>
     class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra&... extra) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(init);
         init.execute(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
     class_ &def(const detail::initimpl::alias_constructor<Args...> &init, const Extra&... extra) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(init);
         init.execute(*this, extra...);
         return *this;
     }

From c14b193308d7877b158e9187079078099d1052ee Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 28 Jul 2021 18:04:14 -0700
Subject: [PATCH 097/638] chore: increase CMake upper limit (#3124)

---
 .github/workflows/configure.yml                             | 2 +-
 CMakeLists.txt                                              | 6 +++---
 tests/CMakeLists.txt                                        | 4 ++--
 tests/test_cmake_build/installed_embed/CMakeLists.txt       | 6 ++++--
 tests/test_cmake_build/installed_function/CMakeLists.txt    | 3 ++-
 tests/test_cmake_build/installed_target/CMakeLists.txt      | 3 ++-
 tests/test_cmake_build/subdirectory_embed/CMakeLists.txt    | 6 ++++--
 tests/test_cmake_build/subdirectory_function/CMakeLists.txt | 3 ++-
 tests/test_cmake_build/subdirectory_target/CMakeLists.txt   | 3 ++-
 tests/test_embed/CMakeLists.txt                             | 1 +
 10 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index abcff1dde5..924088fc37 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -18,7 +18,7 @@ jobs:
       matrix:
         runs-on: [ubuntu-latest, macos-latest, windows-latest]
         arch: [x64]
-        cmake: [3.18]
+        cmake: ["3.21"]
 
         include:
         - runs-on: ubuntu-latest
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b04311fd85..bb01a861ae 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,13 +7,13 @@
 
 cmake_minimum_required(VERSION 3.4)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.4...3.21)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.21)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.21)
 endif()
 
 # Extract project version from source
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index dc70038dba..d71a51e6a0 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -10,10 +10,10 @@ cmake_minimum_required(VERSION 3.4)
 # The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.21)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.21)
 endif()
 
 # Only needed for CMake < 3.5 support
diff --git a/tests/test_cmake_build/installed_embed/CMakeLists.txt b/tests/test_cmake_build/installed_embed/CMakeLists.txt
index 64ae5c4bff..f7d6939982 100644
--- a/tests/test_cmake_build/installed_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_embed/CMakeLists.txt
@@ -22,5 +22,7 @@ set_target_properties(test_installed_embed PROPERTIES OUTPUT_NAME test_cmake_bui
 # This may be needed to resolve header conflicts, e.g. between Python release and debug headers.
 set_target_properties(test_installed_embed PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
 
-add_custom_target(check_installed_embed $<TARGET_FILE:test_installed_embed>
-                                        ${PROJECT_SOURCE_DIR}/../test.py)
+add_custom_target(
+  check_installed_embed
+  $<TARGET_FILE:test_installed_embed> ${PROJECT_SOURCE_DIR}/../test.py
+  DEPENDS test_installed_embed)
diff --git a/tests/test_cmake_build/installed_function/CMakeLists.txt b/tests/test_cmake_build/installed_function/CMakeLists.txt
index 1a502863c0..d7ca4db55d 100644
--- a/tests/test_cmake_build/installed_function/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_function/CMakeLists.txt
@@ -35,4 +35,5 @@ add_custom_target(
   PYTHONPATH=$<TARGET_FILE_DIR:test_installed_function>
   ${_Python_EXECUTABLE}
   ${PROJECT_SOURCE_DIR}/../test.py
-  ${PROJECT_NAME})
+  ${PROJECT_NAME}
+  DEPENDS test_installed_function)
diff --git a/tests/test_cmake_build/installed_target/CMakeLists.txt b/tests/test_cmake_build/installed_target/CMakeLists.txt
index b38eb77470..bc5e101f1d 100644
--- a/tests/test_cmake_build/installed_target/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_target/CMakeLists.txt
@@ -42,4 +42,5 @@ add_custom_target(
   PYTHONPATH=$<TARGET_FILE_DIR:test_installed_target>
   ${_Python_EXECUTABLE}
   ${PROJECT_SOURCE_DIR}/../test.py
-  ${PROJECT_NAME})
+  ${PROJECT_NAME}
+  DEPENDS test_installed_target)
diff --git a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
index dfb9cb8f63..58cdd7cfd1 100644
--- a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
@@ -23,8 +23,10 @@ add_executable(test_subdirectory_embed ../embed.cpp)
 target_link_libraries(test_subdirectory_embed PRIVATE pybind11::embed)
 set_target_properties(test_subdirectory_embed PROPERTIES OUTPUT_NAME test_cmake_build)
 
-add_custom_target(check_subdirectory_embed $<TARGET_FILE:test_subdirectory_embed>
-                                           "${PROJECT_SOURCE_DIR}/../test.py")
+add_custom_target(
+  check_subdirectory_embed
+  $<TARGET_FILE:test_subdirectory_embed> "${PROJECT_SOURCE_DIR}/../test.py"
+  DEPENDS test_subdirectory_embed)
 
 # Test custom export group -- PYBIND11_EXPORT_NAME
 add_library(test_embed_lib ../embed.cpp)
diff --git a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
index 34aedcf6a8..01557c439a 100644
--- a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
@@ -31,4 +31,5 @@ add_custom_target(
   PYTHONPATH=$<TARGET_FILE_DIR:test_subdirectory_function>
   ${_Python_EXECUTABLE}
   ${PROJECT_SOURCE_DIR}/../test.py
-  ${PROJECT_NAME})
+  ${PROJECT_NAME}
+  DEPENDS test_subdirectory_function)
diff --git a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
index 31d862f6ad..ba82fdee2e 100644
--- a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
@@ -37,4 +37,5 @@ add_custom_target(
   PYTHONPATH=$<TARGET_FILE_DIR:test_subdirectory_target>
   ${_Python_EXECUTABLE}
   ${PROJECT_SOURCE_DIR}/../test.py
-  ${PROJECT_NAME})
+  ${PROJECT_NAME}
+  DEPENDS test_subdirectory_target)
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index c960c877a5..3b89d6e584 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -31,6 +31,7 @@ endif()
 add_custom_target(
   cpptest
   COMMAND "$<TARGET_FILE:test_embed>"
+  DEPENDS test_embed
   WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}")
 
 pybind11_add_module(external_module THIN_LTO external_module.cpp)

From ee3ecb8ae2f0d74fe50912364ec65bce1330af51 Mon Sep 17 00:00:00 2001
From: ka-bo <55587089+ka-bo@users.noreply.github.com>
Date: Wed, 21 Jul 2021 18:00:57 +0200
Subject: [PATCH 098/638] Specified encoding in setup.py calls of open()
 (#3137)

* Specified encoding in setup.py calls of open()

* Fix for Python2

Co-authored-by: Karsten Bock <karsten.bock@dlr.de>
---
 setup.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/setup.py b/setup.py
index ced3d69581..7aa151c01b 100644
--- a/setup.py
+++ b/setup.py
@@ -11,6 +11,7 @@
 import subprocess
 import sys
 import tempfile
+import io
 
 import setuptools.command.sdist
 
@@ -70,7 +71,7 @@ def build_expected_version_hex(matches):
 version = loc["__version__"]
 
 # Verify that the version matches the one in C++
-with open("include/pybind11/detail/common.h") as f:
+with io.open("include/pybind11/detail/common.h", encoding="utf8") as f:
     matches = dict(VERSION_REGEX.findall(f.read()))
 cpp_version = "{MAJOR}.{MINOR}.{PATCH}".format(**matches)
 if version != cpp_version:

From b193d42c32763af3c7e3763657b7cba114010121 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 26 Jul 2021 11:28:36 -0700
Subject: [PATCH 099/638] Removing MSVC C4996 from pragma block at the top of
 pybind11.h (#3129)

* Removing MSVC C4996 from pragma block at the top of pybind11.h

* localtime_thread_safe, PYBIND11_COMPAT_STRDUP

* Adding #include <ctime> (attempt to fix MSVC 2015, 2017 errors).
---
 include/pybind11/chrono.h        | 33 +++++++++++++++++++++++---------
 include/pybind11/detail/common.h |  5 +++++
 include/pybind11/pybind11.h      | 18 ++++++++++++-----
 3 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index d32b5b0569..c4e81f5720 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -11,9 +11,14 @@
 #pragma once
 
 #include "pybind11.h"
+
+#include <chrono>
 #include <cmath>
 #include <ctime>
-#include <chrono>
+#include <mutex>
+
+#include <time.h>
+
 #include <datetime.h>
 
 // Backport the PyDateTime_DELTA functions from Python3.3 if required
@@ -95,6 +100,22 @@ template <typename type> class duration_caster {
     PYBIND11_TYPE_CASTER(type, _("datetime.timedelta"));
 };
 
+inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
+#if defined(__STDC_WANT_LIB_EXT1__) || defined(_MSC_VER)
+    if (localtime_s(buf, time))
+        return nullptr;
+    return buf;
+#else
+    static std::mutex mtx;
+    std::lock_guard<std::mutex> lock(mtx);
+    std::tm *tm_ptr = localtime(time);
+    if (tm_ptr != nullptr) {
+        *buf = *tm_ptr;
+    }
+    return tm_ptr;
+#endif
+}
+
 // This is for casting times on the system clock into datetime.datetime instances
 template <typename Duration> class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
 public:
@@ -162,16 +183,10 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         // (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
         std::time_t tt = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
 
-        // std::localtime returns a pointer to a static internal std::tm object on success,
-        // or null pointer otherwise
-        std::tm *localtime_ptr = std::localtime(&tt);
+        std::tm localtime;
+        std::tm *localtime_ptr = localtime_thread_safe(&tt, &localtime);
         if (!localtime_ptr)
             throw cast_error("Unable to represent system_clock in local time");
-
-        // this function uses static memory so it's best to copy it out asap just in case
-        // otherwise other code that is using localtime may break this (not just python code)
-        std::tm localtime = *localtime_ptr;
-
         return PyDateTime_FromDateAndTime(localtime.tm_year + 1900,
                                           localtime.tm_mon + 1,
                                           localtime.tm_mday,
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 52b0193350..3faf3ea327 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -125,6 +125,11 @@
 #  endif
 #endif
 
+// https://en.cppreference.com/w/c/chrono/localtime
+#if defined(__STDC_LIB_EXT1__) && !defined(__STDC_WANT_LIB_EXT1__)
+#    define __STDC_WANT_LIB_EXT1__
+#endif
+
 #include <Python.h>
 #include <frameobject.h>
 #include <pythread.h>
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index af8e730d3f..cd6e411960 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -19,7 +19,6 @@
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
-#  pragma warning(disable: 4996) // warning C4996: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name
 #  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
@@ -43,6 +42,8 @@
 #include <string>
 #include <utility>
 
+#include <string.h>
+
 #if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
 #  define PYBIND11_STD_LAUNDER std::launder
 #  define PYBIND11_HAS_STD_LAUNDER 1
@@ -56,6 +57,12 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+#if defined(_MSC_VER)
+#    define PYBIND11_COMPAT_STRDUP _strdup
+#else
+#    define PYBIND11_COMPAT_STRDUP strdup
+#endif
+
 /// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object
 class cpp_function : public function {
 public:
@@ -253,7 +260,7 @@ class cpp_function : public function {
                 std::free(s);
         }
         char *operator()(const char *s) {
-            auto t = strdup(s);
+            auto t = PYBIND11_COMPAT_STRDUP(s);
             strings.push_back(t);
             return t;
         }
@@ -497,7 +504,8 @@ class cpp_function : public function {
         auto *func = (PyCFunctionObject *) m_ptr;
         std::free(const_cast<char *>(func->m_ml->ml_doc));
         // Install docstring if it's non-empty (when at least one option is enabled)
-        func->m_ml->ml_doc = signatures.empty() ? nullptr : strdup(signatures.c_str());
+        func->m_ml->ml_doc
+            = signatures.empty() ? nullptr : PYBIND11_COMPAT_STRDUP(signatures.c_str());
 
         if (rec->is_method) {
             m_ptr = PYBIND11_INSTANCE_METHOD_NEW(m_ptr, rec->scope.ptr());
@@ -1498,7 +1506,7 @@ class class_ : public detail::generic_type {
            detail::process_attributes<Extra...>::init(extra..., rec_fget);
            if (rec_fget->doc && rec_fget->doc != doc_prev) {
               free(doc_prev);
-              rec_fget->doc = strdup(rec_fget->doc);
+              rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
            }
         }
         if (rec_fset) {
@@ -1506,7 +1514,7 @@ class class_ : public detail::generic_type {
             detail::process_attributes<Extra...>::init(extra..., rec_fset);
             if (rec_fset->doc && rec_fset->doc != doc_prev) {
                 free(doc_prev);
-                rec_fset->doc = strdup(rec_fset->doc);
+                rec_fset->doc = PYBIND11_COMPAT_STRDUP(rec_fset->doc);
             }
             if (! rec_active) rec_active = rec_fset;
         }

From 85b38c69dee5ae57fe23754becd437ebd4e30961 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 26 Jul 2021 12:02:50 -0700
Subject: [PATCH 100/638] Adding pragma warning(disable: 4522) for MSVC <=
 2017. (#3142)

---
 include/pybind11/pybind11.h | 1 -
 include/pybind11/pytypes.h  | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index cd6e411960..b5091ff257 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -19,7 +19,6 @@
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
-#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
 #  pragma GCC diagnostic push
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index b483fb323c..3329982777 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -532,6 +532,10 @@ object object_or_cast(T &&o);
 // Match a PyObject*, which we want to convert directly to handle via its converting constructor
 inline handle object_or_cast(PyObject *ptr) { return ptr; }
 
+#if defined(_MSC_VER) && _MSC_VER < 1920
+#  pragma warning(push)
+#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
+#endif
 template <typename Policy>
 class accessor : public object_api<accessor<Policy>> {
     using key_type = typename Policy::key_type;
@@ -580,6 +584,9 @@ class accessor : public object_api<accessor<Policy>> {
     key_type key;
     mutable object cache;
 };
+#if defined(_MSC_VER) && _MSC_VER < 1920
+#  pragma warning(pop)
+#endif
 
 PYBIND11_NAMESPACE_BEGIN(accessor_policies)
 struct obj_attr {

From c973660d6c5daa2a24bf5629306d640b6447e9ac Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 26 Jul 2021 15:05:58 -0400
Subject: [PATCH 101/638] [pre-commit.ci] pre-commit autoupdate (#3143)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.21.2 → v2.23.0](https://github.com/asottile/pyupgrade/compare/v2.21.2...v2.23.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index aa7b4774e3..510b841260 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.21.2
+  rev: v2.23.0
   hooks:
   - id: pyupgrade
 

From e93d94594b063682a70ead0b7feb8c1329ae0717 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 26 Jul 2021 13:26:36 -0700
Subject: [PATCH 102/638] Removing MSVC C4800 from pragma block at the top of
 pybind11.h (#3141)

* Adding PYBIND11_COMPAT_BOOL_CAST to appease MSVC 2015 warning C4800.

* Replacing PYBIND11_COMPAT_BOOL_CAST with simpler != 0

* Extra parentheses (almost all compilers failed without these).
---
 include/pybind11/buffer_info.h             | 2 +-
 include/pybind11/cast.h                    | 2 +-
 include/pybind11/detail/type_caster_base.h | 4 ++--
 include/pybind11/pybind11.h                | 1 -
 include/pybind11/pytypes.h                 | 6 ++++--
 5 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 47dc39d4ea..eba68d1aa1 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -83,7 +83,7 @@ struct buffer_info {
             view->strides
             ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
             : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
-            view->readonly) {
+            (view->readonly != 0)) {
         this->m_view = view;
         this->ownview = ownview;
     }
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index a748c77c0f..1da432358f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -322,7 +322,7 @@ template <> class type_caster<bool> {
             }
             #endif
             if (res == 0 || res == 1) {
-                value = (bool) res;
+                value = (res != 0);
                 return true;
             }
             PyErr_Clear();
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 451690dc73..39d0740ff8 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -231,7 +231,7 @@ struct value_and_holder {
         return reinterpret_cast<V *&>(vh[0]);
     }
     // True if this `value_and_holder` has a non-null value pointer
-    explicit operator bool() const { return value_ptr(); }
+    explicit operator bool() const { return value_ptr() != nullptr; }
 
     template <typename H> H &holder() const {
         return reinterpret_cast<H &>(vh[1]);
@@ -252,7 +252,7 @@ struct value_and_holder {
     bool instance_registered() const {
         return inst->simple_layout
             ? inst->simple_instance_registered
-            : inst->nonsimple.status[index] & instance::status_instance_registered;
+            : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
     }
     void set_instance_registered(bool v = true) const {
         if (inst->simple_layout)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b5091ff257..6a2bd0f24d 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -18,7 +18,6 @@
 #  pragma warning(push)
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__)
 #  pragma GCC diagnostic push
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 3329982777..cea4e7eb01 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -367,7 +367,9 @@ class PYBIND11_EXPORT error_already_set : public std::runtime_error {
     /// Check if the currently trapped error type matches the given Python exception class (or a
     /// subclass thereof).  May also be passed a tuple to search for any exception class matches in
     /// the given tuple.
-    bool matches(handle exc) const { return PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()); }
+    bool matches(handle exc) const {
+        return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
+    }
 
     const object& type() const { return m_type; }
     const object& value() const { return m_value; }
@@ -853,7 +855,7 @@ PYBIND11_NAMESPACE_END(detail)
         Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) { } \
         Name(handle h, stolen_t) : Parent(h, stolen_t{}) { } \
         PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead") \
-        bool check() const { return m_ptr != nullptr && (bool) CheckFun(m_ptr); } \
+        bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); } \
         static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); } \
         template <typename Policy_> \
         Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }

From fd71bd486d35f8e8a0d37e65e4654c9700990488 Mon Sep 17 00:00:00 2001
From: David Hewitt <1939362+davidhewitt@users.noreply.github.com>
Date: Tue, 27 Jul 2021 19:16:28 +0100
Subject: [PATCH 103/638] Allow python builtins to be used as callbacks (#1413)

* Allow python builtins to be used as callbacks

* Try to fix pypy segfault

* Add expected fail for PyPy

* Fix typo

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add more info to xfail

* Add env

* Try returning false

* Try removing the move for pypy

* Fix bugs

* Try removing move

* Just keep ignoring for PyPy

* Add back xfail

* Fix ctors

* Revert change of std::move

* Change to skip

* Fix bug and edit comments

* Remove clang-tidy bugprone fix skip bug

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/functional.h | 36 ++++++++++++++++++++---------------
 tests/test_callbacks.cpp      |  6 ++++++
 tests/test_callbacks.py       | 11 +++++++++++
 3 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index cc7099c6a3..b9bf38919c 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -43,27 +43,33 @@ struct type_caster<std::function<Return(Args...)>> {
            captured variables), in which case the roundtrip can be avoided.
          */
         if (auto cfunc = func.cpp_function()) {
-            auto c = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(cfunc.ptr()));
-            auto rec = (function_record *) c;
-
-            while (rec != nullptr) {
-                if (rec->is_stateless
-                    && same_type(typeid(function_type),
-                                 *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
-                    struct capture {
-                        function_type f;
-                    };
-                    value = ((capture *) &rec->data)->f;
-                    return true;
+            auto cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
+            if (isinstance<capsule>(cfunc_self)) {
+                auto c = reinterpret_borrow<capsule>(cfunc_self);
+                auto rec = (function_record *) c;
+
+                while (rec != nullptr) {
+                    if (rec->is_stateless
+                        && same_type(typeid(function_type),
+                                     *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
+                        struct capture {
+                            function_type f;
+                        };
+                        value = ((capture *) &rec->data)->f;
+                        return true;
+                    }
+                    rec = rec->next;
                 }
-                rec = rec->next;
             }
+            // PYPY segfaults here when passing builtin function like sum.
+            // Raising an fail exception here works to prevent the segfault, but only on gcc.
+            // See PR #1413 for full details
         }
 
         // ensure GIL is held during functor destruction
         struct func_handle {
             function f;
-            func_handle(function&& f_) : f(std::move(f_)) {}
+            func_handle(function &&f_) noexcept : f(std::move(f_)) {}
             func_handle(const func_handle& f_) {
                 gil_scoped_acquire acq;
                 f = f_.f;
@@ -77,7 +83,7 @@ struct type_caster<std::function<Return(Args...)>> {
         // to emulate 'move initialization capture' in C++11
         struct func_wrapper {
             func_handle hfunc;
-            func_wrapper(func_handle&& hf): hfunc(std::move(hf)) {}
+            func_wrapper(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
                 object retval(hfunc.f(std::forward<Args>(args)...));
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index a208b44d04..a50771038b 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -156,6 +156,12 @@ TEST_SUBMODULE(callbacks, m) {
         .def(py::init<>())
         .def("triple", [](CppBoundMethodTest &, int val) { return 3 * val; });
 
+    // This checks that builtin functions can be passed as callbacks
+    // rather than throwing RuntimeError due to trying to extract as capsule
+    m.def("test_sum_builtin", [](const std::function<double(py::iterable)> &sum_builtin, const py::iterable &i) {
+      return sum_builtin(i);
+    });
+
     // test async Python callbacks
     using callback_f = std::function<void(int)>;
     m.def("test_async_callback", [](const callback_f &f, const py::list &work) {
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 397bf63d24..5bc4d1773d 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -3,6 +3,7 @@
 from pybind11_tests import callbacks as m
 from threading import Thread
 import time
+import env  # NOQA: F401
 
 
 def test_callbacks():
@@ -124,6 +125,16 @@ def test_movable_object():
     assert m.callback_with_movable(lambda _: None) is True
 
 
+@pytest.mark.skipif(
+    "env.PYPY",
+    reason="PyPy segfaults on here. See discussion on #1413.",
+)
+def test_python_builtins():
+    """Test if python builtins like sum() can be used as callbacks"""
+    assert m.test_sum_builtin(sum, [1, 2, 3]) == 6
+    assert m.test_sum_builtin(sum, []) == 0
+
+
 def test_async_callbacks():
     # serves as state for async callback
     class Item:

From 5c6bdb72156f5b290611b33bb2db258a1caa3488 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 27 Jul 2021 14:23:52 -0700
Subject: [PATCH 104/638] fix: the CMake config in Python package had a hard
 coded path (#3144)

---
 CMakeLists.txt                           |  6 ++++++
 tests/extra_python_package/test_files.py | 14 ++++++++++++--
 tools/pybind11Config.cmake.in            |  3 ++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c988ea0b50..b04311fd85 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -203,6 +203,12 @@ if(PYBIND11_INSTALL)
       "${CMAKE_INSTALL_DATAROOTDIR}/cmake/${PROJECT_NAME}"
       CACHE STRING "install path for pybind11Config.cmake")
 
+  if(IS_ABSOLUTE "${CMAKE_INSTALL_INCLUDEDIR}")
+    set(pybind11_INCLUDEDIR "${CMAKE_INSTALL_FULL_INCLUDEDIR}")
+  else()
+    set(pybind11_INCLUDEDIR "\$\{PACKAGE_PREFIX_DIR\}/${CMAKE_INSTALL_INCLUDEDIR}")
+  endif()
+
   configure_package_config_file(
     tools/${PROJECT_NAME}Config.cmake.in "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
     INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 43e93c2633..337a72dfea 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -138,6 +138,16 @@ def test_build_sdist(monkeypatch, tmpdir):
         ) as f:
             pyproject_toml = f.read()
 
+        with contextlib.closing(
+            tar.extractfile(
+                tar.getmember(
+                    start + "pybind11/share/cmake/pybind11/pybind11Config.cmake"
+                )
+            )
+        ) as f:
+            contents = f.read().decode("utf8")
+        assert 'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")' in contents
+
     files = {"pybind11/{}".format(n) for n in all_files}
     files |= sdist_files
     files |= {"pybind11{}".format(n) for n in local_sdist_files}
@@ -151,11 +161,11 @@ def test_build_sdist(monkeypatch, tmpdir):
             .substitute(version=version, extra_cmd="")
             .encode()
         )
-        assert setup_py == contents
+    assert setup_py == contents
 
     with open(os.path.join(MAIN_DIR, "tools", "pyproject.toml"), "rb") as f:
         contents = f.read()
-        assert pyproject_toml == contents
+    assert pyproject_toml == contents
 
 
 def test_build_global_dist(monkeypatch, tmpdir):
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 6fa03a0f24..73ec104a0e 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -201,7 +201,8 @@ Using ``find_package`` with version info is not recommended except for release v
 @PACKAGE_INIT@
 
 # Location of pybind11/pybind11.h
-set(pybind11_INCLUDE_DIR "@CMAKE_INSTALL_FULL_INCLUDEDIR@")
+# This will be relative unless explicitly set as absolute
+set(pybind11_INCLUDE_DIR "@pybind11_INCLUDEDIR@")
 
 set(pybind11_LIBRARY "")
 set(pybind11_DEFINITIONS USING_pybind11)

From 0ac4c8afd6484bc95b84061fb7651ca59e4701e6 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 27 Jul 2021 18:32:26 -0400
Subject: [PATCH 105/638] maint(clang-tidy): Improve code readability with
 explicit boolean casts (#3148)

* maint(clang-tidy) Improve code readability

* Fix minor typos

* Revert optimization that removed test case

* Fix comment formatting

* Revert another optimization to repro an issue

* Remove make_unique since it C++14 and newer only

* eformat comments

* Fix unsignedness of comparison

* Update comment
---
 .clang-tidy                                | 13 +++++++++++++
 include/pybind11/cast.h                    | 16 ++++++++++------
 include/pybind11/detail/class.h            |  7 ++++---
 include/pybind11/detail/internals.h        |  2 +-
 include/pybind11/detail/type_caster_base.h |  4 ++--
 include/pybind11/embed.h                   |  4 ++--
 include/pybind11/numpy.h                   | 19 +++++++++++--------
 include/pybind11/pybind11.h                | 15 +++++++++------
 include/pybind11/pytypes.h                 | 12 ++++++++----
 include/pybind11/stl/filesystem.h          |  4 ++--
 tests/test_embed/test_interpreter.cpp      |  2 +-
 tests/test_methods_and_attributes.cpp      |  1 +
 tests/test_numpy_dtypes.cpp                |  6 ++++--
 tests/test_numpy_vectorize.cpp             |  2 +-
 tests/test_smart_ptr.cpp                   |  4 ++--
 tests/test_stl.cpp                         |  6 ++----
 16 files changed, 73 insertions(+), 44 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 72304528a5..db5077c227 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -5,13 +5,17 @@ cppcoreguidelines-init-variables,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,
+misc-non-copyable-objects,
 misc-static-assert,
 misc-throw-by-value-catch-by-reference,
 misc-uniqueptr-reset-release,
+misc-unused-parameters,
 modernize-avoid-bind,
+modernize-make-shared,
 modernize-redundant-void-arg,
 modernize-replace-auto-ptr,
 modernize-replace-disallow-copy-and-assign-macro,
+modernize-replace-random-shuffle,
 modernize-shrink-to-fit,
 modernize-use-auto,
 modernize-use-bool-literals,
@@ -23,13 +27,20 @@ modernize-use-emplace,
 modernize-use-override,
 modernize-use-using,
 *performance*,
+readability-avoid-const-params-in-decls,
 readability-container-size-empty,
 readability-else-after-return,
+readability-delete-null-pointer,
+readability-implicit-bool-conversion,
 readability-make-member-function-const,
+readability-misplaced-array-index,
+readability-non-const-parameter,
 readability-redundant-function-ptr-dereference,
 readability-redundant-smartptr-get,
 readability-redundant-string-cstr,
 readability-simplify-subscript-expr,
+readability-static-accessed-through-instance,
+readability-static-definition-in-anonymous-namespace,
 readability-string-compare,
 readability-uniqueptr-delete-release,
 '
@@ -39,6 +50,8 @@ CheckOptions:
   value:           true
 - key:             performance-unnecessary-value-param.AllowedTypes
   value:           'exception_ptr$;'
+- key:             readability-implicit-bool-conversion.AllowPointerConditions
+  value:           true
 
 HeaderFilterRegex: 'pybind11/.*h'
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 1da432358f..898047b304 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -181,7 +181,7 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
         // Signed/unsigned checks happen elsewhere
         if (py_err || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T) && py_value != (py_type) (T) py_value)) {
             PyErr_Clear();
-            if (py_err && convert && PyNumber_Check(src.ptr())) {
+            if (py_err && convert && (PyNumber_Check(src.ptr()) != 0)) {
                 auto tmp = reinterpret_steal<object>(std::is_floating_point<T>::value
                                                      ? PyNumber_Float(src.ptr())
                                                      : PyNumber_Long(src.ptr()));
@@ -300,7 +300,7 @@ template <> class type_caster<bool> {
             value = false;
             return true;
         }
-        if (convert || !std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name)) {
+        if (convert || (std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name) == 0)) {
             // (allow non-implicit conversion for numpy booleans)
 
             Py_ssize_t res = -1;
@@ -501,10 +501,14 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         // can fit into a single char value.
         if (StringCaster::UTF_N == 8 && str_len > 1 && str_len <= 4) {
             auto v0 = static_cast<unsigned char>(value[0]);
-            size_t char0_bytes = !(v0 & 0x80) ? 1 : // low bits only: 0-127
-                (v0 & 0xE0) == 0xC0 ? 2 : // 0b110xxxxx - start of 2-byte sequence
-                (v0 & 0xF0) == 0xE0 ? 3 : // 0b1110xxxx - start of 3-byte sequence
-                4; // 0b11110xxx - start of 4-byte sequence
+            // low bits only: 0-127
+            // 0b110xxxxx - start of 2-byte sequence
+            // 0b1110xxxx - start of 3-byte sequence
+            // 0b11110xxx - start of 4-byte sequence
+            size_t char0_bytes = (v0 & 0x80) == 0      ? 1
+                                 : (v0 & 0xE0) == 0xC0 ? 2
+                                 : (v0 & 0xF0) == 0xE0 ? 3
+                                                       : 4;
 
             if (char0_bytes == str_len) {
                 // If we have a 128-255 value, we can decode it into a single char:
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 5fee3318b0..4951830684 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -129,8 +129,9 @@ extern "C" inline int pybind11_meta_setattro(PyObject* obj, PyObject* name, PyOb
     //   2. `Type.static_prop = other_static_prop` --> setattro:  replace existing `static_prop`
     //   3. `Type.regular_attribute = value`       --> setattro:  regular attribute assignment
     const auto static_prop = (PyObject *) get_internals().static_property_type;
-    const auto call_descr_set = descr && value && PyObject_IsInstance(descr, static_prop)
-                                && !PyObject_IsInstance(value, static_prop);
+    const auto call_descr_set = (descr != nullptr) && (value != nullptr)
+                                && (PyObject_IsInstance(descr, static_prop) != 0)
+                                && (PyObject_IsInstance(value, static_prop) == 0);
     if (call_descr_set) {
         // Call `static_property.__set__()` instead of replacing the `static_property`.
 #if !defined(PYPY_VERSION)
@@ -562,7 +563,7 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
     view->len = view->itemsize;
     for (auto s : info->shape)
         view->len *= s;
-    view->readonly = info->readonly;
+    view->readonly = static_cast<int>(info->readonly);
     if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT)
         view->format = const_cast<char *>(info->format.c_str());
     if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES) {
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 5578c65160..273a0dbaf6 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -293,7 +293,7 @@ PYBIND11_NOINLINE inline internals &get_internals() {
         PyThreadState *tstate = PyThreadState_Get();
         #if PY_VERSION_HEX >= 0x03070000
             internals_ptr->tstate = PyThread_tss_alloc();
-            if (!internals_ptr->tstate || PyThread_tss_create(internals_ptr->tstate))
+            if (!internals_ptr->tstate || (PyThread_tss_create(internals_ptr->tstate) != 0))
                 pybind11_fail("get_internals: could not successfully initialize the TSS key!");
             PyThread_tss_set(internals_ptr->tstate, tstate);
         #else
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 39d0740ff8..7a74133f6e 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -238,8 +238,8 @@ struct value_and_holder {
     }
     bool holder_constructed() const {
         return inst->simple_layout
-            ? inst->simple_holder_constructed
-            : inst->nonsimple.status[index] & instance::status_holder_constructed;
+                   ? inst->simple_holder_constructed
+                   : (inst->nonsimple.status[index] & instance::status_holder_constructed) != 0u;
     }
     void set_holder_constructed(bool v = true) const {
         if (inst->simple_layout)
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 204aaf989f..abb1cd3cca 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -76,7 +76,7 @@ struct embedded_module {
     using init_t = void (*)();
 #endif
     embedded_module(const char *name, init_t init) {
-        if (Py_IsInitialized())
+        if (Py_IsInitialized() != 0)
             pybind11_fail("Can't add new modules after the interpreter has been initialized");
 
         auto result = PyImport_AppendInittab(name, init);
@@ -101,7 +101,7 @@ PYBIND11_NAMESPACE_END(detail)
     .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
  \endrst */
 inline void initialize_interpreter(bool init_signal_handlers = true) {
-    if (Py_IsInitialized())
+    if (Py_IsInitialized() != 0)
         pybind11_fail("The interpreter is already running");
 
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index edba8bac92..7313897fe1 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -465,7 +465,9 @@ class dtype : public object {
     explicit dtype(const buffer_info &info) {
         dtype descr(_dtype_from_pep3118()(PYBIND11_STR_TYPE(info.format)));
         // If info.itemsize == 0, use the value calculated from the format string
-        m_ptr = descr.strip_padding(info.itemsize ? info.itemsize : descr.itemsize()).release().ptr();
+        m_ptr = descr.strip_padding(info.itemsize != 0 ? info.itemsize : descr.itemsize())
+                    .release()
+                    .ptr();
     }
 
     explicit dtype(const std::string &format) {
@@ -486,7 +488,7 @@ class dtype : public object {
     /// This is essentially the same as calling numpy.dtype(args) in Python.
     static dtype from_args(object args) {
         PyObject *ptr = nullptr;
-        if (!detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) || !ptr)
+        if ((detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) == 0) || !ptr)
             throw error_already_set();
         return reinterpret_steal<dtype>(ptr);
     }
@@ -542,7 +544,7 @@ class dtype : public object {
             auto name = spec[0].cast<pybind11::str>();
             auto format = spec[1].cast<tuple>()[0].cast<dtype>();
             auto offset = spec[1].cast<tuple>()[1].cast<pybind11::int_>();
-            if (!len(name) && format.kind() == 'V')
+            if ((len(name) == 0u) && format.kind() == 'V')
                 continue;
             field_descriptors.push_back({(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
         }
@@ -872,11 +874,12 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
         : array(std::move(shape), std::move(strides), ptr, base) { }
 
     explicit array_t(ShapeContainer shape, const T *ptr = nullptr, handle base = handle())
-        : array_t(private_ctor{}, std::move(shape),
-                ExtraFlags & f_style
-                ? detail::f_strides(*shape, itemsize())
-                : detail::c_strides(*shape, itemsize()),
-                ptr, base) { }
+        : array_t(private_ctor{},
+                  std::move(shape),
+                  (ExtraFlags & f_style) != 0 ? detail::f_strides(*shape, itemsize())
+                                              : detail::c_strides(*shape, itemsize()),
+                  ptr,
+                  base) {}
 
     explicit array_t(ssize_t count, const T *ptr = nullptr, handle base = handle())
         : array({count}, {}, ptr, base) { }
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 6a2bd0f24d..679c4beb51 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -296,7 +296,8 @@ class cpp_function : public function {
                 a.descr = guarded_strdup(repr(a.value).cast<std::string>().c_str());
         }
 
-        rec->is_constructor = !strcmp(rec->name, "__init__") || !strcmp(rec->name, "__setstate__");
+        rec->is_constructor
+            = (strcmp(rec->name, "__init__") == 0) || (strcmp(rec->name, "__setstate__") == 0);
 
 #if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
@@ -1105,7 +1106,8 @@ class generic_type : public object {
             pybind11_fail("generic_type: cannot initialize type \"" + std::string(rec.name) +
                           "\": an object with that name is already defined");
 
-        if (rec.module_local ? get_local_type_info(*rec.type) : get_global_type_info(*rec.type))
+        if ((rec.module_local ? get_local_type_info(*rec.type) : get_global_type_info(*rec.type))
+            != nullptr)
             pybind11_fail("generic_type: type \"" + std::string(rec.name) +
                           "\" is already registered!");
 
@@ -1183,8 +1185,9 @@ class generic_type : public object {
     void def_property_static_impl(const char *name,
                                   handle fget, handle fset,
                                   detail::function_record *rec_func) {
-        const auto is_static = rec_func && !(rec_func->is_method && rec_func->scope);
-        const auto has_doc = rec_func && rec_func->doc && pybind11::options::show_user_defined_docstrings();
+        const auto is_static = (rec_func != nullptr) && !(rec_func->is_method && rec_func->scope);
+        const auto has_doc = (rec_func != nullptr) && (rec_func->doc != nullptr)
+                             && pybind11::options::show_user_defined_docstrings();
         auto property = handle((PyObject *) (is_static ? get_internals().static_property_type
                                                        : &PyProperty_Type));
         attr(name) = property(fget.ptr() ? fget : none(),
@@ -2154,8 +2157,8 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
        Unfortunately this doesn't work on PyPy. */
 #if !defined(PYPY_VERSION)
     PyFrameObject *frame = PyThreadState_Get()->frame;
-    if (frame && (std::string) str(frame->f_code->co_name) == name &&
-        frame->f_code->co_argcount > 0) {
+    if (frame != nullptr && (std::string) str(frame->f_code->co_name) == name
+        && frame->f_code->co_argcount > 0) {
         PyFrame_FastToLocals(frame);
         PyObject *self_caller = dict_getitem(
             frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index cea4e7eb01..161aed06f4 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -773,7 +773,11 @@ class dict_readonly {
     dict_readonly(handle obj, ssize_t pos) : obj(obj), pos(pos) { increment(); }
 
     reference dereference() const { return {key, value}; }
-    void increment() { if (!PyDict_Next(obj.ptr(), &pos, &key, &value)) { pos = -1; } }
+    void increment() {
+        if (PyDict_Next(obj.ptr(), &pos, &key, &value) == 0) {
+            pos = -1;
+        }
+    }
     bool equal(const dict_readonly &b) const { return pos == b.pos; }
 
 private:
@@ -1169,14 +1173,14 @@ class bool_ : public object {
     bool_() : object(Py_False, borrowed_t{}) { }
     // Allow implicit conversion from and to `bool`:
     bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) { }
-    operator bool() const { return m_ptr && PyLong_AsLong(m_ptr) != 0; }
+    operator bool() const { return (m_ptr != nullptr) && PyLong_AsLong(m_ptr) != 0; }
 
 private:
     /// Return the truth value of an object -- always returns a new reference
     static PyObject *raw_bool(PyObject *op) {
         const auto value = PyObject_IsTrue(op);
         if (value == -1) return nullptr;
-        return handle(value ? Py_True : Py_False).inc_ref().ptr();
+        return handle(value != 0 ? Py_True : Py_False).inc_ref().ptr();
     }
 };
 
@@ -1607,7 +1611,7 @@ inline memoryview memoryview::from_buffer(
     size_t ndim = shape->size();
     if (ndim != strides->size())
         pybind11_fail("memoryview: shape length doesn't match strides length");
-    ssize_t size = ndim ? 1 : 0;
+    ssize_t size = ndim != 0u ? 1 : 0;
     for (size_t i = 0; i < ndim; ++i)
         size *= (*shape)[i];
     Py_buffer view;
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 7a8acdb60b..431b94b4f7 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -67,7 +67,7 @@ template<typename T> struct path_caster {
         }
         PyObject* native = nullptr;
         if constexpr (std::is_same_v<typename T::value_type, char>) {
-            if (PyUnicode_FSConverter(buf, &native)) {
+            if (PyUnicode_FSConverter(buf, &native) != 0) {
                 if (auto c_str = PyBytes_AsString(native)) {
                     // AsString returns a pointer to the internal buffer, which
                     // must not be free'd.
@@ -75,7 +75,7 @@ template<typename T> struct path_caster {
                 }
             }
         } else if constexpr (std::is_same_v<typename T::value_type, wchar_t>) {
-            if (PyUnicode_FSDecoder(buf, &native)) {
+            if (PyUnicode_FSDecoder(buf, &native) != 0) {
                 if (auto c_str = PyUnicode_AsWideCharString(native, nullptr)) {
                     // AsWideCharString returns a new string that must be free'd.
                     value = c_str;  // Copies the string.
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 6925ee9782..cd50e952f6 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -103,7 +103,7 @@ bool has_pybind11_internals_builtin() {
 
 bool has_pybind11_internals_static() {
     auto **&ipp = py::detail::get_internals_pp();
-    return ipp && *ipp;
+    return (ipp != nullptr) && (*ipp != nullptr);
 }
 
 TEST_CASE("Restart the interpreter") {
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 9db31a0b82..4cf6f08b85 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -43,6 +43,7 @@ class ExampleMandA {
     void add6(int other) { value += other; }                        // passing by value
     void add7(int &other) { value += other; }                       // passing by reference
     void add8(const int &other) { value += other; }                 // passing by const reference
+    // NOLINTNEXTLINE(readability-non-const-parameter) Deliberately non-const for testing
     void add9(int *other) { value += *other; }                      // passing by pointer
     void add10(const int *other) { value += *other; }               // passing by const pointer
 
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index edf9cf200f..340c972db2 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -108,9 +108,11 @@ PYBIND11_PACKED(struct EnumStruct {
 
 std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
     os << "a='";
-    for (size_t i = 0; i < 3 && v.a[i]; i++) os << v.a[i];
+    for (size_t i = 0; i < 3 && (v.a[i] != 0); i++)
+        os << v.a[i];
     os << "',b='";
-    for (size_t i = 0; i < 3 && v.b[i]; i++) os << v.b[i];
+    for (size_t i = 0; i < 3 && (v.b[i] != 0); i++)
+        os << v.b[i];
     return os << "'";
 }
 
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index ed08a42bef..b08a9f7edd 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -59,7 +59,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
         .def(py::init<int>())
         .def_readwrite("value", &NonPODClass::value);
     m.def("vec_passthrough",
-          py::vectorize([](double *a,
+          py::vectorize([](const double *a,
                            double b,
                            // Changing this broke things
                            // NOLINTNEXTLINE(performance-unnecessary-value-param)
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 7fd5a9b36e..57b2d894e2 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -101,7 +101,7 @@ class MyObject3 : public std::enable_shared_from_this<MyObject3> {
 // test_unique_nodelete
 // Object with a private destructor
 class MyObject4;
-static std::unordered_set<MyObject4 *> myobject4_instances;
+std::unordered_set<MyObject4 *> myobject4_instances;
 class MyObject4 {
 public:
     MyObject4(int value) : value{value} {
@@ -127,7 +127,7 @@ class MyObject4 {
 // Object with std::unique_ptr<T, D> where D is not matching the base class
 // Object with a protected destructor
 class MyObject4a;
-static std::unordered_set<MyObject4a *> myobject4a_instances;
+std::unordered_set<MyObject4a *> myobject4a_instances;
 class MyObject4a {
 public:
     MyObject4a(int i) {
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index eb8cdab7b5..23e2c07b32 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -102,7 +102,7 @@ TEST_SUBMODULE(stl, m) {
     // test_set
     m.def("cast_set", []() { return std::set<std::string>{"key1", "key2"}; });
     m.def("load_set", [](const std::set<std::string> &set) {
-        return set.count("key1") && set.count("key2") && set.count("key3");
+        return (set.count("key1") != 0u) && (set.count("key2") != 0u) && (set.count("key3") != 0u);
     });
 
     // test_recursive_casting
@@ -196,9 +196,7 @@ TEST_SUBMODULE(stl, m) {
     m.def("double_or_zero", [](const opt_int& x) -> int {
         return x.value_or(0) * 2;
     });
-    m.def("half_or_none", [](int x) -> opt_int {
-        return x ? opt_int(x / 2) : opt_int();
-    });
+    m.def("half_or_none", [](int x) -> opt_int { return x != 0 ? opt_int(x / 2) : opt_int(); });
     m.def("test_nullopt", [](opt_int x) {
         return x.value_or(42);
     }, py::arg_v("x", std::nullopt, "None"));

From ed5fb66bd792fb709c0f4259b60b42b7d7101559 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 27 Jul 2021 15:33:31 -0700
Subject: [PATCH 106/638] Removing __INTEL_COMPILER section from pragma block
 at the top of pybind11.h (#3135)

* Fixing `pragma warning pop` for `__INTEL_COMPILER`.

* Adding push/pop to 3 tests. Removing #878 from top of pybind11.h (it was/is only needed for 1 test).

* Trying again after CI failure, moving the push to the top of 2 tests.

* Trying more after CI failure, adding push/pop to pybind11_tests.h, constructor_stats.h.

* Moving ICC #2196 suppression to CMakeLists.txt

* Fixing condition for `pragma GCC diagnostic push` in pybind11.h

* Moving `pragma warning disable 2196` to common.h

* Revising #ifdef to be more conservative.

* Undoing insertion of notes that will hopefully soon be completely obsolete anyway.
---
 include/pybind11/detail/common.h       | 3 +++
 include/pybind11/pybind11.h            | 8 ++------
 tests/test_constants_and_functions.cpp | 7 +++++++
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 3faf3ea327..0b4e30c18b 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -56,6 +56,9 @@
 #  elif __INTEL_COMPILER < 1900 && defined(PYBIND11_CPP14)
 #    error pybind11 supports only C++11 with Intel C++ compiler v18. Use v19 or newer for C++14.
 #  endif
+/* The following pragma cannot be pop'ed:
+   https://community.intel.com/t5/Intel-C-Compiler/Inline-and-no-inline-warning/td-p/1216764 */
+#  pragma warning disable 2196 // warning #2196: routine is both "inline" and "noinline"
 #elif defined(__clang__) && !defined(__apple_build_version__)
 #  if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
 #    error pybind11 requires clang 3.3 or newer
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 679c4beb51..f4aa9b8814 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,16 +10,12 @@
 
 #pragma once
 
-#if defined(__INTEL_COMPILER)
-#  pragma warning push
-#  pragma warning disable 878   // incompatible exception specifications
-#  pragma warning disable 2196  // warning #2196: routine is both "inline" and "noinline"
-#elif defined(_MSC_VER)
+#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(push)
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
-#elif defined(__GNUG__) && !defined(__clang__)
+#elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wattributes"
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index e7f018540c..c0554503fa 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -133,7 +133,14 @@ TEST_SUBMODULE(constants_and_functions, m) {
         ;
     m.def("f1", f1);
     m.def("f2", f2);
+#if defined(__INTEL_COMPILER)
+#    pragma warning push
+#    pragma warning disable 878 // incompatible exception specifications
+#endif
     m.def("f3", f3);
+#if defined(__INTEL_COMPILER)
+#    pragma warning pop
+#endif
     m.def("f4", f4);
 
     // test_function_record_leaks

From 05852fb6bc2ba9bd89de671faf3cee072e1f7dbd Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 28 Jul 2021 08:58:36 -0700
Subject: [PATCH 107/638] Accommodating environments that define
 __STDC_WANT_LIB_EXT1__ even if __STDC_LIB_EXT1__ is not defined by the
 implementation. (#3151)

Follow-on to PR #3129.
---
 include/pybind11/chrono.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index c4e81f5720..61bbcbc540 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -101,7 +101,7 @@ template <typename type> class duration_caster {
 };
 
 inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
-#if defined(__STDC_WANT_LIB_EXT1__) || defined(_MSC_VER)
+#if (defined(__STDC_LIB_EXT1__) && defined(__STDC_WANT_LIB_EXT1__)) || defined(_MSC_VER)
     if (localtime_s(buf, time))
         return nullptr;
     return buf;

From b1fdbe6954be5afa0a9003c37731da60ac68baff Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 29 Jul 2021 16:10:18 -0700
Subject: [PATCH 108/638] chore: add discussions link (#3159)

---
 .github/ISSUE_TEMPLATE/bug-report.md      | 28 --------------
 .github/ISSUE_TEMPLATE/bug-report.yml     | 45 +++++++++++++++++++++++
 .github/ISSUE_TEMPLATE/config.yml         |  3 ++
 .github/ISSUE_TEMPLATE/feature-request.md | 16 --------
 .github/ISSUE_TEMPLATE/question.md        | 21 -----------
 README.rst                                |  4 +-
 6 files changed, 51 insertions(+), 66 deletions(-)
 delete mode 100644 .github/ISSUE_TEMPLATE/bug-report.md
 create mode 100644 .github/ISSUE_TEMPLATE/bug-report.yml
 delete mode 100644 .github/ISSUE_TEMPLATE/feature-request.md
 delete mode 100644 .github/ISSUE_TEMPLATE/question.md

diff --git a/.github/ISSUE_TEMPLATE/bug-report.md b/.github/ISSUE_TEMPLATE/bug-report.md
deleted file mode 100644
index ae36ea6508..0000000000
--- a/.github/ISSUE_TEMPLATE/bug-report.md
+++ /dev/null
@@ -1,28 +0,0 @@
----
-name: Bug Report
-about: File an issue about a bug
-title: "[BUG] "
----
-
-
-Make sure you've completed the following steps before submitting your issue -- thank you!
-
-1. Make sure you've read the [documentation][]. Your issue may be addressed there.
-2. Search the [issue tracker][] to verify that this hasn't already been reported. +1 or comment there if it has.
-3. Consider asking first in the [Gitter chat room][].
-4. Include a self-contained and minimal piece of code that reproduces the problem. If that's not possible, try to make the description as clear as possible.
-    a. If possible, make a PR with a new, failing test to give us a starting point to work on!
-
-[documentation]: https://pybind11.readthedocs.io
-[issue tracker]: https://github.com/pybind/pybind11/issues
-[Gitter chat room]: https://gitter.im/pybind/Lobby
-
-*After reading, remove this checklist and the template text in parentheses below.*
-
-## Issue description
-
-(Provide a short description, state the expected behavior and what actually happens.)
-
-## Reproducible example code
-
-(The code should be minimal, have no external dependencies, isolate the function(s) that cause breakage. Submit matched and complete C++ and Python snippets that can be easily compiled and run to diagnose the issue.)
diff --git a/.github/ISSUE_TEMPLATE/bug-report.yml b/.github/ISSUE_TEMPLATE/bug-report.yml
new file mode 100644
index 0000000000..bd6a9a8e22
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/bug-report.yml
@@ -0,0 +1,45 @@
+name: Bug Report
+description: File an issue about a bug
+title: "[BUG]: "
+labels: [triage]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Maintainers will only make a best effort to triage PRs. Please do your best to make the issue as easy to act on as possible, and only open if clearly a problem with pybind11 (ask first if unsure).
+  - type: checkboxes
+    id: steps
+    attributes:
+      label: Required prerequisites
+      description: Make sure you've completed the following steps before submitting your issue -- thank you!
+      options:
+        - label: Make sure you've read the [documentation](https://pybind11.readthedocs.io). Your issue may be addressed there.
+          required: true
+        - label: Search the [issue tracker](https://github.com/pybind/pybind11/issues) and [Discussions](https:/pybind/pybind11/discussions) to verify that this hasn't already been reported. +1 or comment there if it has.
+          required: true
+        - label: Consider asking first in the [Gitter chat room](https://gitter.im/pybind/Lobby) or in a [Discussion](https:/pybind/pybind11/discussions/new).
+          required: false
+
+  - type: textarea
+    id: description
+    attributes:
+      label: Problem description
+      placeholder: >-
+        Provide a short description, state the expected behavior and what
+        actually happens. Include relevant information like what version of
+        pybind11 you are using, what system you are on, and any useful commands
+        / output.
+    validations:
+      required: true
+
+  - type: textarea
+    id: code
+    attributes:
+      label: Reproducible example code
+      placeholder: >-
+        The code should be minimal, have no external dependencies, isolate the
+        function(s) that cause breakage. Submit matched and complete C++ and
+        Python snippets that can be easily compiled and run to diagnose the
+        issue. If possible, make a PR with a new, failing test to give us a
+        starting point to work on!
+      render: text
diff --git a/.github/ISSUE_TEMPLATE/config.yml b/.github/ISSUE_TEMPLATE/config.yml
index 20e743136f..27f9a80441 100644
--- a/.github/ISSUE_TEMPLATE/config.yml
+++ b/.github/ISSUE_TEMPLATE/config.yml
@@ -1,5 +1,8 @@
 blank_issues_enabled: false
 contact_links:
+  - name: Ask a question
+    url: https://github.com/pybind/pybind11/discussions/new
+    about: Please ask and answer questions here, or propose new ideas.
   - name: Gitter room
     url: https://gitter.im/pybind/Lobby
     about: A room for discussing pybind11 with an active community
diff --git a/.github/ISSUE_TEMPLATE/feature-request.md b/.github/ISSUE_TEMPLATE/feature-request.md
deleted file mode 100644
index 5f6ec81ec9..0000000000
--- a/.github/ISSUE_TEMPLATE/feature-request.md
+++ /dev/null
@@ -1,16 +0,0 @@
----
-name: Feature Request
-about: File an issue about adding a feature
-title: "[FEAT] "
----
-
-
-Make sure you've completed the following steps before submitting your issue -- thank you!
-
-1. Check if your feature has already been mentioned / rejected / planned in other issues.
-2. If those resources didn't help, consider asking in the [Gitter chat room][] to see if this is interesting / useful to a larger audience and possible to implement reasonably,
-4. If you have a useful feature that passes the previous items (or not suitable for chat), please fill in the details below.
-
-[Gitter chat room]: https://gitter.im/pybind/Lobby
-
-*After reading, remove this checklist.*
diff --git a/.github/ISSUE_TEMPLATE/question.md b/.github/ISSUE_TEMPLATE/question.md
deleted file mode 100644
index b199b6ee8a..0000000000
--- a/.github/ISSUE_TEMPLATE/question.md
+++ /dev/null
@@ -1,21 +0,0 @@
----
-name: Question
-about: File an issue about unexplained behavior
-title: "[QUESTION] "
----
-
-If you have a question, please check the following first:
-
-1. Check if your question has already been answered in the [FAQ][] section.
-2. Make sure you've read the [documentation][]. Your issue may be addressed there.
-3. If those resources didn't help and you only have a short question (not a bug report), consider asking in the [Gitter chat room][]
-4. Search the [issue tracker][], including the closed issues, to see if your question has already been asked/answered. +1 or comment if it has been asked but has no answer.
-5. If you have a more complex question which is not answered in the previous items (or not suitable for chat), please fill in the details below.
-6. Include a self-contained and minimal piece of code that illustrates your question. If that's not possible, try to make the description as clear as possible.
-
-[FAQ]: http://pybind11.readthedocs.io/en/latest/faq.html
-[documentation]: https://pybind11.readthedocs.io
-[issue tracker]: https://github.com/pybind/pybind11/issues
-[Gitter chat room]: https://gitter.im/pybind/Lobby
-
-*After reading, remove this checklist.*
diff --git a/README.rst b/README.rst
index 69a7797e83..57eb06e557 100644
--- a/README.rst
+++ b/README.rst
@@ -3,7 +3,7 @@
 
 **pybind11 — Seamless operability between C++11 and Python**
 
-|Latest Documentation Status| |Stable Documentation Status| |Gitter chat| |CI| |Build status|
+|Latest Documentation Status| |Stable Documentation Status| |Gitter chat| |GitHub Discussions| |CI| |Build status|
 
 |Repology| |PyPI package| |Conda-forge| |Python Versions|
 
@@ -176,3 +176,5 @@ to the terms and conditions of this license.
    :target: https://repology.org/project/python:pybind11/versions
 .. |Python Versions| image:: https://img.shields.io/pypi/pyversions/pybind11.svg
    :target: https://pypi.org/project/pybind11/
+.. |GitHub Discussions| image:: https://img.shields.io/static/v1?label=Discussions&message=Ask&color=blue&logo=github
+   :target: https://github.com/pybind/pybind11/discussions

From b42597291fd59b9bb3af4a9489ca14c910c347d6 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 30 Jul 2021 07:09:55 -0700
Subject: [PATCH 109/638] Limiting pragma for ignoring GCC 7 -Wnoexcept-type to
 the scope of pybind11.h. (#3161)

* Moving pragma for ignoring -Wnoexcept-type to the one location where it is needed.

* Trying a second location.

* The previous commit worked (GitHub Actions green), but see the added comment about the dicy nature of -Wnoexcept-type ("if and only if").

* Applying reviewer suggestion.
---
 include/pybind11/pybind11.h | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 139a4111e9..16615421dc 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -18,9 +18,6 @@
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wattributes"
-#  if __GNUC__ >= 7
-#    pragma GCC diagnostic ignored "-Wnoexcept-type"
-#  endif
 #endif
 
 #include "attr.h"
@@ -48,6 +45,18 @@
 #  include <cxxabi.h>
 #endif
 
+/* https://stackoverflow.com/questions/46798456/handling-gccs-noexcept-type-warning
+   This warning is about ABI compatibility, not code health.
+   It is only actually needed in a couple places, but apparently GCC 7 "generates this warning if
+   and only if the first template instantiation ... involves noexcept" [stackoverflow], therefore
+   it could get triggered from seemingly random places, depending on user code.
+   No other GCC version generates this warning.
+ */
+#if defined(__GNUC__) && __GNUC__ == 7
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wnoexcept-type"
+#endif
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -2376,6 +2385,10 @@ inline function get_overload(const T *this_ptr, const char *name) {
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
+#if defined(__GNUC__) && __GNUC__ == 7
+#    pragma GCC diagnostic pop // -Wnoexcept-type
+#endif
+
 #if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(pop)
 #elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)

From 9e8a741baac7485a7f81904bbb9c06a9ae423c40 Mon Sep 17 00:00:00 2001
From: Jerome Robert <jeromerobert@gmx.com>
Date: Fri, 30 Jul 2021 19:48:41 +0200
Subject: [PATCH 110/638] fix: Mingw64 corrected and add a CI job to test it
 (#3132)

* mingw64 platform string is like mingw_xxx not "mingw"

See https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-python/0099-Change-the-get_platform-method-in-sysconfig-and-dist.patch

* Mingw: Do not dllexport exceptions

This is a fix for errors like:

D:/a/pybind11/pybind11/include/pybind11/detail/common.h:735:23: error: 'dllexport' implies default visibility, but 'class pybind11::builtin_exception' has already been declared with a different visibility
  735 | class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
      |                       ^~~~~~~~~~~~~~~~~

* GHA: Test Mingw64 build

* fix: avoid thin binaries on mingw

* fix: drop lto on MinGW

* Mingw64: disable PYBIND11_DEPRECATED

It trigger many warnings for unknown reasons

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml         | 31 +++++++++++++++++++++++++++++++
 include/pybind11/detail/common.h | 20 +++++++++++++++++---
 include/pybind11/pytypes.h       |  2 +-
 pybind11/setup_helpers.py        |  3 +--
 tests/test_exceptions.h          |  2 +-
 tools/pybind11Common.cmake       |  7 ++++++-
 6 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03c9225c12..73a6fd5199 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -859,3 +859,34 @@ jobs:
 
     - name: Run all checks
       run: cmake --build build -t check
+
+  mingw:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+    - uses: msys2/setup-msys2@v2
+      with:
+        install: >-
+          mingw-w64-x86_64-gcc
+          mingw-w64-x86_64-python-pip
+          mingw-w64-x86_64-cmake
+          mingw-w64-x86_64-make
+          mingw-w64-x86_64-python-pytest
+          mingw-w64-x86_64-eigen3
+          mingw-w64-x86_64-boost
+          mingw-w64-x86_64-catch
+
+    - uses: actions/checkout@v1
+
+    - name: Configure
+      # LTO leads to many undefined reference like
+      # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
+      run: cmake -G "MinGW Makefiles" -S . -B build
+
+    - name: Build
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 0add6272f5..d63e3e9c78 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -89,13 +89,27 @@
 #  endif
 #endif
 
+#if !defined(PYBIND11_EXPORT_EXCEPTION)
+#  ifdef __MINGW32__
+// workaround for:
+// error: 'dllexport' implies default visibility, but xxx has already been declared with a different visibility
+#    define PYBIND11_EXPORT_EXCEPTION
+#  else
+#    define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
+#  endif
+#endif
+
 #if defined(_MSC_VER)
 #  define PYBIND11_NOINLINE __declspec(noinline)
 #else
 #  define PYBIND11_NOINLINE __attribute__ ((noinline))
 #endif
 
-#if defined(PYBIND11_CPP14)
+#if defined(__MINGW32__)
+// For unknown reasons all PYBIND11_DEPRECATED member trigger a warning when declared
+// whether it is used or not
+#  define PYBIND11_DEPRECATED(reason)
+#elif defined(PYBIND11_CPP14)
 #  define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
 #else
 #  define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
@@ -740,7 +754,7 @@ PYBIND11_NAMESPACE_END(detail)
 #  pragma warning(disable: 4275) // warning C4275: An exported class was derived from a class that wasn't exported. Can be ignored when derived from a STL class.
 #endif
 /// C++ bindings of builtin Python exceptions
-class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
+class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
 public:
     using std::runtime_error::runtime_error;
     /// Set the error using the Python C API
@@ -751,7 +765,7 @@ class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
 #endif
 
 #define PYBIND11_RUNTIME_EXCEPTION(name, type) \
-    class PYBIND11_EXPORT name : public builtin_exception { public: \
+    class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception { public: \
         using builtin_exception::builtin_exception; \
         name() : name("") { } \
         void set_error() const override { PyErr_SetString(type, what()); } \
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 161aed06f4..4cf606e8d0 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -327,7 +327,7 @@ PYBIND11_NAMESPACE_END(detail)
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
 /// else falls back to the function dispatcher (which then raises the captured error back to
 /// python).
-class PYBIND11_EXPORT error_already_set : public std::runtime_error {
+class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
 public:
     /// Constructs a new exception from the current Python error indicator, if any.  The current
     /// Python error indicator will be cleared.
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 2b27f1f5ad..0888ab4872 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -59,8 +59,7 @@
 import distutils.errors
 import distutils.ccompiler
 
-
-WIN = sys.platform.startswith("win32") and sysconfig.get_platform() != "mingw"
+WIN = sys.platform.startswith("win32") and "mingw" not in sysconfig.get_platform()
 PY2 = sys.version_info[0] < 3
 MACOS = sys.platform.startswith("darwin")
 STD_TMPL = "/std:c++{}" if WIN else "-std=c++{}"
diff --git a/tests/test_exceptions.h b/tests/test_exceptions.h
index 5d02d1b35b..9d428312eb 100644
--- a/tests/test_exceptions.h
+++ b/tests/test_exceptions.h
@@ -4,7 +4,7 @@
 
 // shared exceptions for cross_module_tests
 
-class PYBIND11_EXPORT shared_exception : public pybind11::builtin_exception {
+class PYBIND11_EXPORT_EXCEPTION shared_exception : public pybind11::builtin_exception {
 public:
     using builtin_exception::builtin_exception;
     explicit shared_exception() : shared_exception("") {}
diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index 57e42536e1..7afb0d0b1a 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -302,13 +302,18 @@ function(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerfla
 endfunction()
 
 function(_pybind11_generate_lto target prefer_thin_lto)
+  if(MINGW)
+    message(STATUS "${target} disabled (problems with undefined symbols for MinGW for now)")
+    return()
+  endif()
+
   if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
     set(cxx_append "")
     set(linker_append "")
     if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT APPLE)
       # Clang Gold plugin does not support -Os; append -O3 to MinSizeRel builds to override it
       set(linker_append ";$<$<CONFIG:MinSizeRel>:-O3>")
-    elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+    elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND NOT MINGW)
       set(cxx_append ";-fno-fat-lto-objects")
     endif()
 

From e2573dc961ec11cd148c50c06abfaee0a6930694 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 30 Jul 2021 10:51:50 -0700
Subject: [PATCH 111/638] Moving pragma for MSVC warning C4505 from pybind11.h
 to existing list in detail/common.h (#3160)

* Moving pragma for C4505 from pybind11.h to existing list in detail/common.h.

* Removing 4 existing suppressions to 1. see what is still needed and 2. capture the MSVC messages.

* It turns out none of the 4 pragmas are needed anymore.
---
 include/pybind11/detail/common.h | 3 ++-
 include/pybind11/pybind11.h      | 1 -
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index d63e3e9c78..d1e9e6591f 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -135,7 +135,8 @@
 #    define HAVE_ROUND 1
 #  endif
 #  pragma warning(push)
-#  pragma warning(disable: 4510 4610 4512 4005)
+// C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
+#  pragma warning(disable: 4505)
 #  if defined(_DEBUG) && !defined(Py_DEBUG)
 #    define PYBIND11_DEBUG_MARKER
 #    undef _DEBUG
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 16615421dc..ec6bd8d351 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -13,7 +13,6 @@
 #if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(push)
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

From 46c51fc03bfc76bfd71e9ab5036bec7efefb4b5d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 30 Jul 2021 07:09:55 -0700
Subject: [PATCH 112/638] Limiting pragma for ignoring GCC 7 -Wnoexcept-type to
 the scope of pybind11.h. (#3161)

* Moving pragma for ignoring -Wnoexcept-type to the one location where it is needed.

* Trying a second location.

* The previous commit worked (GitHub Actions green), but see the added comment about the dicy nature of -Wnoexcept-type ("if and only if").

* Applying reviewer suggestion.
---
 include/pybind11/pybind11.h | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index f4aa9b8814..3eb71f386a 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -19,9 +19,6 @@
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wattributes"
-#  if __GNUC__ >= 7
-#    pragma GCC diagnostic ignored "-Wnoexcept-type"
-#  endif
 #endif
 
 #include "attr.h"
@@ -49,6 +46,18 @@
 #  include <cxxabi.h>
 #endif
 
+/* https://stackoverflow.com/questions/46798456/handling-gccs-noexcept-type-warning
+   This warning is about ABI compatibility, not code health.
+   It is only actually needed in a couple places, but apparently GCC 7 "generates this warning if
+   and only if the first template instantiation ... involves noexcept" [stackoverflow], therefore
+   it could get triggered from seemingly random places, depending on user code.
+   No other GCC version generates this warning.
+ */
+#if defined(__GNUC__) && __GNUC__ == 7
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wnoexcept-type"
+#endif
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 #if defined(_MSC_VER)
@@ -2309,6 +2318,10 @@ inline function get_overload(const T *this_ptr, const char *name) {
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
+#if defined(__GNUC__) && __GNUC__ == 7
+#    pragma GCC diagnostic pop // -Wnoexcept-type
+#endif
+
 #if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(pop)
 #elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)

From c80e0593454411ad38205cc76134d6a0dd70032e Mon Sep 17 00:00:00 2001
From: Jerome Robert <jeromerobert@gmx.com>
Date: Fri, 30 Jul 2021 19:48:41 +0200
Subject: [PATCH 113/638] fix: Mingw64 corrected and add a CI job to test it
 (#3132)

* mingw64 platform string is like mingw_xxx not "mingw"

See https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-python/0099-Change-the-get_platform-method-in-sysconfig-and-dist.patch

* Mingw: Do not dllexport exceptions

This is a fix for errors like:

D:/a/pybind11/pybind11/include/pybind11/detail/common.h:735:23: error: 'dllexport' implies default visibility, but 'class pybind11::builtin_exception' has already been declared with a different visibility
  735 | class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
      |                       ^~~~~~~~~~~~~~~~~

* GHA: Test Mingw64 build

* fix: avoid thin binaries on mingw

* fix: drop lto on MinGW

* Mingw64: disable PYBIND11_DEPRECATED

It trigger many warnings for unknown reasons

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml         | 31 +++++++++++++++++++++++++++++++
 include/pybind11/detail/common.h | 20 +++++++++++++++++---
 include/pybind11/pytypes.h       |  2 +-
 pybind11/setup_helpers.py        |  3 +--
 tests/test_exceptions.h          |  2 +-
 tools/pybind11Common.cmake       |  7 ++++++-
 6 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03c9225c12..73a6fd5199 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -859,3 +859,34 @@ jobs:
 
     - name: Run all checks
       run: cmake --build build -t check
+
+  mingw:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+    - uses: msys2/setup-msys2@v2
+      with:
+        install: >-
+          mingw-w64-x86_64-gcc
+          mingw-w64-x86_64-python-pip
+          mingw-w64-x86_64-cmake
+          mingw-w64-x86_64-make
+          mingw-w64-x86_64-python-pytest
+          mingw-w64-x86_64-eigen3
+          mingw-w64-x86_64-boost
+          mingw-w64-x86_64-catch
+
+    - uses: actions/checkout@v1
+
+    - name: Configure
+      # LTO leads to many undefined reference like
+      # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
+      run: cmake -G "MinGW Makefiles" -S . -B build
+
+    - name: Build
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 0b4e30c18b..09e8717ce4 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -89,13 +89,27 @@
 #  endif
 #endif
 
+#if !defined(PYBIND11_EXPORT_EXCEPTION)
+#  ifdef __MINGW32__
+// workaround for:
+// error: 'dllexport' implies default visibility, but xxx has already been declared with a different visibility
+#    define PYBIND11_EXPORT_EXCEPTION
+#  else
+#    define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
+#  endif
+#endif
+
 #if defined(_MSC_VER)
 #  define PYBIND11_NOINLINE __declspec(noinline)
 #else
 #  define PYBIND11_NOINLINE __attribute__ ((noinline))
 #endif
 
-#if defined(PYBIND11_CPP14)
+#if defined(__MINGW32__)
+// For unknown reasons all PYBIND11_DEPRECATED member trigger a warning when declared
+// whether it is used or not
+#  define PYBIND11_DEPRECATED(reason)
+#elif defined(PYBIND11_CPP14)
 #  define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
 #else
 #  define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
@@ -740,7 +754,7 @@ PYBIND11_NAMESPACE_END(detail)
 #  pragma warning(disable: 4275) // warning C4275: An exported class was derived from a class that wasn't exported. Can be ignored when derived from a STL class.
 #endif
 /// C++ bindings of builtin Python exceptions
-class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
+class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
 public:
     using std::runtime_error::runtime_error;
     /// Set the error using the Python C API
@@ -751,7 +765,7 @@ class PYBIND11_EXPORT builtin_exception : public std::runtime_error {
 #endif
 
 #define PYBIND11_RUNTIME_EXCEPTION(name, type) \
-    class PYBIND11_EXPORT name : public builtin_exception { public: \
+    class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception { public: \
         using builtin_exception::builtin_exception; \
         name() : name("") { } \
         void set_error() const override { PyErr_SetString(type, what()); } \
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 161aed06f4..4cf606e8d0 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -327,7 +327,7 @@ PYBIND11_NAMESPACE_END(detail)
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
 /// else falls back to the function dispatcher (which then raises the captured error back to
 /// python).
-class PYBIND11_EXPORT error_already_set : public std::runtime_error {
+class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
 public:
     /// Constructs a new exception from the current Python error indicator, if any.  The current
     /// Python error indicator will be cleared.
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 2b27f1f5ad..0888ab4872 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -59,8 +59,7 @@
 import distutils.errors
 import distutils.ccompiler
 
-
-WIN = sys.platform.startswith("win32") and sysconfig.get_platform() != "mingw"
+WIN = sys.platform.startswith("win32") and "mingw" not in sysconfig.get_platform()
 PY2 = sys.version_info[0] < 3
 MACOS = sys.platform.startswith("darwin")
 STD_TMPL = "/std:c++{}" if WIN else "-std=c++{}"
diff --git a/tests/test_exceptions.h b/tests/test_exceptions.h
index 5d02d1b35b..9d428312eb 100644
--- a/tests/test_exceptions.h
+++ b/tests/test_exceptions.h
@@ -4,7 +4,7 @@
 
 // shared exceptions for cross_module_tests
 
-class PYBIND11_EXPORT shared_exception : public pybind11::builtin_exception {
+class PYBIND11_EXPORT_EXCEPTION shared_exception : public pybind11::builtin_exception {
 public:
     using builtin_exception::builtin_exception;
     explicit shared_exception() : shared_exception("") {}
diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index 57e42536e1..7afb0d0b1a 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -302,13 +302,18 @@ function(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerfla
 endfunction()
 
 function(_pybind11_generate_lto target prefer_thin_lto)
+  if(MINGW)
+    message(STATUS "${target} disabled (problems with undefined symbols for MinGW for now)")
+    return()
+  endif()
+
   if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
     set(cxx_append "")
     set(linker_append "")
     if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT APPLE)
       # Clang Gold plugin does not support -Os; append -O3 to MinSizeRel builds to override it
       set(linker_append ";$<$<CONFIG:MinSizeRel>:-O3>")
-    elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+    elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND NOT MINGW)
       set(cxx_append ";-fno-fat-lto-objects")
     endif()
 

From b961ac644ff0ec22e3a6edc5925bd9b0f2eff0df Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 30 Jul 2021 10:51:50 -0700
Subject: [PATCH 114/638] Moving pragma for MSVC warning C4505 from pybind11.h
 to existing list in detail/common.h (#3160)

* Moving pragma for C4505 from pybind11.h to existing list in detail/common.h.

* Removing 4 existing suppressions to 1. see what is still needed and 2. capture the MSVC messages.

* It turns out none of the 4 pragmas are needed anymore.
---
 include/pybind11/detail/common.h | 3 ++-
 include/pybind11/pybind11.h      | 1 -
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 09e8717ce4..9df670fa9d 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -135,7 +135,8 @@
 #    define HAVE_ROUND 1
 #  endif
 #  pragma warning(push)
-#  pragma warning(disable: 4510 4610 4512 4005)
+// C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
+#  pragma warning(disable: 4505)
 #  if defined(_DEBUG) && !defined(Py_DEBUG)
 #    define PYBIND11_DEBUG_MARKER
 #    undef _DEBUG
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 3eb71f386a..1cb232d3a7 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -14,7 +14,6 @@
 #  pragma warning(push)
 #  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#  pragma warning(disable: 4505) // warning C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

From dcbda8d7ff6e0a207807208ff0364bbb74e02175 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 30 Jul 2021 11:25:29 -0700
Subject: [PATCH 115/638] Removing MSVC C4127 from pragma block at the top of
 pybind11.h (#3152)

* Removing pragma for 4127 (to see what is still broken with the latest code).

* Using new constexpr_bool() to suppress warning C4127.

* One missed case, Python 2 only.

* PYBIND11_SILENCE_MSVC_C4127 (more similar to the approach for C4100).
---
 include/pybind11/cast.h          | 12 ++++++++----
 include/pybind11/detail/common.h | 11 +++++++++++
 include/pybind11/detail/init.h   |  6 +++---
 include/pybind11/pybind11.h      | 11 +++--------
 include/pybind11/pytypes.h       |  6 +++---
 5 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 5ff0355a6f..211cf09bcd 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -384,7 +384,11 @@ template <typename StringType, bool IsView = false> struct string_caster {
 
         const auto *buffer = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
         size_t length = (size_t) PYBIND11_BYTES_SIZE(utfNbytes.ptr()) / sizeof(CharT);
-        if (UTF_N > 8) { buffer++; length--; } // Skip BOM for UTF-16/32
+        // Skip BOM for UTF-16/32
+        if (PYBIND11_SILENCE_MSVC_C4127(UTF_N > 8)) {
+            buffer++;
+            length--;
+        }
         value = StringType(buffer, length);
 
         // If we're loading a string_view we need to keep the encoded Python object alive:
@@ -499,7 +503,7 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         // out how long the first encoded character is in bytes to distinguish between these two
         // errors.  We also allow want to allow unicode characters U+0080 through U+00FF, as those
         // can fit into a single char value.
-        if (StringCaster::UTF_N == 8 && str_len > 1 && str_len <= 4) {
+        if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 8) && str_len > 1 && str_len <= 4) {
             auto v0 = static_cast<unsigned char>(value[0]);
             // low bits only: 0-127
             // 0b110xxxxx - start of 2-byte sequence
@@ -524,7 +528,7 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         // UTF-16 is much easier: we can only have a surrogate pair for values above U+FFFF, thus a
         // surrogate pair with total length 2 instantly indicates a range error (but not a "your
         // string was too long" error).
-        else if (StringCaster::UTF_N == 16 && str_len == 2) {
+        else if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 16) && str_len == 2) {
             one_char = static_cast<CharT>(value[0]);
             if (one_char >= 0xD800 && one_char < 0xE000)
                 throw value_error("Character code point not in range(0x10000)");
@@ -778,7 +782,7 @@ struct pyobject_caster {
         // For Python 2, without this implicit conversion, Python code would
         // need to be cluttered with six.ensure_text() or similar, only to be
         // un-cluttered later after Python 2 support is dropped.
-        if (std::is_same<T, str>::value && isinstance<bytes>(src)) {
+        if (PYBIND11_SILENCE_MSVC_C4127(std::is_same<T, str>::value) && isinstance<bytes>(src)) {
             PyObject *str_from_bytes = PyUnicode_FromEncodedObject(src.ptr(), "utf-8", nullptr);
             if (!str_from_bytes) throw error_already_set();
             value = reinterpret_steal<type>(str_from_bytes);
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index d1e9e6591f..e8d83ae0db 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -941,5 +941,16 @@ inline constexpr void workaround_incorrect_msvc_c4100(Args &&...) {}
 #    define PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(...)
 #endif
 
+#if defined(_MSC_VER) // All versions (as of July 2021).
+
+// warning C4127: Conditional expression is constant
+constexpr inline bool silence_msvc_c4127(bool cond) { return cond; }
+
+#    define PYBIND11_SILENCE_MSVC_C4127(...) detail::silence_msvc_c4127(__VA_ARGS__)
+
+#else
+#    define PYBIND11_SILENCE_MSVC_C4127(...) __VA_ARGS__
+#endif
+
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 3ebec041f0..e795da7d75 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -96,7 +96,7 @@ template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> *ptr, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     no_nullptr(ptr);
-    if (Class::has_alias && need_alias && !is_alias<Class>(ptr)) {
+    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr)) {
         // We're going to try to construct an alias by moving the cpp type.  Whether or not
         // that succeeds, we still need to destroy the original cpp pointer (either the
         // moved away leftover, if the alias construction works, or the value itself if we
@@ -136,7 +136,7 @@ void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
     auto *ptr = holder_helper<Holder<Class>>::get(holder);
     no_nullptr(ptr);
     // If we need an alias, check that the held pointer is actually an alias instance
-    if (Class::has_alias && need_alias && !is_alias<Class>(ptr))
+    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr))
         throw type_error("pybind11::init(): construction failed: returned holder-wrapped instance "
                          "is not an alias instance");
 
@@ -153,7 +153,7 @@ void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
         "pybind11::init() return-by-value factory function requires a movable class");
-    if (Class::has_alias && need_alias)
+    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias)
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
     else
         v_h.value_ptr() = new Cpp<Class>(std::move(result));
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ec6bd8d351..aeeb3368a8 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,10 +10,7 @@
 
 #pragma once
 
-#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+#if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wattributes"
@@ -166,7 +163,7 @@ class cpp_function : public function {
         auto rec = unique_rec.get();
 
         /* Store the capture object directly in the function record if there is enough space */
-        if (sizeof(capture) <= sizeof(rec->data)) {
+        if (PYBIND11_SILENCE_MSVC_C4127(sizeof(capture) <= sizeof(rec->data))) {
             /* Without these pragmas, GCC warns that there might not be
                enough space to use the placement new operator. However, the
                'if' statement above ensures that this is the case. */
@@ -2388,8 +2385,6 @@ PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 #    pragma GCC diagnostic pop // -Wnoexcept-type
 #endif
 
-#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-#  pragma warning(pop)
-#elif defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+#if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 4cf606e8d0..c7b2501feb 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1191,9 +1191,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
 template <typename Unsigned>
 Unsigned as_unsigned(PyObject *o) {
-    if (sizeof(Unsigned) <= sizeof(unsigned long)
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(Unsigned) <= sizeof(unsigned long))
 #if PY_VERSION_HEX < 0x03000000
-            || PyInt_Check(o)
+        || PyInt_Check(o)
 #endif
     ) {
         unsigned long v = PyLong_AsUnsignedLong(o);
@@ -1212,7 +1212,7 @@ class int_ : public object {
     template <typename T,
               detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     int_(T value) {
-        if (sizeof(T) <= sizeof(long)) {
+        if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
             if (std::is_signed<T>::value)
                 m_ptr = PyLong_FromLong((long) value);
             else

From f4f4632e283ce5476964e9f612ecb7d7915fb035 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:56:57 -0400
Subject: [PATCH 116/638] [pre-commit.ci] pre-commit autoupdate (#3167)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.23.0 → v2.23.1](https://github.com/asottile/pyupgrade/compare/v2.23.0...v2.23.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 510b841260..57beb77793 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.23.0
+  rev: v2.23.1
   hooks:
   - id: pyupgrade
 

From c0756ccd932de6e8d52ef102de0e18558f157db9 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 3 Aug 2021 13:15:48 -0400
Subject: [PATCH 117/638] fix: func_handle for rule of two (#3169)

* Fix func_handle for rule of two

* Apply reviewer suggestion
---
 include/pybind11/functional.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index b9bf38919c..bc8a8af821 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -70,9 +70,11 @@ struct type_caster<std::function<Return(Args...)>> {
         struct func_handle {
             function f;
             func_handle(function &&f_) noexcept : f(std::move(f_)) {}
-            func_handle(const func_handle& f_) {
+            func_handle(const func_handle &f_) { operator=(f_); }
+            func_handle &operator=(const func_handle &f_) {
                 gil_scoped_acquire acq;
                 f = f_.f;
+                return *this;
             }
             ~func_handle() {
                 gil_scoped_acquire acq;

From a2b78a8c279e54f01a0502405fd2335a59c43a6d Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 3 Aug 2021 10:16:14 -0700
Subject: [PATCH 118/638] chore: changelog update (#3163)

* chore: changelog update

* Update docs/changelog.rst
---
 docs/changelog.rst | 49 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 5e8a63258f..2f76abe055 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,9 +6,54 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
-Next version (WIP)
-------------------
+v2.8.0 (WIP)
+------------
 
+* Allow exception translators to be optionally registered local to a module
+  instead of applying globally across all pybind11 modules. Use
+  ``register_local_exception_translator(ExceptionTranslator&& translator)``
+  instead of  ``register_exception_translator(ExceptionTranslator&&
+  translator)`` to keep your exception remapping code local to the module.
+  `#2650 <https://github.com/pybind/pybind11/pull/2650>`_
+
+v2.7.1 (Aug 3, 2021)
+---------------------
+
+Minor missing functionality added:
+
+* Allow Python builtins to be used as callbacks in CPython.
+  `#1413 <https://github.com/pybind/pybind11/pull/1413>`_
+
+Bug fixes:
+
+* Fix regression in CMake Python package config: improper use of absolute path.
+  `#3144 <https://github.com/pybind/pybind11/pull/3144>`_
+
+* Fix Mingw64 and add to the CI testing matrix.
+  `#3132 <https://github.com/pybind/pybind11/pull/3132>`_
+
+* Specified UTF8-encoding in setup.py calls of open().
+  `#3137 <https://github.com/pybind/pybind11/pull/3137>`_
+
+* Add clang-tidy-readability rules to make boolean casts explicit improving
+  code readability. Also enabled other misc and readability clang-tidy checks.
+  `#3148 <https://github.com/pybind/pybind11/pull/3148>`_
+
+* Move object in ``.pop()`` for list.
+  `#3116 <https://github.com/pybind/pybind11/pull/3116>`_
+
+Backend and tidying up:
+
+* Removed and fixed warning suppressions.
+  `#3127 <https://github.com/pybind/pybind11/pull/3127>`_
+  `#3129 <https://github.com/pybind/pybind11/pull/3129>`_
+  `#3135 <https://github.com/pybind/pybind11/pull/3135>`_
+  `#3141 <https://github.com/pybind/pybind11/pull/3141>`_
+  `#3142 <https://github.com/pybind/pybind11/pull/3142>`_
+  `#3150 <https://github.com/pybind/pybind11/pull/3150>`_
+  `#3152 <https://github.com/pybind/pybind11/pull/3152>`_
+  `#3160 <https://github.com/pybind/pybind11/pull/3160>`_
+  `#3161 <https://github.com/pybind/pybind11/pull/3161>`_
 
 
 v2.7.0 (Jul 16, 2021)

From ada6b7910491f5b7fd910d8bf23c474b526f6591 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:56:57 -0400
Subject: [PATCH 119/638] [pre-commit.ci] pre-commit autoupdate (#3167)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.23.0 → v2.23.1](https://github.com/asottile/pyupgrade/compare/v2.23.0...v2.23.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 510b841260..57beb77793 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.23.0
+  rev: v2.23.1
   hooks:
   - id: pyupgrade
 

From 9f204a18573d8a194549ad0fd51afdd3db5596e5 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 3 Aug 2021 13:15:48 -0400
Subject: [PATCH 120/638] fix: func_handle for rule of two (#3169)

* Fix func_handle for rule of two

* Apply reviewer suggestion
---
 include/pybind11/functional.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index b9bf38919c..bc8a8af821 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -70,9 +70,11 @@ struct type_caster<std::function<Return(Args...)>> {
         struct func_handle {
             function f;
             func_handle(function &&f_) noexcept : f(std::move(f_)) {}
-            func_handle(const func_handle& f_) {
+            func_handle(const func_handle &f_) { operator=(f_); }
+            func_handle &operator=(const func_handle &f_) {
                 gil_scoped_acquire acq;
                 f = f_.f;
+                return *this;
             }
             ~func_handle() {
                 gil_scoped_acquire acq;

From 9095984850eb1d0240575a31281d8651ff5e7a2e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 3 Aug 2021 10:16:14 -0700
Subject: [PATCH 121/638] chore: changelog update (#3163)

* chore: changelog update

* Update docs/changelog.rst
---
 docs/changelog.rst | 49 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 5e8a63258f..2f76abe055 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,9 +6,54 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
-Next version (WIP)
-------------------
+v2.8.0 (WIP)
+------------
 
+* Allow exception translators to be optionally registered local to a module
+  instead of applying globally across all pybind11 modules. Use
+  ``register_local_exception_translator(ExceptionTranslator&& translator)``
+  instead of  ``register_exception_translator(ExceptionTranslator&&
+  translator)`` to keep your exception remapping code local to the module.
+  `#2650 <https://github.com/pybind/pybind11/pull/2650>`_
+
+v2.7.1 (Aug 3, 2021)
+---------------------
+
+Minor missing functionality added:
+
+* Allow Python builtins to be used as callbacks in CPython.
+  `#1413 <https://github.com/pybind/pybind11/pull/1413>`_
+
+Bug fixes:
+
+* Fix regression in CMake Python package config: improper use of absolute path.
+  `#3144 <https://github.com/pybind/pybind11/pull/3144>`_
+
+* Fix Mingw64 and add to the CI testing matrix.
+  `#3132 <https://github.com/pybind/pybind11/pull/3132>`_
+
+* Specified UTF8-encoding in setup.py calls of open().
+  `#3137 <https://github.com/pybind/pybind11/pull/3137>`_
+
+* Add clang-tidy-readability rules to make boolean casts explicit improving
+  code readability. Also enabled other misc and readability clang-tidy checks.
+  `#3148 <https://github.com/pybind/pybind11/pull/3148>`_
+
+* Move object in ``.pop()`` for list.
+  `#3116 <https://github.com/pybind/pybind11/pull/3116>`_
+
+Backend and tidying up:
+
+* Removed and fixed warning suppressions.
+  `#3127 <https://github.com/pybind/pybind11/pull/3127>`_
+  `#3129 <https://github.com/pybind/pybind11/pull/3129>`_
+  `#3135 <https://github.com/pybind/pybind11/pull/3135>`_
+  `#3141 <https://github.com/pybind/pybind11/pull/3141>`_
+  `#3142 <https://github.com/pybind/pybind11/pull/3142>`_
+  `#3150 <https://github.com/pybind/pybind11/pull/3150>`_
+  `#3152 <https://github.com/pybind/pybind11/pull/3152>`_
+  `#3160 <https://github.com/pybind/pybind11/pull/3160>`_
+  `#3161 <https://github.com/pybind/pybind11/pull/3161>`_
 
 
 v2.7.0 (Jul 16, 2021)

From 078c1167497c81f866b94df5451939077aba0b6f Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Aug 2021 15:05:54 -0400
Subject: [PATCH 122/638] chore: bump to version 2.7.1

---
 include/pybind11/detail/common.h | 2 +-
 pybind11/_version.py             | 2 +-
 setup.cfg                        | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 9df670fa9d..8006a8df1d 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,7 +11,7 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 7
-#define PYBIND11_VERSION_PATCH 1.dev1
+#define PYBIND11_VERSION_PATCH 1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 2bb14b963d..2bb4fe364d 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.7.1.dev1"
+__version__ = "2.7.1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))
diff --git a/setup.cfg b/setup.cfg
index 31038eb026..95963d2f87 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -20,6 +20,7 @@ classifiers =
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     License :: OSI Approved :: BSD License
     Programming Language :: Python :: Implementation :: PyPy
     Programming Language :: Python :: Implementation :: CPython

From 5f34c42d70d6af0af546106503da9d045efb904e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Aug 2021 15:05:54 -0400
Subject: [PATCH 123/638] chore: bump to version 2.7.1

---
 include/pybind11/detail/common.h | 2 +-
 pybind11/_version.py             | 2 +-
 setup.cfg                        | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index e8d83ae0db..1d77143354 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,7 +11,7 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 7
-#define PYBIND11_VERSION_PATCH 1.dev1
+#define PYBIND11_VERSION_PATCH 1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 2bb14b963d..2bb4fe364d 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.7.1.dev1"
+__version__ = "2.7.1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))
diff --git a/setup.cfg b/setup.cfg
index 31038eb026..95963d2f87 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -20,6 +20,7 @@ classifiers =
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     License :: OSI Approved :: BSD License
     Programming Language :: Python :: Implementation :: PyPy
     Programming Language :: Python :: Implementation :: CPython

From 82adacb31de4d24983e240a60d608dfaed464d1a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Aug 2021 15:20:23 -0400
Subject: [PATCH 124/638] fix: include hex version in bump

---
 include/pybind11/detail/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1d77143354..b918584087 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -15,7 +15,7 @@
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020701D1
+#define PYBIND11_VERSION_HEX 0x02070100
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }

From 787d2c88cafa4d07fb38c9519c485a86323cfcf4 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Aug 2021 15:20:23 -0400
Subject: [PATCH 125/638] fix: include hex version in bump

---
 include/pybind11/detail/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 8006a8df1d..dfd5b5699f 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -15,7 +15,7 @@
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020701D1
+#define PYBIND11_VERSION_HEX 0x02070100
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }

From c30f57d2ede50c0306db54d5fb215f57c1e465a6 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Aug 2021 16:11:07 -0400
Subject: [PATCH 126/638] chore: start development for 2.8.0

---
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index b918584087..adb0009383 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 7
-#define PYBIND11_VERSION_PATCH 1
+#define PYBIND11_VERSION_MINOR 8
+#define PYBIND11_VERSION_PATCH 0.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x02070100
+#define PYBIND11_VERSION_HEX 0x020800D0
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 2bb4fe364d..610d39bf1c 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.7.1"
+__version__ = "2.8.0.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 5f4d725918d7fb90d441b8c1ee1a2cf464407a6a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Aug 2021 17:03:11 -0400
Subject: [PATCH 127/638] fix: version number hex

---
 include/pybind11/detail/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index adb0009383..8b8f5da335 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -15,7 +15,7 @@
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020800D0
+#define PYBIND11_VERSION_HEX 0x020800D1
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }

From 1fafd1b44796f39e56d4c029203c0e2ba18a60dd Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 6 Aug 2021 13:03:26 -0400
Subject: [PATCH 128/638] fix: apply simpler expression with fewer workarounds

---
 include/pybind11/detail/type_caster_base.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index e2d1bcb8cc..a708d87fb4 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -927,18 +927,17 @@ template <typename type> class type_caster_base : public type_caster_generic {
     using Constructor = void *(*)(const void *);
 
     /* Only enabled when the types are {copy,move}-constructible *and* when the type
-       does not have a private operator new implementation. */
+       does not have a private operator new implementation. A comma operator is used in the decltype
+       argument to apply SFINAE to the public copy/move constructors.*/
     template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
-    static auto make_copy_constructor(const T *x) -> decltype(new T(*x), Constructor{}) {
-        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
+    static auto make_copy_constructor(const T *) -> decltype(new T(std::declval<const T>()), Constructor{}) {
         return [](const void *arg) -> void * {
             return new T(*reinterpret_cast<const T *>(arg));
         };
     }
 
     template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
-    static auto make_move_constructor(const T *x) -> decltype(new T(std::move(*const_cast<T *>(x))), Constructor{}) {
-        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
+    static auto make_move_constructor(const T *) -> decltype(new T(std::declval<T&&>()), Constructor{}) {
         return [](const void *arg) -> void * {
             return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
         };

From 089328f77955685a29db9b9cf05e7c0893ee031b Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 6 Aug 2021 13:09:48 -0400
Subject: [PATCH 129/638] Revert "fix: apply simpler expression with fewer
 workarounds"

This reverts commit 1fafd1b44796f39e56d4c029203c0e2ba18a60dd.
---
 include/pybind11/detail/type_caster_base.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a708d87fb4..e2d1bcb8cc 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -927,17 +927,18 @@ template <typename type> class type_caster_base : public type_caster_generic {
     using Constructor = void *(*)(const void *);
 
     /* Only enabled when the types are {copy,move}-constructible *and* when the type
-       does not have a private operator new implementation. A comma operator is used in the decltype
-       argument to apply SFINAE to the public copy/move constructors.*/
+       does not have a private operator new implementation. */
     template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
-    static auto make_copy_constructor(const T *) -> decltype(new T(std::declval<const T>()), Constructor{}) {
+    static auto make_copy_constructor(const T *x) -> decltype(new T(*x), Constructor{}) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
         return [](const void *arg) -> void * {
             return new T(*reinterpret_cast<const T *>(arg));
         };
     }
 
     template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
-    static auto make_move_constructor(const T *) -> decltype(new T(std::declval<T&&>()), Constructor{}) {
+    static auto make_move_constructor(const T *x) -> decltype(new T(std::move(*const_cast<T *>(x))), Constructor{}) {
+        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
         return [](const void *arg) -> void * {
             return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
         };

From 3893f37bcec9f0e9c8ab2c0069cfec8520591860 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 6 Aug 2021 14:30:28 -0400
Subject: [PATCH 130/638] maint(clang-tidy): Bugprone enable checks (#3166)

* Enable bugprone checks

* Reset delta and massage config

* Start to apply bugprone fixes

* try to fix minor bug

* Fix later

* Fix perfect forwarding bugprone

* Remove nolint

* undo constructor delete

* Fix bugprone-perfect-forwarding again

* Remove TODO

* Add another nolint for bugprone-exception-escape in scoped interpreter

* Fix remaining bugprone errors

* Properly apply bugprone-macro-parantheses

* Redo formatting and remove bugprone nolint

* Add coment and revert more whitespace changes

* Fix typo

* Fix parsing bug

* Add back comma

* Fix clang-tidy issue

* Apply remaining clang-tidy fixes
---
 .clang-tidy                         |  4 +++
 include/pybind11/cast.h             | 11 ++++----
 include/pybind11/detail/common.h    | 39 ++++++++++++++---------------
 include/pybind11/embed.h            | 36 +++++++++++++-------------
 include/pybind11/numpy.h            |  7 ++++--
 include/pybind11/pybind11.h         |  2 +-
 tests/object.h                      |  6 ++++-
 tests/pybind11_tests.h              |  9 +++----
 tests/test_buffers.cpp              |  6 ++++-
 tests/test_class.cpp                |  8 +++---
 tests/test_multiple_inheritance.cpp |  5 +++-
 tests/test_numpy_dtypes.cpp         | 12 +++++----
 tests/test_smart_ptr.cpp            |  1 +
 tests/test_tagbased_polymorphic.cpp |  6 ++---
 tests/test_virtual_functions.cpp    |  1 +
 15 files changed, 85 insertions(+), 68 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index db5077c227..c83b9b2f5a 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,6 +1,7 @@
 FormatStyle: file
 
 Checks: '
+*bugprone*,
 cppcoreguidelines-init-variables,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
@@ -43,6 +44,9 @@ readability-static-accessed-through-instance,
 readability-static-definition-in-anonymous-namespace,
 readability-string-compare,
 readability-uniqueptr-delete-release,
+-bugprone-exception-escape,
+-bugprone-reserved-identifier,
+-bugprone-unused-raii,
 '
 
 CheckOptions:
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 211cf09bcd..988a236950 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -102,9 +102,9 @@ public:
         }                                                                                         \
         return cast(*src, policy, parent);                                                        \
     }                                                                                             \
-    operator type *() { return &value; }                                                          \
-    operator type &() { return value; }                                                           \
-    operator type &&() && { return std::move(value); }                                            \
+    operator type *() { return &value; }               /* NOLINT(bugprone-macro-parentheses) */   \
+    operator type &() { return value; }                /* NOLINT(bugprone-macro-parentheses) */   \
+    operator type &&() && { return std::move(value); } /* NOLINT(bugprone-macro-parentheses) */   \
     template <typename T_>                                                                        \
     using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
 
@@ -145,9 +145,8 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
                 py_value = (py_type) PyFloat_AsDouble(src.ptr());
             else
                 return false;
-        } else if (PyFloat_Check(src.ptr())) {
-            return false;
-        } else if (!convert && !PYBIND11_LONG_CHECK(src.ptr()) && !index_check(src.ptr())) {
+        } else if (PyFloat_Check(src.ptr())
+                   || (!convert && !PYBIND11_LONG_CHECK(src.ptr()) && !index_check(src.ptr()))) {
             return false;
         } else {
             handle src_or_index = src;
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 8b8f5da335..27a79bfdd5 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -220,8 +220,8 @@
 #define PYBIND11_BYTES_SIZE PyBytes_Size
 #define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
 #define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
-#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) o)
-#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) o)
+#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
+#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
 #define PYBIND11_BYTES_NAME "bytes"
 #define PYBIND11_STRING_NAME "str"
 #define PYBIND11_SLICE_OBJECT PyObject
@@ -356,24 +356,23 @@ extern "C" {
             });
         }
 \endrst */
-#define PYBIND11_MODULE(name, variable)                                        \
-    static ::pybind11::module_::module_def                                     \
-        PYBIND11_CONCAT(pybind11_module_def_, name) PYBIND11_MAYBE_UNUSED;     \
-    PYBIND11_MAYBE_UNUSED                                                      \
-    static void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ &);  \
-    PYBIND11_PLUGIN_IMPL(name) {                                               \
-        PYBIND11_CHECK_PYTHON_VERSION                                          \
-        PYBIND11_ENSURE_INTERNALS_READY                                        \
-        auto m = ::pybind11::module_::create_extension_module(                 \
-            PYBIND11_TOSTRING(name), nullptr,                                  \
-            &PYBIND11_CONCAT(pybind11_module_def_, name));                     \
-        try {                                                                  \
-            PYBIND11_CONCAT(pybind11_init_, name)(m);                          \
-            return m.ptr();                                                    \
-        } PYBIND11_CATCH_INIT_EXCEPTIONS                                       \
-    }                                                                          \
-    void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ &variable)
-
+#define PYBIND11_MODULE(name, variable)                                                           \
+    static ::pybind11::module_::module_def PYBIND11_CONCAT(pybind11_module_def_, name)            \
+        PYBIND11_MAYBE_UNUSED;                                                                    \
+    PYBIND11_MAYBE_UNUSED                                                                         \
+    static void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ &);                     \
+    PYBIND11_PLUGIN_IMPL(name) {                                                                  \
+        PYBIND11_CHECK_PYTHON_VERSION                                                             \
+        PYBIND11_ENSURE_INTERNALS_READY                                                           \
+        auto m = ::pybind11::module_::create_extension_module(                                    \
+            PYBIND11_TOSTRING(name), nullptr, &PYBIND11_CONCAT(pybind11_module_def_, name));      \
+        try {                                                                                     \
+            PYBIND11_CONCAT(pybind11_init_, name)(m);                                             \
+            return m.ptr();                                                                       \
+        }                                                                                         \
+        PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
+    }                                                                                             \
+    void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ & (variable))
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index abb1cd3cca..6e777830f9 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -45,25 +45,23 @@
             });
         }
  \endrst */
-#define PYBIND11_EMBEDDED_MODULE(name, variable)                                \
-    static ::pybind11::module_::module_def                                      \
-        PYBIND11_CONCAT(pybind11_module_def_, name);                            \
-    static void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ &);   \
-    static PyObject PYBIND11_CONCAT(*pybind11_init_wrapper_, name)() {          \
-        auto m = ::pybind11::module_::create_extension_module(                  \
-            PYBIND11_TOSTRING(name), nullptr,                                   \
-            &PYBIND11_CONCAT(pybind11_module_def_, name));                      \
-        try {                                                                   \
-            PYBIND11_CONCAT(pybind11_init_, name)(m);                           \
-            return m.ptr();                                                     \
-        } PYBIND11_CATCH_INIT_EXCEPTIONS                                        \
-    }                                                                           \
-    PYBIND11_EMBEDDED_MODULE_IMPL(name)                                         \
-    ::pybind11::detail::embedded_module PYBIND11_CONCAT(pybind11_module_, name) \
-                              (PYBIND11_TOSTRING(name),                         \
-                               PYBIND11_CONCAT(pybind11_init_impl_, name));     \
-    void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ &variable)
-
+#define PYBIND11_EMBEDDED_MODULE(name, variable)                                                  \
+    static ::pybind11::module_::module_def PYBIND11_CONCAT(pybind11_module_def_, name);           \
+    static void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ &);                     \
+    static PyObject PYBIND11_CONCAT(*pybind11_init_wrapper_, name)() {                            \
+        auto m = ::pybind11::module_::create_extension_module(                                    \
+            PYBIND11_TOSTRING(name), nullptr, &PYBIND11_CONCAT(pybind11_module_def_, name));      \
+        try {                                                                                     \
+            PYBIND11_CONCAT(pybind11_init_, name)(m);                                             \
+            return m.ptr();                                                                       \
+        }                                                                                         \
+        PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
+    }                                                                                             \
+    PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                           \
+    ::pybind11::detail::embedded_module PYBIND11_CONCAT(pybind11_module_, name)(                  \
+        PYBIND11_TOSTRING(name), PYBIND11_CONCAT(pybind11_init_impl_, name));                     \
+    void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_                                \
+                                               & variable) // NOLINT(bugprone-macro-parentheses)
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 7313897fe1..aa8294e167 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1551,8 +1551,11 @@ struct vectorize_helper {
             "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
 
 public:
-    template <typename T>
-    explicit vectorize_helper(T &&f) : f(std::forward<T>(f)) { }
+    template <typename T,
+              // SFINAE to prevent shadowing the copy constructor.
+              typename = detail::enable_if_t<
+                  !std::is_same<vectorize_helper, typename std::decay<T>::type>::value>>
+    explicit vectorize_helper(T &&f) : f(std::forward<T>(f)) {}
 
     object operator()(typename vectorize_arg<Args>::type... args) {
         return run(args...,
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index aeeb3368a8..54213297dc 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1726,7 +1726,7 @@ struct enum_base {
     m_base.attr(op) = cpp_function(                                                               \
         [](const object &a, const object &b) {                                                    \
             if (!type::handle_of(a).is(type::handle_of(b)))                                       \
-                strict_behavior;                                                                  \
+                strict_behavior; /* NOLINT(bugprone-macro-parentheses) */                         \
             return expr;                                                                          \
         },                                                                                        \
         name(op),                                                                                 \
diff --git a/tests/object.h b/tests/object.h
index 865a9beae8..6851fc6247 100644
--- a/tests/object.h
+++ b/tests/object.h
@@ -110,7 +110,11 @@ template <typename T> class ref {
 
     /// Overwrite this reference with another reference
     ref& operator=(const ref& r) {
-        print_copy_assigned(this, "pointer", r.m_ptr); track_copy_assigned((ref_tag*) this);
+        if (this == &r) {
+            return *this;
+        }
+        print_copy_assigned(this, "pointer", r.m_ptr);
+        track_copy_assigned((ref_tag *) this);
 
         if (m_ptr == r.m_ptr)
             return *this;
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index d970ba8bd4..12d8a777fc 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -23,11 +23,10 @@ class test_initializer {
     test_initializer(const char *submodule_name, Initializer init);
 };
 
-#define TEST_SUBMODULE(name, variable)                   \
-    void test_submodule_##name(py::module_ &);            \
-    test_initializer name(#name, test_submodule_##name); \
-    void test_submodule_##name(py::module_ &variable)
-
+#define TEST_SUBMODULE(name, variable)                                                            \
+    void test_submodule_##name(py::module_ &);                                                    \
+    test_initializer name(#name, test_submodule_##name);                                          \
+    void test_submodule_##name(py::module_ &(variable))
 
 /// Dummy type which is not exported anywhere -- something to trigger a conversion error
 struct UnregisteredType { };
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index e77c626f87..c7e2c7df30 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -40,7 +40,11 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         Matrix &operator=(const Matrix &s) {
-            print_copy_assigned(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            if (this == &s) {
+                return *this;
+            }
+            print_copy_assigned(this,
+                                std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             delete[] m_data;
             m_rows = s.m_rows;
             m_cols = s.m_cols;
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 73de2a61aa..dff758392d 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -492,15 +492,15 @@ using DoesntBreak5 = py::class_<BreaksBase<5>>;
 using DoesntBreak6 = py::class_<BreaksBase<6>, std::shared_ptr<BreaksBase<6>>, BreaksTramp<6>>;
 using DoesntBreak7 = py::class_<BreaksBase<7>, BreaksTramp<7>, std::shared_ptr<BreaksBase<7>>>;
 using DoesntBreak8 = py::class_<BreaksBase<8>, std::shared_ptr<BreaksBase<8>>>;
-#define CHECK_BASE(N) static_assert(std::is_same<typename DoesntBreak##N::type, BreaksBase<N>>::value, \
+#define CHECK_BASE(N) static_assert(std::is_same<typename DoesntBreak##N::type, BreaksBase<(N)>>::value, \
         "DoesntBreak" #N " has wrong type!")
 CHECK_BASE(1); CHECK_BASE(2); CHECK_BASE(3); CHECK_BASE(4); CHECK_BASE(5); CHECK_BASE(6); CHECK_BASE(7); CHECK_BASE(8);
-#define CHECK_ALIAS(N) static_assert(DoesntBreak##N::has_alias && std::is_same<typename DoesntBreak##N::type_alias, BreaksTramp<N>>::value, \
+#define CHECK_ALIAS(N) static_assert(DoesntBreak##N::has_alias && std::is_same<typename DoesntBreak##N::type_alias, BreaksTramp<(N)>>::value, \
         "DoesntBreak" #N " has wrong type_alias!")
 #define CHECK_NOALIAS(N) static_assert(!DoesntBreak##N::has_alias && std::is_void<typename DoesntBreak##N::type_alias>::value, \
         "DoesntBreak" #N " has type alias, but shouldn't!")
 CHECK_ALIAS(1); CHECK_ALIAS(2); CHECK_NOALIAS(3); CHECK_ALIAS(4); CHECK_NOALIAS(5); CHECK_ALIAS(6); CHECK_ALIAS(7); CHECK_NOALIAS(8);
-#define CHECK_HOLDER(N, TYPE) static_assert(std::is_same<typename DoesntBreak##N::holder_type, std::TYPE##_ptr<BreaksBase<N>>>::value, \
+#define CHECK_HOLDER(N, TYPE) static_assert(std::is_same<typename DoesntBreak##N::holder_type, std::TYPE##_ptr<BreaksBase<(N)>>>::value, \
         "DoesntBreak" #N " has wrong holder_type!")
 CHECK_HOLDER(1, unique); CHECK_HOLDER(2, unique); CHECK_HOLDER(3, unique); CHECK_HOLDER(4, unique); CHECK_HOLDER(5, unique);
 CHECK_HOLDER(6, shared); CHECK_HOLDER(7, shared); CHECK_HOLDER(8, shared);
@@ -510,7 +510,7 @@ CHECK_HOLDER(6, shared); CHECK_HOLDER(7, shared); CHECK_HOLDER(8, shared);
 // failures occurs).
 
 // We have to actually look into the type: the typedef alone isn't enough to instantiate the type:
-#define CHECK_BROKEN(N) static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-N>>::value, \
+#define CHECK_BROKEN(N) static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-(N)>>::value, \
         "Breaks1 has wrong type!");
 
 //// Two holder classes:
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index d6b24d34da..b5ca298d91 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -108,7 +108,10 @@ TEST_SUBMODULE(multiple_inheritance, m) {
 
 
     // test_multiple_inheritance_python_many_bases
-    #define PYBIND11_BASEN(N) py::class_<BaseN<N>>(m, "BaseN" #N).def(py::init<int>()).def("f" #N, [](BaseN<N> &b) { return b.i + N; })
+#define PYBIND11_BASEN(N)                                                                         \
+    py::class_<BaseN<(N)>>(m, "BaseN" #N).def(py::init<int>()).def("f" #N, [](BaseN<N> &b) {      \
+        return b.i + (N);                                                                         \
+    })
     PYBIND11_BASEN( 1); PYBIND11_BASEN( 2); PYBIND11_BASEN( 3); PYBIND11_BASEN( 4);
     PYBIND11_BASEN( 5); PYBIND11_BASEN( 6); PYBIND11_BASEN( 7); PYBIND11_BASEN( 8);
     PYBIND11_BASEN( 9); PYBIND11_BASEN(10); PYBIND11_BASEN(11); PYBIND11_BASEN(12);
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index 340c972db2..bf4f4cee74 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -148,11 +148,13 @@ py::array mkarray_via_buffer(size_t n) {
                                      1, { n }, { sizeof(T) }));
 }
 
-#define SET_TEST_VALS(s, i) do { \
-    s.bool_ = (i) % 2 != 0; \
-    s.uint_ = (uint32_t) (i); \
-    s.float_ = (float) (i) * 1.5f; \
-    s.ldbl_ = (long double) (i) * -2.5L; } while (0)
+#define SET_TEST_VALS(s, i)                                                                       \
+    do {                                                                                          \
+        (s).bool_ = (i) % 2 != 0;                                                                 \
+        (s).uint_ = (uint32_t) (i);                                                               \
+        (s).float_ = (float) (i) *1.5f;                                                           \
+        (s).ldbl_ = (long double) (i) * -2.5L;                                                    \
+    } while (0)
 
 template <typename S>
 py::array_t<S, 0> create_recarray(size_t n) {
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 57b2d894e2..eeaa44147a 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -182,6 +182,7 @@ struct SharedPtrRef {
 struct SharedFromThisRef {
     struct B : std::enable_shared_from_this<B> {
         B() { print_created(this); }
+        // NOLINTNEXTLINE(bugprone-copy-constructor-init)
         B(const B &) : std::enable_shared_from_this<B>() { print_copy_created(this); }
         B(B &&) noexcept : std::enable_shared_from_this<B>() { print_move_created(this); }
         ~B() { print_destroyed(this); }
diff --git a/tests/test_tagbased_polymorphic.cpp b/tests/test_tagbased_polymorphic.cpp
index 838a168d2b..90f40e14cc 100644
--- a/tests/test_tagbased_polymorphic.cpp
+++ b/tests/test_tagbased_polymorphic.cpp
@@ -86,13 +86,13 @@ std::vector<std::unique_ptr<Animal>> create_zoo()
 const std::type_info* Animal::type_of_kind(Kind kind)
 {
     switch (kind) {
-        case Kind::Unknown: break;
-
+        case Kind::Unknown:
         case Kind::Dog: break;
+
         case Kind::Labrador: return &typeid(Labrador);
         case Kind::Chihuahua: return &typeid(Chihuahua);
-        case Kind::LastDog: break;
 
+        case Kind::LastDog:
         case Kind::Cat: break;
         case Kind::Panther: return &typeid(Panther);
         case Kind::LastCat: break;
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 5280af8eb6..f83a7364b2 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -454,6 +454,7 @@ template <class Base = B_Tpl>
 class PyB_Tpl : public PyA_Tpl<Base> {
 public:
     using PyA_Tpl<Base>::PyA_Tpl; // Inherit constructors (via PyA_Tpl's inherited constructors)
+    // NOLINTNEXTLINE(bugprone-parent-virtual-call)
     int unlucky_number() override { PYBIND11_OVERRIDE(int, Base, unlucky_number, ); }
     double lucky_number() override { PYBIND11_OVERRIDE(double, Base, lucky_number, ); }
 };

From af7007331ab5a6f82a1fe38f041b624dea0b4084 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 6 Aug 2021 12:27:11 -0700
Subject: [PATCH 131/638] Removing GCC -Wunused-but-set-parameter from pragma
 block at the top of pybind11.h (#3164)

* Cleanup triggered by work on pragma for GCC -Wunused-but-set-parameter.

* Backing out changes to eigen.h (to be worked on later).

* Adding PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER in type_caster_base.h (apparently needed only for older GCCs).

* Apparently older compilers need a simpler overload for silence_unused_warnings().

* clang C++11 compatibility: removing constexpr

* Special case for MSVC 2017: `constexpr void` return

* Trying again without the silence_unused_warnings(const int *) overload.

* Separate macros for ALL_GCC, OLD_GCC_UNUSED_BUT_SET_PARAMETER

* Changing to __GNUC__ <= 2 (turning off)

* Refined condition for PYBIND11_WORKAROUND_INCORRECT_OLD_GCC_UNUSED_BUT_SET_PARAMETER.

* Quick experiment trying out suggestion by @henryiii

* Introducing macro: PYBIND11_INT_ARRAY_WORKING_AROUND_MSVC_CLANG_ISSUES

* Trying henryiii@ (void) expander idea.

* fix: apply simpler expression with fewer workarounds

* Purging new-but-already-obsoleted  macro, made possible by @henryiii's commit.

* Renaming `ALL_GCC` macro back to just `GCC` (because there is no `OLD` anymore, luckily).

* [actions skip] Adding "All GCC versions" to comment, to be clear about it.

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 include/pybind11/attr.h                    | 23 +++++++++++++-------
 include/pybind11/cast.h                    |  5 +++--
 include/pybind11/detail/common.h           | 25 ++++++++++++++--------
 include/pybind11/detail/type_caster_base.h |  9 ++++----
 include/pybind11/pybind11.h                |  1 -
 5 files changed, 38 insertions(+), 25 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 20d119f0ff..7188fd7e3c 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -517,23 +517,30 @@ template <size_t Nurse, size_t Patient> struct process_attribute<keep_alive<Nurs
 template <typename... Args> struct process_attributes {
     static void init(const Args&... args, function_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
-        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::init(args, r), 0) ... };
-        ignore_unused(unused);
+        PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
+        using expander = int[];
+        (void) expander{
+            0, ((void) process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
     }
     static void init(const Args&... args, type_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
-        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::init(args, r), 0) ... };
-        ignore_unused(unused);
+        PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
+        using expander = int[];
+        (void) expander{0,
+                        (process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
     }
     static void precall(function_call &call) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call);
-        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::precall(call), 0) ... };
-        ignore_unused(unused);
+        using expander = int[];
+        (void) expander{0,
+                        (process_attribute<typename std::decay<Args>::type>::precall(call), 0)...};
     }
     static void postcall(function_call &call, handle fn_ret) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call, fn_ret);
-        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::postcall(call, fn_ret), 0) ... };
-        ignore_unused(unused);
+        PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(fn_ret);
+        using expander = int[];
+        (void) expander{
+            0, (process_attribute<typename std::decay<Args>::type>::postcall(call, fn_ret), 0)...};
     }
 };
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 988a236950..718dc2de80 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -609,6 +609,7 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     template <typename T, size_t... Is>
     static handle cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(src, policy, parent);
+        PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(policy, parent);
         std::array<object, size> entries{{
             reinterpret_steal<object>(make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...
         }};
@@ -1235,8 +1236,8 @@ class unpacking_collector {
         // Tuples aren't (easily) resizable so a list is needed for collection,
         // but the actual function call strictly requires a tuple.
         auto args_list = list();
-        int _[] = { 0, (process(args_list, std::forward<Ts>(values)), 0)... };
-        ignore_unused(_);
+        using expander = int[];
+        (void) expander{0, (process(args_list, std::forward<Ts>(values)), 0)...};
 
         m_args = std::move(args_list);
     }
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 27a79bfdd5..08430b5a2e 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -734,9 +734,6 @@ using function_signature_t = conditional_t<
 template <typename T> using is_lambda = satisfies_none_of<remove_reference_t<T>,
         std::is_function, std::is_pointer, std::is_member_pointer>;
 
-/// Ignore that a variable is unused in compiler warnings
-inline void ignore_unused(const int *) { }
-
 // [workaround(intel)] Internal error on fold expression
 /// Apply a function over each element of a parameter pack
 #if defined(__cpp_fold_expressions) && !defined(__INTEL_COMPILER)
@@ -927,19 +924,29 @@ inline static std::shared_ptr<T> try_get_shared_from_this(std::enable_shared_fro
 #endif
 }
 
-#if defined(_MSC_VER) && _MSC_VER <= 1916
-
-// warning C4100: Unreferenced formal parameter
+// For silencing "unused" compiler warnings in special situations.
 template <typename... Args>
-inline constexpr void workaround_incorrect_msvc_c4100(Args &&...) {}
+#if defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER < 1920 // MSVC 2017
+constexpr
+#endif
+inline void silence_unused_warnings(Args &&...) {}
 
+// MSVC warning C4100: Unreferenced formal parameter
+#if defined(_MSC_VER) && _MSC_VER <= 1916
 #    define PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(...)                                         \
-        detail::workaround_incorrect_msvc_c4100(__VA_ARGS__)
-
+        detail::silence_unused_warnings(__VA_ARGS__)
 #else
 #    define PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(...)
 #endif
 
+// GCC -Wunused-but-set-parameter  All GCC versions (as of July 2021).
+#if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+#    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)                   \
+        detail::silence_unused_warnings(__VA_ARGS__)
+#else
+#    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)
+#endif
+
 #if defined(_MSC_VER) // All versions (as of July 2021).
 
 // warning C4127: Conditional expression is constant
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index e2d1bcb8cc..a708d87fb4 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -927,18 +927,17 @@ template <typename type> class type_caster_base : public type_caster_generic {
     using Constructor = void *(*)(const void *);
 
     /* Only enabled when the types are {copy,move}-constructible *and* when the type
-       does not have a private operator new implementation. */
+       does not have a private operator new implementation. A comma operator is used in the decltype
+       argument to apply SFINAE to the public copy/move constructors.*/
     template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
-    static auto make_copy_constructor(const T *x) -> decltype(new T(*x), Constructor{}) {
-        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
+    static auto make_copy_constructor(const T *) -> decltype(new T(std::declval<const T>()), Constructor{}) {
         return [](const void *arg) -> void * {
             return new T(*reinterpret_cast<const T *>(arg));
         };
     }
 
     template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
-    static auto make_move_constructor(const T *x) -> decltype(new T(std::move(*const_cast<T *>(x))), Constructor{}) {
-        PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(x);
+    static auto make_move_constructor(const T *) -> decltype(new T(std::declval<T&&>()), Constructor{}) {
         return [](const void *arg) -> void * {
             return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
         };
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 54213297dc..ba29f96474 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -12,7 +12,6 @@
 
 #if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wattributes"
 #endif
 

From 6ac8efe52dfd8b15caec0e376d677cadd9bec38c Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Fri, 6 Aug 2021 15:51:53 -0400
Subject: [PATCH 132/638] test_eval: Show example of working closure (#2743)

* test_eval: Show example of working closure

* Extend test_eval_closure with weirder examples of closures for py::eval

Co-authored-by: Yannick Jadoul <yannick.jadoul@belgacom.net>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 tests/test_eval.cpp | 18 ++++++++++++++++++
 tests/test_eval.py  | 17 +++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/tests/test_eval.cpp b/tests/test_eval.cpp
index 16cdf17f22..29366f6798 100644
--- a/tests/test_eval.cpp
+++ b/tests/test_eval.cpp
@@ -98,4 +98,22 @@ TEST_SUBMODULE(eval_, m) {
         auto int_class = py::eval("isinstance(42, int)", global);
         return global;
     });
+
+    // test_eval_closure
+    m.def("test_eval_closure", []() {
+        py::dict global;
+        global["closure_value"] = 42;
+        py::dict local;
+        local["closure_value"] = 0;
+        py::exec(R"(
+            local_value = closure_value
+
+            def func_global():
+                return closure_value
+
+            def func_local():
+                return local_value
+            )", global, local);
+        return std::make_pair(global, local);
+    });
 }
diff --git a/tests/test_eval.py b/tests/test_eval.py
index 1bb05af05e..601e526f43 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -33,3 +33,20 @@ def test_eval_empty_globals():
     g = {}
     assert "__builtins__" in m.eval_empty_globals(g)
     assert "__builtins__" in g
+
+
+def test_eval_closure():
+    global_, local = m.test_eval_closure()
+
+    assert global_["closure_value"] == 42
+    assert local["closure_value"] == 0
+
+    assert "local_value" not in global_
+    assert local["local_value"] == 0
+
+    assert "func_global" not in global_
+    assert local["func_global"]() == 42
+
+    assert "func_local" not in global_
+    with pytest.raises(NameError):
+        local["func_local"]()

From 61ee923bb19f38ae7a590ff0e6389d4c62e8360d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 7 Aug 2021 11:51:28 -0700
Subject: [PATCH 133/638] Consistent step name "Python tests". (#3180)

---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 73a6fd5199..7b0280981d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -664,7 +664,7 @@ jobs:
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
       working-directory: /build-tests
 
-    - name: Run tests
+    - name: Python tests
       run: make pytest -j 2
       working-directory: /build-tests
 
@@ -760,7 +760,7 @@ jobs:
     - name: Build C++11
       run: cmake --build build -j 2
 
-    - name: Run tests
+    - name: Python tests
       run: cmake --build build -t pytest
 
   win32-msvc2015:

From ff590c1258abf5b472f64b5ab337c5951922f81d Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 9 Aug 2021 12:48:27 -0400
Subject: [PATCH 134/638] maint(perf): Optimize Numpy constructor to remove
 copies by value. (#3183)

* maint(perf): Optimize Numpy Constructor with additional std::move

* Add more moves
---
 include/pybind11/numpy.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index aa8294e167..f0f3b60eea 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -478,11 +478,11 @@ class dtype : public object {
 
     dtype(list names, list formats, list offsets, ssize_t itemsize) {
         dict args;
-        args["names"] = names;
-        args["formats"] = formats;
-        args["offsets"] = offsets;
+        args["names"] = std::move(names);
+        args["formats"] = std::move(formats);
+        args["offsets"] = std::move(offsets);
         args["itemsize"] = pybind11::int_(itemsize);
-        m_ptr = from_args(args).release().ptr();
+        m_ptr = from_args(std::move(args)).release().ptr();
     }
 
     /// This is essentially the same as calling numpy.dtype(args) in Python.
@@ -560,7 +560,7 @@ class dtype : public object {
             formats.append(descr.format);
             offsets.append(descr.offset);
         }
-        return dtype(names, formats, offsets, itemsize);
+        return dtype(std::move(names), std::move(formats), std::move(offsets), itemsize);
     }
 };
 
@@ -1134,7 +1134,10 @@ inline PYBIND11_NOINLINE void register_structured_dtype(
         formats.append(field.descr);
         offsets.append(pybind11::int_(field.offset));
     }
-    auto dtype_ptr = pybind11::dtype(names, formats, offsets, itemsize).release().ptr();
+    auto dtype_ptr
+        = pybind11::dtype(std::move(names), std::move(formats), std::move(offsets), itemsize)
+              .release()
+              .ptr();
 
     // There is an existing bug in NumPy (as of v1.11): trailing bytes are
     // not encoded explicitly into the format string. This will supposedly

From 4c7e509fa475d0a0ede726267bc451e4f0583446 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 9 Aug 2021 10:10:38 -0700
Subject: [PATCH 135/638] PYBIND11_NOINLINE-related cleanup. (#3179)

* Removing pragma for GCC -Wattributes, fixing forward declarations.

* Introducing PYBIND11_NOINLINE_FWD to deal with CUDA, GCC7, GCC8.

* Updating PYBIND11_NOINLINE_DCL in Doxyfile.

* Trying noinline, noinline for {CUDA, GCC7, GCC8}

* Trying noinline, inline for {CUDA, GCC7, GCC8}

* Adding GCC -Wattributes `pragma` in 3 header files.

* Introducing PYBIND11_NOINLINE_GCC_PRAGMA_ATTRIBUTES_NEEDED, used in 9 header files.

* Removing ICC pragma 2196, to see if it is still needed.

* Trying noinline, noinline for ICC

* Trying noinline, inline for ICC

* Restoring ICC pragma 2196, introducing PYBIND11_NOINLINE_FORCED, defined for testing.

* Removing code accidentally left in (was for experimentation only).

* Removing one-time-test define.

* Removing PYBIND11_NOINLINE_FWD macro (after learning that it makes no sense).

* Testing with PYBIND11_NOINLINE_DISABLED. Minor non-functional enhancements.

* Removing #define PYBIND11_NOINLINE_DISABLED (test was successful).

* Removing PYBIND11_NOINLINE_FORCED and enhancing comments for PYBIND11_NOINLINE.

* WIP stripping back

* Making -Wattributes pragma in pybind11 specific to GCC7, GCC8, CUDA.
---
 include/pybind11/attr.h                    |  2 +-
 include/pybind11/detail/common.h           | 15 +++++++++-----
 include/pybind11/detail/internals.h        |  6 +++---
 include/pybind11/detail/type_caster_base.h | 24 +++++++++++-----------
 include/pybind11/detail/typeid.h           |  2 +-
 include/pybind11/numpy.h                   |  4 ++--
 include/pybind11/pybind11.h                | 10 ++++-----
 include/pybind11/pytypes.h                 |  4 ++--
 8 files changed, 36 insertions(+), 31 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 7188fd7e3c..ab1fe80446 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -124,7 +124,7 @@ enum op_id : int;
 enum op_type : int;
 struct undefined_t;
 template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t> struct op_;
-inline void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret);
+void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret);
 
 /// Internal data structure which holds metadata about a keyword argument
 struct argument_record {
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 08430b5a2e..cc24a52fd3 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -99,10 +99,15 @@
 #  endif
 #endif
 
-#if defined(_MSC_VER)
-#  define PYBIND11_NOINLINE __declspec(noinline)
+// The PYBIND11_NOINLINE macro is for function DEFINITIONS.
+// In contrast, FORWARD DECLARATIONS should never use this macro:
+// https://stackoverflow.com/questions/9317473/forward-declaration-of-inline-functions
+#if defined(PYBIND11_NOINLINE_DISABLED) // Option for maximum portability and experimentation.
+#  define PYBIND11_NOINLINE inline
+#elif defined(_MSC_VER)
+#  define PYBIND11_NOINLINE __declspec(noinline) inline
 #else
-#  define PYBIND11_NOINLINE __attribute__ ((noinline))
+#  define PYBIND11_NOINLINE __attribute__ ((noinline)) inline
 #endif
 
 #if defined(__MINGW32__)
@@ -778,8 +783,8 @@ PYBIND11_RUNTIME_EXCEPTION(import_error, PyExc_ImportError)
 PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or handle::call fail due to a type casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
 
-[[noreturn]] PYBIND11_NOINLINE inline void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
-[[noreturn]] PYBIND11_NOINLINE inline void pybind11_fail(const std::string &reason) { throw std::runtime_error(reason); }
+[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
+[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const std::string &reason) { throw std::runtime_error(reason); }
 
 template <typename T, typename SFINAE = void> struct format_descriptor { };
 
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index a93a83e268..b177801a11 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -257,7 +257,7 @@ inline void translate_local_exception(std::exception_ptr p) {
 #endif
 
 /// Return a reference to the current `internals` data
-PYBIND11_NOINLINE inline internals &get_internals() {
+PYBIND11_NOINLINE internals &get_internals() {
     auto **&internals_pp = get_internals_pp();
     if (internals_pp && *internals_pp)
         return **internals_pp;
@@ -352,14 +352,14 @@ PYBIND11_NAMESPACE_END(detail)
 /// Returns a named pointer that is shared among all extension modules (using the same
 /// pybind11 version) running in the current interpreter. Names starting with underscores
 /// are reserved for internal usage. Returns `nullptr` if no matching entry was found.
-inline PYBIND11_NOINLINE void *get_shared_data(const std::string &name) {
+PYBIND11_NOINLINE void *get_shared_data(const std::string &name) {
     auto &internals = detail::get_internals();
     auto it = internals.shared_data.find(name);
     return it != internals.shared_data.end() ? it->second : nullptr;
 }
 
 /// Set the shared data that can be later recovered by `get_shared_data()`.
-inline PYBIND11_NOINLINE void *set_shared_data(const std::string &name, void *data) {
+PYBIND11_NOINLINE void *set_shared_data(const std::string &name, void *data) {
     detail::get_internals().shared_data[name] = data;
     return data;
 }
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a708d87fb4..14cb27cad2 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -81,7 +81,7 @@ class loader_life_support {
 inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type);
 
 // Populates a just-created cache entry.
-PYBIND11_NOINLINE inline void all_type_info_populate(PyTypeObject *t, std::vector<type_info *> &bases) {
+PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_info *> &bases) {
     std::vector<PyTypeObject *> check;
     for (handle parent : reinterpret_borrow<tuple>(t->tp_bases))
         check.push_back((PyTypeObject *) parent.ptr());
@@ -150,7 +150,7 @@ inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type)
  * ancestors are pybind11-registered.  Throws an exception if there are multiple bases--use
  * `all_type_info` instead if you want to support multiple bases.
  */
-PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type) {
+PYBIND11_NOINLINE detail::type_info* get_type_info(PyTypeObject *type) {
     auto &bases = all_type_info(type);
     if (bases.empty())
         return nullptr;
@@ -176,7 +176,7 @@ inline detail::type_info *get_global_type_info(const std::type_index &tp) {
 }
 
 /// Return the type info for a given C++ type; on lookup failure can either throw or return nullptr.
-PYBIND11_NOINLINE inline detail::type_info *get_type_info(const std::type_index &tp,
+PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
                                                           bool throw_if_missing = false) {
     if (auto ltype = get_local_type_info(tp))
         return ltype;
@@ -191,13 +191,13 @@ PYBIND11_NOINLINE inline detail::type_info *get_type_info(const std::type_index
     return nullptr;
 }
 
-PYBIND11_NOINLINE inline handle get_type_handle(const std::type_info &tp, bool throw_if_missing) {
+PYBIND11_NOINLINE handle get_type_handle(const std::type_info &tp, bool throw_if_missing) {
     detail::type_info *type_info = get_type_info(tp, throw_if_missing);
     return handle(type_info ? ((PyObject *) type_info->type) : nullptr);
 }
 
 // Searches the inheritance graph for a registered Python instance, using all_type_info().
-PYBIND11_NOINLINE inline handle find_registered_python_instance(void *src,
+PYBIND11_NOINLINE handle find_registered_python_instance(void *src,
                                                                 const detail::type_info *tinfo) {
     auto it_instances = get_internals().registered_instances.equal_range(src);
     for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
@@ -325,7 +325,7 @@ struct values_and_holders {
  * The returned object should be short-lived: in particular, it must not outlive the called-upon
  * instance.
  */
-PYBIND11_NOINLINE inline value_and_holder instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/, bool throw_if_missing /*= true in common.h*/) {
+PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/, bool throw_if_missing /*= true in common.h*/) {
     // Optimize common case:
     if (!find_type || Py_TYPE(this) == find_type->type)
         return value_and_holder(this, find_type, 0, 0);
@@ -349,7 +349,7 @@ PYBIND11_NOINLINE inline value_and_holder instance::get_value_and_holder(const t
 #endif
 }
 
-PYBIND11_NOINLINE inline void instance::allocate_layout() {
+PYBIND11_NOINLINE void instance::allocate_layout() {
     auto &tinfo = all_type_info(Py_TYPE(this));
 
     const size_t n_types = tinfo.size();
@@ -397,19 +397,19 @@ PYBIND11_NOINLINE inline void instance::allocate_layout() {
     owned = true;
 }
 
-PYBIND11_NOINLINE inline void instance::deallocate_layout() const {
+PYBIND11_NOINLINE void instance::deallocate_layout() const {
     if (!simple_layout)
         PyMem_Free(nonsimple.values_and_holders);
 }
 
-PYBIND11_NOINLINE inline bool isinstance_generic(handle obj, const std::type_info &tp) {
+PYBIND11_NOINLINE bool isinstance_generic(handle obj, const std::type_info &tp) {
     handle type = detail::get_type_handle(tp, false);
     if (!type)
         return false;
     return isinstance(obj, type);
 }
 
-PYBIND11_NOINLINE inline std::string error_string() {
+PYBIND11_NOINLINE std::string error_string() {
     if (!PyErr_Occurred()) {
         PyErr_SetString(PyExc_RuntimeError, "Unknown internal error occurred");
         return "Unknown internal error occurred";
@@ -456,7 +456,7 @@ PYBIND11_NOINLINE inline std::string error_string() {
     return errorString;
 }
 
-PYBIND11_NOINLINE inline handle get_object_handle(const void *ptr, const detail::type_info *type ) {
+PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_info *type ) {
     auto &instances = get_internals().registered_instances;
     auto range = instances.equal_range(ptr);
     for (auto it = range.first; it != range.second; ++it) {
@@ -483,7 +483,7 @@ inline PyThreadState *get_thread_state_unchecked() {
 }
 
 // Forward declarations
-inline void keep_alive_impl(handle nurse, handle patient);
+void keep_alive_impl(handle nurse, handle patient);
 inline PyObject *make_new_instance(PyTypeObject *type);
 
 class type_caster_generic {
diff --git a/include/pybind11/detail/typeid.h b/include/pybind11/detail/typeid.h
index 148889ffef..39ba8ce0f7 100644
--- a/include/pybind11/detail/typeid.h
+++ b/include/pybind11/detail/typeid.h
@@ -29,7 +29,7 @@ inline void erase_all(std::string &string, const std::string &search) {
     }
 }
 
-PYBIND11_NOINLINE inline void clean_type_id(std::string &name) {
+PYBIND11_NOINLINE void clean_type_id(std::string &name) {
 #if defined(__GNUG__)
     int status = 0;
     std::unique_ptr<char, void (*)(void *)> res {
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index f0f3b60eea..2dc0f29f0b 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -104,7 +104,7 @@ struct numpy_internals {
     }
 };
 
-inline PYBIND11_NOINLINE void load_numpy_internals(numpy_internals* &ptr) {
+PYBIND11_NOINLINE void load_numpy_internals(numpy_internals* &ptr) {
     ptr = &get_or_create_shared_data<numpy_internals>("_numpy_internals");
 }
 
@@ -1110,7 +1110,7 @@ struct field_descriptor {
     dtype descr;
 };
 
-inline PYBIND11_NOINLINE void register_structured_dtype(
+PYBIND11_NOINLINE void register_structured_dtype(
     any_container<field_descriptor> fields,
     const std::type_info& tinfo, ssize_t itemsize,
     bool (*direct_converter)(PyObject *, void *&)) {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ba29f96474..20df6a01fd 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,7 +10,7 @@
 
 #pragma once
 
-#if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+#if defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8))
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wattributes"
 #endif
@@ -1875,7 +1875,7 @@ template <typename Type> class enum_ : public class_<Type> {
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 
-inline void keep_alive_impl(handle nurse, handle patient) {
+PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
     if (!nurse || !patient)
         pybind11_fail("Could not activate keep_alive!");
 
@@ -1902,7 +1902,7 @@ inline void keep_alive_impl(handle nurse, handle patient) {
     }
 }
 
-PYBIND11_NOINLINE inline void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
+PYBIND11_NOINLINE void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
     auto get_arg = [&](size_t n) {
         if (n == 0)
             return ret;
@@ -2152,7 +2152,7 @@ exception<CppException> &register_local_exception(handle scope,
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-PYBIND11_NOINLINE inline void print(const tuple &args, const dict &kwargs) {
+PYBIND11_NOINLINE void print(const tuple &args, const dict &kwargs) {
     auto strings = tuple(args.size());
     for (size_t i = 0; i < args.size(); ++i) {
         strings[i] = str(args[i]);
@@ -2384,6 +2384,6 @@ PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 #    pragma GCC diagnostic pop // -Wnoexcept-type
 #endif
 
-#if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+#if defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8))
 #  pragma GCC diagnostic pop
 #endif
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index c7b2501feb..21e14960cf 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -24,7 +24,7 @@ struct arg; struct arg_v;
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 class args_proxy;
-inline bool isinstance_generic(handle obj, const std::type_info &tp);
+bool isinstance_generic(handle obj, const std::type_info &tp);
 
 // Accessor forward declarations
 template <typename Policy> class accessor;
@@ -316,7 +316,7 @@ template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrow
 template <typename T> T reinterpret_steal(handle h) { return {h, object::stolen_t{}}; }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-inline std::string error_string();
+std::string error_string();
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)

From 0be2ea065eeaf2983964ecb792d30abbcedcdc9d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 9 Aug 2021 15:08:19 -0400
Subject: [PATCH 136/638] [pre-commit.ci] pre-commit autoupdate (#3185)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.23.1 → v2.23.3](https://github.com/asottile/pyupgrade/compare/v2.23.1...v2.23.3)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 57beb77793..ee61258d3f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.23.1
+  rev: v2.23.3
   hooks:
   - id: pyupgrade
 

From 7d3b05715bf1c8f9f7232723671bf9b780a173ac Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 12 Aug 2021 13:21:49 -0700
Subject: [PATCH 137/638] Improved workaround for Centos 8 failure (follow-on
 to PR #3030). (#3193)

* Rollback of PR #3030 (Working around Centos 8 failure).

* Adding `-DCMAKE_BUILD_TYPE=Release`

* Improving existing workaround (undoing the originally intended rollback).

* Fixing minor documentation bug.
---
 .github/workflows/ci.yml      | 6 +++---
 tools/pybind11Config.cmake.in | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7b0280981d..e1c32b96f0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -594,13 +594,13 @@ jobs:
 
     - name: VAR_BUILD_TYPE 7
       if: matrix.centos == 7
-      run: echo Release > VAR_BUILD_TYPE
+      run: echo MinSizeRel > VAR_BUILD_TYPE
 
-    # Using Debug to avoid segfault that appeared around 2021-06-04,
+    # Using Release to avoid segfault that appeared around 2021-06-04,
     # apparently when the gcc version changed from 8.3 to 8.4.
     - name: VAR_BUILD_TYPE 8
       if: matrix.centos == 8
-      run: echo Debug > VAR_BUILD_TYPE
+      run: echo Release > VAR_BUILD_TYPE
 
     - name: Configure
       shell: bash
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 73ec104a0e..8f8701be70 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -147,7 +147,7 @@ Add a module and setup all helpers. You can select the type of the library; the
 default is ``MODULE``. There are several options:
 
 ``OPT_SIZE``
-  Optimize for size, even if the ``CMAKE_BUILD_TYPE`` is not ``RelSize``.
+  Optimize for size, even if the ``CMAKE_BUILD_TYPE`` is not ``MinSizeRel``.
 ``THIN_LTO``
   Use thin TLO instead of regular if there's a choice (pybind11's selection
   is disabled if ``CMAKE_INTERPROCEDURAL_OPTIMIZATIONS`` is set).

From d6841f60cc6a07105222d3650caa14ef2007f949 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Fri, 13 Aug 2021 12:27:54 -0400
Subject: [PATCH 138/638] chore(deps): bump jwlawson/actions-setup-cmake from
 1.9 to 1.10 (#3196)

Bumps [jwlawson/actions-setup-cmake](https://github.com/jwlawson/actions-setup-cmake) from 1.9 to 1.10.
- [Release notes](https://github.com/jwlawson/actions-setup-cmake/releases)
- [Commits](https://github.com/jwlawson/actions-setup-cmake/compare/v1.9...v1.10)

---
updated-dependencies:
- dependency-name: jwlawson/actions-setup-cmake
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 12 ++++++------
 .github/workflows/configure.yml |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e1c32b96f0..be3fa723c9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -75,7 +75,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -193,7 +193,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -445,7 +445,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
 
     - name: Configure
       shell: bash
@@ -738,7 +738,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.9.0
@@ -784,7 +784,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.9.0
@@ -838,7 +838,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
 
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt --prefer-binary
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 924088fc37..d37fa3c2cc 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -55,7 +55,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
       with:
         cmake-version: ${{ matrix.cmake }}
 

From 9df2f1ff13ee37c312b5f04fcb77f4339f92b015 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 13 Aug 2021 12:37:05 -0400
Subject: [PATCH 139/638] maint(precommit): Apply isort (#3195)

* Apply isort

* Tweak isort config

* Add env.py as a known_first_party

* Add one missing known first party

* Make config compat with older isort versions

* Add another comment

* Revert pyproject setting
---
 .pre-commit-config.yaml                    | 5 +++++
 docs/benchmark.py                          | 4 ++--
 docs/conf.py                               | 4 ++--
 noxfile.py                                 | 1 -
 pybind11/__init__.py                       | 5 ++---
 pybind11/__main__.py                       | 2 +-
 pybind11/_version.pyi                      | 2 +-
 pybind11/commands.py                       | 1 -
 pybind11/setup_helpers.py                  | 8 ++++----
 pybind11/setup_helpers.pyi                 | 9 ++++-----
 pyproject.toml                             | 6 ++++++
 setup.py                                   | 2 +-
 tests/extra_setuptools/test_setuphelper.py | 2 +-
 tests/test_buffers.py                      | 5 ++---
 tests/test_builtin_casters.py              | 3 +--
 tests/test_call_policies.py                | 3 +--
 tests/test_callbacks.py                    | 8 +++++---
 tests/test_chrono.py                       | 3 ++-
 tests/test_class.py                        | 3 +--
 tests/test_cmake_build/test.py             | 1 +
 tests/test_copy_move.py                    | 1 +
 tests/test_custom_type_casters.py          | 1 +
 tests/test_eigen.py                        | 1 +
 tests/test_enum.py                         | 1 +
 tests/test_eval.py                         | 1 -
 tests/test_exceptions.py                   | 3 +--
 tests/test_factory_constructors.py         | 6 +++---
 tests/test_iostream.py                     | 4 ++--
 tests/test_kwargs_and_defaults.py          | 1 -
 tests/test_local_bindings.py               | 1 -
 tests/test_methods_and_attributes.py       | 3 +--
 tests/test_modules.py                      | 8 +++++---
 tests/test_multiple_inheritance.py         | 1 -
 tests/test_numpy_array.py                  | 1 -
 tests/test_numpy_dtypes.py                 | 1 -
 tests/test_numpy_vectorize.py              | 1 +
 tests/test_opaque_types.py                 | 3 ++-
 tests/test_operator_overloading.py         | 3 ++-
 tests/test_pickling.py                     | 1 -
 tests/test_pytypes.py                      | 7 ++++---
 tests/test_sequences_and_iterators.py      | 3 ++-
 tests/test_stl.py                          | 3 +--
 tests/test_stl_binders.py                  | 1 -
 tools/libsize.py                           | 3 ++-
 tools/make_changelog.py                    | 2 --
 45 files changed, 72 insertions(+), 66 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index ee61258d3f..a5900df162 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -35,6 +35,11 @@ repos:
   hooks:
   - id: pyupgrade
 
+- repo: https://github.com/PyCQA/isort
+  rev: 5.9.3
+  hooks:
+  - id: isort
+
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
   rev: 21.7b0
diff --git a/docs/benchmark.py b/docs/benchmark.py
index 33d78fb4e6..369470c81f 100644
--- a/docs/benchmark.py
+++ b/docs/benchmark.py
@@ -1,8 +1,8 @@
 # -*- coding: utf-8 -*-
-import random
+import datetime as dt
 import os
+import random
 import time
-import datetime as dt
 
 nfns = 4  # Functions per class
 nargs = 4  # Arguments per function
diff --git a/docs/conf.py b/docs/conf.py
index 6ac054c6b8..458a868866 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -13,12 +13,12 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import sys
 import os
+import re
 import shlex
 import subprocess
+import sys
 from pathlib import Path
-import re
 
 DIR = Path(__file__).parent.resolve()
 
diff --git a/noxfile.py b/noxfile.py
index f0f6680159..55b1d180b2 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -1,6 +1,5 @@
 import nox
 
-
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
 
diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index ad65420893..64e999ba06 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -1,8 +1,7 @@
 # -*- coding: utf-8 -*-
 
-from ._version import version_info, __version__
-from .commands import get_include, get_cmake_dir
-
+from ._version import __version__, version_info
+from .commands import get_cmake_dir, get_include
 
 __all__ = (
     "version_info",
diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 020988c671..3235747bed 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -5,7 +5,7 @@
 import sys
 import sysconfig
 
-from .commands import get_include, get_cmake_dir
+from .commands import get_cmake_dir, get_include
 
 
 def print_includes():
diff --git a/pybind11/_version.pyi b/pybind11/_version.pyi
index 970184c770..d45e5dc907 100644
--- a/pybind11/_version.pyi
+++ b/pybind11/_version.pyi
@@ -1,4 +1,4 @@
-from typing import Union, Tuple
+from typing import Tuple, Union
 
 def _to_int(s: str) -> Union[int, str]: ...
 
diff --git a/pybind11/commands.py b/pybind11/commands.py
index 34dbaf8a89..11f81d2d6d 100644
--- a/pybind11/commands.py
+++ b/pybind11/commands.py
@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 import os
 
-
 DIR = os.path.abspath(os.path.dirname(__file__))
 
 
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 0888ab4872..4ff1a0cb37 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -41,23 +41,23 @@
 
 import contextlib
 import os
+import platform
 import shutil
 import sys
+import sysconfig
 import tempfile
 import threading
-import platform
 import warnings
-import sysconfig
 
 try:
-    from setuptools.command.build_ext import build_ext as _build_ext
     from setuptools import Extension as _Extension
+    from setuptools.command.build_ext import build_ext as _build_ext
 except ImportError:
     from distutils.command.build_ext import build_ext as _build_ext
     from distutils.extension import Extension as _Extension
 
-import distutils.errors
 import distutils.ccompiler
+import distutils.errors
 
 WIN = sys.platform.startswith("win32") and "mingw" not in sysconfig.get_platform()
 PY2 = sys.version_info[0] < 3
diff --git a/pybind11/setup_helpers.pyi b/pybind11/setup_helpers.pyi
index 8b16c0a137..074744eb82 100644
--- a/pybind11/setup_helpers.pyi
+++ b/pybind11/setup_helpers.pyi
@@ -1,13 +1,12 @@
 # IMPORTANT: Should stay in sync with setup_helpers.py (mostly checked by CI /
 # pre-commit).
 
-from typing import Any, Callable, Dict, Iterator, List, Optional, Type, TypeVar, Union
-from types import TracebackType
-
+import contextlib
+import distutils.ccompiler
 from distutils.command.build_ext import build_ext as _build_ext  # type: ignore
 from distutils.extension import Extension as _Extension
-import distutils.ccompiler
-import contextlib
+from types import TracebackType
+from typing import Any, Callable, Dict, Iterator, List, Optional, Type, TypeVar, Union
 
 WIN: bool
 PY2: bool
diff --git a/pyproject.toml b/pyproject.toml
index f86470eef8..7d7a1c8213 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,6 +15,12 @@ ignore = [
     "noxfile.py",
 ]
 
+[tool.isort]
+# Needs the compiled .so modules and env.py from tests
+known_first_party = "env,pybind11_cross_module_tests,pybind11_tests,"
+# For black compatibility
+profile = "black"
+
 [tool.mypy]
 files = "pybind11"
 python_version = "2.7"
diff --git a/setup.py b/setup.py
index 7aa151c01b..a2326287d8 100644
--- a/setup.py
+++ b/setup.py
@@ -4,6 +4,7 @@
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
 
 import contextlib
+import io
 import os
 import re
 import shutil
@@ -11,7 +12,6 @@
 import subprocess
 import sys
 import tempfile
-import io
 
 import setuptools.command.sdist
 
diff --git a/tests/extra_setuptools/test_setuphelper.py b/tests/extra_setuptools/test_setuphelper.py
index fb2d342086..c24f50af8a 100644
--- a/tests/extra_setuptools/test_setuphelper.py
+++ b/tests/extra_setuptools/test_setuphelper.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 import os
-import sys
 import subprocess
+import sys
 from textwrap import dedent
 
 import pytest
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index 50845758b8..e3df7e04f9 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -1,14 +1,13 @@
 # -*- coding: utf-8 -*-
+import ctypes
 import io
 import struct
-import ctypes
 
 import pytest
 
 import env  # noqa: F401
-
-from pybind11_tests import buffers as m
 from pybind11_tests import ConstructorStats
+from pybind11_tests import buffers as m
 
 np = pytest.importorskip("numpy")
 
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 1b9dbb2b40..09b4b08c5e 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -2,9 +2,8 @@
 import pytest
 
 import env  # noqa: F401
-
+from pybind11_tests import IncType, UserType
 from pybind11_tests import builtin_casters as m
-from pybind11_tests import UserType, IncType
 
 
 def test_simple_string():
diff --git a/tests/test_call_policies.py b/tests/test_call_policies.py
index af017e9d0c..3599cf81af 100644
--- a/tests/test_call_policies.py
+++ b/tests/test_call_policies.py
@@ -2,9 +2,8 @@
 import pytest
 
 import env  # noqa: F401
-
-from pybind11_tests import call_policies as m
 from pybind11_tests import ConstructorStats
+from pybind11_tests import call_policies as m
 
 
 @pytest.mark.xfail("env.PYPY", reason="sometimes comes out 1 off on PyPy", strict=False)
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 5bc4d1773d..9dc272a2da 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -1,9 +1,11 @@
 # -*- coding: utf-8 -*-
-import pytest
-from pybind11_tests import callbacks as m
-from threading import Thread
 import time
+from threading import Thread
+
+import pytest
+
 import env  # NOQA: F401
+from pybind11_tests import callbacks as m
 
 
 def test_callbacks():
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index 12312c7207..fdd73d6908 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -1,9 +1,10 @@
 # -*- coding: utf-8 -*-
-from pybind11_tests import chrono as m
 import datetime
+
 import pytest
 
 import env  # noqa: F401
+from pybind11_tests import chrono as m
 
 
 def test_chrono_system_clock():
diff --git a/tests/test_class.py b/tests/test_class.py
index 1ff60fe214..85d4531991 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -2,9 +2,8 @@
 import pytest
 
 import env  # noqa: F401
-
+from pybind11_tests import ConstructorStats, UserType
 from pybind11_tests import class_ as m
-from pybind11_tests import UserType, ConstructorStats
 
 
 def test_repr():
diff --git a/tests/test_cmake_build/test.py b/tests/test_cmake_build/test.py
index 87ed5135ff..d1a290dcc5 100644
--- a/tests/test_cmake_build/test.py
+++ b/tests/test_cmake_build/test.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import sys
+
 import test_cmake_build
 
 assert test_cmake_build.add(1, 2) == 3
diff --git a/tests/test_copy_move.py b/tests/test_copy_move.py
index 1d98952200..eb1efddd50 100644
--- a/tests/test_copy_move.py
+++ b/tests/test_copy_move.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import pytest
+
 from pybind11_tests import copy_move_policies as m
 
 
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
index bb74d54eb3..a10646ff46 100644
--- a/tests/test_custom_type_casters.py
+++ b/tests/test_custom_type_casters.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import pytest
+
 from pybind11_tests import custom_type_casters as m
 
 
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index a131dc15d6..e53826cbbb 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import pytest
+
 from pybind11_tests import ConstructorStats
 
 np = pytest.importorskip("numpy")
diff --git a/tests/test_enum.py b/tests/test_enum.py
index e9732fa74f..62f9426eee 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import pytest
+
 from pybind11_tests import enums as m
 
 
diff --git a/tests/test_eval.py b/tests/test_eval.py
index 601e526f43..1bbd991bc0 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -4,7 +4,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import eval_ as m
 
 
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 966ae07fc0..d1edc39f0e 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -4,9 +4,8 @@
 import pytest
 
 import env  # noqa: F401
-
-from pybind11_tests import exceptions as m
 import pybind11_cross_module_tests as cm
+from pybind11_tests import exceptions as m
 
 
 def test_std_exception(msg):
diff --git a/tests/test_factory_constructors.py b/tests/test_factory_constructors.py
index 8c6ca173ac..8bc0269852 100644
--- a/tests/test_factory_constructors.py
+++ b/tests/test_factory_constructors.py
@@ -1,12 +1,12 @@
 # -*- coding: utf-8 -*-
-import pytest
 import re
 
-import env  # noqa: F401
+import pytest
 
+import env  # noqa: F401
+from pybind11_tests import ConstructorStats
 from pybind11_tests import factory_constructors as m
 from pybind11_tests.factory_constructors import tag
-from pybind11_tests import ConstructorStats
 
 
 def test_init_factory_basic():
diff --git a/tests/test_iostream.py b/tests/test_iostream.py
index e2b74d01cb..7f18ca65c6 100644
--- a/tests/test_iostream.py
+++ b/tests/test_iostream.py
@@ -1,9 +1,9 @@
 # -*- coding: utf-8 -*-
-from pybind11_tests import iostream as m
 import sys
-
 from contextlib import contextmanager
 
+from pybind11_tests import iostream as m
+
 try:
     # Python 3
     from io import StringIO
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index 12fe705b4d..ddc387eeb9 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import kwargs_and_defaults as m
 
 
diff --git a/tests/test_local_bindings.py b/tests/test_local_bindings.py
index a38564b6e1..52b1b63358 100644
--- a/tests/test_local_bindings.py
+++ b/tests/test_local_bindings.py
@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import local_bindings as m
 
 
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 750ec02f89..21909654a5 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -2,9 +2,8 @@
 import pytest
 
 import env  # noqa: F401
-
-from pybind11_tests import methods_and_attributes as m
 from pybind11_tests import ConstructorStats
+from pybind11_tests import methods_and_attributes as m
 
 
 def test_methods_and_attributes():
diff --git a/tests/test_modules.py b/tests/test_modules.py
index 3390031aff..49e1ea5e30 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
+from pybind11_tests import ConstructorStats
 from pybind11_tests import modules as m
 from pybind11_tests.modules import subsubmodule as ms
-from pybind11_tests import ConstructorStats
 
 
 def test_nested_modules():
@@ -54,18 +54,20 @@ def test_reference_internal():
 
 
 def test_importing():
-    from pybind11_tests.modules import OD
     from collections import OrderedDict
 
+    from pybind11_tests.modules import OD
+
     assert OD is OrderedDict
     assert str(OD([(1, "a"), (2, "b")])) == "OrderedDict([(1, 'a'), (2, 'b')])"
 
 
 def test_pydoc():
     """Pydoc needs to be able to provide help() for everything inside a pybind11 module"""
-    import pybind11_tests
     import pydoc
 
+    import pybind11_tests
+
     assert pybind11_tests.__name__ == "pybind11_tests"
     assert pybind11_tests.__doc__ == "pybind11 test module"
     assert pydoc.text.docmodule(pybind11_tests)
diff --git a/tests/test_multiple_inheritance.py b/tests/test_multiple_inheritance.py
index e6a7f9762b..a02c313001 100644
--- a/tests/test_multiple_inheritance.py
+++ b/tests/test_multiple_inheritance.py
@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import ConstructorStats
 from pybind11_tests import multiple_inheritance as m
 
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 548c84bab1..69ba9d4952 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import numpy_array as m
 
 np = pytest.importorskip("numpy")
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 0a5881e49d..6ea064d5bc 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -4,7 +4,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import numpy_dtypes as m
 
 np = pytest.importorskip("numpy")
diff --git a/tests/test_numpy_vectorize.py b/tests/test_numpy_vectorize.py
index 4e6b2d1982..de5c9a607d 100644
--- a/tests/test_numpy_vectorize.py
+++ b/tests/test_numpy_vectorize.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import pytest
+
 from pybind11_tests import numpy_vectorize as m
 
 np = pytest.importorskip("numpy")
diff --git a/tests/test_opaque_types.py b/tests/test_opaque_types.py
index 773794634c..5495cb6b4a 100644
--- a/tests/test_opaque_types.py
+++ b/tests/test_opaque_types.py
@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import opaque_types as m
+
 from pybind11_tests import ConstructorStats, UserType
+from pybind11_tests import opaque_types as m
 
 
 def test_string_list():
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index 5dbfb32c8a..b7137d1592 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import operators as m
+
 from pybind11_tests import ConstructorStats
+from pybind11_tests import operators as m
 
 
 def test_operator_overloading():
diff --git a/tests/test_pickling.py b/tests/test_pickling.py
index 303213068d..e39463d209 100644
--- a/tests/test_pickling.py
+++ b/tests/test_pickling.py
@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import pickling as m
 
 try:
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 66d6d30a0c..8a11b18727 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -1,12 +1,13 @@
 # -*- coding: utf-8 -*-
 from __future__ import division
-import pytest
+
 import sys
 
-import env  # noqa: F401
+import pytest
 
-from pybind11_tests import pytypes as m
+import env  # noqa: F401
 from pybind11_tests import debug_enabled
+from pybind11_tests import pytypes as m
 
 
 def test_int(doc):
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 70fb697f95..a868c542c2 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import sequences_and_iterators as m
+
 from pybind11_tests import ConstructorStats
+from pybind11_tests import sequences_and_iterators as m
 
 
 def isclose(a, b, rel_tol=1e-05, abs_tol=0.0):
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 6f08459043..3f63d6c3a4 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -1,9 +1,8 @@
 # -*- coding: utf-8 -*-
 import pytest
 
+from pybind11_tests import ConstructorStats, UserType
 from pybind11_tests import stl as m
-from pybind11_tests import UserType
-from pybind11_tests import ConstructorStats
 
 
 def test_vector(doc):
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 84132a2b4f..475a9ec400 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import stl_binders as m
 
 
diff --git a/tools/libsize.py b/tools/libsize.py
index 589c317f0d..1551477e66 100644
--- a/tools/libsize.py
+++ b/tools/libsize.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
-from __future__ import print_function, division
+from __future__ import division, print_function
+
 import os
 import sys
 
diff --git a/tools/make_changelog.py b/tools/make_changelog.py
index 4e8fbf5b00..629c284d39 100755
--- a/tools/make_changelog.py
+++ b/tools/make_changelog.py
@@ -4,11 +4,9 @@
 import re
 
 import ghapi.all
-
 from rich import print
 from rich.syntax import Syntax
 
-
 ENTRY = re.compile(
     r"""
     Suggested \s changelog \s entry:

From 1bcd94c481bba513c4c63a62b1f5da13f5e7978d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 14 Aug 2021 07:41:27 -0700
Subject: [PATCH 140/638] Removing last remnants of pragma block at the top of
 pybind11.h (#3186)

* Removing last remnants of pragma block at the top of pybind11.h, defaulting CUDA, GCC7, GCC8 to PYBIND11_NOINLINE_DISABLED, with the option to define PYBIND11_NOINLINE_FORCED.

* Unique SOSIZE prefix to make it easier to extract the sosizes from the GitHub logs.

* Commenting out PYBIND11_WERROR block, for noinline testing.

* Undoing accidental change.

* `#define PYBIND11_NOINLINE_FORCED`

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* `#define PYBIND11_NOINLINE_DISABLED`

* Going back to default (removing `#define PYBIND11_NOINLINE_DISABLED`).

* `#define PYBIND11_NOINLINE_FORCED`

* Undoing all changes releated to measuring sosizes.

* Rollback of PR #3030 (Working around Centos 8 failure).

* Disabling -Werror for GNU (experiment).

* Commenting out the entire `if(PYBIND11_WERROR)` again (although that is not expected to make a difference, but who knows what I am overlooking).

* Adding `-DCMAKE_BUILD_TYPE=Release`

* Undoing change to tests/CMakeLists.txt (uncommenting `if(PYBIND11_WERROR)` block).

* post `git rebase master -X theirs` fixups.

* Adding measurements to comment for `PYBIND11_NOINLINE_FORCED`.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/detail/common.h | 11 +++++++++++
 include/pybind11/pybind11.h      |  9 ---------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index cc24a52fd3..8daa33903e 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -99,6 +99,17 @@
 #  endif
 #endif
 
+// For CUDA, GCC7, GCC8:
+// PYBIND11_NOINLINE_FORCED is incompatible with `-Wattributes -Werror`.
+// When defining PYBIND11_NOINLINE_FORCED, it is best to also use `-Wno-attributes`.
+// However, the measured shared-library size saving when using noinline are only
+// 1.7% for CUDA, -0.2% for GCC7, and 0.0% for GCC8 (using -DCMAKE_BUILD_TYPE=MinSizeRel,
+// the default under pybind11/tests).
+#if !defined(PYBIND11_NOINLINE_FORCED) && \
+    (defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8)))
+#  define PYBIND11_NOINLINE_DISABLED
+#endif
+
 // The PYBIND11_NOINLINE macro is for function DEFINITIONS.
 // In contrast, FORWARD DECLARATIONS should never use this macro:
 // https://stackoverflow.com/questions/9317473/forward-declaration-of-inline-functions
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 20df6a01fd..7b7b3ca71f 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,11 +10,6 @@
 
 #pragma once
 
-#if defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8))
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wattributes"
-#endif
-
 #include "attr.h"
 #include "gil.h"
 #include "options.h"
@@ -2383,7 +2378,3 @@ PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 #if defined(__GNUC__) && __GNUC__ == 7
 #    pragma GCC diagnostic pop // -Wnoexcept-type
 #endif
-
-#if defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8))
-#  pragma GCC diagnostic pop
-#endif

From 617cb653ec513b4e02d7104b05fb75c26d10e79e Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sat, 14 Aug 2021 12:25:54 -0400
Subject: [PATCH 141/638] [Bugfix] Fix errant const methods (#3194)

* Fix errant const methods

* Remove NOLINT since clang-tidy is pretty conservative

* Missed one

* Fix a few more errors

* Add reviewer suggested comments

* Run clang-format
---
 include/pybind11/detail/common.h           |  2 +-
 include/pybind11/detail/type_caster_base.h |  9 ++++++---
 include/pybind11/pytypes.h                 | 10 +++++-----
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 8daa33903e..0d12d734c7 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -522,7 +522,7 @@ struct instance {
     void allocate_layout();
 
     /// Destroys/deallocates all of the above
-    void deallocate_layout() const;
+    void deallocate_layout();
 
     /// Returns the value_and_holder wrapper for the given type (or the first, if `find_type`
     /// omitted).  Returns a default-constructed (with `.inst = nullptr`) object on failure if
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 14cb27cad2..5a5acc2e6a 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -241,7 +241,8 @@ struct value_and_holder {
                    ? inst->simple_holder_constructed
                    : (inst->nonsimple.status[index] & instance::status_holder_constructed) != 0u;
     }
-    void set_holder_constructed(bool v = true) const {
+    // NOLINTNEXTLINE(readability-make-member-function-const)
+    void set_holder_constructed(bool v = true) {
         if (inst->simple_layout)
             inst->simple_holder_constructed = v;
         else if (v)
@@ -254,7 +255,8 @@ struct value_and_holder {
             ? inst->simple_instance_registered
             : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
     }
-    void set_instance_registered(bool v = true) const {
+    // NOLINTNEXTLINE(readability-make-member-function-const)
+    void set_instance_registered(bool v = true) {
         if (inst->simple_layout)
             inst->simple_instance_registered = v;
         else if (v)
@@ -397,7 +399,8 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
     owned = true;
 }
 
-PYBIND11_NOINLINE void instance::deallocate_layout() const {
+// NOLINTNEXTLINE(readability-make-member-function-const)
+PYBIND11_NOINLINE void instance::deallocate_layout() {
     if (!simple_layout)
         PyMem_Free(nonsimple.values_and_holders);
 }
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 21e14960cf..dc1607ff26 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1393,7 +1393,7 @@ class dict : public object {
     bool empty() const { return size() == 0; }
     detail::dict_iterator begin() const { return {*this, 0}; }
     detail::dict_iterator end() const { return {}; }
-    void clear() const { PyDict_Clear(ptr()); }
+    void clear() /* py-non-const */ { PyDict_Clear(ptr()); }
     template <typename T> bool contains(T &&key) const {
         return PyDict_Contains(m_ptr, detail::object_or_cast(std::forward<T>(key)).ptr()) == 1;
     }
@@ -1435,10 +1435,10 @@ class list : public object {
     detail::item_accessor operator[](handle h) const { return object::operator[](h); }
     detail::list_iterator begin() const { return {*this, 0}; }
     detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
-    template <typename T> void append(T &&val) const {
+    template <typename T> void append(T &&val) /* py-non-const */ {
         PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
     }
-    template <typename T> void insert(size_t index, T &&val) const {
+    template <typename T> void insert(size_t index, T &&val) /* py-non-const */ {
         PyList_Insert(m_ptr, static_cast<ssize_t>(index),
             detail::object_or_cast(std::forward<T>(val)).ptr());
     }
@@ -1455,10 +1455,10 @@ class set : public object {
     }
     size_t size() const { return (size_t) PySet_Size(m_ptr); }
     bool empty() const { return size() == 0; }
-    template <typename T> bool add(T &&val) const {
+    template <typename T> bool add(T &&val) /* py-non-const */ {
         return PySet_Add(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 0;
     }
-    void clear() const { PySet_Clear(m_ptr); }
+    void clear() /* py-non-const */ { PySet_Clear(m_ptr); }
     template <typename T> bool contains(T &&val) const {
         return PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 1;
     }

From 774b5ff90bbc2fac198f03a246e3517a53f8c637 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 17 Aug 2021 16:49:39 -0700
Subject: [PATCH 142/638] Removing obsolete eigen.h warning suppression
 pragmas. (#3198)

* Removing all pragma from eigen.h

* Removing -Werror or equivalent from tests/CMakeLists.txt

* Restoring tests/CMakeLists.txt from master.

* Adding 4 PYBIND11_SILENCE_MSVC_C4127.

* Compatibility with -Wconversion, -Wdeprecated

* Introducing PYBIND11_COMPATIBILITY_WDEPRECATED_COPY

* Systematically using --verbose for compilations where possible (cmake 3.14 or newer).

Also changing all `cmake -t` to `--target`, `-v` to `--verbose`, `check` to `pytest`, for consistency (to make it easier to pin-point all commands of a certain type).

Also removing one `-j 2` for `pytest` in hopes of reducing flakes due to races in test_iostream and in prints from destructors.

* Commenting out pragmas as an experiment to reproduce previous observation.

* Removing all (newly added, but already commented-out) pragma code, adding HINT use -isystem (as cmake does).

* Restoring ci.yml from master. Those changes are better handled separately. BTW: in the last CI run there was still a test_iostream flake, even without the -j 2 for running the tests (verfied by inspecting the log).
---
 include/pybind11/eigen.h | 41 ++++++++++------------------------------
 1 file changed, 10 insertions(+), 31 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 218fe27034..b03e15f624 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -9,29 +9,13 @@
 
 #pragma once
 
-#include "numpy.h"
-
-#if defined(__INTEL_COMPILER)
-#  pragma warning(disable: 1682) // implicit conversion of a 64-bit integral type to a smaller integral type (potential portability problem)
-#elif defined(__GNUG__) || defined(__clang__)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wconversion"
-#  pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#  ifdef __clang__
-//   Eigen generates a bunch of implicit-copy-constructor-is-deprecated warnings with -Wdeprecated
-//   under Clang, so disable that warning here:
-#    pragma GCC diagnostic ignored "-Wdeprecated"
-#  endif
-#  if __GNUC__ >= 7
-#    pragma GCC diagnostic ignored "-Wint-in-bool-context"
-#  endif
-#endif
+/* HINT: To suppress warnings originating from the Eigen headers, use -isystem.
+   See also:
+       https://stackoverflow.com/questions/2579576/i-dir-vs-isystem-dir
+       https://stackoverflow.com/questions/1741816/isystem-for-ms-visual-studio-c-compiler
+*/
 
-#if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#  pragma warning(disable: 4996) // warning C4996: std::unary_negate is deprecated in C++17
-#endif
+#include "numpy.h"
 
 #include <Eigen/Core>
 #include <Eigen/SparseCore>
@@ -153,7 +137,8 @@ template <typename Type_> struct EigenProps {
                 np_cols = a.shape(1),
                 np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
                 np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
-            if ((fixed_rows && np_rows != rows) || (fixed_cols && np_cols != cols))
+            if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows) ||
+                (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols))
                 return false;
 
             return {np_rows, np_cols, np_rstride, np_cstride};
@@ -165,7 +150,7 @@ template <typename Type_> struct EigenProps {
               stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
 
         if (vector) { // Eigen type is a compile-time vector
-            if (fixed && size != n)
+            if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n)
                 return false; // Vector size mismatch
             return {rows == 1 ? 1 : n, cols == 1 ? 1 : n, stride};
         }
@@ -179,7 +164,7 @@ template <typename Type_> struct EigenProps {
             if (cols != n) return false;
             return {1, n, stride};
         } // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
-            if (fixed_rows && rows != n) return false;
+            if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) return false;
             return {n, 1, stride};
     }
 
@@ -596,9 +581,3 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
 
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
-
-#if defined(__GNUG__) || defined(__clang__)
-#  pragma GCC diagnostic pop
-#elif defined(_MSC_VER)
-#  pragma warning(pop)
-#endif

From 998d45e4313067d752476338d090f388f0a5d9ed Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 19 Aug 2021 11:37:04 -0700
Subject: [PATCH 143/638] Cleanup of file-scoped and globally-scoped warning
 suppression pragmas across pybind11 header files. (#3201)

* Removing all MSVC C4127 warning suppression pragmas.

* Removing MSVC /WX (WERROR). To get a full list of all warnings.

* Inserting PYBIND11_SILENCE_MSVC_C4127. Changing one runtime if to #if.

* Changing PYBIND11_SILENCE_MSVC_C4127 macro to use absolute namespace (for use outside pybind11 include directory).

* Restoring MSVC /WX (WERROR).

* Removing globally-scoped suppression for clang -Wunsequenced. Based on an experiment under PR #3202 it is obsolete and can simply be removed.
---
 include/pybind11/detail/common.h |  2 +-
 include/pybind11/numpy.h         | 13 ++-----------
 include/pybind11/operators.h     | 14 ++------------
 include/pybind11/stl.h           |  9 ---------
 tests/test_builtin_casters.cpp   | 14 +++++---------
 5 files changed, 10 insertions(+), 42 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 0d12d734c7..cb52aa2749 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -968,7 +968,7 @@ inline void silence_unused_warnings(Args &&...) {}
 // warning C4127: Conditional expression is constant
 constexpr inline bool silence_msvc_c4127(bool cond) { return cond; }
 
-#    define PYBIND11_SILENCE_MSVC_C4127(...) detail::silence_msvc_c4127(__VA_ARGS__)
+#    define PYBIND11_SILENCE_MSVC_C4127(...) ::pybind11::detail::silence_msvc_c4127(__VA_ARGS__)
 
 #else
 #    define PYBIND11_SILENCE_MSVC_C4127(...) __VA_ARGS__
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 2dc0f29f0b..7717059f4a 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -25,11 +25,6 @@
 #include <vector>
 #include <typeindex>
 
-#if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#endif
-
 /* This will be true on all flat address space platforms and allows us to reduce the
    whole npy_intp / ssize_t / Py_intptr_t business down to just ssize_t for all size
    and dimension types (e.g. shape, strides, indexing), instead of inflicting this
@@ -747,7 +742,7 @@ class array : public buffer {
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
     template <typename T, ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
-        if (Dims >= 0 && ndim() != Dims)
+        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims)
             throw std::domain_error("array has incorrect number of dimensions: " + std::to_string(ndim()) +
                     "; expected " + std::to_string(Dims));
         return detail::unchecked_mutable_reference<T, Dims>(mutable_data(), shape(), strides(), ndim());
@@ -761,7 +756,7 @@ class array : public buffer {
      * invalid dimensions or dimension indices.
      */
     template <typename T, ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
-        if (Dims >= 0 && ndim() != Dims)
+        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims)
             throw std::domain_error("array has incorrect number of dimensions: " + std::to_string(ndim()) +
                     "; expected " + std::to_string(Dims));
         return detail::unchecked_reference<T, Dims>(data(), shape(), strides(), ndim());
@@ -1708,7 +1703,3 @@ Helper vectorize(Return (Class::*f)(Args...) const) {
 }
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
-
-#if defined(_MSC_VER)
-#pragma warning(pop)
-#endif
diff --git a/include/pybind11/operators.h b/include/pybind11/operators.h
index 086cb4cfd8..2a61531589 100644
--- a/include/pybind11/operators.h
+++ b/include/pybind11/operators.h
@@ -11,13 +11,6 @@
 
 #include "pybind11.h"
 
-#if defined(__clang__) && !defined(__INTEL_COMPILER)
-#  pragma clang diagnostic ignored "-Wunsequenced" // multiple unsequenced modifications to 'self' (when using def(py::self OP Type()))
-#elif defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#endif
-
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
@@ -58,7 +51,8 @@ template <op_id id, op_type ot, typename L, typename R> struct op_ {
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute, is_operator(), extra...);
         #if PY_MAJOR_VERSION < 3
-        if (id == op_truediv || id == op_itruediv)
+        if (PYBIND11_SILENCE_MSVC_C4127(id == op_truediv) ||
+            PYBIND11_SILENCE_MSVC_C4127(id == op_itruediv))
             cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
                     &op::execute, is_operator(), extra...);
         #endif
@@ -167,7 +161,3 @@ using detail::self;
 using detail::hash;
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
-
-#if defined(_MSC_VER)
-#  pragma warning(pop)
-#endif
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 51994c656b..fe391f70bd 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -19,11 +19,6 @@
 #include <deque>
 #include <valarray>
 
-#if defined(_MSC_VER)
-#pragma warning(push)
-#pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#endif
-
 #ifdef __has_include
 // std::optional (but including it in c++14 mode isn't allowed)
 #  if defined(PYBIND11_CPP17) && __has_include(<optional>)
@@ -390,7 +385,3 @@ inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
 }
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
-
-#if defined(_MSC_VER)
-#pragma warning(pop)
-#endif
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 51e410cadd..be4431aad6 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -10,11 +10,6 @@
 #include "pybind11_tests.h"
 #include <pybind11/complex.h>
 
-#if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
-#endif
-
 struct ConstRefCasted {
   int tag;
 };
@@ -73,7 +68,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     std::wstring wstr;
     wstr.push_back(0x61); // a
     wstr.push_back(0x2e18); // ⸘
-    if (sizeof(wchar_t) == 2) { wstr.push_back(mathbfA16_1); wstr.push_back(mathbfA16_2); } // 𝐀, utf16
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) { wstr.push_back(mathbfA16_1); wstr.push_back(mathbfA16_2); } // 𝐀, utf16
     else { wstr.push_back((wchar_t) mathbfA32); } // 𝐀, utf32
     wstr.push_back(0x7a); // z
 
@@ -83,11 +78,12 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("good_wchar_string", [=]() { return wstr; }); // a‽𝐀z
     m.def("bad_utf8_string", []()  { return std::string("abc\xd0" "def"); });
     m.def("bad_utf16_string", [=]() { return std::u16string({ b16, char16_t(0xd800), z16 }); });
+#if PY_MAJOR_VERSION >= 3
     // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger UnicodeDecodeError
-    if (PY_MAJOR_VERSION >= 3)
-        m.def("bad_utf32_string", [=]() { return std::u32string({ a32, char32_t(0xd800), z32 }); });
-    if (PY_MAJOR_VERSION >= 3 || sizeof(wchar_t) == 2)
+    m.def("bad_utf32_string", [=]() { return std::u32string({ a32, char32_t(0xd800), z32 }); });
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2))
         m.def("bad_wchar_string", [=]() { return std::wstring({ wchar_t(0x61), wchar_t(0xd800) }); });
+#endif
     m.def("u8_Z", []() -> char { return 'Z'; });
     m.def("u8_eacute", []() -> char { return '\xe9'; });
     m.def("u16_ibang", [=]() -> char16_t { return ib16; });

From 4f29b8a45b8d1e52d06d920f7a8140811a925fd9 Mon Sep 17 00:00:00 2001
From: Liam Keegan <liam@keegan.ch>
Date: Thu, 19 Aug 2021 20:42:55 +0200
Subject: [PATCH 144/638] ci: extend msys2 mingw CI (#3207)

* extend msys2 CI

- add 32-bit job
- add c++11/17 c++/interface tests copied from standard ci
- add numpy/scipy

* account for padding of PartialStruct in numpy dtypes test with mingw32

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* msys2 ci: add c++14 tests

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml   | 81 +++++++++++++++++++++++++++++++-------
 tests/test_numpy_dtypes.py | 14 +++++--
 2 files changed, 78 insertions(+), 17 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index be3fa723c9..a3664ddf55 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -861,32 +861,85 @@ jobs:
       run: cmake --build build -t check
 
   mingw:
+    name: "🐍 3 • windows-latest • ${{ matrix.sys }}"
     runs-on: windows-latest
     defaults:
       run:
         shell: msys2 {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { sys: mingw64, env: x86_64 }
+          - { sys: mingw32, env: i686 }
     steps:
     - uses: msys2/setup-msys2@v2
       with:
+        msystem: ${{matrix.sys}}
         install: >-
-          mingw-w64-x86_64-gcc
-          mingw-w64-x86_64-python-pip
-          mingw-w64-x86_64-cmake
-          mingw-w64-x86_64-make
-          mingw-w64-x86_64-python-pytest
-          mingw-w64-x86_64-eigen3
-          mingw-w64-x86_64-boost
-          mingw-w64-x86_64-catch
+          git
+          mingw-w64-${{matrix.env}}-gcc
+          mingw-w64-${{matrix.env}}-python-pip
+          mingw-w64-${{matrix.env}}-python-numpy
+          mingw-w64-${{matrix.env}}-python-scipy
+          mingw-w64-${{matrix.env}}-cmake
+          mingw-w64-${{matrix.env}}-make
+          mingw-w64-${{matrix.env}}-python-pytest
+          mingw-w64-${{matrix.env}}-eigen3
+          mingw-w64-${{matrix.env}}-boost
+          mingw-w64-${{matrix.env}}-catch
 
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
-    - name: Configure
+    - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -S . -B build
 
-    - name: Build
+    - name: Build C++11
       run: cmake --build build -j 2
 
-    - name: Python tests
-      run: cmake --build build --target pytest
+    - name: Python tests C++11
+      run: cmake --build build --target pytest -j 2
+
+    - name: C++11 tests
+      run: cmake --build build --target cpptest -j 2
+
+    - name: Interface test C++11
+      run: cmake --build build --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    - name: Configure C++14
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -S . -B build2
+
+    - name: Build C++14
+      run: cmake --build build2 -j 2
+
+    - name: Python tests C++14
+      run: cmake --build build2 --target pytest -j 2
+
+    - name: C++14 tests
+      run: cmake --build build2 --target cpptest -j 2
+
+    - name: Interface test C++14
+      run: cmake --build build2 --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    - name: Configure C++17
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -S . -B build3
+
+    - name: Build C++17
+      run: cmake --build build3 -j 2
+
+    - name: Python tests C++17
+      run: cmake --build build3 --target pytest -j 2
+
+    - name: C++17 tests
+      run: cmake --build build3 --target cpptest -j 2
+
+    - name: Interface test C++17
+      run: cmake --build build3 --target test_cmake_build
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 6ea064d5bc..06e578329e 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -63,14 +63,20 @@ def partial_ld_offset():
 def partial_dtype_fmt():
     ld = np.dtype("longdouble")
     partial_ld_off = partial_ld_offset()
-    return dt_fmt().format(ld.itemsize, partial_ld_off, partial_ld_off + ld.itemsize)
+    partial_size = partial_ld_off + ld.itemsize
+    partial_end_padding = partial_size % np.dtype("uint64").alignment
+    return dt_fmt().format(
+        ld.itemsize, partial_ld_off, partial_size + partial_end_padding
+    )
 
 
 def partial_nested_fmt():
     ld = np.dtype("longdouble")
     partial_nested_off = 8 + 8 * (ld.alignment > 8)
     partial_ld_off = partial_ld_offset()
-    partial_nested_size = partial_nested_off * 2 + partial_ld_off + ld.itemsize
+    partial_size = partial_ld_off + ld.itemsize
+    partial_end_padding = partial_size % np.dtype("uint64").alignment
+    partial_nested_size = partial_nested_off * 2 + partial_size + partial_end_padding
     return "{{'names':['a'], 'formats':[{}], 'offsets':[{}], 'itemsize':{}}}".format(
         partial_dtype_fmt(), partial_nested_off, partial_nested_size
     )
@@ -91,10 +97,12 @@ def test_format_descriptors():
     ldbl_fmt = ("4x" if ld.alignment > 4 else "") + ld.char
     ss_fmt = "^T{?:bool_:3xI:uint_:f:float_:" + ldbl_fmt + ":ldbl_:}"
     dbl = np.dtype("double")
+    end_padding = ld.itemsize % np.dtype("uint64").alignment
     partial_fmt = (
         "^T{?:bool_:3xI:uint_:f:float_:"
         + str(4 * (dbl.alignment > 4) + dbl.itemsize + 8 * (ld.alignment > 8))
-        + "xg:ldbl_:}"
+        + "xg:ldbl_:"
+        + (str(end_padding) + "x}" if end_padding > 0 else "}")
     )
     nested_extra = str(max(8, ld.alignment))
     assert m.print_format_descriptors() == [

From b3d18f382f3bc37ec4d95cfe2045db72cf0e950d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 23 Aug 2021 15:22:12 -0400
Subject: [PATCH 145/638] [pre-commit.ci] pre-commit autoupdate (#3213)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.23.3 → v2.24.0](https://github.com/asottile/pyupgrade/compare/v2.23.3...v2.24.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index a5900df162..96ddcf7469 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.23.3
+  rev: v2.24.0
   hooks:
   - id: pyupgrade
 

From fdac5fbf7c1c3b63b6f3067734a10db0b409e28c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 23 Aug 2021 15:05:54 -0700
Subject: [PATCH 146/638] chore: support targeting different Python versions
 with nox (#3214)

---
 .github/CONTRIBUTING.md | 4 ++--
 noxfile.py              | 4 +++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index ff1997f989..39c32b2ac5 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -68,8 +68,8 @@ nox -l
 # Run linters
 nox -s lint
 
-# Run tests
-nox -s tests
+# Run tests on Python 3.9
+nox -s tests-3.9
 
 # Build and preview docs
 nox -s docs -- serve
diff --git a/noxfile.py b/noxfile.py
index 55b1d180b2..234179821d 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,6 +2,8 @@
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
+PYTHON_VERISONS = ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9", "3.10"]
+
 
 @nox.session(reuse_venv=True)
 def lint(session: nox.Session) -> None:
@@ -12,7 +14,7 @@ def lint(session: nox.Session) -> None:
     session.run("pre-commit", "run", "-a")
 
 
-@nox.session
+@nox.session(python=PYTHON_VERISONS)
 def tests(session: nox.Session) -> None:
     """
     Run the tests (requires a compiler).

From 6cbabc4b8c86a838216cb9d17dce14167222e6f7 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 23 Aug 2021 18:42:19 -0400
Subject: [PATCH 147/638] maint(clang-tidy): Enable cpp-coreguideline slicing
 checks (#3210)

* maint(clang-tidy): add a clang-tidy slicing check

* Add self + touch up readme

* Fix typo
---
 .clang-tidy                 | 1 +
 README.rst                  | 4 ++--
 include/pybind11/pybind11.h | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index c83b9b2f5a..cefffba1ea 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -3,6 +3,7 @@ FormatStyle: file
 Checks: '
 *bugprone*,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-slicing,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,
diff --git a/README.rst b/README.rst
index 57eb06e557..7ce57b03ae 100644
--- a/README.rst
+++ b/README.rst
@@ -134,9 +134,9 @@ About
 This project was created by `Wenzel
 Jakob <http://rgl.epfl.ch/people/wjakob>`_. Significant features and/or
 improvements to the code were contributed by Jonas Adler, Lori A. Burns,
-Sylvain Corlay, Eric Cousineau, Ralf Grosse-Kunstleve, Trent Houliston, Axel
+Sylvain Corlay, Eric Cousineau, Aaron Gokaslan, Ralf Grosse-Kunstleve, Trent Houliston, Axel
 Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov Johan Mabille, Tomasz Miąsko,
-Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling,  Pim
+Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling, Pim
 Schellart, Henry Schreiner, Ivan Smirnov, Boris Staletic, and Patrick Stewart.
 
 We thank Google for a generous financial contribution to the continuous
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 7b7b3ca71f..47b042147b 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1664,7 +1664,7 @@ inline str enum_name(handle arg) {
 }
 
 struct enum_base {
-    enum_base(handle base, handle parent) : m_base(base), m_parent(parent) { }
+    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) { }
 
     PYBIND11_NOINLINE void init(bool is_arithmetic, bool is_convertible) {
         m_base.attr("__entries") = dict();

From c8ce4b8df854a630a5f02192305c183299778b84 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 23 Aug 2021 17:30:01 -0700
Subject: [PATCH 148/638] Clone of @virtuald's PR #2112 with minor
 enhancements. (#3215)

* Add py::raise_from to enable chaining exceptions on Python 3.3+

* Use 'raise from' in initialization

* Documenting the exact base version of _PyErr_FormatVFromCause, adding back `assert`s.

Co-authored-by: Dustin Spicuzza <dustin@virtualroadside.com>
---
 docs/advanced/exceptions.rst          | 28 ++++++++++++++++++
 include/pybind11/detail/common.h      | 15 ++++++++++
 include/pybind11/pytypes.h            | 41 +++++++++++++++++++++++++++
 tests/test_embed/test_interpreter.cpp | 16 +++++++++++
 tests/test_exceptions.cpp             | 20 +++++++++++++
 tests/test_exceptions.py              | 16 +++++++++++
 6 files changed, 136 insertions(+)

diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index 738fb0ba9c..2aaa0ad323 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -323,6 +323,34 @@ Alternately, to ignore the error, call `PyErr_Clear
 Any Python error must be thrown or cleared, or Python/pybind11 will be left in
 an invalid state.
 
+Chaining exceptions ('raise from')
+==================================
+
+In Python 3.3 a mechanism for indicating that exceptions were caused by other
+exceptions was introduced:
+
+.. code-block:: py
+
+    try:
+        print(1 / 0)
+    except Exception as exc:
+        raise RuntimeError("could not divide by zero") from exc
+
+To do a similar thing in pybind11, you can use the ``py::raise_from`` function. It
+sets the current python error indicator, so to continue propagating the exception
+you should ``throw py::error_already_set()`` (Python 3 only).
+
+.. code-block:: cpp
+
+    try {
+        py::eval("print(1 / 0"));
+    } catch (py::error_already_set &e) {
+        py::raise_from(e, PyExc_RuntimeError, "could not divide by zero");
+        throw py::error_already_set();
+    }
+
+.. versionadded:: 2.8
+
 .. _unraisable_exceptions:
 
 Handling unraisable exceptions
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index cb52aa2749..5050da802a 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -315,6 +315,19 @@ extern "C" {
         }                                                                      \
     }
 
+#if PY_VERSION_HEX >= 0x03030000
+
+#define PYBIND11_CATCH_INIT_EXCEPTIONS \
+        catch (pybind11::error_already_set &e) {                                 \
+            pybind11::raise_from(e, PyExc_ImportError, "initialization failed"); \
+            return nullptr;                                                      \
+        } catch (const std::exception &e) {                                      \
+            PyErr_SetString(PyExc_ImportError, e.what());                        \
+            return nullptr;                                                      \
+        }                                                                        \
+
+#else
+
 #define PYBIND11_CATCH_INIT_EXCEPTIONS \
         catch (pybind11::error_already_set &e) {                               \
             PyErr_SetString(PyExc_ImportError, e.what());                      \
@@ -324,6 +337,8 @@ extern "C" {
             return nullptr;                                                    \
         }                                                                      \
 
+#endif
+
 /** \rst
     ***Deprecated in favor of PYBIND11_MODULE***
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index dc1607ff26..85f6a40a48 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -382,6 +382,47 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
 #  pragma warning(pop)
 #endif
 
+#if PY_VERSION_HEX >= 0x03030000
+
+/// Replaces the current Python error indicator with the chosen error, performing a
+/// 'raise from' to indicate that the chosen error was caused by the original error.
+inline void raise_from(PyObject *type, const char *message) {
+    // Based on _PyErr_FormatVFromCause:
+    // https://github.com/python/cpython/blob/467ab194fc6189d9f7310c89937c51abeac56839/Python/errors.c#L405
+    // See https://github.com/pybind/pybind11/pull/2112 for details.
+    PyObject *exc = nullptr, *val = nullptr, *val2 = nullptr, *tb = nullptr;
+
+    assert(PyErr_Occurred());
+    PyErr_Fetch(&exc, &val, &tb);
+    PyErr_NormalizeException(&exc, &val, &tb);
+    if (tb != nullptr) {
+        PyException_SetTraceback(val, tb);
+        Py_DECREF(tb);
+    }
+    Py_DECREF(exc);
+    assert(!PyErr_Occurred());
+
+    PyErr_SetString(type, message);
+
+    PyErr_Fetch(&exc, &val2, &tb);
+    PyErr_NormalizeException(&exc, &val2, &tb);
+    Py_INCREF(val);
+    PyException_SetCause(val2, val);
+    PyException_SetContext(val2, val);
+    PyErr_Restore(exc, val2, tb);
+}
+
+/// Sets the current Python error indicator with the chosen error, performing a 'raise from'
+/// from the error contained in error_already_set to indicate that the chosen error was
+/// caused by the original error. After this function is called error_already_set will
+/// no longer contain an error.
+inline void raise_from(error_already_set& err, PyObject *type, const char *message) {
+    err.restore();
+    raise_from(type, message);
+}
+
+#endif
+
 /** \defgroup python_builtins _
     Unless stated otherwise, the following C++ functions behave the same
     as their Python counterparts.
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index cd50e952f6..b40ff48175 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -74,8 +74,24 @@ TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
     REQUIRE_THROWS_WITH(py::module_::import("throw_exception"),
                         "ImportError: C++ Error");
+#if PY_VERSION_HEX >= 0x03030000
+    REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
+                        Catch::Contains("ImportError: initialization failed"));
+
+    auto locals = py::dict("is_keyerror"_a=false, "message"_a="not set");
+    py::exec(R"(
+        try:
+            import throw_error_already_set
+        except ImportError as e:
+            is_keyerror = type(e.__cause__) == KeyError
+            message = str(e.__cause__)
+    )", py::globals(), locals);
+    REQUIRE(locals["is_keyerror"].cast<bool>() == true);
+    REQUIRE(locals["message"].cast<std::string>() == "'missing'");
+#else
     REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                         Catch::Contains("ImportError: KeyError"));
+#endif
 }
 
 TEST_CASE("There can be only one interpreter") {
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index e28f0bb798..4805a02490 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -262,4 +262,24 @@ TEST_SUBMODULE(exceptions, m) {
     m.def("simple_bool_passthrough", [](bool x) {return x;});
 
     m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
+
+#if PY_VERSION_HEX >= 0x03030000
+
+    m.def("raise_from", []() {
+        PyErr_SetString(PyExc_ValueError, "inner");
+        py::raise_from(PyExc_ValueError, "outer");
+        throw py::error_already_set();
+    });
+
+    m.def("raise_from_already_set", []() {
+        try {
+            PyErr_SetString(PyExc_ValueError, "inner");
+            throw py::error_already_set();
+        } catch (py::error_already_set& e) {
+            py::raise_from(e, PyExc_ValueError, "outer");
+            throw py::error_already_set();
+        }
+    });
+
+#endif
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index d1edc39f0e..3821eadaa4 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -24,6 +24,22 @@ def test_error_already_set(msg):
     assert msg(excinfo.value) == "foo"
 
 
+@pytest.mark.skipif("env.PY2")
+def test_raise_from(msg):
+    with pytest.raises(ValueError) as excinfo:
+        m.raise_from()
+    assert msg(excinfo.value) == "outer"
+    assert msg(excinfo.value.__cause__) == "inner"
+
+
+@pytest.mark.skipif("env.PY2")
+def test_raise_from_already_set(msg):
+    with pytest.raises(ValueError) as excinfo:
+        m.raise_from_already_set()
+    assert msg(excinfo.value) == "outer"
+    assert msg(excinfo.value.__cause__) == "inner"
+
+
 def test_cross_module_exceptions(msg):
     with pytest.raises(RuntimeError) as excinfo:
         cm.raise_runtime_error()

From 031a700dfd611efc3949d8427d8c87e91a7b6998 Mon Sep 17 00:00:00 2001
From: Jouke Witteveen <j.witteveen@gmail.com>
Date: Thu, 26 Aug 2021 17:04:22 +0200
Subject: [PATCH 149/638] Add make_simple_namespace function and tests (#2840)

Co-authored-by: Jouke Witteveen <j.witteveen@cosine.nl>
---
 docs/advanced/pycpp/object.rst | 43 +++++++++++++++++++++++++++++++++-
 include/pybind11/cast.h        | 10 ++++++++
 tests/test_pytypes.cpp         | 13 ++++++++++
 tests/test_pytypes.py          | 13 ++++++++++
 4 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/docs/advanced/pycpp/object.rst b/docs/advanced/pycpp/object.rst
index 6c7525ceaf..6fa8d07082 100644
--- a/docs/advanced/pycpp/object.rst
+++ b/docs/advanced/pycpp/object.rst
@@ -20,6 +20,47 @@ Available types include :class:`handle`, :class:`object`, :class:`bool_`,
     Be sure to review the :ref:`pytypes_gotchas` before using this heavily in
     your C++ API.
 
+.. _instantiating_compound_types:
+
+Instantiating compound Python types from C++
+============================================
+
+Dictionaries can be initialized in the :class:`dict` constructor:
+
+.. code-block:: cpp
+
+    using namespace pybind11::literals; // to bring in the `_a` literal
+    py::dict d("spam"_a=py::none(), "eggs"_a=42);
+
+A tuple of python objects can be instantiated using :func:`py::make_tuple`:
+
+.. code-block:: cpp
+
+    py::tuple tup = py::make_tuple(42, py::none(), "spam");
+
+Each element is converted to a supported Python type.
+
+A `simple namespace`_ can be instantiated using
+:func:`py::make_simple_namespace`:
+
+.. code-block:: cpp
+
+    using namespace pybind11::literals; // to bring in the `_a` literal
+    py::object ns = py::make_simple_namespace("spam"_a=py::none(), "eggs"_a=42);
+
+Attributes on a namespace can be modified with the :func:`py::delattr`,
+:func:`py::getattr`, and :func:`py::setattr` functions. Simple namespaces can
+be useful as lightweight stand-ins for class instances.
+
+.. note::
+
+    ``make_simple_namespace`` is not available in Python 2.
+
+.. versionchanged:: 2.8
+    ``make_simple_namespace`` added.
+
+.. _simple namespace: https://docs.python.org/3/library/types.html#types.SimpleNamespace
+
 .. _casting_back_and_forth:
 
 Casting back and forth
@@ -30,7 +71,7 @@ types to Python, which can be done using :func:`py::cast`:
 
 .. code-block:: cpp
 
-    MyClass *cls = ..;
+    MyClass *cls = ...;
     py::object obj = py::cast(cls);
 
 The reverse direction uses the following syntax:
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 718dc2de80..79bf506d81 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1018,6 +1018,16 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
     return result;
 }
 
+#if PY_VERSION_HEX >= 0x03030000
+template <typename... Args,
+          typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
+object make_simple_namespace(Args&&... args_) {
+    PyObject *ns = _PyNamespace_New(dict(std::forward<Args>(args_)...).ptr());
+    if (!ns) throw error_already_set();
+    return reinterpret_steal<object>(ns);
+}
+#endif
+
 /// \ingroup annotations
 /// Annotation for arguments
 struct arg {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index d70536d3f0..15d007a437 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -70,6 +70,19 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("dict_contains",
           [](const py::dict &dict, const char *val) { return dict.contains(val); });
 
+    // test_tuple
+    m.def("get_tuple", []() { return py::make_tuple(42, py::none(), "spam"); });
+
+#if PY_VERSION_HEX >= 0x03030000
+    // test_simple_namespace
+    m.def("get_simple_namespace", []() {
+        auto ns = py::make_simple_namespace("attr"_a=42, "x"_a="foo", "wrong"_a=1);
+        py::delattr(ns, "wrong");
+        py::setattr(ns, "right", py::int_(2));
+        return ns;
+    });
+#endif
+
     // test_str
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 8a11b18727..f873658abe 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -99,6 +99,19 @@ def test_dict(capture, doc):
     assert m.dict_keyword_constructor() == {"x": 1, "y": 2, "z": 3}
 
 
+def test_tuple():
+    assert m.get_tuple() == (42, None, "spam")
+
+
+@pytest.mark.skipif("env.PY2")
+def test_simple_namespace():
+    ns = m.get_simple_namespace()
+    assert ns.attr == 42
+    assert ns.x == "foo"
+    assert ns.right == 2
+    assert not hasattr(ns, "wrong")
+
+
 def test_str(doc):
     assert m.str_from_string().encode().decode() == "baz"
     assert m.str_from_bytes().encode().decode() == "boo"

From 59ad1e7d05d96ccc4e7090d5da7a328e4512cb7a Mon Sep 17 00:00:00 2001
From: Nick Cullen <nickmarch31@yahoo.com>
Date: Thu, 26 Aug 2021 17:12:35 +0200
Subject: [PATCH 150/638] reshape for numpy arrays (#984)

* reshape

* more tests

* Update numpy.h

* Update test_numpy_array.py

* Update numpy.h

* Update numpy.h

* Update test_numpy_array.cpp

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix merge bug

* Make clang-tidy happy

* Add xfail for PyPy

* Fix casting issue

* Address reviews on additional tests

* Fix ordering

* Do a little more reordering

* Fix typo

* Try improving tests

* Fix error in reshape

* Add one more reshape test

* streamlining new tests; removing a few stray msg

Co-authored-by: ncullen93 <ncullen.th@dartmouth.edu>
Co-authored-by: NC Cullen <nicholas.c.cullen.th@dartmouth.edu>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/numpy.h   | 21 +++++++++++++++++++--
 tests/test_numpy_array.cpp |  7 +++++++
 tests/test_numpy_array.py  | 31 ++++++++++++++++++++++++++++---
 3 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 7717059f4a..0d0cbdfa89 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -198,6 +198,8 @@ struct npy_api {
     // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
     PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
+    PyObject* (*PyArray_Newshape_)(PyObject*, PyArray_Dims*, int);
+
 private:
     enum functions {
         API_PyArray_GetNDArrayCFeatureVersion = 211,
@@ -212,10 +214,11 @@ struct npy_api {
         API_PyArray_NewCopy = 85,
         API_PyArray_NewFromDescr = 94,
         API_PyArray_DescrNewFromType = 96,
+        API_PyArray_Newshape = 135,
+        API_PyArray_Squeeze = 136,
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
         API_PyArray_GetArrayParamsFromObject = 278,
-        API_PyArray_Squeeze = 136,
         API_PyArray_SetBaseObject = 282
     };
 
@@ -243,11 +246,13 @@ struct npy_api {
         DECL_NPY_API(PyArray_NewCopy);
         DECL_NPY_API(PyArray_NewFromDescr);
         DECL_NPY_API(PyArray_DescrNewFromType);
+        DECL_NPY_API(PyArray_Newshape);
+        DECL_NPY_API(PyArray_Squeeze);
         DECL_NPY_API(PyArray_DescrConverter);
         DECL_NPY_API(PyArray_EquivTypes);
         DECL_NPY_API(PyArray_GetArrayParamsFromObject);
-        DECL_NPY_API(PyArray_Squeeze);
         DECL_NPY_API(PyArray_SetBaseObject);
+
 #undef DECL_NPY_API
         return api;
     }
@@ -785,6 +790,18 @@ class array : public buffer {
         if (isinstance<array>(new_array)) { *this = std::move(new_array); }
     }
 
+    /// Optional `order` parameter omitted, to be added as needed.
+    array reshape(ShapeContainer new_shape) {
+        detail::npy_api::PyArray_Dims d
+            = {reinterpret_cast<Py_intptr_t *>(new_shape->data()), int(new_shape->size())};
+        auto new_array
+            = reinterpret_steal<array>(detail::npy_api::get().PyArray_Newshape_(m_ptr, &d, 0));
+        if (!new_array) {
+            throw error_already_set();
+        }
+        return new_array;
+    }
+
     /// Ensure that the argument is a NumPy array
     /// In case of an error, nullptr is returned and the Python error is cleared.
     static array ensure(handle h, int ExtraFlags = 0) {
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 5c22a3d25b..4ccfd279b0 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -405,6 +405,13 @@ TEST_SUBMODULE(numpy_array, sm) {
         return a;
     });
 
+    sm.def("reshape_initializer_list", [](py::array_t<int> a, size_t N, size_t M, size_t O) {
+        return a.reshape({N, M, O});
+    });
+    sm.def("reshape_tuple", [](py::array_t<int> a, const std::vector<int> &new_shape) {
+        return a.reshape(new_shape);
+    });
+
     sm.def("index_using_ellipsis",
            [](const py::array &a) { return a[py::make_tuple(0, py::ellipsis(), 0)]; });
 
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 69ba9d4952..e96454be48 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -411,7 +411,7 @@ def test_array_unchecked_fixed_dims(msg):
     assert m.proxy_auxiliaries2_const_ref(z1)
 
 
-def test_array_unchecked_dyn_dims(msg):
+def test_array_unchecked_dyn_dims():
     z1 = np.array([[1, 2], [3, 4]], dtype="float64")
     m.proxy_add2_dyn(z1, 10)
     assert np.all(z1 == [[11, 12], [13, 14]])
@@ -444,7 +444,7 @@ def test_initializer_list():
     assert m.array_initializer_list4().shape == (1, 2, 3, 4)
 
 
-def test_array_resize(msg):
+def test_array_resize():
     a = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9], dtype="float64")
     m.array_reshape2(a)
     assert a.size == 9
@@ -470,12 +470,37 @@ def test_array_resize(msg):
 
 
 @pytest.mark.xfail("env.PYPY")
-def test_array_create_and_resize(msg):
+def test_array_create_and_resize():
     a = m.create_and_resize(2)
     assert a.size == 4
     assert np.all(a == 42.0)
 
 
+def test_reshape_initializer_list():
+    a = np.arange(2 * 7 * 3) + 1
+    x = m.reshape_initializer_list(a, 2, 7, 3)
+    assert x.shape == (2, 7, 3)
+    assert list(x[1][4]) == [34, 35, 36]
+    with pytest.raises(ValueError) as excinfo:
+        m.reshape_initializer_list(a, 1, 7, 3)
+    assert str(excinfo.value) == "cannot reshape array of size 42 into shape (1,7,3)"
+
+
+def test_reshape_tuple():
+    a = np.arange(3 * 7 * 2) + 1
+    x = m.reshape_tuple(a, (3, 7, 2))
+    assert x.shape == (3, 7, 2)
+    assert list(x[1][4]) == [23, 24]
+    y = m.reshape_tuple(x, (x.size,))
+    assert y.shape == (42,)
+    with pytest.raises(ValueError) as excinfo:
+        m.reshape_tuple(a, (3, 7, 1))
+    assert str(excinfo.value) == "cannot reshape array of size 42 into shape (3,7,1)"
+    with pytest.raises(ValueError) as excinfo:
+        m.reshape_tuple(a, ())
+    assert str(excinfo.value) == "cannot reshape array of size 42 into shape ()"
+
+
 def test_index_using_ellipsis():
     a = m.index_using_ellipsis(np.zeros((5, 6, 7)))
     assert a.shape == (6,)

From db44afa33b21af09f81c70ee6449c4a4d93fbeca Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 26 Aug 2021 10:52:13 -0700
Subject: [PATCH 151/638] tests: fix pytest usage on Python 3.10 (#3221)

---
 tests/requirements.txt | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/requirements.txt b/tests/requirements.txt
index 00cb5f119f..069122b884 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -2,11 +2,11 @@
 numpy==1.16.6; python_version<"3.6" and sys_platform!="win32"
 numpy==1.18.0; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.6"
 numpy==1.19.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version=="3.6"
-numpy==1.20.0; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
+numpy==1.21.2; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
+numpy==1.21.2; platform_python_implementation!="PyPy" and sys_platform=="linux" and python_version=="3.10"
 pytest==4.6.9; python_version<"3.5"
 pytest==6.1.2; python_version=="3.5"
-pytest==6.2.1; python_version>="3.6" and python_version<="3.9"
-pytest @ git+https://github.com/pytest-dev/pytest@c117bc350ec1e570672fda3b2ad234fd52e72b53; python_version>="3.10"
+pytest==6.2.4; python_version>="3.6"
 pytest-timeout
 scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version<"3.6"
 scipy==1.5.4; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.10"

From 503ff2a6fbb498138c0b7e85419de491c9860a93 Mon Sep 17 00:00:00 2001
From: Nick Cullen <nickmarch31@yahoo.com>
Date: Thu, 26 Aug 2021 23:11:01 +0200
Subject: [PATCH 152/638] view for numpy arrays (#987)

* reshape

* more tests

* Update numpy.h

* Update test_numpy_array.py

* array view

* test

* Update test_numpy_array.cpp

* Update numpy.h

* Update numpy.h

* Update test_numpy_array.cpp

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix merge bug

* Make clang-tidy happy

* Add xfail for PyPy

* Fix casting issue

* Fix formatting

* Apply clang-tidy

* Address reviews on additional tests

* Fix ordering

* Do a little more reordering

* Fix typo

* Try improving tests

* Fix error in reshape

* Add one more reshape test

* Fix bugs and add test

* Relax test

* streamlining new tests; removing a few stray msg

* Fix style revert

* Fix clang-tidy

* Misc tweaks:
* Comment: matching style in file (///), responsibility sentence, consistent punctuation.
* Replacing `unsigned char` with `uint8_t` for max consistency.
* Removing `1` from `array_view1` because there is only one.

* Partial clang-format-diff.

Co-authored-by: ncullen93 <ncullen.th@dartmouth.edu>
Co-authored-by: NC Cullen <nicholas.c.cullen.th@dartmouth.edu>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/numpy.h   | 18 ++++++++++++++++++
 tests/test_numpy_array.cpp |  3 +++
 tests/test_numpy_array.py  | 15 +++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 0d0cbdfa89..fa128efdd0 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -199,6 +199,7 @@ struct npy_api {
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
     PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
     PyObject* (*PyArray_Newshape_)(PyObject*, PyArray_Dims*, int);
+    PyObject* (*PyArray_View_)(PyObject*, PyObject*, PyObject*);
 
 private:
     enum functions {
@@ -216,6 +217,7 @@ struct npy_api {
         API_PyArray_DescrNewFromType = 96,
         API_PyArray_Newshape = 135,
         API_PyArray_Squeeze = 136,
+        API_PyArray_View = 137,
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
         API_PyArray_GetArrayParamsFromObject = 278,
@@ -248,6 +250,7 @@ struct npy_api {
         DECL_NPY_API(PyArray_DescrNewFromType);
         DECL_NPY_API(PyArray_Newshape);
         DECL_NPY_API(PyArray_Squeeze);
+        DECL_NPY_API(PyArray_View);
         DECL_NPY_API(PyArray_DescrConverter);
         DECL_NPY_API(PyArray_EquivTypes);
         DECL_NPY_API(PyArray_GetArrayParamsFromObject);
@@ -802,6 +805,21 @@ class array : public buffer {
         return new_array;
     }
 
+    /// Create a view of an array in a different data type.
+    /// This function may fundamentally reinterpret the data in the array.
+    /// It is the responsibility of the caller to ensure that this is safe.
+    /// Only supports the `dtype` argument, the `type` argument is omitted,
+    /// to be added as needed.
+    array view(const std::string &dtype) {
+        auto &api = detail::npy_api::get();
+        auto new_view = reinterpret_steal<array>(api.PyArray_View_(
+            m_ptr, dtype::from_args(pybind11::str(dtype)).release().ptr(), nullptr));
+        if (!new_view) {
+            throw error_already_set();
+        }
+        return new_view;
+    }
+
     /// Ensure that the argument is a NumPy array
     /// In case of an error, nullptr is returned and the Python error is cleared.
     static array ensure(handle h, int ExtraFlags = 0) {
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 4ccfd279b0..30a71acc9b 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -405,6 +405,9 @@ TEST_SUBMODULE(numpy_array, sm) {
         return a;
     });
 
+    sm.def("array_view",
+           [](py::array_t<uint8_t> a, const std::string &dtype) { return a.view(dtype); });
+
     sm.def("reshape_initializer_list", [](py::array_t<int> a, size_t N, size_t M, size_t O) {
         return a.reshape({N, M, O});
     });
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index e96454be48..e4138f0239 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -476,6 +476,21 @@ def test_array_create_and_resize():
     assert np.all(a == 42.0)
 
 
+def test_array_view():
+    a = np.ones(100 * 4).astype("uint8")
+    a_float_view = m.array_view(a, "float32")
+    assert a_float_view.shape == (100 * 1,)  # 1 / 4 bytes = 8 / 32
+
+    a_int16_view = m.array_view(a, "int16")  # 1 / 2 bytes = 16 / 32
+    assert a_int16_view.shape == (100 * 2,)
+
+
+def test_array_view_invalid():
+    a = np.ones(100 * 4).astype("uint8")
+    with pytest.raises(TypeError):
+        m.array_view(a, "deadly_dtype")
+
+
 def test_reshape_initializer_list():
     a = np.arange(2 * 7 * 3) + 1
     x = m.reshape_initializer_list(a, 2, 7, 3)

From 930bb16c797af642ed4d216cd8972bbd3276dceb Mon Sep 17 00:00:00 2001
From: Dan <drmoose@users.noreply.github.com>
Date: Thu, 26 Aug 2021 17:12:54 -0400
Subject: [PATCH 153/638] Call PySys_SetArgv when initializing interpreter.
 (#2341)

* Call PySys_SetArgv when initializing interpreter.

* Document argc/argv parameters in initialize_interpreter.

* Remove manual memory management from set_interpreter_argv in favor of smart pointers.

* Use size_t for indexers in set_interpreter_argv.

* Minimize macros for flow control in set_interpreter_argv.

* Fix 'unused variable' warning on Py2

* whitespace

* Define wide_char_arg_deleter outside set_interpreter_argv.

* Do sys.path workaround in C++ rather than eval.

* Factor out wchar conversion to a separate function.

* Restore widened_argv variable declaration.

* Fix undeclared widened_arg variable on some paths.

* Use delete[] to match new wchar_t[].

* Fix compiler errors

* Use PY_VERSION_HEX for a cleaner CVE-2008-5983 mode check.

* Fix typo

* Use explicit type for deleter so delete[] works cross-compiler.

* Always use PySys_SetArgvEx because pybind11 doesn't support pythons that don't include it.

* Remove pointless ternary operator.

* Use unique_ptr.reset instead of a second initialization.

* Rename add_program_dir_to_path parameter to clarify intent.

* Add defined() check before evaluating HAVE_BROKEN_MBSTOWCS.

* Apply clang-tidy fixes

* Pre-commit

* refactor: use const for set_interpreter_argv

* Try to fix const issue and allocate vector properly

* fix: copy strings on Python 2

* Applying clang-format-diff relative to master.

The only manual change is an added empty line between pybind11 and system `#include`s.

```
git diff -U0 --no-color master | python3 $HOME/clone/llvm-project/clang/tools/clang-format/clang-format-diff.py -p1 -style=file -i
```

Co-authored-by: Boris Staletic <boris.staletic@gmail.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/embed.h              | 101 ++++++++++++++++++++++++--
 tests/test_embed/test_interpreter.cpp |  24 ++++++
 tests/test_embed/test_interpreter.py  |   5 ++
 3 files changed, 122 insertions(+), 8 deletions(-)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 6e777830f9..7b5d7cd24a 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -12,6 +12,9 @@
 #include "pybind11.h"
 #include "eval.h"
 
+#include <memory>
+#include <vector>
+
 #if defined(PYPY_VERSION)
 #  error Embedding the interpreter is not supported with PyPy
 #endif
@@ -83,29 +86,106 @@ struct embedded_module {
     }
 };
 
+struct wide_char_arg_deleter {
+    void operator()(wchar_t *ptr) const {
+#if PY_VERSION_HEX >= 0x030500f0
+        // API docs: https://docs.python.org/3/c-api/sys.html#c.Py_DecodeLocale
+        PyMem_RawFree(ptr);
+#else
+        delete[] ptr;
+#endif
+    }
+};
+
+inline wchar_t *widen_chars(const char *safe_arg) {
+#if PY_VERSION_HEX >= 0x030500f0
+    wchar_t *widened_arg = Py_DecodeLocale(safe_arg, nullptr);
+#else
+    wchar_t *widened_arg = nullptr;
+#    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
+    size_t count = strlen(safe_arg);
+#    else
+    size_t count = mbstowcs(nullptr, safe_arg, 0);
+#    endif
+    if (count != static_cast<size_t>(-1)) {
+        widened_arg = new wchar_t[count + 1];
+        mbstowcs(widened_arg, safe_arg, count + 1);
+    }
+#endif
+    return widened_arg;
+}
+
+/// Python 2.x/3.x-compatible version of `PySys_SetArgv`
+inline void set_interpreter_argv(int argc, const char *const *argv, bool add_program_dir_to_path) {
+    // Before it was special-cased in python 3.8, passing an empty or null argv
+    // caused a segfault, so we have to reimplement the special case ourselves.
+    bool special_case = (argv == nullptr || argc <= 0);
+
+    const char *const empty_argv[]{"\0"};
+    const char *const *safe_argv = special_case ? empty_argv : argv;
+    if (special_case)
+        argc = 1;
+
+    auto argv_size = static_cast<size_t>(argc);
+#if PY_MAJOR_VERSION >= 3
+    // SetArgv* on python 3 takes wchar_t, so we have to convert.
+    std::unique_ptr<wchar_t *[]> widened_argv(new wchar_t *[argv_size]);
+    std::vector<std::unique_ptr<wchar_t[], wide_char_arg_deleter>> widened_argv_entries;
+    widened_argv_entries.reserve(argv_size);
+    for (size_t ii = 0; ii < argv_size; ++ii) {
+        widened_argv_entries.emplace_back(widen_chars(safe_argv[ii]));
+        if (!widened_argv_entries.back()) {
+            // A null here indicates a character-encoding failure or the python
+            // interpreter out of memory. Give up.
+            return;
+        }
+        widened_argv[ii] = widened_argv_entries.back().get();
+    }
+
+    auto pysys_argv = widened_argv.get();
+#else
+    // python 2.x
+    std::vector<std::string> strings{safe_argv, safe_argv + argv_size};
+    std::vector<char *> char_strings{argv_size};
+    for (std::size_t i = 0; i < argv_size; ++i)
+        char_strings[i] = &strings[i][0];
+    char **pysys_argv = char_strings.data();
+#endif
+
+    PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
+}
+
 PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
     Initialize the Python interpreter. No other pybind11 or CPython API functions can be
     called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
-    optional parameter can be used to skip the registration of signal handlers (see the
-    `Python documentation`_ for details). Calling this function again after the interpreter
-    has already been initialized is a fatal error.
+    optional `init_signal_handlers` parameter can be used to skip the registration of
+    signal handlers (see the `Python documentation`_ for details). Calling this function
+    again after the interpreter has already been initialized is a fatal error.
 
     If initializing the Python interpreter fails, then the program is terminated.  (This
     is controlled by the CPython runtime and is an exception to pybind11's normal behavior
     of throwing exceptions on errors.)
 
+    The remaining optional parameters, `argc`, `argv`, and `add_program_dir_to_path` are
+    used to populate ``sys.argv`` and ``sys.path``.
+    See the |PySys_SetArgvEx documentation|_ for details.
+
     .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
+    .. |PySys_SetArgvEx documentation| replace:: ``PySys_SetArgvEx`` documentation
+    .. _PySys_SetArgvEx documentation: https://docs.python.org/3/c-api/init.html#c.PySys_SetArgvEx
  \endrst */
-inline void initialize_interpreter(bool init_signal_handlers = true) {
+inline void initialize_interpreter(bool init_signal_handlers = true,
+                                   int argc = 0,
+                                   const char *const *argv = nullptr,
+                                   bool add_program_dir_to_path = true) {
     if (Py_IsInitialized() != 0)
         pybind11_fail("The interpreter is already running");
 
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
 
-    // Make .py files in the working directory available by default
-    module_::import("sys").attr("path").cast<list>().append(".");
+    detail::set_interpreter_argv(argc, argv, add_program_dir_to_path);
 }
 
 /** \rst
@@ -167,6 +247,8 @@ inline void finalize_interpreter() {
     Scope guard version of `initialize_interpreter` and `finalize_interpreter`.
     This a move-only guard and only a single instance can exist.
 
+    See `initialize_interpreter` for a discussion of its constructor arguments.
+
     .. code-block:: cpp
 
         #include <pybind11/embed.h>
@@ -178,8 +260,11 @@ inline void finalize_interpreter() {
  \endrst */
 class scoped_interpreter {
 public:
-    scoped_interpreter(bool init_signal_handlers = true) {
-        initialize_interpreter(init_signal_handlers);
+    scoped_interpreter(bool init_signal_handlers = true,
+                       int argc = 0,
+                       const char *const *argv = nullptr,
+                       bool add_program_dir_to_path = true) {
+        initialize_interpreter(init_signal_handlers, argc, argv, add_program_dir_to_path);
     }
 
     scoped_interpreter(const scoped_interpreter &) = delete;
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index b40ff48175..78b64be6b0 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -23,6 +23,7 @@ class Widget {
 
     std::string the_message() const { return message; }
     virtual int the_answer() const = 0;
+    virtual std::string argv0() const = 0;
 
 private:
     std::string message;
@@ -32,6 +33,7 @@ class PyWidget final : public Widget {
     using Widget::Widget;
 
     int the_answer() const override { PYBIND11_OVERRIDE_PURE(int, Widget, the_answer); }
+    std::string argv0() const override { PYBIND11_OVERRIDE_PURE(std::string, Widget, argv0); }
 };
 
 PYBIND11_EMBEDDED_MODULE(widget_module, m) {
@@ -299,3 +301,25 @@ TEST_CASE("Reload module from file") {
     result = module_.attr("test")().cast<int>();
     REQUIRE(result == 2);
 }
+
+TEST_CASE("sys.argv gets initialized properly") {
+    py::finalize_interpreter();
+    {
+        py::scoped_interpreter default_scope;
+        auto module = py::module::import("test_interpreter");
+        auto py_widget = module.attr("DerivedWidget")("The question");
+        const auto &cpp_widget = py_widget.cast<const Widget &>();
+        REQUIRE(cpp_widget.argv0().empty());
+    }
+
+    {
+        char *argv[] = {strdup("a.out")};
+        py::scoped_interpreter argv_scope(true, 1, argv);
+        free(argv[0]);
+        auto module = py::module::import("test_interpreter");
+        auto py_widget = module.attr("DerivedWidget")("The question");
+        const auto &cpp_widget = py_widget.cast<const Widget &>();
+        REQUIRE(cpp_widget.argv0() == "a.out");
+    }
+    py::initialize_interpreter();
+}
diff --git a/tests/test_embed/test_interpreter.py b/tests/test_embed/test_interpreter.py
index 6174ede446..5ab55a4b37 100644
--- a/tests/test_embed/test_interpreter.py
+++ b/tests/test_embed/test_interpreter.py
@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+import sys
+
 from widget_module import Widget
 
 
@@ -8,3 +10,6 @@ def __init__(self, message):
 
     def the_answer(self):
         return 42
+
+    def argv0(self):
+        return sys.argv[0]

From cb60ed49e46fb31cc578b86b2178d8ce574617ad Mon Sep 17 00:00:00 2001
From: Ye Zhihao <vigilans@foxmail.com>
Date: Fri, 27 Aug 2021 05:34:24 +0800
Subject: [PATCH 154/638] Fix enum value's __int__ returning non-int when
 underlying type is bool or of char type (#1334)

* Use equivalent_integer for enum's Scalar decision

* Add test for char underlying enum

* Support translating bool type in enum's Scalar

* Add test for bool underlying enum

* Fix comment in test

* Switch from `PYBIND11_CPP20` macro to `PYBIND11_HAS_U8STRING`

* Refine tests

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/pybind11.h | 21 +++++++++++--
 tests/test_enum.cpp         | 61 +++++++++++++++++++++++++++++++++++++
 tests/test_enum.py          | 28 +++++++++++++++++
 3 files changed, 108 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 47b042147b..89f9cbd9b8 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1814,6 +1814,19 @@ struct enum_base {
     handle m_parent;
 };
 
+template <bool is_signed, size_t length> struct equivalent_integer {};
+template <> struct equivalent_integer<true,  1> { using type = int8_t;   };
+template <> struct equivalent_integer<false, 1> { using type = uint8_t;  };
+template <> struct equivalent_integer<true,  2> { using type = int16_t;  };
+template <> struct equivalent_integer<false, 2> { using type = uint16_t; };
+template <> struct equivalent_integer<true,  4> { using type = int32_t;  };
+template <> struct equivalent_integer<false, 4> { using type = uint32_t; };
+template <> struct equivalent_integer<true,  8> { using type = int64_t;  };
+template <> struct equivalent_integer<false, 8> { using type = uint64_t; };
+
+template <typename IntLike>
+using equivalent_integer_t = typename equivalent_integer<std::is_signed<IntLike>::value, sizeof(IntLike)>::type;
+
 PYBIND11_NAMESPACE_END(detail)
 
 /// Binds C++ enumerations and enumeration classes to Python
@@ -1824,13 +1837,17 @@ template <typename Type> class enum_ : public class_<Type> {
     using Base::attr;
     using Base::def_property_readonly;
     using Base::def_property_readonly_static;
-    using Scalar = typename std::underlying_type<Type>::type;
+    using Underlying = typename std::underlying_type<Type>::type;
+    // Scalar is the integer representation of underlying type
+    using Scalar = detail::conditional_t<detail::any_of<
+        detail::is_std_char_type<Underlying>, std::is_same<Underlying, bool>
+    >::value, detail::equivalent_integer_t<Underlying>, Underlying>;
 
     template <typename... Extra>
     enum_(const handle &scope, const char *name, const Extra&... extra)
       : class_<Type>(scope, name, extra...), m_base(*this, scope) {
         constexpr bool is_arithmetic = detail::any_of<std::is_same<arithmetic, Extra>...>::value;
-        constexpr bool is_convertible = std::is_convertible<Type, Scalar>::value;
+        constexpr bool is_convertible = std::is_convertible<Type, Underlying>::value;
         m_base.init(is_arithmetic, is_convertible);
 
         def(init([](Scalar i) { return static_cast<Type>(i); }), arg("value"));
diff --git a/tests/test_enum.cpp b/tests/test_enum.cpp
index 3153089208..40c48d412a 100644
--- a/tests/test_enum.cpp
+++ b/tests/test_enum.cpp
@@ -84,4 +84,65 @@ TEST_SUBMODULE(enums, m) {
             .value("ONE", SimpleEnum::THREE)
             .export_values();
     });
+
+    // test_enum_scalar
+    enum UnscopedUCharEnum : unsigned char {};
+    enum class ScopedShortEnum : short {};
+    enum class ScopedLongEnum : long {};
+    enum UnscopedUInt64Enum : std::uint64_t {};
+    static_assert(py::detail::all_of<
+        std::is_same<py::enum_<UnscopedUCharEnum>::Scalar, unsigned char>,
+        std::is_same<py::enum_<ScopedShortEnum>::Scalar, short>,
+        std::is_same<py::enum_<ScopedLongEnum>::Scalar, long>,
+        std::is_same<py::enum_<UnscopedUInt64Enum>::Scalar, std::uint64_t>
+    >::value, "Error during the deduction of enum's scalar type with normal integer underlying");
+
+    // test_enum_scalar_with_char_underlying
+    enum class ScopedCharEnum   : char     { Zero, Positive };
+    enum class ScopedWCharEnum  : wchar_t  { Zero, Positive };
+    enum class ScopedChar32Enum : char32_t { Zero, Positive };
+    enum class ScopedChar16Enum : char16_t { Zero, Positive };
+
+    // test the scalar of char type enums according to chapter 'Character types'
+    // from https://en.cppreference.com/w/cpp/language/types
+    static_assert(py::detail::any_of<
+        std::is_same<py::enum_<ScopedCharEnum>::Scalar, signed char>, // e.g. gcc on x86
+        std::is_same<py::enum_<ScopedCharEnum>::Scalar, unsigned char>  // e.g. arm linux
+    >::value, "char should be cast to either signed char or unsigned char");
+    static_assert(
+        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 2 ||
+        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 4
+    , "wchar_t should be either 16 bits (Windows) or 32 (everywhere else)");
+    static_assert(py::detail::all_of<
+        std::is_same<py::enum_<ScopedChar32Enum>::Scalar, std::uint_least32_t>,
+        std::is_same<py::enum_<ScopedChar16Enum>::Scalar, std::uint_least16_t>
+    >::value, "char32_t, char16_t (and char8_t)'s size, signedness, and alignment is determined");
+#if defined(PYBIND11_HAS_U8STRING)
+    enum class ScopedChar8Enum : char8_t { Zero, Positive };
+    static_assert(std::is_same<py::enum_<ScopedChar8Enum>::Scalar, unsigned char>::value);
+#endif
+
+    // test_char_underlying_enum
+    py::enum_<ScopedCharEnum>(m, "ScopedCharEnum")
+        .value("Zero", ScopedCharEnum::Zero)
+        .value("Positive", ScopedCharEnum::Positive);
+    py::enum_<ScopedWCharEnum>(m, "ScopedWCharEnum")
+        .value("Zero", ScopedWCharEnum::Zero)
+        .value("Positive", ScopedWCharEnum::Positive);
+    py::enum_<ScopedChar32Enum>(m, "ScopedChar32Enum")
+        .value("Zero", ScopedChar32Enum::Zero)
+        .value("Positive", ScopedChar32Enum::Positive);
+    py::enum_<ScopedChar16Enum>(m, "ScopedChar16Enum")
+        .value("Zero", ScopedChar16Enum::Zero)
+        .value("Positive", ScopedChar16Enum::Positive);
+
+    // test_bool_underlying_enum
+    enum class ScopedBoolEnum : bool { FALSE, TRUE };
+
+    // bool is unsigned (std::is_signed returns false) and 1-byte long, so represented with u8
+    static_assert(std::is_same<py::enum_<ScopedBoolEnum>::Scalar, std::uint8_t>::value, "");
+
+    py::enum_<ScopedBoolEnum>(m, "ScopedBoolEnum")
+        .value("FALSE", ScopedBoolEnum::FALSE)
+        .value("TRUE", ScopedBoolEnum::TRUE);
 }
diff --git a/tests/test_enum.py b/tests/test_enum.py
index 62f9426eee..11cab6ddf5 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -218,10 +218,16 @@ def test_binary_operators():
 def test_enum_to_int():
     m.test_enum_to_int(m.Flags.Read)
     m.test_enum_to_int(m.ClassWithUnscopedEnum.EMode.EFirstMode)
+    m.test_enum_to_int(m.ScopedCharEnum.Positive)
+    m.test_enum_to_int(m.ScopedBoolEnum.TRUE)
     m.test_enum_to_uint(m.Flags.Read)
     m.test_enum_to_uint(m.ClassWithUnscopedEnum.EMode.EFirstMode)
+    m.test_enum_to_uint(m.ScopedCharEnum.Positive)
+    m.test_enum_to_uint(m.ScopedBoolEnum.TRUE)
     m.test_enum_to_long_long(m.Flags.Read)
     m.test_enum_to_long_long(m.ClassWithUnscopedEnum.EMode.EFirstMode)
+    m.test_enum_to_long_long(m.ScopedCharEnum.Positive)
+    m.test_enum_to_long_long(m.ScopedBoolEnum.TRUE)
 
 
 def test_duplicate_enum_name():
@@ -230,6 +236,28 @@ def test_duplicate_enum_name():
     assert str(excinfo.value) == 'SimpleEnum: element "ONE" already exists!'
 
 
+def test_char_underlying_enum():  # Issue #1331/PR #1334:
+    assert type(m.ScopedCharEnum.Positive.__int__()) is int
+    assert int(m.ScopedChar16Enum.Zero) == 0  # int() call should successfully return
+    assert hash(m.ScopedChar32Enum.Positive) == 1
+    assert m.ScopedCharEnum.Positive.__getstate__() == 1  # return type is long in py2.x
+    assert m.ScopedWCharEnum(1) == m.ScopedWCharEnum.Positive
+    with pytest.raises(TypeError):
+        # Enum should construct with a int, even with char underlying type
+        m.ScopedWCharEnum("0")
+
+
+def test_bool_underlying_enum():
+    assert type(m.ScopedBoolEnum.TRUE.__int__()) is int
+    assert int(m.ScopedBoolEnum.FALSE) == 0
+    assert hash(m.ScopedBoolEnum.TRUE) == 1
+    assert m.ScopedBoolEnum.TRUE.__getstate__() == 1
+    assert m.ScopedBoolEnum(1) == m.ScopedBoolEnum.TRUE
+    # Enum could construct with a bool
+    # (bool is a strict subclass of int, and False will be converted to 0)
+    assert m.ScopedBoolEnum(False) == m.ScopedBoolEnum.FALSE
+
+
 def test_docstring_signatures():
     for enum_type in [m.ScopedEnum, m.UnscopedEnum]:
         for attr in enum_type.__dict__.values():

From 777352fcd10bd9b57a8f626a6c7397596466ee55 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 28 Aug 2021 16:40:46 -0700
Subject: [PATCH 155/638] Adding `ssize_t_cast` to support passing `size_t` or
 `ssize_t` values where `ssize_t` is needed. (#3219)

* Trivial change to avoid (ssize_t) cast.

* Demo for safe_ssize_t idea.

* Removing safe_ssize_t.cpp (proof-of-concept code) to not upset the GHA Format workflow.

* Completing changes in pytypes.h

* New ssize_t_cast (better replacement for safe_ssize_t).

* clang-format-diff (no manual changes).

* bytes_ssize_t -Wnarrowing reproducer (see PR #2692).

* Backing out tuple(), list() ssize_t support, for compatibility with older compilers (to resolve link failures).

* Bug fix: missing `py::` for `py::ssize_t`

* Restoring tuple(), list() ssize_t support, but passing `size` by value, for compatibility with older compilers (to resolve link failures).

* Full test coverage of all functions with modified signatures.
---
 include/pybind11/detail/common.h |  6 +++
 include/pybind11/pytypes.h       | 66 +++++++++++++++++++------------
 include/pybind11/stl.h           |  8 ++--
 tests/test_pytypes.cpp           | 67 ++++++++++++++++++++++++++++++++
 tests/test_pytypes.py            | 39 +++++++++++++++++++
 5 files changed, 158 insertions(+), 28 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 5050da802a..e4f00293ec 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -410,6 +410,12 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 using ssize_t = Py_ssize_t;
 using size_t  = std::size_t;
 
+template <typename IntType>
+inline ssize_t ssize_t_cast(const IntType &val) {
+    static_assert(sizeof(IntType) <= sizeof(ssize_t), "Implicit narrowing is not permitted.");
+    return static_cast<ssize_t>(val);
+}
+
 /// Approach used to cast a previously unknown C++ instance into a Python object
 enum class return_value_policy : uint8_t {
     /** This is the default return value policy, which falls back to the policy
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 85f6a40a48..5e699e53f4 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -661,15 +661,17 @@ struct generic_item {
 struct sequence_item {
     using key_type = size_t;
 
-    static object get(handle obj, size_t index) {
-        PyObject *result = PySequence_GetItem(obj.ptr(), static_cast<ssize_t>(index));
+    template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    static object get(handle obj, const IdxType &index) {
+        PyObject *result = PySequence_GetItem(obj.ptr(), ssize_t_cast(index));
         if (!result) { throw error_already_set(); }
         return reinterpret_steal<object>(result);
     }
 
-    static void set(handle obj, size_t index, handle val) {
+    template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    static void set(handle obj, const IdxType &index, handle val) {
         // PySequence_SetItem does not steal a reference to 'val'
-        if (PySequence_SetItem(obj.ptr(), static_cast<ssize_t>(index), val.ptr()) != 0) {
+        if (PySequence_SetItem(obj.ptr(), ssize_t_cast(index), val.ptr()) != 0) {
             throw error_already_set();
         }
     }
@@ -678,15 +680,17 @@ struct sequence_item {
 struct list_item {
     using key_type = size_t;
 
-    static object get(handle obj, size_t index) {
-        PyObject *result = PyList_GetItem(obj.ptr(), static_cast<ssize_t>(index));
+    template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    static object get(handle obj, const IdxType &index) {
+        PyObject *result = PyList_GetItem(obj.ptr(), ssize_t_cast(index));
         if (!result) { throw error_already_set(); }
         return reinterpret_borrow<object>(result);
     }
 
-    static void set(handle obj, size_t index, handle val) {
+    template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    static void set(handle obj, const IdxType &index, handle val) {
         // PyList_SetItem steals a reference to 'val'
-        if (PyList_SetItem(obj.ptr(), static_cast<ssize_t>(index), val.inc_ref().ptr()) != 0) {
+        if (PyList_SetItem(obj.ptr(), ssize_t_cast(index), val.inc_ref().ptr()) != 0) {
             throw error_already_set();
         }
     }
@@ -695,15 +699,17 @@ struct list_item {
 struct tuple_item {
     using key_type = size_t;
 
-    static object get(handle obj, size_t index) {
-        PyObject *result = PyTuple_GetItem(obj.ptr(), static_cast<ssize_t>(index));
+    template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    static object get(handle obj, const IdxType &index) {
+        PyObject *result = PyTuple_GetItem(obj.ptr(), ssize_t_cast(index));
         if (!result) { throw error_already_set(); }
         return reinterpret_borrow<object>(result);
     }
 
-    static void set(handle obj, size_t index, handle val) {
+    template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    static void set(handle obj, const IdxType &index, handle val) {
         // PyTuple_SetItem steals a reference to 'val'
-        if (PyTuple_SetItem(obj.ptr(), static_cast<ssize_t>(index), val.inc_ref().ptr()) != 0) {
+        if (PyTuple_SetItem(obj.ptr(), ssize_t_cast(index), val.inc_ref().ptr()) != 0) {
             throw error_already_set();
         }
     }
@@ -1043,8 +1049,9 @@ class str : public object {
 public:
     PYBIND11_OBJECT_CVT(str, object, PYBIND11_STR_CHECK_FUN, raw_str)
 
-    str(const char *c, size_t n)
-        : object(PyUnicode_FromStringAndSize(c, (ssize_t) n), stolen_t{}) {
+    template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
+    str(const char *c, const SzType &n)
+        : object(PyUnicode_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate string object!");
     }
 
@@ -1116,8 +1123,9 @@ class bytes : public object {
         if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
     }
 
-    bytes(const char *c, size_t n)
-        : object(PYBIND11_BYTES_FROM_STRING_AND_SIZE(c, (ssize_t) n), stolen_t{}) {
+    template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
+    bytes(const char *c, const SzType &n)
+        : object(PYBIND11_BYTES_FROM_STRING_AND_SIZE(c, ssize_t_cast(n)), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
     }
 
@@ -1160,7 +1168,7 @@ inline str::str(const bytes& b) {
     ssize_t length = 0;
     if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length))
         pybind11_fail("Unable to extract bytes contents!");
-    auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, (ssize_t) length));
+    auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, length));
     if (!obj)
         pybind11_fail("Could not allocate string object!");
     m_ptr = obj.release().ptr();
@@ -1172,8 +1180,9 @@ class bytearray : public object {
 public:
     PYBIND11_OBJECT_CVT(bytearray, object, PyByteArray_Check, PyByteArray_FromObject)
 
-    bytearray(const char *c, size_t n)
-        : object(PyByteArray_FromStringAndSize(c, (ssize_t) n), stolen_t{}) {
+    template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
+    bytearray(const char *c, const SzType &n)
+        : object(PyByteArray_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate bytearray object!");
     }
 
@@ -1398,7 +1407,10 @@ class capsule : public object {
 class tuple : public object {
 public:
     PYBIND11_OBJECT_CVT(tuple, object, PyTuple_Check, PySequence_Tuple)
-    explicit tuple(size_t size = 0) : object(PyTuple_New((ssize_t) size), stolen_t{}) {
+    template <typename SzType = ssize_t,
+              detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
+    // Some compilers generate link errors when using `const SzType &` here:
+    explicit tuple(SzType size = 0) : object(PyTuple_New(ssize_t_cast(size)), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate tuple object!");
     }
     size_t size() const { return (size_t) PyTuple_Size(m_ptr); }
@@ -1467,7 +1479,10 @@ class sequence : public object {
 class list : public object {
 public:
     PYBIND11_OBJECT_CVT(list, object, PyList_Check, PySequence_List)
-    explicit list(size_t size = 0) : object(PyList_New((ssize_t) size), stolen_t{}) {
+    template <typename SzType = ssize_t,
+              detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
+    // Some compilers generate link errors when using `const SzType &` here:
+    explicit list(SzType size = 0) : object(PyList_New(ssize_t_cast(size)), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate list object!");
     }
     size_t size() const { return (size_t) PyList_Size(m_ptr); }
@@ -1479,9 +1494,12 @@ class list : public object {
     template <typename T> void append(T &&val) /* py-non-const */ {
         PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
     }
-    template <typename T> void insert(size_t index, T &&val) /* py-non-const */ {
-        PyList_Insert(m_ptr, static_cast<ssize_t>(index),
-            detail::object_or_cast(std::forward<T>(val)).ptr());
+    template <typename IdxType,
+              typename ValType,
+              detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
+    void insert(const IdxType &index, ValType &&val) /* py-non-const */ {
+        PyList_Insert(
+            m_ptr, ssize_t_cast(index), detail::object_or_cast(std::forward<ValType>(val)).ptr());
     }
 };
 
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index fe391f70bd..99b49d0e2c 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -168,12 +168,12 @@ template <typename Type, typename Value> struct list_caster {
         if (!std::is_lvalue_reference<T>::value)
             policy = return_value_policy_override<Value>::policy(policy);
         list l(src.size());
-        size_t index = 0;
+        ssize_t index = 0;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_)
                 return handle();
-            PyList_SET_ITEM(l.ptr(), (ssize_t) index++, value_.release().ptr()); // steals a reference
+            PyList_SET_ITEM(l.ptr(), index++, value_.release().ptr()); // steals a reference
         }
         return l.release();
     }
@@ -225,12 +225,12 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
         list l(src.size());
-        size_t index = 0;
+        ssize_t index = 0;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_)
                 return handle();
-            PyList_SET_ITEM(l.ptr(), (ssize_t) index++, value_.release().ptr()); // steals a reference
+            PyList_SET_ITEM(l.ptr(), index++, value_.release().ptr()); // steals a reference
         }
         return l.release();
     }
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 15d007a437..96c97351e1 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -20,6 +20,11 @@ TEST_SUBMODULE(pytypes, m) {
     // test_iterable
     m.def("get_iterable", []{return py::iterable();});
     // test_list
+    m.def("list_no_args", []() { return py::list{}; });
+    m.def("list_ssize_t", []() { return py::list{(py::ssize_t) 0}; });
+    m.def("list_size_t", []() { return py::list{(py::size_t) 0}; });
+    m.def("list_insert_ssize_t", [](py::list *l) { return l->insert((py::ssize_t) 1, 83); });
+    m.def("list_insert_size_t", [](py::list *l) { return l->insert((py::size_t) 3, 57); });
     m.def("get_list", []() {
         py::list list;
         list.append("value");
@@ -71,6 +76,9 @@ TEST_SUBMODULE(pytypes, m) {
           [](const py::dict &dict, const char *val) { return dict.contains(val); });
 
     // test_tuple
+    m.def("tuple_no_args", []() { return py::tuple{}; });
+    m.def("tuple_ssize_t", []() { return py::tuple{(py::ssize_t) 0}; });
+    m.def("tuple_size_t", []() { return py::tuple{(py::size_t) 0}; });
     m.def("get_tuple", []() { return py::make_tuple(42, py::none(), "spam"); });
 
 #if PY_VERSION_HEX >= 0x03030000
@@ -84,6 +92,8 @@ TEST_SUBMODULE(pytypes, m) {
 #endif
 
     // test_str
+    m.def("str_from_char_ssize_t", []() { return py::str{"red", (py::ssize_t) 3}; });
+    m.def("str_from_char_size_t", []() { return py::str{"blue", (py::size_t) 4}; });
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });
     m.def("str_from_object", [](const py::object& obj) { return py::str(obj); });
@@ -100,10 +110,14 @@ TEST_SUBMODULE(pytypes, m) {
     });
 
     // test_bytes
+    m.def("bytes_from_char_ssize_t", []() { return py::bytes{"green", (py::ssize_t) 5}; });
+    m.def("bytes_from_char_size_t", []() { return py::bytes{"purple", (py::size_t) 6}; });
     m.def("bytes_from_string", []() { return py::bytes(std::string("foo")); });
     m.def("bytes_from_str", []() { return py::bytes(py::str("bar", 3)); });
 
     // test bytearray
+    m.def("bytearray_from_char_ssize_t", []() { return py::bytearray{"$%", (py::ssize_t) 2}; });
+    m.def("bytearray_from_char_size_t", []() { return py::bytearray{"@$!", (py::size_t) 3}; });
     m.def("bytearray_from_string", []() { return py::bytearray(std::string("foo")); });
     m.def("bytearray_size", []() { return py::bytearray("foo").size(); });
 
@@ -447,4 +461,57 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("weakref_from_object", [](const py::object &o) { return py::weakref(o); });
     m.def("weakref_from_object_and_function",
           [](py::object o, py::function f) { return py::weakref(std::move(o), std::move(f)); });
+
+    // Tests below this line are for pybind11 IMPLEMENTATION DETAILS:
+
+    m.def("sequence_item_get_ssize_t", [](const py::object &o) {
+        return py::detail::accessor_policies::sequence_item::get(o, (py::ssize_t) 1);
+    });
+    m.def("sequence_item_set_ssize_t", [](const py::object &o) {
+        auto s = py::str{"peppa", 5};
+        py::detail::accessor_policies::sequence_item::set(o, (py::ssize_t) 1, s);
+    });
+    m.def("sequence_item_get_size_t", [](const py::object &o) {
+        return py::detail::accessor_policies::sequence_item::get(o, (py::size_t) 2);
+    });
+    m.def("sequence_item_set_size_t", [](const py::object &o) {
+        auto s = py::str{"george", 6};
+        py::detail::accessor_policies::sequence_item::set(o, (py::size_t) 2, s);
+    });
+    m.def("list_item_get_ssize_t", [](const py::object &o) {
+        return py::detail::accessor_policies::list_item::get(o, (py::ssize_t) 3);
+    });
+    m.def("list_item_set_ssize_t", [](const py::object &o) {
+        auto s = py::str{"rebecca", 7};
+        py::detail::accessor_policies::list_item::set(o, (py::ssize_t) 3, s);
+    });
+    m.def("list_item_get_size_t", [](const py::object &o) {
+        return py::detail::accessor_policies::list_item::get(o, (py::size_t) 4);
+    });
+    m.def("list_item_set_size_t", [](const py::object &o) {
+        auto s = py::str{"richard", 7};
+        py::detail::accessor_policies::list_item::set(o, (py::size_t) 4, s);
+    });
+    m.def("tuple_item_get_ssize_t", [](const py::object &o) {
+        return py::detail::accessor_policies::tuple_item::get(o, (py::ssize_t) 5);
+    });
+    m.def("tuple_item_set_ssize_t", []() {
+        auto s0 = py::str{"emely", 5};
+        auto s1 = py::str{"edmond", 6};
+        auto o = py::tuple{2};
+        py::detail::accessor_policies::tuple_item::set(o, (py::ssize_t) 0, s0);
+        py::detail::accessor_policies::tuple_item::set(o, (py::ssize_t) 1, s1);
+        return o;
+    });
+    m.def("tuple_item_get_size_t", [](const py::object &o) {
+        return py::detail::accessor_policies::tuple_item::get(o, (py::size_t) 6);
+    });
+    m.def("tuple_item_set_size_t", []() {
+        auto s0 = py::str{"candy", 5};
+        auto s1 = py::str{"cat", 3};
+        auto o = py::tuple{2};
+        py::detail::accessor_policies::tuple_item::set(o, (py::size_t) 1, s1);
+        py::detail::accessor_policies::tuple_item::set(o, (py::size_t) 0, s0);
+        return o;
+    });
 }
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index f873658abe..18847550f2 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -23,6 +23,15 @@ def test_iterable(doc):
 
 
 def test_list(capture, doc):
+    assert m.list_no_args() == []
+    assert m.list_ssize_t() == []
+    assert m.list_size_t() == []
+    lins = [1, 2]
+    m.list_insert_ssize_t(lins)
+    assert lins == [1, 83, 2]
+    m.list_insert_size_t(lins)
+    assert lins == [1, 83, 2, 57]
+
     with capture:
         lst = m.get_list()
         assert lst == ["inserted-0", "overwritten", "inserted-2"]
@@ -100,6 +109,9 @@ def test_dict(capture, doc):
 
 
 def test_tuple():
+    assert m.tuple_no_args() == ()
+    assert m.tuple_ssize_t() == ()
+    assert m.tuple_size_t() == ()
     assert m.get_tuple() == (42, None, "spam")
 
 
@@ -113,6 +125,8 @@ def test_simple_namespace():
 
 
 def test_str(doc):
+    assert m.str_from_char_ssize_t().encode().decode() == "red"
+    assert m.str_from_char_size_t().encode().decode() == "blue"
     assert m.str_from_string().encode().decode() == "baz"
     assert m.str_from_bytes().encode().decode() == "boo"
 
@@ -157,6 +171,8 @@ def __repr__(self):
 
 
 def test_bytes(doc):
+    assert m.bytes_from_char_ssize_t().decode() == "green"
+    assert m.bytes_from_char_size_t().decode() == "purple"
     assert m.bytes_from_string().decode() == "foo"
     assert m.bytes_from_str().decode() == "bar"
 
@@ -166,6 +182,8 @@ def test_bytes(doc):
 
 
 def test_bytearray(doc):
+    assert m.bytearray_from_char_ssize_t().decode() == "$%"
+    assert m.bytearray_from_char_size_t().decode() == "@$!"
     assert m.bytearray_from_string().decode() == "foo"
     assert m.bytearray_size() == len("foo")
 
@@ -603,3 +621,24 @@ def callback(wr):
     del obj
     pytest.gc_collect()
     assert callback.called
+
+
+def test_implementation_details():
+    lst = [39, 43, 92, 49, 22, 29, 93, 98, 26, 57, 8]
+    tup = tuple(lst)
+    assert m.sequence_item_get_ssize_t(lst) == 43
+    assert m.sequence_item_set_ssize_t(lst) is None
+    assert lst[1] == "peppa"
+    assert m.sequence_item_get_size_t(lst) == 92
+    assert m.sequence_item_set_size_t(lst) is None
+    assert lst[2] == "george"
+    assert m.list_item_get_ssize_t(lst) == 49
+    assert m.list_item_set_ssize_t(lst) is None
+    assert lst[3] == "rebecca"
+    assert m.list_item_get_size_t(lst) == 22
+    assert m.list_item_set_size_t(lst) is None
+    assert lst[4] == "richard"
+    assert m.tuple_item_get_ssize_t(tup) == 29
+    assert m.tuple_item_set_ssize_t() == ("emely", "edmond")
+    assert m.tuple_item_get_size_t(tup) == 93
+    assert m.tuple_item_set_size_t() == ("candy", "cat")

From 76d939de537dc1d95b8c387ea4633c9c3a8448d2 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 30 Aug 2021 16:00:33 -0400
Subject: [PATCH 156/638] [pre-commit.ci] pre-commit autoupdate (#3231)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.24.0 → v2.25.0](https://github.com/asottile/pyupgrade/compare/v2.24.0...v2.25.0)
- [github.com/psf/black: 21.7b0 → 21.8b0](https://github.com/psf/black/compare/21.7b0...21.8b0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 96ddcf7469..06e82fe4b1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.24.0
+  rev: v2.25.0
   hooks:
   - id: pyupgrade
 
@@ -42,7 +42,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.7b0
+  rev: 21.8b0
   hooks:
   - id: black
     # By default, this ignores pyi files, though black supports them

From d6474ed7d28c03ef79acd2e87ca429072727df86 Mon Sep 17 00:00:00 2001
From: Tailing Yuan <yuantailing@gmail.com>
Date: Tue, 31 Aug 2021 09:48:33 +0800
Subject: [PATCH 157/638] fix: memory leak in cpp_function (#3228) (#3229)

* fix: memory leak in cpp_function (#3228)

* add a test case to check objects are deconstructed in cpp_function

* update the test case about cpp_function

* fix the test case about cpp_function: remove "noexcept"

* Actually calling func. CHECK(stat.alive() == 2); Manually verified that the new tests fails without the change in pybind11.h

* Moving new test to test_callbacks.cpp,py, with small enhancements.

* Removing new test from test_interpreter.cpp (after it was moved to test_callbacks.cpp,py). This restores test_interpreter.cpp to the current state on master.

* Using py::detail::silence_unused_warnings(py_func); to make the intent clear.

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/pybind11.h |  2 +-
 tests/test_callbacks.cpp    | 43 +++++++++++++++++++++++++++++++++++--
 tests/test_callbacks.py     |  7 +++++-
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 89f9cbd9b8..990c213049 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -175,7 +175,7 @@ class cpp_function : public function {
 #endif
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
-            if (!std::is_trivially_destructible<Func>::value)
+            if (!std::is_trivially_destructible<capture>::value)
                 rec->free_data = [](function_record *r) {
                     auto data = PYBIND11_STD_LAUNDER((capture *) &r->data);
                     (void) data;
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index a50771038b..58688b6e8b 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -81,16 +81,55 @@ TEST_SUBMODULE(callbacks, m) {
     };
     // Export the payload constructor statistics for testing purposes:
     m.def("payload_cstats", &ConstructorStats::get<Payload>);
-    /* Test cleanup of lambda closure */
-    m.def("test_cleanup", []() -> std::function<void()> {
+    m.def("test_lambda_closure_cleanup", []() -> std::function<void()> {
         Payload p;
 
+        // In this situation, `Func` in the implementation of
+        // `cpp_function::initialize` is NOT trivially destructible.
         return [p]() {
             /* p should be cleaned up when the returned function is garbage collected */
             (void) p;
         };
     });
 
+    class CppCallable {
+    public:
+        CppCallable() { track_default_created(this); }
+        ~CppCallable() { track_destroyed(this); }
+        CppCallable(const CppCallable &) { track_copy_created(this); }
+        CppCallable(CppCallable &&) noexcept { track_move_created(this); }
+        void operator()() {}
+    };
+
+    m.def("test_cpp_callable_cleanup", []() {
+        // Related issue: https://github.com/pybind/pybind11/issues/3228
+        // Related PR: https://github.com/pybind/pybind11/pull/3229
+        py::list alive_counts;
+        ConstructorStats &stat = ConstructorStats::get<CppCallable>();
+        alive_counts.append(stat.alive());
+        {
+            CppCallable cpp_callable;
+            alive_counts.append(stat.alive());
+            {
+                // In this situation, `Func` in the implementation of
+                // `cpp_function::initialize` IS trivially destructible,
+                // only `capture` is not.
+                py::cpp_function py_func(cpp_callable);
+                py::detail::silence_unused_warnings(py_func);
+                alive_counts.append(stat.alive());
+            }
+            alive_counts.append(stat.alive());
+            {
+                py::cpp_function py_func(std::move(cpp_callable));
+                py::detail::silence_unused_warnings(py_func);
+                alive_counts.append(stat.alive());
+            }
+            alive_counts.append(stat.alive());
+        }
+        alive_counts.append(stat.alive());
+        return alive_counts;
+    });
+
     // test_cpp_function_roundtrip
     /* Test if passing a function pointer from C++ -> Python -> C++ yields the original pointer */
     m.def("dummy_function", &dummy_function);
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 9dc272a2da..edbb1890c9 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -79,13 +79,18 @@ def f(*args, **kwargs):
 
 
 def test_lambda_closure_cleanup():
-    m.test_cleanup()
+    m.test_lambda_closure_cleanup()
     cstats = m.payload_cstats()
     assert cstats.alive() == 0
     assert cstats.copy_constructions == 1
     assert cstats.move_constructions >= 1
 
 
+def test_cpp_callable_cleanup():
+    alive_counts = m.test_cpp_callable_cleanup()
+    assert alive_counts == [0, 1, 2, 1, 2, 1, 0]
+
+
 def test_cpp_function_roundtrip():
     """Test if passing a function pointer from C++ -> Python -> C++ yields the original pointer"""
 

From a46f623782df6a92a737146890d9c070fc19b99b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 31 Aug 2021 06:44:14 -0700
Subject: [PATCH 158/638] Minor tweaks. (#3230)

* Minor tweaks.

* Restoring tests/pybind11_tests.h version from master, removing just the comment and empty line that was added in PR #3087; those were made obsolete by the pragma cleanup that concluded with PR #3186.

* [ci skip] Restoring tests/test_enum.py from master.
---
 tests/pybind11_tests.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index 12d8a777fc..8da0a670f2 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -1,9 +1,6 @@
 #pragma once
 
-// This must be kept first for MSVC 2015.
-// Do not remove the empty line between the #includes.
 #include <pybind11/pybind11.h>
-
 #include <pybind11/eval.h>
 
 #if defined(_MSC_VER) && _MSC_VER < 1910

From 49173e472f9d0f38654ccb20daf203d116b83b39 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 31 Aug 2021 08:52:04 -0700
Subject: [PATCH 159/638] Minor follow-on to PR #1334 (Fix enum value's __int__
 returning non-int when underlying type is bool or of char type) (#3232)

* Minor tweaks.

* Restoring tests/pybind11_tests.h version from master, removing just the comment and empty line that was added in PR #3087; those were made obsolete by the pragma cleanup that concluded with PR #3186.

* More-to-the-point test for Python 3.
---
 tests/test_enum.py | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tests/test_enum.py b/tests/test_enum.py
index 11cab6ddf5..85302b0809 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 import pytest
 
+import env
 from pybind11_tests import enums as m
 
 
@@ -238,20 +239,26 @@ def test_duplicate_enum_name():
 
 def test_char_underlying_enum():  # Issue #1331/PR #1334:
     assert type(m.ScopedCharEnum.Positive.__int__()) is int
-    assert int(m.ScopedChar16Enum.Zero) == 0  # int() call should successfully return
+    assert int(m.ScopedChar16Enum.Zero) == 0
     assert hash(m.ScopedChar32Enum.Positive) == 1
-    assert m.ScopedCharEnum.Positive.__getstate__() == 1  # return type is long in py2.x
+    if env.PY2:
+        assert m.ScopedCharEnum.Positive.__getstate__() == 1  # long
+    else:
+        assert type(m.ScopedCharEnum.Positive.__getstate__()) is int
     assert m.ScopedWCharEnum(1) == m.ScopedWCharEnum.Positive
     with pytest.raises(TypeError):
-        # Enum should construct with a int, even with char underlying type
-        m.ScopedWCharEnum("0")
+        # Even if the underlying type is char, only an int can be used to construct the enum:
+        m.ScopedCharEnum("0")
 
 
 def test_bool_underlying_enum():
     assert type(m.ScopedBoolEnum.TRUE.__int__()) is int
     assert int(m.ScopedBoolEnum.FALSE) == 0
     assert hash(m.ScopedBoolEnum.TRUE) == 1
-    assert m.ScopedBoolEnum.TRUE.__getstate__() == 1
+    if env.PY2:
+        assert m.ScopedBoolEnum.TRUE.__getstate__() == 1  # long
+    else:
+        assert type(m.ScopedBoolEnum.TRUE.__getstate__()) is int
     assert m.ScopedBoolEnum(1) == m.ScopedBoolEnum.TRUE
     # Enum could construct with a bool
     # (bool is a strict subclass of int, and False will be converted to 0)

From d71ba0cb73616c493d35699a8a9283aa64ef0f6b Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 2 Sep 2021 15:18:42 -0400
Subject: [PATCH 160/638] (perf): Add a missing noexcept to a pytype
 constructor (#3236)

* Add a missing noexcept to pytypes constructor.

Adds a few missing noexcept to PyType constructors for perf reasons.

* Revert exception ctor
---
 include/pybind11/pytypes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 5e699e53f4..fa50eb1e3a 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -761,7 +761,7 @@ template <typename T>
 struct arrow_proxy {
     T value;
 
-    arrow_proxy(T &&value) : value(std::move(value)) { }
+    arrow_proxy(T &&value) noexcept : value(std::move(value)) { }
     T *operator->() const { return &value; }
 };
 

From 39a0aac88ea2eb9d08293f71f636edc16e536a50 Mon Sep 17 00:00:00 2001
From: Thomas Ballinger <thomasballinger@gmail.com>
Date: Wed, 8 Sep 2021 13:00:00 -0500
Subject: [PATCH 161/638] docs fix to avoid nonexistent SmartCompile (#3241)

---
 docs/compiling.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/compiling.rst b/docs/compiling.rst
index bf7acfc808..eaf3270e0e 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -113,7 +113,7 @@ with the following:
 
     from pybind11.setup_helpers import ParallelCompile, naive_recompile
 
-    SmartCompile("NPY_NUM_BUILD_JOBS", needs_recompile=naive_recompile).install()
+    ParallelCompile("NPY_NUM_BUILD_JOBS", needs_recompile=naive_recompile).install()
 
 
 If you have a more complex build, you can implement a smarter function and pass

From 6abf2baa62063a39ccc4a9535351de571004ddd4 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 8 Sep 2021 18:53:38 -0700
Subject: [PATCH 162/638] CodeHealth: Enabling clang-tidy
 google-explicit-constructor (#3250)

* Adding google-explicit-constructor to .clang-tidy

* clang-tidy explicit attr.h (all automatic)

* clang-tidy explicit cast.h (all automatic)

* clang-tidy detail/init.h (1 NOLINT)

* clang-tidy detail/type_caster_base.h (2 NOLINT)

* clang-tidy pybind11.h (7 NOLINT)

* clang-tidy detail/common.h (3 NOLINT)

* clang-tidy detail/descr.h (2 NOLINT)

* clang-tidy pytypes.h (23 NOLINT, only 1 explicit)

* clang-tidy eigen.h (7 NOLINT, 0 explicit)

* Adding 2 explicit in functional.h

* Adding 4 explicit in iostream.h

* clang-tidy numpy.h (1 NOLINT, 1 explicit)

* clang-tidy embed.h (0 NOLINT, 1 explicit)

* clang-tidy tests/local_bindings.h (0 NOLINT, 4 explicit)

* clang-tidy tests/pybind11_cross_module_tests.cpp (0 NOLINT, 1 explicit)

* clang-tidy tests/pybind11_tests.h (0 NOLINT, 2 explicit)

* clang-tidy tests/test_buffers.cpp (0 NOLINT, 2 explicit)

* clang-tidy tests/test_builtin_casters.cpp (0 NOLINT, 4 explicit)

* clang-tidy tests/test_class.cpp (0 NOLINT, 6 explicit)

* clang-tidy tests/test_copy_move.cpp (0 NOLINT, 7 explicit)

* clang-tidy tests/test_embed/external_module.cpp (0 NOLINT, 1 explicit)

* clang-tidy tests/test_embed/test_interpreter.cpp (0 NOLINT, 1 explicit)

* clang-tidy tests/object.h (0 NOLINT, 2 explicit)

* clang-tidy batch of fully automatic fixes.

* Workaround for MSVC 19.16.27045.0 C++17 Python 2 C++ syntax error.
---
 .clang-tidy                                |  1 +
 include/pybind11/attr.h                    | 24 ++++++++---
 include/pybind11/cast.h                    | 14 ++++---
 include/pybind11/detail/common.h           |  3 ++
 include/pybind11/detail/descr.h            |  2 +
 include/pybind11/detail/init.h             |  5 ++-
 include/pybind11/detail/type_caster_base.h | 18 ++++----
 include/pybind11/eigen.h                   |  7 ++++
 include/pybind11/embed.h                   |  8 ++--
 include/pybind11/functional.h              |  6 ++-
 include/pybind11/iostream.h                | 14 ++++---
 include/pybind11/numpy.h                   |  3 +-
 include/pybind11/pybind11.h                |  9 +++-
 include/pybind11/pytypes.h                 | 25 ++++++++++-
 tests/local_bindings.h                     |  8 ++--
 tests/object.h                             |  4 +-
 tests/pybind11_cross_module_tests.cpp      |  2 +-
 tests/pybind11_tests.h                     |  4 +-
 tests/test_buffers.cpp                     |  4 +-
 tests/test_builtin_casters.cpp             | 22 +++++++---
 tests/test_class.cpp                       | 12 +++---
 tests/test_copy_move.cpp                   | 14 +++----
 tests/test_embed/external_module.cpp       |  2 +-
 tests/test_embed/test_interpreter.cpp      |  2 +-
 tests/test_exceptions.cpp                  |  4 +-
 tests/test_factory_constructors.cpp        | 49 ++++++++++++++--------
 tests/test_local_bindings.cpp              |  2 +-
 tests/test_methods_and_attributes.cpp      |  8 ++--
 tests/test_modules.cpp                     |  2 +-
 tests/test_multiple_inheritance.cpp        | 10 ++---
 tests/test_numpy_vectorize.cpp             |  4 +-
 tests/test_pickling.cpp                    |  4 +-
 tests/test_sequences_and_iterators.cpp     | 16 +++----
 tests/test_smart_ptr.cpp                   | 32 +++++++-------
 tests/test_stl.cpp                         |  3 +-
 tests/test_stl_binders.cpp                 |  2 +-
 tests/test_tagbased_polymorphic.cpp        | 12 +++---
 tests/test_virtual_functions.cpp           |  2 +-
 38 files changed, 231 insertions(+), 132 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index cefffba1ea..a6437dd494 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -5,6 +5,7 @@ Checks: '
 cppcoreguidelines-init-variables,
 cppcoreguidelines-slicing,
 clang-analyzer-optin.cplusplus.VirtualCall,
+google-explicit-constructor,
 llvm-namespace-comment,
 misc-misplaced-const,
 misc-non-copyable-objects,
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index ab1fe80446..13f68bbe8f 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -18,7 +18,9 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 /// @{
 
 /// Annotation for methods
-struct is_method { handle class_; is_method(const handle &c) : class_(c) { } };
+struct is_method { handle class_;
+    explicit is_method(const handle &c) : class_(c) {}
+};
 
 /// Annotation for operators
 struct is_operator { };
@@ -27,16 +29,24 @@ struct is_operator { };
 struct is_final { };
 
 /// Annotation for parent scope
-struct scope { handle value; scope(const handle &s) : value(s) { } };
+struct scope { handle value;
+    explicit scope(const handle &s) : value(s) {}
+};
 
 /// Annotation for documentation
-struct doc { const char *value; doc(const char *value) : value(value) { } };
+struct doc { const char *value;
+    explicit doc(const char *value) : value(value) {}
+};
 
 /// Annotation for function names
-struct name { const char *value; name(const char *value) : value(value) { } };
+struct name { const char *value;
+    explicit name(const char *value) : value(value) {}
+};
 
 /// Annotation indicating that a function is an overload associated with a given "sibling"
-struct sibling { handle value; sibling(const handle &value) : value(value.ptr()) { } };
+struct sibling { handle value;
+    explicit sibling(const handle &value) : value(value.ptr()) {}
+};
 
 /// Annotation indicating that a class derives from another given type
 template <typename T> struct base {
@@ -70,7 +80,9 @@ struct metaclass {
 };
 
 /// Annotation that marks a class as local to the module:
-struct module_local { const bool value; constexpr module_local(bool v = true) : value(v) { } };
+struct module_local { const bool value;
+    constexpr explicit module_local(bool v = true) : value(v) {}
+};
 
 /// Annotation to mark enums as an arithmetic type
 struct arithmetic { };
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 79bf506d81..db79f57cda 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -82,7 +82,7 @@ template <typename type> class type_caster<std::reference_wrapper<type>> {
         return caster_t::cast(&src.get(), policy, parent);
     }
     template <typename T> using cast_op_type = std::reference_wrapper<type>;
-    operator std::reference_wrapper<type>() { return cast_op<type &>(subcaster); }
+    explicit operator std::reference_wrapper<type>() { return cast_op<type &>(subcaster); }
 };
 
 #define PYBIND11_TYPE_CASTER(type, py_name)                                                       \
@@ -279,7 +279,7 @@ template <> class type_caster<void> : public type_caster<void_type> {
     }
 
     template <typename T> using cast_op_type = void*&;
-    operator void *&() { return value; }
+    explicit operator void *&() { return value; }
     static constexpr auto name = _("capsule");
 private:
     void *value = nullptr;
@@ -487,8 +487,10 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         return StringCaster::cast(StringType(1, src), policy, parent);
     }
 
-    operator CharT*() { return none ? nullptr : const_cast<CharT *>(static_cast<StringType &>(str_caster).c_str()); }
-    operator CharT&() {
+    explicit operator CharT *() {
+        return none ? nullptr : const_cast<CharT *>(static_cast<StringType &>(str_caster).c_str());
+    }
+    explicit operator CharT &() {
         if (none)
             throw value_error("Cannot convert None to a character");
 
@@ -581,8 +583,8 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
 
     template <typename T> using cast_op_type = type;
 
-    operator type() & { return implicit_cast(indices{}); }
-    operator type() && { return std::move(*this).implicit_cast(indices{}); }
+    explicit operator type() & { return implicit_cast(indices{}); }
+    explicit operator type() && { return std::move(*this).implicit_cast(indices{}); }
 
 protected:
     template <size_t... Is>
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index e4f00293ec..a8fd7d917e 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -918,6 +918,7 @@ class any_container {
 
     // Implicit conversion constructor from any arbitrary container type with values convertible to T
     template <typename Container, typename = enable_if_t<std::is_convertible<decltype(*std::begin(std::declval<const Container &>())), T>::value>>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     any_container(const Container &c) : any_container(std::begin(c), std::end(c)) { }
 
     // initializer_list's aren't deducible, so don't get matched by the above template; we need this
@@ -926,9 +927,11 @@ class any_container {
     any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) { }
 
     // Avoid copying if given an rvalue vector of the correct type.
+    // NOLINTNEXTLINE(google-explicit-constructor)
     any_container(std::vector<T> &&v) : v(std::move(v)) { }
 
     // Moves the vector out of an rvalue any_container
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator std::vector<T> &&() && { return std::move(v); }
 
     // Dereferencing obtains a reference to the underlying vector
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 0acfc7db37..0b498e5e72 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -26,12 +26,14 @@ struct descr {
     char text[N + 1]{'\0'};
 
     constexpr descr() = default;
+    // NOLINTNEXTLINE(google-explicit-constructor)
     constexpr descr(char const (&s)[N+1]) : descr(s, make_index_sequence<N>()) { }
 
     template <size_t... Is>
     constexpr descr(char const (&s)[N+1], index_sequence<Is...>) : text{s[Is]..., '\0'} { }
 
     template <typename... Chars>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} { }
 
     static constexpr std::array<const std::type_info *, sizeof...(Ts) + 1> types() {
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index e795da7d75..cace352964 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -23,7 +23,7 @@ class type_caster<value_and_holder> {
     }
 
     template <typename> using cast_op_type = value_and_holder &;
-    operator value_and_holder &() { return *value; }
+    explicit operator value_and_holder &() { return *value; }
     static constexpr auto name = _<value_and_holder>();
 
 private:
@@ -222,7 +222,8 @@ template <typename Func, typename Return, typename... Args>
 struct factory<Func, void_type (*)(), Return(Args...)> {
     remove_reference_t<Func> class_factory;
 
-    factory(Func &&f) : class_factory(std::forward<Func>(f)) { }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    factory(Func &&f) : class_factory(std::forward<Func>(f)) {}
 
     // The given class either has no alias or has no separate alias factory;
     // this always constructs the class itself.  If the class is registered with an alias
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 5a5acc2e6a..4c9ac7b8f6 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -225,7 +225,7 @@ struct value_and_holder {
     value_and_holder() = default;
 
     // Used for past-the-end iterator
-    value_and_holder(size_t index) : index{index} {}
+    explicit value_and_holder(size_t index) : index{index} {}
 
     template <typename V = void> V *&value_ptr() const {
         return reinterpret_cast<V *&>(vh[0]);
@@ -274,7 +274,8 @@ struct values_and_holders {
     const type_vec &tinfo;
 
 public:
-    values_and_holders(instance *inst) : inst{inst}, tinfo(all_type_info(Py_TYPE(inst))) {}
+    explicit values_and_holders(instance *inst)
+        : inst{inst}, tinfo(all_type_info(Py_TYPE(inst))) {}
 
     struct iterator {
     private:
@@ -290,7 +291,8 @@ struct values_and_holders {
                  0 /* index */)
         {}
         // Past-the-end iterator:
-        iterator(size_t end) : curr(end) {}
+        explicit iterator(size_t end) : curr(end) {}
+
     public:
         bool operator==(const iterator &other) const { return curr.index == other.curr.index; }
         bool operator!=(const iterator &other) const { return curr.index != other.curr.index; }
@@ -491,11 +493,11 @@ inline PyObject *make_new_instance(PyTypeObject *type);
 
 class type_caster_generic {
 public:
-    PYBIND11_NOINLINE type_caster_generic(const std::type_info &type_info)
-        : typeinfo(get_type_info(type_info)), cpptype(&type_info) { }
+    PYBIND11_NOINLINE explicit type_caster_generic(const std::type_info &type_info)
+        : typeinfo(get_type_info(type_info)), cpptype(&type_info) {}
 
-    type_caster_generic(const type_info *typeinfo)
-        : typeinfo(typeinfo), cpptype(typeinfo ? typeinfo->cpptype : nullptr) { }
+    explicit type_caster_generic(const type_info *typeinfo)
+        : typeinfo(typeinfo), cpptype(typeinfo ? typeinfo->cpptype : nullptr) {}
 
     bool load(handle src, bool convert) {
         return load_impl<type_caster_generic>(src, convert);
@@ -923,7 +925,9 @@ template <typename type> class type_caster_base : public type_caster_generic {
 
     template <typename T> using cast_op_type = detail::cast_op_type<T>;
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator itype*() { return (type *) value; }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator itype&() { if (!value) throw reference_cast_error(); return *((itype *) value); }
 
 protected:
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index b03e15f624..c0363827c3 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -61,6 +61,7 @@ template <bool EigenRowMajor> struct EigenConformable {
     EigenDStride stride{0, 0};      // Only valid if negativestrides is false!
     bool negativestrides = false;   // If true, do not use stride!
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     EigenConformable(bool fits = false) : conformable{fits} {}
     // Matrix type:
     EigenConformable(EigenIndex r, EigenIndex c,
@@ -88,6 +89,7 @@ template <bool EigenRowMajor> struct EigenConformable {
             (props::outer_stride == Eigen::Dynamic || props::outer_stride == stride.outer() ||
                 (EigenRowMajor ? rows : cols) == 1);
     }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator bool() const { return conformable; }
 };
 
@@ -326,8 +328,11 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
 
     static constexpr auto name = props::descriptor;
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator Type*() { return &value; }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator Type&() { return value; }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator Type&&() && { return std::move(value); }
     template <typename T> using cast_op_type = movable_cast_op_type<T>;
 
@@ -451,7 +456,9 @@ struct type_caster<
         return true;
     }
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator Type*() { return ref.get(); }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator Type&() { return *ref; }
     template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
 
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 7b5d7cd24a..9843f0f973 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -260,10 +260,10 @@ inline void finalize_interpreter() {
  \endrst */
 class scoped_interpreter {
 public:
-    scoped_interpreter(bool init_signal_handlers = true,
-                       int argc = 0,
-                       const char *const *argv = nullptr,
-                       bool add_program_dir_to_path = true) {
+    explicit scoped_interpreter(bool init_signal_handlers = true,
+                                int argc = 0,
+                                const char *const *argv = nullptr,
+                                bool add_program_dir_to_path = true) {
         initialize_interpreter(init_signal_handlers, argc, argv, add_program_dir_to_path);
     }
 
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index bc8a8af821..24141ce388 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -69,6 +69,10 @@ struct type_caster<std::function<Return(Args...)>> {
         // ensure GIL is held during functor destruction
         struct func_handle {
             function f;
+#if !(defined(_MSC_VER) && _MSC_VER == 1916 && defined(PYBIND11_CPP17) && PY_MAJOR_VERSION < 3)
+            // This triggers a syntax error under very special conditions (very weird indeed).
+            explicit
+#endif
             func_handle(function &&f_) noexcept : f(std::move(f_)) {}
             func_handle(const func_handle &f_) { operator=(f_); }
             func_handle &operator=(const func_handle &f_) {
@@ -85,7 +89,7 @@ struct type_caster<std::function<Return(Args...)>> {
         // to emulate 'move initialization capture' in C++11
         struct func_wrapper {
             func_handle hfunc;
-            func_wrapper(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
+            explicit func_wrapper(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
                 object retval(hfunc.f(std::forward<Args>(args)...));
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index e4d2095857..95449a07ba 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -123,7 +123,7 @@ class pythonbuf : public std::streambuf {
     }
 
 public:
-    pythonbuf(const object &pyostream, size_t buffer_size = 1024)
+    explicit pythonbuf(const object &pyostream, size_t buffer_size = 1024)
         : buf_size(buffer_size), d_buffer(new char[buf_size]), pywrite(pyostream.attr("write")),
           pyflush(pyostream.attr("flush")) {
         setp(d_buffer.get(), d_buffer.get() + buf_size - 1);
@@ -171,8 +171,9 @@ class scoped_ostream_redirect {
     detail::pythonbuf buffer;
 
 public:
-    scoped_ostream_redirect(std::ostream &costream  = std::cout,
-                            const object &pyostream = module_::import("sys").attr("stdout"))
+    explicit scoped_ostream_redirect(std::ostream &costream = std::cout,
+                                     const object &pyostream
+                                     = module_::import("sys").attr("stdout"))
         : costream(costream), buffer(pyostream) {
         old = costream.rdbuf(&buffer);
     }
@@ -201,8 +202,9 @@ class scoped_ostream_redirect {
 \endrst */
 class scoped_estream_redirect : public scoped_ostream_redirect {
 public:
-    scoped_estream_redirect(std::ostream &costream  = std::cerr,
-                            const object &pyostream = module_::import("sys").attr("stderr"))
+    explicit scoped_estream_redirect(std::ostream &costream = std::cerr,
+                                     const object &pyostream
+                                     = module_::import("sys").attr("stderr"))
         : scoped_ostream_redirect(costream, pyostream) {}
 };
 
@@ -217,7 +219,7 @@ class OstreamRedirect {
     std::unique_ptr<scoped_estream_redirect> redirect_stderr;
 
 public:
-    OstreamRedirect(bool do_stdout = true, bool do_stderr = true)
+    explicit OstreamRedirect(bool do_stdout = true, bool do_stderr = true)
         : do_stdout_(do_stdout), do_stderr_(do_stderr) {}
 
     void enter() {
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index fa128efdd0..d55844086d 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -477,7 +477,7 @@ class dtype : public object {
         m_ptr = from_args(pybind11::str(format)).release().ptr();
     }
 
-    dtype(const char *format) : dtype(std::string(format)) { }
+    explicit dtype(const char *format) : dtype(std::string(format)) {}
 
     dtype(list names, list formats, list offsets, ssize_t itemsize) {
         dict args;
@@ -894,6 +894,7 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
         if (!is_borrowed) Py_XDECREF(h.ptr());
     }
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     array_t(const object &o) : array(raw_array_t(o.ptr()), stolen_t{}) {
         if (!m_ptr) throw error_already_set();
     }
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 990c213049..82d339751e 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -81,10 +81,12 @@ PYBIND11_NAMESPACE_END(detail)
 class cpp_function : public function {
 public:
     cpp_function() = default;
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(std::nullptr_t) { }
 
     /// Construct a cpp_function from a vanilla function pointer
     template <typename Return, typename... Args, typename... Extra>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (*f)(Args...), const Extra&... extra) {
         initialize(f, f, extra...);
     }
@@ -92,6 +94,7 @@ class cpp_function : public function {
     /// Construct a cpp_function from a lambda function (possibly with internal state)
     template <typename Func, typename... Extra,
               typename = detail::enable_if_t<detail::is_lambda<Func>::value>>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Func &&f, const Extra&... extra) {
         initialize(std::forward<Func>(f),
                    (detail::function_signature_t<Func> *) nullptr, extra...);
@@ -99,6 +102,7 @@ class cpp_function : public function {
 
     /// Construct a cpp_function from a class method (non-const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (Class::*f)(Arg...), const Extra&... extra) {
         initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
                    (Return (*) (Class *, Arg...)) nullptr, extra...);
@@ -108,6 +112,7 @@ class cpp_function : public function {
     /// A copy of the overload for non-const functions without explicit ref-qualifier
     /// but with an added `&`.
     template <typename Return, typename Class, typename... Arg, typename... Extra>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (Class::*f)(Arg...)&, const Extra&... extra) {
         initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(args...); },
                    (Return (*) (Class *, Arg...)) nullptr, extra...);
@@ -115,6 +120,7 @@ class cpp_function : public function {
 
     /// Construct a cpp_function from a class method (const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (Class::*f)(Arg...) const, const Extra&... extra) {
         initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
                    (Return (*)(const Class *, Arg ...)) nullptr, extra...);
@@ -124,6 +130,7 @@ class cpp_function : public function {
     /// A copy of the overload for const functions without explicit ref-qualifier
     /// but with an added `&`.
     template <typename Return, typename Class, typename... Arg, typename... Extra>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (Class::*f)(Arg...) const&, const Extra&... extra) {
         initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(args...); },
                    (Return (*)(const Class *, Arg ...)) nullptr, extra...);
@@ -2034,7 +2041,7 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
 template <typename InputType, typename OutputType> void implicitly_convertible() {
     struct set_flag {
         bool &flag;
-        set_flag(bool &flag_) : flag(flag_) { flag_ = true; }
+        explicit set_flag(bool &flag_) : flag(flag_) { flag_ = true; }
         ~set_flag() { flag = false; }
     };
     auto implicit_caster = [](PyObject *obj, PyTypeObject *type) -> PyObject * {
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index fa50eb1e3a..971db85f37 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -178,6 +178,7 @@ class handle : public detail::object_api<handle> {
     /// The default constructor creates a handle with a ``nullptr``-valued pointer
     handle() = default;
     /// Creates a ``handle`` from the given raw Python object pointer
+    // NOLINTNEXTLINE(google-explicit-constructor)
     handle(PyObject *ptr) : m_ptr(ptr) { } // Allow implicit conversion from PyObject*
 
     /// Return the underlying ``PyObject *`` pointer
@@ -612,6 +613,7 @@ class accessor : public object_api<accessor<Policy>> {
         return obj.contains(key);
     }
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator object() const { return get_cache(); }
     PyObject *ptr() const { return get_cache().ptr(); }
     template <typename T> T cast() const { return get_cache().template cast<T>(); }
@@ -761,6 +763,7 @@ template <typename T>
 struct arrow_proxy {
     T value;
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     arrow_proxy(T &&value) noexcept : value(std::move(value)) { }
     T *operator->() const { return &value; }
 };
@@ -909,14 +912,17 @@ PYBIND11_NAMESPACE_END(detail)
         bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); } \
         static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); } \
         template <typename Policy_> \
+        /* NOLINTNEXTLINE(google-explicit-constructor) */ \
         Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }
 
 #define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun) \
     PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
     /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
     Name(const object &o) \
     : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
     { if (!m_ptr) throw error_already_set(); } \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
     Name(object &&o) \
     : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
     { if (!m_ptr) throw error_already_set(); }
@@ -933,8 +939,10 @@ PYBIND11_NAMESPACE_END(detail)
 #define PYBIND11_OBJECT(Name, Parent, CheckFun) \
     PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
     /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
     Name(const object &o) : Parent(o) \
     { if (m_ptr && !check_(m_ptr)) throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr); } \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
     Name(object &&o) : Parent(std::move(o)) \
     { if (m_ptr && !check_(m_ptr)) throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr); }
 
@@ -1056,11 +1064,13 @@ class str : public object {
     }
 
     // 'explicit' is explicitly omitted from the following constructors to allow implicit conversion to py::str from C++ string-like objects
+    // NOLINTNEXTLINE(google-explicit-constructor)
     str(const char *c = "")
         : object(PyUnicode_FromString(c), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate string object!");
     }
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     str(const std::string &s) : str(s.data(), s.size()) { }
 
     explicit str(const bytes &b);
@@ -1071,6 +1081,7 @@ class str : public object {
     \endrst */
     explicit str(handle h) : object(raw_str(h.ptr()), stolen_t{}) { if (!m_ptr) throw error_already_set(); }
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator std::string() const {
         object temp = *this;
         if (PyUnicode_Check(m_ptr)) {
@@ -1118,6 +1129,7 @@ class bytes : public object {
     PYBIND11_OBJECT(bytes, object, PYBIND11_BYTES_CHECK)
 
     // Allow implicit conversion:
+    // NOLINTNEXTLINE(google-explicit-constructor)
     bytes(const char *c = "")
         : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
@@ -1130,10 +1142,12 @@ class bytes : public object {
     }
 
     // Allow implicit conversion:
+    // NOLINTNEXTLINE(google-explicit-constructor)
     bytes(const std::string &s) : bytes(s.data(), s.size()) { }
 
     explicit bytes(const pybind11::str &s);
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator std::string() const {
         char *buffer = nullptr;
         ssize_t length = 0;
@@ -1222,7 +1236,9 @@ class bool_ : public object {
     PYBIND11_OBJECT_CVT(bool_, object, PyBool_Check, raw_bool)
     bool_() : object(Py_False, borrowed_t{}) { }
     // Allow implicit conversion from and to `bool`:
+    // NOLINTNEXTLINE(google-explicit-constructor)
     bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) { }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator bool() const { return (m_ptr != nullptr) && PyLong_AsLong(m_ptr) != 0; }
 
 private:
@@ -1261,6 +1277,7 @@ class int_ : public object {
     // Allow implicit conversion from C++ integral types:
     template <typename T,
               detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     int_(T value) {
         if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
             if (std::is_signed<T>::value)
@@ -1278,6 +1295,7 @@ class int_ : public object {
 
     template <typename T,
               detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator T() const {
         return std::is_unsigned<T>::value
             ? detail::as_unsigned<T>(m_ptr)
@@ -1291,13 +1309,17 @@ class float_ : public object {
 public:
     PYBIND11_OBJECT_CVT(float_, object, PyFloat_Check, PyNumber_Float)
     // Allow implicit conversion from float/double:
+    // NOLINTNEXTLINE(google-explicit-constructor)
     float_(float value) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate float object!");
     }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     float_(double value = .0) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
         if (!m_ptr) pybind11_fail("Could not allocate float object!");
     }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator float() const { return (float) PyFloat_AsDouble(m_ptr); }
+    // NOLINTNEXTLINE(google-explicit-constructor)
     operator double() const { return (double) PyFloat_AsDouble(m_ptr); }
 };
 
@@ -1372,7 +1394,7 @@ class capsule : public object {
             pybind11_fail("Could not set capsule context!");
     }
 
-    capsule(void (*destructor)()) {
+    explicit capsule(void (*destructor)()) {
         m_ptr = PyCapsule_New(reinterpret_cast<void *>(destructor), nullptr, [](PyObject *o) {
             auto destructor = reinterpret_cast<void (*)()>(PyCapsule_GetPointer(o, nullptr));
             destructor();
@@ -1382,6 +1404,7 @@ class capsule : public object {
             pybind11_fail("Could not allocate capsule object!");
     }
 
+    // NOLINTNEXTLINE(google-explicit-constructor)
     template <typename T> operator T *() const {
         return get_pointer<T>();
     }
diff --git a/tests/local_bindings.h b/tests/local_bindings.h
index f11c08e616..4c936c19a5 100644
--- a/tests/local_bindings.h
+++ b/tests/local_bindings.h
@@ -6,7 +6,7 @@
 /// Simple class used to test py::local:
 template <int> class LocalBase {
 public:
-    LocalBase(int i) : i(i) { }
+    explicit LocalBase(int i) : i(i) { }
     int i = -1;
 };
 
@@ -75,11 +75,11 @@ py::class_<T> bind_local(Args && ...args) {
 namespace pets {
 class Pet {
 public:
-    Pet(std::string name) : name_(std::move(name)) {}
+    explicit Pet(std::string name) : name_(std::move(name)) {}
     std::string name_;
     const std::string &name() const { return name_; }
 };
 } // namespace pets
 
-struct MixGL { int i; MixGL(int i) : i{i} {} };
-struct MixGL2 { int i; MixGL2(int i) : i{i} {} };
+struct MixGL { int i; explicit MixGL(int i) : i{i} {} };
+struct MixGL2 { int i; explicit MixGL2(int i) : i{i} {} };
diff --git a/tests/object.h b/tests/object.h
index 6851fc6247..be21bf6316 100644
--- a/tests/object.h
+++ b/tests/object.h
@@ -65,7 +65,7 @@ template <typename T> class ref {
     ref() : m_ptr(nullptr) { print_default_created(this); track_default_created((ref_tag*) this); }
 
     /// Construct a reference from a pointer
-    ref(T *ptr) : m_ptr(ptr) {
+    explicit ref(T *ptr) : m_ptr(ptr) {
         if (m_ptr) ((Object *) m_ptr)->incRef();
 
         print_created(this, "from pointer", m_ptr); track_created((ref_tag*) this, "from pointer");
@@ -165,7 +165,7 @@ template <typename T> class ref {
     const T& operator*() const { return *m_ptr; }
 
     /// Return a pointer to the referenced object
-    operator T* () { return m_ptr; }
+    explicit operator T* () { return m_ptr; }
 
     /// Return a const pointer to the referenced object
     T* get_ptr() { return m_ptr; }
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index 4bfd5302d5..5838cb2746 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -123,7 +123,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
 
     class Dog : public pets::Pet {
     public:
-        Dog(std::string name) : Pet(std::move(name)) {}
+        explicit Dog(std::string name) : Pet(std::move(name)) {}
     };
     py::class_<pets::Pet>(m, "Pet", py::module_local())
         .def("name", &pets::Pet::name);
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index 8da0a670f2..800ddda48b 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -16,7 +16,7 @@ class test_initializer {
     using Initializer = void (*)(py::module_ &);
 
 public:
-    test_initializer(Initializer init);
+    explicit test_initializer(Initializer init);
     test_initializer(const char *submodule_name, Initializer init);
 };
 
@@ -32,7 +32,7 @@ struct UnregisteredType { };
 class UserType {
 public:
     UserType() = default;
-    UserType(int i) : i(i) { }
+    explicit UserType(int i) : i(i) { }
 
     int value() const { return i; }
     void set(int set) { i = set; }
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index c7e2c7df30..3a8e3e7b75 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -122,7 +122,7 @@ TEST_SUBMODULE(buffers, m) {
     // test_inherited_protocol
     class SquareMatrix : public Matrix {
     public:
-        SquareMatrix(py::ssize_t n) : Matrix(n, n) { }
+        explicit SquareMatrix(py::ssize_t n) : Matrix(n, n) {}
     };
     // Derived classes inherit the buffer protocol and the buffer access function
     py::class_<SquareMatrix, Matrix>(m, "SquareMatrix")
@@ -173,7 +173,7 @@ TEST_SUBMODULE(buffers, m) {
 
     struct BufferReadOnly {
         const uint8_t value = 0;
-        BufferReadOnly(uint8_t value): value(value) {}
+        explicit BufferReadOnly(uint8_t value) : value(value) {}
 
         py::buffer_info get_buffer_info() {
             return py::buffer_info(&value, 1);
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index be4431aad6..71c778e8e2 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -25,16 +25,28 @@ class type_caster<ConstRefCasted> {
   // cast operator.
   bool load(handle, bool) { return true; }
 
-  operator ConstRefCasted &&() {
+  explicit operator ConstRefCasted &&() {
       value = {1};
       // NOLINTNEXTLINE(performance-move-const-arg)
       return std::move(value);
   }
-  operator ConstRefCasted&() { value = {2}; return value; }
-  operator ConstRefCasted*() { value = {3}; return &value; }
+  explicit operator ConstRefCasted &() {
+      value = {2};
+      return value;
+  }
+  explicit operator ConstRefCasted *() {
+      value = {3};
+      return &value;
+  }
 
-  operator const ConstRefCasted&() { value = {4}; return value; }
-  operator const ConstRefCasted*() { value = {5}; return &value; }
+  explicit operator const ConstRefCasted &() {
+      value = {4};
+      return value;
+  }
+  explicit operator const ConstRefCasted *() {
+      value = {5};
+      return &value;
+  }
 
   // custom cast_op to explicitly propagate types to the conversion operators.
   template <typename T_>
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index dff758392d..246b6c1fea 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -27,7 +27,7 @@
 
 // test_brace_initialization
 struct NoBraceInitialization {
-    NoBraceInitialization(std::vector<int> v) : vec{std::move(v)} {}
+    explicit NoBraceInitialization(std::vector<int> v) : vec{std::move(v)} {}
     template <typename T>
     NoBraceInitialization(std::initializer_list<T> l) : vec(l) {}
 
@@ -65,18 +65,18 @@ TEST_SUBMODULE(class_, m) {
 
     class Dog : public Pet {
     public:
-        Dog(const std::string &name) : Pet(name, "dog") {}
+        explicit Dog(const std::string &name) : Pet(name, "dog") {}
         std::string bark() const { return "Woof!"; }
     };
 
     class Rabbit : public Pet {
     public:
-        Rabbit(const std::string &name) : Pet(name, "parrot") {}
+        explicit Rabbit(const std::string &name) : Pet(name, "parrot") {}
     };
 
     class Hamster : public Pet {
     public:
-        Hamster(const std::string &name) : Pet(name, "rodent") {}
+        explicit Hamster(const std::string &name) : Pet(name, "rodent") {}
     };
 
     class Chimera : public Pet {
@@ -208,7 +208,7 @@ TEST_SUBMODULE(class_, m) {
     struct ConvertibleFromUserType {
         int i;
 
-        ConvertibleFromUserType(UserType u) : i(u.value()) { }
+        explicit ConvertibleFromUserType(UserType u) : i(u.value()) {}
     };
 
     py::class_<ConvertibleFromUserType>(m, "AcceptsUserType")
@@ -263,7 +263,7 @@ TEST_SUBMODULE(class_, m) {
     };
     struct PyAliasedHasOpNewDelSize : AliasedHasOpNewDelSize {
         PyAliasedHasOpNewDelSize() = default;
-        PyAliasedHasOpNewDelSize(int) { }
+        explicit PyAliasedHasOpNewDelSize(int) {}
         std::uint64_t j;
     };
     struct HasOpNewDelBoth {
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 859da9df7e..5fb0dd810c 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -37,7 +37,7 @@ template <> lacking_move_ctor empty<lacking_move_ctor>::instance_ = {};
 class MoveOnlyInt {
 public:
     MoveOnlyInt() { print_default_created(this); }
-    MoveOnlyInt(int v) : value{v} { print_created(this, value); }
+    explicit MoveOnlyInt(int v) : value{v} { print_created(this, value); }
     MoveOnlyInt(MoveOnlyInt &&m) noexcept {
         print_move_created(this, m.value);
         std::swap(value, m.value);
@@ -56,7 +56,7 @@ class MoveOnlyInt {
 class MoveOrCopyInt {
 public:
     MoveOrCopyInt() { print_default_created(this); }
-    MoveOrCopyInt(int v) : value{v} { print_created(this, value); }
+    explicit MoveOrCopyInt(int v) : value{v} { print_created(this, value); }
     MoveOrCopyInt(MoveOrCopyInt &&m) noexcept {
         print_move_created(this, m.value);
         std::swap(value, m.value);
@@ -75,7 +75,7 @@ class MoveOrCopyInt {
 class CopyOnlyInt {
 public:
     CopyOnlyInt() { print_default_created(this); }
-    CopyOnlyInt(int v) : value{v} { print_created(this, value); }
+    explicit CopyOnlyInt(int v) : value{v} { print_created(this, value); }
     CopyOnlyInt(const CopyOnlyInt &c) { print_copy_created(this, c.value); value = c.value; }
     CopyOnlyInt &operator=(const CopyOnlyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
     ~CopyOnlyInt() { print_destroyed(this); }
@@ -107,8 +107,8 @@ template <> struct type_caster<CopyOnlyInt> {
         if (!src) return none().release();
         return cast(*src, policy, parent);
     }
-    operator CopyOnlyInt*() { return &value; }
-    operator CopyOnlyInt&() { return value; }
+    explicit operator CopyOnlyInt *() { return &value; }
+    explicit operator CopyOnlyInt &() { return value; }
     template <typename T> using cast_op_type = pybind11::detail::cast_op_type<T>;
 };
 PYBIND11_NAMESPACE_END(detail)
@@ -219,7 +219,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
     // #389: rvp::move should fall-through to copy on non-movable objects
     struct MoveIssue1 {
         int v;
-        MoveIssue1(int v) : v{v} {}
+        explicit MoveIssue1(int v) : v{v} {}
         MoveIssue1(const MoveIssue1 &c) = default;
         MoveIssue1(MoveIssue1 &&) = delete;
     };
@@ -227,7 +227,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
 
     struct MoveIssue2 {
         int v;
-        MoveIssue2(int v) : v{v} {}
+        explicit MoveIssue2(int v) : v{v} {}
         MoveIssue2(MoveIssue2 &&) = default;
     };
     py::class_<MoveIssue2>(m, "MoveIssue2").def(py::init<int>()).def_readwrite("value", &MoveIssue2::v);
diff --git a/tests/test_embed/external_module.cpp b/tests/test_embed/external_module.cpp
index e9a6058b17..4909522993 100644
--- a/tests/test_embed/external_module.cpp
+++ b/tests/test_embed/external_module.cpp
@@ -9,7 +9,7 @@ namespace py = pybind11;
 PYBIND11_MODULE(external_module, m) {
     class A {
     public:
-        A(int value) : v{value} {};
+        explicit A(int value) : v{value} {};
         int v;
     };
 
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 78b64be6b0..fae14f7510 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -18,7 +18,7 @@ using namespace py::literals;
 
 class Widget {
 public:
-    Widget(std::string message) : message(std::move(message)) {}
+    explicit Widget(std::string message) : message(std::move(message)) {}
     virtual ~Widget() = default;
 
     std::string the_message() const { return message; }
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 4805a02490..25adb32ed1 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -81,7 +81,7 @@ class MyException6 : public std::exception {
 
 
 struct PythonCallInDestructor {
-    PythonCallInDestructor(const py::dict &d) : d(d) {}
+    explicit PythonCallInDestructor(const py::dict &d) : d(d) {}
     ~PythonCallInDestructor() { d["good"] = true; }
 
     py::dict d;
@@ -90,7 +90,7 @@ struct PythonCallInDestructor {
 
 
 struct PythonAlreadySetInDestructor {
-    PythonAlreadySetInDestructor(const py::str &s) : s(s) {}
+    explicit PythonAlreadySetInDestructor(const py::str &s) : s(s) {}
     ~PythonAlreadySetInDestructor() {
         py::dict foo;
         try {
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 235ec4dca6..660e2896af 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -19,8 +19,9 @@
 class TestFactory1 {
     friend class TestFactoryHelper;
     TestFactory1() : value("(empty)") { print_default_created(this); }
-    TestFactory1(int v) : value(std::to_string(v)) { print_created(this, value); }
-    TestFactory1(std::string v) : value(std::move(v)) { print_created(this, value); }
+    explicit TestFactory1(int v) : value(std::to_string(v)) { print_created(this, value); }
+    explicit TestFactory1(std::string v) : value(std::move(v)) { print_created(this, value); }
+
 public:
     std::string value;
     TestFactory1(TestFactory1 &&) = delete;
@@ -33,8 +34,9 @@ class TestFactory1 {
 class TestFactory2 {
     friend class TestFactoryHelper;
     TestFactory2() : value("(empty2)") { print_default_created(this); }
-    TestFactory2(int v) : value(std::to_string(v)) { print_created(this, value); }
-    TestFactory2(std::string v) : value(std::move(v)) { print_created(this, value); }
+    explicit TestFactory2(int v) : value(std::to_string(v)) { print_created(this, value); }
+    explicit TestFactory2(std::string v) : value(std::move(v)) { print_created(this, value); }
+
 public:
     TestFactory2(TestFactory2 &&m) noexcept {
         value = std::move(m.value);
@@ -53,9 +55,10 @@ class TestFactory3 {
 protected:
     friend class TestFactoryHelper;
     TestFactory3() : value("(empty3)") { print_default_created(this); }
-    TestFactory3(int v) : value(std::to_string(v)) { print_created(this, value); }
+    explicit TestFactory3(int v) : value(std::to_string(v)) { print_created(this, value); }
+
 public:
-    TestFactory3(std::string v) : value(std::move(v)) { print_created(this, value); }
+    explicit TestFactory3(std::string v) : value(std::move(v)) { print_created(this, value); }
     TestFactory3(TestFactory3 &&m) noexcept {
         value = std::move(m.value);
         print_move_created(this);
@@ -72,13 +75,13 @@ class TestFactory3 {
 class TestFactory4 : public TestFactory3 {
 public:
     TestFactory4() : TestFactory3() { print_default_created(this); }
-    TestFactory4(int v) : TestFactory3(v) { print_created(this, v); }
+    explicit TestFactory4(int v) : TestFactory3(v) { print_created(this, v); }
     ~TestFactory4() override { print_destroyed(this); }
 };
 // Another class for an invalid downcast test
 class TestFactory5 : public TestFactory3 {
 public:
-    TestFactory5(int i) : TestFactory3(i) { print_created(this, i); }
+    explicit TestFactory5(int i) : TestFactory3(i) { print_created(this, i); }
     ~TestFactory5() override { print_destroyed(this); }
 };
 
@@ -87,7 +90,7 @@ class TestFactory6 {
     int value;
     bool alias = false;
 public:
-    TestFactory6(int i) : value{i} { print_created(this, i); }
+    explicit TestFactory6(int i) : value{i} { print_created(this, i); }
     TestFactory6(TestFactory6 &&f) noexcept {
         print_move_created(this);
         value = f.value;
@@ -102,11 +105,20 @@ class PyTF6 : public TestFactory6 {
 public:
     // Special constructor that allows the factory to construct a PyTF6 from a TestFactory6 only
     // when an alias is needed:
-    PyTF6(TestFactory6 &&base) : TestFactory6(std::move(base)) { alias = true; print_created(this, "move", value); }
-    PyTF6(int i) : TestFactory6(i) { alias = true; print_created(this, i); }
+    explicit PyTF6(TestFactory6 &&base) : TestFactory6(std::move(base)) {
+        alias = true;
+        print_created(this, "move", value);
+    }
+    explicit PyTF6(int i) : TestFactory6(i) {
+        alias = true;
+        print_created(this, i);
+    }
     PyTF6(PyTF6 &&f) noexcept : TestFactory6(std::move(f)) { print_move_created(this); }
     PyTF6(const PyTF6 &f) : TestFactory6(f) { print_copy_created(this); }
-    PyTF6(std::string s) : TestFactory6((int) s.size()) { alias = true; print_created(this, s); }
+    explicit PyTF6(std::string s) : TestFactory6((int) s.size()) {
+        alias = true;
+        print_created(this, s);
+    }
     ~PyTF6() override { print_destroyed(this); }
     int get() override { PYBIND11_OVERRIDE(int, TestFactory6, get, /*no args*/); }
 };
@@ -116,7 +128,7 @@ class TestFactory7 {
     int value;
     bool alias = false;
 public:
-    TestFactory7(int i) : value{i} { print_created(this, i); }
+    explicit TestFactory7(int i) : value{i} { print_created(this, i); }
     TestFactory7(TestFactory7 &&f) noexcept {
         print_move_created(this);
         value = f.value;
@@ -129,7 +141,10 @@ class TestFactory7 {
 };
 class PyTF7 : public TestFactory7 {
 public:
-    PyTF7(int i) : TestFactory7(i) { alias = true; print_created(this, i); }
+    explicit PyTF7(int i) : TestFactory7(i) {
+        alias = true;
+        print_created(this, i);
+    }
     PyTF7(PyTF7 &&f) noexcept : TestFactory7(std::move(f)) { print_move_created(this); }
     PyTF7(const PyTF7 &f) : TestFactory7(f) { print_copy_created(this); }
     ~PyTF7() override { print_destroyed(this); }
@@ -300,7 +315,7 @@ TEST_SUBMODULE(factory_constructors, m) {
     // Class with a custom new operator but *without* a placement new operator (issue #948)
     class NoPlacementNew {
     public:
-        NoPlacementNew(int i) : i(i) { }
+        explicit NoPlacementNew(int i) : i(i) {}
         static void *operator new(std::size_t s) {
             auto *p = ::operator new(s);
             py::print("operator new called, returning", reinterpret_cast<uintptr_t>(p));
@@ -324,8 +339,8 @@ TEST_SUBMODULE(factory_constructors, m) {
     // Class that has verbose operator_new/operator_delete calls
     struct NoisyAlloc {
         NoisyAlloc(const NoisyAlloc &) = default;
-        NoisyAlloc(int i) { py::print(py::str("NoisyAlloc(int {})").format(i)); }
-        NoisyAlloc(double d) { py::print(py::str("NoisyAlloc(double {})").format(d)); }
+        explicit NoisyAlloc(int i) { py::print(py::str("NoisyAlloc(int {})").format(i)); }
+        explicit NoisyAlloc(double d) { py::print(py::str("NoisyAlloc(double {})").format(d)); }
         ~NoisyAlloc() { py::print("~NoisyAlloc()"); }
 
         static void *operator new(size_t s) { py::print("noisy new"); return ::operator new(s); }
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index 8d6e33f790..a5808e2f2a 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -91,7 +91,7 @@ TEST_SUBMODULE(local_bindings, m) {
 
     class Cat : public pets::Pet {
     public:
-        Cat(std::string name) : Pet(std::move(name)) {}
+        explicit Cat(std::string name) : Pet(std::move(name)) {}
     };
     py::class_<pets::Pet>(m, "Pet", py::module_local())
         .def("get_name", &pets::Pet::name);
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 4cf6f08b85..2d303a44e3 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -19,9 +19,9 @@ using overload_cast_ = pybind11::detail::overload_cast_impl<Args...>;
 class ExampleMandA {
 public:
     ExampleMandA() { print_default_created(this); }
-    ExampleMandA(int value) : value(value) { print_created(this, value); }
+    explicit ExampleMandA(int value) : value(value) { print_created(this, value); }
     ExampleMandA(const ExampleMandA &e) : value(e.value) { print_copy_created(this); }
-    ExampleMandA(std::string&&) {}
+    explicit ExampleMandA(std::string &&) {}
     ExampleMandA(ExampleMandA &&e) noexcept : value(e.value) { print_move_created(this); }
     ~ExampleMandA() { print_destroyed(this); }
 
@@ -124,14 +124,14 @@ class NoneCastTester {
 public:
     int answer = -1;
     NoneCastTester() = default;
-    NoneCastTester(int v) : answer(v) {}
+    explicit NoneCastTester(int v) : answer(v) {}
 };
 
 struct StrIssue {
     int val = -1;
 
     StrIssue() = default;
-    StrIssue(int i) : val{i} {}
+    explicit StrIssue(int i) : val{i} {}
 };
 
 // Issues #854, #910: incompatible function args when member function/pointer is in unregistered base class
diff --git a/tests/test_modules.cpp b/tests/test_modules.cpp
index 5867135404..ce61c1a25c 100644
--- a/tests/test_modules.cpp
+++ b/tests/test_modules.cpp
@@ -20,7 +20,7 @@ TEST_SUBMODULE(modules, m) {
     // test_reference_internal
     class A {
     public:
-        A(int v) : v(v) { print_created(this, v); }
+        explicit A(int v) : v(v) { print_created(this, v); }
         ~A() { print_destroyed(this); }
         A(const A&) { print_copy_created(this); }
         A& operator=(const A &copy) { print_copy_assigned(this); v = copy.v; return *this; }
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index b5ca298d91..6963197a5c 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -16,7 +16,7 @@ namespace {
 // Many bases for testing that multiple inheritance from many classes (i.e. requiring extra
 // space for holder constructed flags) works.
 template <int N> struct BaseN {
-    BaseN(int i) : i(i) { }
+    explicit BaseN(int i) : i(i) {}
     int i;
 };
 
@@ -47,12 +47,12 @@ int VanillaStaticMix2::static_value = 12;
 
 // test_multiple_inheritance_virtbase
 struct Base1a {
-    Base1a(int i) : i(i) { }
+    explicit Base1a(int i) : i(i) {}
     int foo() const { return i; }
     int i;
 };
 struct Base2a {
-    Base2a(int i) : i(i) { }
+    explicit Base2a(int i) : i(i) {}
     int bar() const { return i; }
     int i;
 };
@@ -77,7 +77,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_multiple_inheritance_mix1
     // test_multiple_inheritance_mix2
     struct Base1 {
-        Base1(int i) : i(i) { }
+        explicit Base1(int i) : i(i) {}
         int foo() const { return i; }
         int i;
     };
@@ -86,7 +86,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
       .def("foo", &Base1::foo);
 
     struct Base2 {
-        Base2(int i) : i(i) { }
+        explicit Base2(int i) : i(i) {}
         int bar() const { return i; }
         int i;
     };
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index b08a9f7edd..eb5281fb1d 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -52,7 +52,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     // Passthrough test: references and non-pod types should be automatically passed through (in the
     // function definition below, only `b`, `d`, and `g` are vectorized):
     struct NonPODClass {
-        NonPODClass(int v) : value{v} {}
+        explicit NonPODClass(int v) : value{v} {}
         int value;
     };
     py::class_<NonPODClass>(m, "NonPODClass")
@@ -71,7 +71,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
 
     // test_method_vectorization
     struct VectorizeTestClass {
-        VectorizeTestClass(int v) : value{v} {};
+        explicit VectorizeTestClass(int v) : value{v} {};
         float method(int x, float y) const { return y + (float) (x + value); }
         int value = 0;
     };
diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index 0d5827315f..b77636dd1a 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -67,7 +67,7 @@ TEST_SUBMODULE(pickling, m) {
     // test_roundtrip
     class Pickleable {
     public:
-        Pickleable(const std::string &value) : m_value(value) { }
+        explicit Pickleable(const std::string &value) : m_value(value) { }
         const std::string &value() const { return m_value; }
 
         void setExtra1(int extra1) { m_extra1 = extra1; }
@@ -132,7 +132,7 @@ TEST_SUBMODULE(pickling, m) {
     // test_roundtrip_with_dict
     class PickleableWithDict {
     public:
-        PickleableWithDict(const std::string &value) : value(value) { }
+        explicit PickleableWithDict(const std::string &value) : value(value) { }
 
         std::string value;
         int extra;
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index d49fb1f459..b07fd197a9 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -20,7 +20,7 @@ template<typename T>
 class NonZeroIterator {
     const T* ptr_;
 public:
-    NonZeroIterator(const T* ptr) : ptr_(ptr) {}
+    explicit NonZeroIterator(const T *ptr) : ptr_(ptr) {}
     const T& operator*() const { return *ptr_; }
     NonZeroIterator& operator++() { ++ptr_; return *this; }
 };
@@ -77,9 +77,9 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     // test_sliceable
     class Sliceable{
     public:
-      Sliceable(int n): size(n) {}
-      int start,stop,step;
-      int size;
+        explicit Sliceable(int n) : size(n) {}
+        int start, stop, step;
+        int size;
     };
     py::class_<Sliceable>(m, "Sliceable")
         .def(py::init<int>())
@@ -96,12 +96,12 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     // test_sequence
     class Sequence {
     public:
-        Sequence(size_t size) : m_size(size) {
+        explicit Sequence(size_t size) : m_size(size) {
             print_created(this, "of size", m_size);
             m_data = new float[size];
             memset(m_data, 0, sizeof(float) * size);
         }
-        Sequence(const std::vector<float> &value) : m_size(value.size()) {
+        explicit Sequence(const std::vector<float> &value) : m_size(value.size()) {
             print_created(this, "of size", m_size, "from std::vector");
             m_data = new float[m_size];
             memcpy(m_data, &value[0], sizeof(float) * m_size);
@@ -239,7 +239,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     class StringMap {
     public:
         StringMap() = default;
-        StringMap(std::unordered_map<std::string, std::string> init)
+        explicit StringMap(std::unordered_map<std::string, std::string> init)
             : map(std::move(init)) {}
 
         void set(const std::string &key, std::string val) { map[key] = std::move(val); }
@@ -276,7 +276,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     // test_generalized_iterators
     class IntPairs {
     public:
-        IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
+        explicit IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
         const std::pair<int, int>* begin() const { return data_.data(); }
     private:
         std::vector<std::pair<int, int>> data_;
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index eeaa44147a..94f04330a2 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -24,7 +24,7 @@ template <typename T> class huge_unique_ptr {
     std::unique_ptr<T> ptr;
     uint64_t padding[10];
 public:
-    huge_unique_ptr(T *p) : ptr(p) {}
+    explicit huge_unique_ptr(T *p) : ptr(p) {}
     T *get() { return ptr.get(); }
 };
 
@@ -33,7 +33,7 @@ template <typename T>
 class custom_unique_ptr {
     std::unique_ptr<T> impl;
 public:
-    custom_unique_ptr(T* p) : impl(p) { }
+    explicit custom_unique_ptr(T *p) : impl(p) {}
     T* get() const { return impl.get(); }
     T* release_ptr() { return impl.release(); }
 };
@@ -46,7 +46,7 @@ class shared_ptr_with_addressof_operator {
     std::shared_ptr<T> impl;
 public:
     shared_ptr_with_addressof_operator( ) = default;
-    shared_ptr_with_addressof_operator(T* p) : impl(p) { }
+    explicit shared_ptr_with_addressof_operator(T *p) : impl(p) {}
     T* get() const { return impl.get(); }
     T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
 };
@@ -59,7 +59,7 @@ class unique_ptr_with_addressof_operator {
     std::unique_ptr<T> impl;
 public:
     unique_ptr_with_addressof_operator() = default;
-    unique_ptr_with_addressof_operator(T* p) : impl(p) { }
+    explicit unique_ptr_with_addressof_operator(T *p) : impl(p) {}
     T* get() const { return impl.get(); }
     T* release_ptr() { return impl.release(); }
     T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
@@ -68,7 +68,7 @@ class unique_ptr_with_addressof_operator {
 // Custom object with builtin reference counting (see 'object.h' for the implementation)
 class MyObject1 : public Object {
 public:
-    MyObject1(int value) : value(value) { print_created(this, toString()); }
+    explicit MyObject1(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const override { return "MyObject1[" + std::to_string(value) + "]"; }
 protected:
     ~MyObject1() override { print_destroyed(this); }
@@ -80,7 +80,7 @@ class MyObject1 : public Object {
 class MyObject2 {
 public:
     MyObject2(const MyObject2 &) = default;
-    MyObject2(int value) : value(value) { print_created(this, toString()); }
+    explicit MyObject2(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject2[" + std::to_string(value) + "]"; }
     virtual ~MyObject2() { print_destroyed(this); }
 private:
@@ -91,7 +91,7 @@ class MyObject2 {
 class MyObject3 : public std::enable_shared_from_this<MyObject3> {
 public:
     MyObject3(const MyObject3 &) = default;
-    MyObject3(int value) : value(value) { print_created(this, toString()); }
+    explicit MyObject3(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject3[" + std::to_string(value) + "]"; }
     virtual ~MyObject3() { print_destroyed(this); }
 private:
@@ -104,7 +104,7 @@ class MyObject4;
 std::unordered_set<MyObject4 *> myobject4_instances;
 class MyObject4 {
 public:
-    MyObject4(int value) : value{value} {
+    explicit MyObject4(int value) : value{value} {
         print_created(this);
         myobject4_instances.insert(this);
     }
@@ -130,7 +130,7 @@ class MyObject4a;
 std::unordered_set<MyObject4a *> myobject4a_instances;
 class MyObject4a {
 public:
-    MyObject4a(int i) {
+    explicit MyObject4a(int i) {
         value = i;
         print_created(this);
         myobject4a_instances.insert(this);
@@ -153,14 +153,14 @@ class MyObject4a {
 // Object derived but with public destructor and no Deleter in default holder
 class MyObject4b : public MyObject4a {
 public:
-    MyObject4b(int i) : MyObject4a(i) { print_created(this); }
+    explicit MyObject4b(int i) : MyObject4a(i) { print_created(this); }
     ~MyObject4b() override { print_destroyed(this); }
 };
 
 // test_large_holder
 class MyObject5 { // managed by huge_unique_ptr
 public:
-    MyObject5(int value) : value{value} { print_created(this); }
+    explicit MyObject5(int value) : value{value} { print_created(this); }
     ~MyObject5() { print_destroyed(this); }
     int value;
 };
@@ -222,7 +222,7 @@ struct TypeForHolderWithAddressOf {
 
 // test_move_only_holder_with_addressof_operator
 struct TypeForMoveOnlyHolderWithAddressOf {
-    TypeForMoveOnlyHolderWithAddressOf(int value) : value{value} { print_created(this); }
+    explicit TypeForMoveOnlyHolderWithAddressOf(int value) : value{value} { print_created(this); }
     ~TypeForMoveOnlyHolderWithAddressOf() { print_destroyed(this); }
     std::string toString() const {
         return "MoveOnlyHolderWithAddressOf[" + std::to_string(value) + "]";
@@ -242,7 +242,7 @@ struct ElementBase {
 };
 
 struct ElementA : ElementBase {
-    ElementA(int v) : v(v) { }
+    explicit ElementA(int v) : v(v) {}
     int value() const { return v; }
     int v;
 };
@@ -291,9 +291,9 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::implicitly_convertible<py::int_, MyObject1>();
 
     m.def("make_object_1", []() -> Object * { return new MyObject1(1); });
-    m.def("make_object_2", []() -> ref<Object> { return new MyObject1(2); });
+    m.def("make_object_2", []() -> ref<Object> { return ref<Object>(new MyObject1(2)); });
     m.def("make_myobject1_1", []() -> MyObject1 * { return new MyObject1(4); });
-    m.def("make_myobject1_2", []() -> ref<MyObject1> { return new MyObject1(5); });
+    m.def("make_myobject1_2", []() -> ref<MyObject1> { return ref<MyObject1>(new MyObject1(5)); });
     m.def("print_object_1", [](const Object *obj) { py::print(obj->toString()); });
     m.def("print_object_2", [](ref<Object> obj) { py::print(obj->toString()); });
     m.def("print_object_3", [](const ref<Object> &obj) { py::print(obj->toString()); });
@@ -328,7 +328,7 @@ TEST_SUBMODULE(smart_ptr, m) {
 
     // test_smart_ptr_refcounting
     m.def("test_object1_refcounting", []() {
-        ref<MyObject1> o = new MyObject1(0);
+        auto o = ref<MyObject1>(new MyObject1(0));
         bool good = o->getRefCount() == 1;
         py::object o2 = py::cast(o, py::return_value_policy::reference);
         // always request (partial) ownership for objects with intrusive
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 23e2c07b32..7e3363c5ea 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -45,7 +45,8 @@ PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
 
 /// Issue #528: templated constructor
 struct TplCtorClass {
-    template <typename T> TplCtorClass(const T &) { }
+    template <typename T>
+    explicit TplCtorClass(const T &) {}
     bool operator==(const TplCtorClass &) const { return true; }
 };
 
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index 22847eb7a1..6b23e3529f 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -18,7 +18,7 @@
 class El {
 public:
     El() = delete;
-    El(int v) : a(v) { }
+    explicit El(int v) : a(v) {}
 
     int a;
 };
diff --git a/tests/test_tagbased_polymorphic.cpp b/tests/test_tagbased_polymorphic.cpp
index 90f40e14cc..2c7bad8bbc 100644
--- a/tests/test_tagbased_polymorphic.cpp
+++ b/tests/test_tagbased_polymorphic.cpp
@@ -37,33 +37,35 @@ struct Animal
 
 struct Dog : Animal
 {
-    Dog(const std::string& _name, Kind _kind = Kind::Dog) : Animal(_name, _kind) {}
+    explicit Dog(const std::string &_name, Kind _kind = Kind::Dog) : Animal(_name, _kind) {}
     std::string bark() const { return name_of_kind(kind) + " " + name + " goes " + sound; }
     std::string sound = "WOOF!";
 };
 
 struct Labrador : Dog
 {
-    Labrador(const std::string& _name, int _excitement = 9001)
+    explicit Labrador(const std::string &_name, int _excitement = 9001)
         : Dog(_name, Kind::Labrador), excitement(_excitement) {}
     int excitement;
 };
 
 struct Chihuahua : Dog
 {
-    Chihuahua(const std::string& _name) : Dog(_name, Kind::Chihuahua) { sound = "iyiyiyiyiyi"; }
+    explicit Chihuahua(const std::string &_name) : Dog(_name, Kind::Chihuahua) {
+        sound = "iyiyiyiyiyi";
+    }
     std::string bark() const { return Dog::bark() + " and runs in circles"; }
 };
 
 struct Cat : Animal
 {
-    Cat(const std::string& _name, Kind _kind = Kind::Cat) : Animal(_name, _kind) {}
+    explicit Cat(const std::string &_name, Kind _kind = Kind::Cat) : Animal(_name, _kind) {}
     std::string purr() const { return "mrowr"; }
 };
 
 struct Panther : Cat
 {
-    Panther(const std::string& _name) : Cat(_name, Kind::Panther) {}
+    explicit Panther(const std::string &_name) : Cat(_name, Kind::Panther) {}
     std::string purr() const { return "mrrrRRRRRR"; }
 };
 
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index f83a7364b2..1eba534dd2 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -15,7 +15,7 @@
 /* This is an example class that we'll want to be able to extend from Python */
 class ExampleVirt  {
 public:
-    ExampleVirt(int state) : state(state) { print_created(this, state); }
+    explicit ExampleVirt(int state) : state(state) { print_created(this, state); }
     ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
     ExampleVirt(ExampleVirt &&e) noexcept : state(e.state) {
         print_move_created(this);

From 4c6bee3514679cde3b506d5552a3a11fd09cc6d5 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 9 Sep 2021 14:06:33 -0400
Subject: [PATCH 163/638] fix: Set __file__ constant when using eval_file
 (#1300) (#3233)

* Set __file__ constant when using eval_file

* Use const ref

* Use a move instead

* Revert

* Improve test

* Guard test with Python version

* Fix tests

* Dont support Python2 API

* Drop Python2 eval __file__ support

* Hack

* Semisupport Python2

* Take2

* Remove Python2 support
---
 include/pybind11/eval.h        | 9 +++++++++
 tests/test_cmake_build/test.py | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 33fcdc09d1..e0f58bcf49 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -136,6 +136,15 @@ object eval_file(str fname, object global = globals(), object local = object())
         pybind11_fail("File \"" + fname_str + "\" could not be opened!");
     }
 
+    // In Python2, this should be encoded by getfilesystemencoding.
+    // We don't boher setting it since Python2 is past EOL anyway.
+    // See PR#3233
+#if PY_VERSION_HEX >= 0x03000000
+    if (!global.contains("__file__")) {
+        global["__file__"] = std::move(fname);
+    }
+#endif
+
 #if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
     PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(),
                                   local.ptr());
diff --git a/tests/test_cmake_build/test.py b/tests/test_cmake_build/test.py
index d1a290dcc5..972a27bea4 100644
--- a/tests/test_cmake_build/test.py
+++ b/tests/test_cmake_build/test.py
@@ -3,5 +3,8 @@
 
 import test_cmake_build
 
+if str is not bytes:  # If not Python2
+    assert isinstance(__file__, str)  # Test this is properly set
+
 assert test_cmake_build.add(1, 2) == 3
 print("{} imports, runs, and adds: 1 + 2 = 3".format(sys.argv[1]))

From 4d5ad03e1fd09b8be26843f7cb165051ab9a9c05 Mon Sep 17 00:00:00 2001
From: Jeremy Maitin-Shepard <jbms@google.com>
Date: Thu, 9 Sep 2021 12:56:10 -0700
Subject: [PATCH 164/638] Avoid use of temporary `bytes` object in
 string_caster for UTF-8 (#3257)

Fixes #3252
---
 include/pybind11/cast.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index db79f57cda..3e621eba7d 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -377,6 +377,22 @@ template <typename StringType, bool IsView = false> struct string_caster {
 #endif
         }
 
+#if PY_VERSION_HEX >= 0x03030000
+        // On Python >= 3.3, for UTF-8 we avoid the need for a temporary `bytes`
+        // object by using `PyUnicode_AsUTF8AndSize`.
+        if (PYBIND11_SILENCE_MSVC_C4127(UTF_N == 8)) {
+            Py_ssize_t size = -1;
+            const auto *buffer
+                = reinterpret_cast<const CharT *>(PyUnicode_AsUTF8AndSize(load_src.ptr(), &size));
+            if (!buffer) {
+                PyErr_Clear();
+                return false;
+            }
+            value = StringType(buffer, static_cast<size_t>(size));
+            return true;
+        }
+#endif
+
         auto utfNbytes = reinterpret_steal<object>(PyUnicode_AsEncodedString(
             load_src.ptr(), UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr));
         if (!utfNbytes) { PyErr_Clear(); return false; }

From ae07d4c6c663f8cc2590d28ecd6baa09b055537f Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 10 Sep 2021 00:27:36 -0400
Subject: [PATCH 165/638] maint(Clang-Tidy): readability-const-return (#3254)

* Enable clang-tidy readability-const-return

* PyTest functional

* Fix regression

* Fix actual regression

* Remove one more NOLINT

* Update comment
---
 .clang-tidy                     | 3 ++-
 include/pybind11/cast.h         | 7 +++++--
 include/pybind11/detail/descr.h | 3 ++-
 include/pybind11/pybind11.h     | 4 ++--
 include/pybind11/pytypes.h      | 6 +++---
 tests/test_eigen.cpp            | 4 ++++
 6 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index a6437dd494..dbe85a8b47 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -31,9 +31,10 @@ modernize-use-override,
 modernize-use-using,
 *performance*,
 readability-avoid-const-params-in-decls,
+readability-const-return-type,
 readability-container-size-empty,
-readability-else-after-return,
 readability-delete-null-pointer,
+readability-else-after-return,
 readability-implicit-bool-conversion,
 readability-make-member-function-const,
 readability-misplaced-array-index,
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 3e621eba7d..17b10157b5 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1194,13 +1194,15 @@ class argument_loader {
     }
 
     template <typename Return, typename Guard, typename Func>
+    // NOLINTNEXTLINE(readability-const-return-type)
     enable_if_t<!std::is_void<Return>::value, Return> call(Func &&f) && {
-        return std::move(*this).template call_impl<Return>(std::forward<Func>(f), indices{}, Guard{});
+        return std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
     }
 
     template <typename Return, typename Guard, typename Func>
+    // NOLINTNEXTLINE(readability-const-return-type)
     enable_if_t<std::is_void<Return>::value, void_type> call(Func &&f) && {
-        std::move(*this).template call_impl<Return>(std::forward<Func>(f), indices{}, Guard{});
+        std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
         return void_type();
     }
 
@@ -1222,6 +1224,7 @@ class argument_loader {
     }
 
     template <typename Return, typename Func, size_t... Is, typename Guard>
+    // NOLINTNEXTLINE(readability-const-return-type)
     Return call_impl(Func &&f, index_sequence<Is...>, Guard &&) && {
         return std::forward<Func>(f)(cast_op<Args>(std::move(std::get<Is>(argcasters)))...);
     }
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 0b498e5e72..c62e541bda 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -77,7 +77,8 @@ constexpr enable_if_t<B, T1> _(const T1 &d, const T2 &) { return d; }
 template <bool B, typename T1, typename T2>
 constexpr enable_if_t<!B, T2> _(const T1 &, const T2 &d) { return d; }
 
-template <size_t Size> auto constexpr _() -> decltype(int_to_str<Size / 10, Size % 10>::digits) {
+template <size_t Size>
+auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
     return int_to_str<Size / 10, Size % 10>::digits;
 }
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 82d339751e..c4e5ea6e1f 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2002,13 +2002,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename KeyType = decltype((*std::declval<Iterator>()).first),
 #endif
           typename... Extra>
-iterator make_key_iterator(Iterator first, Sentinel last, Extra &&... extra) {
+iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
     using state = detail::iterator_state<Iterator, Sentinel, true, Policy>;
 
     if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator", pybind11::module_local())
             .def("__iter__", [](state &s) -> state& { return s; })
-            .def("__next__", [](state &s) -> KeyType {
+            .def("__next__", [](state &s) -> detail::remove_cv_t<KeyType> {
                 if (!s.first_or_done)
                     ++s.it;
                 else
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 971db85f37..2de3f5f106 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -773,7 +773,7 @@ class sequence_fast_readonly {
 protected:
     using iterator_category = std::random_access_iterator_tag;
     using value_type = handle;
-    using reference = const handle;
+    using reference = handle;
     using pointer = arrow_proxy<const handle>;
 
     sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) { }
@@ -816,7 +816,7 @@ class dict_readonly {
 protected:
     using iterator_category = std::forward_iterator_tag;
     using value_type = std::pair<handle, handle>;
-    using reference = const value_type;
+    using reference = value_type;
     using pointer = arrow_proxy<const value_type>;
 
     dict_readonly() = default;
@@ -966,7 +966,7 @@ class iterator : public object {
     using iterator_category = std::input_iterator_tag;
     using difference_type = ssize_t;
     using value_type = handle;
-    using reference = const handle;
+    using reference = handle;
     using pointer = const handle *;
 
     PYBIND11_OBJECT_DEFAULT(iterator, object, PyIter_Check)
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index 651be0575f..ad572b2ad7 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -178,6 +178,7 @@ TEST_SUBMODULE(eigen, m) {
         ReturnTester() { print_created(this); }
         ~ReturnTester() { print_destroyed(this); }
         static Eigen::MatrixXd create() { return Eigen::MatrixXd::Ones(10, 10); }
+        // NOLINTNEXTLINE(readability-const-return-type)
         static const Eigen::MatrixXd createConst() { return Eigen::MatrixXd::Ones(10, 10); }
         Eigen::MatrixXd &get() { return mat; }
         Eigen::MatrixXd *getPtr() { return &mat; }
@@ -244,6 +245,9 @@ TEST_SUBMODULE(eigen, m) {
 
     // test_fixed, and various other tests
     m.def("fixed_r", [mat]() -> FixedMatrixR { return FixedMatrixR(mat); });
+    // Our Eigen does a hack which respects constness through the numpy writeable flag.
+    // Therefore, the const return actually affects this type despite being an rvalue.
+    // NOLINTNEXTLINE(readability-const-return-type)
     m.def("fixed_r_const", [mat]() -> const FixedMatrixR { return FixedMatrixR(mat); });
     m.def("fixed_c", [mat]() -> FixedMatrixC { return FixedMatrixC(mat); });
     m.def("fixed_copy_r", [](const FixedMatrixR &m) -> FixedMatrixR { return m; });

From 121b91f99c9044e12ea1f746d7f3e586c41529c8 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 10 Sep 2021 07:16:09 -0700
Subject: [PATCH 166/638] Fixing NOLINT mishap (#3260)

* Removing NOLINT pointed out by Aaron.

* Removing another NOLINT.
---
 include/pybind11/cast.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 17b10157b5..1ec2080f8a 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1200,7 +1200,6 @@ class argument_loader {
     }
 
     template <typename Return, typename Guard, typename Func>
-    // NOLINTNEXTLINE(readability-const-return-type)
     enable_if_t<std::is_void<Return>::value, void_type> call(Func &&f) && {
         std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
         return void_type();
@@ -1224,7 +1223,6 @@ class argument_loader {
     }
 
     template <typename Return, typename Func, size_t... Is, typename Guard>
-    // NOLINTNEXTLINE(readability-const-return-type)
     Return call_impl(Func &&f, index_sequence<Is...>, Guard &&) && {
         return std::forward<Func>(f)(cast_op<Args>(std::move(std::get<Is>(argcasters)))...);
     }

From 0e599589fe821f86d18635c13636f3042d4c06b9 Mon Sep 17 00:00:00 2001
From: Laramie Leavitt <laramiel@users.noreply.github.com>
Date: Fri, 10 Sep 2021 09:29:21 -0700
Subject: [PATCH 167/638] Fix thread safety for pybind11 loader_life_support
 (#3237)

* Fix thread safety for pybind11 loader_life_support

Fixes issue: https://github.com/pybind/pybind11/issues/2765

This converts the vector of PyObjects to either a single void* or
a per-thread void* depending on the WITH_THREAD define.

The new field is used by each thread to construct a stack
of loader_life_support frames that can extend the life of python
objects.

The pointer is updated when the loader_life_support object is allocated
(which happens before a call) as well as on release.

Each loader_life_support maintains a set of PyObject references
that need to be lifetime extended; this is done by storing them
in a c++ std::unordered_set and clearing the references when the
method completes.

* Also update the internals version as the internal struct is no longer compatible

* Add test demonstrating threading works correctly.

It may be appropriate to run this under msan/tsan/etc.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update test to use lifetime-extended references rather than
std::string_view, as that's a C++ 17 feature.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Make loader_life_support members private

* Update version to dev2

* Update test to use python threading rather than concurrent.futures

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Remove unnecessary env in test

* Remove unnecessary pytest in test

* Use native C++ thread_local in place of python per-thread data structures to retain compatability

* clang-format test_thread.cpp

* Add a note about debugging the py::cast() error

* thread_test.py now propagates exceptions on join() calls.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* remove unused sys / merge

* Update include order in test_thread.cpp

* Remove spurious whitespace

* Update comment / whitespace.

* Address review comments

* lint cleanup

* Fix test IntStruct constructor.

* Add explicit to constructor

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/detail/common.h           |  4 +-
 include/pybind11/detail/internals.h        |  6 +-
 include/pybind11/detail/type_caster_base.h | 55 ++++++++++--------
 pybind11/_version.py                       |  2 +-
 tests/CMakeLists.txt                       |  1 +
 tests/test_thread.cpp                      | 66 ++++++++++++++++++++++
 tests/test_thread.py                       | 44 +++++++++++++++
 7 files changed, 148 insertions(+), 30 deletions(-)
 create mode 100644 tests/test_thread.cpp
 create mode 100644 tests/test_thread.py

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index a8fd7d917e..8aeb79fb7d 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 8
-#define PYBIND11_VERSION_PATCH 0.dev1
+#define PYBIND11_VERSION_PATCH 0.dev2
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020800D1
+#define PYBIND11_VERSION_HEX 0x020800D2
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index b177801a11..39c28e7732 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -106,7 +106,7 @@ struct internals {
     std::unordered_map<const PyObject *, std::vector<PyObject *>> patients;
     std::forward_list<ExceptionTranslator> registered_exception_translators;
     std::unordered_map<std::string, void *> shared_data; // Custom data to be shared across extensions
-    std::vector<PyObject *> loader_patient_stack; // Used by `loader_life_support`
+    std::vector<PyObject *> unused_loader_patient_stack_remove_at_v5;
     std::forward_list<std::string> static_strings; // Stores the std::strings backing detail::c_str()
     PyTypeObject *static_property_type;
     PyTypeObject *default_metaclass;
@@ -298,12 +298,12 @@ PYBIND11_NOINLINE internals &get_internals() {
         #if PY_VERSION_HEX >= 0x03070000
             internals_ptr->tstate = PyThread_tss_alloc();
             if (!internals_ptr->tstate || (PyThread_tss_create(internals_ptr->tstate) != 0))
-                pybind11_fail("get_internals: could not successfully initialize the TSS key!");
+                pybind11_fail("get_internals: could not successfully initialize the tstate TSS key!");
             PyThread_tss_set(internals_ptr->tstate, tstate);
         #else
             internals_ptr->tstate = PyThread_create_key();
             if (internals_ptr->tstate == -1)
-                pybind11_fail("get_internals: could not successfully initialize the TLS key!");
+                pybind11_fail("get_internals: could not successfully initialize the tstate TLS key!");
             PyThread_set_key_value(internals_ptr->tstate, tstate);
         #endif
         internals_ptr->istate = tstate->interp;
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 4c9ac7b8f6..fa8433cfec 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -31,47 +31,54 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// A life support system for temporary objects created by `type_caster::load()`.
 /// Adding a patient will keep it alive up until the enclosing function returns.
 class loader_life_support {
+private:
+    loader_life_support* parent = nullptr;
+    std::unordered_set<PyObject *> keep_alive;
+
+    static loader_life_support** get_stack_pp() {
+#if defined(WITH_THREAD)
+        thread_local static loader_life_support* per_thread_stack = nullptr;
+        return &per_thread_stack;
+#else
+        static loader_life_support* global_stack = nullptr;
+        return &global_stack;
+#endif
+    }
+
 public:
     /// A new patient frame is created when a function is entered
     loader_life_support() {
-        get_internals().loader_patient_stack.push_back(nullptr);
+        loader_life_support** stack = get_stack_pp();
+        parent = *stack;
+        *stack = this;
     }
 
     /// ... and destroyed after it returns
     ~loader_life_support() {
-        auto &stack = get_internals().loader_patient_stack;
-        if (stack.empty())
+        loader_life_support** stack = get_stack_pp();
+        if (*stack != this)
             pybind11_fail("loader_life_support: internal error");
-
-        auto ptr = stack.back();
-        stack.pop_back();
-        Py_CLEAR(ptr);
-
-        // A heuristic to reduce the stack's capacity (e.g. after long recursive calls)
-        if (stack.capacity() > 16 && !stack.empty() && stack.capacity() / stack.size() > 2)
-            stack.shrink_to_fit();
+        *stack = parent;
+        for (auto* item : keep_alive)
+            Py_DECREF(item);
     }
 
     /// This can only be used inside a pybind11-bound function, either by `argument_loader`
     /// at argument preparation time or by `py::cast()` at execution time.
     PYBIND11_NOINLINE static void add_patient(handle h) {
-        auto &stack = get_internals().loader_patient_stack;
-        if (stack.empty())
+        loader_life_support* frame =  *get_stack_pp();
+        if (!frame) {
+            // NOTE: It would be nice to include the stack frames here, as this indicates
+            // use of pybind11::cast<> outside the normal call framework, finding such
+            // a location is challenging. Developers could consider printing out
+            // stack frame addresses here using something like __builtin_frame_address(0)
             throw cast_error("When called outside a bound function, py::cast() cannot "
                              "do Python -> C++ conversions which require the creation "
                              "of temporary values");
-
-        auto &list_ptr = stack.back();
-        if (list_ptr == nullptr) {
-            list_ptr = PyList_New(1);
-            if (!list_ptr)
-                pybind11_fail("loader_life_support: error allocating list");
-            PyList_SET_ITEM(list_ptr, 0, h.inc_ref().ptr());
-        } else {
-            auto result = PyList_Append(list_ptr, h.ptr());
-            if (result == -1)
-                pybind11_fail("loader_life_support: error adding patient");
         }
+
+        if (frame->keep_alive.insert(h.ptr()).second)
+            Py_INCREF(h.ptr());
     }
 };
 
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 610d39bf1c..d212f1dfb7 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.8.0.dev1"
+__version__ = "2.8.0.dev2"
 version_info = tuple(_to_int(s) for s in __version__.split("."))
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d71a51e6a0..f014771d54 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -129,6 +129,7 @@ set(PYBIND11_TEST_FILES
     test_stl.cpp
     test_stl_binders.cpp
     test_tagbased_polymorphic.cpp
+    test_thread.cpp
     test_union.cpp
     test_virtual_functions.cpp)
 
diff --git a/tests/test_thread.cpp b/tests/test_thread.cpp
new file mode 100644
index 0000000000..19d91768b3
--- /dev/null
+++ b/tests/test_thread.cpp
@@ -0,0 +1,66 @@
+/*
+    tests/test_thread.cpp -- call pybind11 bound methods in threads
+
+    Copyright (c) 2021 Laramie Leavitt (Google LLC) <lar@google.com>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/cast.h>
+#include <pybind11/pybind11.h>
+
+#include <chrono>
+#include <thread>
+
+#include "pybind11_tests.h"
+
+namespace py = pybind11;
+
+namespace {
+
+struct IntStruct {
+    explicit IntStruct(int v) : value(v) {};
+    ~IntStruct() { value = -value; }
+    IntStruct(const IntStruct&) = default;
+    IntStruct& operator=(const IntStruct&) = default;
+
+    int value;
+};
+
+} // namespace
+
+TEST_SUBMODULE(thread, m) {
+
+    py::class_<IntStruct>(m, "IntStruct").def(py::init([](const int i) { return IntStruct(i); }));
+
+    // implicitly_convertible uses loader_life_support when an implicit
+    // conversion is required in order to lifetime extend the reference.
+    //
+    // This test should be run with ASAN for better effectiveness.
+    py::implicitly_convertible<int, IntStruct>();
+
+    m.def("test", [](int expected, const IntStruct &in) {
+        {
+            py::gil_scoped_release release;
+            std::this_thread::sleep_for(std::chrono::milliseconds(5));
+        }
+
+        if (in.value != expected) {
+            throw std::runtime_error("Value changed!!");
+        }
+    });
+
+    m.def(
+        "test_no_gil",
+        [](int expected, const IntStruct &in) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(5));
+            if (in.value != expected) {
+                throw std::runtime_error("Value changed!!");
+            }
+        },
+        py::call_guard<py::gil_scoped_release>());
+
+    // NOTE: std::string_view also uses loader_life_support to ensure that
+    // the string contents remain alive, but that's a C++ 17 feature.
+}
diff --git a/tests/test_thread.py b/tests/test_thread.py
new file mode 100644
index 0000000000..f9db1babaf
--- /dev/null
+++ b/tests/test_thread.py
@@ -0,0 +1,44 @@
+# -*- coding: utf-8 -*-
+
+import threading
+
+from pybind11_tests import thread as m
+
+
+class Thread(threading.Thread):
+    def __init__(self, fn):
+        super(Thread, self).__init__()
+        self.fn = fn
+        self.e = None
+
+    def run(self):
+        try:
+            for i in range(10):
+                self.fn(i, i)
+        except Exception as e:
+            self.e = e
+
+    def join(self):
+        super(Thread, self).join()
+        if self.e:
+            raise self.e
+
+
+def test_implicit_conversion():
+    a = Thread(m.test)
+    b = Thread(m.test)
+    c = Thread(m.test)
+    for x in [a, b, c]:
+        x.start()
+    for x in [c, b, a]:
+        x.join()
+
+
+def test_implicit_conversion_no_gil():
+    a = Thread(m.test_no_gil)
+    b = Thread(m.test_no_gil)
+    c = Thread(m.test_no_gil)
+    for x in [a, b, c]:
+        x.start()
+    for x in [c, b, a]:
+        x.join()

From 9978ed588baa2cf804794b8ee9f765a316ab16e2 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 10 Sep 2021 14:23:32 -0400
Subject: [PATCH 168/638] Fix capsule bug (#3261)

Thanks Aaron for jumping in fixing this!
---
 include/pybind11/pytypes.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 2de3f5f106..a1cf6bef0f 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1414,14 +1414,19 @@ class capsule : public object {
     T* get_pointer() const {
         auto name = this->name();
         T *result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
-        if (!result) pybind11_fail("Unable to extract capsule contents!");
+        if (!result) {
+            PyErr_Clear();
+            pybind11_fail("Unable to extract capsule contents!");
+        }
         return result;
     }
 
     /// Replaces a capsule's pointer *without* calling the destructor on the existing one.
     void set_pointer(const void *value) {
-        if (PyCapsule_SetPointer(m_ptr, const_cast<void *>(value)) != 0)
+        if (PyCapsule_SetPointer(m_ptr, const_cast<void *>(value)) != 0) {
+            PyErr_Clear();
             pybind11_fail("Could not set capsule pointer");
+        }
     }
 
     const char *name() const { return PyCapsule_GetName(m_ptr); }

From 6c65ab5950a75271bddced3f4238fff2c9a427a5 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 12 Sep 2021 19:53:26 -0700
Subject: [PATCH 169/638] Follow-on to PR #3254, to address user code
 breakages. (#3263)

* Restoring `const` removed from pytypes.h in PR #3254, adding tests reflective of user code that breaks when those `const` are removed.

* clang-tidy NOLINTs (and one collateral fix).

* Inserting PYBIND11_CONST_FOR_STRICT_PLATFORMS

* Trying `defined(__APPLE__)`

* Trying again: `auto it` for strict platforms.

* Adding NOLINTNEXTLINE(bugprone-macro-parentheses), expanding comments.

* Labeling all changes with `PR #3263`, for easy reference, and to make it easy to undo these changes if we decide to do so in the future.
---
 include/pybind11/pybind11.h |  1 +
 include/pybind11/pytypes.h  | 11 +++++++---
 tests/test_pytypes.cpp      | 43 +++++++++++++++++++++++++++++++++++++
 tests/test_pytypes.py       |  6 ++++++
 4 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index c4e5ea6e1f..07d2d04363 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1987,6 +1987,7 @@ iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
                     throw stop_iteration();
                 }
                 return *s.it;
+            // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
             }, std::forward<Extra>(extra)..., Policy);
     }
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index a1cf6bef0f..d1d3dcb05e 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -733,7 +733,9 @@ class generic_iterator : public Policy {
     generic_iterator() = default;
     generic_iterator(handle seq, ssize_t index) : Policy(seq, index) { }
 
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator*() const { return Policy::dereference(); }
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator[](difference_type n) const { return *(*this + n); }
     pointer operator->() const { return **this; }
 
@@ -773,11 +775,12 @@ class sequence_fast_readonly {
 protected:
     using iterator_category = std::random_access_iterator_tag;
     using value_type = handle;
-    using reference = handle;
+    using reference = const handle; // PR #3263
     using pointer = arrow_proxy<const handle>;
 
     sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) { }
 
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference dereference() const { return *ptr; }
     void increment() { ++ptr; }
     void decrement() { --ptr; }
@@ -816,12 +819,13 @@ class dict_readonly {
 protected:
     using iterator_category = std::forward_iterator_tag;
     using value_type = std::pair<handle, handle>;
-    using reference = value_type;
+    using reference = const value_type; // PR #3263
     using pointer = arrow_proxy<const value_type>;
 
     dict_readonly() = default;
     dict_readonly(handle obj, ssize_t pos) : obj(obj), pos(pos) { increment(); }
 
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference dereference() const { return {key, value}; }
     void increment() {
         if (PyDict_Next(obj.ptr(), &pos, &key, &value) == 0) {
@@ -966,7 +970,7 @@ class iterator : public object {
     using iterator_category = std::input_iterator_tag;
     using difference_type = ssize_t;
     using value_type = handle;
-    using reference = handle;
+    using reference = const handle; // PR #3263
     using pointer = const handle *;
 
     PYBIND11_OBJECT_DEFAULT(iterator, object, PyIter_Check)
@@ -982,6 +986,7 @@ class iterator : public object {
         return rv;
     }
 
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator*() const {
         if (m_ptr && !value.ptr()) {
             auto& self = const_cast<iterator &>(*this);
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 96c97351e1..2157dc0973 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -462,6 +462,49 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("weakref_from_object_and_function",
           [](py::object o, py::function f) { return py::weakref(std::move(o), std::move(f)); });
 
+// See PR #3263 for background (https://github.com/pybind/pybind11/pull/3263):
+// pytypes.h could be changed to enforce the "most correct" user code below, by removing
+// `const` from iterator `reference` using type aliases, but that will break existing
+// user code.
+#if (defined(__APPLE__) && defined(__clang__)) || defined(PYPY_VERSION)
+// This is "most correct" and enforced on these platforms.
+#    define PYBIND11_AUTO_IT auto it
+#else
+// This works on many platforms and is (unfortunately) reflective of existing user code.
+// NOLINTNEXTLINE(bugprone-macro-parentheses)
+#    define PYBIND11_AUTO_IT auto &it
+#endif
+
+    m.def("tuple_iterator", []() {
+        auto tup = py::make_tuple(5, 7);
+        int tup_sum = 0;
+        for (PYBIND11_AUTO_IT : tup) {
+            tup_sum += it.cast<int>();
+        }
+        return tup_sum;
+    });
+
+    m.def("dict_iterator", []() {
+        py::dict dct;
+        dct[py::int_(3)] = 5;
+        dct[py::int_(7)] = 11;
+        int kv_sum = 0;
+        for (PYBIND11_AUTO_IT : dct) {
+            kv_sum += it.first.cast<int>() * 100 + it.second.cast<int>();
+        }
+        return kv_sum;
+    });
+
+    m.def("passed_iterator", [](const py::iterator &py_it) {
+        int elem_sum = 0;
+        for (PYBIND11_AUTO_IT : py_it) {
+            elem_sum += it.cast<int>();
+        }
+        return elem_sum;
+    });
+
+#undef PYBIND11_AUTO_IT
+
     // Tests below this line are for pybind11 IMPLEMENTATION DETAILS:
 
     m.def("sequence_item_get_ssize_t", [](const py::object &o) {
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 18847550f2..070538cc9f 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -623,6 +623,12 @@ def callback(wr):
     assert callback.called
 
 
+def test_cpp_iterators():
+    assert m.tuple_iterator() == 12
+    assert m.dict_iterator() == 305 + 711
+    assert m.passed_iterator(iter((-7, 3))) == -4
+
+
 def test_implementation_details():
     lst = [39, 43, 92, 49, 22, 29, 93, 98, 26, 57, 8]
     tup = tuple(lst)

From 3ed31e9289acaecb333e851ecb59912c784cdd3d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 13 Sep 2021 15:58:30 -0400
Subject: [PATCH 170/638] [pre-commit.ci] pre-commit autoupdate (#3266)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.25.0 → v2.26.0](https://github.com/asottile/pyupgrade/compare/v2.25.0...v2.26.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 06e82fe4b1..fd11cf0cda 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.25.0
+  rev: v2.26.0
   hooks:
   - id: pyupgrade
 

From e0031bfcebc189b978e650cf67620788454453d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matthias=20K=C3=B6ppe?= <mkoeppe@math.ucdavis.edu>
Date: Wed, 15 Sep 2021 10:52:32 -0700
Subject: [PATCH 171/638] include/pybind11/numpy.h: gcc 4.8.4 does not have
 is_trivially_copyable (#3270)

---
 include/pybind11/numpy.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index d55844086d..b7747fae2d 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -322,7 +322,7 @@ template <typename T> using remove_all_extents_t = typename array_info<T>::type;
 
 template <typename T> using is_pod_struct = all_of<
     std::is_standard_layout<T>,     // since we're accessing directly in memory we need a standard layout type
-#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150623 || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
+#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623 || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
     // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after 5)
     // don't implement is_trivially_copyable, so approximate it
     std::is_trivially_destructible<T>,

From 04dd3262f0420d48531a82021fa4895ba14bdcb2 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 17 Sep 2021 17:28:26 -0400
Subject: [PATCH 172/638] docs: update CHANGELOG (#3276)

---
 docs/advanced/pycpp/numpy.rst |  39 +++++++++---
 docs/changelog.rst            | 114 ++++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+), 7 deletions(-)

diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index 53ec8c1a3c..cae068e910 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -171,6 +171,31 @@ template parameter, and it ensures that non-conforming arguments are converted
 into an array satisfying the specified requirements instead of trying the next
 function overload.
 
+There are several methods on arrays; the methods listed below under references
+work, as well as the following functions based on the NumPy API:
+
+- ``.dtype()`` returns the type of the contained values.
+
+- ``.strides()`` returns a pointer to the strides of the array (optionally pass
+  an integer axis to get a number).
+
+- ``.flags()`` returns the flag settings. ``.writable()`` and ``.owndata()``
+  are directly available.
+
+- ``.offset_at()`` returns the offset (optionally pass indices).
+
+- ``.squeeze()`` returns a view with length-1 axes removed.
+
+- ``.view(dtype)`` returns a view of the array with a different dtype.
+
+- ``.reshape({i, j, ...})`` returns a view of the array with a different shape.
+  ``.resize({...})`` is also available.
+
+- ``.index_at(i, j, ...)`` gets the count from the beginning to a given index.
+
+
+There are also several methods for getting references (described below).
+
 Structured types
 ================
 
@@ -345,21 +370,21 @@ The returned proxy object supports some of the same methods as ``py::array`` so
 that it can be used as a drop-in replacement for some existing, index-checked
 uses of ``py::array``:
 
-- ``r.ndim()`` returns the number of dimensions
+- ``.ndim()`` returns the number of dimensions
 
-- ``r.data(1, 2, ...)`` and ``r.mutable_data(1, 2, ...)``` returns a pointer to
+- ``.data(1, 2, ...)`` and ``r.mutable_data(1, 2, ...)``` returns a pointer to
   the ``const T`` or ``T`` data, respectively, at the given indices.  The
   latter is only available to proxies obtained via ``a.mutable_unchecked()``.
 
-- ``itemsize()`` returns the size of an item in bytes, i.e. ``sizeof(T)``.
+- ``.itemsize()`` returns the size of an item in bytes, i.e. ``sizeof(T)``.
 
-- ``ndim()`` returns the number of dimensions.
+- ``.ndim()`` returns the number of dimensions.
 
-- ``shape(n)`` returns the size of dimension ``n``
+- ``.shape(n)`` returns the size of dimension ``n``
 
-- ``size()`` returns the total number of elements (i.e. the product of the shapes).
+- ``.size()`` returns the total number of elements (i.e. the product of the shapes).
 
-- ``nbytes()`` returns the number of bytes used by the referenced elements
+- ``.nbytes()`` returns the number of bytes used by the referenced elements
   (i.e. ``itemsize()`` times ``size()``).
 
 .. seealso::
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 2f76abe055..8b9690caaf 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -9,6 +9,11 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 v2.8.0 (WIP)
 ------------
 
+New features:
+
+* Added ``py::raise_from`` to enable chaining exceptions.
+  `#3215 <https://github.com/pybind/pybind11/pull/3215>`_
+
 * Allow exception translators to be optionally registered local to a module
   instead of applying globally across all pybind11 modules. Use
   ``register_local_exception_translator(ExceptionTranslator&& translator)``
@@ -16,6 +21,115 @@ v2.8.0 (WIP)
   translator)`` to keep your exception remapping code local to the module.
   `#2650 <https://github.com/pybind/pybind11/pull/2650>`_
 
+* Add ``make_simple_namespace`` function for instantiating Python
+  ``SimpleNamespace`` objects.
+  `#2840 <https://github.com/pybind/pybind11/pull/2840>`_
+
+* ``pybind11::scoped_interpreter`` and ``initialize_interpreter`` have new
+  arguments to allow ``sys.argv`` initialization.
+  `#2341 <https://github.com/pybind/pybind11/pull/2341>`_
+
+* Allow Python builtins to be used as callbacks in CPython.
+  `#1413 <https://github.com/pybind/pybind11/pull/1413>`_
+
+* Added ``view`` to view arrays with a different datatype.
+  `#987 <https://github.com/pybind/pybind11/pull/987>`_
+
+* Implemented ``reshape`` on arrays.
+  `#984 <https://github.com/pybind/pybind11/pull/984>`_
+
+
+Changes:
+
+* Set ``__file__`` constant when running ``eval_file`` in an embedded interpreter.
+  `#3233 <https://github.com/pybind/pybind11/pull/3233>`_
+
+* The pybind11 proxy types ``str``, ``bytes``, ``bytearray``, ``tuple``,
+  ``list`` now consistently support passing ``ssize_t`` values for sizes and
+  indexes. Previously, only ``size_t`` was accepted in several interfaces.
+  `#3219 <https://github.com/pybind/pybind11/pull/3219>`_
+
+
+Fixes:
+
+* Bug fix: enum value's ``__int__`` returning non-int when underlying type is bool or of char type.
+  `#1334 <https://github.com/pybind/pybind11/pull/1334>`_
+
+* Fixes bug in setting error state in Capsule's pointer methods.
+  `#3261 <https://github.com/pybind/pybind11/pull/3261>`_
+
+* A long-standing memory leak in ``py::cpp_function::initialize`` was fixed.
+  `#3229 <https://github.com/pybind/pybind11/pull/3229>`_
+
+* Fixes thread safety for some ``pybind11::type_caster`` which require lifetime extension, such as for ``std::string_view``.
+  `#3237 <https://github.com/pybind/pybind11/pull/3237>`_
+
+* Restore compatibility with gcc 4.8.4 as distributed by ubuntu-trusty, linuxmint-17.
+  `#3270 <https://github.com/pybind/pybind11/pull/3270>`_
+
+
+Build system improvements:
+
+* Fix regression in CMake Python package config: improper use of absolute path.
+  `#3144 <https://github.com/pybind/pybind11/pull/3144>`_
+
+* Specified UTF8-encoding in setup.py calls of open().
+  `#3137 <https://github.com/pybind/pybind11/pull/3137>`_
+
+
+Backend and tidying up:
+
+* Optimize NumPy array construction with additional moves.
+  `#3183 <https://github.com/pybind/pybind11/pull/3183>`_
+
+* Conversion to ``std::string`` and ``std::string_view`` now avoids making an
+  extra copy of the data on Python >= 3.3.
+  `#3257 <https://github.com/pybind/pybind11/pull/3257>`_
+
+* Remove const modifier from certain C++ methods on Python collections
+  (``list``, ``set``, ``dict``) such as (``clear()``, ``append()``,
+  ``insert()``, etc...) and annotated them with ``py-non-const``.
+
+* Enable readability ``clang-tidy-const-return`` and remove useless consts.
+  `#3254 <https://github.com/pybind/pybind11/pull/3254>`_
+  `#3194 <https://github.com/pybind/pybind11/pull/3194>`_
+
+* The clang-tidy ``google-explicit-constructor`` option was enabled.
+  `#3250 <https://github.com/pybind/pybind11/pull/3250>`_
+
+* Mark a pytype move constructor as noexcept (perf).
+  `#3236 <https://github.com/pybind/pybind11/pull/3236>`_
+
+* Enable clang-tidy check to guard against inheritance slicing.
+  `#3210 <https://github.com/pybind/pybind11/pull/3210>`_
+
+* Legacy warning suppression pragma were removed from eigen.h. On Unix
+  platforms, please use -isystem for Eigen include directories, to suppress
+  compiler warnings originating from Eigen headers. Note that CMake does this
+  by default. No adjustments are needed for Windows.
+  `#3198 <https://github.com/pybind/pybind11/pull/3198>`_
+
+* Format pybind11 with isort consistent ordering of imports
+  `#3195 <https://github.com/pybind/pybind11/pull/3195>`_
+
+* The warnings-suppression "pragma clamp" at the top/bottom of pybind11 was
+  removed, clearing the path to refactoring and IWYU cleanup.
+  `#3186 <https://github.com/pybind/pybind11/pull/3186>`_
+
+* Enable most bugprone checks in clang-tidy and fix the found potential bugs
+  and poor coding styles.
+  `#3166 <https://github.com/pybind/pybind11/pull/3166>`_
+
+* Add ``clang-tidy-readability`` rules to make boolean casts explicit improving
+  code readability. Also enabled other misc and readability clang-tidy checks.
+  `#3148 <https://github.com/pybind/pybind11/pull/3148>`_
+
+* Move object in ``.pop()`` for list.
+  `#3116 <https://github.com/pybind/pybind11/pull/3116>`_
+
+
+
+
 v2.7.1 (Aug 3, 2021)
 ---------------------
 

From 14976c853b8422dc41ce7874742cab122684c97e Mon Sep 17 00:00:00 2001
From: Jeremy Maitin-Shepard <jbms@google.com>
Date: Mon, 20 Sep 2021 04:57:38 -0700
Subject: [PATCH 173/638] Eliminate duplicate TLS keys for loader_life_support
 stack (#3275)

* Eliminate duplicate TLS keys for loader_life_support stack

This revises the existing fix for
https://github.com/pybind/pybind11/issues/2765 in
https://github.com/pybind/pybind11/pull/3237 to reduce the amount of
TLS storage used.

The shared TLS key is stored in two different ways, depending on
`PYBIND11_INTERNALS_VERSION`.  If `PYBIND11_INTERNALS_VERSION ==
4` (as is currently set), the TLS key is stored in the
`internal::shared_data` map to avoid breaking ABI compatibility.  If
`PYBIND11_INTERNALS_VERSION > 4`, the TLS key is stored directly in
the `internals` struct.

* Fix test_pytypes.py::test_issue2361 failure on PyPy3.7

* Add github actions tests for unstable ABI
---
 .github/workflows/ci.yml                   |  18 +++
 CMakeLists.txt                             |   7 +
 include/pybind11/detail/internals.h        | 178 +++++++++++++++------
 include/pybind11/detail/type_caster_base.h |  39 +++--
 include/pybind11/gil.h                     |   4 +-
 tests/test_pytypes.py                      |   3 +-
 6 files changed, 186 insertions(+), 63 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a3664ddf55..2348212f4b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -144,6 +144,24 @@ jobs:
       if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
       run: cmake --build build2 --target cpptest
 
+    # Third build - C++17 mode with unstable ABI
+    - name: Configure (unstable ABI)
+      run: >
+        cmake -S . -B build3
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=17
+        -DPYBIND11_INTERNALS_VERSION=10000000
+        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
+        ${{ matrix.args }}
+
+    - name: Build (unstable ABI)
+      run: cmake --build build3 -j 2
+
+    - name: Python tests (unstable ABI)
+      run: cmake --build build3 --target pytest
+
     - name: Interface test
       run: cmake --build build2 --target test_cmake_build
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bb01a861ae..25cfcec2f6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -89,6 +89,9 @@ endif()
 option(PYBIND11_INSTALL "Install pybind11 header files?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_TEST "Build pybind11 test suite?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_NOPYTHON "Disable search for Python" OFF)
+set(PYBIND11_INTERNALS_VERSION
+    ""
+    CACHE STRING "Override the ABI version, may be used to enable the unstable ABI.")
 
 cmake_dependent_option(
   USE_PYTHON_INCLUDE_DIR
@@ -183,6 +186,10 @@ if(NOT TARGET pybind11_headers)
 
   target_compile_features(pybind11_headers INTERFACE cxx_inheriting_constructors cxx_user_literals
                                                      cxx_right_angle_brackets)
+  if(NOT "${PYBIND11_INTERNALS_VERSION}" STREQUAL "")
+    target_compile_definitions(
+      pybind11_headers INTERFACE "PYBIND11_INTERNALS_VERSION=${PYBIND11_INTERNALS_VERSION}")
+  endif()
 else()
   # It is invalid to install a target twice, too.
   set(PYBIND11_INSTALL OFF)
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 39c28e7732..7c2e499781 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -11,6 +11,24 @@
 
 #include "../pytypes.h"
 
+/// Tracks the `internals` and `type_info` ABI version independent of the main library version.
+///
+/// Some portions of the code use an ABI that is conditional depending on this
+/// version number.  That allows ABI-breaking changes to be "pre-implemented".
+/// Once the default version number is incremented, the conditional logic that
+/// no longer applies can be removed.  Additionally, users that need not
+/// maintain ABI compatibility can increase the version number in order to take
+/// advantage of any functionality/efficiency improvements that depend on the
+/// newer ABI.
+///
+/// WARNING: If you choose to manually increase the ABI version, note that
+/// pybind11 may not be tested as thoroughly with a non-default ABI version, and
+/// further ABI-incompatible changes may be made before the ABI is officially
+/// changed to the new version.
+#ifndef PYBIND11_INTERNALS_VERSION
+#    define PYBIND11_INTERNALS_VERSION 4
+#endif
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 using ExceptionTranslator = void (*)(std::exception_ptr);
@@ -25,30 +43,58 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 // The old Python Thread Local Storage (TLS) API is deprecated in Python 3.7 in favor of the new
 // Thread Specific Storage (TSS) API.
 #if PY_VERSION_HEX >= 0x03070000
-#    define PYBIND11_TLS_KEY_INIT(var) Py_tss_t *var = nullptr
-#    define PYBIND11_TLS_GET_VALUE(key) PyThread_tss_get((key))
-#    define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_tss_set((key), (value))
-#    define PYBIND11_TLS_DELETE_VALUE(key) PyThread_tss_set((key), nullptr)
-#    define PYBIND11_TLS_FREE(key) PyThread_tss_free(key)
+// Avoid unnecessary allocation of `Py_tss_t`, since we cannot use
+// `Py_LIMITED_API` anyway.
+#    if PYBIND11_INTERNALS_VERSION > 4
+#        define PYBIND11_TLS_KEY_REF Py_tss_t &
+#        ifdef __GNUC__
+// Clang on macOS warns due to `Py_tss_NEEDS_INIT` not specifying an initializer
+// for every field.
+#            define PYBIND11_TLS_KEY_INIT(var)                                                    \
+                _Pragma("GCC diagnostic push")                                         /**/       \
+                    _Pragma("GCC diagnostic ignored \"-Wmissing-field-initializers\"") /**/       \
+                    Py_tss_t var                                                                  \
+                    = Py_tss_NEEDS_INIT;                                                          \
+                _Pragma("GCC diagnostic pop")
+#        else
+#            define PYBIND11_TLS_KEY_INIT(var) Py_tss_t var = Py_tss_NEEDS_INIT;
+#        endif
+#        define PYBIND11_TLS_KEY_CREATE(var) (PyThread_tss_create(&(var)) == 0)
+#        define PYBIND11_TLS_GET_VALUE(key) PyThread_tss_get(&(key))
+#        define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_tss_set(&(key), (value))
+#        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_tss_set(&(key), nullptr)
+#        define PYBIND11_TLS_FREE(key) PyThread_tss_delete(&(key))
+#    else
+#        define PYBIND11_TLS_KEY_REF Py_tss_t *
+#        define PYBIND11_TLS_KEY_INIT(var) Py_tss_t *var = nullptr;
+#        define PYBIND11_TLS_KEY_CREATE(var)                                                      \
+            (((var) = PyThread_tss_alloc()) != nullptr && (PyThread_tss_create((var)) == 0))
+#        define PYBIND11_TLS_GET_VALUE(key) PyThread_tss_get((key))
+#        define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_tss_set((key), (value))
+#        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_tss_set((key), nullptr)
+#        define PYBIND11_TLS_FREE(key) PyThread_tss_free(key)
+#    endif
 #else
-    // Usually an int but a long on Cygwin64 with Python 3.x
-#    define PYBIND11_TLS_KEY_INIT(var) decltype(PyThread_create_key()) var = 0
+// Usually an int but a long on Cygwin64 with Python 3.x
+#    define PYBIND11_TLS_KEY_REF decltype(PyThread_create_key())
+#    define PYBIND11_TLS_KEY_INIT(var) PYBIND11_TLS_KEY_REF var = 0;
+#    define PYBIND11_TLS_KEY_CREATE(var) (((var) = PyThread_create_key()) != -1)
 #    define PYBIND11_TLS_GET_VALUE(key) PyThread_get_key_value((key))
-#    if PY_MAJOR_VERSION < 3
-#        define PYBIND11_TLS_DELETE_VALUE(key)                               \
-             PyThread_delete_key_value(key)
-#        define PYBIND11_TLS_REPLACE_VALUE(key, value)                       \
-             do {                                                            \
-                 PyThread_delete_key_value((key));                           \
-                 PyThread_set_key_value((key), (value));                     \
-             } while (false)
+#    if PY_MAJOR_VERSION < 3 || defined(PYPY_VERSION)
+// On CPython < 3.4 and on PyPy, `PyThread_set_key_value` strangely does not set
+// the value if it has already been set.  Instead, it must first be deleted and
+// then set again.
+#        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_delete_key_value(key)
+#        define PYBIND11_TLS_REPLACE_VALUE(key, value)                                            \
+            do {                                                                                  \
+                PyThread_delete_key_value((key));                                                 \
+                PyThread_set_key_value((key), (value));                                           \
+            } while (false)
 #    else
-#        define PYBIND11_TLS_DELETE_VALUE(key)                               \
-             PyThread_set_key_value((key), nullptr)
-#        define PYBIND11_TLS_REPLACE_VALUE(key, value)                       \
-             PyThread_set_key_value((key), (value))
+#        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_set_key_value((key), nullptr)
+#        define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_set_key_value((key), (value))
 #    endif
-#    define PYBIND11_TLS_FREE(key) (void)key
+#    define PYBIND11_TLS_FREE(key) (void) key
 #endif
 
 // Python loads modules by default with dlopen with the RTLD_LOCAL flag; under libc++ and possibly
@@ -106,22 +152,31 @@ struct internals {
     std::unordered_map<const PyObject *, std::vector<PyObject *>> patients;
     std::forward_list<ExceptionTranslator> registered_exception_translators;
     std::unordered_map<std::string, void *> shared_data; // Custom data to be shared across extensions
+#if PYBIND11_INTERNALS_VERSION == 4
     std::vector<PyObject *> unused_loader_patient_stack_remove_at_v5;
+#endif
     std::forward_list<std::string> static_strings; // Stores the std::strings backing detail::c_str()
     PyTypeObject *static_property_type;
     PyTypeObject *default_metaclass;
     PyObject *instance_base;
 #if defined(WITH_THREAD)
-    PYBIND11_TLS_KEY_INIT(tstate);
+    PYBIND11_TLS_KEY_INIT(tstate)
+#    if PYBIND11_INTERNALS_VERSION > 4
+    PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
+#    endif // PYBIND11_INTERNALS_VERSION > 4
     PyInterpreterState *istate = nullptr;
     ~internals() {
+#    if PYBIND11_INTERNALS_VERSION > 4
+        PYBIND11_TLS_FREE(loader_life_support_tls_key);
+#    endif // PYBIND11_INTERNALS_VERSION > 4
+
         // This destructor is called *after* Py_Finalize() in finalize_interpreter().
-        // That *SHOULD BE* fine. The following details what happens when PyThread_tss_free is called.
-        // PYBIND11_TLS_FREE is PyThread_tss_free on python 3.7+. On older python, it does nothing.
-        // PyThread_tss_free calls PyThread_tss_delete and PyMem_RawFree.
-        // PyThread_tss_delete just calls TlsFree (on Windows) or pthread_key_delete (on *NIX). Neither
-        // of those have anything to do with CPython internals.
-        // PyMem_RawFree *requires* that the `tstate` be allocated with the CPython allocator.
+        // That *SHOULD BE* fine. The following details what happens when PyThread_tss_free is
+        // called. PYBIND11_TLS_FREE is PyThread_tss_free on python 3.7+. On older python, it does
+        // nothing. PyThread_tss_free calls PyThread_tss_delete and PyMem_RawFree.
+        // PyThread_tss_delete just calls TlsFree (on Windows) or pthread_key_delete (on *NIX).
+        // Neither of those have anything to do with CPython internals. PyMem_RawFree *requires*
+        // that the `tstate` be allocated with the CPython allocator.
         PYBIND11_TLS_FREE(tstate);
     }
 #endif
@@ -153,9 +208,6 @@ struct type_info {
     bool module_local : 1;
 };
 
-/// Tracks the `internals` and `type_info` ABI version independent of the main library version
-#define PYBIND11_INTERNALS_VERSION 4
-
 /// On MSVC, debug and release builds are not ABI-compatible!
 #if defined(_MSC_VER) && defined(_DEBUG)
 #  define PYBIND11_BUILD_TYPE "_debug"
@@ -291,21 +343,21 @@ PYBIND11_NOINLINE internals &get_internals() {
         internals_ptr = new internals();
 #if defined(WITH_THREAD)
 
-        #if PY_VERSION_HEX < 0x03090000
-                PyEval_InitThreads();
-        #endif
+#    if PY_VERSION_HEX < 0x03090000
+        PyEval_InitThreads();
+#    endif
         PyThreadState *tstate = PyThreadState_Get();
-        #if PY_VERSION_HEX >= 0x03070000
-            internals_ptr->tstate = PyThread_tss_alloc();
-            if (!internals_ptr->tstate || (PyThread_tss_create(internals_ptr->tstate) != 0))
-                pybind11_fail("get_internals: could not successfully initialize the tstate TSS key!");
-            PyThread_tss_set(internals_ptr->tstate, tstate);
-        #else
-            internals_ptr->tstate = PyThread_create_key();
-            if (internals_ptr->tstate == -1)
-                pybind11_fail("get_internals: could not successfully initialize the tstate TLS key!");
-            PyThread_set_key_value(internals_ptr->tstate, tstate);
-        #endif
+        if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->tstate)) {
+            pybind11_fail("get_internals: could not successfully initialize the tstate TSS key!");
+        }
+        PYBIND11_TLS_REPLACE_VALUE(internals_ptr->tstate, tstate);
+
+#    if PYBIND11_INTERNALS_VERSION > 4
+        if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->loader_life_support_tls_key)) {
+            pybind11_fail("get_internals: could not successfully initialize the "
+                          "loader_life_support TSS key!");
+        }
+#    endif
         internals_ptr->istate = tstate->interp;
 #endif
         builtins[id] = capsule(internals_pp);
@@ -317,7 +369,6 @@ PYBIND11_NOINLINE internals &get_internals() {
     return **internals_pp;
 }
 
-
 // the internals struct (above) is shared between all the modules. local_internals are only
 // for a single module. Any changes made to internals may require an update to
 // PYBIND11_INTERNALS_VERSION, breaking backwards compatibility. local_internals is, by design,
@@ -325,8 +376,41 @@ PYBIND11_NOINLINE internals &get_internals() {
 // impact any other modules, because the only things accessing the local internals is the
 // module that contains them.
 struct local_internals {
-  type_map<type_info *> registered_types_cpp;
-  std::forward_list<ExceptionTranslator> registered_exception_translators;
+    type_map<type_info *> registered_types_cpp;
+    std::forward_list<ExceptionTranslator> registered_exception_translators;
+#if defined(WITH_THREAD) && PYBIND11_INTERNALS_VERSION == 4
+
+    // For ABI compatibility, we can't store the loader_life_support TLS key in
+    // the `internals` struct directly.  Instead, we store it in `shared_data` and
+    // cache a copy in `local_internals`.  If we allocated a separate TLS key for
+    // each instance of `local_internals`, we could end up allocating hundreds of
+    // TLS keys if hundreds of different pybind11 modules are loaded (which is a
+    // plausible number).
+    PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
+
+    // Holds the shared TLS key for the loader_life_support stack.
+    struct shared_loader_life_support_data {
+        PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
+        shared_loader_life_support_data() {
+            if (!PYBIND11_TLS_KEY_CREATE(loader_life_support_tls_key)) {
+                pybind11_fail("local_internals: could not successfully initialize the "
+                              "loader_life_support TLS key!");
+            }
+        }
+        // We can't help but leak the TLS key, because Python never unloads extension modules.
+    };
+
+    local_internals() {
+        auto &internals = get_internals();
+        // Get or create the `loader_life_support_stack_key`.
+        auto &ptr = internals.shared_data["_life_support"];
+        if (!ptr) {
+            ptr = new shared_loader_life_support_data;
+        }
+        loader_life_support_tls_key
+            = static_cast<shared_loader_life_support_data *>(ptr)->loader_life_support_tls_key;
+    }
+#endif //  defined(WITH_THREAD) && PYBIND11_INTERNALS_VERSION == 4
 };
 
 /// Works like `get_internals`, but for things which are locally registered.
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index fa8433cfec..f804d9d10c 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -35,30 +35,43 @@ class loader_life_support {
     loader_life_support* parent = nullptr;
     std::unordered_set<PyObject *> keep_alive;
 
-    static loader_life_support** get_stack_pp() {
 #if defined(WITH_THREAD)
-        thread_local static loader_life_support* per_thread_stack = nullptr;
-        return &per_thread_stack;
+    // Store stack pointer in thread-local storage.
+    static PYBIND11_TLS_KEY_REF get_stack_tls_key() {
+#    if PYBIND11_INTERNALS_VERSION == 4
+        return get_local_internals().loader_life_support_tls_key;
+#    else
+        return get_internals().loader_life_support_tls_key;
+#    endif
+    }
+    static loader_life_support *get_stack_top() {
+        return static_cast<loader_life_support *>(PYBIND11_TLS_GET_VALUE(get_stack_tls_key()));
+    }
+    static void set_stack_top(loader_life_support *value) {
+        PYBIND11_TLS_REPLACE_VALUE(get_stack_tls_key(), value);
+    }
 #else
-        static loader_life_support* global_stack = nullptr;
-        return &global_stack;
-#endif
+    // Use single global variable for stack.
+    static loader_life_support **get_stack_pp() {
+        static loader_life_support *global_stack = nullptr;
+        return global_stack;
     }
+    static loader_life_support *get_stack_top() { return *get_stack_pp(); }
+    static void set_stack_top(loader_life_support *value) { *get_stack_pp() = value; }
+#endif
 
 public:
     /// A new patient frame is created when a function is entered
     loader_life_support() {
-        loader_life_support** stack = get_stack_pp();
-        parent = *stack;
-        *stack = this;
+        parent = get_stack_top();
+        set_stack_top(this);
     }
 
     /// ... and destroyed after it returns
     ~loader_life_support() {
-        loader_life_support** stack = get_stack_pp();
-        if (*stack != this)
+        if (get_stack_top() != this)
             pybind11_fail("loader_life_support: internal error");
-        *stack = parent;
+        set_stack_top(parent);
         for (auto* item : keep_alive)
             Py_DECREF(item);
     }
@@ -66,7 +79,7 @@ class loader_life_support {
     /// This can only be used inside a pybind11-bound function, either by `argument_loader`
     /// at argument preparation time or by `py::cast()` at execution time.
     PYBIND11_NOINLINE static void add_patient(handle h) {
-        loader_life_support* frame =  *get_stack_pp();
+        loader_life_support *frame = get_stack_top();
         if (!frame) {
             // NOTE: It would be nice to include the stack frames here, as this indicates
             // use of pybind11::cast<> outside the normal call framework, finding such
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 32f1a8963b..b73aaa3f54 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -50,7 +50,7 @@ PYBIND11_NAMESPACE_END(detail)
 class gil_scoped_acquire {
 public:
     PYBIND11_NOINLINE gil_scoped_acquire() {
-        auto const &internals = detail::get_internals();
+        auto &internals = detail::get_internals();
         tstate = (PyThreadState *) PYBIND11_TLS_GET_VALUE(internals.tstate);
 
         if (!tstate) {
@@ -132,7 +132,7 @@ class gil_scoped_release {
         // `get_internals()` must be called here unconditionally in order to initialize
         // `internals.tstate` for subsequent `gil_scoped_acquire` calls. Otherwise, an
         // initialization race could occur as multiple threads try `gil_scoped_acquire`.
-        const auto &internals = detail::get_internals();
+        auto &internals = detail::get_internals();
         tstate = PyEval_SaveThread();
         if (disassoc) {
             auto key = internals.tstate;
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 070538cc9f..cc27e60a11 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -467,7 +467,8 @@ def test_issue2361():
     assert m.issue2361_str_implicit_copy_none() == "None"
     with pytest.raises(TypeError) as excinfo:
         assert m.issue2361_dict_implicit_copy_none()
-    assert "'NoneType' object is not iterable" in str(excinfo.value)
+    assert "NoneType" in str(excinfo.value)
+    assert "iterable" in str(excinfo.value)
 
 
 @pytest.mark.parametrize(

From d0f3c51f01271b71e6228a1d002bad347dc4aca1 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 20 Sep 2021 10:42:14 -0400
Subject: [PATCH 174/638] Enable defining custom __new__ (#3265)

* Enable defining custom __new__

* See if xfail needed

* Qualify auto self

* Unconditionally defining PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING. Returning pointer from "__init__" instead of reference.

* Use new style __init__

* Simplify __new__ creation

* Reviewer suggestions

* Match indentation

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/pybind11.h |  3 ++-
 tests/test_class.cpp        | 15 +++++++++++++++
 tests/test_class.py         |  8 ++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 07d2d04363..b8f5a6bae1 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -416,7 +416,8 @@ class cpp_function : public function {
         detail::function_record *chain = nullptr, *chain_start = rec;
         if (rec->sibling) {
             if (PyCFunction_Check(rec->sibling.ptr())) {
-                auto rec_capsule = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(rec->sibling.ptr()));
+                auto *self = PyCFunction_GET_SELF(rec->sibling.ptr());
+                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self) : capsule(self);
                 chain = (detail::function_record *) rec_capsule;
                 /* Never append a method to an overload chain of a parent class;
                    instead, hide the parent's overloads in this case */
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 246b6c1fea..0b998330d7 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -47,10 +47,25 @@ TEST_SUBMODULE(class_, m) {
         }
         ~NoConstructor() { print_destroyed(this); }
     };
+    struct NoConstructorNew {
+        NoConstructorNew() = default;
+        NoConstructorNew(const NoConstructorNew &) = default;
+        NoConstructorNew(NoConstructorNew &&) = default;
+        static NoConstructorNew *new_instance() {
+            auto *ptr = new NoConstructorNew();
+            print_created(ptr, "via new_instance");
+            return ptr;
+        }
+        ~NoConstructorNew() { print_destroyed(this); }
+    };
 
     py::class_<NoConstructor>(m, "NoConstructor")
         .def_static("new_instance", &NoConstructor::new_instance, "Return an instance");
 
+    py::class_<NoConstructorNew>(m, "NoConstructorNew")
+        .def(py::init([](NoConstructorNew *self) { return self; })) // Need a NOOP __init__
+        .def_static("__new__", [](const py::object *) { return NoConstructorNew::new_instance(); } );
+
     // test_inheritance
     class Pet {
     public:
diff --git a/tests/test_class.py b/tests/test_class.py
index 85d4531991..caafe2068d 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -25,6 +25,14 @@ def test_instance(msg):
     assert cstats.alive() == 0
 
 
+def test_instance_new(msg):
+    instance = m.NoConstructorNew()  # .__new__(m.NoConstructor.__class__)
+    cstats = ConstructorStats.get(m.NoConstructorNew)
+    assert cstats.alive() == 1
+    del instance
+    assert cstats.alive() == 0
+
+
 def test_type():
     assert m.check_type(1) == m.DerivedClass1
     with pytest.raises(RuntimeError) as execinfo:

From 6e6975e2171cd5fa5efc109a708dc81addae1880 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 20 Sep 2021 16:03:21 -0400
Subject: [PATCH 175/638] Fix test case with __new__ (#3285)

---
 tests/test_class.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 0b998330d7..52a41a3bc0 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -63,8 +63,9 @@ TEST_SUBMODULE(class_, m) {
         .def_static("new_instance", &NoConstructor::new_instance, "Return an instance");
 
     py::class_<NoConstructorNew>(m, "NoConstructorNew")
-        .def(py::init([](NoConstructorNew *self) { return self; })) // Need a NOOP __init__
-        .def_static("__new__", [](const py::object *) { return NoConstructorNew::new_instance(); } );
+        .def(py::init([](const NoConstructorNew &self) { return self; })) // Need a NOOP __init__
+        .def_static("__new__",
+                    [](const py::object &) { return NoConstructorNew::new_instance(); });
 
     // test_inheritance
     class Pet {

From 077a16e9d11bb946babbe8001a1dd42704eae3ec Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 20 Sep 2021 16:18:09 -0400
Subject: [PATCH 176/638] [pre-commit.ci] pre-commit autoupdate (#3286)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/psf/black: 21.8b0 → 21.9b0](https://github.com/psf/black/compare/21.8b0...21.9b0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index fd11cf0cda..b9e37e5fe0 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -42,7 +42,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.8b0
+  rev: 21.9b0
   hooks:
   - id: black
     # By default, this ignores pyi files, though black supports them

From ee0c5ee405e7a532410797687da28a20b89cd62b Mon Sep 17 00:00:00 2001
From: Bruce Merry <1963944+bmerry@users.noreply.github.com>
Date: Tue, 21 Sep 2021 19:37:19 +0200
Subject: [PATCH 177/638] Add make_value_iterator (#3271)

* Add make_value_iterator

This is the counterpart to make_key_iterator, and will allow
implementing a `value` method in `bind_map` (although doing so is left
for a subsequent PR).

I made a few design changes to reduce copy-and-paste boilerplate.
Previously detail::iterator_state had a boolean template parameter to
indicate whether it was being used for make_iterator or
make_key_iterator. I replaced the boolean with a class that determines
how to dereference the iterator. This allows for a generic
implementation of `__next__`.

I also added the ValueType and Extra... parameters to the iterator_state
template args, because I think it was a bug that they were missing: if
make_iterator is called twice with different values of these, only the
first set has effect (because the state class is only registered once).
There is still a potential issue in that the *values* of the extra
arguments are latched on the first call, but since most policies are
empty classes this should be even less common.

* Add some remove_cv_t to appease clang-tidy

* Make iterator_access and friends take reference

For some reason I'd accidentally made it take a const value, which
caused some issues with third-party packages.

* Another attempt to remove remove_cv_t from iterators

Some of the return types were const (non-reference) types because of the
pecularities of decltype: `decltype((*it).first)` is the *declared* type
of the member of the pair, rather than the type of the expression. So if
the reference type of the iterator is `pair<const int, int> &`, then the
decltype is `const int`. Wrapping an extra set of parentheses to form
`decltype(((*it).first))` would instead give `const int &`.

This means that the existing make_key_iterator actually returns by value
from `__next__`, rather than by reference. Since for mapping types, keys
are always const, this probably hasn't been noticed, but it will affect
make_value_iterator if the Python code tries to mutate the returned
objects. I've changed things to use double parentheses so that
make_iterator, make_key_iterator and make_value_iterator should now all
return the reference type of the iterator. I'll still need to add a test
for that; for now I'm just checking whether I can keep Clang-Tidy happy.

* Add back some NOLINTNEXTLINE to appease Clang-Tidy

This is favoured over using remove_cv_t because in some cases a const
value return type is deliberate (particularly for Eigen).

* Add a unit test for iterator referencing

Ensure that make_iterator, make_key_iterator and make_value_iterator
return references to the container elements, rather than copies. The
test for make_key_iterator fails to compile on master, which gives me
confidence that this branch has fixed it.

* Make the iterator_access etc operator() const

I'm actually a little surprised it compiled at all given that the
operator() is called on a temporary, but I don't claim to fully
understand all the different value types in C++11.

* Attempt to work around compiler bugs

https://godbolt.org/ shows an example where ICC gets the wrong result
for a decltype used as the default for a template argument, and CI also
showed problems with PGI. This is a shot in the dark to see if it fixes
things.

* Make a test constructor explicit (Clang-Tidy)

* Fix unit test on GCC 4.8.5

It seems to require the arguments to the std::pair constructor to be
implicitly convertible to the types in the pair, rather than just
requiring is_constructible.

* Remove DOXYGEN_SHOULD_SKIP_THIS guards

Now that a complex decltype expression has been replaced by a simpler
nested type, I'm hoping Doxygen will be able to build it without issues.

* Add comment to explain iterator_state template params
---
 docs/reference.rst                     |   3 +
 include/pybind11/pybind11.h            | 118 ++++++++++++++++++-------
 tests/test_sequences_and_iterators.cpp |  58 ++++++++++++
 tests/test_sequences_and_iterators.py  |  29 ++++++
 4 files changed, 176 insertions(+), 32 deletions(-)

diff --git a/docs/reference.rst b/docs/reference.rst
index a678d41c88..e64a03519d 100644
--- a/docs/reference.rst
+++ b/docs/reference.rst
@@ -63,6 +63,9 @@ Convenience functions converting to Python types
 .. doxygenfunction:: make_key_iterator(Iterator, Sentinel, Extra &&...)
 .. doxygenfunction:: make_key_iterator(Type &, Extra&&...)
 
+.. doxygenfunction:: make_value_iterator(Iterator, Sentinel, Extra &&...)
+.. doxygenfunction:: make_value_iterator(Type &, Extra&&...)
+
 .. _extras:
 
 Passing extra arguments to ``def`` or ``class_``
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b8f5a6bae1..ac95b3a33c 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1955,25 +1955,52 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
     return res;
 }
 
-template <typename Iterator, typename Sentinel, bool KeyIterator, return_value_policy Policy>
+/* There are a large number of apparently unused template arguments because
+ * each combination requires a separate py::class_ registration.
+ */
+template <typename Access, return_value_policy Policy, typename Iterator, typename Sentinel, typename ValueType, typename... Extra>
 struct iterator_state {
     Iterator it;
     Sentinel end;
     bool first_or_done;
 };
 
-PYBIND11_NAMESPACE_END(detail)
+// Note: these helpers take the iterator by non-const reference because some
+// iterators in the wild can't be dereferenced when const.
+template <typename Iterator>
+struct iterator_access {
+    using result_type = decltype((*std::declval<Iterator>()));
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
+    result_type operator()(Iterator &it) const {
+        return *it;
+    }
+};
 
-/// Makes a python iterator from a first and past-the-end C++ InputIterator.
-template <return_value_policy Policy = return_value_policy::reference_internal,
+template <typename Iterator>
+struct iterator_key_access {
+    using result_type = decltype(((*std::declval<Iterator>()).first));
+    result_type operator()(Iterator &it) const {
+        return (*it).first;
+    }
+};
+
+template <typename Iterator>
+struct iterator_value_access {
+    using result_type = decltype(((*std::declval<Iterator>()).second));
+    result_type operator()(Iterator &it) const {
+        return (*it).second;
+    }
+};
+
+template <typename Access,
+          return_value_policy Policy,
           typename Iterator,
           typename Sentinel,
-#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
-          typename ValueType = decltype(*std::declval<Iterator>()),
-#endif
+          typename ValueType,
           typename... Extra>
-iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
-    using state = detail::iterator_state<Iterator, Sentinel, false, Policy>;
+iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
+    using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
+    // TODO: state captures only the types of Extra, not the values
 
     if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator", pybind11::module_local())
@@ -1987,7 +2014,7 @@ iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
                     s.first_or_done = true;
                     throw stop_iteration();
                 }
-                return *s.it;
+                return Access()(s.it);
             // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
             }, std::forward<Extra>(extra)..., Policy);
     }
@@ -1995,35 +2022,55 @@ iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
     return cast(state{first, last, true});
 }
 
-/// Makes an python iterator over the keys (`.first`) of a iterator over pairs from a
+PYBIND11_NAMESPACE_END(detail)
+
+/// Makes a python iterator from a first and past-the-end C++ InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType = typename detail::iterator_access<Iterator>::result_type,
+          typename... Extra>
+iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
+    return detail::make_iterator_impl<
+        detail::iterator_access<Iterator>,
+        Policy,
+        Iterator,
+        Sentinel,
+        ValueType,
+        Extra...>(first, last, std::forward<Extra>(extra)...);
+}
+
+/// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
 /// first and past-the-end InputIterator.
 template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Iterator,
           typename Sentinel,
-#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
-          typename KeyType = decltype((*std::declval<Iterator>()).first),
-#endif
+          typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
           typename... Extra>
 iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    using state = detail::iterator_state<Iterator, Sentinel, true, Policy>;
-
-    if (!detail::get_type_info(typeid(state), false)) {
-        class_<state>(handle(), "iterator", pybind11::module_local())
-            .def("__iter__", [](state &s) -> state& { return s; })
-            .def("__next__", [](state &s) -> detail::remove_cv_t<KeyType> {
-                if (!s.first_or_done)
-                    ++s.it;
-                else
-                    s.first_or_done = false;
-                if (s.it == s.end) {
-                    s.first_or_done = true;
-                    throw stop_iteration();
-                }
-                return (*s.it).first;
-            }, std::forward<Extra>(extra)..., Policy);
-    }
+    return detail::make_iterator_impl<
+        detail::iterator_key_access<Iterator>,
+        Policy,
+        Iterator,
+        Sentinel,
+        KeyType,
+        Extra...>(first, last, std::forward<Extra>(extra)...);
+}
 
-    return cast(state{first, last, true});
+/// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
+/// first and past-the-end InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
+          typename... Extra>
+iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+    return detail::make_iterator_impl<
+        detail::iterator_value_access<Iterator>,
+        Policy, Iterator,
+        Sentinel,
+        ValueType,
+        Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
@@ -2040,6 +2087,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
     return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
+/// Makes an iterator over the values (`.second`) of a stl map-like container supporting
+/// `std::begin()`/`std::end()`
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Type, typename... Extra> iterator make_value_iterator(Type &value, Extra&&... extra) {
+    return make_value_iterator<Policy>(std::begin(value), std::end(value), extra...);
+}
+
 template <typename InputType, typename OutputType> void implicitly_convertible() {
     struct set_flag {
         bool &flag;
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index b07fd197a9..66d647262e 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -15,6 +15,7 @@
 
 #include <algorithm>
 #include <utility>
+#include <vector>
 
 template<typename T>
 class NonZeroIterator {
@@ -32,6 +33,29 @@ bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentine
     return !(*it).first || !(*it).second;
 }
 
+class NonCopyableInt {
+public:
+    explicit NonCopyableInt(int value) : value_(value) {}
+    NonCopyableInt(const NonCopyableInt &) = delete;
+    NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
+        other.value_ = -1;  // detect when an unwanted move occurs
+    }
+    NonCopyableInt &operator=(const NonCopyableInt &) = delete;
+    NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
+        value_ = other.value_;
+        other.value_ = -1;  // detect when an unwanted move occurs
+        return *this;
+    }
+    int get() const { return value_; }
+    void set(int value) { value_ = value; }
+    ~NonCopyableInt() = default;
+private:
+    int value_;
+};
+using NonCopyableIntPair = std::pair<NonCopyableInt, NonCopyableInt>;
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>);
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
+
 template <typename PythonType>
 py::list test_random_access_iterator(PythonType x) {
     if (x.size() < 5)
@@ -271,6 +295,10 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def(
             "items",
             [](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "values",
+            [](const StringMap &map) { return py::make_value_iterator(map.begin(), map.end()); },
             py::keep_alive<0, 1>());
 
     // test_generalized_iterators
@@ -289,8 +317,38 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("nonzero_keys", [](const IntPairs& s) {
             return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
+        .def("nonzero_values", [](const IntPairs& s) {
+            return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
+        }, py::keep_alive<0, 1>())
         ;
 
+    // test_iterater_referencing
+    py::class_<NonCopyableInt>(m, "NonCopyableInt")
+        .def(py::init<int>())
+        .def("set", &NonCopyableInt::set)
+        .def("__int__", &NonCopyableInt::get)
+        ;
+    py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
+        .def(py::init<>())
+        .def("append", [](std::vector<NonCopyableInt> &vec, int value) {
+            vec.emplace_back(value);
+        })
+        .def("__iter__", [](std::vector<NonCopyableInt> &vec) {
+            return py::make_iterator(vec.begin(), vec.end());
+        })
+        ;
+    py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
+        .def(py::init<>())
+        .def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
+            vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
+        })
+        .def("keys", [](std::vector<NonCopyableIntPair> &vec) {
+            return py::make_key_iterator(vec.begin(), vec.end());
+        })
+        .def("values", [](std::vector<NonCopyableIntPair> &vec) {
+            return py::make_value_iterator(vec.begin(), vec.end());
+        })
+        ;
 
 #if 0
     // Obsolete: special data structure for exposing custom iterator types to python
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index a868c542c2..2c73eff292 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -25,6 +25,10 @@ def test_generalized_iterators():
     assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_keys()) == [1]
     assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_keys()) == []
 
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).nonzero_values()) == [2, 4]
+    assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_values()) == [2]
+    assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_values()) == []
+
     # __next__ must continue to raise StopIteration
     it = m.IntPairs([(0, 0)]).nonzero()
     for _ in range(3):
@@ -37,6 +41,30 @@ def test_generalized_iterators():
             next(it)
 
 
+def test_iterator_referencing():
+    """Test that iterators reference rather than copy their referents."""
+    vec = m.VectorNonCopyableInt()
+    vec.append(3)
+    vec.append(5)
+    assert [int(x) for x in vec] == [3, 5]
+    # Increment everything to make sure the referents can be mutated
+    for x in vec:
+        x.set(int(x) + 1)
+    assert [int(x) for x in vec] == [4, 6]
+
+    vec = m.VectorNonCopyableIntPair()
+    vec.append([3, 4])
+    vec.append([5, 7])
+    assert [int(x) for x in vec.keys()] == [3, 5]
+    assert [int(x) for x in vec.values()] == [4, 7]
+    for x in vec.keys():
+        x.set(int(x) + 1)
+    for x in vec.values():
+        x.set(int(x) + 10)
+    assert [int(x) for x in vec.keys()] == [4, 6]
+    assert [int(x) for x in vec.values()] == [14, 17]
+
+
 def test_sliceable():
     sliceable = m.Sliceable(100)
     assert sliceable[::] == (0, 100, 1)
@@ -140,6 +168,7 @@ def test_map_iterator():
         assert sm[k] == expected[k]
     for k, v in sm.items():
         assert v == expected[k]
+    assert list(sm.values()) == [expected[k] for k in sm]
 
     it = iter(m.StringMap({}))
     for _ in range(3):  # __next__ must continue to raise StopIteration

From 0fb981b21966339b811bc770b11f71eddd918f13 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 22 Sep 2021 15:38:50 -0400
Subject: [PATCH 178/638] Add blacken-docs and pycln pre-commit hooks (#3292)

* Apply blacken-docs and fix language-hints

* Add blacken-docs pre-commit hook

* Add pycln pre-commit hook

* Enable a few builtin hooks

* Black no longer ignores pyi files
---
 .pre-commit-config.yaml           | 30 ++++++++++++++++++++---------
 docs/advanced/cast/custom.rst     |  2 ++
 docs/advanced/cast/eigen.rst      |  4 ++--
 docs/advanced/cast/strings.rst    | 32 +++++++++++++++----------------
 docs/advanced/classes.rst         |  8 +++++---
 docs/advanced/embedding.rst       |  1 +
 docs/advanced/functions.rst       |  7 ++++---
 docs/advanced/pycpp/numpy.rst     |  6 +++---
 docs/advanced/pycpp/object.rst    |  1 +
 docs/advanced/pycpp/utilities.rst |  2 +-
 docs/advanced/smart_ptrs.rst      |  1 +
 docs/benchmark.py                 |  1 -
 docs/changelog.rst                |  1 +
 docs/classes.rst                  | 22 ++++++++++-----------
 docs/compiling.rst                | 11 ++---------
 docs/conf.py                      |  1 -
 docs/faq.rst                      |  2 +-
 17 files changed, 72 insertions(+), 60 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b9e37e5fe0..4245641ba3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -19,8 +19,10 @@ repos:
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
+  - id: check-docstring-first
   - id: check-merge-conflict
   - id: check-symlinks
+  - id: check-toml
   - id: check-yaml
   - id: debug-statements
   - id: end-of-file-fixer
@@ -42,12 +44,16 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.9b0
+  rev: 21.9b0 # Keep in sync with blacken-docs
   hooks:
   - id: black
-    # By default, this ignores pyi files, though black supports them
-    types: [text]
-    files: \.pyi?$
+
+- repo: https://github.com/asottile/blacken-docs
+  rev: v1.11.0
+  hooks:
+  - id: blacken-docs
+    additional_dependencies:
+    - black==21.9b0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
@@ -55,6 +61,12 @@ repos:
   hooks:
   - id: remove-tabs
 
+# Autoremoves unused imports
+- repo: https://github.com/hadialqattan/pycln
+  rev: v1.0.3
+  hooks:
+  - id: pycln
+
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
   rev: 3.9.2
@@ -86,7 +98,7 @@ repos:
 
 # Checks the manifest for missing files (native support)
 - repo: https://github.com/mgedmin/check-manifest
-  rev: "0.46"
+  rev: "0.47"
   hooks:
   - id: check-manifest
     # This is a slow hook, so only run this if --hook-stage manual is passed
@@ -100,10 +112,10 @@ repos:
     exclude: ".supp$"
     args: ["-L", "nd,ot,thist"]
 
--   repo: https://github.com/shellcheck-py/shellcheck-py
-    rev: v0.7.2.1
-    hooks:
-    -   id: shellcheck
+- repo: https://github.com/shellcheck-py/shellcheck-py
+  rev: v0.7.2.1
+  hooks:
+  - id: shellcheck
 
 # The original pybind11 checks for a few C++ style items
 - repo: local
diff --git a/docs/advanced/cast/custom.rst b/docs/advanced/cast/custom.rst
index a779444c24..19b9353476 100644
--- a/docs/advanced/cast/custom.rst
+++ b/docs/advanced/cast/custom.rst
@@ -26,7 +26,9 @@ The following Python snippet demonstrates the intended usage from the Python sid
         def __int__(self):
             return 123
 
+
     from example import print
+
     print(A())
 
 To register the necessary conversion routines, it is necessary to add an
diff --git a/docs/advanced/cast/eigen.rst b/docs/advanced/cast/eigen.rst
index e01472d5ae..80f1013430 100644
--- a/docs/advanced/cast/eigen.rst
+++ b/docs/advanced/cast/eigen.rst
@@ -112,7 +112,7 @@ example:
 .. code-block:: python
 
     a = MyClass()
-    m = a.get_matrix()   # flags.writeable = True,  flags.owndata = False
+    m = a.get_matrix()  # flags.writeable = True,  flags.owndata = False
     v = a.view_matrix()  # flags.writeable = False, flags.owndata = False
     c = a.copy_matrix()  # flags.writeable = True,  flags.owndata = True
     # m[5,6] and v[5,6] refer to the same element, c[5,6] does not.
@@ -203,7 +203,7 @@ adding the ``order='F'`` option when creating an array:
 
 .. code-block:: python
 
-    myarray = np.array(source, order='F')
+    myarray = np.array(source, order="F")
 
 Such an object will be passable to a bound function accepting an
 ``Eigen::Ref<MatrixXd>`` (or similar column-major Eigen type).
diff --git a/docs/advanced/cast/strings.rst b/docs/advanced/cast/strings.rst
index e25701ecab..cfd7e7b7a5 100644
--- a/docs/advanced/cast/strings.rst
+++ b/docs/advanced/cast/strings.rst
@@ -36,13 +36,13 @@ everywhere <http://utf8everywhere.org/>`_.
         }
     );
 
-.. code-block:: python
+.. code-block:: pycon
 
-    >>> utf8_test('🎂')
+    >>> utf8_test("🎂")
     utf-8 is icing on the cake.
     🎂
 
-    >>> utf8_charptr('🍕')
+    >>> utf8_charptr("🍕")
     My favorite food is
     🍕
 
@@ -80,7 +80,7 @@ raise a ``UnicodeDecodeError``.
         }
     );
 
-.. code-block:: python
+.. code-block:: pycon
 
     >>> isinstance(example.std_string_return(), str)
     True
@@ -114,7 +114,7 @@ conversion has the same overhead as implicit conversion.
         }
     );
 
-.. code-block:: python
+.. code-block:: pycon
 
     >>> str_output()
     'Send your résumé to Alice in HR'
@@ -143,7 +143,7 @@ returned to Python as ``bytes``, then one can return the data as a
         }
     );
 
-.. code-block:: python
+.. code-block:: pycon
 
     >>> example.return_bytes()
     b'\xba\xd0\xba\xd0'
@@ -160,7 +160,7 @@ encoding, but cannot convert ``std::string`` back to ``bytes`` implicitly.
         }
     );
 
-.. code-block:: python
+.. code-block:: pycon
 
     >>> isinstance(example.asymmetry(b"have some bytes"), str)
     True
@@ -229,16 +229,16 @@ character.
     m.def("pass_char", [](char c) { return c; });
     m.def("pass_wchar", [](wchar_t w) { return w; });
 
-.. code-block:: python
+.. code-block:: pycon
 
-    >>> example.pass_char('A')
+    >>> example.pass_char("A")
     'A'
 
 While C++ will cast integers to character types (``char c = 0x65;``), pybind11
 does not convert Python integers to characters implicitly. The Python function
 ``chr()`` can be used to convert integers to characters.
 
-.. code-block:: python
+.. code-block:: pycon
 
     >>> example.pass_char(0x65)
     TypeError
@@ -259,17 +259,17 @@ a combining acute accent). The combining character will be lost if the
 two-character sequence is passed as an argument, even though it renders as a
 single grapheme.
 
-.. code-block:: python
+.. code-block:: pycon
 
-    >>> example.pass_wchar('é')
+    >>> example.pass_wchar("é")
     'é'
 
-    >>> combining_e_acute = 'e' + '\u0301'
+    >>> combining_e_acute = "e" + "\u0301"
 
     >>> combining_e_acute
     'é'
 
-    >>> combining_e_acute == 'é'
+    >>> combining_e_acute == "é"
     False
 
     >>> example.pass_wchar(combining_e_acute)
@@ -278,9 +278,9 @@ single grapheme.
 Normalizing combining characters before passing the character literal to C++
 may resolve *some* of these issues:
 
-.. code-block:: python
+.. code-block:: pycon
 
-    >>> example.pass_wchar(unicodedata.normalize('NFC', combining_e_acute))
+    >>> example.pass_wchar(unicodedata.normalize("NFC", combining_e_acute))
     'é'
 
 In some languages (Thai for example), there are `graphemes that cannot be
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 9d1b1f0d9b..7f8fcdf4b7 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -136,7 +136,7 @@ a virtual method call.
     u'woof! woof! woof! '
     >>> class Cat(Animal):
     ...     def go(self, n_times):
-    ...             return "meow! " * n_times
+    ...         return "meow! " * n_times
     ...
     >>> c = Cat()
     >>> call_go(c)
@@ -159,8 +159,9 @@ Here is an example:
 
     class Dachshund(Dog):
         def __init__(self, name):
-            Dog.__init__(self) # Without this, a TypeError is raised.
+            Dog.__init__(self)  # Without this, a TypeError is raised.
             self.name = name
+
         def bark(self):
             return "yap!"
 
@@ -1153,6 +1154,7 @@ error:
 
     >>> class PyFinalChild(IsFinal):
     ...     pass
+    ...
     TypeError: type 'IsFinal' is not an acceptable base type
 
 .. note:: This attribute is currently ignored on PyPy
@@ -1247,7 +1249,7 @@ Accessing the type object
 
 You can get the type object from a C++ class that has already been registered using:
 
-.. code-block:: python
+.. code-block:: cpp
 
     py::type T_py = py::type::of<T>();
 
diff --git a/docs/advanced/embedding.rst b/docs/advanced/embedding.rst
index dfdaad2d7f..a435b8a75a 100644
--- a/docs/advanced/embedding.rst
+++ b/docs/advanced/embedding.rst
@@ -122,6 +122,7 @@ embedding the interpreter. This makes it easy to import local Python files:
 
     """calc.py located in the working directory"""
 
+
     def add(i, j):
         return i + j
 
diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index a537cb65ee..1178d07260 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -272,7 +272,7 @@ And used in Python as usual:
 
 .. code-block:: pycon
 
-    >>> print_dict({'foo': 123, 'bar': 'hello'})
+    >>> print_dict({"foo": 123, "bar": "hello"})
     key=foo, value=123
     key=bar, value=hello
 
@@ -377,10 +377,11 @@ argument in a function definition:
     def f(a, *, b):  # a can be positional or via keyword; b must be via keyword
         pass
 
+
     f(a=1, b=2)  # good
     f(b=2, a=1)  # good
-    f(1, b=2)    # good
-    f(1, 2)      # TypeError: f() takes 1 positional argument but 2 were given
+    f(1, b=2)  # good
+    f(1, 2)  # TypeError: f() takes 1 positional argument but 2 were given
 
 Pybind11 provides a ``py::kw_only`` object that allows you to implement
 the same behaviour by specifying the object between positional and keyword-only
diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index cae068e910..30daeefff9 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -258,8 +258,8 @@ by the compiler. The result is returned as a NumPy array of type
 
 .. code-block:: pycon
 
-    >>> x = np.array([[1, 3],[5, 7]])
-    >>> y = np.array([[2, 4],[6, 8]])
+    >>> x = np.array([[1, 3], [5, 7]])
+    >>> y = np.array([[2, 4], [6, 8]])
     >>> z = 3
     >>> result = vectorized_func(x, y, z)
 
@@ -403,7 +403,7 @@ In Python 2, the syntactic sugar ``...`` is not available, but the singleton
 
 .. code-block:: python
 
-   a = # a NumPy array
+   a = ...  # a NumPy array
    b = a[0, ..., 0]
 
 The function ``py::ellipsis()`` function can be used to perform the same
diff --git a/docs/advanced/pycpp/object.rst b/docs/advanced/pycpp/object.rst
index 6fa8d07082..8bffb83e18 100644
--- a/docs/advanced/pycpp/object.rst
+++ b/docs/advanced/pycpp/object.rst
@@ -173,6 +173,7 @@ Keyword arguments are also supported. In Python, there is the usual call syntax:
     def f(number, say, to):
         ...  # function code
 
+
     f(1234, say="hello", to=some_instance)  # keyword call in Python
 
 In C++, the same call can be made using:
diff --git a/docs/advanced/pycpp/utilities.rst b/docs/advanced/pycpp/utilities.rst
index 30429e84d7..bf90a62f8c 100644
--- a/docs/advanced/pycpp/utilities.rst
+++ b/docs/advanced/pycpp/utilities.rst
@@ -66,7 +66,7 @@ extra type, `py::scoped_estream_redirect <scoped_estream_redirect>`, is identica
 except for defaulting to ``std::cerr`` and ``sys.stderr``; this can be useful with
 `py::call_guard`, which allows multiple items, but uses the default constructor:
 
-.. code-block:: py
+.. code-block:: cpp
 
     // Alternative: Call single function using call guard
     m.def("noisy_func", &call_noisy_function,
diff --git a/docs/advanced/smart_ptrs.rst b/docs/advanced/smart_ptrs.rst
index da57748ca5..5a22201095 100644
--- a/docs/advanced/smart_ptrs.rst
+++ b/docs/advanced/smart_ptrs.rst
@@ -77,6 +77,7 @@ segmentation fault).
 .. code-block:: python
 
    from example import Parent
+
    print(Parent().get_child())
 
 The problem is that ``Parent::get_child()`` returns a pointer to an instance of
diff --git a/docs/benchmark.py b/docs/benchmark.py
index 369470c81f..f190793671 100644
--- a/docs/benchmark.py
+++ b/docs/benchmark.py
@@ -2,7 +2,6 @@
 import datetime as dt
 import os
 import random
-import time
 
 nfns = 4  # Functions per class
 nargs = 4  # Arguments per function
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 8b9690caaf..6bdf6a6e45 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1142,6 +1142,7 @@ v2.2.0 (August 31, 2017)
 
       from cpp_module import CppBase1, CppBase2
 
+
       class PyDerived(CppBase1, CppBase2):
           def __init__(self):
               CppBase1.__init__(self)  # C++ bases must be initialized explicitly
diff --git a/docs/classes.rst b/docs/classes.rst
index f3610ef367..a4463e4179 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -44,12 +44,12 @@ interactive Python session demonstrating this example is shown below:
 
     % python
     >>> import example
-    >>> p = example.Pet('Molly')
+    >>> p = example.Pet("Molly")
     >>> print(p)
     <example.Pet object at 0x10cd98060>
     >>> p.getName()
     u'Molly'
-    >>> p.setName('Charly')
+    >>> p.setName("Charly")
     >>> p.getName()
     u'Charly'
 
@@ -122,10 +122,10 @@ This makes it possible to write
 
 .. code-block:: pycon
 
-    >>> p = example.Pet('Molly')
+    >>> p = example.Pet("Molly")
     >>> p.name
     u'Molly'
-    >>> p.name = 'Charly'
+    >>> p.name = "Charly"
     >>> p.name
     u'Charly'
 
@@ -174,10 +174,10 @@ Native Python classes can pick up new attributes dynamically:
 .. code-block:: pycon
 
     >>> class Pet:
-    ...     name = 'Molly'
+    ...     name = "Molly"
     ...
     >>> p = Pet()
-    >>> p.name = 'Charly'  # overwrite existing
+    >>> p.name = "Charly"  # overwrite existing
     >>> p.age = 2  # dynamically add a new attribute
 
 By default, classes exported from C++ do not support this and the only writable
@@ -195,7 +195,7 @@ Trying to set any other attribute results in an error:
 .. code-block:: pycon
 
     >>> p = example.Pet()
-    >>> p.name = 'Charly'  # OK, attribute defined in C++
+    >>> p.name = "Charly"  # OK, attribute defined in C++
     >>> p.age = 2  # fail
     AttributeError: 'Pet' object has no attribute 'age'
 
@@ -213,7 +213,7 @@ Now everything works as expected:
 .. code-block:: pycon
 
     >>> p = example.Pet()
-    >>> p.name = 'Charly'  # OK, overwrite value in C++
+    >>> p.name = "Charly"  # OK, overwrite value in C++
     >>> p.age = 2  # OK, dynamically add a new attribute
     >>> p.__dict__  # just like a native Python class
     {'age': 2}
@@ -280,7 +280,7 @@ expose fields and methods of both types:
 
 .. code-block:: pycon
 
-    >>> p = example.Dog('Molly')
+    >>> p = example.Dog("Molly")
     >>> p.name
     u'Molly'
     >>> p.bark()
@@ -486,7 +486,7 @@ typed enums.
 
 .. code-block:: pycon
 
-    >>> p = Pet('Lucy', Pet.Cat)
+    >>> p = Pet("Lucy", Pet.Cat)
     >>> p.type
     Kind.Cat
     >>> int(p.type)
@@ -508,7 +508,7 @@ The ``name`` property returns the name of the enum value as a unicode string.
 
     .. code-block:: pycon
 
-        >>> p = Pet( "Lucy", Pet.Cat )
+        >>> p = Pet("Lucy", Pet.Cat)
         >>> pet_type = p.type
         >>> pet_type
         Pet.Cat
diff --git a/docs/compiling.rst b/docs/compiling.rst
index eaf3270e0e..0738510484 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -42,10 +42,7 @@ An example of a ``setup.py`` using pybind11's helpers:
         ),
     ]
 
-    setup(
-        ...,
-        ext_modules=ext_modules
-    )
+    setup(..., ext_modules=ext_modules)
 
 If you want to do an automatic search for the highest supported C++ standard,
 that is supported via a ``build_ext`` command override; it will only affect
@@ -64,11 +61,7 @@ that is supported via a ``build_ext`` command override; it will only affect
         ),
     ]
 
-    setup(
-        ...,
-        cmdclass={"build_ext": build_ext},
-        ext_modules=ext_modules
-    )
+    setup(..., cmdclass={"build_ext": build_ext}, ext_modules=ext_modules)
 
 If you have single-file extension modules that are directly stored in the
 Python source tree (``foo.cpp`` in the same directory as where a ``foo.py``
diff --git a/docs/conf.py b/docs/conf.py
index 458a868866..092e274e09 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -15,7 +15,6 @@
 
 import os
 import re
-import shlex
 import subprocess
 import sys
 from pathlib import Path
diff --git a/docs/faq.rst b/docs/faq.rst
index d6a048b06f..e2f477b1f5 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -54,7 +54,7 @@ provided by the caller -- in fact, it does nothing at all.
 .. code-block:: python
 
     def increment(i):
-        i += 1 # nope..
+        i += 1  # nope..
 
 pybind11 is also affected by such language-level conventions, which means that
 binding ``increment`` or ``increment_ptr`` will also create Python functions

From b06a6f4f6294dd3550b1a2b6053421d8df145d3c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 22 Sep 2021 17:41:56 -0400
Subject: [PATCH 179/638] feat: Slice allowing None with py::object or
 std::optional (#1101)

* Adding nullptr slices

Using example from #1095

Some fixes from @wjakob's review

Stop clang-tidy from complaining

New proposal for py::slice constructor

Eric's suggested changes: simplify testing; shift def's

* chore: drop MSVC pragma (hopefully unneeded)

* Apply suggestions from code review
---
 include/pybind11/detail/common.h       | 21 ++++++++++++++++++-
 include/pybind11/pytypes.h             | 25 ++++++++++++++++++++---
 include/pybind11/stl.h                 | 28 ++++++++------------------
 tests/test_sequences_and_iterators.cpp | 17 ++++++++++++++++
 tests/test_sequences_and_iterators.py  | 11 ++++++++++
 5 files changed, 78 insertions(+), 24 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 8aeb79fb7d..3bd84da576 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -161,7 +161,26 @@
 
 // https://en.cppreference.com/w/c/chrono/localtime
 #if defined(__STDC_LIB_EXT1__) && !defined(__STDC_WANT_LIB_EXT1__)
-#    define __STDC_WANT_LIB_EXT1__
+#  define __STDC_WANT_LIB_EXT1__
+#endif
+
+#ifdef __has_include
+// std::optional (but including it in c++14 mode isn't allowed)
+#  if defined(PYBIND11_CPP17) && __has_include(<optional>)
+#    define PYBIND11_HAS_OPTIONAL 1
+#  endif
+// std::experimental::optional (but not allowed in c++11 mode)
+#  if defined(PYBIND11_CPP14) && (__has_include(<experimental/optional>) && \
+                                 !__has_include(<optional>))
+#    define PYBIND11_HAS_EXP_OPTIONAL 1
+#  endif
+// std::variant
+#  if defined(PYBIND11_CPP17) && __has_include(<variant>)
+#    define PYBIND11_HAS_VARIANT 1
+#  endif
+#elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
+#  define PYBIND11_HAS_OPTIONAL 1
+#  define PYBIND11_HAS_VARIANT 1
 #endif
 
 #include <Python.h>
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index d1d3dcb05e..383663b5ed 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -14,6 +14,10 @@
 #include <utility>
 #include <type_traits>
 
+#if defined(PYBIND11_HAS_OPTIONAL)
+#  include <optional>
+#endif
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /* A few forward declarations */
@@ -1345,11 +1349,20 @@ class weakref : public object {
 class slice : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(slice, object, PySlice_Check)
-    slice(ssize_t start_, ssize_t stop_, ssize_t step_) {
-        int_ start(start_), stop(stop_), step(step_);
+    slice(handle start, handle stop, handle step) {
         m_ptr = PySlice_New(start.ptr(), stop.ptr(), step.ptr());
-        if (!m_ptr) pybind11_fail("Could not allocate slice object!");
+        if (!m_ptr)
+            pybind11_fail("Could not allocate slice object!");
     }
+
+#ifdef PYBIND11_HAS_OPTIONAL
+    slice(std::optional<ssize_t> start, std::optional<ssize_t> stop, std::optional<ssize_t> step)
+        : slice(index_to_object(start), index_to_object(stop), index_to_object(step)) {}
+#else
+    slice(ssize_t start_, ssize_t stop_, ssize_t step_)
+        : slice(int_(start_), int_(stop_), int_(step_)) {}
+#endif
+
     bool compute(size_t length, size_t *start, size_t *stop, size_t *step,
                  size_t *slicelength) const {
         return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
@@ -1364,6 +1377,12 @@ class slice : public object {
           stop, step,
           slicelength) == 0;
     }
+
+private:
+    template <typename T>
+    static object index_to_object(T index) {
+        return index ? object(int_(*index)) : object(none());
+    }
 };
 
 class capsule : public object {
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 99b49d0e2c..2c017b4fef 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -9,6 +9,7 @@
 
 #pragma once
 
+#include "detail/common.h"
 #include "pybind11.h"
 #include <set>
 #include <unordered_set>
@@ -19,28 +20,15 @@
 #include <deque>
 #include <valarray>
 
-#ifdef __has_include
-// std::optional (but including it in c++14 mode isn't allowed)
-#  if defined(PYBIND11_CPP17) && __has_include(<optional>)
-#    include <optional>
-#    define PYBIND11_HAS_OPTIONAL 1
-#  endif
-// std::experimental::optional (but not allowed in c++11 mode)
-#  if defined(PYBIND11_CPP14) && (__has_include(<experimental/optional>) && \
-                                 !__has_include(<optional>))
-#    include <experimental/optional>
-#    define PYBIND11_HAS_EXP_OPTIONAL 1
-#  endif
-// std::variant
-#  if defined(PYBIND11_CPP17) && __has_include(<variant>)
-#    include <variant>
-#    define PYBIND11_HAS_VARIANT 1
-#  endif
-#elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
+// See `detail/common.h` for implementation of these guards.
+#if defined(PYBIND11_HAS_OPTIONAL)
 #  include <optional>
+#elif defined(PYBIND11_HAS_EXP_OPTIONAL)
+#  include <experimental/optional>
+#endif
+
+#if defined(PYBIND11_HAS_VARIANT)
 #  include <variant>
-#  define PYBIND11_HAS_OPTIONAL 1
-#  define PYBIND11_HAS_VARIANT 1
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index 66d647262e..72d96cb441 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -17,6 +17,11 @@
 #include <utility>
 #include <vector>
 
+#ifdef PYBIND11_HAS_OPTIONAL
+#include <optional>
+#endif  // PYBIND11_HAS_OPTIONAL
+
+
 template<typename T>
 class NonZeroIterator {
     const T* ptr_;
@@ -117,6 +122,18 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             return std::make_tuple(istart, istop, istep);
         });
 
+    m.def("make_forward_slice_size_t", []() { return py::slice(0, -1, 1); });
+    m.def("make_reversed_slice_object", []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
+#ifdef PYBIND11_HAS_OPTIONAL
+    m.attr("has_optional") = true;
+    m.def("make_reversed_slice_size_t_optional_verbose", []() { return py::slice(std::nullopt, std::nullopt, -1); });
+    // Warning: The following spelling may still compile if optional<> is not present and give wrong answers.
+    // Please use with caution.
+    m.def("make_reversed_slice_size_t_optional", []() { return py::slice({}, {}, -1); });
+#else
+    m.attr("has_optional") = false;
+#endif
+
     // test_sequence
     class Sequence {
     public:
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 2c73eff292..79689391a6 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -16,6 +16,17 @@ def allclose(a_list, b_list, rel_tol=1e-05, abs_tol=0.0):
     )
 
 
+def test_slice_constructors():
+    assert m.make_forward_slice_size_t() == slice(0, -1, 1)
+    assert m.make_reversed_slice_object() == slice(None, None, -1)
+
+
+@pytest.mark.skipif(not m.has_optional, reason="no <optional>")
+def test_slice_constructors_explicit_optional():
+    assert m.make_reversed_slice_size_t_optional() == slice(None, None, -1)
+    assert m.make_reversed_slice_size_t_optional_verbose() == slice(None, None, -1)
+
+
 def test_generalized_iterators():
     assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).nonzero()) == [(1, 2), (3, 4)]
     assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero()) == [(1, 2)]

From 1dc9a23caea407db3b7e148b1e9cb962a235b5ed Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 22 Sep 2021 22:38:04 -0400
Subject: [PATCH 180/638] chore(deps): bump jwlawson/actions-setup-cmake from
 1.10 to 1.11 (#3294)

Bumps [jwlawson/actions-setup-cmake](https://github.com/jwlawson/actions-setup-cmake) from 1.10 to 1.11.
- [Release notes](https://github.com/jwlawson/actions-setup-cmake/releases)
- [Commits](https://github.com/jwlawson/actions-setup-cmake/compare/v1.10...v1.11)

---
updated-dependencies:
- dependency-name: jwlawson/actions-setup-cmake
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 12 ++++++------
 .github/workflows/configure.yml |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2348212f4b..0b4968cc83 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -75,7 +75,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -211,7 +211,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -463,7 +463,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Configure
       shell: bash
@@ -756,7 +756,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.9.0
@@ -802,7 +802,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.9.0
@@ -856,7 +856,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt --prefer-binary
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index d37fa3c2cc..d60025e5c5 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -55,7 +55,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.10
+      uses: jwlawson/actions-setup-cmake@v1.11
       with:
         cmake-version: ${{ matrix.cmake }}
 

From 2fa3fcfda5bb1aa1e8efc4d9cf90951e8055375e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 22 Sep 2021 22:50:29 -0400
Subject: [PATCH 181/638] Revert "Add make_value_iterator (#3271)"

This reverts commit ee0c5ee405e7a532410797687da28a20b89cd62b.
---
 docs/reference.rst                     |   3 -
 include/pybind11/pybind11.h            | 118 +++++++------------------
 tests/test_sequences_and_iterators.cpp |  58 ------------
 tests/test_sequences_and_iterators.py  |  29 ------
 4 files changed, 32 insertions(+), 176 deletions(-)

diff --git a/docs/reference.rst b/docs/reference.rst
index e64a03519d..a678d41c88 100644
--- a/docs/reference.rst
+++ b/docs/reference.rst
@@ -63,9 +63,6 @@ Convenience functions converting to Python types
 .. doxygenfunction:: make_key_iterator(Iterator, Sentinel, Extra &&...)
 .. doxygenfunction:: make_key_iterator(Type &, Extra&&...)
 
-.. doxygenfunction:: make_value_iterator(Iterator, Sentinel, Extra &&...)
-.. doxygenfunction:: make_value_iterator(Type &, Extra&&...)
-
 .. _extras:
 
 Passing extra arguments to ``def`` or ``class_``
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ac95b3a33c..b8f5a6bae1 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1955,52 +1955,25 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
     return res;
 }
 
-/* There are a large number of apparently unused template arguments because
- * each combination requires a separate py::class_ registration.
- */
-template <typename Access, return_value_policy Policy, typename Iterator, typename Sentinel, typename ValueType, typename... Extra>
+template <typename Iterator, typename Sentinel, bool KeyIterator, return_value_policy Policy>
 struct iterator_state {
     Iterator it;
     Sentinel end;
     bool first_or_done;
 };
 
-// Note: these helpers take the iterator by non-const reference because some
-// iterators in the wild can't be dereferenced when const.
-template <typename Iterator>
-struct iterator_access {
-    using result_type = decltype((*std::declval<Iterator>()));
-    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
-    result_type operator()(Iterator &it) const {
-        return *it;
-    }
-};
-
-template <typename Iterator>
-struct iterator_key_access {
-    using result_type = decltype(((*std::declval<Iterator>()).first));
-    result_type operator()(Iterator &it) const {
-        return (*it).first;
-    }
-};
-
-template <typename Iterator>
-struct iterator_value_access {
-    using result_type = decltype(((*std::declval<Iterator>()).second));
-    result_type operator()(Iterator &it) const {
-        return (*it).second;
-    }
-};
+PYBIND11_NAMESPACE_END(detail)
 
-template <typename Access,
-          return_value_policy Policy,
+/// Makes a python iterator from a first and past-the-end C++ InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Iterator,
           typename Sentinel,
-          typename ValueType,
+#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
+          typename ValueType = decltype(*std::declval<Iterator>()),
+#endif
           typename... Extra>
-iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
-    using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
-    // TODO: state captures only the types of Extra, not the values
+iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
+    using state = detail::iterator_state<Iterator, Sentinel, false, Policy>;
 
     if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator", pybind11::module_local())
@@ -2014,7 +1987,7 @@ iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
                     s.first_or_done = true;
                     throw stop_iteration();
                 }
-                return Access()(s.it);
+                return *s.it;
             // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
             }, std::forward<Extra>(extra)..., Policy);
     }
@@ -2022,55 +1995,35 @@ iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
     return cast(state{first, last, true});
 }
 
-PYBIND11_NAMESPACE_END(detail)
-
-/// Makes a python iterator from a first and past-the-end C++ InputIterator.
-template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Iterator,
-          typename Sentinel,
-          typename ValueType = typename detail::iterator_access<Iterator>::result_type,
-          typename... Extra>
-iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_access<Iterator>,
-        Policy,
-        Iterator,
-        Sentinel,
-        ValueType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
-}
-
-/// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
+/// Makes an python iterator over the keys (`.first`) of a iterator over pairs from a
 /// first and past-the-end InputIterator.
 template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Iterator,
           typename Sentinel,
-          typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
+#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
+          typename KeyType = decltype((*std::declval<Iterator>()).first),
+#endif
           typename... Extra>
 iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_key_access<Iterator>,
-        Policy,
-        Iterator,
-        Sentinel,
-        KeyType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
-}
+    using state = detail::iterator_state<Iterator, Sentinel, true, Policy>;
 
-/// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
-/// first and past-the-end InputIterator.
-template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Iterator,
-          typename Sentinel,
-          typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
-          typename... Extra>
-iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_value_access<Iterator>,
-        Policy, Iterator,
-        Sentinel,
-        ValueType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+    if (!detail::get_type_info(typeid(state), false)) {
+        class_<state>(handle(), "iterator", pybind11::module_local())
+            .def("__iter__", [](state &s) -> state& { return s; })
+            .def("__next__", [](state &s) -> detail::remove_cv_t<KeyType> {
+                if (!s.first_or_done)
+                    ++s.it;
+                else
+                    s.first_or_done = false;
+                if (s.it == s.end) {
+                    s.first_or_done = true;
+                    throw stop_iteration();
+                }
+                return (*s.it).first;
+            }, std::forward<Extra>(extra)..., Policy);
+    }
+
+    return cast(state{first, last, true});
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
@@ -2087,13 +2040,6 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
     return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
-/// Makes an iterator over the values (`.second`) of a stl map-like container supporting
-/// `std::begin()`/`std::end()`
-template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_value_iterator(Type &value, Extra&&... extra) {
-    return make_value_iterator<Policy>(std::begin(value), std::end(value), extra...);
-}
-
 template <typename InputType, typename OutputType> void implicitly_convertible() {
     struct set_flag {
         bool &flag;
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index 72d96cb441..f4a78ae998 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -15,7 +15,6 @@
 
 #include <algorithm>
 #include <utility>
-#include <vector>
 
 #ifdef PYBIND11_HAS_OPTIONAL
 #include <optional>
@@ -38,29 +37,6 @@ bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentine
     return !(*it).first || !(*it).second;
 }
 
-class NonCopyableInt {
-public:
-    explicit NonCopyableInt(int value) : value_(value) {}
-    NonCopyableInt(const NonCopyableInt &) = delete;
-    NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
-        other.value_ = -1;  // detect when an unwanted move occurs
-    }
-    NonCopyableInt &operator=(const NonCopyableInt &) = delete;
-    NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
-        value_ = other.value_;
-        other.value_ = -1;  // detect when an unwanted move occurs
-        return *this;
-    }
-    int get() const { return value_; }
-    void set(int value) { value_ = value; }
-    ~NonCopyableInt() = default;
-private:
-    int value_;
-};
-using NonCopyableIntPair = std::pair<NonCopyableInt, NonCopyableInt>;
-PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>);
-PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
-
 template <typename PythonType>
 py::list test_random_access_iterator(PythonType x) {
     if (x.size() < 5)
@@ -312,10 +288,6 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def(
             "items",
             [](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
-            py::keep_alive<0, 1>())
-        .def(
-            "values",
-            [](const StringMap &map) { return py::make_value_iterator(map.begin(), map.end()); },
             py::keep_alive<0, 1>());
 
     // test_generalized_iterators
@@ -334,38 +306,8 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("nonzero_keys", [](const IntPairs& s) {
             return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
-        .def("nonzero_values", [](const IntPairs& s) {
-            return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
         ;
 
-    // test_iterater_referencing
-    py::class_<NonCopyableInt>(m, "NonCopyableInt")
-        .def(py::init<int>())
-        .def("set", &NonCopyableInt::set)
-        .def("__int__", &NonCopyableInt::get)
-        ;
-    py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
-        .def(py::init<>())
-        .def("append", [](std::vector<NonCopyableInt> &vec, int value) {
-            vec.emplace_back(value);
-        })
-        .def("__iter__", [](std::vector<NonCopyableInt> &vec) {
-            return py::make_iterator(vec.begin(), vec.end());
-        })
-        ;
-    py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
-        .def(py::init<>())
-        .def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
-            vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
-        })
-        .def("keys", [](std::vector<NonCopyableIntPair> &vec) {
-            return py::make_key_iterator(vec.begin(), vec.end());
-        })
-        .def("values", [](std::vector<NonCopyableIntPair> &vec) {
-            return py::make_value_iterator(vec.begin(), vec.end());
-        })
-        ;
 
 #if 0
     // Obsolete: special data structure for exposing custom iterator types to python
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 79689391a6..44069fdd15 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -36,10 +36,6 @@ def test_generalized_iterators():
     assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_keys()) == [1]
     assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_keys()) == []
 
-    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).nonzero_values()) == [2, 4]
-    assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_values()) == [2]
-    assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_values()) == []
-
     # __next__ must continue to raise StopIteration
     it = m.IntPairs([(0, 0)]).nonzero()
     for _ in range(3):
@@ -52,30 +48,6 @@ def test_generalized_iterators():
             next(it)
 
 
-def test_iterator_referencing():
-    """Test that iterators reference rather than copy their referents."""
-    vec = m.VectorNonCopyableInt()
-    vec.append(3)
-    vec.append(5)
-    assert [int(x) for x in vec] == [3, 5]
-    # Increment everything to make sure the referents can be mutated
-    for x in vec:
-        x.set(int(x) + 1)
-    assert [int(x) for x in vec] == [4, 6]
-
-    vec = m.VectorNonCopyableIntPair()
-    vec.append([3, 4])
-    vec.append([5, 7])
-    assert [int(x) for x in vec.keys()] == [3, 5]
-    assert [int(x) for x in vec.values()] == [4, 7]
-    for x in vec.keys():
-        x.set(int(x) + 1)
-    for x in vec.values():
-        x.set(int(x) + 10)
-    assert [int(x) for x in vec.keys()] == [4, 6]
-    assert [int(x) for x in vec.values()] == [14, 17]
-
-
 def test_sliceable():
     sliceable = m.Sliceable(100)
     assert sliceable[::] == (0, 100, 1)
@@ -179,7 +151,6 @@ def test_map_iterator():
         assert sm[k] == expected[k]
     for k, v in sm.items():
         assert v == expected[k]
-    assert list(sm.values()) == [expected[k] for k in sm]
 
     it = iter(m.StringMap({}))
     for _ in range(3):  # __next__ must continue to raise StopIteration

From 5f46e47da8ef4c43252a934e9f461296140df1d2 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 23 Sep 2021 08:01:06 -0400
Subject: [PATCH 182/638] tests: check simple iteration of pairs (#3296)

---
 tests/test_sequences_and_iterators.cpp | 13 +++++++++++++
 tests/test_sequences_and_iterators.py  |  9 +++++++++
 2 files changed, 22 insertions(+)

diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index f4a78ae998..16f8f5b23f 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -295,6 +295,8 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     public:
         explicit IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
         const std::pair<int, int>* begin() const { return data_.data(); }
+        // .end() only required for py::make_iterator(self) overload
+        const std::pair<int, int>* end() const { return data_.data() + data_.size(); }
     private:
         std::vector<std::pair<int, int>> data_;
     };
@@ -306,6 +308,17 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("nonzero_keys", [](const IntPairs& s) {
             return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
+        .def("simple_iterator", [](IntPairs& self) {
+            return py::make_iterator(self);
+        }, py::keep_alive<0, 1>())
+        .def("simple_keys", [](IntPairs& self) {
+            return py::make_key_iterator(self);
+        }, py::keep_alive<0, 1>())
+
+        // test iterator with keep_alive (doesn't work so not used at runtime, but tests compile)
+        .def("make_iterator_keep_alive", [](IntPairs& self) {
+            return py::make_iterator(self, py::keep_alive<0, 1>());
+        }, py::keep_alive<0, 1>())
         ;
 
 
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 44069fdd15..902f4914c4 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -48,6 +48,15 @@ def test_generalized_iterators():
             next(it)
 
 
+def test_generalized_iterators_simple():
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_iterator()) == [
+        (1, 2),
+        (3, 4),
+        (0, 5),
+    ]
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_keys()) == [1, 3, 0]
+
+
 def test_sliceable():
     sliceable = m.Sliceable(100)
     assert sliceable[::] == (0, 100, 1)

From 2a78abffd85904849a1c9f9c6705f2d5a0d27018 Mon Sep 17 00:00:00 2001
From: Jeremy Maitin-Shepard <jbms@google.com>
Date: Thu, 23 Sep 2021 10:36:25 -0700
Subject: [PATCH 183/638] Ensure PYBIND11_TLS_REPLACE_VALUE evaluates its
 arguments only once (#3290)

---
 include/pybind11/detail/internals.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 7c2e499781..98d21eb983 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -84,12 +84,13 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 // On CPython < 3.4 and on PyPy, `PyThread_set_key_value` strangely does not set
 // the value if it has already been set.  Instead, it must first be deleted and
 // then set again.
+inline void tls_replace_value(PYBIND11_TLS_KEY_REF key, void *value) {
+    PyThread_delete_key_value(key);
+    PyThread_set_key_value(key, value);
+}
 #        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_delete_key_value(key)
 #        define PYBIND11_TLS_REPLACE_VALUE(key, value)                                            \
-            do {                                                                                  \
-                PyThread_delete_key_value((key));                                                 \
-                PyThread_set_key_value((key), (value));                                           \
-            } while (false)
+            ::pybind11::detail::tls_replace_value((key), (value))
 #    else
 #        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_set_key_value((key), nullptr)
 #        define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_set_key_value((key), (value))

From 21282e645a638600be9bf44dd535dbae5416005e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 23 Sep 2021 15:06:07 -0400
Subject: [PATCH 184/638] feat: reapply fixed version of #3271 (#3293)

* Add make_value_iterator (#3271)

* Add make_value_iterator

This is the counterpart to make_key_iterator, and will allow
implementing a `value` method in `bind_map` (although doing so is left
for a subsequent PR).

I made a few design changes to reduce copy-and-paste boilerplate.
Previously detail::iterator_state had a boolean template parameter to
indicate whether it was being used for make_iterator or
make_key_iterator. I replaced the boolean with a class that determines
how to dereference the iterator. This allows for a generic
implementation of `__next__`.

I also added the ValueType and Extra... parameters to the iterator_state
template args, because I think it was a bug that they were missing: if
make_iterator is called twice with different values of these, only the
first set has effect (because the state class is only registered once).
There is still a potential issue in that the *values* of the extra
arguments are latched on the first call, but since most policies are
empty classes this should be even less common.

* Add some remove_cv_t to appease clang-tidy

* Make iterator_access and friends take reference

For some reason I'd accidentally made it take a const value, which
caused some issues with third-party packages.

* Another attempt to remove remove_cv_t from iterators

Some of the return types were const (non-reference) types because of the
pecularities of decltype: `decltype((*it).first)` is the *declared* type
of the member of the pair, rather than the type of the expression. So if
the reference type of the iterator is `pair<const int, int> &`, then the
decltype is `const int`. Wrapping an extra set of parentheses to form
`decltype(((*it).first))` would instead give `const int &`.

This means that the existing make_key_iterator actually returns by value
from `__next__`, rather than by reference. Since for mapping types, keys
are always const, this probably hasn't been noticed, but it will affect
make_value_iterator if the Python code tries to mutate the returned
objects. I've changed things to use double parentheses so that
make_iterator, make_key_iterator and make_value_iterator should now all
return the reference type of the iterator. I'll still need to add a test
for that; for now I'm just checking whether I can keep Clang-Tidy happy.

* Add back some NOLINTNEXTLINE to appease Clang-Tidy

This is favoured over using remove_cv_t because in some cases a const
value return type is deliberate (particularly for Eigen).

* Add a unit test for iterator referencing

Ensure that make_iterator, make_key_iterator and make_value_iterator
return references to the container elements, rather than copies. The
test for make_key_iterator fails to compile on master, which gives me
confidence that this branch has fixed it.

* Make the iterator_access etc operator() const

I'm actually a little surprised it compiled at all given that the
operator() is called on a temporary, but I don't claim to fully
understand all the different value types in C++11.

* Attempt to work around compiler bugs

https://godbolt.org/ shows an example where ICC gets the wrong result
for a decltype used as the default for a template argument, and CI also
showed problems with PGI. This is a shot in the dark to see if it fixes
things.

* Make a test constructor explicit (Clang-Tidy)

* Fix unit test on GCC 4.8.5

It seems to require the arguments to the std::pair constructor to be
implicitly convertible to the types in the pair, rather than just
requiring is_constructible.

* Remove DOXYGEN_SHOULD_SKIP_THIS guards

Now that a complex decltype expression has been replaced by a simpler
nested type, I'm hoping Doxygen will be able to build it without issues.

* Add comment to explain iterator_state template params

* fix: regression in #3271

Co-authored-by: Bruce Merry <1963944+bmerry@users.noreply.github.com>
---
 docs/reference.rst                     |   3 +
 include/pybind11/pybind11.h            | 120 ++++++++++++++++++-------
 tests/test_sequences_and_iterators.cpp |  77 +++++++++++++++-
 tests/test_sequences_and_iterators.py  |  30 +++++++
 4 files changed, 195 insertions(+), 35 deletions(-)

diff --git a/docs/reference.rst b/docs/reference.rst
index a678d41c88..e64a03519d 100644
--- a/docs/reference.rst
+++ b/docs/reference.rst
@@ -63,6 +63,9 @@ Convenience functions converting to Python types
 .. doxygenfunction:: make_key_iterator(Iterator, Sentinel, Extra &&...)
 .. doxygenfunction:: make_key_iterator(Type &, Extra&&...)
 
+.. doxygenfunction:: make_value_iterator(Iterator, Sentinel, Extra &&...)
+.. doxygenfunction:: make_value_iterator(Type &, Extra&&...)
+
 .. _extras:
 
 Passing extra arguments to ``def`` or ``class_``
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b8f5a6bae1..16535f1951 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1955,25 +1955,54 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
     return res;
 }
 
-template <typename Iterator, typename Sentinel, bool KeyIterator, return_value_policy Policy>
+/* There are a large number of apparently unused template arguments because
+ * each combination requires a separate py::class_ registration.
+ */
+template <typename Access, return_value_policy Policy, typename Iterator, typename Sentinel, typename ValueType, typename... Extra>
 struct iterator_state {
     Iterator it;
     Sentinel end;
     bool first_or_done;
 };
 
-PYBIND11_NAMESPACE_END(detail)
+// Note: these helpers take the iterator by non-const reference because some
+// iterators in the wild can't be dereferenced when const. C++ needs the extra parens in decltype
+// to enforce an lvalue. The & after Iterator is required for MSVC < 16.9. SFINAE cannot be
+// reused for result_type due to bugs in ICC, NVCC, and PGI compilers. See PR #3293.
+template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()))>
+struct iterator_access {
+    using result_type = decltype((*std::declval<Iterator &>()));
+    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
+    result_type operator()(Iterator &it) const {
+        return *it;
+    }
+};
 
-/// Makes a python iterator from a first and past-the-end C++ InputIterator.
-template <return_value_policy Policy = return_value_policy::reference_internal,
+template <typename Iterator, typename SFINAE = decltype(((*std::declval<Iterator &>()).first)) >
+struct iterator_key_access {
+    using result_type = decltype(((*std::declval<Iterator &>()).first));
+    result_type operator()(Iterator &it) const {
+        return (*it).first;
+    }
+};
+
+template <typename Iterator, typename SFINAE = decltype(((*std::declval<Iterator &>()).second))>
+struct iterator_value_access {
+    using result_type = decltype(((*std::declval<Iterator &>()).second));
+    result_type operator()(Iterator &it) const {
+        return (*it).second;
+    }
+};
+
+template <typename Access,
+          return_value_policy Policy,
           typename Iterator,
           typename Sentinel,
-#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
-          typename ValueType = decltype(*std::declval<Iterator>()),
-#endif
+          typename ValueType,
           typename... Extra>
-iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
-    using state = detail::iterator_state<Iterator, Sentinel, false, Policy>;
+iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
+    using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
+    // TODO: state captures only the types of Extra, not the values
 
     if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator", pybind11::module_local())
@@ -1987,7 +2016,7 @@ iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
                     s.first_or_done = true;
                     throw stop_iteration();
                 }
-                return *s.it;
+                return Access()(s.it);
             // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
             }, std::forward<Extra>(extra)..., Policy);
     }
@@ -1995,35 +2024,55 @@ iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
     return cast(state{first, last, true});
 }
 
-/// Makes an python iterator over the keys (`.first`) of a iterator over pairs from a
+PYBIND11_NAMESPACE_END(detail)
+
+/// Makes a python iterator from a first and past-the-end C++ InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType = typename detail::iterator_access<Iterator>::result_type,
+          typename... Extra>
+iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
+    return detail::make_iterator_impl<
+        detail::iterator_access<Iterator>,
+        Policy,
+        Iterator,
+        Sentinel,
+        ValueType,
+        Extra...>(first, last, std::forward<Extra>(extra)...);
+}
+
+/// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
 /// first and past-the-end InputIterator.
 template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Iterator,
           typename Sentinel,
-#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
-          typename KeyType = decltype((*std::declval<Iterator>()).first),
-#endif
+          typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
           typename... Extra>
 iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    using state = detail::iterator_state<Iterator, Sentinel, true, Policy>;
-
-    if (!detail::get_type_info(typeid(state), false)) {
-        class_<state>(handle(), "iterator", pybind11::module_local())
-            .def("__iter__", [](state &s) -> state& { return s; })
-            .def("__next__", [](state &s) -> detail::remove_cv_t<KeyType> {
-                if (!s.first_or_done)
-                    ++s.it;
-                else
-                    s.first_or_done = false;
-                if (s.it == s.end) {
-                    s.first_or_done = true;
-                    throw stop_iteration();
-                }
-                return (*s.it).first;
-            }, std::forward<Extra>(extra)..., Policy);
-    }
+    return detail::make_iterator_impl<
+        detail::iterator_key_access<Iterator>,
+        Policy,
+        Iterator,
+        Sentinel,
+        KeyType,
+        Extra...>(first, last, std::forward<Extra>(extra)...);
+}
 
-    return cast(state{first, last, true});
+/// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
+/// first and past-the-end InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
+          typename... Extra>
+iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+    return detail::make_iterator_impl<
+        detail::iterator_value_access<Iterator>,
+        Policy, Iterator,
+        Sentinel,
+        ValueType,
+        Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
@@ -2040,6 +2089,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
     return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
+/// Makes an iterator over the values (`.second`) of a stl map-like container supporting
+/// `std::begin()`/`std::end()`
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Type, typename... Extra> iterator make_value_iterator(Type &value, Extra&&... extra) {
+    return make_value_iterator<Policy>(std::begin(value), std::end(value), extra...);
+}
+
 template <typename InputType, typename OutputType> void implicitly_convertible() {
     struct set_flag {
         bool &flag;
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index 16f8f5b23f..9de69338bc 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -15,6 +15,7 @@
 
 #include <algorithm>
 #include <utility>
+#include <vector>
 
 #ifdef PYBIND11_HAS_OPTIONAL
 #include <optional>
@@ -37,6 +38,29 @@ bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentine
     return !(*it).first || !(*it).second;
 }
 
+class NonCopyableInt {
+public:
+    explicit NonCopyableInt(int value) : value_(value) {}
+    NonCopyableInt(const NonCopyableInt &) = delete;
+    NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
+        other.value_ = -1;  // detect when an unwanted move occurs
+    }
+    NonCopyableInt &operator=(const NonCopyableInt &) = delete;
+    NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
+        value_ = other.value_;
+        other.value_ = -1;  // detect when an unwanted move occurs
+        return *this;
+    }
+    int get() const { return value_; }
+    void set(int value) { value_ = value; }
+    ~NonCopyableInt() = default;
+private:
+    int value_;
+};
+using NonCopyableIntPair = std::pair<NonCopyableInt, NonCopyableInt>;
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>);
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
+
 template <typename PythonType>
 py::list test_random_access_iterator(PythonType x) {
     if (x.size() < 5)
@@ -288,6 +312,10 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def(
             "items",
             [](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "values",
+            [](const StringMap &map) { return py::make_value_iterator(map.begin(), map.end()); },
             py::keep_alive<0, 1>());
 
     // test_generalized_iterators
@@ -308,19 +336,62 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("nonzero_keys", [](const IntPairs& s) {
             return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
+        .def("nonzero_values", [](const IntPairs& s) {
+            return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
+        }, py::keep_alive<0, 1>())
+
+        // test single-argument make_iterator
         .def("simple_iterator", [](IntPairs& self) {
             return py::make_iterator(self);
         }, py::keep_alive<0, 1>())
         .def("simple_keys", [](IntPairs& self) {
             return py::make_key_iterator(self);
         }, py::keep_alive<0, 1>())
+        .def("simple_values", [](IntPairs& self) {
+            return py::make_value_iterator(self);
+        }, py::keep_alive<0, 1>())
 
-        // test iterator with keep_alive (doesn't work so not used at runtime, but tests compile)
-        .def("make_iterator_keep_alive", [](IntPairs& self) {
-            return py::make_iterator(self, py::keep_alive<0, 1>());
+        // Test iterator with an Extra (doesn't do anything useful, so not used
+        // at runtime, but tests need to be able to compile with the correct
+        // overload. See PR #3293.
+        .def("_make_iterator_extras", [](IntPairs& self) {
+            return py::make_iterator(self, py::call_guard<int>());
+        }, py::keep_alive<0, 1>())
+        .def("_make_key_extras", [](IntPairs& self) {
+            return py::make_key_iterator(self, py::call_guard<int>());
+        }, py::keep_alive<0, 1>())
+        .def("_make_value_extras", [](IntPairs& self) {
+            return py::make_value_iterator(self, py::call_guard<int>());
         }, py::keep_alive<0, 1>())
         ;
 
+    // test_iterater_referencing
+    py::class_<NonCopyableInt>(m, "NonCopyableInt")
+        .def(py::init<int>())
+        .def("set", &NonCopyableInt::set)
+        .def("__int__", &NonCopyableInt::get)
+        ;
+    py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
+        .def(py::init<>())
+        .def("append", [](std::vector<NonCopyableInt> &vec, int value) {
+            vec.emplace_back(value);
+        })
+        .def("__iter__", [](std::vector<NonCopyableInt> &vec) {
+            return py::make_iterator(vec.begin(), vec.end());
+        })
+        ;
+    py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
+        .def(py::init<>())
+        .def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
+            vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
+        })
+        .def("keys", [](std::vector<NonCopyableIntPair> &vec) {
+            return py::make_key_iterator(vec.begin(), vec.end());
+        })
+        .def("values", [](std::vector<NonCopyableIntPair> &vec) {
+            return py::make_value_iterator(vec.begin(), vec.end());
+        })
+        ;
 
 #if 0
     // Obsolete: special data structure for exposing custom iterator types to python
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 902f4914c4..38e2ab5b75 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -36,6 +36,10 @@ def test_generalized_iterators():
     assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_keys()) == [1]
     assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_keys()) == []
 
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).nonzero_values()) == [2, 4]
+    assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_values()) == [2]
+    assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_values()) == []
+
     # __next__ must continue to raise StopIteration
     it = m.IntPairs([(0, 0)]).nonzero()
     for _ in range(3):
@@ -55,6 +59,31 @@ def test_generalized_iterators_simple():
         (0, 5),
     ]
     assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_keys()) == [1, 3, 0]
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_values()) == [2, 4, 5]
+
+
+def test_iterator_referencing():
+    """Test that iterators reference rather than copy their referents."""
+    vec = m.VectorNonCopyableInt()
+    vec.append(3)
+    vec.append(5)
+    assert [int(x) for x in vec] == [3, 5]
+    # Increment everything to make sure the referents can be mutated
+    for x in vec:
+        x.set(int(x) + 1)
+    assert [int(x) for x in vec] == [4, 6]
+
+    vec = m.VectorNonCopyableIntPair()
+    vec.append([3, 4])
+    vec.append([5, 7])
+    assert [int(x) for x in vec.keys()] == [3, 5]
+    assert [int(x) for x in vec.values()] == [4, 7]
+    for x in vec.keys():
+        x.set(int(x) + 1)
+    for x in vec.values():
+        x.set(int(x) + 10)
+    assert [int(x) for x in vec.keys()] == [4, 6]
+    assert [int(x) for x in vec.values()] == [14, 17]
 
 
 def test_sliceable():
@@ -160,6 +189,7 @@ def test_map_iterator():
         assert sm[k] == expected[k]
     for k, v in sm.items():
         assert v == expected[k]
+    assert list(sm.values()) == [expected[k] for k in sm]
 
     it = iter(m.StringMap({}))
     for _ in range(3):  # __next__ must continue to raise StopIteration

From 6ad3f874a797ed554b2fea82dd2b798826a83fa8 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 23 Sep 2021 15:42:16 -0400
Subject: [PATCH 185/638] fix(build): avoid a possible warning about shadowed
 variables and changing behaviors (#3220)

---
 tools/pybind11Tools.cmake | 42 +++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 24 deletions(-)

diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 3231353998..cc5ca21ca3 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -45,31 +45,25 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
 find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} MODULE REQUIRED ${_pybind11_quiet})
 list(REMOVE_AT CMAKE_MODULE_PATH -1)
 
+# Makes a normal variable a cached variable
+macro(_PYBIND11_PROMOTE_TO_CACHE NAME)
+  set(_tmp_ptc "${${NAME}}")
+  # CMake 3.21 complains if a cached variable is shadowed by a normal one
+  unset(${NAME})
+  set(${NAME}
+      "${_tmp_ptc}"
+      CACHE INTERNAL "")
+endmacro()
+
 # Cache variables so pybind11_add_module can be used in parent projects
-set(PYTHON_INCLUDE_DIRS
-    ${PYTHON_INCLUDE_DIRS}
-    CACHE INTERNAL "")
-set(PYTHON_LIBRARIES
-    ${PYTHON_LIBRARIES}
-    CACHE INTERNAL "")
-set(PYTHON_MODULE_PREFIX
-    ${PYTHON_MODULE_PREFIX}
-    CACHE INTERNAL "")
-set(PYTHON_MODULE_EXTENSION
-    ${PYTHON_MODULE_EXTENSION}
-    CACHE INTERNAL "")
-set(PYTHON_VERSION_MAJOR
-    ${PYTHON_VERSION_MAJOR}
-    CACHE INTERNAL "")
-set(PYTHON_VERSION_MINOR
-    ${PYTHON_VERSION_MINOR}
-    CACHE INTERNAL "")
-set(PYTHON_VERSION
-    ${PYTHON_VERSION}
-    CACHE INTERNAL "")
-set(PYTHON_IS_DEBUG
-    "${PYTHON_IS_DEBUG}"
-    CACHE INTERNAL "")
+_pybind11_promote_to_cache(PYTHON_INCLUDE_DIRS)
+_pybind11_promote_to_cache(PYTHON_LIBRARIES)
+_pybind11_promote_to_cache(PYTHON_MODULE_PREFIX)
+_pybind11_promote_to_cache(PYTHON_MODULE_EXTENSION)
+_pybind11_promote_to_cache(PYTHON_VERSION_MAJOR)
+_pybind11_promote_to_cache(PYTHON_VERSION_MINOR)
+_pybind11_promote_to_cache(PYTHON_VERSION)
+_pybind11_promote_to_cache(PYTHON_IS_DEBUG)
 
 if(PYBIND11_MASTER_PROJECT)
   if(PYTHON_MODULE_EXTENSION MATCHES "pypy")

From 409be8336f4c597bcca9d9eaa09df0abc065afff Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel.jakob@epfl.ch>
Date: Fri, 24 Sep 2021 13:03:57 +0200
Subject: [PATCH 186/638] CMake: react to python version changes

The new FindPython-based variant of the CMake scripts caches information
about the chosen Python version that can become stale. For example,
suppose I configure a simple pybind11-based project as follows

```
cmake -S . -B build -GNinja -DPython_ROOT=<path to python 3.8>
```

which will generate `my_extension.cpython-38-x86_64-linux-gnu.so`.
A subsequent change to the python version like

```
cmake -S . -B build -GNinja -DPython_ROOT=<path to python 3.9>
```

does not update all necessary build system information. In particular,
the compiled file is still called
`my_extension.cpython-38-x86_64-linux-gnu.so`.

This commit fixes the problem by detecting changes in
`Python_EXECUTABLE` and re-running Python as needed.

Note that the previous way of detecting Python does not seem to be
affected, it always specifies the right suffix.
---
 tools/pybind11NewTools.cmake | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index a20803bc74..b93f9145e3 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -82,6 +82,15 @@ if(NOT DEFINED ${_Python}_EXECUTABLE)
 
 endif()
 
+if(NOT ${_Python}_EXECUTABLE STREQUAL PYTHON_EXECUTABLE_LAST)
+  # Detect changes to the Python version/binary in subsequent CMake runs, and refresh config if needed
+  unset(PYTHON_IS_DEBUG CACHE)
+  unset(PYTHON_MODULE_EXTENSION CACHE)
+  set(PYTHON_EXECUTABLE_LAST
+      "${${_Python}_EXECUTABLE}"
+      CACHE INTERNAL "Python executable during the last CMake run")
+endif()
+
 if(NOT DEFINED PYTHON_IS_DEBUG)
   # Debug check - see https://stackoverflow.com/questions/646518/python-how-to-detect-debug-Interpreter
   execute_process(

From 62c4909cce37829303329da77e427d9d3a907d3a Mon Sep 17 00:00:00 2001
From: Jeremy Maitin-Shepard <jbms@google.com>
Date: Fri, 24 Sep 2021 12:08:22 -0700
Subject: [PATCH 187/638] Add `custom_type_setup` attribute (#3287)

* Fix `pybind11::object::operator=` to be safe if `*this` is accessible from Python

* Add `custom_type_setup` attribute

This allows for custom modifications to the PyHeapTypeObject prior to
calling `PyType_Ready`.  This may be used, for example, to define
`tp_traverse` and `tp_clear` functions.
---
 docs/advanced/classes.rst        | 34 ++++++++++++++++++++++
 include/pybind11/attr.h          | 29 ++++++++++++++++++
 include/pybind11/detail/class.h  |  6 ++--
 include/pybind11/pytypes.h       |  5 +++-
 tests/CMakeLists.txt             |  1 +
 tests/test_custom_type_setup.cpp | 41 ++++++++++++++++++++++++++
 tests/test_custom_type_setup.py  | 50 ++++++++++++++++++++++++++++++++
 7 files changed, 163 insertions(+), 3 deletions(-)
 create mode 100644 tests/test_custom_type_setup.cpp
 create mode 100644 tests/test_custom_type_setup.py

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 7f8fcdf4b7..5f01a2f11c 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -1261,3 +1261,37 @@ object, just like ``type(ob)`` in Python.
     Other types, like ``py::type::of<int>()``, do not work, see :ref:`type-conversions`.
 
 .. versionadded:: 2.6
+
+Custom type setup
+=================
+
+For advanced use cases, such as enabling garbage collection support, you may
+wish to directly manipulate the `PyHeapTypeObject` corresponding to a
+``py::class_`` definition.
+
+You can do that using ``py::custom_type_setup``:
+
+.. code-block:: cpp
+
+   struct OwnsPythonObjects {
+       py::object value = py::none();
+   };
+   py::class_<OwnsPythonObjects> cls(
+       m, "OwnsPythonObjects", py::custom_type_setup([](PyHeapTypeObject *heap_type) {
+           auto *type = &heap_type->ht_type;
+           type->tp_flags |= Py_TPFLAGS_HAVE_GC;
+           type->tp_traverse = [](PyObject *self_base, visitproc visit, void *arg) {
+               auto &self = py::cast<OwnsPythonObjects&>(py::handle(self_base));
+               Py_VISIT(self.value.ptr());
+               return 0;
+           };
+           type->tp_clear = [](PyObject *self_base) {
+               auto &self = py::cast<OwnsPythonObjects&>(py::handle(self_base));
+               self.value = py::none();
+               return 0;
+           };
+       }));
+   cls.def(py::init<>());
+   cls.def_readwrite("value", &OwnsPythonObjects::value);
+
+.. versionadded:: 2.8
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 13f68bbe8f..0dedbc08dd 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -12,6 +12,8 @@
 
 #include "cast.h"
 
+#include <functional>
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /// \addtogroup annotations
@@ -79,6 +81,23 @@ struct metaclass {
     explicit metaclass(handle value) : value(value) { }
 };
 
+/// Specifies a custom callback with signature `void (PyHeapTypeObject*)` that
+/// may be used to customize the Python type.
+///
+/// The callback is invoked immediately before `PyType_Ready`.
+///
+/// Note: This is an advanced interface, and uses of it may require changes to
+/// work with later versions of pybind11.  You may wish to consult the
+/// implementation of `make_new_python_type` in `detail/classes.h` to understand
+/// the context in which the callback will be run.
+struct custom_type_setup {
+    using callback = std::function<void(PyHeapTypeObject *heap_type)>;
+
+    explicit custom_type_setup(callback value) : value(std::move(value)) {}
+
+    callback value;
+};
+
 /// Annotation that marks a class as local to the module:
 struct module_local { const bool value;
     constexpr explicit module_local(bool v = true) : value(v) {}
@@ -272,6 +291,9 @@ struct type_record {
     /// Custom metaclass (optional)
     handle metaclass;
 
+    /// Custom type setup.
+    custom_type_setup::callback custom_type_setup_callback;
+
     /// Multiple inheritance marker
     bool multiple_inheritance : 1;
 
@@ -476,6 +498,13 @@ struct process_attribute<dynamic_attr> : process_attribute_default<dynamic_attr>
     static void init(const dynamic_attr &, type_record *r) { r->dynamic_attr = true; }
 };
 
+template <>
+struct process_attribute<custom_type_setup> {
+    static void init(const custom_type_setup &value, type_record *r) {
+        r->custom_type_setup_callback = value.value;
+    }
+};
+
 template <>
 struct process_attribute<is_final> : process_attribute_default<is_final> {
     static void init(const is_final &, type_record *r) { r->is_final = true; }
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index f9822c7b35..b9376b4c0b 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -683,11 +683,13 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     if (rec.buffer_protocol)
         enable_buffer_protocol(heap_type);
 
+    if (rec.custom_type_setup_callback)
+        rec.custom_type_setup_callback(heap_type);
+
     if (PyType_Ready(type) < 0)
         pybind11_fail(std::string(rec.name) + ": PyType_Ready failed (" + error_string() + ")!");
 
-    assert(rec.dynamic_attr ? PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC)
-                            : !PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC));
+    assert(!rec.dynamic_attr || PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC));
 
     /* Register type with the parent scope */
     if (rec.scope)
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 383663b5ed..f54d5fad61 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -259,8 +259,11 @@ class object : public handle {
 
     object& operator=(const object &other) {
         other.inc_ref();
-        dec_ref();
+        // Use temporary variable to ensure `*this` remains valid while
+        // `Py_XDECREF` executes, in case `*this` is accessible from Python.
+        handle temp(m_ptr);
         m_ptr = other.m_ptr;
+        temp.dec_ref();
         return *this;
     }
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index f014771d54..70303879f3 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -104,6 +104,7 @@ set(PYBIND11_TEST_FILES
     test_constants_and_functions.cpp
     test_copy_move.cpp
     test_custom_type_casters.cpp
+    test_custom_type_setup.cpp
     test_docstring_options.cpp
     test_eigen.cpp
     test_enum.cpp
diff --git a/tests/test_custom_type_setup.cpp b/tests/test_custom_type_setup.cpp
new file mode 100644
index 0000000000..42fae05d5d
--- /dev/null
+++ b/tests/test_custom_type_setup.cpp
@@ -0,0 +1,41 @@
+/*
+    tests/test_custom_type_setup.cpp -- Tests `pybind11::custom_type_setup`
+
+    Copyright (c) Google LLC
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/pybind11.h>
+
+#include "pybind11_tests.h"
+
+namespace py = pybind11;
+
+namespace {
+
+struct OwnsPythonObjects {
+    py::object value = py::none();
+};
+} // namespace
+
+TEST_SUBMODULE(custom_type_setup, m) {
+    py::class_<OwnsPythonObjects> cls(
+        m, "OwnsPythonObjects", py::custom_type_setup([](PyHeapTypeObject *heap_type) {
+            auto *type = &heap_type->ht_type;
+            type->tp_flags |= Py_TPFLAGS_HAVE_GC;
+            type->tp_traverse = [](PyObject *self_base, visitproc visit, void *arg) {
+                auto &self = py::cast<OwnsPythonObjects &>(py::handle(self_base));
+                Py_VISIT(self.value.ptr());
+                return 0;
+            };
+            type->tp_clear = [](PyObject *self_base) {
+                auto &self = py::cast<OwnsPythonObjects &>(py::handle(self_base));
+                self.value = py::none();
+                return 0;
+            };
+        }));
+    cls.def(py::init<>());
+    cls.def_readwrite("value", &OwnsPythonObjects::value);
+}
diff --git a/tests/test_custom_type_setup.py b/tests/test_custom_type_setup.py
new file mode 100644
index 0000000000..ef96f08141
--- /dev/null
+++ b/tests/test_custom_type_setup.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+
+import gc
+import weakref
+
+import pytest
+
+import env  # noqa: F401
+from pybind11_tests import custom_type_setup as m
+
+
+@pytest.fixture
+def gc_tester():
+    """Tests that an object is garbage collected.
+
+    Assumes that any unreferenced objects are fully collected after calling
+    `gc.collect()`.  That is true on CPython, but does not appear to reliably
+    hold on PyPy.
+    """
+
+    weak_refs = []
+
+    def add_ref(obj):
+        # PyPy does not support `gc.is_tracked`.
+        if hasattr(gc, "is_tracked"):
+            assert gc.is_tracked(obj)
+        weak_refs.append(weakref.ref(obj))
+
+    yield add_ref
+
+    gc.collect()
+    for ref in weak_refs:
+        assert ref() is None
+
+
+# PyPy does not seem to reliably garbage collect.
+@pytest.mark.skipif("env.PYPY")
+def test_self_cycle(gc_tester):
+    obj = m.OwnsPythonObjects()
+    obj.value = obj
+    gc_tester(obj)
+
+
+# PyPy does not seem to reliably garbage collect.
+@pytest.mark.skipif("env.PYPY")
+def test_indirect_cycle(gc_tester):
+    obj = m.OwnsPythonObjects()
+    obj_list = [obj]
+    obj.value = obj_list
+    gc_tester(obj)

From d58699c9ab9d20010b15aa38382ad517a8280179 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 24 Sep 2021 17:47:03 -0400
Subject: [PATCH 188/638] fix(cmake): reduce chance for variable collision
 (#3302)

---
 tools/pybind11NewTools.cmake | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index b93f9145e3..0a7b84706b 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -82,11 +82,11 @@ if(NOT DEFINED ${_Python}_EXECUTABLE)
 
 endif()
 
-if(NOT ${_Python}_EXECUTABLE STREQUAL PYTHON_EXECUTABLE_LAST)
+if(NOT ${_Python}_EXECUTABLE STREQUAL PYBIND11_PYTHON_EXECUTABLE_LAST)
   # Detect changes to the Python version/binary in subsequent CMake runs, and refresh config if needed
   unset(PYTHON_IS_DEBUG CACHE)
   unset(PYTHON_MODULE_EXTENSION CACHE)
-  set(PYTHON_EXECUTABLE_LAST
+  set(PYBIND11_PYTHON_EXECUTABLE_LAST
       "${${_Python}_EXECUTABLE}"
       CACHE INTERNAL "Python executable during the last CMake run")
 endif()

From 6bce3bd72e8d0838cdb1586abd6d3cfb9c598a8f Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 24 Sep 2021 23:48:38 -0400
Subject: [PATCH 189/638] docs: update CHANGELOG (#3304)

---
 docs/changelog.rst | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 6bdf6a6e45..04e2714fc3 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -38,21 +38,42 @@ New features:
 * Implemented ``reshape`` on arrays.
   `#984 <https://github.com/pybind/pybind11/pull/984>`_
 
+* Enable defining custom ``__new__`` methods on classes by fixing bug
+  preventing overriding methods if they have non-pybind11 siblings.
+  `#3265 <https://github.com/pybind/pybind11/pull/3265>`_
+
+* Add ``make_value_iterator()``, and fix ``make_key_iterator()`` to return
+  references instead of copies.
+  `#3293 <https://github.com/pybind/pybind11/pull/3293>`_
+
+* ``pybind11::custom_type_setup`` was added, for customizing the
+  ``PyHeapTypeObject`` corresponding to a class, which may be useful for
+  enabling garbage collection support, among other things.
+  `#3287 <https://github.com/pybind/pybind11/pull/3287>`_
+
+
 
 Changes:
 
 * Set ``__file__`` constant when running ``eval_file`` in an embedded interpreter.
   `#3233 <https://github.com/pybind/pybind11/pull/3233>`_
 
+* Python objects and (C++17) ``std::optional`` now accepted in ``py::slice``
+  constructor.
+  `#1101 <https://github.com/pybind/pybind11/pull/1101>`_
+
 * The pybind11 proxy types ``str``, ``bytes``, ``bytearray``, ``tuple``,
   ``list`` now consistently support passing ``ssize_t`` values for sizes and
   indexes. Previously, only ``size_t`` was accepted in several interfaces.
   `#3219 <https://github.com/pybind/pybind11/pull/3219>`_
 
+* Avoid evaluating ``PYBIND11_TLS_REPLACE_VALUE`` arguments more than once.
+  `#3290 <https://github.com/pybind/pybind11/pull/3290>`_
 
 Fixes:
 
-* Bug fix: enum value's ``__int__`` returning non-int when underlying type is bool or of char type.
+* Bug fix: enum value's ``__int__`` returning non-int when underlying type is
+  bool or of char type.
   `#1334 <https://github.com/pybind/pybind11/pull/1334>`_
 
 * Fixes bug in setting error state in Capsule's pointer methods.
@@ -61,7 +82,8 @@ Fixes:
 * A long-standing memory leak in ``py::cpp_function::initialize`` was fixed.
   `#3229 <https://github.com/pybind/pybind11/pull/3229>`_
 
-* Fixes thread safety for some ``pybind11::type_caster`` which require lifetime extension, such as for ``std::string_view``.
+* Fixes thread safety for some ``pybind11::type_caster`` which require lifetime
+  extension, such as for ``std::string_view``.
   `#3237 <https://github.com/pybind/pybind11/pull/3237>`_
 
 * Restore compatibility with gcc 4.8.4 as distributed by ubuntu-trusty, linuxmint-17.
@@ -73,12 +95,26 @@ Build system improvements:
 * Fix regression in CMake Python package config: improper use of absolute path.
   `#3144 <https://github.com/pybind/pybind11/pull/3144>`_
 
+* Cached Python version information could become stale when CMake was re-run
+  with a different Python version. The build system now detects this and
+  updates this information.
+  `#3299 <https://github.com/pybind/pybind11/pull/3299>`_
+
 * Specified UTF8-encoding in setup.py calls of open().
   `#3137 <https://github.com/pybind/pybind11/pull/3137>`_
 
+* Fix a harmless warning from CMake 3.21 with the classic Python discovery.
+  `#3220 <https://github.com/pybind/pybind11/pull/3220>`_
+
 
 Backend and tidying up:
 
+* Reduced thread-local storage required for keeping alive temporary data for
+  type conversion to one key per ABI version, rather than one key per extension
+  module.  This makes the total thread-local storage required by pybind11 2
+  keys per ABI version.
+  `#3275 <https://github.com/pybind/pybind11/pull/3275>`_
+
 * Optimize NumPy array construction with additional moves.
   `#3183 <https://github.com/pybind/pybind11/pull/3183>`_
 

From 6be64304b7e5cd4792fcd25d031127b99ef474bc Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 28 Sep 2021 10:09:08 -0400
Subject: [PATCH 190/638] [pre-commit.ci] pre-commit autoupdate (#3312)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.26.0 → v2.28.0](https://github.com/asottile/pyupgrade/compare/v2.26.0...v2.28.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4245641ba3..05bfce8517 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -33,7 +33,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.26.0
+  rev: v2.28.0
   hooks:
   - id: pyupgrade
 

From 71fd524135cc73f8d6a6c3c0d7aea6cca1605e32 Mon Sep 17 00:00:00 2001
From: Philipp Bucher <philipp.bucher@tum.de>
Date: Tue, 28 Sep 2021 16:09:38 +0200
Subject: [PATCH 191/638] docs: fix minor typo (#3311)

---
 docs/compiling.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/compiling.rst b/docs/compiling.rst
index bf7acfc808..b4072d9737 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -347,7 +347,7 @@ standard explicitly with
 
     set(CMAKE_CXX_STANDARD 14 CACHE STRING "C++ version selection")  # or 11, 14, 17, 20
     set(CMAKE_CXX_STANDARD_REQUIRED ON)  # optional, ensure standard is supported
-    set(CMAKE_CXX_EXTENSIONS OFF)  # optional, keep compiler extensionsn off
+    set(CMAKE_CXX_EXTENSIONS OFF)  # optional, keep compiler extensions off
 
 The variables can also be set when calling CMake from the command line using
 the ``-D<variable>=<value>`` flag. You can also manually set ``CXX_STANDARD``

From c9bbf8d2eed098f3c10ae461bab2c0f9541d38f7 Mon Sep 17 00:00:00 2001
From: Philipp Bucher <philipp.bucher@tum.de>
Date: Tue, 28 Sep 2021 16:09:38 +0200
Subject: [PATCH 192/638] docs: fix minor typo (#3311)

---
 docs/compiling.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/compiling.rst b/docs/compiling.rst
index 0738510484..75608bd576 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -340,7 +340,7 @@ standard explicitly with
 
     set(CMAKE_CXX_STANDARD 14 CACHE STRING "C++ version selection")  # or 11, 14, 17, 20
     set(CMAKE_CXX_STANDARD_REQUIRED ON)  # optional, ensure standard is supported
-    set(CMAKE_CXX_EXTENSIONS OFF)  # optional, keep compiler extensionsn off
+    set(CMAKE_CXX_EXTENSIONS OFF)  # optional, keep compiler extensions off
 
 The variables can also be set when calling CMake from the command line using
 the ``-D<variable>=<value>`` flag. You can also manually set ``CXX_STANDARD``

From a1830d5e6e27cb4c40955399f3826736a59f5cd5 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 29 Sep 2021 06:18:58 -0400
Subject: [PATCH 193/638] docs: mention title conventions in PR template
 (#3313)

---
 .github/pull_request_template.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
index 97a6ff7dda..54b7f5100d 100644
--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@@ -1,3 +1,7 @@
+<!--
+Title (above): please place [branch_name] at the beginning if you are targeting a branch other than master. *Do not target stable*.
+It is recommended to use conventional commit format, see conventionalcommits.org, but not required.
+-->
 ## Description
 
 <!-- Include relevant issues or PRs here, describe what changed and why -->

From b4e1ab8caa483350fbcfc7397b3b5cb33c49050f Mon Sep 17 00:00:00 2001
From: xaedes <xaedes@googlemail.com>
Date: Thu, 30 Sep 2021 20:45:06 +0200
Subject: [PATCH 194/638] Docs: Demonstrate non-enum internal types in example
 (#3314)

* Docs: Demonstrate non-enum internal types in example

Previously example only demonstrated internal enumeration type.
To show that it works for other internal types the same way the example was updated with an additional struct Pet::Attributes type.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 docs/classes.rst | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/docs/classes.rst b/docs/classes.rst
index a4463e4179..13fa8b5387 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -446,8 +446,7 @@ you can use ``py::detail::overload_cast_impl`` with an additional set of parenth
 Enumerations and internal types
 ===============================
 
-Let's now suppose that the example class contains an internal enumeration type,
-e.g.:
+Let's now suppose that the example class contains internal types like enumerations, e.g.:
 
 .. code-block:: cpp
 
@@ -457,10 +456,15 @@ e.g.:
             Cat
         };
 
+        struct Attributes {
+            float age = 0;
+        };
+
         Pet(const std::string &name, Kind type) : name(name), type(type) { }
 
         std::string name;
         Kind type;
+        Attributes attr;
     };
 
 The binding code for this example looks as follows:
@@ -471,15 +475,21 @@ The binding code for this example looks as follows:
 
     pet.def(py::init<const std::string &, Pet::Kind>())
         .def_readwrite("name", &Pet::name)
-        .def_readwrite("type", &Pet::type);
+        .def_readwrite("type", &Pet::type)
+        .def_readwrite("attr", &Pet::attr);
 
     py::enum_<Pet::Kind>(pet, "Kind")
         .value("Dog", Pet::Kind::Dog)
         .value("Cat", Pet::Kind::Cat)
         .export_values();
 
-To ensure that the ``Kind`` type is created within the scope of ``Pet``, the
-``pet`` :class:`class_` instance must be supplied to the :class:`enum_`.
+    py::class_<Pet::Attributes> attributes(pet, "Attributes")
+        .def(py::init<>())
+        .def_readwrite("age", &Pet::Attributes::age);
+
+
+To ensure that the nested types ``Kind`` and ``Attributes`` are created within the scope of ``Pet``, the
+``pet`` :class:`class_` instance must be supplied to the :class:`enum_` and :class:`class_`
 constructor. The :func:`enum_::export_values` function exports the enum entries
 into the parent scope, which should be skipped for newer C++11-style strongly
 typed enums.

From b3573ac9615b705d6e5b9bf598a3378edf079f06 Mon Sep 17 00:00:00 2001
From: Bruce Merry <1963944+bmerry@users.noreply.github.com>
Date: Fri, 1 Oct 2021 15:24:36 +0200
Subject: [PATCH 195/638] feat: add `.keys` and `.values` to bind_map (#3310)

* Add `.keys` and `.values` to bind_map

Both of these implement views (rather than just iterators), and `.items`
is also upgraded to a view. In practical terms, this allows a view to be
iterated multiple times and have its size taken, neither of which works
with an iterator.

The views implement `__len__`, `__iter__`, and the keys view implements
`__contains__`. Testing membership also works in item and value views
because Python falls back to iteration. This won't be optimal
for item values since it's linear rather than O(log n) or O(1), but I
didn't fancy trying to get all the corner cases to match Python
behaviour (tuple of wrong types, wrong length tuple, not a tuple etc).

Missing relative to Python dictionary views is `__reversed__` (only
added to Python in 3.8). Implementing that could break code that binds
custom map classes which don't provide `rbegin`/`rend` (at least without
doing clever things with SFINAE), so I've not tried.

The size increase on my system is 131072 bytes, which is rather large
(5%) but also suspiciously round (2^17) and makes me suspect some
quantisation effect.

* bind_map: support any object in __contains__

Add extra overload of `__contains__` (for both the map itself and
KeysView) which takes an arbitrary object and returns false.

* Take py::object by const reference in __contains__

To keep clang-tidy happy.

* Removing stray `py::` (detected via interactive testing in Google environment).

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/stl_bind.h | 78 +++++++++++++++++++++++++++++++++++--
 tests/test_stl_binders.py   | 30 +++++++++++++-
 2 files changed, 104 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 82317b3791..050be83cc5 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -595,6 +595,23 @@ template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &
     );
 }
 
+template<typename Map>
+struct keys_view
+{
+    Map &map;
+};
+
+template<typename Map>
+struct values_view
+{
+    Map &map;
+};
+
+template<typename Map>
+struct items_view
+{
+    Map &map;
+};
 
 PYBIND11_NAMESPACE_END(detail)
 
@@ -602,6 +619,9 @@ template <typename Map, typename holder_type = std::unique_ptr<Map>, typename...
 class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&... args) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
+    using KeysView = detail::keys_view<Map>;
+    using ValuesView = detail::values_view<Map>;
+    using ItemsView = detail::items_view<Map>;
     using Class_ = class_<Map, holder_type>;
 
     // If either type is a non-module-local bound type then make the map binding non-local as well;
@@ -615,6 +635,12 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     }
 
     Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
+    class_<KeysView> keys_view(
+        scope, ("KeysView[" + name + "]").c_str(), pybind11::module_local(local));
+    class_<ValuesView> values_view(
+        scope, ("ValuesView[" + name + "]").c_str(), pybind11::module_local(local));
+    class_<ItemsView> items_view(
+        scope, ("ItemsView[" + name + "]").c_str(), pybind11::module_local(local));
 
     cl.def(init<>());
 
@@ -628,12 +654,22 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
 
     cl.def("__iter__",
            [](Map &m) { return make_key_iterator(m.begin(), m.end()); },
-           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+           keep_alive<0, 1>() /* Essential: keep map alive while iterator exists */
+    );
+
+    cl.def("keys",
+           [](Map &m) { return KeysView{m}; },
+           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    );
+
+    cl.def("values",
+           [](Map &m) { return ValuesView{m}; },
+           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def("items",
-           [](Map &m) { return make_iterator(m.begin(), m.end()); },
-           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+           [](Map &m) { return ItemsView{m}; },
+           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def("__getitem__",
@@ -654,6 +690,8 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
            return true;
         }
     );
+    // Fallback for when the object is not of the key type
+    cl.def("__contains__", [](Map &, const object &) -> bool { return false; });
 
     // Assignment provided only if the type is copyable
     detail::map_assignment<Map, Class_>(cl);
@@ -669,6 +707,40 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
 
     cl.def("__len__", &Map::size);
 
+    keys_view.def("__len__", [](KeysView &view) { return view.map.size(); });
+    keys_view.def("__iter__",
+        [](KeysView &view) {
+            return make_key_iterator(view.map.begin(), view.map.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+    );
+    keys_view.def("__contains__",
+        [](KeysView &view, const KeyType &k) -> bool {
+            auto it = view.map.find(k);
+            if (it == view.map.end())
+                return false;
+            return true;
+        }
+    );
+    // Fallback for when the object is not of the key type
+    keys_view.def("__contains__", [](KeysView &, const object &) -> bool { return false; });
+
+    values_view.def("__len__", [](ValuesView &view) { return view.map.size(); });
+    values_view.def("__iter__",
+        [](ValuesView &view) {
+            return make_value_iterator(view.map.begin(), view.map.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+    );
+
+    items_view.def("__len__", [](ItemsView &view) { return view.map.size(); });
+    items_view.def("__iter__",
+        [](ItemsView &view) {
+            return make_iterator(view.map.begin(), view.map.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+    );
+
     return cl;
 }
 
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 475a9ec400..a68dcd31de 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -160,15 +160,43 @@ def test_map_string_double():
     mm["b"] = 2.5
 
     assert list(mm) == ["a", "b"]
-    assert list(mm.items()) == [("a", 1), ("b", 2.5)]
     assert str(mm) == "MapStringDouble{a: 1, b: 2.5}"
+    assert "b" in mm
+    assert "c" not in mm
+    assert 123 not in mm
+
+    # Check that keys, values, items are views, not merely iterable
+    keys = mm.keys()
+    values = mm.values()
+    items = mm.items()
+    assert list(keys) == ["a", "b"]
+    assert len(keys) == 2
+    assert "a" in keys
+    assert "c" not in keys
+    assert 123 not in keys
+    assert list(items) == [("a", 1), ("b", 2.5)]
+    assert len(items) == 2
+    assert ("b", 2.5) in items
+    assert "hello" not in items
+    assert ("b", 2.5, None) not in items
+    assert list(values) == [1, 2.5]
+    assert len(values) == 2
+    assert 1 in values
+    assert 2 not in values
+    # Check that views update when the map is updated
+    mm["c"] = -1
+    assert list(keys) == ["a", "b", "c"]
+    assert list(values) == [1, 2.5, -1]
+    assert list(items) == [("a", 1), ("b", 2.5), ("c", -1)]
 
     um = m.UnorderedMapStringDouble()
     um["ua"] = 1.1
     um["ub"] = 2.6
 
     assert sorted(list(um)) == ["ua", "ub"]
+    assert list(um.keys()) == list(um)
     assert sorted(list(um.items())) == [("ua", 1.1), ("ub", 2.6)]
+    assert list(zip(um.keys(), um.values())) == list(um.items())
     assert "UnorderedMapStringDouble" in str(um)
 
 

From ad9665560597a473774ea19dc87a40aef02090b3 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sun, 3 Oct 2021 20:15:37 -0400
Subject: [PATCH 196/638] fix: replace free() with std::free() (#3321)

* Disambiguate free() to use std::free()

* Add cstdlib include
---
 include/pybind11/pybind11.h           | 5 +++--
 tests/test_embed/test_interpreter.cpp | 3 ++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 16535f1951..370e52cff6 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -16,6 +16,7 @@
 #include "detail/class.h"
 #include "detail/init.h"
 
+#include <cstdlib>
 #include <memory>
 #include <new>
 #include <vector>
@@ -1536,7 +1537,7 @@ class class_ : public detail::generic_type {
            char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific documentation string */
            detail::process_attributes<Extra...>::init(extra..., rec_fget);
            if (rec_fget->doc && rec_fget->doc != doc_prev) {
-              free(doc_prev);
+              std::free(doc_prev);
               rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
            }
         }
@@ -1544,7 +1545,7 @@ class class_ : public detail::generic_type {
             char *doc_prev = rec_fset->doc;
             detail::process_attributes<Extra...>::init(extra..., rec_fset);
             if (rec_fset->doc && rec_fset->doc != doc_prev) {
-                free(doc_prev);
+                std::free(doc_prev);
                 rec_fset->doc = PYBIND11_COMPAT_STRDUP(rec_fset->doc);
             }
             if (! rec_active) rec_active = rec_fset;
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index fae14f7510..20bcade0ac 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -8,6 +8,7 @@
 
 #include <catch.hpp>
 
+#include <cstdlib>
 #include <fstream>
 #include <functional>
 #include <thread>
@@ -315,7 +316,7 @@ TEST_CASE("sys.argv gets initialized properly") {
     {
         char *argv[] = {strdup("a.out")};
         py::scoped_interpreter argv_scope(true, 1, argv);
-        free(argv[0]);
+        std::free(argv[0]);
         auto module = py::module::import("test_interpreter");
         auto py_widget = module.attr("DerivedWidget")("The question");
         const auto &cpp_widget = py_widget.cast<const Widget &>();

From d7a7edc12bc4c7aec4afd16aee1ed032bb974164 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 4 Oct 2021 12:31:53 -0400
Subject: [PATCH 197/638] tests: support Eigen configuration

---
 tests/CMakeLists.txt | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 70303879f3..6ebcba9b6b 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -171,6 +171,14 @@ set(PYBIND11_CROSS_MODULE_TESTS test_exceptions.py test_local_bindings.py test_s
 
 set(PYBIND11_CROSS_MODULE_GIL_TESTS test_gil_scoped.py)
 
+set(PYBIND11_EIGEN_REPO
+    "https://gitlab.com/libeigen/eigen.git"
+    CACHE STRING "Eigen repository to use for tests")
+# This hash is for 3.3.8, using a hash for security reasons
+set(PYBIND11_EIGEN_VERSION
+    "dc252fbf00079ccab57948a164b1421703fe4361"
+    CACHE STRING "Eigen version to use for tests")
+
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
 # skip message).
@@ -184,13 +192,11 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
       message(FATAL_ERROR "CMake 3.11+ required when using DOWNLOAD_EIGEN")
     endif()
 
-    set(EIGEN3_VERSION_STRING "3.3.8")
-
     include(FetchContent)
     FetchContent_Declare(
       eigen
-      GIT_REPOSITORY https://gitlab.com/libeigen/eigen.git
-      GIT_TAG ${EIGEN3_VERSION_STRING})
+      GIT_REPOSITORY "${PYBIND11_EIGEN_REPO}"
+      GIT_TAG "${PYBIND11_EIGEN_VERSION}")
 
     FetchContent_GetProperties(eigen)
     if(NOT eigen_POPULATED)

From 9f146a56227eab9b3bf5e847fc5610853372f587 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 3 Oct 2021 14:57:41 -0700
Subject: [PATCH 198/638] All `-DDOWNLOAD_EIGEN=OFF` (to work around gitlab
 eigen outage).

---
 .github/workflows/ci.yml     | 8 ++++++++
 .github/workflows/format.yml | 1 +
 2 files changed, 9 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0b4968cc83..279a1e7a08 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -102,6 +102,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=11
         ${{ matrix.args }}
 
@@ -129,6 +130,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=17
         ${{ matrix.args }}
         ${{ matrix.args2 }}
@@ -151,6 +153,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=17
         -DPYBIND11_INTERNALS_VERSION=10000000
         "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
@@ -249,6 +252,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=17
 
     - name: Build
@@ -628,6 +632,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=11
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
@@ -774,6 +779,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         ${{ matrix.args }}
     - name: Build C++11
       run: cmake --build build -j 2
@@ -820,6 +826,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
 
     - name: Build C++14
       run: cmake --build build -j 2
@@ -869,6 +876,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
         ${{ matrix.args }}
 
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index ab7b40503a..7869912bf6 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -41,6 +41,7 @@ jobs:
         cmake -S . -B build
         -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy)"
         -DDOWNLOAD_EIGEN=ON
+        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=17
 

From 591db0b930f6739fe276bce9a7d5b6647bd00851 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 1 Oct 2021 09:30:55 -0400
Subject: [PATCH 199/638] docs: update CHANGELOG for 2.8

---
 docs/changelog.rst | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 04e2714fc3..4a58f2d514 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,8 +6,8 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
-v2.8.0 (WIP)
-------------
+v2.8.0 (Oct 4, 2021)
+--------------------
 
 New features:
 
@@ -46,13 +46,17 @@ New features:
   references instead of copies.
   `#3293 <https://github.com/pybind/pybind11/pull/3293>`_
 
+* Improve the classes generated by ``bind_map``: `#3310 <https://github.com/pybind/pybind11/pull/3310>`_
+    * Change ``.items`` from an iterator to a dictionary view.
+    * Add ``.keys`` and ``.values`` (both dictionary views).
+    * Allow ``__contains__`` to take any object.
+
 * ``pybind11::custom_type_setup`` was added, for customizing the
   ``PyHeapTypeObject`` corresponding to a class, which may be useful for
   enabling garbage collection support, among other things.
   `#3287 <https://github.com/pybind/pybind11/pull/3287>`_
 
 
-
 Changes:
 
 * Set ``__file__`` constant when running ``eval_file`` in an embedded interpreter.
@@ -106,6 +110,9 @@ Build system improvements:
 * Fix a harmless warning from CMake 3.21 with the classic Python discovery.
   `#3220 <https://github.com/pybind/pybind11/pull/3220>`_
 
+* Eigen repo and version can now be specified as cmake options.
+  `#3324 <https://github.com/pybind/pybind11/pull/3324>`_
+
 
 Backend and tidying up:
 

From 20aae3e61a91dbae5d71c3b11677369d94a82884 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 4 Oct 2021 14:47:45 -0400
Subject: [PATCH 200/638] ci: disable Eigen due to Cert issue on CentOS

---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 279a1e7a08..416d2a4ec5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -624,6 +624,7 @@ jobs:
       if: matrix.centos == 8
       run: echo Release > VAR_BUILD_TYPE
 
+    # Temporally disabling EIGEN due to SSL issue in CentOS 7
     - name: Configure
       shell: bash
       run: >
@@ -631,8 +632,7 @@ jobs:
         -DCMAKE_BUILD_TYPE=$(cat VAR_BUILD_TYPE)
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
+        -DDOWNLOAD_EIGEN=OFF
         -DCMAKE_CXX_STANDARD=11
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 

From c9a319c607a5fcddf14417483a451bd85083da72 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 4 Oct 2021 15:33:58 -0400
Subject: [PATCH 201/638] chore: version 2.8.0 final

---
 include/pybind11/detail/common.h | 4 ++--
 pybind11/_version.py             | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 3bd84da576..31716e5bfe 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 8
-#define PYBIND11_VERSION_PATCH 0.dev2
+#define PYBIND11_VERSION_PATCH 0
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020800D2
+#define PYBIND11_VERSION_HEX 0x02080000
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index d212f1dfb7..704191b98e 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.8.0.dev2"
+__version__ = "2.8.0"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 3747dc2c4f807fba952380f7bd9f367ab9c53a0a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 4 Oct 2021 16:38:15 -0400
Subject: [PATCH 202/638] Revert "All `-DDOWNLOAD_EIGEN=OFF` (to work around
 gitlab eigen outage)." (#3326)

This reverts commit 9f146a56227eab9b3bf5e847fc5610853372f587.
---
 .github/workflows/ci.yml     | 9 +--------
 .github/workflows/format.yml | 1 -
 2 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 416d2a4ec5..6843a92430 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -102,7 +102,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=11
         ${{ matrix.args }}
 
@@ -130,7 +129,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=17
         ${{ matrix.args }}
         ${{ matrix.args2 }}
@@ -153,7 +151,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=17
         -DPYBIND11_INTERNALS_VERSION=10000000
         "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
@@ -252,7 +249,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=17
 
     - name: Build
@@ -632,7 +628,7 @@ jobs:
         -DCMAKE_BUILD_TYPE=$(cat VAR_BUILD_TYPE)
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=OFF
+        -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
@@ -779,7 +775,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         ${{ matrix.args }}
     - name: Build C++11
       run: cmake --build build -j 2
@@ -826,7 +821,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
 
     - name: Build C++14
       run: cmake --build build -j 2
@@ -876,7 +870,6 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
         ${{ matrix.args }}
 
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 7869912bf6..ab7b40503a 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -41,7 +41,6 @@ jobs:
         cmake -S . -B build
         -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy)"
         -DDOWNLOAD_EIGEN=ON
-        -DPYBIND11_EIGEN_REPO=https://gitlab.com/libeigen/eigen-backup
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=17
 

From 97976c16fb7652f7faf02d76756666ef87adbe7d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 4 Oct 2021 16:38:31 -0400
Subject: [PATCH 203/638] [pre-commit.ci] pre-commit autoupdate (#3325)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.28.0 → v2.29.0](https://github.com/asottile/pyupgrade/compare/v2.28.0...v2.29.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 05bfce8517..2df3146064 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -33,7 +33,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.28.0
+  rev: v2.29.0
   hooks:
   - id: pyupgrade
 

From ba9f919b857f12efd18d3fc43fc62e7ad724c6d9 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 4 Oct 2021 17:37:27 -0400
Subject: [PATCH 204/638] chore: get back to work after 2.8.0

---
 docs/changelog.rst               | 6 ++++++
 docs/release.rst                 | 2 ++
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 4a58f2d514..1dab8765f2 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,6 +6,12 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
+
+IN DEVELOPMENT
+--------------
+
+
+
 v2.8.0 (Oct 4, 2021)
 --------------------
 
diff --git a/docs/release.rst b/docs/release.rst
index e4f3d1902a..7fa254eaf9 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -27,6 +27,7 @@ To release a new version of pybind11:
       ``include/pybind11/detail/common.h``. PATCH should be a simple integer.
     - Update the version HEX just below, as well.
     - Update ``pybind11/_version.py`` (match above)
+    - Run ``nox -s tests_packaging``` to ensure this was done correctly.
     - Ensure that all the information in ``setup.cfg`` is up-to-date, like
       supported Python versions.
     - Add release date in ``docs/changelog.rst``.
@@ -64,6 +65,7 @@ To release a new version of pybind11:
     - Update version macros in ``include/pybind11/detail/common.h`` (set PATCH to
       ``0.dev1`` and increment MINOR).
     - Update ``_version.py`` to match
+    - Run ``nox -s tests_packaging``` to ensure this was done correctly.
     - Add a spot for in-development updates in ``docs/changelog.rst``.
     - ``git add``, ``git commit``, ``git push``
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 31716e5bfe..9ad305a4ee 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 8
-#define PYBIND11_VERSION_PATCH 0
+#define PYBIND11_VERSION_MINOR 9
+#define PYBIND11_VERSION_PATCH 0.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x02080000
+#define PYBIND11_VERSION_HEX 0x020900D1
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 704191b98e..ce894a7740 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.8.0"
+__version__ = "2.9.0.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 47ed124f3728c7886d496c28c15b889c78599b99 Mon Sep 17 00:00:00 2001
From: Bruce Merry <1963944+bmerry@users.noreply.github.com>
Date: Fri, 8 Oct 2021 14:27:38 +0200
Subject: [PATCH 205/638] Fix some formatting in the v2.8.0 changelog (#3339)

[skipci]
---
 docs/changelog.rst | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 1dab8765f2..80c580b180 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -53,9 +53,10 @@ New features:
   `#3293 <https://github.com/pybind/pybind11/pull/3293>`_
 
 * Improve the classes generated by ``bind_map``: `#3310 <https://github.com/pybind/pybind11/pull/3310>`_
-    * Change ``.items`` from an iterator to a dictionary view.
-    * Add ``.keys`` and ``.values`` (both dictionary views).
-    * Allow ``__contains__`` to take any object.
+
+  * Change ``.items`` from an iterator to a dictionary view.
+  * Add ``.keys`` and ``.values`` (both dictionary views).
+  * Allow ``__contains__`` to take any object.
 
 * ``pybind11::custom_type_setup`` was added, for customizing the
   ``PyHeapTypeObject`` corresponding to a class, which may be useful for

From ed09664f063269dcf6a47298944e45fb957b40c4 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Fri, 8 Oct 2021 08:27:52 -0400
Subject: [PATCH 206/638] chore(deps): bump ilammy/msvc-dev-cmd from 1.9.0 to
 1.10.0 (#3338)

Bumps [ilammy/msvc-dev-cmd](https://github.com/ilammy/msvc-dev-cmd) from 1.9.0 to 1.10.0.
- [Release notes](https://github.com/ilammy/msvc-dev-cmd/releases)
- [Commits](https://github.com/ilammy/msvc-dev-cmd/compare/v1.9.0...v1.10.0)

---
updated-dependencies:
- dependency-name: ilammy/msvc-dev-cmd
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6843a92430..5d5222f8b6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -169,7 +169,7 @@ jobs:
     # MSVC, but for now, this action works:
     - name: Prepare compiler environment for Windows 🐍 2.7
       if: matrix.python == 2.7 && runner.os == 'Windows'
-      uses: ilammy/msvc-dev-cmd@v1.9.0
+      uses: ilammy/msvc-dev-cmd@v1.10.0
       with:
         arch: x64
 
@@ -760,7 +760,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.9.0
+      uses: ilammy/msvc-dev-cmd@v1.10.0
       with:
         arch: x86
 
@@ -806,7 +806,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.9.0
+      uses: ilammy/msvc-dev-cmd@v1.10.0
       with:
         toolset: 14.0
 

From f4c81e0877a7d302eb580886f8552bc81d3b3d65 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 8 Oct 2021 08:38:04 -0400
Subject: [PATCH 207/638] maint: Add additional linter-related pre-commit hooks
 (#3337)

* Add additional pygrep pre-commit hooks

* Remove useless noqas with hook

* Fix all single rst backticks

* Simplify mypy pre-commit hook with upstream fixes

* Add back missing comment

* Add one last pygrep hook
---
 .pre-commit-config.yaml              | 25 ++++++++++++++++++++-----
 docs/advanced/classes.rst            |  2 +-
 docs/advanced/embedding.rst          | 26 +++++++++++++-------------
 docs/advanced/exceptions.rst         |  6 +++---
 docs/advanced/functions.rst          |  2 +-
 docs/advanced/misc.rst               |  2 +-
 docs/advanced/pycpp/utilities.rst    | 10 +++++-----
 docs/changelog.rst                   |  6 +++---
 tests/test_buffers.py                |  2 +-
 tests/test_builtin_casters.py        |  2 +-
 tests/test_callbacks.py              |  2 +-
 tests/test_enum.py                   |  6 +++---
 tests/test_methods_and_attributes.py |  4 ++--
 tests/test_pickling.py               |  2 +-
 tests/test_pytypes.py                |  4 ++--
 tests/test_stl_binders.py            |  2 +-
 16 files changed, 59 insertions(+), 44 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2df3146064..17e67ded40 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -67,14 +67,32 @@ repos:
   hooks:
   - id: pycln
 
+- repo: https://github.com/pre-commit/pygrep-hooks
+  rev: v1.9.0
+  hooks:
+  - id: python-check-blanket-noqa
+  - id: python-check-blanket-type-ignore
+  - id: python-no-log-warn
+  - id: rst-backticks
+  - id: rst-directive-colons
+  - id: rst-inline-touching-normal
+
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
   rev: 3.9.2
   hooks:
   - id: flake8
-    additional_dependencies: [flake8-bugbear, pep8-naming]
+    additional_dependencies: &flake8_dependencies
+      - flake8-bugbear
+      - pep8-naming
     exclude: ^(docs/.*|tools/.*)$
 
+- repo: https://github.com/asottile/yesqa
+  rev: v1.2.3
+  hooks:
+  - id: yesqa
+    additional_dependencies: *flake8_dependencies
+
 # CMake formatting
 - repo: https://github.com/cheshirekow/cmake-format-precommit
   rev: v0.6.13
@@ -86,12 +104,9 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.910
+  rev: v0.910-1
   hooks:
   - id: mypy
-    # The default Python type ignores .pyi files, so let's rerun if detected
-    types: [text]
-    files: ^pybind11.*\.pyi?$
     # Running per-file misbehaves a bit, so just run on all files, it's fast
     pass_filenames: false
     additional_dependencies: [typed_ast]
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 5f01a2f11c..6330af5eb4 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -1266,7 +1266,7 @@ Custom type setup
 =================
 
 For advanced use cases, such as enabling garbage collection support, you may
-wish to directly manipulate the `PyHeapTypeObject` corresponding to a
+wish to directly manipulate the ``PyHeapTypeObject`` corresponding to a
 ``py::class_`` definition.
 
 You can do that using ``py::custom_type_setup``:
diff --git a/docs/advanced/embedding.rst b/docs/advanced/embedding.rst
index a435b8a75a..dd980d483a 100644
--- a/docs/advanced/embedding.rst
+++ b/docs/advanced/embedding.rst
@@ -40,15 +40,15 @@ The essential structure of the ``main.cpp`` file looks like this:
     }
 
 The interpreter must be initialized before using any Python API, which includes
-all the functions and classes in pybind11. The RAII guard class `scoped_interpreter`
+all the functions and classes in pybind11. The RAII guard class ``scoped_interpreter``
 takes care of the interpreter lifetime. After the guard is destroyed, the interpreter
 shuts down and clears its memory. No Python functions can be called after this.
 
 Executing Python code
 =====================
 
-There are a few different ways to run Python code. One option is to use `eval`,
-`exec` or `eval_file`, as explained in :ref:`eval`. Here is a quick example in
+There are a few different ways to run Python code. One option is to use ``eval``,
+``exec`` or ``eval_file``, as explained in :ref:`eval`. Here is a quick example in
 the context of an executable with an embedded interpreter:
 
 .. code-block:: cpp
@@ -108,7 +108,7 @@ The two approaches can also be combined:
 Importing modules
 =================
 
-Python modules can be imported using `module_::import()`:
+Python modules can be imported using ``module_::import()``:
 
 .. code-block:: cpp
 
@@ -134,7 +134,7 @@ embedding the interpreter. This makes it easy to import local Python files:
     int n = result.cast<int>();
     assert(n == 3);
 
-Modules can be reloaded using `module_::reload()` if the source is modified e.g.
+Modules can be reloaded using ``module_::reload()`` if the source is modified e.g.
 by an external process. This can be useful in scenarios where the application
 imports a user defined data processing script which needs to be updated after
 changes by the user. Note that this function does not reload modules recursively.
@@ -144,7 +144,7 @@ changes by the user. Note that this function does not reload modules recursively
 Adding embedded modules
 =======================
 
-Embedded binary modules can be added using the `PYBIND11_EMBEDDED_MODULE` macro.
+Embedded binary modules can be added using the ``PYBIND11_EMBEDDED_MODULE`` macro.
 Note that the definition must be placed at global scope. They can be imported
 like any other module.
 
@@ -170,7 +170,7 @@ like any other module.
 
 Unlike extension modules where only a single binary module can be created, on
 the embedded side an unlimited number of modules can be added using multiple
-`PYBIND11_EMBEDDED_MODULE` definitions (as long as they have unique names).
+``PYBIND11_EMBEDDED_MODULE`` definitions (as long as they have unique names).
 
 These modules are added to Python's list of builtins, so they can also be
 imported in pure Python files loaded by the interpreter. Everything interacts
@@ -216,9 +216,9 @@ naturally:
 Interpreter lifetime
 ====================
 
-The Python interpreter shuts down when `scoped_interpreter` is destroyed. After
+The Python interpreter shuts down when ``scoped_interpreter`` is destroyed. After
 this, creating a new instance will restart the interpreter. Alternatively, the
-`initialize_interpreter` / `finalize_interpreter` pair of functions can be used
+``initialize_interpreter`` / ``finalize_interpreter`` pair of functions can be used
 to directly set the state at any time.
 
 Modules created with pybind11 can be safely re-initialized after the interpreter
@@ -230,8 +230,8 @@ global data. All the details can be found in the CPython documentation.
 
 .. warning::
 
-    Creating two concurrent `scoped_interpreter` guards is a fatal error. So is
-    calling `initialize_interpreter` for a second time after the interpreter
+    Creating two concurrent ``scoped_interpreter`` guards is a fatal error. So is
+    calling ``initialize_interpreter`` for a second time after the interpreter
     has already been initialized.
 
     Do not use the raw CPython API functions ``Py_Initialize`` and
@@ -242,7 +242,7 @@ global data. All the details can be found in the CPython documentation.
 Sub-interpreter support
 =======================
 
-Creating multiple copies of `scoped_interpreter` is not possible because it
+Creating multiple copies of ``scoped_interpreter`` is not possible because it
 represents the main Python interpreter. Sub-interpreters are something different
 and they do permit the existence of multiple interpreters. This is an advanced
 feature of the CPython API and should be handled with care. pybind11 does not
@@ -258,5 +258,5 @@ We'll just mention a couple of caveats the sub-interpreters support in pybind11:
  2. Managing multiple threads, multiple interpreters and the GIL can be
     challenging and there are several caveats here, even within the pure
     CPython API (please refer to the Python docs for details). As for
-    pybind11, keep in mind that `gil_scoped_release` and `gil_scoped_acquire`
+    pybind11, keep in mind that ``gil_scoped_release`` and ``gil_scoped_acquire``
     do not take sub-interpreters into account.
diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index 2aaa0ad323..b4825cbcde 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -96,18 +96,18 @@ A matching function is available for registering a local exception translator:
 
 
 It is possible to specify base class for the exception using the third
-parameter, a `handle`:
+parameter, a ``handle``:
 
 .. code-block:: cpp
 
     py::register_exception<CppExp>(module, "PyExp", PyExc_RuntimeError);
     py::register_local_exception<CppExp>(module, "PyExp", PyExc_RuntimeError);
 
-Then `PyExp` can be caught both as `PyExp` and `RuntimeError`.
+Then ``PyExp`` can be caught both as ``PyExp`` and ``RuntimeError``.
 
 The class objects of the built-in Python exceptions are listed in the Python
 documentation on `Standard Exceptions <https://docs.python.org/3/c-api/exceptions.html#standard-exceptions>`_.
-The default base class is `PyExc_Exception`.
+The default base class is ``PyExc_Exception``.
 
 When more advanced exception translation is needed, the functions
 ``py::register_exception_translator(translator)`` and
diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index 1178d07260..abd1084ab5 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -232,7 +232,7 @@ is equivalent to the following pseudocode:
     });
 
 The only requirement is that ``T`` is default-constructible, but otherwise any
-scope guard will work. This is very useful in combination with `gil_scoped_release`.
+scope guard will work. This is very useful in combination with ``gil_scoped_release``.
 See :ref:`gil`.
 
 Multiple guards can also be specified as ``py::call_guard<T1, T2, T3...>``. The
diff --git a/docs/advanced/misc.rst b/docs/advanced/misc.rst
index b3f3b2265a..edab15fcb7 100644
--- a/docs/advanced/misc.rst
+++ b/docs/advanced/misc.rst
@@ -84,7 +84,7 @@ could be realized as follows (important changes highlighted):
         });
     }
 
-The ``call_go`` wrapper can also be simplified using the `call_guard` policy
+The ``call_go`` wrapper can also be simplified using the ``call_guard`` policy
 (see :ref:`call_policies`) which yields the same result:
 
 .. code-block:: cpp
diff --git a/docs/advanced/pycpp/utilities.rst b/docs/advanced/pycpp/utilities.rst
index bf90a62f8c..af0f9cb2b0 100644
--- a/docs/advanced/pycpp/utilities.rst
+++ b/docs/advanced/pycpp/utilities.rst
@@ -28,7 +28,7 @@ Capturing standard output from ostream
 
 Often, a library will use the streams ``std::cout`` and ``std::cerr`` to print,
 but this does not play well with Python's standard ``sys.stdout`` and ``sys.stderr``
-redirection. Replacing a library's printing with `py::print <print>` may not
+redirection. Replacing a library's printing with ``py::print <print>`` may not
 be feasible. This can be fixed using a guard around the library function that
 redirects output to the corresponding Python streams:
 
@@ -62,9 +62,9 @@ This method respects flushes on the output streams and will flush if needed
 when the scoped guard is destroyed. This allows the output to be redirected in
 real time, such as to a Jupyter notebook. The two arguments, the C++ stream and
 the Python output, are optional, and default to standard output if not given. An
-extra type, `py::scoped_estream_redirect <scoped_estream_redirect>`, is identical
+extra type, ``py::scoped_estream_redirect <scoped_estream_redirect>``, is identical
 except for defaulting to ``std::cerr`` and ``sys.stderr``; this can be useful with
-`py::call_guard`, which allows multiple items, but uses the default constructor:
+``py::call_guard``, which allows multiple items, but uses the default constructor:
 
 .. code-block:: cpp
 
@@ -74,7 +74,7 @@ except for defaulting to ``std::cerr`` and ``sys.stderr``; this can be useful wi
                          py::scoped_estream_redirect>());
 
 The redirection can also be done in Python with the addition of a context
-manager, using the `py::add_ostream_redirect() <add_ostream_redirect>` function:
+manager, using the ``py::add_ostream_redirect() <add_ostream_redirect>`` function:
 
 .. code-block:: cpp
 
@@ -103,7 +103,7 @@ arguments to disable one of the streams if needed.
 Evaluating Python expressions from strings and files
 ====================================================
 
-pybind11 provides the `eval`, `exec` and `eval_file` functions to evaluate
+pybind11 provides the ``eval``, ``exec`` and ``eval_file`` functions to evaluate
 Python expressions and statements. The following example illustrates how they
 can be used.
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 80c580b180..0721020db8 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -251,8 +251,8 @@ New features:
 
 Changes:
 
-* ``py::str`` changed to exclusively hold `PyUnicodeObject`. Previously
-  ``py::str`` could also hold `bytes`, which is probably surprising, was
+* ``py::str`` changed to exclusively hold ``PyUnicodeObject``. Previously
+  ``py::str`` could also hold ``bytes``, which is probably surprising, was
   never documented, and can mask bugs (e.g. accidental use of ``py::str``
   instead of ``py::bytes``).
   `#2409 <https://github.com/pybind/pybind11/pull/2409>`_
@@ -1405,7 +1405,7 @@ v2.2.0 (August 31, 2017)
 * Intel C++ compiler compatibility fixes.
   `#937 <https://github.com/pybind/pybind11/pull/937>`_.
 
-* Fixed implicit conversion of `py::enum_` to integer types on Python 2.7.
+* Fixed implicit conversion of ``py::enum_`` to integer types on Python 2.7.
   `#821 <https://github.com/pybind/pybind11/pull/821>`_.
 
 * Added ``py::hash`` to fetch the hash value of Python objects, and
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index e3df7e04f9..adf7cadff2 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -5,7 +5,7 @@
 
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import ConstructorStats
 from pybind11_tests import buffers as m
 
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 09b4b08c5e..2a061c193e 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import IncType, UserType
 from pybind11_tests import builtin_casters as m
 
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index edbb1890c9..f41ad86e7f 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -4,7 +4,7 @@
 
 import pytest
 
-import env  # NOQA: F401
+import env  # noqa: F401
 from pybind11_tests import callbacks as m
 
 
diff --git a/tests/test_enum.py b/tests/test_enum.py
index 85302b0809..14c754e726 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -96,13 +96,13 @@ def test_unscoped_enum():
         y >= object()  # noqa: B015
 
     with pytest.raises(TypeError):
-        y | object()  # noqa: B015
+        y | object()
 
     with pytest.raises(TypeError):
-        y & object()  # noqa: B015
+        y & object()
 
     with pytest.raises(TypeError):
-        y ^ object()  # noqa: B015
+        y ^ object()
 
     assert int(m.UnscopedEnum.ETwo) == 2
     assert str(m.UnscopedEnum(2)) == "UnscopedEnum.ETwo"
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 21909654a5..866b3cea18 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -102,7 +102,7 @@ def test_properties():
     assert instance.def_property == 3
 
     with pytest.raises(AttributeError) as excinfo:
-        dummy = instance.def_property_writeonly  # noqa: F841 unused var
+        dummy = instance.def_property_writeonly  # unused var
     assert "unreadable attribute" in str(excinfo.value)
 
     instance.def_property_writeonly = 4
@@ -127,7 +127,7 @@ def test_static_properties():
     assert m.TestProperties.def_readwrite_static == 2
 
     with pytest.raises(AttributeError) as excinfo:
-        dummy = m.TestProperties.def_writeonly_static  # noqa: F841 unused var
+        dummy = m.TestProperties.def_writeonly_static  # unused var
     assert "unreadable attribute" in str(excinfo.value)
 
     m.TestProperties.def_writeonly_static = 3
diff --git a/tests/test_pickling.py b/tests/test_pickling.py
index e39463d209..9f68f37dcf 100644
--- a/tests/test_pickling.py
+++ b/tests/test_pickling.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import pickling as m
 
 try:
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index cc27e60a11..5215b79bc1 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -5,7 +5,7 @@
 
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import debug_enabled
 from pybind11_tests import pytypes as m
 
@@ -610,7 +610,7 @@ def callback(wr):
 
     obj = WeaklyReferenced()
     assert getweakrefcount(obj) == 0
-    wr = create_weakref(obj)  # noqa: F841
+    wr = create_weakref(obj)
     assert getweakrefcount(obj) == 1
 
     obj = WeaklyReferenced()
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index a68dcd31de..59c5ab6b5d 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import stl_binders as m
 
 

From 750e38dcfdac59231a615580d4e6cb3647b31779 Mon Sep 17 00:00:00 2001
From: NaDDu <nonaddu@gmail.com>
Date: Sun, 10 Oct 2021 00:38:34 +0900
Subject: [PATCH 208/638] Update eval.h (#3344)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

typo correction

pybind11/exec.h → pybind11/eval.h
---
 include/pybind11/eval.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index e0f58bcf49..6cc672e2d5 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -1,5 +1,5 @@
 /*
-    pybind11/exec.h: Support for evaluating Python expressions and statements
+    pybind11/eval.h: Support for evaluating Python expressions and statements
     from strings and files
 
     Copyright (c) 2016 Klemens Morgenstern <klemens.morgenstern@ed-chemnitz.de> and

From 8a7c266d26e5c9de3beb478bedddcee26f026b04 Mon Sep 17 00:00:00 2001
From: Bruce Merry <1963944+bmerry@users.noreply.github.com>
Date: Mon, 11 Oct 2021 17:35:39 +0200
Subject: [PATCH 209/638] Fix make_key_iterator/make_value_iterator for prvalue
 iterators (#3348)

* Add a test showing a flaw in make_key_iterator/make_value_iterator

If the iterator dereference operator returns a value rather than a
reference (and that pair also does not *contain* references),
make_key_iterator and make_value_iterator will return a reference to a
temporary, causing a segfault.

* Fix make_key_iterator/make_value_iterator for prvalue iterators

If an iterator returns a pair<T1, T2> rather than a reference to a pair
or a pair of references, make_key_iterator and make_value_iterator would
return a reference to a temporary, typically leading to a segfault. This
is because the value category of member access to a prvalue is an
xvalue, not a prvalue, so decltype produces an rvalue reference type.
Fix the type calculation to handle this case.

I also removed some decltype parentheses that weren't needed, either
because the expression isn't one of the special cases for decltype or
because decltype was only used for SFINAE. Hopefully that makes the code
a bit more readable.

Closes #3347

* Attempt a workaround for nvcc
---
 include/pybind11/pybind11.h            | 47 ++++++++++++++++++++------
 tests/test_sequences_and_iterators.cpp | 27 ++++++++++++++-
 tests/test_sequences_and_iterators.py  |  7 ++++
 3 files changed, 69 insertions(+), 12 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 370e52cff6..285f3b18cb 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1967,29 +1967,54 @@ struct iterator_state {
 };
 
 // Note: these helpers take the iterator by non-const reference because some
-// iterators in the wild can't be dereferenced when const. C++ needs the extra parens in decltype
-// to enforce an lvalue. The & after Iterator is required for MSVC < 16.9. SFINAE cannot be
-// reused for result_type due to bugs in ICC, NVCC, and PGI compilers. See PR #3293.
-template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()))>
+// iterators in the wild can't be dereferenced when const. The & after Iterator
+// is required for MSVC < 16.9. SFINAE cannot be reused for result_type due to
+// bugs in ICC, NVCC, and PGI compilers. See PR #3293.
+template <typename Iterator, typename SFINAE = decltype(*std::declval<Iterator &>())>
 struct iterator_access {
-    using result_type = decltype((*std::declval<Iterator &>()));
+    using result_type = decltype(*std::declval<Iterator &>());
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     result_type operator()(Iterator &it) const {
         return *it;
     }
 };
 
-template <typename Iterator, typename SFINAE = decltype(((*std::declval<Iterator &>()).first)) >
-struct iterator_key_access {
-    using result_type = decltype(((*std::declval<Iterator &>()).first));
+template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).first) >
+class iterator_key_access {
+private:
+    using pair_type = decltype(*std::declval<Iterator &>());
+
+public:
+    /* If either the pair itself or the element of the pair is a reference, we
+     * want to return a reference, otherwise a value. When the decltype
+     * expression is parenthesized it is based on the value category of the
+     * expression; otherwise it is the declared type of the pair member.
+     * The use of declval<pair_type> in the second branch rather than directly
+     * using *std::declval<Iterator &>() is a workaround for nvcc
+     * (it's not used in the first branch because going via decltype and back
+     * through declval does not perfectly preserve references).
+     */
+    using result_type = conditional_t<
+        std::is_reference<decltype(*std::declval<Iterator &>())>::value,
+        decltype(((*std::declval<Iterator &>()).first)),
+        decltype(std::declval<pair_type>().first)
+    >;
     result_type operator()(Iterator &it) const {
         return (*it).first;
     }
 };
 
-template <typename Iterator, typename SFINAE = decltype(((*std::declval<Iterator &>()).second))>
-struct iterator_value_access {
-    using result_type = decltype(((*std::declval<Iterator &>()).second));
+template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).second)>
+class iterator_value_access {
+private:
+    using pair_type = decltype(*std::declval<Iterator &>());
+
+public:
+    using result_type = conditional_t<
+        std::is_reference<decltype(*std::declval<Iterator &>())>::value,
+        decltype(((*std::declval<Iterator &>()).second)),
+        decltype(std::declval<pair_type>().second)
+    >;
     result_type operator()(Iterator &it) const {
         return (*it).second;
     }
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index 9de69338bc..a378128ae2 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -38,6 +38,17 @@ bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentine
     return !(*it).first || !(*it).second;
 }
 
+/* Iterator where dereferencing returns prvalues instead of references. */
+template<typename T>
+class NonRefIterator {
+    const T* ptr_;
+public:
+    explicit NonRefIterator(const T *ptr) : ptr_(ptr) {}
+    T operator*() const { return T(*ptr_); }
+    NonRefIterator& operator++() { ++ptr_; return *this; }
+    bool operator==(const NonRefIterator &other) const { return ptr_ == other.ptr_; }
+};
+
 class NonCopyableInt {
 public:
     explicit NonCopyableInt(int value) : value_(value) {}
@@ -331,7 +342,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     py::class_<IntPairs>(m, "IntPairs")
         .def(py::init<std::vector<std::pair<int, int>>>())
         .def("nonzero", [](const IntPairs& s) {
-                return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
+            return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
         .def("nonzero_keys", [](const IntPairs& s) {
             return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
@@ -340,6 +351,20 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
 
+        // test iterator that returns values instead of references
+        .def("nonref", [](const IntPairs& s) {
+             return py::make_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                      NonRefIterator<std::pair<int, int>>(s.end()));
+        }, py::keep_alive<0, 1>())
+        .def("nonref_keys", [](const IntPairs& s) {
+             return py::make_key_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                          NonRefIterator<std::pair<int, int>>(s.end()));
+        }, py::keep_alive<0, 1>())
+        .def("nonref_values", [](const IntPairs& s) {
+             return py::make_value_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                            NonRefIterator<std::pair<int, int>>(s.end()));
+        }, py::keep_alive<0, 1>())
+
         // test single-argument make_iterator
         .def("simple_iterator", [](IntPairs& self) {
             return py::make_iterator(self);
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 38e2ab5b75..6985918a11 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -52,6 +52,13 @@ def test_generalized_iterators():
             next(it)
 
 
+def test_nonref_iterators():
+    pairs = m.IntPairs([(1, 2), (3, 4), (0, 5)])
+    assert list(pairs.nonref()) == [(1, 2), (3, 4), (0, 5)]
+    assert list(pairs.nonref_keys()) == [1, 3, 0]
+    assert list(pairs.nonref_values()) == [2, 4, 5]
+
+
 def test_generalized_iterators_simple():
     assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_iterator()) == [
         (1, 2),

From 02c05573d9f580bb1bfcc351e2e22e0c9f539b2b Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 11 Oct 2021 16:03:19 -0400
Subject: [PATCH 210/638] [pre-commit.ci] pre-commit autoupdate (#3353)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/flake8: 3.9.2 → 4.0.1](https://github.com/PyCQA/flake8/compare/3.9.2...4.0.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 17e67ded40..c6652d8367 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -79,7 +79,7 @@ repos:
 
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
-  rev: 3.9.2
+  rev: 4.0.1
   hooks:
   - id: flake8
     additional_dependencies: &flake8_dependencies

From 7c580586f853b5f48603594ff0c11a5211de9007 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 11 Oct 2021 13:13:01 -0700
Subject: [PATCH 211/638] Correct options on Eigen::MappedSparseMatrix & adding
 MSVC C4127 suppression around Eigen includes. (#3352)

* Adding MSVC C4127 suppression around Eigen includes.

* For MSVC 2015 only: also adding the C4127 suppression to test_eigen.cpp

* Copying original change from PR #3343, with extra line breaks to not run past 99 columns (our desired but currently not enforced limit).
---
 include/pybind11/eigen.h | 18 +++++++++++++++++-
 tests/CMakeLists.txt     |  4 ++--
 tests/test_eigen.cpp     |  3 +++
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index c0363827c3..97b1d96b09 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -17,9 +17,23 @@
 
 #include "numpy.h"
 
+// The C4127 suppression was introduced for Eigen 3.4.0. In theory we could
+// make it version specific, or even remove it later, but considering that
+// 1. C4127 is generally far more distracting than useful for modern template code, and
+// 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
+// it is probably best to keep this around indefinitely.
+#if defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable: 4127) // C4127: conditional expression is constant
+#endif
+
 #include <Eigen/Core>
 #include <Eigen/SparseCore>
 
+#if defined(_MSC_VER)
+#  pragma warning(pop)
+#endif
+
 // Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
 // move constructors that break things.  We could detect this an explicitly copy, but an extra copy
 // of matrices seems highly undesirable.
@@ -559,7 +573,9 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         if (!values || !innerIndices || !outerIndices)
             return false;
 
-        value = Eigen::MappedSparseMatrix<Scalar, Type::Flags, StorageIndex>(
+        value = Eigen::MappedSparseMatrix<Scalar,
+                                          Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
+                                          StorageIndex>(
             shape[0].cast<Index>(), shape[1].cast<Index>(), nnz,
             outerIndices.mutable_data(), innerIndices.mutable_data(), values.mutable_data());
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6ebcba9b6b..d4e7b71e1d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -174,9 +174,9 @@ set(PYBIND11_CROSS_MODULE_GIL_TESTS test_gil_scoped.py)
 set(PYBIND11_EIGEN_REPO
     "https://gitlab.com/libeigen/eigen.git"
     CACHE STRING "Eigen repository to use for tests")
-# This hash is for 3.3.8, using a hash for security reasons
+# This hash is for 3.4.0, using a hash for security reasons
 set(PYBIND11_EIGEN_VERSION
-    "dc252fbf00079ccab57948a164b1421703fe4361"
+    "929bc0e191d0927b1735b9a1ddc0e8b77e3a25ec"
     CACHE STRING "Eigen version to use for tests")
 
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index ad572b2ad7..d22a94a1a1 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -13,6 +13,9 @@
 #include <pybind11/stl.h>
 
 #if defined(_MSC_VER)
+#if _MSC_VER < 1910  // VS 2015's MSVC
+#  pragma warning(disable: 4127) // C4127: conditional expression is constant
+#endif
 #  pragma warning(disable: 4996) // C4996: std::unary_negation is deprecated
 #endif
 

From 56b49c2be27dbe440f4236a5ca711950aa788e63 Mon Sep 17 00:00:00 2001
From: Jerome Robert <jeromerobert@gmx.com>
Date: Mon, 18 Oct 2021 03:38:41 +0200
Subject: [PATCH 212/638] ci: fix mingw checks by pinning (#3375)

* Workaround for https://github.com/msys2/setup-msys2/issues/167
* Adapted from https://github.com/cocotb/cocotb/commit/05036cb24d10579647e81dc1a405b126f711a66f
---
 .github/workflows/ci.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5d5222f8b6..e337770ebd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -892,7 +892,8 @@ jobs:
           - { sys: mingw64, env: x86_64 }
           - { sys: mingw32, env: i686 }
     steps:
-    - uses: msys2/setup-msys2@v2
+    # Force version because of https://github.com/msys2/setup-msys2/issues/167
+    - uses: msys2/setup-msys2@v2.4.2
       with:
         msystem: ${{matrix.sys}}
         install: >-

From 931f66440f932c62a38e8112ea8ec2f7d962e64a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sun, 17 Oct 2021 21:40:10 -0400
Subject: [PATCH 213/638] ci: cancel in-progress on repeated pushes (#3370)

---
 .github/workflows/ci.yml | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e337770ebd..09b4000562 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,6 +9,10 @@ on:
       - stable
       - v*
 
+concurrency:
+  group: test-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   # This is the "main" test suite, which tests a large number of different
   # versions of default compilers and Python versions in GitHub Actions.

From f791dc8648e1f6ec33f402d679b6b116a76d4e1b Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 19 Oct 2021 14:39:29 -0400
Subject: [PATCH 214/638] fix: deprecate make_simple_namespace, fix Python 3.11
 (#3374)

* fix: deprecate make_simple_namespace, fix Python 3.11

* docs: update links
---
 docs/advanced/pycpp/object.rst | 13 +++----------
 docs/changelog.rst             |  8 ++++++--
 docs/upgrade.rst               | 13 ++++++++++++-
 include/pybind11/cast.h        | 10 ----------
 include/pybind11/pybind11.h    |  9 +++++++++
 tests/test_pytypes.cpp         |  2 +-
 6 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/docs/advanced/pycpp/object.rst b/docs/advanced/pycpp/object.rst
index 8bffb83e18..93e1a94d8f 100644
--- a/docs/advanced/pycpp/object.rst
+++ b/docs/advanced/pycpp/object.rst
@@ -41,24 +41,17 @@ A tuple of python objects can be instantiated using :func:`py::make_tuple`:
 Each element is converted to a supported Python type.
 
 A `simple namespace`_ can be instantiated using
-:func:`py::make_simple_namespace`:
 
 .. code-block:: cpp
 
-    using namespace pybind11::literals; // to bring in the `_a` literal
-    py::object ns = py::make_simple_namespace("spam"_a=py::none(), "eggs"_a=42);
+    using namespace pybind11::literals;  // to bring in the `_a` literal
+    py::object SimpleNamespace = py::module_::import("types").attr("SimpleNamespace");
+    py::object ns = SimpleNamespace("spam"_a=py::none(), "eggs"_a=42);
 
 Attributes on a namespace can be modified with the :func:`py::delattr`,
 :func:`py::getattr`, and :func:`py::setattr` functions. Simple namespaces can
 be useful as lightweight stand-ins for class instances.
 
-.. note::
-
-    ``make_simple_namespace`` is not available in Python 2.
-
-.. versionchanged:: 2.8
-    ``make_simple_namespace`` added.
-
 .. _simple namespace: https://docs.python.org/3/library/types.html#types.SimpleNamespace
 
 .. _casting_back_and_forth:
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 0721020db8..ee79a18719 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,6 +10,10 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 IN DEVELOPMENT
 --------------
 
+* The simple namespace creation shortcut added in 2.8.0 was deprecated due to
+  usage of CPython internal API, and will be removed soon. Use
+  ``py::module_::import("types").attr("SimpleNamespace")``.
+  `#3374 <https://github.com/pybinyyd/pybind11/pull/3374>`_
 
 
 v2.8.0 (Oct 4, 2021)
@@ -25,10 +29,10 @@ New features:
   ``register_local_exception_translator(ExceptionTranslator&& translator)``
   instead of  ``register_exception_translator(ExceptionTranslator&&
   translator)`` to keep your exception remapping code local to the module.
-  `#2650 <https://github.com/pybind/pybind11/pull/2650>`_
+  `#2650 <https://github.com/pybinyyd/pybind11/pull/2650>`_
 
 * Add ``make_simple_namespace`` function for instantiating Python
-  ``SimpleNamespace`` objects.
+  ``SimpleNamespace`` objects. **Deprecated in 2.8.1.**
   `#2840 <https://github.com/pybind/pybind11/pull/2840>`_
 
 * ``pybind11::scoped_interpreter`` and ``initialize_interpreter`` have new
diff --git a/docs/upgrade.rst b/docs/upgrade.rst
index b2b6b12456..69609ca284 100644
--- a/docs/upgrade.rst
+++ b/docs/upgrade.rst
@@ -8,7 +8,17 @@ to a new version. But it goes into more detail. This includes things like
 deprecated APIs and their replacements, build system changes, general code
 modernization and other useful information.
 
-.. _upgrade-guide-2.6:
+.. _upgrade-guide-2.9:
+
+v2.9
+====
+
+* Any usage of the recently added ``py::make_simple_namespace`` should be
+  converted to using ``py::module_::import("types").attr("SimpleNamespace")``
+  instead.
+
+
+.. _upgrade-guide-2.7:
 
 v2.7
 ====
@@ -34,6 +44,7 @@ to be common:
   careful review and custom fixes.
 
 
+.. _upgrade-guide-2.6:
 
 v2.6
 ====
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 1ec2080f8a..20fbb32587 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1036,16 +1036,6 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
     return result;
 }
 
-#if PY_VERSION_HEX >= 0x03030000
-template <typename... Args,
-          typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
-object make_simple_namespace(Args&&... args_) {
-    PyObject *ns = _PyNamespace_New(dict(std::forward<Args>(args_)...).ptr());
-    if (!ns) throw error_already_set();
-    return reinterpret_steal<object>(ns);
-}
-#endif
-
 /// \ingroup annotations
 /// Annotation for arguments
 struct arg {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 285f3b18cb..095efd9c31 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1124,6 +1124,15 @@ inline dict globals() {
     return reinterpret_borrow<dict>(p ? p : module_::import("__main__").attr("__dict__").ptr());
 }
 
+#if PY_VERSION_HEX >= 0x03030000
+template <typename... Args,
+          typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
+PYBIND11_DEPRECATED("make_simple_namespace should be replaced with py::module_::import(\"types\").attr(\"SimpleNamespace\") ")
+object make_simple_namespace(Args&&... args_) {
+    return module_::import("types").attr("SimpleNamespace")(std::forward<Args>(args_)...);
+}
+#endif
+
 PYBIND11_NAMESPACE_BEGIN(detail)
 /// Generic support for creating new Python heap types
 class generic_type : public object {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 2157dc0973..9a1e918818 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -84,7 +84,7 @@ TEST_SUBMODULE(pytypes, m) {
 #if PY_VERSION_HEX >= 0x03030000
     // test_simple_namespace
     m.def("get_simple_namespace", []() {
-        auto ns = py::make_simple_namespace("attr"_a=42, "x"_a="foo", "wrong"_a=1);
+        auto ns = py::module_::import("types").attr("SimpleNamespace")("attr"_a=42, "x"_a="foo", "wrong"_a=1);
         py::delattr(ns, "wrong");
         py::setattr(ns, "right", py::int_(2));
         return ns;

From 2d6014e417a9be926eb9a3c490570707be35cd42 Mon Sep 17 00:00:00 2001
From: Geoffrey Gunter <12984092+gmgunter@users.noreply.github.com>
Date: Thu, 21 Oct 2021 07:37:54 -0700
Subject: [PATCH 215/638] docs: fix minor typo (#3390)

---
 include/pybind11/numpy.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index b7747fae2d..b43a771684 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -518,7 +518,7 @@ class dtype : public object {
     }
 
     /// Single-character for dtype's type.
-    /// For example, ``float`` is 'f', ``double`` 'd', ``int`` 'i', and ``long`` 'd'.
+    /// For example, ``float`` is 'f', ``double`` 'd', ``int`` 'i', and ``long`` 'l'.
     char char_() const {
         // Note: The signature, `dtype::char_` follows the naming of NumPy's
         // public Python API (i.e., ``dtype.char``), rather than its internal

From 606f81a966e56d1ec0f17b0c032e8d6679430d67 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 22 Oct 2021 16:38:40 -0400
Subject: [PATCH 216/638] style: drop pycln (#3397)

---
 .pre-commit-config.yaml | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c6652d8367..04166de9aa 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -61,12 +61,6 @@ repos:
   hooks:
   - id: remove-tabs
 
-# Autoremoves unused imports
-- repo: https://github.com/hadialqattan/pycln
-  rev: v1.0.3
-  hooks:
-  - id: pycln
-
 - repo: https://github.com/pre-commit/pygrep-hooks
   rev: v1.9.0
   hooks:

From 076c89fc54d3859bb56581555897fda1c621405c Mon Sep 17 00:00:00 2001
From: Dmitry Yershov <dmitry.s.yershov@gmail.com>
Date: Fri, 22 Oct 2021 17:09:15 -0400
Subject: [PATCH 217/638] tests: test recursive dispatch using visitor pattern
 (#3365)

---
 tests/test_virtual_functions.cpp | 40 ++++++++++++++++++++++++++++++++
 tests/test_virtual_functions.py  | 33 ++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 1eba534dd2..6e06db9fc1 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -174,6 +174,25 @@ struct DispatchIssue : Base {
     }
 };
 
+// An abstract adder class that uses visitor pattern to add two data
+// objects and send the result to the visitor functor
+struct AdderBase {
+    struct Data {};
+    using DataVisitor = std::function<void (const Data&)>;
+
+    virtual void operator()(const Data& first, const Data& second, const DataVisitor& visitor) const = 0;
+    virtual ~AdderBase() = default;
+    AdderBase() = default;
+    AdderBase(const AdderBase&) = delete;
+};
+
+struct Adder : AdderBase {
+    void operator()(const Data& first, const Data& second, const DataVisitor& visitor) const override {
+        PYBIND11_OVERRIDE_PURE_NAME(void, AdderBase, "__call__", operator(), first, second, visitor);
+    }
+};
+
+
 static void test_gil() {
     {
         py::gil_scoped_acquire lock;
@@ -295,6 +314,27 @@ TEST_SUBMODULE(virtual_functions, m) {
 
     m.def("dispatch_issue_go", [](const Base * b) { return b->dispatch(); });
 
+    // test_recursive_dispatch_issue
+    // #3357: Recursive dispatch fails to find python function override
+    pybind11::class_<AdderBase, Adder>(m, "Adder")
+        .def(pybind11::init<>())
+        .def("__call__", &AdderBase::operator());
+
+    pybind11::class_<AdderBase::Data>(m, "Data")
+        .def(pybind11::init<>());
+
+    m.def("add2", [](const AdderBase::Data& first, const AdderBase::Data& second,
+                     const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
+        adder(first, second, visitor);
+    });
+
+    m.def("add3", [](const AdderBase::Data& first, const AdderBase::Data& second, const AdderBase::Data& third,
+                     const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
+        adder(first, second, [&] (const AdderBase::Data& first_plus_second) {
+            adder(first_plus_second, third, visitor);
+        });
+    });
+
     // test_override_ref
     // #392/397: overriding reference-returning functions
     class OverrideTest {
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index f7d3bd1e4b..0b550992f1 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -257,6 +257,39 @@ def dispatch(self):
     assert m.dispatch_issue_go(b) == "Yay.."
 
 
+def test_recursive_dispatch_issue(msg):
+    """#3357: Recursive dispatch fails to find python function override"""
+
+    class Data(m.Data):
+        def __init__(self, value):
+            super(Data, self).__init__()
+            self.value = value
+
+    class Adder(m.Adder):
+        def __call__(self, first, second, visitor):
+            # lambda is a workaround, which adds extra frame to the
+            # current CPython thread. Removing lambda reveals the bug
+            # [https://github.com/pybind/pybind11/issues/3357]
+            (lambda: visitor(Data(first.value + second.value)))()
+
+    class StoreResultVisitor:
+        def __init__(self):
+            self.result = None
+
+        def __call__(self, data):
+            self.result = data.value
+
+    store = StoreResultVisitor()
+
+    m.add2(Data(1), Data(2), Adder(), store)
+    assert store.result == 3
+
+    # without lambda in Adder class, this function fails with
+    # RuntimeError: Tried to call pure virtual function "AdderBase::__call__"
+    m.add3(Data(1), Data(2), Data(3), Adder(), store)
+    assert store.result == 6
+
+
 def test_override_ref():
     """#392/397: overriding reference-returning functions"""
     o = m.OverrideTest("asdf")

From 78ee782bd494debcbc166f717379a4f9c2093c0f Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sat, 23 Oct 2021 00:07:22 -0400
Subject: [PATCH 218/638] feat: Add C++ binding to throw AttributeError (#3387)

* Add C++ bindings to throw AttributeError

* Fix formatting bug
---
 docs/advanced/exceptions.rst     | 4 +++-
 include/pybind11/detail/common.h | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index b4825cbcde..40f67d7b83 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -56,7 +56,9 @@ at its exception handler.
 +--------------------------------------+--------------------------------------+
 | :class:`pybind11::buffer_error`      | ``BufferError``                      |
 +--------------------------------------+--------------------------------------+
-| :class:`pybind11::import_error`      | ``import_error``                     |
+| :class:`pybind11::import_error`      | ``ImportError``                      |
++--------------------------------------+--------------------------------------+
+| :class:`pybind11::attribute_error`   | ``AttributeError``                   |
 +--------------------------------------+--------------------------------------+
 | Any other exception                  | ``RuntimeError``                     |
 +--------------------------------------+--------------------------------------+
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 9ad305a4ee..862451fd13 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -831,6 +831,7 @@ PYBIND11_RUNTIME_EXCEPTION(value_error, PyExc_ValueError)
 PYBIND11_RUNTIME_EXCEPTION(type_error, PyExc_TypeError)
 PYBIND11_RUNTIME_EXCEPTION(buffer_error, PyExc_BufferError)
 PYBIND11_RUNTIME_EXCEPTION(import_error, PyExc_ImportError)
+PYBIND11_RUNTIME_EXCEPTION(attribute_error, PyExc_AttributeError)
 PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or handle::call fail due to a type casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
 

From 9379b399d99a784f7e226f135fb117aff6db8013 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 25 Oct 2021 16:01:19 -0400
Subject: [PATCH 219/638] fix: MSVC 2017 C++17 on Python 3 regression (#3407)

* fix: MSVC 2017 C++17 on Python 3 regression

* ci: add 3.7 job on CI
---
 .github/workflows/ci.yml      | 4 ++++
 include/pybind11/functional.h | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 09b4000562..b027640df1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -851,6 +851,10 @@ jobs:
             std: 17
             args: >
               -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR"
+          - python: 3.7
+            std: 17
+            args: >
+              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR"
 
     steps:
     - uses: actions/checkout@v2
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 24141ce388..ad5608c255 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -69,7 +69,7 @@ struct type_caster<std::function<Return(Args...)>> {
         // ensure GIL is held during functor destruction
         struct func_handle {
             function f;
-#if !(defined(_MSC_VER) && _MSC_VER == 1916 && defined(PYBIND11_CPP17) && PY_MAJOR_VERSION < 3)
+#if !(defined(_MSC_VER) && _MSC_VER == 1916 && defined(PYBIND11_CPP17))
             // This triggers a syntax error under very special conditions (very weird indeed).
             explicit
 #endif

From d45a88105c3dab1dc2a1da831f1c83a0f3b57f8b Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 25 Oct 2021 16:06:13 -0400
Subject: [PATCH 220/638] [pre-commit.ci] pre-commit autoupdate (#3409)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/yesqa: v1.2.3 → v1.3.0](https://github.com/asottile/yesqa/compare/v1.2.3...v1.3.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 04166de9aa..b3e5179055 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -82,7 +82,7 @@ repos:
     exclude: ^(docs/.*|tools/.*)$
 
 - repo: https://github.com/asottile/yesqa
-  rev: v1.2.3
+  rev: v1.3.0
   hooks:
   - id: yesqa
     additional_dependencies: *flake8_dependencies

From c2d3e220bd1bfcf664e29d95ac2ed774fd6723f4 Mon Sep 17 00:00:00 2001
From: Ryan Cahoon <ryan.cahoon@zoox.com>
Date: Mon, 25 Oct 2021 19:04:45 -0700
Subject: [PATCH 221/638] fix: the types for return_value_policy_override in
 optional_caster (#3376)

* fix: the types for return_value_policy_override in optional_caster

`return_value_policy_override` was not being applied correctly in
`optional_caster` in two ways:
- The `is_lvalue_reference` condition referenced `T`, which was the
`optional<T>` type parameter from the class, when it should have used `T_`,
which was the parameter to the `cast` function. `T_` can potentially be a
reference type, but `T` will never be.
- The type parameter passed to `return_value_policy_override` should be
`T::value_type`, not `T`. This matches the way that the other STL container
type casters work.

The result of these issues was that a method/property definition which used a
`reference` or `reference_internal` return value policy would create a Python
value that's bound by reference to a temporary C++ object, resulting in
undefined behavior. For reasons that I was not able to figure out fully, it
seems like this causes problems when using old versions of `boost::optional`,
but not with recent versions of `boost::optional` or the `libstdc++`
implementation of `std::optional`. The issue (that the override to
`return_value_policy::move` is never being applied) is present for all
implementations, it just seems like that somehow doesn't result in problems for
the some implementation of `optional`. This change includes a regression type
with a custom optional-like type which was able to reproduce the issue.

Part of the issue with using the wrong types may have stemmed from the type
variables `T` and `T_` having very similar names. This also changes the type
variables in `optional_caster` to use slightly more descriptive names, which
also more closely follow the naming convention used by the other STL casters.

Fixes #3330

* Fix clang-tidy complaints

* Add missing NOLINT

* Apply a couple more fixes

* fix: support GCC 4.8

* tests: avoid warning about unknown compiler for compilers missing C++17

* Remove unneeded test module attribute

* Change test enum to have more unique int values

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 include/pybind11/stl.h |  16 ++--
 tests/CMakeLists.txt   |   6 +-
 tests/test_stl.cpp     | 189 ++++++++++++++++++++++++++++++++++++++++-
 tests/test_stl.py      |  67 +++++++++++++++
 4 files changed, 265 insertions(+), 13 deletions(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 2c017b4fef..3608d2989c 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -245,17 +245,17 @@ template <typename Key, typename Value, typename Hash, typename Equal, typename
   : map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> { };
 
 // This type caster is intended to be used for std::optional and std::experimental::optional
-template<typename T> struct optional_caster {
-    using value_conv = make_caster<typename T::value_type>;
+template<typename Type, typename Value = typename Type::value_type> struct optional_caster {
+    using value_conv = make_caster<Value>;
 
-    template <typename T_>
-    static handle cast(T_ &&src, return_value_policy policy, handle parent) {
+    template <typename T>
+    static handle cast(T &&src, return_value_policy policy, handle parent) {
         if (!src)
             return none().inc_ref();
         if (!std::is_lvalue_reference<T>::value) {
-            policy = return_value_policy_override<T>::policy(policy);
+            policy = return_value_policy_override<Value>::policy(policy);
         }
-        return value_conv::cast(*std::forward<T_>(src), policy, parent);
+        return value_conv::cast(*std::forward<T>(src), policy, parent);
     }
 
     bool load(handle src, bool convert) {
@@ -269,11 +269,11 @@ template<typename T> struct optional_caster {
         if (!inner_caster.load(src, convert))
             return false;
 
-        value.emplace(cast_op<typename T::value_type &&>(std::move(inner_caster)));
+        value.emplace(cast_op<Value &&>(std::move(inner_caster)));
         return true;
     }
 
-    PYBIND11_TYPE_CASTER(T, _("Optional[") + value_conv::name + _("]"));
+    PYBIND11_TYPE_CASTER(Type, _("Optional[") + value_conv::name + _("]"));
 };
 
 #if defined(PYBIND11_HAS_OPTIONAL)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d4e7b71e1d..e1b18dd74b 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -256,7 +256,9 @@ if(Boost_FOUND)
 endif()
 
 # Check if we need to add -lstdc++fs or -lc++fs or nothing
-if(MSVC)
+if(DEFINED CMAKE_CXX_STANDARD AND CMAKE_CXX_STANDARD LESS 17)
+  set(STD_FS_NO_LIB_NEEDED TRUE)
+elseif(MSVC)
   set(STD_FS_NO_LIB_NEEDED TRUE)
 else()
   file(
@@ -286,7 +288,7 @@ elseif(${STD_FS_NEEDS_CXXFS})
 elseif(${STD_FS_NO_LIB_NEEDED})
   set(STD_FS_LIB "")
 else()
-  message(WARNING "Unknown compiler - not passing -lstdc++fs")
+  message(WARNING "Unknown C++17 compiler - not passing -lstdc++fs")
   set(STD_FS_LIB "")
 endif()
 
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 7e3363c5ea..bc5c6553a2 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -19,6 +19,18 @@
 #include <vector>
 #include <string>
 
+#if defined(PYBIND11_TEST_BOOST)
+#include <boost/optional.hpp>
+
+namespace pybind11 { namespace detail {
+template <typename T>
+struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
+
+template <>
+struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
+}} // namespace pybind11::detail
+#endif
+
 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
 #if defined(PYBIND11_HAS_VARIANT)
 using std::variant;
@@ -59,7 +71,8 @@ namespace std {
 template <template <typename> class OptionalImpl, typename T>
 struct OptionalHolder
 {
-    OptionalHolder() = default;
+    // NOLINTNEXTLINE(modernize-use-equals-default): breaks GCC 4.8
+    OptionalHolder() {};
     bool member_initialized() const {
         return member && member->initialized;
     }
@@ -67,6 +80,95 @@ struct OptionalHolder
 };
 
 
+enum class EnumType {
+  kSet = 42,
+  kUnset = 85,
+};
+
+// This is used to test that return-by-ref and return-by-copy policies are
+// handled properly for optional types. This is a regression test for a dangling
+// reference issue. The issue seemed to require the enum value type to
+// reproduce - it didn't seem to happen if the value type is just an integer.
+template <template <typename> class OptionalImpl>
+class OptionalProperties {
+public:
+    using OptionalEnumValue = OptionalImpl<EnumType>;
+
+    OptionalProperties() : value(EnumType::kSet) {}
+    ~OptionalProperties() {
+        // Reset value to detect use-after-destruction.
+        // This is set to a specific value rather than nullopt to ensure that
+        // the memory that contains the value gets re-written.
+        value = EnumType::kUnset;
+    }
+
+    OptionalEnumValue& access_by_ref() { return value; }
+    OptionalEnumValue access_by_copy() { return value; }
+
+private:
+    OptionalEnumValue value;
+};
+
+// This type mimics aspects of boost::optional from old versions of Boost,
+// which exposed a dangling reference bug in Pybind11. Recent versions of
+// boost::optional, as well as libstdc++'s std::optional, don't seem to be
+// affected by the same issue. This is meant to be a minimal implementation
+// required to reproduce the issue, not fully standard-compliant.
+// See issue #3330 for more details.
+template <typename T>
+class ReferenceSensitiveOptional {
+public:
+    using value_type = T;
+
+    ReferenceSensitiveOptional() = default;
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    ReferenceSensitiveOptional(const T& value) : storage{value} {}
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    ReferenceSensitiveOptional(T&& value) : storage{std::move(value)} {}
+    ReferenceSensitiveOptional& operator=(const T& value) {
+        storage = {value};
+        return *this;
+    }
+    ReferenceSensitiveOptional& operator=(T&& value) {
+        storage = {std::move(value)};
+        return *this;
+    }
+
+    template <typename... Args>
+    T& emplace(Args&&... args) {
+        storage.clear();
+        storage.emplace_back(std::forward<Args>(args)...);
+        return storage.back();
+    }
+
+    const T& value() const noexcept {
+        assert(!storage.empty());
+        return storage[0];
+    }
+
+    const T& operator*() const noexcept {
+        return value();
+    }
+
+    const T* operator->() const noexcept {
+        return &value();
+    }
+
+    explicit operator bool() const noexcept {
+        return !storage.empty();
+    }
+
+private:
+    std::vector<T> storage;
+};
+
+namespace pybind11 { namespace detail {
+template <typename T>
+struct type_caster<ReferenceSensitiveOptional<T>> : optional_caster<ReferenceSensitiveOptional<T>> {};
+} // namespace detail
+} // namespace pybind11
+
+
 TEST_SUBMODULE(stl, m) {
     // test_vector
     m.def("cast_vector", []() { return std::vector<int>{1}; });
@@ -145,6 +247,10 @@ TEST_SUBMODULE(stl, m) {
         return v;
     });
 
+    pybind11::enum_<EnumType>(m, "EnumType")
+        .value("kSet", EnumType::kSet)
+        .value("kUnset", EnumType::kUnset);
+
     // test_move_out_container
     struct MoveOutContainer {
         struct Value { int value; };
@@ -213,6 +319,12 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def_readonly("member", &opt_holder::member)
         .def("member_initialized", &opt_holder::member_initialized);
+
+    using opt_props = OptionalProperties<std::optional>;
+    pybind11::class_<opt_props>(m, "OptionalProperties")
+        .def(pybind11::init<>())
+        .def_property_readonly("access_by_ref", &opt_props::access_by_ref)
+        .def_property_readonly("access_by_copy", &opt_props::access_by_copy);
 #endif
 
 #ifdef PYBIND11_HAS_EXP_OPTIONAL
@@ -239,8 +351,75 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def_readonly("member", &opt_exp_holder::member)
         .def("member_initialized", &opt_exp_holder::member_initialized);
+
+    using opt_exp_props = OptionalProperties<std::experimental::optional>;
+    pybind11::class_<opt_exp_props>(m, "OptionalExpProperties")
+        .def(pybind11::init<>())
+        .def_property_readonly("access_by_ref", &opt_exp_props::access_by_ref)
+        .def_property_readonly("access_by_copy", &opt_exp_props::access_by_copy);
 #endif
 
+#if defined(PYBIND11_TEST_BOOST)
+    // test_boost_optional
+    m.attr("has_boost_optional") = true;
+
+    using boost_opt_int = boost::optional<int>;
+    using boost_opt_no_assign = boost::optional<NoAssign>;
+    m.def("double_or_zero_boost", [](const boost_opt_int& x) -> int {
+        return x.value_or(0) * 2;
+    });
+    m.def("half_or_none_boost", [](int x) -> boost_opt_int {
+        return x != 0 ? boost_opt_int(x / 2) : boost_opt_int();
+    });
+    m.def("test_nullopt_boost", [](boost_opt_int x) {
+        return x.value_or(42);
+    }, py::arg_v("x", boost::none, "None"));
+    m.def("test_no_assign_boost", [](const boost_opt_no_assign &x) {
+        return x ? x->value : 42;
+    }, py::arg_v("x", boost::none, "None"));
+
+    using opt_boost_holder = OptionalHolder<boost::optional, MoveOutDetector>;
+    py::class_<opt_boost_holder>(m, "OptionalBoostHolder", "Class with optional member")
+        .def(py::init<>())
+        .def_readonly("member", &opt_boost_holder::member)
+        .def("member_initialized", &opt_boost_holder::member_initialized);
+
+    using opt_boost_props = OptionalProperties<boost::optional>;
+    pybind11::class_<opt_boost_props>(m, "OptionalBoostProperties")
+        .def(pybind11::init<>())
+        .def_property_readonly("access_by_ref", &opt_boost_props::access_by_ref)
+        .def_property_readonly("access_by_copy", &opt_boost_props::access_by_copy);
+#endif
+
+    // test_refsensitive_optional
+    using refsensitive_opt_int = ReferenceSensitiveOptional<int>;
+    using refsensitive_opt_no_assign = ReferenceSensitiveOptional<NoAssign>;
+    m.def("double_or_zero_refsensitive", [](const refsensitive_opt_int& x) -> int {
+        return (x ? x.value() : 0) * 2;
+    });
+    m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
+        return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
+    });
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
+    m.def("test_nullopt_refsensitive", [](refsensitive_opt_int x) {
+        return x ? x.value() : 42;
+    }, py::arg_v("x", refsensitive_opt_int(), "None"));
+    m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
+        return x ? x->value : 42;
+    }, py::arg_v("x", refsensitive_opt_no_assign(), "None"));
+
+    using opt_refsensitive_holder = OptionalHolder<ReferenceSensitiveOptional, MoveOutDetector>;
+    py::class_<opt_refsensitive_holder>(m, "OptionalRefSensitiveHolder", "Class with optional member")
+        .def(py::init<>())
+        .def_readonly("member", &opt_refsensitive_holder::member)
+        .def("member_initialized", &opt_refsensitive_holder::member_initialized);
+
+    using opt_refsensitive_props = OptionalProperties<ReferenceSensitiveOptional>;
+    pybind11::class_<opt_refsensitive_props>(m, "OptionalRefSensitiveProperties")
+        .def(pybind11::init<>())
+        .def_property_readonly("access_by_ref", &opt_refsensitive_props::access_by_ref)
+        .def_property_readonly("access_by_copy", &opt_refsensitive_props::access_by_copy);
+
 #ifdef PYBIND11_HAS_FILESYSTEM
     // test_fs_path
     m.attr("has_filesystem") = true;
@@ -280,8 +459,12 @@ TEST_SUBMODULE(stl, m) {
     m.def("tpl_ctor_set", [](std::unordered_set<TplCtorClass> &) {});
 #if defined(PYBIND11_HAS_OPTIONAL)
     m.def("tpl_constr_optional", [](std::optional<TplCtorClass> &) {});
-#elif defined(PYBIND11_HAS_EXP_OPTIONAL)
-    m.def("tpl_constr_optional", [](std::experimental::optional<TplCtorClass> &) {});
+#endif
+#if defined(PYBIND11_HAS_EXP_OPTIONAL)
+    m.def("tpl_constr_optional_exp", [](std::experimental::optional<TplCtorClass> &) {});
+#endif
+#if defined(PYBIND11_TEST_BOOST)
+    m.def("tpl_constr_optional_boost", [](boost::optional<TplCtorClass> &) {});
 #endif
 
     // test_vec_of_reference_wrapper
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 3f63d6c3a4..e217975944 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -132,6 +132,10 @@ def test_optional():
     assert mvalue.initialized
     assert holder.member_initialized()
 
+    props = m.OptionalProperties()
+    assert int(props.access_by_ref) == 42
+    assert int(props.access_by_copy) == 42
+
 
 @pytest.mark.skipif(
     not hasattr(m, "has_exp_optional"), reason="no <experimental/optional>"
@@ -160,6 +164,69 @@ def test_exp_optional():
     assert mvalue.initialized
     assert holder.member_initialized()
 
+    props = m.OptionalExpProperties()
+    assert int(props.access_by_ref) == 42
+    assert int(props.access_by_copy) == 42
+
+
+@pytest.mark.skipif(not hasattr(m, "has_boost_optional"), reason="no <boost/optional>")
+def test_boost_optional():
+    assert m.double_or_zero_boost(None) == 0
+    assert m.double_or_zero_boost(42) == 84
+    pytest.raises(TypeError, m.double_or_zero_boost, "foo")
+
+    assert m.half_or_none_boost(0) is None
+    assert m.half_or_none_boost(42) == 21
+    pytest.raises(TypeError, m.half_or_none_boost, "foo")
+
+    assert m.test_nullopt_boost() == 42
+    assert m.test_nullopt_boost(None) == 42
+    assert m.test_nullopt_boost(42) == 42
+    assert m.test_nullopt_boost(43) == 43
+
+    assert m.test_no_assign_boost() == 42
+    assert m.test_no_assign_boost(None) == 42
+    assert m.test_no_assign_boost(m.NoAssign(43)) == 43
+    pytest.raises(TypeError, m.test_no_assign_boost, 43)
+
+    holder = m.OptionalBoostHolder()
+    mvalue = holder.member
+    assert mvalue.initialized
+    assert holder.member_initialized()
+
+    props = m.OptionalBoostProperties()
+    assert int(props.access_by_ref) == 42
+    assert int(props.access_by_copy) == 42
+
+
+def test_reference_sensitive_optional():
+    assert m.double_or_zero_refsensitive(None) == 0
+    assert m.double_or_zero_refsensitive(42) == 84
+    pytest.raises(TypeError, m.double_or_zero_refsensitive, "foo")
+
+    assert m.half_or_none_refsensitive(0) is None
+    assert m.half_or_none_refsensitive(42) == 21
+    pytest.raises(TypeError, m.half_or_none_refsensitive, "foo")
+
+    assert m.test_nullopt_refsensitive() == 42
+    assert m.test_nullopt_refsensitive(None) == 42
+    assert m.test_nullopt_refsensitive(42) == 42
+    assert m.test_nullopt_refsensitive(43) == 43
+
+    assert m.test_no_assign_refsensitive() == 42
+    assert m.test_no_assign_refsensitive(None) == 42
+    assert m.test_no_assign_refsensitive(m.NoAssign(43)) == 43
+    pytest.raises(TypeError, m.test_no_assign_refsensitive, 43)
+
+    holder = m.OptionalRefSensitiveHolder()
+    mvalue = holder.member
+    assert mvalue.initialized
+    assert holder.member_initialized()
+
+    props = m.OptionalRefSensitiveProperties()
+    assert int(props.access_by_ref) == 42
+    assert int(props.access_by_copy) == 42
+
 
 @pytest.mark.skipif(not hasattr(m, "has_filesystem"), reason="no <filesystem>")
 def test_fs_path():

From e7e2c79f3f520f78ffc39fcb34f7919003102733 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 26 Oct 2021 14:50:34 -0400
Subject: [PATCH 222/638] fix: improve support for Python 3.11-dev (#3368)

* ci: support Python 3.11-dev

Also update 3.10 to final, better PyPy usage

* fix: use PyFrame_GetCode on Python 3.9+

* ci: some bitiness of pypy not supported on win

* chore: update CMake support to 3.22rc1 to quiet warning

* fix: use dev version of py to fix Py 3.11

* tests: print proper Eigen version

* ci: include pypy2, not sure why

* ci: avoid running on Python 3.11 for now

* ci: fix runs

* ci: simpler PyPy usage, drop unmaintained scipy + pypy index

* ci: only binary numpy, wait on pypy 3.8

* refactor: address review
---
 .github/workflows/ci.yml                   | 66 +++++++++++-----------
 .github/workflows/pip.yml                  |  9 ++-
 CMakeLists.txt                             |  6 +-
 include/pybind11/detail/type_caster_base.h | 11 +++-
 include/pybind11/pybind11.h                | 25 ++++++++
 noxfile.py                                 |  5 +-
 tests/CMakeLists.txt                       | 22 ++++++--
 tests/requirements.txt                     | 16 +++---
 tools/pybind11Tools.cmake                  |  2 +-
 9 files changed, 105 insertions(+), 57 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b027640df1..3694f16363 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,6 +13,9 @@ concurrency:
   group: test-${{ github.ref }}
   cancel-in-progress: true
 
+env:
+  PIP_ONLY_BINARY: numpy
+
 jobs:
   # This is the "main" test suite, which tests a large number of different
   # versions of default compilers and Python versions in GitHub Actions.
@@ -22,13 +25,14 @@ jobs:
       matrix:
         runs-on: [ubuntu-latest, windows-latest, macos-latest]
         python:
-        - 2.7
-        - 3.5
-        - 3.6
-        - 3.9
-        - 3.10-dev
-        - pypy2
-        - pypy3
+        - '2.7'
+        - '3.5'
+        - '3.6'
+        - '3.9'
+        - '3.10'
+        # - '3.11-dev'
+        - 'pypy-3.7-v7.3.5'
+        # - 'pypy-3.8'
 
         # Items in here will either be added to the build matrix (if not
         # present), or add new keys to an existing matrix element if all the
@@ -46,18 +50,8 @@ jobs:
             python: 3.6
             args: >
               -DPYBIND11_FINDPYTHON=ON
-
-        # These items will be removed from the build matrix, keys must match.
-        exclude:
-            # Currently 32bit only, and we build 64bit
-          - runs-on: windows-latest
-            python: pypy2
-          - runs-on: windows-latest
-            python: pypy3
-
-          # TODO: PyPy2 7.3.3 segfaults, while 7.3.2 was fine.
-          - runs-on: ubuntu-latest
-            python: pypy2
+          - runs-on: macos-latest
+            python: pypy-2.7
 
     name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • x64 ${{ matrix.args }}"
     runs-on: ${{ matrix.runs-on }}
@@ -93,7 +87,8 @@ jobs:
         key: ${{ runner.os }}-pip-${{ matrix.python }}-x64-${{ hashFiles('tests/requirements.txt') }}
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt
 
     - name: Setup annotations on Linux
       if: runner.os == 'Linux'
@@ -117,7 +112,7 @@ jobs:
 
     - name: C++11 tests
       # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
+      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11-dev' || matrix.python == 'pypy-3.8'))"
       run: cmake --build .  --target cpptest -j 2
 
     - name: Interface test C++11
@@ -145,7 +140,7 @@ jobs:
 
     - name: C++ tests
       # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
+      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11-dev' || matrix.python == 'pypy-3.8'))"
       run: cmake --build build2 --target cpptest
 
     # Third build - C++17 mode with unstable ABI
@@ -196,11 +191,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
-        - python-version: 3.9
+        # TODO: Fails on 3.10, investigate
+        - python-version: "3.9"
           python-debug: true
           valgrind: true
-        - python-version: 3.10-dev
-          python-debug: false
+      # - python-version: "3.11-dev"
+      #   python-debug: false
 
     name: "🐍 ${{ matrix.python-version }}${{ matrix.python-debug && '-dbg' || '' }} (deadsnakes)${{ matrix.valgrind && ' • Valgrind' || '' }} • x64"
     runs-on: ubuntu-latest
@@ -244,7 +240,8 @@ jobs:
         sudo apt-get install libc6-dbg  # Needed by Valgrind
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt
 
     - name: Configure
       run: >
@@ -521,7 +518,7 @@ jobs:
     - name: Install dependencies
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        python3 -m pip install -r tests/requirements.txt --prefer-binary
+        python3 -m pip install -r tests/requirements.txt
 
     - name: Configure C++11
       run: |
@@ -612,7 +609,8 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Install dependencies
-      run: python3 -m pip install cmake -r tests/requirements.txt --prefer-binary
+      run: |
+        python3 -m pip install cmake -r tests/requirements.txt
 
     - name: VAR_BUILD_TYPE 7
       if: matrix.centos == 7
@@ -739,8 +737,7 @@ jobs:
         - 3.7
         - 3.8
         - 3.9
-        - pypy3
-        # TODO: fix hang on pypy2
+        - pypy-3.6
 
         include:
           - python: 3.9
@@ -769,7 +766,8 @@ jobs:
         arch: x86
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt
 
     # First build - C++11 mode and inplace
     - name: Configure ${{ matrix.args }}
@@ -815,7 +813,8 @@ jobs:
         toolset: 14.0
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt
 
     # First build - C++11 mode and inplace
     - name: Configure
@@ -868,7 +867,8 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt
 
     # First build - C++11 mode and inplace
     - name: Configure
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 5547a5e285..203f350bb1 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -12,6 +12,9 @@ on:
     types:
     - published
 
+env:
+  PIP_ONLY_BINARY: numpy
+
 jobs:
   # This builds the sdists and wheels and makes sure the files are exactly as
   # expected. Using Windows and Python 2.7, since that is often the most
@@ -29,7 +32,8 @@ jobs:
         python-version: 2.7
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt
 
     - name: Python Packaging tests
       run: pytest tests/extra_python_package/
@@ -50,7 +54,8 @@ jobs:
         python-version: 3.8
 
     - name: Prepare env
-      run: python -m pip install -r tests/requirements.txt build twine --prefer-binary
+      run: |
+        python -m pip install -r tests/requirements.txt build twine
 
     - name: Python Packaging tests
       run: pytest tests/extra_python_package/
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 25cfcec2f6..2e81869c3f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,13 +7,13 @@
 
 cmake_minimum_required(VERSION 3.4)
 
-# The `cmake_minimum_required(VERSION 3.4...3.21)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.4...3.22)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.21)
+if(${CMAKE_VERSION} VERSION_LESS 3.22)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.21)
+  cmake_policy(VERSION 3.22)
 endif()
 
 # Extract project version from source
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index f804d9d10c..00ce1a7a1e 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -468,12 +468,19 @@ PYBIND11_NOINLINE std::string error_string() {
         PyFrameObject *frame = trace->tb_frame;
         errorString += "\n\nAt:\n";
         while (frame) {
+#if PY_VERSION_HEX >= 0x03090000
+            PyCodeObject *f_code = PyFrame_GetCode(frame);
+#else
+            PyCodeObject *f_code = frame->f_code;
+            Py_INCREF(f_code);
+#endif
             int lineno = PyFrame_GetLineNumber(frame);
             errorString +=
-                "  " + handle(frame->f_code->co_filename).cast<std::string>() +
+                "  " + handle(f_code->co_filename).cast<std::string>() +
                 "(" + std::to_string(lineno) + "): " +
-                handle(frame->f_code->co_name).cast<std::string>() + "\n";
+                handle(f_code->co_name).cast<std::string>() + "\n";
             frame = frame->f_back;
+            Py_DECREF(f_code);
         }
     }
 #endif
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 095efd9c31..bfc1c368c0 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2335,6 +2335,29 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
     /* Don't call dispatch code if invoked from overridden function.
        Unfortunately this doesn't work on PyPy. */
 #if !defined(PYPY_VERSION)
+
+#if PY_VERSION_HEX >= 0x03090000
+    PyFrameObject *frame = PyThreadState_GetFrame(PyThreadState_Get());
+    if (frame != nullptr) {
+        PyCodeObject *f_code = PyFrame_GetCode(frame);
+        // f_code is guaranteed to not be NULL
+        if ((std::string) str(f_code->co_name) == name && f_code->co_argcount > 0) {
+            PyObject* locals = PyEval_GetLocals();
+            if (locals != nullptr) {
+                PyObject *self_caller = dict_getitem(
+                    locals, PyTuple_GET_ITEM(f_code->co_varnames, 0)
+                );
+                if (self_caller == self.ptr()) {
+                    Py_DECREF(f_code);
+                    Py_DECREF(frame);
+                    return function();
+                }
+            }
+        }
+        Py_DECREF(f_code);
+        Py_DECREF(frame);
+    }
+#else
     PyFrameObject *frame = PyThreadState_Get()->frame;
     if (frame != nullptr && (std::string) str(frame->f_code->co_name) == name
         && frame->f_code->co_argcount > 0) {
@@ -2344,6 +2367,8 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
         if (self_caller == self.ptr())
             return function();
     }
+#endif
+
 #else
     /* PyPy currently doesn't provide a detailed cpyext emulation of
        frame objects, so we have to emulate this using Python. This
diff --git a/noxfile.py b/noxfile.py
index 234179821d..757a53843a 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,7 +2,7 @@
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERISONS = ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9", "3.10"]
+PYTHON_VERISONS = ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
 
 
 @nox.session(reuse_venv=True)
@@ -20,7 +20,8 @@ def tests(session: nox.Session) -> None:
     Run the tests (requires a compiler).
     """
     tmpdir = session.create_tmp()
-    session.install("pytest", "cmake")
+    session.install("cmake")
+    session.install("-r", "tests/requirements.txt")
     session.run(
         "cmake",
         "-S",
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index e1b18dd74b..6dc67a11a3 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -174,10 +174,14 @@ set(PYBIND11_CROSS_MODULE_GIL_TESTS test_gil_scoped.py)
 set(PYBIND11_EIGEN_REPO
     "https://gitlab.com/libeigen/eigen.git"
     CACHE STRING "Eigen repository to use for tests")
-# This hash is for 3.4.0, using a hash for security reasons
-set(PYBIND11_EIGEN_VERSION
-    "929bc0e191d0927b1735b9a1ddc0e8b77e3a25ec"
-    CACHE STRING "Eigen version to use for tests")
+# Always use a hash for reconfigure speed and security reasons
+# Include the version number for pretty printing (keep in sync)
+set(PYBIND11_EIGEN_VERSION_AND_HASH
+    "3.4.0;929bc0e191d0927b1735b9a1ddc0e8b77e3a25ec"
+    CACHE STRING "Eigen version to use for tests, format: VERSION;HASH")
+
+list(GET PYBIND11_EIGEN_VERSION_AND_HASH 0 PYBIND11_EIGEN_VERSION_STRING)
+list(GET PYBIND11_EIGEN_VERSION_AND_HASH 1 PYBIND11_EIGEN_VERSION_HASH)
 
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
@@ -196,16 +200,22 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     FetchContent_Declare(
       eigen
       GIT_REPOSITORY "${PYBIND11_EIGEN_REPO}"
-      GIT_TAG "${PYBIND11_EIGEN_VERSION}")
+      GIT_TAG "${PYBIND11_EIGEN_VERSION_HASH}")
 
     FetchContent_GetProperties(eigen)
     if(NOT eigen_POPULATED)
-      message(STATUS "Downloading Eigen")
+      message(
+        STATUS
+          "Downloading Eigen ${PYBIND11_EIGEN_VERSION_STRING} (${PYBIND11_EIGEN_VERSION_HASH}) from ${PYBIND11_EIGEN_REPO}"
+      )
       FetchContent_Populate(eigen)
     endif()
 
     set(EIGEN3_INCLUDE_DIR ${eigen_SOURCE_DIR})
     set(EIGEN3_FOUND TRUE)
+    # When getting locally, the version is not visible from a superprojet,
+    # so just force it.
+    set(EIGEN3_VERSION "${PYBIND11_EIGEN_VERSION_STRING}")
 
   else()
     find_package(Eigen3 3.2.7 QUIET CONFIG)
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 069122b884..8d2742a71c 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,12 +1,12 @@
---extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010/
-numpy==1.16.6; python_version<"3.6" and sys_platform!="win32"
-numpy==1.18.0; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.6"
-numpy==1.19.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version=="3.6"
-numpy==1.21.2; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
-numpy==1.21.2; platform_python_implementation!="PyPy" and sys_platform=="linux" and python_version=="3.10"
+numpy==1.16.6; python_version<"3.6" and sys_platform!="win32" and platform_python_implementation!="PyPy"
+numpy==1.19.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.6"
+numpy==1.20.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
+numpy==1.19.3; platform_python_implementation!="PyPy" and python_version=="3.6"
+numpy==1.21.3; platform_python_implementation!="PyPy" and python_version>="3.7"
+py @ git+https://github.com/pytest-dev/py; python_version>="3.11"
 pytest==4.6.9; python_version<"3.5"
 pytest==6.1.2; python_version=="3.5"
 pytest==6.2.4; python_version>="3.6"
 pytest-timeout
-scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version<"3.6"
-scipy==1.5.4; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.10"
+scipy==1.2.3; platform_python_implementation!="PyPy" and python_version<"3.6"
+scipy==1.5.4; platform_python_implementation!="PyPy" and python_version>="3.6" and python_version<"3.10"
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index cc5ca21ca3..026069c73d 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -38,7 +38,7 @@ endif()
 
 # A user can set versions manually too
 set(Python_ADDITIONAL_VERSIONS
-    "3.10;3.9;3.8;3.7;3.6;3.5;3.4"
+    "3.11;3.10;3.9;3.8;3.7;3.6;3.5;3.4"
     CACHE INTERNAL "")
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")

From 90707b46f25a22d53fe2716ba3e575653a923cf1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 27 Oct 2021 15:06:02 -0400
Subject: [PATCH 223/638] fix(build): support conan's multiple includes of all
 files (#3420)

---
 tools/pybind11Common.cmake   |  1 +
 tools/pybind11NewTools.cmake | 10 ++++++----
 tools/pybind11Tools.cmake    |  5 +++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index 7afb0d0b1a..69ac4b0f61 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -20,6 +20,7 @@ Adds the following functions::
 #]======================================================]
 
 # CMake 3.10 has an include_guard command, but we can't use that yet
+# include_guard(global) (pre-CMake 3.10)
 if(TARGET pybind11::lto)
   return()
 endif()
diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 0a7b84706b..9e2fd2b40d 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -5,6 +5,12 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
+if(CMAKE_VERSION VERSION_LESS 3.12)
+  message(FATAL_ERROR "You cannot use the new FindPython module with CMake < 3.12")
+endif()
+
+include_guard(GLOBAL)
+
 get_property(
   is_config
   TARGET pybind11::headers
@@ -16,10 +22,6 @@ else()
   set(_pybind11_quiet "")
 endif()
 
-if(CMAKE_VERSION VERSION_LESS 3.12)
-  message(FATAL_ERROR "You cannot use the new FindPython module with CMake < 3.12")
-endif()
-
 if(NOT Python_FOUND
    AND NOT Python3_FOUND
    AND NOT Python2_FOUND)
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 026069c73d..c255e5cfd8 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -5,6 +5,11 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
+# include_guard(global) (pre-CMake 3.10)
+if(TARGET pybind11::python_headers)
+  return()
+endif()
+
 # Built-in in CMake 3.5+
 include(CMakeParseArguments)
 

From f1594cb9609ba4e3b931616815195655ac25e1d0 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 27 Oct 2021 15:08:59 -0400
Subject: [PATCH 224/638] docs: changelog update for 2.8.1 (#3416)

* docs: changelog update for 2.8.1

* chore: add one more entry

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 docs/changelog.rst | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index ee79a18719..f54512174b 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,11 +10,49 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 IN DEVELOPMENT
 --------------
 
+v2.8.0 (Oct 27, 2021)
+---------------------
+
+Changes and additions:
+
 * The simple namespace creation shortcut added in 2.8.0 was deprecated due to
   usage of CPython internal API, and will be removed soon. Use
   ``py::module_::import("types").attr("SimpleNamespace")``.
   `#3374 <https://github.com/pybinyyd/pybind11/pull/3374>`_
 
+* Add C++ Exception type to throw and catch ``AttributeError``. Useful for
+  defining custom ``__setattr__`` and ``__getattr__`` methods.
+  `#3387 <https://github.com/pybind/pybind11/pull/3387>`_
+
+Fixes:
+
+* Fixed the potential for dangling references when using properties with
+  ``std::optional`` types.
+  `#3376 <https://github.com/pybind/pybind11/pull/3376>`_
+
+* Modernize usage of ``PyCodeObject`` on Python 3.9+ (moving toward support for
+  Python 3.11a1)
+  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
+
+* A long-standing bug in ``eigen.h`` was fixed (originally PR #3343). The bug
+  was unmasked by newly added ``static_assert``'s in the Eigen 3.4.0 release.
+  `#3352 <https://github.com/pybind/pybind11/pull/3352>`_
+
+* Support multiple raw inclusion of CMake helper files (Conan.io does this for
+  multi-config generators).
+  `#3420 <https://github.com/pybind/pybind11/pull/3420>`_
+
+* Fix harmless warning on upcoming CMake 3.22.
+  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
+
+* Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3.
+  `#3407 <https://github.com/pybind/pybind11/pull/3407>`_
+
+* Fix 2.8.0 regression that caused undefined behavior (typically
+  segfaults) in ``make_key_iterator``/``make_value_iterator`` if dereferencing
+  the iterator returned a temporary value instead of a reference.
+  `#3348 <https://github.com/pybind/pybind11/pull/3348>`_
+
 
 v2.8.0 (Oct 4, 2021)
 --------------------

From f7b499615e14d70ab098a20deb0cdb3889998a1a Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 27 Oct 2021 14:35:10 -0700
Subject: [PATCH 225/638] [skip ci] Tweaks in preparation for the 2.8.1
 release. (#3421)

---
 docs/changelog.rst               |  2 +-
 docs/release.rst                 | 22 ++++++++++++----------
 include/pybind11/detail/common.h |  6 +++---
 pybind11/_version.py             |  2 +-
 4 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index f54512174b..bb5457eec1 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,7 +10,7 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 IN DEVELOPMENT
 --------------
 
-v2.8.0 (Oct 27, 2021)
+v2.8.1 (Oct 27, 2021)
 ---------------------
 
 Changes and additions:
diff --git a/docs/release.rst b/docs/release.rst
index 7fa254eaf9..b5de60f4e5 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -27,7 +27,7 @@ To release a new version of pybind11:
       ``include/pybind11/detail/common.h``. PATCH should be a simple integer.
     - Update the version HEX just below, as well.
     - Update ``pybind11/_version.py`` (match above)
-    - Run ``nox -s tests_packaging``` to ensure this was done correctly.
+    - Run ``nox -s tests_packaging`` to ensure this was done correctly.
     - Ensure that all the information in ``setup.cfg`` is up-to-date, like
       supported Python versions.
     - Add release date in ``docs/changelog.rst``.
@@ -50,13 +50,15 @@ To release a new version of pybind11:
 - Make a GitHub release (this shows up in the UI, sends new release
   notifications to users watching releases, and also uploads PyPI packages).
   (Note: if you do not use an existing tag, this creates a new lightweight tag
-  for you, so you could skip the above step).
-    - GUI method: click "Create a new release" on the far right, fill in the tag
-      name (if you didn't tag above, it will be made here), fill in a release
-      name like "Version X.Y.Z", and optionally copy-and-paste the changelog into
-      the description (processed as markdown by Pandoc). Check "pre-release" if
-      this is a beta/RC. You can get partway there with
-      ``cat docs/changelog.rst | pandoc -f rst -t gfm``.
+  for you, so you could skip the above step.)
+
+    - GUI method: Under `releases <https://github.com/pybind/pybind11/releases>`_
+      click "Draft a new release" on the far right, fill in the tag name
+      (if you didn't tag above, it will be made here), fill in a release name
+      like "Version X.Y.Z", and copy-and-paste the markdown-formatted (!) changelog
+      into the description (usually ``cat docs/changelog.rst | pandoc -f rst -t gfm``).
+      Check "pre-release" if this is a beta/RC.
+
     - CLI method: with ``gh`` installed, run ``gh release create vX.Y.Z -t "Version X.Y.Z"``
       If this is a pre-release, add ``-p``.
 
@@ -65,7 +67,7 @@ To release a new version of pybind11:
     - Update version macros in ``include/pybind11/detail/common.h`` (set PATCH to
       ``0.dev1`` and increment MINOR).
     - Update ``_version.py`` to match
-    - Run ``nox -s tests_packaging``` to ensure this was done correctly.
+    - Run ``nox -s tests_packaging`` to ensure this was done correctly.
     - Add a spot for in-development updates in ``docs/changelog.rst``.
     - ``git add``, ``git commit``, ``git push``
 
@@ -73,7 +75,7 @@ If a version branch is updated, remember to set PATCH to ``1.dev1``.
 
 If you'd like to bump homebrew, run:
 
-.. code-block::
+.. code-block:: console
 
     brew bump-formula-pr --url https://github.com/pybind/pybind11/archive/vX.Y.Z.tar.gz
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 862451fd13..713de94b03 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 9
-#define PYBIND11_VERSION_PATCH 0.dev1
+#define PYBIND11_VERSION_MINOR 8
+#define PYBIND11_VERSION_PATCH 1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020900D1
+#define PYBIND11_VERSION_HEX 0x02080100
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index ce894a7740..7cc1002869 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.9.0.dev1"
+__version__ = "2.8.1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From a80b22374ae9398962fe9746f84edc7e7982f9f7 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 27 Oct 2021 15:15:11 -0700
Subject: [PATCH 226/638] chore: get back to work after 2.8.1

[skip ci]
---
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 713de94b03..862451fd13 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 8
-#define PYBIND11_VERSION_PATCH 1
+#define PYBIND11_VERSION_MINOR 9
+#define PYBIND11_VERSION_PATCH 0.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x02080100
+#define PYBIND11_VERSION_HEX 0x020900D1
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 7cc1002869..ce894a7740 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.8.1"
+__version__ = "2.9.0.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From e7c9753f1d35061d137ac3ce561e94a7407e5583 Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Fri, 29 Oct 2021 00:16:55 -0300
Subject: [PATCH 227/638] feat: allow kw-only args after a py::args (#3402)

* Simply has_kw_only_args handling

This simplifies tracking the number of kw-only args by instead tracking
the number of positional arguments (which is really what we care about
everywhere this is used).

* Allow keyword-only arguments to follow py::args

This removes the constraint that py::args has to be last (or
second-last, with py::kwargs) and instead makes py::args imply
py::kw_only for any remaining arguments, allowing you to bind a function
that works the same way as a Python function such as:

    def f(a, *args, b):
        return a * b + sum(args)

    f(10, 1, 2, 3, b=20)  # == 206

With this change, you can bind such a function using:

    m.def("f", [](int a, py::args args, int b) { /* ... */ },
        "a"_a, "b"_a);

Or, to be more explicit about the keyword-only arguments:

    m.def("g", [](int a, py::args args, int b) { /* ... */ },
        "a"_a, py::kw_only{}, "b"_a);

(The only difference between the two is that the latter will fail at
binding time if the `kw_only{}` doesn't match the `py::args` position).

This doesn't affect backwards compatibility at all because, currently,
you can't have a py::args anywhere except the end/2nd-last.

* Take args/kwargs by const lvalue ref

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 docs/advanced/functions.rst        | 16 +++++-
 include/pybind11/attr.h            | 28 +++++-----
 include/pybind11/cast.h            | 20 ++++---
 include/pybind11/pybind11.h        | 57 +++++++++++++------
 tests/test_kwargs_and_defaults.cpp | 17 ++++++
 tests/test_kwargs_and_defaults.py  | 90 +++++++++++++++++++++++++++++-
 6 files changed, 186 insertions(+), 42 deletions(-)

diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index abd1084ab5..ea9f352234 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -306,8 +306,9 @@ The class ``py::args`` derives from ``py::tuple`` and ``py::kwargs`` derives
 from ``py::dict``.
 
 You may also use just one or the other, and may combine these with other
-arguments as long as the ``py::args`` and ``py::kwargs`` arguments are the last
-arguments accepted by the function.
+arguments.  Note, however, that ``py::kwargs`` must always be the last argument
+of the function, and ``py::args`` implies that any further arguments are
+keyword-only (see :ref:`keyword_only_arguments`).
 
 Please refer to the other examples for details on how to iterate over these,
 and on how to cast their entries into C++ objects. A demonstration is also
@@ -366,6 +367,8 @@ like so:
     py::class_<MyClass>("MyClass")
         .def("myFunction", py::arg("arg") = static_cast<SomeType *>(nullptr));
 
+.. _keyword_only_arguments:
+
 Keyword-only arguments
 ======================
 
@@ -397,6 +400,15 @@ feature does *not* require Python 3 to work.
 
 .. versionadded:: 2.6
 
+As of pybind11 2.9, a ``py::args`` argument implies that any following arguments
+are keyword-only, as if ``py::kw_only()`` had been specified in the same
+relative location of the argument list as the ``py::args`` argument.  The
+``py::kw_only()`` may be included to be explicit about this, but is not
+required.  (Prior to 2.9 ``py::args`` may only occur at the end of the argument
+list, or immediately before a ``py::kwargs`` argument at the end).
+
+.. versionadded:: 2.9
+
 Positional-only arguments
 =========================
 
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 0dedbc08dd..b95c849046 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -174,7 +174,7 @@ struct function_record {
     function_record()
         : is_constructor(false), is_new_style_constructor(false), is_stateless(false),
           is_operator(false), is_method(false), has_args(false),
-          has_kwargs(false), has_kw_only_args(false), prepend(false) { }
+          has_kwargs(false), prepend(false) { }
 
     /// Function name
     char *name = nullptr; /* why no C++ strings? They generate heavier code.. */
@@ -221,17 +221,15 @@ struct function_record {
     /// True if the function has a '**kwargs' argument
     bool has_kwargs : 1;
 
-    /// True once a 'py::kw_only' is encountered (any following args are keyword-only)
-    bool has_kw_only_args : 1;
-
     /// True if this function is to be inserted at the beginning of the overload resolution chain
     bool prepend : 1;
 
     /// Number of arguments (including py::args and/or py::kwargs, if present)
     std::uint16_t nargs;
 
-    /// Number of trailing arguments (counted in `nargs`) that are keyword-only
-    std::uint16_t nargs_kw_only = 0;
+    /// Number of leading positional arguments, which are terminated by a py::args or py::kwargs
+    /// argument or by a py::kw_only annotation.
+    std::uint16_t nargs_pos = 0;
 
     /// Number of leading arguments (counted in `nargs`) that are positional-only
     std::uint16_t nargs_pos_only = 0;
@@ -411,10 +409,9 @@ template <> struct process_attribute<is_new_style_constructor> : process_attribu
     static void init(const is_new_style_constructor &, function_record *r) { r->is_new_style_constructor = true; }
 };
 
-inline void process_kw_only_arg(const arg &a, function_record *r) {
-    if (!a.name || a.name[0] == '\0')
-        pybind11_fail("arg(): cannot specify an unnamed argument after an kw_only() annotation");
-    ++r->nargs_kw_only;
+inline void check_kw_only_arg(const arg &a, function_record *r) {
+    if (r->args.size() > r->nargs_pos && (!a.name || a.name[0] == '\0'))
+        pybind11_fail("arg(): cannot specify an unnamed argument after a kw_only() annotation or args() argument");
 }
 
 /// Process a keyword argument attribute (*without* a default value)
@@ -424,7 +421,7 @@ template <> struct process_attribute<arg> : process_attribute_default<arg> {
             r->args.emplace_back("self", nullptr, handle(), true /*convert*/, false /*none not allowed*/);
         r->args.emplace_back(a.name, nullptr, handle(), !a.flag_noconvert, a.flag_none);
 
-        if (r->has_kw_only_args) process_kw_only_arg(a, r);
+        check_kw_only_arg(a, r);
     }
 };
 
@@ -457,14 +454,16 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
         }
         r->args.emplace_back(a.name, a.descr, a.value.inc_ref(), !a.flag_noconvert, a.flag_none);
 
-        if (r->has_kw_only_args) process_kw_only_arg(a, r);
+        check_kw_only_arg(a, r);
     }
 };
 
 /// Process a keyword-only-arguments-follow pseudo argument
 template <> struct process_attribute<kw_only> : process_attribute_default<kw_only> {
     static void init(const kw_only &, function_record *r) {
-        r->has_kw_only_args = true;
+        if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size()))
+            pybind11_fail("Mismatched args() and kw_only(): they must occur at the same relative argument location (or omit kw_only() entirely)");
+        r->nargs_pos = static_cast<std::uint16_t>(r->args.size());
     }
 };
 
@@ -472,6 +471,9 @@ template <> struct process_attribute<kw_only> : process_attribute_default<kw_onl
 template <> struct process_attribute<pos_only> : process_attribute_default<pos_only> {
     static void init(const pos_only &, function_record *r) {
         r->nargs_pos_only = static_cast<std::uint16_t>(r->args.size());
+        if (r->nargs_pos_only > r->nargs_pos)
+            pybind11_fail("pos_only(): cannot follow a py::args() argument");
+            // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
     }
 };
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 20fbb32587..4b39827c25 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1130,6 +1130,9 @@ constexpr arg operator"" _a(const char *name, size_t) { return arg(name); }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
+template <typename T> using is_kw_only = std::is_same<intrinsic_t<T>, kw_only>;
+template <typename T> using is_pos_only = std::is_same<intrinsic_t<T>, pos_only>;
+
 // forward declaration (definition in attr.h)
 struct function_record;
 
@@ -1165,17 +1168,18 @@ class argument_loader {
 
     template <typename Arg> using argument_is_args   = std::is_same<intrinsic_t<Arg>, args>;
     template <typename Arg> using argument_is_kwargs = std::is_same<intrinsic_t<Arg>, kwargs>;
-    // Get args/kwargs argument positions relative to the end of the argument list:
-    static constexpr auto args_pos = constexpr_first<argument_is_args, Args...>() - (int) sizeof...(Args),
-                        kwargs_pos = constexpr_first<argument_is_kwargs, Args...>() - (int) sizeof...(Args);
-
-    static constexpr bool args_kwargs_are_last = kwargs_pos >= - 1 && args_pos >= kwargs_pos - 1;
+    // Get kwargs argument position, or -1 if not present:
+    static constexpr auto kwargs_pos = constexpr_last<argument_is_kwargs, Args...>();
 
-    static_assert(args_kwargs_are_last, "py::args/py::kwargs are only permitted as the last argument(s) of a function");
+    static_assert(kwargs_pos == -1 || kwargs_pos == (int) sizeof...(Args) - 1, "py::kwargs is only permitted as the last argument of a function");
 
 public:
-    static constexpr bool has_kwargs = kwargs_pos < 0;
-    static constexpr bool has_args = args_pos < 0;
+    static constexpr bool has_kwargs = kwargs_pos != -1;
+
+    // py::args argument position; -1 if not present.
+    static constexpr int args_pos = constexpr_last<argument_is_args, Args...>();
+
+    static_assert(args_pos == -1 || args_pos == constexpr_first<argument_is_args, Args...>(), "py::args cannot be specified more than once");
 
     static constexpr auto arg_names = concat(type_descr(make_caster<Args>::name)...);
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index bfc1c368c0..124ea37e59 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -203,7 +203,7 @@ class cpp_function : public function {
             conditional_t<std::is_void<Return>::value, void_type, Return>
         >;
 
-        static_assert(expected_num_args<Extra...>(sizeof...(Args), cast_in::has_args, cast_in::has_kwargs),
+        static_assert(expected_num_args<Extra...>(sizeof...(Args), cast_in::args_pos >= 0, cast_in::has_kwargs),
                       "The number of argument annotations does not match the number of function arguments");
 
         /* Dispatch code which converts function arguments and performs the actual function call */
@@ -238,17 +238,27 @@ class cpp_function : public function {
             return result;
         };
 
+        rec->nargs_pos = cast_in::args_pos >= 0
+            ? static_cast<std::uint16_t>(cast_in::args_pos)
+            : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if we have a kw_only
+        rec->has_args = cast_in::args_pos >= 0;
+        rec->has_kwargs = cast_in::has_kwargs;
+
         /* Process any user-provided function attributes */
         process_attributes<Extra...>::init(extra..., rec);
 
         {
             constexpr bool has_kw_only_args = any_of<std::is_same<kw_only, Extra>...>::value,
                            has_pos_only_args = any_of<std::is_same<pos_only, Extra>...>::value,
-                           has_args = any_of<std::is_same<args, Args>...>::value,
                            has_arg_annotations = any_of<is_keyword<Extra>...>::value;
             static_assert(has_arg_annotations || !has_kw_only_args, "py::kw_only requires the use of argument annotations");
             static_assert(has_arg_annotations || !has_pos_only_args, "py::pos_only requires the use of argument annotations (for docstrings and aligning the annotations to the argument)");
-            static_assert(!(has_args && has_kw_only_args), "py::kw_only cannot be combined with a py::args argument");
+
+            static_assert(constexpr_sum(is_kw_only<Extra>::value...) <= 1, "py::kw_only may be specified only once");
+            static_assert(constexpr_sum(is_pos_only<Extra>::value...) <= 1, "py::pos_only may be specified only once");
+            constexpr auto kw_only_pos = constexpr_first<is_kw_only, Extra...>();
+            constexpr auto pos_only_pos = constexpr_first<is_pos_only, Extra...>();
+            static_assert(!(has_kw_only_args && has_pos_only_args) || pos_only_pos < kw_only_pos, "py::pos_only must come before py::kw_only");
         }
 
         /* Generate a readable signature describing the function's arguments and return value types */
@@ -259,9 +269,6 @@ class cpp_function : public function {
         // Pass on the ownership over the `unique_rec` to `initialize_generic`. `rec` stays valid.
         initialize_generic(std::move(unique_rec), signature.text, types.data(), sizeof...(Args));
 
-        if (cast_in::has_args) rec->has_args = true;
-        if (cast_in::has_kwargs) rec->has_kwargs = true;
-
         /* Stash some additional information used by an important optimization in 'functional.h' */
         using FunctionType = Return (*)(Args...);
         constexpr bool is_function_ptr =
@@ -340,16 +347,18 @@ class cpp_function : public function {
         /* Generate a proper function signature */
         std::string signature;
         size_t type_index = 0, arg_index = 0;
+        bool is_starred = false;
         for (auto *pc = text; *pc != '\0'; ++pc) {
             const auto c = *pc;
 
             if (c == '{') {
                 // Write arg name for everything except *args and **kwargs.
-                if (*(pc + 1) == '*')
+                is_starred = *(pc + 1) == '*';
+                if (is_starred)
                     continue;
                 // Separator for keyword-only arguments, placed before the kw
-                // arguments start
-                if (rec->nargs_kw_only > 0 && arg_index + rec->nargs_kw_only == args)
+                // arguments start (unless we are already putting an *args)
+                if (!rec->has_args && arg_index == rec->nargs_pos)
                     signature += "*, ";
                 if (arg_index < rec->args.size() && rec->args[arg_index].name) {
                     signature += rec->args[arg_index].name;
@@ -361,7 +370,7 @@ class cpp_function : public function {
                 signature += ": ";
             } else if (c == '}') {
                 // Write default value if available.
-                if (arg_index < rec->args.size() && rec->args[arg_index].descr) {
+                if (!is_starred && arg_index < rec->args.size() && rec->args[arg_index].descr) {
                     signature += " = ";
                     signature += rec->args[arg_index].descr;
                 }
@@ -369,7 +378,8 @@ class cpp_function : public function {
                 // argument, rather than before like *
                 if (rec->nargs_pos_only > 0 && (arg_index + 1) == rec->nargs_pos_only)
                     signature += ", /";
-                arg_index++;
+                if (!is_starred)
+                    arg_index++;
             } else if (c == '%') {
                 const std::type_info *t = types[type_index++];
                 if (!t)
@@ -395,7 +405,7 @@ class cpp_function : public function {
             }
         }
 
-        if (arg_index != args || types[type_index] != nullptr)
+        if (arg_index != args - rec->has_args - rec->has_kwargs || types[type_index] != nullptr)
             pybind11_fail("Internal error while parsing type signature (2)");
 
 #if PY_MAJOR_VERSION < 3
@@ -631,7 +641,7 @@ class cpp_function : public function {
                       named positional arguments weren't *also* specified via kwarg.
                    2. If we weren't given enough, try to make up the omitted ones by checking
                       whether they were provided by a kwarg matching the `py::arg("name")` name.  If
-                      so, use it (and remove it from kwargs; if not, see if the function binding
+                      so, use it (and remove it from kwargs); if not, see if the function binding
                       provided a default that we can use.
                    3. Ensure that either all keyword arguments were "consumed", or that the function
                       takes a kwargs argument to accept unconsumed kwargs.
@@ -649,7 +659,7 @@ class cpp_function : public function {
                 size_t num_args = func.nargs;    // Number of positional arguments that we need
                 if (func.has_args) --num_args;   // (but don't count py::args
                 if (func.has_kwargs) --num_args; //  or py::kwargs)
-                size_t pos_args = num_args - func.nargs_kw_only;
+                size_t pos_args = func.nargs_pos;
 
                 if (!func.has_args && n_args_in > pos_args)
                     continue; // Too many positional arguments for this overload
@@ -695,6 +705,10 @@ class cpp_function : public function {
                 if (bad_arg)
                     continue; // Maybe it was meant for another overload (issue #688)
 
+                // Keep track of how many position args we copied out in case we need to come back
+                // to copy the rest into a py::args argument.
+                size_t positional_args_copied = args_copied;
+
                 // We'll need to copy this if we steal some kwargs for defaults
                 dict kwargs = reinterpret_borrow<dict>(kwargs_in);
 
@@ -747,6 +761,10 @@ class cpp_function : public function {
                         }
 
                         if (value) {
+                            // If we're at the py::args index then first insert a stub for it to be replaced later
+                            if (func.has_args && call.args.size() == func.nargs_pos)
+                                call.args.push_back(none());
+
                             call.args.push_back(value);
                             call.args_convert.push_back(arg_rec.convert);
                         }
@@ -769,16 +787,19 @@ class cpp_function : public function {
                         // We didn't copy out any position arguments from the args_in tuple, so we
                         // can reuse it directly without copying:
                         extra_args = reinterpret_borrow<tuple>(args_in);
-                    } else if (args_copied >= n_args_in) {
+                    } else if (positional_args_copied >= n_args_in) {
                         extra_args = tuple(0);
                     } else {
-                        size_t args_size = n_args_in - args_copied;
+                        size_t args_size = n_args_in - positional_args_copied;
                         extra_args = tuple(args_size);
                         for (size_t i = 0; i < args_size; ++i) {
-                            extra_args[i] = PyTuple_GET_ITEM(args_in, args_copied + i);
+                            extra_args[i] = PyTuple_GET_ITEM(args_in, positional_args_copied + i);
                         }
                     }
-                    call.args.push_back(extra_args);
+                    if (call.args.size() <= func.nargs_pos)
+                        call.args.push_back(extra_args);
+                    else
+                        call.args[func.nargs_pos] = extra_args;
                     call.args_convert.push_back(false);
                     call.args_ref = std::move(extra_args);
                 }
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 63332d32ea..312596dabb 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -56,6 +56,23 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     m.def("mixed_plus_args_kwargs_defaults", mixed_plus_both,
             py::arg("i") = 1, py::arg("j") = 3.14159);
 
+    m.def("args_kwonly",
+            [](int i, double j, const py::args &args, int z) { return py::make_tuple(i, j, args, z); },
+            "i"_a, "j"_a, "z"_a);
+    m.def("args_kwonly_kwargs",
+            [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+                return py::make_tuple(i, j, args, z, kwargs); },
+            "i"_a, "j"_a, py::kw_only{}, "z"_a);
+    m.def("args_kwonly_kwargs_defaults",
+            [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+                return py::make_tuple(i, j, args, z, kwargs); },
+            "i"_a = 1, "j"_a = 3.14159, "z"_a = 42);
+    m.def("args_kwonly_full_monty",
+            [](int h, int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+                return py::make_tuple(h, i, j, args, z, kwargs); },
+            py::arg() = 1, py::arg() = 2, py::pos_only{}, "j"_a = 3.14159, "z"_a = 42);
+
+
     // test_args_refcount
     // PyPy needs a garbage collection to get the reference count values to match CPython's behaviour
     #ifdef PYPY_VERSION
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index ddc387eeb9..68903bde16 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -141,6 +141,53 @@ def test_mixed_args_and_kwargs(msg):
     """  # noqa: E501 line too long
     )
 
+    # Arguments after a py::args are automatically keyword-only (pybind 2.9+)
+    assert m.args_kwonly(2, 2.5, z=22) == (2, 2.5, (), 22)
+    assert m.args_kwonly(2, 2.5, "a", "b", "c", z=22) == (2, 2.5, ("a", "b", "c"), 22)
+    assert m.args_kwonly(z=22, i=4, j=16) == (4, 16, (), 22)
+
+    with pytest.raises(TypeError) as excinfo:
+        assert m.args_kwonly(2, 2.5, 22)  # missing z= keyword
+    assert (
+        msg(excinfo.value)
+        == """
+        args_kwonly(): incompatible function arguments. The following argument types are supported:
+            1. (i: int, j: float, *args, z: int) -> tuple
+
+        Invoked with: 2, 2.5, 22
+    """
+    )
+
+    assert m.args_kwonly_kwargs(i=1, k=4, j=10, z=-1, y=9) == (
+        1,
+        10,
+        (),
+        -1,
+        {"k": 4, "y": 9},
+    )
+    assert m.args_kwonly_kwargs(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, z=11, y=12) == (
+        1,
+        2,
+        (3, 4, 5, 6, 7, 8, 9, 10),
+        11,
+        {"y": 12},
+    )
+    assert (
+        m.args_kwonly_kwargs.__doc__
+        == "args_kwonly_kwargs(i: int, j: float, *args, z: int, **kwargs) -> tuple\n"
+    )
+
+    assert (
+        m.args_kwonly_kwargs_defaults.__doc__
+        == "args_kwonly_kwargs_defaults(i: int = 1, j: float = 3.14159, *args, z: int = 42, **kwargs) -> tuple\n"  # noqa: E501 line too long
+    )
+    assert m.args_kwonly_kwargs_defaults() == (1, 3.14159, (), 42, {})
+    assert m.args_kwonly_kwargs_defaults(2) == (2, 3.14159, (), 42, {})
+    assert m.args_kwonly_kwargs_defaults(z=-99) == (1, 3.14159, (), -99, {})
+    assert m.args_kwonly_kwargs_defaults(5, 6, 7, 8) == (5, 6, (7, 8), 42, {})
+    assert m.args_kwonly_kwargs_defaults(5, 6, 7, m=8) == (5, 6, (7,), 42, {"m": 8})
+    assert m.args_kwonly_kwargs_defaults(5, 6, 7, m=8, z=9) == (5, 6, (7,), 9, {"m": 8})
+
 
 def test_keyword_only_args(msg):
     assert m.kw_only_all(i=1, j=2) == (1, 2)
@@ -178,7 +225,7 @@ def test_keyword_only_args(msg):
     assert (
         msg(excinfo.value)
         == """
-        arg(): cannot specify an unnamed argument after an kw_only() annotation
+        arg(): cannot specify an unnamed argument after a kw_only() annotation or args() argument
     """
     )
 
@@ -222,6 +269,47 @@ def test_positional_only_args(msg):
         m.pos_only_def_mix(1, j=4)
     assert "incompatible function arguments" in str(excinfo.value)
 
+    # Mix it with args and kwargs:
+    assert (
+        m.args_kwonly_full_monty.__doc__
+        == "args_kwonly_full_monty(arg0: int = 1, arg1: int = 2, /, j: float = 3.14159, *args, z: int = 42, **kwargs) -> tuple\n"  # noqa: E501 line too long
+    )
+    assert m.args_kwonly_full_monty() == (1, 2, 3.14159, (), 42, {})
+    assert m.args_kwonly_full_monty(8) == (8, 2, 3.14159, (), 42, {})
+    assert m.args_kwonly_full_monty(8, 9) == (8, 9, 3.14159, (), 42, {})
+    assert m.args_kwonly_full_monty(8, 9, 10) == (8, 9, 10.0, (), 42, {})
+    assert m.args_kwonly_full_monty(3, 4, 5, 6, 7, m=8, z=9) == (
+        3,
+        4,
+        5.0,
+        (
+            6,
+            7,
+        ),
+        9,
+        {"m": 8},
+    )
+    assert m.args_kwonly_full_monty(3, 4, 5, 6, 7, m=8, z=9) == (
+        3,
+        4,
+        5.0,
+        (
+            6,
+            7,
+        ),
+        9,
+        {"m": 8},
+    )
+    assert m.args_kwonly_full_monty(5, j=7, m=8, z=9) == (5, 2, 7.0, (), 9, {"m": 8})
+    assert m.args_kwonly_full_monty(i=5, j=7, m=8, z=9) == (
+        1,
+        2,
+        7.0,
+        (),
+        9,
+        {"i": 5, "m": 8},
+    )
+
 
 def test_signatures():
     assert "kw_only_all(*, i: int, j: int) -> tuple\n" == m.kw_only_all.__doc__

From dd2d12721c924486e6f5313cb815441a7d3dd256 Mon Sep 17 00:00:00 2001
From: "Chad B. Hovey" <1473854+hovey@users.noreply.github.com>
Date: Mon, 1 Nov 2021 10:01:27 -0600
Subject: [PATCH 228/638] Correct "which" versus "that" error. (#3430)

---
 docs/basics.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/basics.rst b/docs/basics.rst
index 0b1d85cfd3..e0479b298d 100644
--- a/docs/basics.rst
+++ b/docs/basics.rst
@@ -109,7 +109,7 @@ a file named :file:`example.cpp` with the following contents:
     PYBIND11_MODULE(example, m) {
         m.doc() = "pybind11 example plugin"; // optional module docstring
 
-        m.def("add", &add, "A function which adds two numbers");
+        m.def("add", &add, "A function that adds two numbers");
     }
 
 .. [#f1] In practice, implementation and binding code will generally be located

From 6de30d317277c26a72ed1929e09f225b74f23b7a Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 1 Nov 2021 17:22:12 -0400
Subject: [PATCH 229/638] [pre-commit.ci] pre-commit autoupdate (#3432)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/psf/black: 21.9b0 → 21.10b0](https://github.com/psf/black/compare/21.9b0...21.10b0)

* Update blacken-docs too

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b3e5179055..7061946460 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -44,7 +44,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.9b0 # Keep in sync with blacken-docs
+  rev: 21.10b0 # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -53,7 +53,7 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==21.9b0 # keep in sync with black hook
+    - black==21.10b0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks

From a61e354e4279d296df8ab712a66ef4564d4ec04c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 5 Nov 2021 22:48:27 -0400
Subject: [PATCH 230/638] docs: touch up manual release suggestion (#3422)

---
 docs/release.rst | 9 ++++-----
 noxfile.py       | 2 ++
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/docs/release.rst b/docs/release.rst
index b5de60f4e5..e761cdf7a6 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -22,6 +22,9 @@ the version just below.
 To release a new version of pybind11:
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+If you don't have nox, you should either use ``pipx run nox`` instead, or use
+``pipx install nox`` or ``brew install nox`` (Unix).
+
 - Update the version number
     - Update ``PYBIND11_VERSION_MAJOR`` etc. in
       ``include/pybind11/detail/common.h``. PATCH should be a simple integer.
@@ -51,14 +54,12 @@ To release a new version of pybind11:
   notifications to users watching releases, and also uploads PyPI packages).
   (Note: if you do not use an existing tag, this creates a new lightweight tag
   for you, so you could skip the above step.)
-
     - GUI method: Under `releases <https://github.com/pybind/pybind11/releases>`_
       click "Draft a new release" on the far right, fill in the tag name
       (if you didn't tag above, it will be made here), fill in a release name
       like "Version X.Y.Z", and copy-and-paste the markdown-formatted (!) changelog
       into the description (usually ``cat docs/changelog.rst | pandoc -f rst -t gfm``).
       Check "pre-release" if this is a beta/RC.
-
     - CLI method: with ``gh`` installed, run ``gh release create vX.Y.Z -t "Version X.Y.Z"``
       If this is a pre-release, add ``-p``.
 
@@ -90,9 +91,7 @@ If you need to manually upload releases, you can download the releases from the
 
 .. code-block:: bash
 
-    python3 -m pip install build
-    python3 -m build
-    PYBIND11_SDIST_GLOBAL=1 python3 -m build
+    nox -s build
     twine upload dist/*
 
 This makes SDists and wheels, and the final line uploads them.
diff --git a/noxfile.py b/noxfile.py
index 757a53843a..53d87dbcba 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -85,5 +85,7 @@ def build(session: nox.Session) -> None:
     """
 
     session.install("build")
+    session.log("Building normal files")
     session.run("python", "-m", "build")
+    session.log("Building pybind11-global files (PYBIND11_GLOBAL_SDIST=1)")
     session.run("python", "-m", "build", env={"PYBIND11_GLOBAL_SDIST": "1"})

From 01f938e79938fd5b9bb6df2daeff95a625f6211f Mon Sep 17 00:00:00 2001
From: Boris Rasin <Boris-Rasin@users.noreply.github.com>
Date: Mon, 8 Nov 2021 01:35:25 +0200
Subject: [PATCH 231/638] fix: add missing std::forward calls (#3443)

* fix: add missing std::forward calls

Two of the four cpp_function overloads are missing std::forward calls, which seems like a simple oversight.

* add test for https://github.com/pybind/pybind11/pull/3443

* add py tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix test

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pybind11.h           |  4 ++--
 tests/test_methods_and_attributes.cpp | 15 +++++++++++++++
 tests/test_methods_and_attributes.py  |  8 ++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 124ea37e59..b8b7c7a026 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -115,7 +115,7 @@ class cpp_function : public function {
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (Class::*f)(Arg...)&, const Extra&... extra) {
-        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(args...); },
+        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
                    (Return (*) (Class *, Arg...)) nullptr, extra...);
     }
 
@@ -133,7 +133,7 @@ class cpp_function : public function {
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(Return (Class::*f)(Arg...) const&, const Extra&... extra) {
-        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(args...); },
+        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
                    (Return (*)(const Class *, Arg ...)) nullptr, extra...);
     }
 
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 2d303a44e3..9e55452dec 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -159,6 +159,14 @@ struct RefQualified {
     int constRefQualified(int other) const & { return value + other; }
 };
 
+// Test rvalue ref param
+struct RValueRefParam {
+    std::size_t func1(std::string&& s) { return s.size(); }
+    std::size_t func2(std::string&& s) const { return s.size(); }
+    std::size_t func3(std::string&& s) & { return s.size(); }
+    std::size_t func4(std::string&& s) const & { return s.size(); }
+};
+
 TEST_SUBMODULE(methods_and_attributes, m) {
     // test_methods_and_attributes
     py::class_<ExampleMandA> emna(m, "ExampleMandA");
@@ -409,4 +417,11 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def_readonly("value", &RefQualified::value)
         .def("refQualified", &RefQualified::refQualified)
         .def("constRefQualified", &RefQualified::constRefQualified);
+
+    py::class_<RValueRefParam>(m, "RValueRefParam")
+        .def(py::init<>())
+        .def("func1", &RValueRefParam::func1)
+        .def("func2", &RValueRefParam::func2)
+        .def("func3", &RValueRefParam::func3)
+        .def("func4", &RValueRefParam::func4);
 }
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 866b3cea18..fa026f9edd 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -515,3 +515,11 @@ def test_overload_ordering():
     assert "2. (arg0: {}) -> int".format(uni_name) in str(err.value)
     assert "3. (arg0: {}) -> int".format(uni_name) in str(err.value)
     assert "4. (arg0: int) -> int" in str(err.value)
+
+
+def test_rvalue_ref_param():
+    r = m.RValueRefParam()
+    assert r.func1("123") == 3
+    assert r.func2("1234") == 4
+    assert r.func3("12345") == 5
+    assert r.func4("123456") == 6

From b322018e1571b42513de77d9ad9fde1d030c8cc6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 8 Nov 2021 15:56:20 -0500
Subject: [PATCH 232/638] [pre-commit.ci] pre-commit autoupdate (#3449)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/isort: 5.9.3 → 5.10.0](https://github.com/PyCQA/isort/compare/5.9.3...5.10.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7061946460..6f0bb39b12 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -38,7 +38,7 @@ repos:
   - id: pyupgrade
 
 - repo: https://github.com/PyCQA/isort
-  rev: 5.9.3
+  rev: 5.10.0
   hooks:
   - id: isort
 

From b11ff912a6b68edcd67770308ba4703e3a740e7b Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Mon, 8 Nov 2021 22:27:32 +0100
Subject: [PATCH 233/638] fix(setup =_helpers): don't add -g0 CFLAGS sets -g
 (#3436)

On Unix, setuptools prepends $CFLAGS and $CPPFLAGS to the compiler flags
(they always come before extra_compile_args and anything else; see
distutils.sysconfig.customize_compiler).  In practice, the environment
variables are useful e.g. to quickly generate a debug build (e.g. by
setting CFLAGS=-g), but Pybind11Extension currently unconditionally
overwrites this with -g0.

Instead, check the environment variables and only insert -g0 if not
overridden by them.
---
 pybind11/setup_helpers.py                  |  8 +++++++-
 tests/extra_setuptools/test_setuphelper.py | 14 +++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 4ff1a0cb37..d6d84f672a 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -42,6 +42,7 @@
 import contextlib
 import os
 import platform
+import shlex
 import shutil
 import sys
 import sysconfig
@@ -143,7 +144,12 @@ def __init__(self, *args, **kwargs):
         if WIN:
             cflags += ["/EHsc", "/bigobj"]
         else:
-            cflags += ["-fvisibility=hidden", "-g0"]
+            cflags += ["-fvisibility=hidden"]
+            env_cflags = os.environ.get("CFLAGS", "")
+            env_cppflags = os.environ.get("CPPFLAGS", "")
+            c_cpp_flags = shlex.split(env_cflags) + shlex.split(env_cppflags)
+            if not any(opt.startswith("-g") for opt in c_cpp_flags):
+                cflags += ["-g0"]
             if MACOS:
                 cflags += ["-stdlib=libc++"]
                 ldflags += ["-stdlib=libc++"]
diff --git a/tests/extra_setuptools/test_setuphelper.py b/tests/extra_setuptools/test_setuphelper.py
index c24f50af8a..788f368b14 100644
--- a/tests/extra_setuptools/test_setuphelper.py
+++ b/tests/extra_setuptools/test_setuphelper.py
@@ -8,6 +8,7 @@
 
 DIR = os.path.abspath(os.path.dirname(__file__))
 MAIN_DIR = os.path.dirname(os.path.dirname(DIR))
+WIN = sys.platform.startswith("win32") or sys.platform.startswith("cygwin")
 
 
 @pytest.mark.parametrize("parallel", [False, True])
@@ -71,13 +72,20 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
         encoding="ascii",
     )
 
-    subprocess.check_call(
+    out = subprocess.check_output(
         [sys.executable, "setup.py", "build_ext", "--inplace"],
-        stdout=sys.stdout,
-        stderr=sys.stderr,
     )
+    if not WIN:
+        assert b"-g0" in out
+    out = subprocess.check_output(
+        [sys.executable, "setup.py", "build_ext", "--inplace", "--force"],
+        env=dict(os.environ, CFLAGS="-g"),
+    )
+    if not WIN:
+        assert b"-g0" not in out
 
     # Debug helper printout, normally hidden
+    print(out)
     for item in tmpdir.listdir():
         print(item.basename)
 

From aebd21b53c6be5a817a50491327371393aa9d8de Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 10 Nov 2021 12:13:10 -0500
Subject: [PATCH 234/638] docs: rework CI a bit, more modern skipping (#3424)

* docs: rework CI a bit, more modern skipping

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml   |  9 +++------
 docs/Doxyfile              |  3 +--
 docs/requirements.txt      | 13 +++++--------
 include/pybind11/pytypes.h |  8 ++++----
 noxfile.py                 | 10 ++++++----
 5 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3694f16363..2888c420b9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -704,14 +704,11 @@ jobs:
     - name: Install Doxygen
       run: sudo apt-get install -y doxygen librsvg2-bin # Changed to rsvg-convert in 20.04
 
-    - name: Install docs & setup requirements
-      run: python3 -m pip install -r docs/requirements.txt
-
     - name: Build docs
-      run: python3 -m sphinx -W -b html docs docs/.build
+      run: pipx run nox -s docs
 
     - name: Make SDist
-      run: python3 setup.py sdist
+      run: pipx run nox -s build -- --sdist
 
     - run: git status --ignored
 
@@ -723,7 +720,7 @@ jobs:
     - name: Compare Dists (headers only)
       working-directory: include
       run: |
-        python3 -m pip install --user -U ../dist/*
+        python3 -m pip install --user -U ../dist/*.tar.gz
         installed=$(python3 -c "import pybind11; print(pybind11.get_include() + '/pybind11')")
         diff -rq $installed ./pybind11
 
diff --git a/docs/Doxyfile b/docs/Doxyfile
index c8562952ef..62c2675563 100644
--- a/docs/Doxyfile
+++ b/docs/Doxyfile
@@ -18,6 +18,5 @@ ALIASES               += "endrst=\endverbatim"
 QUIET                  = YES
 WARNINGS               = YES
 WARN_IF_UNDOCUMENTED   = NO
-PREDEFINED             = DOXYGEN_SHOULD_SKIP_THIS \
-                         PY_MAJOR_VERSION=3 \
+PREDEFINED             = PY_MAJOR_VERSION=3 \
                          PYBIND11_NOINLINE
diff --git a/docs/requirements.txt b/docs/requirements.txt
index 8f293b5d34..b2801b1f0d 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,8 +1,5 @@
-breathe==4.26.1
-# docutils 0.17 breaks HTML tags & RTD theme
-# https://github.com/sphinx-doc/sphinx/issues/9001
-docutils==0.16
-sphinx==3.3.1
-sphinx_rtd_theme==0.5.0
-sphinxcontrib-moderncmakedomain==3.17
-sphinxcontrib-svg2pdfconverter==1.1.0
+breathe==4.31.0
+sphinx==3.5.4
+sphinx_rtd_theme==1.0.0
+sphinxcontrib-moderncmakedomain==3.19
+sphinxcontrib-svg2pdfconverter==1.1.1
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f54d5fad61..a08fd8ceb6 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -287,10 +287,10 @@ class object : public handle {
     struct borrowed_t { };
     struct stolen_t { };
 
-#ifndef DOXYGEN_SHOULD_SKIP_THIS  // Issue in breathe 4.26.1
+    /// @cond BROKEN
     template <typename T> friend T reinterpret_borrow(handle);
     template <typename T> friend T reinterpret_steal(handle);
-#endif
+    /// @endcond
 
 public:
     // Only accessible from derived classes and the reinterpret_* functions
@@ -1717,7 +1717,7 @@ class memoryview : public object {
 #endif
 };
 
-#ifndef DOXYGEN_SHOULD_SKIP_THIS
+/// @cond DUPLICATE
 inline memoryview memoryview::from_buffer(
     void *ptr, ssize_t itemsize, const char* format,
     detail::any_container<ssize_t> shape,
@@ -1745,7 +1745,7 @@ inline memoryview memoryview::from_buffer(
         throw error_already_set();
     return memoryview(object(obj, stolen_t{}));
 }
-#endif  // DOXYGEN_SHOULD_SKIP_THIS
+/// @endcond
 /// @} pytypes
 
 /// \addtogroup python_builtins
diff --git a/noxfile.py b/noxfile.py
index 53d87dbcba..4adffac2ec 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -57,10 +57,10 @@ def docs(session: nox.Session) -> None:
     session.chdir("docs")
 
     if "pdf" in session.posargs:
-        session.run("sphinx-build", "-M", "latexpdf", ".", "_build")
+        session.run("sphinx-build", "-b", "latexpdf", ".", "_build")
         return
 
-    session.run("sphinx-build", "-M", "html", ".", "_build")
+    session.run("sphinx-build", "-b", "html", ".", "_build")
 
     if "serve" in session.posargs:
         session.log("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")
@@ -86,6 +86,8 @@ def build(session: nox.Session) -> None:
 
     session.install("build")
     session.log("Building normal files")
-    session.run("python", "-m", "build")
+    session.run("python", "-m", "build", *session.posargs)
     session.log("Building pybind11-global files (PYBIND11_GLOBAL_SDIST=1)")
-    session.run("python", "-m", "build", env={"PYBIND11_GLOBAL_SDIST": "1"})
+    session.run(
+        "python", "-m", "build", *session.posargs, env={"PYBIND11_GLOBAL_SDIST": "1"}
+    )

From e450eb62c21c8518c1988c3b17bc5793ea347756 Mon Sep 17 00:00:00 2001
From: Guillaume Jacquenot <Gjacquenot@users.noreply.github.com>
Date: Fri, 12 Nov 2021 16:53:43 +0100
Subject: [PATCH 235/638] Removed duplicated word in
 docs/advanced/cast/eigen.rst (#3458)

---
 docs/advanced/cast/eigen.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/advanced/cast/eigen.rst b/docs/advanced/cast/eigen.rst
index 80f1013430..a5c11a3f14 100644
--- a/docs/advanced/cast/eigen.rst
+++ b/docs/advanced/cast/eigen.rst
@@ -52,7 +52,7 @@ can be mapped *and* if the numpy array is writeable (that is
 the passed variable will be transparently carried out directly on the
 ``numpy.ndarray``.
 
-This means you can can write code such as the following and have it work as
+This means you can write code such as the following and have it work as
 expected:
 
 .. code-block:: cpp

From 270b11d50229e67e2d8d63e96464f9bcd12b527c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sat, 13 Nov 2021 21:32:58 -0500
Subject: [PATCH 236/638] Revert "style: drop pycln" (#3466)

* Revert "style: drop pycln (#3397)"

This reverts commit 606f81a966e56d1ec0f17b0c032e8d6679430d67.

* Update .pre-commit-config.yaml
---
 .pre-commit-config.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 6f0bb39b12..91047b3283 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -61,6 +61,12 @@ repos:
   hooks:
   - id: remove-tabs
 
+# Autoremoves unused imports
+- repo: https://github.com/hadialqattan/pycln
+  rev: v1.1.0
+  hooks:
+  - id: pycln
+
 - repo: https://github.com/pre-commit/pygrep-hooks
   rev: v1.9.0
   hooks:

From afdc09deda50d82eba6cc2e48228df7d909650be Mon Sep 17 00:00:00 2001
From: Trigve <trigves@yahoo.com>
Date: Mon, 15 Nov 2021 19:36:41 +0100
Subject: [PATCH 237/638] [master] Wrong caching of overrides  (#3465)

* override: Fix wrong caching of the overrides

There was a problem when the python type, which was stored in override
cache for C++ functions, was destroyed and  the record wasn't removed from the
override cache. Therefor, dangling pointer was stored there. Then when the
memory was reused and new type was allocated at the given address and the
method with the same name (as previously stored in the cache) was actually
overridden in python, it would wrongly find it in the override cache for C++
functions and therefor override from python wouldn't be called.
The fix is to erase the type from the override cache when the type is destroyed.

* test: Pass by const ref instead of by value (clang-tidy)

* test: Rename classes and move to different files

Rename the classes and files so they're no too generic. Also, better place to
test the stuff is in test_virtual_functions.cpp/.py as we're basically testing
the virtual functions/trampolines.

* Add TODO for erasure code

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pybind11.h           | 10 ++++++
 tests/test_embed/CMakeLists.txt       |  2 +-
 tests/test_embed/test_interpreter.cpp | 49 +++++++++++++++++++++++++++
 tests/test_embed/test_trampoline.py   | 18 ++++++++++
 tests/test_virtual_functions.cpp      | 25 ++++++++++++++
 tests/test_virtual_functions.py       | 19 +++++++++++
 6 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_embed/test_trampoline.py

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b8b7c7a026..c2b88688a5 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1979,6 +1979,16 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
         // gets destroyed:
         weakref((PyObject *) type, cpp_function([type](handle wr) {
             get_internals().registered_types_py.erase(type);
+
+            // TODO consolidate the erasure code in pybind11_meta_dealloc() in class.h
+            auto &cache = get_internals().inactive_override_cache;
+            for (auto it = cache.begin(), last = cache.end(); it != last; ) {
+                if (it->first == reinterpret_cast<PyObject *>(type))
+                    it = cache.erase(it);
+                else
+                    ++it;
+            }
+
             wr.dec_ref();
         })).release();
     }
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 3b89d6e584..edb8961a7d 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -25,7 +25,7 @@ pybind11_enable_warnings(test_embed)
 target_link_libraries(test_embed PRIVATE pybind11::embed Catch2::Catch2 Threads::Threads)
 
 if(NOT CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_CURRENT_BINARY_DIR)
-  file(COPY test_interpreter.py DESTINATION "${CMAKE_CURRENT_BINARY_DIR}")
+  file(COPY test_interpreter.py test_trampoline.py DESTINATION "${CMAKE_CURRENT_BINARY_DIR}")
 endif()
 
 add_custom_target(
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 20bcade0ac..508975eb3c 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -37,6 +37,22 @@ class PyWidget final : public Widget {
     std::string argv0() const override { PYBIND11_OVERRIDE_PURE(std::string, Widget, argv0); }
 };
 
+class test_override_cache_helper {
+
+public:
+    virtual int func() { return 0; }
+
+    test_override_cache_helper() = default;
+    virtual ~test_override_cache_helper() = default;
+    // Non-copyable
+    test_override_cache_helper &operator=(test_override_cache_helper const &Right) = delete;
+    test_override_cache_helper(test_override_cache_helper const &Copy) = delete;
+};
+
+class test_override_cache_helper_trampoline : public test_override_cache_helper {
+    int func() override { PYBIND11_OVERRIDE(int, test_override_cache_helper, func); }
+};
+
 PYBIND11_EMBEDDED_MODULE(widget_module, m) {
     py::class_<Widget, PyWidget>(m, "Widget")
         .def(py::init<std::string>())
@@ -45,6 +61,12 @@ PYBIND11_EMBEDDED_MODULE(widget_module, m) {
     m.def("add", [](int i, int j) { return i + j; });
 }
 
+PYBIND11_EMBEDDED_MODULE(trampoline_module, m) {
+    py::class_<test_override_cache_helper, test_override_cache_helper_trampoline, std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
+        .def(py::init_alias<>())
+        .def("func", &test_override_cache_helper::func);
+}
+
 PYBIND11_EMBEDDED_MODULE(throw_exception, ) {
     throw std::runtime_error("C++ Error");
 }
@@ -73,6 +95,33 @@ TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
     REQUIRE(cpp_widget.the_answer() == 42);
 }
 
+TEST_CASE("Override cache") {
+    auto module_ = py::module_::import("test_trampoline");
+    REQUIRE(py::hasattr(module_, "func"));
+    REQUIRE(py::hasattr(module_, "func2"));
+
+    auto locals = py::dict(**module_.attr("__dict__"));
+
+    int i = 0;
+    for (; i < 1500; ++i) {
+        std::shared_ptr<test_override_cache_helper> p_obj;
+        std::shared_ptr<test_override_cache_helper> p_obj2;
+
+        py::object loc_inst = locals["func"]();
+        p_obj = py::cast<std::shared_ptr<test_override_cache_helper>>(loc_inst);
+
+        int ret = p_obj->func();
+
+        REQUIRE(ret == 42);
+
+        loc_inst = locals["func2"]();
+
+        p_obj2 = py::cast<std::shared_ptr<test_override_cache_helper>>(loc_inst);
+
+        p_obj2->func();
+    }
+}
+
 TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
     REQUIRE_THROWS_WITH(py::module_::import("throw_exception"),
diff --git a/tests/test_embed/test_trampoline.py b/tests/test_embed/test_trampoline.py
new file mode 100644
index 0000000000..87c8fa44c3
--- /dev/null
+++ b/tests/test_embed/test_trampoline.py
@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+
+import trampoline_module
+
+
+def func():
+    class Test(trampoline_module.test_override_cache_helper):
+        def func(self):
+            return 42
+
+    return Test()
+
+
+def func2():
+    class Test(trampoline_module.test_override_cache_helper):
+        pass
+
+    return Test()
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 6e06db9fc1..f1a513180f 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -214,6 +214,25 @@ static void test_gil_from_thread() {
     t.join();
 }
 
+class test_override_cache_helper {
+
+public:
+    virtual int func() { return 0; }
+
+    test_override_cache_helper() = default;
+    virtual ~test_override_cache_helper() = default;
+    // Non-copyable
+    test_override_cache_helper &operator=(test_override_cache_helper const &Right) = delete;
+    test_override_cache_helper(test_override_cache_helper const &Copy) = delete;
+};
+
+class test_override_cache_helper_trampoline : public test_override_cache_helper {
+    int func() override { PYBIND11_OVERRIDE(int, test_override_cache_helper, func); }
+};
+
+inline int test_override_cache(std::shared_ptr<test_override_cache_helper> const &instance) { return instance->func(); }
+
+
 
 // Forward declaration (so that we can put the main tests here; the inherited virtual approaches are
 // rather long).
@@ -378,6 +397,12 @@ TEST_SUBMODULE(virtual_functions, m) {
 //      .def("str_ref", &OverrideTest::str_ref)
         .def("A_value", &OverrideTest::A_value)
         .def("A_ref", &OverrideTest::A_ref);
+
+    py::class_<test_override_cache_helper, test_override_cache_helper_trampoline, std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
+        .def(py::init_alias<>())
+        .def("func", &test_override_cache_helper::func);
+
+    m.def("test_override_cache", test_override_cache);
 }
 
 
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index 0b550992f1..4f25cac4a3 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -439,3 +439,22 @@ def test_issue_1454():
     # Fix issue #1454 (crash when acquiring/releasing GIL on another thread in Python 2.7)
     m.test_gil()
     m.test_gil_from_thread()
+
+
+def test_python_override():
+    def func():
+        class Test(m.test_override_cache_helper):
+            def func(self):
+                return 42
+
+        return Test()
+
+    def func2():
+        class Test(m.test_override_cache_helper):
+            pass
+
+        return Test()
+
+    for _ in range(1500):
+        assert m.test_override_cache(func()) == 42
+        assert m.test_override_cache(func2()) == 0

From 9422d98fcc46cee9193178fdc9323e3d8d384f16 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 15 Nov 2021 22:48:39 -0500
Subject: [PATCH 238/638] [pre-commit.ci] pre-commit autoupdate (#3473)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/isort: 5.10.0 → 5.10.1](https://github.com/PyCQA/isort/compare/5.10.0...5.10.1)
- [github.com/shellcheck-py/shellcheck-py: v0.7.2.1 → v0.8.0.1](https://github.com/shellcheck-py/shellcheck-py/compare/v0.7.2.1...v0.8.0.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 91047b3283..357e2a84b5 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -38,7 +38,7 @@ repos:
   - id: pyupgrade
 
 - repo: https://github.com/PyCQA/isort
-  rev: 5.10.0
+  rev: 5.10.1
   hooks:
   - id: isort
 
@@ -128,7 +128,7 @@ repos:
     args: ["-L", "nd,ot,thist"]
 
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: v0.7.2.1
+  rev: v0.8.0.1
   hooks:
   - id: shellcheck
 

From d2b21316031783fa306ae86e4e379e3db2640a5e Mon Sep 17 00:00:00 2001
From: Sergiu Deitsch <sergiud@users.noreply.github.com>
Date: Tue, 16 Nov 2021 16:03:41 +0100
Subject: [PATCH 239/638] cmake: report version type in the version string
 (#3472)

---
 tools/pybind11Config.cmake.in | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 8f8701be70..262020d14a 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -13,7 +13,7 @@ This module sets the following variables in your project:
 ``pybind11_VERSION``
   pybind11 version in format Major.Minor.Release
 ``pybind11_VERSION_TYPE``
-  pybind11 version type (dev, release)
+  pybind11 version type (``dev*`` or empty for a release)
 ``pybind11_INCLUDE_DIRS``
   Directories where pybind11 and python headers are located.
 ``pybind11_INCLUDE_DIR``
@@ -228,6 +228,6 @@ include("${CMAKE_CURRENT_LIST_DIR}/pybind11Common.cmake")
 if(NOT pybind11_FIND_QUIETLY)
   message(
     STATUS
-      "Found pybind11: ${pybind11_INCLUDE_DIR} (found version \"${pybind11_VERSION}\" ${pybind11_VERSION_TYPE})"
+      "Found pybind11: ${pybind11_INCLUDE_DIR} (found version \"${pybind11_VERSION}${pybind11_VERSION_TYPE}\")"
   )
 endif()

From 1eb59963c78644f3e3a9b3fc6186df9b211093fc Mon Sep 17 00:00:00 2001
From: Guillaume Jacquenot <Gjacquenot@users.noreply.github.com>
Date: Tue, 16 Nov 2021 23:32:01 +0100
Subject: [PATCH 240/638] Removed duplicated word in
 docs/advanced/exceptions.rst (#3476)

---
 docs/advanced/exceptions.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index 40f67d7b83..7cd8447b93 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -64,7 +64,7 @@ at its exception handler.
 +--------------------------------------+--------------------------------------+
 
 Exception translation is not bidirectional. That is, *catching* the C++
-exceptions defined above above will not trap exceptions that originate from
+exceptions defined above will not trap exceptions that originate from
 Python. For that, catch :class:`pybind11::error_already_set`. See :ref:`below
 <handling_python_exceptions_cpp>` for further details.
 

From 72282f75a10a5ec9d34d4ab4305546bfbd8d586d Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 17 Nov 2021 09:44:19 -0500
Subject: [PATCH 241/638] ci: support development releases of Python (#3419)

* ci: support development releases of Python

* fix: better PyPy support

* fix: patch over a few more pypy issues

* Try to patch

* Properly follow pep667

* Fix typo

* Whoops, 667 not in yet

* For testing

* More testing

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Try to backport

* Try to simplify fix

* Nail down the fix

* Try pypy workaround

* Typo

* one last typo

* Replacing 0x03110000 with 0x030B0000

* Add TODO. Drop PyPy

* Fix typo

* Revert catch upgrade

* fix: minor cleanup, try pypy again

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 .github/workflows/ci.yml       |  11 ++--
 .github/workflows/upstream.yml | 112 +++++++++++++++++++++++++++++++++
 include/pybind11/cast.h        |   3 +-
 include/pybind11/eval.h        |   4 +-
 include/pybind11/pybind11.h    |   7 ++-
 tests/requirements.txt         |   2 +-
 tests/test_buffers.py          |   4 ++
 tests/test_builtin_casters.py  |   7 ++-
 tests/test_exceptions.py       |   4 +-
 9 files changed, 137 insertions(+), 17 deletions(-)
 create mode 100644 .github/workflows/upstream.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2888c420b9..dcc61ecd74 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,16 +30,14 @@ jobs:
         - '3.6'
         - '3.9'
         - '3.10'
-        # - '3.11-dev'
-        - 'pypy-3.7-v7.3.5'
-        # - 'pypy-3.8'
+        - 'pypy-3.7-v7.3.7'
+        - 'pypy-3.8-v7.3.7'
 
         # Items in here will either be added to the build matrix (if not
         # present), or add new keys to an existing matrix element if all the
         # existing keys match.
         #
-        # We support three optional keys: args (both build), args1 (first
-        # build), and args2 (second build).
+        # We support an optional keys: args, for cmake args
         include:
           # Just add a key
           - runs-on: ubuntu-latest
@@ -122,7 +120,7 @@ jobs:
       run: git clean -fdx
 
     # Second build - C++17 mode and in a build directory
-    - name: Configure ${{ matrix.args2 }}
+    - name: Configure C++17
       run: >
         cmake -S . -B build2
         -DPYBIND11_WERROR=ON
@@ -130,7 +128,6 @@ jobs:
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         ${{ matrix.args }}
-        ${{ matrix.args2 }}
 
     - name: Build
       run: cmake --build build2 -j 2
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
new file mode 100644
index 0000000000..654947425f
--- /dev/null
+++ b/.github/workflows/upstream.yml
@@ -0,0 +1,112 @@
+
+name: Upstream
+
+on:
+  workflow_dispatch:
+  pull_request:
+
+concurrency:
+  group: upstream-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  PIP_ONLY_BINARY: numpy
+
+jobs:
+  standard:
+    name: "🐍 3.11 dev • ubuntu-latest • x64"
+    runs-on: ubuntu-latest
+    if: "contains(github.event.pull_request.labels.*.name, 'python dev')"
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Python 3.11
+      uses: actions/setup-python@v2
+      with:
+        python-version: "3.11-dev"
+
+    - name: Setup Boost (Linux)
+      if: runner.os == 'Linux'
+      run: sudo apt-get install libboost-dev
+
+    - name: Update CMake
+      uses: jwlawson/actions-setup-cmake@v1.11
+
+    - name: Prepare env
+      run: |
+        python -m pip install -r tests/requirements.txt
+
+    - name: Setup annotations on Linux
+      if: runner.os == 'Linux'
+      run: python -m pip install pytest-github-actions-annotate-failures
+
+    # First build - C++11 mode and inplace
+    - name: Configure C++11
+      run: >
+        cmake -S . -B .
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=11
+
+    - name: Build C++11
+      run: cmake --build . -j 2
+
+    - name: Python tests C++11
+      run: cmake --build . --target pytest -j 2
+
+    - name: C++11 tests
+      run: cmake --build .  --target cpptest -j 2
+
+    - name: Interface test C++11
+      run: cmake --build . --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    # Second build - C++17 mode and in a build directory
+    - name: Configure C++17
+      run: >
+        cmake -S . -B build2
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=17
+        ${{ matrix.args }}
+        ${{ matrix.args2 }}
+
+    - name: Build
+      run: cmake --build build2 -j 2
+
+    - name: Python tests
+      run: cmake --build build2 --target pytest
+
+    - name: C++ tests
+      run: cmake --build build2 --target cpptest
+
+    # Third build - C++17 mode with unstable ABI
+    - name: Configure (unstable ABI)
+      run: >
+        cmake -S . -B build3
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=17
+        -DPYBIND11_INTERNALS_VERSION=10000000
+        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
+        ${{ matrix.args }}
+
+    - name: Build (unstable ABI)
+      run: cmake --build build3 -j 2
+
+    - name: Python tests (unstable ABI)
+      run: cmake --build build3 --target pytest
+
+    - name: Interface test
+      run: cmake --build build2 --target test_cmake_build
+
+    # This makes sure the setup_helpers module can build packages using
+    # setuptools
+    - name: Setuptools helpers test
+      run: pytest tests/extra_setuptools
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 4b39827c25..097d41bdaf 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -150,7 +150,8 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
             return false;
         } else {
             handle src_or_index = src;
-#if PY_VERSION_HEX < 0x03080000
+            // PyPy: 7.3.7's 3.8 does not implement PyLong_*'s __index__ calls.
+#if PY_VERSION_HEX < 0x03080000 || defined(PYPY_VERSION)
             object index;
             if (!PYBIND11_LONG_CHECK(src.ptr())) {  // So: index_check(src.ptr())
                 index = reinterpret_steal<object>(PyNumber_Index(src.ptr()));
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 6cc672e2d5..4248551e9b 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -19,11 +19,11 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline void ensure_builtins_in_globals(object &global) {
-    #if PY_VERSION_HEX < 0x03080000
+    #if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
         // Running exec and eval on Python 2 and 3 adds `builtins` module under
         // `__builtins__` key to globals if not yet present.
         // Python 3.8 made PyRun_String behave similarly. Let's also do that for
-        // older versions, for consistency.
+        // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
         if (!global.contains("__builtins__"))
             global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
     #else
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index c2b88688a5..cfe03f6dbd 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2365,8 +2365,9 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
 
     /* Don't call dispatch code if invoked from overridden function.
        Unfortunately this doesn't work on PyPy. */
-#if !defined(PYPY_VERSION)
-
+#if !defined(PYPY_VERSION) && PY_VERSION_HEX < 0x030B0000
+    // TODO: Remove PyPy workaround for Python 3.11.
+    // Current API fails on 3.11 since co_varnames can be null.
 #if PY_VERSION_HEX >= 0x03090000
     PyFrameObject *frame = PyThreadState_GetFrame(PyThreadState_Get());
     if (frame != nullptr) {
@@ -2374,7 +2375,7 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
         // f_code is guaranteed to not be NULL
         if ((std::string) str(f_code->co_name) == name && f_code->co_argcount > 0) {
             PyObject* locals = PyEval_GetLocals();
-            if (locals != nullptr) {
+            if (locals != nullptr && f_code->co_varnames != nullptr) {
                 PyObject *self_caller = dict_getitem(
                     locals, PyTuple_GET_ITEM(f_code->co_varnames, 0)
                 );
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 8d2742a71c..98ca46d28a 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -2,7 +2,7 @@ numpy==1.16.6; python_version<"3.6" and sys_platform!="win32" and platform_pytho
 numpy==1.19.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.6"
 numpy==1.20.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
 numpy==1.19.3; platform_python_implementation!="PyPy" and python_version=="3.6"
-numpy==1.21.3; platform_python_implementation!="PyPy" and python_version>="3.7"
+numpy==1.21.3; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.11"
 py @ git+https://github.com/pytest-dev/py; python_version>="3.11"
 pytest==4.6.9; python_version<"3.5"
 pytest==6.1.2; python_version=="3.5"
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index adf7cadff2..0877dc0e41 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -36,6 +36,10 @@ def test_from_python():
 
 
 # https://foss.heptapod.net/pypy/pypy/-/issues/2444
+# TODO: fix on recent PyPy
+@pytest.mark.xfail(
+    env.PYPY, reason="PyPy 7.3.7 doesn't clear this anymore", stict=False
+)
 def test_to_python():
     mat = m.Matrix(5, 4)
     assert memoryview(mat).shape == (5, 4)
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 2a061c193e..9c5e17a68e 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -299,7 +299,8 @@ def cant_convert(v):
     assert noconvert(7) == 7
     cant_convert(3.14159)
     # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
-    if (3, 8) <= env.PY < (3, 10):
+    # TODO: PyPy 3.8 does not behave like CPython 3.8 here yet (7.3.7)
+    if (3, 8) <= env.PY < (3, 10) and env.CPYTHON:
         with env.deprecated_call():
             assert convert(Int()) == 42
     else:
@@ -334,7 +335,9 @@ def require_implicit(v):
 
     # The implicit conversion from np.float32 is undesirable but currently accepted.
     # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
-    if (3, 8) <= env.PY < (3, 10):
+    # TODO: PyPy 3.8 does not behave like CPython 3.8 here yet (7.3.7)
+    # https://github.com/pybind/pybind11/issues/3408
+    if (3, 8) <= env.PY < (3, 10) and env.CPYTHON:
         with env.deprecated_call():
             assert convert(np.float32(3.14159)) == 3
     else:
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 3821eadaa4..56201a81c5 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -3,7 +3,7 @@
 
 import pytest
 
-import env  # noqa: F401
+import env
 import pybind11_cross_module_tests as cm
 from pybind11_tests import exceptions as m
 
@@ -97,6 +97,8 @@ def ignore_pytest_unraisable_warning(f):
         return f
 
 
+# TODO: find out why this fails on PyPy, https://foss.heptapod.net/pypy/pypy/-/issues/3583
+@pytest.mark.xfail(env.PYPY, reason="Failure on PyPy 3.8 (7.3.7)", strict=False)
 @ignore_pytest_unraisable_warning
 def test_python_alreadyset_in_destructor(monkeypatch, capsys):
     hooked = False

From ff51fcb773ef7e3cfd6c96d044caf549024d3250 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 18 Nov 2021 08:42:08 -0500
Subject: [PATCH 242/638] docs: fix broken link (again)

---
 README.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.rst b/README.rst
index 7ce57b03ae..45c4af5a60 100644
--- a/README.rst
+++ b/README.rst
@@ -106,7 +106,7 @@ goodies:
 - Binaries are generally smaller by a factor of at least 2 compared to
   equivalent bindings generated by Boost.Python. A recent pybind11
   conversion of PyRosetta, an enormous Boost.Python binding project,
-  `reported <http://graylab.jhu.edu/RosettaCon2016/PyRosetta-4.pdf>`_
+  `reported <https://graylab.jhu.edu/Sergey/2016.RosettaCon/PyRosetta-4.pdf>`_
   a binary size reduction of **5.4x** and compile time reduction by
   **5.8x**.
 

From 15f8d7c12ed5fd78bd3aa8d993e76a334089fa55 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 18 Nov 2021 10:01:24 -0500
Subject: [PATCH 243/638] fix(build): cleaner CMake printouts & IDE folders
 (#3479)

---
 CMakeLists.txt       | 14 ++++++++------
 tests/CMakeLists.txt |  8 ++++++++
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2e81869c3f..3787982cbd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,6 +16,11 @@ else()
   cmake_policy(VERSION 3.22)
 endif()
 
+# Avoid infinite recursion if tests include this as a subdirectory
+if(DEFINED PYBIND11_MASTER_PROJECT)
+  return()
+endif()
+
 # Extract project version from source
 file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/include/pybind11/detail/common.h"
      pybind11_version_defines REGEX "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) ")
@@ -45,13 +50,8 @@ if(NOT pybind11_FIND_QUIETLY)
   message(STATUS "pybind11 v${pybind11_VERSION} ${pybind11_VERSION_TYPE}")
 endif()
 
-# Avoid infinite recursion if tests include this as a subdirectory
-if(DEFINED PYBIND11_MASTER_PROJECT)
-  set(PYBIND11_TEST OFF)
-endif()
-
 # Check if pybind11 is being used directly or via add_subdirectory
-if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR AND NOT DEFINED PYBIND11_MASTER_PROJECT)
+if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
   ### Warn if not an out-of-source builds
   if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_CURRENT_BINARY_DIR)
     set(lines
@@ -80,6 +80,8 @@ if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR AND NOT DEFINED PYBIND11_MASTER_
   endif()
 
   set(pybind11_system "")
+
+  set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 else()
   set(PYBIND11_MASTER_PROJECT OFF)
   set(pybind11_system SYSTEM)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6dc67a11a3..8b19b19670 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -429,6 +429,14 @@ foreach(target ${test_targets})
   endif()
 endforeach()
 
+# Provide nice organisation in IDEs
+if(NOT CMAKE_VERSION VERSION_LESS 3.8)
+  source_group(
+    TREE "${CMAKE_CURRENT_SOURCE_DIR}/../include"
+    PREFIX "Header Files"
+    FILES ${PYBIND11_HEADERS})
+endif()
+
 # Make sure pytest is found or produce a warning
 pybind11_find_import(pytest VERSION 3.1)
 

From 56322dafc9d4d248c46bd1755568df01fbea4994 Mon Sep 17 00:00:00 2001
From: ngc92 <7938269+ngc92@users.noreply.github.com>
Date: Thu, 18 Nov 2021 21:06:04 +0200
Subject: [PATCH 244/638] fixed include for filesystem::path (#3482)

---
 docs/advanced/cast/overview.rst | 180 ++++++++++++++++----------------
 1 file changed, 90 insertions(+), 90 deletions(-)

diff --git a/docs/advanced/cast/overview.rst b/docs/advanced/cast/overview.rst
index 6341fce6d4..6a834a3e51 100644
--- a/docs/advanced/cast/overview.rst
+++ b/docs/advanced/cast/overview.rst
@@ -75,96 +75,96 @@ The following basic data types are supported out of the box (some may require
 an additional extension header to be included). To pass other data structures
 as arguments and return values, refer to the section on binding :ref:`classes`.
 
-+------------------------------------+---------------------------+-------------------------------+
-|  Data type                         |  Description              | Header file                   |
-+====================================+===========================+===============================+
-| ``int8_t``, ``uint8_t``            | 8-bit integers            | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``int16_t``, ``uint16_t``          | 16-bit integers           | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``int32_t``, ``uint32_t``          | 32-bit integers           | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``int64_t``, ``uint64_t``          | 64-bit integers           | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``ssize_t``, ``size_t``            | Platform-dependent size   | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``float``, ``double``              | Floating point types      | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``bool``                           | Two-state Boolean type    | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``char``                           | Character literal         | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``char16_t``                       | UTF-16 character literal  | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``char32_t``                       | UTF-32 character literal  | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``wchar_t``                        | Wide character literal    | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``const char *``                   | UTF-8 string literal      | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``const char16_t *``               | UTF-16 string literal     | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``const char32_t *``               | UTF-32 string literal     | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``const wchar_t *``                | Wide string literal       | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::string``                    | STL dynamic UTF-8 string  | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::u16string``                 | STL dynamic UTF-16 string | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::u32string``                 | STL dynamic UTF-32 string | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::wstring``                   | STL dynamic wide string   | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::string_view``,              | STL C++17 string views    | :file:`pybind11/pybind11.h`   |
-| ``std::u16string_view``, etc.      |                           |                               |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::pair<T1, T2>``              | Pair of two custom types  | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::tuple<...>``                | Arbitrary tuple of types  | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::reference_wrapper<...>``    | Reference type wrapper    | :file:`pybind11/pybind11.h`   |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::complex<T>``                | Complex numbers           | :file:`pybind11/complex.h`    |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::array<T, Size>``            | STL static array          | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::vector<T>``                 | STL dynamic array         | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::deque<T>``                  | STL double-ended queue    | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::valarray<T>``               | STL value array           | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::list<T>``                   | STL linked list           | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::map<T1, T2>``               | STL ordered map           | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::unordered_map<T1, T2>``     | STL unordered map         | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::set<T>``                    | STL ordered set           | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::unordered_set<T>``          | STL unordered set         | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::optional<T>``               | STL optional type (C++17) | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::experimental::optional<T>`` | STL optional type (exp.)  | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::variant<...>``              | Type-safe union (C++17)   | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::filesystem::path<T>``       | STL path (C++17) [#]_     | :file:`pybind11/stl.h`        |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::function<...>``             | STL polymorphic function  | :file:`pybind11/functional.h` |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::chrono::duration<...>``     | STL time duration         | :file:`pybind11/chrono.h`     |
-+------------------------------------+---------------------------+-------------------------------+
-| ``std::chrono::time_point<...>``   | STL date/time             | :file:`pybind11/chrono.h`     |
-+------------------------------------+---------------------------+-------------------------------+
-| ``Eigen::Matrix<...>``             | Eigen: dense matrix       | :file:`pybind11/eigen.h`      |
-+------------------------------------+---------------------------+-------------------------------+
-| ``Eigen::Map<...>``                | Eigen: mapped memory      | :file:`pybind11/eigen.h`      |
-+------------------------------------+---------------------------+-------------------------------+
-| ``Eigen::SparseMatrix<...>``       | Eigen: sparse matrix      | :file:`pybind11/eigen.h`      |
-+------------------------------------+---------------------------+-------------------------------+
++------------------------------------+---------------------------+-----------------------------------+
+|  Data type                         |  Description              | Header file                       |
++====================================+===========================+===================================+
+| ``int8_t``, ``uint8_t``            | 8-bit integers            | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``int16_t``, ``uint16_t``          | 16-bit integers           | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``int32_t``, ``uint32_t``          | 32-bit integers           | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``int64_t``, ``uint64_t``          | 64-bit integers           | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``ssize_t``, ``size_t``            | Platform-dependent size   | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``float``, ``double``              | Floating point types      | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``bool``                           | Two-state Boolean type    | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``char``                           | Character literal         | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``char16_t``                       | UTF-16 character literal  | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``char32_t``                       | UTF-32 character literal  | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``wchar_t``                        | Wide character literal    | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``const char *``                   | UTF-8 string literal      | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``const char16_t *``               | UTF-16 string literal     | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``const char32_t *``               | UTF-32 string literal     | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``const wchar_t *``                | Wide string literal       | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::string``                    | STL dynamic UTF-8 string  | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::u16string``                 | STL dynamic UTF-16 string | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::u32string``                 | STL dynamic UTF-32 string | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::wstring``                   | STL dynamic wide string   | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::string_view``,              | STL C++17 string views    | :file:`pybind11/pybind11.h`       |
+| ``std::u16string_view``, etc.      |                           |                                   |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::pair<T1, T2>``              | Pair of two custom types  | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::tuple<...>``                | Arbitrary tuple of types  | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::reference_wrapper<...>``    | Reference type wrapper    | :file:`pybind11/pybind11.h`       |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::complex<T>``                | Complex numbers           | :file:`pybind11/complex.h`        |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::array<T, Size>``            | STL static array          | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::vector<T>``                 | STL dynamic array         | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::deque<T>``                  | STL double-ended queue    | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::valarray<T>``               | STL value array           | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::list<T>``                   | STL linked list           | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::map<T1, T2>``               | STL ordered map           | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::unordered_map<T1, T2>``     | STL unordered map         | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::set<T>``                    | STL ordered set           | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::unordered_set<T>``          | STL unordered set         | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::optional<T>``               | STL optional type (C++17) | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::experimental::optional<T>`` | STL optional type (exp.)  | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::variant<...>``              | Type-safe union (C++17)   | :file:`pybind11/stl.h`            |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::filesystem::path<T>``       | STL path (C++17) [#]_     | :file:`pybind11/stl/filesystem.h` |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::function<...>``             | STL polymorphic function  | :file:`pybind11/functional.h`     |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::chrono::duration<...>``     | STL time duration         | :file:`pybind11/chrono.h`         |
++------------------------------------+---------------------------+-----------------------------------+
+| ``std::chrono::time_point<...>``   | STL date/time             | :file:`pybind11/chrono.h`         |
++------------------------------------+---------------------------+-----------------------------------+
+| ``Eigen::Matrix<...>``             | Eigen: dense matrix       | :file:`pybind11/eigen.h`          |
++------------------------------------+---------------------------+-----------------------------------+
+| ``Eigen::Map<...>``                | Eigen: mapped memory      | :file:`pybind11/eigen.h`          |
++------------------------------------+---------------------------+-----------------------------------+
+| ``Eigen::SparseMatrix<...>``       | Eigen: sparse matrix      | :file:`pybind11/eigen.h`          |
++------------------------------------+---------------------------+-----------------------------------+
 
 .. [#] ``std::filesystem::path`` is converted to ``pathlib.Path`` and
    ``os.PathLike`` is converted to ``std::filesystem::path``, but this requires

From 673b4be3d7809198cd6a13a476fef270e430977d Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Sat, 20 Nov 2021 20:01:57 -0400
Subject: [PATCH 245/638] Fix py::kw_only when used before the first arg of a
 method (#3488)

* Fix py::kw_only when used before the first arg of a method

The implicit space for the `self` argument isn't added until we hit the
first argument, but this wasn't being done for kw_only or pos_only, and
so a kw_only before the first argument would break.

This fixes it by properly checking whether we need to add the self arg.

(The pos_only issue here was extremely mild -- you didn't get the `/` in
the docstring, but AFAICT it has no other effect since there are no
meaningful arguments before it anyway).

* Style changes

- rename check_have_self_arg -> append_self_arg_if_needed

- move the argument name inline comments before the args instead of
  after
---
 include/pybind11/attr.h            | 12 +++++++++---
 tests/test_kwargs_and_defaults.cpp | 17 +++++++++++++++++
 tests/test_kwargs_and_defaults.py  | 21 +++++++++++++++++++++
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index b95c849046..f1b66fb80c 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -414,11 +414,15 @@ inline void check_kw_only_arg(const arg &a, function_record *r) {
         pybind11_fail("arg(): cannot specify an unnamed argument after a kw_only() annotation or args() argument");
 }
 
+inline void append_self_arg_if_needed(function_record *r) {
+    if (r->is_method && r->args.empty())
+        r->args.emplace_back("self", nullptr, handle(), /*convert=*/ true, /*none=*/ false);
+}
+
 /// Process a keyword argument attribute (*without* a default value)
 template <> struct process_attribute<arg> : process_attribute_default<arg> {
     static void init(const arg &a, function_record *r) {
-        if (r->is_method && r->args.empty())
-            r->args.emplace_back("self", nullptr, handle(), true /*convert*/, false /*none not allowed*/);
+        append_self_arg_if_needed(r);
         r->args.emplace_back(a.name, nullptr, handle(), !a.flag_noconvert, a.flag_none);
 
         check_kw_only_arg(a, r);
@@ -429,7 +433,7 @@ template <> struct process_attribute<arg> : process_attribute_default<arg> {
 template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
     static void init(const arg_v &a, function_record *r) {
         if (r->is_method && r->args.empty())
-            r->args.emplace_back("self", nullptr /*descr*/, handle() /*parent*/, true /*convert*/, false /*none not allowed*/);
+            r->args.emplace_back("self", /*descr=*/ nullptr, /*parent=*/ handle(), /*convert=*/ true, /*none=*/ false);
 
         if (!a.value) {
 #if !defined(NDEBUG)
@@ -461,6 +465,7 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 /// Process a keyword-only-arguments-follow pseudo argument
 template <> struct process_attribute<kw_only> : process_attribute_default<kw_only> {
     static void init(const kw_only &, function_record *r) {
+        append_self_arg_if_needed(r);
         if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size()))
             pybind11_fail("Mismatched args() and kw_only(): they must occur at the same relative argument location (or omit kw_only() entirely)");
         r->nargs_pos = static_cast<std::uint16_t>(r->args.size());
@@ -470,6 +475,7 @@ template <> struct process_attribute<kw_only> : process_attribute_default<kw_onl
 /// Process a positional-only-argument maker
 template <> struct process_attribute<pos_only> : process_attribute_default<pos_only> {
     static void init(const pos_only &, function_record *r) {
+        append_self_arg_if_needed(r);
         r->nargs_pos_only = static_cast<std::uint16_t>(r->args.size());
         if (r->nargs_pos_only > r->nargs_pos)
             pybind11_fail("pos_only(): cannot follow a py::args() argument");
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 312596dabb..34ad2a8647 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -167,4 +167,21 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
         "class_default_argument",
         [](py::object a) { return py::repr(std::move(a)); },
         "a"_a = py::module_::import("decimal").attr("Decimal"));
+
+    // Initial implementation of kw_only was broken when used on a method/constructor before any
+    // other arguments
+    // https://github.com/pybind/pybind11/pull/3402#issuecomment-963341987
+
+    struct first_arg_kw_only {};
+    py::class_<first_arg_kw_only>(m, "first_arg_kw_only")
+        .def(py::init([](int) { return first_arg_kw_only(); }),
+             py::kw_only(), // This being before any args was broken
+             py::arg("i") = 0)
+        .def("method", [](first_arg_kw_only&, int, int) {},
+             py::kw_only(), // and likewise here
+             py::arg("i") = 1, py::arg("j") = 2)
+        // Closely related: pos_only marker didn't show up properly when it was before any other
+        // arguments (although that is fairly useless in practice).
+        .def("pos_only", [](first_arg_kw_only&, int, int) {},
+                py::pos_only{}, py::arg("i"), py::arg("j"));
 }
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index 68903bde16..d61cf2aa58 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -229,6 +229,19 @@ def test_keyword_only_args(msg):
     """
     )
 
+    # https://github.com/pybind/pybind11/pull/3402#issuecomment-963341987
+    x = m.first_arg_kw_only(i=1)
+    x.method()
+    x.method(i=1, j=2)
+    assert (
+        m.first_arg_kw_only.__init__.__doc__
+        == "__init__(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, *, i: int = 0) -> None\n"  # noqa: E501 line too long
+    )
+    assert (
+        m.first_arg_kw_only.method.__doc__
+        == "method(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, *, i: int = 1, j: int = 2) -> None\n"  # noqa: E501 line too long
+    )
+
 
 def test_positional_only_args(msg):
     assert m.pos_only_all(1, 2) == (1, 2)
@@ -310,6 +323,14 @@ def test_positional_only_args(msg):
         {"i": 5, "m": 8},
     )
 
+    # pos_only at the beginning of the argument list was "broken" in how it was displayed (though
+    # this is fairly useless in practice).  Related to:
+    # https://github.com/pybind/pybind11/pull/3402#issuecomment-963341987
+    assert (
+        m.first_arg_kw_only.pos_only.__doc__
+        == "pos_only(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, /, i: int, j: int) -> None\n"  # noqa: E501 line too long
+    )
+
 
 def test_signatures():
     assert "kw_only_all(*, i: int, j: int) -> tuple\n" == m.kw_only_all.__doc__

From 9281faf429970ec43881ee15f9cdf1ee398807ef Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 22 Nov 2021 01:33:03 -0800
Subject: [PATCH 246/638] Fixing `stict` vs `strict` typo. (#3493)

---
 tests/test_buffers.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index 0877dc0e41..0d5bf16c3d 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -38,7 +38,7 @@ def test_from_python():
 # https://foss.heptapod.net/pypy/pypy/-/issues/2444
 # TODO: fix on recent PyPy
 @pytest.mark.xfail(
-    env.PYPY, reason="PyPy 7.3.7 doesn't clear this anymore", stict=False
+    env.PYPY, reason="PyPy 7.3.7 doesn't clear this anymore", strict=False
 )
 def test_to_python():
     mat = m.Matrix(5, 4)

From 5d067e870ab828083cf8b9eec5ff73fade4b3e8b Mon Sep 17 00:00:00 2001
From: Lishen1 <pavel-panteluk@mail.ru>
Date: Mon, 22 Nov 2021 23:27:00 +0300
Subject: [PATCH 247/638] fix: remove redundant copy operation to fix warning
 (#3486)

* fix compiler warning: deprecated implicit copy constructor

* take care of the bug http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747

* add parenthesis for better reading

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update include/pybind11/eigen.h

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 include/pybind11/eigen.h | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 97b1d96b09..e43e484c6b 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -80,14 +80,12 @@ template <bool EigenRowMajor> struct EigenConformable {
     // Matrix type:
     EigenConformable(EigenIndex r, EigenIndex c,
             EigenIndex rstride, EigenIndex cstride) :
-        conformable{true}, rows{r}, cols{c} {
-        // TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity. http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
-        if (rstride < 0 || cstride < 0) {
-            negativestrides = true;
-        } else {
-            stride = {EigenRowMajor ? rstride : cstride /* outer stride */,
-                      EigenRowMajor ? cstride : rstride /* inner stride */ };
-        }
+        conformable{true}, rows{r}, cols{c},
+        //TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity. http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
+        stride{EigenRowMajor ? (rstride > 0 ? rstride : 0) : (cstride > 0 ? cstride : 0) /* outer stride */,
+               EigenRowMajor ? (cstride > 0 ? cstride : 0) : (rstride > 0 ? rstride : 0) /* inner stride */ },
+        negativestrides{rstride < 0 || cstride < 0} {
+
     }
     // Vector type:
     EigenConformable(EigenIndex r, EigenIndex c, EigenIndex stride)

From fe65693c720ca1e859f9734355bf271a1342cbf7 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 22 Nov 2021 16:25:35 -0500
Subject: [PATCH 248/638] [pre-commit.ci] pre-commit autoupdate (#3500)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/asottile/pyupgrade: v2.29.0 → v2.29.1](https://github.com/asottile/pyupgrade/compare/v2.29.0...v2.29.1)
- [github.com/psf/black: 21.10b0 → 21.11b1](https://github.com/psf/black/compare/21.10b0...21.11b1)
- [github.com/asottile/blacken-docs: v1.11.0 → v1.12.0](https://github.com/asottile/blacken-docs/compare/v1.11.0...v1.12.0)

* Keep blacken-docs and black in sync.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <aaronGokaslan@gmail.com>
---
 .pre-commit-config.yaml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 357e2a84b5..6010312431 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -33,7 +33,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.29.0
+  rev: v2.29.1
   hooks:
   - id: pyupgrade
 
@@ -44,16 +44,16 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.10b0 # Keep in sync with blacken-docs
+  rev: 21.11b1 # Keep in sync with blacken-docs
   hooks:
   - id: black
 
 - repo: https://github.com/asottile/blacken-docs
-  rev: v1.11.0
+  rev: v1.12.0
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==21.10b0 # keep in sync with black hook
+    - black==21.11b1 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks

From 70a58c577eaf067748c2ec31bfd0b0a614cffba6 Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <rmlarsen@google.com>
Date: Mon, 22 Nov 2021 17:01:35 -0800
Subject: [PATCH 249/638] Replace usage of deprecated Eigen class
 MappedSparseMatrix. (#3499)

* Replace usage of deprecated Eigen class

Eigen::MappedSparseMatrix has been deprecated since Eigen 3.3 from 2016. Use the equivalent modern syntax Eigen::Map<Eigen::SparseMatrix<...>>.

* Update eigen.h

* Update eigen.h
---
 include/pybind11/eigen.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index e43e484c6b..965d66e8a5 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -50,8 +50,12 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if EIGEN_VERSION_AT_LEAST(3,3,0)
 using EigenIndex = Eigen::Index;
+template<typename Scalar, int Flags, typename StorageIndex>
+using EigenMapSparseMatrix = Eigen::Map<Eigen::SparseMatrix<Scalar, Flags, StorageIndex>>;
 #else
 using EigenIndex = EIGEN_DEFAULT_DENSE_INDEX_TYPE;
+template<typename Scalar, int Flags, typename StorageIndex>
+using EigenMapSparseMatrix = Eigen::MappedSparseMatrix<Scalar, Flags, StorageIndex>;
 #endif
 
 // Matches Eigen::Map, Eigen::Ref, blocks, etc:
@@ -571,9 +575,9 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         if (!values || !innerIndices || !outerIndices)
             return false;
 
-        value = Eigen::MappedSparseMatrix<Scalar,
-                                          Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
-                                          StorageIndex>(
+        value = EigenMapSparseMatrix<Scalar,
+                                     Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
+                                     StorageIndex>(
             shape[0].cast<Index>(), shape[1].cast<Index>(), nnz,
             outerIndices.mutable_data(), innerIndices.mutable_data(), values.mutable_data());
 

From cd176ceeff94ec184abde945ef0867ebe9fb3664 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 2 Dec 2021 16:41:47 -0500
Subject: [PATCH 250/638] chore: update changelog with recent PRs (#3524)

---
 docs/changelog.rst | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index bb5457eec1..dff8ec8081 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,6 +10,76 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 IN DEVELOPMENT
 --------------
 
+New Features:
+
+* Allow ``py::args`` to be followed by other arguments; the remaining arguments
+  are implicitly keyword-only, as if a ``py::kw_only{}`` annotation had been
+  used.
+  `#3402 <https://github.com/pybind/pybind11/pull/3402>`_
+
+* Add C++ Exception type to throw and catch ``AttributeError``. Useful for
+  defining custom ``__setattr__`` and ``__getattr__`` methods.
+  `#3387 <https://github.com/pybind/pybind11/pull/3387>`_
+
+Bug fixes:
+
+* Fix a regression in 2.8.0 that caused undefined behavior (typically
+  segfaults) in ``make_key_iterator``/``make_value_iterator`` if dereferencing
+  the iterator returned a temporary value instead of a reference.
+  `#3348 <https://github.com/pybind/pybind11/pull/3348>`_
+
+* Fix a rare warning about extra copy in an Eigen constructor.
+  `#3486 <https://github.com/pybind/pybind11/pull/3486>`_
+
+* Fix caching of the C++ overrides.
+  `#3465 <https://github.com/pybind/pybind11/pull/3465>`_
+
+* Add missing ``std::forward`` calls to some ``cpp_function`` overloads.
+  `#3443 <https://github.com/pybind/pybind11/pull/3443>`_
+
+* Support PyPy 7.3.7 and the PyPy3.8 beta. Test python-3.11 on PRs with the ``python dev`` label.
+  `#3419 <https://github.com/pybind/pybind11/pull/3419>`_
+
+* Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3.
+  `#3407 <https://github.com/pybind/pybind11/pull/3407>`_
+
+* Modernize usage of ``PyCodeObject`` on Python 3.9 (toward supporting Python
+  3.11a1)
+  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
+
+* A long-standing bug in eigen.h was fixed (originally PR #3343). The bug was
+  unmasked by newly added ``static_assert``'s in the Eigen 3.4.0 release.
+  `#3352 <https://github.com/pybind/pybind11/pull/3352>`_
+
+* Replace usage of deprecated ``Eigen::MappedSparseMatrix`` with
+  ``Eigen::Map<Eigen::SparseMatrix<...>>`` for Eigen 3.3+.
+  `#3499 <https://github.com/pybind/pybind11/pull/3499>`_
+
+* Fixed the potential for dangling references when using properties with
+  ``std::optional`` types.
+  `#3376 <https://github.com/pybind/pybind11/pull/3376>`_
+
+Build system improvements:
+
+* Nicer CMake printout and IDE organisation for pybind11's own tests.
+  `#3479 <https://github.com/pybind/pybind11/pull/3479>`_
+
+* CMake: report version type as part of the version string to avoid a spurious
+  space in the package status message.
+  `#3472 <https://github.com/pybind/pybind11/pull/3472>`_
+
+* Support multiple raw inclusion of CMake helper files (Conan.io does this for
+  multi-config generators).
+  `#3420 <https://github.com/pybind/pybind11/pull/3420>`_
+
+* Fix harmless warning on CMake 3.22.
+  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
+
+* Flags starting with ``-g`` in ``$CFLAGS`` and ``$CPPFLAGS`` are no longer
+  overridden by ``.Pybind11Extension``.
+  `#3436 <https://github.com/pybind/pybind11/pull/3436>`_
+
+
 v2.8.1 (Oct 27, 2021)
 ---------------------
 

From b4939fcbfb9a90f02bea6bb70383eac418c8b3be Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Fri, 3 Dec 2021 13:20:32 -0400
Subject: [PATCH 251/638] Expand std::string_view support to str, bytes,
 memoryview (#3521)

* Expand string_view support to str, bytes, memoryview

1. Allows constructing a str or bytes implicitly from a string_view;
   this is essentially a small shortcut allowing a caller to write
   `py::bytes{sv}` rather than `py::bytes{sv.data(), sv.size()}`.

2. Allows implicit conversion *to* string_view from py::bytes -- this
   saves a fair bit more as currently there is no simple way to get such
   a view of the bytes without copying it (or resorting to Python API
   calls).

   (This is not done for `str` because when the str contains unicode we
   have to allocate to a temporary and so there might not be some string
   data we can properly view without owning.)

3. Allows `memoryview::from_memory` to accept a string_view.  As with
   the other from_memory calls, it's entirely your responsibility to
   keep it alive.

This also required moving the string_view availability detection into
detail/common.h because this PR needs it in pytypes.h, which is higher
up the include chain than cast.h where it was being detected currently.

* Move string_view include to pytypes.h

* CI-testing a fix for the "ambiguous conversion" issue.

This change is known to fix the `tensorflow::tstring` issue reported under https://github.com/pybind/pybind11/pull/3521#issuecomment-985100965

TODO: Minimal reproducer for the `tensorflow::tstring` issue.

* Make clang-tidy happy (hopefully).

* Adding minimal reproducer for the `tensorflow::tstring` issue.

Error without the enable_if trick:

```
/usr/local/google/home/rwgk/forked/pybind11/tests/test_builtin_casters.cpp:169:16: error: ambiguous conversion for functional-style cast from 'TypeWithBothOperatorStringAndStringView' to 'py::bytes'
        return py::bytes(TypeWithBothOperatorStringAndStringView());
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/detail/../pytypes.h:1174:5: note: candidate constructor
    bytes(const std::string &s) : bytes(s.data(), s.size()) { }
    ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/detail/../pytypes.h:1191:5: note: candidate constructor
    bytes(std::string_view s) : bytes(s.data(), s.size()) { }
    ^
```

* Adding missing NOLINTNEXTLINE

* Also apply ambiguous conversion workaround to str()

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/cast.h          | 17 ------------
 include/pybind11/detail/common.h | 15 +++++++++++
 include/pybind11/pytypes.h       | 45 ++++++++++++++++++++++++++++++++
 tests/test_builtin_casters.cpp   | 24 +++++++++++++++++
 tests/test_builtin_casters.py    | 11 ++++++++
 5 files changed, 95 insertions(+), 17 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 097d41bdaf..01dc5df73f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -27,23 +27,6 @@
 #include <utility>
 #include <vector>
 
-#if defined(PYBIND11_CPP17)
-#  if defined(__has_include)
-#    if __has_include(<string_view>)
-#      define PYBIND11_HAS_STRING_VIEW
-#    endif
-#  elif defined(_MSC_VER)
-#    define PYBIND11_HAS_STRING_VIEW
-#  endif
-#endif
-#ifdef PYBIND11_HAS_STRING_VIEW
-#include <string_view>
-#endif
-
-#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
-#  define PYBIND11_HAS_U8STRING
-#endif
-
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 862451fd13..eb5fb08682 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -183,6 +183,21 @@
 #  define PYBIND11_HAS_VARIANT 1
 #endif
 
+#if defined(PYBIND11_CPP17)
+#  if defined(__has_include)
+#    if __has_include(<string_view>)
+#      define PYBIND11_HAS_STRING_VIEW
+#    endif
+#  elif defined(_MSC_VER)
+#    define PYBIND11_HAS_STRING_VIEW
+#  endif
+#endif
+
+#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
+#  define PYBIND11_HAS_U8STRING
+#endif
+
+
 #include <Python.h>
 #include <frameobject.h>
 #include <pythread.h>
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index a08fd8ceb6..f803a05ca7 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -18,6 +18,10 @@
 #  include <optional>
 #endif
 
+#ifdef PYBIND11_HAS_STRING_VIEW
+#  include <string_view>
+#endif
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /* A few forward declarations */
@@ -1085,6 +1089,20 @@ class str : public object {
     // NOLINTNEXTLINE(google-explicit-constructor)
     str(const std::string &s) : str(s.data(), s.size()) { }
 
+#ifdef PYBIND11_HAS_STRING_VIEW
+    // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
+    template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    str(T s) : str(s.data(), s.size()) { }
+
+# ifdef PYBIND11_HAS_U8STRING
+    // reinterpret_cast here is safe (C++20 guarantees char8_t has the same size/alignment as char)
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    str(std::u8string_view s) : str(reinterpret_cast<const char*>(s.data()), s.size()) { }
+# endif
+
+#endif
+
     explicit str(const bytes &b);
 
     /** \rst
@@ -1167,6 +1185,26 @@ class bytes : public object {
             pybind11_fail("Unable to extract bytes contents!");
         return std::string(buffer, (size_t) length);
     }
+
+#ifdef PYBIND11_HAS_STRING_VIEW
+    // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
+    template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    bytes(T s) : bytes(s.data(), s.size()) { }
+
+    // Obtain a string view that views the current `bytes` buffer value.  Note that this is only
+    // valid so long as the `bytes` instance remains alive and so generally should not outlive the
+    // lifetime of the `bytes` instance.
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator std::string_view() const {
+        char *buffer = nullptr;
+        ssize_t length = 0;
+        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length))
+            pybind11_fail("Unable to extract bytes contents!");
+        return {buffer, static_cast<size_t>(length)};
+    }
+#endif
+
 };
 // Note: breathe >= 4.17.0 will fail to build docs if the below two constructors
 // are included in the doxygen group; close here and reopen after as a workaround
@@ -1714,6 +1752,13 @@ class memoryview : public object {
     static memoryview from_memory(const void *mem, ssize_t size) {
         return memoryview::from_memory(const_cast<void*>(mem), size, true);
     }
+
+#ifdef PYBIND11_HAS_STRING_VIEW
+    static memoryview from_memory(std::string_view mem) {
+        return from_memory(const_cast<char*>(mem.data()), static_cast<ssize_t>(mem.size()), true);
+    }
+#endif
+
 #endif
 };
 
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 71c778e8e2..fe629e7c34 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -140,11 +140,35 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("string_view16_return", []() { return std::u16string_view(u"utf16 secret \U0001f382"); });
     m.def("string_view32_return", []() { return std::u32string_view(U"utf32 secret \U0001f382"); });
 
+    // The inner lambdas here are to also test implicit conversion
+    using namespace std::literals;
+    m.def("string_view_bytes", []() { return [](py::bytes b) { return b; }("abc \x80\x80 def"sv); });
+    m.def("string_view_str",   []() { return [](py::str s) { return s; }("abc \342\200\275 def"sv); });
+    m.def("string_view_from_bytes", [](const py::bytes &b) { return [](std::string_view s) { return s; }(b); });
+#if PY_MAJOR_VERSION >= 3
+    m.def("string_view_memoryview", []() {
+        static constexpr auto val = "Have some \360\237\216\202"sv;
+        return py::memoryview::from_memory(val);
+    });
+#endif
+
 #   ifdef PYBIND11_HAS_U8STRING
     m.def("string_view8_print",  [](std::u8string_view s) { py::print(s, s.size()); });
     m.def("string_view8_chars",  [](std::u8string_view s) { py::list l; for (auto c : s) l.append((std::uint8_t) c); return l; });
     m.def("string_view8_return", []() { return std::u8string_view(u8"utf8 secret \U0001f382"); });
+    m.def("string_view8_str",    []() { return py::str{std::u8string_view{u8"abc ‽ def"}}; });
 #   endif
+
+    struct TypeWithBothOperatorStringAndStringView {
+        // NOLINTNEXTLINE(google-explicit-constructor)
+        operator std::string() const { return "success"; }
+        // NOLINTNEXTLINE(google-explicit-constructor)
+        operator std::string_view() const { return "failure"; }
+    };
+    m.def("bytes_from_type_with_both_operator_string_and_string_view",
+          []() { return py::bytes(TypeWithBothOperatorStringAndStringView()); });
+    m.def("str_from_type_with_both_operator_string_and_string_view",
+          []() { return py::str(TypeWithBothOperatorStringAndStringView()); });
 #endif
 
     // test_integer_casting
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 9c5e17a68e..b1f1e395a7 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -206,6 +206,17 @@ def test_string_view(capture):
         """
         )
 
+    assert m.string_view_bytes() == b"abc \x80\x80 def"
+    assert m.string_view_str() == u"abc ‽ def"
+    assert m.string_view_from_bytes(u"abc ‽ def".encode("utf-8")) == u"abc ‽ def"
+    if hasattr(m, "has_u8string"):
+        assert m.string_view8_str() == u"abc ‽ def"
+    if not env.PY2:
+        assert m.string_view_memoryview() == "Have some 🎂".encode()
+
+    assert m.bytes_from_type_with_both_operator_string_and_string_view() == b"success"
+    assert m.str_from_type_with_both_operator_string_and_string_view() == "success"
+
 
 def test_integer_casting():
     """Issue #929 - out-of-range integer values shouldn't be accepted"""

From a224d0cca5f1752acfcdad8e37369e4cda42259e Mon Sep 17 00:00:00 2001
From: Boris Rasin <Boris-Rasin@users.noreply.github.com>
Date: Fri, 3 Dec 2021 21:10:36 +0200
Subject: [PATCH 252/638] fix: vs2022 compilation, issue #3477 (#3497)

* fix: vs2022 compilation, issue #3477

* silence warning for python 2.7

* disable warning around mbstowcs call

* move disable warning code closer to call site

* turn on vs2022 ci test

* ci: don't run helpers on Windows 2022 & Python 3.5

* limit workaround for stdlib shipped with vs2022 or later

* fix for: limit workaround for stdlib shipped with vs2022 or later

* fix 2 for: limit workaround for stdlib shipped with vs2022 or later

* comment

* ci: add a Windows 2019 run

* ci: add Python 2.7 check too

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml         | 16 +++++++++++-----
 include/pybind11/detail/common.h |  8 ++++++++
 include/pybind11/embed.h         | 12 ++++++++++++
 3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dcc61ecd74..8e67baf1cc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,7 +23,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        runs-on: [ubuntu-latest, windows-latest, macos-latest]
+        runs-on: [ubuntu-latest, windows-2022, macos-latest]
         python:
         - '2.7'
         - '3.5'
@@ -37,19 +37,24 @@ jobs:
         # present), or add new keys to an existing matrix element if all the
         # existing keys match.
         #
-        # We support an optional keys: args, for cmake args
+        # We support an optional key: args, for cmake args
         include:
           # Just add a key
           - runs-on: ubuntu-latest
-            python: 3.6
+            python: '3.6'
             args: >
               -DPYBIND11_FINDPYTHON=ON
           - runs-on: windows-latest
-            python: 3.6
+            python: '3.6'
             args: >
               -DPYBIND11_FINDPYTHON=ON
           - runs-on: macos-latest
-            python: pypy-2.7
+            python: 'pypy-2.7'
+          # Inject a couple Windows 2019 runs
+          - runs-on: windows-2019
+            python: '3.9'
+          - runs-on: windows-2019
+            python: '2.7'
 
     name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • x64 ${{ matrix.args }}"
     runs-on: ${{ matrix.runs-on }}
@@ -181,6 +186,7 @@ jobs:
     # setuptools
     - name: Setuptools helpers test
       run: pytest tests/extra_setuptools
+      if: "!(matrix.python == '3.5' && matrix.runs-on == 'windows-2022')"
 
 
   deadsnakes:
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index eb5fb08682..2d57367d0d 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -154,6 +154,14 @@
 // C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #  pragma warning(disable: 4505)
 #  if defined(_DEBUG) && !defined(Py_DEBUG)
+// Workaround for a VS 2022 issue.
+// NOTE: This workaround knowingly violates the Python.h include order requirement:
+// https://docs.python.org/3/c-api/intro.html#include-files
+// See https://github.com/pybind/pybind11/pull/3497 for full context.
+#    include <yvals.h>
+#    if _MSVC_STL_VERSION >= 143
+#      include <crtdefs.h>
+#    endif
 #    define PYBIND11_DEBUG_MARKER
 #    undef _DEBUG
 #  endif
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 9843f0f973..af36340f36 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -102,6 +102,13 @@ inline wchar_t *widen_chars(const char *safe_arg) {
     wchar_t *widened_arg = Py_DecodeLocale(safe_arg, nullptr);
 #else
     wchar_t *widened_arg = nullptr;
+
+// warning C4996: 'mbstowcs': This function or variable may be unsafe.
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(disable:4996)
+#endif
+
 #    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
     size_t count = strlen(safe_arg);
 #    else
@@ -111,6 +118,11 @@ inline wchar_t *widen_chars(const char *safe_arg) {
         widened_arg = new wchar_t[count + 1];
         mbstowcs(widened_arg, safe_arg, count + 1);
     }
+
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
 #endif
     return widened_arg;
 }

From 59aa99860c60bd171b9565e9920f125fdb749267 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 6 Dec 2021 17:12:03 -0500
Subject: [PATCH 253/638] [pre-commit.ci] pre-commit autoupdate (#3533)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/psf/black: 21.11b1 → 21.12b0](https://github.com/psf/black/compare/21.11b1...21.12b0)

* Keep blacken-docs in sync

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 6010312431..4afbd53efd 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -44,7 +44,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.11b1 # Keep in sync with blacken-docs
+  rev: 21.12b0 # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -53,7 +53,7 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==21.11b1 # keep in sync with black hook
+    - black==21.12b0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks

From 7516811315c76321e847cf28955937195c577d2f Mon Sep 17 00:00:00 2001
From: Bobby Impollonia <bobbyi@gmail.com>
Date: Mon, 13 Dec 2021 12:45:33 -0500
Subject: [PATCH 254/638] fix(setup_helpers): ensure ThreadPool is closed
 (#3548)

* Ensure ThreadPool is closed in setup_helpers

The ParallelCompile setup helper using a ThreadPool to enable its
parallelism. It does not properly close the pool when it is done with
it.
This can lead to a "Exception ignored in: <function Pool.__del__..."
message with traceback being printed at shutdown.
Use pool.terminate() instead of context manager for Python 2.7
compatibility

* Add note to remove code that supports Python 2

Co-authored-by: Bobby Impollonia <bobby@k13capital.com>
---
 pybind11/setup_helpers.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index d6d84f672a..5b7c9aab1c 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -466,8 +466,14 @@ def _single_compile(obj):
                     threads = 1
 
             if threads > 1:
-                for _ in ThreadPool(threads).imap_unordered(_single_compile, objects):
-                    pass
+                pool = ThreadPool(threads)
+                # In Python 2, ThreadPool can't be used as a context manager.
+                # Once we are no longer supporting it, this can be 'with pool:'
+                try:
+                    for _ in pool.imap_unordered(_single_compile, objects):
+                        pass
+                finally:
+                    pool.terminate()
             else:
                 for ob in objects:
                     _single_compile(ob)

From d0406c747e9eb79bf7db9473a0da1122600d1866 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 20 Dec 2021 23:11:48 -0500
Subject: [PATCH 255/638] [pre-commit.ci] pre-commit autoupdate (#3563)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/mirrors-mypy: v0.910-1 → v0.920](https://github.com/pre-commit/mirrors-mypy/compare/v0.910-1...v0.920)
- [github.com/shellcheck-py/shellcheck-py: v0.8.0.1 → v0.8.0.2](https://github.com/shellcheck-py/shellcheck-py/compare/v0.8.0.1...v0.8.0.2)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4afbd53efd..972d2472bc 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -104,7 +104,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.910-1
+  rev: v0.920
   hooks:
   - id: mypy
     # Running per-file misbehaves a bit, so just run on all files, it's fast
@@ -128,7 +128,7 @@ repos:
     args: ["-L", "nd,ot,thist"]
 
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: v0.8.0.1
+  rev: v0.8.0.2
   hooks:
   - id: shellcheck
 

From b3d9c3543dcbebde30185c163208b8a00793ae45 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 21 Dec 2021 11:23:49 -0800
Subject: [PATCH 256/638] vi: replacing currently broken ICC Latest C++17 with
 C++14. (#3551)

* Trivial change.

* Trying ICC Latest C++14 instead of C++17.

* Trying ICC Latest C++20 instead of C++17.

* Settling on ICC Latest C++14 for now.

* Undoing trivial change.

* ci: try using SETUPTOOLS_USE_DISTUTILS=stdlib

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8e67baf1cc..f256f05093 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -247,6 +247,8 @@ jobs:
         python -m pip install -r tests/requirements.txt
 
     - name: Configure
+      env:
+        SETUPTOOLS_USE_DISTUTILS: stdlib
       run: >
         cmake -S . -B build
         -DCMAKE_BUILD_TYPE=Debug
@@ -555,37 +557,37 @@ jobs:
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         cmake --build build-11 --target test_cmake_build
 
-    - name: Configure C++17
+    - name: Configure C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake -S . -B build-17     \
+        cmake -S . -B build-14     \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
-        -DCMAKE_CXX_STANDARD=17             \
+        -DCMAKE_CXX_STANDARD=14             \
         -DCMAKE_CXX_COMPILER=$(which icpc)  \
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
-    - name: Build C++17
+    - name: Build C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-17 -j 2 -v
+        cmake --build build-14 -j 2 -v
 
-    - name: Python tests C++17
+    - name: Python tests C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         sudo service apport stop
-        cmake --build build-17 --target check
+        cmake --build build-14 --target check
 
-    - name: C++ tests C++17
+    - name: C++ tests C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-17 --target cpptest
+        cmake --build build-14 --target cpptest
 
-    - name: Interface test C++17
+    - name: Interface test C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-17 --target test_cmake_build
+        cmake --build build-14 --target test_cmake_build
 
 
   # Testing on CentOS (manylinux uses a centos base, and this is an easy way

From 39fbc7992b28188aac6bbcfa7d7814b217f54674 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 21 Dec 2021 14:24:21 -0500
Subject: [PATCH 257/638] fix: avoiding usage of _ if already defined (#3423)

* fix: avoid usage of _

* ci: test _ defined

* docs: include change in docs

* fix: add a test and comment

* refactor: const_str -> const_name
---
 .github/workflows/ci.yml                   |  4 ++-
 docs/advanced/cast/custom.rst              |  2 +-
 docs/upgrade.rst                           |  4 +++
 include/pybind11/cast.h                    | 30 +++++++++++-----------
 include/pybind11/chrono.h                  |  4 +--
 include/pybind11/complex.h                 |  2 +-
 include/pybind11/detail/descr.h            | 28 ++++++++++++--------
 include/pybind11/detail/init.h             |  2 +-
 include/pybind11/detail/type_caster_base.h |  2 +-
 include/pybind11/eigen.h                   | 20 +++++++--------
 include/pybind11/functional.h              |  4 +--
 include/pybind11/numpy.h                   | 28 ++++++++++----------
 include/pybind11/pybind11.h                |  2 +-
 include/pybind11/pytypes.h                 |  2 +-
 include/pybind11/stl.h                     | 12 ++++-----
 include/pybind11/stl/filesystem.h          |  2 +-
 tests/pybind11_tests.h                     |  2 +-
 tests/test_builtin_casters.cpp             |  2 +-
 tests/test_copy_move.cpp                   |  6 ++---
 tests/test_custom_type_casters.cpp         | 11 +++++---
 20 files changed, 94 insertions(+), 75 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f256f05093..7176614de8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -44,6 +44,7 @@ jobs:
             python: '3.6'
             args: >
               -DPYBIND11_FINDPYTHON=ON
+              -DCMAKE_CXX_FLAGS="-D_=1"
           - runs-on: windows-latest
             python: '3.6'
             args: >
@@ -68,7 +69,8 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Setup Boost (Linux)
-      if: runner.os == 'Linux'
+      # Can't use boost + define _
+      if: runner.os == 'Linux' && matrix.python != '3.6'
       run: sudo apt-get install libboost-dev
 
     - name: Setup Boost (macOS)
diff --git a/docs/advanced/cast/custom.rst b/docs/advanced/cast/custom.rst
index 19b9353476..1df4d3e14b 100644
--- a/docs/advanced/cast/custom.rst
+++ b/docs/advanced/cast/custom.rst
@@ -46,7 +46,7 @@ type is explicitly allowed.
              * function signatures and declares a local variable
              * 'value' of type inty
              */
-            PYBIND11_TYPE_CASTER(inty, _("inty"));
+            PYBIND11_TYPE_CASTER(inty, const_name("inty"));
 
             /**
              * Conversion part 1 (Python->C++): convert a PyObject into a inty
diff --git a/docs/upgrade.rst b/docs/upgrade.rst
index 69609ca284..d91d51e6f2 100644
--- a/docs/upgrade.rst
+++ b/docs/upgrade.rst
@@ -17,6 +17,10 @@ v2.9
   converted to using ``py::module_::import("types").attr("SimpleNamespace")``
   instead.
 
+* The use of ``_`` in custom type casters can now be replaced with the more
+  readable ``const_name`` instead. The old ``_`` shortcut has been retained
+  unless it is being used as a macro (like for gettext).
+
 
 .. _upgrade-guide-2.7:
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 01dc5df73f..7930fb994b 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -208,7 +208,7 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
         return PyLong_FromUnsignedLongLong((unsigned long long) src);
     }
 
-    PYBIND11_TYPE_CASTER(T, _<std::is_integral<T>::value>("int", "float"));
+    PYBIND11_TYPE_CASTER(T, const_name<std::is_integral<T>::value>("int", "float"));
 };
 
 template<typename T> struct void_caster {
@@ -221,7 +221,7 @@ template<typename T> struct void_caster {
     static handle cast(T, return_value_policy /* policy */, handle /* parent */) {
         return none().inc_ref();
     }
-    PYBIND11_TYPE_CASTER(T, _("None"));
+    PYBIND11_TYPE_CASTER(T, const_name("None"));
 };
 
 template <> class type_caster<void_type> : public void_caster<void_type> {};
@@ -264,7 +264,7 @@ template <> class type_caster<void> : public type_caster<void_type> {
 
     template <typename T> using cast_op_type = void*&;
     explicit operator void *&() { return value; }
-    static constexpr auto name = _("capsule");
+    static constexpr auto name = const_name("capsule");
 private:
     void *value = nullptr;
 };
@@ -315,7 +315,7 @@ template <> class type_caster<bool> {
     static handle cast(bool src, return_value_policy /* policy */, handle /* parent */) {
         return handle(src ? Py_True : Py_False).inc_ref();
     }
-    PYBIND11_TYPE_CASTER(bool, _("bool"));
+    PYBIND11_TYPE_CASTER(bool, const_name("bool"));
 };
 
 // Helper class for UTF-{8,16,32} C++ stl strings:
@@ -405,7 +405,7 @@ template <typename StringType, bool IsView = false> struct string_caster {
         return s;
     }
 
-    PYBIND11_TYPE_CASTER(StringType, _(PYBIND11_STRING_NAME));
+    PYBIND11_TYPE_CASTER(StringType, const_name(PYBIND11_STRING_NAME));
 
 private:
     static handle decode_utfN(const char *buffer, ssize_t nbytes) {
@@ -542,7 +542,7 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         return one_char;
     }
 
-    static constexpr auto name = _(PYBIND11_STRING_NAME);
+    static constexpr auto name = const_name(PYBIND11_STRING_NAME);
     template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
 };
 
@@ -579,7 +579,7 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
         return cast(*src, policy, parent);
     }
 
-    static constexpr auto name = _("Tuple[") + concat(make_caster<Ts>::name...) + _("]");
+    static constexpr auto name = const_name("Tuple[") + concat(make_caster<Ts>::name...) + const_name("]");
 
     template <typename T> using cast_op_type = type;
 
@@ -764,14 +764,14 @@ template <typename base, typename holder> struct is_holder_type :
 template <typename base, typename deleter> struct is_holder_type<base, std::unique_ptr<base, deleter>> :
     std::true_type {};
 
-template <typename T> struct handle_type_name { static constexpr auto name = _<T>(); };
-template <> struct handle_type_name<bytes> { static constexpr auto name = _(PYBIND11_BYTES_NAME); };
-template <> struct handle_type_name<int_> { static constexpr auto name = _("int"); };
-template <> struct handle_type_name<iterable> { static constexpr auto name = _("Iterable"); };
-template <> struct handle_type_name<iterator> { static constexpr auto name = _("Iterator"); };
-template <> struct handle_type_name<none> { static constexpr auto name = _("None"); };
-template <> struct handle_type_name<args> { static constexpr auto name = _("*args"); };
-template <> struct handle_type_name<kwargs> { static constexpr auto name = _("**kwargs"); };
+template <typename T> struct handle_type_name { static constexpr auto name = const_name<T>(); };
+template <> struct handle_type_name<bytes> { static constexpr auto name = const_name(PYBIND11_BYTES_NAME); };
+template <> struct handle_type_name<int_> { static constexpr auto name = const_name("int"); };
+template <> struct handle_type_name<iterable> { static constexpr auto name = const_name("Iterable"); };
+template <> struct handle_type_name<iterator> { static constexpr auto name = const_name("Iterator"); };
+template <> struct handle_type_name<none> { static constexpr auto name = const_name("None"); };
+template <> struct handle_type_name<args> { static constexpr auto name = const_name("*args"); };
+template <> struct handle_type_name<kwargs> { static constexpr auto name = const_name("**kwargs"); };
 
 template <typename type>
 struct pyobject_caster {
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index 61bbcbc540..007cc17b49 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -97,7 +97,7 @@ template <typename type> class duration_caster {
         return PyDelta_FromDSU(dd.count(), ss.count(), us.count());
     }
 
-    PYBIND11_TYPE_CASTER(type, _("datetime.timedelta"));
+    PYBIND11_TYPE_CASTER(type, const_name("datetime.timedelta"));
 };
 
 inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
@@ -195,7 +195,7 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
                                           localtime.tm_sec,
                                           us.count());
     }
-    PYBIND11_TYPE_CASTER(type, _("datetime.datetime"));
+    PYBIND11_TYPE_CASTER(type, const_name("datetime.datetime"));
 };
 
 // Other clocks that are not the system clock are not measured as datetime.datetime objects
diff --git a/include/pybind11/complex.h b/include/pybind11/complex.h
index f8327eb373..e1ecf43585 100644
--- a/include/pybind11/complex.h
+++ b/include/pybind11/complex.h
@@ -59,7 +59,7 @@ template <typename T> class type_caster<std::complex<T>> {
         return PyComplex_FromDoubles((double) src.real(), (double) src.imag());
     }
 
-    PYBIND11_TYPE_CASTER(std::complex<T>, _("complex"));
+    PYBIND11_TYPE_CASTER(std::complex<T>, const_name("complex"));
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index c62e541bda..ee72eccfe5 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -53,9 +53,17 @@ constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a, c
     return plus_impl(a, b, make_index_sequence<N1>(), make_index_sequence<N2>());
 }
 
+template <size_t N>
+constexpr descr<N - 1> const_name(char const(&text)[N]) { return descr<N - 1>(text); }
+constexpr descr<0> const_name(char const(&)[1]) { return {}; }
+
+// The "_" might be defined as a macro - don't define it if so.
+// Repeating the const_name code to avoid introducing a #define.
+#ifndef _
 template <size_t N>
 constexpr descr<N - 1> _(char const(&text)[N]) { return descr<N - 1>(text); }
 constexpr descr<0> _(char const(&)[1]) { return {}; }
+#endif
 
 template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
 template <size_t...Digits> struct int_to_str<0, Digits...> {
@@ -64,25 +72,25 @@ template <size_t...Digits> struct int_to_str<0, Digits...> {
 
 // Ternary description (like std::conditional)
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> _(char const(&text1)[N1], char const(&)[N2]) {
-    return _(text1);
+constexpr enable_if_t<B, descr<N1 - 1>> const_name(char const(&text1)[N1], char const(&)[N2]) {
+    return const_name(text1);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> _(char const(&)[N1], char const(&text2)[N2]) {
-    return _(text2);
+constexpr enable_if_t<!B, descr<N2 - 1>> const_name(char const(&)[N1], char const(&text2)[N2]) {
+    return const_name(text2);
 }
 
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<B, T1> _(const T1 &d, const T2 &) { return d; }
+constexpr enable_if_t<B, T1> const_name(const T1 &d, const T2 &) { return d; }
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<!B, T2> _(const T1 &, const T2 &d) { return d; }
+constexpr enable_if_t<!B, T2> const_name(const T1 &, const T2 &d) { return d; }
 
 template <size_t Size>
-auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
+auto constexpr const_name() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
     return int_to_str<Size / 10, Size % 10>::digits;
 }
 
-template <typename Type> constexpr descr<1, Type> _() { return {'%'}; }
+template <typename Type> constexpr descr<1, Type> const_name() { return {'%'}; }
 
 constexpr descr<0> concat() { return {}; }
 
@@ -92,12 +100,12 @@ constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) { return descr; }
 template <size_t N, typename... Ts, typename... Args>
 constexpr auto concat(const descr<N, Ts...> &d, const Args &...args)
     -> decltype(std::declval<descr<N + 2, Ts...>>() + concat(args...)) {
-    return d + _(", ") + concat(args...);
+    return d + const_name(", ") + concat(args...);
 }
 
 template <size_t N, typename... Ts>
 constexpr descr<N + 2, Ts...> type_descr(const descr<N, Ts...> &descr) {
-    return _("{") + descr + _("}");
+    return const_name("{") + descr + const_name("}");
 }
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index cace352964..eaaad5a07a 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -24,7 +24,7 @@ class type_caster<value_and_holder> {
 
     template <typename> using cast_op_type = value_and_holder &;
     explicit operator value_and_holder &() { return *value; }
-    static constexpr auto name = _<value_and_holder>();
+    static constexpr auto name = const_name<value_and_holder>();
 
 private:
     value_and_holder *value = nullptr;
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 00ce1a7a1e..48e218b2f3 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -897,7 +897,7 @@ template <typename type> class type_caster_base : public type_caster_generic {
     using itype = intrinsic_t<type>;
 
 public:
-    static constexpr auto name = _<type>();
+    static constexpr auto name = const_name<type>();
 
     type_caster_base() : type_caster_base(typeid(type)) { }
     explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 965d66e8a5..696099fa65 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -192,20 +192,20 @@ template <typename Type_> struct EigenProps {
     static constexpr bool show_f_contiguous = !show_c_contiguous && show_order && requires_col_major;
 
     static constexpr auto descriptor =
-        _("numpy.ndarray[") + npy_format_descriptor<Scalar>::name +
-        _("[")  + _<fixed_rows>(_<(size_t) rows>(), _("m")) +
-        _(", ") + _<fixed_cols>(_<(size_t) cols>(), _("n")) +
-        _("]") +
+        const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name +
+        const_name("[")  + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) +
+        const_name(", ") + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) +
+        const_name("]") +
         // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to be
         // satisfied: writeable=True (for a mutable reference), and, depending on the map's stride
         // options, possibly f_contiguous or c_contiguous.  We include them in the descriptor output
         // to provide some hint as to why a TypeError is occurring (otherwise it can be confusing to
         // see that a function accepts a 'numpy.ndarray[float64[3,2]]' and an error message that you
         // *gave* a numpy.ndarray of the right type and dimensions.
-        _<show_writeable>(", flags.writeable", "") +
-        _<show_c_contiguous>(", flags.c_contiguous", "") +
-        _<show_f_contiguous>(", flags.f_contiguous", "") +
-        _("]");
+        const_name<show_writeable>(", flags.writeable", "") +
+        const_name<show_c_contiguous>(", flags.c_contiguous", "") +
+        const_name<show_f_contiguous>(", flags.f_contiguous", "") +
+        const_name("]");
 };
 
 // Casts an Eigen type to numpy array.  If given a base, the numpy array references the src data,
@@ -600,8 +600,8 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         ).release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, _<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[", "scipy.sparse.csc_matrix[")
-            + npy_format_descriptor<Scalar>::name + _("]"));
+    PYBIND11_TYPE_CASTER(Type, const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[", "scipy.sparse.csc_matrix[")
+            + npy_format_descriptor<Scalar>::name + const_name("]"));
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index ad5608c255..7912aef175 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -113,8 +113,8 @@ struct type_caster<std::function<Return(Args...)>> {
         return cpp_function(std::forward<Func>(f_), policy).release();
     }
 
-    PYBIND11_TYPE_CASTER(type, _("Callable[[") + concat(make_caster<Args>::name...) + _("], ")
-                               + make_caster<retval_type>::name + _("]"));
+    PYBIND11_TYPE_CASTER(type, const_name("Callable[[") + concat(make_caster<Args>::name...) + const_name("], ")
+                               + make_caster<retval_type>::name + const_name("]"));
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index b43a771684..8e83b506e0 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -39,7 +39,7 @@ class array; // Forward declaration
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <> struct handle_type_name<array> { static constexpr auto name = _("numpy.ndarray"); };
+template <> struct handle_type_name<array> { static constexpr auto name = const_name("numpy.ndarray"); };
 
 template <typename type, typename SFINAE = void> struct npy_format_descriptor;
 
@@ -290,7 +290,7 @@ template <typename T> struct array_info_scalar {
     using type = T;
     static constexpr bool is_array = false;
     static constexpr bool is_empty = false;
-    static constexpr auto extents = _("");
+    static constexpr auto extents = const_name("");
     static void append_extents(list& /* shape */) { }
 };
 // Computes underlying type and a comma-separated list of extents for array
@@ -309,8 +309,8 @@ template <typename T, size_t N> struct array_info<std::array<T, N>> {
         array_info<T>::append_extents(shape);
     }
 
-    static constexpr auto extents = _<array_info<T>::is_array>(
-        concat(_<N>(), array_info<T>::extents), _<N>()
+    static constexpr auto extents = const_name<array_info<T>::is_array>(
+        concat(const_name<N>(), array_info<T>::extents), const_name<N>()
     );
 };
 // For numpy we have special handling for arrays of characters, so we don't include
@@ -1021,7 +1021,7 @@ template <typename T>
 struct format_descriptor<T, detail::enable_if_t<detail::array_info<T>::is_array>> {
     static std::string format() {
         using namespace detail;
-        static constexpr auto extents = _("(") + array_info<T>::extents + _(")");
+        static constexpr auto extents = const_name("(") + array_info<T>::extents + const_name(")");
         return extents.text + format_descriptor<remove_all_extents_t<T>>::format();
     }
 };
@@ -1056,28 +1056,28 @@ struct npy_format_descriptor_name;
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_integral<T>::value>> {
-    static constexpr auto name = _<std::is_same<T, bool>::value>(
-        _("bool"), _<std::is_signed<T>::value>("numpy.int", "numpy.uint") + _<sizeof(T)*8>()
+    static constexpr auto name = const_name<std::is_same<T, bool>::value>(
+        const_name("bool"), const_name<std::is_signed<T>::value>("numpy.int", "numpy.uint") + const_name<sizeof(T)*8>()
     );
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::value>> {
-    static constexpr auto name = _<std::is_same<T, float>::value
+    static constexpr auto name = const_name<std::is_same<T, float>::value
                                    || std::is_same<T, const float>::value
                                    || std::is_same<T, double>::value
                                    || std::is_same<T, const double>::value>(
-        _("numpy.float") + _<sizeof(T)*8>(), _("numpy.longdouble")
+        const_name("numpy.float") + const_name<sizeof(T)*8>(), const_name("numpy.longdouble")
     );
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<is_complex<T>::value>> {
-    static constexpr auto name = _<std::is_same<typename T::value_type, float>::value
+    static constexpr auto name = const_name<std::is_same<typename T::value_type, float>::value
                                    || std::is_same<typename T::value_type, const float>::value
                                    || std::is_same<typename T::value_type, double>::value
                                    || std::is_same<typename T::value_type, const double>::value>(
-        _("numpy.complex") + _<sizeof(typename T::value_type)*16>(), _("numpy.longcomplex")
+        const_name("numpy.complex") + const_name<sizeof(typename T::value_type)*16>(), const_name("numpy.longcomplex")
     );
 };
 
@@ -1105,7 +1105,7 @@ struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmet
 };
 
 #define PYBIND11_DECL_CHAR_FMT \
-    static constexpr auto name = _("S") + _<N>(); \
+    static constexpr auto name = const_name("S") + const_name<N>(); \
     static pybind11::dtype dtype() { return pybind11::dtype(std::string("S") + std::to_string(N)); }
 template <size_t N> struct npy_format_descriptor<char[N]> { PYBIND11_DECL_CHAR_FMT };
 template <size_t N> struct npy_format_descriptor<std::array<char, N>> { PYBIND11_DECL_CHAR_FMT };
@@ -1117,7 +1117,7 @@ template<typename T> struct npy_format_descriptor<T, enable_if_t<array_info<T>::
 public:
     static_assert(!array_info<T>::is_empty, "Zero-sized arrays are not supported");
 
-    static constexpr auto name = _("(") + array_info<T>::extents + _(")") + base_descr::name;
+    static constexpr auto name = const_name("(") + array_info<T>::extents + const_name(")") + base_descr::name;
     static pybind11::dtype dtype() {
         list shape;
         array_info<T>::append_extents(shape);
@@ -1705,7 +1705,7 @@ vectorize_extractor(const Func &f, Return (*) (Args ...)) {
 }
 
 template <typename T, int Flags> struct handle_type_name<array_t<T, Flags>> {
-    static constexpr auto name = _("numpy.ndarray[") + npy_format_descriptor<T>::name + _("]");
+    static constexpr auto name = const_name("numpy.ndarray[") + npy_format_descriptor<T>::name + const_name("]");
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index cfe03f6dbd..8c7545ba3a 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -262,7 +262,7 @@ class cpp_function : public function {
         }
 
         /* Generate a readable signature describing the function's arguments and return value types */
-        static constexpr auto signature = _("(") + cast_in::arg_names + _(") -> ") + cast_out::name;
+        static constexpr auto signature = const_name("(") + cast_in::arg_names + const_name(") -> ") + cast_out::name;
         PYBIND11_DESCR_CONSTEXPR auto types = decltype(signature)::types();
 
         /* Register the function with Python from generic (non-templated) code */
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f803a05ca7..902fb1f07d 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -435,7 +435,7 @@ inline void raise_from(error_already_set& err, PyObject *type, const char *messa
 
 #endif
 
-/** \defgroup python_builtins _
+/** \defgroup python_builtins const_name
     Unless stated otherwise, the following C++ functions behave the same
     as their Python counterparts.
  */
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 3608d2989c..4303494827 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -78,7 +78,7 @@ template <typename Type, typename Key> struct set_caster {
         return s.release();
     }
 
-    PYBIND11_TYPE_CASTER(type, _("Set[") + key_conv::name + _("]"));
+    PYBIND11_TYPE_CASTER(type, const_name("Set[") + key_conv::name + const_name("]"));
 };
 
 template <typename Type, typename Key, typename Value> struct map_caster {
@@ -120,7 +120,7 @@ template <typename Type, typename Key, typename Value> struct map_caster {
         return d.release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, _("Dict[") + key_conv::name + _(", ") + value_conv::name + _("]"));
+    PYBIND11_TYPE_CASTER(Type, const_name("Dict[") + key_conv::name + const_name(", ") + value_conv::name + const_name("]"));
 };
 
 template <typename Type, typename Value> struct list_caster {
@@ -166,7 +166,7 @@ template <typename Type, typename Value> struct list_caster {
         return l.release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, _("List[") + value_conv::name + _("]"));
+    PYBIND11_TYPE_CASTER(Type, const_name("List[") + value_conv::name + const_name("]"));
 };
 
 template <typename Type, typename Alloc> struct type_caster<std::vector<Type, Alloc>>
@@ -223,7 +223,7 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
         return l.release();
     }
 
-    PYBIND11_TYPE_CASTER(ArrayType, _("List[") + value_conv::name + _<Resizable>(_(""), _("[") + _<Size>() + _("]")) + _("]"));
+    PYBIND11_TYPE_CASTER(ArrayType, const_name("List[") + value_conv::name + const_name<Resizable>(const_name(""), const_name("[") + const_name<Size>() + const_name("]")) + const_name("]"));
 };
 
 template <typename Type, size_t Size> struct type_caster<std::array<Type, Size>>
@@ -273,7 +273,7 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
         return true;
     }
 
-    PYBIND11_TYPE_CASTER(Type, _("Optional[") + value_conv::name + _("]"));
+    PYBIND11_TYPE_CASTER(Type, const_name("Optional[") + value_conv::name + const_name("]"));
 };
 
 #if defined(PYBIND11_HAS_OPTIONAL)
@@ -353,7 +353,7 @@ struct variant_caster<V<Ts...>> {
     }
 
     using Type = V<Ts...>;
-    PYBIND11_TYPE_CASTER(Type, _("Union[") + detail::concat(make_caster<Ts>::name...) + _("]"));
+    PYBIND11_TYPE_CASTER(Type, const_name("Union[") + detail::concat(make_caster<Ts>::name...) + const_name("]"));
 };
 
 #if defined(PYBIND11_HAS_VARIANT)
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 431b94b4f7..a9a6c8512c 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -92,7 +92,7 @@ template<typename T> struct path_caster {
         return true;
     }
 
-    PYBIND11_TYPE_CASTER(T, _("os.PathLike"));
+    PYBIND11_TYPE_CASTER(T, const_name("os.PathLike"));
 };
 
 template<> struct type_caster<std::filesystem::path>
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index 800ddda48b..9b99923237 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -65,7 +65,7 @@ PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
 template<> class type_caster<RValueCaster> {
 public:
-    PYBIND11_TYPE_CASTER(RValueCaster, _("RValueCaster"));
+    PYBIND11_TYPE_CASTER(RValueCaster, const_name("RValueCaster"));
     static handle cast(RValueCaster &&, return_value_policy, handle) { return py::str("rvalue").release(); }
     static handle cast(const RValueCaster &, return_value_policy, handle) { return py::str("lvalue").release(); }
 };
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index fe629e7c34..4a9f338378 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -19,7 +19,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 template <>
 class type_caster<ConstRefCasted> {
  public:
-  static constexpr auto name = _<ConstRefCasted>();
+  static constexpr auto name = const_name<ConstRefCasted>();
 
   // Input is unimportant, a new value will always be constructed based on the
   // cast operator.
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 5fb0dd810c..4711a94822 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -85,13 +85,13 @@ class CopyOnlyInt {
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <> struct type_caster<MoveOnlyInt> {
-    PYBIND11_TYPE_CASTER(MoveOnlyInt, _("MoveOnlyInt"));
+    PYBIND11_TYPE_CASTER(MoveOnlyInt, const_name("MoveOnlyInt"));
     bool load(handle src, bool) { value = MoveOnlyInt(src.cast<int>()); return true; }
     static handle cast(const MoveOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
 };
 
 template <> struct type_caster<MoveOrCopyInt> {
-    PYBIND11_TYPE_CASTER(MoveOrCopyInt, _("MoveOrCopyInt"));
+    PYBIND11_TYPE_CASTER(MoveOrCopyInt, const_name("MoveOrCopyInt"));
     bool load(handle src, bool) { value = MoveOrCopyInt(src.cast<int>()); return true; }
     static handle cast(const MoveOrCopyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
 };
@@ -100,7 +100,7 @@ template <> struct type_caster<CopyOnlyInt> {
 protected:
     CopyOnlyInt value;
 public:
-    static constexpr auto name = _("CopyOnlyInt");
+    static constexpr auto name = const_name("CopyOnlyInt");
     bool load(handle src, bool) { value = CopyOnlyInt(src.cast<int>()); return true; }
     static handle cast(const CopyOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
     static handle cast(const CopyOnlyInt *src, return_value_policy policy, handle parent) {
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 076777d6f1..8ad584de6d 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -18,7 +18,12 @@ class ArgAlwaysConverts { };
 namespace pybind11 { namespace detail {
 template <> struct type_caster<ArgInspector1> {
 public:
+    // Classic
+#ifndef _
     PYBIND11_TYPE_CASTER(ArgInspector1, _("ArgInspector1"));
+#else
+    PYBIND11_TYPE_CASTER(ArgInspector1, const_name("ArgInspector1"));
+#endif
 
     bool load(handle src, bool convert) {
         value.arg = "loading ArgInspector1 argument " +
@@ -33,7 +38,7 @@ template <> struct type_caster<ArgInspector1> {
 };
 template <> struct type_caster<ArgInspector2> {
 public:
-    PYBIND11_TYPE_CASTER(ArgInspector2, _("ArgInspector2"));
+    PYBIND11_TYPE_CASTER(ArgInspector2, const_name("ArgInspector2"));
 
     bool load(handle src, bool convert) {
         value.arg = "loading ArgInspector2 argument " +
@@ -48,7 +53,7 @@ template <> struct type_caster<ArgInspector2> {
 };
 template <> struct type_caster<ArgAlwaysConverts> {
 public:
-    PYBIND11_TYPE_CASTER(ArgAlwaysConverts, _("ArgAlwaysConverts"));
+    PYBIND11_TYPE_CASTER(ArgAlwaysConverts, const_name("ArgAlwaysConverts"));
 
     bool load(handle, bool convert) {
         return convert;
@@ -76,7 +81,7 @@ class DestructionTester {
 };
 namespace pybind11 { namespace detail {
 template <> struct type_caster<DestructionTester> {
-    PYBIND11_TYPE_CASTER(DestructionTester, _("DestructionTester"));
+    PYBIND11_TYPE_CASTER(DestructionTester, const_name("DestructionTester"));
     bool load(handle, bool) { return true; }
 
     static handle cast(const DestructionTester &, return_value_policy, handle) {

From e50f841de040a9455b2d76dc395c369869c89cdf Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 21 Dec 2021 15:42:34 -0500
Subject: [PATCH 258/638] fix: do not use LTS on mips64 and ppc64le (#3557)

---
 tools/pybind11Common.cmake | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index 69ac4b0f61..df24781213 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -318,13 +318,21 @@ function(_pybind11_generate_lto target prefer_thin_lto)
       set(cxx_append ";-fno-fat-lto-objects")
     endif()
 
-    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND prefer_thin_lto)
+    if(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc64le" OR CMAKE_SYSTEM_PROCESSOR MATCHES "mips64")
+      set(NO_FLTO_ARCH TRUE)
+    else()
+      set(NO_FLTO_ARCH FALSE)
+    endif()
+
+    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang"
+       AND prefer_thin_lto
+       AND NOT NO_FLTO_ARCH)
       _pybind11_return_if_cxx_and_linker_flags_work(
         HAS_FLTO_THIN "-flto=thin${cxx_append}" "-flto=thin${linker_append}"
         PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
     endif()
 
-    if(NOT HAS_FLTO_THIN)
+    if(NOT HAS_FLTO_THIN AND NOT NO_FLTO_ARCH)
       _pybind11_return_if_cxx_and_linker_flags_work(
         HAS_FLTO "-flto${cxx_append}" "-flto${linker_append}" PYBIND11_LTO_CXX_FLAGS
         PYBIND11_LTO_LINKER_FLAGS)

From d4b9f3471f465f0cc6d05556a837c26589b08b29 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 21 Dec 2021 16:28:23 -0500
Subject: [PATCH 259/638] docs: update changelog (#3556)

* docs: update changelog

* Update changelog.rst

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 docs/changelog.rst | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index dff8ec8081..87fce2f2bd 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,6 +10,8 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 IN DEVELOPMENT
 --------------
 
+This is the last version to support Python 2.7 and 3.5.
+
 New Features:
 
 * Allow ``py::args`` to be followed by other arguments; the remaining arguments
@@ -21,6 +23,16 @@ New Features:
   defining custom ``__setattr__`` and ``__getattr__`` methods.
   `#3387 <https://github.com/pybind/pybind11/pull/3387>`_
 
+Changes:
+
+* Make str/bytes/memoryview more interoperable with ``std::string_view``.
+  `#3521 <https://github.com/pybind/pybind11/pull/3521>`_
+
+* Replace ``_`` with ``const_name`` in internals, avoid defining ``pybind::_``
+  if ``_`` defined as macro (common gettext usage)
+  `#3423 <https://github.com/pybind/pybind11/pull/3423>`_
+
+
 Bug fixes:
 
 * Fix a regression in 2.8.0 that caused undefined behavior (typically
@@ -37,7 +49,8 @@ Bug fixes:
 * Add missing ``std::forward`` calls to some ``cpp_function`` overloads.
   `#3443 <https://github.com/pybind/pybind11/pull/3443>`_
 
-* Support PyPy 7.3.7 and the PyPy3.8 beta. Test python-3.11 on PRs with the ``python dev`` label.
+* Support PyPy 7.3.7 and the PyPy3.8 beta. Test python-3.11 on PRs with the
+  ``python dev`` label.
   `#3419 <https://github.com/pybind/pybind11/pull/3419>`_
 
 * Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3.
@@ -59,6 +72,9 @@ Bug fixes:
   ``std::optional`` types.
   `#3376 <https://github.com/pybind/pybind11/pull/3376>`_
 
+* Tweaks to support Microsoft Visual Studio 2022.
+  `#3497 <https://github.com/pybind/pybind11/pull/3497>`_
+
 Build system improvements:
 
 * Nicer CMake printout and IDE organisation for pybind11's own tests.
@@ -79,6 +95,12 @@ Build system improvements:
   overridden by ``.Pybind11Extension``.
   `#3436 <https://github.com/pybind/pybind11/pull/3436>`_
 
+* Ensure ThreadPool is closed in ``setup_helpers``.
+  `#3548 <https://github.com/pybind/pybind11/pull/3548>`_
+
+* Avoid LTS on ``mips64`` and ``ppc64le`` (reported broken).
+  `#3557 <https://github.com/pybind/pybind11/pull/3557>`_
+
 
 v2.8.1 (Oct 27, 2021)
 ---------------------

From cb302305a3d2697f8af17a14c5bf78f45359fb56 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 23 Dec 2021 14:50:10 -0500
Subject: [PATCH 260/638] fix: restore full range of _ functions (#3571)

---
 include/pybind11/detail/descr.h | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index ee72eccfe5..14f9223a50 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -57,14 +57,6 @@ template <size_t N>
 constexpr descr<N - 1> const_name(char const(&text)[N]) { return descr<N - 1>(text); }
 constexpr descr<0> const_name(char const(&)[1]) { return {}; }
 
-// The "_" might be defined as a macro - don't define it if so.
-// Repeating the const_name code to avoid introducing a #define.
-#ifndef _
-template <size_t N>
-constexpr descr<N - 1> _(char const(&text)[N]) { return descr<N - 1>(text); }
-constexpr descr<0> _(char const(&)[1]) { return {}; }
-#endif
-
 template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
 template <size_t...Digits> struct int_to_str<0, Digits...> {
     static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...);
@@ -92,6 +84,31 @@ auto constexpr const_name() -> remove_cv_t<decltype(int_to_str<Size / 10, Size %
 
 template <typename Type> constexpr descr<1, Type> const_name() { return {'%'}; }
 
+// The "_" might be defined as a macro - don't define it if so.
+// Repeating the const_name code to avoid introducing a #define.
+#ifndef _
+template <size_t N>
+constexpr descr<N-1> _(char const(&text)[N]) { return const_name<N>(text); }
+template <bool B, size_t N1, size_t N2>
+constexpr enable_if_t<B, descr<N1 - 1>> _(char const(&text1)[N1], char const(&text2)[N2]) {
+    return const_name<B,N1,N2>(text1, text2);
+}
+template <bool B, size_t N1, size_t N2>
+constexpr enable_if_t<!B, descr<N2 - 1>> _(char const(&text1)[N1], char const(&text2)[N2]) {
+    return const_name<B,N1,N2>(text1, text2);
+}
+template <bool B, typename T1, typename T2>
+constexpr enable_if_t<B, T1> _(const T1 &d1, const T2 &d2) { return const_name<B,T1,T2>(d1, d2); }
+template <bool B, typename T1, typename T2>
+constexpr enable_if_t<!B, T2> _(const T1 &d1, const T2 &d2) { return const_name<B,T1,T2>(d1, d2); }
+
+template <size_t Size>
+auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
+    return const_name<Size>();
+}
+template <typename Type> constexpr descr<1, Type> _() { return const_name<Type>(); }
+#endif
+
 constexpr descr<0> concat() { return {}; }
 
 template <size_t N, typename... Ts>

From 89769e6e6da425546c00a45ba19f63e5437901c4 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 27 Dec 2021 18:28:30 -0500
Subject: [PATCH 261/638] [pre-commit.ci] pre-commit autoupdate (#3574)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/pre-commit-hooks: v4.0.1 → v4.1.0](https://github.com/pre-commit/pre-commit-hooks/compare/v4.0.1...v4.1.0)
- [github.com/pre-commit/mirrors-mypy: v0.920 → v0.930](https://github.com/pre-commit/mirrors-mypy/compare/v0.920...v0.930)
- [github.com/shellcheck-py/shellcheck-py: v0.8.0.2 → v0.8.0.3](https://github.com/shellcheck-py/shellcheck-py/compare/v0.8.0.2...v0.8.0.3)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 972d2472bc..3a6583ccff 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,7 +15,7 @@
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: v4.0.1
+  rev: v4.1.0
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
@@ -104,7 +104,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.920
+  rev: v0.930
   hooks:
   - id: mypy
     # Running per-file misbehaves a bit, so just run on all files, it's fast
@@ -128,7 +128,7 @@ repos:
     args: ["-L", "nd,ot,thist"]
 
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: v0.8.0.2
+  rev: v0.8.0.3
   hooks:
   - id: shellcheck
 

From 45f792efdd92da094548e2095d6efdbfa7e536ee Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 28 Dec 2021 10:47:21 -0500
Subject: [PATCH 262/638] chore: prepare for 2.9

---
 docs/changelog.rst               | 4 ++--
 include/pybind11/detail/common.h | 4 ++--
 pybind11/_version.py             | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 87fce2f2bd..cc3f70efb7 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -7,8 +7,8 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
 
-IN DEVELOPMENT
---------------
+Version 2.9.0 (Dec 28, 2021)
+----------------------------
 
 This is the last version to support Python 2.7 and 3.5.
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 2d57367d0d..b08bbc5590 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 9
-#define PYBIND11_VERSION_PATCH 0.dev1
+#define PYBIND11_VERSION_PATCH 0
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020900D1
+#define PYBIND11_VERSION_HEX 0x02090000
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index ce894a7740..6627d4c7e6 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.9.0.dev1"
+__version__ = "2.9.0"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 9b4f71d12de4f910a77aeb00d37ffb2220e645e7 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 28 Dec 2021 12:19:17 -0500
Subject: [PATCH 263/638] docs: remove duplication in changelog for 2.9.0

---
 docs/changelog.rst | 31 -------------------------------
 1 file changed, 31 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index cc3f70efb7..c05e7d3c55 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -19,10 +19,6 @@ New Features:
   used.
   `#3402 <https://github.com/pybind/pybind11/pull/3402>`_
 
-* Add C++ Exception type to throw and catch ``AttributeError``. Useful for
-  defining custom ``__setattr__`` and ``__getattr__`` methods.
-  `#3387 <https://github.com/pybind/pybind11/pull/3387>`_
-
 Changes:
 
 * Make str/bytes/memoryview more interoperable with ``std::string_view``.
@@ -35,11 +31,6 @@ Changes:
 
 Bug fixes:
 
-* Fix a regression in 2.8.0 that caused undefined behavior (typically
-  segfaults) in ``make_key_iterator``/``make_value_iterator`` if dereferencing
-  the iterator returned a temporary value instead of a reference.
-  `#3348 <https://github.com/pybind/pybind11/pull/3348>`_
-
 * Fix a rare warning about extra copy in an Eigen constructor.
   `#3486 <https://github.com/pybind/pybind11/pull/3486>`_
 
@@ -53,25 +44,10 @@ Bug fixes:
   ``python dev`` label.
   `#3419 <https://github.com/pybind/pybind11/pull/3419>`_
 
-* Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3.
-  `#3407 <https://github.com/pybind/pybind11/pull/3407>`_
-
-* Modernize usage of ``PyCodeObject`` on Python 3.9 (toward supporting Python
-  3.11a1)
-  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
-
-* A long-standing bug in eigen.h was fixed (originally PR #3343). The bug was
-  unmasked by newly added ``static_assert``'s in the Eigen 3.4.0 release.
-  `#3352 <https://github.com/pybind/pybind11/pull/3352>`_
-
 * Replace usage of deprecated ``Eigen::MappedSparseMatrix`` with
   ``Eigen::Map<Eigen::SparseMatrix<...>>`` for Eigen 3.3+.
   `#3499 <https://github.com/pybind/pybind11/pull/3499>`_
 
-* Fixed the potential for dangling references when using properties with
-  ``std::optional`` types.
-  `#3376 <https://github.com/pybind/pybind11/pull/3376>`_
-
 * Tweaks to support Microsoft Visual Studio 2022.
   `#3497 <https://github.com/pybind/pybind11/pull/3497>`_
 
@@ -84,13 +60,6 @@ Build system improvements:
   space in the package status message.
   `#3472 <https://github.com/pybind/pybind11/pull/3472>`_
 
-* Support multiple raw inclusion of CMake helper files (Conan.io does this for
-  multi-config generators).
-  `#3420 <https://github.com/pybind/pybind11/pull/3420>`_
-
-* Fix harmless warning on CMake 3.22.
-  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
-
 * Flags starting with ``-g`` in ``$CFLAGS`` and ``$CPPFLAGS`` are no longer
   overridden by ``.Pybind11Extension``.
   `#3436 <https://github.com/pybind/pybind11/pull/3436>`_

From 1bbaeb3462dcb12ce0b8aeabc56f8dd7a413dbbb Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 29 Dec 2021 12:54:25 -0800
Subject: [PATCH 264/638] Adding dedicated test_const_name. (#3578)

* Adding dedicated test_const_name.

Also exercises pybind11::detail::_ backward compatibility.

See also: PR #3423

* Backing out tests involving int_to_str (requires C++17 or higher).

* Suppressing clang-tidy errors.

* Disabling test_const_name for MSVC 2015 due to bizarre failures.

* Stacking @pytest.mark.parametrize (thanks to @skylion007 for pointing out).
---
 include/pybind11/detail/descr.h    | 10 +++--
 tests/CMakeLists.txt               |  1 +
 tests/test_const_name.cpp          | 70 ++++++++++++++++++++++++++++++
 tests/test_const_name.py           | 31 +++++++++++++
 tests/test_custom_type_casters.cpp |  2 +-
 5 files changed, 110 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_const_name.cpp
 create mode 100644 tests/test_const_name.py

diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 14f9223a50..0f93e06b21 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -59,6 +59,7 @@ constexpr descr<0> const_name(char const(&)[1]) { return {}; }
 
 template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
 template <size_t...Digits> struct int_to_str<0, Digits...> {
+    // WARNING: This only works with C++17 or higher.
     static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...);
 };
 
@@ -84,9 +85,12 @@ auto constexpr const_name() -> remove_cv_t<decltype(int_to_str<Size / 10, Size %
 
 template <typename Type> constexpr descr<1, Type> const_name() { return {'%'}; }
 
-// The "_" might be defined as a macro - don't define it if so.
-// Repeating the const_name code to avoid introducing a #define.
+// If "_" is defined as a macro, py::detail::_ cannot be provided.
+// It is therefore best to use py::detail::const_name universally.
+// This block is for backward compatibility only.
+// (The const_name code is repeated to avoid introducing a "_" #define ourselves.)
 #ifndef _
+#define PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
 template <size_t N>
 constexpr descr<N-1> _(char const(&text)[N]) { return const_name<N>(text); }
 template <bool B, size_t N1, size_t N2>
@@ -107,7 +111,7 @@ auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::dig
     return const_name<Size>();
 }
 template <typename Type> constexpr descr<1, Type> _() { return const_name<Type>(); }
-#endif
+#endif  // #ifndef _
 
 constexpr descr<0> concat() { return {}; }
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 8b19b19670..b00c043ac3 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -101,6 +101,7 @@ set(PYBIND11_TEST_FILES
     test_callbacks.cpp
     test_chrono.cpp
     test_class.cpp
+    test_const_name.cpp
     test_constants_and_functions.cpp
     test_copy_move.cpp
     test_custom_type_casters.cpp
diff --git a/tests/test_const_name.cpp b/tests/test_const_name.cpp
new file mode 100644
index 0000000000..5cb3d16c14
--- /dev/null
+++ b/tests/test_const_name.cpp
@@ -0,0 +1,70 @@
+// Copyright (c) 2021 The Pybind Development Team.
+// All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "pybind11_tests.h"
+
+#if defined(_MSC_VER) && _MSC_VER < 1910
+
+// MSVC 2015 fails in bizarre ways.
+#    define PYBIND11_SKIP_TEST_CONST_NAME
+
+#else // Only test with MSVC 2017 or newer.
+
+// IUT = Implementation Under Test
+#    define CONST_NAME_TESTS(TEST_FUNC, IUT)                                                      \
+        std::string TEST_FUNC(int selector) {                                                     \
+            switch (selector) {                                                                   \
+                case 0:                                                                           \
+                    return IUT("").text;                                                          \
+                case 1:                                                                           \
+                    return IUT("A").text;                                                         \
+                case 2:                                                                           \
+                    return IUT("Bd").text;                                                        \
+                case 3:                                                                           \
+                    return IUT("Cef").text;                                                       \
+                case 4:                                                                           \
+                    return IUT<int>().text; /*NOLINT(bugprone-macro-parentheses)*/                \
+                case 5:                                                                           \
+                    return IUT<std::string>().text; /*NOLINT(bugprone-macro-parentheses)*/        \
+                case 6:                                                                           \
+                    return IUT<true>("T1", "T2").text; /*NOLINT(bugprone-macro-parentheses)*/     \
+                case 7:                                                                           \
+                    return IUT<false>("U1", "U2").text; /*NOLINT(bugprone-macro-parentheses)*/    \
+                case 8:                                                                           \
+                    /*NOLINTNEXTLINE(bugprone-macro-parentheses)*/                                \
+                    return IUT<true>(IUT("D1"), IUT("D2")).text;                                  \
+                case 9:                                                                           \
+                    /*NOLINTNEXTLINE(bugprone-macro-parentheses)*/                                \
+                    return IUT<false>(IUT("E1"), IUT("E2")).text;                                 \
+                case 10:                                                                          \
+                    return IUT("KeepAtEnd").text;                                                 \
+                default:                                                                          \
+                    break;                                                                        \
+            }                                                                                     \
+            throw std::runtime_error("Invalid selector value.");                                  \
+        }
+
+CONST_NAME_TESTS(const_name_tests, py::detail::const_name)
+
+#    ifdef PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
+CONST_NAME_TESTS(underscore_tests, py::detail::_)
+#    endif
+
+#endif // MSVC >= 2017
+
+TEST_SUBMODULE(const_name, m) {
+#ifdef PYBIND11_SKIP_TEST_CONST_NAME
+    m.attr("const_name_tests") = "PYBIND11_SKIP_TEST_CONST_NAME";
+#else
+    m.def("const_name_tests", const_name_tests);
+#endif
+
+#ifdef PYBIND11_SKIP_TEST_CONST_NAME
+    m.attr("underscore_tests") = "PYBIND11_SKIP_TEST_CONST_NAME";
+#elif defined(PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY)
+    m.def("underscore_tests", underscore_tests);
+#else
+    m.attr("underscore_tests") = "PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY not defined.";
+#endif
+}
diff --git a/tests/test_const_name.py b/tests/test_const_name.py
new file mode 100644
index 0000000000..d4e45e5e98
--- /dev/null
+++ b/tests/test_const_name.py
@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+import pytest
+
+import env
+from pybind11_tests import const_name as m
+
+
+@pytest.mark.parametrize("func", (m.const_name_tests, m.underscore_tests))
+@pytest.mark.parametrize(
+    "selector, expected",
+    enumerate(
+        (
+            "",
+            "A",
+            "Bd",
+            "Cef",
+            "%",
+            "%",
+            "T1",
+            "U2",
+            "D1",
+            "E2",
+            "KeepAtEnd",
+        )
+    ),
+)
+def test_const_name(func, selector, expected):
+    if isinstance(func, type(u"") if env.PY2 else str):
+        pytest.skip(func)
+    text = func(selector)
+    assert text == expected
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 8ad584de6d..48613ee5a1 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -19,7 +19,7 @@ namespace pybind11 { namespace detail {
 template <> struct type_caster<ArgInspector1> {
 public:
     // Classic
-#ifndef _
+#ifdef PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
     PYBIND11_TYPE_CASTER(ArgInspector1, _("ArgInspector1"));
 #else
     PYBIND11_TYPE_CASTER(ArgInspector1, const_name("ArgInspector1"));

From 2cd32e5d545ef29efa3eb96e1388ff994c743e2d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 3 Jan 2022 15:55:21 -0800
Subject: [PATCH 265/638] [pre-commit.ci] pre-commit autoupdate (#3589)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.29.1 → v2.31.0](https://github.com/asottile/pyupgrade/compare/v2.29.1...v2.31.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3a6583ccff..57af7cf37f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -33,7 +33,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.29.1
+  rev: v2.31.0
   hooks:
   - id: pyupgrade
 

From fb9a222daa3bc9f24f2620becf7a511d110c234d Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 10 Jan 2022 10:29:30 -0500
Subject: [PATCH 266/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.4.2 to 1.5.0 (#3606)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.4.2 to 1.5.0.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.4.2...v1.5.0)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 203f350bb1..f74b79f0ce 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -96,13 +96,13 @@ jobs:
     - uses: actions/download-artifact@v2
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.4.2
+      uses: pypa/gh-action-pypi-publish@v1.5.0
       with:
         password: ${{ secrets.pypi_password }}
         packages_dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.4.2
+      uses: pypa/gh-action-pypi-publish@v1.5.0
       with:
         password: ${{ secrets.pypi_password_global }}
         packages_dir: global/

From b66328b043ca9fcd993a3380821360625ec6992d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 10 Jan 2022 21:13:24 -0500
Subject: [PATCH 267/638] [pre-commit.ci] pre-commit autoupdate (#3609)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/mirrors-mypy: v0.930 → v0.931](https://github.com/pre-commit/mirrors-mypy/compare/v0.930...v0.931)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 57af7cf37f..2014cb2b42 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -104,7 +104,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.930
+  rev: v0.931
   hooks:
   - id: mypy
     # Running per-file misbehaves a bit, so just run on all files, it's fast

From ef070f7750e72c43963d0aaa36ed305be83caa00 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 10 Jan 2022 21:18:00 -0500
Subject: [PATCH 268/638] Add additional info to TypeError when C++->Python
 casting fails (#3605)

* Add additional info to TypeInfo when C++->Python casting fails

* Fix typo

* Address reviewer comments
---
 include/pybind11/pybind11.h         |  7 +++++++
 tests/test_operator_overloading.cpp | 25 ++++++++++++++++++++++---
 tests/test_operator_overloading.py  | 13 +++++++++++--
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 8c7545ba3a..ec60429b1d 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -996,6 +996,13 @@ class cpp_function : public function {
                               "Python type! The signature was\n\t";
             msg += it->signature;
             append_note_if_missing_header_is_suspected(msg);
+#if PY_VERSION_HEX >= 0x03030000
+            // Attach additional error info to the exception if supported
+            if (PyErr_Occurred()) {
+                raise_from(PyExc_TypeError, msg.c_str());
+                return nullptr;
+            }
+#endif
             PyErr_SetString(PyExc_TypeError, msg.c_str());
             return nullptr;
         }
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index 0b6c496cf2..ffa059d5b5 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -7,10 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
-#include <pybind11/operators.h>
+#include "pybind11_tests.h"
 #include <functional>
+#include <pybind11/operators.h>
+#include <pybind11/stl.h>
 
 class Vector2 {
 public:
@@ -71,6 +72,12 @@ int operator+(const C2 &, const C2 &) { return 22; }
 int operator+(const C2 &, const C1 &) { return 21; }
 int operator+(const C1 &, const C2 &) { return 12; }
 
+struct HashMe {
+    std::string member;
+};
+
+bool operator==(const HashMe &lhs, const HashMe &rhs) { return lhs.member == rhs.member; }
+
 // Note: Specializing explicit within `namespace std { ... }` is done due to a
 // bug in GCC<7. If you are supporting compilers later than this, consider
 // specializing `using template<> struct std::hash<...>` in the global
@@ -82,6 +89,14 @@ namespace std {
         // Not a good hash function, but easy to test
         size_t operator()(const Vector2 &) { return 4; }
     };
+
+    // HashMe has a hash function in C++ but no `__hash__` for Python.
+    template <>
+    struct hash<HashMe> {
+        std::size_t operator()(const HashMe &selector) const {
+            return std::hash<std::string>()(selector.member);
+        }
+    };
 } // namespace std
 
 // Not a good abs function, but easy to test.
@@ -228,8 +243,12 @@ TEST_SUBMODULE(operators, m) {
         .def("__hash__", &Hashable::hash)
         .def(py::init<int>())
         .def(py::self == py::self);
-}
 
+    // define __eq__ but not __hash__
+    py::class_<HashMe>(m, "HashMe").def(py::self == py::self);
+
+    m.def("get_unhashable_HashMe_set", []() { return std::unordered_set<HashMe>{{"one"}}; });
+}
 #if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
   #pragma GCC diagnostic pop
 #endif
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index b7137d1592..8cf375b6da 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 import pytest
 
+import env
 from pybind11_tests import ConstructorStats
 from pybind11_tests import operators as m
 
@@ -135,8 +136,9 @@ def test_overriding_eq_reset_hash():
     assert m.Comparable(15) is not m.Comparable(15)
     assert m.Comparable(15) == m.Comparable(15)
 
-    with pytest.raises(TypeError):
-        hash(m.Comparable(15))  # TypeError: unhashable type: 'm.Comparable'
+    with pytest.raises(TypeError) as excinfo:
+        hash(m.Comparable(15))
+    assert str(excinfo.value).startswith("unhashable type:")
 
     for hashable in (m.Hashable, m.Hashable2):
         assert hashable(15) is not hashable(15)
@@ -144,3 +146,10 @@ def test_overriding_eq_reset_hash():
 
         assert hash(hashable(15)) == 15
         assert hash(hashable(15)) == hash(hashable(15))
+
+
+def test_return_set_of_unhashable():
+    with pytest.raises(TypeError) as excinfo:
+        m.get_unhashable_HashMe_set()
+    if not env.PY2:
+        assert str(excinfo.value.__cause__).startswith("unhashable type:")

From f5888108712d04609d869459887629ec6562a158 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 11 Jan 2022 12:13:02 -0800
Subject: [PATCH 269/638] Replacing ICC C++14 with C++17 (#3570)

* Replacing ICC C++14 with C++17

* ICPC: -diag-disable:conversion

Try to suppress the `-Werror-all` promotion in `#include <variant>`

* Trying `-DPYBIND11_WERROR=OFF`

* Trying `-Wno-conversion` (todo: make specific to C++17 if it works)

* Inserting -Wno-conversion only for C++17

Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja>
---
 .github/workflows/ci.yml | 22 +++++++++++-----------
 tests/CMakeLists.txt     |  3 +++
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7176614de8..c56e4003b3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -559,37 +559,37 @@ jobs:
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         cmake --build build-11 --target test_cmake_build
 
-    - name: Configure C++14
+    - name: Configure C++17
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake -S . -B build-14     \
+        cmake -S . -B build-17     \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
-        -DCMAKE_CXX_STANDARD=14             \
+        -DCMAKE_CXX_STANDARD=17             \
         -DCMAKE_CXX_COMPILER=$(which icpc)  \
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
-    - name: Build C++14
+    - name: Build C++17
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-14 -j 2 -v
+        cmake --build build-17 -j 2 -v
 
-    - name: Python tests C++14
+    - name: Python tests C++17
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         sudo service apport stop
-        cmake --build build-14 --target check
+        cmake --build build-17 --target check
 
-    - name: C++ tests C++14
+    - name: C++ tests C++17
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-14 --target cpptest
+        cmake --build build-17 --target cpptest
 
-    - name: Interface test C++14
+    - name: Interface test C++17
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-14 --target test_cmake_build
+        cmake --build build-17 --target test_cmake_build
 
 
   # Testing on CentOS (manylinux uses a centos base, and this is an easy way
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b00c043ac3..eb8c3228da 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -327,6 +327,9 @@ function(pybind11_enable_warnings target_name)
     elseif(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang|IntelLLVM)")
       target_compile_options(${target_name} PRIVATE -Werror)
     elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+      if(CMAKE_CXX_STANDARD EQUAL 17) # See PR #3570
+        target_compile_options(${target_name} PRIVATE -Wno-conversion)
+      endif()
       target_compile_options(
         ${target_name}
         PRIVATE

From d434b5f31ec5e776cd002f019ad2cdab174358f3 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Tue, 11 Jan 2022 17:57:59 -0500
Subject: [PATCH 270/638] (chore): Remove deprecated c-headers (#3610)

* Remove deprecated c-headers

* Update calls to old cfunctions

* Add missing one

* Add another missing one
---
 include/pybind11/chrono.h       |  4 +---
 include/pybind11/detail/class.h |  4 ++--
 include/pybind11/embed.h        |  6 +++---
 include/pybind11/pybind11.h     | 14 +++++++-------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index 007cc17b49..460a28fa5d 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -17,8 +17,6 @@
 #include <ctime>
 #include <mutex>
 
-#include <time.h>
-
 #include <datetime.h>
 
 // Backport the PyDateTime_DELTA functions from Python3.3 if required
@@ -108,7 +106,7 @@ inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
 #else
     static std::mutex mtx;
     std::lock_guard<std::mutex> lock(mtx);
-    std::tm *tm_ptr = localtime(time);
+    std::tm *tm_ptr = std::localtime(time);
     if (tm_ptr != nullptr) {
         *buf = *tm_ptr;
     }
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index b9376b4c0b..cc1e40ce7a 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -624,9 +624,9 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     if (rec.doc && options::show_user_defined_docstrings()) {
         /* Allocate memory for docstring (using PyObject_MALLOC, since
            Python will free this later on) */
-        size_t size = strlen(rec.doc) + 1;
+        size_t size = std::strlen(rec.doc) + 1;
         tp_doc = (char *) PyObject_MALLOC(size);
-        memcpy((void *) tp_doc, rec.doc, size);
+        std::memcpy((void *) tp_doc, rec.doc, size);
     }
 
     auto &internals = get_internals();
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index af36340f36..9ab1ce9c0a 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -110,13 +110,13 @@ inline wchar_t *widen_chars(const char *safe_arg) {
 #endif
 
 #    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
-    size_t count = strlen(safe_arg);
+    size_t count = std::strlen(safe_arg);
 #    else
-    size_t count = mbstowcs(nullptr, safe_arg, 0);
+    size_t count = std::mbstowcs(nullptr, safe_arg, 0);
 #    endif
     if (count != static_cast<size_t>(-1)) {
         widened_arg = new wchar_t[count + 1];
-        mbstowcs(widened_arg, safe_arg, count + 1);
+        std::mbstowcs(widened_arg, safe_arg, count + 1);
     }
 
 #if defined(_MSC_VER)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ec60429b1d..344a18c569 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -23,7 +23,7 @@
 #include <string>
 #include <utility>
 
-#include <string.h>
+#include <cstring>
 
 #if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
 #  define PYBIND11_STD_LAUNDER std::launder
@@ -327,8 +327,8 @@ class cpp_function : public function {
                 a.descr = guarded_strdup(repr(a.value).cast<std::string>().c_str());
         }
 
-        rec->is_constructor
-            = (strcmp(rec->name, "__init__") == 0) || (strcmp(rec->name, "__setstate__") == 0);
+        rec->is_constructor = (std::strcmp(rec->name, "__init__") == 0)
+                              || (std::strcmp(rec->name, "__setstate__") == 0);
 
 #if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
@@ -409,10 +409,10 @@ class cpp_function : public function {
             pybind11_fail("Internal error while parsing type signature (2)");
 
 #if PY_MAJOR_VERSION < 3
-        if (strcmp(rec->name, "__next__") == 0) {
+        if (std::strcmp(rec->name, "__next__") == 0) {
             std::free(rec->name);
             rec->name = guarded_strdup("next");
-        } else if (strcmp(rec->name, "__bool__") == 0) {
+        } else if (std::strcmp(rec->name, "__bool__") == 0) {
             std::free(rec->name);
             rec->name = guarded_strdup("__nonzero__");
         }
@@ -1302,8 +1302,8 @@ inline void call_operator_delete(void *p, size_t s, size_t a) {
 
 inline void add_class_method(object& cls, const char *name_, const cpp_function &cf) {
     cls.attr(cf.name()) = cf;
-    if (strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
-      cls.attr("__hash__") = none();
+    if (std::strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
+        cls.attr("__hash__") = none();
     }
 }
 

From 21911e126fd1c1e9ed344967427ef6380b433b41 Mon Sep 17 00:00:00 2001
From: Ivor Wanders <iwanders@users.noreply.github.com>
Date: Tue, 11 Jan 2022 20:31:19 -0500
Subject: [PATCH 271/638] A way to register additional test targets and support
 .py only tests. (#3590)

* A way to register additional test targets.

* Support specifying tests with extension.

* Ensure TEST_OVERRIDE is backwards compatible.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Ensure regex is non greedy.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .github/CONTRIBUTING.md |   5 +-
 tests/CMakeLists.txt    | 174 +++++++++++++++++++++++++---------------
 2 files changed, 113 insertions(+), 66 deletions(-)

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 39c32b2ac5..c08bb173f2 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -159,8 +159,9 @@ tests with these targets:
 * `test_cmake_build`: Install / subdirectory tests
 
 If you want to build just a subset of tests, use
-`-DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_pickling.cpp"`. If this is
-empty, all tests will be built.
+`-DPYBIND11_TEST_OVERRIDE="test_callbacks;test_pickling"`. If this is
+empty, all tests will be built. Tests are specified without an extension if they need both a .py and
+.cpp file.
 
 You may also pass flags to the `pytest` target by editing `tests/pytest.ini` or
 by using the `PYTEST_ADDOPTS` environment variable
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index eb8c3228da..9040cf8c06 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -19,7 +19,7 @@ endif()
 # Only needed for CMake < 3.5 support
 include(CMakeParseArguments)
 
-# Filter out items; print an optional message if any items filtered
+# Filter out items; print an optional message if any items filtered. This ignores extensions.
 #
 # Usage:
 #   pybind11_filter_tests(LISTNAME file1.cpp file2.cpp ... MESSAGE "")
@@ -27,10 +27,17 @@ include(CMakeParseArguments)
 macro(pybind11_filter_tests LISTNAME)
   cmake_parse_arguments(ARG "" "MESSAGE" "" ${ARGN})
   set(PYBIND11_FILTER_TESTS_FOUND OFF)
+  # Make a list of the test without any extensions, for easier filtering.
+  set(_TMP_ACTUAL_LIST "${${LISTNAME}};") # enforce ';' at the end to allow matching last item.
+  string(REGEX REPLACE "\\.[^.;]*;" ";" LIST_WITHOUT_EXTENSIONS "${_TMP_ACTUAL_LIST}")
   foreach(filename IN LISTS ARG_UNPARSED_ARGUMENTS)
-    list(FIND ${LISTNAME} ${filename} _FILE_FOUND)
+    string(REGEX REPLACE "\\.[^.]*$" "" filename_no_ext ${filename})
+    # Search in the list without extensions.
+    list(FIND LIST_WITHOUT_EXTENSIONS ${filename_no_ext} _FILE_FOUND)
     if(_FILE_FOUND GREATER -1)
-      list(REMOVE_AT ${LISTNAME} ${_FILE_FOUND})
+      list(REMOVE_AT ${LISTNAME} ${_FILE_FOUND}) # And remove from the list with extensions.
+      list(REMOVE_AT LIST_WITHOUT_EXTENSIONS ${_FILE_FOUND}
+      )# And our search list, to ensure it is in sync.
       set(PYBIND11_FILTER_TESTS_FOUND ON)
     endif()
   endforeach()
@@ -47,6 +54,18 @@ macro(possibly_uninitialized)
   endforeach()
 endmacro()
 
+# Function to add additional targets if any of the provided tests are found.
+# Needles; Specifies the test names to look for.
+# Additions; Specifies the additional test targets to add when any of the needles are found.
+macro(tests_extra_targets needles additions)
+  # Add the index for this relation to the index extra targets map.
+  list(LENGTH PYBIND11_TEST_EXTRA_TARGETS PYBIND11_TEST_EXTRA_TARGETS_LEN)
+  list(APPEND PYBIND11_TEST_EXTRA_TARGETS ${PYBIND11_TEST_EXTRA_TARGETS_LEN})
+  # Add the test names to look for, and the associated test target additions.
+  set(PYBIND11_TEST_EXTRA_TARGETS_NEEDLES_${PYBIND11_TEST_EXTRA_TARGETS_LEN} ${needles})
+  set(PYBIND11_TEST_EXTRA_TARGETS_ADDITION_${PYBIND11_TEST_EXTRA_TARGETS_LEN} ${additions})
+endmacro()
+
 # New Python support
 if(DEFINED Python_EXECUTABLE)
   set(PYTHON_EXECUTABLE "${Python_EXECUTABLE}")
@@ -92,55 +111,67 @@ if(PYBIND11_CUDA_TESTS)
   set(CMAKE_CUDA_STANDARD_REQUIRED ON)
 endif()
 
-# Full set of test files (you can override these; see below)
+# Full set of test files (you can override these; see below, overrides ignore extension)
+# Any test that has no extension is both .py and .cpp, so 'foo' will add 'foo.cpp' and 'foo.py'.
+# Any test that has an extension is exclusively that and handled as such.
 set(PYBIND11_TEST_FILES
-    test_async.cpp
-    test_buffers.cpp
-    test_builtin_casters.cpp
-    test_call_policies.cpp
-    test_callbacks.cpp
-    test_chrono.cpp
-    test_class.cpp
-    test_const_name.cpp
-    test_constants_and_functions.cpp
-    test_copy_move.cpp
-    test_custom_type_casters.cpp
-    test_custom_type_setup.cpp
-    test_docstring_options.cpp
-    test_eigen.cpp
-    test_enum.cpp
-    test_eval.cpp
-    test_exceptions.cpp
-    test_factory_constructors.cpp
-    test_gil_scoped.cpp
-    test_iostream.cpp
-    test_kwargs_and_defaults.cpp
-    test_local_bindings.cpp
-    test_methods_and_attributes.cpp
-    test_modules.cpp
-    test_multiple_inheritance.cpp
-    test_numpy_array.cpp
-    test_numpy_dtypes.cpp
-    test_numpy_vectorize.cpp
-    test_opaque_types.cpp
-    test_operator_overloading.cpp
-    test_pickling.cpp
-    test_pytypes.cpp
-    test_sequences_and_iterators.cpp
-    test_smart_ptr.cpp
-    test_stl.cpp
-    test_stl_binders.cpp
-    test_tagbased_polymorphic.cpp
-    test_thread.cpp
-    test_union.cpp
-    test_virtual_functions.cpp)
+    test_async
+    test_buffers
+    test_builtin_casters
+    test_call_policies
+    test_callbacks
+    test_chrono
+    test_class
+    test_const_name
+    test_constants_and_functions
+    test_copy_move
+    test_custom_type_casters
+    test_custom_type_setup
+    test_docstring_options
+    test_eigen
+    test_enum
+    test_eval
+    test_exceptions
+    test_factory_constructors
+    test_gil_scoped
+    test_iostream
+    test_kwargs_and_defaults
+    test_local_bindings
+    test_methods_and_attributes
+    test_modules
+    test_multiple_inheritance
+    test_numpy_array
+    test_numpy_dtypes
+    test_numpy_vectorize
+    test_opaque_types
+    test_operator_overloading
+    test_pickling
+    test_pytypes
+    test_sequences_and_iterators
+    test_smart_ptr
+    test_stl
+    test_stl_binders
+    test_tagbased_polymorphic
+    test_thread
+    test_union
+    test_virtual_functions)
 
 # Invoking cmake with something like:
 #     cmake -DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_pickling.cpp" ..
 # lets you override the tests that get compiled and run.  You can restore to all tests with:
 #     cmake -DPYBIND11_TEST_OVERRIDE= ..
 if(PYBIND11_TEST_OVERRIDE)
-  set(PYBIND11_TEST_FILES ${PYBIND11_TEST_OVERRIDE})
+  # Instead of doing a direct override here, we iterate over the overrides without extension and
+  # match them against entries from the PYBIND11_TEST_FILES, anything that not matches goes into the filter list.
+  string(REGEX REPLACE "\\.[^.;]*;" ";" TEST_OVERRIDE_NO_EXT "${PYBIND11_TEST_OVERRIDE};")
+  string(REGEX REPLACE "\\.[^.;]*;" ";" TEST_FILES_NO_EXT "${PYBIND11_TEST_FILES};")
+  # This allows the override to be done with extensions, preserving backwards compatibility.
+  foreach(test_name ${TEST_FILES_NO_EXT})
+    if(NOT ${test_name} IN_LIST TEST_OVERRIDE_NO_EXT
+    )# If not in the whitelist, add to be filtered out.
+      list(APPEND PYBIND11_TEST_FILTER ${test_name})
+    endif()
+  endforeach()
 endif()
 
 # You can also filter tests:
@@ -162,15 +193,34 @@ if(PYBIND11_CUDA_TESTS)
     "Skipping test_constants_and_functions due to incompatible exception specifications")
 endif()
 
-string(REPLACE ".cpp" ".py" PYBIND11_PYTEST_FILES "${PYBIND11_TEST_FILES}")
+# Now that the test filtering is complete, we need to split the list into the test for PYTEST
+# and the list for the cpp targets.
+set(PYBIND11_CPPTEST_FILES "")
+set(PYBIND11_PYTEST_FILES "")
+
+foreach(test_name ${PYBIND11_TEST_FILES})
+  if(test_name MATCHES "\\.py$") # Ends in .py, purely python test.
+    list(APPEND PYBIND11_PYTEST_FILES ${test_name})
+  elseif(test_name MATCHES "\\.cpp$") # Ends in .cpp, purely cpp test.
+    list(APPEND PYBIND11_CPPTEST_FILES ${test_name})
+  elseif(NOT test_name MATCHES "\\.") # No extension specified, assume both, add extension.
+    list(APPEND PYBIND11_PYTEST_FILES ${test_name}.py)
+    list(APPEND PYBIND11_CPPTEST_FILES ${test_name}.cpp)
+  else()
+    message(WARNING "Unhanded test extension in test: ${test_name}")
+  endif()
+endforeach()
+set(PYBIND11_TEST_FILES ${PYBIND11_CPPTEST_FILES})
+list(SORT PYBIND11_PYTEST_FILES)
 
 # Contains the set of test files that require pybind11_cross_module_tests to be
 # built; if none of these are built (i.e. because TEST_OVERRIDE is used and
 # doesn't include them) the second module doesn't get built.
-set(PYBIND11_CROSS_MODULE_TESTS test_exceptions.py test_local_bindings.py test_stl.py
-                                test_stl_binders.py)
+tests_extra_targets("test_exceptions.py;test_local_bindings.py;test_stl.py;test_stl_binders.py"
+                    "pybind11_cross_module_tests")
 
-set(PYBIND11_CROSS_MODULE_GIL_TESTS test_gil_scoped.py)
+# And add additional targets for other tests.
+tests_extra_targets("test_gil_scoped.py" "cross_module_gil_utils")
 
 set(PYBIND11_EIGEN_REPO
     "https://gitlab.com/libeigen/eigen.git"
@@ -353,21 +403,17 @@ endfunction()
 
 set(test_targets pybind11_tests)
 
-# Build pybind11_cross_module_tests if any test_whatever.py are being built that require it
-foreach(t ${PYBIND11_CROSS_MODULE_TESTS})
-  list(FIND PYBIND11_PYTEST_FILES ${t} i)
-  if(i GREATER -1)
-    list(APPEND test_targets pybind11_cross_module_tests)
-    break()
-  endif()
-endforeach()
-
-foreach(t ${PYBIND11_CROSS_MODULE_GIL_TESTS})
-  list(FIND PYBIND11_PYTEST_FILES ${t} i)
-  if(i GREATER -1)
-    list(APPEND test_targets cross_module_gil_utils)
-    break()
-  endif()
+# Check if any tests need extra targets by iterating through the mappings registered.
+foreach(i ${PYBIND11_TEST_EXTRA_TARGETS})
+  foreach(needle ${PYBIND11_TEST_EXTRA_TARGETS_NEEDLES_${i}})
+    if(needle IN_LIST PYBIND11_PYTEST_FILES)
+      # Add all the additional targets to the test list. List join in newer cmake.
+      foreach(extra_target ${PYBIND11_TEST_EXTRA_TARGETS_ADDITION_${i}})
+        list(APPEND test_targets ${extra_target})
+      endforeach()
+      break() # Breaks out of the needle search, continues with the next mapping.
+    endif()
+  endforeach()
 endforeach()
 
 # Support CUDA testing by forcing the target file to compile with NVCC

From f8d4aa47b6d9ffc7487d35598099971eb147d0ff Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Tue, 11 Jan 2022 20:34:16 -0500
Subject: [PATCH 272/638] Add clang-tidy readability checks for sus args
 (#3611)

---
 .clang-tidy                      | 1 +
 tests/test_virtual_functions.cpp | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.clang-tidy b/.clang-tidy
index dbe85a8b47..d853a703ce 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -46,6 +46,7 @@ readability-simplify-subscript-expr,
 readability-static-accessed-through-instance,
 readability-static-definition-in-anonymous-namespace,
 readability-string-compare,
+readability-suspicious-call-argument,
 readability-uniqueptr-delete-release,
 -bugprone-exception-escape,
 -bugprone-reserved-identifier,
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index f1a513180f..d98b57f174 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -350,7 +350,7 @@ TEST_SUBMODULE(virtual_functions, m) {
     m.def("add3", [](const AdderBase::Data& first, const AdderBase::Data& second, const AdderBase::Data& third,
                      const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
         adder(first, second, [&] (const AdderBase::Data& first_plus_second) {
-            adder(first_plus_second, third, visitor);
+            adder(first_plus_second, third, visitor); // NOLINT(readability-suspicious-call-argument)
         });
     });
 

From d2ec836712ed126b2726fdeee6a6695e777f7bf7 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Fri, 14 Jan 2022 14:22:47 -0500
Subject: [PATCH 273/638] Add support for nested C++11 exceptions (#3608)

* Add support for nested C++11 exceptions

* Remove wrong include

* Fix if directive

* Fix missing skipif

* Simplify code and try to work around MSVC bug

* Clarify comment

* Further simplify code

* Remove the last extra throw statement

* Qualify auto

* Fix typo

* Add missing return for consistency

* Fix clang-tidy complaint

* Fix python2 stub

* Make clang-tidy happy

* Fix compile error

* Fix python2 function signature

* Extract C++20 utility and backport

* Cleanup code a bit more

* Improve test case

* Consolidate code and fix signature

* Fix typo
---
 include/pybind11/detail/common.h    |  18 +++++
 include/pybind11/detail/internals.h | 108 ++++++++++++++++++++++++----
 tests/test_exceptions.cpp           |  10 ++-
 tests/test_exceptions.py            |   8 +++
 4 files changed, 131 insertions(+), 13 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index b08bbc5590..b3513da83b 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -36,6 +36,9 @@
 #    define PYBIND11_CPP14
 #    if __cplusplus >= 201703L
 #      define PYBIND11_CPP17
+#      if __cplusplus >= 202002L
+#        define PYBIND11_CPP20
+#      endif
 #    endif
 #  endif
 #elif defined(_MSC_VER) && __cplusplus == 199711L
@@ -45,6 +48,9 @@
 #    define PYBIND11_CPP14
 #    if _MSVC_LANG > 201402L && _MSC_VER >= 1910
 #      define PYBIND11_CPP17
+#      if _MSVC_LANG >= 202002L
+#        define PYBIND11_CPP20
+#      endif
 #    endif
 #  endif
 #endif
@@ -612,6 +618,18 @@ template <typename T> using remove_cv_t = typename std::remove_cv<T>::type;
 template <typename T> using remove_reference_t = typename std::remove_reference<T>::type;
 #endif
 
+#if defined(PYBIND11_CPP20)
+using std::remove_cvref;
+using std::remove_cvref_t;
+#else
+template <class T>
+struct remove_cvref {
+    using type = remove_cv_t<remove_reference_t<T>>;
+};
+template <class T>
+using remove_cvref_t = typename remove_cvref<T>::type;
+#endif
+
 /// Index sequences
 #if defined(PYBIND11_CPP14)
 using std::index_sequence;
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 98d21eb983..462d32474e 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "../pytypes.h"
+#include <exception>
 
 /// Tracks the `internals` and `type_info` ABI version independent of the main library version.
 ///
@@ -280,21 +281,104 @@ inline internals **&get_internals_pp() {
     return internals_pp;
 }
 
+#if PY_VERSION_HEX >= 0x03030000
+// forward decl
+inline void translate_exception(std::exception_ptr);
+
+template <class T,
+          enable_if_t<std::is_same<std::nested_exception, remove_cvref_t<T>>::value, int> = 0>
+bool handle_nested_exception(const T &exc, const std::exception_ptr &p) {
+    std::exception_ptr nested = exc.nested_ptr();
+    if (nested != nullptr && nested != p) {
+        translate_exception(nested);
+        return true;
+    }
+    return false;
+}
+
+template <class T,
+          enable_if_t<!std::is_same<std::nested_exception, remove_cvref_t<T>>::value, int> = 0>
+bool handle_nested_exception(const T &exc, const std::exception_ptr &p) {
+    if (auto *nep = dynamic_cast<const std::nested_exception *>(std::addressof(exc))) {
+        return handle_nested_exception(*nep, p);
+    }
+    return false;
+}
+
+#else
+
+template <class T>
+bool handle_nested_exception(const T &, std::exception_ptr &) {
+    return false;
+}
+#endif
+
+inline bool raise_err(PyObject *exc_type, const char *msg) {
+#if PY_VERSION_HEX >= 0x03030000
+    if (PyErr_Occurred()) {
+        raise_from(exc_type, msg);
+        return true;
+    }
+#endif
+    PyErr_SetString(exc_type, msg);
+    return false;
+};
+
 inline void translate_exception(std::exception_ptr p) {
+    if (!p) {
+        return;
+    }
     try {
-        if (p) std::rethrow_exception(p);
-    } catch (error_already_set &e)           { e.restore();                                    return;
-    } catch (const builtin_exception &e)     { e.set_error();                                  return;
-    } catch (const std::bad_alloc &e)        { PyErr_SetString(PyExc_MemoryError,   e.what()); return;
-    } catch (const std::domain_error &e)     { PyErr_SetString(PyExc_ValueError,    e.what()); return;
-    } catch (const std::invalid_argument &e) { PyErr_SetString(PyExc_ValueError,    e.what()); return;
-    } catch (const std::length_error &e)     { PyErr_SetString(PyExc_ValueError,    e.what()); return;
-    } catch (const std::out_of_range &e)     { PyErr_SetString(PyExc_IndexError,    e.what()); return;
-    } catch (const std::range_error &e)      { PyErr_SetString(PyExc_ValueError,    e.what()); return;
-    } catch (const std::overflow_error &e)   { PyErr_SetString(PyExc_OverflowError, e.what()); return;
-    } catch (const std::exception &e)        { PyErr_SetString(PyExc_RuntimeError,  e.what()); return;
+        std::rethrow_exception(p);
+    } catch (error_already_set &e) {
+        handle_nested_exception(e, p);
+        e.restore();
+        return;
+    } catch (const builtin_exception &e) {
+        // Could not use template since it's an abstract class.
+        if (auto *nep = dynamic_cast<const std::nested_exception *>(std::addressof(e))) {
+            handle_nested_exception(*nep, p);
+        }
+        e.set_error();
+        return;
+    } catch (const std::bad_alloc &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_MemoryError, e.what());
+        return;
+    } catch (const std::domain_error &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_ValueError, e.what());
+        return;
+    } catch (const std::invalid_argument &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_ValueError, e.what());
+        return;
+    } catch (const std::length_error &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_ValueError, e.what());
+        return;
+    } catch (const std::out_of_range &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_IndexError, e.what());
+        return;
+    } catch (const std::range_error &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_ValueError, e.what());
+        return;
+    } catch (const std::overflow_error &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_OverflowError, e.what());
+        return;
+    } catch (const std::exception &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_RuntimeError, e.what());
+        return;
+    } catch (const std::nested_exception &e) {
+        handle_nested_exception(e, p);
+        raise_err(PyExc_RuntimeError, "Caught an unknown nested exception!");
+        return;
     } catch (...) {
-        PyErr_SetString(PyExc_RuntimeError, "Caught an unknown exception!");
+        raise_err(PyExc_RuntimeError, "Caught an unknown exception!");
         return;
     }
 }
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 25adb32ed1..3aa9673828 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -11,6 +11,8 @@
 #include "local_bindings.h"
 
 #include "pybind11_tests.h"
+#include <exception>
+#include <stdexcept>
 #include <utility>
 
 // A type that should be raised as an exception in Python
@@ -105,7 +107,6 @@ struct PythonAlreadySetInDestructor {
     py::str s;
 };
 
-
 TEST_SUBMODULE(exceptions, m) {
     m.def("throw_std_exception", []() {
         throw std::runtime_error("This exception was intentionally thrown.");
@@ -281,5 +282,12 @@ TEST_SUBMODULE(exceptions, m) {
         }
     });
 
+    m.def("throw_nested_exception", []() {
+        try {
+            throw std::runtime_error("Inner Exception");
+        } catch (const std::runtime_error &) {
+            std::throw_with_nested(std::runtime_error("Outer Exception"));
+        }
+    });
 #endif
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 56201a81c5..d698b1312e 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -239,6 +239,14 @@ def pycatch(exctype, f, *args):
     assert str(excinfo.value) == "this is a helper-defined translated exception"
 
 
+@pytest.mark.skipif("env.PY2")
+def test_throw_nested_exception():
+    with pytest.raises(RuntimeError) as excinfo:
+        m.throw_nested_exception()
+    assert str(excinfo.value) == "Outer Exception"
+    assert str(excinfo.value.__cause__) == "Inner Exception"
+
+
 # This can often happen if you wrap a pybind11 class in a Python wrapper
 def test_invalid_repr():
     class MyRepr(object):

From 7e7c558530430615d889b5ed41954a2fd7015a31 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 14 Jan 2022 16:16:52 -0800
Subject: [PATCH 274/638] Fixing obvious minor typo (missing `D` in
 `-DOWNLOAD_EIGEN=ON`).

Typo introduced with PR #2377.

Adopting fix from @AWhetter PR #2621 (to keep unrelated changes cleanly separated).
---
 .github/CONTRIBUTING.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index c08bb173f2..e8294c83c3 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -120,7 +120,7 @@ The valid options are:
 * `-DPYBIND11_NOPYTHON=ON`: Disable all Python searching (disables tests)
 * `-DBUILD_TESTING=ON`: Enable the tests
 * `-DDOWNLOAD_CATCH=ON`: Download catch to build the C++ tests
-* `-DOWNLOAD_EIGEN=ON`: Download Eigen for the NumPy tests
+* `-DDOWNLOAD_EIGEN=ON`: Download Eigen for the NumPy tests
 * `-DPYBIND11_INSTALL=ON/OFF`: Enable the install target (on by default for the
   master project)
 * `-DUSE_PYTHON_INSTALL_DIR=ON`: Try to install into the python dir

From 5194855900f0574106877646c60d302cc944a3b8 Mon Sep 17 00:00:00 2001
From: Sergei Izmailov <sergei.a.izmailov@gmail.com>
Date: Sun, 16 Jan 2022 18:05:46 +0300
Subject: [PATCH 275/638] Render `py::bool_` and `py::float_` without `_` in
 docstrings (#3622)

* Render `py::bool_` as `bool` in docstrings

* Render `py::float_` as `float` in docstrings
---
 include/pybind11/cast.h | 2 ++
 tests/test_pytypes.cpp  | 4 ++++
 tests/test_pytypes.py   | 8 ++++++++
 3 files changed, 14 insertions(+)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 7930fb994b..165102443c 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -765,10 +765,12 @@ template <typename base, typename deleter> struct is_holder_type<base, std::uniq
     std::true_type {};
 
 template <typename T> struct handle_type_name { static constexpr auto name = const_name<T>(); };
+template <> struct handle_type_name<bool_> { static constexpr auto name = const_name("bool"); };
 template <> struct handle_type_name<bytes> { static constexpr auto name = const_name(PYBIND11_BYTES_NAME); };
 template <> struct handle_type_name<int_> { static constexpr auto name = const_name("int"); };
 template <> struct handle_type_name<iterable> { static constexpr auto name = const_name("Iterable"); };
 template <> struct handle_type_name<iterator> { static constexpr auto name = const_name("Iterator"); };
+template <> struct handle_type_name<float_> { static constexpr auto name = const_name("float"); };
 template <> struct handle_type_name<none> { static constexpr auto name = const_name("None"); };
 template <> struct handle_type_name<args> { static constexpr auto name = const_name("*args"); };
 template <> struct handle_type_name<kwargs> { static constexpr auto name = const_name("**kwargs"); };
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 9a1e918818..85cb98fcbf 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -13,12 +13,16 @@
 
 
 TEST_SUBMODULE(pytypes, m) {
+    // test_bool
+    m.def("get_bool", []{return py::bool_(false);});
     // test_int
     m.def("get_int", []{return py::int_(0);});
     // test_iterator
     m.def("get_iterator", []{return py::iterator();});
     // test_iterable
     m.def("get_iterable", []{return py::iterable();});
+    // test_float
+    m.def("get_float", []{return py::float_(0.0f);});
     // test_list
     m.def("list_no_args", []() { return py::list{}; });
     m.def("list_ssize_t", []() { return py::list{(py::ssize_t) 0}; });
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 5215b79bc1..2cd6c3f03a 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -10,6 +10,10 @@
 from pybind11_tests import pytypes as m
 
 
+def test_bool(doc):
+    assert doc(m.get_bool) == "get_bool() -> bool"
+
+
 def test_int(doc):
     assert doc(m.get_int) == "get_int() -> int"
 
@@ -22,6 +26,10 @@ def test_iterable(doc):
     assert doc(m.get_iterable) == "get_iterable() -> Iterable"
 
 
+def test_float(doc):
+    assert doc(m.get_float) == "get_float() -> float"
+
+
 def test_list(capture, doc):
     assert m.list_no_args() == []
     assert m.list_ssize_t() == []

From 3a1eddab54e48bd80cc167c242bc1d9f537498c1 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 16 Jan 2022 21:47:58 -0500
Subject: [PATCH 276/638] chore(deps): bump jwlawson/actions-setup-cmake from
 1.11 to 1.12 (#3625)

Bumps [jwlawson/actions-setup-cmake](https://github.com/jwlawson/actions-setup-cmake) from 1.11 to 1.12.
- [Release notes](https://github.com/jwlawson/actions-setup-cmake/releases)
- [Commits](https://github.com/jwlawson/actions-setup-cmake/compare/v1.11...v1.12)

---
updated-dependencies:
- dependency-name: jwlawson/actions-setup-cmake
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 12 ++++++------
 .github/workflows/configure.yml |  2 +-
 .github/workflows/upstream.yml  |  2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c56e4003b3..6e0ffa63ab 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -78,7 +78,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -216,7 +216,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -471,7 +471,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Configure
       shell: bash
@@ -762,7 +762,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.10.0
@@ -809,7 +809,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.10.0
@@ -868,7 +868,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Prepare env
       run: |
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index d60025e5c5..66ab0e3d78 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -55,7 +55,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
       with:
         cmake-version: ${{ matrix.cmake }}
 
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 654947425f..138c9ad292 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -31,7 +31,7 @@ jobs:
       run: sudo apt-get install libboost-dev
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.11
+      uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Prepare env
       run: |

From 9ec1128c7aac3d069a4ec2bd1dfc7f57c6526d1c Mon Sep 17 00:00:00 2001
From: Nimrod <Nimrodcowboy@gmail.com>
Date: Wed, 19 Jan 2022 15:22:42 +0800
Subject: [PATCH 277/638] Fix typo in doc (#3628)

---
 docs/advanced/functions.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index ea9f352234..d37b8ecab1 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -120,7 +120,7 @@ targeted arguments can be passed through the :class:`cpp_function` constructor:
 .. code-block:: cpp
 
     class_<MyClass>(m, "MyClass")
-        .def_property("data"
+        .def_property("data",
             py::cpp_function(&MyClass::getData, py::return_value_policy::copy),
             py::cpp_function(&MyClass::setData)
         );

From dedda228f44a64d73afff120fd6e47b2a27170c2 Mon Sep 17 00:00:00 2001
From: yangliz5 <li002252@umn.edu>
Date: Wed, 26 Jan 2022 00:32:33 -0600
Subject: [PATCH 278/638] Fix a typo in class.rst (#3648)

Fix a typo in class.rst
---
 docs/advanced/classes.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 6330af5eb4..ba006252a4 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -9,7 +9,7 @@ that you are already familiar with the basics from :doc:`/classes`.
 Overriding virtual functions in Python
 ======================================
 
-Suppose that a C++ class or interface has a virtual function that we'd like to
+Suppose that a C++ class or interface has a virtual function that we'd like
 to override from within Python (we'll focus on the class ``Animal``; ``Dog`` is
 given as a specific example of how one would do this with traditional C++
 code).

From bcb6d63ce99752dd735b5abf128f498458999a66 Mon Sep 17 00:00:00 2001
From: Liam Keegan <liam@keegan.ch>
Date: Wed, 26 Jan 2022 17:18:08 +0100
Subject: [PATCH 279/638] fix msys ci python issue (#3651)

* msys ci: un-pin setup-msys2 action version

* msys ci: explicitly set PYTHONHOME and PYTHONPATH for c++ and interface tests (to workaround https://github.com/msys2/setup-msys2/issues/167)
---
 .github/workflows/ci.yml | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6e0ffa63ab..38b85aeef4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -904,8 +904,7 @@ jobs:
           - { sys: mingw64, env: x86_64 }
           - { sys: mingw32, env: i686 }
     steps:
-    # Force version because of https://github.com/msys2/setup-msys2/issues/167
-    - uses: msys2/setup-msys2@v2.4.2
+    - uses: msys2/setup-msys2@v2
       with:
         msystem: ${{matrix.sys}}
         install: >-
@@ -935,10 +934,10 @@ jobs:
       run: cmake --build build --target pytest -j 2
 
     - name: C++11 tests
-      run: cmake --build build --target cpptest -j 2
+      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build --target cpptest -j 2
 
     - name: Interface test C++11
-      run: cmake --build build --target test_cmake_build
+      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build --target test_cmake_build
 
     - name: Clean directory
       run: git clean -fdx
@@ -953,10 +952,10 @@ jobs:
       run: cmake --build build2 --target pytest -j 2
 
     - name: C++14 tests
-      run: cmake --build build2 --target cpptest -j 2
+      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target cpptest -j 2
 
     - name: Interface test C++14
-      run: cmake --build build2 --target test_cmake_build
+      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target test_cmake_build
 
     - name: Clean directory
       run: git clean -fdx
@@ -971,7 +970,7 @@ jobs:
       run: cmake --build build3 --target pytest -j 2
 
     - name: C++17 tests
-      run: cmake --build build3 --target cpptest -j 2
+      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build3 --target cpptest -j 2
 
     - name: Interface test C++17
-      run: cmake --build build3 --target test_cmake_build
+      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build3 --target test_cmake_build

From ec81e8e778accff323d76cd0ab0f3f280dc05f26 Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Wed, 26 Jan 2022 20:03:52 -0500
Subject: [PATCH 280/638] Propagate py::multiple_inheritance to all children
 (#3650)

* Add tests demonstrating smart_holder issues with multiple inheritance

* Propagate C++ multiple inheritance markers to all children

- Makes py::multiple_inheritance only needed in base classes hidden from pybind11
---
 include/pybind11/pybind11.h         |   3 +
 tests/test_multiple_inheritance.cpp |  83 ++++++++++++++++++++
 tests/test_multiple_inheritance.py  | 114 ++++++++++++++++++++++++++++
 3 files changed, 200 insertions(+)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 344a18c569..df33d51829 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1206,10 +1206,13 @@ class generic_type : public object {
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {
             mark_parents_nonsimple(tinfo->type);
             tinfo->simple_ancestors = false;
+            tinfo->simple_type = false;
         }
         else if (rec.bases.size() == 1) {
             auto parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
             tinfo->simple_ancestors = parent_tinfo->simple_ancestors;
+            // a child of a non-simple type can never be a simple type
+            tinfo->simple_type = parent_tinfo->simple_type;
         }
 
         if (rec.module_local) {
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index 6963197a5c..44b9876eb4 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -230,4 +230,87 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def("c1", [](C1 *self) { return self; });
     py::class_<D, C0, C1>(m, "D")
         .def(py::init<>());
+
+    // test_pr3635_diamond_*
+    // - functions are get_{base}_{var}, return {var}
+    struct MVB {
+        MVB() = default;
+        MVB(const MVB&) = default;
+        virtual ~MVB() = default;
+
+        int b = 1;
+        int get_b_b() const { return b; }
+    };
+    struct MVC : virtual MVB {
+        int c = 2;
+        int get_c_b() const { return b; }
+        int get_c_c() const { return c; }
+    };
+    struct MVD0 : virtual MVC {
+        int d0 = 3;
+        int get_d0_b() const { return b; }
+        int get_d0_c() const { return c; }
+        int get_d0_d0() const { return d0; }
+    };
+    struct MVD1 : virtual MVC {
+        int d1 = 4;
+        int get_d1_b() const { return b; }
+        int get_d1_c() const { return c; }
+        int get_d1_d1() const { return d1; }
+    };
+    struct MVE : virtual MVD0, virtual MVD1 {
+        int e = 5;
+        int get_e_b() const { return b; }
+        int get_e_c() const { return c; }
+        int get_e_d0() const { return d0; }
+        int get_e_d1() const { return d1; }
+        int get_e_e() const { return e; }
+    };
+    struct MVF : virtual MVE {
+        int f = 6;
+        int get_f_b() const { return b; }
+        int get_f_c() const { return c; }
+        int get_f_d0() const { return d0; }
+        int get_f_d1() const { return d1; }
+        int get_f_e() const { return e; }
+        int get_f_f() const { return f; }
+    };
+    py::class_<MVB>(m, "MVB")
+        .def(py::init<>())
+        .def("get_b_b", &MVB::get_b_b)
+        .def_readwrite("b", &MVB::b);
+    py::class_<MVC, MVB>(m, "MVC")
+        .def(py::init<>())
+        .def("get_c_b", &MVC::get_c_b)
+        .def("get_c_c", &MVC::get_c_c)
+        .def_readwrite("c", &MVC::c);
+    py::class_<MVD0, MVC>(m, "MVD0")
+        .def(py::init<>())
+        .def("get_d0_b", &MVD0::get_d0_b)
+        .def("get_d0_c", &MVD0::get_d0_c)
+        .def("get_d0_d0", &MVD0::get_d0_d0)
+        .def_readwrite("d0", &MVD0::d0);
+    py::class_<MVD1, MVC>(m, "MVD1")
+        .def(py::init<>())
+        .def("get_d1_b", &MVD1::get_d1_b)
+        .def("get_d1_c", &MVD1::get_d1_c)
+        .def("get_d1_d1", &MVD1::get_d1_d1)
+        .def_readwrite("d1", &MVD1::d1);
+    py::class_<MVE, MVD0, MVD1>(m, "MVE")
+        .def(py::init<>())
+        .def("get_e_b", &MVE::get_e_b)
+        .def("get_e_c", &MVE::get_e_c)
+        .def("get_e_d0", &MVE::get_e_d0)
+        .def("get_e_d1", &MVE::get_e_d1)
+        .def("get_e_e", &MVE::get_e_e)
+        .def_readwrite("e", &MVE::e);
+    py::class_<MVF, MVE>(m, "MVF")
+        .def(py::init<>())
+        .def("get_f_b", &MVF::get_f_b)
+        .def("get_f_c", &MVF::get_f_c)
+        .def("get_f_d0", &MVF::get_f_d0)
+        .def("get_f_d1", &MVF::get_f_d1)
+        .def("get_f_e", &MVF::get_f_e)
+        .def("get_f_f", &MVF::get_f_f)
+        .def_readwrite("f", &MVF::f);
 }
diff --git a/tests/test_multiple_inheritance.py b/tests/test_multiple_inheritance.py
index a02c313001..71741b9256 100644
--- a/tests/test_multiple_inheritance.py
+++ b/tests/test_multiple_inheritance.py
@@ -358,3 +358,117 @@ def test_diamond_inheritance():
     assert d is d.c0().b()
     assert d is d.c1().b()
     assert d is d.c0().c1().b().c0().b()
+
+
+def test_pr3635_diamond_b():
+    o = m.MVB()
+    assert o.b == 1
+
+    assert o.get_b_b() == 1
+
+
+def test_pr3635_diamond_c():
+    o = m.MVC()
+    assert o.b == 1
+    assert o.c == 2
+
+    assert o.get_b_b() == 1
+    assert o.get_c_b() == 1
+
+    assert o.get_c_c() == 2
+
+
+def test_pr3635_diamond_d0():
+    o = m.MVD0()
+    assert o.b == 1
+    assert o.c == 2
+    assert o.d0 == 3
+
+    assert o.get_b_b() == 1
+    assert o.get_c_b() == 1
+    assert o.get_d0_b() == 1
+
+    assert o.get_c_c() == 2
+    assert o.get_d0_c() == 2
+
+    assert o.get_d0_d0() == 3
+
+
+def test_pr3635_diamond_d1():
+    o = m.MVD1()
+    assert o.b == 1
+    assert o.c == 2
+    assert o.d1 == 4
+
+    assert o.get_b_b() == 1
+    assert o.get_c_b() == 1
+    assert o.get_d1_b() == 1
+
+    assert o.get_c_c() == 2
+    assert o.get_d1_c() == 2
+
+    assert o.get_d1_d1() == 4
+
+
+def test_pr3635_diamond_e():
+    o = m.MVE()
+    assert o.b == 1
+    assert o.c == 2
+    assert o.d0 == 3
+    assert o.d1 == 4
+    assert o.e == 5
+
+    assert o.get_b_b() == 1
+    assert o.get_c_b() == 1
+    assert o.get_d0_b() == 1
+    assert o.get_d1_b() == 1
+    assert o.get_e_b() == 1
+
+    assert o.get_c_c() == 2
+    assert o.get_d0_c() == 2
+    assert o.get_d1_c() == 2
+    assert o.get_e_c() == 2
+
+    assert o.get_d0_d0() == 3
+    assert o.get_e_d0() == 3
+
+    assert o.get_d1_d1() == 4
+    assert o.get_e_d1() == 4
+
+    assert o.get_e_e() == 5
+
+
+def test_pr3635_diamond_f():
+    o = m.MVF()
+    assert o.b == 1
+    assert o.c == 2
+    assert o.d0 == 3
+    assert o.d1 == 4
+    assert o.e == 5
+    assert o.f == 6
+
+    assert o.get_b_b() == 1
+    assert o.get_c_b() == 1
+    assert o.get_d0_b() == 1
+    assert o.get_d1_b() == 1
+    assert o.get_e_b() == 1
+    assert o.get_f_b() == 1
+
+    assert o.get_c_c() == 2
+    assert o.get_d0_c() == 2
+    assert o.get_d1_c() == 2
+    assert o.get_e_c() == 2
+    assert o.get_f_c() == 2
+
+    assert o.get_d0_d0() == 3
+    assert o.get_e_d0() == 3
+    assert o.get_f_d0() == 3
+
+    assert o.get_d1_d1() == 4
+    assert o.get_e_d1() == 4
+    assert o.get_f_d1() == 4
+
+    assert o.get_e_e() == 5
+    assert o.get_f_e() == 5
+
+    assert o.get_f_f() == 6

From 177928840ec1f7dc7ba8675056cf334f84aab193 Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Sat, 29 Jan 2022 17:38:30 -0500
Subject: [PATCH 281/638] Document how to bind templates (#3665)

---
 docs/advanced/classes.rst   | 52 +++++++++++++++++++++++++++++++++++++
 docs/advanced/functions.rst | 35 +++++++++++++++++++++++++
 2 files changed, 87 insertions(+)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index ba006252a4..f3339336dc 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -1161,6 +1161,58 @@ error:
 
 .. versionadded:: 2.6
 
+Binding classes with template parameters
+========================================
+
+pybind11 can also wrap classes that have template parameters. Consider these classes:
+
+.. code-block:: cpp
+
+    struct Cat {};
+    struct Dog {};
+
+    template <typename PetType>
+    struct Cage {
+        Cage(PetType& pet);
+        PetType& get();
+    };
+
+C++ templates may only be instantiated at compile time, so pybind11 can only
+wrap instantiated templated classes. You cannot wrap a non-instantiated template:
+
+.. code-block:: cpp
+
+    // BROKEN (this will not compile)
+    py::class_<Cage>(m, "Cage");
+        .def("get", &Cage::get);
+
+You must explicitly specify each template/type combination that you want to
+wrap separately.
+
+.. code-block:: cpp
+
+    // ok
+    py::class_<Cage<Cat>>(m, "CatCage")
+        .def("get", &Cage<Cat>::get);
+
+    // ok
+    py::class_<Cage<Dog>>(m, "DogCage")
+        .def("get", &Cage<Dog>::get);
+
+If your class methods have template parameters you can wrap those as well,
+but once again each instantiation must be explicitly specified:
+
+.. code-block:: cpp
+
+    typename <typename T>
+    struct MyClass {
+        template <typename V>
+        T fn(V v);
+    };
+
+    py::class<MyClass<int>>(m, "MyClassT")
+        .def("fn", &MyClass<int>::fn<std::string>);
+
 Custom automatic downcasters
 ============================
 
diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index d37b8ecab1..bf5b5fa00d 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -578,3 +578,38 @@ prefers earlier-defined overloads to later-defined ones.
 .. versionadded:: 2.6
 
     The ``py::prepend()`` tag.
+
+Binding functions with template parameters
+==========================================
+
+You can bind functions that have template parameters. Here's a function:
+
+.. code-block:: cpp
+
+    template <typename T>
+    void set(T t);
+
+C++ templates cannot be instantiated at runtime, so you cannot bind the
+non-instantiated function:
+
+.. code-block:: cpp
+
+    // BROKEN (this will not compile)
+    m.def("set", &set);
+
+You must bind each instantiated function template separately. You may bind
+each instantiation with the same name, which will be treated the same as
+an overloaded function:
+
+.. code-block:: cpp
+
+    m.def("set", &set<int>);
+    m.def("set", &set<std::string>);
+
+Sometimes it's more clear to bind them with separate names, which is also
+an option:
+
+.. code-block:: cpp
+
+    m.def("setInt", &set<int>);
+    m.def("setString", &set<std::string>);

From 07103d6570f9d89ad2bdf05c3758addeaad78443 Mon Sep 17 00:00:00 2001
From: Mattia Basaglia <glax@dragon.best>
Date: Sat, 29 Jan 2022 23:44:48 +0100
Subject: [PATCH 282/638] Remove extra semicolon (#3666)

---
 include/pybind11/detail/internals.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 462d32474e..5c11b40a41 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -322,7 +322,7 @@ inline bool raise_err(PyObject *exc_type, const char *msg) {
 #endif
     PyErr_SetString(exc_type, msg);
     return false;
-};
+}
 
 inline void translate_exception(std::exception_ptr p) {
     if (!p) {

From dc4717bac28b2a320e32e3f823eb4d7da3736aeb Mon Sep 17 00:00:00 2001
From: Mattia Basaglia <glax@dragon.best>
Date: Mon, 31 Jan 2022 17:10:45 +0100
Subject: [PATCH 283/638] fix: module extension detection for python 3.10
 (#3663)

* Fix module extension detection for python 3.10

* Fix for python < 3.10

* Use importlib
---
 tools/pybind11NewTools.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 9e2fd2b40d..0b4e21ccef 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -110,7 +110,7 @@ if(NOT DEFINED PYTHON_MODULE_EXTENSION)
   execute_process(
     COMMAND
       "${${_Python}_EXECUTABLE}" "-c"
-      "from distutils import sysconfig as s;print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'))"
+      "import sys, importlib; s = importlib.import_module('distutils.sysconfig' if sys.version_info < (3, 10) else 'sysconfig'); print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'))"
     OUTPUT_VARIABLE _PYTHON_MODULE_EXTENSION
     ERROR_VARIABLE _PYTHON_MODULE_EXTENSION_ERR
     OUTPUT_STRIP_TRAILING_WHITESPACE)

From bf7e5f9284a977d9d177b4dc4128542c291818f0 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 31 Jan 2022 11:38:06 -0500
Subject: [PATCH 284/638] fix(setup): support overriding CMake args (#3577)

* fix: support conda-forge

* Update setup.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 setup.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/setup.py b/setup.py
index a2326287d8..0e73489820 100644
--- a/setup.py
+++ b/setup.py
@@ -146,6 +146,13 @@ def remove_output(*sources):
             "-DBUILD_TESTING=OFF",
             "-DPYBIND11_NOPYTHON=ON",
         ]
+        if "CMAKE_ARGS" in os.environ:
+            fcommand = [
+                c
+                for c in os.environ["CMAKE_ARGS"].split()
+                if "DCMAKE_INSTALL_PREFIX" not in c
+            ]
+            cmd += fcommand
         cmake_opts = dict(cwd=DIR, stdout=sys.stdout, stderr=sys.stderr)
         subprocess.check_call(cmd, **cmake_opts)
         subprocess.check_call(["cmake", "--install", tmpdir], **cmake_opts)

From 3a8d92308d3291e21c55baca8aa7b8dd5b3a8d56 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 31 Jan 2022 12:19:48 -0500
Subject: [PATCH 285/638] Fix caster optimization regression introduced in
 #3650 (#3659)

* Fix optimization bug introduced in #3650

* Add simple Python extension test for MVF

* Improve comments

* Clarify comment

* Clarify another comment

* Add test docstring

* Fix typo
---
 include/pybind11/detail/internals.h |  4 +++-
 include/pybind11/pybind11.h         | 11 ++++++-----
 tests/test_multiple_inheritance.cpp |  2 +-
 tests/test_multiple_inheritance.py  | 22 ++++++++++++++++++++++
 4 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 5c11b40a41..9edb9492e2 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -200,7 +200,9 @@ struct type_info {
     void *get_buffer_data = nullptr;
     void *(*module_local_load)(PyObject *, const type_info *) = nullptr;
     /* A simple type never occurs as a (direct or indirect) parent
-     * of a class that makes use of multiple inheritance */
+     * of a class that makes use of multiple inheritance.
+     * A type can be simple even if it has non-simple ancestors as long as it has no descendants.
+     */
     bool simple_type : 1;
     /* True if there is no multiple inheritance in this type's inheritance tree */
     bool simple_ancestors : 1;
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index df33d51829..fd60ea29f2 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1206,13 +1206,14 @@ class generic_type : public object {
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {
             mark_parents_nonsimple(tinfo->type);
             tinfo->simple_ancestors = false;
-            tinfo->simple_type = false;
         }
         else if (rec.bases.size() == 1) {
-            auto parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
-            tinfo->simple_ancestors = parent_tinfo->simple_ancestors;
-            // a child of a non-simple type can never be a simple type
-            tinfo->simple_type = parent_tinfo->simple_type;
+            auto *parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
+            assert(parent_tinfo != nullptr);
+            bool parent_simple_ancestors = parent_tinfo->simple_ancestors;
+            tinfo->simple_ancestors = parent_simple_ancestors;
+            // The parent can no longer be a simple type if it has MI and has a child
+            parent_tinfo->simple_type = parent_tinfo->simple_type && parent_simple_ancestors;
         }
 
         if (rec.module_local) {
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index 44b9876eb4..4689df4e46 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -235,7 +235,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // - functions are get_{base}_{var}, return {var}
     struct MVB {
         MVB() = default;
-        MVB(const MVB&) = default;
+        MVB(const MVB &) = default;
         virtual ~MVB() = default;
 
         int b = 1;
diff --git a/tests/test_multiple_inheritance.py b/tests/test_multiple_inheritance.py
index 71741b9256..abdf25d608 100644
--- a/tests/test_multiple_inheritance.py
+++ b/tests/test_multiple_inheritance.py
@@ -472,3 +472,25 @@ def test_pr3635_diamond_f():
     assert o.get_f_e() == 5
 
     assert o.get_f_f() == 6
+
+
+def test_python_inherit_from_mi():
+    """Tests extending a Python class from a single inheritor of a MI class"""
+
+    class PyMVF(m.MVF):
+        g = 7
+
+        def get_g_g(self):
+            return self.g
+
+    o = PyMVF()
+
+    assert o.b == 1
+    assert o.c == 2
+    assert o.d0 == 3
+    assert o.d1 == 4
+    assert o.e == 5
+    assert o.f == 6
+    assert o.g == 7
+
+    assert o.get_g_g() == 7

From 978617f6b548cdf15aba81fd79caacf455131e84 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 31 Jan 2022 12:57:32 -0500
Subject: [PATCH 286/638] fix issue 3668 by removing bool casts in numpy.h
 (#3669)

---
 include/pybind11/numpy.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 8e83b506e0..95a743acec 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -170,10 +170,10 @@ struct npy_api {
     }
 
     bool PyArray_Check_(PyObject *obj) const {
-        return (bool) PyObject_TypeCheck(obj, PyArray_Type_);
+        return PyObject_TypeCheck(obj, PyArray_Type_) != 0;
     }
     bool PyArrayDescr_Check_(PyObject *obj) const {
-        return (bool) PyObject_TypeCheck(obj, PyArrayDescr_Type_);
+        return PyObject_TypeCheck(obj, PyArrayDescr_Type_) != 0;
     }
 
     unsigned int (*PyArray_GetNDArrayCFeatureVersion_)();

From ce18721d830a9deb8cf1883b513bcb8f98090c35 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 31 Jan 2022 15:13:05 -0500
Subject: [PATCH 287/638] Ensure TypeError use raise_from for C++->Python
 overload res. (#3671)

---
 include/pybind11/pybind11.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index fd60ea29f2..ede35e1867 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -988,6 +988,13 @@ class cpp_function : public function {
             }
 
             append_note_if_missing_header_is_suspected(msg);
+#if PY_VERSION_HEX >= 0x03030000
+            // Attach additional error info to the exception if supported
+            if (PyErr_Occurred()) {
+                raise_from(PyExc_TypeError, msg.c_str());
+                return nullptr;
+            }
+#endif
             PyErr_SetString(PyExc_TypeError, msg.c_str());
             return nullptr;
         }

From 21e10945a06bcf3e15d9a72f64cf832147dbaab2 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 2 Feb 2022 11:25:28 -0500
Subject: [PATCH 288/638] ci: move centos 8 to stream (#3675)

---
 .github/workflows/ci.yml | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 38b85aeef4..050c525cee 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -600,11 +600,11 @@ jobs:
       fail-fast: false
       matrix:
         centos:
-          - 7  # GCC 4.8
-          - 8
+          - centos7  # GCC 4.8
+          - stream8
 
     name: "🐍 3 • CentOS ${{ matrix.centos }} • x64"
-    container: "centos:${{ matrix.centos }}"
+    container: "quay.io/centos/centos:${{ matrix.centos }}"
 
     steps:
     - uses: actions/checkout@v2
@@ -619,22 +619,11 @@ jobs:
       run: |
         python3 -m pip install cmake -r tests/requirements.txt
 
-    - name: VAR_BUILD_TYPE 7
-      if: matrix.centos == 7
-      run: echo MinSizeRel > VAR_BUILD_TYPE
-
-    # Using Release to avoid segfault that appeared around 2021-06-04,
-    # apparently when the gcc version changed from 8.3 to 8.4.
-    - name: VAR_BUILD_TYPE 8
-      if: matrix.centos == 8
-      run: echo Release > VAR_BUILD_TYPE
-
-    # Temporally disabling EIGEN due to SSL issue in CentOS 7
     - name: Configure
       shell: bash
       run: >
         cmake -S . -B build
-        -DCMAKE_BUILD_TYPE=$(cat VAR_BUILD_TYPE)
+        -DCMAKE_BUILD_TYPE=MinSizeRel
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON

From 0f6ad9105ca8376863e10b0eaf1cbc1a5d561038 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 2 Feb 2022 16:08:44 -0500
Subject: [PATCH 289/638] docs: update changelog for 2.9.1 (#3670)

* docs: update changelog for 2.9.1

* Update changelog.rst

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update changelog.rst

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 docs/changelog.rst | 53 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index c05e7d3c55..16bf3aa3f3 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,6 +6,59 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
+Version 2.9.1 (Feb 2, 2022)
+---------------------------
+
+Changes:
+
+* If possible, attach Python exception with ``py::raise_from`` to ``TypeError``
+  when casting from C++ to Python. This will give additional info if Python
+  exceptions occur in the caster. Adds a test case of trying to convert a set
+  from C++ to Python when the hash function is not defined in Python.
+  `#3605 <https://github.com/pybind/pybind11/pull/3605>`_
+
+* Add a mapping of C++11 nested exceptions to their Python exception
+  equivalent using ``py::raise_from``. This attaches the nested exceptions in
+  Python using the ``__cause__`` field.
+  `#3608 <https://github.com/pybind/pybind11/pull/3608>`_
+
+* Propagate Python exception traceback using ``raise_from`` if a pybind11
+  function runs out of overloads.
+  `#3671 <https://github.com/pybind/pybind11/pull/3671>`_
+
+* ``py::multiple_inheritance`` is now only needed when C++ bases are hidden
+  from pybind11.
+  `#3650 <https://github.com/pybind/pybind11/pull/3650>`_ and
+  `#3659 <https://github.com/pybind/pybind11/pull/3659>`_
+
+
+Bug fixes:
+
+* Remove a boolean cast in ``numpy.h`` that causes MSVC C4800 warnings when
+  compiling against Python 3.10 or newer.
+  `#3669 <https://github.com/pybind/pybind11/pull/3669>`_
+
+* Render ``py::bool_`` and ``py::float_`` as ``bool`` and ``float``
+  respectively.
+  `#3622 <https://github.com/pybind/pybind11/pull/3622>`_
+
+Build system improvements:
+
+* Fix CMake extension suffix computation on Python 3.10+.
+  `#3663 <https://github.com/pybind/pybind11/pull/3663>`_
+
+* Allow ``CMAKE_ARGS`` to override CMake args in pybind11's own ``setup.py``.
+  `#3577 <https://github.com/pybind/pybind11/pull/3577>`_
+
+* Remove a few deprecated c-headers.
+  `#3610 <https://github.com/pybind/pybind11/pull/3610>`_
+
+* More uniform handling of test targets.
+  `#3590 <https://github.com/pybind/pybind11/pull/3590>`_
+
+* Add clang-tidy readability check to catch potentially swapped function args.
+  `#3611 <https://github.com/pybind/pybind11/pull/3611>`_
+
 
 Version 2.9.0 (Dec 28, 2021)
 ----------------------------

From 3899dc65b91f189f9ac03f2f9ec7d9c25b76134b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 2 Feb 2022 13:16:44 -0800
Subject: [PATCH 290/638] Documenting missing unit test coverage. (#3673)

---
 include/pybind11/pybind11.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ede35e1867..7aa93bb5aa 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -991,6 +991,7 @@ class cpp_function : public function {
 #if PY_VERSION_HEX >= 0x03030000
             // Attach additional error info to the exception if supported
             if (PyErr_Occurred()) {
+                // #HelpAppreciated: unit test coverage for this branch.
                 raise_from(PyExc_TypeError, msg.c_str());
                 return nullptr;
             }

From ffa346860b306c9bbfb341aed9c14c067751feb8 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 2 Feb 2022 17:34:15 -0500
Subject: [PATCH 291/638] chore: bump to 2.9.1

---
 include/pybind11/detail/common.h | 4 ++--
 pybind11/_version.py             | 2 +-
 setup.cfg                        | 9 ++++++++-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index b3513da83b..5c59b41417 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 9
-#define PYBIND11_VERSION_PATCH 0
+#define PYBIND11_VERSION_PATCH 1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x02090000
+#define PYBIND11_VERSION_HEX 0x02090100
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 6627d4c7e6..9d39b77a41 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.9.0"
+__version__ = "2.9.1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))
diff --git a/setup.cfg b/setup.cfg
index 95963d2f87..317c44bbf6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -31,8 +31,15 @@ keywords =
     C++11
     Python bindings
 
+project_urls =
+    Documentation = https://pybind11.readthedocs.io/
+    Bug Tracker = https://github.com/pybind/pybind11/issues
+    Discussions = https://github.com/pybind/pybind11/discussions
+    Changelog = https://pybind11.readthedocs.io/en/latest/changelog.html
+    Chat = https://gitter.im/pybind/Lobby
+
 [options]
-python_requires = >=2.7, !=3.0, !=3.1, !=3.2, !=3.3, !=3.4
+python_requires = >=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*
 zip_safe = False
 
 [bdist_wheel]

From 1d3b04e805c8a7dd4d8b68e2a311c75a66cae1d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20G=C3=B3rny?= <mgorny@gentoo.org>
Date: Thu, 3 Feb 2022 18:29:46 +0100
Subject: [PATCH 292/638] test: Strip whitespace when comparing numpy dtypes
 for 1.22 compat (#3682)

* test: Strip whitespace when comparing numpy dtypes for 1.22 compat

Strip whitespace when comparing numpy dtype str() in order to preserve
test compatibility with both numpy 1.22 and older versions whose output
differ by whitespace.

Fixes #3680

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 tests/test_numpy_dtypes.py | 44 +++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 06e578329e..0098eccb87 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -32,8 +32,8 @@ def dt_fmt():
     e = "<" if byteorder == "little" else ">"
     return (
         "{{'names':['bool_','uint_','float_','ldbl_'],"
-        " 'formats':['?','" + e + "u4','" + e + "f4','" + e + "f{}'],"
-        " 'offsets':[0,4,8,{}], 'itemsize':{}}}"
+        "'formats':['?','" + e + "u4','" + e + "f4','" + e + "f{}'],"
+        "'offsets':[0,4,8,{}],'itemsize':{}}}"
     )
 
 
@@ -46,7 +46,7 @@ def simple_dtype_fmt():
 def packed_dtype_fmt():
     from sys import byteorder
 
-    return "[('bool_', '?'), ('uint_', '{e}u4'), ('float_', '{e}f4'), ('ldbl_', '{e}f{}')]".format(
+    return "[('bool_','?'),('uint_','{e}u4'),('float_','{e}f4'),('ldbl_','{e}f{}')]".format(
         np.dtype("longdouble").itemsize, e="<" if byteorder == "little" else ">"
     )
 
@@ -77,7 +77,7 @@ def partial_nested_fmt():
     partial_size = partial_ld_off + ld.itemsize
     partial_end_padding = partial_size % np.dtype("uint64").alignment
     partial_nested_size = partial_nested_off * 2 + partial_size + partial_end_padding
-    return "{{'names':['a'], 'formats':[{}], 'offsets':[{}], 'itemsize':{}}}".format(
+    return "{{'names':['a'],'formats':[{}],'offsets':[{}],'itemsize':{}}}".format(
         partial_dtype_fmt(), partial_nested_off, partial_nested_size
     )
 
@@ -123,25 +123,25 @@ def test_dtype(simple_dtype):
 
     e = "<" if byteorder == "little" else ">"
 
-    assert m.print_dtypes() == [
+    assert [x.replace(" ", "") for x in m.print_dtypes()] == [
         simple_dtype_fmt(),
         packed_dtype_fmt(),
-        "[('a', {}), ('b', {})]".format(simple_dtype_fmt(), packed_dtype_fmt()),
+        "[('a',{}),('b',{})]".format(simple_dtype_fmt(), packed_dtype_fmt()),
         partial_dtype_fmt(),
         partial_nested_fmt(),
-        "[('a', 'S3'), ('b', 'S3')]",
+        "[('a','S3'),('b','S3')]",
         (
-            "{{'names':['a','b','c','d'], "
-            + "'formats':[('S4', (3,)),('"
+            "{{'names':['a','b','c','d'],"
+            + "'formats':[('S4',(3,)),('"
             + e
-            + "i4', (2,)),('u1', (3,)),('"
+            + "i4',(2,)),('u1',(3,)),('"
             + e
-            + "f4', (4, 2))], "
-            + "'offsets':[0,12,20,24], 'itemsize':56}}"
+            + "f4',(4,2))],"
+            + "'offsets':[0,12,20,24],'itemsize':56}}"
         ).format(e=e),
-        "[('e1', '" + e + "i8'), ('e2', 'u1')]",
-        "[('x', 'i1'), ('y', '" + e + "u8')]",
-        "[('cflt', '" + e + "c8'), ('cdbl', '" + e + "c16')]",
+        "[('e1','" + e + "i8'),('e2','u1')]",
+        "[('x','i1'),('y','" + e + "u8')]",
+        "[('cflt','" + e + "c8'),('cdbl','" + e + "c16')]",
     ]
 
     d1 = np.dtype(
@@ -238,7 +238,7 @@ def test_recarray(simple_dtype, packed_dtype):
     ]
 
     arr = m.create_rec_partial(3)
-    assert str(arr.dtype) == partial_dtype_fmt()
+    assert str(arr.dtype).replace(" ", "") == partial_dtype_fmt()
     partial_dtype = arr.dtype
     assert "" not in arr.dtype.fields
     assert partial_dtype.itemsize > simple_dtype.itemsize
@@ -246,7 +246,7 @@ def test_recarray(simple_dtype, packed_dtype):
     assert_equal(arr, elements, packed_dtype)
 
     arr = m.create_rec_partial_nested(3)
-    assert str(arr.dtype) == partial_nested_fmt()
+    assert str(arr.dtype).replace(" ", "") == partial_nested_fmt()
     assert "" not in arr.dtype.fields
     assert "" not in arr.dtype.fields["a"][0].fields
     assert arr.dtype.itemsize > partial_dtype.itemsize
@@ -285,12 +285,12 @@ def test_array_array():
     e = "<" if byteorder == "little" else ">"
 
     arr = m.create_array_array(3)
-    assert str(arr.dtype) == (
-        "{{'names':['a','b','c','d'], "
-        + "'formats':[('S4', (3,)),('"
+    assert str(arr.dtype).replace(" ", "") == (
+        "{{'names':['a','b','c','d'],"
+        + "'formats':[('S4',(3,)),('"
         + e
-        + "i4', (2,)),('u1', (3,)),('{e}f4', (4, 2))], "
-        + "'offsets':[0,12,20,24], 'itemsize':56}}"
+        + "i4',(2,)),('u1',(3,)),('{e}f4',(4,2))],"
+        + "'offsets':[0,12,20,24],'itemsize':56}}"
     ).format(e=e)
     assert m.print_array_array(arr) == [
         "a={{A,B,C,D},{K,L,M,N},{U,V,W,X}},b={0,1},"

From 36813cfa1228f9414aac669d239a0d3255fc25c3 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 3 Feb 2022 12:44:02 -0500
Subject: [PATCH 293/638] chore: back to work

---
 docs/changelog.rst               | 6 ++++++
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 setup.py                         | 7 +++++--
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 16bf3aa3f3..63c7f41d8f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,6 +6,12 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
+IN DEVELOPMENT
+--------------
+
+Changes will be added here periodically.
+
+
 Version 2.9.1 (Feb 2, 2022)
 ---------------------------
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 5c59b41417..d9f838236a 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 9
-#define PYBIND11_VERSION_PATCH 1
+#define PYBIND11_VERSION_MINOR 10
+#define PYBIND11_VERSION_PATCH 0.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x02090100
+#define PYBIND11_VERSION_HEX 0x020A00D1
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 9d39b77a41..7519ac903b 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s):
         return s
 
 
-__version__ = "2.9.1"
+__version__ = "2.10.0.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))
diff --git a/setup.py b/setup.py
index 0e73489820..f838379190 100644
--- a/setup.py
+++ b/setup.py
@@ -45,8 +45,11 @@ def build_expected_version_hex(matches):
     if serial is None:
         msg = 'Invalid PYBIND11_VERSION_PATCH: "{}"'.format(patch_level_serial)
         raise RuntimeError(msg)
-    return "0x{:02x}{:02x}{:02x}{}{:x}".format(
-        major, minor, patch, level[:1].upper(), serial
+    return (
+        "0x"
+        + "{:02x}{:02x}{:02x}{}{:x}".format(
+            major, minor, patch, level[:1], serial
+        ).upper()
     )
 
 

From 94a948722f2be3834c00e5e158d277d623750c44 Mon Sep 17 00:00:00 2001
From: Sebastian Koslowski <sebastian.koslowski@gmail.com>
Date: Sun, 6 Feb 2022 01:11:59 +0100
Subject: [PATCH 294/638] docs: fix imported target name (#3689)

---
 docs/compiling.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/compiling.rst b/docs/compiling.rst
index 75608bd576..25adb9fcf2 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -475,7 +475,7 @@ available in all modes. The targets provided are:
      Everything for extension modules - ``pybind11::pybind11`` + ``Python::Module`` (FindPython CMake 3.15+) or ``pybind11::python_link_helper``
 
    ``pybind11::embed``
-     Everything for embedding the Python interpreter - ``pybind11::pybind11`` + ``Python::Embed`` (FindPython) or Python libs
+     Everything for embedding the Python interpreter - ``pybind11::pybind11`` + ``Python::Python`` (FindPython) or Python libs
 
    ``pybind11::lto`` / ``pybind11::thin_lto``
      An alternative to `INTERPROCEDURAL_OPTIMIZATION` for adding link-time optimization.

From 96b943be1d39958661047eadac506745ba92b2bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20G=C3=B3rny?= <mgorny@gentoo.org>
Date: Sun, 6 Feb 2022 05:53:02 +0100
Subject: [PATCH 295/638] tests: update catch to 2.13.5 to fix glibc 2.34
 failures (#3679)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Download catch for MinGw

* Fix rest of MinGW

* fix: update catch to 2.13.5 to fix glibc 2.34 failures

Update the downloaded Catch version to 2.13.5, in order to fix build
failure on glibc 2.34:

```
In file included from /usr/include/signal.h:328,
                 from /tmp/pybind11/.nox/tests-3-9/tmp/tests/catch/catch.hpp:8030,
                 from /tmp/pybind11/tests/test_embed/catch.cpp:13:
/tmp/pybind11/.nox/tests-3-9/tmp/tests/catch/catch.hpp:10818:58: error: call to non-‘constexpr’ function ‘long int sysconf(int)’
10818 |     static constexpr std::size_t sigStackSize = 32768 >= MINSIGSTKSZ ? 32768 : MINSIGSTKSZ;
      |                                                          ^~~~~~~~~~~
In file included from /usr/include/python3.9/Python.h:36,
                 from /tmp/pybind11/include/pybind11/detail/common.h:215,
                 from /tmp/pybind11/include/pybind11/pytypes.h:12,
                 from /tmp/pybind11/include/pybind11/cast.h:13,
                 from /tmp/pybind11/include/pybind11/attr.h:13,
                 from /tmp/pybind11/include/pybind11/pybind11.h:13,
                 from /tmp/pybind11/include/pybind11/embed.h:12,
                 from /tmp/pybind11/tests/test_embed/catch.cpp:4:
/usr/include/unistd.h:640:17: note: ‘long int sysconf(int)’ declared here
  640 | extern long int sysconf (int __name) __THROW;
      |                 ^~~~~~~
In file included from /tmp/pybind11/tests/test_embed/catch.cpp:13:
/tmp/pybind11/.nox/tests-3-9/tmp/tests/catch/catch.hpp:10877:45: error: size of array ‘altStackMem’ is not an integral constant-expression
10877 |     char FatalConditionHandler::altStackMem[sigStackSize] = {};
      |                                             ^~~~~~~~~~~~
```

The newest Catch version cannot be used yet because of regression:
https://github.com/catchorg/Catch2/pull/2364

* fix: add option for _ check, only define on pybind11

* Revert "fix: add option for _ check, only define on pybind11"

This reverts commit 86817db488c547816e21e20d678db318bb286384.

* fix: only undef _ for catch cpp creation.

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml        | 6 +++---
 tests/test_embed/CMakeLists.txt | 2 +-
 tests/test_embed/catch.cpp      | 5 +++++
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 050c525cee..b52c306181 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -914,7 +914,7 @@ jobs:
     - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DDOWNLOAD_CATCH=ON -S . -B build
 
     - name: Build C++11
       run: cmake --build build -j 2
@@ -932,7 +932,7 @@ jobs:
       run: git clean -fdx
 
     - name: Configure C++14
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -S . -B build2
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DDOWNLOAD_CATCH=ON -S . -B build2
 
     - name: Build C++14
       run: cmake --build build2 -j 2
@@ -950,7 +950,7 @@ jobs:
       run: git clean -fdx
 
     - name: Configure C++17
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -S . -B build3
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DDOWNLOAD_CATCH=ON -S . -B build3
 
     - name: Build C++17
       run: cmake --build build3 -j 2
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index edb8961a7d..69c33bbd54 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -7,7 +7,7 @@ if("${PYTHON_MODULE_EXTENSION}" MATCHES "pypy" OR "${Python_INTERPRETER_ID}" STR
   return()
 endif()
 
-find_package(Catch 2.13.2)
+find_package(Catch 2.13.5)
 
 if(CATCH_FOUND)
   message(STATUS "Building interpreter tests using Catch v${CATCH_VERSION}")
diff --git a/tests/test_embed/catch.cpp b/tests/test_embed/catch.cpp
index dd137385cb..67a8d51432 100644
--- a/tests/test_embed/catch.cpp
+++ b/tests/test_embed/catch.cpp
@@ -9,6 +9,11 @@
 #  pragma warning(disable: 4996)
 #endif
 
+// Catch uses _ internally, which breaks gettext style defines
+#ifdef _
+#undef _
+#endif
+
 #define CATCH_CONFIG_RUNNER
 #include <catch.hpp>
 

From 1b84188330aa07c5ca5babbc0305746ad577b2a9 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 7 Feb 2022 15:29:25 -0500
Subject: [PATCH 296/638] Minor change to improve readability (#3695)

---
 include/pybind11/detail/class.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index cc1e40ce7a..dd8c60bacf 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -568,8 +568,8 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
         view->format = const_cast<char *>(info->format.c_str());
     if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES) {
         view->ndim = (int) info->ndim;
-        view->strides = &info->strides[0];
-        view->shape = &info->shape[0];
+        view->strides = info->strides.data();
+        view->shape = info->shape.data();
     }
     Py_INCREF(view->obj);
     return 0;

From af056b65d3312d2fb19b2900741413a7b06b9de2 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 8 Feb 2022 11:47:30 -0500
Subject: [PATCH 297/638] fix: __index__ on Enum should always be present.
 (#3700)

* chore: minor odd py version cleanup

* Update include/pybind11/pybind11.h

* fix: always make __index__ available
---
 include/pybind11/detail/common.h | 3 ---
 include/pybind11/pybind11.h      | 5 +----
 2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index d9f838236a..14788b6523 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -153,9 +153,6 @@
 
 /// Include Python header, disable linking to pythonX_d.lib on Windows in debug mode
 #if defined(_MSC_VER)
-#  if (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION < 4)
-#    define HAVE_ROUND 1
-#  endif
 #  pragma warning(push)
 // C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
 #  pragma warning(disable: 4505)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 7aa93bb5aa..7dcea95b42 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1911,13 +1911,10 @@ template <typename Type> class enum_ : public class_<Type> {
         def(init([](Scalar i) { return static_cast<Type>(i); }), arg("value"));
         def_property_readonly("value", [](Type value) { return (Scalar) value; });
         def("__int__", [](Type value) { return (Scalar) value; });
+        def("__index__", [](Type value) { return (Scalar) value; });
         #if PY_MAJOR_VERSION < 3
             def("__long__", [](Type value) { return (Scalar) value; });
         #endif
-        #if PY_MAJOR_VERSION > 3 || (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION >= 8)
-            def("__index__", [](Type value) { return (Scalar) value; });
-        #endif
-
         attr("__setstate__") = cpp_function(
             [](detail::value_and_holder &v_h, Scalar arg) {
                 detail::initimpl::setstate<Base>(v_h, static_cast<Type>(arg),

From 8581584e6091cd09372dcc3d51670b118c4847cc Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 7 Feb 2022 16:17:32 -0800
Subject: [PATCH 298/638] Manual fix-ups in preparation for clang-tidy
 readability-braces-around-statements.

Informed by experiments under PR #3698.
---
 include/pybind11/cast.h                    | 16 ++++++++++------
 include/pybind11/detail/init.h             |  5 +++--
 include/pybind11/detail/type_caster_base.h | 15 ++++++++++-----
 include/pybind11/pybind11.h                |  3 ++-
 4 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 165102443c..a392400870 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -915,7 +915,7 @@ template <> inline void handle::cast() const { return; }
 
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
-    if (obj.ref_count() > 1)
+    if (obj.ref_count() > 1) {
 #if defined(NDEBUG)
         throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
             " (compile in debug mode for details)");
@@ -923,6 +923,7 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
         throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj)) +
                 " instance to C++ " + type_id<T>() + " instance: instance has multiple references");
 #endif
+    }
 
     // Move into a temporary and return that, because the reference may be a local value of `conv`
     T ret = std::move(detail::load_type<T>(obj).operator T&());
@@ -1192,12 +1193,15 @@ class argument_loader {
     template <size_t... Is>
     bool load_impl_sequence(function_call &call, index_sequence<Is...>) {
 #ifdef __cpp_fold_expressions
-        if ((... || !std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])))
+        if ((... || !std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is]))) {
             return false;
+        }
 #else
-        for (bool r : {std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])...})
-            if (!r)
+        for (bool r : {std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])...}) {
+            if (!r) {
                 return false;
+            }
+        }
 #endif
         return true;
     }
@@ -1286,13 +1290,13 @@ class unpacking_collector {
     }
 
     void process(list &/*args_list*/, arg_v a) {
-        if (!a.name)
+        if (!a.name) {
 #if defined(NDEBUG)
             nameless_argument_error();
 #else
             nameless_argument_error(a.type);
 #endif
-
+        }
         if (m_kwargs.contains(a.name)) {
 #if defined(NDEBUG)
             multiple_values_error();
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index eaaad5a07a..65b823e549 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -276,12 +276,13 @@ struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
         cl.def("__init__", [class_func, alias_func]
         #endif
         (value_and_holder &v_h, CArgs... args) {
-            if (Py_TYPE(v_h.inst) == v_h.type->type)
+            if (Py_TYPE(v_h.inst) == v_h.type->type) {
                 // If the instance type equals the registered type we don't have inheritance, so
                 // don't need the alias and can construct using the class function:
                 construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
-            else
+            } else {
                 construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
+            }
         }, is_new_style_constructor(), extra...);
     }
 };
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 48e218b2f3..87a4087a01 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -625,12 +625,15 @@ class type_caster_generic {
                 vptr = type->operator_new(type->type_size);
             } else {
                 #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
-                    if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+                    if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
                         vptr = ::operator new(type->type_size,
                                               std::align_val_t(type->type_align));
-                    else
+                    } else {
+                        vptr = ::operator new(type->type_size);
+                    }
+                #else
+                    vptr = ::operator new(type->type_size);
                 #endif
-                vptr = ::operator new(type->type_size);
             }
         }
         value = vptr;
@@ -778,8 +781,9 @@ class type_caster_generic {
     // with .second = nullptr.  (p.first = nullptr is not an error: it becomes None).
     PYBIND11_NOINLINE static std::pair<const void *, const type_info *> src_and_type(
             const void *src, const std::type_info &cast_type, const std::type_info *rtti_type = nullptr) {
-        if (auto *tpi = get_type_info(cast_type))
+        if (auto *tpi = get_type_info(cast_type)) {
             return {src, const_cast<const type_info *>(tpi)};
+        }
 
         // Not found, set error:
         std::string tname = rtti_type ? rtti_type->name() : cast_type.name();
@@ -928,8 +932,9 @@ template <typename type> class type_caster_base : public type_caster_generic {
             // except via a user-provided specialization of polymorphic_type_hook,
             // and the user has promised that no this-pointer adjustment is
             // required in that case, so it's OK to use static_cast.
-            if (const auto *tpi = get_type_info(*instance_type))
+            if (const auto *tpi = get_type_info(*instance_type)) {
                 return {vsrc, tpi};
+            }
         }
         // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer, so
         // don't do a cast
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 7dcea95b42..b64d426869 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -183,12 +183,13 @@ class cpp_function : public function {
 #endif
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
-            if (!std::is_trivially_destructible<capture>::value)
+            if (!std::is_trivially_destructible<capture>::value) {
                 rec->free_data = [](function_record *r) {
                     auto data = PYBIND11_STD_LAUNDER((capture *) &r->data);
                     (void) data;
                     data->~capture();
                 };
+            }
 #if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif

From ddbc74c67411b21dfe29fe4ec535be74225ff593 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 7 Feb 2022 16:23:20 -0800
Subject: [PATCH 299/638] Adding .clang-tidy
 readability-braces-around-statements option.

clang-tidy automatic changes. NO manual changes.
---
 .clang-tidy                                |   1 +
 include/pybind11/attr.h                    |  32 +-
 include/pybind11/buffer_info.h             |  15 +-
 include/pybind11/cast.h                    | 113 +++++--
 include/pybind11/chrono.h                  |  17 +-
 include/pybind11/complex.h                 |   6 +-
 include/pybind11/detail/class.h            | 108 ++++--
 include/pybind11/detail/init.h             |  31 +-
 include/pybind11/detail/internals.h        |   7 +-
 include/pybind11/detail/type_caster_base.h | 168 ++++++---
 include/pybind11/detail/typeid.h           |   7 +-
 include/pybind11/eigen.h                   |  86 +++--
 include/pybind11/embed.h                   |  18 +-
 include/pybind11/eval.h                    |  12 +-
 include/pybind11/functional.h              |  13 +-
 include/pybind11/gil.h                     |  14 +-
 include/pybind11/iostream.h                |  22 +-
 include/pybind11/numpy.h                   | 173 ++++++----
 include/pybind11/pybind11.h                | 374 ++++++++++++++-------
 include/pybind11/pytypes.h                 | 174 +++++++---
 include/pybind11/stl.h                     |  58 ++--
 include/pybind11/stl_bind.h                | 108 +++---
 tests/constructor_stats.h                  |  21 +-
 tests/object.h                             |  39 ++-
 tests/pybind11_cross_module_tests.cpp      |   4 +-
 tests/pybind11_tests.cpp                   |   3 +-
 tests/test_buffers.cpp                     |   9 +-
 tests/test_builtin_casters.cpp             |  25 +-
 tests/test_call_policies.cpp               |   3 +-
 tests/test_callbacks.cpp                   |  18 +-
 tests/test_class.cpp                       |  13 +-
 tests/test_copy_move.cpp                   |   7 +-
 tests/test_eigen.cpp                       |  22 +-
 tests/test_embed/test_interpreter.cpp      |   6 +-
 tests/test_eval.cpp                        |   3 +-
 tests/test_exceptions.cpp                  |  35 +-
 tests/test_iostream.cpp                    |   3 +-
 tests/test_kwargs_and_defaults.cpp         |   9 +-
 tests/test_local_bindings.cpp              |   3 +-
 tests/test_numpy_array.cpp                 |  72 ++--
 tests/test_numpy_dtypes.cpp                |  71 ++--
 tests/test_opaque_types.cpp                |   3 +-
 tests/test_pickling.cpp                    |  18 +-
 tests/test_pytypes.cpp                     |  15 +-
 tests/test_sequences_and_iterators.cpp     |  40 ++-
 tests/test_smart_ptr.cpp                   |   9 +-
 tests/test_stl_binders.cpp                 |  22 +-
 tests/test_tagbased_polymorphic.cpp        |   8 +-
 tests/test_virtual_functions.cpp           |   3 +-
 49 files changed, 1363 insertions(+), 678 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index d853a703ce..97bbd53968 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -31,6 +31,7 @@ modernize-use-override,
 modernize-use-using,
 *performance*,
 readability-avoid-const-params-in-decls,
+readability-braces-around-statements,
 readability-const-return-type,
 readability-container-size-empty,
 readability-delete-null-pointer,
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index f1b66fb80c..f23582b1bf 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -330,11 +330,13 @@ struct type_record {
 
         bases.append((PyObject *) base_info->type);
 
-        if (base_info->type->tp_dictoffset != 0)
+        if (base_info->type->tp_dictoffset != 0) {
             dynamic_attr = true;
+        }
 
-        if (caster)
+        if (caster) {
             base_info->implicit_casts.emplace_back(type, caster);
+        }
     }
 };
 
@@ -410,13 +412,16 @@ template <> struct process_attribute<is_new_style_constructor> : process_attribu
 };
 
 inline void check_kw_only_arg(const arg &a, function_record *r) {
-    if (r->args.size() > r->nargs_pos && (!a.name || a.name[0] == '\0'))
-        pybind11_fail("arg(): cannot specify an unnamed argument after a kw_only() annotation or args() argument");
+    if (r->args.size() > r->nargs_pos && (!a.name || a.name[0] == '\0')) {
+        pybind11_fail("arg(): cannot specify an unnamed argument after a kw_only() annotation or "
+                      "args() argument");
+    }
 }
 
 inline void append_self_arg_if_needed(function_record *r) {
-    if (r->is_method && r->args.empty())
-        r->args.emplace_back("self", nullptr, handle(), /*convert=*/ true, /*none=*/ false);
+    if (r->is_method && r->args.empty()) {
+        r->args.emplace_back("self", nullptr, handle(), /*convert=*/true, /*none=*/false);
+    }
 }
 
 /// Process a keyword argument attribute (*without* a default value)
@@ -432,8 +437,10 @@ template <> struct process_attribute<arg> : process_attribute_default<arg> {
 /// Process a keyword argument attribute (*with* a default value)
 template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
     static void init(const arg_v &a, function_record *r) {
-        if (r->is_method && r->args.empty())
-            r->args.emplace_back("self", /*descr=*/ nullptr, /*parent=*/ handle(), /*convert=*/ true, /*none=*/ false);
+        if (r->is_method && r->args.empty()) {
+            r->args.emplace_back(
+                "self", /*descr=*/nullptr, /*parent=*/handle(), /*convert=*/true, /*none=*/false);
+        }
 
         if (!a.value) {
 #if !defined(NDEBUG)
@@ -466,8 +473,10 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 template <> struct process_attribute<kw_only> : process_attribute_default<kw_only> {
     static void init(const kw_only &, function_record *r) {
         append_self_arg_if_needed(r);
-        if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size()))
-            pybind11_fail("Mismatched args() and kw_only(): they must occur at the same relative argument location (or omit kw_only() entirely)");
+        if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size())) {
+            pybind11_fail("Mismatched args() and kw_only(): they must occur at the same relative "
+                          "argument location (or omit kw_only() entirely)");
+        }
         r->nargs_pos = static_cast<std::uint16_t>(r->args.size());
     }
 };
@@ -477,8 +486,9 @@ template <> struct process_attribute<pos_only> : process_attribute_default<pos_o
     static void init(const pos_only &, function_record *r) {
         append_self_arg_if_needed(r);
         r->nargs_pos_only = static_cast<std::uint16_t>(r->args.size());
-        if (r->nargs_pos_only > r->nargs_pos)
+        if (r->nargs_pos_only > r->nargs_pos) {
             pybind11_fail("pos_only(): cannot follow a py::args() argument");
+        }
             // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
     }
 };
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index eba68d1aa1..1dd6955527 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -19,9 +19,11 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 inline std::vector<ssize_t> c_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
     auto ndim = shape.size();
     std::vector<ssize_t> strides(ndim, itemsize);
-    if (ndim > 0)
-        for (size_t i = ndim - 1; i > 0; --i)
+    if (ndim > 0) {
+        for (size_t i = ndim - 1; i > 0; --i) {
             strides[i - 1] = strides[i] * shape[i];
+        }
+    }
     return strides;
 }
 
@@ -29,8 +31,9 @@ inline std::vector<ssize_t> c_strides(const std::vector<ssize_t> &shape, ssize_t
 inline std::vector<ssize_t> f_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
     auto ndim = shape.size();
     std::vector<ssize_t> strides(ndim, itemsize);
-    for (size_t i = 1; i < ndim; ++i)
+    for (size_t i = 1; i < ndim; ++i) {
         strides[i] = strides[i - 1] * shape[i - 1];
+    }
     return strides;
 }
 
@@ -53,10 +56,12 @@ struct buffer_info {
                 detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
     : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
       shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
-        if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size())
+        if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size()) {
             pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
-        for (size_t i = 0; i < (size_t) ndim; ++i)
+        }
+        for (size_t i = 0; i < (size_t) ndim; ++i) {
             size *= shape[i];
+        }
     }
 
     template <typename T>
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index a392400870..71b8c2f0ff 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -60,8 +60,10 @@ template <typename type> class type_caster<std::reference_wrapper<type>> {
     static constexpr auto name = caster_t::name;
     static handle cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
         // It is definitely wrong to take ownership of this pointer, so mask that rvp
-        if (policy == return_value_policy::take_ownership || policy == return_value_policy::automatic)
+        if (policy == return_value_policy::take_ownership
+            || policy == return_value_policy::automatic) {
             policy = return_value_policy::automatic_reference;
+        }
         return caster_t::cast(&src.get(), policy, parent);
     }
     template <typename T> using cast_op_type = std::reference_wrapper<type>;
@@ -112,8 +114,9 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
     bool load(handle src, bool convert) {
         py_type py_value;
 
-        if (!src)
+        if (!src) {
             return false;
+        }
 
 #if !defined(PYPY_VERSION)
         auto index_check = [](PyObject *o) { return PyIndex_Check(o); };
@@ -124,10 +127,11 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
 #endif
 
         if (std::is_floating_point<T>::value) {
-            if (convert || PyFloat_Check(src.ptr()))
+            if (convert || PyFloat_Check(src.ptr())) {
                 py_value = (py_type) PyFloat_AsDouble(src.ptr());
-            else
+            } else {
                 return false;
+            }
         } else if (PyFloat_Check(src.ptr())
                    || (!convert && !PYBIND11_LONG_CHECK(src.ptr()) && !index_check(src.ptr()))) {
             return false;
@@ -214,8 +218,9 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
 template<typename T> struct void_caster {
 public:
     bool load(handle src, bool) {
-        if (src && src.is_none())
+        if (src && src.is_none()) {
             return true;
+        }
         return false;
     }
     static handle cast(T, return_value_policy /* policy */, handle /* parent */) {
@@ -257,8 +262,9 @@ template <> class type_caster<void> : public type_caster<void_type> {
     }
 
     static handle cast(const void *ptr, return_value_policy /* policy */, handle /* parent */) {
-        if (ptr)
+        if (ptr) {
             return capsule(ptr).release();
+        }
         return none().inc_ref();
     }
 
@@ -274,7 +280,9 @@ template <> class type_caster<std::nullptr_t> : public void_caster<std::nullptr_
 template <> class type_caster<bool> {
 public:
     bool load(handle src, bool convert) {
-        if (!src) return false;
+        if (!src) {
+            return false;
+        }
         if (src.ptr() == Py_True) {
             value = true;
             return true;
@@ -391,8 +399,9 @@ template <typename StringType, bool IsView = false> struct string_caster {
         value = StringType(buffer, length);
 
         // If we're loading a string_view we need to keep the encoded Python object alive:
-        if (IsView)
+        if (IsView) {
             loader_life_support::add_patient(utfNbytes);
+        }
 
         return true;
     }
@@ -401,7 +410,9 @@ template <typename StringType, bool IsView = false> struct string_caster {
         const char *buffer = reinterpret_cast<const char *>(src.data());
         auto nbytes = ssize_t(src.size() * sizeof(CharT));
         handle s = decode_utfN(buffer, nbytes);
-        if (!s) throw error_already_set();
+        if (!s) {
+            throw error_already_set();
+        }
         return s;
     }
 
@@ -463,10 +474,14 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
     CharT one_char = 0;
 public:
     bool load(handle src, bool convert) {
-        if (!src) return false;
+        if (!src) {
+            return false;
+        }
         if (src.is_none()) {
             // Defer accepting None to other overloads (if we aren't in convert mode):
-            if (!convert) return false;
+            if (!convert) {
+                return false;
+            }
             none = true;
             return true;
         }
@@ -474,14 +489,18 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
     }
 
     static handle cast(const CharT *src, return_value_policy policy, handle parent) {
-        if (src == nullptr) return pybind11::none().inc_ref();
+        if (src == nullptr) {
+            return pybind11::none().inc_ref();
+        }
         return StringCaster::cast(StringType(src), policy, parent);
     }
 
     static handle cast(CharT src, return_value_policy policy, handle parent) {
         if (std::is_same<char, CharT>::value) {
             handle s = PyUnicode_DecodeLatin1((const char *) &src, 1, nullptr);
-            if (!s) throw error_already_set();
+            if (!s) {
+                throw error_already_set();
+            }
             return s;
         }
         return StringCaster::cast(StringType(1, src), policy, parent);
@@ -491,13 +510,15 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         return none ? nullptr : const_cast<CharT *>(static_cast<StringType &>(str_caster).c_str());
     }
     explicit operator CharT &() {
-        if (none)
+        if (none) {
             throw value_error("Cannot convert None to a character");
+        }
 
         auto &value = static_cast<StringType &>(str_caster);
         size_t str_len = value.size();
-        if (str_len == 0)
+        if (str_len == 0) {
             throw value_error("Cannot convert empty string to a character");
+        }
 
         // If we're in UTF-8 mode, we have two possible failures: one for a unicode character that
         // is too high, and one for multiple unicode characters (caught later), so we need to figure
@@ -531,12 +552,14 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         // string was too long" error).
         else if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 16) && str_len == 2) {
             one_char = static_cast<CharT>(value[0]);
-            if (one_char >= 0xD800 && one_char < 0xE000)
+            if (one_char >= 0xD800 && one_char < 0xE000) {
                 throw value_error("Character code point not in range(0x10000)");
+            }
         }
 
-        if (str_len != 1)
+        if (str_len != 1) {
             throw value_error("Expected a character, but multi-character string found");
+        }
 
         one_char = value[0];
         return one_char;
@@ -554,11 +577,13 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
 public:
 
     bool load(handle src, bool convert) {
-        if (!isinstance<sequence>(src))
+        if (!isinstance<sequence>(src)) {
             return false;
+        }
         const auto seq = reinterpret_borrow<sequence>(src);
-        if (seq.size() != size)
+        if (seq.size() != size) {
             return false;
+        }
         return load_impl(seq, convert, indices{});
     }
 
@@ -570,7 +595,9 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     // copied from the PYBIND11_TYPE_CASTER macro
     template <typename T>
     static handle cast(T *src, return_value_policy policy, handle parent) {
-        if (!src) return none().release();
+        if (!src) {
+            return none().release();
+        }
         if (policy == return_value_policy::take_ownership) {
             auto h = cast(std::move(*src), policy, parent);
             delete src;
@@ -597,8 +624,9 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     template <size_t... Is>
     bool load_impl(const sequence &seq, bool convert, index_sequence<Is...>) {
 #ifdef __cpp_fold_expressions
-        if ((... || !std::get<Is>(subcasters).load(seq[Is], convert)))
+        if ((... || !std::get<Is>(subcasters).load(seq[Is], convert))) {
             return false;
+        }
 #else
         for (bool r : {std::get<Is>(subcasters).load(seq[Is], convert)...})
             if (!r)
@@ -615,13 +643,16 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
         std::array<object, size> entries{{
             reinterpret_steal<object>(make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...
         }};
-        for (const auto &entry: entries)
-            if (!entry)
+        for (const auto &entry : entries) {
+            if (!entry) {
                 return handle();
+            }
+        }
         tuple result(size);
         int counter = 0;
-        for (auto & entry: entries)
+        for (auto &entry : entries) {
             PyTuple_SET_ITEM(result.ptr(), counter++, entry.release().ptr());
+        }
         return result.release();
     }
 
@@ -676,8 +707,9 @@ struct copyable_holder_caster : public type_caster_base<type> {
 protected:
     friend class type_caster_generic;
     void check_holder_compat() {
-        if (typeinfo->default_holder)
+        if (typeinfo->default_holder) {
             throw cast_error("Unable to load a custom holder type from a default-holder instance");
+        }
     }
 
     bool load_value(value_and_holder &&v_h) {
@@ -793,8 +825,9 @@ struct pyobject_caster {
             return true;
         }
 #endif
-        if (!isinstance<type>(src))
+        if (!isinstance<type>(src)) {
             return false;
+        }
         value = reinterpret_borrow<type>(src);
         return true;
     }
@@ -901,12 +934,14 @@ template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> =
 object cast(T &&value, return_value_policy policy = return_value_policy::automatic_reference,
             handle parent = handle()) {
     using no_ref_T = typename std::remove_reference<T>::type;
-    if (policy == return_value_policy::automatic)
+    if (policy == return_value_policy::automatic) {
         policy = std::is_pointer<no_ref_T>::value ? return_value_policy::take_ownership :
                  std::is_lvalue_reference<T>::value ? return_value_policy::copy : return_value_policy::move;
-    else if (policy == return_value_policy::automatic_reference)
-        policy = std::is_pointer<no_ref_T>::value ? return_value_policy::reference :
-                 std::is_lvalue_reference<T>::value ? return_value_policy::copy : return_value_policy::move;
+    } else if (policy == return_value_policy::automatic_reference) {
+        policy = std::is_pointer<no_ref_T>::value     ? return_value_policy::reference
+                 : std::is_lvalue_reference<T>::value ? return_value_policy::copy
+                                                      : return_value_policy::move;
+    }
     return reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
 }
 
@@ -939,8 +974,9 @@ template <typename T> detail::enable_if_t<detail::move_always<T>::value, T> cast
     return move<T>(std::move(object));
 }
 template <typename T> detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
-    if (object.ref_count() > 1)
+    if (object.ref_count() > 1) {
         return cast<T>(object);
+    }
     return move<T>(std::move(object));
 }
 template <typename T> detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
@@ -1018,8 +1054,9 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
     }
     tuple result(size);
     int counter = 0;
-    for (auto &arg_value : args)
+    for (auto &arg_value : args) {
         PyTuple_SET_ITEM(result.ptr(), counter++, arg_value.release().ptr());
+    }
     return result;
 }
 
@@ -1231,8 +1268,9 @@ class simple_collector {
     /// Call a Python function and pass the collected arguments
     object call(PyObject *ptr) const {
         PyObject *result = PyObject_CallObject(ptr, m_args.ptr());
-        if (!result)
+        if (!result) {
             throw error_already_set();
+        }
         return reinterpret_steal<object>(result);
     }
 
@@ -1264,8 +1302,9 @@ class unpacking_collector {
     /// Call a Python function and pass the collected arguments
     object call(PyObject *ptr) const {
         PyObject *result = PyObject_Call(ptr, m_args.ptr(), m_kwargs.ptr());
-        if (!result)
+        if (!result) {
             throw error_already_set();
+        }
         return reinterpret_steal<object>(result);
     }
 
@@ -1285,8 +1324,9 @@ class unpacking_collector {
     }
 
     void process(list &args_list, detail::args_proxy ap) {
-        for (auto a : ap)
+        for (auto a : ap) {
             args_list.append(a);
+        }
     }
 
     void process(list &/*args_list*/, arg_v a) {
@@ -1315,8 +1355,9 @@ class unpacking_collector {
     }
 
     void process(list &/*args_list*/, detail::kwargs_proxy kp) {
-        if (!kp)
+        if (!kp) {
             return;
+        }
         for (auto k : reinterpret_borrow<dict>(kp)) {
             if (m_kwargs.contains(k.first)) {
 #if defined(NDEBUG)
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index 460a28fa5d..b24533b903 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -46,7 +46,9 @@ template <typename type> class duration_caster {
         // Lazy initialise the PyDateTime import
         if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
 
-        if (!src) return false;
+        if (!src) {
+            return false;
+        }
         // If invoked with datetime.delta object
         if (PyDelta_Check(src.ptr())) {
             value = type(duration_cast<duration<rep, period>>(
@@ -124,7 +126,9 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         // Lazy initialise the PyDateTime import
         if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
 
-        if (!src) return false;
+        if (!src) {
+            return false;
+        }
 
         std::tm cal;
         microseconds msecs;
@@ -156,8 +160,9 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
             cal.tm_year  = 70;  // earliest available date for Python's datetime
             cal.tm_isdst = -1;
             msecs        = microseconds(PyDateTime_TIME_GET_MICROSECOND(src.ptr()));
+        } else {
+            return false;
         }
-        else return false;
 
         value = time_point_cast<Duration>(system_clock::from_time_t(std::mktime(&cal)) + msecs);
         return true;
@@ -173,8 +178,9 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         // (cfr. https://github.com/pybind/pybind11/issues/2417)
         using us_t = duration<int, std::micro>;
         auto us = duration_cast<us_t>(src.time_since_epoch() % seconds(1));
-        if (us.count() < 0)
+        if (us.count() < 0) {
             us += seconds(1);
+        }
 
         // Subtract microseconds BEFORE `system_clock::to_time_t`, because:
         // > If std::time_t has lower precision, it is implementation-defined whether the value is rounded or truncated.
@@ -183,8 +189,9 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
 
         std::tm localtime;
         std::tm *localtime_ptr = localtime_thread_safe(&tt, &localtime);
-        if (!localtime_ptr)
+        if (!localtime_ptr) {
             throw cast_error("Unable to represent system_clock in local time");
+        }
         return PyDateTime_FromDateAndTime(localtime.tm_year + 1900,
                                           localtime.tm_mon + 1,
                                           localtime.tm_mday,
diff --git a/include/pybind11/complex.h b/include/pybind11/complex.h
index e1ecf43585..72c87359bc 100644
--- a/include/pybind11/complex.h
+++ b/include/pybind11/complex.h
@@ -42,10 +42,12 @@ template <typename T> struct is_fmt_numeric<std::complex<T>, detail::enable_if_t
 template <typename T> class type_caster<std::complex<T>> {
 public:
     bool load(handle src, bool convert) {
-        if (!src)
+        if (!src) {
             return false;
-        if (!convert && !PyComplex_Check(src.ptr()))
+        }
+        if (!convert && !PyComplex_Check(src.ptr())) {
             return false;
+        }
         Py_complex result = PyComplex_AsCComplex(src.ptr());
         if (result.real == -1.0 && PyErr_Occurred()) {
             PyErr_Clear();
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index dd8c60bacf..28edc12903 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -66,8 +66,9 @@ inline PyTypeObject *make_static_property_type() {
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
     auto heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
-    if (!heap_type)
+    if (!heap_type) {
         pybind11_fail("make_static_property_type(): error allocating type!");
+    }
 
     heap_type->ht_name = name_obj.inc_ref().ptr();
 #ifdef PYBIND11_BUILTIN_QUALNAME
@@ -81,8 +82,9 @@ inline PyTypeObject *make_static_property_type() {
     type->tp_descr_get = pybind11_static_get;
     type->tp_descr_set = pybind11_static_set;
 
-    if (PyType_Ready(type) < 0)
+    if (PyType_Ready(type) < 0) {
         pybind11_fail("make_static_property_type(): failure in PyType_Ready()!");
+    }
 
     setattr((PyObject *) type, "__module__", str("pybind11_builtins"));
     PYBIND11_SET_OLDPY_QUALNAME(type, name_obj);
@@ -209,19 +211,21 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
         auto tindex = std::type_index(*tinfo->cpptype);
         internals.direct_conversions.erase(tindex);
 
-        if (tinfo->module_local)
+        if (tinfo->module_local) {
             get_local_internals().registered_types_cpp.erase(tindex);
-        else
+        } else {
             internals.registered_types_cpp.erase(tindex);
+        }
         internals.registered_types_py.erase(tinfo->type);
 
         // Actually just `std::erase_if`, but that's only available in C++20
         auto &cache = internals.inactive_override_cache;
         for (auto it = cache.begin(), last = cache.end(); it != last; ) {
-            if (it->first == (PyObject *) tinfo->type)
+            if (it->first == (PyObject *) tinfo->type) {
                 it = cache.erase(it);
-            else
+            } else {
                 ++it;
+            }
         }
 
         delete tinfo;
@@ -242,8 +246,9 @@ inline PyTypeObject* make_default_metaclass() {
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
     auto heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
-    if (!heap_type)
+    if (!heap_type) {
         pybind11_fail("make_default_metaclass(): error allocating metaclass!");
+    }
 
     heap_type->ht_name = name_obj.inc_ref().ptr();
 #ifdef PYBIND11_BUILTIN_QUALNAME
@@ -264,8 +269,9 @@ inline PyTypeObject* make_default_metaclass() {
 
     type->tp_dealloc = pybind11_meta_dealloc;
 
-    if (PyType_Ready(type) < 0)
+    if (PyType_Ready(type) < 0) {
         pybind11_fail("make_default_metaclass(): failure in PyType_Ready()!");
+    }
 
     setattr((PyObject *) type, "__module__", str("pybind11_builtins"));
     PYBIND11_SET_OLDPY_QUALNAME(type, name_obj);
@@ -283,8 +289,9 @@ inline void traverse_offset_bases(void *valueptr, const detail::type_info *tinfo
             for (auto &c : parent_tinfo->implicit_casts) {
                 if (c.first == tinfo->cpptype) {
                     auto *parentptr = c.second(valueptr);
-                    if (parentptr != valueptr)
+                    if (parentptr != valueptr) {
                         f(parentptr, self);
+                    }
                     traverse_offset_bases(parentptr, parent_tinfo, self, f);
                     break;
                 }
@@ -311,14 +318,16 @@ inline bool deregister_instance_impl(void *ptr, instance *self) {
 
 inline void register_instance(instance *self, void *valptr, const type_info *tinfo) {
     register_instance_impl(valptr, self);
-    if (!tinfo->simple_ancestors)
+    if (!tinfo->simple_ancestors) {
         traverse_offset_bases(valptr, tinfo, self, register_instance_impl);
+    }
 }
 
 inline bool deregister_instance(instance *self, void *valptr, const type_info *tinfo) {
     bool ret = deregister_instance_impl(valptr, self);
-    if (!tinfo->simple_ancestors)
+    if (!tinfo->simple_ancestors) {
         traverse_offset_bases(valptr, tinfo, self, deregister_instance_impl);
+    }
     return ret;
 }
 
@@ -377,8 +386,9 @@ inline void clear_patients(PyObject *self) {
     auto patients = std::move(pos->second);
     internals.patients.erase(pos);
     instance->has_patients = false;
-    for (PyObject *&patient : patients)
+    for (PyObject *&patient : patients) {
         Py_CLEAR(patient);
+    }
 }
 
 /// Clears all internal data from the instance and removes it from registered instances in
@@ -392,25 +402,32 @@ inline void clear_instance(PyObject *self) {
 
             // We have to deregister before we call dealloc because, for virtual MI types, we still
             // need to be able to get the parent pointers.
-            if (v_h.instance_registered() && !deregister_instance(instance, v_h.value_ptr(), v_h.type))
-                pybind11_fail("pybind11_object_dealloc(): Tried to deallocate unregistered instance!");
+            if (v_h.instance_registered()
+                && !deregister_instance(instance, v_h.value_ptr(), v_h.type)) {
+                pybind11_fail(
+                    "pybind11_object_dealloc(): Tried to deallocate unregistered instance!");
+            }
 
-            if (instance->owned || v_h.holder_constructed())
+            if (instance->owned || v_h.holder_constructed()) {
                 v_h.type->dealloc(v_h);
+            }
         }
     }
     // Deallocate the value/holder layout internals:
     instance->deallocate_layout();
 
-    if (instance->weakrefs)
+    if (instance->weakrefs) {
         PyObject_ClearWeakRefs(self);
+    }
 
     PyObject **dict_ptr = _PyObject_GetDictPtr(self);
-    if (dict_ptr)
+    if (dict_ptr) {
         Py_CLEAR(*dict_ptr);
+    }
 
-    if (instance->has_patients)
+    if (instance->has_patients) {
         clear_patients(self);
+    }
 }
 
 /// Instance destructor function for all pybind11 types. It calls `type_info.dealloc`
@@ -448,8 +465,9 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
     auto heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
-    if (!heap_type)
+    if (!heap_type) {
         pybind11_fail("make_object_base_type(): error allocating type!");
+    }
 
     heap_type->ht_name = name_obj.inc_ref().ptr();
 #ifdef PYBIND11_BUILTIN_QUALNAME
@@ -469,8 +487,9 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
     /* Support weak references (needed for the keep_alive feature) */
     type->tp_weaklistoffset = offsetof(instance, weakrefs);
 
-    if (PyType_Ready(type) < 0)
+    if (PyType_Ready(type) < 0) {
         pybind11_fail("PyType_Ready failed in make_object_base_type():" + error_string());
+    }
 
     setattr((PyObject *) type, "__module__", str("pybind11_builtins"));
     PYBIND11_SET_OLDPY_QUALNAME(type, name_obj);
@@ -482,8 +501,9 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
 /// dynamic_attr: Support for `d = instance.__dict__`.
 extern "C" inline PyObject *pybind11_get_dict(PyObject *self, void *) {
     PyObject *&dict = *_PyObject_GetDictPtr(self);
-    if (!dict)
+    if (!dict) {
         dict = PyDict_New();
+    }
     Py_XINCREF(dict);
     return dict;
 }
@@ -538,12 +558,14 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
     type_info *tinfo = nullptr;
     for (auto type : reinterpret_borrow<tuple>(Py_TYPE(obj)->tp_mro)) {
         tinfo = get_type_info((PyTypeObject *) type.ptr());
-        if (tinfo && tinfo->get_buffer)
+        if (tinfo && tinfo->get_buffer) {
             break;
+        }
     }
     if (view == nullptr || !tinfo || !tinfo->get_buffer) {
-        if (view)
+        if (view) {
             view->obj = nullptr;
+        }
         PyErr_SetString(PyExc_BufferError, "pybind11_getbuffer(): Internal error");
         return -1;
     }
@@ -561,11 +583,13 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
     view->buf = info->ptr;
     view->itemsize = info->itemsize;
     view->len = view->itemsize;
-    for (auto s : info->shape)
+    for (auto s : info->shape) {
         view->len *= s;
+    }
     view->readonly = static_cast<int>(info->readonly);
-    if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT)
+    if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT) {
         view->format = const_cast<char *>(info->format.c_str());
+    }
     if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES) {
         view->ndim = (int) info->ndim;
         view->strides = info->strides.data();
@@ -608,10 +632,11 @@ inline PyObject* make_new_python_type(const type_record &rec) {
 
     object module_;
     if (rec.scope) {
-        if (hasattr(rec.scope, "__module__"))
+        if (hasattr(rec.scope, "__module__")) {
             module_ = rec.scope.attr("__module__");
-        else if (hasattr(rec.scope, "__name__"))
+        } else if (hasattr(rec.scope, "__name__")) {
             module_ = rec.scope.attr("__name__");
+        }
     }
 
     auto full_name = c_str(
@@ -642,8 +667,9 @@ inline PyObject* make_new_python_type(const type_record &rec) {
                                          : internals.default_metaclass;
 
     auto heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
-    if (!heap_type)
+    if (!heap_type) {
         pybind11_fail(std::string(rec.name) + ": Unable to create type object!");
+    }
 
     heap_type->ht_name = name.release().ptr();
 #ifdef PYBIND11_BUILTIN_QUALNAME
@@ -655,8 +681,9 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     type->tp_doc = tp_doc;
     type->tp_base = type_incref((PyTypeObject *)base);
     type->tp_basicsize = static_cast<ssize_t>(sizeof(instance));
-    if (!bases.empty())
+    if (!bases.empty()) {
         type->tp_bases = bases.release().ptr();
+    }
 
     /* Don't inherit base __init__ */
     type->tp_init = pybind11_object_init;
@@ -674,31 +701,38 @@ inline PyObject* make_new_python_type(const type_record &rec) {
 #if PY_MAJOR_VERSION < 3
     type->tp_flags |= Py_TPFLAGS_CHECKTYPES;
 #endif
-    if (!rec.is_final)
+    if (!rec.is_final) {
         type->tp_flags |= Py_TPFLAGS_BASETYPE;
+    }
 
-    if (rec.dynamic_attr)
+    if (rec.dynamic_attr) {
         enable_dynamic_attributes(heap_type);
+    }
 
-    if (rec.buffer_protocol)
+    if (rec.buffer_protocol) {
         enable_buffer_protocol(heap_type);
+    }
 
-    if (rec.custom_type_setup_callback)
+    if (rec.custom_type_setup_callback) {
         rec.custom_type_setup_callback(heap_type);
+    }
 
-    if (PyType_Ready(type) < 0)
+    if (PyType_Ready(type) < 0) {
         pybind11_fail(std::string(rec.name) + ": PyType_Ready failed (" + error_string() + ")!");
+    }
 
     assert(!rec.dynamic_attr || PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC));
 
     /* Register type with the parent scope */
-    if (rec.scope)
+    if (rec.scope) {
         setattr(rec.scope, rec.name, (PyObject *) type);
-    else
+    } else {
         Py_INCREF(type); // Keep it alive forever (reference leak)
+    }
 
-    if (module_) // Needed by pydoc
+    if (module_) { // Needed by pydoc
         setattr((PyObject *) type, "__module__", module_);
+    }
 
     PYBIND11_SET_OLDPY_QUALNAME(type, qualname);
 
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 65b823e549..ba408d76cc 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -33,7 +33,9 @@ class type_caster<value_and_holder> {
 PYBIND11_NAMESPACE_BEGIN(initimpl)
 
 inline void no_nullptr(void *ptr) {
-    if (!ptr) throw type_error("pybind11::init(): factory function returned nullptr");
+    if (!ptr) {
+        throw type_error("pybind11::init(): factory function returned nullptr");
+    }
 }
 
 // Implementing functions for all forms of py::init<...> and py::init(...)
@@ -136,9 +138,10 @@ void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
     auto *ptr = holder_helper<Holder<Class>>::get(holder);
     no_nullptr(ptr);
     // If we need an alias, check that the held pointer is actually an alias instance
-    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr))
+    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr)) {
         throw type_error("pybind11::init(): construction failed: returned holder-wrapped instance "
                          "is not an alias instance");
+    }
 
     v_h.value_ptr() = ptr;
     v_h.type->init_instance(v_h.inst, &holder);
@@ -153,10 +156,11 @@ void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
         "pybind11::init() return-by-value factory function requires a movable class");
-    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias)
+    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias) {
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
-    else
+    } else {
         v_h.value_ptr() = new Cpp<Class>(std::move(result));
+    }
 }
 
 // return-by-value version 2: returning a value of the alias type itself.  We move-construct an
@@ -183,12 +187,19 @@ struct constructor {
               enable_if_t<Class::has_alias &&
                           std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
     static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            if (Py_TYPE(v_h.inst) == v_h.type->type)
-                v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
-            else
-                v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                if (Py_TYPE(v_h.inst) == v_h.type->type) {
+                    v_h.value_ptr()
+                        = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
+                } else {
+                    v_h.value_ptr()
+                        = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
+                }
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 
     template <typename Class, typename... Extra,
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 9edb9492e2..661acf5dad 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -398,8 +398,9 @@ inline void translate_local_exception(std::exception_ptr p) {
 /// Return a reference to the current `internals` data
 PYBIND11_NOINLINE internals &get_internals() {
     auto **&internals_pp = get_internals_pp();
-    if (internals_pp && *internals_pp)
+    if (internals_pp && *internals_pp) {
         return **internals_pp;
+    }
 
     // Ensure that the GIL is held since we will need to make Python calls.
     // Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
@@ -425,7 +426,9 @@ PYBIND11_NOINLINE internals &get_internals() {
         (*internals_pp)->registered_exception_translators.push_front(&translate_local_exception);
 #endif
     } else {
-        if (!internals_pp) internals_pp = new internals*();
+        if (!internals_pp) {
+            internals_pp = new internals *();
+        }
         auto *&internals_ptr = *internals_pp;
         internals_ptr = new internals();
 #if defined(WITH_THREAD)
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 87a4087a01..212a944afe 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -69,11 +69,13 @@ class loader_life_support {
 
     /// ... and destroyed after it returns
     ~loader_life_support() {
-        if (get_stack_top() != this)
+        if (get_stack_top() != this) {
             pybind11_fail("loader_life_support: internal error");
+        }
         set_stack_top(parent);
-        for (auto* item : keep_alive)
+        for (auto *item : keep_alive) {
             Py_DECREF(item);
+        }
     }
 
     /// This can only be used inside a pybind11-bound function, either by `argument_loader`
@@ -90,8 +92,9 @@ class loader_life_support {
                              "of temporary values");
         }
 
-        if (frame->keep_alive.insert(h.ptr()).second)
+        if (frame->keep_alive.insert(h.ptr()).second) {
             Py_INCREF(h.ptr());
+        }
     }
 };
 
@@ -103,14 +106,17 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
 // Populates a just-created cache entry.
 PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_info *> &bases) {
     std::vector<PyTypeObject *> check;
-    for (handle parent : reinterpret_borrow<tuple>(t->tp_bases))
+    for (handle parent : reinterpret_borrow<tuple>(t->tp_bases)) {
         check.push_back((PyTypeObject *) parent.ptr());
+    }
 
     auto const &type_dict = get_internals().registered_types_py;
     for (size_t i = 0; i < check.size(); i++) {
         auto type = check[i];
         // Ignore Python2 old-style class super type:
-        if (!PyType_Check((PyObject *) type)) continue;
+        if (!PyType_Check((PyObject *) type)) {
+            continue;
+        }
 
         // Check `type` in the current set of registered python types:
         auto it = type_dict.find(type);
@@ -127,7 +133,9 @@ PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_
                 for (auto *known : bases) {
                     if (known == tinfo) { found = true; break; }
                 }
-                if (!found) bases.push_back(tinfo);
+                if (!found) {
+                    bases.push_back(tinfo);
+                }
             }
         }
         else if (type->tp_bases) {
@@ -140,8 +148,9 @@ PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_
                 check.pop_back();
                 i--;
             }
-            for (handle parent : reinterpret_borrow<tuple>(type->tp_bases))
+            for (handle parent : reinterpret_borrow<tuple>(type->tp_bases)) {
                 check.push_back((PyTypeObject *) parent.ptr());
+            }
         }
     }
 }
@@ -158,9 +167,10 @@ PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_
  */
 inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type) {
     auto ins = all_type_info_get_cache(type);
-    if (ins.second)
+    if (ins.second) {
         // New cache entry: populate it
         all_type_info_populate(type, ins.first->second);
+    }
 
     return ins.first->second;
 }
@@ -172,36 +182,43 @@ inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type)
  */
 PYBIND11_NOINLINE detail::type_info* get_type_info(PyTypeObject *type) {
     auto &bases = all_type_info(type);
-    if (bases.empty())
+    if (bases.empty()) {
         return nullptr;
-    if (bases.size() > 1)
-        pybind11_fail("pybind11::detail::get_type_info: type has multiple pybind11-registered bases");
+    }
+    if (bases.size() > 1) {
+        pybind11_fail(
+            "pybind11::detail::get_type_info: type has multiple pybind11-registered bases");
+    }
     return bases.front();
 }
 
 inline detail::type_info *get_local_type_info(const std::type_index &tp) {
     auto &locals = get_local_internals().registered_types_cpp;
     auto it = locals.find(tp);
-    if (it != locals.end())
+    if (it != locals.end()) {
         return it->second;
+    }
     return nullptr;
 }
 
 inline detail::type_info *get_global_type_info(const std::type_index &tp) {
     auto &types = get_internals().registered_types_cpp;
     auto it = types.find(tp);
-    if (it != types.end())
+    if (it != types.end()) {
         return it->second;
+    }
     return nullptr;
 }
 
 /// Return the type info for a given C++ type; on lookup failure can either throw or return nullptr.
 PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
                                                           bool throw_if_missing = false) {
-    if (auto ltype = get_local_type_info(tp))
+    if (auto ltype = get_local_type_info(tp)) {
         return ltype;
-    if (auto gtype = get_global_type_info(tp))
+    }
+    if (auto gtype = get_global_type_info(tp)) {
         return gtype;
+    }
 
     if (throw_if_missing) {
         std::string tname = tp.name();
@@ -222,8 +239,9 @@ PYBIND11_NOINLINE handle find_registered_python_instance(void *src,
     auto it_instances = get_internals().registered_instances.equal_range(src);
     for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
         for (auto instance_type : detail::all_type_info(Py_TYPE(it_i->second))) {
-            if (instance_type && same_type(*instance_type->cpptype, *tinfo->cpptype))
+            if (instance_type && same_type(*instance_type->cpptype, *tinfo->cpptype)) {
                 return handle((PyObject *) it_i->second).inc_ref();
+            }
         }
     }
     return handle();
@@ -263,12 +281,13 @@ struct value_and_holder {
     }
     // NOLINTNEXTLINE(readability-make-member-function-const)
     void set_holder_constructed(bool v = true) {
-        if (inst->simple_layout)
+        if (inst->simple_layout) {
             inst->simple_holder_constructed = v;
-        else if (v)
+        } else if (v) {
             inst->nonsimple.status[index] |= instance::status_holder_constructed;
-        else
+        } else {
             inst->nonsimple.status[index] &= (std::uint8_t) ~instance::status_holder_constructed;
+        }
     }
     bool instance_registered() const {
         return inst->simple_layout
@@ -277,12 +296,13 @@ struct value_and_holder {
     }
     // NOLINTNEXTLINE(readability-make-member-function-const)
     void set_instance_registered(bool v = true) {
-        if (inst->simple_layout)
+        if (inst->simple_layout) {
             inst->simple_instance_registered = v;
-        else if (v)
+        } else if (v) {
             inst->nonsimple.status[index] |= instance::status_instance_registered;
-        else
+        } else {
             inst->nonsimple.status[index] &= (std::uint8_t) ~instance::status_instance_registered;
+        }
     }
 };
 
@@ -317,8 +337,9 @@ struct values_and_holders {
         bool operator==(const iterator &other) const { return curr.index == other.curr.index; }
         bool operator!=(const iterator &other) const { return curr.index != other.curr.index; }
         iterator &operator++() {
-            if (!inst->simple_layout)
+            if (!inst->simple_layout) {
                 curr.vh += 1 + (*types)[curr.index]->holder_size_in_ptrs;
+            }
             ++curr.index;
             curr.type = curr.index < types->size() ? (*types)[curr.index] : nullptr;
             return *this;
@@ -332,7 +353,9 @@ struct values_and_holders {
 
     iterator find(const type_info *find_type) {
         auto it = begin(), endit = end();
-        while (it != endit && it->type != find_type) ++it;
+        while (it != endit && it->type != find_type) {
+            ++it;
+        }
         return it;
     }
 
@@ -351,16 +374,19 @@ struct values_and_holders {
  */
 PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/, bool throw_if_missing /*= true in common.h*/) {
     // Optimize common case:
-    if (!find_type || Py_TYPE(this) == find_type->type)
+    if (!find_type || Py_TYPE(this) == find_type->type) {
         return value_and_holder(this, find_type, 0, 0);
+    }
 
     detail::values_and_holders vhs(this);
     auto it = vhs.find(find_type);
-    if (it != vhs.end())
+    if (it != vhs.end()) {
         return *it;
+    }
 
-    if (!throw_if_missing)
+    if (!throw_if_missing) {
         return value_and_holder();
+    }
 
 #if defined(NDEBUG)
     pybind11_fail("pybind11::detail::instance::get_value_and_holder: "
@@ -378,8 +404,10 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
 
     const size_t n_types = tinfo.size();
 
-    if (n_types == 0)
-        pybind11_fail("instance allocation failed: new instance has no pybind11-registered base types");
+    if (n_types == 0) {
+        pybind11_fail(
+            "instance allocation failed: new instance has no pybind11-registered base types");
+    }
 
     simple_layout =
         n_types == 1 && tinfo.front()->holder_size_in_ptrs <= instance_simple_holder_in_ptrs();
@@ -410,7 +438,9 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
         // just wrappers around malloc.
 #if PY_VERSION_HEX >= 0x03050000
         nonsimple.values_and_holders = (void **) PyMem_Calloc(space, sizeof(void *));
-        if (!nonsimple.values_and_holders) throw std::bad_alloc();
+        if (!nonsimple.values_and_holders) {
+            throw std::bad_alloc();
+        }
 #else
         nonsimple.values_and_holders = (void **) PyMem_New(void *, space);
         if (!nonsimple.values_and_holders) throw std::bad_alloc();
@@ -423,14 +453,16 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
 
 // NOLINTNEXTLINE(readability-make-member-function-const)
 PYBIND11_NOINLINE void instance::deallocate_layout() {
-    if (!simple_layout)
+    if (!simple_layout) {
         PyMem_Free(nonsimple.values_and_holders);
+    }
 }
 
 PYBIND11_NOINLINE bool isinstance_generic(handle obj, const std::type_info &tp) {
     handle type = detail::get_type_handle(tp, false);
-    if (!type)
+    if (!type) {
         return false;
+    }
     return isinstance(obj, type);
 }
 
@@ -447,14 +479,16 @@ PYBIND11_NOINLINE std::string error_string() {
         errorString += handle(scope.type).attr("__name__").cast<std::string>();
         errorString += ": ";
     }
-    if (scope.value)
+    if (scope.value) {
         errorString += (std::string) str(scope.value);
+    }
 
     PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
 
 #if PY_MAJOR_VERSION >= 3
-    if (scope.trace != nullptr)
+    if (scope.trace != nullptr) {
         PyException_SetTraceback(scope.value, scope.trace);
+    }
 #endif
 
 #if !defined(PYPY_VERSION)
@@ -462,8 +496,9 @@ PYBIND11_NOINLINE std::string error_string() {
         auto *trace = (PyTracebackObject *) scope.trace;
 
         /* Get the deepest trace possible */
-        while (trace->tb_next)
+        while (trace->tb_next) {
             trace = trace->tb_next;
+        }
 
         PyFrameObject *frame = trace->tb_frame;
         errorString += "\n\nAt:\n";
@@ -493,8 +528,9 @@ PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_i
     auto range = instances.equal_range(ptr);
     for (auto it = range.first; it != range.second; ++it) {
         for (const auto &vh : values_and_holders(it->second)) {
-            if (vh.type == type)
+            if (vh.type == type) {
                 return handle((PyObject *) it->second);
+            }
         }
     }
     return handle();
@@ -535,15 +571,18 @@ class type_caster_generic {
                                          void *(*copy_constructor)(const void *),
                                          void *(*move_constructor)(const void *),
                                          const void *existing_holder = nullptr) {
-        if (!tinfo) // no type info: error will be set already
+        if (!tinfo) { // no type info: error will be set already
             return handle();
+        }
 
         void *src = const_cast<void *>(_src);
-        if (src == nullptr)
+        if (src == nullptr) {
             return none().release();
+        }
 
-        if (handle registered_inst = find_registered_python_instance(src, tinfo))
+        if (handle registered_inst = find_registered_python_instance(src, tinfo)) {
             return registered_inst;
+        }
 
         auto inst = reinterpret_steal<object>(make_new_instance(tinfo->type));
         auto wrapper = reinterpret_cast<instance *>(inst.ptr());
@@ -564,9 +603,9 @@ class type_caster_generic {
                 break;
 
             case return_value_policy::copy:
-                if (copy_constructor)
+                if (copy_constructor) {
                     valueptr = copy_constructor(src);
-                else {
+                } else {
 #if defined(NDEBUG)
                     throw cast_error("return_value_policy = copy, but type is "
                                      "non-copyable! (compile in debug mode for details)");
@@ -581,11 +620,11 @@ class type_caster_generic {
                 break;
 
             case return_value_policy::move:
-                if (move_constructor)
+                if (move_constructor) {
                     valueptr = move_constructor(src);
-                else if (copy_constructor)
+                } else if (copy_constructor) {
                     valueptr = copy_constructor(src);
-                else {
+                } else {
 #if defined(NDEBUG)
                     throw cast_error("return_value_policy = move, but type is neither "
                                      "movable nor copyable! "
@@ -650,8 +689,9 @@ class type_caster_generic {
     }
     bool try_direct_conversions(handle src) {
         for (auto &converter : *typeinfo->direct_conversions) {
-            if (converter(src.ptr(), value))
+            if (converter(src.ptr(), value)) {
                 return true;
+            }
         }
         return false;
     }
@@ -659,8 +699,9 @@ class type_caster_generic {
 
     PYBIND11_NOINLINE static void *local_load(PyObject *src, const type_info *ti) {
         auto caster = type_caster_generic(ti);
-        if (caster.load(src, false))
+        if (caster.load(src, false)) {
             return caster.value;
+        }
         return nullptr;
     }
 
@@ -669,14 +710,16 @@ class type_caster_generic {
     PYBIND11_NOINLINE bool try_load_foreign_module_local(handle src) {
         constexpr auto *local_key = PYBIND11_MODULE_LOCAL_ID;
         const auto pytype = type::handle_of(src);
-        if (!hasattr(pytype, local_key))
+        if (!hasattr(pytype, local_key)) {
             return false;
+        }
 
         type_info *foreign_typeinfo = reinterpret_borrow<capsule>(getattr(pytype, local_key));
         // Only consider this foreign loader if actually foreign and is a loader of the correct cpp type
         if (foreign_typeinfo->module_local_load == &local_load
-            || (cpptype && !same_type(*cpptype, *foreign_typeinfo->cpptype)))
+            || (cpptype && !same_type(*cpptype, *foreign_typeinfo->cpptype))) {
             return false;
+        }
 
         if (auto result = foreign_typeinfo->module_local_load(src.ptr(), foreign_typeinfo)) {
             value = result;
@@ -690,8 +733,12 @@ class type_caster_generic {
     // logic (without having to resort to virtual inheritance).
     template <typename ThisT>
     PYBIND11_NOINLINE bool load_impl(handle src, bool convert) {
-        if (!src) return false;
-        if (!typeinfo) return try_load_foreign_module_local(src);
+        if (!src) {
+            return false;
+        }
+        if (!typeinfo) {
+            return try_load_foreign_module_local(src);
+        }
 
         auto &this_ = static_cast<ThisT &>(*this);
         this_.check_holder_compat();
@@ -734,8 +781,9 @@ class type_caster_generic {
             // Case 2c: C++ multiple inheritance is involved and we couldn't find an exact type match
             // in the registered bases, above, so try implicit casting (needed for proper C++ casting
             // when MI is involved).
-            if (this_.try_implicit_casts(src, convert))
+            if (this_.try_implicit_casts(src, convert)) {
                 return true;
+            }
         }
 
         // Perform an implicit conversion
@@ -747,8 +795,9 @@ class type_caster_generic {
                     return true;
                 }
             }
-            if (this_.try_direct_conversions(src))
+            if (this_.try_direct_conversions(src)) {
                 return true;
+            }
         }
 
         // Failed to match local typeinfo. Try again with global.
@@ -767,7 +816,9 @@ class type_caster_generic {
         // Custom converters didn't take None, now we convert None to nullptr.
         if (src.is_none()) {
            // Defer accepting None to other overloads (if we aren't in convert mode):
-           if (!convert) return false;
+           if (!convert) {
+               return false;
+           }
            value = nullptr;
            return true;
         }
@@ -907,8 +958,10 @@ template <typename type> class type_caster_base : public type_caster_generic {
     explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
 
     static handle cast(const itype &src, return_value_policy policy, handle parent) {
-        if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
             policy = return_value_policy::copy;
+        }
         return cast(&src, policy, parent);
     }
 
@@ -960,7 +1013,12 @@ template <typename type> class type_caster_base : public type_caster_generic {
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator itype*() { return (type *) value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator itype&() { if (!value) throw reference_cast_error(); return *((itype *) value); }
+    operator itype&() {
+        if (!value) {
+            throw reference_cast_error();
+        }
+        return *((itype *) value);
+    }
 
 protected:
     using Constructor = void *(*)(const void *);
diff --git a/include/pybind11/detail/typeid.h b/include/pybind11/detail/typeid.h
index 39ba8ce0f7..53c166bebc 100644
--- a/include/pybind11/detail/typeid.h
+++ b/include/pybind11/detail/typeid.h
@@ -24,7 +24,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 inline void erase_all(std::string &string, const std::string &search) {
     for (size_t pos = 0;;) {
         pos = string.find(search, pos);
-        if (pos == std::string::npos) break;
+        if (pos == std::string::npos) {
+            break;
+        }
         string.erase(pos, search.length());
     }
 }
@@ -34,8 +36,9 @@ PYBIND11_NOINLINE void clean_type_id(std::string &name) {
     int status = 0;
     std::unique_ptr<char, void (*)(void *)> res {
         abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status), std::free };
-    if (status == 0)
+    if (status == 0) {
         name = res.get();
+    }
 #else
     detail::erase_all(name, "class ");
     detail::erase_all(name, "struct ");
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 696099fa65..87f4e9f888 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -145,8 +145,9 @@ template <typename Type_> struct EigenProps {
     // (preferring the latter if it will fit in either, i.e. for a fully dynamic matrix type).
     static EigenConformable<row_major> conformable(const array &a) {
         const auto dims = a.ndim();
-        if (dims < 1 || dims > 2)
+        if (dims < 1 || dims > 2) {
             return false;
+        }
 
         if (dims == 2) { // Matrix type: require exact match (or dynamic)
 
@@ -155,9 +156,10 @@ template <typename Type_> struct EigenProps {
                 np_cols = a.shape(1),
                 np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
                 np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
-            if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows) ||
-                (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols))
+            if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows)
+                || (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols)) {
                 return false;
+            }
 
             return {np_rows, np_cols, np_rstride, np_cstride};
         }
@@ -168,8 +170,9 @@ template <typename Type_> struct EigenProps {
               stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
 
         if (vector) { // Eigen type is a compile-time vector
-            if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n)
+            if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n) {
                 return false; // Vector size mismatch
+            }
             return {rows == 1 ? 1 : n, cols == 1 ? 1 : n, stride};
         }
         if (fixed) {
@@ -179,10 +182,14 @@ template <typename Type_> struct EigenProps {
         if (fixed_cols) {
             // Since this isn't a vector, cols must be != 1.  We allow this only if it exactly
             // equals the number of elements (rows is Dynamic, and so 1 row is allowed).
-            if (cols != n) return false;
+            if (cols != n) {
+                return false;
+            }
             return {1, n, stride};
         } // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
-            if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) return false;
+        if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) {
+            return false;
+        }
             return {n, 1, stride};
     }
 
@@ -213,14 +220,18 @@ template <typename Type_> struct EigenProps {
 template <typename props> handle eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
     constexpr ssize_t elem_size = sizeof(typename props::Scalar);
     array a;
-    if (props::vector)
+    if (props::vector) {
         a = array({ src.size() }, { elem_size * src.innerStride() }, src.data(), base);
-    else
-        a = array({ src.rows(), src.cols() }, { elem_size * src.rowStride(), elem_size * src.colStride() },
-                  src.data(), base);
+    } else {
+        a = array({src.rows(), src.cols()},
+                  {elem_size * src.rowStride(), elem_size * src.colStride()},
+                  src.data(),
+                  base);
+    }
 
-    if (!writeable)
+    if (!writeable) {
         array_proxy(a.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
+    }
 
     return a.release();
 }
@@ -255,28 +266,35 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
 
     bool load(handle src, bool convert) {
         // If we're in no-convert mode, only load if given an array of the correct type
-        if (!convert && !isinstance<array_t<Scalar>>(src))
+        if (!convert && !isinstance<array_t<Scalar>>(src)) {
             return false;
+        }
 
         // Coerce into an array, but don't do type conversion yet; the copy below handles it.
         auto buf = array::ensure(src);
 
-        if (!buf)
+        if (!buf) {
             return false;
+        }
 
         auto dims = buf.ndim();
-        if (dims < 1 || dims > 2)
+        if (dims < 1 || dims > 2) {
             return false;
+        }
 
         auto fits = props::conformable(buf);
-        if (!fits)
+        if (!fits) {
             return false;
+        }
 
         // Allocate the new type, then build a numpy reference into it
         value = Type(fits.rows, fits.cols);
         auto ref = reinterpret_steal<array>(eigen_ref_array<props>(value));
-        if (dims == 1) ref = ref.squeeze();
-        else if (ref.ndim() == 1) buf = buf.squeeze();
+        if (dims == 1) {
+            ref = ref.squeeze();
+        } else if (ref.ndim() == 1) {
+            buf = buf.squeeze();
+        }
 
         int result = detail::npy_api::get().PyArray_CopyInto_(ref.ptr(), buf.ptr());
 
@@ -323,14 +341,18 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     }
     // lvalue reference return; default (automatic) becomes copy
     static handle cast(Type &src, return_value_policy policy, handle parent) {
-        if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
             policy = return_value_policy::copy;
+        }
         return cast_impl(&src, policy, parent);
     }
     // const lvalue reference return; default (automatic) becomes copy
     static handle cast(const Type &src, return_value_policy policy, handle parent) {
-        if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
             policy = return_value_policy::copy;
+        }
         return cast(&src, policy, parent);
     }
     // non-const pointer return
@@ -439,11 +461,14 @@ struct type_caster<
 
             if (aref && (!need_writeable || aref.writeable())) {
                 fits = props::conformable(aref);
-                if (!fits) return false; // Incompatible dimensions
-                if (!fits.template stride_compatible<props>())
+                if (!fits) {
+                    return false; // Incompatible dimensions
+                }
+                if (!fits.template stride_compatible<props>()) {
                     need_copy = true;
-                else
+                } else {
                     copy_or_ref = std::move(aref);
+                }
             }
             else {
                 need_copy = true;
@@ -454,13 +479,18 @@ struct type_caster<
             // We need to copy: If we need a mutable reference, or we're not supposed to convert
             // (either because we're in the no-convert overload pass, or because we're explicitly
             // instructed not to copy (via `py::arg().noconvert()`) we have to fail loading.
-            if (!convert || need_writeable) return false;
+            if (!convert || need_writeable) {
+                return false;
+            }
 
             Array copy = Array::ensure(src);
-            if (!copy) return false;
+            if (!copy) {
+                return false;
+            }
             fits = props::conformable(copy);
-            if (!fits || !fits.template stride_compatible<props>())
+            if (!fits || !fits.template stride_compatible<props>()) {
                 return false;
+            }
             copy_or_ref = std::move(copy);
             loader_life_support::add_patient(copy_or_ref);
         }
@@ -550,8 +580,9 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
     static constexpr bool rowMajor = Type::IsRowMajor;
 
     bool load(handle src, bool) {
-        if (!src)
+        if (!src) {
             return false;
+        }
 
         auto obj = reinterpret_borrow<object>(src);
         object sparse_module = module_::import("scipy.sparse");
@@ -572,8 +603,9 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         auto shape = pybind11::tuple((pybind11::object) obj.attr("shape"));
         auto nnz = obj.attr("nnz").cast<Index>();
 
-        if (!values || !innerIndices || !outerIndices)
+        if (!values || !innerIndices || !outerIndices) {
             return false;
+        }
 
         value = EigenMapSparseMatrix<Scalar,
                                      Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 9ab1ce9c0a..9da2862f38 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -77,12 +77,14 @@ struct embedded_module {
     using init_t = void (*)();
 #endif
     embedded_module(const char *name, init_t init) {
-        if (Py_IsInitialized() != 0)
+        if (Py_IsInitialized() != 0) {
             pybind11_fail("Can't add new modules after the interpreter has been initialized");
+        }
 
         auto result = PyImport_AppendInittab(name, init);
-        if (result == -1)
+        if (result == -1) {
             pybind11_fail("Insufficient memory to add a new module");
+        }
     }
 };
 
@@ -135,8 +137,9 @@ inline void set_interpreter_argv(int argc, const char *const *argv, bool add_pro
 
     const char *const empty_argv[]{"\0"};
     const char *const *safe_argv = special_case ? empty_argv : argv;
-    if (special_case)
+    if (special_case) {
         argc = 1;
+    }
 
     auto argv_size = static_cast<size_t>(argc);
 #if PY_MAJOR_VERSION >= 3
@@ -192,8 +195,9 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
                                    int argc = 0,
                                    const char *const *argv = nullptr,
                                    bool add_program_dir_to_path = true) {
-    if (Py_IsInitialized() != 0)
+    if (Py_IsInitialized() != 0) {
         pybind11_fail("The interpreter is already running");
+    }
 
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
 
@@ -244,8 +248,9 @@ inline void finalize_interpreter() {
     // during destruction), so we get the pointer-pointer here and check it after Py_Finalize().
     detail::internals **internals_ptr_ptr = detail::get_internals_pp();
     // It could also be stashed in builtins, so look there too:
-    if (builtins.contains(id) && isinstance<capsule>(builtins[id]))
+    if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
         internals_ptr_ptr = capsule(builtins[id]);
+    }
 
     Py_Finalize();
 
@@ -285,8 +290,9 @@ class scoped_interpreter {
     scoped_interpreter &operator=(scoped_interpreter &&) = delete;
 
     ~scoped_interpreter() {
-        if (is_valid)
+        if (is_valid) {
             finalize_interpreter();
+        }
     }
 
 private:
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 4248551e9b..8009fbde58 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -46,8 +46,9 @@ enum eval_mode {
 
 template <eval_mode mode = eval_expr>
 object eval(const str &expr, object global = globals(), object local = object()) {
-    if (!local)
+    if (!local) {
         local = global;
+    }
 
     detail::ensure_builtins_in_globals(global);
 
@@ -64,8 +65,9 @@ object eval(const str &expr, object global = globals(), object local = object())
     }
 
     PyObject *result = PyRun_String(buffer.c_str(), start, global.ptr(), local.ptr());
-    if (!result)
+    if (!result) {
         throw error_already_set();
+    }
     return reinterpret_steal<object>(result);
 }
 
@@ -102,8 +104,9 @@ object eval_file(str) {
 #else
 template <eval_mode mode = eval_statements>
 object eval_file(str fname, object global = globals(), object local = object()) {
-    if (!local)
+    if (!local) {
         local = global;
+    }
 
     detail::ensure_builtins_in_globals(global);
 
@@ -154,8 +157,9 @@ object eval_file(str fname, object global = globals(), object local = object())
                                     local.ptr(), closeFile);
 #endif
 
-    if (!result)
+    if (!result) {
         throw error_already_set();
+    }
     return reinterpret_steal<object>(result);
 }
 #endif
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 7912aef175..9e2f0b5b6b 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -25,12 +25,15 @@ struct type_caster<std::function<Return(Args...)>> {
     bool load(handle src, bool convert) {
         if (src.is_none()) {
             // Defer accepting None to other overloads (if we aren't in convert mode):
-            if (!convert) return false;
+            if (!convert) {
+                return false;
+            }
             return true;
         }
 
-        if (!isinstance<function>(src))
+        if (!isinstance<function>(src)) {
             return false;
+        }
 
         auto func = reinterpret_borrow<function>(src);
 
@@ -104,12 +107,14 @@ struct type_caster<std::function<Return(Args...)>> {
 
     template <typename Func>
     static handle cast(Func &&f_, return_value_policy policy, handle /* parent */) {
-        if (!f_)
+        if (!f_) {
             return none().inc_ref();
+        }
 
         auto result = f_.template target<function_type>();
-        if (result)
+        if (result) {
             return cpp_function(*result, policy).release();
+        }
         return cpp_function(std::forward<Func>(f_), policy).release();
     }
 
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index b73aaa3f54..b493fd145b 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -99,8 +99,9 @@ class gil_scoped_acquire {
                     pybind11_fail("scoped_acquire::dec_ref(): internal error!");
             #endif
             PyThreadState_Clear(tstate);
-            if (active)
+            if (active) {
                 PyThreadState_DeleteCurrent();
+            }
             PYBIND11_TLS_DELETE_VALUE(detail::get_internals().tstate);
             release = false;
         }
@@ -117,8 +118,9 @@ class gil_scoped_acquire {
 
     PYBIND11_NOINLINE ~gil_scoped_acquire() {
         dec_ref();
-        if (release)
-           PyEval_SaveThread();
+        if (release) {
+            PyEval_SaveThread();
+        }
     }
 private:
     PyThreadState *tstate = nullptr;
@@ -150,11 +152,13 @@ class gil_scoped_release {
     }
 
     ~gil_scoped_release() {
-        if (!tstate)
+        if (!tstate) {
             return;
+        }
         // `PyEval_RestoreThread()` should not be called if runtime is finalizing
-        if (active)
+        if (active) {
             PyEval_RestoreThread(tstate);
+        }
         if (disassoc) {
             auto key = detail::get_internals().tstate;
             PYBIND11_TLS_REPLACE_VALUE(key, tstate);
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 95449a07ba..8c0772c281 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -71,23 +71,26 @@ class pythonbuf : public std::streambuf {
             return static_cast<unsigned char>(c) <= 0xEF;
         };
         // If the last character is ASCII, there are no incomplete code points
-        if (is_ascii(*rpptr))
+        if (is_ascii(*rpptr)) {
             return 0;
+        }
         // Otherwise, work back from the end of the buffer and find the first
         // UTF-8 leading byte
         const auto rpend   = rbase - rpptr >= 3 ? rpptr + 3 : rbase;
         const auto leading = std::find_if(rpptr, rpend, is_leading);
-        if (leading == rbase)
+        if (leading == rbase) {
             return 0;
+        }
         const auto dist    = static_cast<size_t>(leading - rpptr);
         size_t remainder   = 0;
 
-        if (dist == 0)
+        if (dist == 0) {
             remainder = 1; // 1-byte code point is impossible
-        else if (dist == 1)
+        } else if (dist == 1) {
             remainder = is_leading_2b(*leading) ? 0 : dist + 1;
-        else if (dist == 2)
+        } else if (dist == 2) {
             remainder = is_leading_3b(*leading) ? 0 : dist + 1;
+        }
         // else if (dist >= 3), at least 4 bytes before encountering an UTF-8
         // leading byte, either no remainder or invalid UTF-8.
         // Invalid UTF-8 will cause an exception later when converting
@@ -110,8 +113,9 @@ class pythonbuf : public std::streambuf {
             }
 
             // Copy the remainder at the end of the buffer to the beginning:
-            if (remainder > 0)
+            if (remainder > 0) {
                 std::memmove(pbase(), pptr() - remainder, remainder);
+            }
             setp(pbase(), epptr());
             pbump(static_cast<int>(remainder));
         }
@@ -223,10 +227,12 @@ class OstreamRedirect {
         : do_stdout_(do_stdout), do_stderr_(do_stderr) {}
 
     void enter() {
-        if (do_stdout_)
+        if (do_stdout_) {
             redirect_stdout.reset(new scoped_ostream_redirect());
-        if (do_stderr_)
+        }
+        if (do_stderr_) {
             redirect_stderr.reset(new scoped_estream_redirect());
+        }
     }
 
     void exit() {
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 95a743acec..40bbff8ea0 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -87,10 +87,12 @@ struct numpy_internals {
 
     numpy_type_info *get_type_info(const std::type_info& tinfo, bool throw_if_missing = true) {
         auto it = registered_dtypes.find(std::type_index(tinfo));
-        if (it != registered_dtypes.end())
+        if (it != registered_dtypes.end()) {
             return &(it->second);
-        if (throw_if_missing)
+        }
+        if (throw_if_missing) {
             pybind11_fail(std::string("NumPy type info missing for ") + tinfo.name());
+        }
         return nullptr;
     }
 
@@ -105,8 +107,9 @@ PYBIND11_NOINLINE void load_numpy_internals(numpy_internals* &ptr) {
 
 inline numpy_internals& get_numpy_internals() {
     static numpy_internals* ptr = nullptr;
-    if (!ptr)
+    if (!ptr) {
         load_numpy_internals(ptr);
+    }
     return *ptr;
 }
 
@@ -235,8 +238,9 @@ struct npy_api {
         npy_api api;
 #define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
         DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
-        if (api.PyArray_GetNDArrayCFeatureVersion_() < 0x7)
+        if (api.PyArray_GetNDArrayCFeatureVersion_() < 0x7) {
             pybind11_fail("pybind11 numpy support requires numpy >= 1.7.0");
+        }
         DECL_NPY_API(PyArray_Type);
         DECL_NPY_API(PyVoidArrType_Type);
         DECL_NPY_API(PyArrayDescr_Type);
@@ -491,8 +495,9 @@ class dtype : public object {
     /// This is essentially the same as calling numpy.dtype(args) in Python.
     static dtype from_args(object args) {
         PyObject *ptr = nullptr;
-        if ((detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) == 0) || !ptr)
+        if ((detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) == 0) || !ptr) {
             throw error_already_set();
+        }
         return reinterpret_steal<dtype>(ptr);
     }
 
@@ -536,8 +541,9 @@ class dtype : public object {
     dtype strip_padding(ssize_t itemsize) {
         // Recursively strip all void fields with empty names that are generated for
         // padding fields (as of NumPy v1.11).
-        if (!has_fields())
+        if (!has_fields()) {
             return *this;
+        }
 
         struct field_descr { PYBIND11_STR_TYPE name; object format; pybind11::int_ offset; };
         std::vector<field_descr> field_descriptors;
@@ -547,8 +553,9 @@ class dtype : public object {
             auto name = spec[0].cast<pybind11::str>();
             auto format = spec[1].cast<tuple>()[0].cast<dtype>();
             auto offset = spec[1].cast<tuple>()[1].cast<pybind11::int_>();
-            if ((len(name) == 0u) && format.kind() == 'V')
+            if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
+            }
             field_descriptors.push_back({(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
         }
 
@@ -586,22 +593,25 @@ class array : public buffer {
     array(const pybind11::dtype &dt, ShapeContainer shape, StridesContainer strides,
           const void *ptr = nullptr, handle base = handle()) {
 
-        if (strides->empty())
+        if (strides->empty()) {
             *strides = detail::c_strides(*shape, dt.itemsize());
+        }
 
         auto ndim = shape->size();
-        if (ndim != strides->size())
+        if (ndim != strides->size()) {
             pybind11_fail("NumPy: shape ndim doesn't match strides ndim");
+        }
         auto descr = dt;
 
         int flags = 0;
         if (base && ptr) {
-            if (isinstance<array>(base))
+            if (isinstance<array>(base)) {
                 /* Copy flags from base (except ownership bit) */
                 flags = reinterpret_borrow<array>(base).flags() & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
-            else
+            } else {
                 /* Writable by default, easy to downgrade later on if needed */
                 flags = detail::npy_api::NPY_ARRAY_WRITEABLE_;
+            }
         }
 
         auto &api = detail::npy_api::get();
@@ -611,8 +621,9 @@ class array : public buffer {
             reinterpret_cast<Py_intptr_t*>(shape->data()),
             reinterpret_cast<Py_intptr_t*>(strides->data()),
             const_cast<void *>(ptr), flags, nullptr));
-        if (!tmp)
+        if (!tmp) {
             throw error_already_set();
+        }
         if (ptr) {
             if (base) {
                 api.PyArray_SetBaseObject_(tmp.ptr(), base.inc_ref().ptr());
@@ -681,8 +692,9 @@ class array : public buffer {
 
     /// Dimension along a given axis
     ssize_t shape(ssize_t dim) const {
-        if (dim >= ndim())
+        if (dim >= ndim()) {
             fail_dim_check(dim, "invalid axis");
+        }
         return shape()[dim];
     }
 
@@ -693,8 +705,9 @@ class array : public buffer {
 
     /// Stride along a given axis
     ssize_t strides(ssize_t dim) const {
-        if (dim >= ndim())
+        if (dim >= ndim()) {
             fail_dim_check(dim, "invalid axis");
+        }
         return strides()[dim];
     }
 
@@ -730,8 +743,9 @@ class array : public buffer {
     /// Byte offset from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
     template<typename... Ix> ssize_t offset_at(Ix... index) const {
-        if ((ssize_t) sizeof...(index) > ndim())
+        if ((ssize_t) sizeof...(index) > ndim()) {
             fail_dim_check(sizeof...(index), "too many indices for an array");
+        }
         return byte_offset(ssize_t(index)...);
     }
 
@@ -750,9 +764,11 @@ class array : public buffer {
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
     template <typename T, ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
-        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims)
-            throw std::domain_error("array has incorrect number of dimensions: " + std::to_string(ndim()) +
-                    "; expected " + std::to_string(Dims));
+        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
+            throw std::domain_error("array has incorrect number of dimensions: "
+                                    + std::to_string(ndim()) + "; expected "
+                                    + std::to_string(Dims));
+        }
         return detail::unchecked_mutable_reference<T, Dims>(mutable_data(), shape(), strides(), ndim());
     }
 
@@ -764,9 +780,11 @@ class array : public buffer {
      * invalid dimensions or dimension indices.
      */
     template <typename T, ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
-        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims)
-            throw std::domain_error("array has incorrect number of dimensions: " + std::to_string(ndim()) +
-                    "; expected " + std::to_string(Dims));
+        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
+            throw std::domain_error("array has incorrect number of dimensions: "
+                                    + std::to_string(ndim()) + "; expected "
+                                    + std::to_string(Dims));
+        }
         return detail::unchecked_reference<T, Dims>(data(), shape(), strides(), ndim());
     }
 
@@ -789,7 +807,9 @@ class array : public buffer {
         auto new_array = reinterpret_steal<object>(
             detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1)
         );
-        if (!new_array) throw error_already_set();
+        if (!new_array) {
+            throw error_already_set();
+        }
         if (isinstance<array>(new_array)) { *this = std::move(new_array); }
     }
 
@@ -824,8 +844,9 @@ class array : public buffer {
     /// In case of an error, nullptr is returned and the Python error is cleared.
     static array ensure(handle h, int ExtraFlags = 0) {
         auto result = reinterpret_steal<array>(raw_array(h.ptr(), ExtraFlags));
-        if (!result)
+        if (!result) {
             PyErr_Clear();
+        }
         return result;
     }
 
@@ -843,8 +864,9 @@ class array : public buffer {
     }
 
     void check_writeable() const {
-        if (!writeable())
+        if (!writeable()) {
             throw std::domain_error("array is not writeable");
+        }
     }
 
     template<typename... Ix> void check_dimensions(Ix... index) const {
@@ -890,13 +912,19 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
 
     PYBIND11_DEPRECATED("Use array_t<T>::ensure() instead")
     array_t(handle h, bool is_borrowed) : array(raw_array_t(h.ptr()), stolen_t{}) {
-        if (!m_ptr) PyErr_Clear();
-        if (!is_borrowed) Py_XDECREF(h.ptr());
+        if (!m_ptr) {
+            PyErr_Clear();
+        }
+        if (!is_borrowed) {
+            Py_XDECREF(h.ptr());
+        }
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     array_t(const object &o) : array(raw_array_t(o.ptr()), stolen_t{}) {
-        if (!m_ptr) throw error_already_set();
+        if (!m_ptr) {
+            throw error_already_set();
+        }
     }
 
     explicit array_t(const buffer_info& info, handle base = handle()) : array(info, base) { }
@@ -933,15 +961,17 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
 
     // Reference to element at a given index
     template<typename... Ix> const T& at(Ix... index) const {
-        if ((ssize_t) sizeof...(index) != ndim())
+        if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
+        }
         return *(static_cast<const T*>(array::data()) + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     // Mutable reference to element at a given index
     template<typename... Ix> T& mutable_at(Ix... index) {
-        if ((ssize_t) sizeof...(index) != ndim())
+        if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
+        }
         return *(static_cast<T*>(array::mutable_data()) + byte_offset(ssize_t(index)...) / itemsize());
     }
 
@@ -970,8 +1000,9 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
     /// it).  In case of an error, nullptr is returned and the Python error is cleared.
     static array_t ensure(handle h) {
         auto result = reinterpret_steal<array_t>(raw_array_t(h.ptr()));
-        if (!result)
+        if (!result) {
             PyErr_Clear();
+        }
         return result;
     }
 
@@ -1032,8 +1063,9 @@ struct pyobject_caster<array_t<T, ExtraFlags>> {
     using type = array_t<T, ExtraFlags>;
 
     bool load(handle src, bool convert) {
-        if (!convert && !type::check_(src))
+        if (!convert && !type::check_(src)) {
             return false;
+        }
         value = type::ensure(src);
         return static_cast<bool>(value);
     }
@@ -1098,8 +1130,9 @@ struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmet
     static constexpr int value = values[detail::is_fmt_numeric<T>::index];
 
     static pybind11::dtype dtype() {
-        if (auto ptr = npy_api::get().PyArray_DescrFromType_(value))
+        if (auto ptr = npy_api::get().PyArray_DescrFromType_(value)) {
             return reinterpret_steal<pybind11::dtype>(ptr);
+        }
         pybind11_fail("Unsupported buffer format!");
     }
 };
@@ -1147,8 +1180,9 @@ PYBIND11_NOINLINE void register_structured_dtype(
     bool (*direct_converter)(PyObject *, void *&)) {
 
     auto& numpy_internals = get_numpy_internals();
-    if (numpy_internals.get_type_info(tinfo, false))
+    if (numpy_internals.get_type_info(tinfo, false)) {
         pybind11_fail("NumPy: dtype is already registered");
+    }
 
     // Use ordered fields because order matters as of NumPy 1.14:
     // https://docs.scipy.org/doc/numpy/release.html#multiple-field-indexing-assignment-of-structured-arrays
@@ -1158,9 +1192,10 @@ PYBIND11_NOINLINE void register_structured_dtype(
 
     list names, formats, offsets;
     for (auto& field : ordered_fields) {
-        if (!field.descr)
-            pybind11_fail(std::string("NumPy: unsupported field dtype: `") +
-                            field.name + "` @ " + tinfo.name());
+        if (!field.descr) {
+            pybind11_fail(std::string("NumPy: unsupported field dtype: `") + field.name + "` @ "
+                          + tinfo.name());
+        }
         names.append(PYBIND11_STR_TYPE(field.name));
         formats.append(field.descr);
         offsets.append(pybind11::int_(field.offset));
@@ -1186,21 +1221,24 @@ PYBIND11_NOINLINE void register_structured_dtype(
     // isn't guaranteed to work due to https://github.com/numpy/numpy/issues/9049
     oss << "^T{";
     for (auto& field : ordered_fields) {
-        if (field.offset > offset)
+        if (field.offset > offset) {
             oss << (field.offset - offset) << 'x';
+        }
         oss << field.format << ':' << field.name << ':';
         offset = field.offset + field.size;
     }
-    if (itemsize > offset)
+    if (itemsize > offset) {
         oss << (itemsize - offset) << 'x';
+    }
     oss << '}';
     auto format_str = oss.str();
 
     // Sanity check: verify that NumPy properly parses our buffer format string
     auto& api = npy_api::get();
     auto arr =  array(buffer_info(nullptr, itemsize, format_str, 1));
-    if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr()))
+    if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr())) {
         pybind11_fail("NumPy: invalid buffer descriptor!");
+    }
 
     auto tindex = std::type_index(tinfo);
     numpy_internals.registered_dtypes[tindex] = { dtype_ptr, format_str };
@@ -1234,8 +1272,9 @@ template <typename T, typename SFINAE> struct npy_format_descriptor {
 
     static bool direct_converter(PyObject *obj, void*& value) {
         auto& api = npy_api::get();
-        if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_))
+        if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_)) {
             return false;
+        }
         if (auto descr = reinterpret_steal<object>(api.PyArray_DescrFromScalar_(obj))) {
             if (api.PyArray_EquivTypes_(dtype_ptr(), descr.ptr())) {
                 value = ((PyVoidScalarObject_Proxy *) obj)->obval;
@@ -1363,12 +1402,14 @@ template <size_t N> class multi_array_iterator {
           m_common_iterator() {
 
         // Manual copy to avoid conversion warning if using std::copy
-        for (size_t i = 0; i < shape.size(); ++i)
+        for (size_t i = 0; i < shape.size(); ++i) {
             m_shape[i] = shape[i];
+        }
 
         container_type strides(shape.size());
-        for (size_t i = 0; i < N; ++i)
+        for (size_t i = 0; i < N; ++i) {
             init_common_iterator(buffers[i], shape, m_common_iterator[i], strides);
+        }
     }
 
     multi_array_iterator& operator++() {
@@ -1401,10 +1442,11 @@ template <size_t N> class multi_array_iterator {
         auto strides_iter = strides.rbegin();
 
         while (buffer_shape_iter != buffer.shape.rend()) {
-            if (*shape_iter == *buffer_shape_iter)
+            if (*shape_iter == *buffer_shape_iter) {
                 *strides_iter = *buffer_strides_iter;
-            else
+            } else {
                 *strides_iter = 0;
+            }
 
             ++buffer_shape_iter;
             ++buffer_strides_iter;
@@ -1417,8 +1459,9 @@ template <size_t N> class multi_array_iterator {
     }
 
     void increment_common_iterator(size_t dim) {
-        for (auto &iter : m_common_iterator)
+        for (auto &iter : m_common_iterator) {
             iter.increment(dim);
+        }
     }
 
     container_type m_shape;
@@ -1451,26 +1494,30 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
             auto &dim_size_out = *res_iter;
 
             // Each input dimension can either be 1 or `n`, but `n` values must match across buffers
-            if (dim_size_out == 1)
+            if (dim_size_out == 1) {
                 dim_size_out = dim_size_in;
-            else if (dim_size_in != 1 && dim_size_in != dim_size_out)
+            } else if (dim_size_in != 1 && dim_size_in != dim_size_out) {
                 pybind11_fail("pybind11::vectorize: incompatible size/dimension of inputs!");
+            }
         }
     }
 
     bool trivial_broadcast_c = true;
     bool trivial_broadcast_f = true;
     for (size_t i = 0; i < N && (trivial_broadcast_c || trivial_broadcast_f); ++i) {
-        if (buffers[i].size == 1)
+        if (buffers[i].size == 1) {
             continue;
+        }
 
         // Require the same number of dimensions:
-        if (buffers[i].ndim != ndim)
+        if (buffers[i].ndim != ndim) {
             return broadcast_trivial::non_trivial;
+        }
 
         // Require all dimensions be full-size:
-        if (!std::equal(buffers[i].shape.cbegin(), buffers[i].shape.cend(), shape.cbegin()))
+        if (!std::equal(buffers[i].shape.cbegin(), buffers[i].shape.cend(), shape.cbegin())) {
             return broadcast_trivial::non_trivial;
+        }
 
         // Check for C contiguity (but only if previous inputs were also C contiguous)
         if (trivial_broadcast_c) {
@@ -1478,10 +1525,11 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
             auto end = buffers[i].shape.crend();
             for (auto shape_iter = buffers[i].shape.crbegin(), stride_iter = buffers[i].strides.crbegin();
                     trivial_broadcast_c && shape_iter != end; ++shape_iter, ++stride_iter) {
-                if (expect_stride == *stride_iter)
+                if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
-                else
+                } else {
                     trivial_broadcast_c = false;
+                }
             }
         }
 
@@ -1491,10 +1539,11 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
             auto end = buffers[i].shape.cend();
             for (auto shape_iter = buffers[i].shape.cbegin(), stride_iter = buffers[i].strides.cbegin();
                     trivial_broadcast_f && shape_iter != end; ++shape_iter, ++stride_iter) {
-                if (expect_stride == *stride_iter)
+                if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
-                else
+                } else {
                     trivial_broadcast_f = false;
+                }
             }
         }
     }
@@ -1527,8 +1576,9 @@ struct vectorize_returned_array {
     using Type = array_t<Return>;
 
     static Type create(broadcast_trivial trivial, const std::vector<ssize_t> &shape) {
-        if (trivial == broadcast_trivial::f_trivial)
+        if (trivial == broadcast_trivial::f_trivial) {
             return array_t<Return, array::f_style>(shape);
+        }
         return array_t<Return>(shape);
     }
 
@@ -1644,14 +1694,17 @@ struct vectorize_helper {
 
         auto result = returned_array::create(trivial, shape);
 
-        if (size == 0) return std::move(result);
+        if (size == 0) {
+            return std::move(result);
+        }
 
         /* Call the function */
         auto mutable_data = returned_array::mutable_data(result);
-        if (trivial == broadcast_trivial::non_trivial)
+        if (trivial == broadcast_trivial::non_trivial) {
             apply_broadcast(buffers, params, mutable_data, size, shape, i_seq, vi_seq, bi_seq);
-        else
+        } else {
             apply_trivial(buffers, params, mutable_data, size, i_seq, vi_seq, bi_seq);
+        }
 
         return std::move(result);
     }
@@ -1675,7 +1728,9 @@ struct vectorize_helper {
 
         for (size_t i = 0; i < size; ++i) {
             returned_array::call(out, i, f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...);
-            for (auto &x : vecparams) x.first += x.second;
+            for (auto &x : vecparams) {
+                x.first += x.second;
+            }
         }
     }
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b64d426869..14e84513fd 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -212,8 +212,9 @@ class cpp_function : public function {
             cast_in args_converter;
 
             /* Try to cast the function arguments into the C++ domain */
-            if (!args_converter.load_args(call))
+            if (!args_converter.load_args(call)) {
                 return PYBIND11_TRY_NEXT_OVERLOAD;
+            }
 
             /* Invoke call policy pre-call hook */
             process_attributes<Extra...>::precall(call);
@@ -286,8 +287,9 @@ class cpp_function : public function {
     class strdup_guard {
     public:
         ~strdup_guard() {
-            for (auto s : strings)
+            for (auto s : strings) {
                 std::free(s);
+            }
         }
         char *operator()(const char *s) {
             auto t = PYBIND11_COMPAT_STRDUP(s);
@@ -318,14 +320,18 @@ class cpp_function : public function {
 
         /* Create copies of all referenced C-style strings */
         rec->name = guarded_strdup(rec->name ? rec->name : "");
-        if (rec->doc) rec->doc = guarded_strdup(rec->doc);
+        if (rec->doc) {
+            rec->doc = guarded_strdup(rec->doc);
+        }
         for (auto &a: rec->args) {
-            if (a.name)
+            if (a.name) {
                 a.name = guarded_strdup(a.name);
-            if (a.descr)
+            }
+            if (a.descr) {
                 a.descr = guarded_strdup(a.descr);
-            else if (a.value)
+            } else if (a.value) {
                 a.descr = guarded_strdup(repr(a.value).cast<std::string>().c_str());
+            }
         }
 
         rec->is_constructor = (std::strcmp(rec->name, "__init__") == 0)
@@ -355,12 +361,14 @@ class cpp_function : public function {
             if (c == '{') {
                 // Write arg name for everything except *args and **kwargs.
                 is_starred = *(pc + 1) == '*';
-                if (is_starred)
+                if (is_starred) {
                     continue;
+                }
                 // Separator for keyword-only arguments, placed before the kw
                 // arguments start (unless we are already putting an *args)
-                if (!rec->has_args && arg_index == rec->nargs_pos)
+                if (!rec->has_args && arg_index == rec->nargs_pos) {
                     signature += "*, ";
+                }
                 if (arg_index < rec->args.size() && rec->args[arg_index].name) {
                     signature += rec->args[arg_index].name;
                 } else if (arg_index == 0 && rec->is_method) {
@@ -377,14 +385,17 @@ class cpp_function : public function {
                 }
                 // Separator for positional-only arguments (placed after the
                 // argument, rather than before like *
-                if (rec->nargs_pos_only > 0 && (arg_index + 1) == rec->nargs_pos_only)
+                if (rec->nargs_pos_only > 0 && (arg_index + 1) == rec->nargs_pos_only) {
                     signature += ", /";
-                if (!is_starred)
+                }
+                if (!is_starred) {
                     arg_index++;
+                }
             } else if (c == '%') {
                 const std::type_info *t = types[type_index++];
-                if (!t)
+                if (!t) {
                     pybind11_fail("Internal error while parsing type signature (1)");
+                }
                 if (auto tinfo = detail::get_type_info(*t)) {
                     handle th((PyObject *) tinfo->type);
                     signature +=
@@ -406,8 +417,9 @@ class cpp_function : public function {
             }
         }
 
-        if (arg_index != args - rec->has_args - rec->has_kwargs || types[type_index] != nullptr)
+        if (arg_index != args - rec->has_args - rec->has_kwargs || types[type_index] != nullptr) {
             pybind11_fail("Internal error while parsing type signature (2)");
+        }
 
 #if PY_MAJOR_VERSION < 3
         if (std::strcmp(rec->name, "__next__") == 0) {
@@ -422,8 +434,9 @@ class cpp_function : public function {
         rec->args.shrink_to_fit();
         rec->nargs = (std::uint16_t) args;
 
-        if (rec->sibling && PYBIND11_INSTANCE_METHOD_CHECK(rec->sibling.ptr()))
+        if (rec->sibling && PYBIND11_INSTANCE_METHOD_CHECK(rec->sibling.ptr())) {
             rec->sibling = PYBIND11_INSTANCE_METHOD_GET_FUNCTION(rec->sibling.ptr());
+        }
 
         detail::function_record *chain = nullptr, *chain_start = rec;
         if (rec->sibling) {
@@ -433,13 +446,16 @@ class cpp_function : public function {
                 chain = (detail::function_record *) rec_capsule;
                 /* Never append a method to an overload chain of a parent class;
                    instead, hide the parent's overloads in this case */
-                if (!chain->scope.is(rec->scope))
+                if (!chain->scope.is(rec->scope)) {
                     chain = nullptr;
+                }
+            }
+            // Don't trigger for things like the default __init__, which are wrapper_descriptors
+            // that we are intentionally replacing
+            else if (!rec->sibling.is_none() && rec->name[0] != '_') {
+                pybind11_fail("Cannot overload existing non-function object \""
+                              + std::string(rec->name) + "\" with a function of the same name");
             }
-            // Don't trigger for things like the default __init__, which are wrapper_descriptors that we are intentionally replacing
-            else if (!rec->sibling.is_none() && rec->name[0] != '_')
-                pybind11_fail("Cannot overload existing non-function object \"" + std::string(rec->name) +
-                        "\" with a function of the same name");
         }
 
         if (!chain) {
@@ -466,21 +482,26 @@ class cpp_function : public function {
             }
 
             m_ptr = PyCFunction_NewEx(rec->def, rec_capsule.ptr(), scope_module.ptr());
-            if (!m_ptr)
+            if (!m_ptr) {
                 pybind11_fail("cpp_function::cpp_function(): Could not allocate function object");
+            }
         } else {
             /* Append at the beginning or end of the overload chain */
             m_ptr = rec->sibling.ptr();
             inc_ref();
-            if (chain->is_method != rec->is_method)
-                pybind11_fail("overloading a method with both static and instance methods is not supported; "
-                    #if defined(NDEBUG)
-                        "compile in debug mode for more details"
+            if (chain->is_method != rec->is_method) {
+                pybind11_fail(
+                    "overloading a method with both static and instance methods is not supported; "
+#if defined(NDEBUG)
+                    "compile in debug mode for more details"
                     #else
-                        "error while attempting to bind " + std::string(rec->is_method ? "instance" : "static") + " method " +
-                        std::string(pybind11::str(rec->scope.attr("__name__"))) + "." + std::string(rec->name) + signature
+                    "error while attempting to bind "
+                    + std::string(rec->is_method ? "instance" : "static") + " method "
+                    + std::string(pybind11::str(rec->scope.attr("__name__"))) + "."
+                    + std::string(rec->name) + signature
                     #endif
                 );
+            }
 
             if (rec->prepend) {
                 // Beginning of chain; we need to replace the capsule's current head-of-the-chain
@@ -494,8 +515,9 @@ class cpp_function : public function {
             } else {
                 // Or end of chain (normal behavior)
                 chain_start = chain;
-                while (chain->next)
+                while (chain->next) {
                     chain = chain->next;
+                }
                 chain->next = unique_rec.release();
                 guarded_strdup.release();
             }
@@ -515,9 +537,12 @@ class cpp_function : public function {
         bool first_user_def = true;
         for (auto it = chain_start; it != nullptr; it = it->next) {
             if (options::show_function_signatures()) {
-                if (index > 0) signatures += "\n";
-                if (chain)
+                if (index > 0) {
+                    signatures += "\n";
+                }
+                if (chain) {
                     signatures += std::to_string(++index) + ". ";
+                }
                 signatures += rec->name;
                 signatures += it->signature;
                 signatures += "\n";
@@ -526,12 +551,19 @@ class cpp_function : public function {
                 // If we're appending another docstring, and aren't printing function signatures, we
                 // need to append a newline first:
                 if (!options::show_function_signatures()) {
-                    if (first_user_def) first_user_def = false;
-                    else signatures += "\n";
+                    if (first_user_def) {
+                        first_user_def = false;
+                    } else {
+                        signatures += "\n";
+                    }
+                }
+                if (options::show_function_signatures()) {
+                    signatures += "\n";
                 }
-                if (options::show_function_signatures()) signatures += "\n";
                 signatures += it->doc;
-                if (options::show_function_signatures()) signatures += "\n";
+                if (options::show_function_signatures()) {
+                    signatures += "\n";
+                }
             }
         }
 
@@ -544,8 +576,10 @@ class cpp_function : public function {
 
         if (rec->is_method) {
             m_ptr = PYBIND11_INSTANCE_METHOD_NEW(m_ptr, rec->scope.ptr());
-            if (!m_ptr)
-                pybind11_fail("cpp_function::cpp_function(): Could not allocate instance method object");
+            if (!m_ptr) {
+                pybind11_fail(
+                    "cpp_function::cpp_function(): Could not allocate instance method object");
+            }
             Py_DECREF(func);
         }
     }
@@ -560,8 +594,9 @@ class cpp_function : public function {
 
         while (rec) {
             detail::function_record *next = rec->next;
-            if (rec->free_data)
+            if (rec->free_data) {
                 rec->free_data(rec);
+            }
             // During initialization, these strings might not have been copied yet,
             // so they cannot be freed. Once the function has been created, they can.
             // Check `make_function_record` for more details.
@@ -574,17 +609,19 @@ class cpp_function : public function {
                     std::free(const_cast<char *>(arg.descr));
                 }
             }
-            for (auto &arg: rec->args)
+            for (auto &arg : rec->args) {
                 arg.value.dec_ref();
+            }
             if (rec->def) {
                 std::free(const_cast<char *>(rec->def->ml_doc));
                 // Python 3.9.0 decref's these in the wrong order; rec->def
                 // If loaded on 3.9.0, let these leak (use Python 3.9.1 at runtime to fix)
                 // See https://github.com/python/cpython/pull/22670
                 #if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
-                    if (!is_zero)
-                        delete rec->def;
-                #else
+                if (!is_zero) {
+                    delete rec->def;
+                }
+#else
                     delete rec->def;
                 #endif
             }
@@ -621,8 +658,9 @@ class cpp_function : public function {
 
             // If this value is already registered it must mean __init__ is invoked multiple times;
             // we really can't support that in C++, so just ignore the second __init__.
-            if (self_value_and_holder.instance_registered())
+            if (self_value_and_holder.instance_registered()) {
                 return none().release().ptr();
+            }
         }
 
         try {
@@ -658,15 +696,22 @@ class cpp_function : public function {
 
                 const function_record &func = *it;
                 size_t num_args = func.nargs;    // Number of positional arguments that we need
-                if (func.has_args) --num_args;   // (but don't count py::args
-                if (func.has_kwargs) --num_args; //  or py::kwargs)
+                if (func.has_args) {
+                    --num_args; // (but don't count py::args
+                }
+                if (func.has_kwargs) {
+                    --num_args; //  or py::kwargs)
+                }
                 size_t pos_args = func.nargs_pos;
 
-                if (!func.has_args && n_args_in > pos_args)
+                if (!func.has_args && n_args_in > pos_args) {
                     continue; // Too many positional arguments for this overload
+                }
 
-                if (n_args_in < pos_args && func.args.size() < pos_args)
-                    continue; // Not enough positional arguments given, and not enough defaults to fill in the blanks
+                if (n_args_in < pos_args && func.args.size() < pos_args) {
+                    continue; // Not enough positional arguments given, and not enough defaults to
+                              // fill in the blanks
+                }
 
                 function_call call(func, parent);
 
@@ -677,8 +722,9 @@ class cpp_function : public function {
                 if (func.is_new_style_constructor) {
                     // The `value` may have been preallocated by an old-style `__init__`
                     // if it was a preceding candidate for overload resolution.
-                    if (self_value_and_holder)
+                    if (self_value_and_holder) {
                         self_value_and_holder.type->dealloc(self_value_and_holder);
+                    }
 
                     call.init_self = PyTuple_GET_ITEM(args_in, 0);
                     call.args.emplace_back(reinterpret_cast<PyObject *>(&self_value_and_holder));
@@ -703,8 +749,9 @@ class cpp_function : public function {
                     call.args.push_back(arg);
                     call.args_convert.push_back(arg_rec ? arg_rec->convert : true);
                 }
-                if (bad_arg)
+                if (bad_arg) {
                     continue; // Maybe it was meant for another overload (issue #688)
+                }
 
                 // Keep track of how many position args we copied out in case we need to come back
                 // to copy the rest into a py::args argument.
@@ -725,12 +772,14 @@ class cpp_function : public function {
                         if (value) {
                             call.args.push_back(value);
                             call.args_convert.push_back(arg_rec.convert);
-                        } else
+                        } else {
                             break;
+                        }
                     }
 
-                    if (args_copied < func.nargs_pos_only)
+                    if (args_copied < func.nargs_pos_only) {
                         continue; // Not enough defaults to fill the positional arguments
+                    }
                 }
 
                 // 2. Check kwargs and, failing that, defaults that may help complete the list
@@ -741,8 +790,9 @@ class cpp_function : public function {
                         const auto &arg_rec = func.args[args_copied];
 
                         handle value;
-                        if (kwargs_in && arg_rec.name)
+                        if (kwargs_in && arg_rec.name) {
                             value = dict_getitemstring(kwargs.ptr(), arg_rec.name);
+                        }
 
                         if (value) {
                             // Consume a kwargs value
@@ -763,23 +813,27 @@ class cpp_function : public function {
 
                         if (value) {
                             // If we're at the py::args index then first insert a stub for it to be replaced later
-                            if (func.has_args && call.args.size() == func.nargs_pos)
+                            if (func.has_args && call.args.size() == func.nargs_pos) {
                                 call.args.push_back(none());
+                            }
 
                             call.args.push_back(value);
                             call.args_convert.push_back(arg_rec.convert);
-                        }
-                        else
+                        } else {
                             break;
+                        }
                     }
 
-                    if (args_copied < num_args)
-                        continue; // Not enough arguments, defaults, or kwargs to fill the positional arguments
+                    if (args_copied < num_args) {
+                        continue; // Not enough arguments, defaults, or kwargs to fill the
+                                  // positional arguments
+                    }
                 }
 
                 // 3. Check everything was consumed (unless we have a kwargs arg)
-                if (kwargs && !kwargs.empty() && !func.has_kwargs)
+                if (kwargs && !kwargs.empty() && !func.has_kwargs) {
                     continue; // Unconsumed kwargs, but no py::kwargs argument to accept them
+                }
 
                 // 4a. If we have a py::args argument, create a new tuple with leftovers
                 if (func.has_args) {
@@ -797,18 +851,20 @@ class cpp_function : public function {
                             extra_args[i] = PyTuple_GET_ITEM(args_in, positional_args_copied + i);
                         }
                     }
-                    if (call.args.size() <= func.nargs_pos)
+                    if (call.args.size() <= func.nargs_pos) {
                         call.args.push_back(extra_args);
-                    else
+                    } else {
                         call.args[func.nargs_pos] = extra_args;
+                    }
                     call.args_convert.push_back(false);
                     call.args_ref = std::move(extra_args);
                 }
 
                 // 4b. If we have a py::kwargs, pass on any remaining kwargs
                 if (func.has_kwargs) {
-                    if (!kwargs.ptr())
+                    if (!kwargs.ptr()) {
                         kwargs = dict(); // If we didn't get one, send an empty one
+                    }
                     call.args.push_back(kwargs);
                     call.args_convert.push_back(false);
                     call.kwargs_ref = std::move(kwargs);
@@ -838,8 +894,9 @@ class cpp_function : public function {
                     result = PYBIND11_TRY_NEXT_OVERLOAD;
                 }
 
-                if (result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD)
+                if (result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD) {
                     break;
+                }
 
                 if (overloaded) {
                     // The (overloaded) call failed; if the call has at least one argument that
@@ -870,8 +927,9 @@ class cpp_function : public function {
                     if (result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD) {
                         // The error reporting logic below expects 'it' to be valid, as it would be
                         // if we'd encountered this failure in the first-pass loop.
-                        if (!result)
+                        if (!result) {
                             it = &call.func;
+                        }
                         break;
                     }
                 }
@@ -923,8 +981,9 @@ class cpp_function : public function {
         };
 
         if (result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) {
-            if (overloads->is_operator)
+            if (overloads->is_operator) {
                 return handle(Py_NotImplemented).inc_ref().ptr();
+            }
 
             std::string msg = std::string(overloads->name) + "(): incompatible " +
                 std::string(overloads->is_constructor ? "constructor" : "function") +
@@ -944,7 +1003,9 @@ class cpp_function : public function {
                         size_t end = sig.find(", "), next = end + 2;
                         size_t ret = sig.rfind(" -> ");
                         // Or the ), if there is no comma:
-                        if (end >= sig.size()) next = end = sig.find(')');
+                        if (end >= sig.size()) {
+                            next = end = sig.find(')');
+                        }
                         if (start < end && next < sig.size()) {
                             msg.append(sig, start, end - start);
                             msg += '(';
@@ -953,7 +1014,9 @@ class cpp_function : public function {
                         }
                     }
                 }
-                if (!wrote_sig) msg += it2->signature;
+                if (!wrote_sig) {
+                    msg += it2->signature;
+                }
 
                 msg += "\n";
             }
@@ -961,8 +1024,11 @@ class cpp_function : public function {
             auto args_ = reinterpret_borrow<tuple>(args_in);
             bool some_args = false;
             for (size_t ti = overloads->is_constructor ? 1 : 0; ti < args_.size(); ++ti) {
-                if (!some_args) some_args = true;
-                else msg += ", ";
+                if (!some_args) {
+                    some_args = true;
+                } else {
+                    msg += ", ";
+                }
                 try {
                     msg += pybind11::repr(args_[ti]);
                 } catch (const error_already_set&) {
@@ -972,12 +1038,17 @@ class cpp_function : public function {
             if (kwargs_in) {
                 auto kwargs = reinterpret_borrow<dict>(kwargs_in);
                 if (!kwargs.empty()) {
-                    if (some_args) msg += "; ";
+                    if (some_args) {
+                        msg += "; ";
+                    }
                     msg += "kwargs: ";
                     bool first = true;
                     for (auto kwarg : kwargs) {
-                        if (first) first = false;
-                        else msg += ", ";
+                        if (first) {
+                            first = false;
+                        } else {
+                            msg += ", ";
+                        }
                         msg += pybind11::str("{}=").format(kwarg.first);
                         try {
                             msg += pybind11::repr(kwarg.second);
@@ -1068,8 +1139,9 @@ class module_ : public object {
         std::string full_name = std::string(PyModule_GetName(m_ptr))
             + std::string(".") + std::string(name);
         auto result = reinterpret_borrow<module_>(PyImport_AddModule(full_name.c_str()));
-        if (doc && options::show_user_defined_docstrings())
+        if (doc && options::show_user_defined_docstrings()) {
             result.attr("__doc__") = pybind11::str(doc);
+        }
         attr(name) = result;
         return result;
     }
@@ -1077,16 +1149,18 @@ class module_ : public object {
     /// Import and return a module or throws `error_already_set`.
     static module_ import(const char *name) {
         PyObject *obj = PyImport_ImportModule(name);
-        if (!obj)
+        if (!obj) {
             throw error_already_set();
+        }
         return reinterpret_steal<module_>(obj);
     }
 
     /// Reload the module or throws `error_already_set`.
     void reload() {
         PyObject *obj = PyImport_ReloadModule(ptr());
-        if (!obj)
+        if (!obj) {
             throw error_already_set();
+        }
         *this = reinterpret_steal<module_>(obj);
     }
 
@@ -1098,9 +1172,11 @@ class module_ : public object {
         established will, in most cases, break things.
     \endrst */
     PYBIND11_NOINLINE void add_object(const char *name, handle obj, bool overwrite = false) {
-        if (!overwrite && hasattr(*this, name))
-            pybind11_fail("Error during initialization: multiple incompatible definitions with name \"" +
-                    std::string(name) + "\"");
+        if (!overwrite && hasattr(*this, name)) {
+            pybind11_fail(
+                "Error during initialization: multiple incompatible definitions with name \""
+                + std::string(name) + "\"");
+        }
 
         PyModule_AddObject(ptr(), name, obj.inc_ref().ptr() /* steals a reference */);
     }
@@ -1138,8 +1214,9 @@ class module_ : public object {
         auto m = Py_InitModule3(name, nullptr, options::show_user_defined_docstrings() ? doc : nullptr);
 #endif
         if (m == nullptr) {
-            if (PyErr_Occurred())
+            if (PyErr_Occurred()) {
                 throw error_already_set();
+            }
             pybind11_fail("Internal error in module_::create_extension_module()");
         }
         // TODO: Should be reinterpret_steal for Python 3, but Python also steals it again when returned from PyInit_...
@@ -1177,14 +1254,17 @@ class generic_type : public object {
     PYBIND11_OBJECT_DEFAULT(generic_type, object, PyType_Check)
 protected:
     void initialize(const type_record &rec) {
-        if (rec.scope && hasattr(rec.scope, "__dict__") && rec.scope.attr("__dict__").contains(rec.name))
-            pybind11_fail("generic_type: cannot initialize type \"" + std::string(rec.name) +
-                          "\": an object with that name is already defined");
+        if (rec.scope && hasattr(rec.scope, "__dict__")
+            && rec.scope.attr("__dict__").contains(rec.name)) {
+            pybind11_fail("generic_type: cannot initialize type \"" + std::string(rec.name)
+                          + "\": an object with that name is already defined");
+        }
 
         if ((rec.module_local ? get_local_type_info(*rec.type) : get_global_type_info(*rec.type))
-            != nullptr)
-            pybind11_fail("generic_type: type \"" + std::string(rec.name) +
-                          "\" is already registered!");
+            != nullptr) {
+            pybind11_fail("generic_type: type \"" + std::string(rec.name)
+                          + "\" is already registered!");
+        }
 
         m_ptr = make_new_python_type(rec);
 
@@ -1206,10 +1286,11 @@ class generic_type : public object {
         auto &internals = get_internals();
         auto tindex = std::type_index(*rec.type);
         tinfo->direct_conversions = &internals.direct_conversions[tindex];
-        if (rec.module_local)
+        if (rec.module_local) {
             get_local_internals().registered_types_cpp[tindex] = tinfo;
-        else
+        } else {
             internals.registered_types_cpp[tindex] = tinfo;
+        }
         internals.registered_types_py[(PyTypeObject *) m_ptr] = { tinfo };
 
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {
@@ -1237,8 +1318,9 @@ class generic_type : public object {
         auto t = reinterpret_borrow<tuple>(value->tp_bases);
         for (handle h : t) {
             auto tinfo2 = get_type_info((PyTypeObject *) h.ptr());
-            if (tinfo2)
+            if (tinfo2) {
                 tinfo2->simple_type = false;
+            }
             mark_parents_nonsimple((PyTypeObject *) h.ptr());
         }
     }
@@ -1249,12 +1331,12 @@ class generic_type : public object {
         auto *type = (PyHeapTypeObject*) m_ptr;
         auto tinfo = detail::get_type_info(&type->ht_type);
 
-        if (!type->ht_type.tp_as_buffer)
-            pybind11_fail(
-                "To be able to register buffer protocol support for the type '" +
-                get_fully_qualified_tp_name(tinfo->type) +
-                "' the associated class<>(..) invocation must "
-                "include the pybind11::buffer_protocol() annotation!");
+        if (!type->ht_type.tp_as_buffer) {
+            pybind11_fail("To be able to register buffer protocol support for the type '"
+                          + get_fully_qualified_tp_name(tinfo->type)
+                          + "' the associated class<>(..) invocation must "
+                            "include the pybind11::buffer_protocol() annotation!");
+        }
 
         tinfo->get_buffer = get_buffer;
         tinfo->get_buffer_data = get_buffer_data;
@@ -1475,8 +1557,9 @@ class class_ : public detail::generic_type {
         auto *ptr = new capture { std::forward<Func>(func) };
         install_buffer_funcs([](PyObject *obj, void *ptr) -> buffer_info* {
             detail::make_caster<type> caster;
-            if (!caster.load(obj, false))
+            if (!caster.load(obj, false)) {
                 return nullptr;
+            }
             return new buffer_info(((capture *) ptr)->func(caster));
         }, ptr);
         weakref(m_ptr, cpp_function([ptr](handle wr) {
@@ -1598,7 +1681,9 @@ class class_ : public detail::generic_type {
                 std::free(doc_prev);
                 rec_fset->doc = PYBIND11_COMPAT_STRDUP(rec_fset->doc);
             }
-            if (! rec_active) rec_active = rec_fset;
+            if (!rec_active) {
+                rec_active = rec_fset;
+            }
         }
         def_property_static_impl(name, fget, fset, rec_active);
         return *this;
@@ -1716,8 +1801,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 inline str enum_name(handle arg) {
     dict entries = arg.get_type().attr("__entries");
     for (auto kv : entries) {
-        if (handle(kv.second[int_(0)]).equal(arg))
+        if (handle(kv.second[int_(0)]).equal(arg)) {
             return pybind11::str(kv.first);
+        }
     }
     return "???";
 }
@@ -1752,15 +1838,17 @@ struct enum_base {
             [](handle arg) -> std::string {
                 std::string docstring;
                 dict entries = arg.attr("__entries");
-                if (((PyTypeObject *) arg.ptr())->tp_doc)
+                if (((PyTypeObject *) arg.ptr())->tp_doc) {
                     docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
+                }
                 docstring += "Members:";
                 for (auto kv : entries) {
                     auto key = std::string(pybind11::str(kv.first));
                     auto comment = kv.second[int_(1)];
                     docstring += "\n\n  " + key;
-                    if (!comment.is_none())
+                    if (!comment.is_none()) {
                         docstring += " : " + (std::string) pybind11::str(comment);
+                    }
                 }
                 return docstring;
             }, name("__doc__")
@@ -1769,8 +1857,9 @@ struct enum_base {
         m_base.attr("__members__") = static_property(cpp_function(
             [](handle arg) -> dict {
                 dict entries = arg.attr("__entries"), m;
-                for (auto kv : entries)
+                for (auto kv : entries) {
                     m[kv.first] = kv.second[int_(0)];
+                }
                 return m;
             }, name("__members__")), none(), none(), ""
         );
@@ -1865,8 +1954,9 @@ struct enum_base {
 
     PYBIND11_NOINLINE void export_values() {
         dict entries = m_base.attr("__entries");
-        for (auto kv : entries)
+        for (auto kv : entries) {
             m_parent.attr(kv.first) = kv.second[int_(0)];
+        }
     }
 
     handle m_base;
@@ -1944,11 +2034,13 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 
 PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
-    if (!nurse || !patient)
+    if (!nurse || !patient) {
         pybind11_fail("Could not activate keep_alive!");
+    }
 
-    if (patient.is_none() || nurse.is_none())
+    if (patient.is_none() || nurse.is_none()) {
         return; /* Nothing to keep alive or nothing to be kept alive by */
+    }
 
     auto tinfo = all_type_info(Py_TYPE(nurse.ptr()));
     if (!tinfo.empty()) {
@@ -1972,12 +2064,15 @@ PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
 
 PYBIND11_NOINLINE void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
     auto get_arg = [&](size_t n) {
-        if (n == 0)
+        if (n == 0) {
             return ret;
-        if (n == 1 && call.init_self)
+        }
+        if (n == 1 && call.init_self) {
             return call.init_self;
-        if (n <= call.args.size())
+        }
+        if (n <= call.args.size()) {
             return call.args[n - 1];
+        }
         return handle();
     };
 
@@ -2000,10 +2095,11 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
             // TODO consolidate the erasure code in pybind11_meta_dealloc() in class.h
             auto &cache = get_internals().inactive_override_cache;
             for (auto it = cache.begin(), last = cache.end(); it != last; ) {
-                if (it->first == reinterpret_cast<PyObject *>(type))
+                if (it->first == reinterpret_cast<PyObject *>(type)) {
                     it = cache.erase(it);
-                else
+                } else {
                     ++it;
+                }
             }
 
             wr.dec_ref();
@@ -2089,19 +2185,24 @@ iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
 
     if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator", pybind11::module_local())
-            .def("__iter__", [](state &s) -> state& { return s; })
-            .def("__next__", [](state &s) -> ValueType {
-                if (!s.first_or_done)
-                    ++s.it;
-                else
-                    s.first_or_done = false;
-                if (s.it == s.end) {
-                    s.first_or_done = true;
-                    throw stop_iteration();
-                }
-                return Access()(s.it);
-            // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
-            }, std::forward<Extra>(extra)..., Policy);
+            .def("__iter__", [](state &s) -> state & { return s; })
+            .def(
+                "__next__",
+                [](state &s) -> ValueType {
+                    if (!s.first_or_done) {
+                        ++s.it;
+                    } else {
+                        s.first_or_done = false;
+                    }
+                    if (s.it == s.end) {
+                        s.first_or_done = true;
+                        throw stop_iteration();
+                    }
+                    return Access()(s.it);
+                    // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
+                },
+                std::forward<Extra>(extra)...,
+                Policy);
     }
 
     return cast(state{first, last, true});
@@ -2187,23 +2288,27 @@ template <typename InputType, typename OutputType> void implicitly_convertible()
     };
     auto implicit_caster = [](PyObject *obj, PyTypeObject *type) -> PyObject * {
         static bool currently_used = false;
-        if (currently_used) // implicit conversions are non-reentrant
+        if (currently_used) { // implicit conversions are non-reentrant
             return nullptr;
+        }
         set_flag flag_helper(currently_used);
-        if (!detail::make_caster<InputType>().load(obj, false))
+        if (!detail::make_caster<InputType>().load(obj, false)) {
             return nullptr;
+        }
         tuple args(1);
         args[0] = obj;
         PyObject *result = PyObject_Call((PyObject *) type, args.ptr(), nullptr);
-        if (result == nullptr)
+        if (result == nullptr) {
             PyErr_Clear();
+        }
         return result;
     };
 
-    if (auto tinfo = detail::get_type_info(typeid(OutputType)))
+    if (auto tinfo = detail::get_type_info(typeid(OutputType))) {
         tinfo->implicit_conversions.push_back(implicit_caster);
-    else
+    } else {
         pybind11_fail("implicitly_convertible: Unable to find type " + type_id<OutputType>());
+    }
 }
 
 
@@ -2239,9 +2344,11 @@ class exception : public object {
         std::string full_name = scope.attr("__name__").cast<std::string>() +
                                 std::string(".") + name;
         m_ptr = PyErr_NewException(const_cast<char *>(full_name.c_str()), base.ptr(), NULL);
-        if (hasattr(scope, "__dict__") && scope.attr("__dict__").contains(name))
+        if (hasattr(scope, "__dict__") && scope.attr("__dict__").contains(name)) {
             pybind11_fail("Error during initialization: multiple incompatible "
-                          "definitions with name \"" + std::string(name) + "\"");
+                          "definitions with name \""
+                          + std::string(name) + "\"");
+        }
         scope.attr(name) = *this;
     }
 
@@ -2265,13 +2372,17 @@ exception<CppException> &register_exception_impl(handle scope,
                                                 handle base,
                                                 bool isLocal) {
     auto &ex = detail::get_exception_object<CppException>();
-    if (!ex) ex = exception<CppException>(scope, name, base);
+    if (!ex) {
+        ex = exception<CppException>(scope, name, base);
+    }
 
     auto register_func = isLocal ? &register_local_exception_translator
                                  : &register_exception_translator;
 
     register_func([](std::exception_ptr p) {
-        if (!p) return;
+        if (!p) {
+            return;
+        }
         try {
             std::rethrow_exception(p);
         } catch (const CppException &e) {
@@ -2339,8 +2450,9 @@ PYBIND11_NOINLINE void print(const tuple &args, const dict &kwargs) {
     write(line);
     write(kwargs.contains("end") ? kwargs["end"] : cast("\n"));
 
-    if (kwargs.contains("flush") && kwargs["flush"].cast<bool>())
+    if (kwargs.contains("flush") && kwargs["flush"].cast<bool>()) {
         file.attr("flush")();
+    }
 }
 PYBIND11_NAMESPACE_END(detail)
 
@@ -2363,16 +2475,18 @@ error_already_set::~error_already_set() {
 PYBIND11_NAMESPACE_BEGIN(detail)
 inline function get_type_override(const void *this_ptr, const type_info *this_type, const char *name)  {
     handle self = get_object_handle(this_ptr, this_type);
-    if (!self)
+    if (!self) {
         return function();
+    }
     handle type = type::handle_of(self);
     auto key = std::make_pair(type.ptr(), name);
 
     /* Cache functions that aren't overridden in Python to avoid
        many costly Python dictionary lookups below */
     auto &cache = get_internals().inactive_override_cache;
-    if (cache.find(key) != cache.end())
+    if (cache.find(key) != cache.end()) {
         return function();
+    }
 
     function override = getattr(self, name, function());
     if (override.is_cpp_function()) {
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 902fb1f07d..74388349b0 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -242,7 +242,11 @@ class object : public handle {
 public:
     object() = default;
     PYBIND11_DEPRECATED("Use reinterpret_borrow<object>() or reinterpret_steal<object>()")
-    object(handle h, bool is_borrowed) : handle(h) { if (is_borrowed) inc_ref(); }
+    object(handle h, bool is_borrowed) : handle(h) {
+        if (is_borrowed) {
+            inc_ref();
+        }
+    }
     /// Copy constructor; always increases the reference count
     object(const object &o) : handle(o) { inc_ref(); }
     /// Move constructor; steals the object from ``other`` and preserves its reference count
@@ -458,8 +462,9 @@ template <> inline bool isinstance<object>(handle obj) { return obj.ptr() != nul
 /// Return true if ``obj`` is an instance of the ``type``.
 inline bool isinstance(handle obj, handle type) {
     const auto result = PyObject_IsInstance(obj.ptr(), type.ptr());
-    if (result == -1)
+    if (result == -1) {
         throw error_already_set();
+    }
     return result != 0;
 }
 
@@ -529,12 +534,13 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 inline handle get_function(handle value) {
     if (value) {
 #if PY_MAJOR_VERSION >= 3
-        if (PyInstanceMethod_Check(value.ptr()))
+        if (PyInstanceMethod_Check(value.ptr())) {
             value = PyInstanceMethod_GET_FUNCTION(value.ptr());
-        else
+        } else
 #endif
-        if (PyMethod_Check(value.ptr()))
+            if (PyMethod_Check(value.ptr())) {
             value = PyMethod_GET_FUNCTION(value.ptr());
+        }
     }
     return value;
 }
@@ -1076,14 +1082,18 @@ class str : public object {
     template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
     str(const char *c, const SzType &n)
         : object(PyUnicode_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate string object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate string object!");
+        }
     }
 
     // 'explicit' is explicitly omitted from the following constructors to allow implicit conversion to py::str from C++ string-like objects
     // NOLINTNEXTLINE(google-explicit-constructor)
     str(const char *c = "")
         : object(PyUnicode_FromString(c), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate string object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate string object!");
+        }
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
@@ -1109,20 +1119,26 @@ class str : public object {
         Return a string representation of the object. This is analogous to
         the ``str()`` function in Python.
     \endrst */
-    explicit str(handle h) : object(raw_str(h.ptr()), stolen_t{}) { if (!m_ptr) throw error_already_set(); }
+    explicit str(handle h) : object(raw_str(h.ptr()), stolen_t{}) {
+        if (!m_ptr) {
+            throw error_already_set();
+        }
+    }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator std::string() const {
         object temp = *this;
         if (PyUnicode_Check(m_ptr)) {
             temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(m_ptr));
-            if (!temp)
+            if (!temp) {
                 throw error_already_set();
+            }
         }
         char *buffer = nullptr;
         ssize_t length = 0;
-        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length))
+        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length)) {
             pybind11_fail("Unable to extract string contents! (invalid type)");
+        }
         return std::string(buffer, (size_t) length);
     }
 
@@ -1162,13 +1178,17 @@ class bytes : public object {
     // NOLINTNEXTLINE(google-explicit-constructor)
     bytes(const char *c = "")
         : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate bytes object!");
+        }
     }
 
     template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
     bytes(const char *c, const SzType &n)
         : object(PYBIND11_BYTES_FROM_STRING_AND_SIZE(c, ssize_t_cast(n)), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate bytes object!");
+        }
     }
 
     // Allow implicit conversion:
@@ -1181,8 +1201,9 @@ class bytes : public object {
     operator std::string() const {
         char *buffer = nullptr;
         ssize_t length = 0;
-        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length))
+        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length)) {
             pybind11_fail("Unable to extract bytes contents!");
+        }
         return std::string(buffer, (size_t) length);
     }
 
@@ -1199,8 +1220,9 @@ class bytes : public object {
     operator std::string_view() const {
         char *buffer = nullptr;
         ssize_t length = 0;
-        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length))
+        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length)) {
             pybind11_fail("Unable to extract bytes contents!");
+        }
         return {buffer, static_cast<size_t>(length)};
     }
 #endif
@@ -1214,27 +1236,32 @@ inline bytes::bytes(const pybind11::str &s) {
     object temp = s;
     if (PyUnicode_Check(s.ptr())) {
         temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(s.ptr()));
-        if (!temp)
+        if (!temp) {
             pybind11_fail("Unable to extract string contents! (encoding issue)");
+        }
     }
     char *buffer = nullptr;
     ssize_t length = 0;
-    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length))
+    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length)) {
         pybind11_fail("Unable to extract string contents! (invalid type)");
+    }
     auto obj = reinterpret_steal<object>(PYBIND11_BYTES_FROM_STRING_AND_SIZE(buffer, length));
-    if (!obj)
+    if (!obj) {
         pybind11_fail("Could not allocate bytes object!");
+    }
     m_ptr = obj.release().ptr();
 }
 
 inline str::str(const bytes& b) {
     char *buffer = nullptr;
     ssize_t length = 0;
-    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length))
+    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length)) {
         pybind11_fail("Unable to extract bytes contents!");
+    }
     auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, length));
-    if (!obj)
+    if (!obj) {
         pybind11_fail("Could not allocate string object!");
+    }
     m_ptr = obj.release().ptr();
 }
 
@@ -1247,7 +1274,9 @@ class bytearray : public object {
     template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
     bytearray(const char *c, const SzType &n)
         : object(PyByteArray_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate bytearray object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate bytearray object!");
+        }
     }
 
     bytearray()
@@ -1295,7 +1324,9 @@ class bool_ : public object {
     /// Return the truth value of an object -- always returns a new reference
     static PyObject *raw_bool(PyObject *op) {
         const auto value = PyObject_IsTrue(op);
-        if (value == -1) return nullptr;
+        if (value == -1) {
+            return nullptr;
+        }
         return handle(value != 0 ? Py_True : Py_False).inc_ref().ptr();
     }
 };
@@ -1330,17 +1361,21 @@ class int_ : public object {
     // NOLINTNEXTLINE(google-explicit-constructor)
     int_(T value) {
         if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
-            if (std::is_signed<T>::value)
+            if (std::is_signed<T>::value) {
                 m_ptr = PyLong_FromLong((long) value);
-            else
+            } else {
                 m_ptr = PyLong_FromUnsignedLong((unsigned long) value);
+            }
         } else {
-            if (std::is_signed<T>::value)
+            if (std::is_signed<T>::value) {
                 m_ptr = PyLong_FromLongLong((long long) value);
-            else
+            } else {
                 m_ptr = PyLong_FromUnsignedLongLong((unsigned long long) value);
+            }
+        }
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate int object!");
         }
-        if (!m_ptr) pybind11_fail("Could not allocate int object!");
     }
 
     template <typename T,
@@ -1361,11 +1396,15 @@ class float_ : public object {
     // Allow implicit conversion from float/double:
     // NOLINTNEXTLINE(google-explicit-constructor)
     float_(float value) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate float object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate float object!");
+        }
     }
     // NOLINTNEXTLINE(google-explicit-constructor)
     float_(double value = .0) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate float object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate float object!");
+        }
     }
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator float() const { return (float) PyFloat_AsDouble(m_ptr); }
@@ -1378,7 +1417,9 @@ class weakref : public object {
     PYBIND11_OBJECT_CVT_DEFAULT(weakref, object, PyWeakref_Check, raw_weakref)
     explicit weakref(handle obj, handle callback = {})
         : object(PyWeakref_NewRef(obj.ptr(), callback.ptr()), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate weak reference!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate weak reference!");
+        }
     }
 
 private:
@@ -1392,8 +1433,9 @@ class slice : public object {
     PYBIND11_OBJECT_DEFAULT(slice, object, PySlice_Check)
     slice(handle start, handle stop, handle step) {
         m_ptr = PySlice_New(start.ptr(), stop.ptr(), step.ptr());
-        if (!m_ptr)
+        if (!m_ptr) {
             pybind11_fail("Could not allocate slice object!");
+        }
     }
 
 #ifdef PYBIND11_HAS_OPTIONAL
@@ -1434,15 +1476,17 @@ class capsule : public object {
 
     explicit capsule(const void *value, const char *name = nullptr, void (*destructor)(PyObject *) = nullptr)
         : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
-        if (!m_ptr)
+        if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
+        }
     }
 
     PYBIND11_DEPRECATED("Please pass a destructor that takes a void pointer as input")
     capsule(const void *value, void (*destruct)(PyObject *))
         : object(PyCapsule_New(const_cast<void*>(value), nullptr, destruct), stolen_t{}) {
-        if (!m_ptr)
+        if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
+        }
     }
 
     capsule(const void *value, void (*destructor)(void *)) {
@@ -1452,11 +1496,13 @@ class capsule : public object {
             destructor(ptr);
         });
 
-        if (!m_ptr)
+        if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
+        }
 
-        if (PyCapsule_SetContext(m_ptr, (void *) destructor) != 0)
+        if (PyCapsule_SetContext(m_ptr, (void *) destructor) != 0) {
             pybind11_fail("Could not set capsule context!");
+        }
     }
 
     explicit capsule(void (*destructor)()) {
@@ -1465,8 +1511,9 @@ class capsule : public object {
             destructor();
         });
 
-        if (!m_ptr)
+        if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
+        }
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
@@ -1504,7 +1551,9 @@ class tuple : public object {
               detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
     // Some compilers generate link errors when using `const SzType &` here:
     explicit tuple(SzType size = 0) : object(PyTuple_New(ssize_t_cast(size)), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate tuple object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate tuple object!");
+        }
     }
     size_t size() const { return (size_t) PyTuple_Size(m_ptr); }
     bool empty() const { return size() == 0; }
@@ -1527,7 +1576,9 @@ class dict : public object {
 public:
     PYBIND11_OBJECT_CVT(dict, object, PyDict_Check, raw_dict)
     dict() : object(PyDict_New(), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate dict object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate dict object!");
+        }
     }
     template <typename... Args,
               typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>,
@@ -1547,8 +1598,9 @@ class dict : public object {
 private:
     /// Call the `dict` Python type -- always returns a new reference
     static PyObject *raw_dict(PyObject *op) {
-        if (PyDict_Check(op))
+        if (PyDict_Check(op)) {
             return handle(op).inc_ref().ptr();
+        }
         return PyObject_CallFunctionObjArgs((PyObject *) &PyDict_Type, op, nullptr);
     }
 };
@@ -1558,8 +1610,9 @@ class sequence : public object {
     PYBIND11_OBJECT_DEFAULT(sequence, object, PySequence_Check)
     size_t size() const {
         ssize_t result = PySequence_Size(m_ptr);
-        if (result == -1)
+        if (result == -1) {
             throw error_already_set();
+        }
         return (size_t) result;
     }
     bool empty() const { return size() == 0; }
@@ -1576,7 +1629,9 @@ class list : public object {
               detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
     // Some compilers generate link errors when using `const SzType &` here:
     explicit list(SzType size = 0) : object(PyList_New(ssize_t_cast(size)), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate list object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate list object!");
+        }
     }
     size_t size() const { return (size_t) PyList_Size(m_ptr); }
     bool empty() const { return size() == 0; }
@@ -1603,7 +1658,9 @@ class set : public object {
 public:
     PYBIND11_OBJECT_CVT(set, object, PySet_Check, PySet_New)
     set() : object(PySet_New(nullptr), stolen_t{}) {
-        if (!m_ptr) pybind11_fail("Could not allocate set object!");
+        if (!m_ptr) {
+            pybind11_fail("Could not allocate set object!");
+        }
     }
     size_t size() const { return (size_t) PySet_Size(m_ptr); }
     bool empty() const { return size() == 0; }
@@ -1621,8 +1678,9 @@ class function : public object {
     PYBIND11_OBJECT_DEFAULT(function, object, PyCallable_Check)
     handle cpp_function() const {
         handle fun = detail::get_function(m_ptr);
-        if (fun && PyCFunction_Check(fun.ptr()))
+        if (fun && PyCFunction_Check(fun.ptr())) {
             return fun;
+        }
         return handle();
     }
     bool is_cpp_function() const { return (bool) cpp_function(); }
@@ -1639,7 +1697,9 @@ class buffer : public object {
 
     buffer_info request(bool writable = false) const {
         int flags = PyBUF_STRIDES | PyBUF_FORMAT;
-        if (writable) flags |= PyBUF_WRITABLE;
+        if (writable) {
+            flags |= PyBUF_WRITABLE;
+        }
         auto *view = new Py_buffer();
         if (PyObject_GetBuffer(m_ptr, view, flags) != 0) {
             delete view;
@@ -1663,14 +1723,16 @@ class memoryview : public object {
         use ``memoryview(const object& obj)`` instead of this constructor.
      \endrst */
     explicit memoryview(const buffer_info& info) {
-        if (!info.view())
+        if (!info.view()) {
             pybind11_fail("Prohibited to create memoryview without Py_buffer");
+        }
         // Note: PyMemoryView_FromBuffer never increments obj reference.
         m_ptr = (info.view()->obj) ?
             PyMemoryView_FromObject(info.view()->obj) :
             PyMemoryView_FromBuffer(info.view());
-        if (!m_ptr)
+        if (!m_ptr) {
             pybind11_fail("Unable to create memoryview from buffer descriptor");
+        }
     }
 
     /** \rst
@@ -1744,8 +1806,9 @@ class memoryview : public object {
         PyObject* ptr = PyMemoryView_FromMemory(
             reinterpret_cast<char*>(mem), size,
             (readonly) ? PyBUF_READ : PyBUF_WRITE);
-        if (!ptr)
+        if (!ptr) {
             pybind11_fail("Could not allocate memoryview object!");
+        }
         return memoryview(object(ptr, stolen_t{}));
     }
 
@@ -1768,11 +1831,13 @@ inline memoryview memoryview::from_buffer(
     detail::any_container<ssize_t> shape,
     detail::any_container<ssize_t> strides, bool readonly) {
     size_t ndim = shape->size();
-    if (ndim != strides->size())
+    if (ndim != strides->size()) {
         pybind11_fail("memoryview: shape length doesn't match strides length");
+    }
     ssize_t size = ndim != 0u ? 1 : 0;
-    for (size_t i = 0; i < ndim; ++i)
+    for (size_t i = 0; i < ndim; ++i) {
         size *= (*shape)[i];
+    }
     Py_buffer view;
     view.buf = ptr;
     view.obj = nullptr;
@@ -1786,8 +1851,9 @@ inline memoryview memoryview::from_buffer(
     view.suboffsets = nullptr;
     view.internal = nullptr;
     PyObject* obj = PyMemoryView_FromBuffer(&view);
-    if (!obj)
+    if (!obj) {
         throw error_already_set();
+    }
     return memoryview(object(obj, stolen_t{}));
 }
 /// @endcond
@@ -1799,8 +1865,9 @@ inline memoryview memoryview::from_buffer(
 /// Get the length of a Python object.
 inline size_t len(handle h) {
     ssize_t result = PyObject_Length(h.ptr());
-    if (result < 0)
+    if (result < 0) {
         throw error_already_set();
+    }
     return (size_t) result;
 }
 
@@ -1823,7 +1890,9 @@ inline size_t len_hint(handle h) {
 
 inline str repr(handle h) {
     PyObject *str_value = PyObject_Repr(h.ptr());
-    if (!str_value) throw error_already_set();
+    if (!str_value) {
+        throw error_already_set();
+    }
 #if PY_MAJOR_VERSION < 3
     PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
     Py_XDECREF(str_value); str_value = unicode;
@@ -1873,8 +1942,9 @@ handle object_api<D>::get_type() const { return type::handle_of(derived()); }
 template <typename D>
 bool object_api<D>::rich_compare(object_api const &other, int value) const {
     int rv = PyObject_RichCompareBool(derived().ptr(), other.derived().ptr(), value);
-    if (rv == -1)
+    if (rv == -1) {
         throw error_already_set();
+    }
     return rv == 1;
 }
 
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 4303494827..fb1eea67bf 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -52,14 +52,16 @@ template <typename Type, typename Key> struct set_caster {
     using key_conv = make_caster<Key>;
 
     bool load(handle src, bool convert) {
-        if (!isinstance<pybind11::set>(src))
+        if (!isinstance<pybind11::set>(src)) {
             return false;
+        }
         auto s = reinterpret_borrow<pybind11::set>(src);
         value.clear();
         for (auto entry : s) {
             key_conv conv;
-            if (!conv.load(entry, convert))
+            if (!conv.load(entry, convert)) {
                 return false;
+            }
             value.insert(cast_op<Key &&>(std::move(conv)));
         }
         return true;
@@ -67,13 +69,15 @@ template <typename Type, typename Key> struct set_caster {
 
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
-        if (!std::is_lvalue_reference<T>::value)
+        if (!std::is_lvalue_reference<T>::value) {
             policy = return_value_policy_override<Key>::policy(policy);
+        }
         pybind11::set s;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(key_conv::cast(forward_like<T>(value), policy, parent));
-            if (!value_ || !s.add(value_))
+            if (!value_ || !s.add(value_)) {
                 return handle();
+            }
         }
         return s.release();
     }
@@ -86,16 +90,17 @@ template <typename Type, typename Key, typename Value> struct map_caster {
     using value_conv = make_caster<Value>;
 
     bool load(handle src, bool convert) {
-        if (!isinstance<dict>(src))
+        if (!isinstance<dict>(src)) {
             return false;
+        }
         auto d = reinterpret_borrow<dict>(src);
         value.clear();
         for (auto it : d) {
             key_conv kconv;
             value_conv vconv;
-            if (!kconv.load(it.first.ptr(), convert) ||
-                !vconv.load(it.second.ptr(), convert))
+            if (!kconv.load(it.first.ptr(), convert) || !vconv.load(it.second.ptr(), convert)) {
                 return false;
+            }
             value.emplace(cast_op<Key &&>(std::move(kconv)), cast_op<Value &&>(std::move(vconv)));
         }
         return true;
@@ -113,8 +118,9 @@ template <typename Type, typename Key, typename Value> struct map_caster {
         for (auto &&kv : src) {
             auto key = reinterpret_steal<object>(key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
             auto value = reinterpret_steal<object>(value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
-            if (!key || !value)
+            if (!key || !value) {
                 return handle();
+            }
             d[key] = value;
         }
         return d.release();
@@ -127,15 +133,17 @@ template <typename Type, typename Value> struct list_caster {
     using value_conv = make_caster<Value>;
 
     bool load(handle src, bool convert) {
-        if (!isinstance<sequence>(src) || isinstance<bytes>(src) || isinstance<str>(src))
+        if (!isinstance<sequence>(src) || isinstance<bytes>(src) || isinstance<str>(src)) {
             return false;
+        }
         auto s = reinterpret_borrow<sequence>(src);
         value.clear();
         reserve_maybe(s, &value);
         for (auto it : s) {
             value_conv conv;
-            if (!conv.load(it, convert))
+            if (!conv.load(it, convert)) {
                 return false;
+            }
             value.push_back(cast_op<Value &&>(std::move(conv)));
         }
         return true;
@@ -153,14 +161,16 @@ template <typename Type, typename Value> struct list_caster {
 public:
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
-        if (!std::is_lvalue_reference<T>::value)
+        if (!std::is_lvalue_reference<T>::value) {
             policy = return_value_policy_override<Value>::policy(policy);
+        }
         list l(src.size());
         ssize_t index = 0;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
-            if (!value_)
+            if (!value_) {
                 return handle();
+            }
             PyList_SET_ITEM(l.ptr(), index++, value_.release().ptr()); // steals a reference
         }
         return l.release();
@@ -184,8 +194,9 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
 private:
     template <bool R = Resizable>
     bool require_size(enable_if_t<R, size_t> size) {
-        if (value.size() != size)
+        if (value.size() != size) {
             value.resize(size);
+        }
         return true;
     }
     template <bool R = Resizable>
@@ -195,16 +206,19 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
 
 public:
     bool load(handle src, bool convert) {
-        if (!isinstance<sequence>(src))
+        if (!isinstance<sequence>(src)) {
             return false;
+        }
         auto l = reinterpret_borrow<sequence>(src);
-        if (!require_size(l.size()))
+        if (!require_size(l.size())) {
             return false;
+        }
         size_t ctr = 0;
         for (auto it : l) {
             value_conv conv;
-            if (!conv.load(it, convert))
+            if (!conv.load(it, convert)) {
                 return false;
+            }
             value[ctr++] = cast_op<Value &&>(std::move(conv));
         }
         return true;
@@ -216,8 +230,9 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
         ssize_t index = 0;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
-            if (!value_)
+            if (!value_) {
                 return handle();
+            }
             PyList_SET_ITEM(l.ptr(), index++, value_.release().ptr()); // steals a reference
         }
         return l.release();
@@ -250,8 +265,9 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
 
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
-        if (!src)
+        if (!src) {
             return none().inc_ref();
+        }
         if (!std::is_lvalue_reference<T>::value) {
             policy = return_value_policy_override<Value>::policy(policy);
         }
@@ -266,8 +282,9 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
             return true;  // default-constructed value is already empty
         }
         value_conv inner_caster;
-        if (!inner_caster.load(src, convert))
+        if (!inner_caster.load(src, convert)) {
             return false;
+        }
 
         value.emplace(cast_op<Value &&>(std::move(inner_caster)));
         return true;
@@ -341,8 +358,9 @@ struct variant_caster<V<Ts...>> {
         // E.g. `py::int_(1).cast<variant<double, int>>()` needs to fill the `int`
         // slot of the variant. Without two-pass loading `double` would be filled
         // because it appears first and a conversion is possible.
-        if (convert && load_alternative(src, false, type_list<Ts...>{}))
+        if (convert && load_alternative(src, false, type_list<Ts...>{})) {
             return true;
+        }
         return load_alternative(src, convert, type_list<Ts...>{});
     }
 
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 050be83cc5..8ae6829653 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -87,10 +87,11 @@ void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_>
 
     cl.def("remove", [](Vector &v, const T &x) {
             auto p = std::find(v.begin(), v.end(), x);
-            if (p != v.end())
+            if (p != v.end()) {
                 v.erase(p);
-            else
+            } else {
                 throw value_error();
+            }
         },
         arg("x"),
         "Remove the first item from the list whose value is x. "
@@ -116,10 +117,12 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
     using DiffType = typename Vector::difference_type;
 
     auto wrap_i = [](DiffType i, SizeType n) {
-        if (i < 0)
+        if (i < 0) {
             i += n;
-        if (i < 0 || (SizeType)i >= n)
+        }
+        if (i < 0 || (SizeType) i >= n) {
             throw index_error();
+        }
         return i;
     };
 
@@ -131,8 +134,9 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
     cl.def(init([](const iterable &it) {
         auto v = std::unique_ptr<Vector>(new Vector());
         v->reserve(len_hint(it));
-        for (handle h : it)
+        for (handle h : it) {
             v->push_back(h.cast<T>());
+        }
         return v.release();
     }));
 
@@ -177,26 +181,29 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
     cl.def("insert",
         [](Vector &v, DiffType i, const T &x) {
             // Can't use wrap_i; i == v.size() is OK
-            if (i < 0)
+            if (i < 0) {
                 i += v.size();
-            if (i < 0 || (SizeType)i > v.size())
+            }
+            if (i < 0 || (SizeType) i > v.size()) {
                 throw index_error();
+            }
             v.insert(v.begin() + i, x);
         },
         arg("i") , arg("x"),
         "Insert an item at a given position."
     );
 
-    cl.def("pop",
+    cl.def(
+        "pop",
         [](Vector &v) {
-            if (v.empty())
+            if (v.empty()) {
                 throw index_error();
+            }
             T t = std::move(v.back());
             v.pop_back();
             return t;
         },
-        "Remove and return the last item"
-    );
+        "Remove and return the last item");
 
     cl.def("pop",
         [wrap_i](Vector &v, DiffType i) {
@@ -222,8 +229,9 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         [](const Vector &v, slice slice) -> Vector * {
             size_t start = 0, stop = 0, step = 0, slicelength = 0;
 
-            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
+            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
                 throw error_already_set();
+            }
 
             auto *seq = new Vector();
             seq->reserve((size_t) slicelength);
@@ -241,11 +249,14 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         "__setitem__",
         [](Vector &v, slice slice, const Vector &value) {
             size_t start = 0, stop = 0, step = 0, slicelength = 0;
-            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
+            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
                 throw error_already_set();
+            }
 
-            if (slicelength != value.size())
-                throw std::runtime_error("Left and right hand size of slice assignment have different sizes!");
+            if (slicelength != value.size()) {
+                throw std::runtime_error(
+                    "Left and right hand size of slice assignment have different sizes!");
+            }
 
             for (size_t i=0; i<slicelength; ++i) {
                 v[start] = value[i];
@@ -267,8 +278,9 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         [](Vector &v, slice slice) {
             size_t start = 0, stop = 0, step = 0, slicelength = 0;
 
-            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
+            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
                 throw error_already_set();
+            }
 
             if (step == 1 && false) {
                 v.erase(v.begin() + (DiffType) start, v.begin() + DiffType(start + slicelength));
@@ -296,10 +308,12 @@ void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl)
     using ItType   = typename Vector::iterator;
 
     auto wrap_i = [](DiffType i, SizeType n) {
-        if (i < 0)
+        if (i < 0) {
             i += n;
-        if (i < 0 || (SizeType)i >= n)
+        }
+        if (i < 0 || (SizeType) i >= n) {
             throw index_error();
+        }
         return i;
     };
 
@@ -328,15 +342,15 @@ void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl)
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
     using ItType   = typename Vector::iterator;
-    cl.def("__getitem__",
-        [](const Vector &v, DiffType i) -> T {
-            if (i < 0 && (i += v.size()) < 0)
-                throw index_error();
-            if ((SizeType)i >= v.size())
-                throw index_error();
-            return v[(SizeType)i];
+    cl.def("__getitem__", [](const Vector &v, DiffType i) -> T {
+        if (i < 0 && (i += v.size()) < 0) {
+            throw index_error();
         }
-    );
+        if ((SizeType) i >= v.size()) {
+            throw index_error();
+        }
+        return v[(SizeType) i];
+    });
 
     cl.def("__iter__",
            [](Vector &v) {
@@ -358,8 +372,9 @@ template <typename Vector, typename Class_> auto vector_if_insertion_operator(Cl
             s << name << '[';
             for (size_type i=0; i < v.size(); ++i) {
                 s << v[i];
-                if (i != v.size() - 1)
+                if (i != v.size() - 1) {
                     s << ", ";
+                }
             }
             s << ']';
             return s.str();
@@ -402,10 +417,14 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
 
     cl.def(init([](const buffer &buf) {
         auto info = buf.request();
-        if (info.ndim != 1 || info.strides[0] % static_cast<ssize_t>(sizeof(T)))
+        if (info.ndim != 1 || info.strides[0] % static_cast<ssize_t>(sizeof(T))) {
             throw type_error("Only valid 1D buffers can be copied to a vector");
-        if (!detail::compare_buffer_info<T>::compare(info) || (ssize_t) sizeof(T) != info.itemsize)
-            throw type_error("Format mismatch (Python: " + info.format + " C++: " + format_descriptor<T>::format() + ")");
+        }
+        if (!detail::compare_buffer_info<T>::compare(info)
+            || (ssize_t) sizeof(T) != info.itemsize) {
+            throw type_error("Format mismatch (Python: " + info.format
+                             + " C++: " + format_descriptor<T>::format() + ")");
+        }
 
         T *p = static_cast<T*>(info.ptr);
         ssize_t step = info.strides[0] / static_cast<ssize_t>(sizeof(T));
@@ -415,8 +434,9 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
         }
         Vector vec;
         vec.reserve((size_t) info.shape[0]);
-        for (; p != end; p += step)
+        for (; p != end; p += step) {
             vec.push_back(*p);
+        }
         return vec;
 
     }));
@@ -545,8 +565,11 @@ void map_assignment(enable_if_t<is_copy_assignable<typename Map::mapped_type>::v
     cl.def("__setitem__",
            [](Map &m, const KeyType &k, const MappedType &v) {
                auto it = m.find(k);
-               if (it != m.end()) it->second = v;
-               else m.emplace(k, v);
+               if (it != m.end()) {
+                   it->second = v;
+               } else {
+                   m.emplace(k, v);
+               }
            }
     );
 }
@@ -583,8 +606,9 @@ template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &
             s << name << '{';
             bool f = false;
             for (auto const &kv : m) {
-                if (f)
+                if (f) {
                     s << ", ";
+                }
                 s << kv.first << ": " << kv.second;
                 f = true;
             }
@@ -675,8 +699,9 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     cl.def("__getitem__",
         [](Map &m, const KeyType &k) -> MappedType & {
             auto it = m.find(k);
-            if (it == m.end())
-              throw key_error();
+            if (it == m.end()) {
+                throw key_error();
+            }
            return it->second;
         },
         return_value_policy::reference_internal // ref + keepalive
@@ -685,8 +710,9 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     cl.def("__contains__",
         [](Map &m, const KeyType &k) -> bool {
             auto it = m.find(k);
-            if (it == m.end())
-              return false;
+            if (it == m.end()) {
+                return false;
+            }
            return true;
         }
     );
@@ -699,8 +725,9 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     cl.def("__delitem__",
            [](Map &m, const KeyType &k) {
                auto it = m.find(k);
-               if (it == m.end())
+               if (it == m.end()) {
                    throw key_error();
+               }
                m.erase(it);
            }
     );
@@ -717,8 +744,9 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     keys_view.def("__contains__",
         [](KeysView &view, const KeyType &k) -> bool {
             auto it = view.map.find(k);
-            if (it == view.map.end())
+            if (it == view.map.end()) {
                 return false;
+            }
             return true;
         }
     );
diff --git a/tests/constructor_stats.h b/tests/constructor_stats.h
index 805968a09b..8ee4047925 100644
--- a/tests/constructor_stats.h
+++ b/tests/constructor_stats.h
@@ -101,10 +101,11 @@ class ConstructorStats {
     }
 
     void destroyed(void *inst) {
-        if (--_instances[inst] < 0)
+        if (--_instances[inst] < 0) {
             throw std::runtime_error("cstats.destroyed() called with unknown "
                                      "instance; potential double-destruction "
                                      "or a missing cstats.created()");
+        }
     }
 
     static void gc() {
@@ -127,9 +128,11 @@ class ConstructorStats {
     int alive() {
         gc();
         int total = 0;
-        for (const auto &p : _instances)
-            if (p.second > 0)
+        for (const auto &p : _instances) {
+            if (p.second > 0) {
                 total += p.second;
+            }
+        }
         return total;
     }
 
@@ -145,7 +148,9 @@ class ConstructorStats {
     // Move out stored values
     py::list values() {
         py::list l;
-        for (const auto &v : _values) l.append(py::cast(v));
+        for (const auto &v : _values) {
+            l.append(py::cast(v));
+        }
         _values.clear();
         return l;
     }
@@ -181,7 +186,9 @@ class ConstructorStats {
             }
         }
         catch (const std::out_of_range&) {}
-        if (!t1) throw std::runtime_error("Unknown class passed to ConstructorStats::get()");
+        if (!t1) {
+            throw std::runtime_error("Unknown class passed to ConstructorStats::get()");
+        }
         auto &cs1 = get(*t1);
         // If we have both a t1 and t2 match, one is probably the trampoline class; return whichever
         // has more constructions (typically one or the other will be 0)
@@ -189,7 +196,9 @@ class ConstructorStats {
             auto &cs2 = get(*t2);
             int cs1_total = cs1.default_constructions + cs1.copy_constructions + cs1.move_constructions + (int) cs1._values.size();
             int cs2_total = cs2.default_constructions + cs2.copy_constructions + cs2.move_constructions + (int) cs2._values.size();
-            if (cs2_total > cs1_total) return cs2;
+            if (cs2_total > cs1_total) {
+                return cs2;
+            }
         }
         return cs1;
     }
diff --git a/tests/object.h b/tests/object.h
index be21bf6316..6365457c34 100644
--- a/tests/object.h
+++ b/tests/object.h
@@ -27,10 +27,11 @@ class Object {
      */
     void decRef(bool dealloc = true) const {
         --m_refCount;
-        if (m_refCount == 0 && dealloc)
+        if (m_refCount == 0 && dealloc) {
             delete this;
-        else if (m_refCount < 0)
+        } else if (m_refCount < 0) {
             throw std::runtime_error("Internal error: reference count < 0!");
+        }
     }
 
     virtual std::string toString() const = 0;
@@ -66,7 +67,9 @@ template <typename T> class ref {
 
     /// Construct a reference from a pointer
     explicit ref(T *ptr) : m_ptr(ptr) {
-        if (m_ptr) ((Object *) m_ptr)->incRef();
+        if (m_ptr) {
+            ((Object *) m_ptr)->incRef();
+        }
 
         print_created(this, "from pointer", m_ptr); track_created((ref_tag*) this, "from pointer");
 
@@ -74,8 +77,9 @@ template <typename T> class ref {
 
     /// Copy constructor
     ref(const ref &r) : m_ptr(r.m_ptr) {
-        if (m_ptr)
+        if (m_ptr) {
             ((Object *) m_ptr)->incRef();
+        }
 
         print_copy_created(this, "with pointer", m_ptr); track_copy_created((ref_tag*) this);
     }
@@ -89,8 +93,9 @@ template <typename T> class ref {
 
     /// Destroy this reference
     ~ref() {
-        if (m_ptr)
+        if (m_ptr) {
             ((Object *) m_ptr)->decRef();
+        }
 
         print_destroyed(this); track_destroyed((ref_tag*) this);
     }
@@ -99,10 +104,12 @@ template <typename T> class ref {
     ref &operator=(ref &&r) noexcept {
         print_move_assigned(this, "pointer", r.m_ptr); track_move_assigned((ref_tag*) this);
 
-        if (*this == r)
+        if (*this == r) {
             return *this;
-        if (m_ptr)
+        }
+        if (m_ptr) {
             ((Object *) m_ptr)->decRef();
+        }
         m_ptr = r.m_ptr;
         r.m_ptr = nullptr;
         return *this;
@@ -116,13 +123,16 @@ template <typename T> class ref {
         print_copy_assigned(this, "pointer", r.m_ptr);
         track_copy_assigned((ref_tag *) this);
 
-        if (m_ptr == r.m_ptr)
+        if (m_ptr == r.m_ptr) {
             return *this;
-        if (m_ptr)
+        }
+        if (m_ptr) {
             ((Object *) m_ptr)->decRef();
+        }
         m_ptr = r.m_ptr;
-        if (m_ptr)
+        if (m_ptr) {
             ((Object *) m_ptr)->incRef();
+        }
         return *this;
     }
 
@@ -130,13 +140,16 @@ template <typename T> class ref {
     ref& operator=(T *ptr) {
         print_values(this, "assigned pointer"); track_values((ref_tag*) this, "assigned pointer");
 
-        if (m_ptr == ptr)
+        if (m_ptr == ptr) {
             return *this;
-        if (m_ptr)
+        }
+        if (m_ptr) {
             ((Object *) m_ptr)->decRef();
+        }
         m_ptr = ptr;
-        if (m_ptr)
+        if (m_ptr) {
             ((Object *) m_ptr)->incRef();
+        }
         return *this;
     }
 
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index 5838cb2746..82228a440a 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -39,7 +39,9 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("throw_local_simple_error", []() { throw LocalSimpleException("external mod"); });
     py::register_exception_translator([](std::exception_ptr p) {
       try {
-          if (p) std::rethrow_exception(p);
+          if (p) {
+              std::rethrow_exception(p);
+          }
       } catch (const shared_exception &e) {
           PyErr_SetString(PyExc_KeyError, e.what());
       }
diff --git a/tests/pybind11_tests.cpp b/tests/pybind11_tests.cpp
index 439cd40129..ec4581efd2 100644
--- a/tests/pybind11_tests.cpp
+++ b/tests/pybind11_tests.cpp
@@ -86,6 +86,7 @@ PYBIND11_MODULE(pybind11_tests, m) {
         .def(py::init<int>())
         .def("__repr__", [](const IncType& u) { return "IncType({})"_s.format(u.value()); });
 
-    for (const auto &initializer : initializers())
+    for (const auto &initializer : initializers()) {
         initializer(m);
+    }
 }
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 3a8e3e7b75..0920363966 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -85,8 +85,9 @@ TEST_SUBMODULE(buffers, m) {
         /// Construct from a buffer
         .def(py::init([](const py::buffer &b) {
             py::buffer_info info = b.request();
-            if (info.format != py::format_descriptor<float>::format() || info.ndim != 2)
+            if (info.format != py::format_descriptor<float>::format() || info.ndim != 2) {
                 throw std::runtime_error("Incompatible buffer format!");
+            }
 
             auto v = new Matrix(info.shape[0], info.shape[1]);
             memcpy(v->data(), info.ptr, sizeof(float) * (size_t) (v->rows() * v->cols()));
@@ -99,14 +100,16 @@ TEST_SUBMODULE(buffers, m) {
         /// Bare bones interface
         .def("__getitem__",
              [](const Matrix &m, std::pair<py::ssize_t, py::ssize_t> i) {
-                 if (i.first >= m.rows() || i.second >= m.cols())
+                 if (i.first >= m.rows() || i.second >= m.cols()) {
                      throw py::index_error();
+                 }
                  return m(i.first, i.second);
              })
         .def("__setitem__",
              [](Matrix &m, std::pair<py::ssize_t, py::ssize_t> i, float v) {
-                 if (i.first >= m.rows() || i.second >= m.cols())
+                 if (i.first >= m.rows() || i.second >= m.cols()) {
                      throw py::index_error();
+                 }
                  m(i.first, i.second) = v;
              })
         /// Provide buffer access
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 4a9f338378..5ff5a8fc4f 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -93,8 +93,11 @@ TEST_SUBMODULE(builtin_casters, m) {
 #if PY_MAJOR_VERSION >= 3
     // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger UnicodeDecodeError
     m.def("bad_utf32_string", [=]() { return std::u32string({ a32, char32_t(0xd800), z32 }); });
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2))
-        m.def("bad_wchar_string", [=]() { return std::wstring({ wchar_t(0x61), wchar_t(0xd800) }); });
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+        m.def("bad_wchar_string", [=]() {
+            return std::wstring({wchar_t(0x61), wchar_t(0xd800)});
+        });
+    }
 #endif
     m.def("u8_Z", []() -> char { return 'Z'; });
     m.def("u8_eacute", []() -> char { return '\xe9'; });
@@ -133,9 +136,21 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("string_view_print",   [](std::string_view s)    { py::print(s, s.size()); });
     m.def("string_view16_print", [](std::u16string_view s) { py::print(s, s.size()); });
     m.def("string_view32_print", [](std::u32string_view s) { py::print(s, s.size()); });
-    m.def("string_view_chars",   [](std::string_view s)    { py::list l; for (auto c : s) l.append((std::uint8_t) c); return l; });
-    m.def("string_view16_chars", [](std::u16string_view s) { py::list l; for (auto c : s) l.append((int) c); return l; });
-    m.def("string_view32_chars", [](std::u32string_view s) { py::list l; for (auto c : s) l.append((int) c); return l; });
+    m.def("string_view_chars",   [](std::string_view s)    { py::list l;
+        for (auto c : s) {
+            l.append((std::uint8_t) c);
+        }
+        return l; });
+    m.def("string_view16_chars", [](std::u16string_view s) { py::list l;
+        for (auto c : s) {
+            l.append((int) c);
+        }
+        return l; });
+    m.def("string_view32_chars", [](std::u32string_view s) { py::list l;
+        for (auto c : s) {
+            l.append((int) c);
+        }
+        return l; });
     m.def("string_view_return",   []() { return std::string_view((const char*)u8"utf8 secret \U0001f382"); });
     m.def("string_view16_return", []() { return std::u16string_view(u"utf16 secret \U0001f382"); });
     m.def("string_view32_return", []() { return std::u32string_view(U"utf32 secret \U0001f382"); });
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index 7cb98d0d86..cdbd9d42fe 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -95,8 +95,9 @@ TEST_SUBMODULE(call_policies, m) {
     // but it's unclear how to test it without `PyGILState_GetThisThreadState`.
     auto report_gil_status = []() {
         auto is_gil_held = false;
-        if (auto tstate = py::detail::get_thread_state_unchecked())
+        if (auto tstate = py::detail::get_thread_state_unchecked()) {
             is_gil_held = (tstate == PyGILState_GetThisThreadState());
+        }
 
         return is_gil_held ? "GIL held" : "GIL released";
     };
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 58688b6e8b..b73a623709 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -136,11 +136,16 @@ TEST_SUBMODULE(callbacks, m) {
     m.def("dummy_function_overloaded", [](int i, int j) { return i + j; });
     m.def("dummy_function_overloaded", &dummy_function);
     m.def("dummy_function2", [](int i, int j) { return i + j; });
-    m.def("roundtrip", [](std::function<int(int)> f, bool expect_none = false) {
-        if (expect_none && f)
-            throw std::runtime_error("Expected None to be converted to empty std::function");
-        return f;
-    }, py::arg("f"), py::arg("expect_none")=false);
+    m.def(
+        "roundtrip",
+        [](std::function<int(int)> f, bool expect_none = false) {
+            if (expect_none && f) {
+                throw std::runtime_error("Expected None to be converted to empty std::function");
+            }
+            return f;
+        },
+        py::arg("f"),
+        py::arg("expect_none") = false);
     m.def("test_dummy_function", [](const std::function<int(int)> &f) -> std::string {
         using fn_type = int (*)(int);
         auto result = f.target<fn_type>();
@@ -215,8 +220,9 @@ TEST_SUBMODULE(callbacks, m) {
         };
 
         // spawn worker threads
-        for (auto i : work)
+        for (auto i : work) {
             start_f(py::cast<int>(i));
+        }
     });
 
     m.def("callback_num_times", [](const py::function &f, std::size_t num) {
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 52a41a3bc0..977297e572 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -139,9 +139,13 @@ TEST_SUBMODULE(class_, m) {
 
     m.def("return_class_1", []() -> BaseClass* { return new DerivedClass1(); });
     m.def("return_class_2", []() -> BaseClass* { return new DerivedClass2(); });
-    m.def("return_class_n", [](int n) -> BaseClass* {
-        if (n == 1) return new DerivedClass1();
-        if (n == 2) return new DerivedClass2();
+    m.def("return_class_n", [](int n) -> BaseClass * {
+        if (n == 1) {
+            return new DerivedClass1();
+        }
+        if (n == 2) {
+            return new DerivedClass2();
+        }
         return new BaseClass();
     });
     m.def("return_none", []() -> BaseClass* { return nullptr; });
@@ -167,8 +171,9 @@ TEST_SUBMODULE(class_, m) {
         // See https://github.com/pybind/pybind11/issues/2486
         // if (category == 2)
         //     return py::type::of<int>();
-        if (category == 1)
+        if (category == 1) {
             return py::type::of<DerivedClass1>();
+        }
         return py::type::of<Invalid>();
     });
 
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 4711a94822..850edcb4d9 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -104,7 +104,9 @@ template <> struct type_caster<CopyOnlyInt> {
     bool load(handle src, bool) { value = CopyOnlyInt(src.cast<int>()); return true; }
     static handle cast(const CopyOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
     static handle cast(const CopyOnlyInt *src, return_value_policy policy, handle parent) {
-        if (!src) return none().release();
+        if (!src) {
+            return none().release();
+        }
         return cast(*src, policy, parent);
     }
     explicit operator CopyOnlyInt *() { return &value; }
@@ -203,8 +205,9 @@ TEST_SUBMODULE(copy_move_policies, m) {
     private:
         void *operator new(size_t bytes) {
             void *ptr = std::malloc(bytes);
-            if (ptr)
+            if (ptr) {
                 return ptr;
+            }
             throw std::bad_alloc{};
         }
     };
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index d22a94a1a1..d7b62ef784 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -28,8 +28,11 @@ using MatrixXdR = Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::R
 // Sets/resets a testing reference matrix to have values of 10*r + c, where r and c are the
 // (1-based) row/column number.
 template <typename M> void reset_ref(M &x) {
-    for (int i = 0; i < x.rows(); i++) for (int j = 0; j < x.cols(); j++)
-        x(i, j) = 11 + 10*i + j;
+    for (int i = 0; i < x.rows(); i++) {
+        for (int j = 0; j < x.cols(); j++) {
+            x(i, j) = 11 + 10 * i + j;
+        }
+    }
 }
 
 // Returns a static, column-major matrix
@@ -63,9 +66,11 @@ double get_elem(const Eigen::Ref<const Eigen::MatrixXd> &m) { return m(2, 1); };
 // reference is referencing rows/columns correctly).
 template <typename MatrixArgType> Eigen::MatrixXd adjust_matrix(MatrixArgType m) {
     Eigen::MatrixXd ret(m);
-    for (int c = 0; c < m.cols(); c++)
-        for (int r = 0; r < m.rows(); r++)
-            ret(r, c) += 10*r + 100*c;  // NOLINT(clang-analyzer-core.uninitialized.Assign)
+    for (int c = 0; c < m.cols(); c++) {
+        for (int r = 0; r < m.rows(); r++) {
+            ret(r, c) += 10 * r + 100 * c; // NOLINT(clang-analyzer-core.uninitialized.Assign)
+        }
+    }
     return ret;
 }
 
@@ -225,7 +230,9 @@ TEST_SUBMODULE(eigen, m) {
     // Returns a DiagonalMatrix with diagonal (1,2,3,...)
     m.def("incr_diag", [](int k) {
         Eigen::DiagonalMatrix<int, Eigen::Dynamic> m(k);
-        for (int i = 0; i < k; i++) m.diagonal()[i] = i+1;
+        for (int i = 0; i < k; i++) {
+            m.diagonal()[i] = i + 1;
+        }
         return m;
     });
 
@@ -320,8 +327,9 @@ TEST_SUBMODULE(eigen, m) {
         "matrix_multiply",
         [](const py::EigenDRef<const Eigen::MatrixXd> &A,
            const py::EigenDRef<const Eigen::MatrixXd> &B) -> Eigen::MatrixXd {
-            if (A.cols() != B.rows())
+            if (A.cols() != B.rows()) {
                 throw std::domain_error("Nonconformable matrices!");
+            }
             return A * B;
         },
         py::arg("A"),
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 508975eb3c..9ffc257ba0 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -307,7 +307,11 @@ TEST_CASE("Threads") {
 struct scope_exit {
     std::function<void()> f_;
     explicit scope_exit(std::function<void()> f) noexcept : f_(std::move(f)) {}
-    ~scope_exit() { if (f_) f_(); }
+    ~scope_exit() {
+        if (f_) {
+            f_();
+        }
+    }
 };
 
 TEST_CASE("Reload module from file") {
diff --git a/tests/test_eval.cpp b/tests/test_eval.cpp
index 29366f6798..e40dde70ec 100644
--- a/tests/test_eval.cpp
+++ b/tests/test_eval.cpp
@@ -93,8 +93,9 @@ TEST_SUBMODULE(eval_, m) {
 
     // test_eval_empty_globals
     m.def("eval_empty_globals", [](py::object global) {
-        if (global.is_none())
+        if (global.is_none()) {
             global = py::dict();
+        }
         auto int_class = py::eval("isinstance(42, int)", global);
         return global;
     });
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 3aa9673828..ab7dfbf691 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -116,7 +116,9 @@ TEST_SUBMODULE(exceptions, m) {
     static py::exception<MyException> ex(m, "MyException");
     py::register_exception_translator([](std::exception_ptr p) {
         try {
-            if (p) std::rethrow_exception(p);
+            if (p) {
+                std::rethrow_exception(p);
+            }
         } catch (const MyException &e) {
             // Set MyException as the active python error
             ex(e.what());
@@ -128,7 +130,9 @@ TEST_SUBMODULE(exceptions, m) {
     // never by visible from Python
     py::register_exception_translator([](std::exception_ptr p) {
         try {
-            if (p) std::rethrow_exception(p);
+            if (p) {
+                std::rethrow_exception(p);
+            }
         } catch (const MyException2 &e) {
             // Translate this exception to a standard RuntimeError
             PyErr_SetString(PyExc_RuntimeError, e.what());
@@ -140,7 +144,9 @@ TEST_SUBMODULE(exceptions, m) {
     // translator for MyException by throwing a new exception
     py::register_exception_translator([](std::exception_ptr p) {
         try {
-            if (p) std::rethrow_exception(p);
+            if (p) {
+                std::rethrow_exception(p);
+            }
         } catch (const MyException4 &e) {
             throw MyException(e.what());
         }
@@ -181,7 +187,9 @@ TEST_SUBMODULE(exceptions, m) {
             py::object o = foo["bar"];
         }
         catch (py::error_already_set& ex) {
-            if (!ex.matches(PyExc_KeyError)) throw;
+            if (!ex.matches(PyExc_KeyError)) {
+                throw;
+            }
             return true;
         }
         return false;
@@ -193,7 +201,9 @@ TEST_SUBMODULE(exceptions, m) {
             py::object o = foo["bar"];
         }
         catch (py::error_already_set &ex) {
-            if (!ex.matches(PyExc_Exception)) throw;
+            if (!ex.matches(PyExc_Exception)) {
+                throw;
+            }
             return true;
         }
         return false;
@@ -204,15 +214,18 @@ TEST_SUBMODULE(exceptions, m) {
             py::module_::import("nonexistent");
         }
         catch (py::error_already_set &ex) {
-            if (!ex.matches(PyExc_ImportError)) throw;
+            if (!ex.matches(PyExc_ImportError)) {
+                throw;
+            }
             return true;
         }
         return false;
     });
 
     m.def("throw_already_set", [](bool err) {
-        if (err)
+        if (err) {
             PyErr_SetString(PyExc_ValueError, "foo");
+        }
         try {
             throw py::error_already_set();
         } catch (const std::runtime_error& e) {
@@ -224,8 +237,9 @@ TEST_SUBMODULE(exceptions, m) {
             }
         }
         PyErr_Clear();
-        if (err)
+        if (err) {
             PyErr_SetString(PyExc_ValueError, "foo");
+        }
         throw py::error_already_set();
     });
 
@@ -252,10 +266,11 @@ TEST_SUBMODULE(exceptions, m) {
               try {
                   f(*args);
               } catch (py::error_already_set &ex) {
-                  if (ex.matches(exc_type))
+                  if (ex.matches(exc_type)) {
                       py::print(ex.what());
-                  else
+                  } else {
                       throw;
+                  }
               }
           });
 
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index c620b59493..ef54b0a1c5 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -22,8 +22,9 @@
 void noisy_function(const std::string &msg, bool flush) {
 
     std::cout << msg;
-    if (flush)
+    if (flush) {
         std::cout << std::flush;
+    }
 }
 
 void noisy_funct_dual(const std::string &msg, const std::string &emsg) {
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 34ad2a8647..0e262dad2f 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -26,8 +26,9 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     std::vector<int> list{{13, 17}};
     m.def("kw_func4", [](const std::vector<int> &entries) {
         std::string ret = "{";
-        for (int i : entries)
+        for (int i : entries) {
             ret += std::to_string(i) + " ";
+        }
         ret.back() = '}';
         return ret;
     }, py::arg("myList") = list);
@@ -89,18 +90,20 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     m.def("args_refcount", [](py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size());
-        for (size_t i = 0; i < a.size(); i++)
+        for (size_t i = 0; i < a.size(); i++) {
             // Use raw Python API here to avoid an extra, intermediate incref on the tuple item:
             t[i] = (int) Py_REFCNT(PyTuple_GET_ITEM(a.ptr(), static_cast<py::ssize_t>(i)));
+        }
         return t;
     });
     m.def("mixed_args_refcount", [](const py::object &o, py::args a) {
         GC_IF_NEEDED;
         py::tuple t(a.size() + 1);
         t[0] = o.ref_count();
-        for (size_t i = 0; i < a.size(); i++)
+        for (size_t i = 0; i < a.size(); i++) {
             // Use raw Python API here to avoid an extra, intermediate incref on the tuple item:
             t[i + 1] = (int) Py_REFCNT(PyTuple_GET_ITEM(a.ptr(), static_cast<py::ssize_t>(i)));
+        }
         return t;
     });
 
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index a5808e2f2a..0fb3ecc19f 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -47,8 +47,9 @@ TEST_SUBMODULE(local_bindings, m) {
         auto main = py::module_::import("pybind11_tests");
         if (py::hasattr(main, "class_")) {
             bind_local<LocalExternal, 7>(m, "LocalExternal", py::module_local());
+        } else {
+            throw std::runtime_error("test_class not enabled");
         }
-        else throw std::runtime_error("test_class not enabled");
     });
 
     // test_stl_bind_local
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 30a71acc9b..4712c80925 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -90,15 +90,17 @@ template<typename... Ix> arr data_t(const arr_t& a, Ix... index) {
 
 template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
     auto ptr = (uint8_t *) a.mutable_data(index...);
-    for (py::ssize_t i = 0; i < a.nbytes() - a.offset_at(index...); i++)
+    for (py::ssize_t i = 0; i < a.nbytes() - a.offset_at(index...); i++) {
         ptr[i] = (uint8_t) (ptr[i] * 2);
+    }
     return a;
 }
 
 template<typename... Ix> arr_t& mutate_data_t(arr_t& a, Ix... index) {
     auto ptr = a.mutable_data(index...);
-    for (py::ssize_t i = 0; i < a.size() - a.index_at(index...); i++)
+    for (py::ssize_t i = 0; i < a.size() - a.index_at(index...); i++) {
         ptr[i]++;
+    }
     return a;
 }
 
@@ -116,7 +118,9 @@ template<typename... Ix> arr_t& mutate_at_t(arr_t& a, Ix... idx) { a.mutable_at(
     sm.def(#name, [](type a, int i, int j, int k) { return name(a, i, j, k); });
 
 template <typename T, typename T2> py::handle auxiliaries(T &&r, T2 &&r2) {
-    if (r.ndim() != 2) throw std::domain_error("error: ndim != 2");
+    if (r.ndim() != 2) {
+        throw std::domain_error("error: ndim != 2");
+    }
     py::list l;
     l.append(*r.data(0, 0));
     l.append(*r2.mutable_data(0, 0));
@@ -292,34 +296,43 @@ TEST_SUBMODULE(numpy_array, sm) {
     // test_array_unchecked_fixed_dims
     sm.def("proxy_add2", [](py::array_t<double> a, double v) {
         auto r = a.mutable_unchecked<2>();
-        for (py::ssize_t i = 0; i < r.shape(0); i++)
-            for (py::ssize_t j = 0; j < r.shape(1); j++)
+        for (py::ssize_t i = 0; i < r.shape(0); i++) {
+            for (py::ssize_t j = 0; j < r.shape(1); j++) {
                 r(i, j) += v;
+            }
+        }
     }, py::arg{}.noconvert(), py::arg());
 
     sm.def("proxy_init3", [](double start) {
         py::array_t<double, py::array::c_style> a({ 3, 3, 3 });
         auto r = a.mutable_unchecked<3>();
-        for (py::ssize_t i = 0; i < r.shape(0); i++)
-        for (py::ssize_t j = 0; j < r.shape(1); j++)
-        for (py::ssize_t k = 0; k < r.shape(2); k++)
-            r(i, j, k) = start++;
+        for (py::ssize_t i = 0; i < r.shape(0); i++) {
+            for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                for (py::ssize_t k = 0; k < r.shape(2); k++) {
+                    r(i, j, k) = start++;
+                }
+            }
+        }
         return a;
     });
     sm.def("proxy_init3F", [](double start) {
         py::array_t<double, py::array::f_style> a({ 3, 3, 3 });
         auto r = a.mutable_unchecked<3>();
-        for (py::ssize_t k = 0; k < r.shape(2); k++)
-        for (py::ssize_t j = 0; j < r.shape(1); j++)
-        for (py::ssize_t i = 0; i < r.shape(0); i++)
-            r(i, j, k) = start++;
+        for (py::ssize_t k = 0; k < r.shape(2); k++) {
+            for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                for (py::ssize_t i = 0; i < r.shape(0); i++) {
+                    r(i, j, k) = start++;
+                }
+            }
+        }
         return a;
     });
     sm.def("proxy_squared_L2_norm", [](const py::array_t<double> &a) {
         auto r = a.unchecked<1>();
         double sumsq = 0;
-        for (py::ssize_t i = 0; i < r.shape(0); i++)
+        for (py::ssize_t i = 0; i < r.shape(0); i++) {
             sumsq += r[i] * r(i); // Either notation works for a 1D array
+        }
         return sumsq;
     });
 
@@ -345,19 +358,28 @@ TEST_SUBMODULE(numpy_array, sm) {
     // Same as the above, but without a compile-time dimensions specification:
     sm.def("proxy_add2_dyn", [](py::array_t<double> a, double v) {
         auto r = a.mutable_unchecked();
-        if (r.ndim() != 2) throw std::domain_error("error: ndim != 2");
-        for (py::ssize_t i = 0; i < r.shape(0); i++)
-            for (py::ssize_t j = 0; j < r.shape(1); j++)
+        if (r.ndim() != 2) {
+            throw std::domain_error("error: ndim != 2");
+        }
+        for (py::ssize_t i = 0; i < r.shape(0); i++) {
+            for (py::ssize_t j = 0; j < r.shape(1); j++) {
                 r(i, j) += v;
+            }
+        }
     }, py::arg{}.noconvert(), py::arg());
     sm.def("proxy_init3_dyn", [](double start) {
         py::array_t<double, py::array::c_style> a({ 3, 3, 3 });
         auto r = a.mutable_unchecked();
-        if (r.ndim() != 3) throw std::domain_error("error: ndim != 3");
-        for (py::ssize_t i = 0; i < r.shape(0); i++)
-        for (py::ssize_t j = 0; j < r.shape(1); j++)
-        for (py::ssize_t k = 0; k < r.shape(2); k++)
-            r(i, j, k) = start++;
+        if (r.ndim() != 3) {
+            throw std::domain_error("error: ndim != 3");
+        }
+        for (py::ssize_t i = 0; i < r.shape(0); i++) {
+            for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                for (py::ssize_t k = 0; k < r.shape(2); k++) {
+                    r(i, j, k) = start++;
+                }
+            }
+        }
         return a;
     });
     sm.def("proxy_auxiliaries2_dyn", [](py::array_t<double> a) {
@@ -386,8 +408,10 @@ TEST_SUBMODULE(numpy_array, sm) {
     // reshape array to 2D without changing size
     sm.def("array_reshape2", [](py::array_t<double> a) {
         const auto dim_sz = (py::ssize_t)std::sqrt(a.size());
-        if (dim_sz * dim_sz != a.size())
-            throw std::domain_error("array_reshape2: input array total size is not a squared integer");
+        if (dim_sz * dim_sz != a.size()) {
+            throw std::domain_error(
+                "array_reshape2: input array total size is not a squared integer");
+        }
         a.resize({dim_sz, dim_sz});
     });
 
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index bf4f4cee74..bd702e403c 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -108,30 +108,35 @@ PYBIND11_PACKED(struct EnumStruct {
 
 std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
     os << "a='";
-    for (size_t i = 0; i < 3 && (v.a[i] != 0); i++)
+    for (size_t i = 0; i < 3 && (v.a[i] != 0); i++) {
         os << v.a[i];
+    }
     os << "',b='";
-    for (size_t i = 0; i < 3 && (v.b[i] != 0); i++)
+    for (size_t i = 0; i < 3 && (v.b[i] != 0); i++) {
         os << v.b[i];
+    }
     return os << "'";
 }
 
 std::ostream& operator<<(std::ostream& os, const ArrayStruct& v) {
     os << "a={";
     for (int i = 0; i < 3; i++) {
-        if (i > 0)
+        if (i > 0) {
             os << ',';
+        }
         os << '{';
-        for (int j = 0; j < 3; j++)
+        for (int j = 0; j < 3; j++) {
             os << v.a[i][j] << ',';
+        }
         os << v.a[i][3] << '}';
     }
     os << "},b={" << v.b[0] << ',' << v.b[1];
     os << "},c={" << int(v.c[0]) << ',' << int(v.c[1]) << ',' << int(v.c[2]);
     os << "},d={";
     for (int i = 0; i < 4; i++) {
-        if (i > 0)
+        if (i > 0) {
             os << ',';
+        }
         os << '{' << v.d[i][0] << ',' << v.d[i][1] << '}';
     }
     return os << '}';
@@ -198,7 +203,9 @@ py::array_t<int32_t, 0> test_array_ctors(int i) {
 
     auto fill = [](py::array arr) {
         auto req = arr.request();
-        for (int i = 0; i < 6; i++) ((int32_t *) req.ptr)[i] = i + 1;
+        for (int i = 0; i < 6; i++) {
+            ((int32_t *) req.ptr)[i] = i + 1;
+        }
         return arr;
     };
 
@@ -373,32 +380,33 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 
     m.def("print_dtypes", []() {
         py::list l;
-        for (const py::handle &d : {
-            py::dtype::of<SimpleStruct>(),
-            py::dtype::of<PackedStruct>(),
-            py::dtype::of<NestedStruct>(),
-            py::dtype::of<PartialStruct>(),
-            py::dtype::of<PartialNestedStruct>(),
-            py::dtype::of<StringStruct>(),
-            py::dtype::of<ArrayStruct>(),
-            py::dtype::of<EnumStruct>(),
-            py::dtype::of<StructWithUglyNames>(),
-            py::dtype::of<ComplexStruct>()
-        })
+        for (const py::handle &d : {py::dtype::of<SimpleStruct>(),
+                                    py::dtype::of<PackedStruct>(),
+                                    py::dtype::of<NestedStruct>(),
+                                    py::dtype::of<PartialStruct>(),
+                                    py::dtype::of<PartialNestedStruct>(),
+                                    py::dtype::of<StringStruct>(),
+                                    py::dtype::of<ArrayStruct>(),
+                                    py::dtype::of<EnumStruct>(),
+                                    py::dtype::of<StructWithUglyNames>(),
+                                    py::dtype::of<ComplexStruct>()}) {
             l.append(py::str(d));
+        }
         return l;
     });
     m.def("test_dtype_ctors", &test_dtype_ctors);
     m.def("test_dtype_kind", [dtype_names]() {
         py::list list;
-        for (auto& dt_name : dtype_names)
+        for (auto &dt_name : dtype_names) {
             list.append(py::dtype(dt_name).kind());
+        }
         return list;
     });
     m.def("test_dtype_char_", [dtype_names]() {
         py::list list;
-        for (auto& dt_name : dtype_names)
+        for (auto &dt_name : dtype_names) {
             list.append(py::dtype(dt_name).char_());
+        }
         return list;
     });
     m.def("test_dtype_methods", []() {
@@ -423,8 +431,9 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         if (non_empty) {
             auto req = arr.request();
             auto ptr = static_cast<StringStruct*>(req.ptr);
-            for (py::ssize_t i = 0; i < req.size * req.itemsize; i++)
-                static_cast<char*>(req.ptr)[i] = 0;
+            for (py::ssize_t i = 0; i < req.size * req.itemsize; i++) {
+                static_cast<char *>(req.ptr)[i] = 0;
+            }
             ptr[1].a[0] = 'a'; ptr[1].b[0] = 'a';
             ptr[2].a[0] = 'a'; ptr[2].b[0] = 'a';
             ptr[3].a[0] = 'a'; ptr[3].b[0] = 'a';
@@ -443,16 +452,22 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         py::array_t<ArrayStruct, 0> arr = mkarray_via_buffer<ArrayStruct>(n);
         auto ptr = (ArrayStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
-            for (size_t j = 0; j < 3; j++)
-                for (size_t k = 0; k < 4; k++)
+            for (size_t j = 0; j < 3; j++) {
+                for (size_t k = 0; k < 4; k++) {
                     ptr[i].a[j][k] = char('A' + (i * 100 + j * 10 + k) % 26);
-            for (size_t j = 0; j < 2; j++)
+                }
+            }
+            for (size_t j = 0; j < 2; j++) {
                 ptr[i].b[j] = int32_t(i * 1000 + j);
-            for (size_t j = 0; j < 3; j++)
+            }
+            for (size_t j = 0; j < 3; j++) {
                 ptr[i].c[j] = uint8_t(i * 10 + j);
-            for (size_t j = 0; j < 4; j++)
-                for (size_t k = 0; k < 2; k++)
+            }
+            for (size_t j = 0; j < 4; j++) {
+                for (size_t k = 0; k < 2; k++) {
                     ptr[i].d[j][k] = float(i) * 100.0f + float(j) * 10.0f + float(k);
+                }
+            }
         }
         return arr;
     });
diff --git a/tests/test_opaque_types.cpp b/tests/test_opaque_types.cpp
index 804de6d4ff..2da2457474 100644
--- a/tests/test_opaque_types.cpp
+++ b/tests/test_opaque_types.cpp
@@ -45,8 +45,9 @@ TEST_SUBMODULE(opaque_types, m) {
         std::string ret = "Opaque list: [";
         bool first = true;
         for (const auto &entry : l) {
-            if (!first)
+            if (!first) {
                 ret += ", ";
+            }
             ret += entry;
             first = false;
         }
diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index b77636dd1a..efe0463df0 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -39,13 +39,15 @@ void wrap(py::module m) {
         .def(py::pickle(
             [](const py::object &self) {
                 py::dict d;
-                if (py::hasattr(self, "__dict__"))
+                if (py::hasattr(self, "__dict__")) {
                     d = self.attr("__dict__");
+                }
                 return py::make_tuple(self.attr("num"), d);
             },
             [](const py::tuple &t) {
-                if (t.size() != 2)
+                if (t.size() != 2) {
                     throw std::runtime_error("Invalid state!");
+                }
                 auto cpp_state = std::unique_ptr<SimpleBase>(new SimpleBaseTrampoline);
                 cpp_state->num = t[0].cast<int>();
                 auto py_state  = t[1].cast<py::dict>();
@@ -101,8 +103,9 @@ TEST_SUBMODULE(pickling, m) {
         });
     ignoreOldStyleInitWarnings([&pyPickleable]() {
         pyPickleable.def("__setstate__", [](Pickleable &p, const py::tuple &t) {
-            if (t.size() != 3)
+            if (t.size() != 3) {
                 throw std::runtime_error("Invalid state!");
+}
             /* Invoke the constructor (need to use in-place version) */
             new (&p) Pickleable(t[0].cast<std::string>());
 
@@ -119,8 +122,9 @@ TEST_SUBMODULE(pickling, m) {
                 return py::make_tuple(p.value(), p.extra1(), p.extra2());
             },
             [](const py::tuple &t) {
-                if (t.size() != 3)
+                if (t.size() != 3) {
                     throw std::runtime_error("Invalid state!");
+}
                 auto p = PickleableNew(t[0].cast<std::string>());
 
                 p.setExtra1(t[1].cast<int>());
@@ -153,8 +157,9 @@ TEST_SUBMODULE(pickling, m) {
         });
     ignoreOldStyleInitWarnings([&pyPickleableWithDict]() {
         pyPickleableWithDict.def("__setstate__", [](const py::object &self, const py::tuple &t) {
-            if (t.size() != 3)
+            if (t.size() != 3) {
                 throw std::runtime_error("Invalid state!");
+}
             /* Cast and construct */
             auto &p = self.cast<PickleableWithDict &>();
             new (&p) PickleableWithDict(t[0].cast<std::string>());
@@ -174,8 +179,9 @@ TEST_SUBMODULE(pickling, m) {
                 return py::make_tuple(self.attr("value"), self.attr("extra"), self.attr("__dict__"));
             },
             [](const py::tuple &t) {
-                if (t.size() != 3)
+                if (t.size() != 3) {
                     throw std::runtime_error("Invalid state!");
+}
 
                 auto cpp_state = PickleableWithDictNew(t[0].cast<std::string>());
                 cpp_state.extra = t[1].cast<int>();
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 85cb98fcbf..3605ad8eac 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -40,8 +40,9 @@ TEST_SUBMODULE(pytypes, m) {
     });
     m.def("print_list", [](const py::list &list) {
         int index = 0;
-        for (auto item : list)
+        for (auto item : list) {
             py::print("list item {}: {}"_s.format(index++, item));
+        }
     });
     // test_none
     m.def("get_none", []{return py::none();});
@@ -56,8 +57,9 @@ TEST_SUBMODULE(pytypes, m) {
         return set;
     });
     m.def("print_set", [](const py::set &set) {
-        for (auto item : set)
+        for (auto item : set) {
             py::print("key:", item);
+        }
     });
     m.def("set_contains",
           [](const py::set &set, const py::object &key) { return set.contains(key); });
@@ -66,8 +68,9 @@ TEST_SUBMODULE(pytypes, m) {
     // test_dict
     m.def("get_dict", []() { return py::dict("key"_a="value"); });
     m.def("print_dict", [](const py::dict &dict) {
-        for (auto item : dict)
+        for (auto item : dict) {
             py::print("key: {}, value={}"_s.format(item.first, item.second));
+        }
     });
     m.def("dict_keyword_constructor", []() {
         auto d1 = py::dict("x"_a=1, "y"_a=2);
@@ -405,9 +408,9 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("test_memoryview_from_buffer", [](bool is_unsigned) {
         static const int16_t si16[] = { 3, 1, 4, 1, 5 };
         static const uint16_t ui16[] = { 2, 7, 1, 8 };
-        if (is_unsigned)
-            return py::memoryview::from_buffer(
-                ui16, { 4 }, { sizeof(uint16_t) });
+        if (is_unsigned) {
+            return py::memoryview::from_buffer(ui16, {4}, {sizeof(uint16_t)});
+        }
         return py::memoryview::from_buffer(si16, {5}, {sizeof(int16_t)});
     });
 
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index a378128ae2..a5b746cad4 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -74,8 +74,9 @@ PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
 
 template <typename PythonType>
 py::list test_random_access_iterator(PythonType x) {
-    if (x.size() < 5)
+    if (x.size() < 5) {
         throw py::value_error("Please provide at least 5 elements for testing.");
+    }
 
     auto checks = py::list();
     auto assert_equal = [&checks](py::handle a, py::handle b) {
@@ -125,8 +126,9 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def(py::init<int>())
         .def("__getitem__", [](const Sliceable &s, const py::slice &slice) {
             py::ssize_t start = 0, stop = 0, step = 0, slicelength = 0;
-            if (!slice.compute(s.size, &start, &stop, &step, &slicelength))
+            if (!slice.compute(s.size, &start, &stop, &step, &slicelength)) {
                 throw py::error_already_set();
+            }
             int istart = static_cast<int>(start);
             int istop  = static_cast<int>(stop);
             int istep  = static_cast<int>(step);
@@ -195,10 +197,14 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         }
 
         bool operator==(const Sequence &s) const {
-            if (m_size != s.size()) return false;
-            for (size_t i = 0; i < m_size; ++i)
-                if (m_data[i] != s[i])
+            if (m_size != s.size()) {
+                return false;
+            }
+            for (size_t i = 0; i < m_size; ++i) {
+                if (m_data[i] != s[i]) {
                     return false;
+                }
+            }
             return true;
         }
         bool operator!=(const Sequence &s) const { return !operator==(s); }
@@ -207,16 +213,19 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         float &operator[](size_t index) { return m_data[index]; }
 
         bool contains(float v) const {
-            for (size_t i = 0; i < m_size; ++i)
-                if (v == m_data[i])
+            for (size_t i = 0; i < m_size; ++i) {
+                if (v == m_data[i]) {
                     return true;
+                }
+            }
             return false;
         }
 
         Sequence reversed() const {
             Sequence result(m_size);
-            for (size_t i = 0; i < m_size; ++i)
+            for (size_t i = 0; i < m_size; ++i) {
                 result[m_size - i - 1] = m_data[i];
+            }
             return result;
         }
 
@@ -235,14 +244,16 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         /// Bare bones interface
         .def("__getitem__",
              [](const Sequence &s, size_t i) {
-                 if (i >= s.size())
+                 if (i >= s.size()) {
                      throw py::index_error();
+                 }
                  return s[i];
              })
         .def("__setitem__",
              [](Sequence &s, size_t i, float v) {
-                 if (i >= s.size())
+                 if (i >= s.size()) {
                      throw py::index_error();
+                 }
                  s[i] = v;
              })
         .def("__len__", &Sequence::size)
@@ -257,8 +268,9 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("__getitem__",
              [](const Sequence &s, const py::slice &slice) -> Sequence * {
                  size_t start = 0, stop = 0, step = 0, slicelength = 0;
-                 if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
+                 if (!slice.compute(s.size(), &start, &stop, &step, &slicelength)) {
                      throw py::error_already_set();
+                 }
                  auto *seq = new Sequence(slicelength);
                  for (size_t i = 0; i < slicelength; ++i) {
                      (*seq)[i] = s[start];
@@ -269,11 +281,13 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("__setitem__",
              [](Sequence &s, const py::slice &slice, const Sequence &value) {
                  size_t start = 0, stop = 0, step = 0, slicelength = 0;
-                 if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
+                 if (!slice.compute(s.size(), &start, &stop, &step, &slicelength)) {
                      throw py::error_already_set();
-                 if (slicelength != value.size())
+                 }
+                 if (slicelength != value.size()) {
                      throw std::runtime_error(
                          "Left and right hand size of slice assignment have different sizes!");
+                 }
                  for (size_t i = 0; i < slicelength; ++i) {
                      s[start] = value[i];
                      start += step;
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 94f04330a2..5bd77eae33 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -113,8 +113,9 @@ class MyObject4 {
     static void cleanupAllInstances() {
         auto tmp = std::move(myobject4_instances);
         myobject4_instances.clear();
-        for (auto o : tmp)
+        for (auto o : tmp) {
             delete o;
+        }
     }
 private:
     ~MyObject4() {
@@ -140,8 +141,9 @@ class MyObject4a {
     static void cleanupAllInstances() {
         auto tmp = std::move(myobject4a_instances);
         myobject4a_instances.clear();
-        for (auto o : tmp)
+        for (auto o : tmp) {
             delete o;
+        }
     }
 protected:
     virtual ~MyObject4a() {
@@ -445,8 +447,9 @@ TEST_SUBMODULE(smart_ptr, m) {
         .def("add", &ElementList::add)
         .def("get", [](ElementList &el) {
             py::list list;
-            for (auto &e : el.l)
+            for (auto &e : el.l) {
                 list.append(py::cast(e));
+            }
             return list;
         });
 }
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index 6b23e3529f..7fb973ca43 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -42,23 +42,27 @@ class E_nc {
 
 template <class Container> Container *one_to_n(int n) {
     auto v = new Container();
-    for (int i = 1; i <= n; i++)
+    for (int i = 1; i <= n; i++) {
         v->emplace_back(i);
+    }
     return v;
 }
 
 template <class Map> Map *times_ten(int n) {
     auto m = new Map();
-    for (int i = 1; i <= n; i++)
-        m->emplace(int(i), E_nc(10*i));
+    for (int i = 1; i <= n; i++) {
+        m->emplace(int(i), E_nc(10 * i));
+    }
     return m;
 }
 
 template <class NestMap> NestMap *times_hundred(int n) {
     auto m = new NestMap();
-    for (int i = 1; i <= n; i++)
-        for (int j = 1; j <= n; j++)
-            (*m)[i].emplace(int(j*10), E_nc(100*j));
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            (*m)[i].emplace(int(j * 10), E_nc(100 * j));
+        }
+    }
     return m;
 }
 
@@ -98,9 +102,11 @@ TEST_SUBMODULE(stl_binders, m) {
     m.def("get_nvnc", [](int n)
         {
             auto m = new std::map<int, std::vector<E_nc>>();
-            for (int i = 1; i <= n; i++)
-                for (int j = 1; j <= n; j++)
+            for (int i = 1; i <= n; i++) {
+                for (int j = 1; j <= n; j++) {
                     (*m)[i].emplace_back(j);
+                }
+            }
             return m;
         });
     py::bind_map<std::map<int, std::map<int, E_nc>>>(m, "MapMapENC");
diff --git a/tests/test_tagbased_polymorphic.cpp b/tests/test_tagbased_polymorphic.cpp
index 2c7bad8bbc..d54d1fd325 100644
--- a/tests/test_tagbased_polymorphic.cpp
+++ b/tests/test_tagbased_polymorphic.cpp
@@ -100,8 +100,12 @@ const std::type_info* Animal::type_of_kind(Kind kind)
         case Kind::LastCat: break;
     }
 
-    if (kind >= Kind::Dog && kind <= Kind::LastDog) return &typeid(Dog);
-    if (kind >= Kind::Cat && kind <= Kind::LastCat) return &typeid(Cat);
+    if (kind >= Kind::Dog && kind <= Kind::LastDog) {
+        return &typeid(Dog);
+    }
+    if (kind >= Kind::Cat && kind <= Kind::LastCat) {
+        return &typeid(Cat);
+    }
     return nullptr;
 }
 
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index d98b57f174..7fb90cc591 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -112,8 +112,9 @@ class NonCopyable {
     void operator=(const NonCopyable &) = delete;
     void operator=(NonCopyable &&) = delete;
     std::string get_value() const {
-        if (value)
+        if (value) {
             return std::to_string(*value);
+        }
         return "(null)";
     }
     ~NonCopyable() { print_destroyed(this); }

From b4f5350d0d3cc8813202becad31de06bb17112b3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 8 Feb 2022 19:08:31 -0800
Subject: [PATCH 300/638] chore: use member initializer (#3704)

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/detail/type_caster_base.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 212a944afe..071de23b56 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -62,10 +62,7 @@ class loader_life_support {
 
 public:
     /// A new patient frame is created when a function is entered
-    loader_life_support() {
-        parent = get_stack_top();
-        set_stack_top(this);
-    }
+    loader_life_support() : parent{get_stack_top()} { set_stack_top(this); }
 
     /// ... and destroyed after it returns
     ~loader_life_support() {

From 7769e7719c8bf8cb2f75f59221c263617408564d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 9 Feb 2022 06:24:57 -0800
Subject: [PATCH 301/638] clang-tidy readability-qualified-auto (#3702)

* Adding readability-qualified-auto to .clang-tidy

Ported from @henryiii's https://github.com/pybind/pybind11/pull/3683/commits/287527f705c8badee8ba9f6278d691fe0450ae43

* fix: support Python < 3.6

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .clang-tidy                                |  1 +
 include/pybind11/attr.h                    |  2 +-
 include/pybind11/cast.h                    |  4 +-
 include/pybind11/detail/class.h            | 45 +++++++++++-----------
 include/pybind11/detail/internals.h        |  4 +-
 include/pybind11/detail/type_caster_base.h | 32 +++++++--------
 include/pybind11/embed.h                   |  2 +-
 include/pybind11/functional.h              |  4 +-
 include/pybind11/gil.h                     |  4 ++
 include/pybind11/numpy.h                   |  6 +--
 include/pybind11/pybind11.h                | 32 +++++++--------
 include/pybind11/pytypes.h                 |  2 +-
 include/pybind11/stl/filesystem.h          |  4 +-
 include/pybind11/stl_bind.h                |  4 +-
 tests/test_buffers.cpp                     |  2 +-
 tests/test_builtin_casters.cpp             |  2 +-
 tests/test_call_policies.cpp               |  2 +-
 tests/test_callbacks.cpp                   |  2 +-
 tests/test_class.cpp                       |  2 +-
 tests/test_embed/test_interpreter.cpp      |  4 +-
 tests/test_numpy_array.cpp                 |  2 +-
 tests/test_numpy_dtypes.cpp                | 24 ++++++------
 tests/test_pytypes.cpp                     |  2 +-
 tests/test_smart_ptr.cpp                   |  4 +-
 tests/test_stl_binders.cpp                 | 23 ++++++-----
 25 files changed, 109 insertions(+), 106 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 97bbd53968..1957b8690e 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -40,6 +40,7 @@ readability-implicit-bool-conversion,
 readability-make-member-function-const,
 readability-misplaced-array-index,
 readability-non-const-parameter,
+readability-qualified-auto,
 readability-redundant-function-ptr-dereference,
 readability-redundant-smartptr-get,
 readability-redundant-string-cstr,
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index f23582b1bf..669c72614e 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -311,7 +311,7 @@ struct type_record {
     bool is_final : 1;
 
     PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *)) {
-        auto base_info = detail::get_type_info(base, false);
+        auto *base_info = detail::get_type_info(base, false);
         if (!base_info) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 71b8c2f0ff..cfec7e5f0e 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -251,7 +251,7 @@ template <> class type_caster<void> : public type_caster<void_type> {
         }
 
         /* Check if this is a C++ type */
-        auto &bases = all_type_info((PyTypeObject *) type::handle_of(h).ptr());
+        const auto &bases = all_type_info((PyTypeObject *) type::handle_of(h).ptr());
         if (bases.size() == 1) { // Only allowing loading from a single-value type
             value = values_and_holders(reinterpret_cast<instance *>(h.ptr())).begin()->value_ptr();
             return true;
@@ -306,7 +306,7 @@ template <> class type_caster<bool> {
             #else
             // Alternate approach for CPython: this does the same as the above, but optimized
             // using the CPython API so as to avoid an unneeded attribute lookup.
-            else if (auto tp_as_number = src.ptr()->ob_type->tp_as_number) {
+            else if (auto *tp_as_number = src.ptr()->ob_type->tp_as_number) {
                 if (PYBIND11_NB_BOOL(tp_as_number)) {
                     res = (*PYBIND11_NB_BOOL(tp_as_number))(src.ptr());
                 }
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 28edc12903..e50c8060fb 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -65,7 +65,7 @@ inline PyTypeObject *make_static_property_type() {
        issue no Python C API calls which could potentially invoke the
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
-    auto heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
+    auto *heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
     if (!heap_type) {
         pybind11_fail("make_static_property_type(): error allocating type!");
     }
@@ -75,7 +75,7 @@ inline PyTypeObject *make_static_property_type() {
     heap_type->ht_qualname = name_obj.inc_ref().ptr();
 #endif
 
-    auto type = &heap_type->ht_type;
+    auto *type = &heap_type->ht_type;
     type->tp_name = name;
     type->tp_base = type_incref(&PyProperty_Type);
     type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;
@@ -130,7 +130,7 @@ extern "C" inline int pybind11_meta_setattro(PyObject* obj, PyObject* name, PyOb
     //   1. `Type.static_prop = value`             --> descr_set: `Type.static_prop.__set__(value)`
     //   2. `Type.static_prop = other_static_prop` --> setattro:  replace existing `static_prop`
     //   3. `Type.regular_attribute = value`       --> setattro:  regular attribute assignment
-    const auto static_prop = (PyObject *) get_internals().static_property_type;
+    auto *const static_prop = (PyObject *) get_internals().static_property_type;
     const auto call_descr_set = (descr != nullptr) && (value != nullptr)
                                 && (PyObject_IsInstance(descr, static_prop) != 0)
                                 && (PyObject_IsInstance(value, static_prop) == 0);
@@ -179,7 +179,7 @@ extern "C" inline PyObject *pybind11_meta_call(PyObject *type, PyObject *args, P
     }
 
     // This must be a pybind11 instance
-    auto instance = reinterpret_cast<detail::instance *>(self);
+    auto *instance = reinterpret_cast<detail::instance *>(self);
 
     // Ensure that the base __init__ function(s) were called
     for (const auto &vh : values_and_holders(instance)) {
@@ -245,7 +245,7 @@ inline PyTypeObject* make_default_metaclass() {
        issue no Python C API calls which could potentially invoke the
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
-    auto heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
+    auto *heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
     if (!heap_type) {
         pybind11_fail("make_default_metaclass(): error allocating metaclass!");
     }
@@ -255,7 +255,7 @@ inline PyTypeObject* make_default_metaclass() {
     heap_type->ht_qualname = name_obj.inc_ref().ptr();
 #endif
 
-    auto type = &heap_type->ht_type;
+    auto *type = &heap_type->ht_type;
     type->tp_name = name;
     type->tp_base = type_incref(&PyType_Type);
     type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;
@@ -285,7 +285,7 @@ inline PyTypeObject* make_default_metaclass() {
 inline void traverse_offset_bases(void *valueptr, const detail::type_info *tinfo, instance *self,
         bool (*f)(void * /*parentptr*/, instance * /*self*/)) {
     for (handle h : reinterpret_borrow<tuple>(tinfo->type->tp_bases)) {
-        if (auto parent_tinfo = get_type_info((PyTypeObject *) h.ptr())) {
+        if (auto *parent_tinfo = get_type_info((PyTypeObject *) h.ptr())) {
             for (auto &c : parent_tinfo->implicit_casts) {
                 if (c.first == tinfo->cpptype) {
                     auto *parentptr = c.second(valueptr);
@@ -344,7 +344,7 @@ inline PyObject *make_new_instance(PyTypeObject *type) {
     }
 #endif
     PyObject *self = type->tp_alloc(type, 0);
-    auto inst = reinterpret_cast<instance *>(self);
+    auto *inst = reinterpret_cast<instance *>(self);
     // Allocate the value/holder internals:
     inst->allocate_layout();
 
@@ -369,14 +369,14 @@ extern "C" inline int pybind11_object_init(PyObject *self, PyObject *, PyObject
 
 inline void add_patient(PyObject *nurse, PyObject *patient) {
     auto &internals = get_internals();
-    auto instance = reinterpret_cast<detail::instance *>(nurse);
+    auto *instance = reinterpret_cast<detail::instance *>(nurse);
     instance->has_patients = true;
     Py_INCREF(patient);
     internals.patients[nurse].push_back(patient);
 }
 
 inline void clear_patients(PyObject *self) {
-    auto instance = reinterpret_cast<detail::instance *>(self);
+    auto *instance = reinterpret_cast<detail::instance *>(self);
     auto &internals = get_internals();
     auto pos = internals.patients.find(self);
     assert(pos != internals.patients.end());
@@ -394,7 +394,7 @@ inline void clear_patients(PyObject *self) {
 /// Clears all internal data from the instance and removes it from registered instances in
 /// preparation for deallocation.
 inline void clear_instance(PyObject *self) {
-    auto instance = reinterpret_cast<detail::instance *>(self);
+    auto *instance = reinterpret_cast<detail::instance *>(self);
 
     // Deallocate any values/holders, if present:
     for (auto &v_h : values_and_holders(instance)) {
@@ -435,7 +435,7 @@ inline void clear_instance(PyObject *self) {
 extern "C" inline void pybind11_object_dealloc(PyObject *self) {
     clear_instance(self);
 
-    auto type = Py_TYPE(self);
+    auto *type = Py_TYPE(self);
     type->tp_free(self);
 
 #if PY_VERSION_HEX < 0x03080000
@@ -464,7 +464,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
        issue no Python C API calls which could potentially invoke the
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
-    auto heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
+    auto *heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
     if (!heap_type) {
         pybind11_fail("make_object_base_type(): error allocating type!");
     }
@@ -474,7 +474,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
     heap_type->ht_qualname = name_obj.inc_ref().ptr();
 #endif
 
-    auto type = &heap_type->ht_type;
+    auto *type = &heap_type->ht_type;
     type->tp_name = name;
     type->tp_base = type_incref(&PyBaseObject_Type);
     type->tp_basicsize = static_cast<ssize_t>(sizeof(instance));
@@ -538,7 +538,7 @@ extern "C" inline int pybind11_clear(PyObject *self) {
 
 /// Give instances of this type a `__dict__` and opt into garbage collection.
 inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
-    auto type = &heap_type->ht_type;
+    auto *type = &heap_type->ht_type;
     type->tp_flags |= Py_TPFLAGS_HAVE_GC;
     type->tp_dictoffset = type->tp_basicsize; // place dict at the end
     type->tp_basicsize += (ssize_t)sizeof(PyObject *); // and allocate enough space for it
@@ -639,11 +639,11 @@ inline PyObject* make_new_python_type(const type_record &rec) {
         }
     }
 
-    auto full_name = c_str(
+    const auto *full_name = c_str(
 #if !defined(PYPY_VERSION)
         module_ ? str(module_).cast<std::string>() + "." + rec.name :
 #endif
-        rec.name);
+                rec.name);
 
     char *tp_doc = nullptr;
     if (rec.doc && options::show_user_defined_docstrings()) {
@@ -656,17 +656,16 @@ inline PyObject* make_new_python_type(const type_record &rec) {
 
     auto &internals = get_internals();
     auto bases = tuple(rec.bases);
-    auto base = (bases.empty()) ? internals.instance_base
-                                    : bases[0].ptr();
+    auto *base = (bases.empty()) ? internals.instance_base : bases[0].ptr();
 
     /* Danger zone: from now (and until PyType_Ready), make sure to
        issue no Python C API calls which could potentially invoke the
        garbage collector (the GC will call type_traverse(), which will in
        turn find the newly constructed type in an invalid state) */
-    auto metaclass = rec.metaclass.ptr() ? (PyTypeObject *) rec.metaclass.ptr()
-                                         : internals.default_metaclass;
+    auto *metaclass
+        = rec.metaclass.ptr() ? (PyTypeObject *) rec.metaclass.ptr() : internals.default_metaclass;
 
-    auto heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
+    auto *heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
     if (!heap_type) {
         pybind11_fail(std::string(rec.name) + ": Unable to create type object!");
     }
@@ -676,7 +675,7 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     heap_type->ht_qualname = qualname.inc_ref().ptr();
 #endif
 
-    auto type = &heap_type->ht_type;
+    auto *type = &heap_type->ht_type;
     type->tp_name = full_name;
     type->tp_doc = tp_doc;
     type->tp_base = type_incref((PyTypeObject *)base);
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 661acf5dad..911ec3df41 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -301,7 +301,7 @@ bool handle_nested_exception(const T &exc, const std::exception_ptr &p) {
 template <class T,
           enable_if_t<!std::is_same<std::nested_exception, remove_cvref_t<T>>::value, int> = 0>
 bool handle_nested_exception(const T &exc, const std::exception_ptr &p) {
-    if (auto *nep = dynamic_cast<const std::nested_exception *>(std::addressof(exc))) {
+    if (const auto *nep = dynamic_cast<const std::nested_exception *>(std::addressof(exc))) {
         return handle_nested_exception(*nep, p);
     }
     return false;
@@ -338,7 +338,7 @@ inline void translate_exception(std::exception_ptr p) {
         return;
     } catch (const builtin_exception &e) {
         // Could not use template since it's an abstract class.
-        if (auto *nep = dynamic_cast<const std::nested_exception *>(std::addressof(e))) {
+        if (const auto *nep = dynamic_cast<const std::nested_exception *>(std::addressof(e))) {
             handle_nested_exception(*nep, p);
         }
         e.set_error();
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 071de23b56..ea5ef6a2be 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -109,7 +109,7 @@ PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_
 
     auto const &type_dict = get_internals().registered_types_py;
     for (size_t i = 0; i < check.size(); i++) {
-        auto type = check[i];
+        auto *type = check[i];
         // Ignore Python2 old-style class super type:
         if (!PyType_Check((PyObject *) type)) {
             continue;
@@ -178,7 +178,7 @@ inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type)
  * `all_type_info` instead if you want to support multiple bases.
  */
 PYBIND11_NOINLINE detail::type_info* get_type_info(PyTypeObject *type) {
-    auto &bases = all_type_info(type);
+    const auto &bases = all_type_info(type);
     if (bases.empty()) {
         return nullptr;
     }
@@ -210,10 +210,10 @@ inline detail::type_info *get_global_type_info(const std::type_index &tp) {
 /// Return the type info for a given C++ type; on lookup failure can either throw or return nullptr.
 PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
                                                           bool throw_if_missing = false) {
-    if (auto ltype = get_local_type_info(tp)) {
+    if (auto *ltype = get_local_type_info(tp)) {
         return ltype;
     }
-    if (auto gtype = get_global_type_info(tp)) {
+    if (auto *gtype = get_global_type_info(tp)) {
         return gtype;
     }
 
@@ -235,7 +235,7 @@ PYBIND11_NOINLINE handle find_registered_python_instance(void *src,
                                                                 const detail::type_info *tinfo) {
     auto it_instances = get_internals().registered_instances.equal_range(src);
     for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
-        for (auto instance_type : detail::all_type_info(Py_TYPE(it_i->second))) {
+        for (auto *instance_type : detail::all_type_info(Py_TYPE(it_i->second))) {
             if (instance_type && same_type(*instance_type->cpptype, *tinfo->cpptype)) {
                 return handle((PyObject *) it_i->second).inc_ref();
             }
@@ -397,7 +397,7 @@ PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_inf
 }
 
 PYBIND11_NOINLINE void instance::allocate_layout() {
-    auto &tinfo = all_type_info(Py_TYPE(this));
+    const auto &tinfo = all_type_info(Py_TYPE(this));
 
     const size_t n_types = tinfo.size();
 
@@ -421,7 +421,7 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
         // values that tracks whether each associated holder has been initialized.  Each [block] is
         // padded, if necessary, to an integer multiple of sizeof(void *).
         size_t space = 0;
-        for (auto t : tinfo) {
+        for (auto *t : tinfo) {
             space += 1; // value pointer
             space += t->holder_size_in_ptrs; // holder instance
         }
@@ -582,7 +582,7 @@ class type_caster_generic {
         }
 
         auto inst = reinterpret_steal<object>(make_new_instance(tinfo->type));
-        auto wrapper = reinterpret_cast<instance *>(inst.ptr());
+        auto *wrapper = reinterpret_cast<instance *>(inst.ptr());
         wrapper->owned = false;
         void *&valueptr = values_and_holders(wrapper).begin()->value_ptr();
 
@@ -656,7 +656,7 @@ class type_caster_generic {
         auto *&vptr = v_h.value_ptr();
         // Lazy allocation for unallocated values:
         if (vptr == nullptr) {
-            auto *type = v_h.type ? v_h.type : typeinfo;
+            const auto *type = v_h.type ? v_h.type : typeinfo;
             if (type->operator_new) {
                 vptr = type->operator_new(type->type_size);
             } else {
@@ -675,7 +675,7 @@ class type_caster_generic {
         value = vptr;
     }
     bool try_implicit_casts(handle src, bool convert) {
-        for (auto &cast : typeinfo->implicit_casts) {
+        for (const auto &cast : typeinfo->implicit_casts) {
             type_caster_generic sub_caster(*cast.first);
             if (sub_caster.load(src, convert)) {
                 value = cast.second(sub_caster.value);
@@ -718,7 +718,7 @@ class type_caster_generic {
             return false;
         }
 
-        if (auto result = foreign_typeinfo->module_local_load(src.ptr(), foreign_typeinfo)) {
+        if (auto *result = foreign_typeinfo->module_local_load(src.ptr(), foreign_typeinfo)) {
             value = result;
             return true;
         }
@@ -750,7 +750,7 @@ class type_caster_generic {
         }
         // Case 2: We have a derived class
         if (PyType_IsSubtype(srctype, typeinfo->type)) {
-            auto &bases = all_type_info(srctype);
+            const auto &bases = all_type_info(srctype);
             bool no_cpp_mi = typeinfo->simple_type;
 
             // Case 2a: the python type is a Python-inherited derived class that inherits from just
@@ -767,7 +767,7 @@ class type_caster_generic {
             // we can find an exact match (or, for a simple C++ type, an inherited match); if so, we
             // can safely reinterpret_cast to the relevant pointer.
             if (bases.size() > 1) {
-                for (auto base : bases) {
+                for (auto *base : bases) {
                     if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type) : base->type == typeinfo->type) {
                         this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base));
                         return true;
@@ -785,7 +785,7 @@ class type_caster_generic {
 
         // Perform an implicit conversion
         if (convert) {
-            for (auto &converter : typeinfo->implicit_conversions) {
+            for (const auto &converter : typeinfo->implicit_conversions) {
                 auto temp = reinterpret_steal<object>(converter(src.ptr(), typeinfo->type));
                 if (load_impl<ThisT>(temp, false)) {
                     loader_life_support::add_patient(temp);
@@ -799,7 +799,7 @@ class type_caster_generic {
 
         // Failed to match local typeinfo. Try again with global.
         if (typeinfo->module_local) {
-            if (auto gtype = get_global_type_info(*typeinfo->cpptype)) {
+            if (auto *gtype = get_global_type_info(*typeinfo->cpptype)) {
                 typeinfo = gtype;
                 return load(src, false);
             }
@@ -970,7 +970,7 @@ template <typename type> class type_caster_base : public type_caster_generic {
     // polymorphic type (using RTTI by default, but can be overridden by specializing
     // polymorphic_type_hook). If the instance isn't derived, returns the base version.
     static std::pair<const void *, const type_info *> src_and_type(const itype *src) {
-        auto &cast_type = typeid(itype);
+        const auto &cast_type = typeid(itype);
         const std::type_info *instance_type = nullptr;
         const void *vsrc = polymorphic_type_hook<itype>::get(src, instance_type);
         if (instance_type && !same_type(cast_type, *instance_type)) {
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 9da2862f38..0c3f778136 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -157,7 +157,7 @@ inline void set_interpreter_argv(int argc, const char *const *argv, bool add_pro
         widened_argv[ii] = widened_argv_entries.back().get();
     }
 
-    auto pysys_argv = widened_argv.get();
+    auto *pysys_argv = widened_argv.get();
 #else
     // python 2.x
     std::vector<std::string> strings{safe_argv, safe_argv + argv_size};
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 9e2f0b5b6b..95a1a02af7 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -46,10 +46,10 @@ struct type_caster<std::function<Return(Args...)>> {
            captured variables), in which case the roundtrip can be avoided.
          */
         if (auto cfunc = func.cpp_function()) {
-            auto cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
+            auto *cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
             if (isinstance<capsule>(cfunc_self)) {
                 auto c = reinterpret_borrow<capsule>(cfunc_self);
-                auto rec = (function_record *) c;
+                auto *rec = (function_record *) c;
 
                 while (rec != nullptr) {
                     if (rec->is_stateless
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index b493fd145b..22864adb20 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -137,6 +137,8 @@ class gil_scoped_release {
         auto &internals = detail::get_internals();
         tstate = PyEval_SaveThread();
         if (disassoc) {
+            // Python >= 3.7 can remove this, it's an int before 3.7
+            // NOLINTNEXTLINE(readability-qualified-auto)
             auto key = internals.tstate;
             PYBIND11_TLS_DELETE_VALUE(key);
         }
@@ -160,6 +162,8 @@ class gil_scoped_release {
             PyEval_RestoreThread(tstate);
         }
         if (disassoc) {
+            // Python >= 3.7 can remove this, it's an int before 3.7
+            // NOLINTNEXTLINE(readability-qualified-auto)
             auto key = detail::get_internals().tstate;
             PYBIND11_TLS_REPLACE_VALUE(key, tstate);
         }
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 40bbff8ea0..57f0c90948 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1130,7 +1130,7 @@ struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmet
     static constexpr int value = values[detail::is_fmt_numeric<T>::index];
 
     static pybind11::dtype dtype() {
-        if (auto ptr = npy_api::get().PyArray_DescrFromType_(value)) {
+        if (auto *ptr = npy_api::get().PyArray_DescrFromType_(value)) {
             return reinterpret_steal<pybind11::dtype>(ptr);
         }
         pybind11_fail("Unsupported buffer format!");
@@ -1200,7 +1200,7 @@ PYBIND11_NOINLINE void register_structured_dtype(
         formats.append(field.descr);
         offsets.append(pybind11::int_(field.offset));
     }
-    auto dtype_ptr
+    auto *dtype_ptr
         = pybind11::dtype(std::move(names), std::move(formats), std::move(offsets), itemsize)
               .release()
               .ptr();
@@ -1699,7 +1699,7 @@ struct vectorize_helper {
         }
 
         /* Call the function */
-        auto mutable_data = returned_array::mutable_data(result);
+        auto *mutable_data = returned_array::mutable_data(result);
         if (trivial == broadcast_trivial::non_trivial) {
             apply_broadcast(buffers, params, mutable_data, size, shape, i_seq, vi_seq, bi_seq);
         } else {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 14e84513fd..560c3e0c1b 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -162,7 +162,7 @@ class cpp_function : public function {
         /* Store the function including any extra state it might have (e.g. a lambda capture object) */
         // The unique_ptr makes sure nothing is leaked in case of an exception.
         auto unique_rec = make_function_record();
-        auto rec = unique_rec.get();
+        auto *rec = unique_rec.get();
 
         /* Store the capture object directly in the function record if there is enough space */
         if (PYBIND11_SILENCE_MSVC_C4127(sizeof(capture) <= sizeof(rec->data))) {
@@ -220,8 +220,8 @@ class cpp_function : public function {
             process_attributes<Extra...>::precall(call);
 
             /* Get a pointer to the capture object */
-            auto data = (sizeof(capture) <= sizeof(call.func.data)
-                         ? &call.func.data : call.func.data[0]);
+            const auto *data = (sizeof(capture) <= sizeof(call.func.data) ? &call.func.data
+                                                                          : call.func.data[0]);
             auto *cap = const_cast<capture *>(reinterpret_cast<const capture *>(data));
 
             /* Override policy for rvalues -- usually to enforce rvp::move on an rvalue */
@@ -287,12 +287,12 @@ class cpp_function : public function {
     class strdup_guard {
     public:
         ~strdup_guard() {
-            for (auto s : strings) {
+            for (auto *s : strings) {
                 std::free(s);
             }
         }
         char *operator()(const char *s) {
-            auto t = PYBIND11_COMPAT_STRDUP(s);
+            auto *t = PYBIND11_COMPAT_STRDUP(s);
             strings.push_back(t);
             return t;
         }
@@ -309,7 +309,7 @@ class cpp_function : public function {
         // Do NOT receive `unique_rec` by value. If this function fails to move out the unique_ptr,
         // we do not want this to destuct the pointer. `initialize` (the caller) still relies on the
         // pointee being alive after this call. Only move out if a `capsule` is going to keep it alive.
-        auto rec = unique_rec.get();
+        auto *rec = unique_rec.get();
 
         // Keep track of strdup'ed strings, and clean them up as long as the function's capsule
         // has not taken ownership yet (when `unique_rec.release()` is called).
@@ -355,7 +355,7 @@ class cpp_function : public function {
         std::string signature;
         size_t type_index = 0, arg_index = 0;
         bool is_starred = false;
-        for (auto *pc = text; *pc != '\0'; ++pc) {
+        for (const auto *pc = text; *pc != '\0'; ++pc) {
             const auto c = *pc;
 
             if (c == '{') {
@@ -396,7 +396,7 @@ class cpp_function : public function {
                 if (!t) {
                     pybind11_fail("Internal error while parsing type signature (1)");
                 }
-                if (auto tinfo = detail::get_type_info(*t)) {
+                if (auto *tinfo = detail::get_type_info(*t)) {
                     handle th((PyObject *) tinfo->type);
                     signature +=
                         th.attr("__module__").cast<std::string>() + "." +
@@ -535,7 +535,7 @@ class cpp_function : public function {
         }
         // Then specific overload signatures
         bool first_user_def = true;
-        for (auto it = chain_start; it != nullptr; it = it->next) {
+        for (auto *it = chain_start; it != nullptr; it = it->next) {
             if (options::show_function_signatures()) {
                 if (index > 0) {
                     signatures += "\n";
@@ -652,8 +652,8 @@ class cpp_function : public function {
                 return nullptr;
             }
 
-            const auto tinfo = get_type_info((PyTypeObject *) overloads->scope.ptr());
-            const auto pi = reinterpret_cast<instance *>(parent.ptr());
+            auto *const tinfo = get_type_info((PyTypeObject *) overloads->scope.ptr());
+            auto *const pi = reinterpret_cast<instance *>(parent.ptr());
             self_value_and_holder = pi->get_value_and_holder(tinfo, true);
 
             // If this value is already registered it must mean __init__ is invoked multiple times;
@@ -1207,7 +1207,7 @@ class module_ : public object {
             /* m_clear */    nullptr,
             /* m_free */     nullptr
         };
-        auto m = PyModule_Create(def);
+        auto *m = PyModule_Create(def);
 #else
         // Ignore module_def *def; only necessary for Python 3
         (void) def;
@@ -1317,7 +1317,7 @@ class generic_type : public object {
     void mark_parents_nonsimple(PyTypeObject *value) {
         auto t = reinterpret_borrow<tuple>(value->tp_bases);
         for (handle h : t) {
-            auto tinfo2 = get_type_info((PyTypeObject *) h.ptr());
+            auto *tinfo2 = get_type_info((PyTypeObject *) h.ptr());
             if (tinfo2) {
                 tinfo2->simple_type = false;
             }
@@ -1329,7 +1329,7 @@ class generic_type : public object {
             buffer_info *(*get_buffer)(PyObject *, void *),
             void *get_buffer_data) {
         auto *type = (PyHeapTypeObject*) m_ptr;
-        auto tinfo = detail::get_type_info(&type->ht_type);
+        auto *tinfo = detail::get_type_info(&type->ht_type);
 
         if (!type->ht_type.tp_as_buffer) {
             pybind11_fail("To be able to register buffer protocol support for the type '"
@@ -2304,7 +2304,7 @@ template <typename InputType, typename OutputType> void implicitly_convertible()
         return result;
     };
 
-    if (auto tinfo = detail::get_type_info(typeid(OutputType))) {
+    if (auto *tinfo = detail::get_type_info(typeid(OutputType))) {
         tinfo->implicit_conversions.push_back(implicit_caster);
     } else {
         pybind11_fail("implicitly_convertible: Unable to find type " + type_id<OutputType>());
@@ -2568,7 +2568,7 @@ PYBIND11_NAMESPACE_END(detail)
   :return: The Python method by this name from the object or an empty function wrapper.
  \endrst */
 template <class T> function get_override(const T *this_ptr, const char *name) {
-    auto tinfo = detail::get_type_info(typeid(T));
+    auto *tinfo = detail::get_type_info(typeid(T));
     return tinfo ? detail::get_type_override(this_ptr, tinfo, name) : function();
 }
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 74388349b0..339f0fff5f 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1524,7 +1524,7 @@ class capsule : public object {
     /// Get the pointer the capsule holds.
     template<typename T = void>
     T* get_pointer() const {
-        auto name = this->name();
+        const auto *name = this->name();
         T *result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
         if (!result) {
             PyErr_Clear();
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index a9a6c8512c..59ac38b9ba 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -68,7 +68,7 @@ template<typename T> struct path_caster {
         PyObject* native = nullptr;
         if constexpr (std::is_same_v<typename T::value_type, char>) {
             if (PyUnicode_FSConverter(buf, &native) != 0) {
-                if (auto c_str = PyBytes_AsString(native)) {
+                if (auto *c_str = PyBytes_AsString(native)) {
                     // AsString returns a pointer to the internal buffer, which
                     // must not be free'd.
                     value = c_str;
@@ -76,7 +76,7 @@ template<typename T> struct path_caster {
             }
         } else if constexpr (std::is_same_v<typename T::value_type, wchar_t>) {
             if (PyUnicode_FSDecoder(buf, &native) != 0) {
-                if (auto c_str = PyUnicode_AsWideCharString(native, nullptr)) {
+                if (auto *c_str = PyUnicode_AsWideCharString(native, nullptr)) {
                     // AsWideCharString returns a new string that must be free'd.
                     value = c_str;  // Copies the string.
                     PyMem_Free(c_str);
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 8ae6829653..6db1faf404 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -464,7 +464,7 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
     // If the value_type is unregistered (e.g. a converting type) or is itself registered
     // module-local then make the vector binding module-local as well:
     using vtype = typename Vector::value_type;
-    auto vtype_info = detail::get_type_info(typeid(vtype));
+    auto *vtype_info = detail::get_type_info(typeid(vtype));
     bool local = !vtype_info || vtype_info->module_local;
 
     Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
@@ -651,7 +651,7 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     // If either type is a non-module-local bound type then make the map binding non-local as well;
     // otherwise (e.g. both types are either module-local or converting) the map will be
     // module-local.
-    auto tinfo = detail::get_type_info(typeid(MappedType));
+    auto *tinfo = detail::get_type_info(typeid(MappedType));
     bool local = !tinfo || tinfo->module_local;
     if (local) {
         tinfo = detail::get_type_info(typeid(KeyType));
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 0920363966..cedbb73eac 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -89,7 +89,7 @@ TEST_SUBMODULE(buffers, m) {
                 throw std::runtime_error("Incompatible buffer format!");
             }
 
-            auto v = new Matrix(info.shape[0], info.shape[1]);
+            auto *v = new Matrix(info.shape[0], info.shape[1]);
             memcpy(v->data(), info.ptr, sizeof(float) * (size_t) (v->rows() * v->cols()));
             return v;
         }))
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 5ff5a8fc4f..96519d44e9 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -277,7 +277,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("refwrap_list", [](bool copy) {
         static IncType x1(1), x2(2);
         py::list l;
-        for (auto &f : {std::ref(x1), std::ref(x2)}) {
+        for (const auto &f : {std::ref(x1), std::ref(x2)}) {
             l.append(py::cast(f, copy ? py::return_value_policy::copy
                                       : py::return_value_policy::reference));
         }
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index cdbd9d42fe..8136bf4f8e 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -95,7 +95,7 @@ TEST_SUBMODULE(call_policies, m) {
     // but it's unclear how to test it without `PyGILState_GetThisThreadState`.
     auto report_gil_status = []() {
         auto is_gil_held = false;
-        if (auto tstate = py::detail::get_thread_state_unchecked()) {
+        if (auto *tstate = py::detail::get_thread_state_unchecked()) {
             is_gil_held = (tstate == PyGILState_GetThisThreadState());
         }
 
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index b73a623709..55f9c86148 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -148,7 +148,7 @@ TEST_SUBMODULE(callbacks, m) {
         py::arg("expect_none") = false);
     m.def("test_dummy_function", [](const std::function<int(int)> &f) -> std::string {
         using fn_type = int (*)(int);
-        auto result = f.target<fn_type>();
+        const auto *result = f.target<fn_type>();
         if (!result) {
             auto r = f(1);
             return "can't convert to function pointer: eval(1) = " + std::to_string(r);
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 977297e572..7445b3c026 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -255,7 +255,7 @@ TEST_SUBMODULE(class_, m) {
             return py::str().release().ptr();
         };
 
-        auto def = new PyMethodDef{"f", f, METH_VARARGS, nullptr};
+        auto *def = new PyMethodDef{"f", f, METH_VARARGS, nullptr};
         py::capsule def_capsule(def, [](void *ptr) { delete reinterpret_cast<PyMethodDef *>(ptr); });
         return py::reinterpret_steal<py::object>(PyCFunction_NewEx(def, def_capsule.ptr(), m.ptr()));
     }());
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 9ffc257ba0..601a19092f 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -240,8 +240,8 @@ TEST_CASE("Subinterpreter") {
     REQUIRE(has_pybind11_internals_static());
 
     /// Create and switch to a subinterpreter.
-    auto main_tstate = PyThreadState_Get();
-    auto sub_tstate = Py_NewInterpreter();
+    auto *main_tstate = PyThreadState_Get();
+    auto *sub_tstate = Py_NewInterpreter();
 
     // Subinterpreters get their own copy of builtins. detail::get_internals() still
     // works by returning from the static variable, i.e. all interpreters share a single
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 4712c80925..bc1797845b 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -89,7 +89,7 @@ template<typename... Ix> arr data_t(const arr_t& a, Ix... index) {
 }
 
 template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
-    auto ptr = (uint8_t *) a.mutable_data(index...);
+    auto *ptr = (uint8_t *) a.mutable_data(index...);
     for (py::ssize_t i = 0; i < a.nbytes() - a.offset_at(index...); i++) {
         ptr[i] = (uint8_t) (ptr[i] * 2);
     }
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index bd702e403c..468a89a3c9 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -165,7 +165,7 @@ template <typename S>
 py::array_t<S, 0> create_recarray(size_t n) {
     auto arr = mkarray_via_buffer<S>(n);
     auto req = arr.request();
-    auto ptr = static_cast<S*>(req.ptr);
+    auto *ptr = static_cast<S *>(req.ptr);
     for (size_t i = 0; i < n; i++) {
         SET_TEST_VALS(ptr[i], i);
     }
@@ -175,7 +175,7 @@ py::array_t<S, 0> create_recarray(size_t n) {
 template <typename S>
 py::list print_recarray(py::array_t<S, 0> arr) {
     const auto req = arr.request();
-    const auto ptr = static_cast<S*>(req.ptr);
+    auto *const ptr = static_cast<S *>(req.ptr);
     auto l = py::list();
     for (py::ssize_t i = 0; i < req.size; i++) {
         std::stringstream ss;
@@ -192,8 +192,8 @@ py::array_t<int32_t, 0> test_array_ctors(int i) {
     std::vector<py::ssize_t> shape { 3, 2 };
     std::vector<py::ssize_t> strides { 8, 4 };
 
-    auto ptr = data.data();
-    auto vptr = (void *) ptr;
+    auto *ptr = data.data();
+    auto *vptr = (void *) ptr;
     auto dtype = py::dtype("int32");
 
     py::buffer_info buf_ndim1(vptr, 4, "i", 6);
@@ -328,7 +328,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("create_rec_nested", [](size_t n) { // test_signature
         py::array_t<NestedStruct, 0> arr = mkarray_via_buffer<NestedStruct>(n);
         auto req = arr.request();
-        auto ptr = static_cast<NestedStruct*>(req.ptr);
+        auto *ptr = static_cast<NestedStruct *>(req.ptr);
         for (size_t i = 0; i < n; i++) {
             SET_TEST_VALS(ptr[i].a, i);
             SET_TEST_VALS(ptr[i].b, i + 1);
@@ -339,7 +339,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("create_rec_partial_nested", [](size_t n) {
         py::array_t<PartialNestedStruct, 0> arr = mkarray_via_buffer<PartialNestedStruct>(n);
         auto req = arr.request();
-        auto ptr = static_cast<PartialNestedStruct*>(req.ptr);
+        auto *ptr = static_cast<PartialNestedStruct *>(req.ptr);
         for (size_t i = 0; i < n; i++) {
             SET_TEST_VALS(ptr[i].a, i);
         }
@@ -397,14 +397,14 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("test_dtype_ctors", &test_dtype_ctors);
     m.def("test_dtype_kind", [dtype_names]() {
         py::list list;
-        for (auto &dt_name : dtype_names) {
+        for (const auto &dt_name : dtype_names) {
             list.append(py::dtype(dt_name).kind());
         }
         return list;
     });
     m.def("test_dtype_char_", [dtype_names]() {
         py::list list;
-        for (auto &dt_name : dtype_names) {
+        for (const auto &dt_name : dtype_names) {
             list.append(py::dtype(dt_name).char_());
         }
         return list;
@@ -430,7 +430,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         py::array_t<StringStruct, 0> arr = mkarray_via_buffer<StringStruct>(non_empty ? 4 : 0);
         if (non_empty) {
             auto req = arr.request();
-            auto ptr = static_cast<StringStruct*>(req.ptr);
+            auto *ptr = static_cast<StringStruct *>(req.ptr);
             for (py::ssize_t i = 0; i < req.size * req.itemsize; i++) {
                 static_cast<char *>(req.ptr)[i] = 0;
             }
@@ -450,7 +450,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     // test_array_array
     m.def("create_array_array", [](size_t n) {
         py::array_t<ArrayStruct, 0> arr = mkarray_via_buffer<ArrayStruct>(n);
-        auto ptr = (ArrayStruct *) arr.mutable_data();
+        auto *ptr = (ArrayStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
             for (size_t j = 0; j < 3; j++) {
                 for (size_t k = 0; k < 4; k++) {
@@ -476,7 +476,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     // test_enum_array
     m.def("create_enum_array", [](size_t n) {
         py::array_t<EnumStruct, 0> arr = mkarray_via_buffer<EnumStruct>(n);
-        auto ptr = (EnumStruct *) arr.mutable_data();
+        auto *ptr = (EnumStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
             ptr[i].e1 = static_cast<E1>(-1 + ((int) i % 2) * 2);
             ptr[i].e2 = static_cast<E2>(1 + (i % 2));
@@ -488,7 +488,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     // test_complex_array
     m.def("create_complex_array", [](size_t n) {
         py::array_t<ComplexStruct, 0> arr = mkarray_via_buffer<ComplexStruct>(n);
-        auto ptr = (ComplexStruct *) arr.mutable_data();
+        auto *ptr = (ComplexStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
             ptr[i].cflt.real(float(i));
             ptr[i].cflt.imag(float(i) + 0.25f);
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 3605ad8eac..196a54c41f 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -146,7 +146,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("return_capsule_with_name_and_destructor", []() {
         auto capsule = py::capsule((void *) 12345, "pointer type description", [](PyObject *ptr) {
             if (ptr) {
-                auto name = PyCapsule_GetName(ptr);
+                const auto *name = PyCapsule_GetName(ptr);
                 py::print("destructing capsule ({}, '{}')"_s.format(
                     (size_t) PyCapsule_GetPointer(ptr, name), name
                 ));
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 5bd77eae33..c86bed1ce0 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -113,7 +113,7 @@ class MyObject4 {
     static void cleanupAllInstances() {
         auto tmp = std::move(myobject4_instances);
         myobject4_instances.clear();
-        for (auto o : tmp) {
+        for (auto *o : tmp) {
             delete o;
         }
     }
@@ -141,7 +141,7 @@ class MyObject4a {
     static void cleanupAllInstances() {
         auto tmp = std::move(myobject4a_instances);
         myobject4a_instances.clear();
-        for (auto o : tmp) {
+        for (auto *o : tmp) {
             delete o;
         }
     }
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index 7fb973ca43..bf534aec8d 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -41,7 +41,7 @@ class E_nc {
 };
 
 template <class Container> Container *one_to_n(int n) {
-    auto v = new Container();
+    auto *v = new Container();
     for (int i = 1; i <= n; i++) {
         v->emplace_back(i);
     }
@@ -49,7 +49,7 @@ template <class Container> Container *one_to_n(int n) {
 }
 
 template <class Map> Map *times_ten(int n) {
-    auto m = new Map();
+    auto *m = new Map();
     for (int i = 1; i <= n; i++) {
         m->emplace(int(i), E_nc(10 * i));
     }
@@ -57,7 +57,7 @@ template <class Map> Map *times_ten(int n) {
 }
 
 template <class NestMap> NestMap *times_hundred(int n) {
-    auto m = new NestMap();
+    auto *m = new NestMap();
     for (int i = 1; i <= n; i++) {
         for (int j = 1; j <= n; j++) {
             (*m)[i].emplace(int(j * 10), E_nc(100 * j));
@@ -99,16 +99,15 @@ TEST_SUBMODULE(stl_binders, m) {
     m.def("get_umnc", &times_ten<std::unordered_map<int, E_nc>>);
     // Issue #1885: binding nested std::map<X, Container<E>> with E non-copyable
     py::bind_map<std::map<int, std::vector<E_nc>>>(m, "MapVecENC");
-    m.def("get_nvnc", [](int n)
-        {
-            auto m = new std::map<int, std::vector<E_nc>>();
-            for (int i = 1; i <= n; i++) {
-                for (int j = 1; j <= n; j++) {
-                    (*m)[i].emplace_back(j);
-                }
+    m.def("get_nvnc", [](int n) {
+        auto *m = new std::map<int, std::vector<E_nc>>();
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                (*m)[i].emplace_back(j);
             }
-            return m;
-        });
+        }
+        return m;
+    });
     py::bind_map<std::map<int, std::map<int, E_nc>>>(m, "MapMapENC");
     m.def("get_nmnc", &times_hundred<std::map<int, std::map<int, E_nc>>>);
     py::bind_map<std::unordered_map<int, std::unordered_map<int, E_nc>>>(m, "UmapUmapENC");

From abc38690dc77abd43710e30e9d659fb9abca8543 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 9 Feb 2022 06:32:41 -0800
Subject: [PATCH 302/638] Manually applying two clang-format changes that need
 fix-ups for clang-tidy. (#3705)

---
 include/pybind11/pytypes.h | 4 ++--
 tests/test_stl.cpp         | 9 +++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 339f0fff5f..d39e71045c 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1516,8 +1516,8 @@ class capsule : public object {
         }
     }
 
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    template <typename T> operator T *() const {
+    template <typename T>
+    operator T *() const { // NOLINT(google-explicit-constructor)
         return get_pointer<T>();
     }
 
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index bc5c6553a2..77fc9b99b7 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -400,10 +400,11 @@ TEST_SUBMODULE(stl, m) {
     m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
         return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
     });
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    m.def("test_nullopt_refsensitive", [](refsensitive_opt_int x) {
-        return x ? x.value() : 42;
-    }, py::arg_v("x", refsensitive_opt_int(), "None"));
+    m.def(
+        "test_nullopt_refsensitive",
+        // NOLINTNEXTLINE(performance-unnecessary-value-param)
+        [](refsensitive_opt_int x) { return x ? x.value() : 42; },
+        py::arg_v("x", refsensitive_opt_int(), "None"));
     m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
         return x ? x->value : 42;
     }, py::arg_v("x", refsensitive_opt_no_assign(), "None"));

From 7f9758165d117ec20adf2c8e41cfe095bdc6f4b2 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 9 Feb 2022 12:37:45 -0500
Subject: [PATCH 303/638] chore(clang-tidy): Enable static downcast and decl
 naming check (#3709)

* Enable static downcast check

* Add inconsistent declaration naming check
---
 .clang-tidy | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.clang-tidy b/.clang-tidy
index 1957b8690e..3818d3ab77 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -3,6 +3,7 @@ FormatStyle: file
 Checks: '
 *bugprone*,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-pro-type-static-cast-downcast,
 cppcoreguidelines-slicing,
 clang-analyzer-optin.cplusplus.VirtualCall,
 google-explicit-constructor,
@@ -37,6 +38,7 @@ readability-container-size-empty,
 readability-delete-null-pointer,
 readability-else-after-return,
 readability-implicit-bool-conversion,
+readability-inconsistent-declaration-parameter-name,
 readability-make-member-function-const,
 readability-misplaced-array-index,
 readability-non-const-parameter,

From dc9803cef260593f4dafca001213b51a811532f2 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 10 Feb 2022 12:23:15 -0500
Subject: [PATCH 304/638] Add missing clang-tidy fixes (#3715)

---
 include/pybind11/attr.h             |  9 ++++++---
 include/pybind11/cast.h             |  6 ++++--
 include/pybind11/detail/internals.h |  7 +++++--
 include/pybind11/gil.h              | 26 +++++++++++++++-----------
 include/pybind11/pybind11.h         |  8 +++++---
 tests/test_cmake_build/embed.cpp    |  8 +++++---
 6 files changed, 40 insertions(+), 24 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 669c72614e..3e894eef07 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -445,13 +445,16 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
         if (!a.value) {
 #if !defined(NDEBUG)
             std::string descr("'");
-            if (a.name) descr += std::string(a.name) + ": ";
+            if (a.name) {
+                descr += std::string(a.name) + ": ";
+            }
             descr += a.type + "'";
             if (r->is_method) {
-                if (r->name)
+                if (r->name) {
                     descr += " in method '" + (std::string) str(r->scope) + "." + (std::string) r->name + "'";
-                else
+                } else {
                     descr += " in method of '" + (std::string) str(r->scope) + "'";
+                }
             } else if (r->name) {
                 descr += " in function '" + (std::string) r->name + "'";
             }
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index cfec7e5f0e..4277d87ab5 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -628,9 +628,11 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
             return false;
         }
 #else
-        for (bool r : {std::get<Is>(subcasters).load(seq[Is], convert)...})
-            if (!r)
+        for (bool r : {std::get<Is>(subcasters).load(seq[Is], convert)...}) {
+            if (!r) {
                 return false;
+            }
+        }
 #endif
         return true;
     }
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 911ec3df41..5377190642 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -118,8 +118,9 @@ struct type_hash {
     size_t operator()(const std::type_index &t) const {
         size_t hash = 5381;
         const char *ptr = t.name();
-        while (auto c = static_cast<unsigned char>(*ptr++))
+        while (auto c = static_cast<unsigned char>(*ptr++)) {
             hash = (hash * 33) ^ c;
+        }
         return hash;
     }
 };
@@ -388,7 +389,9 @@ inline void translate_exception(std::exception_ptr p) {
 #if !defined(__GLIBCXX__)
 inline void translate_local_exception(std::exception_ptr p) {
     try {
-        if (p) std::rethrow_exception(p);
+        if (p) {
+            std::rethrow_exception(p);
+        }
     } catch (error_already_set &e)       { e.restore();   return;
     } catch (const builtin_exception &e) { e.set_error(); return;
     }
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 22864adb20..0a6c2bcc50 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -65,9 +65,10 @@ class gil_scoped_acquire {
         if (!tstate) {
             tstate = PyThreadState_New(internals.istate);
             #if !defined(NDEBUG)
-                if (!tstate)
-                    pybind11_fail("scoped_acquire: could not create thread state!");
-            #endif
+            if (!tstate) {
+                pybind11_fail("scoped_acquire: could not create thread state!");
+            }
+#endif
             tstate->gilstate_counter = 0;
             PYBIND11_TLS_REPLACE_VALUE(internals.tstate, tstate);
         } else {
@@ -88,16 +89,19 @@ class gil_scoped_acquire {
     PYBIND11_NOINLINE void dec_ref() {
         --tstate->gilstate_counter;
         #if !defined(NDEBUG)
-            if (detail::get_thread_state_unchecked() != tstate)
-                pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
-            if (tstate->gilstate_counter < 0)
-                pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
-        #endif
+        if (detail::get_thread_state_unchecked() != tstate) {
+            pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
+        }
+        if (tstate->gilstate_counter < 0) {
+            pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
+        }
+#endif
         if (tstate->gilstate_counter == 0) {
             #if !defined(NDEBUG)
-                if (!release)
-                    pybind11_fail("scoped_acquire::dec_ref(): internal error!");
-            #endif
+            if (!release) {
+                pybind11_fail("scoped_acquire::dec_ref(): internal error!");
+            }
+#endif
             PyThreadState_Clear(tstate);
             if (active) {
                 PyThreadState_DeleteCurrent();
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 560c3e0c1b..58ac559965 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -873,9 +873,10 @@ class cpp_function : public function {
                 // 5. Put everything in a vector.  Not technically step 5, we've been building it
                 // in `call.args` all along.
                 #if !defined(NDEBUG)
-                if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs)
+                if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs) {
                     pybind11_fail("Internal error: function call dispatcher inserted wrong number of arguments!");
-                #endif
+                }
+#endif
 
                 std::vector<bool> second_pass_convert;
                 if (overloaded) {
@@ -2527,8 +2528,9 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
         PyFrame_FastToLocals(frame);
         PyObject *self_caller = dict_getitem(
             frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
-        if (self_caller == self.ptr())
+        if (self_caller == self.ptr()) {
             return function();
+        }
     }
 #endif
 
diff --git a/tests/test_cmake_build/embed.cpp b/tests/test_cmake_build/embed.cpp
index a3abc8a84d..30bc4f1e14 100644
--- a/tests/test_cmake_build/embed.cpp
+++ b/tests/test_cmake_build/embed.cpp
@@ -6,15 +6,17 @@ PYBIND11_EMBEDDED_MODULE(test_cmake_build, m) {
 }
 
 int main(int argc, char *argv[]) {
-    if (argc != 2)
+    if (argc != 2) {
         throw std::runtime_error("Expected test.py file as the first argument");
-    auto test_py_file = argv[1];
+    }
+    auto *test_py_file = argv[1];
 
     py::scoped_interpreter guard{};
 
     auto m = py::module_::import("test_cmake_build");
-    if (m.attr("add")(1, 2).cast<int>() != 3)
+    if (m.attr("add")(1, 2).cast<int>() != 3) {
         throw std::runtime_error("embed.cpp failed");
+    }
 
     py::module_::import("sys").attr("argv") = py::make_tuple("test.py", "embed.cpp");
     py::eval_file(test_py_file, py::globals());

From d6c66d25bb803f0cf361817eaa0b47abe7f38b21 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 10 Feb 2022 12:45:46 -0500
Subject: [PATCH 305/638] chore(clang-tidy): Add clang-tidy rules:
 prefer-member-initializer and optin.performance.Padding (#3716)

* Add clang-tidy prefer-member-initializer

* Fix clang-tdy config

* Fix incorrect change

* Fix sorting of .clang-tidy
---
 .clang-tidy                            |  4 +++-
 include/pybind11/buffer_info.h         |  2 ++
 include/pybind11/gil.h                 |  1 +
 tests/test_buffers.cpp                 |  4 +++-
 tests/test_copy_move.cpp               | 12 ++++++++++--
 tests/test_factory_constructors.cpp    | 27 ++++++++++++++++++++------
 tests/test_sequences_and_iterators.cpp |  3 +++
 tests/test_smart_ptr.cpp               |  3 +--
 tests/test_virtual_functions.cpp       | 12 +++---------
 9 files changed, 47 insertions(+), 21 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 3818d3ab77..d01ca352cc 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -2,10 +2,12 @@ FormatStyle: file
 
 Checks: '
 *bugprone*,
+clang-analyzer-optin.performance.Padding,
+clang-analyzer-optin.cplusplus.VirtualCall,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-prefer-member-initializer,
 cppcoreguidelines-pro-type-static-cast-downcast,
 cppcoreguidelines-slicing,
-clang-analyzer-optin.cplusplus.VirtualCall,
 google-explicit-constructor,
 llvm-namespace-comment,
 misc-misplaced-const,
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 1dd6955527..052551ff30 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -89,7 +89,9 @@ struct buffer_info {
             ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
             : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
             (view->readonly != 0)) {
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         this->m_view = view;
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         this->ownview = ownview;
     }
 
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 0a6c2bcc50..345177f84f 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -139,6 +139,7 @@ class gil_scoped_release {
         // `internals.tstate` for subsequent `gil_scoped_acquire` calls. Otherwise, an
         // initialization race could occur as multiple threads try `gil_scoped_acquire`.
         auto &internals = detail::get_internals();
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         tstate = PyEval_SaveThread();
         if (disassoc) {
             // Python >= 3.7 can remove this, it's an int before 3.7
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index cedbb73eac..3a4d304676 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -17,12 +17,14 @@ TEST_SUBMODULE(buffers, m) {
     public:
         Matrix(py::ssize_t rows, py::ssize_t cols) : m_rows(rows), m_cols(cols) {
             print_created(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
-            m_data = new float[(size_t) (rows*cols)];
+            // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+            m_data = new float[(size_t) (rows * cols)];
             memset(m_data, 0, sizeof(float) * (size_t) (rows * cols));
         }
 
         Matrix(const Matrix &s) : m_rows(s.m_rows), m_cols(s.m_cols) {
             print_copy_created(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[(size_t) (m_rows * m_cols)];
             memcpy(m_data, s.m_data, sizeof(float) * (size_t) (m_rows * m_cols));
         }
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 850edcb4d9..007b96c5b3 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -66,7 +66,11 @@ class MoveOrCopyInt {
         std::swap(value, m.value);
         return *this;
     }
-    MoveOrCopyInt(const MoveOrCopyInt &c) { print_copy_created(this, c.value); value = c.value; }
+    MoveOrCopyInt(const MoveOrCopyInt &c) {
+        print_copy_created(this, c.value);
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+        value = c.value;
+    }
     MoveOrCopyInt &operator=(const MoveOrCopyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
     ~MoveOrCopyInt() { print_destroyed(this); }
 
@@ -76,7 +80,11 @@ class CopyOnlyInt {
 public:
     CopyOnlyInt() { print_default_created(this); }
     explicit CopyOnlyInt(int v) : value{v} { print_created(this, value); }
-    CopyOnlyInt(const CopyOnlyInt &c) { print_copy_created(this, c.value); value = c.value; }
+    CopyOnlyInt(const CopyOnlyInt &c) {
+        print_copy_created(this, c.value);
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+        value = c.value;
+    }
     CopyOnlyInt &operator=(const CopyOnlyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
     ~CopyOnlyInt() { print_destroyed(this); }
 
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 660e2896af..455c75d536 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -38,8 +38,7 @@ class TestFactory2 {
     explicit TestFactory2(std::string v) : value(std::move(v)) { print_created(this, value); }
 
 public:
-    TestFactory2(TestFactory2 &&m) noexcept {
-        value = std::move(m.value);
+    TestFactory2(TestFactory2 &&m) noexcept : value{std::move(m.value)} {
         print_move_created(this);
     }
     TestFactory2 &operator=(TestFactory2 &&m) noexcept {
@@ -59,8 +58,7 @@ class TestFactory3 {
 
 public:
     explicit TestFactory3(std::string v) : value(std::move(v)) { print_created(this, value); }
-    TestFactory3(TestFactory3 &&m) noexcept {
-        value = std::move(m.value);
+    TestFactory3(TestFactory3 &&m) noexcept : value{std::move(m.value)} {
         print_move_created(this);
     }
     TestFactory3 &operator=(TestFactory3 &&m) noexcept {
@@ -93,10 +91,18 @@ class TestFactory6 {
     explicit TestFactory6(int i) : value{i} { print_created(this, i); }
     TestFactory6(TestFactory6 &&f) noexcept {
         print_move_created(this);
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+        value = f.value;
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+        alias = f.alias;
+    }
+    TestFactory6(const TestFactory6 &f) {
+        print_copy_created(this);
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         value = f.value;
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         alias = f.alias;
     }
-    TestFactory6(const TestFactory6 &f) { print_copy_created(this); value = f.value; alias = f.alias; }
     virtual ~TestFactory6() { print_destroyed(this); }
     virtual int get() { return value; }
     bool has_alias() const { return alias; }
@@ -131,10 +137,18 @@ class TestFactory7 {
     explicit TestFactory7(int i) : value{i} { print_created(this, i); }
     TestFactory7(TestFactory7 &&f) noexcept {
         print_move_created(this);
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+        value = f.value;
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+        alias = f.alias;
+    }
+    TestFactory7(const TestFactory7 &f) {
+        print_copy_created(this);
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         value = f.value;
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         alias = f.alias;
     }
-    TestFactory7(const TestFactory7 &f) { print_copy_created(this); value = f.value; alias = f.alias; }
     virtual ~TestFactory7() { print_destroyed(this); }
     virtual int get() { return value; }
     bool has_alias() const { return alias; }
@@ -142,6 +156,7 @@ class TestFactory7 {
 class PyTF7 : public TestFactory7 {
 public:
     explicit PyTF7(int i) : TestFactory7(i) {
+        // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         alias = true;
         print_created(this, i);
     }
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index a5b746cad4..5d4275f36d 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -152,16 +152,19 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     public:
         explicit Sequence(size_t size) : m_size(size) {
             print_created(this, "of size", m_size);
+            // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[size];
             memset(m_data, 0, sizeof(float) * size);
         }
         explicit Sequence(const std::vector<float> &value) : m_size(value.size()) {
             print_created(this, "of size", m_size, "from std::vector");
+            // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[m_size];
             memcpy(m_data, &value[0], sizeof(float) * m_size);
         }
         Sequence(const Sequence &s) : m_size(s.m_size) {
             print_copy_created(this);
+            // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[m_size];
             memcpy(m_data, s.m_data, sizeof(float)*m_size);
         }
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index c86bed1ce0..b2b91a62db 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -131,8 +131,7 @@ class MyObject4a;
 std::unordered_set<MyObject4a *> myobject4a_instances;
 class MyObject4a {
 public:
-    explicit MyObject4a(int i) {
-        value = i;
+    explicit MyObject4a(int i) : value{i} {
         print_created(this);
         myobject4a_instances.insert(this);
     };
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 7fb90cc591..558cd94406 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -103,10 +103,7 @@ class PyExampleVirt : public ExampleVirt {
 class NonCopyable {
 public:
     NonCopyable(int a, int b) : value{new int(a*b)} { print_created(this, a, b); }
-    NonCopyable(NonCopyable &&o) noexcept {
-        value = std::move(o.value);
-        print_move_created(this);
-    }
+    NonCopyable(NonCopyable &&o) noexcept : value{std::move(o.value)} { print_move_created(this); }
     NonCopyable(const NonCopyable &) = delete;
     NonCopyable() = delete;
     void operator=(const NonCopyable &) = delete;
@@ -128,11 +125,8 @@ class NonCopyable {
 class Movable {
 public:
     Movable(int a, int b) : value{a+b} { print_created(this, a, b); }
-    Movable(const Movable &m) { value = m.value; print_copy_created(this); }
-    Movable(Movable &&m) noexcept {
-        value = m.value;
-        print_move_created(this);
-    }
+    Movable(const Movable &m) : value{m.value} { print_copy_created(this); }
+    Movable(Movable &&m) noexcept : value{m.value} { print_move_created(this); }
     std::string get_value() const { return std::to_string(value); }
     ~Movable() { print_destroyed(this); }
 private:

From e96221befff9108f46a497bff96be0b28f0fa80c Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 10 Feb 2022 11:42:03 -0800
Subject: [PATCH 306/638] Final manual curation in preparation for global
 `clang-format`ing (#3712)

* Manual line breaks to pre-empt undesired `clang-format`ing.

Informed by work under https://github.com/pybind/pybind11/pull/3683:

https://github.com/pybind/pybind11/commit/60b7eb410fefe2b23aeb6906f2a9184e91b11a15

https://github.com/pybind/pybind11/commit/59572e65598b4b9f2c9ae0b8a0e5fcb6d65c7f92

* Manual curation of clang-format diffs involving source code comments.

Very labor-intensive and dull.

* Pulling .clang-format change from @henryiii's https://github.com/pybind/pybind11/pull/3683/commits/9057962d40ca520b9d26abbe0ff125796e2323dd

* Adding commonly used .clang-format `CommentPragmas:`

* Ensure short lambdas are allowed

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 .clang-format                              | 19 ++++++++
 include/pybind11/buffer_info.h             |  6 ++-
 include/pybind11/cast.h                    |  7 ++-
 include/pybind11/chrono.h                  |  3 +-
 include/pybind11/detail/common.h           | 24 +++++----
 include/pybind11/detail/internals.h        | 12 +++--
 include/pybind11/detail/type_caster_base.h |  3 +-
 include/pybind11/iostream.h                |  3 +-
 include/pybind11/numpy.h                   |  3 +-
 include/pybind11/options.h                 |  3 +-
 include/pybind11/pybind11.h                | 57 +++++++++++++---------
 include/pybind11/pytypes.h                 | 13 +++--
 include/pybind11/stl_bind.h                |  9 ++--
 tests/constructor_stats.h                  |  6 ++-
 tests/pybind11_tests.h                     |  3 +-
 tests/test_class.cpp                       | 43 ++++++++--------
 tests/test_kwargs_and_defaults.cpp         |  6 ++-
 tests/test_modules.cpp                     |  3 +-
 tests/test_numpy_array.cpp                 |  3 +-
 tests/test_numpy_dtypes.cpp                |  8 +--
 tests/test_virtual_functions.cpp           | 27 +++++-----
 21 files changed, 167 insertions(+), 94 deletions(-)

diff --git a/.clang-format b/.clang-format
index 8e0fd8b014..b477a16037 100644
--- a/.clang-format
+++ b/.clang-format
@@ -3,17 +3,36 @@
 # clang-format --style=llvm --dump-config
 BasedOnStyle: LLVM
 AccessModifierOffset: -4
+AllowShortLambdasOnASingleLine: true
 AlwaysBreakTemplateDeclarations: Yes
 BinPackArguments: false
 BinPackParameters: false
 BreakBeforeBinaryOperators: All
 BreakConstructorInitializers: BeforeColon
 ColumnLimit: 99
+CommentPragmas: 'NOLINT:.*|^ IWYU pragma:'
+IncludeBlocks: Regroup
 IndentCaseLabels: true
 IndentPPDirectives: AfterHash
 IndentWidth: 4
 Language: Cpp
 SpaceAfterCStyleCast: true
 Standard: Cpp11
+StatementMacros: ['PyObject_HEAD']
 TabWidth: 4
+IncludeCategories:
+  - Regex:           '<pybind11/.*'
+    Priority:        -1
+  - Regex:           'pybind11.h"$'
+    Priority:        1
+  - Regex:           '^".*/?detail/'
+    Priority:        1
+    SortPriority:    2
+  - Regex:           '^"'
+    Priority:        1
+    SortPriority:    3
+  - Regex:           '<[[:alnum:]._]+>'
+    Priority:        4
+  - Regex:           '.*'
+    Priority:        5
 ...
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 052551ff30..9f1d047801 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -44,10 +44,12 @@ struct buffer_info {
     void *ptr = nullptr;          // Pointer to the underlying storage
     ssize_t itemsize = 0;         // Size of individual items in bytes
     ssize_t size = 0;             // Total number of entries
-    std::string format;           // For homogeneous buffers, this should be set to format_descriptor<T>::format()
+    std::string format; // For homogeneous buffers, this should be set to
+                        // format_descriptor<T>::format()
     ssize_t ndim = 0;             // Number of dimensions
     std::vector<ssize_t> shape;   // Shape of the tensor (1 entry per dimension)
-    std::vector<ssize_t> strides; // Number of bytes between adjacent entries (for each per dimension)
+    std::vector<ssize_t> strides; // Number of bytes between adjacent entries
+                                  // (for each per dimension)
     bool readonly = false;        // flag to indicate if the underlying storage may be written to
 
     buffer_info() = default;
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 4277d87ab5..4f65356e08 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -996,7 +996,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename T, enable_if_t<!is_pyobject<T>::value, int>>
 object object_or_cast(T &&o) { return pybind11::cast(std::forward<T>(o)); }
 
-struct override_unused {}; // Placeholder type for the unneeded (and dead code) static variable in the PYBIND11_OVERRIDE_OVERRIDE macro
+// Placeholder type for the unneeded (and dead code) static variable in the
+// PYBIND11_OVERRIDE_OVERRIDE macro
+struct override_unused {};
 template <typename ret_type> using override_caster_t = conditional_t<
     cast_is_temporary_value_reference<ret_type>::value, make_caster<ret_type>, override_unused>;
 
@@ -1463,7 +1465,8 @@ handle type::handle_of() {
     }}
 
 /// Lets you pass a type containing a `,` through a macro parameter without needing a separate
-/// typedef, e.g.: `PYBIND11_OVERRIDE(PYBIND11_TYPE(ReturnType<A, B>), PYBIND11_TYPE(Parent<C, D>), f, arg)`
+/// typedef, e.g.:
+/// `PYBIND11_OVERRIDE(PYBIND11_TYPE(ReturnType<A, B>), PYBIND11_TYPE(Parent<C, D>), f, arg)`
 #define PYBIND11_TYPE(...) __VA_ARGS__
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index b24533b903..cfa635a011 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -38,7 +38,8 @@ template <typename type> class duration_caster {
     using rep = typename type::rep;
     using period = typename type::period;
 
-    using days = std::chrono::duration<int_least32_t, std::ratio<86400>>; // signed 25 bits required by the standard.
+    // signed 25 bits required by the standard.
+    using days = std::chrono::duration<int_least32_t, std::ratio<86400>>;
 
     bool load(handle src, bool) {
         using namespace std::chrono;
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 14788b6523..aa3c617c49 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -42,8 +42,9 @@
 #    endif
 #  endif
 #elif defined(_MSC_VER) && __cplusplus == 199711L
-// MSVC sets _MSVC_LANG rather than __cplusplus (supposedly until the standard is fully implemented)
-// Unless you use the /Zc:__cplusplus flag on Visual Studio 2017 15.7 Preview 3 or newer
+// MSVC sets _MSVC_LANG rather than __cplusplus (supposedly until the standard is fully
+// implemented). Unless you use the /Zc:__cplusplus flag on Visual Studio 2017 15.7 Preview 3
+// or newer.
 #  if _MSVC_LANG >= 201402L
 #    define PYBIND11_CPP14
 #    if _MSVC_LANG > 201402L && _MSC_VER >= 1910
@@ -722,8 +723,8 @@ template <typename T, typename... Ts>
 constexpr int last(int i, int result, T v, Ts... vs) { return last(i + 1, v ? i : result, vs...); }
 PYBIND11_NAMESPACE_END(constexpr_impl)
 
-/// Return the index of the first type in Ts which satisfies Predicate<T>.  Returns sizeof...(Ts) if
-/// none match.
+/// Return the index of the first type in Ts which satisfies Predicate<T>.
+/// Returns sizeof...(Ts) if none match.
 template <template<typename> class Predicate, typename... Ts>
 constexpr int constexpr_first() { return constexpr_impl::first(0, Predicate<Ts>::value...); }
 
@@ -842,7 +843,9 @@ PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
 #  pragma warning(push)
-#  pragma warning(disable: 4275) // warning C4275: An exported class was derived from a class that wasn't exported. Can be ignored when derived from a STL class.
+#  pragma warning(disable: 4275)
+//     warning C4275: An exported class was derived from a class that wasn't exported.
+//     Can be ignored when derived from a STL class.
 #endif
 /// C++ bindings of builtin Python exceptions
 class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
@@ -870,7 +873,9 @@ PYBIND11_RUNTIME_EXCEPTION(type_error, PyExc_TypeError)
 PYBIND11_RUNTIME_EXCEPTION(buffer_error, PyExc_BufferError)
 PYBIND11_RUNTIME_EXCEPTION(import_error, PyExc_ImportError)
 PYBIND11_RUNTIME_EXCEPTION(attribute_error, PyExc_AttributeError)
-PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or handle::call fail due to a type casting error
+PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or
+                                                           /// handle::call fail due to a type
+                                                           /// casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
 
 [[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
@@ -974,13 +979,14 @@ class any_container {
     template <typename It, typename = enable_if_t<is_input_iterator<It>::value>>
     any_container(It first, It last) : v(first, last) { }
 
-    // Implicit conversion constructor from any arbitrary container type with values convertible to T
+    // Implicit conversion constructor from any arbitrary container type
+    // with values convertible to T
     template <typename Container, typename = enable_if_t<std::is_convertible<decltype(*std::begin(std::declval<const Container &>())), T>::value>>
     // NOLINTNEXTLINE(google-explicit-constructor)
     any_container(const Container &c) : any_container(std::begin(c), std::end(c)) { }
 
-    // initializer_list's aren't deducible, so don't get matched by the above template; we need this
-    // to explicitly allow implicit conversion from one:
+    // initializer_list's aren't deducible, so don't get matched by the above template;
+    // we need this to explicitly allow implicit conversion from one:
     template <typename TIn, typename = enable_if_t<std::is_convertible<TIn, T>::value>>
     any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) { }
 
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 5377190642..5bddbe35fd 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -147,18 +147,22 @@ struct override_hash {
 /// Whenever binary incompatible changes are made to this structure,
 /// `PYBIND11_INTERNALS_VERSION` must be incremented.
 struct internals {
-    type_map<type_info *> registered_types_cpp; // std::type_index -> pybind11's type information
-    std::unordered_map<PyTypeObject *, std::vector<type_info *>> registered_types_py; // PyTypeObject* -> base type_info(s)
+    // std::type_index -> pybind11's type information
+    type_map<type_info *> registered_types_cpp;
+    // PyTypeObject* -> base type_info(s)
+    std::unordered_map<PyTypeObject *, std::vector<type_info *>> registered_types_py;
     std::unordered_multimap<const void *, instance*> registered_instances; // void * -> instance*
     std::unordered_set<std::pair<const PyObject *, const char *>, override_hash> inactive_override_cache;
     type_map<std::vector<bool (*)(PyObject *, void *&)>> direct_conversions;
     std::unordered_map<const PyObject *, std::vector<PyObject *>> patients;
     std::forward_list<ExceptionTranslator> registered_exception_translators;
-    std::unordered_map<std::string, void *> shared_data; // Custom data to be shared across extensions
+    std::unordered_map<std::string, void *> shared_data; // Custom data to be shared across
+                                                         // extensions
 #if PYBIND11_INTERNALS_VERSION == 4
     std::vector<PyObject *> unused_loader_patient_stack_remove_at_v5;
 #endif
-    std::forward_list<std::string> static_strings; // Stores the std::strings backing detail::c_str()
+    std::forward_list<std::string> static_strings; // Stores the std::strings backing
+                                                   // detail::c_str()
     PyTypeObject *static_property_type;
     PyTypeObject *default_metaclass;
     PyObject *instance_base;
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index ea5ef6a2be..34100c3ae2 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -426,7 +426,8 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
             space += t->holder_size_in_ptrs; // holder instance
         }
         size_t flags_at = space;
-        space += size_in_ptrs(n_types); // status bytes (holder_constructed and instance_registered)
+        space += size_in_ptrs(n_types); // status bytes (holder_constructed and
+                                        // instance_registered)
 
         // Allocate space for flags, values, and holders, and initialize it to 0 (flags and values,
         // in particular, need to be 0).  Use Python's memory allocation functions: in Python 3.6
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 8c0772c281..d6cf223726 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -164,7 +164,8 @@ PYBIND11_NAMESPACE_END(detail)
     .. code-block:: cpp
 
         {
-            py::scoped_ostream_redirect output{std::cerr, py::module::import("sys").attr("stderr")};
+            py::scoped_ostream_redirect output{
+                std::cerr, py::module::import("sys").attr("stderr")};
             std::cout << "Hello, World!";
         }
  \endrst */
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 57f0c90948..489587835d 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -325,7 +325,8 @@ template <typename T, size_t N> struct array_info<T[N]> : array_info<std::array<
 template <typename T> using remove_all_extents_t = typename array_info<T>::type;
 
 template <typename T> using is_pod_struct = all_of<
-    std::is_standard_layout<T>,     // since we're accessing directly in memory we need a standard layout type
+    std::is_standard_layout<T>,     // since we're accessing directly in memory
+                                    // we need a standard layout type
 #if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623 || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
     // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after 5)
     // don't implement is_trivially_copyable, so approximate it
diff --git a/include/pybind11/options.h b/include/pybind11/options.h
index d74db1c68d..810e5e0104 100644
--- a/include/pybind11/options.h
+++ b/include/pybind11/options.h
@@ -51,7 +51,8 @@ class options {
 
     struct state {
         bool show_user_defined_docstrings = true;  //< Include user-supplied texts in docstrings.
-        bool show_function_signatures = true;      //< Include auto-generated function signatures in docstrings.
+        bool show_function_signatures = true;      //< Include auto-generated function signatures
+                                                   //  in docstrings.
     };
 
     static state &global_state() {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 58ac559965..754f22e9b7 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -242,7 +242,8 @@ class cpp_function : public function {
 
         rec->nargs_pos = cast_in::args_pos >= 0
             ? static_cast<std::uint16_t>(cast_in::args_pos)
-            : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if we have a kw_only
+            : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if
+                                                     // we have a kw_only
         rec->has_args = cast_in::args_pos >= 0;
         rec->has_kwargs = cast_in::has_kwargs;
 
@@ -263,7 +264,8 @@ class cpp_function : public function {
             static_assert(!(has_kw_only_args && has_pos_only_args) || pos_only_pos < kw_only_pos, "py::pos_only must come before py::kw_only");
         }
 
-        /* Generate a readable signature describing the function's arguments and return value types */
+        /* Generate a readable signature describing the function's arguments and return
+           value types */
         static constexpr auto signature = const_name("(") + cast_in::arg_names + const_name(") -> ") + cast_out::name;
         PYBIND11_DESCR_CONSTEXPR auto types = decltype(signature)::types();
 
@@ -400,7 +402,8 @@ class cpp_function : public function {
                     handle th((PyObject *) tinfo->type);
                     signature +=
                         th.attr("__module__").cast<std::string>() + "." +
-                        th.attr("__qualname__").cast<std::string>(); // Python 3.3+, but we backport it to earlier versions
+                        // Python 3.3+, but we backport it to earlier versions
+                        th.attr("__qualname__").cast<std::string>();
                 } else if (rec->is_new_style_constructor && arg_index == 0) {
                     // A new-style `__init__` takes `self` as `value_and_holder`.
                     // Rewrite it to the proper class type.
@@ -639,7 +642,8 @@ class cpp_function : public function {
         const function_record *overloads = (function_record *) PyCapsule_GetPointer(self, nullptr),
                               *it = overloads;
 
-        /* Need to know how many arguments + keyword arguments there are to pick the right overload */
+        /* Need to know how many arguments + keyword arguments there are to pick the right
+           overload */
         const auto n_args_in = (size_t) PyTuple_GET_SIZE(args_in);
 
         handle parent = n_args_in > 0 ? PyTuple_GET_ITEM(args_in, 0) : nullptr,
@@ -715,7 +719,8 @@ class cpp_function : public function {
 
                 function_call call(func, parent);
 
-                size_t args_to_copy = (std::min)(pos_args, n_args_in); // Protect std::min with parentheses
+                // Protect std::min with parentheses
+                size_t args_to_copy = (std::min)(pos_args, n_args_in);
                 size_t args_copied = 0;
 
                 // 0. Inject new-style `self` argument
@@ -956,7 +961,8 @@ class cpp_function : public function {
                 - catch the exception and call PyErr_SetString or PyErr_SetObject
                   to set a standard (or custom) Python exception, or
                 - do nothing and let the exception fall through to the next translator, or
-                - delegate translation to the next translator by throwing a new type of exception. */
+                - delegate translation to the next translator by throwing a new type of exception.
+             */
 
             auto &local_exception_translators = get_local_internals().registered_exception_translators;
             if (detail::apply_exception_translators(local_exception_translators)) {
@@ -1169,8 +1175,8 @@ class module_ : public object {
         Adds an object to the module using the given name.  Throws if an object with the given name
         already exists.
 
-        ``overwrite`` should almost always be false: attempting to overwrite objects that pybind11 has
-        established will, in most cases, break things.
+        ``overwrite`` should almost always be false: attempting to overwrite objects that pybind11
+        has established will, in most cases, break things.
     \endrst */
     PYBIND11_NOINLINE void add_object(const char *name, handle obj, bool overwrite = false) {
         if (!overwrite && hasattr(*this, name)) {
@@ -1197,7 +1203,8 @@ class module_ : public object {
     static module_ create_extension_module(const char *name, const char *doc, module_def *def) {
 #if PY_MAJOR_VERSION >= 3
         // module_def is PyModuleDef
-        def = new (def) PyModuleDef {  // Placement new (not an allocation).
+        // Placement new (not an allocation).
+        def = new (def) PyModuleDef {
             /* m_base */     PyModuleDef_HEAD_INIT,
             /* m_name */     name,
             /* m_doc */      options::show_user_defined_docstrings() ? doc : nullptr,
@@ -1456,7 +1463,8 @@ class class_ : public detail::generic_type {
             none_of<is_pyobject<Extra>...>::value || // no base class arguments, or:
             (   constexpr_sum(is_pyobject<Extra>::value...) == 1 && // Exactly one base
                 constexpr_sum(is_base<options>::value...)   == 0 && // no template option bases
-                none_of<std::is_same<multiple_inheritance, Extra>...>::value), // no multiple_inheritance attr
+                // no multiple_inheritance attr
+                none_of<std::is_same<multiple_inheritance, Extra>...>::value),
             "Error: multiple inheritance bases must be specified via class_ template options");
 
         type_record record;
@@ -2562,10 +2570,11 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
 PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
-  Try to retrieve a python method by the provided name from the instance pointed to by the this_ptr.
+  Try to retrieve a python method by the provided name from the instance pointed to by the
+  this_ptr.
 
-  :this_ptr: The pointer to the object the overridden method should be retrieved for. This should be
-             the first non-trampoline class encountered in the inheritance chain.
+  :this_ptr: The pointer to the object the overridden method should be retrieved for. This should
+             be the first non-trampoline class encountered in the inheritance chain.
   :name: The name of the overridden Python method to retrieve.
   :return: The Python method by this name from the object or an empty function wrapper.
  \endrst */
@@ -2590,9 +2599,10 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
     } while (false)
 
 /** \rst
-    Macro to populate the virtual method in the trampoline class. This macro tries to look up a method named 'fn'
-    from the Python side, deals with the :ref:`gil` and necessary argument conversions to call this method and return
-    the appropriate type. See :ref:`overriding_virtuals` for more information. This macro should be used when the method
+    Macro to populate the virtual method in the trampoline class. This macro tries to look up a
+    method named 'fn' from the Python side, deals with the :ref:`gil` and necessary argument
+    conversions to call this method and return the appropriate type.
+    See :ref:`overriding_virtuals` for more information. This macro should be used when the method
     name in C is not the same as the method name in Python. For example with `__str__`.
 
     .. code-block:: cpp
@@ -2613,8 +2623,8 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
     } while (false)
 
 /** \rst
-    Macro for pure virtual functions, this function is identical to :c:macro:`PYBIND11_OVERRIDE_NAME`, except that it
-    throws if no override can be found.
+    Macro for pure virtual functions, this function is identical to
+    :c:macro:`PYBIND11_OVERRIDE_NAME`, except that it throws if no override can be found.
 \endrst */
 #define PYBIND11_OVERRIDE_PURE_NAME(ret_type, cname, name, fn, ...) \
     do { \
@@ -2623,9 +2633,10 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
     } while (false)
 
 /** \rst
-    Macro to populate the virtual method in the trampoline class. This macro tries to look up the method
-    from the Python side, deals with the :ref:`gil` and necessary argument conversions to call this method and return
-    the appropriate type. This macro should be used if the method name in C and in Python are identical.
+    Macro to populate the virtual method in the trampoline class. This macro tries to look up the
+    method from the Python side, deals with the :ref:`gil` and necessary argument conversions to
+    call this method and return the appropriate type. This macro should be used if the method name
+    in C and in Python are identical.
     See :ref:`overriding_virtuals` for more information.
 
     .. code-block:: cpp
@@ -2650,8 +2661,8 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
     PYBIND11_OVERRIDE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
 
 /** \rst
-    Macro for pure virtual functions, this function is identical to :c:macro:`PYBIND11_OVERRIDE`, except that it throws
-    if no override can be found.
+    Macro for pure virtual functions, this function is identical to :c:macro:`PYBIND11_OVERRIDE`,
+    except that it throws if no override can be found.
 \endrst */
 #define PYBIND11_OVERRIDE_PURE(ret_type, cname, fn, ...) \
     PYBIND11_OVERRIDE_PURE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index d39e71045c..bdb3b9174f 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -161,7 +161,8 @@ class object_api : public pyobject_tag {
     /// Return the object's current reference count
     int ref_count() const { return static_cast<int>(Py_REFCNT(derived().ptr())); }
 
-    // TODO PYBIND11_DEPRECATED("Call py::type::handle_of(h) or py::type::of(h) instead of h.get_type()")
+    // TODO PYBIND11_DEPRECATED(
+    //     "Call py::type::handle_of(h) or py::type::of(h) instead of h.get_type()")
     handle get_type() const;
 
 private:
@@ -337,7 +338,9 @@ PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
 #  pragma warning(push)
-#  pragma warning(disable: 4275 4251) // warning C4275: An exported class was derived from a class that wasn't exported. Can be ignored when derived from a STL class.
+#  pragma warning(disable: 4275 4251)
+//     warning C4275: An exported class was derived from a class that wasn't exported.
+//     Can be ignored when derived from a STL class.
 #endif
 /// Fetch and hold an error which was already set in Python.  An instance of this is typically
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
@@ -1745,7 +1748,8 @@ class memoryview : public object {
 
         See also: Python C API documentation for `PyMemoryView_FromBuffer`_.
 
-        .. _PyMemoryView_FromBuffer: https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromBuffer
+        .. _PyMemoryView_FromBuffer:
+           https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromBuffer
 
         :param ptr: Pointer to the buffer.
         :param itemsize: Byte size of an element.
@@ -1800,7 +1804,8 @@ class memoryview : public object {
 
         See also: Python C API documentation for `PyMemoryView_FromBuffer`_.
 
-        .. _PyMemoryView_FromMemory: https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromMemory
+        .. _PyMemoryView_FromMemory:
+           https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromMemory
      \endrst */
     static memoryview from_memory(void *mem, ssize_t size, bool readonly = false) {
         PyObject* ptr = PyMemoryView_FromMemory(
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 6db1faf404..2f997d6b03 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -44,7 +44,8 @@ struct is_comparable<
                    container_traits<T>::is_comparable>>
     : std::true_type { };
 
-/* For a vector/map data structure, recursively check the value type (which is std::pair for maps) */
+/* For a vector/map data structure, recursively check the value type
+   (which is std::pair for maps) */
 template <typename T>
 struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
     static constexpr const bool value =
@@ -384,7 +385,8 @@ template <typename Vector, typename Class_> auto vector_if_insertion_operator(Cl
 }
 
 // Provide the buffer interface for vectors if we have data() and we have a format for it
-// GCC seems to have "void std::vector<bool>::data()" - doing SFINAE on the existence of data() is insufficient, we need to check it returns an appropriate pointer
+// GCC seems to have "void std::vector<bool>::data()" - doing SFINAE on the existence of data()
+// is insufficient, we need to check it returns an appropriate pointer
 template <typename Vector, typename = void>
 struct vector_has_data_and_format : std::false_type {};
 template <typename Vector>
@@ -408,7 +410,8 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
 
     static_assert(vector_has_data_and_format<Vector>::value, "There is not an appropriate format descriptor for this vector");
 
-    // numpy.h declares this for arbitrary types, but it may raise an exception and crash hard at runtime if PYBIND11_NUMPY_DTYPE hasn't been called, so check here
+    // numpy.h declares this for arbitrary types, but it may raise an exception and crash hard
+    // at runtime if PYBIND11_NUMPY_DTYPE hasn't been called, so check here
     format_descriptor<T>::format();
 
     cl.def_buffer([](Vector& v) -> buffer_info {
diff --git a/tests/constructor_stats.h b/tests/constructor_stats.h
index 8ee4047925..ccb623e1c3 100644
--- a/tests/constructor_stats.h
+++ b/tests/constructor_stats.h
@@ -72,8 +72,10 @@ inspection/testing in python) by using the functions with `print_` replaced with
 
 class ConstructorStats {
 protected:
-    std::unordered_map<void*, int> _instances; // Need a map rather than set because members can shared address with parents
-    std::list<std::string> _values; // Used to track values (e.g. of value constructors)
+    std::unordered_map<void*, int> _instances; // Need a map rather than set because members can
+                                               // shared address with parents
+    std::list<std::string> _values; // Used to track values
+                                    // (e.g. of value constructors)
 public:
     int default_constructions = 0;
     int copy_constructions = 0;
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index 9b99923237..f6e1a6523b 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -5,8 +5,7 @@
 
 #if defined(_MSC_VER) && _MSC_VER < 1910
 // We get some really long type names here which causes MSVC 2015 to emit warnings
-#    pragma warning(                                                                              \
-        disable : 4503) // warning C4503: decorated name length exceeded, name was truncated
+#    pragma warning(disable : 4503) // NOLINT: warning C4503: decorated name length exceeded, name was truncated
 #endif
 
 namespace py = pybind11;
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 7445b3c026..851bc00ca0 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -22,7 +22,8 @@
 #include <utility>
 
 #if defined(_MSC_VER)
-#  pragma warning(disable: 4324) // warning C4324: structure was padded due to alignment specifier
+#  pragma warning(disable: 4324)
+//     warning C4324: structure was padded due to alignment specifier
 #endif
 
 // test_brace_initialization
@@ -534,22 +535,24 @@ CHECK_HOLDER(6, shared); CHECK_HOLDER(7, shared); CHECK_HOLDER(8, shared);
 #define CHECK_BROKEN(N) static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-(N)>>::value, \
         "Breaks1 has wrong type!");
 
-//// Two holder classes:
-//typedef py::class_<BreaksBase<-1>, std::unique_ptr<BreaksBase<-1>>, std::unique_ptr<BreaksBase<-1>>> Breaks1;
-//CHECK_BROKEN(1);
-//// Two aliases:
-//typedef py::class_<BreaksBase<-2>, BreaksTramp<-2>, BreaksTramp<-2>> Breaks2;
-//CHECK_BROKEN(2);
-//// Holder + 2 aliases
-//typedef py::class_<BreaksBase<-3>, std::unique_ptr<BreaksBase<-3>>, BreaksTramp<-3>, BreaksTramp<-3>> Breaks3;
-//CHECK_BROKEN(3);
-//// Alias + 2 holders
-//typedef py::class_<BreaksBase<-4>, std::unique_ptr<BreaksBase<-4>>, BreaksTramp<-4>, std::shared_ptr<BreaksBase<-4>>> Breaks4;
-//CHECK_BROKEN(4);
-//// Invalid option (not a subclass or holder)
-//typedef py::class_<BreaksBase<-5>, BreaksTramp<-4>> Breaks5;
-//CHECK_BROKEN(5);
-//// Invalid option: multiple inheritance not supported:
-//template <> struct BreaksBase<-8> : BreaksBase<-6>, BreaksBase<-7> {};
-//typedef py::class_<BreaksBase<-8>, BreaksBase<-6>, BreaksBase<-7>> Breaks8;
-//CHECK_BROKEN(8);
+#ifdef PYBIND11_NEVER_DEFINED_EVER
+// Two holder classes:
+typedef py::class_<BreaksBase<-1>, std::unique_ptr<BreaksBase<-1>>, std::unique_ptr<BreaksBase<-1>>> Breaks1;
+CHECK_BROKEN(1);
+// Two aliases:
+typedef py::class_<BreaksBase<-2>, BreaksTramp<-2>, BreaksTramp<-2>> Breaks2;
+CHECK_BROKEN(2);
+// Holder + 2 aliases
+typedef py::class_<BreaksBase<-3>, std::unique_ptr<BreaksBase<-3>>, BreaksTramp<-3>, BreaksTramp<-3>> Breaks3;
+CHECK_BROKEN(3);
+// Alias + 2 holders
+typedef py::class_<BreaksBase<-4>, std::unique_ptr<BreaksBase<-4>>, BreaksTramp<-4>, std::shared_ptr<BreaksBase<-4>>> Breaks4;
+CHECK_BROKEN(4);
+// Invalid option (not a subclass or holder)
+typedef py::class_<BreaksBase<-5>, BreaksTramp<-4>> Breaks5;
+CHECK_BROKEN(5);
+// Invalid option: multiple inheritance not supported:
+template <> struct BreaksBase<-8> : BreaksBase<-6>, BreaksBase<-7> {};
+typedef py::class_<BreaksBase<-8>, BreaksBase<-6>, BreaksBase<-7>> Breaks8;
+CHECK_BROKEN(8);
+#endif
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 0e262dad2f..d09630a8cd 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -153,10 +153,12 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
 
 
     // These should fail to compile:
+#ifdef PYBIND11_NEVER_DEFINED_EVER
     // argument annotations are required when using kw_only
-//    m.def("bad_kw_only1", [](int) {}, py::kw_only());
+    m.def("bad_kw_only1", [](int) {}, py::kw_only());
     // can't specify both `py::kw_only` and a `py::args` argument
-//    m.def("bad_kw_only2", [](int i, py::args) {}, py::kw_only(), "i"_a);
+    m.def("bad_kw_only2", [](int i, py::args) {}, py::kw_only(), "i"_a);
+#endif
 
     // test_function_signatures (along with most of the above)
     struct KWClass { void foo(int, float) {} };
diff --git a/tests/test_modules.cpp b/tests/test_modules.cpp
index ce61c1a25c..ba80a64c9a 100644
--- a/tests/test_modules.cpp
+++ b/tests/test_modules.cpp
@@ -49,7 +49,8 @@ TEST_SUBMODULE(modules, m) {
         .def(py::init<>())
         .def("get_a1", &B::get_a1, "Return the internal A 1", py::return_value_policy::reference_internal)
         .def("get_a2", &B::get_a2, "Return the internal A 2", py::return_value_policy::reference_internal)
-        .def_readwrite("a1", &B::a1)  // def_readonly uses an internal reference return policy by default
+        .def_readwrite("a1", &B::a1)  // def_readonly uses an internal
+                                      // reference return policy by default
         .def_readwrite("a2", &B::a2);
 
     // This is intentionally "py::module" to verify it still can be used in place of "py::module_"
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index bc1797845b..17fc4de2ec 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -399,7 +399,8 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_initializer_list
     // Issue (unnumbered; reported in #788): regression: initializer lists can be ambiguous
-    sm.def("array_initializer_list1", []() { return py::array_t<float>(1); }); // { 1 } also works, but clang warns about it
+    sm.def("array_initializer_list1", []() { return py::array_t<float>(1); });
+    // { 1 } also works for the above, but clang warns about it
     sm.def("array_initializer_list2", []() { return py::array_t<float>({ 1, 2 }); });
     sm.def("array_initializer_list3", []() { return py::array_t<float>({ 1, 2, 3 }); });
     sm.def("array_initializer_list4", []() { return py::array_t<float>({ 1, 2, 3, 4 }); });
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index 468a89a3c9..a6566c5c65 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -308,10 +308,12 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 
     PYBIND11_NUMPY_DTYPE_EX(StructWithUglyNames, __x__, "x", __y__, "y");
 
-    // If uncommented, this should produce a static_assert failure telling the user that the struct
+#ifdef PYBIND11_NEVER_DEFINED_EVER
+    // If enabled, this should produce a static_assert failure telling the user that the struct
     // is not a POD type
-//    struct NotPOD { std::string v; NotPOD() : v("hi") {}; };
-//    PYBIND11_NUMPY_DTYPE(NotPOD, v);
+    struct NotPOD { std::string v; NotPOD() : v("hi") {}; };
+    PYBIND11_NUMPY_DTYPE(NotPOD, v);
+#endif
 
     // Check that dtypes can be registered programmatically, both from
     // initializer lists of field descriptors and from other containers.
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 558cd94406..1e47b367d2 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -370,9 +370,12 @@ TEST_SUBMODULE(virtual_functions, m) {
     public:
         using OverrideTest::OverrideTest;
         std::string str_value() override { PYBIND11_OVERRIDE(std::string, OverrideTest, str_value); }
-        // Not allowed (uncommenting should hit a static_assert failure): we can't get a reference
-        // to a python numeric value, since we only copy values in the numeric type caster:
-//      std::string &str_ref() override { PYBIND11_OVERRIDE(std::string &, OverrideTest, str_ref); }
+        // Not allowed (enabling the below should hit a static_assert failure): we can't get a
+        // reference to a python numeric value, since we only copy values in the numeric type
+        // caster:
+#ifdef PYBIND11_NEVER_DEFINED_EVER
+        std::string &str_ref() override { PYBIND11_OVERRIDE(std::string &, OverrideTest, str_ref); }
+#endif
         // But we can work around it like this:
     private:
         std::string _tmp;
@@ -389,7 +392,9 @@ TEST_SUBMODULE(virtual_functions, m) {
     py::class_<OverrideTest, PyOverrideTest>(m, "OverrideTest")
         .def(py::init<const std::string &>())
         .def("str_value", &OverrideTest::str_value)
-//      .def("str_ref", &OverrideTest::str_ref)
+#ifdef PYBIND11_NEVER_DEFINED_EVER
+        .def("str_ref", &OverrideTest::str_ref)
+#endif
         .def("A_value", &OverrideTest::A_value)
         .def("A_ref", &OverrideTest::A_ref);
 
@@ -492,11 +497,11 @@ class PyD_Repeat : public D_Repeat {
 // Inheritance approach 2: templated trampoline classes.
 //
 // Advantages:
-// - we have only 2 (template) class and 4 method declarations (one per virtual method, plus one for
-//   any override of a pure virtual method), versus 4 classes and 6 methods (MI) or 4 classes and 11
-//   methods (repeat).
-// - Compared to MI, we also don't have to change the non-trampoline inheritance to virtual, and can
-//   properly inherit constructors.
+// - we have only 2 (template) class and 4 method declarations (one per virtual method, plus one
+//   for any override of a pure virtual method), versus 4 classes and 6 methods (MI) or 4 classes
+//   and 11 methods (repeat).
+// - Compared to MI, we also don't have to change the non-trampoline inheritance to virtual, and
+//   can properly inherit constructors.
 //
 // Disadvantage:
 // - the compiler must still generate and compile 14 different methods (more, even, than the 11
@@ -518,8 +523,8 @@ class PyB_Tpl : public PyA_Tpl<Base> {
     int unlucky_number() override { PYBIND11_OVERRIDE(int, Base, unlucky_number, ); }
     double lucky_number() override { PYBIND11_OVERRIDE(double, Base, lucky_number, ); }
 };
-// Since C_Tpl and D_Tpl don't declare any new virtual methods, we don't actually need these (we can
-// use PyB_Tpl<C_Tpl> and PyB_Tpl<D_Tpl> for the trampoline classes instead):
+// Since C_Tpl and D_Tpl don't declare any new virtual methods, we don't actually need these
+// (we can use PyB_Tpl<C_Tpl> and PyB_Tpl<D_Tpl> for the trampoline classes instead):
 /*
 template <class Base = C_Tpl> class PyC_Tpl : public PyB_Tpl<Base> {
 public:

From ec24786eab4d170f21536c92422a59959e14dde4 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 10 Feb 2022 12:17:07 -0800
Subject: [PATCH 307/638] Fully-automatic clang-format with include reordering
 (#3713)

* chore: add clang-format

* Removing check-style (Classic check-style)

Ported from @henryiii's https://github.com/pybind/pybind11/pull/3683/commits/53056b1b0eeb4136b0d7362a8261b6b59658e0a7

* Automatic clang-format changes (NO manual changes).

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .pre-commit-config.yaml                    |   10 +-
 include/pybind11/attr.h                    |  207 ++--
 include/pybind11/buffer_info.h             |  104 +-
 include/pybind11/cast.h                    |  743 +++++++-----
 include/pybind11/chrono.h                  |  115 +-
 include/pybind11/complex.h                 |   23 +-
 include/pybind11/detail/class.h            |   66 +-
 include/pybind11/detail/common.h           |  882 ++++++++------
 include/pybind11/detail/descr.h            |   81 +-
 include/pybind11/detail/init.h             |  238 ++--
 include/pybind11/detail/internals.h        |  115 +-
 include/pybind11/detail/type_caster_base.h |  309 ++---
 include/pybind11/detail/typeid.h           |    9 +-
 include/pybind11/eigen.h                   |  395 ++++---
 include/pybind11/embed.h                   |   34 +-
 include/pybind11/eval.h                    |   87 +-
 include/pybind11/functional.h              |   13 +-
 include/pybind11/gil.h                     |   30 +-
 include/pybind11/iostream.h                |   41 +-
 include/pybind11/numpy.h                   | 1027 ++++++++++-------
 include/pybind11/operators.h               |  253 ++--
 include/pybind11/options.h                 |   42 +-
 include/pybind11/pybind11.h                | 1211 +++++++++++---------
 include/pybind11/pytypes.h                 |  816 +++++++------
 include/pybind11/stl.h                     |  139 ++-
 include/pybind11/stl/filesystem.h          |   46 +-
 include/pybind11/stl_bind.h                |  465 ++++----
 tests/constructor_stats.h                  |  124 +-
 tests/cross_module_gil_utils.cpp           |   37 +-
 tests/local_bindings.h                     |   41 +-
 tests/object.h                             |   61 +-
 tests/pybind11_cross_module_tests.cpp      |   86 +-
 tests/pybind11_tests.cpp                   |   20 +-
 tests/pybind11_tests.h                     |   29 +-
 tests/test_async.cpp                       |    5 +-
 tests/test_buffers.cpp                     |   67 +-
 tests/test_builtin_casters.cpp             |  298 +++--
 tests/test_call_policies.cpp               |   43 +-
 tests/test_callbacks.cpp                   |   60 +-
 tests/test_chrono.cpp                      |   33 +-
 tests/test_class.cpp                       |  265 +++--
 tests/test_constants_and_functions.cpp     |   67 +-
 tests/test_copy_move.cpp                   |  163 ++-
 tests/test_custom_type_casters.cpp         |  100 +-
 tests/test_docstring_options.cpp           |   55 +-
 tests/test_eigen.cpp                       |  185 +--
 tests/test_embed/catch.cpp                 |    8 +-
 tests/test_embed/external_module.cpp       |    9 +-
 tests/test_embed/test_interpreter.cpp      |   59 +-
 tests/test_enum.cpp                        |   83 +-
 tests/test_eval.cpp                        |   28 +-
 tests/test_exceptions.cpp                  |   95 +-
 tests/test_exceptions.h                    |    1 +
 tests/test_factory_constructors.cpp        |   83 +-
 tests/test_gil_scoped.cpp                  |   44 +-
 tests/test_iostream.cpp                    |   30 +-
 tests/test_kwargs_and_defaults.cpp         |  241 ++--
 tests/test_local_bindings.cpp              |   38 +-
 tests/test_methods_and_attributes.cpp      |  194 ++--
 tests/test_modules.cpp                     |   66 +-
 tests/test_multiple_inheritance.cpp        |  137 ++-
 tests/test_numpy_array.cpp                 |  249 ++--
 tests/test_numpy_dtypes.cpp                |  240 ++--
 tests/test_numpy_vectorize.cpp             |   32 +-
 tests/test_opaque_types.cpp                |   15 +-
 tests/test_operator_overloading.cpp        |  176 +--
 tests/test_pickling.cpp                    |    6 +-
 tests/test_pytypes.cpp                     |  167 ++-
 tests/test_sequences_and_iterators.cpp     |  225 ++--
 tests/test_smart_ptr.cpp                   |   90 +-
 tests/test_stl.cpp                         |  236 ++--
 tests/test_stl_binders.cpp                 |   54 +-
 tests/test_tagbased_polymorphic.cpp        |   85 +-
 tests/test_thread.cpp                      |   10 +-
 tests/test_virtual_functions.cpp           |  278 ++---
 75 files changed, 7067 insertions(+), 5152 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2014cb2b42..c31cab71c7 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -141,11 +141,7 @@ repos:
     entry: PyBind|Numpy|Cmake|CCache|PyTest
     exclude: .pre-commit-config.yaml
 
-- repo: local
+- repo: https://github.com/pre-commit/mirrors-clang-format
+  rev: "v13.0.0"
   hooks:
-  - id: check-style
-    name: Classic check-style
-    language: system
-    types:
-    - c++
-    entry: ./tools/check-style.sh
+  - id: clang-format
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 3e894eef07..de95f89d0f 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -20,54 +20,62 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 /// @{
 
 /// Annotation for methods
-struct is_method { handle class_;
+struct is_method {
+    handle class_;
     explicit is_method(const handle &c) : class_(c) {}
 };
 
 /// Annotation for operators
-struct is_operator { };
+struct is_operator {};
 
 /// Annotation for classes that cannot be subclassed
-struct is_final { };
+struct is_final {};
 
 /// Annotation for parent scope
-struct scope { handle value;
+struct scope {
+    handle value;
     explicit scope(const handle &s) : value(s) {}
 };
 
 /// Annotation for documentation
-struct doc { const char *value;
+struct doc {
+    const char *value;
     explicit doc(const char *value) : value(value) {}
 };
 
 /// Annotation for function names
-struct name { const char *value;
+struct name {
+    const char *value;
     explicit name(const char *value) : value(value) {}
 };
 
 /// Annotation indicating that a function is an overload associated with a given "sibling"
-struct sibling { handle value;
+struct sibling {
+    handle value;
     explicit sibling(const handle &value) : value(value.ptr()) {}
 };
 
 /// Annotation indicating that a class derives from another given type
-template <typename T> struct base {
+template <typename T>
+struct base {
 
-    PYBIND11_DEPRECATED("base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
-    base() { } // NOLINT(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
+    PYBIND11_DEPRECATED(
+        "base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
+    base() {} // NOLINT(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
 };
 
 /// Keep patient alive while nurse lives
-template <size_t Nurse, size_t Patient> struct keep_alive { };
+template <size_t Nurse, size_t Patient>
+struct keep_alive {};
 
 /// Annotation indicating that a class is involved in a multiple inheritance relationship
-struct multiple_inheritance { };
+struct multiple_inheritance {};
 
 /// Annotation which enables dynamic attributes, i.e. adds `__dict__` to a class
-struct dynamic_attr { };
+struct dynamic_attr {};
 
 /// Annotation which enables the buffer protocol for a type
-struct buffer_protocol { };
+struct buffer_protocol {};
 
 /// Annotation which requests that a special metaclass is created for a type
 struct metaclass {
@@ -78,7 +86,7 @@ struct metaclass {
     metaclass() {}
 
     /// Override pybind11's default metaclass
-    explicit metaclass(handle value) : value(value) { }
+    explicit metaclass(handle value) : value(value) {}
 };
 
 /// Specifies a custom callback with signature `void (PyHeapTypeObject*)` that
@@ -99,15 +107,16 @@ struct custom_type_setup {
 };
 
 /// Annotation that marks a class as local to the module:
-struct module_local { const bool value;
+struct module_local {
+    const bool value;
     constexpr explicit module_local(bool v = true) : value(v) {}
 };
 
 /// Annotation to mark enums as an arithmetic type
-struct arithmetic { };
+struct arithmetic {};
 
 /// Mark a function for addition at the beginning of the existing overload chain instead of the end
-struct prepend { };
+struct prepend {};
 
 /** \rst
     A call policy which places one or more guard variables (``Ts...``) around the function call.
@@ -127,9 +136,13 @@ struct prepend { };
             return foo(args...); // forwarded arguments
         });
  \endrst */
-template <typename... Ts> struct call_guard;
+template <typename... Ts>
+struct call_guard;
 
-template <> struct call_guard<> { using type = detail::void_type; };
+template <>
+struct call_guard<> {
+    using type = detail::void_type;
+};
 
 template <typename T>
 struct call_guard<T> {
@@ -154,7 +167,8 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 enum op_id : int;
 enum op_type : int;
 struct undefined_t;
-template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t> struct op_;
+template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t>
+struct op_;
 void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret);
 
 /// Internal data structure which holds metadata about a keyword argument
@@ -166,15 +180,16 @@ struct argument_record {
     bool none : 1;     ///< True if None is allowed when loading
 
     argument_record(const char *name, const char *descr, handle value, bool convert, bool none)
-        : name(name), descr(descr), value(value), convert(convert), none(none) { }
+        : name(name), descr(descr), value(value), convert(convert), none(none) {}
 };
 
-/// Internal data structure which holds metadata about a bound function (signature, overloads, etc.)
+/// Internal data structure which holds metadata about a bound function (signature, overloads,
+/// etc.)
 struct function_record {
     function_record()
         : is_constructor(false), is_new_style_constructor(false), is_stateless(false),
-          is_operator(false), is_method(false), has_args(false),
-          has_kwargs(false), prepend(false) { }
+          is_operator(false), is_method(false), has_args(false), has_kwargs(false),
+          prepend(false) {}
 
     /// Function name
     char *name = nullptr; /* why no C++ strings? They generate heavier code.. */
@@ -189,13 +204,13 @@ struct function_record {
     std::vector<argument_record> args;
 
     /// Pointer to lambda function which converts arguments and performs the actual call
-    handle (*impl) (function_call &) = nullptr;
+    handle (*impl)(function_call &) = nullptr;
 
     /// Storage for the wrapped function pointer and captured data, if any
-    void *data[3] = { };
+    void *data[3] = {};
 
     /// Pointer to custom destructor for 'data' (if needed)
-    void (*free_data) (function_record *ptr) = nullptr;
+    void (*free_data)(function_record *ptr) = nullptr;
 
     /// Return value policy associated with this function
     return_value_policy policy = return_value_policy::automatic;
@@ -251,7 +266,7 @@ struct function_record {
 struct type_record {
     PYBIND11_NOINLINE type_record()
         : multiple_inheritance(false), dynamic_attr(false), buffer_protocol(false),
-          default_holder(true), module_local(false), is_final(false) { }
+          default_holder(true), module_local(false), is_final(false) {}
 
     /// Handle to the parent scope
     handle scope;
@@ -310,22 +325,22 @@ struct type_record {
     /// Is the class inheritable from python classes?
     bool is_final : 1;
 
-    PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *)) {
+    PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *) ) {
         auto *base_info = detail::get_type_info(base, false);
         if (!base_info) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
-            pybind11_fail("generic_type: type \"" + std::string(name) +
-                          "\" referenced unknown base type \"" + tname + "\"");
+            pybind11_fail("generic_type: type \"" + std::string(name)
+                          + "\" referenced unknown base type \"" + tname + "\"");
         }
 
         if (default_holder != base_info->default_holder) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
-            pybind11_fail("generic_type: type \"" + std::string(name) + "\" " +
-                    (default_holder ? "does not have" : "has") +
-                    " a non-default holder type while its base \"" + tname + "\" " +
-                    (base_info->default_holder ? "does not" : "does"));
+            pybind11_fail("generic_type: type \"" + std::string(name) + "\" "
+                          + (default_holder ? "does not have" : "has")
+                          + " a non-default holder type while its base \"" + tname + "\" "
+                          + (base_info->default_holder ? "does not" : "does"));
         }
 
         bases.append((PyObject *) base_info->type);
@@ -340,14 +355,13 @@ struct type_record {
     }
 };
 
-inline function_call::function_call(const function_record &f, handle p) :
-        func(f), parent(p) {
+inline function_call::function_call(const function_record &f, handle p) : func(f), parent(p) {
     args.reserve(f.nargs);
     args_convert.reserve(f.nargs);
 }
 
 /// Tag for a new-style `__init__` defined in `detail/init.h`
-struct is_new_style_constructor { };
+struct is_new_style_constructor {};
 
 /**
  * Partial template specializations to process custom attributes provided to
@@ -355,60 +369,79 @@ struct is_new_style_constructor { };
  * fields in the type_record and function_record data structures or executed at
  * runtime to deal with custom call policies (e.g. keep_alive).
  */
-template <typename T, typename SFINAE = void> struct process_attribute;
+template <typename T, typename SFINAE = void>
+struct process_attribute;
 
-template <typename T> struct process_attribute_default {
+template <typename T>
+struct process_attribute_default {
     /// Default implementation: do nothing
-    static void init(const T &, function_record *) { }
-    static void init(const T &, type_record *) { }
-    static void precall(function_call &) { }
-    static void postcall(function_call &, handle) { }
+    static void init(const T &, function_record *) {}
+    static void init(const T &, type_record *) {}
+    static void precall(function_call &) {}
+    static void postcall(function_call &, handle) {}
 };
 
 /// Process an attribute specifying the function's name
-template <> struct process_attribute<name> : process_attribute_default<name> {
+template <>
+struct process_attribute<name> : process_attribute_default<name> {
     static void init(const name &n, function_record *r) { r->name = const_cast<char *>(n.value); }
 };
 
 /// Process an attribute specifying the function's docstring
-template <> struct process_attribute<doc> : process_attribute_default<doc> {
+template <>
+struct process_attribute<doc> : process_attribute_default<doc> {
     static void init(const doc &n, function_record *r) { r->doc = const_cast<char *>(n.value); }
 };
 
 /// Process an attribute specifying the function's docstring (provided as a C-style string)
-template <> struct process_attribute<const char *> : process_attribute_default<const char *> {
+template <>
+struct process_attribute<const char *> : process_attribute_default<const char *> {
     static void init(const char *d, function_record *r) { r->doc = const_cast<char *>(d); }
     static void init(const char *d, type_record *r) { r->doc = const_cast<char *>(d); }
 };
-template <> struct process_attribute<char *> : process_attribute<const char *> { };
+template <>
+struct process_attribute<char *> : process_attribute<const char *> {};
 
 /// Process an attribute indicating the function's return value policy
-template <> struct process_attribute<return_value_policy> : process_attribute_default<return_value_policy> {
+template <>
+struct process_attribute<return_value_policy> : process_attribute_default<return_value_policy> {
     static void init(const return_value_policy &p, function_record *r) { r->policy = p; }
 };
 
-/// Process an attribute which indicates that this is an overloaded function associated with a given sibling
-template <> struct process_attribute<sibling> : process_attribute_default<sibling> {
+/// Process an attribute which indicates that this is an overloaded function associated with a
+/// given sibling
+template <>
+struct process_attribute<sibling> : process_attribute_default<sibling> {
     static void init(const sibling &s, function_record *r) { r->sibling = s.value; }
 };
 
 /// Process an attribute which indicates that this function is a method
-template <> struct process_attribute<is_method> : process_attribute_default<is_method> {
-    static void init(const is_method &s, function_record *r) { r->is_method = true; r->scope = s.class_; }
+template <>
+struct process_attribute<is_method> : process_attribute_default<is_method> {
+    static void init(const is_method &s, function_record *r) {
+        r->is_method = true;
+        r->scope = s.class_;
+    }
 };
 
 /// Process an attribute which indicates the parent scope of a method
-template <> struct process_attribute<scope> : process_attribute_default<scope> {
+template <>
+struct process_attribute<scope> : process_attribute_default<scope> {
     static void init(const scope &s, function_record *r) { r->scope = s.value; }
 };
 
 /// Process an attribute which indicates that this function is an operator
-template <> struct process_attribute<is_operator> : process_attribute_default<is_operator> {
+template <>
+struct process_attribute<is_operator> : process_attribute_default<is_operator> {
     static void init(const is_operator &, function_record *r) { r->is_operator = true; }
 };
 
-template <> struct process_attribute<is_new_style_constructor> : process_attribute_default<is_new_style_constructor> {
-    static void init(const is_new_style_constructor &, function_record *r) { r->is_new_style_constructor = true; }
+template <>
+struct process_attribute<is_new_style_constructor>
+    : process_attribute_default<is_new_style_constructor> {
+    static void init(const is_new_style_constructor &, function_record *r) {
+        r->is_new_style_constructor = true;
+    }
 };
 
 inline void check_kw_only_arg(const arg &a, function_record *r) {
@@ -425,7 +458,8 @@ inline void append_self_arg_if_needed(function_record *r) {
 }
 
 /// Process a keyword argument attribute (*without* a default value)
-template <> struct process_attribute<arg> : process_attribute_default<arg> {
+template <>
+struct process_attribute<arg> : process_attribute_default<arg> {
     static void init(const arg &a, function_record *r) {
         append_self_arg_if_needed(r);
         r->args.emplace_back(a.name, nullptr, handle(), !a.flag_noconvert, a.flag_none);
@@ -435,7 +469,8 @@ template <> struct process_attribute<arg> : process_attribute_default<arg> {
 };
 
 /// Process a keyword argument attribute (*with* a default value)
-template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
+template <>
+struct process_attribute<arg_v> : process_attribute_default<arg_v> {
     static void init(const arg_v &a, function_record *r) {
         if (r->is_method && r->args.empty()) {
             r->args.emplace_back(
@@ -451,15 +486,16 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
             descr += a.type + "'";
             if (r->is_method) {
                 if (r->name) {
-                    descr += " in method '" + (std::string) str(r->scope) + "." + (std::string) r->name + "'";
+                    descr += " in method '" + (std::string) str(r->scope) + "."
+                             + (std::string) r->name + "'";
                 } else {
                     descr += " in method of '" + (std::string) str(r->scope) + "'";
                 }
             } else if (r->name) {
                 descr += " in function '" + (std::string) r->name + "'";
             }
-            pybind11_fail("arg(): could not convert default argument "
-                          + descr + " into a Python object (type not registered yet?)");
+            pybind11_fail("arg(): could not convert default argument " + descr
+                          + " into a Python object (type not registered yet?)");
 #else
             pybind11_fail("arg(): could not convert default argument "
                           "into a Python object (type not registered yet?). "
@@ -473,7 +509,8 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 };
 
 /// Process a keyword-only-arguments-follow pseudo argument
-template <> struct process_attribute<kw_only> : process_attribute_default<kw_only> {
+template <>
+struct process_attribute<kw_only> : process_attribute_default<kw_only> {
     static void init(const kw_only &, function_record *r) {
         append_self_arg_if_needed(r);
         if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size())) {
@@ -485,20 +522,23 @@ template <> struct process_attribute<kw_only> : process_attribute_default<kw_onl
 };
 
 /// Process a positional-only-argument maker
-template <> struct process_attribute<pos_only> : process_attribute_default<pos_only> {
+template <>
+struct process_attribute<pos_only> : process_attribute_default<pos_only> {
     static void init(const pos_only &, function_record *r) {
         append_self_arg_if_needed(r);
         r->nargs_pos_only = static_cast<std::uint16_t>(r->args.size());
         if (r->nargs_pos_only > r->nargs_pos) {
             pybind11_fail("pos_only(): cannot follow a py::args() argument");
         }
-            // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
+        // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
     }
 };
 
-/// Process a parent class attribute.  Single inheritance only (class_ itself already guarantees that)
+/// Process a parent class attribute.  Single inheritance only (class_ itself already guarantees
+/// that)
 template <typename T>
-struct process_attribute<T, enable_if_t<is_pyobject<T>::value>> : process_attribute_default<handle> {
+struct process_attribute<T, enable_if_t<is_pyobject<T>::value>>
+    : process_attribute_default<handle> {
     static void init(const handle &h, type_record *r) { r->bases.append(h); }
 };
 
@@ -511,7 +551,9 @@ struct process_attribute<base<T>> : process_attribute_default<base<T>> {
 /// Process a multiple inheritance attribute
 template <>
 struct process_attribute<multiple_inheritance> : process_attribute_default<multiple_inheritance> {
-    static void init(const multiple_inheritance &, type_record *r) { r->multiple_inheritance = true; }
+    static void init(const multiple_inheritance &, type_record *r) {
+        r->multiple_inheritance = true;
+    }
 };
 
 template <>
@@ -557,34 +599,41 @@ template <>
 struct process_attribute<arithmetic> : process_attribute_default<arithmetic> {};
 
 template <typename... Ts>
-struct process_attribute<call_guard<Ts...>> : process_attribute_default<call_guard<Ts...>> { };
+struct process_attribute<call_guard<Ts...>> : process_attribute_default<call_guard<Ts...>> {};
 
 /**
  * Process a keep_alive call policy -- invokes keep_alive_impl during the
  * pre-call handler if both Nurse, Patient != 0 and use the post-call handler
  * otherwise
  */
-template <size_t Nurse, size_t Patient> struct process_attribute<keep_alive<Nurse, Patient>> : public process_attribute_default<keep_alive<Nurse, Patient>> {
+template <size_t Nurse, size_t Patient>
+struct process_attribute<keep_alive<Nurse, Patient>>
+    : public process_attribute_default<keep_alive<Nurse, Patient>> {
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
-    static void precall(function_call &call) { keep_alive_impl(Nurse, Patient, call, handle()); }
+    static void precall(function_call &call) {
+        keep_alive_impl(Nurse, Patient, call, handle());
+    }
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
-    static void postcall(function_call &, handle) { }
+    static void postcall(function_call &, handle) {}
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
-    static void precall(function_call &) { }
+    static void precall(function_call &) {}
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
-    static void postcall(function_call &call, handle ret) { keep_alive_impl(Nurse, Patient, call, ret); }
+    static void postcall(function_call &call, handle ret) {
+        keep_alive_impl(Nurse, Patient, call, ret);
+    }
 };
 
 /// Recursively iterate over variadic template arguments
-template <typename... Args> struct process_attributes {
-    static void init(const Args&... args, function_record *r) {
+template <typename... Args>
+struct process_attributes {
+    static void init(const Args &...args, function_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
         (void) expander{
             0, ((void) process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
     }
-    static void init(const Args&... args, type_record *r) {
+    static void init(const Args &...args, type_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
@@ -616,7 +665,7 @@ using extract_guard_t = typename exactly_one_t<is_call_guard, call_guard<>, Extr
 /// Check the number of named arguments at compile time
 template <typename... Extra,
           size_t named = constexpr_sum(std::is_base_of<arg, Extra>::value...),
-          size_t self  = constexpr_sum(std::is_same<is_method, Extra>::value...)>
+          size_t self = constexpr_sum(std::is_same<is_method, Extra>::value...)>
 constexpr bool expected_num_args(size_t nargs, bool has_args, bool has_kwargs) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(nargs, has_args, has_kwargs);
     return named == 0 || (self + named + size_t(has_args) + size_t(has_kwargs)) == nargs;
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 9f1d047801..06120d5563 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -44,8 +44,8 @@ struct buffer_info {
     void *ptr = nullptr;          // Pointer to the underlying storage
     ssize_t itemsize = 0;         // Size of individual items in bytes
     ssize_t size = 0;             // Total number of entries
-    std::string format; // For homogeneous buffers, this should be set to
-                        // format_descriptor<T>::format()
+    std::string format;           // For homogeneous buffers, this should be set to
+                                  // format_descriptor<T>::format()
     ssize_t ndim = 0;             // Number of dimensions
     std::vector<ssize_t> shape;   // Shape of the tensor (1 entry per dimension)
     std::vector<ssize_t> strides; // Number of bytes between adjacent entries
@@ -54,10 +54,15 @@ struct buffer_info {
 
     buffer_info() = default;
 
-    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
-                detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
-    : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
-      shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
+    buffer_info(void *ptr,
+                ssize_t itemsize,
+                const std::string &format,
+                ssize_t ndim,
+                detail::any_container<ssize_t> shape_in,
+                detail::any_container<ssize_t> strides_in,
+                bool readonly = false)
+        : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
+          shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
         if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size()) {
             pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
         }
@@ -67,29 +72,48 @@ struct buffer_info {
     }
 
     template <typename T>
-    buffer_info(T *ptr, detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
-    : buffer_info(private_ctr_tag(), ptr, sizeof(T), format_descriptor<T>::format(), static_cast<ssize_t>(shape_in->size()), std::move(shape_in), std::move(strides_in), readonly) { }
-
-    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t size, bool readonly=false)
-    : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}, readonly) { }
+    buffer_info(T *ptr,
+                detail::any_container<ssize_t> shape_in,
+                detail::any_container<ssize_t> strides_in,
+                bool readonly = false)
+        : buffer_info(private_ctr_tag(),
+                      ptr,
+                      sizeof(T),
+                      format_descriptor<T>::format(),
+                      static_cast<ssize_t>(shape_in->size()),
+                      std::move(shape_in),
+                      std::move(strides_in),
+                      readonly) {}
+
+    buffer_info(void *ptr,
+                ssize_t itemsize,
+                const std::string &format,
+                ssize_t size,
+                bool readonly = false)
+        : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}, readonly) {}
 
     template <typename T>
-    buffer_info(T *ptr, ssize_t size, bool readonly=false)
-    : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size, readonly) { }
+    buffer_info(T *ptr, ssize_t size, bool readonly = false)
+        : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size, readonly) {}
 
     template <typename T>
-    buffer_info(const T *ptr, ssize_t size, bool readonly=true)
-    : buffer_info(const_cast<T*>(ptr), sizeof(T), format_descriptor<T>::format(), size, readonly) { }
+    buffer_info(const T *ptr, ssize_t size, bool readonly = true)
+        : buffer_info(
+            const_cast<T *>(ptr), sizeof(T), format_descriptor<T>::format(), size, readonly) {}
 
     explicit buffer_info(Py_buffer *view, bool ownview = true)
-    : buffer_info(view->buf, view->itemsize, view->format, view->ndim,
+        : buffer_info(
+            view->buf,
+            view->itemsize,
+            view->format,
+            view->ndim,
             {view->shape, view->shape + view->ndim},
             /* Though buffer::request() requests PyBUF_STRIDES, ctypes objects
              * ignore this flag and return a view with NULL strides.
              * When strides are NULL, build them manually.  */
             view->strides
-            ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
-            : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
+                ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
+                : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
             (view->readonly != 0)) {
         // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         this->m_view = view;
@@ -98,7 +122,7 @@ struct buffer_info {
     }
 
     buffer_info(const buffer_info &) = delete;
-    buffer_info& operator=(const buffer_info &) = delete;
+    buffer_info &operator=(const buffer_info &) = delete;
 
     buffer_info(buffer_info &&other) noexcept { (*this) = std::move(other); }
 
@@ -117,17 +141,28 @@ struct buffer_info {
     }
 
     ~buffer_info() {
-        if (m_view && ownview) { PyBuffer_Release(m_view); delete m_view; }
+        if (m_view && ownview) {
+            PyBuffer_Release(m_view);
+            delete m_view;
+        }
     }
 
     Py_buffer *view() const { return m_view; }
     Py_buffer *&view() { return m_view; }
-private:
-    struct private_ctr_tag { };
 
-    buffer_info(private_ctr_tag, void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
-                detail::any_container<ssize_t> &&shape_in, detail::any_container<ssize_t> &&strides_in, bool readonly)
-    : buffer_info(ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) { }
+private:
+    struct private_ctr_tag {};
+
+    buffer_info(private_ctr_tag,
+                void *ptr,
+                ssize_t itemsize,
+                const std::string &format,
+                ssize_t ndim,
+                detail::any_container<ssize_t> &&shape_in,
+                detail::any_container<ssize_t> &&strides_in,
+                bool readonly)
+        : buffer_info(
+            ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) {}
 
     Py_buffer *m_view = nullptr;
     bool ownview = false;
@@ -135,17 +170,22 @@ struct buffer_info {
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T, typename SFINAE = void> struct compare_buffer_info {
-    static bool compare(const buffer_info& b) {
+template <typename T, typename SFINAE = void>
+struct compare_buffer_info {
+    static bool compare(const buffer_info &b) {
         return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
     }
 };
 
-template <typename T> struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
-    static bool compare(const buffer_info& b) {
-        return (size_t) b.itemsize == sizeof(T) && (b.format == format_descriptor<T>::value ||
-            ((sizeof(T) == sizeof(long)) && b.format == (std::is_unsigned<T>::value ? "L" : "l")) ||
-            ((sizeof(T) == sizeof(size_t)) && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
+template <typename T>
+struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
+    static bool compare(const buffer_info &b) {
+        return (size_t) b.itemsize == sizeof(T)
+               && (b.format == format_descriptor<T>::value
+                   || ((sizeof(T) == sizeof(long))
+                       && b.format == (std::is_unsigned<T>::value ? "L" : "l"))
+                   || ((sizeof(T) == sizeof(size_t))
+                       && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
     }
 };
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 4f65356e08..2622e5819d 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -10,11 +10,12 @@
 
 #pragma once
 
-#include "pytypes.h"
 #include "detail/common.h"
 #include "detail/descr.h"
 #include "detail/type_caster_base.h"
 #include "detail/typeid.h"
+#include "pytypes.h"
+
 #include <array>
 #include <cstring>
 #include <functional>
@@ -30,35 +31,42 @@
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename type, typename SFINAE = void> class type_caster : public type_caster_base<type> { };
-template <typename type> using make_caster = type_caster<intrinsic_t<type>>;
+template <typename type, typename SFINAE = void>
+class type_caster : public type_caster_base<type> {};
+template <typename type>
+using make_caster = type_caster<intrinsic_t<type>>;
 
 // Shortcut for calling a caster's `cast_op_type` cast operator for casting a type_caster to a T
-template <typename T> typename make_caster<T>::template cast_op_type<T> cast_op(make_caster<T> &caster) {
+template <typename T>
+typename make_caster<T>::template cast_op_type<T> cast_op(make_caster<T> &caster) {
     return caster.operator typename make_caster<T>::template cast_op_type<T>();
 }
-template <typename T> typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>
+template <typename T>
+typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>
 cast_op(make_caster<T> &&caster) {
-    return std::move(caster).operator
-        typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>();
+    return std::move(caster).operator typename make_caster<T>::
+        template cast_op_type<typename std::add_rvalue_reference<T>::type>();
 }
 
-template <typename type> class type_caster<std::reference_wrapper<type>> {
+template <typename type>
+class type_caster<std::reference_wrapper<type>> {
 private:
     using caster_t = make_caster<type>;
     caster_t subcaster;
-    using reference_t = type&;
-    using subcaster_cast_op_type =
-        typename caster_t::template cast_op_type<reference_t>;
-
-    static_assert(std::is_same<typename std::remove_const<type>::type &, subcaster_cast_op_type>::value ||
-                  std::is_same<reference_t, subcaster_cast_op_type>::value,
-                  "std::reference_wrapper<T> caster requires T to have a caster with an "
-                  "`operator T &()` or `operator const T &()`");
+    using reference_t = type &;
+    using subcaster_cast_op_type = typename caster_t::template cast_op_type<reference_t>;
+
+    static_assert(
+        std::is_same<typename std::remove_const<type>::type &, subcaster_cast_op_type>::value
+            || std::is_same<reference_t, subcaster_cast_op_type>::value,
+        "std::reference_wrapper<T> caster requires T to have a caster with an "
+        "`operator T &()` or `operator const T &()`");
+
 public:
     bool load(handle src, bool convert) { return subcaster.load(src, convert); }
     static constexpr auto name = caster_t::name;
-    static handle cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
+    static handle
+    cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
         // It is definitely wrong to take ownership of this pointer, so mask that rvp
         if (policy == return_value_policy::take_ownership
             || policy == return_value_policy::automatic) {
@@ -66,7 +74,8 @@ template <typename type> class type_caster<std::reference_wrapper<type>> {
         }
         return caster_t::cast(&src.get(), policy, parent);
     }
-    template <typename T> using cast_op_type = std::reference_wrapper<type>;
+    template <typename T>
+    using cast_op_type = std::reference_wrapper<type>;
     explicit operator std::reference_wrapper<type>() { return cast_op<type &>(subcaster); }
 };
 
@@ -93,24 +102,25 @@ public:
     template <typename T_>                                                                        \
     using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
 
-template <typename CharT> using is_std_char_type = any_of<
-    std::is_same<CharT, char>, /* std::string */
+template <typename CharT>
+using is_std_char_type = any_of<std::is_same<CharT, char>, /* std::string */
 #if defined(PYBIND11_HAS_U8STRING)
-    std::is_same<CharT, char8_t>, /* std::u8string */
+                                std::is_same<CharT, char8_t>, /* std::u8string */
 #endif
-    std::is_same<CharT, char16_t>, /* std::u16string */
-    std::is_same<CharT, char32_t>, /* std::u32string */
-    std::is_same<CharT, wchar_t> /* std::wstring */
->;
-
+                                std::is_same<CharT, char16_t>, /* std::u16string */
+                                std::is_same<CharT, char32_t>, /* std::u32string */
+                                std::is_same<CharT, wchar_t>   /* std::wstring */
+                                >;
 
 template <typename T>
 struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_type<T>::value>> {
     using _py_type_0 = conditional_t<sizeof(T) <= sizeof(long), long, long long>;
-    using _py_type_1 = conditional_t<std::is_signed<T>::value, _py_type_0, typename std::make_unsigned<_py_type_0>::type>;
+    using _py_type_1 = conditional_t<std::is_signed<T>::value,
+                                     _py_type_0,
+                                     typename std::make_unsigned<_py_type_0>::type>;
     using py_type = conditional_t<std::is_floating_point<T>::value, double, _py_type_1>;
-public:
 
+public:
     bool load(handle src, bool convert) {
         py_type py_value;
 
@@ -140,14 +150,13 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
             // PyPy: 7.3.7's 3.8 does not implement PyLong_*'s __index__ calls.
 #if PY_VERSION_HEX < 0x03080000 || defined(PYPY_VERSION)
             object index;
-            if (!PYBIND11_LONG_CHECK(src.ptr())) {  // So: index_check(src.ptr())
+            if (!PYBIND11_LONG_CHECK(src.ptr())) { // So: index_check(src.ptr())
                 index = reinterpret_steal<object>(PyNumber_Index(src.ptr()));
                 if (!index) {
                     PyErr_Clear();
                     if (!convert)
                         return false;
-                }
-                else {
+                } else {
                     src_or_index = index;
                 }
             }
@@ -156,8 +165,8 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
                 py_value = as_unsigned<py_type>(src_or_index.ptr());
             } else { // signed integer:
                 py_value = sizeof(T) <= sizeof(long)
-                    ? (py_type) PyLong_AsLong(src_or_index.ptr())
-                    : (py_type) PYBIND11_LONG_AS_LONGLONG(src_or_index.ptr());
+                               ? (py_type) PyLong_AsLong(src_or_index.ptr())
+                               : (py_type) PYBIND11_LONG_AS_LONGLONG(src_or_index.ptr());
             }
         }
 
@@ -166,12 +175,14 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
 
         // Check to see if the conversion is valid (integers should match exactly)
         // Signed/unsigned checks happen elsewhere
-        if (py_err || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T) && py_value != (py_type) (T) py_value)) {
+        if (py_err
+            || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T)
+                && py_value != (py_type) (T) py_value)) {
             PyErr_Clear();
             if (py_err && convert && (PyNumber_Check(src.ptr()) != 0)) {
                 auto tmp = reinterpret_steal<object>(std::is_floating_point<T>::value
-                                                     ? PyNumber_Float(src.ptr())
-                                                     : PyNumber_Long(src.ptr()));
+                                                         ? PyNumber_Float(src.ptr())
+                                                         : PyNumber_Long(src.ptr()));
                 PyErr_Clear();
                 return load(tmp, false);
             }
@@ -182,32 +193,40 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
         return true;
     }
 
-    template<typename U = T>
+    template <typename U = T>
     static typename std::enable_if<std::is_floating_point<U>::value, handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PyFloat_FromDouble((double) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) <= sizeof(long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value
+                                       && (sizeof(U) <= sizeof(long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PYBIND11_LONG_FROM_SIGNED((long) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) <= sizeof(unsigned long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value
+                                       && (sizeof(U) <= sizeof(unsigned long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PYBIND11_LONG_FROM_UNSIGNED((unsigned long) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) > sizeof(long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value
+                                       && (sizeof(U) > sizeof(long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PyLong_FromLongLong((long long) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) > sizeof(unsigned long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value
+                                       && (sizeof(U) > sizeof(unsigned long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PyLong_FromUnsignedLongLong((unsigned long long) src);
     }
@@ -215,7 +234,8 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
     PYBIND11_TYPE_CASTER(T, const_name<std::is_integral<T>::value>("int", "float"));
 };
 
-template<typename T> struct void_caster {
+template <typename T>
+struct void_caster {
 public:
     bool load(handle src, bool) {
         if (src && src.is_none()) {
@@ -229,9 +249,11 @@ template<typename T> struct void_caster {
     PYBIND11_TYPE_CASTER(T, const_name("None"));
 };
 
-template <> class type_caster<void_type> : public void_caster<void_type> {};
+template <>
+class type_caster<void_type> : public void_caster<void_type> {};
 
-template <> class type_caster<void> : public type_caster<void_type> {
+template <>
+class type_caster<void> : public type_caster<void_type> {
 public:
     using type_caster<void_type>::cast;
 
@@ -268,16 +290,20 @@ template <> class type_caster<void> : public type_caster<void_type> {
         return none().inc_ref();
     }
 
-    template <typename T> using cast_op_type = void*&;
+    template <typename T>
+    using cast_op_type = void *&;
     explicit operator void *&() { return value; }
     static constexpr auto name = const_name("capsule");
+
 private:
     void *value = nullptr;
 };
 
-template <> class type_caster<std::nullptr_t> : public void_caster<std::nullptr_t> { };
+template <>
+class type_caster<std::nullptr_t> : public void_caster<std::nullptr_t> {};
 
-template <> class type_caster<bool> {
+template <>
+class type_caster<bool> {
 public:
     bool load(handle src, bool convert) {
         if (!src) {
@@ -296,14 +322,14 @@ template <> class type_caster<bool> {
 
             Py_ssize_t res = -1;
             if (src.is_none()) {
-                res = 0;  // None is implicitly converted to False
+                res = 0; // None is implicitly converted to False
             }
-            #if defined(PYPY_VERSION)
+#if defined(PYPY_VERSION)
             // On PyPy, check that "__bool__" (or "__nonzero__" on Python 2.7) attr exists
             else if (hasattr(src, PYBIND11_BOOL_ATTR)) {
                 res = PyObject_IsTrue(src.ptr());
             }
-            #else
+#else
             // Alternate approach for CPython: this does the same as the above, but optimized
             // using the CPython API so as to avoid an unneeded attribute lookup.
             else if (auto *tp_as_number = src.ptr()->ob_type->tp_as_number) {
@@ -311,7 +337,7 @@ template <> class type_caster<bool> {
                     res = (*PYBIND11_NB_BOOL(tp_as_number))(src.ptr());
                 }
             }
-            #endif
+#endif
             if (res == 0 || res == 1) {
                 value = (res != 0);
                 return true;
@@ -327,20 +353,25 @@ template <> class type_caster<bool> {
 };
 
 // Helper class for UTF-{8,16,32} C++ stl strings:
-template <typename StringType, bool IsView = false> struct string_caster {
+template <typename StringType, bool IsView = false>
+struct string_caster {
     using CharT = typename StringType::value_type;
 
     // Simplify life by being able to assume standard char sizes (the standard only guarantees
     // minimums, but Python requires exact sizes)
-    static_assert(!std::is_same<CharT, char>::value || sizeof(CharT) == 1, "Unsupported char size != 1");
+    static_assert(!std::is_same<CharT, char>::value || sizeof(CharT) == 1,
+                  "Unsupported char size != 1");
 #if defined(PYBIND11_HAS_U8STRING)
-    static_assert(!std::is_same<CharT, char8_t>::value || sizeof(CharT) == 1, "Unsupported char8_t size != 1");
+    static_assert(!std::is_same<CharT, char8_t>::value || sizeof(CharT) == 1,
+                  "Unsupported char8_t size != 1");
 #endif
-    static_assert(!std::is_same<CharT, char16_t>::value || sizeof(CharT) == 2, "Unsupported char16_t size != 2");
-    static_assert(!std::is_same<CharT, char32_t>::value || sizeof(CharT) == 4, "Unsupported char32_t size != 4");
+    static_assert(!std::is_same<CharT, char16_t>::value || sizeof(CharT) == 2,
+                  "Unsupported char16_t size != 2");
+    static_assert(!std::is_same<CharT, char32_t>::value || sizeof(CharT) == 4,
+                  "Unsupported char32_t size != 4");
     // wchar_t can be either 16 bits (Windows) or 32 (everywhere else)
     static_assert(!std::is_same<CharT, wchar_t>::value || sizeof(CharT) == 2 || sizeof(CharT) == 4,
-            "Unsupported wchar_t size != 2/4");
+                  "Unsupported wchar_t size != 2/4");
     static constexpr size_t UTF_N = 8 * sizeof(CharT);
 
     bool load(handle src, bool) {
@@ -364,7 +395,10 @@ template <typename StringType, bool IsView = false> struct string_caster {
                 return false;
 
             temp = reinterpret_steal<object>(PyUnicode_FromObject(load_src.ptr()));
-            if (!temp) { PyErr_Clear(); return false; }
+            if (!temp) {
+                PyErr_Clear();
+                return false;
+            }
             load_src = temp;
 #endif
         }
@@ -385,11 +419,19 @@ template <typename StringType, bool IsView = false> struct string_caster {
         }
 #endif
 
-        auto utfNbytes = reinterpret_steal<object>(PyUnicode_AsEncodedString(
-            load_src.ptr(), UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr));
-        if (!utfNbytes) { PyErr_Clear(); return false; }
+        auto utfNbytes
+            = reinterpret_steal<object>(PyUnicode_AsEncodedString(load_src.ptr(),
+                                                                  UTF_N == 8    ? "utf-8"
+                                                                  : UTF_N == 16 ? "utf-16"
+                                                                                : "utf-32",
+                                                                  nullptr));
+        if (!utfNbytes) {
+            PyErr_Clear();
+            return false;
+        }
 
-        const auto *buffer = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
+        const auto *buffer
+            = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
         size_t length = (size_t) PYBIND11_BYTES_SIZE(utfNbytes.ptr()) / sizeof(CharT);
         // Skip BOM for UTF-16/32
         if (PYBIND11_SILENCE_MSVC_C4127(UTF_N > 8)) {
@@ -406,7 +448,8 @@ template <typename StringType, bool IsView = false> struct string_caster {
         return true;
     }
 
-    static handle cast(const StringType &src, return_value_policy /* policy */, handle /* parent */) {
+    static handle
+    cast(const StringType &src, return_value_policy /* policy */, handle /* parent */) {
         const char *buffer = reinterpret_cast<const char *>(src.data());
         auto nbytes = ssize_t(src.size() * sizeof(CharT));
         handle s = decode_utfN(buffer, nbytes);
@@ -421,14 +464,19 @@ template <typename StringType, bool IsView = false> struct string_caster {
 private:
     static handle decode_utfN(const char *buffer, ssize_t nbytes) {
 #if !defined(PYPY_VERSION)
-        return
-            UTF_N == 8  ? PyUnicode_DecodeUTF8(buffer, nbytes, nullptr) :
-            UTF_N == 16 ? PyUnicode_DecodeUTF16(buffer, nbytes, nullptr, nullptr) :
-                          PyUnicode_DecodeUTF32(buffer, nbytes, nullptr, nullptr);
+        return UTF_N == 8    ? PyUnicode_DecodeUTF8(buffer, nbytes, nullptr)
+               : UTF_N == 16 ? PyUnicode_DecodeUTF16(buffer, nbytes, nullptr, nullptr)
+                             : PyUnicode_DecodeUTF32(buffer, nbytes, nullptr, nullptr);
 #else
-        // PyPy segfaults when on PyUnicode_DecodeUTF16 (and possibly on PyUnicode_DecodeUTF32 as well),
-        // so bypass the whole thing by just passing the encoding as a string value, which works properly:
-        return PyUnicode_Decode(buffer, nbytes, UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr);
+        // PyPy segfaults when on PyUnicode_DecodeUTF16 (and possibly on PyUnicode_DecodeUTF32 as
+        // well), so bypass the whole thing by just passing the encoding as a string value, which
+        // works properly:
+        return PyUnicode_Decode(buffer,
+                                nbytes,
+                                UTF_N == 8    ? "utf-8"
+                                : UTF_N == 16 ? "utf-16"
+                                              : "utf-32",
+                                nullptr);
 #endif
     }
 
@@ -451,27 +499,33 @@ template <typename StringType, bool IsView = false> struct string_caster {
     }
 
     template <typename C = CharT>
-    bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) { return false; }
+    bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) {
+        return false;
+    }
 };
 
 template <typename CharT, class Traits, class Allocator>
-struct type_caster<std::basic_string<CharT, Traits, Allocator>, enable_if_t<is_std_char_type<CharT>::value>>
+struct type_caster<std::basic_string<CharT, Traits, Allocator>,
+                   enable_if_t<is_std_char_type<CharT>::value>>
     : string_caster<std::basic_string<CharT, Traits, Allocator>> {};
 
 #ifdef PYBIND11_HAS_STRING_VIEW
 template <typename CharT, class Traits>
-struct type_caster<std::basic_string_view<CharT, Traits>, enable_if_t<is_std_char_type<CharT>::value>>
+struct type_caster<std::basic_string_view<CharT, Traits>,
+                   enable_if_t<is_std_char_type<CharT>::value>>
     : string_caster<std::basic_string_view<CharT, Traits>, true> {};
 #endif
 
 // Type caster for C-style strings.  We basically use a std::string type caster, but also add the
 // ability to use None as a nullptr char* (which the string caster doesn't allow).
-template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
+template <typename CharT>
+struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
     using StringType = std::basic_string<CharT>;
     using StringCaster = type_caster<StringType>;
     StringCaster str_caster;
     bool none = false;
     CharT one_char = 0;
+
 public:
     bool load(handle src, bool convert) {
         if (!src) {
@@ -521,10 +575,10 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         }
 
         // If we're in UTF-8 mode, we have two possible failures: one for a unicode character that
-        // is too high, and one for multiple unicode characters (caught later), so we need to figure
-        // out how long the first encoded character is in bytes to distinguish between these two
-        // errors.  We also allow want to allow unicode characters U+0080 through U+00FF, as those
-        // can fit into a single char value.
+        // is too high, and one for multiple unicode characters (caught later), so we need to
+        // figure out how long the first encoded character is in bytes to distinguish between these
+        // two errors.  We also allow want to allow unicode characters U+0080 through U+00FF, as
+        // those can fit into a single char value.
         if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 8) && str_len > 1 && str_len <= 4) {
             auto v0 = static_cast<unsigned char>(value[0]);
             // low bits only: 0-127
@@ -539,7 +593,8 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
             if (char0_bytes == str_len) {
                 // If we have a 128-255 value, we can decode it into a single char:
                 if (char0_bytes == 2 && (v0 & 0xFC) == 0xC0) { // 0x110000xx 0x10xxxxxx
-                    one_char = static_cast<CharT>(((v0 & 3) << 6) + (static_cast<unsigned char>(value[1]) & 0x3F));
+                    one_char = static_cast<CharT>(((v0 & 3) << 6)
+                                                  + (static_cast<unsigned char>(value[1]) & 0x3F));
                     return one_char;
                 }
                 // Otherwise we have a single character, but it's > U+00FF
@@ -566,16 +621,18 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
     }
 
     static constexpr auto name = const_name(PYBIND11_STRING_NAME);
-    template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
+    template <typename _T>
+    using cast_op_type = pybind11::detail::cast_op_type<_T>;
 };
 
 // Base implementation for std::tuple and std::pair
-template <template<typename...> class Tuple, typename... Ts> class tuple_caster {
+template <template <typename...> class Tuple, typename... Ts>
+class tuple_caster {
     using type = Tuple<Ts...>;
     static constexpr auto size = sizeof...(Ts);
     using indices = make_index_sequence<size>;
-public:
 
+public:
     bool load(handle src, bool convert) {
         if (!isinstance<sequence>(src)) {
             return false;
@@ -606,18 +663,24 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
         return cast(*src, policy, parent);
     }
 
-    static constexpr auto name = const_name("Tuple[") + concat(make_caster<Ts>::name...) + const_name("]");
+    static constexpr auto name
+        = const_name("Tuple[") + concat(make_caster<Ts>::name...) + const_name("]");
 
-    template <typename T> using cast_op_type = type;
+    template <typename T>
+    using cast_op_type = type;
 
     explicit operator type() & { return implicit_cast(indices{}); }
     explicit operator type() && { return std::move(*this).implicit_cast(indices{}); }
 
 protected:
     template <size_t... Is>
-    type implicit_cast(index_sequence<Is...>) & { return type(cast_op<Ts>(std::get<Is>(subcasters))...); }
+    type implicit_cast(index_sequence<Is...>) & {
+        return type(cast_op<Ts>(std::get<Is>(subcasters))...);
+    }
     template <size_t... Is>
-    type implicit_cast(index_sequence<Is...>) && { return type(cast_op<Ts>(std::move(std::get<Is>(subcasters)))...); }
+    type implicit_cast(index_sequence<Is...>) && {
+        return type(cast_op<Ts>(std::move(std::get<Is>(subcasters)))...);
+    }
 
     static constexpr bool load_impl(const sequence &, bool, index_sequence<>) { return true; }
 
@@ -639,12 +702,12 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
 
     /* Implementation: Convert a C++ tuple into a Python tuple */
     template <typename T, size_t... Is>
-    static handle cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
+    static handle
+    cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(src, policy, parent);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(policy, parent);
-        std::array<object, size> entries{{
-            reinterpret_steal<object>(make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...
-        }};
+        std::array<object, size> entries{{reinterpret_steal<object>(
+            make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...}};
         for (const auto &entry : entries) {
             if (!entry) {
                 return handle();
@@ -661,11 +724,11 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     Tuple<make_caster<Ts>...> subcasters;
 };
 
-template <typename T1, typename T2> class type_caster<std::pair<T1, T2>>
-    : public tuple_caster<std::pair, T1, T2> {};
+template <typename T1, typename T2>
+class type_caster<std::pair<T1, T2>> : public tuple_caster<std::pair, T1, T2> {};
 
-template <typename... Ts> class type_caster<std::tuple<Ts...>>
-    : public tuple_caster<std::tuple, Ts...> {};
+template <typename... Ts>
+class type_caster<std::tuple<Ts...>> : public tuple_caster<std::tuple, Ts...> {};
 
 /// Helper class which abstracts away certain actions. Users can provide specializations for
 /// custom holders, but it's only necessary if the type has a non-standard interface.
@@ -684,7 +747,7 @@ struct copyable_holder_caster : public type_caster_base<type> {
 public:
     using base = type_caster_base<type>;
     static_assert(std::is_base_of<base, type_caster<type>>::value,
-            "Holder classes are only supported for custom types");
+                  "Holder classes are only supported for custom types");
     using base::base;
     using base::cast;
     using base::typeinfo;
@@ -694,12 +757,12 @@ struct copyable_holder_caster : public type_caster_base<type> {
         return base::template load_impl<copyable_holder_caster<type, holder_type>>(src, convert);
     }
 
-    explicit operator type*() { return this->value; }
+    explicit operator type *() { return this->value; }
     // static_cast works around compiler error with MSVC 17 and CUDA 10.2
     // see issue #2180
-    explicit operator type&() { return *(static_cast<type *>(this->value)); }
-    explicit operator holder_type*() { return std::addressof(holder); }
-    explicit operator holder_type&() { return holder; }
+    explicit operator type &() { return *(static_cast<type *>(this->value)); }
+    explicit operator holder_type *() { return std::addressof(holder); }
+    explicit operator holder_type &() { return holder; }
 
     static handle cast(const holder_type &src, return_value_policy, handle) {
         const auto *ptr = holder_helper<holder_type>::get(src);
@@ -729,10 +792,14 @@ struct copyable_holder_caster : public type_caster_base<type> {
 #endif
     }
 
-    template <typename T = holder_type, detail::enable_if_t<!std::is_constructible<T, const T &, type*>::value, int> = 0>
-    bool try_implicit_casts(handle, bool) { return false; }
+    template <typename T = holder_type,
+              detail::enable_if_t<!std::is_constructible<T, const T &, type *>::value, int> = 0>
+    bool try_implicit_casts(handle, bool) {
+        return false;
+    }
 
-    template <typename T = holder_type, detail::enable_if_t<std::is_constructible<T, const T &, type*>::value, int> = 0>
+    template <typename T = holder_type,
+              detail::enable_if_t<std::is_constructible<T, const T &, type *>::value, int> = 0>
     bool try_implicit_casts(handle src, bool convert) {
         for (auto &cast : typeinfo->implicit_casts) {
             copyable_holder_caster sub_caster(*cast.first);
@@ -747,13 +814,12 @@ struct copyable_holder_caster : public type_caster_base<type> {
 
     static bool try_direct_conversions(handle) { return false; }
 
-
     holder_type holder;
 };
 
 /// Specialize for the common std::shared_ptr, so users don't need to
 template <typename T>
-class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::shared_ptr<T>> { };
+class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::shared_ptr<T>> {};
 
 /// Type caster for holder types like std::unique_ptr.
 /// Please consider the SFINAE hook an implementation detail, as explained
@@ -761,7 +827,7 @@ class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::sh
 template <typename type, typename holder_type, typename SFINAE = void>
 struct move_only_holder_caster {
     static_assert(std::is_base_of<type_caster_base<type>, type_caster<type>>::value,
-            "Holder classes are only supported for custom types");
+                  "Holder classes are only supported for custom types");
 
     static handle cast(holder_type &&src, return_value_policy, handle) {
         auto *ptr = holder_helper<holder_type>::get(src);
@@ -772,47 +838,87 @@ struct move_only_holder_caster {
 
 template <typename type, typename deleter>
 class type_caster<std::unique_ptr<type, deleter>>
-    : public move_only_holder_caster<type, std::unique_ptr<type, deleter>> { };
+    : public move_only_holder_caster<type, std::unique_ptr<type, deleter>> {};
 
 template <typename type, typename holder_type>
 using type_caster_holder = conditional_t<is_copy_constructible<holder_type>::value,
                                          copyable_holder_caster<type, holder_type>,
                                          move_only_holder_caster<type, holder_type>>;
 
-template <typename T, bool Value = false> struct always_construct_holder { static constexpr bool value = Value; };
+template <typename T, bool Value = false>
+struct always_construct_holder {
+    static constexpr bool value = Value;
+};
 
 /// Create a specialization for custom holder types (silently ignores std::shared_ptr)
-#define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type, ...) \
-    namespace pybind11 { namespace detail { \
-    template <typename type> \
-    struct always_construct_holder<holder_type> : always_construct_holder<void, ##__VA_ARGS__>  { }; \
-    template <typename type> \
-    class type_caster<holder_type, enable_if_t<!is_shared_ptr<holder_type>::value>> \
-        : public type_caster_holder<type, holder_type> { }; \
-    }}
+#define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type, ...)                                      \
+    namespace pybind11 {                                                                          \
+    namespace detail {                                                                            \
+    template <typename type>                                                                      \
+    struct always_construct_holder<holder_type> : always_construct_holder<void, ##__VA_ARGS__> {  \
+    };                                                                                            \
+    template <typename type>                                                                      \
+    class type_caster<holder_type, enable_if_t<!is_shared_ptr<holder_type>::value>>               \
+        : public type_caster_holder<type, holder_type> {};                                        \
+    }                                                                                             \
+    }
 
 // PYBIND11_DECLARE_HOLDER_TYPE holder types:
-template <typename base, typename holder> struct is_holder_type :
-    std::is_base_of<detail::type_caster_holder<base, holder>, detail::type_caster<holder>> {};
+template <typename base, typename holder>
+struct is_holder_type
+    : std::is_base_of<detail::type_caster_holder<base, holder>, detail::type_caster<holder>> {};
 // Specialization for always-supported unique_ptr holders:
-template <typename base, typename deleter> struct is_holder_type<base, std::unique_ptr<base, deleter>> :
-    std::true_type {};
-
-template <typename T> struct handle_type_name { static constexpr auto name = const_name<T>(); };
-template <> struct handle_type_name<bool_> { static constexpr auto name = const_name("bool"); };
-template <> struct handle_type_name<bytes> { static constexpr auto name = const_name(PYBIND11_BYTES_NAME); };
-template <> struct handle_type_name<int_> { static constexpr auto name = const_name("int"); };
-template <> struct handle_type_name<iterable> { static constexpr auto name = const_name("Iterable"); };
-template <> struct handle_type_name<iterator> { static constexpr auto name = const_name("Iterator"); };
-template <> struct handle_type_name<float_> { static constexpr auto name = const_name("float"); };
-template <> struct handle_type_name<none> { static constexpr auto name = const_name("None"); };
-template <> struct handle_type_name<args> { static constexpr auto name = const_name("*args"); };
-template <> struct handle_type_name<kwargs> { static constexpr auto name = const_name("**kwargs"); };
+template <typename base, typename deleter>
+struct is_holder_type<base, std::unique_ptr<base, deleter>> : std::true_type {};
+
+template <typename T>
+struct handle_type_name {
+    static constexpr auto name = const_name<T>();
+};
+template <>
+struct handle_type_name<bool_> {
+    static constexpr auto name = const_name("bool");
+};
+template <>
+struct handle_type_name<bytes> {
+    static constexpr auto name = const_name(PYBIND11_BYTES_NAME);
+};
+template <>
+struct handle_type_name<int_> {
+    static constexpr auto name = const_name("int");
+};
+template <>
+struct handle_type_name<iterable> {
+    static constexpr auto name = const_name("Iterable");
+};
+template <>
+struct handle_type_name<iterator> {
+    static constexpr auto name = const_name("Iterator");
+};
+template <>
+struct handle_type_name<float_> {
+    static constexpr auto name = const_name("float");
+};
+template <>
+struct handle_type_name<none> {
+    static constexpr auto name = const_name("None");
+};
+template <>
+struct handle_type_name<args> {
+    static constexpr auto name = const_name("*args");
+};
+template <>
+struct handle_type_name<kwargs> {
+    static constexpr auto name = const_name("**kwargs");
+};
 
 template <typename type>
 struct pyobject_caster {
     template <typename T = type, enable_if_t<std::is_same<T, handle>::value, int> = 0>
-    bool load(handle src, bool /* convert */) { value = src; return static_cast<bool>(value); }
+    bool load(handle src, bool /* convert */) {
+        value = src;
+        return static_cast<bool>(value);
+    }
 
     template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) {
@@ -822,7 +928,8 @@ struct pyobject_caster {
         // un-cluttered later after Python 2 support is dropped.
         if (PYBIND11_SILENCE_MSVC_C4127(std::is_same<T, str>::value) && isinstance<bytes>(src)) {
             PyObject *str_from_bytes = PyUnicode_FromEncodedObject(src.ptr(), "utf-8", nullptr);
-            if (!str_from_bytes) throw error_already_set();
+            if (!str_from_bytes)
+                throw error_already_set();
             value = reinterpret_steal<type>(str_from_bytes);
             return true;
         }
@@ -841,7 +948,7 @@ struct pyobject_caster {
 };
 
 template <typename T>
-class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caster<T> { };
+class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caster<T> {};
 
 // Our conditions for enabling moving are quite restrictive:
 // At compile time:
@@ -852,65 +959,81 @@ class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caste
 // - if the type is non-copy-constructible, the object must be the sole owner of the type (i.e. it
 //   must have ref_count() == 1)h
 // If any of the above are not satisfied, we fall back to copying.
-template <typename T> using move_is_plain_type = satisfies_none_of<T,
-    std::is_void, std::is_pointer, std::is_reference, std::is_const
->;
-template <typename T, typename SFINAE = void> struct move_always : std::false_type {};
-template <typename T> struct move_always<T, enable_if_t<all_of<
-    move_is_plain_type<T>,
-    negation<is_copy_constructible<T>>,
-    std::is_move_constructible<T>,
-    std::is_same<decltype(std::declval<make_caster<T>>().operator T&()), T&>
->::value>> : std::true_type {};
-template <typename T, typename SFINAE = void> struct move_if_unreferenced : std::false_type {};
-template <typename T> struct move_if_unreferenced<T, enable_if_t<all_of<
-    move_is_plain_type<T>,
-    negation<move_always<T>>,
-    std::is_move_constructible<T>,
-    std::is_same<decltype(std::declval<make_caster<T>>().operator T&()), T&>
->::value>> : std::true_type {};
-template <typename T> using move_never = none_of<move_always<T>, move_if_unreferenced<T>>;
+template <typename T>
+using move_is_plain_type
+    = satisfies_none_of<T, std::is_void, std::is_pointer, std::is_reference, std::is_const>;
+template <typename T, typename SFINAE = void>
+struct move_always : std::false_type {};
+template <typename T>
+struct move_always<
+    T,
+    enable_if_t<
+        all_of<move_is_plain_type<T>,
+               negation<is_copy_constructible<T>>,
+               std::is_move_constructible<T>,
+               std::is_same<decltype(std::declval<make_caster<T>>().operator T &()), T &>>::value>>
+    : std::true_type {};
+template <typename T, typename SFINAE = void>
+struct move_if_unreferenced : std::false_type {};
+template <typename T>
+struct move_if_unreferenced<
+    T,
+    enable_if_t<
+        all_of<move_is_plain_type<T>,
+               negation<move_always<T>>,
+               std::is_move_constructible<T>,
+               std::is_same<decltype(std::declval<make_caster<T>>().operator T &()), T &>>::value>>
+    : std::true_type {};
+template <typename T>
+using move_never = none_of<move_always<T>, move_if_unreferenced<T>>;
 
 // Detect whether returning a `type` from a cast on type's type_caster is going to result in a
 // reference or pointer to a local variable of the type_caster.  Basically, only
 // non-reference/pointer `type`s and reference/pointers from a type_caster_generic are safe;
 // everything else returns a reference/pointer to a local variable.
-template <typename type> using cast_is_temporary_value_reference = bool_constant<
-    (std::is_reference<type>::value || std::is_pointer<type>::value) &&
-    !std::is_base_of<type_caster_generic, make_caster<type>>::value &&
-    !std::is_same<intrinsic_t<type>, void>::value
->;
+template <typename type>
+using cast_is_temporary_value_reference
+    = bool_constant<(std::is_reference<type>::value || std::is_pointer<type>::value)
+                    && !std::is_base_of<type_caster_generic, make_caster<type>>::value
+                    && !std::is_same<intrinsic_t<type>, void>::value>;
 
 // When a value returned from a C++ function is being cast back to Python, we almost always want to
 // force `policy = move`, regardless of the return value policy the function/method was declared
 // with.
-template <typename Return, typename SFINAE = void> struct return_value_policy_override {
+template <typename Return, typename SFINAE = void>
+struct return_value_policy_override {
     static return_value_policy policy(return_value_policy p) { return p; }
 };
 
-template <typename Return> struct return_value_policy_override<Return,
-        detail::enable_if_t<std::is_base_of<type_caster_generic, make_caster<Return>>::value, void>> {
+template <typename Return>
+struct return_value_policy_override<
+    Return,
+    detail::enable_if_t<std::is_base_of<type_caster_generic, make_caster<Return>>::value, void>> {
     static return_value_policy policy(return_value_policy p) {
-        return !std::is_lvalue_reference<Return>::value &&
-               !std::is_pointer<Return>::value
-                   ? return_value_policy::move : p;
+        return !std::is_lvalue_reference<Return>::value && !std::is_pointer<Return>::value
+                   ? return_value_policy::move
+                   : p;
     }
 };
 
 // Basic python -> C++ casting; throws if casting fails
-template <typename T, typename SFINAE> type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
+template <typename T, typename SFINAE>
+type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
     if (!conv.load(handle, true)) {
 #if defined(NDEBUG)
-        throw cast_error("Unable to cast Python instance to C++ type (compile in debug mode for details)");
+        throw cast_error(
+            "Unable to cast Python instance to C++ type (compile in debug mode for details)");
 #else
-        throw cast_error("Unable to cast Python instance of type " +
-            (std::string) str(type::handle_of(handle)) + " to C++ type '" + type_id<T>() + "'");
+        throw cast_error("Unable to cast Python instance of type "
+                         + (std::string) str(type::handle_of(handle)) + " to C++ type '"
+                         + type_id<T>() + "'");
 #endif
     }
     return conv;
 }
 // Wrapper around the above that also constructs and returns a type_caster
-template <typename T> make_caster<T> load_type(const handle &handle) {
+template <typename T>
+make_caster<T> load_type(const handle &handle) {
     make_caster<T> conv;
     load_type(conv, handle);
     return conv;
@@ -923,47 +1046,60 @@ template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> =
 T cast(const handle &handle) {
     using namespace detail;
     static_assert(!cast_is_temporary_value_reference<T>::value,
-            "Unable to cast type to reference: value is local to type caster");
+                  "Unable to cast type to reference: value is local to type caster");
     return cast_op<T>(load_type<T>(handle));
 }
 
 // pytype -> pytype (calls converting constructor)
 template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
-T cast(const handle &handle) { return T(reinterpret_borrow<object>(handle)); }
+T cast(const handle &handle) {
+    return T(reinterpret_borrow<object>(handle));
+}
 
 // C++ type -> py::object
 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
-object cast(T &&value, return_value_policy policy = return_value_policy::automatic_reference,
+object cast(T &&value,
+            return_value_policy policy = return_value_policy::automatic_reference,
             handle parent = handle()) {
     using no_ref_T = typename std::remove_reference<T>::type;
     if (policy == return_value_policy::automatic) {
-        policy = std::is_pointer<no_ref_T>::value ? return_value_policy::take_ownership :
-                 std::is_lvalue_reference<T>::value ? return_value_policy::copy : return_value_policy::move;
+        policy = std::is_pointer<no_ref_T>::value     ? return_value_policy::take_ownership
+                 : std::is_lvalue_reference<T>::value ? return_value_policy::copy
+                                                      : return_value_policy::move;
     } else if (policy == return_value_policy::automatic_reference) {
         policy = std::is_pointer<no_ref_T>::value     ? return_value_policy::reference
                  : std::is_lvalue_reference<T>::value ? return_value_policy::copy
                                                       : return_value_policy::move;
     }
-    return reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
+    return reinterpret_steal<object>(
+        detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
 }
 
-template <typename T> T handle::cast() const { return pybind11::cast<T>(*this); }
-template <> inline void handle::cast() const { return; }
+template <typename T>
+T handle::cast() const {
+    return pybind11::cast<T>(*this);
+}
+template <>
+inline void handle::cast() const {
+    return;
+}
 
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1) {
 #if defined(NDEBUG)
-        throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
+        throw cast_error(
+            "Unable to cast Python instance to C++ rvalue: instance has multiple references"
             " (compile in debug mode for details)");
 #else
-        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj)) +
-                " instance to C++ " + type_id<T>() + " instance: instance has multiple references");
+        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj))
+                         + " instance to C++ " + type_id<T>()
+                         + " instance: instance has multiple references");
 #endif
     }
 
     // Move into a temporary and return that, because the reference may be a local value of `conv`
-    T ret = std::move(detail::load_type<T>(obj).operator T&());
+    T ret = std::move(detail::load_type<T>(obj).operator T &());
     return ret;
 }
 
@@ -972,52 +1108,81 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
 //   object has multiple references, but trying to copy will fail to compile.
 // - If both movable and copyable, check ref count: if 1, move; otherwise copy
 // - Otherwise (not movable), copy.
-template <typename T> detail::enable_if_t<detail::move_always<T>::value, T> cast(object &&object) {
+template <typename T>
+detail::enable_if_t<detail::move_always<T>::value, T> cast(object &&object) {
     return move<T>(std::move(object));
 }
-template <typename T> detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
+template <typename T>
+detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
     if (object.ref_count() > 1) {
         return cast<T>(object);
     }
     return move<T>(std::move(object));
 }
-template <typename T> detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
+template <typename T>
+detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
     return cast<T>(object);
 }
 
-template <typename T> T object::cast() const & { return pybind11::cast<T>(*this); }
-template <typename T> T object::cast() && { return pybind11::cast<T>(std::move(*this)); }
-template <> inline void object::cast() const & { return; }
-template <> inline void object::cast() && { return; }
+template <typename T>
+T object::cast() const & {
+    return pybind11::cast<T>(*this);
+}
+template <typename T>
+T object::cast() && {
+    return pybind11::cast<T>(std::move(*this));
+}
+template <>
+inline void object::cast() const & {
+    return;
+}
+template <>
+inline void object::cast() && {
+    return;
+}
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Declared in pytypes.h:
 template <typename T, enable_if_t<!is_pyobject<T>::value, int>>
-object object_or_cast(T &&o) { return pybind11::cast(std::forward<T>(o)); }
+object object_or_cast(T &&o) {
+    return pybind11::cast(std::forward<T>(o));
+}
 
 // Placeholder type for the unneeded (and dead code) static variable in the
 // PYBIND11_OVERRIDE_OVERRIDE macro
 struct override_unused {};
-template <typename ret_type> using override_caster_t = conditional_t<
-    cast_is_temporary_value_reference<ret_type>::value, make_caster<ret_type>, override_unused>;
+template <typename ret_type>
+using override_caster_t = conditional_t<cast_is_temporary_value_reference<ret_type>::value,
+                                        make_caster<ret_type>,
+                                        override_unused>;
 
 // Trampoline use: for reference/pointer types to value-converted values, we do a value cast, then
 // store the result in the given variable.  For other types, this is a no-op.
-template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&o, make_caster<T> &caster) {
+template <typename T>
+enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&o,
+                                                                     make_caster<T> &caster) {
     return cast_op<T>(load_type(caster, o));
 }
-template <typename T> enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&, override_unused &) {
-    pybind11_fail("Internal error: cast_ref fallback invoked"); }
-
-// Trampoline use: Having a pybind11::cast with an invalid reference type is going to static_assert, even
-// though if it's in dead code, so we provide a "trampoline" to pybind11::cast that only does anything in
-// cases where pybind11::cast is valid.
-template <typename T> enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&o) {
-    return pybind11::cast<T>(std::move(o)); }
-template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&) {
-    pybind11_fail("Internal error: cast_safe fallback invoked"); }
-template <> inline void cast_safe<void>(object &&) {}
+template <typename T>
+enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&,
+                                                                      override_unused &) {
+    pybind11_fail("Internal error: cast_ref fallback invoked");
+}
+
+// Trampoline use: Having a pybind11::cast with an invalid reference type is going to
+// static_assert, even though if it's in dead code, so we provide a "trampoline" to pybind11::cast
+// that only does anything in cases where pybind11::cast is valid.
+template <typename T>
+enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&o) {
+    return pybind11::cast<T>(std::move(o));
+}
+template <typename T>
+enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&) {
+    pybind11_fail("Internal error: cast_safe fallback invoked");
+}
+template <>
+inline void cast_safe<void>(object &&) {}
 
 PYBIND11_NAMESPACE_END(detail)
 
@@ -1037,21 +1202,21 @@ inline cast_error cast_error_unable_to_convert_call_arg(const std::string &name,
 #endif
 
 template <return_value_policy policy = return_value_policy::automatic_reference>
-tuple make_tuple() { return tuple(0); }
+tuple make_tuple() {
+    return tuple(0);
+}
 
-template <return_value_policy policy = return_value_policy::automatic_reference,
-          typename... Args> tuple make_tuple(Args&&... args_) {
+template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+tuple make_tuple(Args &&...args_) {
     constexpr size_t size = sizeof...(Args);
-    std::array<object, size> args {
-        { reinterpret_steal<object>(detail::make_caster<Args>::cast(
-            std::forward<Args>(args_), policy, nullptr))... }
-    };
+    std::array<object, size> args{{reinterpret_steal<object>(
+        detail::make_caster<Args>::cast(std::forward<Args>(args_), policy, nullptr))...}};
     for (size_t i = 0; i < args.size(); i++) {
         if (!args[i]) {
 #if defined(NDEBUG)
             throw cast_error_unable_to_convert_call_arg();
 #else
-            std::array<std::string, size> argtypes { {type_id<Args>()...} };
+            std::array<std::string, size> argtypes{{type_id<Args>()...}};
             throw cast_error_unable_to_convert_call_arg(std::to_string(i), argtypes[i]);
 #endif
         }
@@ -1067,18 +1232,28 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
 /// \ingroup annotations
 /// Annotation for arguments
 struct arg {
-    /// Constructs an argument with the name of the argument; if null or omitted, this is a positional argument.
-    constexpr explicit arg(const char *name = nullptr) : name(name), flag_noconvert(false), flag_none(true) { }
+    /// Constructs an argument with the name of the argument; if null or omitted, this is a
+    /// positional argument.
+    constexpr explicit arg(const char *name = nullptr)
+        : name(name), flag_noconvert(false), flag_none(true) {}
     /// Assign a value to this argument
-    template <typename T> arg_v operator=(T &&value) const;
+    template <typename T>
+    arg_v operator=(T &&value) const;
     /// Indicate that the type should not be converted in the type caster
-    arg &noconvert(bool flag = true) { flag_noconvert = flag; return *this; }
+    arg &noconvert(bool flag = true) {
+        flag_noconvert = flag;
+        return *this;
+    }
     /// Indicates that the argument should/shouldn't allow None (e.g. for nullable pointer args)
-    arg &none(bool flag = true) { flag_none = flag; return *this; }
+    arg &none(bool flag = true) {
+        flag_none = flag;
+        return *this;
+    }
 
-    const char *name; ///< If non-null, this is a named kwargs argument
-    bool flag_noconvert : 1; ///< If set, do not allow conversion (requires a supporting type caster!)
-    bool flag_none : 1; ///< If set (the default), allow None to be passed to this argument
+    const char *name;        ///< If non-null, this is a named kwargs argument
+    bool flag_noconvert : 1; ///< If set, do not allow conversion (requires a supporting type
+                             ///< caster!)
+    bool flag_none : 1;      ///< If set (the default), allow None to be passed to this argument
 };
 
 /// \ingroup annotations
@@ -1087,13 +1262,12 @@ struct arg_v : arg {
 private:
     template <typename T>
     arg_v(arg &&base, T &&x, const char *descr = nullptr)
-        : arg(base),
-          value(reinterpret_steal<object>(
-              detail::make_caster<T>::cast(x, return_value_policy::automatic, {})
-          )),
+        : arg(base), value(reinterpret_steal<object>(
+                         detail::make_caster<T>::cast(x, return_value_policy::automatic, {}))),
           descr(descr)
 #if !defined(NDEBUG)
-        , type(type_id<T>())
+          ,
+          type(type_id<T>())
 #endif
     {
         // Workaround! See:
@@ -1108,18 +1282,24 @@ struct arg_v : arg {
     /// Direct construction with name, default, and description
     template <typename T>
     arg_v(const char *name, T &&x, const char *descr = nullptr)
-        : arg_v(arg(name), std::forward<T>(x), descr) { }
+        : arg_v(arg(name), std::forward<T>(x), descr) {}
 
     /// Called internally when invoking `py::arg("a") = value`
     template <typename T>
     arg_v(const arg &base, T &&x, const char *descr = nullptr)
-        : arg_v(arg(base), std::forward<T>(x), descr) { }
+        : arg_v(arg(base), std::forward<T>(x), descr) {}
 
     /// Same as `arg::noconvert()`, but returns *this as arg_v&, not arg&
-    arg_v &noconvert(bool flag = true) { arg::noconvert(flag); return *this; }
+    arg_v &noconvert(bool flag = true) {
+        arg::noconvert(flag);
+        return *this;
+    }
 
     /// Same as `arg::nonone()`, but returns *this as arg_v&, not arg&
-    arg_v &none(bool flag = true) { arg::none(flag); return *this; }
+    arg_v &none(bool flag = true) {
+        arg::none(flag);
+        return *this;
+    }
 
     /// The default value
     object value;
@@ -1132,13 +1312,13 @@ struct arg_v : arg {
 };
 
 /// \ingroup annotations
-/// Annotation indicating that all following arguments are keyword-only; the is the equivalent of an
-/// unnamed '*' argument (in Python 3)
+/// Annotation indicating that all following arguments are keyword-only; the is the equivalent of
+/// an unnamed '*' argument (in Python 3)
 struct kw_only {};
 
 /// \ingroup annotations
-/// Annotation indicating that all previous arguments are positional-only; the is the equivalent of an
-/// unnamed '/' argument (in Python 3.8)
+/// Annotation indicating that all previous arguments are positional-only; the is the equivalent of
+/// an unnamed '/' argument (in Python 3.8)
 struct pos_only {};
 
 template <typename T>
@@ -1147,7 +1327,8 @@ arg_v arg::operator=(T &&value) const {
 }
 
 /// Alias for backward compatibility -- to be removed in version 2.0
-template <typename /*unused*/> using arg_t = arg_v;
+template <typename /*unused*/>
+using arg_t = arg_v;
 
 inline namespace literals {
 /** \rst
@@ -1158,8 +1339,10 @@ constexpr arg operator"" _a(const char *name, size_t) { return arg(name); }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T> using is_kw_only = std::is_same<intrinsic_t<T>, kw_only>;
-template <typename T> using is_pos_only = std::is_same<intrinsic_t<T>, pos_only>;
+template <typename T>
+using is_kw_only = std::is_same<intrinsic_t<T>, kw_only>;
+template <typename T>
+using is_pos_only = std::is_same<intrinsic_t<T>, pos_only>;
 
 // forward declaration (definition in attr.h)
 struct function_record;
@@ -1188,18 +1371,20 @@ struct function_call {
     handle init_self;
 };
 
-
 /// Helper class which loads arguments for C++ functions called from Python
 template <typename... Args>
 class argument_loader {
     using indices = make_index_sequence<sizeof...(Args)>;
 
-    template <typename Arg> using argument_is_args   = std::is_same<intrinsic_t<Arg>, args>;
-    template <typename Arg> using argument_is_kwargs = std::is_same<intrinsic_t<Arg>, kwargs>;
+    template <typename Arg>
+    using argument_is_args = std::is_same<intrinsic_t<Arg>, args>;
+    template <typename Arg>
+    using argument_is_kwargs = std::is_same<intrinsic_t<Arg>, kwargs>;
     // Get kwargs argument position, or -1 if not present:
     static constexpr auto kwargs_pos = constexpr_last<argument_is_kwargs, Args...>();
 
-    static_assert(kwargs_pos == -1 || kwargs_pos == (int) sizeof...(Args) - 1, "py::kwargs is only permitted as the last argument of a function");
+    static_assert(kwargs_pos == -1 || kwargs_pos == (int) sizeof...(Args) - 1,
+                  "py::kwargs is only permitted as the last argument of a function");
 
 public:
     static constexpr bool has_kwargs = kwargs_pos != -1;
@@ -1207,28 +1392,28 @@ class argument_loader {
     // py::args argument position; -1 if not present.
     static constexpr int args_pos = constexpr_last<argument_is_args, Args...>();
 
-    static_assert(args_pos == -1 || args_pos == constexpr_first<argument_is_args, Args...>(), "py::args cannot be specified more than once");
+    static_assert(args_pos == -1 || args_pos == constexpr_first<argument_is_args, Args...>(),
+                  "py::args cannot be specified more than once");
 
     static constexpr auto arg_names = concat(type_descr(make_caster<Args>::name)...);
 
-    bool load_args(function_call &call) {
-        return load_impl_sequence(call, indices{});
-    }
+    bool load_args(function_call &call) { return load_impl_sequence(call, indices{}); }
 
     template <typename Return, typename Guard, typename Func>
     // NOLINTNEXTLINE(readability-const-return-type)
     enable_if_t<!std::is_void<Return>::value, Return> call(Func &&f) && {
-        return std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
+        return std::move(*this).template call_impl<remove_cv_t<Return>>(
+            std::forward<Func>(f), indices{}, Guard{});
     }
 
     template <typename Return, typename Guard, typename Func>
     enable_if_t<std::is_void<Return>::value, void_type> call(Func &&f) && {
-        std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
+        std::move(*this).template call_impl<remove_cv_t<Return>>(
+            std::forward<Func>(f), indices{}, Guard{});
         return void_type();
     }
 
 private:
-
     static bool load_impl_sequence(function_call &, index_sequence<>) { return true; }
 
     template <size_t... Is>
@@ -1262,7 +1447,7 @@ class simple_collector {
 public:
     template <typename... Ts>
     explicit simple_collector(Ts &&...values)
-        : m_args(pybind11::make_tuple<policy>(std::forward<Ts>(values)...)) { }
+        : m_args(pybind11::make_tuple<policy>(std::forward<Ts>(values)...)) {}
 
     const tuple &args() const & { return m_args; }
     dict kwargs() const { return {}; }
@@ -1315,13 +1500,14 @@ class unpacking_collector {
 private:
     template <typename T>
     void process(list &args_list, T &&x) {
-        auto o = reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
+        auto o = reinterpret_steal<object>(
+            detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
         if (!o) {
 #if defined(NDEBUG)
             throw cast_error_unable_to_convert_call_arg();
 #else
-            throw cast_error_unable_to_convert_call_arg(
-                std::to_string(args_list.size()), type_id<T>());
+            throw cast_error_unable_to_convert_call_arg(std::to_string(args_list.size()),
+                                                        type_id<T>());
 #endif
         }
         args_list.append(o);
@@ -1333,7 +1519,7 @@ class unpacking_collector {
         }
     }
 
-    void process(list &/*args_list*/, arg_v a) {
+    void process(list & /*args_list*/, arg_v a) {
         if (!a.name) {
 #if defined(NDEBUG)
             nameless_argument_error();
@@ -1358,7 +1544,7 @@ class unpacking_collector {
         m_kwargs[a.name] = a.value;
     }
 
-    void process(list &/*args_list*/, detail::kwargs_proxy kp) {
+    void process(list & /*args_list*/, detail::kwargs_proxy kp) {
         if (!kp) {
             return;
         }
@@ -1380,8 +1566,9 @@ class unpacking_collector {
                          "(compile in debug mode for details)");
     }
     [[noreturn]] static void nameless_argument_error(const std::string &type) {
-        throw type_error("Got kwargs without a name of type '" + type + "'; only named "
-                         "arguments may be passed via py::arg() to a python function call. ");
+        throw type_error("Got kwargs without a name of type '" + type
+                         + "'; only named "
+                           "arguments may be passed via py::arg() to a python function call. ");
     }
     [[noreturn]] static void multiple_values_error() {
         throw type_error("Got multiple values for keyword argument "
@@ -1402,29 +1589,30 @@ class unpacking_collector {
 // fails to compile enable_if_t<!all_of<is_positional<Args>...>::value>
 // (tested with ICC 2021.1 Beta 20200827).
 template <typename... Args>
-constexpr bool args_are_all_positional()
-{
-  return all_of<is_positional<Args>...>::value;
+constexpr bool args_are_all_positional() {
+    return all_of<is_positional<Args>...>::value;
 }
 
 /// Collect only positional arguments for a Python function call
-template <return_value_policy policy, typename... Args,
+template <return_value_policy policy,
+          typename... Args,
           typename = enable_if_t<args_are_all_positional<Args...>()>>
 simple_collector<policy> collect_arguments(Args &&...args) {
     return simple_collector<policy>(std::forward<Args>(args)...);
 }
 
 /// Collect all arguments, including keywords and unpacking (only instantiated when needed)
-template <return_value_policy policy, typename... Args,
+template <return_value_policy policy,
+          typename... Args,
           typename = enable_if_t<!args_are_all_positional<Args...>()>>
 unpacking_collector<policy> collect_arguments(Args &&...args) {
     // Following argument order rules for generalized unpacking according to PEP 448
-    static_assert(
-        constexpr_last<is_positional, Args...>() < constexpr_first<is_keyword_or_ds, Args...>()
-        && constexpr_last<is_s_unpacking, Args...>() < constexpr_first<is_ds_unpacking, Args...>(),
-        "Invalid function call: positional args must precede keywords and ** unpacking; "
-        "* unpacking must precede ** unpacking"
-    );
+    static_assert(constexpr_last<is_positional, Args...>()
+                          < constexpr_first<is_keyword_or_ds, Args...>()
+                      && constexpr_last<is_s_unpacking, Args...>()
+                             < constexpr_first<is_ds_unpacking, Args...>(),
+                  "Invalid function call: positional args must precede keywords and ** unpacking; "
+                  "* unpacking must precede ** unpacking");
     return unpacking_collector<policy>(std::forward<Args>(args)...);
 }
 
@@ -1447,22 +1635,21 @@ object object_api<Derived>::call(Args &&...args) const {
 
 PYBIND11_NAMESPACE_END(detail)
 
-
-template<typename T>
+template <typename T>
 handle type::handle_of() {
-   static_assert(
-      std::is_base_of<detail::type_caster_generic, detail::make_caster<T>>::value,
-      "py::type::of<T> only supports the case where T is a registered C++ types."
-    );
+    static_assert(std::is_base_of<detail::type_caster_generic, detail::make_caster<T>>::value,
+                  "py::type::of<T> only supports the case where T is a registered C++ types.");
 
     return detail::get_type_handle(typeid(T), true);
 }
 
-
-#define PYBIND11_MAKE_OPAQUE(...) \
-    namespace pybind11 { namespace detail { \
-        template<> class type_caster<__VA_ARGS__> : public type_caster_base<__VA_ARGS__> { }; \
-    }}
+#define PYBIND11_MAKE_OPAQUE(...)                                                                 \
+    namespace pybind11 {                                                                          \
+    namespace detail {                                                                            \
+    template <>                                                                                   \
+    class type_caster<__VA_ARGS__> : public type_caster_base<__VA_ARGS__> {};                     \
+    }                                                                                             \
+    }
 
 /// Lets you pass a type containing a `,` through a macro parameter without needing a separate
 /// typedef, e.g.:
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index cfa635a011..ad5e97b024 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -15,25 +15,25 @@
 #include <chrono>
 #include <cmath>
 #include <ctime>
-#include <mutex>
-
 #include <datetime.h>
+#include <mutex>
 
 // Backport the PyDateTime_DELTA functions from Python3.3 if required
 #ifndef PyDateTime_DELTA_GET_DAYS
-#define PyDateTime_DELTA_GET_DAYS(o)         (((PyDateTime_Delta*)o)->days)
+#    define PyDateTime_DELTA_GET_DAYS(o) (((PyDateTime_Delta *) o)->days)
 #endif
 #ifndef PyDateTime_DELTA_GET_SECONDS
-#define PyDateTime_DELTA_GET_SECONDS(o)      (((PyDateTime_Delta*)o)->seconds)
+#    define PyDateTime_DELTA_GET_SECONDS(o) (((PyDateTime_Delta *) o)->seconds)
 #endif
 #ifndef PyDateTime_DELTA_GET_MICROSECONDS
-#define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta*)o)->microseconds)
+#    define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta *) o)->microseconds)
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename type> class duration_caster {
+template <typename type>
+class duration_caster {
 public:
     using rep = typename type::rep;
     using period = typename type::period;
@@ -45,7 +45,9 @@ template <typename type> class duration_caster {
         using namespace std::chrono;
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
         if (!src) {
             return false;
@@ -53,26 +55,30 @@ template <typename type> class duration_caster {
         // If invoked with datetime.delta object
         if (PyDelta_Check(src.ptr())) {
             value = type(duration_cast<duration<rep, period>>(
-                  days(PyDateTime_DELTA_GET_DAYS(src.ptr()))
+                days(PyDateTime_DELTA_GET_DAYS(src.ptr()))
                 + seconds(PyDateTime_DELTA_GET_SECONDS(src.ptr()))
                 + microseconds(PyDateTime_DELTA_GET_MICROSECONDS(src.ptr()))));
             return true;
         }
         // If invoked with a float we assume it is seconds and convert
         if (PyFloat_Check(src.ptr())) {
-            value = type(duration_cast<duration<rep, period>>(duration<double>(PyFloat_AsDouble(src.ptr()))));
+            value = type(duration_cast<duration<rep, period>>(
+                duration<double>(PyFloat_AsDouble(src.ptr()))));
             return true;
         }
         return false;
     }
 
     // If this is a duration just return it back
-    static const std::chrono::duration<rep, period>& get_duration(const std::chrono::duration<rep, period> &src) {
+    static const std::chrono::duration<rep, period> &
+    get_duration(const std::chrono::duration<rep, period> &src) {
         return src;
     }
 
     // If this is a time_point get the time_since_epoch
-    template <typename Clock> static std::chrono::duration<rep, period> get_duration(const std::chrono::time_point<Clock, std::chrono::duration<rep, period>> &src) {
+    template <typename Clock>
+    static std::chrono::duration<rep, period>
+    get_duration(const std::chrono::time_point<Clock, std::chrono::duration<rep, period>> &src) {
         return src.time_since_epoch();
     }
 
@@ -84,9 +90,12 @@ template <typename type> class duration_caster {
         auto d = get_duration(src);
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
-        // Declare these special duration types so the conversions happen with the correct primitive types (int)
+        // Declare these special duration types so the conversions happen with the correct
+        // primitive types (int)
         using dd_t = duration<int, std::ratio<86400>>;
         using ss_t = duration<int, std::ratio<1>>;
         using us_t = duration<int, std::micro>;
@@ -118,14 +127,17 @@ inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
 }
 
 // This is for casting times on the system clock into datetime.datetime instances
-template <typename Duration> class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
+template <typename Duration>
+class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
 public:
     using type = std::chrono::time_point<std::chrono::system_clock, Duration>;
     bool load(handle src, bool) {
         using namespace std::chrono;
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
         if (!src) {
             return false;
@@ -135,32 +147,32 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         microseconds msecs;
 
         if (PyDateTime_Check(src.ptr())) {
-            cal.tm_sec   = PyDateTime_DATE_GET_SECOND(src.ptr());
-            cal.tm_min   = PyDateTime_DATE_GET_MINUTE(src.ptr());
-            cal.tm_hour  = PyDateTime_DATE_GET_HOUR(src.ptr());
-            cal.tm_mday  = PyDateTime_GET_DAY(src.ptr());
-            cal.tm_mon   = PyDateTime_GET_MONTH(src.ptr()) - 1;
-            cal.tm_year  = PyDateTime_GET_YEAR(src.ptr()) - 1900;
+            cal.tm_sec = PyDateTime_DATE_GET_SECOND(src.ptr());
+            cal.tm_min = PyDateTime_DATE_GET_MINUTE(src.ptr());
+            cal.tm_hour = PyDateTime_DATE_GET_HOUR(src.ptr());
+            cal.tm_mday = PyDateTime_GET_DAY(src.ptr());
+            cal.tm_mon = PyDateTime_GET_MONTH(src.ptr()) - 1;
+            cal.tm_year = PyDateTime_GET_YEAR(src.ptr()) - 1900;
             cal.tm_isdst = -1;
-            msecs        = microseconds(PyDateTime_DATE_GET_MICROSECOND(src.ptr()));
+            msecs = microseconds(PyDateTime_DATE_GET_MICROSECOND(src.ptr()));
         } else if (PyDate_Check(src.ptr())) {
-            cal.tm_sec   = 0;
-            cal.tm_min   = 0;
-            cal.tm_hour  = 0;
-            cal.tm_mday  = PyDateTime_GET_DAY(src.ptr());
-            cal.tm_mon   = PyDateTime_GET_MONTH(src.ptr()) - 1;
-            cal.tm_year  = PyDateTime_GET_YEAR(src.ptr()) - 1900;
+            cal.tm_sec = 0;
+            cal.tm_min = 0;
+            cal.tm_hour = 0;
+            cal.tm_mday = PyDateTime_GET_DAY(src.ptr());
+            cal.tm_mon = PyDateTime_GET_MONTH(src.ptr()) - 1;
+            cal.tm_year = PyDateTime_GET_YEAR(src.ptr()) - 1900;
             cal.tm_isdst = -1;
-            msecs        = microseconds(0);
+            msecs = microseconds(0);
         } else if (PyTime_Check(src.ptr())) {
-            cal.tm_sec   = PyDateTime_TIME_GET_SECOND(src.ptr());
-            cal.tm_min   = PyDateTime_TIME_GET_MINUTE(src.ptr());
-            cal.tm_hour  = PyDateTime_TIME_GET_HOUR(src.ptr());
-            cal.tm_mday  = 1;   // This date (day, month, year) = (1, 0, 70)
-            cal.tm_mon   = 0;   // represents 1-Jan-1970, which is the first
-            cal.tm_year  = 70;  // earliest available date for Python's datetime
+            cal.tm_sec = PyDateTime_TIME_GET_SECOND(src.ptr());
+            cal.tm_min = PyDateTime_TIME_GET_MINUTE(src.ptr());
+            cal.tm_hour = PyDateTime_TIME_GET_HOUR(src.ptr());
+            cal.tm_mday = 1;  // This date (day, month, year) = (1, 0, 70)
+            cal.tm_mon = 0;   // represents 1-Jan-1970, which is the first
+            cal.tm_year = 70; // earliest available date for Python's datetime
             cal.tm_isdst = -1;
-            msecs        = microseconds(PyDateTime_TIME_GET_MICROSECOND(src.ptr()));
+            msecs = microseconds(PyDateTime_TIME_GET_MICROSECOND(src.ptr()));
         } else {
             return false;
         }
@@ -169,14 +181,18 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         return true;
     }
 
-    static handle cast(const std::chrono::time_point<std::chrono::system_clock, Duration> &src, return_value_policy /* policy */, handle /* parent */) {
+    static handle cast(const std::chrono::time_point<std::chrono::system_clock, Duration> &src,
+                       return_value_policy /* policy */,
+                       handle /* parent */) {
         using namespace std::chrono;
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
-        // Get out microseconds, and make sure they are positive, to avoid bug in eastern hemisphere time zones
-        // (cfr. https://github.com/pybind/pybind11/issues/2417)
+        // Get out microseconds, and make sure they are positive, to avoid bug in eastern
+        // hemisphere time zones (cfr. https://github.com/pybind/pybind11/issues/2417)
         using us_t = duration<int, std::micro>;
         auto us = duration_cast<us_t>(src.time_since_epoch() % seconds(1));
         if (us.count() < 0) {
@@ -184,9 +200,10 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         }
 
         // Subtract microseconds BEFORE `system_clock::to_time_t`, because:
-        // > If std::time_t has lower precision, it is implementation-defined whether the value is rounded or truncated.
-        // (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
-        std::time_t tt = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
+        // > If std::time_t has lower precision, it is implementation-defined whether the value is
+        // rounded or truncated. (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
+        std::time_t tt
+            = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
 
         std::tm localtime;
         std::tm *localtime_ptr = localtime_thread_safe(&tt, &localtime);
@@ -207,13 +224,13 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
 // Other clocks that are not the system clock are not measured as datetime.datetime objects
 // since they are not measured on calendar time. So instead we just make them timedeltas
 // Or if they have passed us a time as a float we convert that
-template <typename Clock, typename Duration> class type_caster<std::chrono::time_point<Clock, Duration>>
-: public duration_caster<std::chrono::time_point<Clock, Duration>> {
-};
+template <typename Clock, typename Duration>
+class type_caster<std::chrono::time_point<Clock, Duration>>
+    : public duration_caster<std::chrono::time_point<Clock, Duration>> {};
 
-template <typename Rep, typename Period> class type_caster<std::chrono::duration<Rep, Period>>
-: public duration_caster<std::chrono::duration<Rep, Period>> {
-};
+template <typename Rep, typename Period>
+class type_caster<std::chrono::duration<Rep, Period>>
+    : public duration_caster<std::chrono::duration<Rep, Period>> {};
 
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/complex.h b/include/pybind11/complex.h
index 72c87359bc..8a831c12ce 100644
--- a/include/pybind11/complex.h
+++ b/include/pybind11/complex.h
@@ -10,36 +10,42 @@
 #pragma once
 
 #include "pybind11.h"
+
 #include <complex>
 
 /// glibc defines I as a macro which breaks things, e.g., boost template names
 #ifdef I
-#  undef I
+#    undef I
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
-template <typename T> struct format_descriptor<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
+template <typename T>
+struct format_descriptor<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr const char c = format_descriptor<T>::c;
-    static constexpr const char value[3] = { 'Z', c, '\0' };
+    static constexpr const char value[3] = {'Z', c, '\0'};
     static std::string format() { return std::string(value); }
 };
 
 #ifndef PYBIND11_CPP17
 
-template <typename T> constexpr const char format_descriptor<
-    std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>>::value[3];
+template <typename T>
+constexpr const char
+    format_descriptor<std::complex<T>,
+                      detail::enable_if_t<std::is_floating_point<T>::value>>::value[3];
 
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T> struct is_fmt_numeric<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
+template <typename T>
+struct is_fmt_numeric<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr bool value = true;
     static constexpr int index = is_fmt_numeric<T>::index + 3;
 };
 
-template <typename T> class type_caster<std::complex<T>> {
+template <typename T>
+class type_caster<std::complex<T>> {
 public:
     bool load(handle src, bool convert) {
         if (!src) {
@@ -57,7 +63,8 @@ template <typename T> class type_caster<std::complex<T>> {
         return true;
     }
 
-    static handle cast(const std::complex<T> &src, return_value_policy /* policy */, handle /* parent */) {
+    static handle
+    cast(const std::complex<T> &src, return_value_policy /* policy */, handle /* parent */) {
         return PyComplex_FromDoubles((double) src.real(), (double) src.imag());
     }
 
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index e50c8060fb..ac92ddd632 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -16,12 +16,13 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if PY_VERSION_HEX >= 0x03030000 && !defined(PYPY_VERSION)
-#  define PYBIND11_BUILTIN_QUALNAME
-#  define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
+#    define PYBIND11_BUILTIN_QUALNAME
+#    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
 #else
 // In pre-3.3 Python, we still set __qualname__ so that we can produce reliable function type
 // signatures; in 3.3+ this macro expands to nothing:
-#  define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj) setattr((PyObject *) obj, "__qualname__", nameobj)
+#    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)                                             \
+        setattr((PyObject *) obj, "__qualname__", nameobj)
 #endif
 
 inline std::string get_fully_qualified_tp_name(PyTypeObject *type) {
@@ -71,9 +72,9 @@ inline PyTypeObject *make_static_property_type() {
     }
 
     heap_type->ht_name = name_obj.inc_ref().ptr();
-#ifdef PYBIND11_BUILTIN_QUALNAME
+#    ifdef PYBIND11_BUILTIN_QUALNAME
     heap_type->ht_qualname = name_obj.inc_ref().ptr();
-#endif
+#    endif
 
     auto *type = &heap_type->ht_type;
     type->tp_name = name;
@@ -107,8 +108,10 @@ inline PyTypeObject *make_static_property_type() {
             def __set__(self, obj, value):
                 cls = obj if isinstance(obj, type) else type(obj)
                 property.__set__(self, cls, value)
-        )", Py_file_input, d.ptr(), d.ptr()
-    );
+        )",
+                                    Py_file_input,
+                                    d.ptr(),
+                                    d.ptr());
     if (result == nullptr)
         throw error_already_set();
     Py_DECREF(result);
@@ -121,7 +124,7 @@ inline PyTypeObject *make_static_property_type() {
     By default, Python replaces the `static_property` itself, but for wrapped C++ types
     we need to call `static_property.__set__()` in order to propagate the new value to
     the underlying C++ data structure. */
-extern "C" inline int pybind11_meta_setattro(PyObject* obj, PyObject* name, PyObject* value) {
+extern "C" inline int pybind11_meta_setattro(PyObject *obj, PyObject *name, PyObject *value) {
     // Use `_PyType_Lookup()` instead of `PyObject_GetAttr()` in order to get the raw
     // descriptor (`property`) instead of calling `tp_descr_get` (`property.__get__()`).
     PyObject *descr = _PyType_Lookup((PyTypeObject *) obj, name);
@@ -184,7 +187,8 @@ extern "C" inline PyObject *pybind11_meta_call(PyObject *type, PyObject *args, P
     // Ensure that the base __init__ function(s) were called
     for (const auto &vh : values_and_holders(instance)) {
         if (!vh.holder_constructed()) {
-            PyErr_Format(PyExc_TypeError, "%.200s.__init__() must be called when overriding __init__",
+            PyErr_Format(PyExc_TypeError,
+                         "%.200s.__init__() must be called when overriding __init__",
                          get_fully_qualified_tp_name(vh.type->type).c_str());
             Py_DECREF(self);
             return nullptr;
@@ -203,9 +207,8 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
     // 1) be found in internals.registered_types_py
     // 2) have exactly one associated `detail::type_info`
     auto found_type = internals.registered_types_py.find(type);
-    if (found_type != internals.registered_types_py.end() &&
-        found_type->second.size() == 1 &&
-        found_type->second[0]->type == type) {
+    if (found_type != internals.registered_types_py.end() && found_type->second.size() == 1
+        && found_type->second[0]->type == type) {
 
         auto *tinfo = found_type->second[0];
         auto tindex = std::type_index(*tinfo->cpptype);
@@ -220,7 +223,7 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
 
         // Actually just `std::erase_if`, but that's only available in C++20
         auto &cache = internals.inactive_override_cache;
-        for (auto it = cache.begin(), last = cache.end(); it != last; ) {
+        for (auto it = cache.begin(), last = cache.end(); it != last;) {
             if (it->first == (PyObject *) tinfo->type) {
                 it = cache.erase(it);
             } else {
@@ -237,7 +240,7 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
 /** This metaclass is assigned by default to all pybind11 types and is required in order
     for static properties to function correctly. Users may override this using `py::metaclass`.
     Return value: New reference. */
-inline PyTypeObject* make_default_metaclass() {
+inline PyTypeObject *make_default_metaclass() {
     constexpr auto *name = "pybind11_type";
     auto name_obj = reinterpret_steal<object>(PYBIND11_FROM_STRING(name));
 
@@ -281,9 +284,12 @@ inline PyTypeObject* make_default_metaclass() {
 
 /// For multiple inheritance types we need to recursively register/deregister base pointers for any
 /// base classes with pointers that are difference from the instance value pointer so that we can
-/// correctly recognize an offset base class pointer. This calls a function with any offset base ptrs.
-inline void traverse_offset_bases(void *valueptr, const detail::type_info *tinfo, instance *self,
-        bool (*f)(void * /*parentptr*/, instance * /*self*/)) {
+/// correctly recognize an offset base class pointer. This calls a function with any offset base
+/// ptrs.
+inline void traverse_offset_bases(void *valueptr,
+                                  const detail::type_info *tinfo,
+                                  instance *self,
+                                  bool (*f)(void * /*parentptr*/, instance * /*self*/)) {
     for (handle h : reinterpret_borrow<tuple>(tinfo->type->tp_bases)) {
         if (auto *parent_tinfo = get_type_info((PyTypeObject *) h.ptr())) {
             for (auto &c : parent_tinfo->implicit_casts) {
@@ -331,13 +337,13 @@ inline bool deregister_instance(instance *self, void *valptr, const type_info *t
     return ret;
 }
 
-/// Instance creation function for all pybind11 types. It allocates the internal instance layout for
-/// holding C++ objects and holders.  Allocation is done lazily (the first time the instance is cast
-/// to a reference or pointer), and initialization is done by an `__init__` function.
+/// Instance creation function for all pybind11 types. It allocates the internal instance layout
+/// for holding C++ objects and holders.  Allocation is done lazily (the first time the instance is
+/// cast to a reference or pointer), and initialization is done by an `__init__` function.
 inline PyObject *make_new_instance(PyTypeObject *type) {
 #if defined(PYPY_VERSION)
-    // PyPy gets tp_basicsize wrong (issue 2482) under multiple inheritance when the first inherited
-    // object is a plain Python type (i.e. not derived from an extension type).  Fix it.
+    // PyPy gets tp_basicsize wrong (issue 2482) under multiple inheritance when the first
+    // inherited object is a plain Python type (i.e. not derived from an extension type).  Fix it.
     ssize_t instance_size = static_cast<ssize_t>(sizeof(instance));
     if (type->tp_basicsize < instance_size) {
         type->tp_basicsize = instance_size;
@@ -511,7 +517,8 @@ extern "C" inline PyObject *pybind11_get_dict(PyObject *self, void *) {
 /// dynamic_attr: Support for `instance.__dict__ = dict()`.
 extern "C" inline int pybind11_set_dict(PyObject *self, PyObject *new_dict, void *) {
     if (!PyDict_Check(new_dict)) {
-        PyErr_Format(PyExc_TypeError, "__dict__ must be set to a dictionary, not a '%.200s'",
+        PyErr_Format(PyExc_TypeError,
+                     "__dict__ must be set to a dictionary, not a '%.200s'",
                      get_fully_qualified_tp_name(Py_TYPE(new_dict)).c_str());
         return -1;
     }
@@ -540,15 +547,14 @@ extern "C" inline int pybind11_clear(PyObject *self) {
 inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
     auto *type = &heap_type->ht_type;
     type->tp_flags |= Py_TPFLAGS_HAVE_GC;
-    type->tp_dictoffset = type->tp_basicsize; // place dict at the end
-    type->tp_basicsize += (ssize_t)sizeof(PyObject *); // and allocate enough space for it
+    type->tp_dictoffset = type->tp_basicsize;           // place dict at the end
+    type->tp_basicsize += (ssize_t) sizeof(PyObject *); // and allocate enough space for it
     type->tp_traverse = pybind11_traverse;
     type->tp_clear = pybind11_clear;
 
     static PyGetSetDef getset[] = {
-        {const_cast<char*>("__dict__"), pybind11_get_dict, pybind11_set_dict, nullptr, nullptr},
-        {nullptr, nullptr, nullptr, nullptr, nullptr}
-    };
+        {const_cast<char *>("__dict__"), pybind11_get_dict, pybind11_set_dict, nullptr, nullptr},
+        {nullptr, nullptr, nullptr, nullptr, nullptr}};
     type->tp_getset = getset;
 }
 
@@ -617,7 +623,7 @@ inline void enable_buffer_protocol(PyHeapTypeObject *heap_type) {
 
 /** Create a brand new Python type according to the `type_record` specification.
     Return value: New reference. */
-inline PyObject* make_new_python_type(const type_record &rec) {
+inline PyObject *make_new_python_type(const type_record &rec) {
     auto name = reinterpret_steal<object>(PYBIND11_FROM_STRING(rec.name));
 
     auto qualname = name;
@@ -678,7 +684,7 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     auto *type = &heap_type->ht_type;
     type->tp_name = full_name;
     type->tp_doc = tp_doc;
-    type->tp_base = type_incref((PyTypeObject *)base);
+    type->tp_base = type_incref((PyTypeObject *) base);
     type->tp_basicsize = static_cast<ssize_t>(sizeof(instance));
     if (!bases.empty()) {
         type->tp_bases = bases.release().ptr();
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index aa3c617c49..8aefaa393b 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -21,89 +21,90 @@
 #define PYBIND11_NAMESPACE_END(name) }
 
 // Robust support for some features and loading modules compiled against different pybind versions
-// requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute on
-// the main `pybind11` namespace.
+// requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute
+// on the main `pybind11` namespace.
 #if !defined(PYBIND11_NAMESPACE)
-#  ifdef __GNUG__
-#    define PYBIND11_NAMESPACE pybind11 __attribute__((visibility("hidden")))
-#  else
-#    define PYBIND11_NAMESPACE pybind11
-#  endif
+#    ifdef __GNUG__
+#        define PYBIND11_NAMESPACE pybind11 __attribute__((visibility("hidden")))
+#    else
+#        define PYBIND11_NAMESPACE pybind11
+#    endif
 #endif
 
 #if !(defined(_MSC_VER) && __cplusplus == 199711L)
-#  if __cplusplus >= 201402L
-#    define PYBIND11_CPP14
-#    if __cplusplus >= 201703L
-#      define PYBIND11_CPP17
-#      if __cplusplus >= 202002L
-#        define PYBIND11_CPP20
-#      endif
+#    if __cplusplus >= 201402L
+#        define PYBIND11_CPP14
+#        if __cplusplus >= 201703L
+#            define PYBIND11_CPP17
+#            if __cplusplus >= 202002L
+#                define PYBIND11_CPP20
+#            endif
+#        endif
 #    endif
-#  endif
 #elif defined(_MSC_VER) && __cplusplus == 199711L
 // MSVC sets _MSVC_LANG rather than __cplusplus (supposedly until the standard is fully
 // implemented). Unless you use the /Zc:__cplusplus flag on Visual Studio 2017 15.7 Preview 3
 // or newer.
-#  if _MSVC_LANG >= 201402L
-#    define PYBIND11_CPP14
-#    if _MSVC_LANG > 201402L && _MSC_VER >= 1910
-#      define PYBIND11_CPP17
-#      if _MSVC_LANG >= 202002L
-#        define PYBIND11_CPP20
-#      endif
+#    if _MSVC_LANG >= 201402L
+#        define PYBIND11_CPP14
+#        if _MSVC_LANG > 201402L && _MSC_VER >= 1910
+#            define PYBIND11_CPP17
+#            if _MSVC_LANG >= 202002L
+#                define PYBIND11_CPP20
+#            endif
+#        endif
 #    endif
-#  endif
 #endif
 
 // Compiler version assertions
 #if defined(__INTEL_COMPILER)
-#  if __INTEL_COMPILER < 1800
-#    error pybind11 requires Intel C++ compiler v18 or newer
-#  elif __INTEL_COMPILER < 1900 && defined(PYBIND11_CPP14)
-#    error pybind11 supports only C++11 with Intel C++ compiler v18. Use v19 or newer for C++14.
-#  endif
+#    if __INTEL_COMPILER < 1800
+#        error pybind11 requires Intel C++ compiler v18 or newer
+#    elif __INTEL_COMPILER < 1900 && defined(PYBIND11_CPP14)
+#        error pybind11 supports only C++11 with Intel C++ compiler v18. Use v19 or newer for C++14.
+#    endif
 /* The following pragma cannot be pop'ed:
    https://community.intel.com/t5/Intel-C-Compiler/Inline-and-no-inline-warning/td-p/1216764 */
-#  pragma warning disable 2196 // warning #2196: routine is both "inline" and "noinline"
+#    pragma warning disable 2196 // warning #2196: routine is both "inline" and "noinline"
 #elif defined(__clang__) && !defined(__apple_build_version__)
-#  if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
-#    error pybind11 requires clang 3.3 or newer
-#  endif
+#    if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
+#        error pybind11 requires clang 3.3 or newer
+#    endif
 #elif defined(__clang__)
 // Apple changes clang version macros to its Xcode version; the first Xcode release based on
 // (upstream) clang 3.3 was Xcode 5:
-#  if __clang_major__ < 5
-#    error pybind11 requires Xcode/clang 5.0 or newer
-#  endif
+#    if __clang_major__ < 5
+#        error pybind11 requires Xcode/clang 5.0 or newer
+#    endif
 #elif defined(__GNUG__)
-#  if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8)
-#    error pybind11 requires gcc 4.8 or newer
-#  endif
+#    if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8)
+#        error pybind11 requires gcc 4.8 or newer
+#    endif
 #elif defined(_MSC_VER)
 // Pybind hits various compiler bugs in 2015u2 and earlier, and also makes use of some stl features
 // (e.g. std::negation) added in 2015u3:
-#  if _MSC_FULL_VER < 190024210
-#    error pybind11 requires MSVC 2015 update 3 or newer
-#  endif
+#    if _MSC_FULL_VER < 190024210
+#        error pybind11 requires MSVC 2015 update 3 or newer
+#    endif
 #endif
 
 #if !defined(PYBIND11_EXPORT)
-#  if defined(WIN32) || defined(_WIN32)
-#    define PYBIND11_EXPORT __declspec(dllexport)
-#  else
-#    define PYBIND11_EXPORT __attribute__ ((visibility("default")))
-#  endif
+#    if defined(WIN32) || defined(_WIN32)
+#        define PYBIND11_EXPORT __declspec(dllexport)
+#    else
+#        define PYBIND11_EXPORT __attribute__((visibility("default")))
+#    endif
 #endif
 
 #if !defined(PYBIND11_EXPORT_EXCEPTION)
-#  ifdef __MINGW32__
+#    ifdef __MINGW32__
 // workaround for:
-// error: 'dllexport' implies default visibility, but xxx has already been declared with a different visibility
-#    define PYBIND11_EXPORT_EXCEPTION
-#  else
-#    define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
-#  endif
+// error: 'dllexport' implies default visibility, but xxx has already been declared with a
+// different visibility
+#        define PYBIND11_EXPORT_EXCEPTION
+#    else
+#        define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
+#    endif
 #endif
 
 // For CUDA, GCC7, GCC8:
@@ -112,104 +113,103 @@
 // However, the measured shared-library size saving when using noinline are only
 // 1.7% for CUDA, -0.2% for GCC7, and 0.0% for GCC8 (using -DCMAKE_BUILD_TYPE=MinSizeRel,
 // the default under pybind11/tests).
-#if !defined(PYBIND11_NOINLINE_FORCED) && \
-    (defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8)))
-#  define PYBIND11_NOINLINE_DISABLED
+#if !defined(PYBIND11_NOINLINE_FORCED)                                                            \
+    && (defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8)))
+#    define PYBIND11_NOINLINE_DISABLED
 #endif
 
 // The PYBIND11_NOINLINE macro is for function DEFINITIONS.
 // In contrast, FORWARD DECLARATIONS should never use this macro:
 // https://stackoverflow.com/questions/9317473/forward-declaration-of-inline-functions
 #if defined(PYBIND11_NOINLINE_DISABLED) // Option for maximum portability and experimentation.
-#  define PYBIND11_NOINLINE inline
+#    define PYBIND11_NOINLINE inline
 #elif defined(_MSC_VER)
-#  define PYBIND11_NOINLINE __declspec(noinline) inline
+#    define PYBIND11_NOINLINE __declspec(noinline) inline
 #else
-#  define PYBIND11_NOINLINE __attribute__ ((noinline)) inline
+#    define PYBIND11_NOINLINE __attribute__((noinline)) inline
 #endif
 
 #if defined(__MINGW32__)
 // For unknown reasons all PYBIND11_DEPRECATED member trigger a warning when declared
 // whether it is used or not
-#  define PYBIND11_DEPRECATED(reason)
+#    define PYBIND11_DEPRECATED(reason)
 #elif defined(PYBIND11_CPP14)
-#  define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
+#    define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
 #else
-#  define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
+#    define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
 #endif
 
 #if defined(PYBIND11_CPP17)
-#  define PYBIND11_MAYBE_UNUSED [[maybe_unused]]
+#    define PYBIND11_MAYBE_UNUSED [[maybe_unused]]
 #elif defined(_MSC_VER) && !defined(__clang__)
-#  define PYBIND11_MAYBE_UNUSED
+#    define PYBIND11_MAYBE_UNUSED
 #else
-#  define PYBIND11_MAYBE_UNUSED __attribute__ ((__unused__))
+#    define PYBIND11_MAYBE_UNUSED __attribute__((__unused__))
 #endif
 
 /* Don't let Python.h #define (v)snprintf as macro because they are implemented
    properly in Visual Studio since 2015. */
 #if defined(_MSC_VER) && _MSC_VER >= 1900
-#  define HAVE_SNPRINTF 1
+#    define HAVE_SNPRINTF 1
 #endif
 
 /// Include Python header, disable linking to pythonX_d.lib on Windows in debug mode
 #if defined(_MSC_VER)
-#  pragma warning(push)
+#    pragma warning(push)
 // C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
-#  pragma warning(disable: 4505)
-#  if defined(_DEBUG) && !defined(Py_DEBUG)
+#    pragma warning(disable : 4505)
+#    if defined(_DEBUG) && !defined(Py_DEBUG)
 // Workaround for a VS 2022 issue.
 // NOTE: This workaround knowingly violates the Python.h include order requirement:
 // https://docs.python.org/3/c-api/intro.html#include-files
 // See https://github.com/pybind/pybind11/pull/3497 for full context.
-#    include <yvals.h>
-#    if _MSVC_STL_VERSION >= 143
-#      include <crtdefs.h>
+#        include <yvals.h>
+#        if _MSVC_STL_VERSION >= 143
+#            include <crtdefs.h>
+#        endif
+#        define PYBIND11_DEBUG_MARKER
+#        undef _DEBUG
 #    endif
-#    define PYBIND11_DEBUG_MARKER
-#    undef _DEBUG
-#  endif
 #endif
 
 // https://en.cppreference.com/w/c/chrono/localtime
 #if defined(__STDC_LIB_EXT1__) && !defined(__STDC_WANT_LIB_EXT1__)
-#  define __STDC_WANT_LIB_EXT1__
+#    define __STDC_WANT_LIB_EXT1__
 #endif
 
 #ifdef __has_include
 // std::optional (but including it in c++14 mode isn't allowed)
-#  if defined(PYBIND11_CPP17) && __has_include(<optional>)
-#    define PYBIND11_HAS_OPTIONAL 1
-#  endif
+#    if defined(PYBIND11_CPP17) && __has_include(<optional>)
+#        define PYBIND11_HAS_OPTIONAL 1
+#    endif
 // std::experimental::optional (but not allowed in c++11 mode)
-#  if defined(PYBIND11_CPP14) && (__has_include(<experimental/optional>) && \
+#    if defined(PYBIND11_CPP14) && (__has_include(<experimental/optional>) && \
                                  !__has_include(<optional>))
-#    define PYBIND11_HAS_EXP_OPTIONAL 1
-#  endif
+#        define PYBIND11_HAS_EXP_OPTIONAL 1
+#    endif
 // std::variant
-#  if defined(PYBIND11_CPP17) && __has_include(<variant>)
-#    define PYBIND11_HAS_VARIANT 1
-#  endif
+#    if defined(PYBIND11_CPP17) && __has_include(<variant>)
+#        define PYBIND11_HAS_VARIANT 1
+#    endif
 #elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
-#  define PYBIND11_HAS_OPTIONAL 1
-#  define PYBIND11_HAS_VARIANT 1
+#    define PYBIND11_HAS_OPTIONAL 1
+#    define PYBIND11_HAS_VARIANT 1
 #endif
 
 #if defined(PYBIND11_CPP17)
-#  if defined(__has_include)
-#    if __has_include(<string_view>)
-#      define PYBIND11_HAS_STRING_VIEW
+#    if defined(__has_include)
+#        if __has_include(<string_view>)
+#            define PYBIND11_HAS_STRING_VIEW
+#        endif
+#    elif defined(_MSC_VER)
+#        define PYBIND11_HAS_STRING_VIEW
 #    endif
-#  elif defined(_MSC_VER)
-#    define PYBIND11_HAS_STRING_VIEW
-#  endif
 #endif
 
 #if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
-#  define PYBIND11_HAS_U8STRING
+#    define PYBIND11_HAS_U8STRING
 #endif
 
-
 #include <Python.h>
 #include <frameobject.h>
 #include <pythread.h>
@@ -218,43 +218,43 @@
    tends to weak havok in C++ codebases that expect these to work
    like regular functions (potentially with several overloads) */
 #if defined(isalnum)
-#  undef isalnum
-#  undef isalpha
-#  undef islower
-#  undef isspace
-#  undef isupper
-#  undef tolower
-#  undef toupper
+#    undef isalnum
+#    undef isalpha
+#    undef islower
+#    undef isspace
+#    undef isupper
+#    undef tolower
+#    undef toupper
 #endif
 
 #if defined(copysign)
-#  undef copysign
+#    undef copysign
 #endif
 
 #if defined(_MSC_VER)
-#  if defined(PYBIND11_DEBUG_MARKER)
-#    define _DEBUG
-#    undef PYBIND11_DEBUG_MARKER
-#  endif
-#  pragma warning(pop)
+#    if defined(PYBIND11_DEBUG_MARKER)
+#        define _DEBUG
+#        undef PYBIND11_DEBUG_MARKER
+#    endif
+#    pragma warning(pop)
 #endif
 
 #include <cstddef>
 #include <cstring>
-#include <forward_list>
-#include <vector>
-#include <string>
-#include <stdexcept>
 #include <exception>
-#include <unordered_set>
-#include <unordered_map>
+#include <forward_list>
 #include <memory>
-#include <typeindex>
+#include <stdexcept>
+#include <string>
 #include <type_traits>
+#include <typeindex>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
 #if defined(__has_include)
-#  if __has_include(<version>)
-#    include <version>
-#  endif
+#    if __has_include(<version>)
+#        include <version>
+#    endif
 #endif
 
 // #define PYBIND11_STR_LEGACY_PERMISSIVE
@@ -271,70 +271,71 @@
 //               behavior.
 
 #if PY_MAJOR_VERSION >= 3 /// Compatibility macros for various Python versions
-#define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
-#define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
-#define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
-#define PYBIND11_BYTES_CHECK PyBytes_Check
-#define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
-#define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
-#define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
-#define PYBIND11_BYTES_AS_STRING PyBytes_AsString
-#define PYBIND11_BYTES_SIZE PyBytes_Size
-#define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
-#define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
-#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
-#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
-#define PYBIND11_BYTES_NAME "bytes"
-#define PYBIND11_STRING_NAME "str"
-#define PYBIND11_SLICE_OBJECT PyObject
-#define PYBIND11_FROM_STRING PyUnicode_FromString
-#define PYBIND11_STR_TYPE ::pybind11::str
-#define PYBIND11_BOOL_ATTR "__bool__"
-#define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
-#define PYBIND11_BUILTINS_MODULE "builtins"
+#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
+#    define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
+#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
+#    define PYBIND11_BYTES_CHECK PyBytes_Check
+#    define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
+#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
+#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
+#    define PYBIND11_BYTES_AS_STRING PyBytes_AsString
+#    define PYBIND11_BYTES_SIZE PyBytes_Size
+#    define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
+#    define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
+#    define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
+#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
+#    define PYBIND11_BYTES_NAME "bytes"
+#    define PYBIND11_STRING_NAME "str"
+#    define PYBIND11_SLICE_OBJECT PyObject
+#    define PYBIND11_FROM_STRING PyUnicode_FromString
+#    define PYBIND11_STR_TYPE ::pybind11::str
+#    define PYBIND11_BOOL_ATTR "__bool__"
+#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
+#    define PYBIND11_BUILTINS_MODULE "builtins"
 // Providing a separate declaration to make Clang's -Wmissing-prototypes happy.
 // See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#define PYBIND11_PLUGIN_IMPL(name) \
-    extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name(); \
-    extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
+#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
+        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();               \
+        extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
 
 #else
-#define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
-#define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
-#define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
-#define PYBIND11_BYTES_CHECK PyString_Check
-#define PYBIND11_BYTES_FROM_STRING PyString_FromString
-#define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
-#define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
-#define PYBIND11_BYTES_AS_STRING PyString_AsString
-#define PYBIND11_BYTES_SIZE PyString_Size
-#define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
-#define PYBIND11_LONG_AS_LONGLONG(o) (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
-#define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
-#define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
-#define PYBIND11_BYTES_NAME "str"
-#define PYBIND11_STRING_NAME "unicode"
-#define PYBIND11_SLICE_OBJECT PySliceObject
-#define PYBIND11_FROM_STRING PyString_FromString
-#define PYBIND11_STR_TYPE ::pybind11::bytes
-#define PYBIND11_BOOL_ATTR "__nonzero__"
-#define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
-#define PYBIND11_BUILTINS_MODULE "__builtin__"
+#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
+#    define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
+#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
+#    define PYBIND11_BYTES_CHECK PyString_Check
+#    define PYBIND11_BYTES_FROM_STRING PyString_FromString
+#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
+#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
+#    define PYBIND11_BYTES_AS_STRING PyString_AsString
+#    define PYBIND11_BYTES_SIZE PyString_Size
+#    define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
+#    define PYBIND11_LONG_AS_LONGLONG(o)                                                          \
+        (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
+#    define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
+#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
+#    define PYBIND11_BYTES_NAME "str"
+#    define PYBIND11_STRING_NAME "unicode"
+#    define PYBIND11_SLICE_OBJECT PySliceObject
+#    define PYBIND11_FROM_STRING PyString_FromString
+#    define PYBIND11_STR_TYPE ::pybind11::bytes
+#    define PYBIND11_BOOL_ATTR "__nonzero__"
+#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
+#    define PYBIND11_BUILTINS_MODULE "__builtin__"
 // Providing a separate PyInit decl to make Clang's -Wmissing-prototypes happy.
 // See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#define PYBIND11_PLUGIN_IMPL(name) \
-    static PyObject *pybind11_init_wrapper();                           \
-    extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT void init##name(); \
-    extern "C" PYBIND11_EXPORT void init##name() {                      \
-        (void)pybind11_init_wrapper();                                  \
-    }                                                                   \
-    PyObject *pybind11_init_wrapper()
+#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
+        static PyObject *pybind11_init_wrapper();                                                 \
+        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT void init##name();                       \
+        extern "C" PYBIND11_EXPORT void init##name() { (void) pybind11_init_wrapper(); }          \
+        PyObject *pybind11_init_wrapper()
 #endif
 
 #if PY_VERSION_HEX >= 0x03050000 && PY_VERSION_HEX < 0x03050200
 extern "C" {
-    struct _Py_atomic_address { void *value; };
-    PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
+struct _Py_atomic_address {
+    void *value;
+};
+PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
 }
 #endif
 
@@ -342,46 +343,48 @@ extern "C" {
 #define PYBIND11_STRINGIFY(x) #x
 #define PYBIND11_TOSTRING(x) PYBIND11_STRINGIFY(x)
 #define PYBIND11_CONCAT(first, second) first##second
-#define PYBIND11_ENSURE_INTERNALS_READY \
-    pybind11::detail::get_internals();
-
-#define PYBIND11_CHECK_PYTHON_VERSION \
-    {                                                                          \
-        const char *compiled_ver = PYBIND11_TOSTRING(PY_MAJOR_VERSION)         \
-            "." PYBIND11_TOSTRING(PY_MINOR_VERSION);                           \
-        const char *runtime_ver = Py_GetVersion();                             \
-        size_t len = std::strlen(compiled_ver);                                \
-        if (std::strncmp(runtime_ver, compiled_ver, len) != 0                  \
-                || (runtime_ver[len] >= '0' && runtime_ver[len] <= '9')) {     \
-            PyErr_Format(PyExc_ImportError,                                    \
-                "Python version mismatch: module was compiled for Python %s, " \
-                "but the interpreter version is incompatible: %s.",            \
-                compiled_ver, runtime_ver);                                    \
-            return nullptr;                                                    \
-        }                                                                      \
+#define PYBIND11_ENSURE_INTERNALS_READY pybind11::detail::get_internals();
+
+#define PYBIND11_CHECK_PYTHON_VERSION                                                             \
+    {                                                                                             \
+        const char *compiled_ver                                                                  \
+            = PYBIND11_TOSTRING(PY_MAJOR_VERSION) "." PYBIND11_TOSTRING(PY_MINOR_VERSION);        \
+        const char *runtime_ver = Py_GetVersion();                                                \
+        size_t len = std::strlen(compiled_ver);                                                   \
+        if (std::strncmp(runtime_ver, compiled_ver, len) != 0                                     \
+            || (runtime_ver[len] >= '0' && runtime_ver[len] <= '9')) {                            \
+            PyErr_Format(PyExc_ImportError,                                                       \
+                         "Python version mismatch: module was compiled for Python %s, "           \
+                         "but the interpreter version is incompatible: %s.",                      \
+                         compiled_ver,                                                            \
+                         runtime_ver);                                                            \
+            return nullptr;                                                                       \
+        }                                                                                         \
     }
 
 #if PY_VERSION_HEX >= 0x03030000
 
-#define PYBIND11_CATCH_INIT_EXCEPTIONS \
-        catch (pybind11::error_already_set &e) {                                 \
-            pybind11::raise_from(e, PyExc_ImportError, "initialization failed"); \
-            return nullptr;                                                      \
-        } catch (const std::exception &e) {                                      \
-            PyErr_SetString(PyExc_ImportError, e.what());                        \
-            return nullptr;                                                      \
-        }                                                                        \
+#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
+        catch (pybind11::error_already_set & e) {                                                 \
+            pybind11::raise_from(e, PyExc_ImportError, "initialization failed");                  \
+            return nullptr;                                                                       \
+        }                                                                                         \
+        catch (const std::exception &e) {                                                         \
+            PyErr_SetString(PyExc_ImportError, e.what());                                         \
+            return nullptr;                                                                       \
+        }
 
 #else
 
-#define PYBIND11_CATCH_INIT_EXCEPTIONS \
-        catch (pybind11::error_already_set &e) {                               \
-            PyErr_SetString(PyExc_ImportError, e.what());                      \
-            return nullptr;                                                    \
-        } catch (const std::exception &e) {                                    \
-            PyErr_SetString(PyExc_ImportError, e.what());                      \
-            return nullptr;                                                    \
-        }                                                                      \
+#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
+        catch (pybind11::error_already_set & e) {                                                 \
+            PyErr_SetString(PyExc_ImportError, e.what());                                         \
+            return nullptr;                                                                       \
+        }                                                                                         \
+        catch (const std::exception &e) {                                                         \
+            PyErr_SetString(PyExc_ImportError, e.what());                                         \
+            return nullptr;                                                                       \
+        }
 
 #endif
 
@@ -400,16 +403,17 @@ extern "C" {
             return m.ptr();
         }
 \endrst */
-#define PYBIND11_PLUGIN(name)                                                  \
-    PYBIND11_DEPRECATED("PYBIND11_PLUGIN is deprecated, use PYBIND11_MODULE")  \
-    static PyObject *pybind11_init();                                          \
-    PYBIND11_PLUGIN_IMPL(name) {                                               \
-        PYBIND11_CHECK_PYTHON_VERSION                                          \
-        PYBIND11_ENSURE_INTERNALS_READY                                        \
-        try {                                                                  \
-            return pybind11_init();                                            \
-        } PYBIND11_CATCH_INIT_EXCEPTIONS                                       \
-    }                                                                          \
+#define PYBIND11_PLUGIN(name)                                                                     \
+    PYBIND11_DEPRECATED("PYBIND11_PLUGIN is deprecated, use PYBIND11_MODULE")                     \
+    static PyObject *pybind11_init();                                                             \
+    PYBIND11_PLUGIN_IMPL(name) {                                                                  \
+        PYBIND11_CHECK_PYTHON_VERSION                                                             \
+        PYBIND11_ENSURE_INTERNALS_READY                                                           \
+        try {                                                                                     \
+            return pybind11_init();                                                               \
+        }                                                                                         \
+        PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
+    }                                                                                             \
     PyObject *pybind11_init()
 
 /** \rst
@@ -454,7 +458,7 @@ extern "C" {
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 using ssize_t = Py_ssize_t;
-using size_t  = std::size_t;
+using size_t = std::size_t;
 
 template <typename IntType>
 inline ssize_t ssize_t_cast(const IntType &val) {
@@ -516,10 +520,14 @@ enum class return_value_policy : uint8_t {
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-inline static constexpr int log2(size_t n, int k = 0) { return (n <= 1) ? k : log2(n >> 1, k + 1); }
+inline static constexpr int log2(size_t n, int k = 0) {
+    return (n <= 1) ? k : log2(n >> 1, k + 1);
+}
 
 // Returns the size as a multiple of sizeof(void *), rounded up.
-inline static constexpr size_t size_in_ptrs(size_t s) { return 1 + ((s - 1) >> log2(sizeof(void *))); }
+inline static constexpr size_t size_in_ptrs(size_t s) {
+    return 1 + ((s - 1) >> log2(sizeof(void *)));
+}
 
 /**
  * The space to allocate for simple layout instance holders (see below) in multiple of the size of
@@ -529,7 +537,7 @@ inline static constexpr size_t size_in_ptrs(size_t s) { return 1 + ((s - 1) >> l
  */
 constexpr size_t instance_simple_holder_in_ptrs() {
     static_assert(sizeof(std::shared_ptr<int>) >= sizeof(std::unique_ptr<int>),
-            "pybind assumes std::shared_ptrs are at least as big as std::unique_ptrs");
+                  "pybind assumes std::shared_ptrs are at least as big as std::unique_ptrs");
     return size_in_ptrs(sizeof(std::shared_ptr<int>));
 }
 
@@ -557,21 +565,21 @@ struct instance {
     /**
      * An instance has two possible value/holder layouts.
      *
-     * Simple layout (when this flag is true), means the `simple_value_holder` is set with a pointer
-     * and the holder object governing that pointer, i.e. [val1*][holder].  This layout is applied
-     * whenever there is no python-side multiple inheritance of bound C++ types *and* the type's
-     * holder will fit in the default space (which is large enough to hold either a std::unique_ptr
-     * or std::shared_ptr).
+     * Simple layout (when this flag is true), means the `simple_value_holder` is set with a
+     * pointer and the holder object governing that pointer, i.e. [val1*][holder].  This layout is
+     * applied whenever there is no python-side multiple inheritance of bound C++ types *and* the
+     * type's holder will fit in the default space (which is large enough to hold either a
+     * std::unique_ptr or std::shared_ptr).
      *
-     * Non-simple layout applies when using custom holders that require more space than `shared_ptr`
-     * (which is typically the size of two pointers), or when multiple inheritance is used on the
-     * python side.  Non-simple layout allocates the required amount of memory to have multiple
-     * bound C++ classes as parents.  Under this layout, `nonsimple.values_and_holders` is set to a
-     * pointer to allocated space of the required space to hold a sequence of value pointers and
-     * holders followed `status`, a set of bit flags (1 byte each), i.e.
-     * [val1*][holder1][val2*][holder2]...[bb...]  where each [block] is rounded up to a multiple of
-     * `sizeof(void *)`.  `nonsimple.status` is, for convenience, a pointer to the
-     * beginning of the [bb...] block (but not independently allocated).
+     * Non-simple layout applies when using custom holders that require more space than
+     * `shared_ptr` (which is typically the size of two pointers), or when multiple inheritance is
+     * used on the python side.  Non-simple layout allocates the required amount of memory to have
+     * multiple bound C++ classes as parents.  Under this layout, `nonsimple.values_and_holders` is
+     * set to a pointer to allocated space of the required space to hold a sequence of value
+     * pointers and holders followed `status`, a set of bit flags (1 byte each), i.e.
+     * [val1*][holder1][val2*][holder2]...[bb...]  where each [block] is rounded up to a multiple
+     * of `sizeof(void *)`.  `nonsimple.status` is, for convenience, a pointer to the beginning of
+     * the [bb...] block (but not independently allocated).
      *
      * Status bits indicate whether the associated holder is constructed (&
      * status_holder_constructed) and whether the value pointer is registered (&
@@ -585,7 +593,8 @@ struct instance {
     /// If true, get_internals().patients has an entry for this object
     bool has_patients : 1;
 
-    /// Initializes all of the above type/values/holders data (but not the instance values themselves)
+    /// Initializes all of the above type/values/holders data (but not the instance values
+    /// themselves)
     void allocate_layout();
 
     /// Destroys/deallocates all of the above
@@ -594,26 +603,32 @@ struct instance {
     /// Returns the value_and_holder wrapper for the given type (or the first, if `find_type`
     /// omitted).  Returns a default-constructed (with `.inst = nullptr`) object on failure if
     /// `throw_if_missing` is false.
-    value_and_holder get_value_and_holder(const type_info *find_type = nullptr, bool throw_if_missing = true);
+    value_and_holder get_value_and_holder(const type_info *find_type = nullptr,
+                                          bool throw_if_missing = true);
 
     /// Bit values for the non-simple status flags
-    static constexpr uint8_t status_holder_constructed  = 1;
+    static constexpr uint8_t status_holder_constructed = 1;
     static constexpr uint8_t status_instance_registered = 2;
 };
 
-static_assert(std::is_standard_layout<instance>::value, "Internal error: `pybind11::detail::instance` is not standard layout!");
+static_assert(std::is_standard_layout<instance>::value,
+              "Internal error: `pybind11::detail::instance` is not standard layout!");
 
 /// from __cpp_future__ import (convenient aliases from C++14/17)
 #if defined(PYBIND11_CPP14) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
-using std::enable_if_t;
 using std::conditional_t;
+using std::enable_if_t;
 using std::remove_cv_t;
 using std::remove_reference_t;
 #else
-template <bool B, typename T = void> using enable_if_t = typename std::enable_if<B, T>::type;
-template <bool B, typename T, typename F> using conditional_t = typename std::conditional<B, T, F>::type;
-template <typename T> using remove_cv_t = typename std::remove_cv<T>::type;
-template <typename T> using remove_reference_t = typename std::remove_reference<T>::type;
+template <bool B, typename T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+template <bool B, typename T, typename F>
+using conditional_t = typename std::conditional<B, T, F>::type;
+template <typename T>
+using remove_cv_t = typename std::remove_cv<T>::type;
+template <typename T>
+using remove_reference_t = typename std::remove_reference<T>::type;
 #endif
 
 #if defined(PYBIND11_CPP20)
@@ -633,114 +648,189 @@ using remove_cvref_t = typename remove_cvref<T>::type;
 using std::index_sequence;
 using std::make_index_sequence;
 #else
-template<size_t ...> struct index_sequence  { };
-template<size_t N, size_t ...S> struct make_index_sequence_impl : make_index_sequence_impl <N - 1, N - 1, S...> { };
-template<size_t ...S> struct make_index_sequence_impl <0, S...> { using type = index_sequence<S...>; };
-template<size_t N> using make_index_sequence = typename make_index_sequence_impl<N>::type;
+template <size_t...>
+struct index_sequence {};
+template <size_t N, size_t... S>
+struct make_index_sequence_impl : make_index_sequence_impl<N - 1, N - 1, S...> {};
+template <size_t... S>
+struct make_index_sequence_impl<0, S...> {
+    using type = index_sequence<S...>;
+};
+template <size_t N>
+using make_index_sequence = typename make_index_sequence_impl<N>::type;
 #endif
 
 /// Make an index sequence of the indices of true arguments
-template <typename ISeq, size_t, bool...> struct select_indices_impl { using type = ISeq; };
-template <size_t... IPrev, size_t I, bool B, bool... Bs> struct select_indices_impl<index_sequence<IPrev...>, I, B, Bs...>
-    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>, I + 1, Bs...> {};
-template <bool... Bs> using select_indices = typename select_indices_impl<index_sequence<>, 0, Bs...>::type;
+template <typename ISeq, size_t, bool...>
+struct select_indices_impl {
+    using type = ISeq;
+};
+template <size_t... IPrev, size_t I, bool B, bool... Bs>
+struct select_indices_impl<index_sequence<IPrev...>, I, B, Bs...>
+    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>,
+                          I + 1,
+                          Bs...> {};
+template <bool... Bs>
+using select_indices = typename select_indices_impl<index_sequence<>, 0, Bs...>::type;
 
 /// Backports of std::bool_constant and std::negation to accommodate older compilers
-template <bool B> using bool_constant = std::integral_constant<bool, B>;
-template <typename T> struct negation : bool_constant<!T::value> { };
+template <bool B>
+using bool_constant = std::integral_constant<bool, B>;
+template <typename T>
+struct negation : bool_constant<!T::value> {};
 
 // PGI/Intel cannot detect operator delete with the "compatible" void_t impl, so
 // using the new one (C++14 defect, so generally works on newer compilers, even
 // if not in C++17 mode)
 #if defined(__PGIC__) || defined(__INTEL_COMPILER)
-template<typename... > using void_t = void;
+template <typename...>
+using void_t = void;
 #else
-template <typename...> struct void_t_impl { using type = void; };
-template <typename... Ts> using void_t = typename void_t_impl<Ts...>::type;
+template <typename...>
+struct void_t_impl {
+    using type = void;
+};
+template <typename... Ts>
+using void_t = typename void_t_impl<Ts...>::type;
 #endif
 
-
 /// Compile-time all/any/none of that check the boolean value of all template types
 #if defined(__cpp_fold_expressions) && !(defined(_MSC_VER) && (_MSC_VER < 1916))
-template <class... Ts> using all_of = bool_constant<(Ts::value && ...)>;
-template <class... Ts> using any_of = bool_constant<(Ts::value || ...)>;
+template <class... Ts>
+using all_of = bool_constant<(Ts::value && ...)>;
+template <class... Ts>
+using any_of = bool_constant<(Ts::value || ...)>;
 #elif !defined(_MSC_VER)
-template <bool...> struct bools {};
-template <class... Ts> using all_of = std::is_same<
-    bools<Ts::value..., true>,
-    bools<true, Ts::value...>>;
-template <class... Ts> using any_of = negation<all_of<negation<Ts>...>>;
+template <bool...>
+struct bools {};
+template <class... Ts>
+using all_of = std::is_same<bools<Ts::value..., true>, bools<true, Ts::value...>>;
+template <class... Ts>
+using any_of = negation<all_of<negation<Ts>...>>;
 #else
 // MSVC has trouble with the above, but supports std::conjunction, which we can use instead (albeit
 // at a slight loss of compilation efficiency).
-template <class... Ts> using all_of = std::conjunction<Ts...>;
-template <class... Ts> using any_of = std::disjunction<Ts...>;
+template <class... Ts>
+using all_of = std::conjunction<Ts...>;
+template <class... Ts>
+using any_of = std::disjunction<Ts...>;
 #endif
-template <class... Ts> using none_of = negation<any_of<Ts...>>;
+template <class... Ts>
+using none_of = negation<any_of<Ts...>>;
 
-template <class T, template<class> class... Predicates> using satisfies_all_of = all_of<Predicates<T>...>;
-template <class T, template<class> class... Predicates> using satisfies_any_of = any_of<Predicates<T>...>;
-template <class T, template<class> class... Predicates> using satisfies_none_of = none_of<Predicates<T>...>;
+template <class T, template <class> class... Predicates>
+using satisfies_all_of = all_of<Predicates<T>...>;
+template <class T, template <class> class... Predicates>
+using satisfies_any_of = any_of<Predicates<T>...>;
+template <class T, template <class> class... Predicates>
+using satisfies_none_of = none_of<Predicates<T>...>;
 
 /// Strip the class from a method type
-template <typename T> struct remove_class { };
-template <typename C, typename R, typename... A> struct remove_class<R (C::*)(A...)> { using type = R (A...); };
-template <typename C, typename R, typename... A> struct remove_class<R (C::*)(A...) const> { using type = R (A...); };
+template <typename T>
+struct remove_class {};
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...)> {
+    using type = R(A...);
+};
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...) const> {
+    using type = R(A...);
+};
 
 /// Helper template to strip away type modifiers
-template <typename T> struct intrinsic_type                       { using type = T; };
-template <typename T> struct intrinsic_type<const T>              { using type = typename intrinsic_type<T>::type; };
-template <typename T> struct intrinsic_type<T*>                   { using type = typename intrinsic_type<T>::type; };
-template <typename T> struct intrinsic_type<T&>                   { using type = typename intrinsic_type<T>::type; };
-template <typename T> struct intrinsic_type<T&&>                  { using type = typename intrinsic_type<T>::type; };
-template <typename T, size_t N> struct intrinsic_type<const T[N]> { using type = typename intrinsic_type<T>::type; };
-template <typename T, size_t N> struct intrinsic_type<T[N]>       { using type = typename intrinsic_type<T>::type; };
-template <typename T> using intrinsic_t = typename intrinsic_type<T>::type;
+template <typename T>
+struct intrinsic_type {
+    using type = T;
+};
+template <typename T>
+struct intrinsic_type<const T> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+struct intrinsic_type<T *> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+struct intrinsic_type<T &> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+struct intrinsic_type<T &&> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T, size_t N>
+struct intrinsic_type<const T[N]> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T, size_t N>
+struct intrinsic_type<T[N]> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+using intrinsic_t = typename intrinsic_type<T>::type;
 
 /// Helper type to replace 'void' in some expressions
-struct void_type { };
+struct void_type {};
 
 /// Helper template which holds a list of types
-template <typename...> struct type_list { };
+template <typename...>
+struct type_list {};
 
 /// Compile-time integer sum
 #ifdef __cpp_fold_expressions
-template <typename... Ts> constexpr size_t constexpr_sum(Ts... ns) { return (0 + ... + size_t{ns}); }
+template <typename... Ts>
+constexpr size_t constexpr_sum(Ts... ns) {
+    return (0 + ... + size_t{ns});
+}
 #else
 constexpr size_t constexpr_sum() { return 0; }
 template <typename T, typename... Ts>
-constexpr size_t constexpr_sum(T n, Ts... ns) { return size_t{n} + constexpr_sum(ns...); }
+constexpr size_t constexpr_sum(T n, Ts... ns) {
+    return size_t{n} + constexpr_sum(ns...);
+}
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(constexpr_impl)
 /// Implementation details for constexpr functions
 constexpr int first(int i) { return i; }
 template <typename T, typename... Ts>
-constexpr int first(int i, T v, Ts... vs) { return v ? i : first(i + 1, vs...); }
+constexpr int first(int i, T v, Ts... vs) {
+    return v ? i : first(i + 1, vs...);
+}
 
 constexpr int last(int /*i*/, int result) { return result; }
 template <typename T, typename... Ts>
-constexpr int last(int i, int result, T v, Ts... vs) { return last(i + 1, v ? i : result, vs...); }
+constexpr int last(int i, int result, T v, Ts... vs) {
+    return last(i + 1, v ? i : result, vs...);
+}
 PYBIND11_NAMESPACE_END(constexpr_impl)
 
 /// Return the index of the first type in Ts which satisfies Predicate<T>.
 /// Returns sizeof...(Ts) if none match.
-template <template<typename> class Predicate, typename... Ts>
-constexpr int constexpr_first() { return constexpr_impl::first(0, Predicate<Ts>::value...); }
+template <template <typename> class Predicate, typename... Ts>
+constexpr int constexpr_first() {
+    return constexpr_impl::first(0, Predicate<Ts>::value...);
+}
 
 /// Return the index of the last type in Ts which satisfies Predicate<T>, or -1 if none match.
-template <template<typename> class Predicate, typename... Ts>
-constexpr int constexpr_last() { return constexpr_impl::last(0, -1, Predicate<Ts>::value...); }
+template <template <typename> class Predicate, typename... Ts>
+constexpr int constexpr_last() {
+    return constexpr_impl::last(0, -1, Predicate<Ts>::value...);
+}
 
 /// Return the Nth element from the parameter pack
 template <size_t N, typename T, typename... Ts>
-struct pack_element { using type = typename pack_element<N - 1, Ts...>::type; };
+struct pack_element {
+    using type = typename pack_element<N - 1, Ts...>::type;
+};
 template <typename T, typename... Ts>
-struct pack_element<0, T, Ts...> { using type = T; };
+struct pack_element<0, T, Ts...> {
+    using type = T;
+};
 
 /// Return the one and only type which matches the predicate, or Default if none match.
 /// If more than one type matches the predicate, fail at compile-time.
-template <template<typename> class Predicate, typename Default, typename... Ts>
+template <template <typename> class Predicate, typename Default, typename... Ts>
 struct exactly_one {
     static constexpr auto found = constexpr_sum(Predicate<Ts>::value...);
     static_assert(found <= 1, "Found more than one type matching the predicate");
@@ -748,62 +838,81 @@ struct exactly_one {
     static constexpr auto index = found ? constexpr_first<Predicate, Ts...>() : 0;
     using type = conditional_t<found, typename pack_element<index, Ts...>::type, Default>;
 };
-template <template<typename> class P, typename Default>
-struct exactly_one<P, Default> { using type = Default; };
+template <template <typename> class P, typename Default>
+struct exactly_one<P, Default> {
+    using type = Default;
+};
 
-template <template<typename> class Predicate, typename Default, typename... Ts>
+template <template <typename> class Predicate, typename Default, typename... Ts>
 using exactly_one_t = typename exactly_one<Predicate, Default, Ts...>::type;
 
 /// Defer the evaluation of type T until types Us are instantiated
-template <typename T, typename... /*Us*/> struct deferred_type { using type = T; };
-template <typename T, typename... Us> using deferred_t = typename deferred_type<T, Us...>::type;
+template <typename T, typename... /*Us*/>
+struct deferred_type {
+    using type = T;
+};
+template <typename T, typename... Us>
+using deferred_t = typename deferred_type<T, Us...>::type;
 
 /// Like is_base_of, but requires a strict base (i.e. `is_strict_base_of<T, T>::value == false`,
 /// unlike `std::is_base_of`)
-template <typename Base, typename Derived> using is_strict_base_of = bool_constant<
-    std::is_base_of<Base, Derived>::value && !std::is_same<Base, Derived>::value>;
-
-/// Like is_base_of, but also requires that the base type is accessible (i.e. that a Derived pointer
-/// can be converted to a Base pointer)
-/// For unions, `is_base_of<T, T>::value` is False, so we need to check `is_same` as well.
-template <typename Base, typename Derived> using is_accessible_base_of = bool_constant<
-    (std::is_same<Base, Derived>::value || std::is_base_of<Base, Derived>::value) && std::is_convertible<Derived *, Base *>::value>;
-
-template <template<typename...> class Base>
+template <typename Base, typename Derived>
+using is_strict_base_of
+    = bool_constant<std::is_base_of<Base, Derived>::value && !std::is_same<Base, Derived>::value>;
+
+/// Like is_base_of, but also requires that the base type is accessible (i.e. that a Derived
+/// pointer can be converted to a Base pointer) For unions, `is_base_of<T, T>::value` is False, so
+/// we need to check `is_same` as well.
+template <typename Base, typename Derived>
+using is_accessible_base_of
+    = bool_constant<(std::is_same<Base, Derived>::value || std::is_base_of<Base, Derived>::value)
+                    && std::is_convertible<Derived *, Base *>::value>;
+
+template <template <typename...> class Base>
 struct is_template_base_of_impl {
-    template <typename... Us> static std::true_type check(Base<Us...> *);
+    template <typename... Us>
+    static std::true_type check(Base<Us...> *);
     static std::false_type check(...);
 };
 
 /// Check if a template is the base of a type. For example:
 /// `is_template_base_of<Base, T>` is true if `struct T : Base<U> {}` where U can be anything
-template <template<typename...> class Base, typename T>
+template <template <typename...> class Base, typename T>
 #if !defined(_MSC_VER)
-using is_template_base_of = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T>*)nullptr));
+using is_template_base_of
+    = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr));
 #else // MSVC2015 has trouble with decltype in template aliases
-struct is_template_base_of : decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T>*)nullptr)) { };
+struct is_template_base_of
+    : decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr)) {
+};
 #endif
 
 /// Check if T is an instantiation of the template `Class`. For example:
 /// `is_instantiation<shared_ptr, T>` is true if `T == shared_ptr<U>` where U can be anything.
-template <template<typename...> class Class, typename T>
-struct is_instantiation : std::false_type { };
-template <template<typename...> class Class, typename... Us>
-struct is_instantiation<Class, Class<Us...>> : std::true_type { };
+template <template <typename...> class Class, typename T>
+struct is_instantiation : std::false_type {};
+template <template <typename...> class Class, typename... Us>
+struct is_instantiation<Class, Class<Us...>> : std::true_type {};
 
 /// Check if T is std::shared_ptr<U> where U can be anything
-template <typename T> using is_shared_ptr = is_instantiation<std::shared_ptr, T>;
+template <typename T>
+using is_shared_ptr = is_instantiation<std::shared_ptr, T>;
 
 /// Check if T looks like an input iterator
-template <typename T, typename = void> struct is_input_iterator : std::false_type {};
+template <typename T, typename = void>
+struct is_input_iterator : std::false_type {};
 template <typename T>
-struct is_input_iterator<T, void_t<decltype(*std::declval<T &>()), decltype(++std::declval<T &>())>>
+struct is_input_iterator<T,
+                         void_t<decltype(*std::declval<T &>()), decltype(++std::declval<T &>())>>
     : std::true_type {};
 
-template <typename T> using is_function_pointer = bool_constant<
-    std::is_pointer<T>::value && std::is_function<typename std::remove_pointer<T>::type>::value>;
+template <typename T>
+using is_function_pointer
+    = bool_constant<std::is_pointer<T>::value
+                    && std::is_function<typename std::remove_pointer<T>::type>::value>;
 
-template <typename F> struct strip_function_object {
+template <typename F>
+struct strip_function_object {
     // If you are encountering an
     // 'error: name followed by "::" must be a class or namespace name'
     // with the Intel compiler and a noexcept function here,
@@ -816,34 +925,35 @@ template <typename Function, typename F = remove_reference_t<Function>>
 using function_signature_t = conditional_t<
     std::is_function<F>::value,
     F,
-    typename conditional_t<
-        std::is_pointer<F>::value || std::is_member_pointer<F>::value,
-        std::remove_pointer<F>,
-        strip_function_object<F>
-    >::type
->;
+    typename conditional_t<std::is_pointer<F>::value || std::is_member_pointer<F>::value,
+                           std::remove_pointer<F>,
+                           strip_function_object<F>>::type>;
 
 /// Returns true if the type looks like a lambda: that is, isn't a function, pointer or member
 /// pointer.  Note that this can catch all sorts of other things, too; this is intended to be used
 /// in a place where passing a lambda makes sense.
-template <typename T> using is_lambda = satisfies_none_of<remove_reference_t<T>,
-        std::is_function, std::is_pointer, std::is_member_pointer>;
+template <typename T>
+using is_lambda = satisfies_none_of<remove_reference_t<T>,
+                                    std::is_function,
+                                    std::is_pointer,
+                                    std::is_member_pointer>;
 
 // [workaround(intel)] Internal error on fold expression
 /// Apply a function over each element of a parameter pack
 #if defined(__cpp_fold_expressions) && !defined(__INTEL_COMPILER)
 // Intel compiler produces an internal error on this fold expression (tested with ICC 19.0.2)
-#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
+#    define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
 #else
 using expand_side_effects = bool[];
-#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (void)pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
+#    define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN)                                                 \
+        (void) pybind11::detail::expand_side_effects { ((PATTERN), void(), false)..., false }
 #endif
 
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4275)
+#    pragma warning(push)
+#    pragma warning(disable : 4275)
 //     warning C4275: An exported class was derived from a class that wasn't exported.
 //     Can be ignored when derived from a STL class.
 #endif
@@ -855,14 +965,15 @@ class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
     virtual void set_error() const = 0;
 };
 #if defined(_MSC_VER)
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
-#define PYBIND11_RUNTIME_EXCEPTION(name, type) \
-    class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception { public: \
-        using builtin_exception::builtin_exception; \
-        name() : name("") { } \
-        void set_error() const override { PyErr_SetString(type, what()); } \
+#define PYBIND11_RUNTIME_EXCEPTION(name, type)                                                    \
+    class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception {                             \
+    public:                                                                                       \
+        using builtin_exception::builtin_exception;                                               \
+        name() : name("") {}                                                                      \
+        void set_error() const override { PyErr_SetString(type, what()); }                        \
     };
 
 PYBIND11_RUNTIME_EXCEPTION(stop_iteration, PyExc_StopIteration)
@@ -878,10 +989,15 @@ PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybin
                                                            /// casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
 
-[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
-[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const std::string &reason) { throw std::runtime_error(reason); }
+[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) {
+    throw std::runtime_error(reason);
+}
+[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const std::string &reason) {
+    throw std::runtime_error(reason);
+}
 
-template <typename T, typename SFINAE = void> struct format_descriptor { };
+template <typename T, typename SFINAE = void>
+struct format_descriptor {};
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 // Returns the index of the given type in the type char array below, and in the list in numpy.h
@@ -889,25 +1005,38 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // complex float,double,long double.  Note that the long double types only participate when long
 // double is actually longer than double (it isn't under MSVC).
 // NB: not only the string below but also complex.h and numpy.h rely on this order.
-template <typename T, typename SFINAE = void> struct is_fmt_numeric { static constexpr bool value = false; };
-template <typename T> struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
+template <typename T, typename SFINAE = void>
+struct is_fmt_numeric {
+    static constexpr bool value = false;
+};
+template <typename T>
+struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
     static constexpr bool value = true;
-    static constexpr int index = std::is_same<T, bool>::value ? 0 : 1 + (
-        std::is_integral<T>::value ? detail::log2(sizeof(T))*2 + std::is_unsigned<T>::value : 8 + (
-        std::is_same<T, double>::value ? 1 : std::is_same<T, long double>::value ? 2 : 0));
+    static constexpr int index
+        = std::is_same<T, bool>::value
+              ? 0
+              : 1
+                    + (std::is_integral<T>::value
+                           ? detail::log2(sizeof(T)) * 2 + std::is_unsigned<T>::value
+                           : 8
+                                 + (std::is_same<T, double>::value        ? 1
+                                    : std::is_same<T, long double>::value ? 2
+                                                                          : 0));
 };
 PYBIND11_NAMESPACE_END(detail)
 
-template <typename T> struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
+template <typename T>
+struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
     static constexpr const char c = "?bBhHiIqQfdg"[detail::is_fmt_numeric<T>::index];
-    static constexpr const char value[2] = { c, '\0' };
+    static constexpr const char value[2] = {c, '\0'};
     static std::string format() { return std::string(1, c); }
 };
 
 #if !defined(PYBIND11_CPP17)
 
-template <typename T> constexpr const char format_descriptor<
-    T, detail::enable_if_t<std::is_arithmetic<T>::value>>::value[2];
+template <typename T>
+constexpr const char
+    format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>>::value[2];
 
 #endif
 
@@ -919,7 +1048,10 @@ struct error_scope {
 };
 
 /// Dummy destructor wrapper that can be used to expose classes with a private destructor
-struct nodelete { template <typename T> void operator()(T*) { } };
+struct nodelete {
+    template <typename T>
+    void operator()(T *) {}
+};
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename... Args>
@@ -928,22 +1060,27 @@ struct overload_cast_impl {
     constexpr overload_cast_impl() {}
 
     template <typename Return>
-    constexpr auto operator()(Return (*pf)(Args...)) const noexcept
-                              -> decltype(pf) { return pf; }
+    constexpr auto operator()(Return (*pf)(Args...)) const noexcept -> decltype(pf) {
+        return pf;
+    }
 
     template <typename Return, typename Class>
     constexpr auto operator()(Return (Class::*pmf)(Args...), std::false_type = {}) const noexcept
-                              -> decltype(pmf) { return pmf; }
+        -> decltype(pmf) {
+        return pmf;
+    }
 
     template <typename Return, typename Class>
     constexpr auto operator()(Return (Class::*pmf)(Args...) const, std::true_type) const noexcept
-                              -> decltype(pmf) { return pmf; }
+        -> decltype(pmf) {
+        return pmf;
+    }
 };
 PYBIND11_NAMESPACE_END(detail)
 
 // overload_cast requires variable templates: C++14
 #if defined(PYBIND11_CPP14)
-#define PYBIND11_OVERLOAD_CAST 1
+#    define PYBIND11_OVERLOAD_CAST 1
 /// Syntax sugar for resolving overloaded function pointers:
 ///  - regular: static_cast<Return (Class::*)(Arg0, Arg1, Arg2)>(&Class::func)
 ///  - sweet:   overload_cast<Arg0, Arg1, Arg2>(&Class::func)
@@ -958,7 +1095,8 @@ static constexpr detail::overload_cast_impl<Args...> overload_cast = {};
 static constexpr auto const_ = std::true_type{};
 
 #if !defined(PYBIND11_CPP14) // no overload_cast: providing something that static_assert-fails:
-template <typename... Args> struct overload_cast {
+template <typename... Args>
+struct overload_cast {
     static_assert(detail::deferred_t<std::false_type, Args...>::value,
                   "pybind11::overload_cast<...> requires compiling in C++14 mode");
 };
@@ -972,27 +1110,31 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename T>
 class any_container {
     std::vector<T> v;
+
 public:
     any_container() = default;
 
     // Can construct from a pair of iterators
     template <typename It, typename = enable_if_t<is_input_iterator<It>::value>>
-    any_container(It first, It last) : v(first, last) { }
+    any_container(It first, It last) : v(first, last) {}
 
     // Implicit conversion constructor from any arbitrary container type
     // with values convertible to T
-    template <typename Container, typename = enable_if_t<std::is_convertible<decltype(*std::begin(std::declval<const Container &>())), T>::value>>
+    template <typename Container,
+              typename = enable_if_t<
+                  std::is_convertible<decltype(*std::begin(std::declval<const Container &>())),
+                                      T>::value>>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    any_container(const Container &c) : any_container(std::begin(c), std::end(c)) { }
+    any_container(const Container &c) : any_container(std::begin(c), std::end(c)) {}
 
     // initializer_list's aren't deducible, so don't get matched by the above template;
     // we need this to explicitly allow implicit conversion from one:
     template <typename TIn, typename = enable_if_t<std::is_convertible<TIn, T>::value>>
-    any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) { }
+    any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) {}
 
     // Avoid copying if given an rvalue vector of the correct type.
     // NOLINTNEXTLINE(google-explicit-constructor)
-    any_container(std::vector<T> &&v) : v(std::move(v)) { }
+    any_container(std::vector<T> &&v) : v(std::move(v)) {}
 
     // Moves the vector out of an rvalue any_container
     // NOLINTNEXTLINE(google-explicit-constructor)
@@ -1008,10 +1150,11 @@ class any_container {
 };
 
 // Forward-declaration; see detail/class.h
-std::string get_fully_qualified_tp_name(PyTypeObject*);
+std::string get_fully_qualified_tp_name(PyTypeObject *);
 
 template <typename T>
-inline static std::shared_ptr<T> try_get_shared_from_this(std::enable_shared_from_this<T> *holder_value_ptr) {
+inline static std::shared_ptr<T>
+try_get_shared_from_this(std::enable_shared_from_this<T> *holder_value_ptr) {
 // Pre C++17, this code path exploits undefined behavior, but is known to work on many platforms.
 // Use at your own risk!
 // See also https://en.cppreference.com/w/cpp/memory/enable_shared_from_this, and in particular
@@ -1021,8 +1164,7 @@ inline static std::shared_ptr<T> try_get_shared_from_this(std::enable_shared_fro
 #else
     try {
         return holder_value_ptr->shared_from_this();
-    }
-    catch (const std::bad_weak_ptr &) {
+    } catch (const std::bad_weak_ptr &) {
         return nullptr;
     }
 #endif
@@ -1033,7 +1175,9 @@ template <typename... Args>
 #if defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER < 1920 // MSVC 2017
 constexpr
 #endif
-inline void silence_unused_warnings(Args &&...) {}
+    inline void
+    silence_unused_warnings(Args &&...) {
+}
 
 // MSVC warning C4100: Unreferenced formal parameter
 #if defined(_MSC_VER) && _MSC_VER <= 1916
@@ -1045,7 +1189,7 @@ inline void silence_unused_warnings(Args &&...) {}
 
 // GCC -Wunused-but-set-parameter  All GCC versions (as of July 2021).
 #if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)                   \
+#    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)                       \
         detail::silence_unused_warnings(__VA_ARGS__)
 #else
 #    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 0f93e06b21..e7a5e2c145 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -15,9 +15,9 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if !defined(_MSC_VER)
-#  define PYBIND11_DESCR_CONSTEXPR static constexpr
+#    define PYBIND11_DESCR_CONSTEXPR static constexpr
 #else
-#  define PYBIND11_DESCR_CONSTEXPR const
+#    define PYBIND11_DESCR_CONSTEXPR const
 #endif
 
 /* Concatenate type signatures at compile time */
@@ -27,14 +27,14 @@ struct descr {
 
     constexpr descr() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
-    constexpr descr(char const (&s)[N+1]) : descr(s, make_index_sequence<N>()) { }
+    constexpr descr(char const (&s)[N + 1]) : descr(s, make_index_sequence<N>()) {}
 
     template <size_t... Is>
-    constexpr descr(char const (&s)[N+1], index_sequence<Is...>) : text{s[Is]..., '\0'} { }
+    constexpr descr(char const (&s)[N + 1], index_sequence<Is...>) : text{s[Is]..., '\0'} {}
 
     template <typename... Chars>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} { }
+    constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} {}
 
     static constexpr std::array<const std::type_info *, sizeof...(Ts) + 1> types() {
         return {{&typeid(Ts)..., nullptr}};
@@ -42,81 +42,106 @@ struct descr {
 };
 
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2, size_t... Is1, size_t... Is2>
-constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b,
-                                                   index_sequence<Is1...>, index_sequence<Is2...>) {
+constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a,
+                                                   const descr<N2, Ts2...> &b,
+                                                   index_sequence<Is1...>,
+                                                   index_sequence<Is2...>) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(b);
     return {a.text[Is1]..., b.text[Is2]...};
 }
 
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2>
-constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b) {
+constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a,
+                                                   const descr<N2, Ts2...> &b) {
     return plus_impl(a, b, make_index_sequence<N1>(), make_index_sequence<N2>());
 }
 
 template <size_t N>
-constexpr descr<N - 1> const_name(char const(&text)[N]) { return descr<N - 1>(text); }
-constexpr descr<0> const_name(char const(&)[1]) { return {}; }
+constexpr descr<N - 1> const_name(char const (&text)[N]) {
+    return descr<N - 1>(text);
+}
+constexpr descr<0> const_name(char const (&)[1]) { return {}; }
 
-template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
-template <size_t...Digits> struct int_to_str<0, Digits...> {
+template <size_t Rem, size_t... Digits>
+struct int_to_str : int_to_str<Rem / 10, Rem % 10, Digits...> {};
+template <size_t... Digits>
+struct int_to_str<0, Digits...> {
     // WARNING: This only works with C++17 or higher.
     static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...);
 };
 
 // Ternary description (like std::conditional)
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> const_name(char const(&text1)[N1], char const(&)[N2]) {
+constexpr enable_if_t<B, descr<N1 - 1>> const_name(char const (&text1)[N1], char const (&)[N2]) {
     return const_name(text1);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> const_name(char const(&)[N1], char const(&text2)[N2]) {
+constexpr enable_if_t<!B, descr<N2 - 1>> const_name(char const (&)[N1], char const (&text2)[N2]) {
     return const_name(text2);
 }
 
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<B, T1> const_name(const T1 &d, const T2 &) { return d; }
+constexpr enable_if_t<B, T1> const_name(const T1 &d, const T2 &) {
+    return d;
+}
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<!B, T2> const_name(const T1 &, const T2 &d) { return d; }
+constexpr enable_if_t<!B, T2> const_name(const T1 &, const T2 &d) {
+    return d;
+}
 
 template <size_t Size>
 auto constexpr const_name() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
     return int_to_str<Size / 10, Size % 10>::digits;
 }
 
-template <typename Type> constexpr descr<1, Type> const_name() { return {'%'}; }
+template <typename Type>
+constexpr descr<1, Type> const_name() {
+    return {'%'};
+}
 
 // If "_" is defined as a macro, py::detail::_ cannot be provided.
 // It is therefore best to use py::detail::const_name universally.
 // This block is for backward compatibility only.
 // (The const_name code is repeated to avoid introducing a "_" #define ourselves.)
 #ifndef _
-#define PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
+#    define PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
 template <size_t N>
-constexpr descr<N-1> _(char const(&text)[N]) { return const_name<N>(text); }
+constexpr descr<N - 1> _(char const (&text)[N]) {
+    return const_name<N>(text);
+}
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> _(char const(&text1)[N1], char const(&text2)[N2]) {
-    return const_name<B,N1,N2>(text1, text2);
+constexpr enable_if_t<B, descr<N1 - 1>> _(char const (&text1)[N1], char const (&text2)[N2]) {
+    return const_name<B, N1, N2>(text1, text2);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> _(char const(&text1)[N1], char const(&text2)[N2]) {
-    return const_name<B,N1,N2>(text1, text2);
+constexpr enable_if_t<!B, descr<N2 - 1>> _(char const (&text1)[N1], char const (&text2)[N2]) {
+    return const_name<B, N1, N2>(text1, text2);
 }
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<B, T1> _(const T1 &d1, const T2 &d2) { return const_name<B,T1,T2>(d1, d2); }
+constexpr enable_if_t<B, T1> _(const T1 &d1, const T2 &d2) {
+    return const_name<B, T1, T2>(d1, d2);
+}
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<!B, T2> _(const T1 &d1, const T2 &d2) { return const_name<B,T1,T2>(d1, d2); }
+constexpr enable_if_t<!B, T2> _(const T1 &d1, const T2 &d2) {
+    return const_name<B, T1, T2>(d1, d2);
+}
 
 template <size_t Size>
 auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
     return const_name<Size>();
 }
-template <typename Type> constexpr descr<1, Type> _() { return const_name<Type>(); }
-#endif  // #ifndef _
+template <typename Type>
+constexpr descr<1, Type> _() {
+    return const_name<Type>();
+}
+#endif // #ifndef _
 
 constexpr descr<0> concat() { return {}; }
 
 template <size_t N, typename... Ts>
-constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) { return descr; }
+constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) {
+    return descr;
+}
 
 template <size_t N, typename... Ts, typename... Args>
 constexpr auto concat(const descr<N, Ts...> &d, const Args &...args)
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index ba408d76cc..e1e665a69b 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -22,7 +22,8 @@ class type_caster<value_and_holder> {
         return true;
     }
 
-    template <typename> using cast_op_type = value_and_holder &;
+    template <typename>
+    using cast_op_type = value_and_holder &;
     explicit operator value_and_holder &() { return *value; }
     static constexpr auto name = const_name<value_and_holder>();
 
@@ -39,11 +40,15 @@ inline void no_nullptr(void *ptr) {
 }
 
 // Implementing functions for all forms of py::init<...> and py::init(...)
-template <typename Class> using Cpp = typename Class::type;
-template <typename Class> using Alias = typename Class::type_alias;
-template <typename Class> using Holder = typename Class::holder_type;
+template <typename Class>
+using Cpp = typename Class::type;
+template <typename Class>
+using Alias = typename Class::type_alias;
+template <typename Class>
+using Holder = typename Class::holder_type;
 
-template <typename Class> using is_alias_constructible = std::is_constructible<Alias<Class>, Cpp<Class> &&>;
+template <typename Class>
+using is_alias_constructible = std::is_constructible<Alias<Class>, Cpp<Class> &&>;
 
 // Takes a Cpp pointer and returns true if it actually is a polymorphic Alias instance.
 template <typename Class, enable_if_t<Class::has_alias, int> = 0>
@@ -52,17 +57,27 @@ bool is_alias(Cpp<Class> *ptr) {
 }
 // Failing fallback version of the above for a no-alias class (always returns false)
 template <typename /*Class*/>
-constexpr bool is_alias(void *) { return false; }
+constexpr bool is_alias(void *) {
+    return false;
+}
 
 // Constructs and returns a new object; if the given arguments don't map to a constructor, we fall
 // back to brace aggregate initiailization so that for aggregate initialization can be used with
 // py::init, e.g.  `py::init<int, int>` to initialize a `struct T { int a; int b; }`.  For
 // non-aggregate types, we need to use an ordinary T(...) constructor (invoking as `T{...}` usually
 // works, but will not do the expected thing when `T` has an `initializer_list<T>` constructor).
-template <typename Class, typename... Args, detail::enable_if_t<std::is_constructible<Class, Args...>::value, int> = 0>
-inline Class *construct_or_initialize(Args &&...args) { return new Class(std::forward<Args>(args)...); }
-template <typename Class, typename... Args, detail::enable_if_t<!std::is_constructible<Class, Args...>::value, int> = 0>
-inline Class *construct_or_initialize(Args &&...args) { return new Class{std::forward<Args>(args)...}; }
+template <typename Class,
+          typename... Args,
+          detail::enable_if_t<std::is_constructible<Class, Args...>::value, int> = 0>
+inline Class *construct_or_initialize(Args &&...args) {
+    return new Class(std::forward<Args>(args)...);
+}
+template <typename Class,
+          typename... Args,
+          detail::enable_if_t<!std::is_constructible<Class, Args...>::value, int> = 0>
+inline Class *construct_or_initialize(Args &&...args) {
+    return new Class{std::forward<Args>(args)...};
+}
 
 // Attempts to constructs an alias using a `Alias(Cpp &&)` constructor.  This allows types with
 // an alias to provide only a single Cpp factory function as long as the Alias can be
@@ -71,12 +86,14 @@ inline Class *construct_or_initialize(Args &&...args) { return new Class{std::fo
 // inherit all the base class constructors.
 template <typename Class>
 void construct_alias_from_cpp(std::true_type /*is_alias_constructible*/,
-                              value_and_holder &v_h, Cpp<Class> &&base) {
+                              value_and_holder &v_h,
+                              Cpp<Class> &&base) {
     v_h.value_ptr() = new Alias<Class>(std::move(base));
 }
 template <typename Class>
 [[noreturn]] void construct_alias_from_cpp(std::false_type /*!is_alias_constructible*/,
-                                           value_and_holder &, Cpp<Class> &&) {
+                                           value_and_holder &,
+                                           Cpp<Class> &&) {
     throw type_error("pybind11::init(): unable to convert returned instance to required "
                      "alias class: no `Alias<Class>(Class &&)` constructor available");
 }
@@ -86,8 +103,8 @@ template <typename Class>
 template <typename Class>
 void construct(...) {
     static_assert(!std::is_same<Class, Class>::value /* always false */,
-            "pybind11::init(): init function must return a compatible pointer, "
-            "holder, or value");
+                  "pybind11::init(): init function must return a compatible pointer, "
+                  "holder, or value");
 }
 
 // Pointer return v1: the factory function returns a class pointer for a registered class.
@@ -108,7 +125,7 @@ void construct(value_and_holder &v_h, Cpp<Class> *ptr, bool need_alias) {
         // the holder and destruction happens when we leave the C++ scope, and the holder
         // class gets to handle the destruction however it likes.
         v_h.value_ptr() = ptr;
-        v_h.set_instance_registered(true); // To prevent init_instance from registering it
+        v_h.set_instance_registered(true);          // To prevent init_instance from registering it
         v_h.type->init_instance(v_h.inst, nullptr); // Set up the holder
         Holder<Class> temp_holder(std::move(v_h.holder<Holder<Class>>())); // Steal the holder
         v_h.type->dealloc(v_h); // Destroys the moved-out holder remains, resets value ptr to null
@@ -131,7 +148,8 @@ void construct(value_and_holder &v_h, Alias<Class> *alias_ptr, bool) {
 
 // Holder return: copy its pointer, and move or copy the returned holder into the new instance's
 // holder.  This also handles types like std::shared_ptr<T> and std::unique_ptr<T> where T is a
-// derived type (through those holder's implicit conversion from derived class holder constructors).
+// derived type (through those holder's implicit conversion from derived class holder
+// constructors).
 template <typename Class>
 void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
@@ -155,7 +173,7 @@ template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
-        "pybind11::init() return-by-value factory function requires a movable class");
+                  "pybind11::init() return-by-value factory function requires a movable class");
     if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias) {
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
     } else {
@@ -168,7 +186,8 @@ void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
 // cases where Alias initialization is always desired.
 template <typename Class>
 void construct(value_and_holder &v_h, Alias<Class> &&result, bool) {
-    static_assert(std::is_move_constructible<Alias<Class>>::value,
+    static_assert(
+        std::is_move_constructible<Alias<Class>>::value,
         "pybind11::init() return-by-alias-value factory function requires a movable alias class");
     v_h.value_ptr() = new Alias<Class>(std::move(result));
 }
@@ -177,16 +196,21 @@ void construct(value_and_holder &v_h, Alias<Class> &&result, bool) {
 template <typename... Args>
 struct constructor {
     template <typename Class, typename... Extra, enable_if_t<!Class::has_alias, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+    static void execute(Class &cl, const Extra &...extra) {
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 
-    template <typename Class, typename... Extra,
-              enable_if_t<Class::has_alias &&
-                          std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
+    template <typename Class,
+              typename... Extra,
+              enable_if_t<Class::has_alias && std::is_constructible<Cpp<Class>, Args...>::value,
+                          int> = 0>
+    static void execute(Class &cl, const Extra &...extra) {
         cl.def(
             "__init__",
             [](value_and_holder &v_h, Args... args) {
@@ -202,30 +226,46 @@ struct constructor {
             extra...);
     }
 
-    template <typename Class, typename... Extra,
-              enable_if_t<Class::has_alias &&
-                          !std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+    template <typename Class,
+              typename... Extra,
+              enable_if_t<Class::has_alias && !std::is_constructible<Cpp<Class>, Args...>::value,
+                          int> = 0>
+    static void execute(Class &cl, const Extra &...extra) {
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                v_h.value_ptr()
+                    = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
 // Implementing class for py::init_alias<...>()
-template <typename... Args> struct alias_constructor {
-    template <typename Class, typename... Extra,
-              enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+template <typename... Args>
+struct alias_constructor {
+    template <typename Class,
+              typename... Extra,
+              enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value,
+                          int> = 0>
+    static void execute(Class &cl, const Extra &...extra) {
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                v_h.value_ptr()
+                    = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
 // Implementation class for py::init(Func) and py::init(Func, AliasFunc)
-template <typename CFunc, typename AFunc = void_type (*)(),
-          typename = function_signature_t<CFunc>, typename = function_signature_t<AFunc>>
+template <typename CFunc,
+          typename AFunc = void_type (*)(),
+          typename = function_signature_t<CFunc>,
+          typename = function_signature_t<AFunc>>
 struct factory;
 
 // Specialization for py::init(Func)
@@ -243,22 +283,32 @@ struct factory<Func, void_type (*)(), Return(Args...)> {
     // instance, or the alias needs to be constructible from a `Class &&` argument.
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) && {
-        #if defined(PYBIND11_CPP14)
-        cl.def("__init__", [func = std::move(class_factory)]
-        #else
+#if defined(PYBIND11_CPP14)
+        cl.def(
+            "__init__",
+            [func = std::move(class_factory)]
+#else
         auto &func = class_factory;
-        cl.def("__init__", [func]
-        #endif
-        (value_and_holder &v_h, Args... args) {
-            construct<Class>(v_h, func(std::forward<Args>(args)...),
-                             Py_TYPE(v_h.inst) != v_h.type->type);
-        }, is_new_style_constructor(), extra...);
+        cl.def(
+            "__init__",
+            [func]
+#endif
+            (value_and_holder &v_h, Args... args) {
+                construct<Class>(
+                    v_h, func(std::forward<Args>(args)...), Py_TYPE(v_h.inst) != v_h.type->type);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
 // Specialization for py::init(Func, AliasFunc)
-template <typename CFunc, typename AFunc,
-          typename CReturn, typename... CArgs, typename AReturn, typename... AArgs>
+template <typename CFunc,
+          typename AFunc,
+          typename CReturn,
+          typename... CArgs,
+          typename AReturn,
+          typename... AArgs>
 struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
     static_assert(sizeof...(CArgs) == sizeof...(AArgs),
                   "pybind11::init(class_factory, alias_factory): class and alias factories "
@@ -271,30 +321,37 @@ struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
     remove_reference_t<AFunc> alias_factory;
 
     factory(CFunc &&c, AFunc &&a)
-        : class_factory(std::forward<CFunc>(c)), alias_factory(std::forward<AFunc>(a)) { }
+        : class_factory(std::forward<CFunc>(c)), alias_factory(std::forward<AFunc>(a)) {}
 
     // The class factory is called when the `self` type passed to `__init__` is the direct
     // class (i.e. not inherited), the alias factory when `self` is a Python-side subtype.
     template <typename Class, typename... Extra>
-    void execute(Class &cl, const Extra&... extra) && {
-        static_assert(Class::has_alias, "The two-argument version of `py::init()` can "
-                                        "only be used if the class has an alias");
-        #if defined(PYBIND11_CPP14)
-        cl.def("__init__", [class_func = std::move(class_factory), alias_func = std::move(alias_factory)]
-        #else
+    void execute(Class &cl, const Extra &...extra) && {
+        static_assert(Class::has_alias,
+                      "The two-argument version of `py::init()` can "
+                      "only be used if the class has an alias");
+#if defined(PYBIND11_CPP14)
+        cl.def(
+            "__init__",
+            [class_func = std::move(class_factory), alias_func = std::move(alias_factory)]
+#else
         auto &class_func = class_factory;
         auto &alias_func = alias_factory;
-        cl.def("__init__", [class_func, alias_func]
-        #endif
-        (value_and_holder &v_h, CArgs... args) {
-            if (Py_TYPE(v_h.inst) == v_h.type->type) {
-                // If the instance type equals the registered type we don't have inheritance, so
-                // don't need the alias and can construct using the class function:
-                construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
-            } else {
-                construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
-            }
-        }, is_new_style_constructor(), extra...);
+        cl.def(
+            "__init__",
+            [class_func, alias_func]
+#endif
+            (value_and_holder &v_h, CArgs... args) {
+                if (Py_TYPE(v_h.inst) == v_h.type->type) {
+                    // If the instance type equals the registered type we don't have inheritance,
+                    // so don't need the alias and can construct using the class function:
+                    construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
+                } else {
+                    construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
+                }
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
@@ -305,7 +362,9 @@ void setstate(value_and_holder &v_h, T &&result, bool need_alias) {
 }
 
 /// Set both the C++ and Python states
-template <typename Class, typename T, typename O,
+template <typename Class,
+          typename T,
+          typename O,
           enable_if_t<std::is_convertible<O, handle>::value, int> = 0>
 void setstate(value_and_holder &v_h, std::pair<T, O> &&result, bool need_alias) {
     construct<Class>(v_h, std::move(result.first), need_alias);
@@ -319,12 +378,18 @@ void setstate(value_and_holder &v_h, std::pair<T, O> &&result, bool need_alias)
 }
 
 /// Implementation for py::pickle(GetState, SetState)
-template <typename Get, typename Set,
-          typename = function_signature_t<Get>, typename = function_signature_t<Set>>
+template <typename Get,
+          typename Set,
+          typename = function_signature_t<Get>,
+          typename = function_signature_t<Set>>
 struct pickle_factory;
 
-template <typename Get, typename Set,
-          typename RetState, typename Self, typename NewInstance, typename ArgState>
+template <typename Get,
+          typename Set,
+          typename RetState,
+          typename Self,
+          typename NewInstance,
+          typename ArgState>
 struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
     static_assert(std::is_same<intrinsic_t<RetState>, intrinsic_t<ArgState>>::value,
                   "The type returned by `__getstate__` must be the same "
@@ -333,23 +398,28 @@ struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
     remove_reference_t<Get> get;
     remove_reference_t<Set> set;
 
-    pickle_factory(Get get, Set set)
-        : get(std::forward<Get>(get)), set(std::forward<Set>(set)) { }
+    pickle_factory(Get get, Set set) : get(std::forward<Get>(get)), set(std::forward<Set>(set)) {}
 
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) && {
         cl.def("__getstate__", std::move(get));
 
 #if defined(PYBIND11_CPP14)
-        cl.def("__setstate__", [func = std::move(set)]
+        cl.def(
+            "__setstate__",
+            [func = std::move(set)]
 #else
         auto &func = set;
-        cl.def("__setstate__", [func]
+        cl.def(
+            "__setstate__",
+            [func]
 #endif
-        (value_and_holder &v_h, ArgState state) {
-            setstate<Class>(v_h, func(std::forward<ArgState>(state)),
-                            Py_TYPE(v_h.inst) != v_h.type->type);
-        }, is_new_style_constructor(), extra...);
+            (value_and_holder &v_h, ArgState state) {
+                setstate<Class>(
+                    v_h, func(std::forward<ArgState>(state)), Py_TYPE(v_h.inst) != v_h.type->type);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 5bddbe35fd..76b4faa8f2 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "../pytypes.h"
+
 #include <exception>
 
 /// Tracks the `internals` and `type_info` ABI version independent of the main library version.
@@ -136,9 +137,9 @@ template <typename value_type>
 using type_map = std::unordered_map<std::type_index, value_type, type_hash, type_equal_to>;
 
 struct override_hash {
-    inline size_t operator()(const std::pair<const PyObject *, const char *>& v) const {
+    inline size_t operator()(const std::pair<const PyObject *, const char *> &v) const {
         size_t value = std::hash<const void *>()(v.first);
-        value ^= std::hash<const void *>()(v.second) + 0x9e3779b9 + (value<<6) + (value>>2);
+        value ^= std::hash<const void *>()(v.second) + 0x9e3779b9 + (value << 6) + (value >> 2);
         return value;
     }
 };
@@ -151,8 +152,9 @@ struct internals {
     type_map<type_info *> registered_types_cpp;
     // PyTypeObject* -> base type_info(s)
     std::unordered_map<PyTypeObject *, std::vector<type_info *>> registered_types_py;
-    std::unordered_multimap<const void *, instance*> registered_instances; // void * -> instance*
-    std::unordered_set<std::pair<const PyObject *, const char *>, override_hash> inactive_override_cache;
+    std::unordered_multimap<const void *, instance *> registered_instances; // void * -> instance*
+    std::unordered_set<std::pair<const PyObject *, const char *>, override_hash>
+        inactive_override_cache;
     type_map<std::vector<bool (*)(PyObject *, void *&)>> direct_conversions;
     std::unordered_map<const PyObject *, std::vector<PyObject *>> patients;
     std::forward_list<ExceptionTranslator> registered_exception_translators;
@@ -198,8 +200,8 @@ struct type_info {
     void *(*operator_new)(size_t);
     void (*init_instance)(instance *, const void *);
     void (*dealloc)(value_and_holder &v_h);
-    std::vector<PyObject *(*)(PyObject *, PyTypeObject *)> implicit_conversions;
-    std::vector<std::pair<const std::type_info *, void *(*)(void *)>> implicit_casts;
+    std::vector<PyObject *(*) (PyObject *, PyTypeObject *)> implicit_conversions;
+    std::vector<std::pair<const std::type_info *, void *(*) (void *)>> implicit_casts;
     std::vector<bool (*)(PyObject *, void *&)> *direct_conversions;
     buffer_info *(*get_buffer)(PyObject *, void *) = nullptr;
     void *get_buffer_data = nullptr;
@@ -219,67 +221,71 @@ struct type_info {
 
 /// On MSVC, debug and release builds are not ABI-compatible!
 #if defined(_MSC_VER) && defined(_DEBUG)
-#  define PYBIND11_BUILD_TYPE "_debug"
+#    define PYBIND11_BUILD_TYPE "_debug"
 #else
-#  define PYBIND11_BUILD_TYPE ""
+#    define PYBIND11_BUILD_TYPE ""
 #endif
 
 /// Let's assume that different compilers are ABI-incompatible.
 /// A user can manually set this string if they know their
 /// compiler is compatible.
 #ifndef PYBIND11_COMPILER_TYPE
-#  if defined(_MSC_VER)
-#    define PYBIND11_COMPILER_TYPE "_msvc"
-#  elif defined(__INTEL_COMPILER)
-#    define PYBIND11_COMPILER_TYPE "_icc"
-#  elif defined(__clang__)
-#    define PYBIND11_COMPILER_TYPE "_clang"
-#  elif defined(__PGI)
-#    define PYBIND11_COMPILER_TYPE "_pgi"
-#  elif defined(__MINGW32__)
-#    define PYBIND11_COMPILER_TYPE "_mingw"
-#  elif defined(__CYGWIN__)
-#    define PYBIND11_COMPILER_TYPE "_gcc_cygwin"
-#  elif defined(__GNUC__)
-#    define PYBIND11_COMPILER_TYPE "_gcc"
-#  else
-#    define PYBIND11_COMPILER_TYPE "_unknown"
-#  endif
+#    if defined(_MSC_VER)
+#        define PYBIND11_COMPILER_TYPE "_msvc"
+#    elif defined(__INTEL_COMPILER)
+#        define PYBIND11_COMPILER_TYPE "_icc"
+#    elif defined(__clang__)
+#        define PYBIND11_COMPILER_TYPE "_clang"
+#    elif defined(__PGI)
+#        define PYBIND11_COMPILER_TYPE "_pgi"
+#    elif defined(__MINGW32__)
+#        define PYBIND11_COMPILER_TYPE "_mingw"
+#    elif defined(__CYGWIN__)
+#        define PYBIND11_COMPILER_TYPE "_gcc_cygwin"
+#    elif defined(__GNUC__)
+#        define PYBIND11_COMPILER_TYPE "_gcc"
+#    else
+#        define PYBIND11_COMPILER_TYPE "_unknown"
+#    endif
 #endif
 
 /// Also standard libs
 #ifndef PYBIND11_STDLIB
-#  if defined(_LIBCPP_VERSION)
-#    define PYBIND11_STDLIB "_libcpp"
-#  elif defined(__GLIBCXX__) || defined(__GLIBCPP__)
-#    define PYBIND11_STDLIB "_libstdcpp"
-#  else
-#    define PYBIND11_STDLIB ""
-#  endif
+#    if defined(_LIBCPP_VERSION)
+#        define PYBIND11_STDLIB "_libcpp"
+#    elif defined(__GLIBCXX__) || defined(__GLIBCPP__)
+#        define PYBIND11_STDLIB "_libstdcpp"
+#    else
+#        define PYBIND11_STDLIB ""
+#    endif
 #endif
 
 /// On Linux/OSX, changes in __GXX_ABI_VERSION__ indicate ABI incompatibility.
 #ifndef PYBIND11_BUILD_ABI
-#  if defined(__GXX_ABI_VERSION)
-#    define PYBIND11_BUILD_ABI "_cxxabi" PYBIND11_TOSTRING(__GXX_ABI_VERSION)
-#  else
-#    define PYBIND11_BUILD_ABI ""
-#  endif
+#    if defined(__GXX_ABI_VERSION)
+#        define PYBIND11_BUILD_ABI "_cxxabi" PYBIND11_TOSTRING(__GXX_ABI_VERSION)
+#    else
+#        define PYBIND11_BUILD_ABI ""
+#    endif
 #endif
 
 #ifndef PYBIND11_INTERNALS_KIND
-#  if defined(WITH_THREAD)
-#    define PYBIND11_INTERNALS_KIND ""
-#  else
-#    define PYBIND11_INTERNALS_KIND "_without_thread"
-#  endif
+#    if defined(WITH_THREAD)
+#        define PYBIND11_INTERNALS_KIND ""
+#    else
+#        define PYBIND11_INTERNALS_KIND "_without_thread"
+#    endif
 #endif
 
-#define PYBIND11_INTERNALS_ID "__pybind11_internals_v" \
-    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI PYBIND11_BUILD_TYPE "__"
+#define PYBIND11_INTERNALS_ID                                                                     \
+    "__pybind11_internals_v" PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION)                        \
+        PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI         \
+            PYBIND11_BUILD_TYPE "__"
 
-#define PYBIND11_MODULE_LOCAL_ID "__pybind11_module_local_v" \
-    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI PYBIND11_BUILD_TYPE "__"
+#define PYBIND11_MODULE_LOCAL_ID                                                                  \
+    "__pybind11_module_local_v" PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION)                     \
+        PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI         \
+            PYBIND11_BUILD_TYPE "__"
 
 /// Each module locally stores a pointer to the `internals` data. The data
 /// itself is shared among modules with the same `PYBIND11_INTERNALS_ID`.
@@ -396,8 +402,12 @@ inline void translate_local_exception(std::exception_ptr p) {
         if (p) {
             std::rethrow_exception(p);
         }
-    } catch (error_already_set &e)       { e.restore();   return;
-    } catch (const builtin_exception &e) { e.set_error(); return;
+    } catch (error_already_set &e) {
+        e.restore();
+        return;
+    } catch (const builtin_exception &e) {
+        e.set_error();
+        return;
     }
 }
 #endif
@@ -412,7 +422,7 @@ PYBIND11_NOINLINE internals &get_internals() {
     // Ensure that the GIL is held since we will need to make Python calls.
     // Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
     struct gil_scoped_acquire_local {
-        gil_scoped_acquire_local() : state (PyGILState_Ensure()) {}
+        gil_scoped_acquire_local() : state(PyGILState_Ensure()) {}
         ~gil_scoped_acquire_local() { PyGILState_Release(state); }
         const PyGILState_STATE state;
     } gil;
@@ -512,11 +522,10 @@ struct local_internals {
 
 /// Works like `get_internals`, but for things which are locally registered.
 inline local_internals &get_local_internals() {
-  static local_internals locals;
-  return locals;
+    static local_internals locals;
+    return locals;
 }
 
-
 /// Constructs a std::string with the given arguments, stores it in `internals`, and returns its
 /// `c_str()`.  Such strings objects have a long storage duration -- the internal strings are only
 /// cleared when the program exits or after interpreter shutdown (when embedding), and so are
@@ -548,7 +557,7 @@ PYBIND11_NOINLINE void *set_shared_data(const std::string &name, void *data) {
 /// Returns a typed reference to a shared data entry (by using `get_shared_data()`) if
 /// such entry exists. Otherwise, a new object of default-constructible type `T` is
 /// added to the shared data under the given name and a reference to it is returned.
-template<typename T>
+template <typename T>
 T &get_or_create_shared_data(const std::string &name) {
     auto &internals = detail::get_internals();
     auto it = internals.shared_data.find(name);
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 34100c3ae2..134e85b96a 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -14,6 +14,7 @@
 #include "descr.h"
 #include "internals.h"
 #include "typeid.h"
+
 #include <cstdint>
 #include <iterator>
 #include <new>
@@ -32,7 +33,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// Adding a patient will keep it alive up until the enclosing function returns.
 class loader_life_support {
 private:
-    loader_life_support* parent = nullptr;
+    loader_life_support *parent = nullptr;
     std::unordered_set<PyObject *> keep_alive;
 
 #if defined(WITH_THREAD)
@@ -98,7 +99,8 @@ class loader_life_support {
 // Gets the cache entry for the given type, creating it if necessary.  The return value is the pair
 // returned by emplace, i.e. an iterator for the entry and a bool set to `true` if the entry was
 // just created.
-inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type);
+inline std::pair<decltype(internals::registered_types_py)::iterator, bool>
+all_type_info_get_cache(PyTypeObject *type);
 
 // Populates a just-created cache entry.
 PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_info *> &bases) {
@@ -119,23 +121,25 @@ PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_
         auto it = type_dict.find(type);
         if (it != type_dict.end()) {
             // We found a cache entry for it, so it's either pybind-registered or has pre-computed
-            // pybind bases, but we have to make sure we haven't already seen the type(s) before: we
-            // want to follow Python/virtual C++ rules that there should only be one instance of a
-            // common base.
+            // pybind bases, but we have to make sure we haven't already seen the type(s) before:
+            // we want to follow Python/virtual C++ rules that there should only be one instance of
+            // a common base.
             for (auto *tinfo : it->second) {
                 // NB: Could use a second set here, rather than doing a linear search, but since
                 // having a large number of immediate pybind11-registered types seems fairly
                 // unlikely, that probably isn't worthwhile.
                 bool found = false;
                 for (auto *known : bases) {
-                    if (known == tinfo) { found = true; break; }
+                    if (known == tinfo) {
+                        found = true;
+                        break;
+                    }
                 }
                 if (!found) {
                     bases.push_back(tinfo);
                 }
             }
-        }
-        else if (type->tp_bases) {
+        } else if (type->tp_bases) {
             // It's some python type, so keep follow its bases classes to look for one or more
             // registered types
             if (i + 1 == check.size()) {
@@ -177,7 +181,7 @@ inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type)
  * ancestors are pybind11-registered.  Throws an exception if there are multiple bases--use
  * `all_type_info` instead if you want to support multiple bases.
  */
-PYBIND11_NOINLINE detail::type_info* get_type_info(PyTypeObject *type) {
+PYBIND11_NOINLINE detail::type_info *get_type_info(PyTypeObject *type) {
     const auto &bases = all_type_info(type);
     if (bases.empty()) {
         return nullptr;
@@ -207,9 +211,10 @@ inline detail::type_info *get_global_type_info(const std::type_index &tp) {
     return nullptr;
 }
 
-/// Return the type info for a given C++ type; on lookup failure can either throw or return nullptr.
+/// Return the type info for a given C++ type; on lookup failure can either throw or return
+/// nullptr.
 PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
-                                                          bool throw_if_missing = false) {
+                                                   bool throw_if_missing = false) {
     if (auto *ltype = get_local_type_info(tp)) {
         return ltype;
     }
@@ -220,7 +225,8 @@ PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
     if (throw_if_missing) {
         std::string tname = tp.name();
         detail::clean_type_id(tname);
-        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname + "\"");
+        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname
+                      + "\"");
     }
     return nullptr;
 }
@@ -232,7 +238,7 @@ PYBIND11_NOINLINE handle get_type_handle(const std::type_info &tp, bool throw_if
 
 // Searches the inheritance graph for a registered Python instance, using all_type_info().
 PYBIND11_NOINLINE handle find_registered_python_instance(void *src,
-                                                                const detail::type_info *tinfo) {
+                                                         const detail::type_info *tinfo) {
     auto it_instances = get_internals().registered_instances.equal_range(src);
     for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
         for (auto *instance_type : detail::all_type_info(Py_TYPE(it_i->second))) {
@@ -251,10 +257,10 @@ struct value_and_holder {
     void **vh = nullptr;
 
     // Main constructor for a found value/holder:
-    value_and_holder(instance *i, const detail::type_info *type, size_t vpos, size_t index) :
-        inst{i}, index{index}, type{type},
-        vh{inst->simple_layout ? inst->simple_value_holder : &inst->nonsimple.values_and_holders[vpos]}
-    {}
+    value_and_holder(instance *i, const detail::type_info *type, size_t vpos, size_t index)
+        : inst{i}, index{index}, type{type}, vh{inst->simple_layout
+                                                    ? inst->simple_value_holder
+                                                    : &inst->nonsimple.values_and_holders[vpos]} {}
 
     // Default constructor (used to signal a value-and-holder not found by get_value_and_holder())
     value_and_holder() = default;
@@ -262,13 +268,15 @@ struct value_and_holder {
     // Used for past-the-end iterator
     explicit value_and_holder(size_t index) : index{index} {}
 
-    template <typename V = void> V *&value_ptr() const {
+    template <typename V = void>
+    V *&value_ptr() const {
         return reinterpret_cast<V *&>(vh[0]);
     }
     // True if this `value_and_holder` has a non-null value pointer
     explicit operator bool() const { return value_ptr() != nullptr; }
 
-    template <typename H> H &holder() const {
+    template <typename H>
+    H &holder() const {
         return reinterpret_cast<H &>(vh[1]);
     }
     bool holder_constructed() const {
@@ -288,8 +296,8 @@ struct value_and_holder {
     }
     bool instance_registered() const {
         return inst->simple_layout
-            ? inst->simple_instance_registered
-            : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
+                   ? inst->simple_instance_registered
+                   : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
     }
     // NOLINTNEXTLINE(readability-make-member-function-const)
     void set_instance_registered(bool v = true) {
@@ -322,11 +330,10 @@ struct values_and_holders {
         friend struct values_and_holders;
         iterator(instance *inst, const type_vec *tinfo)
             : inst{inst}, types{tinfo},
-            curr(inst /* instance */,
-                 types->empty() ? nullptr : (*types)[0] /* type info */,
-                 0, /* vpos: (non-simple types only): the first vptr comes first */
-                 0 /* index */)
-        {}
+              curr(inst /* instance */,
+                   types->empty() ? nullptr : (*types)[0] /* type info */,
+                   0, /* vpos: (non-simple types only): the first vptr comes first */
+                   0 /* index */) {}
         // Past-the-end iterator:
         explicit iterator(size_t end) : curr(end) {}
 
@@ -369,7 +376,9 @@ struct values_and_holders {
  * The returned object should be short-lived: in particular, it must not outlive the called-upon
  * instance.
  */
-PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/, bool throw_if_missing /*= true in common.h*/) {
+PYBIND11_NOINLINE value_and_holder
+instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/,
+                               bool throw_if_missing /*= true in common.h*/) {
     // Optimize common case:
     if (!find_type || Py_TYPE(this) == find_type->type) {
         return value_and_holder(this, find_type, 0, 0);
@@ -387,12 +396,13 @@ PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_inf
 
 #if defined(NDEBUG)
     pybind11_fail("pybind11::detail::instance::get_value_and_holder: "
-            "type is not a pybind11 base of the given instance "
-            "(compile in debug mode for type details)");
+                  "type is not a pybind11 base of the given instance "
+                  "(compile in debug mode for type details)");
 #else
-    pybind11_fail("pybind11::detail::instance::get_value_and_holder: `" +
-            get_fully_qualified_tp_name(find_type->type) + "' is not a pybind11 base of the given `" +
-            get_fully_qualified_tp_name(Py_TYPE(this)) + "' instance");
+    pybind11_fail("pybind11::detail::instance::get_value_and_holder: `"
+                  + get_fully_qualified_tp_name(find_type->type)
+                  + "' is not a pybind11 base of the given `"
+                  + get_fully_qualified_tp_name(Py_TYPE(this)) + "' instance");
 #endif
 }
 
@@ -406,23 +416,22 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
             "instance allocation failed: new instance has no pybind11-registered base types");
     }
 
-    simple_layout =
-        n_types == 1 && tinfo.front()->holder_size_in_ptrs <= instance_simple_holder_in_ptrs();
+    simple_layout
+        = n_types == 1 && tinfo.front()->holder_size_in_ptrs <= instance_simple_holder_in_ptrs();
 
     // Simple path: no python-side multiple inheritance, and a small-enough holder
     if (simple_layout) {
         simple_value_holder[0] = nullptr;
         simple_holder_constructed = false;
         simple_instance_registered = false;
-    }
-    else { // multiple base types or a too-large holder
+    } else { // multiple base types or a too-large holder
         // Allocate space to hold: [v1*][h1][v2*][h2]...[bb...] where [vN*] is a value pointer,
         // [hN] is the (uninitialized) holder instance for value N, and [bb...] is a set of bool
         // values that tracks whether each associated holder has been initialized.  Each [block] is
         // padded, if necessary, to an integer multiple of sizeof(void *).
         size_t space = 0;
         for (auto *t : tinfo) {
-            space += 1; // value pointer
+            space += 1;                      // value pointer
             space += t->holder_size_in_ptrs; // holder instance
         }
         size_t flags_at = space;
@@ -441,10 +450,12 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
         }
 #else
         nonsimple.values_and_holders = (void **) PyMem_New(void *, space);
-        if (!nonsimple.values_and_holders) throw std::bad_alloc();
+        if (!nonsimple.values_and_holders)
+            throw std::bad_alloc();
         std::memset(nonsimple.values_and_holders, 0, space * sizeof(void *));
 #endif
-        nonsimple.status = reinterpret_cast<std::uint8_t *>(&nonsimple.values_and_holders[flags_at]);
+        nonsimple.status
+            = reinterpret_cast<std::uint8_t *>(&nonsimple.values_and_holders[flags_at]);
     }
     owned = true;
 }
@@ -501,17 +512,16 @@ PYBIND11_NOINLINE std::string error_string() {
         PyFrameObject *frame = trace->tb_frame;
         errorString += "\n\nAt:\n";
         while (frame) {
-#if PY_VERSION_HEX >= 0x03090000
+#    if PY_VERSION_HEX >= 0x03090000
             PyCodeObject *f_code = PyFrame_GetCode(frame);
-#else
+#    else
             PyCodeObject *f_code = frame->f_code;
             Py_INCREF(f_code);
-#endif
+#    endif
             int lineno = PyFrame_GetLineNumber(frame);
-            errorString +=
-                "  " + handle(f_code->co_filename).cast<std::string>() +
-                "(" + std::to_string(lineno) + "): " +
-                handle(f_code->co_name).cast<std::string>() + "\n";
+            errorString += "  " + handle(f_code->co_filename).cast<std::string>() + "("
+                           + std::to_string(lineno)
+                           + "): " + handle(f_code->co_name).cast<std::string>() + "\n";
             frame = frame->f_back;
             Py_DECREF(f_code);
         }
@@ -521,7 +531,7 @@ PYBIND11_NOINLINE std::string error_string() {
     return errorString;
 }
 
-PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_info *type ) {
+PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_info *type) {
     auto &instances = get_internals().registered_instances;
     auto range = instances.equal_range(ptr);
     for (auto it = range.first; it != range.second; ++it) {
@@ -540,9 +550,9 @@ inline PyThreadState *get_thread_state_unchecked() {
 #elif PY_VERSION_HEX < 0x03000000
     return _PyThreadState_Current;
 #elif PY_VERSION_HEX < 0x03050000
-    return (PyThreadState*) _Py_atomic_load_relaxed(&_PyThreadState_Current);
+    return (PyThreadState *) _Py_atomic_load_relaxed(&_PyThreadState_Current);
 #elif PY_VERSION_HEX < 0x03050200
-    return (PyThreadState*) _PyThreadState_Current.value;
+    return (PyThreadState *) _PyThreadState_Current.value;
 #else
     return _PyThreadState_UncheckedGet();
 #endif
@@ -560,11 +570,11 @@ class type_caster_generic {
     explicit type_caster_generic(const type_info *typeinfo)
         : typeinfo(typeinfo), cpptype(typeinfo ? typeinfo->cpptype : nullptr) {}
 
-    bool load(handle src, bool convert) {
-        return load_impl<type_caster_generic>(src, convert);
-    }
+    bool load(handle src, bool convert) { return load_impl<type_caster_generic>(src, convert); }
 
-    PYBIND11_NOINLINE static handle cast(const void *_src, return_value_policy policy, handle parent,
+    PYBIND11_NOINLINE static handle cast(const void *_src,
+                                         return_value_policy policy,
+                                         handle parent,
                                          const detail::type_info *tinfo,
                                          void *(*copy_constructor)(const void *),
                                          void *(*move_constructor)(const void *),
@@ -610,8 +620,8 @@ class type_caster_generic {
 #else
                     std::string type_name(tinfo->cpptype->name());
                     detail::clean_type_id(type_name);
-                    throw cast_error("return_value_policy = copy, but type " +
-                                     type_name + " is non-copyable!");
+                    throw cast_error("return_value_policy = copy, but type " + type_name
+                                     + " is non-copyable!");
 #endif
                 }
                 wrapper->owned = true;
@@ -630,8 +640,8 @@ class type_caster_generic {
 #else
                     std::string type_name(tinfo->cpptype->name());
                     detail::clean_type_id(type_name);
-                    throw cast_error("return_value_policy = move, but type " +
-                                     type_name + " is neither movable nor copyable!");
+                    throw cast_error("return_value_policy = move, but type " + type_name
+                                     + " is neither movable nor copyable!");
 #endif
                 }
                 wrapper->owned = true;
@@ -661,16 +671,15 @@ class type_caster_generic {
             if (type->operator_new) {
                 vptr = type->operator_new(type->type_size);
             } else {
-                #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
-                    if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
-                        vptr = ::operator new(type->type_size,
-                                              std::align_val_t(type->type_align));
-                    } else {
-                        vptr = ::operator new(type->type_size);
-                    }
-                #else
+#if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
+                if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
+                    vptr = ::operator new(type->type_size, std::align_val_t(type->type_align));
+                } else {
                     vptr = ::operator new(type->type_size);
-                #endif
+                }
+#else
+                vptr = ::operator new(type->type_size);
+#endif
             }
         }
         value = vptr;
@@ -713,7 +722,8 @@ class type_caster_generic {
         }
 
         type_info *foreign_typeinfo = reinterpret_borrow<capsule>(getattr(pytype, local_key));
-        // Only consider this foreign loader if actually foreign and is a loader of the correct cpp type
+        // Only consider this foreign loader if actually foreign and is a loader of the correct cpp
+        // type
         if (foreign_typeinfo->module_local_load == &local_load
             || (cpptype && !same_type(*cpptype, *foreign_typeinfo->cpptype))) {
             return false;
@@ -764,21 +774,23 @@ class type_caster_generic {
                 this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder());
                 return true;
             }
-            // Case 2b: the python type inherits from multiple C++ bases.  Check the bases to see if
-            // we can find an exact match (or, for a simple C++ type, an inherited match); if so, we
-            // can safely reinterpret_cast to the relevant pointer.
+            // Case 2b: the python type inherits from multiple C++ bases.  Check the bases to see
+            // if we can find an exact match (or, for a simple C++ type, an inherited match); if
+            // so, we can safely reinterpret_cast to the relevant pointer.
             if (bases.size() > 1) {
                 for (auto *base : bases) {
-                    if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type) : base->type == typeinfo->type) {
-                        this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base));
+                    if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type)
+                                  : base->type == typeinfo->type) {
+                        this_.load_value(
+                            reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base));
                         return true;
                     }
                 }
             }
 
-            // Case 2c: C++ multiple inheritance is involved and we couldn't find an exact type match
-            // in the registered bases, above, so try implicit casting (needed for proper C++ casting
-            // when MI is involved).
+            // Case 2c: C++ multiple inheritance is involved and we couldn't find an exact type
+            // match in the registered bases, above, so try implicit casting (needed for proper C++
+            // casting when MI is involved).
             if (this_.try_implicit_casts(src, convert)) {
                 return true;
             }
@@ -808,28 +820,29 @@ class type_caster_generic {
 
         // Global typeinfo has precedence over foreign module_local
         if (try_load_foreign_module_local(src)) {
-           return true;
+            return true;
         }
 
         // Custom converters didn't take None, now we convert None to nullptr.
         if (src.is_none()) {
-           // Defer accepting None to other overloads (if we aren't in convert mode):
-           if (!convert) {
-               return false;
-           }
-           value = nullptr;
-           return true;
+            // Defer accepting None to other overloads (if we aren't in convert mode):
+            if (!convert) {
+                return false;
+            }
+            value = nullptr;
+            return true;
         }
 
         return false;
     }
 
-
     // Called to do type lookup and wrap the pointer and type in a pair when a dynamic_cast
     // isn't needed or can't be used.  If the type is unknown, sets the error and returns a pair
     // with .second = nullptr.  (p.first = nullptr is not an error: it becomes None).
-    PYBIND11_NOINLINE static std::pair<const void *, const type_info *> src_and_type(
-            const void *src, const std::type_info &cast_type, const std::type_info *rtti_type = nullptr) {
+    PYBIND11_NOINLINE static std::pair<const void *, const type_info *>
+    src_and_type(const void *src,
+                 const std::type_info &cast_type,
+                 const std::type_info *rtti_type = nullptr) {
         if (auto *tpi = get_type_info(cast_type)) {
             return {src, const_cast<const type_info *>(tpi)};
         }
@@ -855,10 +868,9 @@ class type_caster_generic {
  * `movable_cast_op_type` instead.
  */
 template <typename T>
-using cast_op_type =
-    conditional_t<std::is_pointer<remove_reference_t<T>>::value,
-        typename std::add_pointer<intrinsic_t<T>>::type,
-        typename std::add_lvalue_reference<intrinsic_t<T>>::type>;
+using cast_op_type = conditional_t<std::is_pointer<remove_reference_t<T>>::value,
+                                   typename std::add_pointer<intrinsic_t<T>>::type,
+                                   typename std::add_lvalue_reference<intrinsic_t<T>>::type>;
 
 /**
  * Determine suitable casting operator for a type caster with a movable value.  Such a type caster
@@ -868,40 +880,50 @@ using cast_op_type =
  * These operator are automatically provided when using the PYBIND11_TYPE_CASTER macro.
  */
 template <typename T>
-using movable_cast_op_type =
-    conditional_t<std::is_pointer<typename std::remove_reference<T>::type>::value,
-        typename std::add_pointer<intrinsic_t<T>>::type,
-    conditional_t<std::is_rvalue_reference<T>::value,
-        typename std::add_rvalue_reference<intrinsic_t<T>>::type,
-        typename std::add_lvalue_reference<intrinsic_t<T>>::type>>;
+using movable_cast_op_type
+    = conditional_t<std::is_pointer<typename std::remove_reference<T>::type>::value,
+                    typename std::add_pointer<intrinsic_t<T>>::type,
+                    conditional_t<std::is_rvalue_reference<T>::value,
+                                  typename std::add_rvalue_reference<intrinsic_t<T>>::type,
+                                  typename std::add_lvalue_reference<intrinsic_t<T>>::type>>;
 
 // std::is_copy_constructible isn't quite enough: it lets std::vector<T> (and similar) through when
 // T is non-copyable, but code containing such a copy constructor fails to actually compile.
-template <typename T, typename SFINAE = void> struct is_copy_constructible : std::is_copy_constructible<T> {};
+template <typename T, typename SFINAE = void>
+struct is_copy_constructible : std::is_copy_constructible<T> {};
 
 // Specialization for types that appear to be copy constructible but also look like stl containers
 // (we specifically check for: has `value_type` and `reference` with `reference = value_type&`): if
 // so, copy constructability depends on whether the value_type is copy constructible.
-template <typename Container> struct is_copy_constructible<Container, enable_if_t<all_of<
-        std::is_copy_constructible<Container>,
-        std::is_same<typename Container::value_type &, typename Container::reference>,
-        // Avoid infinite recursion
-        negation<std::is_same<Container, typename Container::value_type>>
-    >::value>> : is_copy_constructible<typename Container::value_type> {};
+template <typename Container>
+struct is_copy_constructible<
+    Container,
+    enable_if_t<
+        all_of<std::is_copy_constructible<Container>,
+               std::is_same<typename Container::value_type &, typename Container::reference>,
+               // Avoid infinite recursion
+               negation<std::is_same<Container, typename Container::value_type>>>::value>>
+    : is_copy_constructible<typename Container::value_type> {};
 
 // Likewise for std::pair
-// (after C++17 it is mandatory that the copy constructor not exist when the two types aren't themselves
-// copy constructible, but this can not be relied upon when T1 or T2 are themselves containers).
-template <typename T1, typename T2> struct is_copy_constructible<std::pair<T1, T2>>
+// (after C++17 it is mandatory that the copy constructor not exist when the two types aren't
+// themselves copy constructible, but this can not be relied upon when T1 or T2 are themselves
+// containers).
+template <typename T1, typename T2>
+struct is_copy_constructible<std::pair<T1, T2>>
     : all_of<is_copy_constructible<T1>, is_copy_constructible<T2>> {};
 
 // The same problems arise with std::is_copy_assignable, so we use the same workaround.
-template <typename T, typename SFINAE = void> struct is_copy_assignable : std::is_copy_assignable<T> {};
-template <typename Container> struct is_copy_assignable<Container, enable_if_t<all_of<
-        std::is_copy_assignable<Container>,
-        std::is_same<typename Container::value_type &, typename Container::reference>
-    >::value>> : is_copy_assignable<typename Container::value_type> {};
-template <typename T1, typename T2> struct is_copy_assignable<std::pair<T1, T2>>
+template <typename T, typename SFINAE = void>
+struct is_copy_assignable : std::is_copy_assignable<T> {};
+template <typename Container>
+struct is_copy_assignable<Container,
+                          enable_if_t<all_of<std::is_copy_assignable<Container>,
+                                             std::is_same<typename Container::value_type &,
+                                                          typename Container::reference>>::value>>
+    : is_copy_assignable<typename Container::value_type> {};
+template <typename T1, typename T2>
+struct is_copy_assignable<std::pair<T1, T2>>
     : all_of<is_copy_assignable<T1>, is_copy_assignable<T2>> {};
 
 PYBIND11_NAMESPACE_END(detail)
@@ -928,16 +950,14 @@ PYBIND11_NAMESPACE_END(detail)
 // std::enable_if. User provided specializations will always have higher priority than
 // the default implementation and specialization provided in polymorphic_type_hook_base.
 template <typename itype, typename SFINAE = void>
-struct polymorphic_type_hook_base
-{
-    static const void *get(const itype *src, const std::type_info*&) { return src; }
+struct polymorphic_type_hook_base {
+    static const void *get(const itype *src, const std::type_info *&) { return src; }
 };
 template <typename itype>
-struct polymorphic_type_hook_base<itype, detail::enable_if_t<std::is_polymorphic<itype>::value>>
-{
-    static const void *get(const itype *src, const std::type_info*& type) {
+struct polymorphic_type_hook_base<itype, detail::enable_if_t<std::is_polymorphic<itype>::value>> {
+    static const void *get(const itype *src, const std::type_info *&type) {
         type = src ? &typeid(*src) : nullptr;
-        return dynamic_cast<const void*>(src);
+        return dynamic_cast<const void *>(src);
     }
 };
 template <typename itype, typename SFINAE = void>
@@ -946,14 +966,15 @@ struct polymorphic_type_hook : public polymorphic_type_hook_base<itype> {};
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Generic type caster for objects stored on the heap
-template <typename type> class type_caster_base : public type_caster_generic {
+template <typename type>
+class type_caster_base : public type_caster_generic {
     using itype = intrinsic_t<type>;
 
 public:
     static constexpr auto name = const_name<type>();
 
-    type_caster_base() : type_caster_base(typeid(type)) { }
-    explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
+    type_caster_base() : type_caster_base(typeid(type)) {}
+    explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) {}
 
     static handle cast(const itype &src, return_value_policy policy, handle parent) {
         if (policy == return_value_policy::automatic
@@ -987,31 +1008,39 @@ template <typename type> class type_caster_base : public type_caster_generic {
                 return {vsrc, tpi};
             }
         }
-        // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer, so
-        // don't do a cast
+        // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer,
+        // so don't do a cast
         return type_caster_generic::src_and_type(src, cast_type, instance_type);
     }
 
     static handle cast(const itype *src, return_value_policy policy, handle parent) {
         auto st = src_and_type(src);
-        return type_caster_generic::cast(
-            st.first, policy, parent, st.second,
-            make_copy_constructor(src), make_move_constructor(src));
+        return type_caster_generic::cast(st.first,
+                                         policy,
+                                         parent,
+                                         st.second,
+                                         make_copy_constructor(src),
+                                         make_move_constructor(src));
     }
 
     static handle cast_holder(const itype *src, const void *holder) {
         auto st = src_and_type(src);
-        return type_caster_generic::cast(
-            st.first, return_value_policy::take_ownership, {}, st.second,
-            nullptr, nullptr, holder);
+        return type_caster_generic::cast(st.first,
+                                         return_value_policy::take_ownership,
+                                         {},
+                                         st.second,
+                                         nullptr,
+                                         nullptr,
+                                         holder);
     }
 
-    template <typename T> using cast_op_type = detail::cast_op_type<T>;
+    template <typename T>
+    using cast_op_type = detail::cast_op_type<T>;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator itype*() { return (type *) value; }
+    operator itype *() { return (type *) value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator itype&() {
+    operator itype &() {
         if (!value) {
             throw reference_cast_error();
         }
@@ -1019,20 +1048,20 @@ template <typename type> class type_caster_base : public type_caster_generic {
     }
 
 protected:
-    using Constructor = void *(*)(const void *);
+    using Constructor = void *(*) (const void *);
 
     /* Only enabled when the types are {copy,move}-constructible *and* when the type
-       does not have a private operator new implementation. A comma operator is used in the decltype
-       argument to apply SFINAE to the public copy/move constructors.*/
+       does not have a private operator new implementation. A comma operator is used in the
+       decltype argument to apply SFINAE to the public copy/move constructors.*/
     template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
-    static auto make_copy_constructor(const T *) -> decltype(new T(std::declval<const T>()), Constructor{}) {
-        return [](const void *arg) -> void * {
-            return new T(*reinterpret_cast<const T *>(arg));
-        };
+    static auto make_copy_constructor(const T *)
+        -> decltype(new T(std::declval<const T>()), Constructor{}) {
+        return [](const void *arg) -> void * { return new T(*reinterpret_cast<const T *>(arg)); };
     }
 
     template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
-    static auto make_move_constructor(const T *) -> decltype(new T(std::declval<T&&>()), Constructor{}) {
+    static auto make_move_constructor(const T *)
+        -> decltype(new T(std::declval<T &&>()), Constructor{}) {
         return [](const void *arg) -> void * {
             return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
         };
diff --git a/include/pybind11/detail/typeid.h b/include/pybind11/detail/typeid.h
index 53c166bebc..8d99fc0286 100644
--- a/include/pybind11/detail/typeid.h
+++ b/include/pybind11/detail/typeid.h
@@ -13,7 +13,7 @@
 #include <cstdlib>
 
 #if defined(__GNUG__)
-#include <cxxabi.h>
+#    include <cxxabi.h>
 #endif
 
 #include "common.h"
@@ -34,8 +34,8 @@ inline void erase_all(std::string &string, const std::string &search) {
 PYBIND11_NOINLINE void clean_type_id(std::string &name) {
 #if defined(__GNUG__)
     int status = 0;
-    std::unique_ptr<char, void (*)(void *)> res {
-        abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status), std::free };
+    std::unique_ptr<char, void (*)(void *)> res{
+        abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status), std::free};
     if (status == 0) {
         name = res.get();
     }
@@ -49,7 +49,8 @@ PYBIND11_NOINLINE void clean_type_id(std::string &name) {
 PYBIND11_NAMESPACE_END(detail)
 
 /// Return a string representation of a C++ type
-template <typename T> static std::string type_id() {
+template <typename T>
+static std::string type_id() {
     std::string name(typeid(T).name());
     detail::clean_type_id(name);
     return name;
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 87f4e9f888..47820ce895 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -23,122 +23,145 @@
 // 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
 // it is probably best to keep this around indefinitely.
 #if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // C4127: conditional expression is constant
+#    pragma warning(push)
+#    pragma warning(disable : 4127) // C4127: conditional expression is constant
 #endif
 
 #include <Eigen/Core>
 #include <Eigen/SparseCore>
 
 #if defined(_MSC_VER)
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
 // Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
 // move constructors that break things.  We could detect this an explicitly copy, but an extra copy
 // of matrices seems highly undesirable.
-static_assert(EIGEN_VERSION_AT_LEAST(3,2,7), "Eigen support in pybind11 requires Eigen >= 3.2.7");
+static_assert(EIGEN_VERSION_AT_LEAST(3, 2, 7),
+              "Eigen support in pybind11 requires Eigen >= 3.2.7");
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 // Provide a convenience alias for easier pass-by-ref usage with fully dynamic strides:
 using EigenDStride = Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic>;
-template <typename MatrixType> using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
-template <typename MatrixType> using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
+template <typename MatrixType>
+using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
+template <typename MatrixType>
+using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-#if EIGEN_VERSION_AT_LEAST(3,3,0)
+#if EIGEN_VERSION_AT_LEAST(3, 3, 0)
 using EigenIndex = Eigen::Index;
-template<typename Scalar, int Flags, typename StorageIndex>
+template <typename Scalar, int Flags, typename StorageIndex>
 using EigenMapSparseMatrix = Eigen::Map<Eigen::SparseMatrix<Scalar, Flags, StorageIndex>>;
 #else
 using EigenIndex = EIGEN_DEFAULT_DENSE_INDEX_TYPE;
-template<typename Scalar, int Flags, typename StorageIndex>
+template <typename Scalar, int Flags, typename StorageIndex>
 using EigenMapSparseMatrix = Eigen::MappedSparseMatrix<Scalar, Flags, StorageIndex>;
 #endif
 
 // Matches Eigen::Map, Eigen::Ref, blocks, etc:
-template <typename T> using is_eigen_dense_map = all_of<is_template_base_of<Eigen::DenseBase, T>, std::is_base_of<Eigen::MapBase<T, Eigen::ReadOnlyAccessors>, T>>;
-template <typename T> using is_eigen_mutable_map = std::is_base_of<Eigen::MapBase<T, Eigen::WriteAccessors>, T>;
-template <typename T> using is_eigen_dense_plain = all_of<negation<is_eigen_dense_map<T>>, is_template_base_of<Eigen::PlainObjectBase, T>>;
-template <typename T> using is_eigen_sparse = is_template_base_of<Eigen::SparseMatrixBase, T>;
+template <typename T>
+using is_eigen_dense_map = all_of<is_template_base_of<Eigen::DenseBase, T>,
+                                  std::is_base_of<Eigen::MapBase<T, Eigen::ReadOnlyAccessors>, T>>;
+template <typename T>
+using is_eigen_mutable_map = std::is_base_of<Eigen::MapBase<T, Eigen::WriteAccessors>, T>;
+template <typename T>
+using is_eigen_dense_plain
+    = all_of<negation<is_eigen_dense_map<T>>, is_template_base_of<Eigen::PlainObjectBase, T>>;
+template <typename T>
+using is_eigen_sparse = is_template_base_of<Eigen::SparseMatrixBase, T>;
 // Test for objects inheriting from EigenBase<Derived> that aren't captured by the above.  This
 // basically covers anything that can be assigned to a dense matrix but that don't have a typical
 // matrix data layout that can be copied from their .data().  For example, DiagonalMatrix and
 // SelfAdjointView fall into this category.
-template <typename T> using is_eigen_other = all_of<
-    is_template_base_of<Eigen::EigenBase, T>,
-    negation<any_of<is_eigen_dense_map<T>, is_eigen_dense_plain<T>, is_eigen_sparse<T>>>
->;
+template <typename T>
+using is_eigen_other
+    = all_of<is_template_base_of<Eigen::EigenBase, T>,
+             negation<any_of<is_eigen_dense_map<T>, is_eigen_dense_plain<T>, is_eigen_sparse<T>>>>;
 
 // Captures numpy/eigen conformability status (returned by EigenProps::conformable()):
-template <bool EigenRowMajor> struct EigenConformable {
+template <bool EigenRowMajor>
+struct EigenConformable {
     bool conformable = false;
     EigenIndex rows = 0, cols = 0;
-    EigenDStride stride{0, 0};      // Only valid if negativestrides is false!
-    bool negativestrides = false;   // If true, do not use stride!
+    EigenDStride stride{0, 0};    // Only valid if negativestrides is false!
+    bool negativestrides = false; // If true, do not use stride!
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     EigenConformable(bool fits = false) : conformable{fits} {}
     // Matrix type:
-    EigenConformable(EigenIndex r, EigenIndex c,
-            EigenIndex rstride, EigenIndex cstride) :
-        conformable{true}, rows{r}, cols{c},
-        //TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity. http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
-        stride{EigenRowMajor ? (rstride > 0 ? rstride : 0) : (cstride > 0 ? cstride : 0) /* outer stride */,
-               EigenRowMajor ? (cstride > 0 ? cstride : 0) : (rstride > 0 ? rstride : 0) /* inner stride */ },
-        negativestrides{rstride < 0 || cstride < 0} {
-
-    }
+    EigenConformable(EigenIndex r, EigenIndex c, EigenIndex rstride, EigenIndex cstride)
+        : conformable{true}, rows{r}, cols{c},
+          // TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity.
+          // http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
+          stride{EigenRowMajor ? (rstride > 0 ? rstride : 0)
+                               : (cstride > 0 ? cstride : 0) /* outer stride */,
+                 EigenRowMajor ? (cstride > 0 ? cstride : 0)
+                               : (rstride > 0 ? rstride : 0) /* inner stride */},
+          negativestrides{rstride < 0 || cstride < 0} {}
     // Vector type:
     EigenConformable(EigenIndex r, EigenIndex c, EigenIndex stride)
-        : EigenConformable(r, c, r == 1 ? c*stride : stride, c == 1 ? r : r*stride) {}
+        : EigenConformable(r, c, r == 1 ? c * stride : stride, c == 1 ? r : r * stride) {}
 
-    template <typename props> bool stride_compatible() const {
+    template <typename props>
+    bool stride_compatible() const {
         // To have compatible strides, we need (on both dimensions) one of fully dynamic strides,
-        // matching strides, or a dimension size of 1 (in which case the stride value is irrelevant)
-        return
-            !negativestrides &&
-            (props::inner_stride == Eigen::Dynamic || props::inner_stride == stride.inner() ||
-                (EigenRowMajor ? cols : rows) == 1) &&
-            (props::outer_stride == Eigen::Dynamic || props::outer_stride == stride.outer() ||
-                (EigenRowMajor ? rows : cols) == 1);
+        // matching strides, or a dimension size of 1 (in which case the stride value is
+        // irrelevant)
+        return !negativestrides
+               && (props::inner_stride == Eigen::Dynamic || props::inner_stride == stride.inner()
+                   || (EigenRowMajor ? cols : rows) == 1)
+               && (props::outer_stride == Eigen::Dynamic || props::outer_stride == stride.outer()
+                   || (EigenRowMajor ? rows : cols) == 1);
     }
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator bool() const { return conformable; }
 };
 
-template <typename Type> struct eigen_extract_stride { using type = Type; };
+template <typename Type>
+struct eigen_extract_stride {
+    using type = Type;
+};
 template <typename PlainObjectType, int MapOptions, typename StrideType>
-struct eigen_extract_stride<Eigen::Map<PlainObjectType, MapOptions, StrideType>> { using type = StrideType; };
+struct eigen_extract_stride<Eigen::Map<PlainObjectType, MapOptions, StrideType>> {
+    using type = StrideType;
+};
 template <typename PlainObjectType, int Options, typename StrideType>
-struct eigen_extract_stride<Eigen::Ref<PlainObjectType, Options, StrideType>> { using type = StrideType; };
+struct eigen_extract_stride<Eigen::Ref<PlainObjectType, Options, StrideType>> {
+    using type = StrideType;
+};
 
 // Helper struct for extracting information from an Eigen type
-template <typename Type_> struct EigenProps {
+template <typename Type_>
+struct EigenProps {
     using Type = Type_;
     using Scalar = typename Type::Scalar;
     using StrideType = typename eigen_extract_stride<Type>::type;
-    static constexpr EigenIndex
-        rows = Type::RowsAtCompileTime,
-        cols = Type::ColsAtCompileTime,
-        size = Type::SizeAtCompileTime;
-    static constexpr bool
-        row_major = Type::IsRowMajor,
-        vector = Type::IsVectorAtCompileTime, // At least one dimension has fixed size 1
-        fixed_rows = rows != Eigen::Dynamic,
-        fixed_cols = cols != Eigen::Dynamic,
-        fixed = size != Eigen::Dynamic, // Fully-fixed size
-        dynamic = !fixed_rows && !fixed_cols; // Fully-dynamic size
-
-    template <EigenIndex i, EigenIndex ifzero> using if_zero = std::integral_constant<EigenIndex, i == 0 ? ifzero : i>;
-    static constexpr EigenIndex inner_stride = if_zero<StrideType::InnerStrideAtCompileTime, 1>::value,
-                                outer_stride = if_zero<StrideType::OuterStrideAtCompileTime,
-                                                       vector ? size : row_major ? cols : rows>::value;
-    static constexpr bool dynamic_stride = inner_stride == Eigen::Dynamic && outer_stride == Eigen::Dynamic;
-    static constexpr bool requires_row_major = !dynamic_stride && !vector && (row_major ? inner_stride : outer_stride) == 1;
-    static constexpr bool requires_col_major = !dynamic_stride && !vector && (row_major ? outer_stride : inner_stride) == 1;
+    static constexpr EigenIndex rows = Type::RowsAtCompileTime, cols = Type::ColsAtCompileTime,
+                                size = Type::SizeAtCompileTime;
+    static constexpr bool row_major = Type::IsRowMajor,
+                          vector
+                          = Type::IsVectorAtCompileTime, // At least one dimension has fixed size 1
+        fixed_rows = rows != Eigen::Dynamic, fixed_cols = cols != Eigen::Dynamic,
+                          fixed = size != Eigen::Dynamic, // Fully-fixed size
+        dynamic = !fixed_rows && !fixed_cols;             // Fully-dynamic size
+
+    template <EigenIndex i, EigenIndex ifzero>
+    using if_zero = std::integral_constant<EigenIndex, i == 0 ? ifzero : i>;
+    static constexpr EigenIndex inner_stride
+        = if_zero<StrideType::InnerStrideAtCompileTime, 1>::value,
+        outer_stride = if_zero < StrideType::OuterStrideAtCompileTime,
+        vector      ? size
+        : row_major ? cols
+                    : rows > ::value;
+    static constexpr bool dynamic_stride
+        = inner_stride == Eigen::Dynamic && outer_stride == Eigen::Dynamic;
+    static constexpr bool requires_row_major
+        = !dynamic_stride && !vector && (row_major ? inner_stride : outer_stride) == 1;
+    static constexpr bool requires_col_major
+        = !dynamic_stride && !vector && (row_major ? outer_stride : inner_stride) == 1;
 
     // Takes an input array and determines whether we can make it fit into the Eigen type.  If
     // the array is a vector, we attempt to fit it into either an Eigen 1xN or Nx1 vector
@@ -151,11 +174,9 @@ template <typename Type_> struct EigenProps {
 
         if (dims == 2) { // Matrix type: require exact match (or dynamic)
 
-            EigenIndex
-                np_rows = a.shape(0),
-                np_cols = a.shape(1),
-                np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
-                np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
+            EigenIndex np_rows = a.shape(0), np_cols = a.shape(1),
+                       np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
+                       np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
             if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows)
                 || (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols)) {
                 return false;
@@ -164,10 +185,10 @@ template <typename Type_> struct EigenProps {
             return {np_rows, np_cols, np_rstride, np_cstride};
         }
 
-        // Otherwise we're storing an n-vector.  Only one of the strides will be used, but whichever
-        // is used, we want the (single) numpy stride value.
+        // Otherwise we're storing an n-vector.  Only one of the strides will be used, but
+        // whichever is used, we want the (single) numpy stride value.
         const EigenIndex n = a.shape(0),
-              stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
+                         stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
 
         if (vector) { // Eigen type is a compile-time vector
             if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n) {
@@ -190,38 +211,41 @@ template <typename Type_> struct EigenProps {
         if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) {
             return false;
         }
-            return {n, 1, stride};
+        return {n, 1, stride};
     }
 
-    static constexpr bool show_writeable = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
+    static constexpr bool show_writeable
+        = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
     static constexpr bool show_order = is_eigen_dense_map<Type>::value;
     static constexpr bool show_c_contiguous = show_order && requires_row_major;
-    static constexpr bool show_f_contiguous = !show_c_contiguous && show_order && requires_col_major;
-
-    static constexpr auto descriptor =
-        const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name +
-        const_name("[")  + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) +
-        const_name(", ") + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) +
-        const_name("]") +
-        // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to be
-        // satisfied: writeable=True (for a mutable reference), and, depending on the map's stride
-        // options, possibly f_contiguous or c_contiguous.  We include them in the descriptor output
-        // to provide some hint as to why a TypeError is occurring (otherwise it can be confusing to
-        // see that a function accepts a 'numpy.ndarray[float64[3,2]]' and an error message that you
-        // *gave* a numpy.ndarray of the right type and dimensions.
-        const_name<show_writeable>(", flags.writeable", "") +
-        const_name<show_c_contiguous>(", flags.c_contiguous", "") +
-        const_name<show_f_contiguous>(", flags.f_contiguous", "") +
-        const_name("]");
+    static constexpr bool show_f_contiguous
+        = !show_c_contiguous && show_order && requires_col_major;
+
+    static constexpr auto descriptor
+        = const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name + const_name("[")
+          + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) + const_name(", ")
+          + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) + const_name("]")
+          +
+          // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to
+          // be satisfied: writeable=True (for a mutable reference), and, depending on the map's
+          // stride options, possibly f_contiguous or c_contiguous.  We include them in the
+          // descriptor output to provide some hint as to why a TypeError is occurring (otherwise
+          // it can be confusing to see that a function accepts a 'numpy.ndarray[float64[3,2]]' and
+          // an error message that you *gave* a numpy.ndarray of the right type and dimensions.
+          const_name<show_writeable>(", flags.writeable", "")
+          + const_name<show_c_contiguous>(", flags.c_contiguous", "")
+          + const_name<show_f_contiguous>(", flags.f_contiguous", "") + const_name("]");
 };
 
 // Casts an Eigen type to numpy array.  If given a base, the numpy array references the src data,
 // otherwise it'll make a copy.  writeable lets you turn off the writeable flag for the array.
-template <typename props> handle eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
+template <typename props>
+handle
+eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
     constexpr ssize_t elem_size = sizeof(typename props::Scalar);
     array a;
     if (props::vector) {
-        a = array({ src.size() }, { elem_size * src.innerStride() }, src.data(), base);
+        a = array({src.size()}, {elem_size * src.innerStride()}, src.data(), base);
     } else {
         a = array({src.rows(), src.cols()},
                   {elem_size * src.rowStride(), elem_size * src.colStride()},
@@ -247,10 +271,10 @@ handle eigen_ref_array(Type &src, handle parent = none()) {
     return eigen_array_cast<props>(src, parent, !std::is_const<Type>::value);
 }
 
-// Takes a pointer to some dense, plain Eigen type, builds a capsule around it, then returns a numpy
-// array that references the encapsulated data with a python-side reference to the capsule to tie
-// its destruction to that of any dependent python objects.  Const-ness is determined by whether or
-// not the Type of the pointer given is const.
+// Takes a pointer to some dense, plain Eigen type, builds a capsule around it, then returns a
+// numpy array that references the encapsulated data with a python-side reference to the capsule to
+// tie its destruction to that of any dependent python objects.  Const-ness is determined by
+// whether or not the Type of the pointer given is const.
 template <typename props, typename Type, typename = enable_if_t<is_eigen_dense_plain<Type>::value>>
 handle eigen_encapsulate(Type *src) {
     capsule base(src, [](void *o) { delete static_cast<Type *>(o); });
@@ -259,7 +283,7 @@ handle eigen_encapsulate(Type *src) {
 
 // Type caster for regular, dense matrix types (e.g. MatrixXd), but not maps/refs/etc. of dense
 // types.
-template<typename Type>
+template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     using Scalar = typename Type::Scalar;
     using props = EigenProps<Type>;
@@ -307,7 +331,6 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     }
 
 private:
-
     // Cast implementation
     template <typename CType>
     static handle cast_impl(CType *src, return_value_policy policy, handle parent) {
@@ -330,7 +353,6 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     }
 
 public:
-
     // Normal returned non-reference, non-const value:
     static handle cast(Type &&src, return_value_policy /* policy */, handle parent) {
         return cast_impl(&src, return_value_policy::move, parent);
@@ -367,30 +389,31 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     static constexpr auto name = props::descriptor;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type*() { return &value; }
+    operator Type *() { return &value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type&() { return value; }
+    operator Type &() { return value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type&&() && { return std::move(value); }
-    template <typename T> using cast_op_type = movable_cast_op_type<T>;
+    operator Type &&() && { return std::move(value); }
+    template <typename T>
+    using cast_op_type = movable_cast_op_type<T>;
 
 private:
     Type value;
 };
 
 // Base class for casting reference/map/block/etc. objects back to python.
-template <typename MapType> struct eigen_map_caster {
+template <typename MapType>
+struct eigen_map_caster {
 private:
     using props = EigenProps<MapType>;
 
 public:
-
     // Directly referencing a ref/map's data is a bit dangerous (whatever the map/ref points to has
-    // to stay around), but we'll allow it under the assumption that you know what you're doing (and
-    // have an appropriate keep_alive in place).  We return a numpy array pointing directly at the
-    // ref's data (The numpy array ends up read-only if the ref was to a const matrix type.) Note
-    // that this means you need to ensure you don't destroy the object in some other way (e.g. with
-    // an appropriate keep_alive, or with a reference to a statically allocated matrix).
+    // to stay around), but we'll allow it under the assumption that you know what you're doing
+    // (and have an appropriate keep_alive in place).  We return a numpy array pointing directly at
+    // the ref's data (The numpy array ends up read-only if the ref was to a const matrix type.)
+    // Note that this means you need to ensure you don't destroy the object in some other way (e.g.
+    // with an appropriate keep_alive, or with a reference to a statically allocated matrix).
     static handle cast(const MapType &src, return_value_policy policy, handle parent) {
         switch (policy) {
             case return_value_policy::copy:
@@ -414,43 +437,50 @@ template <typename MapType> struct eigen_map_caster {
     // you end up here if you try anyway.
     bool load(handle, bool) = delete;
     operator MapType() = delete;
-    template <typename> using cast_op_type = MapType;
+    template <typename>
+    using cast_op_type = MapType;
 };
 
 // We can return any map-like object (but can only load Refs, specialized next):
-template <typename Type> struct type_caster<Type, enable_if_t<is_eigen_dense_map<Type>::value>>
-    : eigen_map_caster<Type> {};
+template <typename Type>
+struct type_caster<Type, enable_if_t<is_eigen_dense_map<Type>::value>> : eigen_map_caster<Type> {};
 
 // Loader for Ref<...> arguments.  See the documentation for info on how to make this work without
 // copying (it requires some extra effort in many cases).
 template <typename PlainObjectType, typename StrideType>
 struct type_caster<
     Eigen::Ref<PlainObjectType, 0, StrideType>,
-    enable_if_t<is_eigen_dense_map<Eigen::Ref<PlainObjectType, 0, StrideType>>::value>
-> : public eigen_map_caster<Eigen::Ref<PlainObjectType, 0, StrideType>> {
+    enable_if_t<is_eigen_dense_map<Eigen::Ref<PlainObjectType, 0, StrideType>>::value>>
+    : public eigen_map_caster<Eigen::Ref<PlainObjectType, 0, StrideType>> {
 private:
     using Type = Eigen::Ref<PlainObjectType, 0, StrideType>;
     using props = EigenProps<Type>;
     using Scalar = typename props::Scalar;
     using MapType = Eigen::Map<PlainObjectType, 0, StrideType>;
-    using Array = array_t<Scalar, array::forcecast |
-                ((props::row_major ? props::inner_stride : props::outer_stride) == 1 ? array::c_style :
-                 (props::row_major ? props::outer_stride : props::inner_stride) == 1 ? array::f_style : 0)>;
+    using Array
+        = array_t<Scalar,
+                  array::forcecast
+                      | ((props::row_major ? props::inner_stride : props::outer_stride) == 1
+                             ? array::c_style
+                         : (props::row_major ? props::outer_stride : props::inner_stride) == 1
+                             ? array::f_style
+                             : 0)>;
     static constexpr bool need_writeable = is_eigen_mutable_map<Type>::value;
     // Delay construction (these have no default constructor)
     std::unique_ptr<MapType> map;
     std::unique_ptr<Type> ref;
     // Our array.  When possible, this is just a numpy array pointing to the source data, but
-    // sometimes we can't avoid copying (e.g. input is not a numpy array at all, has an incompatible
-    // layout, or is an array of a type that needs to be converted).  Using a numpy temporary
-    // (rather than an Eigen temporary) saves an extra copy when we need both type conversion and
-    // storage order conversion.  (Note that we refuse to use this temporary copy when loading an
-    // argument for a Ref<M> with M non-const, i.e. a read-write reference).
+    // sometimes we can't avoid copying (e.g. input is not a numpy array at all, has an
+    // incompatible layout, or is an array of a type that needs to be converted).  Using a numpy
+    // temporary (rather than an Eigen temporary) saves an extra copy when we need both type
+    // conversion and storage order conversion.  (Note that we refuse to use this temporary copy
+    // when loading an argument for a Ref<M> with M non-const, i.e. a read-write reference).
     Array copy_or_ref;
+
 public:
     bool load(handle src, bool convert) {
-        // First check whether what we have is already an array of the right type.  If not, we can't
-        // avoid a copy (because the copy is also going to do type conversion).
+        // First check whether what we have is already an array of the right type.  If not, we
+        // can't avoid a copy (because the copy is also going to do type conversion).
         bool need_copy = !isinstance<Array>(src);
 
         EigenConformable<props::row_major> fits;
@@ -469,8 +499,7 @@ struct type_caster<
                 } else {
                     copy_or_ref = std::move(aref);
                 }
-            }
-            else {
+            } else {
                 need_copy = true;
             }
         }
@@ -496,54 +525,76 @@ struct type_caster<
         }
 
         ref.reset();
-        map.reset(new MapType(data(copy_or_ref), fits.rows, fits.cols, make_stride(fits.stride.outer(), fits.stride.inner())));
+        map.reset(new MapType(data(copy_or_ref),
+                              fits.rows,
+                              fits.cols,
+                              make_stride(fits.stride.outer(), fits.stride.inner())));
         ref.reset(new Type(*map));
 
         return true;
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type*() { return ref.get(); }
+    operator Type *() { return ref.get(); }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type&() { return *ref; }
-    template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
+    operator Type &() { return *ref; }
+    template <typename _T>
+    using cast_op_type = pybind11::detail::cast_op_type<_T>;
 
 private:
     template <typename T = Type, enable_if_t<is_eigen_mutable_map<T>::value, int> = 0>
-    Scalar *data(Array &a) { return a.mutable_data(); }
+    Scalar *data(Array &a) {
+        return a.mutable_data();
+    }
 
     template <typename T = Type, enable_if_t<!is_eigen_mutable_map<T>::value, int> = 0>
-    const Scalar *data(Array &a) { return a.data(); }
+    const Scalar *data(Array &a) {
+        return a.data();
+    }
 
     // Attempt to figure out a constructor of `Stride` that will work.
     // If both strides are fixed, use a default constructor:
-    template <typename S> using stride_ctor_default = bool_constant<
-        S::InnerStrideAtCompileTime != Eigen::Dynamic && S::OuterStrideAtCompileTime != Eigen::Dynamic &&
-        std::is_default_constructible<S>::value>;
+    template <typename S>
+    using stride_ctor_default = bool_constant<S::InnerStrideAtCompileTime != Eigen::Dynamic
+                                              && S::OuterStrideAtCompileTime != Eigen::Dynamic
+                                              && std::is_default_constructible<S>::value>;
     // Otherwise, if there is a two-index constructor, assume it is (outer,inner) like
     // Eigen::Stride, and use it:
-    template <typename S> using stride_ctor_dual = bool_constant<
-        !stride_ctor_default<S>::value && std::is_constructible<S, EigenIndex, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_dual
+        = bool_constant<!stride_ctor_default<S>::value
+                        && std::is_constructible<S, EigenIndex, EigenIndex>::value>;
     // Otherwise, if there is a one-index constructor, and just one of the strides is dynamic, use
     // it (passing whichever stride is dynamic).
-    template <typename S> using stride_ctor_outer = bool_constant<
-        !any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value &&
-        S::OuterStrideAtCompileTime == Eigen::Dynamic && S::InnerStrideAtCompileTime != Eigen::Dynamic &&
-        std::is_constructible<S, EigenIndex>::value>;
-    template <typename S> using stride_ctor_inner = bool_constant<
-        !any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value &&
-        S::InnerStrideAtCompileTime == Eigen::Dynamic && S::OuterStrideAtCompileTime != Eigen::Dynamic &&
-        std::is_constructible<S, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_outer
+        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
+                        && S::OuterStrideAtCompileTime == Eigen::Dynamic
+                        && S::InnerStrideAtCompileTime != Eigen::Dynamic
+                        && std::is_constructible<S, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_inner
+        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
+                        && S::InnerStrideAtCompileTime == Eigen::Dynamic
+                        && S::OuterStrideAtCompileTime != Eigen::Dynamic
+                        && std::is_constructible<S, EigenIndex>::value>;
 
     template <typename S = StrideType, enable_if_t<stride_ctor_default<S>::value, int> = 0>
-    static S make_stride(EigenIndex, EigenIndex) { return S(); }
+    static S make_stride(EigenIndex, EigenIndex) {
+        return S();
+    }
     template <typename S = StrideType, enable_if_t<stride_ctor_dual<S>::value, int> = 0>
-    static S make_stride(EigenIndex outer, EigenIndex inner) { return S(outer, inner); }
+    static S make_stride(EigenIndex outer, EigenIndex inner) {
+        return S(outer, inner);
+    }
     template <typename S = StrideType, enable_if_t<stride_ctor_outer<S>::value, int> = 0>
-    static S make_stride(EigenIndex outer, EigenIndex) { return S(outer); }
+    static S make_stride(EigenIndex outer, EigenIndex) {
+        return S(outer);
+    }
     template <typename S = StrideType, enable_if_t<stride_ctor_inner<S>::value, int> = 0>
-    static S make_stride(EigenIndex, EigenIndex inner) { return S(inner); }
-
+    static S make_stride(EigenIndex, EigenIndex inner) {
+        return S(inner);
+    }
 };
 
 // type_caster for special matrix types (e.g. DiagonalMatrix), which are EigenBase, but not
@@ -553,14 +604,18 @@ struct type_caster<
 template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
 protected:
-    using Matrix = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
+    using Matrix
+        = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
     using props = EigenProps<Matrix>;
+
 public:
     static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
         handle h = eigen_encapsulate<props>(new Matrix(src));
         return h;
     }
-    static handle cast(const Type *src, return_value_policy policy, handle parent) { return cast(*src, policy, parent); }
+    static handle cast(const Type *src, return_value_policy policy, handle parent) {
+        return cast(*src, policy, parent);
+    }
 
     static constexpr auto name = props::descriptor;
 
@@ -569,10 +624,11 @@ struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
     // you end up here if you try anyway.
     bool load(handle, bool) = delete;
     operator Type() = delete;
-    template <typename> using cast_op_type = Type;
+    template <typename>
+    using cast_op_type = Type;
 };
 
-template<typename Type>
+template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
     using Scalar = typename Type::Scalar;
     using StorageIndex = remove_reference_t<decltype(*std::declval<Type>().outerIndexPtr())>;
@@ -586,8 +642,7 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
 
         auto obj = reinterpret_borrow<object>(src);
         object sparse_module = module_::import("scipy.sparse");
-        object matrix_type = sparse_module.attr(
-            rowMajor ? "csr_matrix" : "csc_matrix");
+        object matrix_type = sparse_module.attr(rowMajor ? "csr_matrix" : "csc_matrix");
 
         if (!type::handle_of(obj).is(matrix_type)) {
             try {
@@ -608,32 +663,36 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         }
 
         value = EigenMapSparseMatrix<Scalar,
-                                     Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
-                                     StorageIndex>(
-            shape[0].cast<Index>(), shape[1].cast<Index>(), nnz,
-            outerIndices.mutable_data(), innerIndices.mutable_data(), values.mutable_data());
+                                     Type::Flags &(Eigen::RowMajor | Eigen::ColMajor),
+                                     StorageIndex>(shape[0].cast<Index>(),
+                                                   shape[1].cast<Index>(),
+                                                   nnz,
+                                                   outerIndices.mutable_data(),
+                                                   innerIndices.mutable_data(),
+                                                   values.mutable_data());
 
         return true;
     }
 
     static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
-        const_cast<Type&>(src).makeCompressed();
+        const_cast<Type &>(src).makeCompressed();
 
-        object matrix_type = module_::import("scipy.sparse").attr(
-            rowMajor ? "csr_matrix" : "csc_matrix");
+        object matrix_type
+            = module_::import("scipy.sparse").attr(rowMajor ? "csr_matrix" : "csc_matrix");
 
         array data(src.nonZeros(), src.valuePtr());
         array outerIndices((rowMajor ? src.rows() : src.cols()) + 1, src.outerIndexPtr());
         array innerIndices(src.nonZeros(), src.innerIndexPtr());
 
-        return matrix_type(
-            std::make_tuple(data, innerIndices, outerIndices),
-            std::make_pair(src.rows(), src.cols())
-        ).release();
+        return matrix_type(std::make_tuple(data, innerIndices, outerIndices),
+                           std::make_pair(src.rows(), src.cols()))
+            .release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[", "scipy.sparse.csc_matrix[")
-            + npy_format_descriptor<Scalar>::name + const_name("]"));
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[",
+                                                             "scipy.sparse.csc_matrix[")
+                             + npy_format_descriptor<Scalar>::name + const_name("]"));
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 0c3f778136..84e4422212 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -16,21 +16,17 @@
 #include <vector>
 
 #if defined(PYPY_VERSION)
-#  error Embedding the interpreter is not supported with PyPy
+#    error Embedding the interpreter is not supported with PyPy
 #endif
 
 #if PY_MAJOR_VERSION >= 3
-#  define PYBIND11_EMBEDDED_MODULE_IMPL(name)            \
-      extern "C" PyObject *pybind11_init_impl_##name();  \
-      extern "C" PyObject *pybind11_init_impl_##name() { \
-          return pybind11_init_wrapper_##name();         \
-      }
+#    define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                   \
+        extern "C" PyObject *pybind11_init_impl_##name();                                         \
+        extern "C" PyObject *pybind11_init_impl_##name() { return pybind11_init_wrapper_##name(); }
 #else
-#  define PYBIND11_EMBEDDED_MODULE_IMPL(name)            \
-      extern "C" void pybind11_init_impl_##name();       \
-      extern "C" void pybind11_init_impl_##name() {      \
-          pybind11_init_wrapper_##name();                \
-      }
+#    define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                   \
+        extern "C" void pybind11_init_impl_##name();                                              \
+        extern "C" void pybind11_init_impl_##name() { pybind11_init_wrapper_##name(); }
 #endif
 
 /** \rst
@@ -72,7 +68,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
 struct embedded_module {
 #if PY_MAJOR_VERSION >= 3
-    using init_t = PyObject *(*)();
+    using init_t = PyObject *(*) ();
 #else
     using init_t = void (*)();
 #endif
@@ -106,10 +102,10 @@ inline wchar_t *widen_chars(const char *safe_arg) {
     wchar_t *widened_arg = nullptr;
 
 // warning C4996: 'mbstowcs': This function or variable may be unsafe.
-#if defined(_MSC_VER)
-#pragma warning(push)
-#pragma warning(disable:4996)
-#endif
+#    if defined(_MSC_VER)
+#        pragma warning(push)
+#        pragma warning(disable : 4996)
+#    endif
 
 #    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
     size_t count = std::strlen(safe_arg);
@@ -121,9 +117,9 @@ inline wchar_t *widen_chars(const char *safe_arg) {
         std::mbstowcs(widened_arg, safe_arg, count + 1);
     }
 
-#if defined(_MSC_VER)
-#pragma warning(pop)
-#endif
+#    if defined(_MSC_VER)
+#        pragma warning(pop)
+#    endif
 
 #endif
     return widened_arg;
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 8009fbde58..731dedd4b1 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -11,24 +11,24 @@
 
 #pragma once
 
-#include <utility>
-
 #include "pybind11.h"
 
+#include <utility>
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline void ensure_builtins_in_globals(object &global) {
-    #if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
-        // Running exec and eval on Python 2 and 3 adds `builtins` module under
-        // `__builtins__` key to globals if not yet present.
-        // Python 3.8 made PyRun_String behave similarly. Let's also do that for
-        // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
-        if (!global.contains("__builtins__"))
-            global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
-    #else
-        (void) global;
-    #endif
+#if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
+    // Running exec and eval on Python 2 and 3 adds `builtins` module under
+    // `__builtins__` key to globals if not yet present.
+    // Python 3.8 made PyRun_String behave similarly. Let's also do that for
+    // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
+    if (!global.contains("__builtins__"))
+        global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
+#else
+    (void) global;
+#endif
 }
 
 PYBIND11_NAMESPACE_END(detail)
@@ -58,10 +58,17 @@ object eval(const str &expr, object global = globals(), object local = object())
 
     int start = 0;
     switch (mode) {
-        case eval_expr:             start = Py_eval_input;   break;
-        case eval_single_statement: start = Py_single_input; break;
-        case eval_statements:       start = Py_file_input;   break;
-        default: pybind11_fail("invalid evaluation mode");
+        case eval_expr:
+            start = Py_eval_input;
+            break;
+        case eval_single_statement:
+            start = Py_single_input;
+            break;
+        case eval_statements:
+            start = Py_file_input;
+            break;
+        default:
+            pybind11_fail("invalid evaluation mode");
     }
 
     PyObject *result = PyRun_String(buffer.c_str(), start, global.ptr(), local.ptr());
@@ -74,8 +81,7 @@ object eval(const str &expr, object global = globals(), object local = object())
 template <eval_mode mode = eval_expr, size_t N>
 object eval(const char (&s)[N], object global = globals(), object local = object()) {
     /* Support raw string literals by removing common leading whitespace */
-    auto expr = (s[0] == '\n') ? str(module_::import("textwrap").attr("dedent")(s))
-                               : str(s);
+    auto expr = (s[0] == '\n') ? str(module_::import("textwrap").attr("dedent")(s)) : str(s);
     return eval<mode>(expr, global, local);
 }
 
@@ -112,28 +118,34 @@ object eval_file(str fname, object global = globals(), object local = object())
 
     int start = 0;
     switch (mode) {
-        case eval_expr:             start = Py_eval_input;   break;
-        case eval_single_statement: start = Py_single_input; break;
-        case eval_statements:       start = Py_file_input;   break;
-        default: pybind11_fail("invalid evaluation mode");
+        case eval_expr:
+            start = Py_eval_input;
+            break;
+        case eval_single_statement:
+            start = Py_single_input;
+            break;
+        case eval_statements:
+            start = Py_file_input;
+            break;
+        default:
+            pybind11_fail("invalid evaluation mode");
     }
 
     int closeFile = 1;
     std::string fname_str = (std::string) fname;
-#if PY_VERSION_HEX >= 0x03040000
+#    if PY_VERSION_HEX >= 0x03040000
     FILE *f = _Py_fopen_obj(fname.ptr(), "r");
-#elif PY_VERSION_HEX >= 0x03000000
+#    elif PY_VERSION_HEX >= 0x03000000
     FILE *f = _Py_fopen(fname.ptr(), "r");
-#else
+#    else
     /* No unicode support in open() :( */
-    auto fobj = reinterpret_steal<object>(PyFile_FromString(
-        const_cast<char *>(fname_str.c_str()),
-        const_cast<char*>("r")));
+    auto fobj = reinterpret_steal<object>(
+        PyFile_FromString(const_cast<char *>(fname_str.c_str()), const_cast<char *>("r")));
     FILE *f = nullptr;
     if (fobj)
         f = PyFile_AsFile(fobj.ptr());
     closeFile = 0;
-#endif
+#    endif
     if (!f) {
         PyErr_Clear();
         pybind11_fail("File \"" + fname_str + "\" could not be opened!");
@@ -142,20 +154,19 @@ object eval_file(str fname, object global = globals(), object local = object())
     // In Python2, this should be encoded by getfilesystemencoding.
     // We don't boher setting it since Python2 is past EOL anyway.
     // See PR#3233
-#if PY_VERSION_HEX >= 0x03000000
+#    if PY_VERSION_HEX >= 0x03000000
     if (!global.contains("__file__")) {
         global["__file__"] = std::move(fname);
     }
-#endif
+#    endif
 
-#if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
-    PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(),
-                                  local.ptr());
+#    if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
+    PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(), local.ptr());
     (void) closeFile;
-#else
-    PyObject *result = PyRun_FileEx(f, fname_str.c_str(), start, global.ptr(),
-                                    local.ptr(), closeFile);
-#endif
+#    else
+    PyObject *result
+        = PyRun_FileEx(f, fname_str.c_str(), start, global.ptr(), local.ptr(), closeFile);
+#    endif
 
     if (!result) {
         throw error_already_set();
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 95a1a02af7..69cfed5476 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "pybind11.h"
+
 #include <functional>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -19,7 +20,7 @@ template <typename Return, typename... Args>
 struct type_caster<std::function<Return(Args...)>> {
     using type = std::function<Return(Args...)>;
     using retval_type = conditional_t<std::is_same<Return, void>::value, void_type, Return>;
-    using function_type = Return (*) (Args...);
+    using function_type = Return (*)(Args...);
 
 public:
     bool load(handle src, bool convert) {
@@ -76,7 +77,9 @@ struct type_caster<std::function<Return(Args...)>> {
             // This triggers a syntax error under very special conditions (very weird indeed).
             explicit
 #endif
-            func_handle(function &&f_) noexcept : f(std::move(f_)) {}
+                func_handle(function &&f_) noexcept
+                : f(std::move(f_)) {
+            }
             func_handle(const func_handle &f_) { operator=(f_); }
             func_handle &operator=(const func_handle &f_) {
                 gil_scoped_acquire acq;
@@ -118,8 +121,10 @@ struct type_caster<std::function<Return(Args...)>> {
         return cpp_function(std::forward<Func>(f_), policy).release();
     }
 
-    PYBIND11_TYPE_CASTER(type, const_name("Callable[[") + concat(make_caster<Args>::name...) + const_name("], ")
-                               + make_caster<retval_type>::name + const_name("]"));
+    PYBIND11_TYPE_CASTER(type,
+                         const_name("Callable[[") + concat(make_caster<Args>::name...)
+                             + const_name("], ") + make_caster<retval_type>::name
+                             + const_name("]"));
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 345177f84f..446f4620b2 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -14,7 +14,6 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
-
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 // forward declarations
@@ -22,7 +21,6 @@ PyThreadState *get_thread_state_unchecked();
 
 PYBIND11_NAMESPACE_END(detail)
 
-
 #if defined(WITH_THREAD) && !defined(PYPY_VERSION)
 
 /* The functions below essentially reproduce the PyGILState_* API using a RAII
@@ -64,11 +62,11 @@ class gil_scoped_acquire {
 
         if (!tstate) {
             tstate = PyThreadState_New(internals.istate);
-            #if !defined(NDEBUG)
+#    if !defined(NDEBUG)
             if (!tstate) {
                 pybind11_fail("scoped_acquire: could not create thread state!");
             }
-#endif
+#    endif
             tstate->gilstate_counter = 0;
             PYBIND11_TLS_REPLACE_VALUE(internals.tstate, tstate);
         } else {
@@ -82,26 +80,24 @@ class gil_scoped_acquire {
         inc_ref();
     }
 
-    void inc_ref() {
-        ++tstate->gilstate_counter;
-    }
+    void inc_ref() { ++tstate->gilstate_counter; }
 
     PYBIND11_NOINLINE void dec_ref() {
         --tstate->gilstate_counter;
-        #if !defined(NDEBUG)
+#    if !defined(NDEBUG)
         if (detail::get_thread_state_unchecked() != tstate) {
             pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
         }
         if (tstate->gilstate_counter < 0) {
             pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
         }
-#endif
+#    endif
         if (tstate->gilstate_counter == 0) {
-            #if !defined(NDEBUG)
+#    if !defined(NDEBUG)
             if (!release) {
                 pybind11_fail("scoped_acquire::dec_ref(): internal error!");
             }
-#endif
+#    endif
             PyThreadState_Clear(tstate);
             if (active) {
                 PyThreadState_DeleteCurrent();
@@ -116,9 +112,7 @@ class gil_scoped_acquire {
     /// could be shutting down when this is called, as thread deletion is not
     /// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
     /// protect subsequent code.
-    PYBIND11_NOINLINE void disarm() {
-        active = false;
-    }
+    PYBIND11_NOINLINE void disarm() { active = false; }
 
     PYBIND11_NOINLINE ~gil_scoped_acquire() {
         dec_ref();
@@ -126,6 +120,7 @@ class gil_scoped_acquire {
             PyEval_SaveThread();
         }
     }
+
 private:
     PyThreadState *tstate = nullptr;
     bool release = true;
@@ -154,9 +149,7 @@ class gil_scoped_release {
     /// could be shutting down when this is called, as thread deletion is not
     /// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
     /// protect subsequent code.
-    PYBIND11_NOINLINE void disarm() {
-        active = false;
-    }
+    PYBIND11_NOINLINE void disarm() { active = false; }
 
     ~gil_scoped_release() {
         if (!tstate) {
@@ -173,6 +166,7 @@ class gil_scoped_release {
             PYBIND11_TLS_REPLACE_VALUE(key, tstate);
         }
     }
+
 private:
     PyThreadState *tstate;
     bool disassoc;
@@ -181,6 +175,7 @@ class gil_scoped_release {
 #elif defined(PYPY_VERSION)
 class gil_scoped_acquire {
     PyGILState_STATE state;
+
 public:
     gil_scoped_acquire() { state = PyGILState_Ensure(); }
     ~gil_scoped_acquire() { PyGILState_Release(state); }
@@ -189,6 +184,7 @@ class gil_scoped_acquire {
 
 class gil_scoped_release {
     PyThreadState *state;
+
 public:
     gil_scoped_release() { state = PyEval_SaveThread(); }
     ~gil_scoped_release() { PyEval_RestoreThread(state); }
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index d6cf223726..12e1f19f0c 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -58,31 +58,23 @@ class pythonbuf : public std::streambuf {
     size_t utf8_remainder() const {
         const auto rbase = std::reverse_iterator<char *>(pbase());
         const auto rpptr = std::reverse_iterator<char *>(pptr());
-        auto is_ascii = [](char c) {
-            return (static_cast<unsigned char>(c) & 0x80) == 0x00;
-        };
-        auto is_leading = [](char c) {
-            return (static_cast<unsigned char>(c) & 0xC0) == 0xC0;
-        };
-        auto is_leading_2b = [](char c) {
-            return static_cast<unsigned char>(c) <= 0xDF;
-        };
-        auto is_leading_3b = [](char c) {
-            return static_cast<unsigned char>(c) <= 0xEF;
-        };
+        auto is_ascii = [](char c) { return (static_cast<unsigned char>(c) & 0x80) == 0x00; };
+        auto is_leading = [](char c) { return (static_cast<unsigned char>(c) & 0xC0) == 0xC0; };
+        auto is_leading_2b = [](char c) { return static_cast<unsigned char>(c) <= 0xDF; };
+        auto is_leading_3b = [](char c) { return static_cast<unsigned char>(c) <= 0xEF; };
         // If the last character is ASCII, there are no incomplete code points
         if (is_ascii(*rpptr)) {
             return 0;
         }
         // Otherwise, work back from the end of the buffer and find the first
         // UTF-8 leading byte
-        const auto rpend   = rbase - rpptr >= 3 ? rpptr + 3 : rbase;
+        const auto rpend = rbase - rpptr >= 3 ? rpptr + 3 : rbase;
         const auto leading = std::find_if(rpptr, rpend, is_leading);
         if (leading == rbase) {
             return 0;
         }
-        const auto dist    = static_cast<size_t>(leading - rpptr);
-        size_t remainder   = 0;
+        const auto dist = static_cast<size_t>(leading - rpptr);
+        size_t remainder = 0;
 
         if (dist == 0) {
             remainder = 1; // 1-byte code point is impossible
@@ -103,7 +95,7 @@ class pythonbuf : public std::streambuf {
         if (pbase() != pptr()) { // If buffer is not empty
             gil_scoped_acquire tmp;
             // This subtraction cannot be negative, so dropping the sign.
-            auto size        = static_cast<size_t>(pptr() - pbase());
+            auto size = static_cast<size_t>(pptr() - pbase());
             size_t remainder = utf8_remainder();
 
             if (size > remainder) {
@@ -122,9 +114,7 @@ class pythonbuf : public std::streambuf {
         return 0;
     }
 
-    int sync() override {
-        return _sync();
-    }
+    int sync() override { return _sync(); }
 
 public:
     explicit pythonbuf(const object &pyostream, size_t buffer_size = 1024)
@@ -133,17 +123,14 @@ class pythonbuf : public std::streambuf {
         setp(d_buffer.get(), d_buffer.get() + buf_size - 1);
     }
 
-    pythonbuf(pythonbuf&&) = default;
+    pythonbuf(pythonbuf &&) = default;
 
     /// Sync before destroy
-    ~pythonbuf() override {
-        _sync();
-    }
+    ~pythonbuf() override { _sync(); }
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
-
 /** \rst
     This a move-only guard that redirects output.
 
@@ -183,9 +170,7 @@ class scoped_ostream_redirect {
         old = costream.rdbuf(&buffer);
     }
 
-    ~scoped_ostream_redirect() {
-        costream.rdbuf(old);
-    }
+    ~scoped_ostream_redirect() { costream.rdbuf(old); }
 
     scoped_ostream_redirect(const scoped_ostream_redirect &) = delete;
     scoped_ostream_redirect(scoped_ostream_redirect &&other) = default;
@@ -193,7 +178,6 @@ class scoped_ostream_redirect {
     scoped_ostream_redirect &operator=(scoped_ostream_redirect &&) = delete;
 };
 
-
 /** \rst
     Like `scoped_ostream_redirect`, but redirects cerr by default. This class
     is provided primary to make ``py::call_guard`` easier to make.
@@ -213,7 +197,6 @@ class scoped_estream_redirect : public scoped_ostream_redirect {
         : scoped_ostream_redirect(costream, pyostream) {}
 };
 
-
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Class to redirect output as a context manager. C++ backend.
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 489587835d..9f4d516f5f 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -11,19 +11,20 @@
 
 #include "pybind11.h"
 #include "complex.h"
-#include <numeric>
+
 #include <algorithm>
 #include <array>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
+#include <functional>
+#include <numeric>
 #include <sstream>
 #include <string>
-#include <functional>
 #include <type_traits>
+#include <typeindex>
 #include <utility>
 #include <vector>
-#include <typeindex>
 
 /* This will be true on all flat address space platforms and allows us to reduce the
    whole npy_intp / ssize_t / Py_intptr_t business down to just ssize_t for all size
@@ -39,9 +40,13 @@ class array; // Forward declaration
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <> struct handle_type_name<array> { static constexpr auto name = const_name("numpy.ndarray"); };
+template <>
+struct handle_type_name<array> {
+    static constexpr auto name = const_name("numpy.ndarray");
+};
 
-template <typename type, typename SFINAE = void> struct npy_format_descriptor;
+template <typename type, typename SFINAE = void>
+struct npy_format_descriptor;
 
 struct PyArrayDescr_Proxy {
     PyObject_HEAD
@@ -70,22 +75,21 @@ struct PyArray_Proxy {
 };
 
 struct PyVoidScalarObject_Proxy {
-    PyObject_VAR_HEAD
-    char *obval;
+    PyObject_VAR_HEAD char *obval;
     PyArrayDescr_Proxy *descr;
     int flags;
     PyObject *base;
 };
 
 struct numpy_type_info {
-    PyObject* dtype_ptr;
+    PyObject *dtype_ptr;
     std::string format_str;
 };
 
 struct numpy_internals {
     std::unordered_map<std::type_index, numpy_type_info> registered_dtypes;
 
-    numpy_type_info *get_type_info(const std::type_info& tinfo, bool throw_if_missing = true) {
+    numpy_type_info *get_type_info(const std::type_info &tinfo, bool throw_if_missing = true) {
         auto it = registered_dtypes.find(std::type_index(tinfo));
         if (it != registered_dtypes.end()) {
             return &(it->second);
@@ -96,28 +100,34 @@ struct numpy_internals {
         return nullptr;
     }
 
-    template<typename T> numpy_type_info *get_type_info(bool throw_if_missing = true) {
+    template <typename T>
+    numpy_type_info *get_type_info(bool throw_if_missing = true) {
         return get_type_info(typeid(typename std::remove_cv<T>::type), throw_if_missing);
     }
 };
 
-PYBIND11_NOINLINE void load_numpy_internals(numpy_internals* &ptr) {
+PYBIND11_NOINLINE void load_numpy_internals(numpy_internals *&ptr) {
     ptr = &get_or_create_shared_data<numpy_internals>("_numpy_internals");
 }
 
-inline numpy_internals& get_numpy_internals() {
-    static numpy_internals* ptr = nullptr;
+inline numpy_internals &get_numpy_internals() {
+    static numpy_internals *ptr = nullptr;
     if (!ptr) {
         load_numpy_internals(ptr);
     }
     return *ptr;
 }
 
-template <typename T> struct same_size {
-    template <typename U> using as = bool_constant<sizeof(T) == sizeof(U)>;
+template <typename T>
+struct same_size {
+    template <typename U>
+    using as = bool_constant<sizeof(T) == sizeof(U)>;
 };
 
-template <typename Concrete> constexpr int platform_lookup() { return -1; }
+template <typename Concrete>
+constexpr int platform_lookup() {
+    return -1;
+}
 
 // Lookup a type according to its size, and return a value corresponding to the NumPy typenum.
 template <typename Concrete, typename T, typename... Ts, typename... Ints>
@@ -135,15 +145,26 @@ struct npy_api {
         NPY_ARRAY_ALIGNED_ = 0x0100,
         NPY_ARRAY_WRITEABLE_ = 0x0400,
         NPY_BOOL_ = 0,
-        NPY_BYTE_, NPY_UBYTE_,
-        NPY_SHORT_, NPY_USHORT_,
-        NPY_INT_, NPY_UINT_,
-        NPY_LONG_, NPY_ULONG_,
-        NPY_LONGLONG_, NPY_ULONGLONG_,
-        NPY_FLOAT_, NPY_DOUBLE_, NPY_LONGDOUBLE_,
-        NPY_CFLOAT_, NPY_CDOUBLE_, NPY_CLONGDOUBLE_,
+        NPY_BYTE_,
+        NPY_UBYTE_,
+        NPY_SHORT_,
+        NPY_USHORT_,
+        NPY_INT_,
+        NPY_UINT_,
+        NPY_LONG_,
+        NPY_ULONG_,
+        NPY_LONGLONG_,
+        NPY_ULONGLONG_,
+        NPY_FLOAT_,
+        NPY_DOUBLE_,
+        NPY_LONGDOUBLE_,
+        NPY_CFLOAT_,
+        NPY_CDOUBLE_,
+        NPY_CLONGDOUBLE_,
         NPY_OBJECT_ = 17,
-        NPY_STRING_, NPY_UNICODE_, NPY_VOID_,
+        NPY_STRING_,
+        NPY_UNICODE_,
+        NPY_VOID_,
         // Platform-dependent normalization
         NPY_INT8_ = NPY_BYTE_,
         NPY_UINT8_ = NPY_UBYTE_,
@@ -152,13 +173,14 @@ struct npy_api {
         // `npy_common.h` defines the integer aliases. In order, it checks:
         // NPY_BITSOF_LONG, NPY_BITSOF_LONGLONG, NPY_BITSOF_INT, NPY_BITSOF_SHORT, NPY_BITSOF_CHAR
         // and assigns the alias to the first matching size, so we should check in this order.
-        NPY_INT32_ = platform_lookup<std::int32_t, long, int, short>(
-            NPY_LONG_, NPY_INT_, NPY_SHORT_),
+        NPY_INT32_
+        = platform_lookup<std::int32_t, long, int, short>(NPY_LONG_, NPY_INT_, NPY_SHORT_),
         NPY_UINT32_ = platform_lookup<std::uint32_t, unsigned long, unsigned int, unsigned short>(
             NPY_ULONG_, NPY_UINT_, NPY_USHORT_),
-        NPY_INT64_ = platform_lookup<std::int64_t, long, long long, int>(
-            NPY_LONG_, NPY_LONGLONG_, NPY_INT_),
-        NPY_UINT64_ = platform_lookup<std::uint64_t, unsigned long, unsigned long long, unsigned int>(
+        NPY_INT64_
+        = platform_lookup<std::int64_t, long, long long, int>(NPY_LONG_, NPY_LONGLONG_, NPY_INT_),
+        NPY_UINT64_
+        = platform_lookup<std::uint64_t, unsigned long, unsigned long long, unsigned int>(
             NPY_ULONG_, NPY_ULONGLONG_, NPY_UINT_),
     };
 
@@ -167,7 +189,7 @@ struct npy_api {
         int len;
     };
 
-    static npy_api& get() {
+    static npy_api &get() {
         static npy_api api = lookup();
         return api;
     }
@@ -181,9 +203,14 @@ struct npy_api {
 
     unsigned int (*PyArray_GetNDArrayCFeatureVersion_)();
     PyObject *(*PyArray_DescrFromType_)(int);
-    PyObject *(*PyArray_NewFromDescr_)
-        (PyTypeObject *, PyObject *, int, Py_intptr_t const *,
-         Py_intptr_t const *, void *, int, PyObject *);
+    PyObject *(*PyArray_NewFromDescr_)(PyTypeObject *,
+                                       PyObject *,
+                                       int,
+                                       Py_intptr_t const *,
+                                       Py_intptr_t const *,
+                                       void *,
+                                       int,
+                                       PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     PyObject *(*PyArray_DescrNewFromType_)(int);
     int (*PyArray_CopyInto_)(PyObject *, PyObject *);
@@ -192,17 +219,23 @@ struct npy_api {
     PyTypeObject *PyVoidArrType_Type_;
     PyTypeObject *PyArrayDescr_Type_;
     PyObject *(*PyArray_DescrFromScalar_)(PyObject *);
-    PyObject *(*PyArray_FromAny_) (PyObject *, PyObject *, int, int, int, PyObject *);
-    int (*PyArray_DescrConverter_) (PyObject *, PyObject **);
-    bool (*PyArray_EquivTypes_) (PyObject *, PyObject *);
-    int (*PyArray_GetArrayParamsFromObject_)(PyObject *, PyObject *, unsigned char, PyObject **, int *,
-                                             Py_intptr_t *, PyObject **, PyObject *);
+    PyObject *(*PyArray_FromAny_)(PyObject *, PyObject *, int, int, int, PyObject *);
+    int (*PyArray_DescrConverter_)(PyObject *, PyObject **);
+    bool (*PyArray_EquivTypes_)(PyObject *, PyObject *);
+    int (*PyArray_GetArrayParamsFromObject_)(PyObject *,
+                                             PyObject *,
+                                             unsigned char,
+                                             PyObject **,
+                                             int *,
+                                             Py_intptr_t *,
+                                             PyObject **,
+                                             PyObject *);
     PyObject *(*PyArray_Squeeze_)(PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
-    PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
-    PyObject* (*PyArray_Newshape_)(PyObject*, PyArray_Dims*, int);
-    PyObject* (*PyArray_View_)(PyObject*, PyObject*, PyObject*);
+    PyObject *(*PyArray_Resize_)(PyObject *, PyArray_Dims *, int, int);
+    PyObject *(*PyArray_Newshape_)(PyObject *, PyArray_Dims *, int);
+    PyObject *(*PyArray_View_)(PyObject *, PyObject *, PyObject *);
 
 private:
     enum functions {
@@ -265,86 +298,103 @@ struct npy_api {
     }
 };
 
-inline PyArray_Proxy* array_proxy(void* ptr) {
-    return reinterpret_cast<PyArray_Proxy*>(ptr);
-}
+inline PyArray_Proxy *array_proxy(void *ptr) { return reinterpret_cast<PyArray_Proxy *>(ptr); }
 
-inline const PyArray_Proxy* array_proxy(const void* ptr) {
-    return reinterpret_cast<const PyArray_Proxy*>(ptr);
+inline const PyArray_Proxy *array_proxy(const void *ptr) {
+    return reinterpret_cast<const PyArray_Proxy *>(ptr);
 }
 
-inline PyArrayDescr_Proxy* array_descriptor_proxy(PyObject* ptr) {
-   return reinterpret_cast<PyArrayDescr_Proxy*>(ptr);
+inline PyArrayDescr_Proxy *array_descriptor_proxy(PyObject *ptr) {
+    return reinterpret_cast<PyArrayDescr_Proxy *>(ptr);
 }
 
-inline const PyArrayDescr_Proxy* array_descriptor_proxy(const PyObject* ptr) {
-   return reinterpret_cast<const PyArrayDescr_Proxy*>(ptr);
+inline const PyArrayDescr_Proxy *array_descriptor_proxy(const PyObject *ptr) {
+    return reinterpret_cast<const PyArrayDescr_Proxy *>(ptr);
 }
 
-inline bool check_flags(const void* ptr, int flag) {
+inline bool check_flags(const void *ptr, int flag) {
     return (flag == (array_proxy(ptr)->flags & flag));
 }
 
-template <typename T> struct is_std_array : std::false_type { };
-template <typename T, size_t N> struct is_std_array<std::array<T, N>> : std::true_type { };
-template <typename T> struct is_complex : std::false_type { };
-template <typename T> struct is_complex<std::complex<T>> : std::true_type { };
+template <typename T>
+struct is_std_array : std::false_type {};
+template <typename T, size_t N>
+struct is_std_array<std::array<T, N>> : std::true_type {};
+template <typename T>
+struct is_complex : std::false_type {};
+template <typename T>
+struct is_complex<std::complex<T>> : std::true_type {};
 
-template <typename T> struct array_info_scalar {
+template <typename T>
+struct array_info_scalar {
     using type = T;
     static constexpr bool is_array = false;
     static constexpr bool is_empty = false;
     static constexpr auto extents = const_name("");
-    static void append_extents(list& /* shape */) { }
+    static void append_extents(list & /* shape */) {}
 };
 // Computes underlying type and a comma-separated list of extents for array
 // types (any mix of std::array and built-in arrays). An array of char is
 // treated as scalar because it gets special handling.
-template <typename T> struct array_info : array_info_scalar<T> { };
-template <typename T, size_t N> struct array_info<std::array<T, N>> {
+template <typename T>
+struct array_info : array_info_scalar<T> {};
+template <typename T, size_t N>
+struct array_info<std::array<T, N>> {
     using type = typename array_info<T>::type;
     static constexpr bool is_array = true;
     static constexpr bool is_empty = (N == 0) || array_info<T>::is_empty;
     static constexpr size_t extent = N;
 
     // appends the extents to shape
-    static void append_extents(list& shape) {
+    static void append_extents(list &shape) {
         shape.append(N);
         array_info<T>::append_extents(shape);
     }
 
     static constexpr auto extents = const_name<array_info<T>::is_array>(
-        concat(const_name<N>(), array_info<T>::extents), const_name<N>()
-    );
+        concat(const_name<N>(), array_info<T>::extents), const_name<N>());
 };
 // For numpy we have special handling for arrays of characters, so we don't include
 // the size in the array extents.
-template <size_t N> struct array_info<char[N]> : array_info_scalar<char[N]> { };
-template <size_t N> struct array_info<std::array<char, N>> : array_info_scalar<std::array<char, N>> { };
-template <typename T, size_t N> struct array_info<T[N]> : array_info<std::array<T, N>> { };
-template <typename T> using remove_all_extents_t = typename array_info<T>::type;
-
-template <typename T> using is_pod_struct = all_of<
-    std::is_standard_layout<T>,     // since we're accessing directly in memory
-                                    // we need a standard layout type
-#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623 || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
-    // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after 5)
-    // don't implement is_trivially_copyable, so approximate it
-    std::is_trivially_destructible<T>,
-    satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
+template <size_t N>
+struct array_info<char[N]> : array_info_scalar<char[N]> {};
+template <size_t N>
+struct array_info<std::array<char, N>> : array_info_scalar<std::array<char, N>> {};
+template <typename T, size_t N>
+struct array_info<T[N]> : array_info<std::array<T, N>> {};
+template <typename T>
+using remove_all_extents_t = typename array_info<T>::type;
+
+template <typename T>
+using is_pod_struct
+    = all_of<std::is_standard_layout<T>, // since we're accessing directly in memory
+                                         // we need a standard layout type
+#if defined(__GLIBCXX__)                                                                          \
+    && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623              \
+        || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
+             // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after
+             // 5) don't implement is_trivially_copyable, so approximate it
+             std::is_trivially_destructible<T>,
+             satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
 #else
-    std::is_trivially_copyable<T>,
+             std::is_trivially_copyable<T>,
 #endif
-    satisfies_none_of<T, std::is_reference, std::is_array, is_std_array, std::is_arithmetic, is_complex, std::is_enum>
->;
+             satisfies_none_of<T,
+                               std::is_reference,
+                               std::is_array,
+                               is_std_array,
+                               std::is_arithmetic,
+                               is_complex,
+                               std::is_enum>>;
 
 // Replacement for std::is_pod (deprecated in C++20)
-template <typename T> using is_pod = all_of<
-    std::is_standard_layout<T>,
-    std::is_trivial<T>
->;
+template <typename T>
+using is_pod = all_of<std::is_standard_layout<T>, std::is_trivial<T>>;
 
-template <ssize_t Dim = 0, typename Strides> ssize_t byte_offset_unsafe(const Strides &) { return 0; }
+template <ssize_t Dim = 0, typename Strides>
+ssize_t byte_offset_unsafe(const Strides &) {
+    return 0;
+}
 template <ssize_t Dim = 0, typename Strides, typename... Ix>
 ssize_t byte_offset_unsafe(const Strides &strides, ssize_t i, Ix... index) {
     return i * strides[Dim] + byte_offset_unsafe<Dim + 1>(strides, index...);
@@ -352,7 +402,7 @@ ssize_t byte_offset_unsafe(const Strides &strides, ssize_t i, Ix... index) {
 
 /**
  * Proxy class providing unsafe, unchecked const access to array data.  This is constructed through
- * the `unchecked<T, N>()` method of `array` or the `unchecked<N>()` method of `array_t<T>`.  `Dims`
+ * the `unchecked<T, N>()` method of `array` or the `unchecked<N>()` method of `array_t<T>`. `Dims`
  * will be -1 for dimensions determined at runtime.
  */
 template <typename T, ssize_t Dims>
@@ -362,15 +412,17 @@ class unchecked_reference {
     const unsigned char *data_;
     // Storing the shape & strides in local variables (i.e. these arrays) allows the compiler to
     // make large performance gains on big, nested loops, but requires compile-time dimensions
-    conditional_t<Dynamic, const ssize_t *, std::array<ssize_t, (size_t) Dims>>
-            shape_, strides_;
+    conditional_t<Dynamic, const ssize_t *, std::array<ssize_t, (size_t) Dims>> shape_, strides_;
     const ssize_t dims_;
 
     friend class pybind11::array;
     // Constructor for compile-time dimensions:
     template <bool Dyn = Dynamic>
-    unchecked_reference(const void *data, const ssize_t *shape, const ssize_t *strides, enable_if_t<!Dyn, ssize_t>)
-    : data_{reinterpret_cast<const unsigned char *>(data)}, dims_{Dims} {
+    unchecked_reference(const void *data,
+                        const ssize_t *shape,
+                        const ssize_t *strides,
+                        enable_if_t<!Dyn, ssize_t>)
+        : data_{reinterpret_cast<const unsigned char *>(data)}, dims_{Dims} {
         for (size_t i = 0; i < (size_t) dims_; i++) {
             shape_[i] = shape[i];
             strides_[i] = strides[i];
@@ -378,8 +430,12 @@ class unchecked_reference {
     }
     // Constructor for runtime dimensions:
     template <bool Dyn = Dynamic>
-    unchecked_reference(const void *data, const ssize_t *shape, const ssize_t *strides, enable_if_t<Dyn, ssize_t> dims)
-    : data_{reinterpret_cast<const unsigned char *>(data)}, shape_{shape}, strides_{strides}, dims_{dims} {}
+    unchecked_reference(const void *data,
+                        const ssize_t *shape,
+                        const ssize_t *strides,
+                        enable_if_t<Dyn, ssize_t> dims)
+        : data_{reinterpret_cast<const unsigned char *>(data)}, shape_{shape}, strides_{strides},
+          dims_{dims} {}
 
 public:
     /**
@@ -387,20 +443,27 @@ class unchecked_reference {
      * number of dimensions, this requires the correct number of arguments; for run-time
      * dimensionality, this is not checked (and so is up to the caller to use safely).
      */
-    template <typename... Ix> const T &operator()(Ix... index) const {
+    template <typename... Ix>
+    const T &operator()(Ix... index) const {
         static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
-                "Invalid number of indices for unchecked array reference");
-        return *reinterpret_cast<const T *>(data_ + byte_offset_unsafe(strides_, ssize_t(index)...));
+                      "Invalid number of indices for unchecked array reference");
+        return *reinterpret_cast<const T *>(data_
+                                            + byte_offset_unsafe(strides_, ssize_t(index)...));
     }
     /**
      * Unchecked const reference access to data; this operator only participates if the reference
      * is to a 1-dimensional array.  When present, this is exactly equivalent to `obj(index)`.
      */
     template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
-    const T &operator[](ssize_t index) const { return operator()(index); }
+    const T &operator[](ssize_t index) const {
+        return operator()(index);
+    }
 
     /// Pointer access to the data at the given indices.
-    template <typename... Ix> const T *data(Ix... ix) const { return &operator()(ssize_t(ix)...); }
+    template <typename... Ix>
+    const T *data(Ix... ix) const {
+        return &operator()(ssize_t(ix)...);
+    }
 
     /// Returns the item size, i.e. sizeof(T)
     constexpr static ssize_t itemsize() { return sizeof(T); }
@@ -411,21 +474,22 @@ class unchecked_reference {
     /// Returns the number of dimensions of the array
     ssize_t ndim() const { return dims_; }
 
-    /// Returns the total number of elements in the referenced array, i.e. the product of the shapes
+    /// Returns the total number of elements in the referenced array, i.e. the product of the
+    /// shapes
     template <bool Dyn = Dynamic>
     enable_if_t<!Dyn, ssize_t> size() const {
-        return std::accumulate(shape_.begin(), shape_.end(), (ssize_t) 1, std::multiplies<ssize_t>());
+        return std::accumulate(
+            shape_.begin(), shape_.end(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
     template <bool Dyn = Dynamic>
     enable_if_t<Dyn, ssize_t> size() const {
         return std::accumulate(shape_, shape_ + ndim(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
 
-    /// Returns the total number of bytes used by the referenced data.  Note that the actual span in
-    /// memory may be larger if the referenced array has non-contiguous strides (e.g. for a slice).
-    ssize_t nbytes() const {
-        return size() * itemsize();
-    }
+    /// Returns the total number of bytes used by the referenced data.  Note that the actual span
+    /// in memory may be larger if the referenced array has non-contiguous strides (e.g. for a
+    /// slice).
+    ssize_t nbytes() const { return size() * itemsize(); }
 };
 
 template <typename T, ssize_t Dims>
@@ -434,15 +498,17 @@ class unchecked_mutable_reference : public unchecked_reference<T, Dims> {
     using ConstBase = unchecked_reference<T, Dims>;
     using ConstBase::ConstBase;
     using ConstBase::Dynamic;
+
 public:
     // Bring in const-qualified versions from base class
     using ConstBase::operator();
     using ConstBase::operator[];
 
     /// Mutable, unchecked access to data at the given indices.
-    template <typename... Ix> T& operator()(Ix... index) {
+    template <typename... Ix>
+    T &operator()(Ix... index) {
         static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
-                "Invalid number of indices for unchecked array reference");
+                      "Invalid number of indices for unchecked array reference");
         return const_cast<T &>(ConstBase::operator()(index...));
     }
     /**
@@ -451,18 +517,25 @@ class unchecked_mutable_reference : public unchecked_reference<T, Dims> {
      * exactly equivalent to `obj(index)`.
      */
     template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
-    T &operator[](ssize_t index) { return operator()(index); }
+    T &operator[](ssize_t index) {
+        return operator()(index);
+    }
 
     /// Mutable pointer access to the data at the given indices.
-    template <typename... Ix> T *mutable_data(Ix... ix) { return &operator()(ssize_t(ix)...); }
+    template <typename... Ix>
+    T *mutable_data(Ix... ix) {
+        return &operator()(ssize_t(ix)...);
+    }
 };
 
 template <typename T, ssize_t Dim>
 struct type_caster<unchecked_reference<T, Dim>> {
-    static_assert(Dim == 0 && Dim > 0 /* always fail */, "unchecked array proxy object is not castable");
+    static_assert(Dim == 0 && Dim > 0 /* always fail */,
+                  "unchecked array proxy object is not castable");
 };
 template <typename T, ssize_t Dim>
-struct type_caster<unchecked_mutable_reference<T, Dim>> : type_caster<unchecked_reference<T, Dim>> {};
+struct type_caster<unchecked_mutable_reference<T, Dim>>
+    : type_caster<unchecked_reference<T, Dim>> {};
 
 PYBIND11_NAMESPACE_END(detail)
 
@@ -503,25 +576,20 @@ class dtype : public object {
     }
 
     /// Return dtype associated with a C++ type.
-    template <typename T> static dtype of() {
+    template <typename T>
+    static dtype of() {
         return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::dtype();
     }
 
     /// Size of the data type in bytes.
-    ssize_t itemsize() const {
-        return detail::array_descriptor_proxy(m_ptr)->elsize;
-    }
+    ssize_t itemsize() const { return detail::array_descriptor_proxy(m_ptr)->elsize; }
 
     /// Returns true for structured data types.
-    bool has_fields() const {
-        return detail::array_descriptor_proxy(m_ptr)->names != nullptr;
-    }
+    bool has_fields() const { return detail::array_descriptor_proxy(m_ptr)->names != nullptr; }
 
     /// Single-character code for dtype's kind.
     /// For example, floating point types are 'f' and integral types are 'i'.
-    char kind() const {
-        return detail::array_descriptor_proxy(m_ptr)->kind;
-    }
+    char kind() const { return detail::array_descriptor_proxy(m_ptr)->kind; }
 
     /// Single-character for dtype's type.
     /// For example, ``float`` is 'f', ``double`` 'd', ``int`` 'i', and ``long`` 'l'.
@@ -535,7 +603,10 @@ class dtype : public object {
 private:
     static object _dtype_from_pep3118() {
         static PyObject *obj = module_::import("numpy.core._internal")
-            .attr("_dtype_from_pep3118").cast<object>().release().ptr();
+                                   .attr("_dtype_from_pep3118")
+                                   .cast<object>()
+                                   .release()
+                                   .ptr();
         return reinterpret_borrow<object>(obj);
     }
 
@@ -546,7 +617,11 @@ class dtype : public object {
             return *this;
         }
 
-        struct field_descr { PYBIND11_STR_TYPE name; object format; pybind11::int_ offset; };
+        struct field_descr {
+            PYBIND11_STR_TYPE name;
+            object format;
+            pybind11::int_ offset;
+        };
         std::vector<field_descr> field_descriptors;
 
         for (auto field : attr("fields").attr("items")()) {
@@ -557,16 +632,18 @@ class dtype : public object {
             if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
             }
-            field_descriptors.push_back({(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
+            field_descriptors.push_back(
+                {(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
         }
 
-        std::sort(field_descriptors.begin(), field_descriptors.end(),
-                  [](const field_descr& a, const field_descr& b) {
+        std::sort(field_descriptors.begin(),
+                  field_descriptors.end(),
+                  [](const field_descr &a, const field_descr &b) {
                       return a.offset.cast<int>() < b.offset.cast<int>();
                   });
 
         list names, formats, offsets;
-        for (auto& descr : field_descriptors) {
+        for (auto &descr : field_descriptors) {
             names.append(descr.name);
             formats.append(descr.format);
             offsets.append(descr.offset);
@@ -591,8 +668,11 @@ class array : public buffer {
     using StridesContainer = detail::any_container<ssize_t>;
 
     // Constructs an array taking shape/strides from arbitrary container types
-    array(const pybind11::dtype &dt, ShapeContainer shape, StridesContainer strides,
-          const void *ptr = nullptr, handle base = handle()) {
+    array(const pybind11::dtype &dt,
+          ShapeContainer shape,
+          StridesContainer strides,
+          const void *ptr = nullptr,
+          handle base = handle()) {
 
         if (strides->empty()) {
             *strides = detail::c_strides(*shape, dt.itemsize());
@@ -608,7 +688,8 @@ class array : public buffer {
         if (base && ptr) {
             if (isinstance<array>(base)) {
                 /* Copy flags from base (except ownership bit) */
-                flags = reinterpret_borrow<array>(base).flags() & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
+                flags = reinterpret_borrow<array>(base).flags()
+                        & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
             } else {
                 /* Writable by default, easy to downgrade later on if needed */
                 flags = detail::npy_api::NPY_ARRAY_WRITEABLE_;
@@ -617,11 +698,15 @@ class array : public buffer {
 
         auto &api = detail::npy_api::get();
         auto tmp = reinterpret_steal<object>(api.PyArray_NewFromDescr_(
-            api.PyArray_Type_, descr.release().ptr(), (int) ndim,
+            api.PyArray_Type_,
+            descr.release().ptr(),
+            (int) ndim,
             // Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
-            reinterpret_cast<Py_intptr_t*>(shape->data()),
-            reinterpret_cast<Py_intptr_t*>(strides->data()),
-            const_cast<void *>(ptr), flags, nullptr));
+            reinterpret_cast<Py_intptr_t *>(shape->data()),
+            reinterpret_cast<Py_intptr_t *>(strides->data()),
+            const_cast<void *>(ptr),
+            flags,
+            nullptr));
         if (!tmp) {
             throw error_already_set();
         }
@@ -629,32 +714,39 @@ class array : public buffer {
             if (base) {
                 api.PyArray_SetBaseObject_(tmp.ptr(), base.inc_ref().ptr());
             } else {
-                tmp = reinterpret_steal<object>(api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */));
+                tmp = reinterpret_steal<object>(
+                    api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */));
             }
         }
         m_ptr = tmp.release().ptr();
     }
 
-    array(const pybind11::dtype &dt, ShapeContainer shape, const void *ptr = nullptr, handle base = handle())
-        : array(dt, std::move(shape), {}, ptr, base) { }
+    array(const pybind11::dtype &dt,
+          ShapeContainer shape,
+          const void *ptr = nullptr,
+          handle base = handle())
+        : array(dt, std::move(shape), {}, ptr, base) {}
 
-    template <typename T, typename = detail::enable_if_t<std::is_integral<T>::value && !std::is_same<bool, T>::value>>
+    template <typename T,
+              typename
+              = detail::enable_if_t<std::is_integral<T>::value && !std::is_same<bool, T>::value>>
     array(const pybind11::dtype &dt, T count, const void *ptr = nullptr, handle base = handle())
-        : array(dt, {{count}}, ptr, base) { }
+        : array(dt, {{count}}, ptr, base) {}
 
     template <typename T>
     array(ShapeContainer shape, StridesContainer strides, const T *ptr, handle base = handle())
-        : array(pybind11::dtype::of<T>(), std::move(shape), std::move(strides), ptr, base) { }
+        : array(pybind11::dtype::of<T>(), std::move(shape), std::move(strides), ptr, base) {}
 
     template <typename T>
     array(ShapeContainer shape, const T *ptr, handle base = handle())
-        : array(std::move(shape), {}, ptr, base) { }
+        : array(std::move(shape), {}, ptr, base) {}
 
     template <typename T>
-    explicit array(ssize_t count, const T *ptr, handle base = handle()) : array({count}, {}, ptr, base) { }
+    explicit array(ssize_t count, const T *ptr, handle base = handle())
+        : array({count}, {}, ptr, base) {}
 
     explicit array(const buffer_info &info, handle base = handle())
-    : array(pybind11::dtype(info), info.shape, info.strides, info.ptr, base) { }
+        : array(pybind11::dtype(info), info.shape, info.strides, info.ptr, base) {}
 
     /// Array descriptor (dtype)
     pybind11::dtype dtype() const {
@@ -672,24 +764,16 @@ class array : public buffer {
     }
 
     /// Total number of bytes
-    ssize_t nbytes() const {
-        return size() * itemsize();
-    }
+    ssize_t nbytes() const { return size() * itemsize(); }
 
     /// Number of dimensions
-    ssize_t ndim() const {
-        return detail::array_proxy(m_ptr)->nd;
-    }
+    ssize_t ndim() const { return detail::array_proxy(m_ptr)->nd; }
 
     /// Base object
-    object base() const {
-        return reinterpret_borrow<object>(detail::array_proxy(m_ptr)->base);
-    }
+    object base() const { return reinterpret_borrow<object>(detail::array_proxy(m_ptr)->base); }
 
     /// Dimensions of the array
-    const ssize_t* shape() const {
-        return detail::array_proxy(m_ptr)->dimensions;
-    }
+    const ssize_t *shape() const { return detail::array_proxy(m_ptr)->dimensions; }
 
     /// Dimension along a given axis
     ssize_t shape(ssize_t dim) const {
@@ -700,9 +784,7 @@ class array : public buffer {
     }
 
     /// Strides of the array
-    const ssize_t* strides() const {
-        return detail::array_proxy(m_ptr)->strides;
-    }
+    const ssize_t *strides() const { return detail::array_proxy(m_ptr)->strides; }
 
     /// Stride along a given axis
     ssize_t strides(ssize_t dim) const {
@@ -713,9 +795,7 @@ class array : public buffer {
     }
 
     /// Return the NumPy array flags
-    int flags() const {
-        return detail::array_proxy(m_ptr)->flags;
-    }
+    int flags() const { return detail::array_proxy(m_ptr)->flags; }
 
     /// If set, the array is writeable (otherwise the buffer is read-only)
     bool writeable() const {
@@ -729,21 +809,24 @@ class array : public buffer {
 
     /// Pointer to the contained data. If index is not provided, points to the
     /// beginning of the buffer. May throw if the index would lead to out of bounds access.
-    template<typename... Ix> const void* data(Ix... index) const {
+    template <typename... Ix>
+    const void *data(Ix... index) const {
         return static_cast<const void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
     }
 
     /// Mutable pointer to the contained data. If index is not provided, points to the
     /// beginning of the buffer. May throw if the index would lead to out of bounds access.
     /// May throw if the array is not writeable.
-    template<typename... Ix> void* mutable_data(Ix... index) {
+    template <typename... Ix>
+    void *mutable_data(Ix... index) {
         check_writeable();
         return static_cast<void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
     }
 
     /// Byte offset from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
-    template<typename... Ix> ssize_t offset_at(Ix... index) const {
+    template <typename... Ix>
+    ssize_t offset_at(Ix... index) const {
         if ((ssize_t) sizeof...(index) > ndim()) {
             fail_dim_check(sizeof...(index), "too many indices for an array");
         }
@@ -754,7 +837,8 @@ class array : public buffer {
 
     /// Item count from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
-    template<typename... Ix> ssize_t index_at(Ix... index) const {
+    template <typename... Ix>
+    ssize_t index_at(Ix... index) const {
         return offset_at(index...) / itemsize();
     }
 
@@ -764,23 +848,26 @@ class array : public buffer {
      * care: the array must not be destroyed or reshaped for the duration of the returned object,
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
-    template <typename T, ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
+    template <typename T, ssize_t Dims = -1>
+    detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
         if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
         }
-        return detail::unchecked_mutable_reference<T, Dims>(mutable_data(), shape(), strides(), ndim());
+        return detail::unchecked_mutable_reference<T, Dims>(
+            mutable_data(), shape(), strides(), ndim());
     }
 
     /**
      * Returns a proxy object that provides const access to the array's data without bounds or
      * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
-     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed or
-     * reshaped for the duration of the returned object, and the caller must take care not to access
-     * invalid dimensions or dimension indices.
+     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed
+     * or reshaped for the duration of the returned object, and the caller must take care not to
+     * access invalid dimensions or dimension indices.
      */
-    template <typename T, ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
+    template <typename T, ssize_t Dims = -1>
+    detail::unchecked_reference<T, Dims> unchecked() const & {
         if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
@@ -791,7 +878,7 @@ class array : public buffer {
 
     /// Return a new view with all of the dimensions of length 1 removed
     array squeeze() {
-        auto& api = detail::npy_api::get();
+        auto &api = detail::npy_api::get();
         return reinterpret_steal<array>(api.PyArray_Squeeze_(m_ptr));
     }
 
@@ -799,19 +886,19 @@ class array : public buffer {
     /// If refcheck is true and more that one reference exist to this array
     /// then resize will succeed only if it makes a reshape, i.e. original size doesn't change
     void resize(ShapeContainer new_shape, bool refcheck = true) {
-        detail::npy_api::PyArray_Dims d = {
-            // Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
-            reinterpret_cast<Py_intptr_t*>(new_shape->data()),
-            int(new_shape->size())
-        };
+        detail::npy_api::PyArray_Dims d
+            = {// Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
+               reinterpret_cast<Py_intptr_t *>(new_shape->data()),
+               int(new_shape->size())};
         // try to resize, set ordering param to -1 cause it's not used anyway
         auto new_array = reinterpret_steal<object>(
-            detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1)
-        );
+            detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1));
         if (!new_array) {
             throw error_already_set();
         }
-        if (isinstance<array>(new_array)) { *this = std::move(new_array); }
+        if (isinstance<array>(new_array)) {
+            *this = std::move(new_array);
+        }
     }
 
     /// Optional `order` parameter omitted, to be added as needed.
@@ -852,14 +939,16 @@ class array : public buffer {
     }
 
 protected:
-    template<typename, typename> friend struct detail::npy_format_descriptor;
+    template <typename, typename>
+    friend struct detail::npy_format_descriptor;
 
-    void fail_dim_check(ssize_t dim, const std::string& msg) const {
-        throw index_error(msg + ": " + std::to_string(dim) +
-                          " (ndim = " + std::to_string(ndim()) + ")");
+    void fail_dim_check(ssize_t dim, const std::string &msg) const {
+        throw index_error(msg + ": " + std::to_string(dim) + " (ndim = " + std::to_string(ndim())
+                          + ")");
     }
 
-    template<typename... Ix> ssize_t byte_offset(Ix... index) const {
+    template <typename... Ix>
+    ssize_t byte_offset(Ix... index) const {
         check_dimensions(index...);
         return detail::byte_offset_unsafe(strides(), ssize_t(index)...);
     }
@@ -870,17 +959,19 @@ class array : public buffer {
         }
     }
 
-    template<typename... Ix> void check_dimensions(Ix... index) const {
+    template <typename... Ix>
+    void check_dimensions(Ix... index) const {
         check_dimensions_impl(ssize_t(0), shape(), ssize_t(index)...);
     }
 
-    void check_dimensions_impl(ssize_t, const ssize_t*) const { }
+    void check_dimensions_impl(ssize_t, const ssize_t *) const {}
 
-    template<typename... Ix> void check_dimensions_impl(ssize_t axis, const ssize_t* shape, ssize_t i, Ix... index) const {
+    template <typename... Ix>
+    void check_dimensions_impl(ssize_t axis, const ssize_t *shape, ssize_t i, Ix... index) const {
         if (i >= *shape) {
-            throw index_error(std::string("index ") + std::to_string(i) +
-                              " is out of bounds for axis " + std::to_string(axis) +
-                              " with size " + std::to_string(*shape));
+            throw index_error(std::string("index ") + std::to_string(i)
+                              + " is out of bounds for axis " + std::to_string(axis)
+                              + " with size " + std::to_string(*shape));
         }
         check_dimensions_impl(axis + 1, shape + 1, index...);
     }
@@ -896,20 +987,26 @@ class array : public buffer {
     }
 };
 
-template <typename T, int ExtraFlags = array::forcecast> class array_t : public array {
+template <typename T, int ExtraFlags = array::forcecast>
+class array_t : public array {
 private:
     struct private_ctor {};
     // Delegating constructor needed when both moving and accessing in the same constructor
-    array_t(private_ctor, ShapeContainer &&shape, StridesContainer &&strides, const T *ptr, handle base)
+    array_t(private_ctor,
+            ShapeContainer &&shape,
+            StridesContainer &&strides,
+            const T *ptr,
+            handle base)
         : array(std::move(shape), std::move(strides), ptr, base) {}
+
 public:
     static_assert(!detail::array_info<T>::is_array, "Array types cannot be used with array_t");
 
     using value_type = T;
 
     array_t() : array(0, static_cast<const T *>(nullptr)) {}
-    array_t(handle h, borrowed_t) : array(h, borrowed_t{}) { }
-    array_t(handle h, stolen_t) : array(h, stolen_t{}) { }
+    array_t(handle h, borrowed_t) : array(h, borrowed_t{}) {}
+    array_t(handle h, stolen_t) : array(h, stolen_t{}) {}
 
     PYBIND11_DEPRECATED("Use array_t<T>::ensure() instead")
     array_t(handle h, bool is_borrowed) : array(raw_array_t(h.ptr()), stolen_t{}) {
@@ -928,10 +1025,13 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
         }
     }
 
-    explicit array_t(const buffer_info& info, handle base = handle()) : array(info, base) { }
+    explicit array_t(const buffer_info &info, handle base = handle()) : array(info, base) {}
 
-    array_t(ShapeContainer shape, StridesContainer strides, const T *ptr = nullptr, handle base = handle())
-        : array(std::move(shape), std::move(strides), ptr, base) { }
+    array_t(ShapeContainer shape,
+            StridesContainer strides,
+            const T *ptr = nullptr,
+            handle base = handle())
+        : array(std::move(shape), std::move(strides), ptr, base) {}
 
     explicit array_t(ShapeContainer shape, const T *ptr = nullptr, handle base = handle())
         : array_t(private_ctor{},
@@ -942,38 +1042,43 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
                   base) {}
 
     explicit array_t(ssize_t count, const T *ptr = nullptr, handle base = handle())
-        : array({count}, {}, ptr, base) { }
+        : array({count}, {}, ptr, base) {}
 
-    constexpr ssize_t itemsize() const {
-        return sizeof(T);
-    }
+    constexpr ssize_t itemsize() const { return sizeof(T); }
 
-    template<typename... Ix> ssize_t index_at(Ix... index) const {
+    template <typename... Ix>
+    ssize_t index_at(Ix... index) const {
         return offset_at(index...) / itemsize();
     }
 
-    template<typename... Ix> const T* data(Ix... index) const {
-        return static_cast<const T*>(array::data(index...));
+    template <typename... Ix>
+    const T *data(Ix... index) const {
+        return static_cast<const T *>(array::data(index...));
     }
 
-    template<typename... Ix> T* mutable_data(Ix... index) {
-        return static_cast<T*>(array::mutable_data(index...));
+    template <typename... Ix>
+    T *mutable_data(Ix... index) {
+        return static_cast<T *>(array::mutable_data(index...));
     }
 
     // Reference to element at a given index
-    template<typename... Ix> const T& at(Ix... index) const {
+    template <typename... Ix>
+    const T &at(Ix... index) const {
         if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
         }
-        return *(static_cast<const T*>(array::data()) + byte_offset(ssize_t(index)...) / itemsize());
+        return *(static_cast<const T *>(array::data())
+                 + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     // Mutable reference to element at a given index
-    template<typename... Ix> T& mutable_at(Ix... index) {
+    template <typename... Ix>
+    T &mutable_at(Ix... index) {
         if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
         }
-        return *(static_cast<T*>(array::mutable_data()) + byte_offset(ssize_t(index)...) / itemsize());
+        return *(static_cast<T *>(array::mutable_data())
+                 + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     /**
@@ -982,7 +1087,8 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
      * care: the array must not be destroyed or reshaped for the duration of the returned object,
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
-    template <ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
+    template <ssize_t Dims = -1>
+    detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
         return array::mutable_unchecked<T, Dims>();
     }
 
@@ -993,7 +1099,8 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
      * for the duration of the returned object, and the caller must take care not to access invalid
      * dimensions or dimension indices.
      */
-    template <ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
+    template <ssize_t Dims = -1>
+    detail::unchecked_reference<T, Dims> unchecked() const & {
         return array::unchecked<T, Dims>();
     }
 
@@ -1010,7 +1117,8 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
     static bool check_(handle h) {
         const auto &api = detail::npy_api::get();
         return api.PyArray_Check_(h.ptr())
-               && api.PyArray_EquivTypes_(detail::array_proxy(h.ptr())->descr, dtype::of<T>().ptr())
+               && api.PyArray_EquivTypes_(detail::array_proxy(h.ptr())->descr,
+                                          dtype::of<T>().ptr())
                && detail::check_flags(h.ptr(), ExtraFlags & (array::c_style | array::f_style));
     }
 
@@ -1021,9 +1129,13 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
             PyErr_SetString(PyExc_ValueError, "cannot create a pybind11::array_t from a nullptr");
             return nullptr;
         }
-        return detail::npy_api::get().PyArray_FromAny_(
-            ptr, dtype::of<T>().release().ptr(), 0, 0,
-            detail::npy_api::NPY_ARRAY_ENSUREARRAY_ | ExtraFlags, nullptr);
+        return detail::npy_api::get().PyArray_FromAny_(ptr,
+                                                       dtype::of<T>().release().ptr(),
+                                                       0,
+                                                       0,
+                                                       detail::npy_api::NPY_ARRAY_ENSUREARRAY_
+                                                           | ExtraFlags,
+                                                       nullptr);
     }
 };
 
@@ -1034,10 +1146,12 @@ struct format_descriptor<T, detail::enable_if_t<detail::is_pod_struct<T>::value>
     }
 };
 
-template <size_t N> struct format_descriptor<char[N]> {
+template <size_t N>
+struct format_descriptor<char[N]> {
     static std::string format() { return std::to_string(N) + "s"; }
 };
-template <size_t N> struct format_descriptor<std::array<char, N>> {
+template <size_t N>
+struct format_descriptor<std::array<char, N>> {
     static std::string format() { return std::to_string(N) + "s"; }
 };
 
@@ -1079,7 +1193,7 @@ struct pyobject_caster<array_t<T, ExtraFlags>> {
 
 template <typename T>
 struct compare_buffer_info<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
-    static bool compare(const buffer_info& b) {
+    static bool compare(const buffer_info &b) {
         return npy_api::get().PyArray_EquivTypes_(dtype::of<T>().ptr(), dtype(b).ptr());
     }
 };
@@ -1090,42 +1204,54 @@ struct npy_format_descriptor_name;
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_integral<T>::value>> {
     static constexpr auto name = const_name<std::is_same<T, bool>::value>(
-        const_name("bool"), const_name<std::is_signed<T>::value>("numpy.int", "numpy.uint") + const_name<sizeof(T)*8>()
-    );
+        const_name("bool"),
+        const_name<std::is_signed<T>::value>("numpy.int", "numpy.uint")
+            + const_name<sizeof(T) * 8>());
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::value>> {
-    static constexpr auto name = const_name<std::is_same<T, float>::value
-                                   || std::is_same<T, const float>::value
-                                   || std::is_same<T, double>::value
-                                   || std::is_same<T, const double>::value>(
-        const_name("numpy.float") + const_name<sizeof(T)*8>(), const_name("numpy.longdouble")
-    );
+    static constexpr auto name = const_name < std::is_same<T, float>::value
+                                 || std::is_same<T, const float>::value
+                                 || std::is_same<T, double>::value
+                                 || std::is_same<T, const double>::value
+                                        > (const_name("numpy.float") + const_name<sizeof(T) * 8>(),
+                                           const_name("numpy.longdouble"));
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<is_complex<T>::value>> {
-    static constexpr auto name = const_name<std::is_same<typename T::value_type, float>::value
-                                   || std::is_same<typename T::value_type, const float>::value
-                                   || std::is_same<typename T::value_type, double>::value
-                                   || std::is_same<typename T::value_type, const double>::value>(
-        const_name("numpy.complex") + const_name<sizeof(typename T::value_type)*16>(), const_name("numpy.longcomplex")
-    );
+    static constexpr auto name = const_name < std::is_same<typename T::value_type, float>::value
+                                 || std::is_same<typename T::value_type, const float>::value
+                                 || std::is_same<typename T::value_type, double>::value
+                                 || std::is_same<typename T::value_type, const double>::value
+                                        > (const_name("numpy.complex")
+                                               + const_name<sizeof(typename T::value_type) * 16>(),
+                                           const_name("numpy.longcomplex"));
 };
 
 template <typename T>
-struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmetic, is_complex>::value>>
+struct npy_format_descriptor<
+    T,
+    enable_if_t<satisfies_any_of<T, std::is_arithmetic, is_complex>::value>>
     : npy_format_descriptor_name<T> {
 private:
     // NB: the order here must match the one in common.h
-    constexpr static const int values[15] = {
-        npy_api::NPY_BOOL_,
-        npy_api::NPY_BYTE_,   npy_api::NPY_UBYTE_,   npy_api::NPY_INT16_,    npy_api::NPY_UINT16_,
-        npy_api::NPY_INT32_,  npy_api::NPY_UINT32_,  npy_api::NPY_INT64_,    npy_api::NPY_UINT64_,
-        npy_api::NPY_FLOAT_,  npy_api::NPY_DOUBLE_,  npy_api::NPY_LONGDOUBLE_,
-        npy_api::NPY_CFLOAT_, npy_api::NPY_CDOUBLE_, npy_api::NPY_CLONGDOUBLE_
-    };
+    constexpr static const int values[15] = {npy_api::NPY_BOOL_,
+                                             npy_api::NPY_BYTE_,
+                                             npy_api::NPY_UBYTE_,
+                                             npy_api::NPY_INT16_,
+                                             npy_api::NPY_UINT16_,
+                                             npy_api::NPY_INT32_,
+                                             npy_api::NPY_UINT32_,
+                                             npy_api::NPY_INT64_,
+                                             npy_api::NPY_UINT64_,
+                                             npy_api::NPY_FLOAT_,
+                                             npy_api::NPY_DOUBLE_,
+                                             npy_api::NPY_LONGDOUBLE_,
+                                             npy_api::NPY_CFLOAT_,
+                                             npy_api::NPY_CDOUBLE_,
+                                             npy_api::NPY_CLONGDOUBLE_};
 
 public:
     static constexpr int value = values[detail::is_fmt_numeric<T>::index];
@@ -1138,20 +1264,31 @@ struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmet
     }
 };
 
-#define PYBIND11_DECL_CHAR_FMT \
-    static constexpr auto name = const_name("S") + const_name<N>(); \
-    static pybind11::dtype dtype() { return pybind11::dtype(std::string("S") + std::to_string(N)); }
-template <size_t N> struct npy_format_descriptor<char[N]> { PYBIND11_DECL_CHAR_FMT };
-template <size_t N> struct npy_format_descriptor<std::array<char, N>> { PYBIND11_DECL_CHAR_FMT };
+#define PYBIND11_DECL_CHAR_FMT                                                                    \
+    static constexpr auto name = const_name("S") + const_name<N>();                               \
+    static pybind11::dtype dtype() {                                                              \
+        return pybind11::dtype(std::string("S") + std::to_string(N));                             \
+    }
+template <size_t N>
+struct npy_format_descriptor<char[N]> {
+    PYBIND11_DECL_CHAR_FMT
+};
+template <size_t N>
+struct npy_format_descriptor<std::array<char, N>> {
+    PYBIND11_DECL_CHAR_FMT
+};
 #undef PYBIND11_DECL_CHAR_FMT
 
-template<typename T> struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
+template <typename T>
+struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
 private:
     using base_descr = npy_format_descriptor<typename array_info<T>::type>;
+
 public:
     static_assert(!array_info<T>::is_empty, "Zero-sized arrays are not supported");
 
-    static constexpr auto name = const_name("(") + array_info<T>::extents + const_name(")") + base_descr::name;
+    static constexpr auto name
+        = const_name("(") + array_info<T>::extents + const_name(")") + base_descr::name;
     static pybind11::dtype dtype() {
         list shape;
         array_info<T>::append_extents(shape);
@@ -1159,9 +1296,11 @@ template<typename T> struct npy_format_descriptor<T, enable_if_t<array_info<T>::
     }
 };
 
-template<typename T> struct npy_format_descriptor<T, enable_if_t<std::is_enum<T>::value>> {
+template <typename T>
+struct npy_format_descriptor<T, enable_if_t<std::is_enum<T>::value>> {
 private:
     using base_descr = npy_format_descriptor<typename std::underlying_type<T>::type>;
+
 public:
     static constexpr auto name = base_descr::name;
     static pybind11::dtype dtype() { return base_descr::dtype(); }
@@ -1175,12 +1314,12 @@ struct field_descriptor {
     dtype descr;
 };
 
-PYBIND11_NOINLINE void register_structured_dtype(
-    any_container<field_descriptor> fields,
-    const std::type_info& tinfo, ssize_t itemsize,
-    bool (*direct_converter)(PyObject *, void *&)) {
+PYBIND11_NOINLINE void register_structured_dtype(any_container<field_descriptor> fields,
+                                                 const std::type_info &tinfo,
+                                                 ssize_t itemsize,
+                                                 bool (*direct_converter)(PyObject *, void *&)) {
 
-    auto& numpy_internals = get_numpy_internals();
+    auto &numpy_internals = get_numpy_internals();
     if (numpy_internals.get_type_info(tinfo, false)) {
         pybind11_fail("NumPy: dtype is already registered");
     }
@@ -1188,11 +1327,13 @@ PYBIND11_NOINLINE void register_structured_dtype(
     // Use ordered fields because order matters as of NumPy 1.14:
     // https://docs.scipy.org/doc/numpy/release.html#multiple-field-indexing-assignment-of-structured-arrays
     std::vector<field_descriptor> ordered_fields(std::move(fields));
-    std::sort(ordered_fields.begin(), ordered_fields.end(),
+    std::sort(
+        ordered_fields.begin(),
+        ordered_fields.end(),
         [](const field_descriptor &a, const field_descriptor &b) { return a.offset < b.offset; });
 
     list names, formats, offsets;
-    for (auto& field : ordered_fields) {
+    for (auto &field : ordered_fields) {
         if (!field.descr) {
             pybind11_fail(std::string("NumPy: unsupported field dtype: `") + field.name + "` @ "
                           + tinfo.name());
@@ -1221,7 +1362,7 @@ PYBIND11_NOINLINE void register_structured_dtype(
     // overriding the endianness. Putting the ^ in front of individual fields
     // isn't guaranteed to work due to https://github.com/numpy/numpy/issues/9049
     oss << "^T{";
-    for (auto& field : ordered_fields) {
+    for (auto &field : ordered_fields) {
         if (field.offset > offset) {
             oss << (field.offset - offset) << 'x';
         }
@@ -1235,25 +1376,25 @@ PYBIND11_NOINLINE void register_structured_dtype(
     auto format_str = oss.str();
 
     // Sanity check: verify that NumPy properly parses our buffer format string
-    auto& api = npy_api::get();
-    auto arr =  array(buffer_info(nullptr, itemsize, format_str, 1));
+    auto &api = npy_api::get();
+    auto arr = array(buffer_info(nullptr, itemsize, format_str, 1));
     if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr())) {
         pybind11_fail("NumPy: invalid buffer descriptor!");
     }
 
     auto tindex = std::type_index(tinfo);
-    numpy_internals.registered_dtypes[tindex] = { dtype_ptr, format_str };
+    numpy_internals.registered_dtypes[tindex] = {dtype_ptr, format_str};
     get_internals().direct_conversions[tindex].push_back(direct_converter);
 }
 
-template <typename T, typename SFINAE> struct npy_format_descriptor {
-    static_assert(is_pod_struct<T>::value, "Attempt to use a non-POD or unimplemented POD type as a numpy dtype");
+template <typename T, typename SFINAE>
+struct npy_format_descriptor {
+    static_assert(is_pod_struct<T>::value,
+                  "Attempt to use a non-POD or unimplemented POD type as a numpy dtype");
 
     static constexpr auto name = make_caster<T>::name;
 
-    static pybind11::dtype dtype() {
-        return reinterpret_borrow<pybind11::dtype>(dtype_ptr());
-    }
+    static pybind11::dtype dtype() { return reinterpret_borrow<pybind11::dtype>(dtype_ptr()); }
 
     static std::string format() {
         static auto format_str = get_numpy_internals().get_type_info<T>(true)->format_str;
@@ -1261,18 +1402,20 @@ template <typename T, typename SFINAE> struct npy_format_descriptor {
     }
 
     static void register_dtype(any_container<field_descriptor> fields) {
-        register_structured_dtype(std::move(fields), typeid(typename std::remove_cv<T>::type),
-                                  sizeof(T), &direct_converter);
+        register_structured_dtype(std::move(fields),
+                                  typeid(typename std::remove_cv<T>::type),
+                                  sizeof(T),
+                                  &direct_converter);
     }
 
 private:
-    static PyObject* dtype_ptr() {
-        static PyObject* ptr = get_numpy_internals().get_type_info<T>(true)->dtype_ptr;
+    static PyObject *dtype_ptr() {
+        static PyObject *ptr = get_numpy_internals().get_type_info<T>(true)->dtype_ptr;
         return ptr;
     }
 
-    static bool direct_converter(PyObject *obj, void*& value) {
-        auto& api = npy_api::get();
+    static bool direct_converter(PyObject *obj, void *&value) {
+        auto &api = npy_api::get();
         if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_)) {
             return false;
         }
@@ -1287,78 +1430,80 @@ template <typename T, typename SFINAE> struct npy_format_descriptor {
 };
 
 #ifdef __CLION_IDE__ // replace heavy macro with dummy code for the IDE (doesn't affect code)
-# define PYBIND11_NUMPY_DTYPE(Type, ...) ((void)0)
-# define PYBIND11_NUMPY_DTYPE_EX(Type, ...) ((void)0)
+#    define PYBIND11_NUMPY_DTYPE(Type, ...) ((void) 0)
+#    define PYBIND11_NUMPY_DTYPE_EX(Type, ...) ((void) 0)
 #else
 
-#define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
-    ::pybind11::detail::field_descriptor {                                                    \
-        Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
-        ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),           \
-        ::pybind11::detail::npy_format_descriptor<decltype(std::declval<T>().Field)>::dtype() \
-    }
+#    define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
+        ::pybind11::detail::field_descriptor {                                                    \
+            Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
+                ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),       \
+                ::pybind11::detail::npy_format_descriptor<                                        \
+                    decltype(std::declval<T>().Field)>::dtype()                                   \
+        }
 
 // Extract name, offset and format descriptor for a struct field
-#define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
+#    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #    Field)
 
 // The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
 // (C) William Swanson, Paul Fultz
-#define PYBIND11_EVAL0(...) __VA_ARGS__
-#define PYBIND11_EVAL1(...) PYBIND11_EVAL0 (PYBIND11_EVAL0 (PYBIND11_EVAL0 (__VA_ARGS__)))
-#define PYBIND11_EVAL2(...) PYBIND11_EVAL1 (PYBIND11_EVAL1 (PYBIND11_EVAL1 (__VA_ARGS__)))
-#define PYBIND11_EVAL3(...) PYBIND11_EVAL2 (PYBIND11_EVAL2 (PYBIND11_EVAL2 (__VA_ARGS__)))
-#define PYBIND11_EVAL4(...) PYBIND11_EVAL3 (PYBIND11_EVAL3 (PYBIND11_EVAL3 (__VA_ARGS__)))
-#define PYBIND11_EVAL(...)  PYBIND11_EVAL4 (PYBIND11_EVAL4 (PYBIND11_EVAL4 (__VA_ARGS__)))
-#define PYBIND11_MAP_END(...)
-#define PYBIND11_MAP_OUT
-#define PYBIND11_MAP_COMMA ,
-#define PYBIND11_MAP_GET_END() 0, PYBIND11_MAP_END
-#define PYBIND11_MAP_NEXT0(test, next, ...) next PYBIND11_MAP_OUT
-#define PYBIND11_MAP_NEXT1(test, next) PYBIND11_MAP_NEXT0 (test, next, 0)
-#define PYBIND11_MAP_NEXT(test, next)  PYBIND11_MAP_NEXT1 (PYBIND11_MAP_GET_END test, next)
-#if defined(_MSC_VER) && !defined(__clang__) // MSVC is not as eager to expand macros, hence this workaround
-#define PYBIND11_MAP_LIST_NEXT1(test, next) \
-    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
-#else
-#define PYBIND11_MAP_LIST_NEXT1(test, next) \
-    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
-#endif
-#define PYBIND11_MAP_LIST_NEXT(test, next) \
-    PYBIND11_MAP_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
-#define PYBIND11_MAP_LIST0(f, t, x, peek, ...) \
-    f(t, x) PYBIND11_MAP_LIST_NEXT (peek, PYBIND11_MAP_LIST1) (f, t, peek, __VA_ARGS__)
-#define PYBIND11_MAP_LIST1(f, t, x, peek, ...) \
-    f(t, x) PYBIND11_MAP_LIST_NEXT (peek, PYBIND11_MAP_LIST0) (f, t, peek, __VA_ARGS__)
+#    define PYBIND11_EVAL0(...) __VA_ARGS__
+#    define PYBIND11_EVAL1(...) PYBIND11_EVAL0(PYBIND11_EVAL0(PYBIND11_EVAL0(__VA_ARGS__)))
+#    define PYBIND11_EVAL2(...) PYBIND11_EVAL1(PYBIND11_EVAL1(PYBIND11_EVAL1(__VA_ARGS__)))
+#    define PYBIND11_EVAL3(...) PYBIND11_EVAL2(PYBIND11_EVAL2(PYBIND11_EVAL2(__VA_ARGS__)))
+#    define PYBIND11_EVAL4(...) PYBIND11_EVAL3(PYBIND11_EVAL3(PYBIND11_EVAL3(__VA_ARGS__)))
+#    define PYBIND11_EVAL(...) PYBIND11_EVAL4(PYBIND11_EVAL4(PYBIND11_EVAL4(__VA_ARGS__)))
+#    define PYBIND11_MAP_END(...)
+#    define PYBIND11_MAP_OUT
+#    define PYBIND11_MAP_COMMA ,
+#    define PYBIND11_MAP_GET_END() 0, PYBIND11_MAP_END
+#    define PYBIND11_MAP_NEXT0(test, next, ...) next PYBIND11_MAP_OUT
+#    define PYBIND11_MAP_NEXT1(test, next) PYBIND11_MAP_NEXT0(test, next, 0)
+#    define PYBIND11_MAP_NEXT(test, next) PYBIND11_MAP_NEXT1(PYBIND11_MAP_GET_END test, next)
+#    if defined(_MSC_VER)                                                                         \
+        && !defined(__clang__) // MSVC is not as eager to expand macros, hence this workaround
+#        define PYBIND11_MAP_LIST_NEXT1(test, next)                                               \
+            PYBIND11_EVAL0(PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0))
+#    else
+#        define PYBIND11_MAP_LIST_NEXT1(test, next)                                               \
+            PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0)
+#    endif
+#    define PYBIND11_MAP_LIST_NEXT(test, next)                                                    \
+        PYBIND11_MAP_LIST_NEXT1(PYBIND11_MAP_GET_END test, next)
+#    define PYBIND11_MAP_LIST0(f, t, x, peek, ...)                                                \
+        f(t, x) PYBIND11_MAP_LIST_NEXT(peek, PYBIND11_MAP_LIST1)(f, t, peek, __VA_ARGS__)
+#    define PYBIND11_MAP_LIST1(f, t, x, peek, ...)                                                \
+        f(t, x) PYBIND11_MAP_LIST_NEXT(peek, PYBIND11_MAP_LIST0)(f, t, peek, __VA_ARGS__)
 // PYBIND11_MAP_LIST(f, t, a1, a2, ...) expands to f(t, a1), f(t, a2), ...
-#define PYBIND11_MAP_LIST(f, t, ...) \
-    PYBIND11_EVAL (PYBIND11_MAP_LIST1 (f, t, __VA_ARGS__, (), 0))
-
-#define PYBIND11_NUMPY_DTYPE(Type, ...) \
-    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
-        (::std::vector<::pybind11::detail::field_descriptor> \
-         {PYBIND11_MAP_LIST (PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
-
-#if defined(_MSC_VER) && !defined(__clang__)
-#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
-    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
-#else
-#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
-    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
-#endif
-#define PYBIND11_MAP2_LIST_NEXT(test, next) \
-    PYBIND11_MAP2_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
-#define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...) \
-    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST1) (f, t, peek, __VA_ARGS__)
-#define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...) \
-    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST0) (f, t, peek, __VA_ARGS__)
+#    define PYBIND11_MAP_LIST(f, t, ...)                                                          \
+        PYBIND11_EVAL(PYBIND11_MAP_LIST1(f, t, __VA_ARGS__, (), 0))
+
+#    define PYBIND11_NUMPY_DTYPE(Type, ...)                                                       \
+        ::pybind11::detail::npy_format_descriptor<Type>::register_dtype(                          \
+            ::std::vector<::pybind11::detail::field_descriptor>{                                  \
+                PYBIND11_MAP_LIST(PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
+
+#    if defined(_MSC_VER) && !defined(__clang__)
+#        define PYBIND11_MAP2_LIST_NEXT1(test, next)                                              \
+            PYBIND11_EVAL0(PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0))
+#    else
+#        define PYBIND11_MAP2_LIST_NEXT1(test, next)                                              \
+            PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0)
+#    endif
+#    define PYBIND11_MAP2_LIST_NEXT(test, next)                                                   \
+        PYBIND11_MAP2_LIST_NEXT1(PYBIND11_MAP_GET_END test, next)
+#    define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...)                                          \
+        f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT(peek, PYBIND11_MAP2_LIST1)(f, t, peek, __VA_ARGS__)
+#    define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...)                                          \
+        f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT(peek, PYBIND11_MAP2_LIST0)(f, t, peek, __VA_ARGS__)
 // PYBIND11_MAP2_LIST(f, t, a1, a2, ...) expands to f(t, a1, a2), f(t, a3, a4), ...
-#define PYBIND11_MAP2_LIST(f, t, ...) \
-    PYBIND11_EVAL (PYBIND11_MAP2_LIST1 (f, t, __VA_ARGS__, (), 0))
+#    define PYBIND11_MAP2_LIST(f, t, ...)                                                         \
+        PYBIND11_EVAL(PYBIND11_MAP2_LIST1(f, t, __VA_ARGS__, (), 0))
 
-#define PYBIND11_NUMPY_DTYPE_EX(Type, ...) \
-    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
-        (::std::vector<::pybind11::detail::field_descriptor> \
-         {PYBIND11_MAP2_LIST (PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
+#    define PYBIND11_NUMPY_DTYPE_EX(Type, ...)                                                    \
+        ::pybind11::detail::npy_format_descriptor<Type>::register_dtype(                          \
+            ::std::vector<::pybind11::detail::field_descriptor>{                                  \
+                PYBIND11_MAP2_LIST(PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
 
 #endif // __CLION_IDE__
 
@@ -1370,8 +1515,8 @@ class common_iterator {
 
     common_iterator() : m_strides() {}
 
-    common_iterator(void* ptr, const container_type& strides, const container_type& shape)
-        : p_ptr(reinterpret_cast<char*>(ptr)), m_strides(strides.size()) {
+    common_iterator(void *ptr, const container_type &strides, const container_type &shape)
+        : p_ptr(reinterpret_cast<char *>(ptr)), m_strides(strides.size()) {
         m_strides.back() = static_cast<value_type>(strides.back());
         for (size_type i = m_strides.size() - 1; i != 0; --i) {
             size_type j = i - 1;
@@ -1380,27 +1525,22 @@ class common_iterator {
         }
     }
 
-    void increment(size_type dim) {
-        p_ptr += m_strides[dim];
-    }
+    void increment(size_type dim) { p_ptr += m_strides[dim]; }
 
-    void* data() const {
-        return p_ptr;
-    }
+    void *data() const { return p_ptr; }
 
 private:
     char *p_ptr{0};
     container_type m_strides;
 };
 
-template <size_t N> class multi_array_iterator {
+template <size_t N>
+class multi_array_iterator {
 public:
     using container_type = std::vector<ssize_t>;
 
-    multi_array_iterator(const std::array<buffer_info, N> &buffers,
-                         const container_type &shape)
-        : m_shape(shape.size()), m_index(shape.size(), 0),
-          m_common_iterator() {
+    multi_array_iterator(const std::array<buffer_info, N> &buffers, const container_type &shape)
+        : m_shape(shape.size()), m_index(shape.size(), 0), m_common_iterator() {
 
         // Manual copy to avoid conversion warning if using std::copy
         for (size_t i = 0; i < shape.size(); ++i) {
@@ -1413,7 +1553,7 @@ template <size_t N> class multi_array_iterator {
         }
     }
 
-    multi_array_iterator& operator++() {
+    multi_array_iterator &operator++() {
         for (size_t j = m_index.size(); j != 0; --j) {
             size_t i = j - 1;
             if (++m_index[i] != m_shape[i]) {
@@ -1425,12 +1565,12 @@ template <size_t N> class multi_array_iterator {
         return *this;
     }
 
-    template <size_t K, class T = void> T* data() const {
-        return reinterpret_cast<T*>(m_common_iterator[K].data());
+    template <size_t K, class T = void>
+    T *data() const {
+        return reinterpret_cast<T *>(m_common_iterator[K].data());
     }
 
 private:
-
     using common_iter = common_iterator;
 
     void init_common_iterator(const buffer_info &buffer,
@@ -1472,29 +1612,33 @@ template <size_t N> class multi_array_iterator {
 
 enum class broadcast_trivial { non_trivial, c_trivial, f_trivial };
 
-// Populates the shape and number of dimensions for the set of buffers.  Returns a broadcast_trivial
-// enum value indicating whether the broadcast is "trivial"--that is, has each buffer being either a
-// singleton or a full-size, C-contiguous (`c_trivial`) or Fortran-contiguous (`f_trivial`) storage
-// buffer; returns `non_trivial` otherwise.
+// Populates the shape and number of dimensions for the set of buffers.  Returns a
+// broadcast_trivial enum value indicating whether the broadcast is "trivial"--that is, has each
+// buffer being either a singleton or a full-size, C-contiguous (`c_trivial`) or Fortran-contiguous
+// (`f_trivial`) storage buffer; returns `non_trivial` otherwise.
 template <size_t N>
-broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &ndim, std::vector<ssize_t> &shape) {
-    ndim = std::accumulate(buffers.begin(), buffers.end(), ssize_t(0), [](ssize_t res, const buffer_info &buf) {
-        return std::max(res, buf.ndim);
-    });
+broadcast_trivial
+broadcast(const std::array<buffer_info, N> &buffers, ssize_t &ndim, std::vector<ssize_t> &shape) {
+    ndim = std::accumulate(
+        buffers.begin(), buffers.end(), ssize_t(0), [](ssize_t res, const buffer_info &buf) {
+            return std::max(res, buf.ndim);
+        });
 
     shape.clear();
     shape.resize((size_t) ndim, 1);
 
-    // Figure out the output size, and make sure all input arrays conform (i.e. are either size 1 or
-    // the full size).
+    // Figure out the output size, and make sure all input arrays conform (i.e. are either size 1
+    // or the full size).
     for (size_t i = 0; i < N; ++i) {
         auto res_iter = shape.rbegin();
         auto end = buffers[i].shape.rend();
-        for (auto shape_iter = buffers[i].shape.rbegin(); shape_iter != end; ++shape_iter, ++res_iter) {
+        for (auto shape_iter = buffers[i].shape.rbegin(); shape_iter != end;
+             ++shape_iter, ++res_iter) {
             const auto &dim_size_in = *shape_iter;
             auto &dim_size_out = *res_iter;
 
-            // Each input dimension can either be 1 or `n`, but `n` values must match across buffers
+            // Each input dimension can either be 1 or `n`, but `n` values must match across
+            // buffers
             if (dim_size_out == 1) {
                 dim_size_out = dim_size_in;
             } else if (dim_size_in != 1 && dim_size_in != dim_size_out) {
@@ -1524,8 +1668,10 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
         if (trivial_broadcast_c) {
             ssize_t expect_stride = buffers[i].itemsize;
             auto end = buffers[i].shape.crend();
-            for (auto shape_iter = buffers[i].shape.crbegin(), stride_iter = buffers[i].strides.crbegin();
-                    trivial_broadcast_c && shape_iter != end; ++shape_iter, ++stride_iter) {
+            for (auto shape_iter = buffers[i].shape.crbegin(),
+                      stride_iter = buffers[i].strides.crbegin();
+                 trivial_broadcast_c && shape_iter != end;
+                 ++shape_iter, ++stride_iter) {
                 if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
                 } else {
@@ -1538,8 +1684,10 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
         if (trivial_broadcast_f) {
             ssize_t expect_stride = buffers[i].itemsize;
             auto end = buffers[i].shape.cend();
-            for (auto shape_iter = buffers[i].shape.cbegin(), stride_iter = buffers[i].strides.cbegin();
-                    trivial_broadcast_f && shape_iter != end; ++shape_iter, ++stride_iter) {
+            for (auto shape_iter = buffers[i].shape.cbegin(),
+                      stride_iter = buffers[i].strides.cbegin();
+                 trivial_broadcast_f && shape_iter != end;
+                 ++shape_iter, ++stride_iter) {
                 if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
                 } else {
@@ -1549,28 +1697,31 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
         }
     }
 
-    return
-        trivial_broadcast_c ? broadcast_trivial::c_trivial :
-        trivial_broadcast_f ? broadcast_trivial::f_trivial :
-        broadcast_trivial::non_trivial;
+    return trivial_broadcast_c   ? broadcast_trivial::c_trivial
+           : trivial_broadcast_f ? broadcast_trivial::f_trivial
+                                 : broadcast_trivial::non_trivial;
 }
 
 template <typename T>
 struct vectorize_arg {
-    static_assert(!std::is_rvalue_reference<T>::value, "Functions with rvalue reference arguments cannot be vectorized");
+    static_assert(!std::is_rvalue_reference<T>::value,
+                  "Functions with rvalue reference arguments cannot be vectorized");
     // The wrapped function gets called with this type:
     using call_type = remove_reference_t<T>;
     // Is this a vectorized argument?
-    static constexpr bool vectorize =
-        satisfies_any_of<call_type, std::is_arithmetic, is_complex, is_pod>::value &&
-        satisfies_none_of<call_type, std::is_pointer, std::is_array, is_std_array, std::is_enum>::value &&
-        (!std::is_reference<T>::value ||
-         (std::is_lvalue_reference<T>::value && std::is_const<call_type>::value));
+    static constexpr bool vectorize
+        = satisfies_any_of<call_type, std::is_arithmetic, is_complex, is_pod>::value
+          && satisfies_none_of<call_type,
+                               std::is_pointer,
+                               std::is_array,
+                               is_std_array,
+                               std::is_enum>::value
+          && (!std::is_reference<T>::value
+              || (std::is_lvalue_reference<T>::value && std::is_const<call_type>::value));
     // Accept this type: an array for vectorized types, otherwise the type as-is:
     using type = conditional_t<vectorize, array_t<remove_cv_t<call_type>, array::forcecast>, T>;
 };
 
-
 // py::vectorize when a return type is present
 template <typename Func, typename Return, typename... Args>
 struct vectorize_returned_array {
@@ -1583,17 +1734,11 @@ struct vectorize_returned_array {
         return array_t<Return>(shape);
     }
 
-    static Return *mutable_data(Type &array) {
-        return array.mutable_data();
-    }
+    static Return *mutable_data(Type &array) { return array.mutable_data(); }
 
-    static Return call(Func &f, Args &... args) {
-        return f(args...);
-    }
+    static Return call(Func &f, Args &...args) { return f(args...); }
 
-    static void call(Return *out, size_t i, Func &f, Args &... args) {
-        out[i] = f(args...);
-    }
+    static void call(Return *out, size_t i, Func &f, Args &...args) { out[i] = f(args...); }
 };
 
 // py::vectorize when a return type is not present
@@ -1601,25 +1746,18 @@ template <typename Func, typename... Args>
 struct vectorize_returned_array<Func, void, Args...> {
     using Type = none;
 
-    static Type create(broadcast_trivial, const std::vector<ssize_t> &) {
-        return none();
-    }
+    static Type create(broadcast_trivial, const std::vector<ssize_t> &) { return none(); }
 
-    static void *mutable_data(Type &) {
-        return nullptr;
-    }
+    static void *mutable_data(Type &) { return nullptr; }
 
-    static detail::void_type call(Func &f, Args &... args) {
+    static detail::void_type call(Func &f, Args &...args) {
         f(args...);
         return {};
     }
 
-    static void call(void *, size_t, Func &f, Args &... args) {
-        f(args...);
-    }
+    static void call(void *, size_t, Func &f, Args &...args) { f(args...); }
 };
 
-
 template <typename Func, typename Return, typename... Args>
 struct vectorize_helper {
 
@@ -1632,8 +1770,9 @@ struct vectorize_helper {
 
     static constexpr size_t N = sizeof...(Args);
     static constexpr size_t NVectorized = constexpr_sum(vectorize_arg<Args>::vectorize...);
-    static_assert(NVectorized >= 1,
-            "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
+    static_assert(
+        NVectorized >= 1,
+        "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
 
 public:
     template <typename T,
@@ -1652,10 +1791,11 @@ struct vectorize_helper {
 private:
     remove_reference_t<Func> f;
 
-    // Internal compiler error in MSVC 19.16.27025.1 (Visual Studio 2017 15.9.4), when compiling with "/permissive-" flag
-    // when arg_call_types is manually inlined.
+    // Internal compiler error in MSVC 19.16.27025.1 (Visual Studio 2017 15.9.4), when compiling
+    // with "/permissive-" flag when arg_call_types is manually inlined.
     using arg_call_types = std::tuple<typename vectorize_arg<Args>::call_type...>;
-    template <size_t Index> using param_n_t = typename std::tuple_element<Index, arg_call_types>::type;
+    template <size_t Index>
+    using param_n_t = typename std::tuple_element<Index, arg_call_types>::type;
 
     using returned_array = vectorize_returned_array<Func, Return, Args...>;
 
@@ -1666,17 +1806,20 @@ struct vectorize_helper {
     //     - BIndex is a incremental sequence (beginning at 0) of the same size as VIndex, so that
     //       we can store vectorized buffer_infos in an array (argument VIndex has its buffer at
     //       index BIndex in the array).
-    template <size_t... Index, size_t... VIndex, size_t... BIndex> object run(
-            typename vectorize_arg<Args>::type &...args,
-            index_sequence<Index...> i_seq, index_sequence<VIndex...> vi_seq, index_sequence<BIndex...> bi_seq) {
+    template <size_t... Index, size_t... VIndex, size_t... BIndex>
+    object run(typename vectorize_arg<Args>::type &...args,
+               index_sequence<Index...> i_seq,
+               index_sequence<VIndex...> vi_seq,
+               index_sequence<BIndex...> bi_seq) {
 
         // Pointers to values the function was called with; the vectorized ones set here will start
         // out as array_t<T> pointers, but they will be changed them to T pointers before we make
         // call the wrapped function.  Non-vectorized pointers are left as-is.
-        std::array<void *, N> params{{ &args... }};
+        std::array<void *, N> params{{&args...}};
 
         // The array of `buffer_info`s of vectorized arguments:
-        std::array<buffer_info, NVectorized> buffers{{ reinterpret_cast<array *>(params[VIndex])->request()... }};
+        std::array<buffer_info, NVectorized> buffers{
+            {reinterpret_cast<array *>(params[VIndex])->request()...}};
 
         /* Determine dimensions parameters of output array */
         ssize_t nd = 0;
@@ -1684,13 +1827,15 @@ struct vectorize_helper {
         auto trivial = broadcast(buffers, nd, shape);
         auto ndim = (size_t) nd;
 
-        size_t size = std::accumulate(shape.begin(), shape.end(), (size_t) 1, std::multiplies<size_t>());
+        size_t size
+            = std::accumulate(shape.begin(), shape.end(), (size_t) 1, std::multiplies<size_t>());
 
         // If all arguments are 0-dimension arrays (i.e. single values) return a plain value (i.e.
         // not wrapped in an array).
         if (size == 1 && ndim == 0) {
             PYBIND11_EXPAND_SIDE_EFFECTS(params[VIndex] = buffers[BIndex].ptr);
-            return cast(returned_array::call(f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...));
+            return cast(
+                returned_array::call(f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...));
         }
 
         auto result = returned_array::create(trivial, shape);
@@ -1715,20 +1860,21 @@ struct vectorize_helper {
                        std::array<void *, N> &params,
                        Return *out,
                        size_t size,
-                       index_sequence<Index...>, index_sequence<VIndex...>, index_sequence<BIndex...>) {
+                       index_sequence<Index...>,
+                       index_sequence<VIndex...>,
+                       index_sequence<BIndex...>) {
 
         // Initialize an array of mutable byte references and sizes with references set to the
         // appropriate pointer in `params`; as we iterate, we'll increment each pointer by its size
         // (except for singletons, which get an increment of 0).
-        std::array<std::pair<unsigned char *&, const size_t>, NVectorized> vecparams{{
-            std::pair<unsigned char *&, const size_t>(
-                    reinterpret_cast<unsigned char *&>(params[VIndex] = buffers[BIndex].ptr),
-                    buffers[BIndex].size == 1 ? 0 : sizeof(param_n_t<VIndex>)
-            )...
-        }};
+        std::array<std::pair<unsigned char *&, const size_t>, NVectorized> vecparams{
+            {std::pair<unsigned char *&, const size_t>(
+                reinterpret_cast<unsigned char *&>(params[VIndex] = buffers[BIndex].ptr),
+                buffers[BIndex].size == 1 ? 0 : sizeof(param_n_t<VIndex>))...}};
 
         for (size_t i = 0; i < size; ++i) {
-            returned_array::call(out, i, f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...);
+            returned_array::call(
+                out, i, f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...);
             for (auto &x : vecparams) {
                 x.first += x.second;
             }
@@ -1741,55 +1887,70 @@ struct vectorize_helper {
                          Return *out,
                          size_t size,
                          const std::vector<ssize_t> &output_shape,
-                         index_sequence<Index...>, index_sequence<VIndex...>, index_sequence<BIndex...>) {
+                         index_sequence<Index...>,
+                         index_sequence<VIndex...>,
+                         index_sequence<BIndex...>) {
 
         multi_array_iterator<NVectorized> input_iter(buffers, output_shape);
 
         for (size_t i = 0; i < size; ++i, ++input_iter) {
-            PYBIND11_EXPAND_SIDE_EFFECTS((
-                params[VIndex] = input_iter.template data<BIndex>()
-            ));
-            returned_array::call(out, i, f, *reinterpret_cast<param_n_t<Index> *>(std::get<Index>(params))...);
+            PYBIND11_EXPAND_SIDE_EFFECTS((params[VIndex] = input_iter.template data<BIndex>()));
+            returned_array::call(
+                out, i, f, *reinterpret_cast<param_n_t<Index> *>(std::get<Index>(params))...);
         }
     }
 };
 
 template <typename Func, typename Return, typename... Args>
-vectorize_helper<Func, Return, Args...>
-vectorize_extractor(const Func &f, Return (*) (Args ...)) {
+vectorize_helper<Func, Return, Args...> vectorize_extractor(const Func &f, Return (*)(Args...)) {
     return detail::vectorize_helper<Func, Return, Args...>(f);
 }
 
-template <typename T, int Flags> struct handle_type_name<array_t<T, Flags>> {
-    static constexpr auto name = const_name("numpy.ndarray[") + npy_format_descriptor<T>::name + const_name("]");
+template <typename T, int Flags>
+struct handle_type_name<array_t<T, Flags>> {
+    static constexpr auto name
+        = const_name("numpy.ndarray[") + npy_format_descriptor<T>::name + const_name("]");
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
 // Vanilla pointer vectorizer:
 template <typename Return, typename... Args>
-detail::vectorize_helper<Return (*)(Args...), Return, Args...>
-vectorize(Return (*f) (Args ...)) {
+detail::vectorize_helper<Return (*)(Args...), Return, Args...> vectorize(Return (*f)(Args...)) {
     return detail::vectorize_helper<Return (*)(Args...), Return, Args...>(f);
 }
 
 // lambda vectorizer:
 template <typename Func, detail::enable_if_t<detail::is_lambda<Func>::value, int> = 0>
-auto vectorize(Func &&f) -> decltype(
-        detail::vectorize_extractor(std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr)) {
-    return detail::vectorize_extractor(std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr);
+auto vectorize(Func &&f)
+    -> decltype(detail::vectorize_extractor(std::forward<Func>(f),
+                                            (detail::function_signature_t<Func> *) nullptr)) {
+    return detail::vectorize_extractor(std::forward<Func>(f),
+                                       (detail::function_signature_t<Func> *) nullptr);
 }
 
 // Vectorize a class method (non-const):
-template <typename Return, typename Class, typename... Args,
-          typename Helper = detail::vectorize_helper<decltype(std::mem_fn(std::declval<Return (Class::*)(Args...)>())), Return, Class *, Args...>>
+template <typename Return,
+          typename Class,
+          typename... Args,
+          typename Helper = detail::vectorize_helper<
+              decltype(std::mem_fn(std::declval<Return (Class::*)(Args...)>())),
+              Return,
+              Class *,
+              Args...>>
 Helper vectorize(Return (Class::*f)(Args...)) {
     return Helper(std::mem_fn(f));
 }
 
 // Vectorize a class method (const):
-template <typename Return, typename Class, typename... Args,
-          typename Helper = detail::vectorize_helper<decltype(std::mem_fn(std::declval<Return (Class::*)(Args...) const>())), Return, const Class *, Args...>>
+template <typename Return,
+          typename Class,
+          typename... Args,
+          typename Helper = detail::vectorize_helper<
+              decltype(std::mem_fn(std::declval<Return (Class::*)(Args...) const>())),
+              Return,
+              const Class *,
+              Args...>>
 Helper vectorize(Return (Class::*f)(Args...) const) {
     return Helper(std::mem_fn(f));
 }
diff --git a/include/pybind11/operators.h b/include/pybind11/operators.h
index 2a61531589..7865d35e10 100644
--- a/include/pybind11/operators.h
+++ b/include/pybind11/operators.h
@@ -16,12 +16,50 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Enumeration with all supported operator types
 enum op_id : int {
-    op_add, op_sub, op_mul, op_div, op_mod, op_divmod, op_pow, op_lshift,
-    op_rshift, op_and, op_xor, op_or, op_neg, op_pos, op_abs, op_invert,
-    op_int, op_long, op_float, op_str, op_cmp, op_gt, op_ge, op_lt, op_le,
-    op_eq, op_ne, op_iadd, op_isub, op_imul, op_idiv, op_imod, op_ilshift,
-    op_irshift, op_iand, op_ixor, op_ior, op_complex, op_bool, op_nonzero,
-    op_repr, op_truediv, op_itruediv, op_hash
+    op_add,
+    op_sub,
+    op_mul,
+    op_div,
+    op_mod,
+    op_divmod,
+    op_pow,
+    op_lshift,
+    op_rshift,
+    op_and,
+    op_xor,
+    op_or,
+    op_neg,
+    op_pos,
+    op_abs,
+    op_invert,
+    op_int,
+    op_long,
+    op_float,
+    op_str,
+    op_cmp,
+    op_gt,
+    op_ge,
+    op_lt,
+    op_le,
+    op_eq,
+    op_ne,
+    op_iadd,
+    op_isub,
+    op_imul,
+    op_idiv,
+    op_imod,
+    op_ilshift,
+    op_irshift,
+    op_iand,
+    op_ixor,
+    op_ior,
+    op_complex,
+    op_bool,
+    op_nonzero,
+    op_repr,
+    op_truediv,
+    op_itruediv,
+    op_hash
 };
 
 enum op_type : int {
@@ -30,126 +68,145 @@ enum op_type : int {
     op_u  /* unary operator */
 };
 
-struct self_t { };
+struct self_t {};
 static const self_t self = self_t();
 
 /// Type for an unused type slot
-struct undefined_t { };
+struct undefined_t {};
 
 /// Don't warn about an unused variable
 inline self_t __self() { return self; }
 
 /// base template of operator implementations
-template <op_id, op_type, typename B, typename L, typename R> struct op_impl { };
+template <op_id, op_type, typename B, typename L, typename R>
+struct op_impl {};
 
 /// Operator implementation generator
-template <op_id id, op_type ot, typename L, typename R> struct op_ {
-    template <typename Class, typename... Extra> void execute(Class &cl, const Extra&... extra) const {
+template <op_id id, op_type ot, typename L, typename R>
+struct op_ {
+    template <typename Class, typename... Extra>
+    void execute(Class &cl, const Extra &...extra) const {
         using Base = typename Class::type;
         using L_type = conditional_t<std::is_same<L, self_t>::value, Base, L>;
         using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute, is_operator(), extra...);
-        #if PY_MAJOR_VERSION < 3
-        if (PYBIND11_SILENCE_MSVC_C4127(id == op_truediv) ||
-            PYBIND11_SILENCE_MSVC_C4127(id == op_itruediv))
-            cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
-                    &op::execute, is_operator(), extra...);
-        #endif
+#if PY_MAJOR_VERSION < 3
+        if (PYBIND11_SILENCE_MSVC_C4127(id == op_truediv)
+            || PYBIND11_SILENCE_MSVC_C4127(id == op_itruediv))
+            cl.def(id == op_itruediv ? "__idiv__"
+                   : ot == op_l      ? "__div__"
+                                     : "__rdiv__",
+                   &op::execute,
+                   is_operator(),
+                   extra...);
+#endif
     }
-    template <typename Class, typename... Extra> void execute_cast(Class &cl, const Extra&... extra) const {
+    template <typename Class, typename... Extra>
+    void execute_cast(Class &cl, const Extra &...extra) const {
         using Base = typename Class::type;
         using L_type = conditional_t<std::is_same<L, self_t>::value, Base, L>;
         using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute_cast, is_operator(), extra...);
-        #if PY_MAJOR_VERSION < 3
+#if PY_MAJOR_VERSION < 3
         if (id == op_truediv || id == op_itruediv)
-            cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
-                    &op::execute, is_operator(), extra...);
-        #endif
+            cl.def(id == op_itruediv ? "__idiv__"
+                   : ot == op_l      ? "__div__"
+                                     : "__rdiv__",
+                   &op::execute,
+                   is_operator(),
+                   extra...);
+#endif
     }
 };
 
-#define PYBIND11_BINARY_OPERATOR(id, rid, op, expr)                                    \
-template <typename B, typename L, typename R> struct op_impl<op_##id, op_l, B, L, R> { \
-    static char const* name() { return "__" #id "__"; }                                \
-    static auto execute(const L &l, const R &r) -> decltype(expr) { return (expr); }   \
-    static B execute_cast(const L &l, const R &r) { return B(expr); }                  \
-};                                                                                     \
-template <typename B, typename L, typename R> struct op_impl<op_##id, op_r, B, L, R> { \
-    static char const* name() { return "__" #rid "__"; }                               \
-    static auto execute(const R &r, const L &l) -> decltype(expr) { return (expr); }   \
-    static B execute_cast(const R &r, const L &l) { return B(expr); }                  \
-};                                                                                     \
-inline op_<op_##id, op_l, self_t, self_t> op(const self_t &, const self_t &) {         \
-    return op_<op_##id, op_l, self_t, self_t>();                                       \
-}                                                                                      \
-template <typename T> op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {    \
-    return op_<op_##id, op_l, self_t, T>();                                            \
-}                                                                                      \
-template <typename T> op_<op_##id, op_r, T, self_t> op(const T &, const self_t &) {    \
-    return op_<op_##id, op_r, T, self_t>();                                            \
-}
-
-#define PYBIND11_INPLACE_OPERATOR(id, op, expr)                                        \
-template <typename B, typename L, typename R> struct op_impl<op_##id, op_l, B, L, R> { \
-    static char const* name() { return "__" #id "__"; }                                \
-    static auto execute(L &l, const R &r) -> decltype(expr) { return expr; }           \
-    static B execute_cast(L &l, const R &r) { return B(expr); }                        \
-};                                                                                     \
-template <typename T> op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {    \
-    return op_<op_##id, op_l, self_t, T>();                                            \
-}
-
-#define PYBIND11_UNARY_OPERATOR(id, op, expr)                                          \
-template <typename B, typename L> struct op_impl<op_##id, op_u, B, L, undefined_t> {   \
-    static char const* name() { return "__" #id "__"; }                                \
-    static auto execute(const L &l) -> decltype(expr) { return expr; }                 \
-    static B execute_cast(const L &l) { return B(expr); }                              \
-};                                                                                     \
-inline op_<op_##id, op_u, self_t, undefined_t> op(const self_t &) {                    \
-    return op_<op_##id, op_u, self_t, undefined_t>();                                  \
-}
-
-PYBIND11_BINARY_OPERATOR(sub,       rsub,         operator-,    l - r)
-PYBIND11_BINARY_OPERATOR(add,       radd,         operator+,    l + r)
-PYBIND11_BINARY_OPERATOR(mul,       rmul,         operator*,    l * r)
-PYBIND11_BINARY_OPERATOR(truediv,   rtruediv,     operator/,    l / r)
-PYBIND11_BINARY_OPERATOR(mod,       rmod,         operator%,    l % r)
-PYBIND11_BINARY_OPERATOR(lshift,    rlshift,      operator<<,   l << r)
-PYBIND11_BINARY_OPERATOR(rshift,    rrshift,      operator>>,   l >> r)
-PYBIND11_BINARY_OPERATOR(and,       rand,         operator&,    l & r)
-PYBIND11_BINARY_OPERATOR(xor,       rxor,         operator^,    l ^ r)
-PYBIND11_BINARY_OPERATOR(eq,        eq,           operator==,   l == r)
-PYBIND11_BINARY_OPERATOR(ne,        ne,           operator!=,   l != r)
-PYBIND11_BINARY_OPERATOR(or,        ror,          operator|,    l | r)
-PYBIND11_BINARY_OPERATOR(gt,        lt,           operator>,    l > r)
-PYBIND11_BINARY_OPERATOR(ge,        le,           operator>=,   l >= r)
-PYBIND11_BINARY_OPERATOR(lt,        gt,           operator<,    l < r)
-PYBIND11_BINARY_OPERATOR(le,        ge,           operator<=,   l <= r)
-//PYBIND11_BINARY_OPERATOR(pow,       rpow,         pow,          std::pow(l,  r))
-PYBIND11_INPLACE_OPERATOR(iadd,     operator+=,   l += r)
-PYBIND11_INPLACE_OPERATOR(isub,     operator-=,   l -= r)
-PYBIND11_INPLACE_OPERATOR(imul,     operator*=,   l *= r)
-PYBIND11_INPLACE_OPERATOR(itruediv, operator/=,   l /= r)
-PYBIND11_INPLACE_OPERATOR(imod,     operator%=,   l %= r)
-PYBIND11_INPLACE_OPERATOR(ilshift,  operator<<=,  l <<= r)
-PYBIND11_INPLACE_OPERATOR(irshift,  operator>>=,  l >>= r)
-PYBIND11_INPLACE_OPERATOR(iand,     operator&=,   l &= r)
-PYBIND11_INPLACE_OPERATOR(ixor,     operator^=,   l ^= r)
-PYBIND11_INPLACE_OPERATOR(ior,      operator|=,   l |= r)
-PYBIND11_UNARY_OPERATOR(neg,        operator-,    -l)
-PYBIND11_UNARY_OPERATOR(pos,        operator+,    +l)
+#define PYBIND11_BINARY_OPERATOR(id, rid, op, expr)                                               \
+    template <typename B, typename L, typename R>                                                 \
+    struct op_impl<op_##id, op_l, B, L, R> {                                                      \
+        static char const *name() { return "__" #id "__"; }                                       \
+        static auto execute(const L &l, const R &r) -> decltype(expr) { return (expr); }          \
+        static B execute_cast(const L &l, const R &r) { return B(expr); }                         \
+    };                                                                                            \
+    template <typename B, typename L, typename R>                                                 \
+    struct op_impl<op_##id, op_r, B, L, R> {                                                      \
+        static char const *name() { return "__" #rid "__"; }                                      \
+        static auto execute(const R &r, const L &l) -> decltype(expr) { return (expr); }          \
+        static B execute_cast(const R &r, const L &l) { return B(expr); }                         \
+    };                                                                                            \
+    inline op_<op_##id, op_l, self_t, self_t> op(const self_t &, const self_t &) {                \
+        return op_<op_##id, op_l, self_t, self_t>();                                              \
+    }                                                                                             \
+    template <typename T>                                                                         \
+    op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {                                 \
+        return op_<op_##id, op_l, self_t, T>();                                                   \
+    }                                                                                             \
+    template <typename T>                                                                         \
+    op_<op_##id, op_r, T, self_t> op(const T &, const self_t &) {                                 \
+        return op_<op_##id, op_r, T, self_t>();                                                   \
+    }
+
+#define PYBIND11_INPLACE_OPERATOR(id, op, expr)                                                   \
+    template <typename B, typename L, typename R>                                                 \
+    struct op_impl<op_##id, op_l, B, L, R> {                                                      \
+        static char const *name() { return "__" #id "__"; }                                       \
+        static auto execute(L &l, const R &r) -> decltype(expr) { return expr; }                  \
+        static B execute_cast(L &l, const R &r) { return B(expr); }                               \
+    };                                                                                            \
+    template <typename T>                                                                         \
+    op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {                                 \
+        return op_<op_##id, op_l, self_t, T>();                                                   \
+    }
+
+#define PYBIND11_UNARY_OPERATOR(id, op, expr)                                                     \
+    template <typename B, typename L>                                                             \
+    struct op_impl<op_##id, op_u, B, L, undefined_t> {                                            \
+        static char const *name() { return "__" #id "__"; }                                       \
+        static auto execute(const L &l) -> decltype(expr) { return expr; }                        \
+        static B execute_cast(const L &l) { return B(expr); }                                     \
+    };                                                                                            \
+    inline op_<op_##id, op_u, self_t, undefined_t> op(const self_t &) {                           \
+        return op_<op_##id, op_u, self_t, undefined_t>();                                         \
+    }
+
+PYBIND11_BINARY_OPERATOR(sub, rsub, operator-, l - r)
+PYBIND11_BINARY_OPERATOR(add, radd, operator+, l + r)
+PYBIND11_BINARY_OPERATOR(mul, rmul, operator*, l *r)
+PYBIND11_BINARY_OPERATOR(truediv, rtruediv, operator/, l / r)
+PYBIND11_BINARY_OPERATOR(mod, rmod, operator%, l % r)
+PYBIND11_BINARY_OPERATOR(lshift, rlshift, operator<<, l << r)
+PYBIND11_BINARY_OPERATOR(rshift, rrshift, operator>>, l >> r)
+PYBIND11_BINARY_OPERATOR(and, rand, operator&, l &r)
+PYBIND11_BINARY_OPERATOR(xor, rxor, operator^, l ^ r)
+PYBIND11_BINARY_OPERATOR(eq, eq, operator==, l == r)
+PYBIND11_BINARY_OPERATOR(ne, ne, operator!=, l != r)
+PYBIND11_BINARY_OPERATOR(or, ror, operator|, l | r)
+PYBIND11_BINARY_OPERATOR(gt, lt, operator>, l > r)
+PYBIND11_BINARY_OPERATOR(ge, le, operator>=, l >= r)
+PYBIND11_BINARY_OPERATOR(lt, gt, operator<, l < r)
+PYBIND11_BINARY_OPERATOR(le, ge, operator<=, l <= r)
+// PYBIND11_BINARY_OPERATOR(pow,       rpow,         pow,          std::pow(l,  r))
+PYBIND11_INPLACE_OPERATOR(iadd, operator+=, l += r)
+PYBIND11_INPLACE_OPERATOR(isub, operator-=, l -= r)
+PYBIND11_INPLACE_OPERATOR(imul, operator*=, l *= r)
+PYBIND11_INPLACE_OPERATOR(itruediv, operator/=, l /= r)
+PYBIND11_INPLACE_OPERATOR(imod, operator%=, l %= r)
+PYBIND11_INPLACE_OPERATOR(ilshift, operator<<=, l <<= r)
+PYBIND11_INPLACE_OPERATOR(irshift, operator>>=, l >>= r)
+PYBIND11_INPLACE_OPERATOR(iand, operator&=, l &= r)
+PYBIND11_INPLACE_OPERATOR(ixor, operator^=, l ^= r)
+PYBIND11_INPLACE_OPERATOR(ior, operator|=, l |= r)
+PYBIND11_UNARY_OPERATOR(neg, operator-, -l)
+PYBIND11_UNARY_OPERATOR(pos, operator+, +l)
 // WARNING: This usage of `abs` should only be done for existing STL overloads.
 // Adding overloads directly in to the `std::` namespace is advised against:
 // https://en.cppreference.com/w/cpp/language/extending_std
-PYBIND11_UNARY_OPERATOR(abs,        abs,          std::abs(l))
-PYBIND11_UNARY_OPERATOR(hash,       hash,         std::hash<L>()(l))
-PYBIND11_UNARY_OPERATOR(invert,     operator~,    (~l))
-PYBIND11_UNARY_OPERATOR(bool,       operator!,    !!l)
-PYBIND11_UNARY_OPERATOR(int,        int_,         (int) l)
-PYBIND11_UNARY_OPERATOR(float,      float_,       (double) l)
+PYBIND11_UNARY_OPERATOR(abs, abs, std::abs(l))
+PYBIND11_UNARY_OPERATOR(hash, hash, std::hash<L>()(l))
+PYBIND11_UNARY_OPERATOR(invert, operator~, (~l))
+PYBIND11_UNARY_OPERATOR(bool, operator!, !!l)
+PYBIND11_UNARY_OPERATOR(int, int_, (int) l)
+PYBIND11_UNARY_OPERATOR(float, float_, (double) l)
 
 #undef PYBIND11_BINARY_OPERATOR
 #undef PYBIND11_INPLACE_OPERATOR
diff --git a/include/pybind11/options.h b/include/pybind11/options.h
index 810e5e0104..1e493bdcc4 100644
--- a/include/pybind11/options.h
+++ b/include/pybind11/options.h
@@ -15,44 +15,54 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 class options {
 public:
-
     // Default RAII constructor, which leaves settings as they currently are.
     options() : previous_state(global_state()) {}
 
     // Class is non-copyable.
-    options(const options&) = delete;
-    options& operator=(const options&) = delete;
+    options(const options &) = delete;
+    options &operator=(const options &) = delete;
 
     // Destructor, which restores settings that were in effect before.
-    ~options() {
-        global_state() = previous_state;
-    }
+    ~options() { global_state() = previous_state; }
 
     // Setter methods (affect the global state):
 
-    options& disable_user_defined_docstrings() & { global_state().show_user_defined_docstrings = false; return *this; }
+    options &disable_user_defined_docstrings() & {
+        global_state().show_user_defined_docstrings = false;
+        return *this;
+    }
 
-    options& enable_user_defined_docstrings() & { global_state().show_user_defined_docstrings = true; return *this; }
+    options &enable_user_defined_docstrings() & {
+        global_state().show_user_defined_docstrings = true;
+        return *this;
+    }
 
-    options& disable_function_signatures() & { global_state().show_function_signatures = false; return *this; }
+    options &disable_function_signatures() & {
+        global_state().show_function_signatures = false;
+        return *this;
+    }
 
-    options& enable_function_signatures() & { global_state().show_function_signatures = true; return *this; }
+    options &enable_function_signatures() & {
+        global_state().show_function_signatures = true;
+        return *this;
+    }
 
     // Getter methods (return the global state):
 
-    static bool show_user_defined_docstrings() { return global_state().show_user_defined_docstrings; }
+    static bool show_user_defined_docstrings() {
+        return global_state().show_user_defined_docstrings;
+    }
 
     static bool show_function_signatures() { return global_state().show_function_signatures; }
 
     // This type is not meant to be allocated on the heap.
-    void* operator new(size_t) = delete;
+    void *operator new(size_t) = delete;
 
 private:
-
     struct state {
-        bool show_user_defined_docstrings = true;  //< Include user-supplied texts in docstrings.
-        bool show_function_signatures = true;      //< Include auto-generated function signatures
-                                                   //  in docstrings.
+        bool show_user_defined_docstrings = true; //< Include user-supplied texts in docstrings.
+        bool show_function_signatures = true;     //< Include auto-generated function signatures
+                                                  //  in docstrings.
     };
 
     static state &global_state() {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 754f22e9b7..b95f31a60e 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,30 +10,29 @@
 
 #pragma once
 
+#include "detail/class.h"
+#include "detail/init.h"
 #include "attr.h"
 #include "gil.h"
 #include "options.h"
-#include "detail/class.h"
-#include "detail/init.h"
 
 #include <cstdlib>
+#include <cstring>
 #include <memory>
 #include <new>
-#include <vector>
 #include <string>
 #include <utility>
-
-#include <cstring>
+#include <vector>
 
 #if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
-#  define PYBIND11_STD_LAUNDER std::launder
-#  define PYBIND11_HAS_STD_LAUNDER 1
+#    define PYBIND11_STD_LAUNDER std::launder
+#    define PYBIND11_HAS_STD_LAUNDER 1
 #else
-#  define PYBIND11_STD_LAUNDER
-#  define PYBIND11_HAS_STD_LAUNDER 0
+#    define PYBIND11_STD_LAUNDER
+#    define PYBIND11_HAS_STD_LAUNDER 0
 #endif
 #if defined(__GNUG__) && !defined(__clang__)
-#  include <cxxabi.h>
+#    include <cxxabi.h>
 #endif
 
 /* https://stackoverflow.com/questions/46798456/handling-gccs-noexcept-type-warning
@@ -56,7 +55,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // Return true if one of the translators completed without raising an exception
 // itself. Return of false indicates that if there are other translators
 // available, they should be tried.
-inline bool apply_exception_translators(std::forward_list<ExceptionTranslator>& translators) {
+inline bool apply_exception_translators(std::forward_list<ExceptionTranslator> &translators) {
     auto last_exception = std::current_exception();
 
     for (auto &translator : translators) {
@@ -83,30 +82,33 @@ class cpp_function : public function {
 public:
     cpp_function() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(std::nullptr_t) { }
+    cpp_function(std::nullptr_t) {}
 
     /// Construct a cpp_function from a vanilla function pointer
     template <typename Return, typename... Args, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (*f)(Args...), const Extra&... extra) {
+    cpp_function(Return (*f)(Args...), const Extra &...extra) {
         initialize(f, f, extra...);
     }
 
     /// Construct a cpp_function from a lambda function (possibly with internal state)
-    template <typename Func, typename... Extra,
+    template <typename Func,
+              typename... Extra,
               typename = detail::enable_if_t<detail::is_lambda<Func>::value>>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Func &&f, const Extra&... extra) {
-        initialize(std::forward<Func>(f),
-                   (detail::function_signature_t<Func> *) nullptr, extra...);
+    cpp_function(Func &&f, const Extra &...extra) {
+        initialize(
+            std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr, extra...);
     }
 
     /// Construct a cpp_function from a class method (non-const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...), const Extra&... extra) {
-        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*) (Class *, Arg...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...), const Extra &...extra) {
+        initialize(
+            [f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+            (Return(*)(Class *, Arg...)) nullptr,
+            extra...);
     }
 
     /// Construct a cpp_function from a class method (non-const, lvalue ref-qualifier)
@@ -114,17 +116,21 @@ class cpp_function : public function {
     /// but with an added `&`.
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...)&, const Extra&... extra) {
-        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*) (Class *, Arg...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...) &, const Extra &...extra) {
+        initialize(
+            [f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+            (Return(*)(Class *, Arg...)) nullptr,
+            extra...);
     }
 
     /// Construct a cpp_function from a class method (const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...) const, const Extra&... extra) {
-        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*)(const Class *, Arg ...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...) const, const Extra &...extra) {
+        initialize([f](const Class *c,
+                       Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+                   (Return(*)(const Class *, Arg...)) nullptr,
+                   extra...);
     }
 
     /// Construct a cpp_function from a class method (const, lvalue ref-qualifier)
@@ -132,9 +138,11 @@ class cpp_function : public function {
     /// but with an added `&`.
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...) const&, const Extra&... extra) {
-        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*)(const Class *, Arg ...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...) const &, const Extra &...extra) {
+        initialize([f](const Class *c,
+                       Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+                   (Return(*)(const Class *, Arg...)) nullptr,
+                   extra...);
     }
 
     /// Return the function name
@@ -144,9 +152,10 @@ class cpp_function : public function {
     struct InitializingFunctionRecordDeleter {
         // `destruct(function_record, false)`: `initialize_generic` copies strings and
         // takes care of cleaning up in case of exceptions. So pass `false` to `free_strings`.
-        void operator()(detail::function_record * rec) { destruct(rec, false); }
+        void operator()(detail::function_record *rec) { destruct(rec, false); }
     };
-    using unique_function_record = std::unique_ptr<detail::function_record, InitializingFunctionRecordDeleter>;
+    using unique_function_record
+        = std::unique_ptr<detail::function_record, InitializingFunctionRecordDeleter>;
 
     /// Space optimization: don't inline this frequently instantiated fragment
     PYBIND11_NOINLINE unique_function_record make_function_record() {
@@ -155,11 +164,14 @@ class cpp_function : public function {
 
     /// Special internal constructor for functors, lambda functions, etc.
     template <typename Func, typename Return, typename... Args, typename... Extra>
-    void initialize(Func &&f, Return (*)(Args...), const Extra&... extra) {
+    void initialize(Func &&f, Return (*)(Args...), const Extra &...extra) {
         using namespace detail;
-        struct capture { remove_reference_t<Func> f; };
+        struct capture {
+            remove_reference_t<Func> f;
+        };
 
-        /* Store the function including any extra state it might have (e.g. a lambda capture object) */
+        /* Store the function including any extra state it might have (e.g. a lambda capture
+         * object) */
         // The unique_ptr makes sure nothing is leaked in case of an exception.
         auto unique_rec = make_function_record();
         auto *rec = unique_rec.get();
@@ -170,16 +182,16 @@ class cpp_function : public function {
                enough space to use the placement new operator. However, the
                'if' statement above ensures that this is the case. */
 #if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wplacement-new"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wplacement-new"
 #endif
-            new ((capture *) &rec->data) capture { std::forward<Func>(f) };
+            new ((capture *) &rec->data) capture{std::forward<Func>(f)};
 #if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
 #if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wstrict-aliasing"
 #endif
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
@@ -191,21 +203,22 @@ class cpp_function : public function {
                 };
             }
 #if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
         } else {
-            rec->data[0] = new capture { std::forward<Func>(f) };
+            rec->data[0] = new capture{std::forward<Func>(f)};
             rec->free_data = [](function_record *r) { delete ((capture *) r->data[0]); };
         }
 
         /* Type casters for the function arguments and return value */
         using cast_in = argument_loader<Args...>;
-        using cast_out = make_caster<
-            conditional_t<std::is_void<Return>::value, void_type, Return>
-        >;
+        using cast_out
+            = make_caster<conditional_t<std::is_void<Return>::value, void_type, Return>>;
 
-        static_assert(expected_num_args<Extra...>(sizeof...(Args), cast_in::args_pos >= 0, cast_in::has_kwargs),
-                      "The number of argument annotations does not match the number of function arguments");
+        static_assert(
+            expected_num_args<Extra...>(
+                sizeof...(Args), cast_in::args_pos >= 0, cast_in::has_kwargs),
+            "The number of argument annotations does not match the number of function arguments");
 
         /* Dispatch code which converts function arguments and performs the actual function call */
         rec->impl = [](function_call &call) -> handle {
@@ -225,14 +238,17 @@ class cpp_function : public function {
             auto *cap = const_cast<capture *>(reinterpret_cast<const capture *>(data));
 
             /* Override policy for rvalues -- usually to enforce rvp::move on an rvalue */
-            return_value_policy policy = return_value_policy_override<Return>::policy(call.func.policy);
+            return_value_policy policy
+                = return_value_policy_override<Return>::policy(call.func.policy);
 
             /* Function scope guard -- defaults to the compile-to-nothing `void_type` */
             using Guard = extract_guard_t<Extra...>;
 
             /* Perform the function call */
-            handle result = cast_out::cast(
-                std::move(args_converter).template call<Return, Guard>(cap->f), policy, call.parent);
+            handle result
+                = cast_out::cast(std::move(args_converter).template call<Return, Guard>(cap->f),
+                                 policy,
+                                 call.parent);
 
             /* Invoke call policy post-call hook */
             process_attributes<Extra...>::postcall(call, result);
@@ -241,9 +257,9 @@ class cpp_function : public function {
         };
 
         rec->nargs_pos = cast_in::args_pos >= 0
-            ? static_cast<std::uint16_t>(cast_in::args_pos)
-            : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if
-                                                     // we have a kw_only
+                             ? static_cast<std::uint16_t>(cast_in::args_pos)
+                             : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if
+                                                                      // we have a kw_only
         rec->has_args = cast_in::args_pos >= 0;
         rec->has_kwargs = cast_in::has_kwargs;
 
@@ -254,19 +270,26 @@ class cpp_function : public function {
             constexpr bool has_kw_only_args = any_of<std::is_same<kw_only, Extra>...>::value,
                            has_pos_only_args = any_of<std::is_same<pos_only, Extra>...>::value,
                            has_arg_annotations = any_of<is_keyword<Extra>...>::value;
-            static_assert(has_arg_annotations || !has_kw_only_args, "py::kw_only requires the use of argument annotations");
-            static_assert(has_arg_annotations || !has_pos_only_args, "py::pos_only requires the use of argument annotations (for docstrings and aligning the annotations to the argument)");
-
-            static_assert(constexpr_sum(is_kw_only<Extra>::value...) <= 1, "py::kw_only may be specified only once");
-            static_assert(constexpr_sum(is_pos_only<Extra>::value...) <= 1, "py::pos_only may be specified only once");
+            static_assert(has_arg_annotations || !has_kw_only_args,
+                          "py::kw_only requires the use of argument annotations");
+            static_assert(has_arg_annotations || !has_pos_only_args,
+                          "py::pos_only requires the use of argument annotations (for docstrings "
+                          "and aligning the annotations to the argument)");
+
+            static_assert(constexpr_sum(is_kw_only<Extra>::value...) <= 1,
+                          "py::kw_only may be specified only once");
+            static_assert(constexpr_sum(is_pos_only<Extra>::value...) <= 1,
+                          "py::pos_only may be specified only once");
             constexpr auto kw_only_pos = constexpr_first<is_kw_only, Extra...>();
             constexpr auto pos_only_pos = constexpr_first<is_pos_only, Extra...>();
-            static_assert(!(has_kw_only_args && has_pos_only_args) || pos_only_pos < kw_only_pos, "py::pos_only must come before py::kw_only");
+            static_assert(!(has_kw_only_args && has_pos_only_args) || pos_only_pos < kw_only_pos,
+                          "py::pos_only must come before py::kw_only");
         }
 
         /* Generate a readable signature describing the function's arguments and return
            value types */
-        static constexpr auto signature = const_name("(") + cast_in::arg_names + const_name(") -> ") + cast_out::name;
+        static constexpr auto signature
+            = const_name("(") + cast_in::arg_names + const_name(") -> ") + cast_out::name;
         PYBIND11_DESCR_CONSTEXPR auto types = decltype(signature)::types();
 
         /* Register the function with Python from generic (non-templated) code */
@@ -275,17 +298,18 @@ class cpp_function : public function {
 
         /* Stash some additional information used by an important optimization in 'functional.h' */
         using FunctionType = Return (*)(Args...);
-        constexpr bool is_function_ptr =
-            std::is_convertible<Func, FunctionType>::value &&
-            sizeof(capture) == sizeof(void *);
+        constexpr bool is_function_ptr
+            = std::is_convertible<Func, FunctionType>::value && sizeof(capture) == sizeof(void *);
         if (is_function_ptr) {
             rec->is_stateless = true;
-            rec->data[1] = const_cast<void *>(reinterpret_cast<const void *>(&typeid(FunctionType)));
+            rec->data[1]
+                = const_cast<void *>(reinterpret_cast<const void *>(&typeid(FunctionType)));
         }
     }
 
-    // Utility class that keeps track of all duplicated strings, and cleans them up in its destructor,
-    // unless they are released. Basically a RAII-solution to deal with exceptions along the way.
+    // Utility class that keeps track of all duplicated strings, and cleans them up in its
+    // destructor, unless they are released. Basically a RAII-solution to deal with exceptions
+    // along the way.
     class strdup_guard {
     public:
         ~strdup_guard() {
@@ -298,26 +322,29 @@ class cpp_function : public function {
             strings.push_back(t);
             return t;
         }
-        void release() {
-            strings.clear();
-        }
+        void release() { strings.clear(); }
+
     private:
         std::vector<char *> strings;
     };
 
     /// Register a function call with Python (generic non-templated code goes here)
-    void initialize_generic(unique_function_record &&unique_rec, const char *text,
-                            const std::type_info *const *types, size_t args) {
+    void initialize_generic(unique_function_record &&unique_rec,
+                            const char *text,
+                            const std::type_info *const *types,
+                            size_t args) {
         // Do NOT receive `unique_rec` by value. If this function fails to move out the unique_ptr,
-        // we do not want this to destuct the pointer. `initialize` (the caller) still relies on the
-        // pointee being alive after this call. Only move out if a `capsule` is going to keep it alive.
+        // we do not want this to destuct the pointer. `initialize` (the caller) still relies on
+        // the pointee being alive after this call. Only move out if a `capsule` is going to keep
+        // it alive.
         auto *rec = unique_rec.get();
 
         // Keep track of strdup'ed strings, and clean them up as long as the function's capsule
         // has not taken ownership yet (when `unique_rec.release()` is called).
-        // Note: This cannot easily be fixed by a `unique_ptr` with custom deleter, because the strings
-        // are only referenced before strdup'ing. So only *after* the following block could `destruct`
-        // safely be called, but even then, `repr` could still throw in the middle of copying all strings.
+        // Note: This cannot easily be fixed by a `unique_ptr` with custom deleter, because the
+        // strings are only referenced before strdup'ing. So only *after* the following block could
+        // `destruct` safely be called, but even then, `repr` could still throw in the middle of
+        // copying all strings.
         strdup_guard guarded_strdup;
 
         /* Create copies of all referenced C-style strings */
@@ -325,7 +352,7 @@ class cpp_function : public function {
         if (rec->doc) {
             rec->doc = guarded_strdup(rec->doc);
         }
-        for (auto &a: rec->args) {
+        for (auto &a : rec->args) {
             if (a.name) {
                 a.name = guarded_strdup(a.name);
             }
@@ -341,15 +368,19 @@ class cpp_function : public function {
 
 #if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
-            const auto class_name = detail::get_fully_qualified_tp_name((PyTypeObject *) rec->scope.ptr());
+            const auto class_name
+                = detail::get_fully_qualified_tp_name((PyTypeObject *) rec->scope.ptr());
             const auto func_name = std::string(rec->name);
-            PyErr_WarnEx(
-                PyExc_FutureWarning,
-                ("pybind11-bound class '" + class_name + "' is using an old-style "
-                 "placement-new '" + func_name + "' which has been deprecated. See "
-                 "the upgrade guide in pybind11's docs. This message is only visible "
-                 "when compiled in debug mode.").c_str(), 0
-            );
+            PyErr_WarnEx(PyExc_FutureWarning,
+                         ("pybind11-bound class '" + class_name
+                          + "' is using an old-style "
+                            "placement-new '"
+                          + func_name
+                          + "' which has been deprecated. See "
+                            "the upgrade guide in pybind11's docs. This message is only visible "
+                            "when compiled in debug mode.")
+                             .c_str(),
+                         0);
         }
 #endif
 
@@ -400,16 +431,14 @@ class cpp_function : public function {
                 }
                 if (auto *tinfo = detail::get_type_info(*t)) {
                     handle th((PyObject *) tinfo->type);
-                    signature +=
-                        th.attr("__module__").cast<std::string>() + "." +
-                        // Python 3.3+, but we backport it to earlier versions
-                        th.attr("__qualname__").cast<std::string>();
+                    signature += th.attr("__module__").cast<std::string>() + "." +
+                                 // Python 3.3+, but we backport it to earlier versions
+                                 th.attr("__qualname__").cast<std::string>();
                 } else if (rec->is_new_style_constructor && arg_index == 0) {
                     // A new-style `__init__` takes `self` as `value_and_holder`.
                     // Rewrite it to the proper class type.
-                    signature +=
-                        rec->scope.attr("__module__").cast<std::string>() + "." +
-                        rec->scope.attr("__qualname__").cast<std::string>();
+                    signature += rec->scope.attr("__module__").cast<std::string>() + "."
+                                 + rec->scope.attr("__qualname__").cast<std::string>();
                 } else {
                     std::string tname(t->name());
                     detail::clean_type_id(tname);
@@ -445,7 +474,8 @@ class cpp_function : public function {
         if (rec->sibling) {
             if (PyCFunction_Check(rec->sibling.ptr())) {
                 auto *self = PyCFunction_GET_SELF(rec->sibling.ptr());
-                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self) : capsule(self);
+                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self)
+                                                                : capsule(self);
                 chain = (detail::function_record *) rec_capsule;
                 /* Never append a method to an overload chain of a parent class;
                    instead, hide the parent's overloads in this case */
@@ -470,9 +500,8 @@ class cpp_function : public function {
                 = reinterpret_cast<PyCFunction>(reinterpret_cast<void (*)()>(dispatcher));
             rec->def->ml_flags = METH_VARARGS | METH_KEYWORDS;
 
-            capsule rec_capsule(unique_rec.release(), [](void *ptr) {
-                destruct((detail::function_record *) ptr);
-            });
+            capsule rec_capsule(unique_rec.release(),
+                                [](void *ptr) { destruct((detail::function_record *) ptr); });
             guarded_strdup.release();
 
             object scope_module;
@@ -497,12 +526,12 @@ class cpp_function : public function {
                     "overloading a method with both static and instance methods is not supported; "
 #if defined(NDEBUG)
                     "compile in debug mode for more details"
-                    #else
+#else
                     "error while attempting to bind "
                     + std::string(rec->is_method ? "instance" : "static") + " method "
                     + std::string(pybind11::str(rec->scope.attr("__name__"))) + "."
                     + std::string(rec->name) + signature
-                    #endif
+#endif
                 );
             }
 
@@ -512,7 +541,8 @@ class cpp_function : public function {
                 // chain.
                 chain_start = rec;
                 rec->next = chain;
-                auto rec_capsule = reinterpret_borrow<capsule>(((PyCFunctionObject *) m_ptr)->m_self);
+                auto rec_capsule
+                    = reinterpret_borrow<capsule>(((PyCFunctionObject *) m_ptr)->m_self);
                 rec_capsule.set_pointer(unique_rec.release());
                 guarded_strdup.release();
             } else {
@@ -551,8 +581,8 @@ class cpp_function : public function {
                 signatures += "\n";
             }
             if (it->doc && it->doc[0] != '\0' && options::show_user_defined_docstrings()) {
-                // If we're appending another docstring, and aren't printing function signatures, we
-                // need to append a newline first:
+                // If we're appending another docstring, and aren't printing function signatures,
+                // we need to append a newline first:
                 if (!options::show_function_signatures()) {
                     if (first_user_def) {
                         first_user_def = false;
@@ -589,11 +619,11 @@ class cpp_function : public function {
 
     /// When a cpp_function is GCed, release any memory allocated by pybind11
     static void destruct(detail::function_record *rec, bool free_strings = true) {
-        // If on Python 3.9, check the interpreter "MICRO" (patch) version.
-        // If this is running on 3.9.0, we have to work around a bug.
-        #if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
-            static bool is_zero = Py_GetVersion()[4] == '0';
-        #endif
+// If on Python 3.9, check the interpreter "MICRO" (patch) version.
+// If this is running on 3.9.0, we have to work around a bug.
+#if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
+        static bool is_zero = Py_GetVersion()[4] == '0';
+#endif
 
         while (rec) {
             detail::function_record *next = rec->next;
@@ -607,7 +637,7 @@ class cpp_function : public function {
                 std::free((char *) rec->name);
                 std::free((char *) rec->doc);
                 std::free((char *) rec->signature);
-                for (auto &arg: rec->args) {
+                for (auto &arg : rec->args) {
                     std::free(const_cast<char *>(arg.name));
                     std::free(const_cast<char *>(arg.descr));
                 }
@@ -617,23 +647,22 @@ class cpp_function : public function {
             }
             if (rec->def) {
                 std::free(const_cast<char *>(rec->def->ml_doc));
-                // Python 3.9.0 decref's these in the wrong order; rec->def
-                // If loaded on 3.9.0, let these leak (use Python 3.9.1 at runtime to fix)
-                // See https://github.com/python/cpython/pull/22670
-                #if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
+// Python 3.9.0 decref's these in the wrong order; rec->def
+// If loaded on 3.9.0, let these leak (use Python 3.9.1 at runtime to fix)
+// See https://github.com/python/cpython/pull/22670
+#if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
                 if (!is_zero) {
                     delete rec->def;
                 }
 #else
-                    delete rec->def;
-                #endif
+                delete rec->def;
+#endif
             }
             delete rec;
             rec = next;
         }
     }
 
-
     /// Main dispatch logic for calls to functions bound using pybind11
     static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) {
         using namespace detail;
@@ -651,8 +680,11 @@ class cpp_function : public function {
 
         auto self_value_and_holder = value_and_holder();
         if (overloads->is_constructor) {
-            if (!parent || !PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
-                PyErr_SetString(PyExc_TypeError, "__init__(self, ...) called with invalid or missing `self` argument");
+            if (!parent
+                || !PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
+                PyErr_SetString(
+                    PyExc_TypeError,
+                    "__init__(self, ...) called with invalid or missing `self` argument");
                 return nullptr;
             }
 
@@ -683,23 +715,23 @@ class cpp_function : public function {
                    1. Copy all positional arguments we were given, also checking to make sure that
                       named positional arguments weren't *also* specified via kwarg.
                    2. If we weren't given enough, try to make up the omitted ones by checking
-                      whether they were provided by a kwarg matching the `py::arg("name")` name.  If
+                      whether they were provided by a kwarg matching the `py::arg("name")` name. If
                       so, use it (and remove it from kwargs); if not, see if the function binding
                       provided a default that we can use.
-                   3. Ensure that either all keyword arguments were "consumed", or that the function
-                      takes a kwargs argument to accept unconsumed kwargs.
+                   3. Ensure that either all keyword arguments were "consumed", or that the
+                   function takes a kwargs argument to accept unconsumed kwargs.
                    4. Any positional arguments still left get put into a tuple (for args), and any
                       leftover kwargs get put into a dict.
                    5. Pack everything into a vector; if we have py::args or py::kwargs, they are an
                       extra tuple or dict at the end of the positional arguments.
                    6. Call the function call dispatcher (function_record::impl)
 
-                   If one of these fail, move on to the next overload and keep trying until we get a
-                   result other than PYBIND11_TRY_NEXT_OVERLOAD.
+                   If one of these fail, move on to the next overload and keep trying until we get
+                   a result other than PYBIND11_TRY_NEXT_OVERLOAD.
                  */
 
                 const function_record &func = *it;
-                size_t num_args = func.nargs;    // Number of positional arguments that we need
+                size_t num_args = func.nargs; // Number of positional arguments that we need
                 if (func.has_args) {
                     --num_args; // (but don't count py::args
                 }
@@ -740,8 +772,10 @@ class cpp_function : public function {
                 // 1. Copy any position arguments given.
                 bool bad_arg = false;
                 for (; args_copied < args_to_copy; ++args_copied) {
-                    const argument_record *arg_rec = args_copied < func.args.size() ? &func.args[args_copied] : nullptr;
-                    if (kwargs_in && arg_rec && arg_rec->name && dict_getitemstring(kwargs_in, arg_rec->name)) {
+                    const argument_record *arg_rec
+                        = args_copied < func.args.size() ? &func.args[args_copied] : nullptr;
+                    if (kwargs_in && arg_rec && arg_rec->name
+                        && dict_getitemstring(kwargs_in, arg_rec->name)) {
                         bad_arg = true;
                         break;
                     }
@@ -817,7 +851,8 @@ class cpp_function : public function {
                         }
 
                         if (value) {
-                            // If we're at the py::args index then first insert a stub for it to be replaced later
+                            // If we're at the py::args index then first insert a stub for it to be
+                            // replaced later
                             if (func.has_args && call.args.size() == func.nargs_pos) {
                                 call.args.push_back(none());
                             }
@@ -875,11 +910,12 @@ class cpp_function : public function {
                     call.kwargs_ref = std::move(kwargs);
                 }
 
-                // 5. Put everything in a vector.  Not technically step 5, we've been building it
-                // in `call.args` all along.
-                #if !defined(NDEBUG)
+// 5. Put everything in a vector.  Not technically step 5, we've been building it
+// in `call.args` all along.
+#if !defined(NDEBUG)
                 if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs) {
-                    pybind11_fail("Internal error: function call dispatcher inserted wrong number of arguments!");
+                    pybind11_fail("Internal error: function call dispatcher inserted wrong number "
+                                  "of arguments!");
                 }
 #endif
 
@@ -921,7 +957,8 @@ class cpp_function : public function {
             }
 
             if (overloaded && !second_pass.empty() && result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) {
-                // The no-conversion pass finished without success, try again with conversion allowed
+                // The no-conversion pass finished without success, try again with conversion
+                // allowed
                 for (auto &call : second_pass) {
                     try {
                         loader_life_support guard{};
@@ -944,7 +981,7 @@ class cpp_function : public function {
             e.restore();
             return nullptr;
 #ifdef __GLIBCXX__
-        } catch ( abi::__forced_unwind& ) {
+        } catch (abi::__forced_unwind &) {
             throw;
 #endif
         } catch (...) {
@@ -964,7 +1001,8 @@ class cpp_function : public function {
                 - delegate translation to the next translator by throwing a new type of exception.
              */
 
-            auto &local_exception_translators = get_local_internals().registered_exception_translators;
+            auto &local_exception_translators
+                = get_local_internals().registered_exception_translators;
             if (detail::apply_exception_translators(local_exception_translators)) {
                 return nullptr;
             }
@@ -973,7 +1011,8 @@ class cpp_function : public function {
                 return nullptr;
             }
 
-            PyErr_SetString(PyExc_SystemError, "Exception escaped from default exception translator!");
+            PyErr_SetString(PyExc_SystemError,
+                            "Exception escaped from default exception translator!");
             return nullptr;
         }
 
@@ -992,17 +1031,18 @@ class cpp_function : public function {
                 return handle(Py_NotImplemented).inc_ref().ptr();
             }
 
-            std::string msg = std::string(overloads->name) + "(): incompatible " +
-                std::string(overloads->is_constructor ? "constructor" : "function") +
-                " arguments. The following argument types are supported:\n";
+            std::string msg = std::string(overloads->name) + "(): incompatible "
+                              + std::string(overloads->is_constructor ? "constructor" : "function")
+                              + " arguments. The following argument types are supported:\n";
 
             int ctr = 0;
             for (const function_record *it2 = overloads; it2 != nullptr; it2 = it2->next) {
-                msg += "    "+ std::to_string(++ctr) + ". ";
+                msg += "    " + std::to_string(++ctr) + ". ";
 
                 bool wrote_sig = false;
                 if (overloads->is_constructor) {
-                    // For a constructor, rewrite `(self: Object, arg0, ...) -> NoneType` as `Object(arg0, ...)`
+                    // For a constructor, rewrite `(self: Object, arg0, ...) -> NoneType` as
+                    // `Object(arg0, ...)`
                     std::string sig = it2->signature;
                     size_t start = sig.find('(') + 7; // skip "(self: "
                     if (start < sig.size()) {
@@ -1038,7 +1078,7 @@ class cpp_function : public function {
                 }
                 try {
                     msg += pybind11::repr(args_[ti]);
-                } catch (const error_already_set&) {
+                } catch (const error_already_set &) {
                     msg += "<repr raised Error>";
                 }
             }
@@ -1059,7 +1099,7 @@ class cpp_function : public function {
                         msg += pybind11::str("{}=").format(kwarg.first);
                         try {
                             msg += pybind11::repr(kwarg.second);
-                        } catch (const error_already_set&) {
+                        } catch (const error_already_set &) {
                             msg += "<repr raised Error>";
                         }
                     }
@@ -1101,7 +1141,6 @@ class cpp_function : public function {
     }
 };
 
-
 /// Wrapper for Python extension modules
 class module_ : public object {
 public:
@@ -1123,11 +1162,15 @@ class module_ : public object {
         details on the ``Extra&& ... extra`` argument, see section :ref:`extras`.
     \endrst */
     template <typename Func, typename... Extra>
-    module_ &def(const char *name_, Func &&f, const Extra& ... extra) {
-        cpp_function func(std::forward<Func>(f), name(name_), scope(*this),
-                          sibling(getattr(*this, name_, none())), extra...);
+    module_ &def(const char *name_, Func &&f, const Extra &...extra) {
+        cpp_function func(std::forward<Func>(f),
+                          name(name_),
+                          scope(*this),
+                          sibling(getattr(*this, name_, none())),
+                          extra...);
         // NB: allow overwriting here because cpp_function sets up a chain with the intention of
-        // overwriting (and has already checked internally that it isn't overwriting non-functions).
+        // overwriting (and has already checked internally that it isn't overwriting
+        // non-functions).
         add_object(name_, func, true /* overwrite */);
         return *this;
     }
@@ -1143,8 +1186,8 @@ class module_ : public object {
             py::module_ m3 = m2.def_submodule("subsub", "A submodule of 'example.sub'");
     \endrst */
     module_ def_submodule(const char *name, const char *doc = nullptr) {
-        std::string full_name = std::string(PyModule_GetName(m_ptr))
-            + std::string(".") + std::string(name);
+        std::string full_name
+            = std::string(PyModule_GetName(m_ptr)) + std::string(".") + std::string(name);
         auto result = reinterpret_borrow<module_>(PyImport_AddModule(full_name.c_str()));
         if (doc && options::show_user_defined_docstrings()) {
             result.attr("__doc__") = pybind11::str(doc);
@@ -1204,22 +1247,22 @@ class module_ : public object {
 #if PY_MAJOR_VERSION >= 3
         // module_def is PyModuleDef
         // Placement new (not an allocation).
-        def = new (def) PyModuleDef {
-            /* m_base */     PyModuleDef_HEAD_INIT,
-            /* m_name */     name,
-            /* m_doc */      options::show_user_defined_docstrings() ? doc : nullptr,
-            /* m_size */     -1,
-            /* m_methods */  nullptr,
-            /* m_slots */    nullptr,
-            /* m_traverse */ nullptr,
-            /* m_clear */    nullptr,
-            /* m_free */     nullptr
-        };
+        def = new (def)
+            PyModuleDef{/* m_base */ PyModuleDef_HEAD_INIT,
+                        /* m_name */ name,
+                        /* m_doc */ options::show_user_defined_docstrings() ? doc : nullptr,
+                        /* m_size */ -1,
+                        /* m_methods */ nullptr,
+                        /* m_slots */ nullptr,
+                        /* m_traverse */ nullptr,
+                        /* m_clear */ nullptr,
+                        /* m_free */ nullptr};
         auto *m = PyModule_Create(def);
 #else
         // Ignore module_def *def; only necessary for Python 3
         (void) def;
-        auto m = Py_InitModule3(name, nullptr, options::show_user_defined_docstrings() ? doc : nullptr);
+        auto m = Py_InitModule3(
+            name, nullptr, options::show_user_defined_docstrings() ? doc : nullptr);
 #endif
         if (m == nullptr) {
             if (PyErr_Occurred()) {
@@ -1227,7 +1270,8 @@ class module_ : public object {
             }
             pybind11_fail("Internal error in module_::create_extension_module()");
         }
-        // TODO: Should be reinterpret_steal for Python 3, but Python also steals it again when returned from PyInit_...
+        // TODO: Should be reinterpret_steal for Python 3, but Python also steals it again when
+        // returned from PyInit_...
         //       For Python 2, reinterpret_borrow is correct.
         return reinterpret_borrow<module_>(m);
     }
@@ -1247,10 +1291,10 @@ inline dict globals() {
 }
 
 #if PY_VERSION_HEX >= 0x03030000
-template <typename... Args,
-          typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
-PYBIND11_DEPRECATED("make_simple_namespace should be replaced with py::module_::import(\"types\").attr(\"SimpleNamespace\") ")
-object make_simple_namespace(Args&&... args_) {
+template <typename... Args, typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
+PYBIND11_DEPRECATED("make_simple_namespace should be replaced with "
+                    "py::module_::import(\"types\").attr(\"SimpleNamespace\") ")
+object make_simple_namespace(Args &&...args_) {
     return module_::import("types").attr("SimpleNamespace")(std::forward<Args>(args_)...);
 }
 #endif
@@ -1299,13 +1343,12 @@ class generic_type : public object {
         } else {
             internals.registered_types_cpp[tindex] = tinfo;
         }
-        internals.registered_types_py[(PyTypeObject *) m_ptr] = { tinfo };
+        internals.registered_types_py[(PyTypeObject *) m_ptr] = {tinfo};
 
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {
             mark_parents_nonsimple(tinfo->type);
             tinfo->simple_ancestors = false;
-        }
-        else if (rec.bases.size() == 1) {
+        } else if (rec.bases.size() == 1) {
             auto *parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
             assert(parent_tinfo != nullptr);
             bool parent_simple_ancestors = parent_tinfo->simple_ancestors;
@@ -1333,10 +1376,9 @@ class generic_type : public object {
         }
     }
 
-    void install_buffer_funcs(
-            buffer_info *(*get_buffer)(PyObject *, void *),
-            void *get_buffer_data) {
-        auto *type = (PyHeapTypeObject*) m_ptr;
+    void install_buffer_funcs(buffer_info *(*get_buffer)(PyObject *, void *),
+                              void *get_buffer_data) {
+        auto *type = (PyHeapTypeObject *) m_ptr;
         auto *tinfo = detail::get_type_info(&type->ht_type);
 
         if (!type->ht_type.tp_as_buffer) {
@@ -1352,58 +1394,76 @@ class generic_type : public object {
 
     // rec_func must be set for either fget or fset.
     void def_property_static_impl(const char *name,
-                                  handle fget, handle fset,
+                                  handle fget,
+                                  handle fset,
                                   detail::function_record *rec_func) {
         const auto is_static = (rec_func != nullptr) && !(rec_func->is_method && rec_func->scope);
         const auto has_doc = (rec_func != nullptr) && (rec_func->doc != nullptr)
                              && pybind11::options::show_user_defined_docstrings();
-        auto property = handle((PyObject *) (is_static ? get_internals().static_property_type
-                                                       : &PyProperty_Type));
+        auto property = handle(
+            (PyObject *) (is_static ? get_internals().static_property_type : &PyProperty_Type));
         attr(name) = property(fget.ptr() ? fget : none(),
                               fset.ptr() ? fset : none(),
-                              /*deleter*/none(),
+                              /*deleter*/ none(),
                               pybind11::str(has_doc ? rec_func->doc : ""));
     }
 };
 
 /// Set the pointer to operator new if it exists. The cast is needed because it can be overloaded.
-template <typename T, typename = void_t<decltype(static_cast<void *(*)(size_t)>(T::operator new))>>
-void set_operator_new(type_record *r) { r->operator_new = &T::operator new; }
-
-template <typename> void set_operator_new(...) { }
+template <typename T,
+          typename = void_t<decltype(static_cast<void *(*) (size_t)>(T::operator new))>>
+void set_operator_new(type_record *r) {
+    r->operator_new = &T::operator new;
+}
 
-template <typename T, typename SFINAE = void> struct has_operator_delete : std::false_type { };
-template <typename T> struct has_operator_delete<T, void_t<decltype(static_cast<void (*)(void *)>(T::operator delete))>>
-    : std::true_type { };
-template <typename T, typename SFINAE = void> struct has_operator_delete_size : std::false_type { };
-template <typename T> struct has_operator_delete_size<T, void_t<decltype(static_cast<void (*)(void *, size_t)>(T::operator delete))>>
-    : std::true_type { };
+template <typename>
+void set_operator_new(...) {}
+
+template <typename T, typename SFINAE = void>
+struct has_operator_delete : std::false_type {};
+template <typename T>
+struct has_operator_delete<T, void_t<decltype(static_cast<void (*)(void *)>(T::operator delete))>>
+    : std::true_type {};
+template <typename T, typename SFINAE = void>
+struct has_operator_delete_size : std::false_type {};
+template <typename T>
+struct has_operator_delete_size<
+    T,
+    void_t<decltype(static_cast<void (*)(void *, size_t)>(T::operator delete))>> : std::true_type {
+};
 /// Call class-specific delete if it exists or global otherwise. Can also be an overload set.
 template <typename T, enable_if_t<has_operator_delete<T>::value, int> = 0>
-void call_operator_delete(T *p, size_t, size_t) { T::operator delete(p); }
-template <typename T, enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
-void call_operator_delete(T *p, size_t s, size_t) { T::operator delete(p, s); }
+void call_operator_delete(T *p, size_t, size_t) {
+    T::operator delete(p);
+}
+template <
+    typename T,
+    enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
+void call_operator_delete(T *p, size_t s, size_t) {
+    T::operator delete(p, s);
+}
 
 inline void call_operator_delete(void *p, size_t s, size_t a) {
-    (void)s; (void)a;
-    #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
-        if (a > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
-            #ifdef __cpp_sized_deallocation
-                ::operator delete(p, s, std::align_val_t(a));
-            #else
-                ::operator delete(p, std::align_val_t(a));
-            #endif
-            return;
-        }
-    #endif
-    #ifdef __cpp_sized_deallocation
-        ::operator delete(p, s);
-    #else
-        ::operator delete(p);
-    #endif
+    (void) s;
+    (void) a;
+#if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
+    if (a > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
+#    ifdef __cpp_sized_deallocation
+        ::operator delete(p, s, std::align_val_t(a));
+#    else
+        ::operator delete(p, std::align_val_t(a));
+#    endif
+        return;
+    }
+#endif
+#ifdef __cpp_sized_deallocation
+    ::operator delete(p, s);
+#else
+    ::operator delete(p);
+#endif
 }
 
-inline void add_class_method(object& cls, const char *name_, const cpp_function &cf) {
+inline void add_class_method(object &cls, const char *name_, const cpp_function &cf) {
     cls.attr(cf.name()) = cf;
     if (std::strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
         cls.attr("__hash__") = none();
@@ -1415,30 +1475,37 @@ PYBIND11_NAMESPACE_END(detail)
 /// Given a pointer to a member function, cast it to its `Derived` version.
 /// Forward everything else unchanged.
 template <typename /*Derived*/, typename F>
-auto method_adaptor(F &&f) -> decltype(std::forward<F>(f)) { return std::forward<F>(f); }
+auto method_adaptor(F &&f) -> decltype(std::forward<F>(f)) {
+    return std::forward<F>(f);
+}
 
 template <typename Derived, typename Return, typename Class, typename... Args>
 auto method_adaptor(Return (Class::*pmf)(Args...)) -> Return (Derived::*)(Args...) {
-    static_assert(detail::is_accessible_base_of<Class, Derived>::value,
+    static_assert(
+        detail::is_accessible_base_of<Class, Derived>::value,
         "Cannot bind an inaccessible base class method; use a lambda definition instead");
     return pmf;
 }
 
 template <typename Derived, typename Return, typename Class, typename... Args>
 auto method_adaptor(Return (Class::*pmf)(Args...) const) -> Return (Derived::*)(Args...) const {
-    static_assert(detail::is_accessible_base_of<Class, Derived>::value,
+    static_assert(
+        detail::is_accessible_base_of<Class, Derived>::value,
         "Cannot bind an inaccessible base class method; use a lambda definition instead");
     return pmf;
 }
 
 template <typename type_, typename... options>
 class class_ : public detail::generic_type {
-    template <typename T> using is_holder = detail::is_holder_type<type_, T>;
-    template <typename T> using is_subtype = detail::is_strict_base_of<type_, T>;
-    template <typename T> using is_base = detail::is_strict_base_of<T, type_>;
+    template <typename T>
+    using is_holder = detail::is_holder_type<type_, T>;
+    template <typename T>
+    using is_subtype = detail::is_strict_base_of<type_, T>;
+    template <typename T>
+    using is_base = detail::is_strict_base_of<T, type_>;
     // struct instead of using here to help MSVC:
-    template <typename T> struct is_valid_class_option :
-        detail::any_of<is_holder<T>, is_subtype<T>, is_base<T>> {};
+    template <typename T>
+    struct is_valid_class_option : detail::any_of<is_holder<T>, is_subtype<T>, is_base<T>> {};
 
 public:
     using type = type_;
@@ -1447,24 +1514,24 @@ class class_ : public detail::generic_type {
     using holder_type = detail::exactly_one_t<is_holder, std::unique_ptr<type>, options...>;
 
     static_assert(detail::all_of<is_valid_class_option<options>...>::value,
-            "Unknown/invalid class_ template parameters provided");
+                  "Unknown/invalid class_ template parameters provided");
 
     static_assert(!has_alias || std::is_polymorphic<type>::value,
-            "Cannot use an alias class with a non-polymorphic type");
+                  "Cannot use an alias class with a non-polymorphic type");
 
     PYBIND11_OBJECT(class_, generic_type, PyType_Check)
 
     template <typename... Extra>
-    class_(handle scope, const char *name, const Extra &... extra) {
+    class_(handle scope, const char *name, const Extra &...extra) {
         using namespace detail;
 
         // MI can only be specified via class_ template options, not constructor parameters
         static_assert(
             none_of<is_pyobject<Extra>...>::value || // no base class arguments, or:
-            (   constexpr_sum(is_pyobject<Extra>::value...) == 1 && // Exactly one base
-                constexpr_sum(is_base<options>::value...)   == 0 && // no template option bases
-                // no multiple_inheritance attr
-                none_of<std::is_same<multiple_inheritance, Extra>...>::value),
+                (constexpr_sum(is_pyobject<Extra>::value...) == 1 && // Exactly one base
+                 constexpr_sum(is_base<options>::value...) == 0 &&   // no template option bases
+                 // no multiple_inheritance attr
+                 none_of<std::is_same<multiple_inheritance, Extra>...>::value),
             "Error: multiple inheritance bases must be specified via class_ template options");
 
         type_record record;
@@ -1472,7 +1539,7 @@ class class_ : public detail::generic_type {
         record.name = name;
         record.type = &typeid(type);
         record.type_size = sizeof(conditional_t<has_alias, type_alias, type>);
-        record.type_align = alignof(conditional_t<has_alias, type_alias, type>&);
+        record.type_align = alignof(conditional_t<has_alias, type_alias, type> &);
         record.holder_size = sizeof(holder_type);
         record.init_instance = init_instance;
         record.dealloc = dealloc;
@@ -1489,8 +1556,10 @@ class class_ : public detail::generic_type {
         generic_type::initialize(record);
 
         if (has_alias) {
-            auto &instances = record.module_local ? get_local_internals().registered_types_cpp : get_internals().registered_types_cpp;
-            instances[std::type_index(typeid(type_alias))] = instances[std::type_index(typeid(type))];
+            auto &instances = record.module_local ? get_local_internals().registered_types_cpp
+                                                  : get_internals().registered_types_cpp;
+            instances[std::type_index(typeid(type_alias))]
+                = instances[std::type_index(typeid(type))];
         }
     }
 
@@ -1502,54 +1571,60 @@ class class_ : public detail::generic_type {
     }
 
     template <typename Base, detail::enable_if_t<!is_base<Base>::value, int> = 0>
-    static void add_base(detail::type_record &) { }
+    static void add_base(detail::type_record &) {}
 
     template <typename Func, typename... Extra>
-    class_ &def(const char *name_, Func&& f, const Extra&... extra) {
-        cpp_function cf(method_adaptor<type>(std::forward<Func>(f)), name(name_), is_method(*this),
-                        sibling(getattr(*this, name_, none())), extra...);
+    class_ &def(const char *name_, Func &&f, const Extra &...extra) {
+        cpp_function cf(method_adaptor<type>(std::forward<Func>(f)),
+                        name(name_),
+                        is_method(*this),
+                        sibling(getattr(*this, name_, none())),
+                        extra...);
         add_class_method(*this, name_, cf);
         return *this;
     }
 
-    template <typename Func, typename... Extra> class_ &
-    def_static(const char *name_, Func &&f, const Extra&... extra) {
+    template <typename Func, typename... Extra>
+    class_ &def_static(const char *name_, Func &&f, const Extra &...extra) {
         static_assert(!std::is_member_function_pointer<Func>::value,
-                "def_static(...) called with a non-static member function pointer");
-        cpp_function cf(std::forward<Func>(f), name(name_), scope(*this),
-                        sibling(getattr(*this, name_, none())), extra...);
+                      "def_static(...) called with a non-static member function pointer");
+        cpp_function cf(std::forward<Func>(f),
+                        name(name_),
+                        scope(*this),
+                        sibling(getattr(*this, name_, none())),
+                        extra...);
         attr(cf.name()) = staticmethod(cf);
         return *this;
     }
 
     template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
-    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra&... extra) {
+    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
         op.execute(*this, extra...);
         return *this;
     }
 
     template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
-    class_ & def_cast(const detail::op_<id, ot, L, R> &op, const Extra&... extra) {
+    class_ &def_cast(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
         op.execute_cast(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
-    class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra&... extra) {
+    class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra &...extra) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(init);
         init.execute(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
-    class_ &def(const detail::initimpl::alias_constructor<Args...> &init, const Extra&... extra) {
+    class_ &def(const detail::initimpl::alias_constructor<Args...> &init, const Extra &...extra) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(init);
         init.execute(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
-    class_ &def(detail::initimpl::factory<Args...> &&init, const Extra&... extra) {
+    class_ &def(detail::initimpl::factory<Args...> &&init, const Extra &...extra) {
         std::move(init).execute(*this, extra...);
         return *this;
     }
@@ -1561,52 +1636,59 @@ class class_ : public detail::generic_type {
     }
 
     template <typename Func>
-    class_& def_buffer(Func &&func) {
-        struct capture { Func func; };
-        auto *ptr = new capture { std::forward<Func>(func) };
-        install_buffer_funcs([](PyObject *obj, void *ptr) -> buffer_info* {
-            detail::make_caster<type> caster;
-            if (!caster.load(obj, false)) {
-                return nullptr;
-            }
-            return new buffer_info(((capture *) ptr)->func(caster));
-        }, ptr);
+    class_ &def_buffer(Func &&func) {
+        struct capture {
+            Func func;
+        };
+        auto *ptr = new capture{std::forward<Func>(func)};
+        install_buffer_funcs(
+            [](PyObject *obj, void *ptr) -> buffer_info * {
+                detail::make_caster<type> caster;
+                if (!caster.load(obj, false)) {
+                    return nullptr;
+                }
+                return new buffer_info(((capture *) ptr)->func(caster));
+            },
+            ptr);
         weakref(m_ptr, cpp_function([ptr](handle wr) {
-            delete ptr;
-            wr.dec_ref();
-        })).release();
+                    delete ptr;
+                    wr.dec_ref();
+                }))
+            .release();
         return *this;
     }
 
     template <typename Return, typename Class, typename... Args>
     class_ &def_buffer(Return (Class::*func)(Args...)) {
-        return def_buffer([func] (type &obj) { return (obj.*func)(); });
+        return def_buffer([func](type &obj) { return (obj.*func)(); });
     }
 
     template <typename Return, typename Class, typename... Args>
     class_ &def_buffer(Return (Class::*func)(Args...) const) {
-        return def_buffer([func] (const type &obj) { return (obj.*func)(); });
+        return def_buffer([func](const type &obj) { return (obj.*func)(); });
     }
 
     template <typename C, typename D, typename... Extra>
-    class_ &def_readwrite(const char *name, D C::*pm, const Extra&... extra) {
-        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value, "def_readwrite() requires a class member (or base class member)");
-        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this)),
-                     fset([pm](type &c, const D &value) { c.*pm = value; }, is_method(*this));
+    class_ &def_readwrite(const char *name, D C::*pm, const Extra &...extra) {
+        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value,
+                      "def_readwrite() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D & { return c.*pm; }, is_method(*this)),
+            fset([pm](type &c, const D &value) { c.*pm = value; }, is_method(*this));
         def_property(name, fget, fset, return_value_policy::reference_internal, extra...);
         return *this;
     }
 
     template <typename C, typename D, typename... Extra>
-    class_ &def_readonly(const char *name, const D C::*pm, const Extra& ...extra) {
-        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value, "def_readonly() requires a class member (or base class member)");
-        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this));
+    class_ &def_readonly(const char *name, const D C::*pm, const Extra &...extra) {
+        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value,
+                      "def_readonly() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D & { return c.*pm; }, is_method(*this));
         def_property_readonly(name, fget, return_value_policy::reference_internal, extra...);
         return *this;
     }
 
     template <typename D, typename... Extra>
-    class_ &def_readwrite_static(const char *name, D *pm, const Extra& ...extra) {
+    class_ &def_readwrite_static(const char *name, D *pm, const Extra &...extra) {
         cpp_function fget([pm](const object &) -> const D & { return *pm; }, scope(*this)),
             fset([pm](const object &, const D &value) { *pm = value; }, scope(*this));
         def_property_static(name, fget, fset, return_value_policy::reference, extra...);
@@ -1614,7 +1696,7 @@ class class_ : public detail::generic_type {
     }
 
     template <typename D, typename... Extra>
-    class_ &def_readonly_static(const char *name, const D *pm, const Extra& ...extra) {
+    class_ &def_readonly_static(const char *name, const D *pm, const Extra &...extra) {
         cpp_function fget([pm](const object &) -> const D & { return *pm; }, scope(*this));
         def_property_readonly_static(name, fget, return_value_policy::reference, extra...);
         return *this;
@@ -1622,66 +1704,91 @@ class class_ : public detail::generic_type {
 
     /// Uses return_value_policy::reference_internal by default
     template <typename Getter, typename... Extra>
-    class_ &def_property_readonly(const char *name, const Getter &fget, const Extra& ...extra) {
-        return def_property_readonly(name, cpp_function(method_adaptor<type>(fget)),
-                                     return_value_policy::reference_internal, extra...);
+    class_ &def_property_readonly(const char *name, const Getter &fget, const Extra &...extra) {
+        return def_property_readonly(name,
+                                     cpp_function(method_adaptor<type>(fget)),
+                                     return_value_policy::reference_internal,
+                                     extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property_readonly(const char *name, const cpp_function &fget, const Extra& ...extra) {
+    class_ &
+    def_property_readonly(const char *name, const cpp_function &fget, const Extra &...extra) {
         return def_property(name, fget, nullptr, extra...);
     }
 
     /// Uses return_value_policy::reference by default
     template <typename Getter, typename... Extra>
-    class_ &def_property_readonly_static(const char *name, const Getter &fget, const Extra& ...extra) {
-        return def_property_readonly_static(name, cpp_function(fget), return_value_policy::reference, extra...);
+    class_ &
+    def_property_readonly_static(const char *name, const Getter &fget, const Extra &...extra) {
+        return def_property_readonly_static(
+            name, cpp_function(fget), return_value_policy::reference, extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property_readonly_static(const char *name, const cpp_function &fget, const Extra& ...extra) {
+    class_ &def_property_readonly_static(const char *name,
+                                         const cpp_function &fget,
+                                         const Extra &...extra) {
         return def_property_static(name, fget, nullptr, extra...);
     }
 
     /// Uses return_value_policy::reference_internal by default
     template <typename Getter, typename Setter, typename... Extra>
-    class_ &def_property(const char *name, const Getter &fget, const Setter &fset, const Extra& ...extra) {
+    class_ &
+    def_property(const char *name, const Getter &fget, const Setter &fset, const Extra &...extra) {
         return def_property(name, fget, cpp_function(method_adaptor<type>(fset)), extra...);
     }
     template <typename Getter, typename... Extra>
-    class_ &def_property(const char *name, const Getter &fget, const cpp_function &fset, const Extra& ...extra) {
-        return def_property(name, cpp_function(method_adaptor<type>(fget)), fset,
-                            return_value_policy::reference_internal, extra...);
+    class_ &def_property(const char *name,
+                         const Getter &fget,
+                         const cpp_function &fset,
+                         const Extra &...extra) {
+        return def_property(name,
+                            cpp_function(method_adaptor<type>(fget)),
+                            fset,
+                            return_value_policy::reference_internal,
+                            extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
+    class_ &def_property(const char *name,
+                         const cpp_function &fget,
+                         const cpp_function &fset,
+                         const Extra &...extra) {
         return def_property_static(name, fget, fset, is_method(*this), extra...);
     }
 
     /// Uses return_value_policy::reference by default
     template <typename Getter, typename... Extra>
-    class_ &def_property_static(const char *name, const Getter &fget, const cpp_function &fset, const Extra& ...extra) {
-        return def_property_static(name, cpp_function(fget), fset, return_value_policy::reference, extra...);
+    class_ &def_property_static(const char *name,
+                                const Getter &fget,
+                                const cpp_function &fset,
+                                const Extra &...extra) {
+        return def_property_static(
+            name, cpp_function(fget), fset, return_value_policy::reference, extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property_static(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
-        static_assert( 0 == detail::constexpr_sum(std::is_base_of<arg, Extra>::value...),
+    class_ &def_property_static(const char *name,
+                                const cpp_function &fget,
+                                const cpp_function &fset,
+                                const Extra &...extra) {
+        static_assert(0 == detail::constexpr_sum(std::is_base_of<arg, Extra>::value...),
                       "Argument annotations are not allowed for properties");
         auto rec_fget = get_function_record(fget), rec_fset = get_function_record(fset);
         auto *rec_active = rec_fget;
         if (rec_fget) {
-           char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific documentation string */
-           detail::process_attributes<Extra...>::init(extra..., rec_fget);
-           if (rec_fget->doc && rec_fget->doc != doc_prev) {
-              std::free(doc_prev);
-              rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
-           }
+            char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific
+                                               documentation string */
+            detail::process_attributes<Extra...>::init(extra..., rec_fget);
+            if (rec_fget->doc && rec_fget->doc != doc_prev) {
+                std::free(doc_prev);
+                rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
+            }
         }
         if (rec_fset) {
             char *doc_prev = rec_fset->doc;
@@ -1701,11 +1808,13 @@ class class_ : public detail::generic_type {
 private:
     /// Initialize holder object, variant 1: object derives from enable_shared_from_this
     template <typename T>
-    static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
-            const holder_type * /* unused */, const std::enable_shared_from_this<T> * /* dummy */) {
+    static void init_holder(detail::instance *inst,
+                            detail::value_and_holder &v_h,
+                            const holder_type * /* unused */,
+                            const std::enable_shared_from_this<T> * /* dummy */) {
 
         auto sh = std::dynamic_pointer_cast<typename holder_type::element_type>(
-                detail::try_get_shared_from_this(v_h.value_ptr<type>()));
+            detail::try_get_shared_from_this(v_h.value_ptr<type>()));
         if (sh) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(std::move(sh));
             v_h.set_holder_constructed();
@@ -1718,18 +1827,25 @@ class class_ : public detail::generic_type {
     }
 
     static void init_holder_from_existing(const detail::value_and_holder &v_h,
-            const holder_type *holder_ptr, std::true_type /*is_copy_constructible*/) {
-        new (std::addressof(v_h.holder<holder_type>())) holder_type(*reinterpret_cast<const holder_type *>(holder_ptr));
+                                          const holder_type *holder_ptr,
+                                          std::true_type /*is_copy_constructible*/) {
+        new (std::addressof(v_h.holder<holder_type>()))
+            holder_type(*reinterpret_cast<const holder_type *>(holder_ptr));
     }
 
     static void init_holder_from_existing(const detail::value_and_holder &v_h,
-            const holder_type *holder_ptr, std::false_type /*is_copy_constructible*/) {
-        new (std::addressof(v_h.holder<holder_type>())) holder_type(std::move(*const_cast<holder_type *>(holder_ptr)));
-    }
-
-    /// Initialize holder object, variant 2: try to construct from existing holder object, if possible
-    static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
-            const holder_type *holder_ptr, const void * /* dummy -- not enable_shared_from_this<T>) */) {
+                                          const holder_type *holder_ptr,
+                                          std::false_type /*is_copy_constructible*/) {
+        new (std::addressof(v_h.holder<holder_type>()))
+            holder_type(std::move(*const_cast<holder_type *>(holder_ptr)));
+    }
+
+    /// Initialize holder object, variant 2: try to construct from existing holder object, if
+    /// possible
+    static void init_holder(detail::instance *inst,
+                            detail::value_and_holder &v_h,
+                            const holder_type *holder_ptr,
+                            const void * /* dummy -- not enable_shared_from_this<T>) */) {
         if (holder_ptr) {
             init_holder_from_existing(v_h, holder_ptr, std::is_copy_constructible<holder_type>());
             v_h.set_holder_constructed();
@@ -1740,8 +1856,8 @@ class class_ : public detail::generic_type {
     }
 
     /// Performs instance initialization including constructing a holder and registering the known
-    /// instance.  Should be called as soon as the `type` value_ptr is set for an instance.  Takes an
-    /// optional pointer to an existing holder to use; if not specified and the instance is
+    /// instance.  Should be called as soon as the `type` value_ptr is set for an instance.  Takes
+    /// an optional pointer to an existing holder to use; if not specified and the instance is
     /// `.owned`, a new holder will be constructed to manage the value pointer.
     static void init_instance(detail::instance *inst, const void *holder_ptr) {
         auto v_h = inst->get_value_and_holder(detail::get_type_info(typeid(type)));
@@ -1764,35 +1880,42 @@ class class_ : public detail::generic_type {
         if (v_h.holder_constructed()) {
             v_h.holder<holder_type>().~holder_type();
             v_h.set_holder_constructed(false);
-        }
-        else {
-            detail::call_operator_delete(v_h.value_ptr<type>(),
-                v_h.type->type_size,
-                v_h.type->type_align
-            );
+        } else {
+            detail::call_operator_delete(
+                v_h.value_ptr<type>(), v_h.type->type_size, v_h.type->type_align);
         }
         v_h.value_ptr() = nullptr;
     }
 
     static detail::function_record *get_function_record(handle h) {
         h = detail::get_function(h);
-        return h ? (detail::function_record *) reinterpret_borrow<capsule>(PyCFunction_GET_SELF(h.ptr()))
+        return h ? (detail::function_record *) reinterpret_borrow<capsule>(
+                   PyCFunction_GET_SELF(h.ptr()))
                  : nullptr;
     }
 };
 
 /// Binds an existing constructor taking arguments Args...
-template <typename... Args> detail::initimpl::constructor<Args...> init() { return {}; }
+template <typename... Args>
+detail::initimpl::constructor<Args...> init() {
+    return {};
+}
 /// Like `init<Args...>()`, but the instance is always constructed through the alias class (even
 /// when not inheriting on the Python side).
-template <typename... Args> detail::initimpl::alias_constructor<Args...> init_alias() { return {}; }
+template <typename... Args>
+detail::initimpl::alias_constructor<Args...> init_alias() {
+    return {};
+}
 
 /// Binds a factory function as a constructor
 template <typename Func, typename Ret = detail::initimpl::factory<Func>>
-Ret init(Func &&f) { return {std::forward<Func>(f)}; }
+Ret init(Func &&f) {
+    return {std::forward<Func>(f)};
+}
 
-/// Dual-argument factory function: the first function is called when no alias is needed, the second
-/// when an alias is needed (i.e. due to python-side inheritance).  Arguments must be identical.
+/// Dual-argument factory function: the first function is called when no alias is needed, the
+/// second when an alias is needed (i.e. due to python-side inheritance).  Arguments must be
+/// identical.
 template <typename CFunc, typename AFunc, typename Ret = detail::initimpl::factory<CFunc, AFunc>>
 Ret init(CFunc &&c, AFunc &&a) {
     return {std::forward<CFunc>(c), std::forward<AFunc>(a)};
@@ -1818,7 +1941,7 @@ inline str enum_name(handle arg) {
 }
 
 struct enum_base {
-    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) { }
+    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) {}
 
     PYBIND11_NOINLINE void init(bool is_arithmetic, bool is_convertible) {
         m_base.attr("__entries") = dict();
@@ -1840,38 +1963,47 @@ struct enum_base {
             [](handle arg) -> str {
                 object type_name = type::handle_of(arg).attr("__name__");
                 return pybind11::str("{}.{}").format(type_name, enum_name(arg));
-            }, name("name"), is_method(m_base)
-        );
+            },
+            name("name"),
+            is_method(m_base));
 
-        m_base.attr("__doc__") = static_property(cpp_function(
-            [](handle arg) -> std::string {
-                std::string docstring;
-                dict entries = arg.attr("__entries");
-                if (((PyTypeObject *) arg.ptr())->tp_doc) {
-                    docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
-                }
-                docstring += "Members:";
-                for (auto kv : entries) {
-                    auto key = std::string(pybind11::str(kv.first));
-                    auto comment = kv.second[int_(1)];
-                    docstring += "\n\n  " + key;
-                    if (!comment.is_none()) {
-                        docstring += " : " + (std::string) pybind11::str(comment);
+        m_base.attr("__doc__") = static_property(
+            cpp_function(
+                [](handle arg) -> std::string {
+                    std::string docstring;
+                    dict entries = arg.attr("__entries");
+                    if (((PyTypeObject *) arg.ptr())->tp_doc) {
+                        docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
                     }
-                }
-                return docstring;
-            }, name("__doc__")
-        ), none(), none(), "");
+                    docstring += "Members:";
+                    for (auto kv : entries) {
+                        auto key = std::string(pybind11::str(kv.first));
+                        auto comment = kv.second[int_(1)];
+                        docstring += "\n\n  " + key;
+                        if (!comment.is_none()) {
+                            docstring += " : " + (std::string) pybind11::str(comment);
+                        }
+                    }
+                    return docstring;
+                },
+                name("__doc__")),
+            none(),
+            none(),
+            "");
 
         m_base.attr("__members__") = static_property(cpp_function(
-            [](handle arg) -> dict {
-                dict entries = arg.attr("__entries"), m;
-                for (auto kv : entries) {
-                    m[kv.first] = kv.second[int_(0)];
-                }
-                return m;
-            }, name("__members__")), none(), none(), ""
-        );
+                                                         [](handle arg) -> dict {
+                                                             dict entries = arg.attr("__entries"),
+                                                                  m;
+                                                             for (auto kv : entries) {
+                                                                 m[kv.first] = kv.second[int_(0)];
+                                                             }
+                                                             return m;
+                                                         },
+                                                         name("__members__")),
+                                                     none(),
+                                                     none(),
+                                                     "");
 
 #define PYBIND11_ENUM_OP_STRICT(op, expr, strict_behavior)                                        \
     m_base.attr(op) = cpp_function(                                                               \
@@ -1905,42 +2037,42 @@ struct enum_base {
         arg("other"))
 
         if (is_convertible) {
-            PYBIND11_ENUM_OP_CONV_LHS("__eq__", !b.is_none() &&  a.equal(b));
-            PYBIND11_ENUM_OP_CONV_LHS("__ne__",  b.is_none() || !a.equal(b));
+            PYBIND11_ENUM_OP_CONV_LHS("__eq__", !b.is_none() && a.equal(b));
+            PYBIND11_ENUM_OP_CONV_LHS("__ne__", b.is_none() || !a.equal(b));
 
             if (is_arithmetic) {
-                PYBIND11_ENUM_OP_CONV("__lt__",   a <  b);
-                PYBIND11_ENUM_OP_CONV("__gt__",   a >  b);
-                PYBIND11_ENUM_OP_CONV("__le__",   a <= b);
-                PYBIND11_ENUM_OP_CONV("__ge__",   a >= b);
-                PYBIND11_ENUM_OP_CONV("__and__",  a &  b);
-                PYBIND11_ENUM_OP_CONV("__rand__", a &  b);
-                PYBIND11_ENUM_OP_CONV("__or__",   a |  b);
-                PYBIND11_ENUM_OP_CONV("__ror__",  a |  b);
-                PYBIND11_ENUM_OP_CONV("__xor__",  a ^  b);
-                PYBIND11_ENUM_OP_CONV("__rxor__", a ^  b);
+                PYBIND11_ENUM_OP_CONV("__lt__", a < b);
+                PYBIND11_ENUM_OP_CONV("__gt__", a > b);
+                PYBIND11_ENUM_OP_CONV("__le__", a <= b);
+                PYBIND11_ENUM_OP_CONV("__ge__", a >= b);
+                PYBIND11_ENUM_OP_CONV("__and__", a & b);
+                PYBIND11_ENUM_OP_CONV("__rand__", a & b);
+                PYBIND11_ENUM_OP_CONV("__or__", a | b);
+                PYBIND11_ENUM_OP_CONV("__ror__", a | b);
+                PYBIND11_ENUM_OP_CONV("__xor__", a ^ b);
+                PYBIND11_ENUM_OP_CONV("__rxor__", a ^ b);
                 m_base.attr("__invert__")
                     = cpp_function([](const object &arg) { return ~(int_(arg)); },
                                    name("__invert__"),
                                    is_method(m_base));
             }
         } else {
-            PYBIND11_ENUM_OP_STRICT("__eq__",  int_(a).equal(int_(b)), return false);
+            PYBIND11_ENUM_OP_STRICT("__eq__", int_(a).equal(int_(b)), return false);
             PYBIND11_ENUM_OP_STRICT("__ne__", !int_(a).equal(int_(b)), return true);
 
             if (is_arithmetic) {
-                #define PYBIND11_THROW throw type_error("Expected an enumeration of matching type!");
-                PYBIND11_ENUM_OP_STRICT("__lt__", int_(a) <  int_(b), PYBIND11_THROW);
-                PYBIND11_ENUM_OP_STRICT("__gt__", int_(a) >  int_(b), PYBIND11_THROW);
+#define PYBIND11_THROW throw type_error("Expected an enumeration of matching type!");
+                PYBIND11_ENUM_OP_STRICT("__lt__", int_(a) < int_(b), PYBIND11_THROW);
+                PYBIND11_ENUM_OP_STRICT("__gt__", int_(a) > int_(b), PYBIND11_THROW);
                 PYBIND11_ENUM_OP_STRICT("__le__", int_(a) <= int_(b), PYBIND11_THROW);
                 PYBIND11_ENUM_OP_STRICT("__ge__", int_(a) >= int_(b), PYBIND11_THROW);
-                #undef PYBIND11_THROW
+#undef PYBIND11_THROW
             }
         }
 
-        #undef PYBIND11_ENUM_OP_CONV_LHS
-        #undef PYBIND11_ENUM_OP_CONV
-        #undef PYBIND11_ENUM_OP_STRICT
+#undef PYBIND11_ENUM_OP_CONV_LHS
+#undef PYBIND11_ENUM_OP_CONV
+#undef PYBIND11_ENUM_OP_STRICT
 
         m_base.attr("__getstate__") = cpp_function(
             [](const object &arg) { return int_(arg); }, name("__getstate__"), is_method(m_base));
@@ -1949,12 +2081,13 @@ struct enum_base {
             [](const object &arg) { return int_(arg); }, name("__hash__"), is_method(m_base));
     }
 
-    PYBIND11_NOINLINE void value(char const* name_, object value, const char *doc = nullptr) {
+    PYBIND11_NOINLINE void value(char const *name_, object value, const char *doc = nullptr) {
         dict entries = m_base.attr("__entries");
         str name(name_);
         if (entries.contains(name)) {
             std::string type_name = (std::string) str(m_base.attr("__name__"));
-            throw value_error(type_name + ": element \"" + std::string(name_) + "\" already exists!");
+            throw value_error(type_name + ": element \"" + std::string(name_)
+                              + "\" already exists!");
         }
 
         entries[name] = std::make_pair(value, doc);
@@ -1972,38 +2105,66 @@ struct enum_base {
     handle m_parent;
 };
 
-template <bool is_signed, size_t length> struct equivalent_integer {};
-template <> struct equivalent_integer<true,  1> { using type = int8_t;   };
-template <> struct equivalent_integer<false, 1> { using type = uint8_t;  };
-template <> struct equivalent_integer<true,  2> { using type = int16_t;  };
-template <> struct equivalent_integer<false, 2> { using type = uint16_t; };
-template <> struct equivalent_integer<true,  4> { using type = int32_t;  };
-template <> struct equivalent_integer<false, 4> { using type = uint32_t; };
-template <> struct equivalent_integer<true,  8> { using type = int64_t;  };
-template <> struct equivalent_integer<false, 8> { using type = uint64_t; };
+template <bool is_signed, size_t length>
+struct equivalent_integer {};
+template <>
+struct equivalent_integer<true, 1> {
+    using type = int8_t;
+};
+template <>
+struct equivalent_integer<false, 1> {
+    using type = uint8_t;
+};
+template <>
+struct equivalent_integer<true, 2> {
+    using type = int16_t;
+};
+template <>
+struct equivalent_integer<false, 2> {
+    using type = uint16_t;
+};
+template <>
+struct equivalent_integer<true, 4> {
+    using type = int32_t;
+};
+template <>
+struct equivalent_integer<false, 4> {
+    using type = uint32_t;
+};
+template <>
+struct equivalent_integer<true, 8> {
+    using type = int64_t;
+};
+template <>
+struct equivalent_integer<false, 8> {
+    using type = uint64_t;
+};
 
 template <typename IntLike>
-using equivalent_integer_t = typename equivalent_integer<std::is_signed<IntLike>::value, sizeof(IntLike)>::type;
+using equivalent_integer_t =
+    typename equivalent_integer<std::is_signed<IntLike>::value, sizeof(IntLike)>::type;
 
 PYBIND11_NAMESPACE_END(detail)
 
 /// Binds C++ enumerations and enumeration classes to Python
-template <typename Type> class enum_ : public class_<Type> {
+template <typename Type>
+class enum_ : public class_<Type> {
 public:
     using Base = class_<Type>;
-    using Base::def;
     using Base::attr;
+    using Base::def;
     using Base::def_property_readonly;
     using Base::def_property_readonly_static;
     using Underlying = typename std::underlying_type<Type>::type;
     // Scalar is the integer representation of underlying type
-    using Scalar = detail::conditional_t<detail::any_of<
-        detail::is_std_char_type<Underlying>, std::is_same<Underlying, bool>
-    >::value, detail::equivalent_integer_t<Underlying>, Underlying>;
+    using Scalar = detail::conditional_t<detail::any_of<detail::is_std_char_type<Underlying>,
+                                                        std::is_same<Underlying, bool>>::value,
+                                         detail::equivalent_integer_t<Underlying>,
+                                         Underlying>;
 
     template <typename... Extra>
-    enum_(const handle &scope, const char *name, const Extra&... extra)
-      : class_<Type>(scope, name, extra...), m_base(*this, scope) {
+    enum_(const handle &scope, const char *name, const Extra &...extra)
+        : class_<Type>(scope, name, extra...), m_base(*this, scope) {
         constexpr bool is_arithmetic = detail::any_of<std::is_same<arithmetic, Extra>...>::value;
         constexpr bool is_convertible = std::is_convertible<Type, Underlying>::value;
         m_base.init(is_arithmetic, is_convertible);
@@ -2012,25 +2173,28 @@ template <typename Type> class enum_ : public class_<Type> {
         def_property_readonly("value", [](Type value) { return (Scalar) value; });
         def("__int__", [](Type value) { return (Scalar) value; });
         def("__index__", [](Type value) { return (Scalar) value; });
-        #if PY_MAJOR_VERSION < 3
-            def("__long__", [](Type value) { return (Scalar) value; });
-        #endif
+#if PY_MAJOR_VERSION < 3
+        def("__long__", [](Type value) { return (Scalar) value; });
+#endif
         attr("__setstate__") = cpp_function(
             [](detail::value_and_holder &v_h, Scalar arg) {
-                detail::initimpl::setstate<Base>(v_h, static_cast<Type>(arg),
-                        Py_TYPE(v_h.inst) != v_h.type->type); },
+                detail::initimpl::setstate<Base>(
+                    v_h, static_cast<Type>(arg), Py_TYPE(v_h.inst) != v_h.type->type);
+            },
             detail::is_new_style_constructor(),
-            pybind11::name("__setstate__"), is_method(*this), arg("state"));
+            pybind11::name("__setstate__"),
+            is_method(*this),
+            arg("state"));
     }
 
     /// Export enumeration entries into the parent scope
-    enum_& export_values() {
+    enum_ &export_values() {
         m_base.export_values();
         return *this;
     }
 
     /// Add an enumeration entry
-    enum_& value(char const* name, Type value, const char *doc = nullptr) {
+    enum_ &value(char const *name, Type value, const char *doc = nullptr) {
         m_base.value(name, pybind11::cast(value, return_value_policy::copy), doc);
         return *this;
     }
@@ -2041,7 +2205,6 @@ template <typename Type> class enum_ : public class_<Type> {
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-
 PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
     if (!nurse || !patient) {
         pybind11_fail("Could not activate keep_alive!");
@@ -2056,13 +2219,14 @@ PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
         /* It's a pybind-registered type, so we can store the patient in the
          * internal list. */
         add_patient(nurse.ptr(), patient.ptr());
-    }
-    else {
+    } else {
         /* Fall back to clever approach based on weak references taken from
          * Boost.Python. This is not used for pybind-registered types because
          * the objects can be destroyed out-of-order in a GC pass. */
-        cpp_function disable_lifesupport(
-            [patient](handle weakref) { patient.dec_ref(); weakref.dec_ref(); });
+        cpp_function disable_lifesupport([patient](handle weakref) {
+            patient.dec_ref();
+            weakref.dec_ref();
+        });
 
         weakref wr(nurse, disable_lifesupport);
 
@@ -2071,7 +2235,8 @@ PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
     }
 }
 
-PYBIND11_NOINLINE void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
+PYBIND11_NOINLINE void
+keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
     auto get_arg = [&](size_t n) {
         if (n == 0) {
             return ret;
@@ -2088,31 +2253,34 @@ PYBIND11_NOINLINE void keep_alive_impl(size_t Nurse, size_t Patient, function_ca
     keep_alive_impl(get_arg(Nurse), get_arg(Patient));
 }
 
-inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type) {
-    auto res = get_internals().registered_types_py
+inline std::pair<decltype(internals::registered_types_py)::iterator, bool>
+all_type_info_get_cache(PyTypeObject *type) {
+    auto res = get_internals()
+                   .registered_types_py
 #ifdef __cpp_lib_unordered_map_try_emplace
-        .try_emplace(type);
+                   .try_emplace(type);
 #else
-        .emplace(type, std::vector<detail::type_info *>());
+                   .emplace(type, std::vector<detail::type_info *>());
 #endif
     if (res.second) {
         // New cache entry created; set up a weak reference to automatically remove it if the type
         // gets destroyed:
         weakref((PyObject *) type, cpp_function([type](handle wr) {
-            get_internals().registered_types_py.erase(type);
+                    get_internals().registered_types_py.erase(type);
 
-            // TODO consolidate the erasure code in pybind11_meta_dealloc() in class.h
-            auto &cache = get_internals().inactive_override_cache;
-            for (auto it = cache.begin(), last = cache.end(); it != last; ) {
-                if (it->first == reinterpret_cast<PyObject *>(type)) {
-                    it = cache.erase(it);
-                } else {
-                    ++it;
-                }
-            }
+                    // TODO consolidate the erasure code in pybind11_meta_dealloc() in class.h
+                    auto &cache = get_internals().inactive_override_cache;
+                    for (auto it = cache.begin(), last = cache.end(); it != last;) {
+                        if (it->first == reinterpret_cast<PyObject *>(type)) {
+                            it = cache.erase(it);
+                        } else {
+                            ++it;
+                        }
+                    }
 
-            wr.dec_ref();
-        })).release();
+                    wr.dec_ref();
+                }))
+            .release();
     }
 
     return res;
@@ -2121,7 +2289,12 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
 /* There are a large number of apparently unused template arguments because
  * each combination requires a separate py::class_ registration.
  */
-template <typename Access, return_value_policy Policy, typename Iterator, typename Sentinel, typename ValueType, typename... Extra>
+template <typename Access,
+          return_value_policy Policy,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType,
+          typename... Extra>
 struct iterator_state {
     Iterator it;
     Sentinel end;
@@ -2136,12 +2309,10 @@ template <typename Iterator, typename SFINAE = decltype(*std::declval<Iterator &
 struct iterator_access {
     using result_type = decltype(*std::declval<Iterator &>());
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
-    result_type operator()(Iterator &it) const {
-        return *it;
-    }
+    result_type operator()(Iterator &it) const { return *it; }
 };
 
-template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).first) >
+template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).first)>
 class iterator_key_access {
 private:
     using pair_type = decltype(*std::declval<Iterator &>());
@@ -2156,14 +2327,11 @@ class iterator_key_access {
      * (it's not used in the first branch because going via decltype and back
      * through declval does not perfectly preserve references).
      */
-    using result_type = conditional_t<
-        std::is_reference<decltype(*std::declval<Iterator &>())>::value,
-        decltype(((*std::declval<Iterator &>()).first)),
-        decltype(std::declval<pair_type>().first)
-    >;
-    result_type operator()(Iterator &it) const {
-        return (*it).first;
-    }
+    using result_type
+        = conditional_t<std::is_reference<decltype(*std::declval<Iterator &>())>::value,
+                        decltype(((*std::declval<Iterator &>()).first)),
+                        decltype(std::declval<pair_type>().first)>;
+    result_type operator()(Iterator &it) const { return (*it).first; }
 };
 
 template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).second)>
@@ -2172,14 +2340,11 @@ class iterator_value_access {
     using pair_type = decltype(*std::declval<Iterator &>());
 
 public:
-    using result_type = conditional_t<
-        std::is_reference<decltype(*std::declval<Iterator &>())>::value,
-        decltype(((*std::declval<Iterator &>()).second)),
-        decltype(std::declval<pair_type>().second)
-    >;
-    result_type operator()(Iterator &it) const {
-        return (*it).second;
-    }
+    using result_type
+        = conditional_t<std::is_reference<decltype(*std::declval<Iterator &>())>::value,
+                        decltype(((*std::declval<Iterator &>()).second)),
+                        decltype(std::declval<pair_type>().second)>;
+    result_type operator()(Iterator &it) const { return (*it).second; }
 };
 
 template <typename Access,
@@ -2188,7 +2353,7 @@ template <typename Access,
           typename Sentinel,
           typename ValueType,
           typename... Extra>
-iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
+iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&...extra) {
     using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
     // TODO: state captures only the types of Extra, not the values
 
@@ -2225,14 +2390,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename ValueType = typename detail::iterator_access<Iterator>::result_type,
           typename... Extra>
-iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_access<Iterator>,
-        Policy,
-        Iterator,
-        Sentinel,
-        ValueType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+iterator make_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+    return detail::make_iterator_impl<detail::iterator_access<Iterator>,
+                                      Policy,
+                                      Iterator,
+                                      Sentinel,
+                                      ValueType,
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
@@ -2243,13 +2407,12 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
           typename... Extra>
 iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_key_access<Iterator>,
-        Policy,
-        Iterator,
-        Sentinel,
-        KeyType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+    return detail::make_iterator_impl<detail::iterator_key_access<Iterator>,
+                                      Policy,
+                                      Iterator,
+                                      Sentinel,
+                                      KeyType,
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
@@ -2260,36 +2423,43 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
           typename... Extra>
 iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_value_access<Iterator>,
-        Policy, Iterator,
-        Sentinel,
-        ValueType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+    return detail::make_iterator_impl<detail::iterator_value_access<Iterator>,
+                                      Policy,
+                                      Iterator,
+                                      Sentinel,
+                                      ValueType,
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
 /// `std::begin()`/`std::end()`
 template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_iterator(Type &value, Extra&&... extra) {
+          typename Type,
+          typename... Extra>
+iterator make_iterator(Type &value, Extra &&...extra) {
     return make_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
 /// Makes an iterator over the keys (`.first`) of a stl map-like container supporting
 /// `std::begin()`/`std::end()`
 template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_key_iterator(Type &value, Extra&&... extra) {
+          typename Type,
+          typename... Extra>
+iterator make_key_iterator(Type &value, Extra &&...extra) {
     return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
 /// Makes an iterator over the values (`.second`) of a stl map-like container supporting
 /// `std::begin()`/`std::end()`
 template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_value_iterator(Type &value, Extra&&... extra) {
+          typename Type,
+          typename... Extra>
+iterator make_value_iterator(Type &value, Extra &&...extra) {
     return make_value_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
-template <typename InputType, typename OutputType> void implicitly_convertible() {
+template <typename InputType, typename OutputType>
+void implicitly_convertible() {
     struct set_flag {
         bool &flag;
         explicit set_flag(bool &flag_) : flag(flag_) { flag_ = true; }
@@ -2320,19 +2490,17 @@ template <typename InputType, typename OutputType> void implicitly_convertible()
     }
 }
 
-
 inline void register_exception_translator(ExceptionTranslator &&translator) {
     detail::get_internals().registered_exception_translators.push_front(
         std::forward<ExceptionTranslator>(translator));
 }
 
-
 /**
-  * Add a new module-local exception translator. Locally registered functions
-  * will be tried before any globally registered exception translators, which
-  * will only be invoked if the module-local handlers do not deal with
-  * the exception.
-  */
+ * Add a new module-local exception translator. Locally registered functions
+ * will be tried before any globally registered exception translators, which
+ * will only be invoked if the module-local handlers do not deal with
+ * the exception.
+ */
 inline void register_local_exception_translator(ExceptionTranslator &&translator) {
     detail::get_local_internals().registered_exception_translators.push_front(
         std::forward<ExceptionTranslator>(translator));
@@ -2350,8 +2518,8 @@ class exception : public object {
 public:
     exception() = default;
     exception(handle scope, const char *name, handle base = PyExc_Exception) {
-        std::string full_name = scope.attr("__name__").cast<std::string>() +
-                                std::string(".") + name;
+        std::string full_name
+            = scope.attr("__name__").cast<std::string>() + std::string(".") + name;
         m_ptr = PyErr_NewException(const_cast<char *>(full_name.c_str()), base.ptr(), NULL);
         if (hasattr(scope, "__dict__") && scope.attr("__dict__").contains(name)) {
             pybind11_fail("Error during initialization: multiple incompatible "
@@ -2362,9 +2530,7 @@ class exception : public object {
     }
 
     // Sets the current python exception to this exception object with the given message
-    void operator()(const char *message) {
-        PyErr_SetString(m_ptr, message);
-    }
+    void operator()(const char *message) { PyErr_SetString(m_ptr, message); }
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -2372,21 +2538,22 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // register_exception approach below.  (It would be simpler to have the static local variable
 // directly in register_exception, but that makes clang <3.5 segfault - issue #1349).
 template <typename CppException>
-exception<CppException> &get_exception_object() { static exception<CppException> ex; return ex; }
+exception<CppException> &get_exception_object() {
+    static exception<CppException> ex;
+    return ex;
+}
 
 // Helper function for register_exception and register_local_exception
 template <typename CppException>
-exception<CppException> &register_exception_impl(handle scope,
-                                                const char *name,
-                                                handle base,
-                                                bool isLocal) {
+exception<CppException> &
+register_exception_impl(handle scope, const char *name, handle base, bool isLocal) {
     auto &ex = detail::get_exception_object<CppException>();
     if (!ex) {
         ex = exception<CppException>(scope, name, base);
     }
 
-    auto register_func = isLocal ? &register_local_exception_translator
-                                 : &register_exception_translator;
+    auto register_func
+        = isLocal ? &register_local_exception_translator : &register_exception_translator;
 
     register_func([](std::exception_ptr p) {
         if (!p) {
@@ -2410,9 +2577,8 @@ PYBIND11_NAMESPACE_END(detail)
  * exception object and translator directly.
  */
 template <typename CppException>
-exception<CppException> &register_exception(handle scope,
-                                            const char *name,
-                                            handle base = PyExc_Exception) {
+exception<CppException> &
+register_exception(handle scope, const char *name, handle base = PyExc_Exception) {
     return detail::register_exception_impl<CppException>(scope, name, base, false /* isLocal */);
 }
 
@@ -2425,9 +2591,8 @@ exception<CppException> &register_exception(handle scope,
  * exception object and translator directly.
  */
 template <typename CppException>
-exception<CppException> &register_local_exception(handle scope,
-                                                  const char *name,
-                                                  handle base = PyExc_Exception) {
+exception<CppException> &
+register_local_exception(handle scope, const char *name, handle base = PyExc_Exception) {
     return detail::register_exception_impl<CppException>(scope, name, base, true /* isLocal */);
 }
 
@@ -2482,7 +2647,8 @@ error_already_set::~error_already_set() {
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-inline function get_type_override(const void *this_ptr, const type_info *this_type, const char *name)  {
+inline function
+get_type_override(const void *this_ptr, const type_info *this_type, const char *name) {
     handle self = get_object_handle(this_ptr, this_type);
     if (!self) {
         return function();
@@ -2508,17 +2674,16 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
 #if !defined(PYPY_VERSION) && PY_VERSION_HEX < 0x030B0000
     // TODO: Remove PyPy workaround for Python 3.11.
     // Current API fails on 3.11 since co_varnames can be null.
-#if PY_VERSION_HEX >= 0x03090000
+#    if PY_VERSION_HEX >= 0x03090000
     PyFrameObject *frame = PyThreadState_GetFrame(PyThreadState_Get());
     if (frame != nullptr) {
         PyCodeObject *f_code = PyFrame_GetCode(frame);
         // f_code is guaranteed to not be NULL
         if ((std::string) str(f_code->co_name) == name && f_code->co_argcount > 0) {
-            PyObject* locals = PyEval_GetLocals();
+            PyObject *locals = PyEval_GetLocals();
             if (locals != nullptr && f_code->co_varnames != nullptr) {
-                PyObject *self_caller = dict_getitem(
-                    locals, PyTuple_GET_ITEM(f_code->co_varnames, 0)
-                );
+                PyObject *self_caller
+                    = dict_getitem(locals, PyTuple_GET_ITEM(f_code->co_varnames, 0));
                 if (self_caller == self.ptr()) {
                     Py_DECREF(f_code);
                     Py_DECREF(frame);
@@ -2529,35 +2694,39 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
         Py_DECREF(f_code);
         Py_DECREF(frame);
     }
-#else
+#    else
     PyFrameObject *frame = PyThreadState_Get()->frame;
     if (frame != nullptr && (std::string) str(frame->f_code->co_name) == name
         && frame->f_code->co_argcount > 0) {
         PyFrame_FastToLocals(frame);
-        PyObject *self_caller = dict_getitem(
-            frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
+        PyObject *self_caller
+            = dict_getitem(frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
         if (self_caller == self.ptr()) {
             return function();
         }
     }
-#endif
+#    endif
 
 #else
     /* PyPy currently doesn't provide a detailed cpyext emulation of
        frame objects, so we have to emulate this using Python. This
        is going to be slow..*/
-    dict d; d["self"] = self; d["name"] = pybind11::str(name);
-    PyObject *result = PyRun_String(
-        "import inspect\n"
-        "frame = inspect.currentframe()\n"
-        "if frame is not None:\n"
-        "    frame = frame.f_back\n"
-        "    if frame is not None and str(frame.f_code.co_name) == name and "
-        "frame.f_code.co_argcount > 0:\n"
-        "        self_caller = frame.f_locals[frame.f_code.co_varnames[0]]\n"
-        "        if self_caller == self:\n"
-        "            self = None\n",
-        Py_file_input, d.ptr(), d.ptr());
+    dict d;
+    d["self"] = self;
+    d["name"] = pybind11::str(name);
+    PyObject *result
+        = PyRun_String("import inspect\n"
+                       "frame = inspect.currentframe()\n"
+                       "if frame is not None:\n"
+                       "    frame = frame.f_back\n"
+                       "    if frame is not None and str(frame.f_code.co_name) == name and "
+                       "frame.f_code.co_argcount > 0:\n"
+                       "        self_caller = frame.f_locals[frame.f_code.co_varnames[0]]\n"
+                       "        if self_caller == self:\n"
+                       "            self = None\n",
+                       Py_file_input,
+                       d.ptr(),
+                       d.ptr());
     if (result == nullptr)
         throw error_already_set();
     if (d["self"].is_none())
@@ -2578,7 +2747,8 @@ PYBIND11_NAMESPACE_END(detail)
   :name: The name of the overridden Python method to retrieve.
   :return: The Python method by this name from the object or an empty function wrapper.
  \endrst */
-template <class T> function get_override(const T *this_ptr, const char *name) {
+template <class T>
+function get_override(const T *this_ptr, const char *name) {
     auto *tinfo = detail::get_type_info(typeid(T));
     return tinfo ? detail::get_type_override(this_ptr, tinfo, name) : function();
 }
@@ -2616,20 +2786,21 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
         );
       }
 \endrst */
-#define PYBIND11_OVERRIDE_NAME(ret_type, cname, name, fn, ...) \
-    do { \
+#define PYBIND11_OVERRIDE_NAME(ret_type, cname, name, fn, ...)                                    \
+    do {                                                                                          \
         PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
-        return cname::fn(__VA_ARGS__); \
+        return cname::fn(__VA_ARGS__);                                                            \
     } while (false)
 
 /** \rst
     Macro for pure virtual functions, this function is identical to
     :c:macro:`PYBIND11_OVERRIDE_NAME`, except that it throws if no override can be found.
 \endrst */
-#define PYBIND11_OVERRIDE_PURE_NAME(ret_type, cname, name, fn, ...) \
-    do { \
+#define PYBIND11_OVERRIDE_PURE_NAME(ret_type, cname, name, fn, ...)                               \
+    do {                                                                                          \
         PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
-        pybind11::pybind11_fail("Tried to call pure virtual function \"" PYBIND11_STRINGIFY(cname) "::" name "\""); \
+        pybind11::pybind11_fail(                                                                  \
+            "Tried to call pure virtual function \"" PYBIND11_STRINGIFY(cname) "::" name "\"");   \
     } while (false)
 
 /** \rst
@@ -2657,21 +2828,22 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
           }
       };
 \endrst */
-#define PYBIND11_OVERRIDE(ret_type, cname, fn, ...) \
+#define PYBIND11_OVERRIDE(ret_type, cname, fn, ...)                                               \
     PYBIND11_OVERRIDE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
 
 /** \rst
     Macro for pure virtual functions, this function is identical to :c:macro:`PYBIND11_OVERRIDE`,
     except that it throws if no override can be found.
 \endrst */
-#define PYBIND11_OVERRIDE_PURE(ret_type, cname, fn, ...) \
-    PYBIND11_OVERRIDE_PURE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
-
+#define PYBIND11_OVERRIDE_PURE(ret_type, cname, fn, ...)                                          \
+    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
+        PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
 
 // Deprecated versions
 
 PYBIND11_DEPRECATED("get_type_overload has been deprecated")
-inline function get_type_overload(const void *this_ptr, const detail::type_info *this_type, const char *name) {
+inline function
+get_type_overload(const void *this_ptr, const detail::type_info *this_type, const char *name) {
     return detail::get_type_override(this_ptr, this_type, name);
 }
 
@@ -2680,15 +2852,16 @@ inline function get_overload(const T *this_ptr, const char *name) {
     return get_override(this_ptr, name);
 }
 
-#define PYBIND11_OVERLOAD_INT(ret_type, cname, name, ...) \
+#define PYBIND11_OVERLOAD_INT(ret_type, cname, name, ...)                                         \
     PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__)
-#define PYBIND11_OVERLOAD_NAME(ret_type, cname, name, fn, ...) \
+#define PYBIND11_OVERLOAD_NAME(ret_type, cname, name, fn, ...)                                    \
     PYBIND11_OVERRIDE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, fn, __VA_ARGS__)
-#define PYBIND11_OVERLOAD_PURE_NAME(ret_type, cname, name, fn, ...) \
-    PYBIND11_OVERRIDE_PURE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, fn, __VA_ARGS__);
-#define PYBIND11_OVERLOAD(ret_type, cname, fn, ...) \
+#define PYBIND11_OVERLOAD_PURE_NAME(ret_type, cname, name, fn, ...)                               \
+    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
+        PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, fn, __VA_ARGS__);
+#define PYBIND11_OVERLOAD(ret_type, cname, fn, ...)                                               \
     PYBIND11_OVERRIDE(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), fn, __VA_ARGS__)
-#define PYBIND11_OVERLOAD_PURE(ret_type, cname, fn, ...) \
+#define PYBIND11_OVERLOAD_PURE(ret_type, cname, fn, ...)                                          \
     PYBIND11_OVERRIDE_PURE(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), fn, __VA_ARGS__);
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index bdb3b9174f..75ea7de88e 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -11,38 +11,43 @@
 
 #include "detail/common.h"
 #include "buffer_info.h"
-#include <utility>
+
 #include <type_traits>
+#include <utility>
 
 #if defined(PYBIND11_HAS_OPTIONAL)
-#  include <optional>
+#    include <optional>
 #endif
 
 #ifdef PYBIND11_HAS_STRING_VIEW
-#  include <string_view>
+#    include <string_view>
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /* A few forward declarations */
-class handle; class object;
-class str; class iterator;
+class handle;
+class object;
+class str;
+class iterator;
 class type;
-struct arg; struct arg_v;
+struct arg;
+struct arg_v;
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 class args_proxy;
 bool isinstance_generic(handle obj, const std::type_info &tp);
 
 // Accessor forward declarations
-template <typename Policy> class accessor;
+template <typename Policy>
+class accessor;
 namespace accessor_policies {
-    struct obj_attr;
-    struct str_attr;
-    struct generic_item;
-    struct sequence_item;
-    struct list_item;
-    struct tuple_item;
+struct obj_attr;
+struct str_attr;
+struct generic_item;
+struct sequence_item;
+struct list_item;
+struct tuple_item;
 } // namespace accessor_policies
 using obj_attr_accessor = accessor<accessor_policies::obj_attr>;
 using str_attr_accessor = accessor<accessor_policies::str_attr>;
@@ -52,8 +57,9 @@ using list_accessor = accessor<accessor_policies::list_item>;
 using tuple_accessor = accessor<accessor_policies::tuple_item>;
 
 /// Tag and check to identify a class which implements the Python object API
-class pyobject_tag { };
-template <typename T> using is_pyobject = std::is_base_of<pyobject_tag, remove_reference_t<T>>;
+class pyobject_tag {};
+template <typename T>
+using is_pyobject = std::is_base_of<pyobject_tag, remove_reference_t<T>>;
 
 /** \rst
     A mixin class which adds common functions to `handle`, `object` and various accessors.
@@ -101,7 +107,8 @@ class object_api : public pyobject_tag {
     args_proxy operator*() const;
 
     /// Check if the given item is contained within this object, i.e. ``item in obj``.
-    template <typename T> bool contains(T &&item) const;
+    template <typename T>
+    bool contains(T &&item) const;
 
     /** \rst
         Assuming the Python object is a function or implements the ``__call__``
@@ -113,22 +120,24 @@ class object_api : public pyobject_tag {
         function will throw a `cast_error` exception. When the Python function
         call fails, a `error_already_set` exception is thrown.
     \endrst */
-    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    template <return_value_policy policy = return_value_policy::automatic_reference,
+              typename... Args>
     object operator()(Args &&...args) const;
-    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    template <return_value_policy policy = return_value_policy::automatic_reference,
+              typename... Args>
     PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
-        object call(Args&&... args) const;
+    object call(Args &&...args) const;
 
     /// Equivalent to ``obj is other`` in Python.
-    bool is(object_api const& other) const { return derived().ptr() == other.derived().ptr(); }
+    bool is(object_api const &other) const { return derived().ptr() == other.derived().ptr(); }
     /// Equivalent to ``obj is None`` in Python.
     bool is_none() const { return derived().ptr() == Py_None; }
     /// Equivalent to obj == other in Python
-    bool equal(object_api const &other) const      { return rich_compare(other, Py_EQ); }
-    bool not_equal(object_api const &other) const  { return rich_compare(other, Py_NE); }
-    bool operator<(object_api const &other) const  { return rich_compare(other, Py_LT); }
+    bool equal(object_api const &other) const { return rich_compare(other, Py_EQ); }
+    bool not_equal(object_api const &other) const { return rich_compare(other, Py_NE); }
+    bool operator<(object_api const &other) const { return rich_compare(other, Py_LT); }
     bool operator<=(object_api const &other) const { return rich_compare(other, Py_LE); }
-    bool operator>(object_api const &other) const  { return rich_compare(other, Py_GT); }
+    bool operator>(object_api const &other) const { return rich_compare(other, Py_GT); }
     bool operator>=(object_api const &other) const { return rich_compare(other, Py_GE); }
 
     object operator-() const;
@@ -188,7 +197,7 @@ class handle : public detail::object_api<handle> {
     handle() = default;
     /// Creates a ``handle`` from the given raw Python object pointer
     // NOLINTNEXTLINE(google-explicit-constructor)
-    handle(PyObject *ptr) : m_ptr(ptr) { } // Allow implicit conversion from PyObject*
+    handle(PyObject *ptr) : m_ptr(ptr) {} // Allow implicit conversion from PyObject*
 
     /// Return the underlying ``PyObject *`` pointer
     PyObject *ptr() const { return m_ptr; }
@@ -199,20 +208,27 @@ class handle : public detail::object_api<handle> {
         preferable to use the `object` class which derives from `handle` and calls
         this function automatically. Returns a reference to itself.
     \endrst */
-    const handle& inc_ref() const & { Py_XINCREF(m_ptr); return *this; }
+    const handle &inc_ref() const & {
+        Py_XINCREF(m_ptr);
+        return *this;
+    }
 
     /** \rst
         Manually decrease the reference count of the Python object. Usually, it is
         preferable to use the `object` class which derives from `handle` and calls
         this function automatically. Returns a reference to itself.
     \endrst */
-    const handle& dec_ref() const & { Py_XDECREF(m_ptr); return *this; }
+    const handle &dec_ref() const & {
+        Py_XDECREF(m_ptr);
+        return *this;
+    }
 
     /** \rst
         Attempt to cast the Python object into the given C++ type. A `cast_error`
         will be throw upon failure.
     \endrst */
-    template <typename T> T cast() const;
+    template <typename T>
+    T cast() const;
     /// Return ``true`` when the `handle` wraps a valid Python object
     explicit operator bool() const { return m_ptr != nullptr; }
     /** \rst
@@ -225,6 +241,7 @@ class handle : public detail::object_api<handle> {
     bool operator!=(const handle &h) const { return m_ptr != h.m_ptr; }
     PYBIND11_DEPRECATED("Use handle::operator bool() instead")
     bool check() const { return m_ptr != nullptr; }
+
 protected:
     PyObject *m_ptr = nullptr;
 };
@@ -251,7 +268,10 @@ class object : public handle {
     /// Copy constructor; always increases the reference count
     object(const object &o) : handle(o) { inc_ref(); }
     /// Move constructor; steals the object from ``other`` and preserves its reference count
-    object(object &&other) noexcept { m_ptr = other.m_ptr; other.m_ptr = nullptr; }
+    object(object &&other) noexcept {
+        m_ptr = other.m_ptr;
+        other.m_ptr = nullptr;
+    }
     /// Destructor; automatically calls `handle::dec_ref()`
     ~object() { dec_ref(); }
 
@@ -261,12 +281,12 @@ class object : public handle {
         Python object.
     \endrst */
     handle release() {
-      PyObject *tmp = m_ptr;
-      m_ptr = nullptr;
-      return handle(tmp);
+        PyObject *tmp = m_ptr;
+        m_ptr = nullptr;
+        return handle(tmp);
     }
 
-    object& operator=(const object &other) {
+    object &operator=(const object &other) {
         other.inc_ref();
         // Use temporary variable to ensure `*this` remains valid while
         // `Py_XDECREF` executes, in case `*this` is accessible from Python.
@@ -276,7 +296,7 @@ class object : public handle {
         return *this;
     }
 
-    object& operator=(object &&other) noexcept {
+    object &operator=(object &&other) noexcept {
         if (this != &other) {
             handle temp(m_ptr);
             m_ptr = other.m_ptr;
@@ -287,24 +307,28 @@ class object : public handle {
     }
 
     // Calling cast() on an object lvalue just copies (via handle::cast)
-    template <typename T> T cast() const &;
+    template <typename T>
+    T cast() const &;
     // Calling on an object rvalue does a move, if needed and/or possible
-    template <typename T> T cast() &&;
+    template <typename T>
+    T cast() &&;
 
 protected:
     // Tags for choosing constructors from raw PyObject *
-    struct borrowed_t { };
-    struct stolen_t { };
+    struct borrowed_t {};
+    struct stolen_t {};
 
     /// @cond BROKEN
-    template <typename T> friend T reinterpret_borrow(handle);
-    template <typename T> friend T reinterpret_steal(handle);
+    template <typename T>
+    friend T reinterpret_borrow(handle);
+    template <typename T>
+    friend T reinterpret_steal(handle);
     /// @endcond
 
 public:
     // Only accessible from derived classes and the reinterpret_* functions
     object(handle h, borrowed_t) : handle(h) { inc_ref(); }
-    object(handle h, stolen_t) : handle(h) { }
+    object(handle h, stolen_t) : handle(h) {}
 };
 
 /** \rst
@@ -320,7 +344,10 @@ class object : public handle {
         // or
         py::tuple t = reinterpret_borrow<py::tuple>(p); // <-- `p` must be already be a `tuple`
 \endrst */
-template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrowed_t{}}; }
+template <typename T>
+T reinterpret_borrow(handle h) {
+    return {h, object::borrowed_t{}};
+}
 
 /** \rst
     Like `reinterpret_borrow`, but steals the reference.
@@ -330,15 +357,18 @@ template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrow
         PyObject *p = PyObject_Str(obj);
         py::str s = reinterpret_steal<py::str>(p); // <-- `p` must be already be a `str`
 \endrst */
-template <typename T> T reinterpret_steal(handle h) { return {h, object::stolen_t{}}; }
+template <typename T>
+T reinterpret_steal(handle h) {
+    return {h, object::stolen_t{}};
+}
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 std::string error_string();
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4275 4251)
+#    pragma warning(push)
+#    pragma warning(disable : 4275 4251)
 //     warning C4275: An exported class was derived from a class that wasn't exported.
 //     Can be ignored when derived from a STL class.
 #endif
@@ -362,19 +392,22 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
     /// Give the currently-held error back to Python, if any.  If there is currently a Python error
     /// already set it is cleared first.  After this call, the current object no longer stores the
     /// error variables (but the `.what()` string is still available).
-    void restore() { PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr()); }
+    void restore() {
+        PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr());
+    }
 
-    /// If it is impossible to raise the currently-held error, such as in a destructor, we can write
-    /// it out using Python's unraisable hook (`sys.unraisablehook`). The error context should be
-    /// some object whose `repr()` helps identify the location of the error. Python already knows the
-    /// type and value of the error, so there is no need to repeat that. After this call, the current
-    /// object no longer stores the error variables, and neither does Python.
+    /// If it is impossible to raise the currently-held error, such as in a destructor, we can
+    /// write it out using Python's unraisable hook (`sys.unraisablehook`). The error context
+    /// should be some object whose `repr()` helps identify the location of the error. Python
+    /// already knows the type and value of the error, so there is no need to repeat that. After
+    /// this call, the current object no longer stores the error variables, and neither does
+    /// Python.
     void discard_as_unraisable(object err_context) {
         restore();
         PyErr_WriteUnraisable(err_context.ptr());
     }
-    /// An alternate version of `discard_as_unraisable()`, where a string provides information on the
-    /// location of the error. For example, `__func__` could be helpful.
+    /// An alternate version of `discard_as_unraisable()`, where a string provides information on
+    /// the location of the error. For example, `__func__` could be helpful.
     void discard_as_unraisable(const char *err_context) {
         discard_as_unraisable(reinterpret_steal<object>(PYBIND11_FROM_STRING(err_context)));
     }
@@ -390,15 +423,15 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
         return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
     }
 
-    const object& type() const { return m_type; }
-    const object& value() const { return m_value; }
-    const object& trace() const { return m_trace; }
+    const object &type() const { return m_type; }
+    const object &value() const { return m_value; }
+    const object &trace() const { return m_trace; }
 
 private:
     object m_type, m_value, m_trace;
 };
 #if defined(_MSC_VER)
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
 #if PY_VERSION_HEX >= 0x03030000
@@ -435,7 +468,7 @@ inline void raise_from(PyObject *type, const char *message) {
 /// from the error contained in error_already_set to indicate that the chosen error was
 /// caused by the original error. After this function is called error_already_set will
 /// no longer contain an error.
-inline void raise_from(error_already_set& err, PyObject *type, const char *message) {
+inline void raise_from(error_already_set &err, PyObject *type, const char *message) {
     err.restore();
     raise_from(type, message);
 }
@@ -453,13 +486,21 @@ inline void raise_from(error_already_set& err, PyObject *type, const char *messa
     `object` or a class which was exposed to Python as ``py::class_<T>``.
 \endrst */
 template <typename T, detail::enable_if_t<std::is_base_of<object, T>::value, int> = 0>
-bool isinstance(handle obj) { return T::check_(obj); }
+bool isinstance(handle obj) {
+    return T::check_(obj);
+}
 
 template <typename T, detail::enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
-bool isinstance(handle obj) { return detail::isinstance_generic(obj, typeid(T)); }
+bool isinstance(handle obj) {
+    return detail::isinstance_generic(obj, typeid(T));
+}
 
-template <> inline bool isinstance<handle>(handle) = delete;
-template <> inline bool isinstance<object>(handle obj) { return obj.ptr() != nullptr; }
+template <>
+inline bool isinstance<handle>(handle) = delete;
+template <>
+inline bool isinstance<object>(handle obj) {
+    return obj.ptr() != nullptr;
+}
 
 /// \ingroup python_builtins
 /// Return true if ``obj`` is an instance of the ``type``.
@@ -482,22 +523,30 @@ inline bool hasattr(handle obj, const char *name) {
 }
 
 inline void delattr(handle obj, handle name) {
-    if (PyObject_DelAttr(obj.ptr(), name.ptr()) != 0) { throw error_already_set(); }
+    if (PyObject_DelAttr(obj.ptr(), name.ptr()) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline void delattr(handle obj, const char *name) {
-    if (PyObject_DelAttrString(obj.ptr(), name) != 0) { throw error_already_set(); }
+    if (PyObject_DelAttrString(obj.ptr(), name) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline object getattr(handle obj, handle name) {
     PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr());
-    if (!result) { throw error_already_set(); }
+    if (!result) {
+        throw error_already_set();
+    }
     return reinterpret_steal<object>(result);
 }
 
 inline object getattr(handle obj, const char *name) {
     PyObject *result = PyObject_GetAttrString(obj.ptr(), name);
-    if (!result) { throw error_already_set(); }
+    if (!result) {
+        throw error_already_set();
+    }
     return reinterpret_steal<object>(result);
 }
 
@@ -518,16 +567,22 @@ inline object getattr(handle obj, const char *name, handle default_) {
 }
 
 inline void setattr(handle obj, handle name, handle value) {
-    if (PyObject_SetAttr(obj.ptr(), name.ptr(), value.ptr()) != 0) { throw error_already_set(); }
+    if (PyObject_SetAttr(obj.ptr(), name.ptr(), value.ptr()) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline void setattr(handle obj, const char *name, handle value) {
-    if (PyObject_SetAttrString(obj.ptr(), name, value.ptr()) != 0) { throw error_already_set(); }
+    if (PyObject_SetAttrString(obj.ptr(), name, value.ptr()) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline ssize_t hash(handle obj) {
     auto h = PyObject_Hash(obj.ptr());
-    if (h == -1) { throw error_already_set(); }
+    if (h == -1) {
+        throw error_already_set();
+    }
     return h;
 }
 
@@ -552,8 +607,7 @@ inline handle get_function(handle value) {
 // aren't swallowed (see #2862)
 
 // copied from cpython _PyDict_GetItemStringWithError
-inline PyObject * dict_getitemstring(PyObject *v, const char *key)
-{
+inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
 #if PY_MAJOR_VERSION >= 3
     PyObject *kv = nullptr, *rv = nullptr;
     kv = PyUnicode_FromString(key);
@@ -572,8 +626,7 @@ inline PyObject * dict_getitemstring(PyObject *v, const char *key)
 #endif
 }
 
-inline PyObject * dict_getitem(PyObject *v, PyObject *key)
-{
+inline PyObject *dict_getitem(PyObject *v, PyObject *key) {
 #if PY_MAJOR_VERSION >= 3
     PyObject *rv = PyDict_GetItemWithError(v, key);
     if (rv == NULL && PyErr_Occurred()) {
@@ -585,11 +638,13 @@ inline PyObject * dict_getitem(PyObject *v, PyObject *key)
 #endif
 }
 
-// Helper aliases/functions to support implicit casting of values given to python accessors/methods.
-// When given a pyobject, this simply returns the pyobject as-is; for other C++ type, the value goes
-// through pybind11::cast(obj) to convert it to an `object`.
+// Helper aliases/functions to support implicit casting of values given to python
+// accessors/methods. When given a pyobject, this simply returns the pyobject as-is; for other C++
+// type, the value goes through pybind11::cast(obj) to convert it to an `object`.
 template <typename T, enable_if_t<is_pyobject<T>::value, int> = 0>
-auto object_or_cast(T &&o) -> decltype(std::forward<T>(o)) { return std::forward<T>(o); }
+auto object_or_cast(T &&o) -> decltype(std::forward<T>(o)) {
+    return std::forward<T>(o);
+}
 // The following casting version is implemented in cast.h:
 template <typename T, enable_if_t<!is_pyobject<T>::value, int> = 0>
 object object_or_cast(T &&o);
@@ -597,50 +652,61 @@ object object_or_cast(T &&o);
 inline handle object_or_cast(PyObject *ptr) { return ptr; }
 
 #if defined(_MSC_VER) && _MSC_VER < 1920
-#  pragma warning(push)
-#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
+#    pragma warning(push)
+#    pragma warning(disable : 4522) // warning C4522: multiple assignment operators specified
 #endif
 template <typename Policy>
 class accessor : public object_api<accessor<Policy>> {
     using key_type = typename Policy::key_type;
 
 public:
-    accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) { }
+    accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) {}
     accessor(const accessor &) = default;
     accessor(accessor &&) noexcept = default;
 
-    // accessor overload required to override default assignment operator (templates are not allowed
-    // to replace default compiler-generated assignments).
+    // accessor overload required to override default assignment operator (templates are not
+    // allowed to replace default compiler-generated assignments).
     void operator=(const accessor &a) && { std::move(*this).operator=(handle(a)); }
     void operator=(const accessor &a) & { operator=(handle(a)); }
 
-    template <typename T> void operator=(T &&value) && {
+    template <typename T>
+    void operator=(T &&value) && {
         Policy::set(obj, key, object_or_cast(std::forward<T>(value)));
     }
-    template <typename T> void operator=(T &&value) & {
+    template <typename T>
+    void operator=(T &&value) & {
         get_cache() = reinterpret_borrow<object>(object_or_cast(std::forward<T>(value)));
     }
 
     template <typename T = Policy>
-    PYBIND11_DEPRECATED("Use of obj.attr(...) as bool is deprecated in favor of pybind11::hasattr(obj, ...)")
-    explicit operator enable_if_t<std::is_same<T, accessor_policies::str_attr>::value ||
-            std::is_same<T, accessor_policies::obj_attr>::value, bool>() const {
+    PYBIND11_DEPRECATED(
+        "Use of obj.attr(...) as bool is deprecated in favor of pybind11::hasattr(obj, ...)")
+    explicit
+    operator enable_if_t<std::is_same<T, accessor_policies::str_attr>::value
+                             || std::is_same<T, accessor_policies::obj_attr>::value,
+                         bool>() const {
         return hasattr(obj, key);
     }
     template <typename T = Policy>
     PYBIND11_DEPRECATED("Use of obj[key] as bool is deprecated in favor of obj.contains(key)")
-    explicit operator enable_if_t<std::is_same<T, accessor_policies::generic_item>::value, bool>() const {
+    explicit
+    operator enable_if_t<std::is_same<T, accessor_policies::generic_item>::value, bool>() const {
         return obj.contains(key);
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator object() const { return get_cache(); }
     PyObject *ptr() const { return get_cache().ptr(); }
-    template <typename T> T cast() const { return get_cache().template cast<T>(); }
+    template <typename T>
+    T cast() const {
+        return get_cache().template cast<T>();
+    }
 
 private:
     object &get_cache() const {
-        if (!cache) { cache = Policy::get(obj, key); }
+        if (!cache) {
+            cache = Policy::get(obj, key);
+        }
         return cache;
     }
 
@@ -650,7 +716,7 @@ class accessor : public object_api<accessor<Policy>> {
     mutable object cache;
 };
 #if defined(_MSC_VER) && _MSC_VER < 1920
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(accessor_policies)
@@ -671,12 +737,16 @@ struct generic_item {
 
     static object get(handle obj, handle key) {
         PyObject *result = PyObject_GetItem(obj.ptr(), key.ptr());
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_steal<object>(result);
     }
 
     static void set(handle obj, handle key, handle val) {
-        if (PyObject_SetItem(obj.ptr(), key.ptr(), val.ptr()) != 0) { throw error_already_set(); }
+        if (PyObject_SetItem(obj.ptr(), key.ptr(), val.ptr()) != 0) {
+            throw error_already_set();
+        }
     }
 };
 
@@ -686,7 +756,9 @@ struct sequence_item {
     template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     static object get(handle obj, const IdxType &index) {
         PyObject *result = PySequence_GetItem(obj.ptr(), ssize_t_cast(index));
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_steal<object>(result);
     }
 
@@ -705,7 +777,9 @@ struct list_item {
     template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     static object get(handle obj, const IdxType &index) {
         PyObject *result = PyList_GetItem(obj.ptr(), ssize_t_cast(index));
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_borrow<object>(result);
     }
 
@@ -724,7 +798,9 @@ struct tuple_item {
     template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     static object get(handle obj, const IdxType &index) {
         PyObject *result = PyTuple_GetItem(obj.ptr(), ssize_t_cast(index));
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_borrow<object>(result);
     }
 
@@ -751,7 +827,7 @@ class generic_iterator : public Policy {
     using pointer = typename Policy::pointer;
 
     generic_iterator() = default;
-    generic_iterator(handle seq, ssize_t index) : Policy(seq, index) { }
+    generic_iterator(handle seq, ssize_t index) : Policy(seq, index) {}
 
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator*() const { return Policy::dereference(); }
@@ -759,22 +835,48 @@ class generic_iterator : public Policy {
     reference operator[](difference_type n) const { return *(*this + n); }
     pointer operator->() const { return **this; }
 
-    It &operator++() { Policy::increment(); return *this; }
-    It operator++(int) { auto copy = *this; Policy::increment(); return copy; }
-    It &operator--() { Policy::decrement(); return *this; }
-    It operator--(int) { auto copy = *this; Policy::decrement(); return copy; }
-    It &operator+=(difference_type n) { Policy::advance(n); return *this; }
-    It &operator-=(difference_type n) { Policy::advance(-n); return *this; }
+    It &operator++() {
+        Policy::increment();
+        return *this;
+    }
+    It operator++(int) {
+        auto copy = *this;
+        Policy::increment();
+        return copy;
+    }
+    It &operator--() {
+        Policy::decrement();
+        return *this;
+    }
+    It operator--(int) {
+        auto copy = *this;
+        Policy::decrement();
+        return copy;
+    }
+    It &operator+=(difference_type n) {
+        Policy::advance(n);
+        return *this;
+    }
+    It &operator-=(difference_type n) {
+        Policy::advance(-n);
+        return *this;
+    }
 
-    friend It operator+(const It &a, difference_type n) { auto copy = a; return copy += n; }
+    friend It operator+(const It &a, difference_type n) {
+        auto copy = a;
+        return copy += n;
+    }
     friend It operator+(difference_type n, const It &b) { return b + n; }
-    friend It operator-(const It &a, difference_type n) { auto copy = a; return copy -= n; }
+    friend It operator-(const It &a, difference_type n) {
+        auto copy = a;
+        return copy -= n;
+    }
     friend difference_type operator-(const It &a, const It &b) { return a.distance_to(b); }
 
     friend bool operator==(const It &a, const It &b) { return a.equal(b); }
     friend bool operator!=(const It &a, const It &b) { return !(a == b); }
-    friend bool operator< (const It &a, const It &b) { return b - a > 0; }
-    friend bool operator> (const It &a, const It &b) { return b < a; }
+    friend bool operator<(const It &a, const It &b) { return b - a > 0; }
+    friend bool operator>(const It &a, const It &b) { return b < a; }
     friend bool operator>=(const It &a, const It &b) { return !(a < b); }
     friend bool operator<=(const It &a, const It &b) { return !(a > b); }
 };
@@ -786,7 +888,7 @@ struct arrow_proxy {
     T value;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    arrow_proxy(T &&value) noexcept : value(std::move(value)) { }
+    arrow_proxy(T &&value) noexcept : value(std::move(value)) {}
     T *operator->() const { return &value; }
 };
 
@@ -798,7 +900,7 @@ class sequence_fast_readonly {
     using reference = const handle; // PR #3263
     using pointer = arrow_proxy<const handle>;
 
-    sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) { }
+    sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) {}
 
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference dereference() const { return *ptr; }
@@ -820,7 +922,7 @@ class sequence_slow_readwrite {
     using reference = sequence_accessor;
     using pointer = arrow_proxy<const sequence_accessor>;
 
-    sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) { }
+    sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) {}
 
     reference dereference() const { return {obj, static_cast<size_t>(index)}; }
     void increment() { ++index; }
@@ -886,33 +988,38 @@ inline bool PyNone_Check(PyObject *o) { return o == Py_None; }
 inline bool PyEllipsis_Check(PyObject *o) { return o == Py_Ellipsis; }
 
 #ifdef PYBIND11_STR_LEGACY_PERMISSIVE
-inline bool PyUnicode_Check_Permissive(PyObject *o) { return PyUnicode_Check(o) || PYBIND11_BYTES_CHECK(o); }
-#define PYBIND11_STR_CHECK_FUN detail::PyUnicode_Check_Permissive
+inline bool PyUnicode_Check_Permissive(PyObject *o) {
+    return PyUnicode_Check(o) || PYBIND11_BYTES_CHECK(o);
+}
+#    define PYBIND11_STR_CHECK_FUN detail::PyUnicode_Check_Permissive
 #else
-#define PYBIND11_STR_CHECK_FUN PyUnicode_Check
+#    define PYBIND11_STR_CHECK_FUN PyUnicode_Check
 #endif
 
 inline bool PyStaticMethod_Check(PyObject *o) { return o->ob_type == &PyStaticMethod_Type; }
 
 class kwargs_proxy : public handle {
 public:
-    explicit kwargs_proxy(handle h) : handle(h) { }
+    explicit kwargs_proxy(handle h) : handle(h) {}
 };
 
 class args_proxy : public handle {
 public:
-    explicit args_proxy(handle h) : handle(h) { }
+    explicit args_proxy(handle h) : handle(h) {}
     kwargs_proxy operator*() const { return kwargs_proxy(*this); }
 };
 
 /// Python argument categories (using PEP 448 terms)
-template <typename T> using is_keyword = std::is_base_of<arg, T>;
-template <typename T> using is_s_unpacking = std::is_same<args_proxy, T>; // * unpacking
-template <typename T> using is_ds_unpacking = std::is_same<kwargs_proxy, T>; // ** unpacking
-template <typename T> using is_positional = satisfies_none_of<T,
-    is_keyword, is_s_unpacking, is_ds_unpacking
->;
-template <typename T> using is_keyword_or_ds = satisfies_any_of<T, is_keyword, is_ds_unpacking>;
+template <typename T>
+using is_keyword = std::is_base_of<arg, T>;
+template <typename T>
+using is_s_unpacking = std::is_same<args_proxy, T>; // * unpacking
+template <typename T>
+using is_ds_unpacking = std::is_same<kwargs_proxy, T>; // ** unpacking
+template <typename T>
+using is_positional = satisfies_none_of<T, is_keyword, is_s_unpacking, is_ds_unpacking>;
+template <typename T>
+using is_keyword_or_ds = satisfies_any_of<T, is_keyword, is_ds_unpacking>;
 
 // Call argument collector forward declarations
 template <return_value_policy policy = return_value_policy::automatic_reference>
@@ -926,53 +1033,60 @@ PYBIND11_NAMESPACE_END(detail)
 //       inheriting ctors: `using Parent::Parent`. It's not an option right now because
 //       the `using` statement triggers the parent deprecation warning even if the ctor
 //       isn't even used.
-#define PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
-    public: \
-        PYBIND11_DEPRECATED("Use reinterpret_borrow<"#Name">() or reinterpret_steal<"#Name">()") \
-        Name(handle h, bool is_borrowed) : Parent(is_borrowed ? Parent(h, borrowed_t{}) : Parent(h, stolen_t{})) { } \
-        Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) { } \
-        Name(handle h, stolen_t) : Parent(h, stolen_t{}) { } \
-        PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead") \
-        bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); } \
-        static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); } \
-        template <typename Policy_> \
-        /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-        Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }
-
-#define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun) \
-    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
-    /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(const object &o) \
-    : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
-    { if (!m_ptr) throw error_already_set(); } \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(object &&o) \
-    : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
-    { if (!m_ptr) throw error_already_set(); }
-
-#define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun) \
-    PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun) \
-    Name() : Parent() { }
-
-#define PYBIND11_OBJECT_CHECK_FAILED(Name, o_ptr) \
-    ::pybind11::type_error("Object of type '" + \
-                           ::pybind11::detail::get_fully_qualified_tp_name(Py_TYPE(o_ptr)) + \
-                           "' is not an instance of '" #Name "'")
-
-#define PYBIND11_OBJECT(Name, Parent, CheckFun) \
-    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
-    /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(const object &o) : Parent(o) \
-    { if (m_ptr && !check_(m_ptr)) throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr); } \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(object &&o) : Parent(std::move(o)) \
-    { if (m_ptr && !check_(m_ptr)) throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr); }
-
-#define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun) \
-    PYBIND11_OBJECT(Name, Parent, CheckFun) \
-    Name() : Parent() { }
+#define PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                            \
+public:                                                                                           \
+    PYBIND11_DEPRECATED("Use reinterpret_borrow<" #Name ">() or reinterpret_steal<" #Name ">()")  \
+    Name(handle h, bool is_borrowed)                                                              \
+        : Parent(is_borrowed ? Parent(h, borrowed_t{}) : Parent(h, stolen_t{})) {}                \
+    Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) {}                                       \
+    Name(handle h, stolen_t) : Parent(h, stolen_t{}) {}                                           \
+    PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead")                       \
+    bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); }                     \
+    static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); }              \
+    template <typename Policy_> /* NOLINTNEXTLINE(google-explicit-constructor) */                 \
+    Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) {}
+
+#define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                   \
+    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                                \
+    /* This is deliberately not 'explicit' to allow implicit conversion from object: */           \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(const object &o)                                                                         \
+        : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) {               \
+        if (!m_ptr)                                                                               \
+            throw error_already_set();                                                            \
+    }                                                                                             \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(object &&o) : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) {  \
+        if (!m_ptr)                                                                               \
+            throw error_already_set();                                                            \
+    }
+
+#define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun)                           \
+    PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                       \
+    Name() : Parent() {}
+
+#define PYBIND11_OBJECT_CHECK_FAILED(Name, o_ptr)                                                 \
+    ::pybind11::type_error("Object of type '"                                                     \
+                           + ::pybind11::detail::get_fully_qualified_tp_name(Py_TYPE(o_ptr))      \
+                           + "' is not an instance of '" #Name "'")
+
+#define PYBIND11_OBJECT(Name, Parent, CheckFun)                                                   \
+    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                                \
+    /* This is deliberately not 'explicit' to allow implicit conversion from object: */           \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(const object &o) : Parent(o) {                                                           \
+        if (m_ptr && !check_(m_ptr))                                                              \
+            throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr);                                      \
+    }                                                                                             \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(object &&o) : Parent(std::move(o)) {                                                     \
+        if (m_ptr && !check_(m_ptr))                                                              \
+            throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr);                                      \
+    }
+
+#define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun)                                           \
+    PYBIND11_OBJECT(Name, Parent, CheckFun)                                                       \
+    Name() : Parent() {}
 
 /// \addtogroup pytypes
 /// @{
@@ -995,7 +1109,7 @@ class iterator : public object {
 
     PYBIND11_OBJECT_DEFAULT(iterator, object, PyIter_Check)
 
-    iterator& operator++() {
+    iterator &operator++() {
         advance();
         return *this;
     }
@@ -1009,13 +1123,16 @@ class iterator : public object {
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator*() const {
         if (m_ptr && !value.ptr()) {
-            auto& self = const_cast<iterator &>(*this);
+            auto &self = const_cast<iterator &>(*this);
             self.advance();
         }
         return value;
     }
 
-    pointer operator->() const { operator*(); return &value; }
+    pointer operator->() const {
+        operator*();
+        return &value;
+    }
 
     /** \rst
          The value which marks the end of the iteration. ``it == iterator::sentinel()``
@@ -1038,21 +1155,21 @@ class iterator : public object {
 private:
     void advance() {
         value = reinterpret_steal<object>(PyIter_Next(m_ptr));
-        if (PyErr_Occurred()) { throw error_already_set(); }
+        if (PyErr_Occurred()) {
+            throw error_already_set();
+        }
     }
 
 private:
     object value = {};
 };
 
-
-
 class type : public object {
 public:
     PYBIND11_OBJECT(type, object, PyType_Check)
 
     /// Return a type handle from a handle or an object
-    static handle handle_of(handle h) { return handle((PyObject*) Py_TYPE(h.ptr())); }
+    static handle handle_of(handle h) { return handle((PyObject *) Py_TYPE(h.ptr())); }
 
     /// Return a type object from a handle or an object
     static type of(handle h) { return type(type::handle_of(h), borrowed_t{}); }
@@ -1061,14 +1178,16 @@ class type : public object {
     /// Convert C++ type to handle if previously registered. Does not convert
     /// standard types, like int, float. etc. yet.
     /// See https://github.com/pybind/pybind11/issues/2486
-    template<typename T>
+    template <typename T>
     static handle handle_of();
 
     /// Convert C++ type to type if previously registered. Does not convert
     /// standard types, like int, float. etc. yet.
     /// See https://github.com/pybind/pybind11/issues/2486
-    template<typename T>
-    static type of() {return type(type::handle_of<T>(), borrowed_t{}); }
+    template <typename T>
+    static type of() {
+        return type(type::handle_of<T>(), borrowed_t{});
+    }
 };
 
 class iterable : public object {
@@ -1090,29 +1209,29 @@ class str : public object {
         }
     }
 
-    // 'explicit' is explicitly omitted from the following constructors to allow implicit conversion to py::str from C++ string-like objects
+    // 'explicit' is explicitly omitted from the following constructors to allow implicit
+    // conversion to py::str from C++ string-like objects
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(const char *c = "")
-        : object(PyUnicode_FromString(c), stolen_t{}) {
+    str(const char *c = "") : object(PyUnicode_FromString(c), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate string object!");
         }
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(const std::string &s) : str(s.data(), s.size()) { }
+    str(const std::string &s) : str(s.data(), s.size()) {}
 
 #ifdef PYBIND11_HAS_STRING_VIEW
     // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
     template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(T s) : str(s.data(), s.size()) { }
+    str(T s) : str(s.data(), s.size()) {}
 
-# ifdef PYBIND11_HAS_U8STRING
+#    ifdef PYBIND11_HAS_U8STRING
     // reinterpret_cast here is safe (C++20 guarantees char8_t has the same size/alignment as char)
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(std::u8string_view s) : str(reinterpret_cast<const char*>(s.data()), s.size()) { }
-# endif
+    str(std::u8string_view s) : str(reinterpret_cast<const char *>(s.data()), s.size()) {}
+#    endif
 
 #endif
 
@@ -1155,9 +1274,11 @@ class str : public object {
     static PyObject *raw_str(PyObject *op) {
         PyObject *str_value = PyObject_Str(op);
 #if PY_MAJOR_VERSION < 3
-        if (!str_value) throw error_already_set();
+        if (!str_value)
+            throw error_already_set();
         PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
-        Py_XDECREF(str_value); str_value = unicode;
+        Py_XDECREF(str_value);
+        str_value = unicode;
 #endif
         return str_value;
     }
@@ -1179,8 +1300,7 @@ class bytes : public object {
 
     // Allow implicit conversion:
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bytes(const char *c = "")
-        : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
+    bytes(const char *c = "") : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate bytes object!");
         }
@@ -1196,7 +1316,7 @@ class bytes : public object {
 
     // Allow implicit conversion:
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bytes(const std::string &s) : bytes(s.data(), s.size()) { }
+    bytes(const std::string &s) : bytes(s.data(), s.size()) {}
 
     explicit bytes(const pybind11::str &s);
 
@@ -1214,7 +1334,7 @@ class bytes : public object {
     // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
     template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bytes(T s) : bytes(s.data(), s.size()) { }
+    bytes(T s) : bytes(s.data(), s.size()) {}
 
     // Obtain a string view that views the current `bytes` buffer value.  Note that this is only
     // valid so long as the `bytes` instance remains alive and so generally should not outlive the
@@ -1229,7 +1349,6 @@ class bytes : public object {
         return {buffer, static_cast<size_t>(length)};
     }
 #endif
-
 };
 // Note: breathe >= 4.17.0 will fail to build docs if the below two constructors
 // are included in the doxygen group; close here and reopen after as a workaround
@@ -1255,7 +1374,7 @@ inline bytes::bytes(const pybind11::str &s) {
     m_ptr = obj.release().ptr();
 }
 
-inline str::str(const bytes& b) {
+inline str::str(const bytes &b) {
     char *buffer = nullptr;
     ssize_t length = 0;
     if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length)) {
@@ -1282,10 +1401,9 @@ class bytearray : public object {
         }
     }
 
-    bytearray()
-        : bytearray("", 0) {}
+    bytearray() : bytearray("", 0) {}
 
-    explicit bytearray(const std::string &s) : bytearray(s.data(), s.size()) { }
+    explicit bytearray(const std::string &s) : bytearray(s.data(), s.size()) {}
 
     size_t size() const { return static_cast<size_t>(PyByteArray_Size(m_ptr)); }
 
@@ -1304,22 +1422,22 @@ class bytearray : public object {
 class none : public object {
 public:
     PYBIND11_OBJECT(none, object, detail::PyNone_Check)
-    none() : object(Py_None, borrowed_t{}) { }
+    none() : object(Py_None, borrowed_t{}) {}
 };
 
 class ellipsis : public object {
 public:
     PYBIND11_OBJECT(ellipsis, object, detail::PyEllipsis_Check)
-    ellipsis() : object(Py_Ellipsis, borrowed_t{}) { }
+    ellipsis() : object(Py_Ellipsis, borrowed_t{}) {}
 };
 
 class bool_ : public object {
 public:
     PYBIND11_OBJECT_CVT(bool_, object, PyBool_Check, raw_bool)
-    bool_() : object(Py_False, borrowed_t{}) { }
+    bool_() : object(Py_False, borrowed_t{}) {}
     // Allow implicit conversion from and to `bool`:
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) { }
+    bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) {}
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator bool() const { return (m_ptr != nullptr) && PyLong_AsLong(m_ptr) != 0; }
 
@@ -1357,10 +1475,9 @@ PYBIND11_NAMESPACE_END(detail)
 class int_ : public object {
 public:
     PYBIND11_OBJECT_CVT(int_, object, PYBIND11_LONG_CHECK, PyNumber_Long)
-    int_() : object(PyLong_FromLong(0), stolen_t{}) { }
+    int_() : object(PyLong_FromLong(0), stolen_t{}) {}
     // Allow implicit conversion from C++ integral types:
-    template <typename T,
-              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     int_(T value) {
         if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
@@ -1381,15 +1498,12 @@ class int_ : public object {
         }
     }
 
-    template <typename T,
-              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator T() const {
-        return std::is_unsigned<T>::value
-            ? detail::as_unsigned<T>(m_ptr)
-            : sizeof(T) <= sizeof(long)
-              ? (T) PyLong_AsLong(m_ptr)
-              : (T) PYBIND11_LONG_AS_LONGLONG(m_ptr);
+        return std::is_unsigned<T>::value  ? detail::as_unsigned<T>(m_ptr)
+               : sizeof(T) <= sizeof(long) ? (T) PyLong_AsLong(m_ptr)
+                                           : (T) PYBIND11_LONG_AS_LONGLONG(m_ptr);
     }
 };
 
@@ -1426,9 +1540,7 @@ class weakref : public object {
     }
 
 private:
-    static PyObject *raw_weakref(PyObject *o) {
-        return PyWeakref_NewRef(o, nullptr);
-    }
+    static PyObject *raw_weakref(PyObject *o) { return PyWeakref_NewRef(o, nullptr); }
 };
 
 class slice : public object {
@@ -1449,19 +1561,21 @@ class slice : public object {
         : slice(int_(start_), int_(stop_), int_(step_)) {}
 #endif
 
-    bool compute(size_t length, size_t *start, size_t *stop, size_t *step,
-                 size_t *slicelength) const {
+    bool
+    compute(size_t length, size_t *start, size_t *stop, size_t *step, size_t *slicelength) const {
         return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
-                                    (ssize_t) length, (ssize_t *) start,
-                                    (ssize_t *) stop, (ssize_t *) step,
-                                    (ssize_t *) slicelength) == 0;
+                                    (ssize_t) length,
+                                    (ssize_t *) start,
+                                    (ssize_t *) stop,
+                                    (ssize_t *) step,
+                                    (ssize_t *) slicelength)
+               == 0;
     }
-    bool compute(ssize_t length, ssize_t *start, ssize_t *stop, ssize_t *step,
-      ssize_t *slicelength) const {
-      return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
-          length, start,
-          stop, step,
-          slicelength) == 0;
+    bool compute(
+        ssize_t length, ssize_t *start, ssize_t *stop, ssize_t *step, ssize_t *slicelength) const {
+        return PySlice_GetIndicesEx(
+                   (PYBIND11_SLICE_OBJECT *) m_ptr, length, start, stop, step, slicelength)
+               == 0;
     }
 
 private:
@@ -1475,9 +1589,12 @@ class capsule : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(capsule, object, PyCapsule_CheckExact)
     PYBIND11_DEPRECATED("Use reinterpret_borrow<capsule>() or reinterpret_steal<capsule>()")
-    capsule(PyObject *ptr, bool is_borrowed) : object(is_borrowed ? object(ptr, borrowed_t{}) : object(ptr, stolen_t{})) { }
+    capsule(PyObject *ptr, bool is_borrowed)
+        : object(is_borrowed ? object(ptr, borrowed_t{}) : object(ptr, stolen_t{})) {}
 
-    explicit capsule(const void *value, const char *name = nullptr, void (*destructor)(PyObject *) = nullptr)
+    explicit capsule(const void *value,
+                     const char *name = nullptr,
+                     void (*destructor)(PyObject *) = nullptr)
         : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
@@ -1486,7 +1603,7 @@ class capsule : public object {
 
     PYBIND11_DEPRECATED("Please pass a destructor that takes a void pointer as input")
     capsule(const void *value, void (*destruct)(PyObject *))
-        : object(PyCapsule_New(const_cast<void*>(value), nullptr, destruct), stolen_t{}) {
+        : object(PyCapsule_New(const_cast<void *>(value), nullptr, destruct), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
         }
@@ -1525,8 +1642,8 @@ class capsule : public object {
     }
 
     /// Get the pointer the capsule holds.
-    template<typename T = void>
-    T* get_pointer() const {
+    template <typename T = void>
+    T *get_pointer() const {
         const auto *name = this->name();
         T *result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
         if (!result) {
@@ -1570,9 +1687,8 @@ class tuple : public object {
 // fails to compile enable_if_t<all_of<is_keyword_or_ds<Args>...>::value> part below
 // (tested with ICC 2021.1 Beta 20200827).
 template <typename... Args>
-constexpr bool args_are_all_keyword_or_ds()
-{
-  return detail::all_of<detail::is_keyword_or_ds<Args>...>::value;
+constexpr bool args_are_all_keyword_or_ds() {
+    return detail::all_of<detail::is_keyword_or_ds<Args>...>::value;
 }
 
 class dict : public object {
@@ -1585,16 +1701,18 @@ class dict : public object {
     }
     template <typename... Args,
               typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>,
-              // MSVC workaround: it can't compile an out-of-line definition, so defer the collector
+              // MSVC workaround: it can't compile an out-of-line definition, so defer the
+              // collector
               typename collector = detail::deferred_t<detail::unpacking_collector<>, Args...>>
-    explicit dict(Args &&...args) : dict(collector(std::forward<Args>(args)...).kwargs()) { }
+    explicit dict(Args &&...args) : dict(collector(std::forward<Args>(args)...).kwargs()) {}
 
     size_t size() const { return (size_t) PyDict_Size(m_ptr); }
     bool empty() const { return size() == 0; }
     detail::dict_iterator begin() const { return {*this, 0}; }
     detail::dict_iterator end() const { return {}; }
     void clear() /* py-non-const */ { PyDict_Clear(ptr()); }
-    template <typename T> bool contains(T &&key) const {
+    template <typename T>
+    bool contains(T &&key) const {
         return PyDict_Contains(m_ptr, detail::object_or_cast(std::forward<T>(key)).ptr()) == 1;
     }
 
@@ -1642,7 +1760,8 @@ class list : public object {
     detail::item_accessor operator[](handle h) const { return object::operator[](h); }
     detail::list_iterator begin() const { return {*this, 0}; }
     detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
-    template <typename T> void append(T &&val) /* py-non-const */ {
+    template <typename T>
+    void append(T &&val) /* py-non-const */ {
         PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
     }
     template <typename IdxType,
@@ -1654,8 +1773,12 @@ class list : public object {
     }
 };
 
-class args : public tuple { PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check) };
-class kwargs : public dict { PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)  };
+class args : public tuple {
+    PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check)
+};
+class kwargs : public dict {
+    PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)
+};
 
 class set : public object {
 public:
@@ -1667,11 +1790,13 @@ class set : public object {
     }
     size_t size() const { return (size_t) PySet_Size(m_ptr); }
     bool empty() const { return size() == 0; }
-    template <typename T> bool add(T &&val) /* py-non-const */ {
+    template <typename T>
+    bool add(T &&val) /* py-non-const */ {
         return PySet_Add(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 0;
     }
     void clear() /* py-non-const */ { PySet_Clear(m_ptr); }
-    template <typename T> bool contains(T &&val) const {
+    template <typename T>
+    bool contains(T &&val) const {
         return PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 1;
     }
 };
@@ -1725,14 +1850,13 @@ class memoryview : public object {
         For creating a ``memoryview`` from objects that support buffer protocol,
         use ``memoryview(const object& obj)`` instead of this constructor.
      \endrst */
-    explicit memoryview(const buffer_info& info) {
+    explicit memoryview(const buffer_info &info) {
         if (!info.view()) {
             pybind11_fail("Prohibited to create memoryview without Py_buffer");
         }
         // Note: PyMemoryView_FromBuffer never increments obj reference.
-        m_ptr = (info.view()->obj) ?
-            PyMemoryView_FromObject(info.view()->obj) :
-            PyMemoryView_FromBuffer(info.view());
+        m_ptr = (info.view()->obj) ? PyMemoryView_FromObject(info.view()->obj)
+                                   : PyMemoryView_FromBuffer(info.view());
         if (!m_ptr) {
             pybind11_fail("Unable to create memoryview from buffer descriptor");
         }
@@ -1762,34 +1886,40 @@ class memoryview : public object {
         :param readonly: Flag to indicate if the underlying storage may be
             written to.
      \endrst */
-    static memoryview from_buffer(
-        void *ptr, ssize_t itemsize, const char *format,
-        detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides, bool readonly = false);
-
-    static memoryview from_buffer(
-        const void *ptr, ssize_t itemsize, const char *format,
-        detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides) {
+    static memoryview from_buffer(void *ptr,
+                                  ssize_t itemsize,
+                                  const char *format,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides,
+                                  bool readonly = false);
+
+    static memoryview from_buffer(const void *ptr,
+                                  ssize_t itemsize,
+                                  const char *format,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides) {
         return memoryview::from_buffer(
             const_cast<void *>(ptr), itemsize, format, std::move(shape), std::move(strides), true);
     }
 
-    template<typename T>
-    static memoryview from_buffer(
-        T *ptr, detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides, bool readonly = false) {
-        return memoryview::from_buffer(
-            reinterpret_cast<void*>(ptr), sizeof(T),
-            format_descriptor<T>::value, shape, strides, readonly);
+    template <typename T>
+    static memoryview from_buffer(T *ptr,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides,
+                                  bool readonly = false) {
+        return memoryview::from_buffer(reinterpret_cast<void *>(ptr),
+                                       sizeof(T),
+                                       format_descriptor<T>::value,
+                                       shape,
+                                       strides,
+                                       readonly);
     }
 
-    template<typename T>
-    static memoryview from_buffer(
-        const T *ptr, detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides) {
-        return memoryview::from_buffer(
-            const_cast<T*>(ptr), shape, strides, true);
+    template <typename T>
+    static memoryview from_buffer(const T *ptr,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides) {
+        return memoryview::from_buffer(const_cast<T *>(ptr), shape, strides, true);
     }
 
 #if PY_MAJOR_VERSION >= 3
@@ -1808,9 +1938,8 @@ class memoryview : public object {
            https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromMemory
      \endrst */
     static memoryview from_memory(void *mem, ssize_t size, bool readonly = false) {
-        PyObject* ptr = PyMemoryView_FromMemory(
-            reinterpret_cast<char*>(mem), size,
-            (readonly) ? PyBUF_READ : PyBUF_WRITE);
+        PyObject *ptr = PyMemoryView_FromMemory(
+            reinterpret_cast<char *>(mem), size, (readonly) ? PyBUF_READ : PyBUF_WRITE);
         if (!ptr) {
             pybind11_fail("Could not allocate memoryview object!");
         }
@@ -1818,23 +1947,25 @@ class memoryview : public object {
     }
 
     static memoryview from_memory(const void *mem, ssize_t size) {
-        return memoryview::from_memory(const_cast<void*>(mem), size, true);
+        return memoryview::from_memory(const_cast<void *>(mem), size, true);
     }
 
-#ifdef PYBIND11_HAS_STRING_VIEW
+#    ifdef PYBIND11_HAS_STRING_VIEW
     static memoryview from_memory(std::string_view mem) {
-        return from_memory(const_cast<char*>(mem.data()), static_cast<ssize_t>(mem.size()), true);
+        return from_memory(const_cast<char *>(mem.data()), static_cast<ssize_t>(mem.size()), true);
     }
-#endif
+#    endif
 
 #endif
 };
 
 /// @cond DUPLICATE
-inline memoryview memoryview::from_buffer(
-    void *ptr, ssize_t itemsize, const char* format,
-    detail::any_container<ssize_t> shape,
-    detail::any_container<ssize_t> strides, bool readonly) {
+inline memoryview memoryview::from_buffer(void *ptr,
+                                          ssize_t itemsize,
+                                          const char *format,
+                                          detail::any_container<ssize_t> shape,
+                                          detail::any_container<ssize_t> strides,
+                                          bool readonly) {
     size_t ndim = shape->size();
     if (ndim != strides->size()) {
         pybind11_fail("memoryview: shape length doesn't match strides length");
@@ -1849,13 +1980,13 @@ inline memoryview memoryview::from_buffer(
     view.len = size * itemsize;
     view.readonly = static_cast<int>(readonly);
     view.itemsize = itemsize;
-    view.format = const_cast<char*>(format);
+    view.format = const_cast<char *>(format);
     view.ndim = static_cast<int>(ndim);
     view.shape = shape->data();
     view.strides = strides->data();
     view.suboffsets = nullptr;
     view.internal = nullptr;
-    PyObject* obj = PyMemoryView_FromBuffer(&view);
+    PyObject *obj = PyMemoryView_FromBuffer(&view);
     if (!obj) {
         throw error_already_set();
     }
@@ -1900,49 +2031,72 @@ inline str repr(handle h) {
     }
 #if PY_MAJOR_VERSION < 3
     PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
-    Py_XDECREF(str_value); str_value = unicode;
-    if (!str_value) throw error_already_set();
+    Py_XDECREF(str_value);
+    str_value = unicode;
+    if (!str_value)
+        throw error_already_set();
 #endif
     return reinterpret_steal<str>(str_value);
 }
 
 inline iterator iter(handle obj) {
     PyObject *result = PyObject_GetIter(obj.ptr());
-    if (!result) { throw error_already_set(); }
+    if (!result) {
+        throw error_already_set();
+    }
     return reinterpret_steal<iterator>(result);
 }
 /// @} python_builtins
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-template <typename D> iterator object_api<D>::begin() const { return iter(derived()); }
-template <typename D> iterator object_api<D>::end() const { return iterator::sentinel(); }
-template <typename D> item_accessor object_api<D>::operator[](handle key) const {
+template <typename D>
+iterator object_api<D>::begin() const {
+    return iter(derived());
+}
+template <typename D>
+iterator object_api<D>::end() const {
+    return iterator::sentinel();
+}
+template <typename D>
+item_accessor object_api<D>::operator[](handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
 }
-template <typename D> item_accessor object_api<D>::operator[](const char *key) const {
+template <typename D>
+item_accessor object_api<D>::operator[](const char *key) const {
     return {derived(), pybind11::str(key)};
 }
-template <typename D> obj_attr_accessor object_api<D>::attr(handle key) const {
+template <typename D>
+obj_attr_accessor object_api<D>::attr(handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
 }
-template <typename D> str_attr_accessor object_api<D>::attr(const char *key) const {
+template <typename D>
+str_attr_accessor object_api<D>::attr(const char *key) const {
     return {derived(), key};
 }
-template <typename D> args_proxy object_api<D>::operator*() const {
+template <typename D>
+args_proxy object_api<D>::operator*() const {
     return args_proxy(derived().ptr());
 }
-template <typename D> template <typename T> bool object_api<D>::contains(T &&item) const {
+template <typename D>
+template <typename T>
+bool object_api<D>::contains(T &&item) const {
     return attr("__contains__")(std::forward<T>(item)).template cast<bool>();
 }
 
 template <typename D>
-pybind11::str object_api<D>::str() const { return pybind11::str(derived()); }
+pybind11::str object_api<D>::str() const {
+    return pybind11::str(derived());
+}
 
 template <typename D>
-str_attr_accessor object_api<D>::doc() const { return attr("__doc__"); }
+str_attr_accessor object_api<D>::doc() const {
+    return attr("__doc__");
+}
 
 template <typename D>
-handle object_api<D>::get_type() const { return type::handle_of(derived()); }
+handle object_api<D>::get_type() const {
+    return type::handle_of(derived());
+}
 
 template <typename D>
 bool object_api<D>::rich_compare(object_api const &other, int value) const {
@@ -1953,43 +2107,43 @@ bool object_api<D>::rich_compare(object_api const &other, int value) const {
     return rv == 1;
 }
 
-#define PYBIND11_MATH_OPERATOR_UNARY(op, fn)                                   \
-    template <typename D> object object_api<D>::op() const {                   \
-        object result = reinterpret_steal<object>(fn(derived().ptr()));        \
-        if (!result.ptr())                                                     \
-            throw error_already_set();                                         \
-        return result;                                                         \
-    }
-
-#define PYBIND11_MATH_OPERATOR_BINARY(op, fn)                                  \
-    template <typename D>                                                      \
-    object object_api<D>::op(object_api const &other) const {                  \
-        object result = reinterpret_steal<object>(                             \
-            fn(derived().ptr(), other.derived().ptr()));                       \
-        if (!result.ptr())                                                     \
-            throw error_already_set();                                         \
-        return result;                                                         \
-    }
-
-PYBIND11_MATH_OPERATOR_UNARY (operator~,   PyNumber_Invert)
-PYBIND11_MATH_OPERATOR_UNARY (operator-,   PyNumber_Negative)
-PYBIND11_MATH_OPERATOR_BINARY(operator+,   PyNumber_Add)
-PYBIND11_MATH_OPERATOR_BINARY(operator+=,  PyNumber_InPlaceAdd)
-PYBIND11_MATH_OPERATOR_BINARY(operator-,   PyNumber_Subtract)
-PYBIND11_MATH_OPERATOR_BINARY(operator-=,  PyNumber_InPlaceSubtract)
-PYBIND11_MATH_OPERATOR_BINARY(operator*,   PyNumber_Multiply)
-PYBIND11_MATH_OPERATOR_BINARY(operator*=,  PyNumber_InPlaceMultiply)
-PYBIND11_MATH_OPERATOR_BINARY(operator/,   PyNumber_TrueDivide)
-PYBIND11_MATH_OPERATOR_BINARY(operator/=,  PyNumber_InPlaceTrueDivide)
-PYBIND11_MATH_OPERATOR_BINARY(operator|,   PyNumber_Or)
-PYBIND11_MATH_OPERATOR_BINARY(operator|=,  PyNumber_InPlaceOr)
-PYBIND11_MATH_OPERATOR_BINARY(operator&,   PyNumber_And)
-PYBIND11_MATH_OPERATOR_BINARY(operator&=,  PyNumber_InPlaceAnd)
-PYBIND11_MATH_OPERATOR_BINARY(operator^,   PyNumber_Xor)
-PYBIND11_MATH_OPERATOR_BINARY(operator^=,  PyNumber_InPlaceXor)
-PYBIND11_MATH_OPERATOR_BINARY(operator<<,  PyNumber_Lshift)
+#define PYBIND11_MATH_OPERATOR_UNARY(op, fn)                                                      \
+    template <typename D>                                                                         \
+    object object_api<D>::op() const {                                                            \
+        object result = reinterpret_steal<object>(fn(derived().ptr()));                           \
+        if (!result.ptr())                                                                        \
+            throw error_already_set();                                                            \
+        return result;                                                                            \
+    }
+
+#define PYBIND11_MATH_OPERATOR_BINARY(op, fn)                                                     \
+    template <typename D>                                                                         \
+    object object_api<D>::op(object_api const &other) const {                                     \
+        object result = reinterpret_steal<object>(fn(derived().ptr(), other.derived().ptr()));    \
+        if (!result.ptr())                                                                        \
+            throw error_already_set();                                                            \
+        return result;                                                                            \
+    }
+
+PYBIND11_MATH_OPERATOR_UNARY(operator~, PyNumber_Invert)
+PYBIND11_MATH_OPERATOR_UNARY(operator-, PyNumber_Negative)
+PYBIND11_MATH_OPERATOR_BINARY(operator+, PyNumber_Add)
+PYBIND11_MATH_OPERATOR_BINARY(operator+=, PyNumber_InPlaceAdd)
+PYBIND11_MATH_OPERATOR_BINARY(operator-, PyNumber_Subtract)
+PYBIND11_MATH_OPERATOR_BINARY(operator-=, PyNumber_InPlaceSubtract)
+PYBIND11_MATH_OPERATOR_BINARY(operator*, PyNumber_Multiply)
+PYBIND11_MATH_OPERATOR_BINARY(operator*=, PyNumber_InPlaceMultiply)
+PYBIND11_MATH_OPERATOR_BINARY(operator/, PyNumber_TrueDivide)
+PYBIND11_MATH_OPERATOR_BINARY(operator/=, PyNumber_InPlaceTrueDivide)
+PYBIND11_MATH_OPERATOR_BINARY(operator|, PyNumber_Or)
+PYBIND11_MATH_OPERATOR_BINARY(operator|=, PyNumber_InPlaceOr)
+PYBIND11_MATH_OPERATOR_BINARY(operator&, PyNumber_And)
+PYBIND11_MATH_OPERATOR_BINARY(operator&=, PyNumber_InPlaceAnd)
+PYBIND11_MATH_OPERATOR_BINARY(operator^, PyNumber_Xor)
+PYBIND11_MATH_OPERATOR_BINARY(operator^=, PyNumber_InPlaceXor)
+PYBIND11_MATH_OPERATOR_BINARY(operator<<, PyNumber_Lshift)
 PYBIND11_MATH_OPERATOR_BINARY(operator<<=, PyNumber_InPlaceLshift)
-PYBIND11_MATH_OPERATOR_BINARY(operator>>,  PyNumber_Rshift)
+PYBIND11_MATH_OPERATOR_BINARY(operator>>, PyNumber_Rshift)
 PYBIND11_MATH_OPERATOR_BINARY(operator>>=, PyNumber_InPlaceRshift)
 
 #undef PYBIND11_MATH_OPERATOR_UNARY
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index fb1eea67bf..b661296887 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -9,26 +9,27 @@
 
 #pragma once
 
-#include "detail/common.h"
 #include "pybind11.h"
-#include <set>
-#include <unordered_set>
-#include <map>
-#include <unordered_map>
+#include "detail/common.h"
+
+#include <deque>
 #include <iostream>
 #include <list>
-#include <deque>
+#include <map>
+#include <set>
+#include <unordered_map>
+#include <unordered_set>
 #include <valarray>
 
 // See `detail/common.h` for implementation of these guards.
 #if defined(PYBIND11_HAS_OPTIONAL)
-#  include <optional>
+#    include <optional>
 #elif defined(PYBIND11_HAS_EXP_OPTIONAL)
-#  include <experimental/optional>
+#    include <experimental/optional>
 #endif
 
 #if defined(PYBIND11_HAS_VARIANT)
-#  include <variant>
+#    include <variant>
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -37,8 +38,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// Extracts an const lvalue reference or rvalue reference for U based on the type of T (e.g. for
 /// forwarding a container element).  Typically used indirect via forwarded_type(), below.
 template <typename T, typename U>
-using forwarded_type = conditional_t<
-    std::is_lvalue_reference<T>::value, remove_reference_t<U> &, remove_reference_t<U> &&>;
+using forwarded_type = conditional_t<std::is_lvalue_reference<T>::value,
+                                     remove_reference_t<U> &,
+                                     remove_reference_t<U> &&>;
 
 /// Forwards a value U as rvalue or lvalue according to whether T is rvalue or lvalue; typically
 /// used for forwarding a container's elements.
@@ -47,7 +49,8 @@ forwarded_type<T, U> forward_like(U &&u) {
     return std::forward<detail::forwarded_type<T, U>>(std::forward<U>(u));
 }
 
-template <typename Type, typename Key> struct set_caster {
+template <typename Type, typename Key>
+struct set_caster {
     using type = Type;
     using key_conv = make_caster<Key>;
 
@@ -74,7 +77,8 @@ template <typename Type, typename Key> struct set_caster {
         }
         pybind11::set s;
         for (auto &&value : src) {
-            auto value_ = reinterpret_steal<object>(key_conv::cast(forward_like<T>(value), policy, parent));
+            auto value_ = reinterpret_steal<object>(
+                key_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_ || !s.add(value_)) {
                 return handle();
             }
@@ -85,8 +89,9 @@ template <typename Type, typename Key> struct set_caster {
     PYBIND11_TYPE_CASTER(type, const_name("Set[") + key_conv::name + const_name("]"));
 };
 
-template <typename Type, typename Key, typename Value> struct map_caster {
-    using key_conv   = make_caster<Key>;
+template <typename Type, typename Key, typename Value>
+struct map_caster {
+    using key_conv = make_caster<Key>;
     using value_conv = make_caster<Value>;
 
     bool load(handle src, bool convert) {
@@ -116,8 +121,10 @@ template <typename Type, typename Key, typename Value> struct map_caster {
             policy_value = return_value_policy_override<Value>::policy(policy_value);
         }
         for (auto &&kv : src) {
-            auto key = reinterpret_steal<object>(key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
-            auto value = reinterpret_steal<object>(value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
+            auto key = reinterpret_steal<object>(
+                key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
+            auto value = reinterpret_steal<object>(
+                value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
             if (!key || !value) {
                 return handle();
             }
@@ -126,10 +133,13 @@ template <typename Type, typename Key, typename Value> struct map_caster {
         return d.release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, const_name("Dict[") + key_conv::name + const_name(", ") + value_conv::name + const_name("]"));
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name("Dict[") + key_conv::name + const_name(", ") + value_conv::name
+                             + const_name("]"));
 };
 
-template <typename Type, typename Value> struct list_caster {
+template <typename Type, typename Value>
+struct list_caster {
     using value_conv = make_caster<Value>;
 
     bool load(handle src, bool convert) {
@@ -151,7 +161,7 @@ template <typename Type, typename Value> struct list_caster {
 
 private:
     template <
-        typename T                                                                          = Type,
+        typename T = Type,
         enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
     void reserve_maybe(const sequence &s, Type *) {
         value.reserve(s.size());
@@ -167,7 +177,8 @@ template <typename Type, typename Value> struct list_caster {
         list l(src.size());
         ssize_t index = 0;
         for (auto &&value : src) {
-            auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
+            auto value_ = reinterpret_steal<object>(
+                value_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_) {
                 return handle();
             }
@@ -179,16 +190,17 @@ template <typename Type, typename Value> struct list_caster {
     PYBIND11_TYPE_CASTER(Type, const_name("List[") + value_conv::name + const_name("]"));
 };
 
-template <typename Type, typename Alloc> struct type_caster<std::vector<Type, Alloc>>
- : list_caster<std::vector<Type, Alloc>, Type> { };
+template <typename Type, typename Alloc>
+struct type_caster<std::vector<Type, Alloc>> : list_caster<std::vector<Type, Alloc>, Type> {};
 
-template <typename Type, typename Alloc> struct type_caster<std::deque<Type, Alloc>>
- : list_caster<std::deque<Type, Alloc>, Type> { };
+template <typename Type, typename Alloc>
+struct type_caster<std::deque<Type, Alloc>> : list_caster<std::deque<Type, Alloc>, Type> {};
 
-template <typename Type, typename Alloc> struct type_caster<std::list<Type, Alloc>>
- : list_caster<std::list<Type, Alloc>, Type> { };
+template <typename Type, typename Alloc>
+struct type_caster<std::list<Type, Alloc>> : list_caster<std::list<Type, Alloc>, Type> {};
 
-template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> struct array_caster {
+template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0>
+struct array_caster {
     using value_conv = make_caster<Value>;
 
 private:
@@ -229,7 +241,8 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
         list l(src.size());
         ssize_t index = 0;
         for (auto &&value : src) {
-            auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
+            auto value_ = reinterpret_steal<object>(
+                value_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_) {
                 return handle();
             }
@@ -238,29 +251,40 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
         return l.release();
     }
 
-    PYBIND11_TYPE_CASTER(ArrayType, const_name("List[") + value_conv::name + const_name<Resizable>(const_name(""), const_name("[") + const_name<Size>() + const_name("]")) + const_name("]"));
+    PYBIND11_TYPE_CASTER(ArrayType,
+                         const_name("List[") + value_conv::name
+                             + const_name<Resizable>(const_name(""),
+                                                     const_name("[") + const_name<Size>()
+                                                         + const_name("]"))
+                             + const_name("]"));
 };
 
-template <typename Type, size_t Size> struct type_caster<std::array<Type, Size>>
- : array_caster<std::array<Type, Size>, Type, false, Size> { };
+template <typename Type, size_t Size>
+struct type_caster<std::array<Type, Size>>
+    : array_caster<std::array<Type, Size>, Type, false, Size> {};
 
-template <typename Type> struct type_caster<std::valarray<Type>>
- : array_caster<std::valarray<Type>, Type, true> { };
+template <typename Type>
+struct type_caster<std::valarray<Type>> : array_caster<std::valarray<Type>, Type, true> {};
 
-template <typename Key, typename Compare, typename Alloc> struct type_caster<std::set<Key, Compare, Alloc>>
-  : set_caster<std::set<Key, Compare, Alloc>, Key> { };
+template <typename Key, typename Compare, typename Alloc>
+struct type_caster<std::set<Key, Compare, Alloc>>
+    : set_caster<std::set<Key, Compare, Alloc>, Key> {};
 
-template <typename Key, typename Hash, typename Equal, typename Alloc> struct type_caster<std::unordered_set<Key, Hash, Equal, Alloc>>
-  : set_caster<std::unordered_set<Key, Hash, Equal, Alloc>, Key> { };
+template <typename Key, typename Hash, typename Equal, typename Alloc>
+struct type_caster<std::unordered_set<Key, Hash, Equal, Alloc>>
+    : set_caster<std::unordered_set<Key, Hash, Equal, Alloc>, Key> {};
 
-template <typename Key, typename Value, typename Compare, typename Alloc> struct type_caster<std::map<Key, Value, Compare, Alloc>>
-  : map_caster<std::map<Key, Value, Compare, Alloc>, Key, Value> { };
+template <typename Key, typename Value, typename Compare, typename Alloc>
+struct type_caster<std::map<Key, Value, Compare, Alloc>>
+    : map_caster<std::map<Key, Value, Compare, Alloc>, Key, Value> {};
 
-template <typename Key, typename Value, typename Hash, typename Equal, typename Alloc> struct type_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>>
-  : map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> { };
+template <typename Key, typename Value, typename Hash, typename Equal, typename Alloc>
+struct type_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>>
+    : map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> {};
 
 // This type caster is intended to be used for std::optional and std::experimental::optional
-template<typename Type, typename Value = typename Type::value_type> struct optional_caster {
+template <typename Type, typename Value = typename Type::value_type>
+struct optional_caster {
     using value_conv = make_caster<Value>;
 
     template <typename T>
@@ -279,7 +303,7 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
             return false;
         }
         if (src.is_none()) {
-            return true;  // default-constructed value is already empty
+            return true; // default-constructed value is already empty
         }
         value_conv inner_caster;
         if (!inner_caster.load(src, convert)) {
@@ -294,18 +318,20 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
 };
 
 #if defined(PYBIND11_HAS_OPTIONAL)
-template<typename T> struct type_caster<std::optional<T>>
-    : public optional_caster<std::optional<T>> {};
+template <typename T>
+struct type_caster<std::optional<T>> : public optional_caster<std::optional<T>> {};
 
-template<> struct type_caster<std::nullopt_t>
-    : public void_caster<std::nullopt_t> {};
+template <>
+struct type_caster<std::nullopt_t> : public void_caster<std::nullopt_t> {};
 #endif
 
 #if defined(PYBIND11_HAS_EXP_OPTIONAL)
-template<typename T> struct type_caster<std::experimental::optional<T>>
+template <typename T>
+struct type_caster<std::experimental::optional<T>>
     : public optional_caster<std::experimental::optional<T>> {};
 
-template<> struct type_caster<std::experimental::nullopt_t>
+template <>
+struct type_caster<std::experimental::nullopt_t>
     : public void_caster<std::experimental::nullopt_t> {};
 #endif
 
@@ -326,7 +352,7 @@ struct variant_caster_visitor {
 /// `namespace::variant` types which provide a `namespace::visit()` function are handled here
 /// automatically using argument-dependent lookup. Users can provide specializations for other
 /// variant-like classes, e.g. `boost::variant` and `boost::apply_visitor`.
-template <template<typename...> class Variant>
+template <template <typename...> class Variant>
 struct visit_helper {
     template <typename... Args>
     static auto call(Args &&...args) -> decltype(visit(std::forward<Args>(args)...)) {
@@ -335,9 +361,10 @@ struct visit_helper {
 };
 
 /// Generic variant caster
-template <typename Variant> struct variant_caster;
+template <typename Variant>
+struct variant_caster;
 
-template <template<typename...> class V, typename... Ts>
+template <template <typename...> class V, typename... Ts>
 struct variant_caster<V<Ts...>> {
     static_assert(sizeof...(Ts) > 0, "Variant must consist of at least one alternative.");
 
@@ -371,12 +398,14 @@ struct variant_caster<V<Ts...>> {
     }
 
     using Type = V<Ts...>;
-    PYBIND11_TYPE_CASTER(Type, const_name("Union[") + detail::concat(make_caster<Ts>::name...) + const_name("]"));
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name("Union[") + detail::concat(make_caster<Ts>::name...)
+                             + const_name("]"));
 };
 
 #if defined(PYBIND11_HAS_VARIANT)
 template <typename... Ts>
-struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> { };
+struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> {};
 #endif
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 59ac38b9ba..747992f51c 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -4,21 +4,20 @@
 
 #pragma once
 
-#include "../cast.h"
 #include "../pybind11.h"
-#include "../pytypes.h"
-
 #include "../detail/common.h"
 #include "../detail/descr.h"
+#include "../cast.h"
+#include "../pytypes.h"
 
 #include <string>
 
 #ifdef __has_include
-#  if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
+#    if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
       PY_VERSION_HEX >= 0x03060000
-#    include <filesystem>
-#    define PYBIND11_HAS_FILESYSTEM 1
-#  endif
+#        include <filesystem>
+#        define PYBIND11_HAS_FILESYSTEM 1
+#    endif
 #endif
 
 #if !defined(PYBIND11_HAS_FILESYSTEM) && !defined(PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL)
@@ -30,28 +29,29 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if defined(PYBIND11_HAS_FILESYSTEM)
-template<typename T> struct path_caster {
+template <typename T>
+struct path_caster {
 
 private:
-    static PyObject* unicode_from_fs_native(const std::string& w) {
-#if !defined(PYPY_VERSION)
+    static PyObject *unicode_from_fs_native(const std::string &w) {
+#    if !defined(PYPY_VERSION)
         return PyUnicode_DecodeFSDefaultAndSize(w.c_str(), ssize_t(w.size()));
-#else
+#    else
         // PyPy mistakenly declares the first parameter as non-const.
-        return PyUnicode_DecodeFSDefaultAndSize(
-            const_cast<char*>(w.c_str()), ssize_t(w.size()));
-#endif
+        return PyUnicode_DecodeFSDefaultAndSize(const_cast<char *>(w.c_str()), ssize_t(w.size()));
+#    endif
     }
 
-    static PyObject* unicode_from_fs_native(const std::wstring& w) {
+    static PyObject *unicode_from_fs_native(const std::wstring &w) {
         return PyUnicode_FromWideChar(w.c_str(), ssize_t(w.size()));
     }
 
 public:
-    static handle cast(const T& path, return_value_policy, handle) {
+    static handle cast(const T &path, return_value_policy, handle) {
         if (auto py_str = unicode_from_fs_native(path.native())) {
-            return module_::import("pathlib").attr("Path")(reinterpret_steal<object>(py_str))
-                   .release();
+            return module_::import("pathlib")
+                .attr("Path")(reinterpret_steal<object>(py_str))
+                .release();
         }
         return nullptr;
     }
@@ -60,12 +60,12 @@ template<typename T> struct path_caster {
         // PyUnicode_FSConverter and PyUnicode_FSDecoder normally take care of
         // calling PyOS_FSPath themselves, but that's broken on PyPy (PyPy
         // issue #3168) so we do it ourselves instead.
-        PyObject* buf = PyOS_FSPath(handle.ptr());
+        PyObject *buf = PyOS_FSPath(handle.ptr());
         if (!buf) {
             PyErr_Clear();
             return false;
         }
-        PyObject* native = nullptr;
+        PyObject *native = nullptr;
         if constexpr (std::is_same_v<typename T::value_type, char>) {
             if (PyUnicode_FSConverter(buf, &native) != 0) {
                 if (auto *c_str = PyBytes_AsString(native)) {
@@ -78,7 +78,7 @@ template<typename T> struct path_caster {
             if (PyUnicode_FSDecoder(buf, &native) != 0) {
                 if (auto *c_str = PyUnicode_AsWideCharString(native, nullptr)) {
                     // AsWideCharString returns a new string that must be free'd.
-                    value = c_str;  // Copies the string.
+                    value = c_str; // Copies the string.
                     PyMem_Free(c_str);
                 }
             }
@@ -95,8 +95,8 @@ template<typename T> struct path_caster {
     PYBIND11_TYPE_CASTER(T, const_name("os.PathLike"));
 };
 
-template<> struct type_caster<std::filesystem::path>
-    : public path_caster<std::filesystem::path> {};
+template <>
+struct type_caster<std::filesystem::path> : public path_caster<std::filesystem::path> {};
 #endif // PYBIND11_HAS_FILESYSTEM
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 2f997d6b03..3a3e54dd48 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -19,74 +19,87 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 /* SFINAE helper class used by 'is_comparable */
-template <typename T>  struct container_traits {
-    template <typename T2> static std::true_type test_comparable(decltype(std::declval<const T2 &>() == std::declval<const T2 &>())*);
-    template <typename T2> static std::false_type test_comparable(...);
-    template <typename T2> static std::true_type test_value(typename T2::value_type *);
-    template <typename T2> static std::false_type test_value(...);
-    template <typename T2> static std::true_type test_pair(typename T2::first_type *, typename T2::second_type *);
-    template <typename T2> static std::false_type test_pair(...);
-
-    static constexpr const bool is_comparable = std::is_same<std::true_type, decltype(test_comparable<T>(nullptr))>::value;
-    static constexpr const bool is_pair = std::is_same<std::true_type, decltype(test_pair<T>(nullptr, nullptr))>::value;
-    static constexpr const bool is_vector = std::is_same<std::true_type, decltype(test_value<T>(nullptr))>::value;
+template <typename T>
+struct container_traits {
+    template <typename T2>
+    static std::true_type
+    test_comparable(decltype(std::declval<const T2 &>() == std::declval<const T2 &>()) *);
+    template <typename T2>
+    static std::false_type test_comparable(...);
+    template <typename T2>
+    static std::true_type test_value(typename T2::value_type *);
+    template <typename T2>
+    static std::false_type test_value(...);
+    template <typename T2>
+    static std::true_type test_pair(typename T2::first_type *, typename T2::second_type *);
+    template <typename T2>
+    static std::false_type test_pair(...);
+
+    static constexpr const bool is_comparable
+        = std::is_same<std::true_type, decltype(test_comparable<T>(nullptr))>::value;
+    static constexpr const bool is_pair
+        = std::is_same<std::true_type, decltype(test_pair<T>(nullptr, nullptr))>::value;
+    static constexpr const bool is_vector
+        = std::is_same<std::true_type, decltype(test_value<T>(nullptr))>::value;
     static constexpr const bool is_element = !is_pair && !is_vector;
 };
 
 /* Default: is_comparable -> std::false_type */
 template <typename T, typename SFINAE = void>
-struct is_comparable : std::false_type { };
+struct is_comparable : std::false_type {};
 
 /* For non-map data structures, check whether operator== can be instantiated */
 template <typename T>
 struct is_comparable<
-    T, enable_if_t<container_traits<T>::is_element &&
-                   container_traits<T>::is_comparable>>
-    : std::true_type { };
+    T,
+    enable_if_t<container_traits<T>::is_element && container_traits<T>::is_comparable>>
+    : std::true_type {};
 
 /* For a vector/map data structure, recursively check the value type
    (which is std::pair for maps) */
 template <typename T>
 struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
-    static constexpr const bool value =
-        is_comparable<typename T::value_type>::value;
+    static constexpr const bool value = is_comparable<typename T::value_type>::value;
 };
 
 /* For pairs, recursively check the two data types */
 template <typename T>
 struct is_comparable<T, enable_if_t<container_traits<T>::is_pair>> {
-    static constexpr const bool value =
-        is_comparable<typename T::first_type>::value &&
-        is_comparable<typename T::second_type>::value;
+    static constexpr const bool value = is_comparable<typename T::first_type>::value
+                                        && is_comparable<typename T::second_type>::value;
 };
 
 /* Fallback functions */
-template <typename, typename, typename... Args> void vector_if_copy_constructible(const Args &...) { }
-template <typename, typename, typename... Args> void vector_if_equal_operator(const Args &...) { }
-template <typename, typename, typename... Args> void vector_if_insertion_operator(const Args &...) { }
-template <typename, typename, typename... Args> void vector_modifiers(const Args &...) { }
+template <typename, typename, typename... Args>
+void vector_if_copy_constructible(const Args &...) {}
+template <typename, typename, typename... Args>
+void vector_if_equal_operator(const Args &...) {}
+template <typename, typename, typename... Args>
+void vector_if_insertion_operator(const Args &...) {}
+template <typename, typename, typename... Args>
+void vector_modifiers(const Args &...) {}
 
-template<typename Vector, typename Class_>
+template <typename Vector, typename Class_>
 void vector_if_copy_constructible(enable_if_t<is_copy_constructible<Vector>::value, Class_> &cl) {
     cl.def(init<const Vector &>(), "Copy constructor");
 }
 
-template<typename Vector, typename Class_>
+template <typename Vector, typename Class_>
 void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_> &cl) {
     using T = typename Vector::value_type;
 
     cl.def(self == self);
     cl.def(self != self);
 
-    cl.def("count",
-        [](const Vector &v, const T &x) {
-            return std::count(v.begin(), v.end(), x);
-        },
+    cl.def(
+        "count",
+        [](const Vector &v, const T &x) { return std::count(v.begin(), v.end(), x); },
         arg("x"),
-        "Return the number of times ``x`` appears in the list"
-    );
+        "Return the number of times ``x`` appears in the list");
 
-    cl.def("remove", [](Vector &v, const T &x) {
+    cl.def(
+        "remove",
+        [](Vector &v, const T &x) {
             auto p = std::find(v.begin(), v.end(), x);
             if (p != v.end()) {
                 v.erase(p);
@@ -96,23 +109,21 @@ void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_>
         },
         arg("x"),
         "Remove the first item from the list whose value is x. "
-        "It is an error if there is no such item."
-    );
+        "It is an error if there is no such item.");
 
-    cl.def("__contains__",
-        [](const Vector &v, const T &x) {
-            return std::find(v.begin(), v.end(), x) != v.end();
-        },
+    cl.def(
+        "__contains__",
+        [](const Vector &v, const T &x) { return std::find(v.begin(), v.end(), x) != v.end(); },
         arg("x"),
-        "Return true the container contains ``x``"
-    );
+        "Return true the container contains ``x``");
 }
 
 // Vector modifiers -- requires a copyable vector_type:
-// (Technically, some of these (pop and __delitem__) don't actually require copyability, but it seems
-// silly to allow deletion but not insertion, so include them here too.)
+// (Technically, some of these (pop and __delitem__) don't actually require copyability, but it
+// seems silly to allow deletion but not insertion, so include them here too.)
 template <typename Vector, typename Class_>
-void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_type>::value, Class_> &cl) {
+void vector_modifiers(
+    enable_if_t<is_copy_constructible<typename Vector::value_type>::value, Class_> &cl) {
     using T = typename Vector::value_type;
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
@@ -127,10 +138,11 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         return i;
     };
 
-    cl.def("append",
-           [](Vector &v, const T &value) { v.push_back(value); },
-           arg("x"),
-           "Add an item to the end of the list");
+    cl.def(
+        "append",
+        [](Vector &v, const T &value) { v.push_back(value); },
+        arg("x"),
+        "Add an item to the end of the list");
 
     cl.def(init([](const iterable &it) {
         auto v = std::unique_ptr<Vector>(new Vector());
@@ -141,20 +153,14 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         return v.release();
     }));
 
-    cl.def("clear",
-        [](Vector &v) {
-            v.clear();
-        },
-        "Clear the contents"
-    );
+    cl.def(
+        "clear", [](Vector &v) { v.clear(); }, "Clear the contents");
 
-    cl.def("extend",
-       [](Vector &v, const Vector &src) {
-           v.insert(v.end(), src.begin(), src.end());
-       },
-       arg("L"),
-       "Extend the list by appending all the items in the given list"
-    );
+    cl.def(
+        "extend",
+        [](Vector &v, const Vector &src) { v.insert(v.end(), src.begin(), src.end()); },
+        arg("L"),
+        "Extend the list by appending all the items in the given list");
 
     cl.def(
         "extend",
@@ -179,7 +185,8 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         arg("L"),
         "Extend the list by appending all the items in the given list");
 
-    cl.def("insert",
+    cl.def(
+        "insert",
         [](Vector &v, DiffType i, const T &x) {
             // Can't use wrap_i; i == v.size() is OK
             if (i < 0) {
@@ -190,9 +197,9 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             }
             v.insert(v.begin() + i, x);
         },
-        arg("i") , arg("x"),
-        "Insert an item at a given position."
-    );
+        arg("i"),
+        arg("x"),
+        "Insert an item at a given position.");
 
     cl.def(
         "pop",
@@ -206,7 +213,8 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         },
         "Remove and return the last item");
 
-    cl.def("pop",
+    cl.def(
+        "pop",
         [wrap_i](Vector &v, DiffType i) {
             i = wrap_i(i, v.size());
             T t = std::move(v[(SizeType) i]);
@@ -214,15 +222,12 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             return t;
         },
         arg("i"),
-        "Remove and return the item at index ``i``"
-    );
+        "Remove and return the item at index ``i``");
 
-    cl.def("__setitem__",
-        [wrap_i](Vector &v, DiffType i, const T &t) {
-            i = wrap_i(i, v.size());
-            v[(SizeType)i] = t;
-        }
-    );
+    cl.def("__setitem__", [wrap_i](Vector &v, DiffType i, const T &t) {
+        i = wrap_i(i, v.size());
+        v[(SizeType) i] = t;
+    });
 
     /// Slicing protocol
     cl.def(
@@ -237,7 +242,7 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             auto *seq = new Vector();
             seq->reserve((size_t) slicelength);
 
-            for (size_t i=0; i<slicelength; ++i) {
+            for (size_t i = 0; i < slicelength; ++i) {
                 seq->push_back(v[start]);
                 start += step;
             }
@@ -259,20 +264,20 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
                     "Left and right hand size of slice assignment have different sizes!");
             }
 
-            for (size_t i=0; i<slicelength; ++i) {
+            for (size_t i = 0; i < slicelength; ++i) {
                 v[start] = value[i];
                 start += step;
             }
         },
         "Assign list elements using a slice object");
 
-    cl.def("__delitem__",
+    cl.def(
+        "__delitem__",
         [wrap_i](Vector &v, DiffType i) {
             i = wrap_i(i, v.size());
             v.erase(v.begin() + i);
         },
-        "Delete the list elements at index ``i``"
-    );
+        "Delete the list elements at index ``i``");
 
     cl.def(
         "__delitem__",
@@ -297,8 +302,10 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
 
 // If the type has an operator[] that doesn't return a reference (most notably std::vector<bool>),
 // we have to access by copying; otherwise we return by reference.
-template <typename Vector> using vector_needs_copy = negation<
-    std::is_same<decltype(std::declval<Vector>()[typename Vector::size_type()]), typename Vector::value_type &>>;
+template <typename Vector>
+using vector_needs_copy
+    = negation<std::is_same<decltype(std::declval<Vector>()[typename Vector::size_type()]),
+                            typename Vector::value_type &>>;
 
 // The usual case: access and iterate by reference
 template <typename Vector, typename Class_>
@@ -306,7 +313,7 @@ void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl)
     using T = typename Vector::value_type;
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
-    using ItType   = typename Vector::iterator;
+    using ItType = typename Vector::iterator;
 
     auto wrap_i = [](DiffType i, SizeType n) {
         if (i < 0) {
@@ -318,21 +325,22 @@ void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl)
         return i;
     };
 
-    cl.def("__getitem__",
+    cl.def(
+        "__getitem__",
         [wrap_i](Vector &v, DiffType i) -> T & {
             i = wrap_i(i, v.size());
-            return v[(SizeType)i];
+            return v[(SizeType) i];
         },
         return_value_policy::reference_internal // ref + keepalive
     );
 
-    cl.def("__iter__",
-           [](Vector &v) {
-               return make_iterator<
-                   return_value_policy::reference_internal, ItType, ItType, T&>(
-                   v.begin(), v.end());
-           },
-           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    cl.def(
+        "__iter__",
+        [](Vector &v) {
+            return make_iterator<return_value_policy::reference_internal, ItType, ItType, T &>(
+                v.begin(), v.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
     );
 }
 
@@ -342,7 +350,7 @@ void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl)
     using T = typename Vector::value_type;
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
-    using ItType   = typename Vector::iterator;
+    using ItType = typename Vector::iterator;
     cl.def("__getitem__", [](const Vector &v, DiffType i) -> T {
         if (i < 0 && (i += v.size()) < 0) {
             throw index_error();
@@ -353,25 +361,27 @@ void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl)
         return v[(SizeType) i];
     });
 
-    cl.def("__iter__",
-           [](Vector &v) {
-               return make_iterator<
-                   return_value_policy::copy, ItType, ItType, T>(
-                   v.begin(), v.end());
-           },
-           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    cl.def(
+        "__iter__",
+        [](Vector &v) {
+            return make_iterator<return_value_policy::copy, ItType, ItType, T>(v.begin(), v.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
     );
 }
 
-template <typename Vector, typename Class_> auto vector_if_insertion_operator(Class_ &cl, std::string const &name)
-    -> decltype(std::declval<std::ostream&>() << std::declval<typename Vector::value_type>(), void()) {
+template <typename Vector, typename Class_>
+auto vector_if_insertion_operator(Class_ &cl, std::string const &name)
+    -> decltype(std::declval<std::ostream &>() << std::declval<typename Vector::value_type>(),
+                void()) {
     using size_type = typename Vector::size_type;
 
-    cl.def("__repr__",
-           [name](Vector &v) {
+    cl.def(
+        "__repr__",
+        [name](Vector &v) {
             std::ostringstream s;
             s << name << '[';
-            for (size_type i=0; i < v.size(); ++i) {
+            for (size_type i = 0; i < v.size(); ++i) {
                 s << v[i];
                 if (i != v.size() - 1) {
                     s << ", ";
@@ -380,8 +390,7 @@ template <typename Vector, typename Class_> auto vector_if_insertion_operator(Cl
             s << ']';
             return s.str();
         },
-        "Return the canonical string representation of this list."
-    );
+        "Return the canonical string representation of this list.");
 }
 
 // Provide the buffer interface for vectors if we have data() and we have a format for it
@@ -390,7 +399,11 @@ template <typename Vector, typename Class_> auto vector_if_insertion_operator(Cl
 template <typename Vector, typename = void>
 struct vector_has_data_and_format : std::false_type {};
 template <typename Vector>
-struct vector_has_data_and_format<Vector, enable_if_t<std::is_same<decltype(format_descriptor<typename Vector::value_type>::format(), std::declval<Vector>().data()), typename Vector::value_type*>::value>> : std::true_type {};
+struct vector_has_data_and_format<
+    Vector,
+    enable_if_t<std::is_same<decltype(format_descriptor<typename Vector::value_type>::format(),
+                                      std::declval<Vector>().data()),
+                             typename Vector::value_type *>::value>> : std::true_type {};
 
 // [workaround(intel)] Separate function required here
 // Workaround as the Intel compiler does not compile the enable_if_t part below
@@ -405,17 +418,23 @@ constexpr bool args_any_are_buffer() {
 
 // Add the buffer interface to a vector
 template <typename Vector, typename Class_, typename... Args>
-void vector_buffer_impl(Class_& cl, std::true_type) {
+void vector_buffer_impl(Class_ &cl, std::true_type) {
     using T = typename Vector::value_type;
 
-    static_assert(vector_has_data_and_format<Vector>::value, "There is not an appropriate format descriptor for this vector");
+    static_assert(vector_has_data_and_format<Vector>::value,
+                  "There is not an appropriate format descriptor for this vector");
 
     // numpy.h declares this for arbitrary types, but it may raise an exception and crash hard
     // at runtime if PYBIND11_NUMPY_DTYPE hasn't been called, so check here
     format_descriptor<T>::format();
 
-    cl.def_buffer([](Vector& v) -> buffer_info {
-        return buffer_info(v.data(), static_cast<ssize_t>(sizeof(T)), format_descriptor<T>::format(), 1, {v.size()}, {sizeof(T)});
+    cl.def_buffer([](Vector &v) -> buffer_info {
+        return buffer_info(v.data(),
+                           static_cast<ssize_t>(sizeof(T)),
+                           format_descriptor<T>::format(),
+                           1,
+                           {v.size()},
+                           {sizeof(T)});
     });
 
     cl.def(init([](const buffer &buf) {
@@ -429,7 +448,7 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
                              + " C++: " + format_descriptor<T>::format() + ")");
         }
 
-        T *p = static_cast<T*>(info.ptr);
+        T *p = static_cast<T *>(info.ptr);
         ssize_t step = info.strides[0] / static_cast<ssize_t>(sizeof(T));
         T *end = p + info.shape[0] * step;
         if (step == 1) {
@@ -441,18 +460,18 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
             vec.push_back(*p);
         }
         return vec;
-
     }));
 
     return;
 }
 
 template <typename Vector, typename Class_, typename... Args>
-void vector_buffer_impl(Class_&, std::false_type) {}
+void vector_buffer_impl(Class_ &, std::false_type) {}
 
 template <typename Vector, typename Class_, typename... Args>
-void vector_buffer(Class_& cl) {
-    vector_buffer_impl<Vector, Class_, Args...>(cl, detail::any_of<std::is_same<Args, buffer_protocol>...>{});
+void vector_buffer(Class_ &cl) {
+    vector_buffer_impl<Vector, Class_, Args...>(
+        cl, detail::any_of<std::is_same<Args, buffer_protocol>...>{});
 }
 
 PYBIND11_NAMESPACE_END(detail)
@@ -461,7 +480,7 @@ PYBIND11_NAMESPACE_END(detail)
 // std::vector
 //
 template <typename Vector, typename holder_type = std::unique_ptr<Vector>, typename... Args>
-class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, Args&&... args) {
+class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, Args &&...args) {
     using Class_ = class_<Vector, holder_type>;
 
     // If the value_type is unregistered (e.g. a converting type) or is itself registered
@@ -492,18 +511,13 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
     // Accessor and iterator; return by value if copyable, otherwise we return by ref + keep-alive
     detail::vector_accessor<Vector, Class_>(cl);
 
-    cl.def("__bool__",
-        [](const Vector &v) -> bool {
-            return !v.empty();
-        },
-        "Check whether the list is nonempty"
-    );
+    cl.def(
+        "__bool__",
+        [](const Vector &v) -> bool { return !v.empty(); },
+        "Check whether the list is nonempty");
 
     cl.def("__len__", &Vector::size);
 
-
-
-
 #if 0
     // C++ style functions deprecated, leaving it here as an example
     cl.def(init<size_type>());
@@ -547,8 +561,6 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
     return cl;
 }
 
-
-
 //
 // std::map, std::unordered_map
 //
@@ -556,55 +568,58 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 /* Fallback functions */
-template <typename, typename, typename... Args> void map_if_insertion_operator(const Args &...) { }
-template <typename, typename, typename... Args> void map_assignment(const Args &...) { }
+template <typename, typename, typename... Args>
+void map_if_insertion_operator(const Args &...) {}
+template <typename, typename, typename... Args>
+void map_assignment(const Args &...) {}
 
 // Map assignment when copy-assignable: just copy the value
 template <typename Map, typename Class_>
-void map_assignment(enable_if_t<is_copy_assignable<typename Map::mapped_type>::value, Class_> &cl) {
+void map_assignment(
+    enable_if_t<is_copy_assignable<typename Map::mapped_type>::value, Class_> &cl) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
 
-    cl.def("__setitem__",
-           [](Map &m, const KeyType &k, const MappedType &v) {
-               auto it = m.find(k);
-               if (it != m.end()) {
-                   it->second = v;
-               } else {
-                   m.emplace(k, v);
-               }
-           }
-    );
+    cl.def("__setitem__", [](Map &m, const KeyType &k, const MappedType &v) {
+        auto it = m.find(k);
+        if (it != m.end()) {
+            it->second = v;
+        } else {
+            m.emplace(k, v);
+        }
+    });
 }
 
-// Not copy-assignable, but still copy-constructible: we can update the value by erasing and reinserting
-template<typename Map, typename Class_>
-void map_assignment(enable_if_t<
-        !is_copy_assignable<typename Map::mapped_type>::value &&
-        is_copy_constructible<typename Map::mapped_type>::value,
-        Class_> &cl) {
+// Not copy-assignable, but still copy-constructible: we can update the value by erasing and
+// reinserting
+template <typename Map, typename Class_>
+void map_assignment(enable_if_t<!is_copy_assignable<typename Map::mapped_type>::value
+                                    && is_copy_constructible<typename Map::mapped_type>::value,
+                                Class_> &cl) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
 
-    cl.def("__setitem__",
-           [](Map &m, const KeyType &k, const MappedType &v) {
-               // We can't use m[k] = v; because value type might not be default constructable
-               auto r = m.emplace(k, v);
-               if (!r.second) {
-                   // value type is not copy assignable so the only way to insert it is to erase it first...
-                   m.erase(r.first);
-                   m.emplace(k, v);
-               }
-           }
-    );
+    cl.def("__setitem__", [](Map &m, const KeyType &k, const MappedType &v) {
+        // We can't use m[k] = v; because value type might not be default constructable
+        auto r = m.emplace(k, v);
+        if (!r.second) {
+            // value type is not copy assignable so the only way to insert it is to erase it
+            // first...
+            m.erase(r.first);
+            m.emplace(k, v);
+        }
+    });
 }
 
+template <typename Map, typename Class_>
+auto map_if_insertion_operator(Class_ &cl, std::string const &name)
+    -> decltype(std::declval<std::ostream &>() << std::declval<typename Map::key_type>()
+                                               << std::declval<typename Map::mapped_type>(),
+                void()) {
 
-template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &cl, std::string const &name)
--> decltype(std::declval<std::ostream&>() << std::declval<typename Map::key_type>() << std::declval<typename Map::mapped_type>(), void()) {
-
-    cl.def("__repr__",
-           [name](Map &m) {
+    cl.def(
+        "__repr__",
+        [name](Map &m) {
             std::ostringstream s;
             s << name << '{';
             bool f = false;
@@ -618,32 +633,28 @@ template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &
             s << '}';
             return s.str();
         },
-        "Return the canonical string representation of this map."
-    );
+        "Return the canonical string representation of this map.");
 }
 
-template<typename Map>
-struct keys_view
-{
+template <typename Map>
+struct keys_view {
     Map &map;
 };
 
-template<typename Map>
-struct values_view
-{
+template <typename Map>
+struct values_view {
     Map &map;
 };
 
-template<typename Map>
-struct items_view
-{
+template <typename Map>
+struct items_view {
     Map &map;
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
 template <typename Map, typename holder_type = std::unique_ptr<Map>, typename... Args>
-class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&... args) {
+class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&...args) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
     using KeysView = detail::keys_view<Map>;
@@ -674,101 +685,97 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     // Register stream insertion operator (if possible)
     detail::map_if_insertion_operator<Map, Class_>(cl, name);
 
-    cl.def("__bool__",
+    cl.def(
+        "__bool__",
         [](const Map &m) -> bool { return !m.empty(); },
-        "Check whether the map is nonempty"
-    );
+        "Check whether the map is nonempty");
 
-    cl.def("__iter__",
-           [](Map &m) { return make_key_iterator(m.begin(), m.end()); },
-           keep_alive<0, 1>() /* Essential: keep map alive while iterator exists */
+    cl.def(
+        "__iter__",
+        [](Map &m) { return make_key_iterator(m.begin(), m.end()); },
+        keep_alive<0, 1>() /* Essential: keep map alive while iterator exists */
     );
 
-    cl.def("keys",
-           [](Map &m) { return KeysView{m}; },
-           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    cl.def(
+        "keys",
+        [](Map &m) { return KeysView{m}; },
+        keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
-    cl.def("values",
-           [](Map &m) { return ValuesView{m}; },
-           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    cl.def(
+        "values",
+        [](Map &m) { return ValuesView{m}; },
+        keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
-    cl.def("items",
-           [](Map &m) { return ItemsView{m}; },
-           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    cl.def(
+        "items",
+        [](Map &m) { return ItemsView{m}; },
+        keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
-    cl.def("__getitem__",
+    cl.def(
+        "__getitem__",
         [](Map &m, const KeyType &k) -> MappedType & {
             auto it = m.find(k);
             if (it == m.end()) {
                 throw key_error();
             }
-           return it->second;
+            return it->second;
         },
         return_value_policy::reference_internal // ref + keepalive
     );
 
-    cl.def("__contains__",
-        [](Map &m, const KeyType &k) -> bool {
-            auto it = m.find(k);
-            if (it == m.end()) {
-                return false;
-            }
-           return true;
+    cl.def("__contains__", [](Map &m, const KeyType &k) -> bool {
+        auto it = m.find(k);
+        if (it == m.end()) {
+            return false;
         }
-    );
+        return true;
+    });
     // Fallback for when the object is not of the key type
     cl.def("__contains__", [](Map &, const object &) -> bool { return false; });
 
     // Assignment provided only if the type is copyable
     detail::map_assignment<Map, Class_>(cl);
 
-    cl.def("__delitem__",
-           [](Map &m, const KeyType &k) {
-               auto it = m.find(k);
-               if (it == m.end()) {
-                   throw key_error();
-               }
-               m.erase(it);
-           }
-    );
+    cl.def("__delitem__", [](Map &m, const KeyType &k) {
+        auto it = m.find(k);
+        if (it == m.end()) {
+            throw key_error();
+        }
+        m.erase(it);
+    });
 
     cl.def("__len__", &Map::size);
 
     keys_view.def("__len__", [](KeysView &view) { return view.map.size(); });
-    keys_view.def("__iter__",
-        [](KeysView &view) {
-            return make_key_iterator(view.map.begin(), view.map.end());
-        },
+    keys_view.def(
+        "__iter__",
+        [](KeysView &view) { return make_key_iterator(view.map.begin(), view.map.end()); },
         keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
     );
-    keys_view.def("__contains__",
-        [](KeysView &view, const KeyType &k) -> bool {
-            auto it = view.map.find(k);
-            if (it == view.map.end()) {
-                return false;
-            }
-            return true;
+    keys_view.def("__contains__", [](KeysView &view, const KeyType &k) -> bool {
+        auto it = view.map.find(k);
+        if (it == view.map.end()) {
+            return false;
         }
-    );
+        return true;
+    });
     // Fallback for when the object is not of the key type
     keys_view.def("__contains__", [](KeysView &, const object &) -> bool { return false; });
 
     values_view.def("__len__", [](ValuesView &view) { return view.map.size(); });
-    values_view.def("__iter__",
-        [](ValuesView &view) {
-            return make_value_iterator(view.map.begin(), view.map.end());
-        },
+    values_view.def(
+        "__iter__",
+        [](ValuesView &view) { return make_value_iterator(view.map.begin(), view.map.end()); },
         keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
     );
 
     items_view.def("__len__", [](ItemsView &view) { return view.map.size(); });
-    items_view.def("__iter__",
-        [](ItemsView &view) {
-            return make_iterator(view.map.begin(), view.map.end());
-        },
+    items_view.def(
+        "__iter__",
+        [](ItemsView &view) { return make_iterator(view.map.begin(), view.map.end()); },
         keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
     );
 
diff --git a/tests/constructor_stats.h b/tests/constructor_stats.h
index ccb623e1c3..a3835c21e6 100644
--- a/tests/constructor_stats.h
+++ b/tests/constructor_stats.h
@@ -56,7 +56,8 @@ from the ConstructorStats instance `.values()` method.
 In some cases, when you need to track instances of a C++ class not registered with pybind11, you
 need to add a function returning the ConstructorStats for the C++ class; this can be done with:
 
-    m.def("get_special_cstats", &ConstructorStats::get<SpecialClass>, py::return_value_policy::reference)
+    m.def("get_special_cstats", &ConstructorStats::get<SpecialClass>,
+py::return_value_policy::reference)
 
 Finally, you can suppress the output messages, but keep the constructor tracking (for
 inspection/testing in python) by using the functions with `print_` replaced with `track_` (e.g.
@@ -65,17 +66,18 @@ inspection/testing in python) by using the functions with `print_` replaced with
 */
 
 #include "pybind11_tests.h"
-#include <unordered_map>
+
 #include <list>
-#include <typeindex>
 #include <sstream>
+#include <typeindex>
+#include <unordered_map>
 
 class ConstructorStats {
 protected:
-    std::unordered_map<void*, int> _instances; // Need a map rather than set because members can
-                                               // shared address with parents
-    std::list<std::string> _values; // Used to track values
-                                    // (e.g. of value constructors)
+    std::unordered_map<void *, int> _instances; // Need a map rather than set because members can
+                                                // shared address with parents
+    std::list<std::string> _values;             // Used to track values
+                                                // (e.g. of value constructors)
 public:
     int default_constructions = 0;
     int copy_constructions = 0;
@@ -98,9 +100,7 @@ class ConstructorStats {
         default_constructions++;
     }
 
-    void created(void *inst) {
-        ++_instances[inst];
-    }
+    void created(void *inst) { ++_instances[inst]; }
 
     void destroyed(void *inst) {
         if (--_instances[inst] < 0) {
@@ -114,11 +114,12 @@ class ConstructorStats {
         // Force garbage collection to ensure any pending destructors are invoked:
 #if defined(PYPY_VERSION)
         PyObject *globals = PyEval_GetGlobals();
-        PyObject *result = PyRun_String(
-            "import gc\n"
-            "for i in range(2):"
-            "    gc.collect()\n",
-            Py_file_input, globals, globals);
+        PyObject *result = PyRun_String("import gc\n"
+                                        "for i in range(2):"
+                                        "    gc.collect()\n",
+                                        Py_file_input,
+                                        globals,
+                                        globals);
         if (result == nullptr)
             throw py::error_already_set();
         Py_DECREF(result);
@@ -140,7 +141,8 @@ class ConstructorStats {
 
     void value() {} // Recursion terminator
     // Takes one or more values, converts them to strings, then stores them.
-    template <typename T, typename... Tmore> void value(const T &v, Tmore &&...args) {
+    template <typename T, typename... Tmore>
+    void value(const T &v, Tmore &&...args) {
         std::ostringstream oss;
         oss << v;
         _values.push_back(oss.str());
@@ -158,13 +160,14 @@ class ConstructorStats {
     }
 
     // Gets constructor stats from a C++ type index
-    static ConstructorStats& get(std::type_index type) {
+    static ConstructorStats &get(std::type_index type) {
         static std::unordered_map<std::type_index, ConstructorStats> all_cstats;
         return all_cstats[type];
     }
 
     // Gets constructor stats from a C++ type
-    template <typename T> static ConstructorStats& get() {
+    template <typename T>
+    static ConstructorStats &get() {
 #if defined(PYPY_VERSION)
         gc();
 #endif
@@ -172,11 +175,12 @@ class ConstructorStats {
     }
 
     // Gets constructor stats from a Python class
-    static ConstructorStats& get(py::object class_) {
+    static ConstructorStats &get(py::object class_) {
         auto &internals = py::detail::get_internals();
         const std::type_index *t1 = nullptr, *t2 = nullptr;
         try {
-            auto *type_info = internals.registered_types_py.at((PyTypeObject *) class_.ptr()).at(0);
+            auto *type_info
+                = internals.registered_types_py.at((PyTypeObject *) class_.ptr()).at(0);
             for (auto &p : internals.registered_types_cpp) {
                 if (p.second == type_info) {
                     if (t1) {
@@ -186,18 +190,20 @@ class ConstructorStats {
                     t1 = &p.first;
                 }
             }
+        } catch (const std::out_of_range &) {
         }
-        catch (const std::out_of_range&) {}
         if (!t1) {
             throw std::runtime_error("Unknown class passed to ConstructorStats::get()");
         }
         auto &cs1 = get(*t1);
-        // If we have both a t1 and t2 match, one is probably the trampoline class; return whichever
-        // has more constructions (typically one or the other will be 0)
+        // If we have both a t1 and t2 match, one is probably the trampoline class; return
+        // whichever has more constructions (typically one or the other will be 0)
         if (t2) {
             auto &cs2 = get(*t2);
-            int cs1_total = cs1.default_constructions + cs1.copy_constructions + cs1.move_constructions + (int) cs1._values.size();
-            int cs2_total = cs2.default_constructions + cs2.copy_constructions + cs2.move_constructions + (int) cs2._values.size();
+            int cs1_total = cs1.default_constructions + cs1.copy_constructions
+                            + cs1.move_constructions + (int) cs1._values.size();
+            int cs2_total = cs2.default_constructions + cs2.copy_constructions
+                            + cs2.move_constructions + (int) cs2._values.size();
             if (cs2_total > cs1_total) {
                 return cs2;
             }
@@ -209,78 +215,108 @@ class ConstructorStats {
 // To track construction/destruction, you need to call these methods from the various
 // constructors/operators.  The ones that take extra values record the given values in the
 // constructor stats values for later inspection.
-template <class T> void track_copy_created(T *inst) { ConstructorStats::get<T>().copy_created(inst); }
-template <class T> void track_move_created(T *inst) { ConstructorStats::get<T>().move_created(inst); }
-template <class T, typename... Values> void track_copy_assigned(T *, Values &&...values) {
+template <class T>
+void track_copy_created(T *inst) {
+    ConstructorStats::get<T>().copy_created(inst);
+}
+template <class T>
+void track_move_created(T *inst) {
+    ConstructorStats::get<T>().move_created(inst);
+}
+template <class T, typename... Values>
+void track_copy_assigned(T *, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.copy_assignments++;
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_move_assigned(T *, Values &&...values) {
+template <class T, typename... Values>
+void track_move_assigned(T *, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.move_assignments++;
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_default_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void track_default_created(T *inst, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.default_created(inst);
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void track_created(T *inst, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.created(inst);
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_destroyed(T *inst) {
+template <class T, typename... Values>
+void track_destroyed(T *inst) {
     ConstructorStats::get<T>().destroyed(inst);
 }
-template <class T, typename... Values> void track_values(T *, Values &&...values) {
+template <class T, typename... Values>
+void track_values(T *, Values &&...values) {
     ConstructorStats::get<T>().value(std::forward<Values>(values)...);
 }
 
 /// Don't cast pointers to Python, print them as strings
 inline const char *format_ptrs(const char *p) { return p; }
 template <typename T>
-py::str format_ptrs(T *p) { return "{:#x}"_s.format(reinterpret_cast<std::uintptr_t>(p)); }
+py::str format_ptrs(T *p) {
+    return "{:#x}"_s.format(reinterpret_cast<std::uintptr_t>(p));
+}
 template <typename T>
-auto format_ptrs(T &&x) -> decltype(std::forward<T>(x)) { return std::forward<T>(x); }
+auto format_ptrs(T &&x) -> decltype(std::forward<T>(x)) {
+    return std::forward<T>(x);
+}
 
 template <class T, typename... Output>
 void print_constr_details(T *inst, const std::string &action, Output &&...output) {
-    py::print("###", py::type_id<T>(), "@", format_ptrs(inst), action,
+    py::print("###",
+              py::type_id<T>(),
+              "@",
+              format_ptrs(inst),
+              action,
               format_ptrs(std::forward<Output>(output))...);
 }
 
 // Verbose versions of the above:
-template <class T, typename... Values> void print_copy_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
+template <class T, typename... Values>
+void print_copy_created(T *inst,
+                        Values &&...values) { // NB: this prints, but doesn't store, given values
     print_constr_details(inst, "created via copy constructor", values...);
     track_copy_created(inst);
 }
-template <class T, typename... Values> void print_move_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
+template <class T, typename... Values>
+void print_move_created(T *inst,
+                        Values &&...values) { // NB: this prints, but doesn't store, given values
     print_constr_details(inst, "created via move constructor", values...);
     track_move_created(inst);
 }
-template <class T, typename... Values> void print_copy_assigned(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_copy_assigned(T *inst, Values &&...values) {
     print_constr_details(inst, "assigned via copy assignment", values...);
     track_copy_assigned(inst, values...);
 }
-template <class T, typename... Values> void print_move_assigned(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_move_assigned(T *inst, Values &&...values) {
     print_constr_details(inst, "assigned via move assignment", values...);
     track_move_assigned(inst, values...);
 }
-template <class T, typename... Values> void print_default_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_default_created(T *inst, Values &&...values) {
     print_constr_details(inst, "created via default constructor", values...);
     track_default_created(inst, values...);
 }
-template <class T, typename... Values> void print_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_created(T *inst, Values &&...values) {
     print_constr_details(inst, "created", values...);
     track_created(inst, values...);
 }
-template <class T, typename... Values> void print_destroyed(T *inst, Values &&...values) { // Prints but doesn't store given values
+template <class T, typename... Values>
+void print_destroyed(T *inst, Values &&...values) { // Prints but doesn't store given values
     print_constr_details(inst, "destroyed", values...);
     track_destroyed(inst);
 }
-template <class T, typename... Values> void print_values(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_values(T *inst, Values &&...values) {
     print_constr_details(inst, ":", values...);
     track_values(inst, values...);
 }
diff --git a/tests/cross_module_gil_utils.cpp b/tests/cross_module_gil_utils.cpp
index 07db9f6e48..f3aca1561a 100644
--- a/tests/cross_module_gil_utils.cpp
+++ b/tests/cross_module_gil_utils.cpp
@@ -7,6 +7,7 @@
     BSD-style license that can be found in the LICENSE file.
 */
 #include <pybind11/pybind11.h>
+
 #include <cstdint>
 
 // This file mimics a DSO that makes pybind11 calls but does not define a
@@ -25,34 +26,25 @@ void gil_acquire() { py::gil_scoped_acquire gil; }
 constexpr char kModuleName[] = "cross_module_gil_utils";
 
 #if PY_MAJOR_VERSION >= 3
-struct PyModuleDef moduledef = {
-    PyModuleDef_HEAD_INIT,
-    kModuleName,
-    NULL,
-    0,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL
-};
+struct PyModuleDef moduledef
+    = {PyModuleDef_HEAD_INIT, kModuleName, NULL, 0, NULL, NULL, NULL, NULL, NULL};
 #else
-PyMethodDef module_methods[] = {
-    {NULL, NULL, 0, NULL}
-};
+PyMethodDef module_methods[] = {{NULL, NULL, 0, NULL}};
 #endif
 
-}  // namespace
+} // namespace
 
 extern "C" PYBIND11_EXPORT
 #if PY_MAJOR_VERSION >= 3
-PyObject* PyInit_cross_module_gil_utils()
+    PyObject *
+    PyInit_cross_module_gil_utils()
 #else
-void initcross_module_gil_utils()
+    void
+    initcross_module_gil_utils()
 #endif
 {
 
-    PyObject* m =
+    PyObject *m =
 #if PY_MAJOR_VERSION >= 3
         PyModule_Create(&moduledef);
 #else
@@ -60,11 +52,10 @@ void initcross_module_gil_utils()
 #endif
 
     if (m != NULL) {
-        static_assert(
-            sizeof(&gil_acquire) == sizeof(void*),
-            "Function pointer must have the same size as void*");
-        PyModule_AddObject(m, "gil_acquire_funcaddr",
-                           PyLong_FromVoidPtr(reinterpret_cast<void*>(&gil_acquire)));
+        static_assert(sizeof(&gil_acquire) == sizeof(void *),
+                      "Function pointer must have the same size as void*");
+        PyModule_AddObject(
+            m, "gil_acquire_funcaddr", PyLong_FromVoidPtr(reinterpret_cast<void *>(&gil_acquire)));
     }
 
 #if PY_MAJOR_VERSION >= 3
diff --git a/tests/local_bindings.h b/tests/local_bindings.h
index 4c936c19a5..01d2785353 100644
--- a/tests/local_bindings.h
+++ b/tests/local_bindings.h
@@ -1,12 +1,13 @@
 #pragma once
-#include <utility>
-
 #include "pybind11_tests.h"
 
+#include <utility>
+
 /// Simple class used to test py::local:
-template <int> class LocalBase {
+template <int>
+class LocalBase {
 public:
-    explicit LocalBase(int i) : i(i) { }
+    explicit LocalBase(int i) : i(i) {}
     int i = -1;
 };
 
@@ -35,12 +36,12 @@ using NonLocalVec2 = std::vector<NonLocal2>;
 using NonLocalMap = std::unordered_map<std::string, NonLocalType>;
 using NonLocalMap2 = std::unordered_map<std::string, uint8_t>;
 
-
 // Exception that will be caught via the module local translator.
 class LocalException : public std::exception {
 public:
-    explicit LocalException(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit LocalException(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -48,8 +49,9 @@ class LocalException : public std::exception {
 // Exception that will be registered with register_local_exception_translator
 class LocalSimpleException : public std::exception {
 public:
-    explicit LocalSimpleException(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit LocalSimpleException(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -58,17 +60,16 @@ PYBIND11_MAKE_OPAQUE(LocalVec);
 PYBIND11_MAKE_OPAQUE(LocalVec2);
 PYBIND11_MAKE_OPAQUE(LocalMap);
 PYBIND11_MAKE_OPAQUE(NonLocalVec);
-//PYBIND11_MAKE_OPAQUE(NonLocalVec2); // same type as LocalVec2
+// PYBIND11_MAKE_OPAQUE(NonLocalVec2); // same type as LocalVec2
 PYBIND11_MAKE_OPAQUE(NonLocalMap);
 PYBIND11_MAKE_OPAQUE(NonLocalMap2);
 
-
 // Simple bindings (used with the above):
 template <typename T, int Adjust = 0, typename... Args>
-py::class_<T> bind_local(Args && ...args) {
-    return py::class_<T>(std::forward<Args>(args)...)
-        .def(py::init<int>())
-        .def("get", [](T &i) { return i.i + Adjust; });
+py::class_<T> bind_local(Args &&...args) {
+    return py::class_<T>(std::forward<Args>(args)...).def(py::init<int>()).def("get", [](T &i) {
+        return i.i + Adjust;
+    });
 };
 
 // Simulate a foreign library base class (to match the example in the docs):
@@ -81,5 +82,11 @@ class Pet {
 };
 } // namespace pets
 
-struct MixGL { int i; explicit MixGL(int i) : i{i} {} };
-struct MixGL2 { int i; explicit MixGL2(int i) : i{i} {} };
+struct MixGL {
+    int i;
+    explicit MixGL(int i) : i{i} {}
+};
+struct MixGL2 {
+    int i;
+    explicit MixGL2(int i) : i{i} {}
+};
diff --git a/tests/object.h b/tests/object.h
index 6365457c34..564dd4a7a5 100644
--- a/tests/object.h
+++ b/tests/object.h
@@ -1,8 +1,9 @@
 #if !defined(__OBJECT_H)
-#define __OBJECT_H
+#    define __OBJECT_H
 
-#include <atomic>
-#include "constructor_stats.h"
+#    include "constructor_stats.h"
+
+#    include <atomic>
 
 /// Reference counted object base class
 class Object {
@@ -35,13 +36,15 @@ class Object {
     }
 
     virtual std::string toString() const = 0;
+
 protected:
     /** \brief Virtual protected deconstructor.
      * (Will only be called by \ref ref)
      */
     virtual ~Object() { print_destroyed(this); }
+
 private:
-    mutable std::atomic<int> m_refCount { 0 };
+    mutable std::atomic<int> m_refCount{0};
 };
 
 // Tag class used to track constructions of ref objects.  When we track constructors, below, we
@@ -60,10 +63,14 @@ class ref_tag {};
  *
  * \ingroup libcore
  */
-template <typename T> class ref {
+template <typename T>
+class ref {
 public:
     /// Create a nullptr reference
-    ref() : m_ptr(nullptr) { print_default_created(this); track_default_created((ref_tag*) this); }
+    ref() : m_ptr(nullptr) {
+        print_default_created(this);
+        track_default_created((ref_tag *) this);
+    }
 
     /// Construct a reference from a pointer
     explicit ref(T *ptr) : m_ptr(ptr) {
@@ -71,8 +78,8 @@ template <typename T> class ref {
             ((Object *) m_ptr)->incRef();
         }
 
-        print_created(this, "from pointer", m_ptr); track_created((ref_tag*) this, "from pointer");
-
+        print_created(this, "from pointer", m_ptr);
+        track_created((ref_tag *) this, "from pointer");
     }
 
     /// Copy constructor
@@ -81,14 +88,16 @@ template <typename T> class ref {
             ((Object *) m_ptr)->incRef();
         }
 
-        print_copy_created(this, "with pointer", m_ptr); track_copy_created((ref_tag*) this);
+        print_copy_created(this, "with pointer", m_ptr);
+        track_copy_created((ref_tag *) this);
     }
 
     /// Move constructor
     ref(ref &&r) noexcept : m_ptr(r.m_ptr) {
         r.m_ptr = nullptr;
 
-        print_move_created(this, "with pointer", m_ptr); track_move_created((ref_tag*) this);
+        print_move_created(this, "with pointer", m_ptr);
+        track_move_created((ref_tag *) this);
     }
 
     /// Destroy this reference
@@ -97,12 +106,14 @@ template <typename T> class ref {
             ((Object *) m_ptr)->decRef();
         }
 
-        print_destroyed(this); track_destroyed((ref_tag*) this);
+        print_destroyed(this);
+        track_destroyed((ref_tag *) this);
     }
 
     /// Move another reference into the current one
     ref &operator=(ref &&r) noexcept {
-        print_move_assigned(this, "pointer", r.m_ptr); track_move_assigned((ref_tag*) this);
+        print_move_assigned(this, "pointer", r.m_ptr);
+        track_move_assigned((ref_tag *) this);
 
         if (*this == r) {
             return *this;
@@ -116,7 +127,7 @@ template <typename T> class ref {
     }
 
     /// Overwrite this reference with another reference
-    ref& operator=(const ref& r) {
+    ref &operator=(const ref &r) {
         if (this == &r) {
             return *this;
         }
@@ -137,8 +148,9 @@ template <typename T> class ref {
     }
 
     /// Overwrite this reference with a pointer to another object
-    ref& operator=(T *ptr) {
-        print_values(this, "assigned pointer"); track_values((ref_tag*) this, "assigned pointer");
+    ref &operator=(T *ptr) {
+        print_values(this, "assigned pointer");
+        track_values((ref_tag *) this, "assigned pointer");
 
         if (m_ptr == ptr) {
             return *this;
@@ -160,31 +172,32 @@ template <typename T> class ref {
     bool operator!=(const ref &r) const { return m_ptr != r.m_ptr; }
 
     /// Compare this reference with a pointer
-    bool operator==(const T* ptr) const { return m_ptr == ptr; }
+    bool operator==(const T *ptr) const { return m_ptr == ptr; }
 
     /// Compare this reference with a pointer
-    bool operator!=(const T* ptr) const { return m_ptr != ptr; }
+    bool operator!=(const T *ptr) const { return m_ptr != ptr; }
 
     /// Access the object referenced by this reference
-    T* operator->() { return m_ptr; }
+    T *operator->() { return m_ptr; }
 
     /// Access the object referenced by this reference
-    const T* operator->() const { return m_ptr; }
+    const T *operator->() const { return m_ptr; }
 
     /// Return a C++ reference to the referenced object
-    T& operator*() { return *m_ptr; }
+    T &operator*() { return *m_ptr; }
 
     /// Return a const C++ reference to the referenced object
-    const T& operator*() const { return *m_ptr; }
+    const T &operator*() const { return *m_ptr; }
 
     /// Return a pointer to the referenced object
-    explicit operator T* () { return m_ptr; }
+    explicit operator T *() { return m_ptr; }
 
     /// Return a const pointer to the referenced object
-    T* get_ptr() { return m_ptr; }
+    T *get_ptr() { return m_ptr; }
 
     /// Return a pointer to the referenced object
-    const T* get_ptr() const { return m_ptr; }
+    const T *get_ptr() const { return m_ptr; }
+
 private:
     T *m_ptr;
 };
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index 82228a440a..9379f3f259 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -7,12 +7,12 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
+#include <pybind11/stl_bind.h>
+
 #include "local_bindings.h"
+#include "pybind11_tests.h"
 #include "test_exceptions.h"
 
-#include <pybind11/stl_bind.h>
-
 #include <numeric>
 #include <utility>
 
@@ -30,39 +30,45 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
 
     // test_exceptions.py
     py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException");
-    m.def("raise_runtime_error", []() { PyErr_SetString(PyExc_RuntimeError, "My runtime error"); throw py::error_already_set(); });
-    m.def("raise_value_error", []() { PyErr_SetString(PyExc_ValueError, "My value error"); throw py::error_already_set(); });
+    m.def("raise_runtime_error", []() {
+        PyErr_SetString(PyExc_RuntimeError, "My runtime error");
+        throw py::error_already_set();
+    });
+    m.def("raise_value_error", []() {
+        PyErr_SetString(PyExc_ValueError, "My value error");
+        throw py::error_already_set();
+    });
     m.def("throw_pybind_value_error", []() { throw py::value_error("pybind11 value error"); });
     m.def("throw_pybind_type_error", []() { throw py::type_error("pybind11 type error"); });
     m.def("throw_stop_iteration", []() { throw py::stop_iteration(); });
     m.def("throw_local_error", []() { throw LocalException("just local"); });
     m.def("throw_local_simple_error", []() { throw LocalSimpleException("external mod"); });
     py::register_exception_translator([](std::exception_ptr p) {
-      try {
-          if (p) {
-              std::rethrow_exception(p);
-          }
-      } catch (const shared_exception &e) {
-          PyErr_SetString(PyExc_KeyError, e.what());
-      }
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const shared_exception &e) {
+            PyErr_SetString(PyExc_KeyError, e.what());
+        }
     });
 
     // translate the local exception into a key error but only in this module
     py::register_local_exception_translator([](std::exception_ptr p) {
-      try {
-          if (p) {
-            std::rethrow_exception(p);
-          }
-      } catch (const LocalException &e) {
-        PyErr_SetString(PyExc_KeyError, e.what());
-      }
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const LocalException &e) {
+            PyErr_SetString(PyExc_KeyError, e.what());
+        }
     });
 
     // test_local_bindings.py
     // Local to both:
-    bind_local<LocalType, 1>(m, "LocalType", py::module_local())
-        .def("get2", [](LocalType &t) { return t.i + 2; })
-        ;
+    bind_local<LocalType, 1>(m, "LocalType", py::module_local()).def("get2", [](LocalType &t) {
+        return t.i + 2;
+    });
 
     // Can only be called with our python type:
     m.def("local_value", [](LocalType &l) { return l.i; });
@@ -70,9 +76,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_nonlocal_failure
     // This registration will fail (global registration when LocalFail is already registered
     // globally in the main test module):
-    m.def("register_nonlocal", [m]() {
-        bind_local<NonLocalType, 0>(m, "NonLocalType");
-    });
+    m.def("register_nonlocal", [m]() { bind_local<NonLocalType, 0>(m, "NonLocalType"); });
 
     // test_stl_bind_local
     // stl_bind.h binders defaults to py::module_local if the types are local or converting:
@@ -82,27 +86,21 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_stl_bind_global
     // and global if the type (or one of the types, for the map) is global (so these will fail,
     // assuming pybind11_tests is already loaded):
-    m.def("register_nonlocal_vec", [m]() {
-        py::bind_vector<NonLocalVec>(m, "NonLocalVec");
-    });
-    m.def("register_nonlocal_map", [m]() {
-        py::bind_map<NonLocalMap>(m, "NonLocalMap");
-    });
+    m.def("register_nonlocal_vec", [m]() { py::bind_vector<NonLocalVec>(m, "NonLocalVec"); });
+    m.def("register_nonlocal_map", [m]() { py::bind_map<NonLocalMap>(m, "NonLocalMap"); });
     // The default can, however, be overridden to global using `py::module_local()` or
     // `py::module_local(false)`.
     // Explicitly made local:
     py::bind_vector<NonLocalVec2>(m, "NonLocalVec2", py::module_local());
     // Explicitly made global (and so will fail to bind):
-    m.def("register_nonlocal_map2", [m]() {
-        py::bind_map<NonLocalMap2>(m, "NonLocalMap2", py::module_local(false));
-    });
+    m.def("register_nonlocal_map2",
+          [m]() { py::bind_map<NonLocalMap2>(m, "NonLocalMap2", py::module_local(false)); });
 
     // test_mixed_local_global
     // We try this both with the global type registered first and vice versa (the order shouldn't
     // matter).
-    m.def("register_mixed_global_local", [m]() {
-        bind_local<MixedGlobalLocal, 200>(m, "MixedGlobalLocal", py::module_local());
-    });
+    m.def("register_mixed_global_local",
+          [m]() { bind_local<MixedGlobalLocal, 200>(m, "MixedGlobalLocal", py::module_local()); });
     m.def("register_mixed_local_global", [m]() {
         bind_local<MixedLocalGlobal, 2000>(m, "MixedLocalGlobal", py::module_local(false));
     });
@@ -110,14 +108,14 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); });
 
     // test_internal_locals_differ
-    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
+    m.def("local_cpp_types_addr",
+          []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
 
     // test_stl_caster_vs_stl_bind
     py::bind_vector<std::vector<int>>(m, "VectorInt");
 
-    m.def("load_vector_via_binding", [](std::vector<int> &v) {
-        return std::accumulate(v.begin(), v.end(), 0);
-    });
+    m.def("load_vector_via_binding",
+          [](std::vector<int> &v) { return std::accumulate(v.begin(), v.end(), 0); });
 
     // test_cross_module_calls
     m.def("return_self", [](LocalVec *v) { return v; });
@@ -127,11 +125,9 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     public:
         explicit Dog(std::string name) : Pet(std::move(name)) {}
     };
-    py::class_<pets::Pet>(m, "Pet", py::module_local())
-        .def("name", &pets::Pet::name);
+    py::class_<pets::Pet>(m, "Pet", py::module_local()).def("name", &pets::Pet::name);
     // Binding for local extending class:
-    py::class_<Dog, pets::Pet>(m, "Dog")
-        .def(py::init<std::string>());
+    py::class_<Dog, pets::Pet>(m, "Dog").def(py::init<std::string>());
     m.def("pet_name", [](pets::Pet &p) { return p.name(); });
 
     py::class_<MixGL>(m, "MixGL", py::module_local()).def(py::init<int>());
diff --git a/tests/pybind11_tests.cpp b/tests/pybind11_tests.cpp
index ec4581efd2..d9b88fcc24 100644
--- a/tests/pybind11_tests.cpp
+++ b/tests/pybind11_tests.cpp
@@ -8,6 +8,7 @@
 */
 
 #include "pybind11_tests.h"
+
 #include "constructor_stats.h"
 
 #include <functional>
@@ -31,9 +32,7 @@ std::list<std::function<void(py::module_ &)>> &initializers() {
     return inits;
 }
 
-test_initializer::test_initializer(Initializer init) {
-    initializers().emplace_back(init);
-}
+test_initializer::test_initializer(Initializer init) { initializers().emplace_back(init); }
 
 test_initializer::test_initializer(const char *submodule_name, Initializer init) {
     initializers().emplace_back([=](py::module_ &parent) {
@@ -51,15 +50,16 @@ void bind_ConstructorStats(py::module_ &m) {
         .def_readwrite("move_assignments", &ConstructorStats::move_assignments)
         .def_readwrite("copy_constructions", &ConstructorStats::copy_constructions)
         .def_readwrite("move_constructions", &ConstructorStats::move_constructions)
-        .def_static("get", (ConstructorStats &(*)(py::object)) &ConstructorStats::get, py::return_value_policy::reference_internal)
+        .def_static("get",
+                    (ConstructorStats & (*) (py::object)) & ConstructorStats::get,
+                    py::return_value_policy::reference_internal)
 
-        // Not exactly ConstructorStats, but related: expose the internal pybind number of registered instances
-        // to allow instance cleanup checks (invokes a GC first)
+        // Not exactly ConstructorStats, but related: expose the internal pybind number of
+        // registered instances to allow instance cleanup checks (invokes a GC first)
         .def_static("detail_reg_inst", []() {
             ConstructorStats::gc();
             return py::detail::get_internals().registered_instances.size();
-        })
-        ;
+        });
 }
 
 PYBIND11_MODULE(pybind11_tests, m) {
@@ -79,12 +79,12 @@ PYBIND11_MODULE(pybind11_tests, m) {
         .def("get_value", &UserType::value, "Get value using a method")
         .def("set_value", &UserType::set, "Set value using a method")
         .def_property("value", &UserType::value, &UserType::set, "Get/set value using a property")
-        .def("__repr__", [](const UserType& u) { return "UserType({})"_s.format(u.value()); });
+        .def("__repr__", [](const UserType &u) { return "UserType({})"_s.format(u.value()); });
 
     py::class_<IncType, UserType>(m, "IncType")
         .def(py::init<>())
         .def(py::init<int>())
-        .def("__repr__", [](const IncType& u) { return "IncType({})"_s.format(u.value()); });
+        .def("__repr__", [](const IncType &u) { return "IncType({})"_s.format(u.value()); });
 
     for (const auto &initializer : initializers()) {
         initializer(m);
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index f6e1a6523b..283801a1b7 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -1,11 +1,12 @@
 #pragma once
 
-#include <pybind11/pybind11.h>
 #include <pybind11/eval.h>
+#include <pybind11/pybind11.h>
 
 #if defined(_MSC_VER) && _MSC_VER < 1910
 // We get some really long type names here which causes MSVC 2015 to emit warnings
-#    pragma warning(disable : 4503) // NOLINT: warning C4503: decorated name length exceeded, name was truncated
+#    pragma warning(                                                                              \
+        disable : 4503) // NOLINT: warning C4503: decorated name length exceeded, name was truncated
 #endif
 
 namespace py = pybind11;
@@ -25,13 +26,13 @@ class test_initializer {
     void test_submodule_##name(py::module_ &(variable))
 
 /// Dummy type which is not exported anywhere -- something to trigger a conversion error
-struct UnregisteredType { };
+struct UnregisteredType {};
 
 /// A user-defined type which is exported and can be used by any test
 class UserType {
 public:
     UserType() = default;
-    explicit UserType(int i) : i(i) { }
+    explicit UserType(int i) : i(i) {}
 
     int value() const { return i; }
     void set(int set) { i = set; }
@@ -45,7 +46,7 @@ class IncType : public UserType {
 public:
     using UserType::UserType;
     IncType() = default;
-    IncType(const IncType &other) : IncType(other.value() + 1) { }
+    IncType(const IncType &other) : IncType(other.value() + 1) {}
     IncType(IncType &&) = delete;
     IncType &operator=(const IncType &) = delete;
     IncType &operator=(IncType &&) = delete;
@@ -57,16 +58,21 @@ union IntFloat {
     float f;
 };
 
-/// Custom cast-only type that casts to a string "rvalue" or "lvalue" depending on the cast context.
-/// Used to test recursive casters (e.g. std::tuple, stl containers).
+/// Custom cast-only type that casts to a string "rvalue" or "lvalue" depending on the cast
+/// context. Used to test recursive casters (e.g. std::tuple, stl containers).
 struct RValueCaster {};
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
-template<> class type_caster<RValueCaster> {
+template <>
+class type_caster<RValueCaster> {
 public:
     PYBIND11_TYPE_CASTER(RValueCaster, const_name("RValueCaster"));
-    static handle cast(RValueCaster &&, return_value_policy, handle) { return py::str("rvalue").release(); }
-    static handle cast(const RValueCaster &, return_value_policy, handle) { return py::str("lvalue").release(); }
+    static handle cast(RValueCaster &&, return_value_policy, handle) {
+        return py::str("rvalue").release();
+    }
+    static handle cast(const RValueCaster &, return_value_policy, handle) {
+        return py::str("lvalue").release();
+    }
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
@@ -80,5 +86,6 @@ void ignoreOldStyleInitWarnings(F &&body) {
     with warnings.catch_warnings():
         warnings.filterwarnings("ignore", message=message, category=FutureWarning)
         body()
-    )", py::dict(py::arg("body") = py::cpp_function(body)));
+    )",
+             py::dict(py::arg("body") = py::cpp_function(body)));
 }
diff --git a/tests/test_async.cpp b/tests/test_async.cpp
index e6e01d72c9..a5d7224657 100644
--- a/tests/test_async.cpp
+++ b/tests/test_async.cpp
@@ -11,12 +11,11 @@
 
 TEST_SUBMODULE(async_module, m) {
     struct DoesNotSupportAsync {};
-    py::class_<DoesNotSupportAsync>(m, "DoesNotSupportAsync")
-        .def(py::init<>());
+    py::class_<DoesNotSupportAsync>(m, "DoesNotSupportAsync").def(py::init<>());
     struct SupportsAsync {};
     py::class_<SupportsAsync>(m, "SupportsAsync")
         .def(py::init<>())
-        .def("__await__", [](const SupportsAsync& self) -> py::object {
+        .def("__await__", [](const SupportsAsync &self) -> py::object {
             static_cast<void>(self);
             py::object loop = py::module_::import("asyncio.events").attr("get_event_loop")();
             py::object f = loop.attr("create_future")();
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 3a4d304676..6b6e8cba7f 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -7,10 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 TEST_SUBMODULE(buffers, m) {
     // test_from_python / test_to_python:
     class Matrix {
@@ -23,7 +24,8 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         Matrix(const Matrix &s) : m_rows(s.m_rows), m_cols(s.m_cols) {
-            print_copy_created(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            print_copy_created(this,
+                               std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[(size_t) (m_rows * m_cols)];
             memcpy(m_data, s.m_data, sizeof(float) * (size_t) (m_rows * m_cols));
@@ -37,7 +39,8 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         ~Matrix() {
-            print_destroyed(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            print_destroyed(this,
+                            std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             delete[] m_data;
         }
 
@@ -56,27 +59,33 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         Matrix &operator=(Matrix &&s) noexcept {
-            print_move_assigned(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            print_move_assigned(this,
+                                std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             if (&s != this) {
                 delete[] m_data;
-                m_rows = s.m_rows; m_cols = s.m_cols; m_data = s.m_data;
-                s.m_rows = 0; s.m_cols = 0; s.m_data = nullptr;
+                m_rows = s.m_rows;
+                m_cols = s.m_cols;
+                m_data = s.m_data;
+                s.m_rows = 0;
+                s.m_cols = 0;
+                s.m_data = nullptr;
             }
             return *this;
         }
 
         float operator()(py::ssize_t i, py::ssize_t j) const {
-            return m_data[(size_t) (i*m_cols + j)];
+            return m_data[(size_t) (i * m_cols + j)];
         }
 
         float &operator()(py::ssize_t i, py::ssize_t j) {
-            return m_data[(size_t) (i*m_cols + j)];
+            return m_data[(size_t) (i * m_cols + j)];
         }
 
         float *data() { return m_data; }
 
         py::ssize_t rows() const { return m_rows; }
         py::ssize_t cols() const { return m_cols; }
+
     private:
         py::ssize_t m_rows;
         py::ssize_t m_cols;
@@ -117,11 +126,10 @@ TEST_SUBMODULE(buffers, m) {
         /// Provide buffer access
         .def_buffer([](Matrix &m) -> py::buffer_info {
             return py::buffer_info(
-                m.data(),                               /* Pointer to buffer */
-                { m.rows(), m.cols() },                 /* Buffer dimensions */
-                { sizeof(float) * size_t(m.cols()),     /* Strides (in bytes) for each index */
-                  sizeof(float) }
-            );
+                m.data(),                          /* Pointer to buffer */
+                {m.rows(), m.cols()},              /* Buffer dimensions */
+                {sizeof(float) * size_t(m.cols()), /* Strides (in bytes) for each index */
+                 sizeof(float)});
         });
 
     // test_inherited_protocol
@@ -130,9 +138,7 @@ TEST_SUBMODULE(buffers, m) {
         explicit SquareMatrix(py::ssize_t n) : Matrix(n, n) {}
     };
     // Derived classes inherit the buffer protocol and the buffer access function
-    py::class_<SquareMatrix, Matrix>(m, "SquareMatrix")
-        .def(py::init<py::ssize_t>());
-
+    py::class_<SquareMatrix, Matrix>(m, "SquareMatrix").def(py::init<py::ssize_t>());
 
     // test_pointer_to_member_fn
     // Tests that passing a pointer to member to the base class works in
@@ -141,8 +147,8 @@ TEST_SUBMODULE(buffers, m) {
         int32_t value = 0;
 
         py::buffer_info get_buffer_info() {
-            return py::buffer_info(&value, sizeof(value),
-                                   py::format_descriptor<int32_t>::format(), 1);
+            return py::buffer_info(
+                &value, sizeof(value), py::format_descriptor<int32_t>::format(), 1);
         }
     };
     py::class_<Buffer>(m, "Buffer", py::buffer_protocol())
@@ -150,7 +156,6 @@ TEST_SUBMODULE(buffers, m) {
         .def_readwrite("value", &Buffer::value)
         .def_buffer(&Buffer::get_buffer_info);
 
-
     class ConstBuffer {
         std::unique_ptr<int32_t> value;
 
@@ -159,8 +164,8 @@ TEST_SUBMODULE(buffers, m) {
         void set_value(int32_t v) { *value = v; }
 
         py::buffer_info get_buffer_info() const {
-            return py::buffer_info(value.get(), sizeof(*value),
-                                   py::format_descriptor<int32_t>::format(), 1);
+            return py::buffer_info(
+                value.get(), sizeof(*value), py::format_descriptor<int32_t>::format(), 1);
         }
 
         ConstBuffer() : value(new int32_t{0}) {}
@@ -170,7 +175,7 @@ TEST_SUBMODULE(buffers, m) {
         .def_property("value", &ConstBuffer::get_value, &ConstBuffer::set_value)
         .def_buffer(&ConstBuffer::get_buffer_info);
 
-    struct DerivedBuffer : public Buffer { };
+    struct DerivedBuffer : public Buffer {};
     py::class_<DerivedBuffer>(m, "DerivedBuffer", py::buffer_protocol())
         .def(py::init<>())
         .def_readwrite("value", (int32_t DerivedBuffer::*) &DerivedBuffer::value)
@@ -180,9 +185,7 @@ TEST_SUBMODULE(buffers, m) {
         const uint8_t value = 0;
         explicit BufferReadOnly(uint8_t value) : value(value) {}
 
-        py::buffer_info get_buffer_info() {
-            return py::buffer_info(&value, 1);
-        }
+        py::buffer_info get_buffer_info() { return py::buffer_info(&value, 1); }
     };
     py::class_<BufferReadOnly>(m, "BufferReadOnly", py::buffer_protocol())
         .def(py::init<uint8_t>())
@@ -192,9 +195,7 @@ TEST_SUBMODULE(buffers, m) {
         uint8_t value = 0;
         bool readonly = false;
 
-        py::buffer_info get_buffer_info() {
-            return py::buffer_info(&value, 1, readonly);
-        }
+        py::buffer_info get_buffer_info() { return py::buffer_info(&value, 1, readonly); }
     };
     py::class_<BufferReadOnlySelect>(m, "BufferReadOnlySelect", py::buffer_protocol())
         .def(py::init<>())
@@ -213,9 +214,11 @@ TEST_SUBMODULE(buffers, m) {
         .def_readonly("strides", &py::buffer_info::strides)
         .def_readonly("readonly", &py::buffer_info::readonly)
         .def("__repr__", [](py::handle self) {
-             return py::str("itemsize={0.itemsize!r}, size={0.size!r}, format={0.format!r}, ndim={0.ndim!r}, shape={0.shape!r}, strides={0.strides!r}, readonly={0.readonly!r}").format(self);
-        })
-        ;
+            return py::str("itemsize={0.itemsize!r}, size={0.size!r}, format={0.format!r}, "
+                           "ndim={0.ndim!r}, shape={0.shape!r}, strides={0.strides!r}, "
+                           "readonly={0.readonly!r}")
+                .format(self);
+        });
 
     m.def("get_buffer_info", [](const py::buffer &buffer) { return buffer.request(); });
 }
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 96519d44e9..320ddd8aa2 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -7,64 +7,67 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/complex.h>
 
+#include "pybind11_tests.h"
+
 struct ConstRefCasted {
-  int tag;
+    int tag;
 };
 
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <>
 class type_caster<ConstRefCasted> {
- public:
-  static constexpr auto name = const_name<ConstRefCasted>();
-
-  // Input is unimportant, a new value will always be constructed based on the
-  // cast operator.
-  bool load(handle, bool) { return true; }
-
-  explicit operator ConstRefCasted &&() {
-      value = {1};
-      // NOLINTNEXTLINE(performance-move-const-arg)
-      return std::move(value);
-  }
-  explicit operator ConstRefCasted &() {
-      value = {2};
-      return value;
-  }
-  explicit operator ConstRefCasted *() {
-      value = {3};
-      return &value;
-  }
-
-  explicit operator const ConstRefCasted &() {
-      value = {4};
-      return value;
-  }
-  explicit operator const ConstRefCasted *() {
-      value = {5};
-      return &value;
-  }
-
-  // custom cast_op to explicitly propagate types to the conversion operators.
-  template <typename T_>
-  using cast_op_type =
-      /// const
-      conditional_t<
-          std::is_same<remove_reference_t<T_>, const ConstRefCasted*>::value, const ConstRefCasted*,
-      conditional_t<
-          std::is_same<T_, const ConstRefCasted&>::value, const ConstRefCasted&,
-      /// non-const
-      conditional_t<
-          std::is_same<remove_reference_t<T_>, ConstRefCasted*>::value, ConstRefCasted*,
-      conditional_t<
-          std::is_same<T_, ConstRefCasted&>::value, ConstRefCasted&,
-          /* else */ConstRefCasted&&>>>>;
-
- private:
-  ConstRefCasted value = {0};
+public:
+    static constexpr auto name = const_name<ConstRefCasted>();
+
+    // Input is unimportant, a new value will always be constructed based on the
+    // cast operator.
+    bool load(handle, bool) { return true; }
+
+    explicit operator ConstRefCasted &&() {
+        value = {1};
+        // NOLINTNEXTLINE(performance-move-const-arg)
+        return std::move(value);
+    }
+    explicit operator ConstRefCasted &() {
+        value = {2};
+        return value;
+    }
+    explicit operator ConstRefCasted *() {
+        value = {3};
+        return &value;
+    }
+
+    explicit operator const ConstRefCasted &() {
+        value = {4};
+        return value;
+    }
+    explicit operator const ConstRefCasted *() {
+        value = {5};
+        return &value;
+    }
+
+    // custom cast_op to explicitly propagate types to the conversion operators.
+    template <typename T_>
+    using cast_op_type =
+        /// const
+        conditional_t<
+            std::is_same<remove_reference_t<T_>, const ConstRefCasted *>::value,
+            const ConstRefCasted *,
+            conditional_t<
+                std::is_same<T_, const ConstRefCasted &>::value,
+                const ConstRefCasted &,
+                /// non-const
+                conditional_t<std::is_same<remove_reference_t<T_>, ConstRefCasted *>::value,
+                              ConstRefCasted *,
+                              conditional_t<std::is_same<T_, ConstRefCasted &>::value,
+                                            ConstRefCasted &,
+                                            /* else */ ConstRefCasted &&>>>>;
+
+private:
+    ConstRefCasted value = {0};
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
@@ -74,25 +77,43 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("string_roundtrip", [](const char *s) { return s; });
 
     // test_unicode_conversion
-    // Some test characters in utf16 and utf32 encodings.  The last one (the 𝐀) contains a null byte
-    char32_t a32 = 0x61 /*a*/, z32 = 0x7a /*z*/, ib32 = 0x203d /*‽*/, cake32 = 0x1f382 /*🎂*/,              mathbfA32 = 0x1d400 /*𝐀*/;
-    char16_t b16 = 0x62 /*b*/, z16 = 0x7a,       ib16 = 0x203d,       cake16_1 = 0xd83c, cake16_2 = 0xdf82, mathbfA16_1 = 0xd835, mathbfA16_2 = 0xdc00;
+    // Some test characters in utf16 and utf32 encodings.  The last one (the 𝐀) contains a null
+    // byte
+    char32_t a32 = 0x61 /*a*/, z32 = 0x7a /*z*/, ib32 = 0x203d /*‽*/, cake32 = 0x1f382 /*🎂*/,
+             mathbfA32 = 0x1d400 /*𝐀*/;
+    char16_t b16 = 0x62 /*b*/, z16 = 0x7a, ib16 = 0x203d, cake16_1 = 0xd83c, cake16_2 = 0xdf82,
+             mathbfA16_1 = 0xd835, mathbfA16_2 = 0xdc00;
     std::wstring wstr;
-    wstr.push_back(0x61); // a
+    wstr.push_back(0x61);   // a
     wstr.push_back(0x2e18); // ⸘
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) { wstr.push_back(mathbfA16_1); wstr.push_back(mathbfA16_2); } // 𝐀, utf16
-    else { wstr.push_back((wchar_t) mathbfA32); } // 𝐀, utf32
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+        wstr.push_back(mathbfA16_1);
+        wstr.push_back(mathbfA16_2);
+    } // 𝐀, utf16
+    else {
+        wstr.push_back((wchar_t) mathbfA32);
+    }                     // 𝐀, utf32
     wstr.push_back(0x7a); // z
 
-    m.def("good_utf8_string", []() { return std::string((const char*)u8"Say utf8\u203d \U0001f382 \U0001d400"); }); // Say utf8‽ 🎂 𝐀
-    m.def("good_utf16_string", [=]() { return std::u16string({ b16, ib16, cake16_1, cake16_2, mathbfA16_1, mathbfA16_2, z16 }); }); // b‽🎂𝐀z
-    m.def("good_utf32_string", [=]() { return std::u32string({ a32, mathbfA32, cake32, ib32, z32 }); }); // a𝐀🎂‽z
+    m.def("good_utf8_string", []() {
+        return std::string((const char *) u8"Say utf8\u203d \U0001f382 \U0001d400");
+    }); // Say utf8‽ 🎂 𝐀
+    m.def("good_utf16_string", [=]() {
+        return std::u16string({b16, ib16, cake16_1, cake16_2, mathbfA16_1, mathbfA16_2, z16});
+    }); // b‽🎂𝐀z
+    m.def("good_utf32_string", [=]() {
+        return std::u32string({a32, mathbfA32, cake32, ib32, z32});
+    });                                                 // a𝐀🎂‽z
     m.def("good_wchar_string", [=]() { return wstr; }); // a‽𝐀z
-    m.def("bad_utf8_string", []()  { return std::string("abc\xd0" "def"); });
-    m.def("bad_utf16_string", [=]() { return std::u16string({ b16, char16_t(0xd800), z16 }); });
+    m.def("bad_utf8_string", []() {
+        return std::string("abc\xd0"
+                           "def");
+    });
+    m.def("bad_utf16_string", [=]() { return std::u16string({b16, char16_t(0xd800), z16}); });
 #if PY_MAJOR_VERSION >= 3
-    // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger UnicodeDecodeError
-    m.def("bad_utf32_string", [=]() { return std::u32string({ a32, char32_t(0xd800), z32 }); });
+    // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger
+    // UnicodeDecodeError
+    m.def("bad_utf32_string", [=]() { return std::u32string({a32, char32_t(0xd800), z32}); });
     if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
         m.def("bad_wchar_string", [=]() {
             return std::wstring({wchar_t(0x61), wchar_t(0xd800)});
@@ -120,8 +141,13 @@ TEST_SUBMODULE(builtin_casters, m) {
 
 #ifdef PYBIND11_HAS_U8STRING
     m.attr("has_u8string") = true;
-    m.def("good_utf8_u8string", []() { return std::u8string(u8"Say utf8\u203d \U0001f382 \U0001d400"); }); // Say utf8‽ 🎂 𝐀
-    m.def("bad_utf8_u8string", []()  { return std::u8string((const char8_t*)"abc\xd0" "def"); });
+    m.def("good_utf8_u8string", []() {
+        return std::u8string(u8"Say utf8\u203d \U0001f382 \U0001d400");
+    }); // Say utf8‽ 🎂 𝐀
+    m.def("bad_utf8_u8string", []() {
+        return std::u8string((const char8_t *) "abc\xd0"
+                                               "def");
+    });
 
     m.def("u8_char8_Z", []() -> char8_t { return u8'Z'; });
 
@@ -133,46 +159,63 @@ TEST_SUBMODULE(builtin_casters, m) {
     // test_string_view
 #ifdef PYBIND11_HAS_STRING_VIEW
     m.attr("has_string_view") = true;
-    m.def("string_view_print",   [](std::string_view s)    { py::print(s, s.size()); });
+    m.def("string_view_print", [](std::string_view s) { py::print(s, s.size()); });
     m.def("string_view16_print", [](std::u16string_view s) { py::print(s, s.size()); });
     m.def("string_view32_print", [](std::u32string_view s) { py::print(s, s.size()); });
-    m.def("string_view_chars",   [](std::string_view s)    { py::list l;
+    m.def("string_view_chars", [](std::string_view s) {
+        py::list l;
         for (auto c : s) {
             l.append((std::uint8_t) c);
         }
-        return l; });
-    m.def("string_view16_chars", [](std::u16string_view s) { py::list l;
+        return l;
+    });
+    m.def("string_view16_chars", [](std::u16string_view s) {
+        py::list l;
         for (auto c : s) {
             l.append((int) c);
         }
-        return l; });
-    m.def("string_view32_chars", [](std::u32string_view s) { py::list l;
+        return l;
+    });
+    m.def("string_view32_chars", [](std::u32string_view s) {
+        py::list l;
         for (auto c : s) {
             l.append((int) c);
         }
-        return l; });
-    m.def("string_view_return",   []() { return std::string_view((const char*)u8"utf8 secret \U0001f382"); });
-    m.def("string_view16_return", []() { return std::u16string_view(u"utf16 secret \U0001f382"); });
-    m.def("string_view32_return", []() { return std::u32string_view(U"utf32 secret \U0001f382"); });
+        return l;
+    });
+    m.def("string_view_return",
+          []() { return std::string_view((const char *) u8"utf8 secret \U0001f382"); });
+    m.def("string_view16_return",
+          []() { return std::u16string_view(u"utf16 secret \U0001f382"); });
+    m.def("string_view32_return",
+          []() { return std::u32string_view(U"utf32 secret \U0001f382"); });
 
     // The inner lambdas here are to also test implicit conversion
     using namespace std::literals;
-    m.def("string_view_bytes", []() { return [](py::bytes b) { return b; }("abc \x80\x80 def"sv); });
-    m.def("string_view_str",   []() { return [](py::str s) { return s; }("abc \342\200\275 def"sv); });
-    m.def("string_view_from_bytes", [](const py::bytes &b) { return [](std::string_view s) { return s; }(b); });
-#if PY_MAJOR_VERSION >= 3
+    m.def("string_view_bytes",
+          []() { return [](py::bytes b) { return b; }("abc \x80\x80 def"sv); });
+    m.def("string_view_str",
+          []() { return [](py::str s) { return s; }("abc \342\200\275 def"sv); });
+    m.def("string_view_from_bytes",
+          [](const py::bytes &b) { return [](std::string_view s) { return s; }(b); });
+#    if PY_MAJOR_VERSION >= 3
     m.def("string_view_memoryview", []() {
         static constexpr auto val = "Have some \360\237\216\202"sv;
         return py::memoryview::from_memory(val);
     });
-#endif
+#    endif
 
-#   ifdef PYBIND11_HAS_U8STRING
-    m.def("string_view8_print",  [](std::u8string_view s) { py::print(s, s.size()); });
-    m.def("string_view8_chars",  [](std::u8string_view s) { py::list l; for (auto c : s) l.append((std::uint8_t) c); return l; });
+#    ifdef PYBIND11_HAS_U8STRING
+    m.def("string_view8_print", [](std::u8string_view s) { py::print(s, s.size()); });
+    m.def("string_view8_chars", [](std::u8string_view s) {
+        py::list l;
+        for (auto c : s)
+            l.append((std::uint8_t) c);
+        return l;
+    });
     m.def("string_view8_return", []() { return std::u8string_view(u8"utf8 secret \U0001f382"); });
-    m.def("string_view8_str",    []() { return py::str{std::u8string_view{u8"abc ‽ def"}}; });
-#   endif
+    m.def("string_view8_str", []() { return py::str{std::u8string_view{u8"abc ‽ def"}}; });
+#    endif
 
     struct TypeWithBothOperatorStringAndStringView {
         // NOLINTNEXTLINE(google-explicit-constructor)
@@ -194,7 +237,8 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_int_convert
     m.def("int_passthrough", [](int arg) { return arg; });
-    m.def("int_passthrough_noconvert", [](int arg) { return arg; }, py::arg{}.noconvert());
+    m.def(
+        "int_passthrough_noconvert", [](int arg) { return arg; }, py::arg{}.noconvert());
 
     // test_tuple
     m.def(
@@ -203,19 +247,27 @@ TEST_SUBMODULE(builtin_casters, m) {
             return std::make_pair(input.second, input.first);
         },
         "Return a pair in reversed order");
-    m.def("tuple_passthrough", [](std::tuple<bool, std::string, int> input) {
-        return std::make_tuple(std::get<2>(input), std::get<1>(input), std::get<0>(input));
-    }, "Return a triple in reversed order");
+    m.def(
+        "tuple_passthrough",
+        [](std::tuple<bool, std::string, int> input) {
+            return std::make_tuple(std::get<2>(input), std::get<1>(input), std::get<0>(input));
+        },
+        "Return a triple in reversed order");
     m.def("empty_tuple", []() { return std::tuple<>(); });
     static std::pair<RValueCaster, RValueCaster> lvpair;
     static std::tuple<RValueCaster, RValueCaster, RValueCaster> lvtuple;
-    static std::pair<RValueCaster, std::tuple<RValueCaster, std::pair<RValueCaster, RValueCaster>>> lvnested;
+    static std::pair<RValueCaster, std::tuple<RValueCaster, std::pair<RValueCaster, RValueCaster>>>
+        lvnested;
     m.def("rvalue_pair", []() { return std::make_pair(RValueCaster{}, RValueCaster{}); });
     m.def("lvalue_pair", []() -> const decltype(lvpair) & { return lvpair; });
-    m.def("rvalue_tuple", []() { return std::make_tuple(RValueCaster{}, RValueCaster{}, RValueCaster{}); });
+    m.def("rvalue_tuple",
+          []() { return std::make_tuple(RValueCaster{}, RValueCaster{}, RValueCaster{}); });
     m.def("lvalue_tuple", []() -> const decltype(lvtuple) & { return lvtuple; });
     m.def("rvalue_nested", []() {
-        return std::make_pair(RValueCaster{}, std::make_tuple(RValueCaster{}, std::make_pair(RValueCaster{}, RValueCaster{}))); });
+        return std::make_pair(
+            RValueCaster{},
+            std::make_tuple(RValueCaster{}, std::make_pair(RValueCaster{}, RValueCaster{})));
+    });
     m.def("lvalue_nested", []() -> const decltype(lvnested) & { return lvnested; });
 
     static std::pair<int, std::string> int_string_pair{2, "items"};
@@ -223,11 +275,11 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_builtins_cast_return_none
     m.def("return_none_string", []() -> std::string * { return nullptr; });
-    m.def("return_none_char",   []() -> const char *  { return nullptr; });
-    m.def("return_none_bool",   []() -> bool *        { return nullptr; });
-    m.def("return_none_int",    []() -> int *         { return nullptr; });
-    m.def("return_none_float",  []() -> float *       { return nullptr; });
-    m.def("return_none_pair",   []() -> std::pair<int,int> * { return nullptr; });
+    m.def("return_none_char", []() -> const char * { return nullptr; });
+    m.def("return_none_bool", []() -> bool * { return nullptr; });
+    m.def("return_none_int", []() -> int * { return nullptr; });
+    m.def("return_none_float", []() -> float * { return nullptr; });
+    m.def("return_none_pair", []() -> std::pair<int, int> * { return nullptr; });
 
     // test_none_deferred
     m.def("defer_none_cstring", [](char *) { return false; });
@@ -245,7 +297,8 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_bool_caster
     m.def("bool_passthrough", [](bool arg) { return arg; });
-    m.def("bool_passthrough_noconvert", [](bool arg) { return arg; }, py::arg{}.noconvert());
+    m.def(
+        "bool_passthrough_noconvert", [](bool arg) { return arg; }, py::arg{}.noconvert());
 
     // TODO: This should be disabled and fixed in future Intel compilers
 #if !defined(__INTEL_COMPILER)
@@ -253,13 +306,15 @@ TEST_SUBMODULE(builtin_casters, m) {
     // When compiled with the Intel compiler, this results in segmentation faults when importing
     // the module. Tested with icc (ICC) 2021.1 Beta 20200827, this should be tested again when
     // a newer version of icc is available.
-    m.def("bool_passthrough_noconvert2", [](bool arg) { return arg; }, py::arg().noconvert());
+    m.def(
+        "bool_passthrough_noconvert2", [](bool arg) { return arg; }, py::arg().noconvert());
 #endif
 
     // test_reference_wrapper
     m.def("refwrap_builtin", [](std::reference_wrapper<int> p) { return 10 * p.get(); });
     m.def("refwrap_usertype", [](std::reference_wrapper<UserType> p) { return p.get().value(); });
-    m.def("refwrap_usertype_const", [](std::reference_wrapper<const UserType> p) { return p.get().value(); });
+    m.def("refwrap_usertype_const",
+          [](std::reference_wrapper<const UserType> p) { return p.get().value(); });
 
     m.def("refwrap_lvalue", []() -> std::reference_wrapper<UserType> {
         static UserType x(1);
@@ -272,17 +327,20 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // Not currently supported (std::pair caster has return-by-value cast operator);
     // triggers static_assert failure.
-    //m.def("refwrap_pair", [](std::reference_wrapper<std::pair<int, int>>) { });
+    // m.def("refwrap_pair", [](std::reference_wrapper<std::pair<int, int>>) { });
 
-    m.def("refwrap_list", [](bool copy) {
-        static IncType x1(1), x2(2);
-        py::list l;
-        for (const auto &f : {std::ref(x1), std::ref(x2)}) {
-            l.append(py::cast(f, copy ? py::return_value_policy::copy
-                                      : py::return_value_policy::reference));
-        }
-        return l;
-    }, "copy"_a);
+    m.def(
+        "refwrap_list",
+        [](bool copy) {
+            static IncType x1(1), x2(2);
+            py::list l;
+            for (const auto &f : {std::ref(x1), std::ref(x2)}) {
+                l.append(py::cast(
+                    f, copy ? py::return_value_policy::copy : py::return_value_policy::reference));
+            }
+            return l;
+        },
+        "copy"_a);
 
     m.def("refwrap_iiw", [](const IncType &w) { return w.value(); });
     m.def("refwrap_call_iiw", [](IncType &w, const py::function &f) {
@@ -299,12 +357,13 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_complex
     m.def("complex_cast", [](float x) { return "{}"_s.format(x); });
-    m.def("complex_cast", [](std::complex<float> x) { return "({}, {})"_s.format(x.real(), x.imag()); });
+    m.def("complex_cast",
+          [](std::complex<float> x) { return "({}, {})"_s.format(x.real(), x.imag()); });
 
     // test int vs. long (Python 2)
-    m.def("int_cast", []() {return (int) 42;});
-    m.def("long_cast", []() {return (long) 42;});
-    m.def("longlong_cast", []() {return  ULLONG_MAX;});
+    m.def("int_cast", []() { return (int) 42; });
+    m.def("long_cast", []() { return (long) 42; });
+    m.def("longlong_cast", []() { return ULLONG_MAX; });
 
     /// test void* cast operator
     m.def("test_void_caster", []() -> bool {
@@ -315,11 +374,12 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // Tests const/non-const propagation in cast_op.
     m.def("takes", [](ConstRefCasted x) { return x.tag; });
-    m.def("takes_move", [](ConstRefCasted&& x) { return x.tag; });
-    m.def("takes_ptr", [](ConstRefCasted* x) { return x->tag; });
-    m.def("takes_ref", [](ConstRefCasted& x) { return x.tag; });
+    m.def("takes_move", [](ConstRefCasted &&x) { return x.tag; });
+    m.def("takes_ptr", [](ConstRefCasted *x) { return x->tag; });
+    m.def("takes_ref", [](ConstRefCasted &x) { return x.tag; });
     m.def("takes_ref_wrap", [](std::reference_wrapper<ConstRefCasted> x) { return x.get().tag; });
-    m.def("takes_const_ptr", [](const ConstRefCasted* x) { return x->tag; });
-    m.def("takes_const_ref", [](const ConstRefCasted& x) { return x.tag; });
-    m.def("takes_const_ref_wrap", [](std::reference_wrapper<const ConstRefCasted> x) { return x.get().tag; });
+    m.def("takes_const_ptr", [](const ConstRefCasted *x) { return x->tag; });
+    m.def("takes_const_ref", [](const ConstRefCasted &x) { return x.tag; });
+    m.def("takes_const_ref_wrap",
+          [](std::reference_wrapper<const ConstRefCasted> x) { return x.get().tag; });
 }
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index 8136bf4f8e..d177008cfe 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -40,18 +40,17 @@ TEST_SUBMODULE(call_policies, m) {
         Child(Child &&) = default;
         ~Child() { py::print("Releasing child."); }
     };
-    py::class_<Child>(m, "Child")
-        .def(py::init<>());
+    py::class_<Child>(m, "Child").def(py::init<>());
 
     class Parent {
     public:
         Parent() { py::print("Allocating parent."); }
-        Parent(const Parent& parent) = default;
+        Parent(const Parent &parent) = default;
         ~Parent() { py::print("Releasing parent."); }
-        void addChild(Child *) { }
+        void addChild(Child *) {}
         Child *returnChild() { return new Child(); }
         Child *returnNullChild() { return nullptr; }
-        static Child *staticFunction(Parent*) { return new Child(); }
+        static Child *staticFunction(Parent *) { return new Child(); }
     };
     py::class_<Parent>(m, "Parent")
         .def(py::init<>())
@@ -62,11 +61,12 @@ TEST_SUBMODULE(call_policies, m) {
         .def("returnChildKeepAlive", &Parent::returnChild, py::keep_alive<1, 0>())
         .def("returnNullChildKeepAliveChild", &Parent::returnNullChild, py::keep_alive<1, 0>())
         .def("returnNullChildKeepAliveParent", &Parent::returnNullChild, py::keep_alive<0, 1>())
-        .def_static(
-            "staticFunction", &Parent::staticFunction, py::keep_alive<1, 0>());
+        .def_static("staticFunction", &Parent::staticFunction, py::keep_alive<1, 0>());
 
-    m.def("free_function", [](Parent*, Child*) {}, py::keep_alive<1, 2>());
-    m.def("invalid_arg_index", []{}, py::keep_alive<0, 1>());
+    m.def(
+        "free_function", [](Parent *, Child *) {}, py::keep_alive<1, 2>());
+    m.def(
+        "invalid_arg_index", [] {}, py::keep_alive<0, 1>());
 
 #if !defined(PYPY_VERSION)
     // test_alive_gc
@@ -74,21 +74,28 @@ TEST_SUBMODULE(call_policies, m) {
     public:
         using Parent::Parent;
     };
-    py::class_<ParentGC, Parent>(m, "ParentGC", py::dynamic_attr())
-        .def(py::init<>());
+    py::class_<ParentGC, Parent>(m, "ParentGC", py::dynamic_attr()).def(py::init<>());
 #endif
 
     // test_call_guard
     m.def("unguarded_call", &CustomGuard::report_status);
     m.def("guarded_call", &CustomGuard::report_status, py::call_guard<CustomGuard>());
 
-    m.def("multiple_guards_correct_order", []() {
-        return CustomGuard::report_status() + std::string(" & ") + DependentGuard::report_status();
-    }, py::call_guard<CustomGuard, DependentGuard>());
-
-    m.def("multiple_guards_wrong_order", []() {
-        return DependentGuard::report_status() + std::string(" & ") + CustomGuard::report_status();
-    }, py::call_guard<DependentGuard, CustomGuard>());
+    m.def(
+        "multiple_guards_correct_order",
+        []() {
+            return CustomGuard::report_status() + std::string(" & ")
+                   + DependentGuard::report_status();
+        },
+        py::call_guard<CustomGuard, DependentGuard>());
+
+    m.def(
+        "multiple_guards_wrong_order",
+        []() {
+            return DependentGuard::report_status() + std::string(" & ")
+                   + CustomGuard::report_status();
+        },
+        py::call_guard<DependentGuard, CustomGuard>());
 
 #if defined(WITH_THREAD) && !defined(PYPY_VERSION)
     // `py::call_guard<py::gil_scoped_release>()` should work in PyPy as well,
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 55f9c86148..92b8053de4 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -7,11 +7,12 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/functional.h>
-#include <thread>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
+#include <thread>
 
 int dummy_function(int i) { return i + 1; }
 
@@ -20,11 +21,12 @@ TEST_SUBMODULE(callbacks, m) {
     m.def("test_callback1", [](const py::object &func) { return func(); });
     m.def("test_callback2", [](const py::object &func) { return func("Hello", 'x', true, 5); });
     m.def("test_callback3", [](const std::function<int(int)> &func) {
-        return "func(43) = " + std::to_string(func(43)); });
-    m.def("test_callback4", []() -> std::function<int(int)> { return [](int i) { return i+1; }; });
-    m.def("test_callback5", []() {
-        return py::cpp_function([](int i) { return i+1; }, py::arg("number"));
+        return "func(43) = " + std::to_string(func(43));
     });
+    m.def("test_callback4",
+          []() -> std::function<int(int)> { return [](int i) { return i + 1; }; });
+    m.def("test_callback5",
+          []() { return py::cpp_function([](int i) { return i + 1; }, py::arg("number")); });
 
     // test_keyword_args_and_generalized_unpacking
     m.def("test_tuple_unpacking", [](const py::function &f) {
@@ -34,9 +36,9 @@ TEST_SUBMODULE(callbacks, m) {
     });
 
     m.def("test_dict_unpacking", [](const py::function &f) {
-        auto d1 = py::dict("key"_a="value", "a"_a=1);
+        auto d1 = py::dict("key"_a = "value", "a"_a = 1);
         auto d2 = py::dict();
-        auto d3 = py::dict("b"_a=2);
+        auto d3 = py::dict("b"_a = 2);
         return f("positional", 1, **d1, **d2, **d3);
     });
 
@@ -44,32 +46,40 @@ TEST_SUBMODULE(callbacks, m) {
 
     m.def("test_unpacking_and_keywords1", [](const py::function &f) {
         auto args = py::make_tuple(2);
-        auto kwargs = py::dict("d"_a=4);
-        return f(1, *args, "c"_a=3, **kwargs);
+        auto kwargs = py::dict("d"_a = 4);
+        return f(1, *args, "c"_a = 3, **kwargs);
     });
 
     m.def("test_unpacking_and_keywords2", [](const py::function &f) {
-        auto kwargs1 = py::dict("a"_a=1);
-        auto kwargs2 = py::dict("c"_a=3, "d"_a=4);
-        return f("positional", *py::make_tuple(1), 2, *py::make_tuple(3, 4), 5,
-                 "key"_a="value", **kwargs1, "b"_a=2, **kwargs2, "e"_a=5);
+        auto kwargs1 = py::dict("a"_a = 1);
+        auto kwargs2 = py::dict("c"_a = 3, "d"_a = 4);
+        return f("positional",
+                 *py::make_tuple(1),
+                 2,
+                 *py::make_tuple(3, 4),
+                 5,
+                 "key"_a = "value",
+                 **kwargs1,
+                 "b"_a = 2,
+                 **kwargs2,
+                 "e"_a = 5);
     });
 
     m.def("test_unpacking_error1", [](const py::function &f) {
-        auto kwargs = py::dict("x"_a=3);
-        return f("x"_a=1, "y"_a=2, **kwargs); // duplicate ** after keyword
+        auto kwargs = py::dict("x"_a = 3);
+        return f("x"_a = 1, "y"_a = 2, **kwargs); // duplicate ** after keyword
     });
 
     m.def("test_unpacking_error2", [](const py::function &f) {
-        auto kwargs = py::dict("x"_a=3);
-        return f(**kwargs, "x"_a=1); // duplicate keyword after **
+        auto kwargs = py::dict("x"_a = 3);
+        return f(**kwargs, "x"_a = 1); // duplicate keyword after **
     });
 
     m.def("test_arg_conversion_error1",
           [](const py::function &f) { f(234, UnregisteredType(), "kw"_a = 567); });
 
     m.def("test_arg_conversion_error2", [](const py::function &f) {
-        f(234, "expected_name"_a=UnregisteredType(), "kw"_a=567);
+        f(234, "expected_name"_a = UnregisteredType(), "kw"_a = 567);
     });
 
     // test_lambda_closure_cleanup
@@ -158,7 +168,6 @@ TEST_SUBMODULE(callbacks, m) {
             return "matches dummy_function: eval(1) = " + std::to_string(r);
         }
         return "argument does NOT match dummy_function. This should never happen!";
-
     });
 
     class AbstractBase {
@@ -190,7 +199,7 @@ TEST_SUBMODULE(callbacks, m) {
     // test_movable_object
     m.def("callback_with_movable", [](const std::function<void(MovableObject &)> &f) {
         auto x = MovableObject();
-        f(x); // lvalue reference shouldn't move out object
+        f(x);           // lvalue reference shouldn't move out object
         return x.valid; // must still return `true`
     });
 
@@ -202,9 +211,10 @@ TEST_SUBMODULE(callbacks, m) {
 
     // This checks that builtin functions can be passed as callbacks
     // rather than throwing RuntimeError due to trying to extract as capsule
-    m.def("test_sum_builtin", [](const std::function<double(py::iterable)> &sum_builtin, const py::iterable &i) {
-      return sum_builtin(i);
-    });
+    m.def("test_sum_builtin",
+          [](const std::function<double(py::iterable)> &sum_builtin, const py::iterable &i) {
+              return sum_builtin(i);
+          });
 
     // test async Python callbacks
     using callback_f = std::function<void(int)>;
diff --git a/tests/test_chrono.cpp b/tests/test_chrono.cpp
index 6537050803..8be0ffd183 100644
--- a/tests/test_chrono.cpp
+++ b/tests/test_chrono.cpp
@@ -8,21 +8,20 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/chrono.h>
+
+#include "pybind11_tests.h"
+
 #include <chrono>
 
 struct different_resolutions {
-    using time_point_h = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::hours>;
-    using time_point_m = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::minutes>;
-    using time_point_s = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::seconds>;
-    using time_point_ms = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::milliseconds>;
-    using time_point_us = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::microseconds>;
+    using time_point_h = std::chrono::time_point<std::chrono::system_clock, std::chrono::hours>;
+    using time_point_m = std::chrono::time_point<std::chrono::system_clock, std::chrono::minutes>;
+    using time_point_s = std::chrono::time_point<std::chrono::system_clock, std::chrono::seconds>;
+    using time_point_ms
+        = std::chrono::time_point<std::chrono::system_clock, std::chrono::milliseconds>;
+    using time_point_us
+        = std::chrono::time_point<std::chrono::system_clock, std::chrono::microseconds>;
     time_point_h timestamp_h;
     time_point_m timestamp_m;
     time_point_s timestamp_s;
@@ -65,12 +64,11 @@ TEST_SUBMODULE(chrono, m) {
     // Roundtrip a duration in microseconds from a float argument
     m.def("test_chrono7", [](std::chrono::microseconds t) { return t; });
     // Float durations (issue #719)
-    m.def("test_chrono_float_diff", [](std::chrono::duration<float> a, std::chrono::duration<float> b) {
-        return a - b; });
+    m.def("test_chrono_float_diff",
+          [](std::chrono::duration<float> a, std::chrono::duration<float> b) { return a - b; });
 
-    m.def("test_nano_timepoint", [](timestamp start, timespan delta) -> timestamp {
-        return start + delta;
-    });
+    m.def("test_nano_timepoint",
+          [](timestamp start, timespan delta) -> timestamp { return start + delta; });
 
     // Test different resolutions
     py::class_<different_resolutions>(m, "different_resolutions")
@@ -79,6 +77,5 @@ TEST_SUBMODULE(chrono, m) {
         .def_readwrite("timestamp_m", &different_resolutions::timestamp_m)
         .def_readwrite("timestamp_s", &different_resolutions::timestamp_s)
         .def_readwrite("timestamp_ms", &different_resolutions::timestamp_ms)
-        .def_readwrite("timestamp_us", &different_resolutions::timestamp_us)
-        ;
+        .def_readwrite("timestamp_us", &different_resolutions::timestamp_us);
 }
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 851bc00ca0..329c9fe7b6 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -11,18 +11,19 @@
 // Intel compiler requires a separate header file to support aligned new operators
 // and does not set the __cpp_aligned_new feature macro.
 // This header needs to be included before pybind11.
-#include <aligned_new>
+#    include <aligned_new>
 #endif
 
-#include "pybind11_tests.h"
+#include <pybind11/stl.h>
+
 #include "constructor_stats.h"
 #include "local_bindings.h"
-#include <pybind11/stl.h>
+#include "pybind11_tests.h"
 
 #include <utility>
 
 #if defined(_MSC_VER)
-#  pragma warning(disable: 4324)
+#    pragma warning(disable : 4324)
 //     warning C4324: structure was padded due to alignment specifier
 #endif
 
@@ -75,6 +76,7 @@ TEST_SUBMODULE(class_, m) {
             : m_name(name), m_species(species) {}
         std::string name() const { return m_name; }
         std::string species() const { return m_species; }
+
     private:
         std::string m_name;
         std::string m_species;
@@ -101,27 +103,24 @@ TEST_SUBMODULE(class_, m) {
     };
 
     py::class_<Pet> pet_class(m, "Pet");
-    pet_class
-        .def(py::init<std::string, std::string>())
+    pet_class.def(py::init<std::string, std::string>())
         .def("name", &Pet::name)
         .def("species", &Pet::species);
 
     /* One way of declaring a subclass relationship: reference parent's class_ object */
-    py::class_<Dog>(m, "Dog", pet_class)
-        .def(py::init<std::string>());
+    py::class_<Dog>(m, "Dog", pet_class).def(py::init<std::string>());
 
     /* Another way of declaring a subclass relationship: reference parent's C++ type */
-    py::class_<Rabbit, Pet>(m, "Rabbit")
-        .def(py::init<std::string>());
+    py::class_<Rabbit, Pet>(m, "Rabbit").def(py::init<std::string>());
 
     /* And another: list parent in class template arguments */
-    py::class_<Hamster, Pet>(m, "Hamster")
-        .def(py::init<std::string>());
+    py::class_<Hamster, Pet>(m, "Hamster").def(py::init<std::string>());
 
     /* Constructors are not inherited by default */
     py::class_<Chimera, Pet>(m, "Chimera");
 
-    m.def("pet_name_species", [](const Pet &pet) { return pet.name() + " is a " + pet.species(); });
+    m.def("pet_name_species",
+          [](const Pet &pet) { return pet.name() + " is a " + pet.species(); });
     m.def("dog_bark", [](const Dog &dog) { return dog.bark(); });
 
     // test_automatic_upcasting
@@ -131,15 +130,15 @@ TEST_SUBMODULE(class_, m) {
         BaseClass(BaseClass &&) = default;
         virtual ~BaseClass() = default;
     };
-    struct DerivedClass1 : BaseClass { };
-    struct DerivedClass2 : BaseClass { };
+    struct DerivedClass1 : BaseClass {};
+    struct DerivedClass2 : BaseClass {};
 
     py::class_<BaseClass>(m, "BaseClass").def(py::init<>());
     py::class_<DerivedClass1>(m, "DerivedClass1").def(py::init<>());
     py::class_<DerivedClass2>(m, "DerivedClass2").def(py::init<>());
 
-    m.def("return_class_1", []() -> BaseClass* { return new DerivedClass1(); });
-    m.def("return_class_2", []() -> BaseClass* { return new DerivedClass2(); });
+    m.def("return_class_1", []() -> BaseClass * { return new DerivedClass1(); });
+    m.def("return_class_2", []() -> BaseClass * { return new DerivedClass2(); });
     m.def("return_class_n", [](int n) -> BaseClass * {
         if (n == 1) {
             return new DerivedClass1();
@@ -149,19 +148,17 @@ TEST_SUBMODULE(class_, m) {
         }
         return new BaseClass();
     });
-    m.def("return_none", []() -> BaseClass* { return nullptr; });
+    m.def("return_none", []() -> BaseClass * { return nullptr; });
 
     // test_isinstance
     m.def("check_instances", [](const py::list &l) {
-        return py::make_tuple(
-            py::isinstance<py::tuple>(l[0]),
-            py::isinstance<py::dict>(l[1]),
-            py::isinstance<Pet>(l[2]),
-            py::isinstance<Pet>(l[3]),
-            py::isinstance<Dog>(l[4]),
-            py::isinstance<Rabbit>(l[5]),
-            py::isinstance<UnregisteredType>(l[6])
-        );
+        return py::make_tuple(py::isinstance<py::tuple>(l[0]),
+                              py::isinstance<py::dict>(l[1]),
+                              py::isinstance<Pet>(l[2]),
+                              py::isinstance<Pet>(l[3]),
+                              py::isinstance<Dog>(l[4]),
+                              py::isinstance<Rabbit>(l[5]),
+                              py::isinstance<UnregisteredType>(l[6]));
     });
 
     struct Invalid {};
@@ -180,18 +177,16 @@ TEST_SUBMODULE(class_, m) {
 
     m.def("get_type_of", [](py::object ob) { return py::type::of(std::move(ob)); });
 
-    m.def("get_type_classic", [](py::handle h) {
-        return h.get_type();
-    });
+    m.def("get_type_classic", [](py::handle h) { return h.get_type(); });
 
     m.def("as_type", [](const py::object &ob) { return py::type(ob); });
 
     // test_mismatched_holder
-    struct MismatchBase1 { };
-    struct MismatchDerived1 : MismatchBase1 { };
+    struct MismatchBase1 {};
+    struct MismatchDerived1 : MismatchBase1 {};
 
-    struct MismatchBase2 { };
-    struct MismatchDerived2 : MismatchBase2 { };
+    struct MismatchBase2 {};
+    struct MismatchDerived2 : MismatchBase2 {};
 
     m.def("mismatched_holder_1", []() {
         auto mod = py::module_::import("__main__");
@@ -201,16 +196,14 @@ TEST_SUBMODULE(class_, m) {
     m.def("mismatched_holder_2", []() {
         auto mod = py::module_::import("__main__");
         py::class_<MismatchBase2>(mod, "MismatchBase2");
-        py::class_<MismatchDerived2, std::shared_ptr<MismatchDerived2>,
-                   MismatchBase2>(mod, "MismatchDerived2");
+        py::class_<MismatchDerived2, std::shared_ptr<MismatchDerived2>, MismatchBase2>(
+            mod, "MismatchDerived2");
     });
 
     // test_override_static
     // #511: problem with inheritance + overwritten def_static
     struct MyBase {
-        static std::unique_ptr<MyBase> make() {
-            return std::unique_ptr<MyBase>(new MyBase());
-        }
+        static std::unique_ptr<MyBase> make() { return std::unique_ptr<MyBase>(new MyBase()); }
     };
 
     struct MyDerived : MyBase {
@@ -219,8 +212,7 @@ TEST_SUBMODULE(class_, m) {
         }
     };
 
-    py::class_<MyBase>(m, "MyBase")
-        .def_static("make", &MyBase::make);
+    py::class_<MyBase>(m, "MyBase").def_static("make", &MyBase::make);
 
     py::class_<MyDerived, MyBase>(m, "MyDerived")
         .def_static("make", &MyDerived::make)
@@ -233,8 +225,7 @@ TEST_SUBMODULE(class_, m) {
         explicit ConvertibleFromUserType(UserType u) : i(u.value()) {}
     };
 
-    py::class_<ConvertibleFromUserType>(m, "AcceptsUserType")
-        .def(py::init<UserType>());
+    py::class_<ConvertibleFromUserType>(m, "AcceptsUserType").def(py::init<UserType>());
     py::implicitly_convertible<UserType, ConvertibleFromUserType>();
 
     m.def("implicitly_convert_argument", [](const ConvertibleFromUserType &r) { return r.i; });
@@ -257,31 +248,60 @@ TEST_SUBMODULE(class_, m) {
         };
 
         auto *def = new PyMethodDef{"f", f, METH_VARARGS, nullptr};
-        py::capsule def_capsule(def, [](void *ptr) { delete reinterpret_cast<PyMethodDef *>(ptr); });
-        return py::reinterpret_steal<py::object>(PyCFunction_NewEx(def, def_capsule.ptr(), m.ptr()));
+        py::capsule def_capsule(def,
+                                [](void *ptr) { delete reinterpret_cast<PyMethodDef *>(ptr); });
+        return py::reinterpret_steal<py::object>(
+            PyCFunction_NewEx(def, def_capsule.ptr(), m.ptr()));
     }());
 
     // test_operator_new_delete
     struct HasOpNewDel {
         std::uint64_t i;
-        static void *operator new(size_t s) { py::print("A new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("A placement-new", s); return ptr; }
-        static void operator delete(void *p) { py::print("A delete"); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("A new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("A placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p) {
+            py::print("A delete");
+            return ::operator delete(p);
+        }
     };
     struct HasOpNewDelSize {
         std::uint32_t i;
-        static void *operator new(size_t s) { py::print("B new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("B placement-new", s); return ptr; }
-        static void operator delete(void *p, size_t s) { py::print("B delete", s); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("B new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("B placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p, size_t s) {
+            py::print("B delete", s);
+            return ::operator delete(p);
+        }
     };
     struct AliasedHasOpNewDelSize {
         std::uint64_t i;
-        static void *operator new(size_t s) { py::print("C new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("C placement-new", s); return ptr; }
-        static void operator delete(void *p, size_t s) { py::print("C delete", s); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("C new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("C placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p, size_t s) {
+            py::print("C delete", s);
+            return ::operator delete(p);
+        }
         virtual ~AliasedHasOpNewDelSize() = default;
         AliasedHasOpNewDelSize() = default;
-        AliasedHasOpNewDelSize(const AliasedHasOpNewDelSize&) = delete;
+        AliasedHasOpNewDelSize(const AliasedHasOpNewDelSize &) = delete;
     };
     struct PyAliasedHasOpNewDelSize : AliasedHasOpNewDelSize {
         PyAliasedHasOpNewDelSize() = default;
@@ -290,15 +310,28 @@ TEST_SUBMODULE(class_, m) {
     };
     struct HasOpNewDelBoth {
         std::uint32_t i[8];
-        static void *operator new(size_t s) { py::print("D new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("D placement-new", s); return ptr; }
-        static void operator delete(void *p) { py::print("D delete"); return ::operator delete(p); }
-        static void operator delete(void *p, size_t s) { py::print("D wrong delete", s); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("D new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("D placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p) {
+            py::print("D delete");
+            return ::operator delete(p);
+        }
+        static void operator delete(void *p, size_t s) {
+            py::print("D wrong delete", s);
+            return ::operator delete(p);
+        }
     };
     py::class_<HasOpNewDel>(m, "HasOpNewDel").def(py::init<>());
     py::class_<HasOpNewDelSize>(m, "HasOpNewDelSize").def(py::init<>());
     py::class_<HasOpNewDelBoth>(m, "HasOpNewDelBoth").def(py::init<>());
-    py::class_<AliasedHasOpNewDelSize, PyAliasedHasOpNewDelSize> aliased(m, "AliasedHasOpNewDelSize");
+    py::class_<AliasedHasOpNewDelSize, PyAliasedHasOpNewDelSize> aliased(m,
+                                                                         "AliasedHasOpNewDelSize");
     aliased.def(py::init<>());
     aliased.attr("size_noalias") = py::int_(sizeof(AliasedHasOpNewDelSize));
     aliased.attr("size_alias") = py::int_(sizeof(PyAliasedHasOpNewDelSize));
@@ -352,7 +385,7 @@ TEST_SUBMODULE(class_, m) {
         // [workaround(intel)] = default does not work here
         // Removing or defaulting this destructor results in linking errors with the Intel compiler
         // (in Debug builds only, tested with icpc (ICC) 2021.1 Beta 20200827)
-        ~PublicistB() override {};  // NOLINT(modernize-use-equals-default)
+        ~PublicistB() override{}; // NOLINT(modernize-use-equals-default)
         using ProtectedB::foo;
     };
 
@@ -402,8 +435,8 @@ TEST_SUBMODULE(class_, m) {
     py::class_<Nested>(base, "Nested")
         .def(py::init<>())
         .def("fn", [](Nested &, int, NestBase &, Nested &) {})
-        .def("fa", [](Nested &, int, NestBase &, Nested &) {},
-                "a"_a, "b"_a, "c"_a);
+        .def(
+            "fa", [](Nested &, int, NestBase &, Nested &) {}, "a"_a, "b"_a, "c"_a);
     base.def("g", [](NestBase &, Nested &) {});
     base.def("h", []() { return NestBase(); });
 
@@ -413,21 +446,21 @@ TEST_SUBMODULE(class_, m) {
     // generate a useful error message
 
     struct NotRegistered {};
-    struct StringWrapper { std::string str; };
+    struct StringWrapper {
+        std::string str;
+    };
     m.def("test_error_after_conversions", [](int) {});
     m.def("test_error_after_conversions",
           [](const StringWrapper &) -> NotRegistered { return {}; });
     py::class_<StringWrapper>(m, "StringWrapper").def(py::init<std::string>());
     py::implicitly_convertible<std::string, StringWrapper>();
 
-    #if defined(PYBIND11_CPP17)
-        struct alignas(1024) Aligned {
-            std::uintptr_t ptr() const { return (uintptr_t) this; }
-        };
-        py::class_<Aligned>(m, "Aligned")
-            .def(py::init<>())
-            .def("ptr", &Aligned::ptr);
-    #endif
+#if defined(PYBIND11_CPP17)
+    struct alignas(1024) Aligned {
+        std::uintptr_t ptr() const { return (uintptr_t) this; }
+    };
+    py::class_<Aligned>(m, "Aligned").def(py::init<>()).def("ptr", &Aligned::ptr);
+#endif
 
     // test_final
     struct IsFinal final {};
@@ -440,9 +473,7 @@ TEST_SUBMODULE(class_, m) {
     // test_exception_rvalue_abort
     struct PyPrintDestructor {
         PyPrintDestructor() = default;
-        ~PyPrintDestructor() {
-            py::print("Print from destructor");
-        }
+        ~PyPrintDestructor() { py::print("Print from destructor"); }
         void throw_something() { throw std::runtime_error("error"); }
     };
     py::class_<PyPrintDestructor>(m, "PyPrintDestructor")
@@ -456,8 +487,7 @@ TEST_SUBMODULE(class_, m) {
         .def(py::init([]() { return &samePointer; }));
 
     struct Empty {};
-    py::class_<Empty>(m, "Empty")
-        .def(py::init<>());
+    py::class_<Empty>(m, "Empty").def(py::init<>());
 
     // test_base_and_derived_nested_scope
     struct BaseWithNested {
@@ -499,12 +529,15 @@ TEST_SUBMODULE(class_, m) {
     });
 }
 
-template <int N> class BreaksBase { public:
+template <int N>
+class BreaksBase {
+public:
     virtual ~BreaksBase() = default;
     BreaksBase() = default;
-    BreaksBase(const BreaksBase&) = delete;
+    BreaksBase(const BreaksBase &) = delete;
 };
-template <int N> class BreaksTramp : public BreaksBase<N> {};
+template <int N>
+class BreaksTramp : public BreaksBase<N> {};
 // These should all compile just fine:
 using DoesntBreak1 = py::class_<BreaksBase<1>, std::unique_ptr<BreaksBase<1>>, BreaksTramp<1>>;
 using DoesntBreak2 = py::class_<BreaksBase<2>, BreaksTramp<2>, std::unique_ptr<BreaksBase<2>>>;
@@ -514,45 +547,83 @@ using DoesntBreak5 = py::class_<BreaksBase<5>>;
 using DoesntBreak6 = py::class_<BreaksBase<6>, std::shared_ptr<BreaksBase<6>>, BreaksTramp<6>>;
 using DoesntBreak7 = py::class_<BreaksBase<7>, BreaksTramp<7>, std::shared_ptr<BreaksBase<7>>>;
 using DoesntBreak8 = py::class_<BreaksBase<8>, std::shared_ptr<BreaksBase<8>>>;
-#define CHECK_BASE(N) static_assert(std::is_same<typename DoesntBreak##N::type, BreaksBase<(N)>>::value, \
-        "DoesntBreak" #N " has wrong type!")
-CHECK_BASE(1); CHECK_BASE(2); CHECK_BASE(3); CHECK_BASE(4); CHECK_BASE(5); CHECK_BASE(6); CHECK_BASE(7); CHECK_BASE(8);
-#define CHECK_ALIAS(N) static_assert(DoesntBreak##N::has_alias && std::is_same<typename DoesntBreak##N::type_alias, BreaksTramp<(N)>>::value, \
+#define CHECK_BASE(N)                                                                             \
+    static_assert(std::is_same<typename DoesntBreak##N::type, BreaksBase<(N)>>::value,            \
+                  "DoesntBreak" #N " has wrong type!")
+CHECK_BASE(1);
+CHECK_BASE(2);
+CHECK_BASE(3);
+CHECK_BASE(4);
+CHECK_BASE(5);
+CHECK_BASE(6);
+CHECK_BASE(7);
+CHECK_BASE(8);
+#define CHECK_ALIAS(N)                                                                            \
+    static_assert(                                                                                \
+        DoesntBreak##N::has_alias                                                                 \
+            && std::is_same<typename DoesntBreak##N::type_alias, BreaksTramp<(N)>>::value,        \
         "DoesntBreak" #N " has wrong type_alias!")
-#define CHECK_NOALIAS(N) static_assert(!DoesntBreak##N::has_alias && std::is_void<typename DoesntBreak##N::type_alias>::value, \
-        "DoesntBreak" #N " has type alias, but shouldn't!")
-CHECK_ALIAS(1); CHECK_ALIAS(2); CHECK_NOALIAS(3); CHECK_ALIAS(4); CHECK_NOALIAS(5); CHECK_ALIAS(6); CHECK_ALIAS(7); CHECK_NOALIAS(8);
-#define CHECK_HOLDER(N, TYPE) static_assert(std::is_same<typename DoesntBreak##N::holder_type, std::TYPE##_ptr<BreaksBase<(N)>>>::value, \
-        "DoesntBreak" #N " has wrong holder_type!")
-CHECK_HOLDER(1, unique); CHECK_HOLDER(2, unique); CHECK_HOLDER(3, unique); CHECK_HOLDER(4, unique); CHECK_HOLDER(5, unique);
-CHECK_HOLDER(6, shared); CHECK_HOLDER(7, shared); CHECK_HOLDER(8, shared);
+#define CHECK_NOALIAS(N)                                                                          \
+    static_assert(!DoesntBreak##N::has_alias                                                      \
+                      && std::is_void<typename DoesntBreak##N::type_alias>::value,                \
+                  "DoesntBreak" #N " has type alias, but shouldn't!")
+CHECK_ALIAS(1);
+CHECK_ALIAS(2);
+CHECK_NOALIAS(3);
+CHECK_ALIAS(4);
+CHECK_NOALIAS(5);
+CHECK_ALIAS(6);
+CHECK_ALIAS(7);
+CHECK_NOALIAS(8);
+#define CHECK_HOLDER(N, TYPE)                                                                     \
+    static_assert(std::is_same<typename DoesntBreak##N::holder_type,                              \
+                               std::TYPE##_ptr<BreaksBase<(N)>>>::value,                          \
+                  "DoesntBreak" #N " has wrong holder_type!")
+CHECK_HOLDER(1, unique);
+CHECK_HOLDER(2, unique);
+CHECK_HOLDER(3, unique);
+CHECK_HOLDER(4, unique);
+CHECK_HOLDER(5, unique);
+CHECK_HOLDER(6, shared);
+CHECK_HOLDER(7, shared);
+CHECK_HOLDER(8, shared);
 
 // There's no nice way to test that these fail because they fail to compile; leave them here,
 // though, so that they can be manually tested by uncommenting them (and seeing that compilation
 // failures occurs).
 
 // We have to actually look into the type: the typedef alone isn't enough to instantiate the type:
-#define CHECK_BROKEN(N) static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-(N)>>::value, \
-        "Breaks1 has wrong type!");
+#define CHECK_BROKEN(N)                                                                           \
+    static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-(N)>>::value,                \
+                  "Breaks1 has wrong type!");
 
 #ifdef PYBIND11_NEVER_DEFINED_EVER
 // Two holder classes:
-typedef py::class_<BreaksBase<-1>, std::unique_ptr<BreaksBase<-1>>, std::unique_ptr<BreaksBase<-1>>> Breaks1;
+typedef py::
+    class_<BreaksBase<-1>, std::unique_ptr<BreaksBase<-1>>, std::unique_ptr<BreaksBase<-1>>>
+        Breaks1;
 CHECK_BROKEN(1);
 // Two aliases:
 typedef py::class_<BreaksBase<-2>, BreaksTramp<-2>, BreaksTramp<-2>> Breaks2;
 CHECK_BROKEN(2);
 // Holder + 2 aliases
-typedef py::class_<BreaksBase<-3>, std::unique_ptr<BreaksBase<-3>>, BreaksTramp<-3>, BreaksTramp<-3>> Breaks3;
+typedef py::
+    class_<BreaksBase<-3>, std::unique_ptr<BreaksBase<-3>>, BreaksTramp<-3>, BreaksTramp<-3>>
+        Breaks3;
 CHECK_BROKEN(3);
 // Alias + 2 holders
-typedef py::class_<BreaksBase<-4>, std::unique_ptr<BreaksBase<-4>>, BreaksTramp<-4>, std::shared_ptr<BreaksBase<-4>>> Breaks4;
+typedef py::class_<BreaksBase<-4>,
+                   std::unique_ptr<BreaksBase<-4>>,
+                   BreaksTramp<-4>,
+                   std::shared_ptr<BreaksBase<-4>>>
+    Breaks4;
 CHECK_BROKEN(4);
 // Invalid option (not a subclass or holder)
 typedef py::class_<BreaksBase<-5>, BreaksTramp<-4>> Breaks5;
 CHECK_BROKEN(5);
 // Invalid option: multiple inheritance not supported:
-template <> struct BreaksBase<-8> : BreaksBase<-6>, BreaksBase<-7> {};
+template <>
+struct BreaksBase<-8> : BreaksBase<-6>, BreaksBase<-7> {};
 typedef py::class_<BreaksBase<-8>, BreaksBase<-6>, BreaksBase<-7>> Breaks8;
 CHECK_BROKEN(8);
 #endif
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index c0554503fa..7a6dae1a10 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -12,20 +12,14 @@
 
 enum MyEnum { EFirstEntry = 1, ESecondEntry };
 
-std::string test_function1() {
-    return "test_function()";
-}
+std::string test_function1() { return "test_function()"; }
 
-std::string test_function2(MyEnum k) {
-    return "test_function(enum=" + std::to_string(k) + ")";
-}
+std::string test_function2(MyEnum k) { return "test_function(enum=" + std::to_string(k) + ")"; }
 
-std::string test_function3(int i) {
-    return "test_function(" + std::to_string(i) + ")";
-}
+std::string test_function3(int i) { return "test_function(" + std::to_string(i) + ")"; }
 
-py::str test_function4()           { return "test_function()"; }
-py::str test_function4(char *)     { return "test_function(char *)"; }
+py::str test_function4() { return "test_function()"; }
+py::str test_function4(char *) { return "test_function(char *)"; }
 py::str test_function4(int, float) { return "test_function(int, float)"; }
 py::str test_function4(float, int) { return "test_function(float, int)"; }
 
@@ -44,50 +38,50 @@ std::string print_bytes(const py::bytes &bytes) {
     return ret;
 }
 
-// Test that we properly handle C++17 exception specifiers (which are part of the function signature
-// in C++17).  These should all still work before C++17, but don't affect the function signature.
+// Test that we properly handle C++17 exception specifiers (which are part of the function
+// signature in C++17).  These should all still work before C++17, but don't affect the function
+// signature.
 namespace test_exc_sp {
 // [workaround(intel)] Unable to use noexcept instead of noexcept(true)
 // Make the f1 test basically the same as the f2 test in C++17 mode for the Intel compiler as
 // it fails to compile with a plain noexcept (tested with icc (ICC) 2021.1 Beta 20200827).
 #if defined(__INTEL_COMPILER) && defined(PYBIND11_CPP17)
-int f1(int x) noexcept(true) { return x+1; }
+int f1(int x) noexcept(true) { return x + 1; }
 #else
-int f1(int x) noexcept { return x+1; }
+int f1(int x) noexcept { return x + 1; }
 #endif
-int f2(int x) noexcept(true) { return x+2; }
-int f3(int x) noexcept(false) { return x+3; }
+int f2(int x) noexcept(true) { return x + 2; }
+int f3(int x) noexcept(false) { return x + 3; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wdeprecated"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
 // NOLINTNEXTLINE(modernize-use-noexcept)
-int f4(int x) throw() { return x+4; } // Deprecated equivalent to noexcept(true)
+int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
 struct C {
-    int m1(int x) noexcept { return x-1; }
-    int m2(int x) const noexcept { return x-2; }
-    int m3(int x) noexcept(true) { return x-3; }
-    int m4(int x) const noexcept(true) { return x-4; }
-    int m5(int x) noexcept(false) { return x-5; }
-    int m6(int x) const noexcept(false) { return x-6; }
+    int m1(int x) noexcept { return x - 1; }
+    int m2(int x) const noexcept { return x - 2; }
+    int m3(int x) noexcept(true) { return x - 3; }
+    int m4(int x) const noexcept(true) { return x - 4; }
+    int m5(int x) noexcept(false) { return x - 5; }
+    int m6(int x) const noexcept(false) { return x - 6; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wdeprecated"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m7(int x) throw() { return x - 7; }
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m8(int x) const throw() { return x - 8; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
 };
 } // namespace test_exc_sp
 
-
 TEST_SUBMODULE(constants_and_functions, m) {
     // test_constants
     m.attr("some_constant") = py::int_(14);
@@ -129,8 +123,7 @@ TEST_SUBMODULE(constants_and_functions, m) {
         .def("m5", &C::m5)
         .def("m6", &C::m6)
         .def("m7", &C::m7)
-        .def("m8", &C::m8)
-        ;
+        .def("m8", &C::m8);
     m.def("f1", f1);
     m.def("f2", f2);
 #if defined(__INTEL_COMPILER)
@@ -150,8 +143,12 @@ TEST_SUBMODULE(constants_and_functions, m) {
         uint64_t zeros[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
     };
     m.def("register_large_capture_with_invalid_arguments", [](py::module_ m) {
-        LargeCapture capture;  // VS 2015's MSVC is acting up if we create the array here
-        m.def("should_raise", [capture](int) { return capture.zeros[9] + 33; }, py::kw_only(), py::arg());
+        LargeCapture capture; // VS 2015's MSVC is acting up if we create the array here
+        m.def(
+            "should_raise",
+            [capture](int) { return capture.zeros[9] + 33; },
+            py::kw_only(),
+            py::arg());
     });
     m.def("register_with_raising_repr", [](py::module_ m, const py::object &default_value) {
         m.def(
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 007b96c5b3..6e1bdd8568 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -8,30 +8,33 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 template <typename derived>
 struct empty {
-    static const derived& get_one() { return instance_; }
+    static const derived &get_one() { return instance_; }
     static derived instance_;
 };
 
 struct lacking_copy_ctor : public empty<lacking_copy_ctor> {
     lacking_copy_ctor() = default;
-    lacking_copy_ctor(const lacking_copy_ctor& other) = delete;
+    lacking_copy_ctor(const lacking_copy_ctor &other) = delete;
 };
 
-template <> lacking_copy_ctor empty<lacking_copy_ctor>::instance_ = {};
+template <>
+lacking_copy_ctor empty<lacking_copy_ctor>::instance_ = {};
 
 struct lacking_move_ctor : public empty<lacking_move_ctor> {
     lacking_move_ctor() = default;
-    lacking_move_ctor(const lacking_move_ctor& other) = delete;
-    lacking_move_ctor(lacking_move_ctor&& other) = delete;
+    lacking_move_ctor(const lacking_move_ctor &other) = delete;
+    lacking_move_ctor(lacking_move_ctor &&other) = delete;
 };
 
-template <> lacking_move_ctor empty<lacking_move_ctor>::instance_ = {};
+template <>
+lacking_move_ctor empty<lacking_move_ctor>::instance_ = {};
 
 /* Custom type caster move/copy test classes */
 class MoveOnlyInt {
@@ -71,7 +74,11 @@ class MoveOrCopyInt {
         // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         value = c.value;
     }
-    MoveOrCopyInt &operator=(const MoveOrCopyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
+    MoveOrCopyInt &operator=(const MoveOrCopyInt &c) {
+        print_copy_assigned(this, c.value);
+        value = c.value;
+        return *this;
+    }
     ~MoveOrCopyInt() { print_destroyed(this); }
 
     int value;
@@ -85,32 +92,55 @@ class CopyOnlyInt {
         // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         value = c.value;
     }
-    CopyOnlyInt &operator=(const CopyOnlyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
+    CopyOnlyInt &operator=(const CopyOnlyInt &c) {
+        print_copy_assigned(this, c.value);
+        value = c.value;
+        return *this;
+    }
     ~CopyOnlyInt() { print_destroyed(this); }
 
     int value;
 };
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
-template <> struct type_caster<MoveOnlyInt> {
+template <>
+struct type_caster<MoveOnlyInt> {
     PYBIND11_TYPE_CASTER(MoveOnlyInt, const_name("MoveOnlyInt"));
-    bool load(handle src, bool) { value = MoveOnlyInt(src.cast<int>()); return true; }
-    static handle cast(const MoveOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
+    bool load(handle src, bool) {
+        value = MoveOnlyInt(src.cast<int>());
+        return true;
+    }
+    static handle cast(const MoveOnlyInt &m, return_value_policy r, handle p) {
+        return pybind11::cast(m.value, r, p);
+    }
 };
 
-template <> struct type_caster<MoveOrCopyInt> {
+template <>
+struct type_caster<MoveOrCopyInt> {
     PYBIND11_TYPE_CASTER(MoveOrCopyInt, const_name("MoveOrCopyInt"));
-    bool load(handle src, bool) { value = MoveOrCopyInt(src.cast<int>()); return true; }
-    static handle cast(const MoveOrCopyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
+    bool load(handle src, bool) {
+        value = MoveOrCopyInt(src.cast<int>());
+        return true;
+    }
+    static handle cast(const MoveOrCopyInt &m, return_value_policy r, handle p) {
+        return pybind11::cast(m.value, r, p);
+    }
 };
 
-template <> struct type_caster<CopyOnlyInt> {
+template <>
+struct type_caster<CopyOnlyInt> {
 protected:
     CopyOnlyInt value;
+
 public:
     static constexpr auto name = const_name("CopyOnlyInt");
-    bool load(handle src, bool) { value = CopyOnlyInt(src.cast<int>()); return true; }
-    static handle cast(const CopyOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
+    bool load(handle src, bool) {
+        value = CopyOnlyInt(src.cast<int>());
+        return true;
+    }
+    static handle cast(const CopyOnlyInt &m, return_value_policy r, handle p) {
+        return pybind11::cast(m.value, r, p);
+    }
     static handle cast(const CopyOnlyInt *src, return_value_policy policy, handle parent) {
         if (!src) {
             return none().release();
@@ -119,7 +149,8 @@ template <> struct type_caster<CopyOnlyInt> {
     }
     explicit operator CopyOnlyInt *() { return &value; }
     explicit operator CopyOnlyInt &() { return value; }
-    template <typename T> using cast_op_type = pybind11::detail::cast_op_type<T>;
+    template <typename T>
+    using cast_op_type = pybind11::detail::cast_op_type<T>;
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
@@ -127,23 +158,21 @@ PYBIND11_NAMESPACE_END(pybind11)
 TEST_SUBMODULE(copy_move_policies, m) {
     // test_lacking_copy_ctor
     py::class_<lacking_copy_ctor>(m, "lacking_copy_ctor")
-        .def_static("get_one", &lacking_copy_ctor::get_one,
-                    py::return_value_policy::copy);
+        .def_static("get_one", &lacking_copy_ctor::get_one, py::return_value_policy::copy);
     // test_lacking_move_ctor
     py::class_<lacking_move_ctor>(m, "lacking_move_ctor")
-        .def_static("get_one", &lacking_move_ctor::get_one,
-                    py::return_value_policy::move);
+        .def_static("get_one", &lacking_move_ctor::get_one, py::return_value_policy::move);
 
     // test_move_and_copy_casts
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("move_and_copy_casts", [](const py::object &o) {
         int r = 0;
         r += py::cast<MoveOrCopyInt>(o).value; /* moves */
-        r += py::cast<MoveOnlyInt>(o).value; /* moves */
-        r += py::cast<CopyOnlyInt>(o).value; /* copies */
-        auto m1(py::cast<MoveOrCopyInt>(o)); /* moves */
-        auto m2(py::cast<MoveOnlyInt>(o)); /* moves */
-        auto m3(py::cast<CopyOnlyInt>(o)); /* copies */
+        r += py::cast<MoveOnlyInt>(o).value;   /* moves */
+        r += py::cast<CopyOnlyInt>(o).value;   /* copies */
+        auto m1(py::cast<MoveOrCopyInt>(o));   /* moves */
+        auto m2(py::cast<MoveOnlyInt>(o));     /* moves */
+        auto m3(py::cast<CopyOnlyInt>(o));     /* copies */
         r += m1.value + m2.value + m3.value;
 
         return r;
@@ -157,28 +186,34 @@ TEST_SUBMODULE(copy_move_policies, m) {
     // Changing this breaks the existing test: needs careful review.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("copy_only", [](CopyOnlyInt m) { return m.value; });
-    m.def("move_pair", [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) {
-        return p.first.value + p.second.value;
-    });
+    m.def("move_pair",
+          [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) { return p.first.value + p.second.value; });
     m.def("move_tuple", [](std::tuple<MoveOnlyInt, MoveOrCopyInt, MoveOnlyInt> t) {
         return std::get<0>(t).value + std::get<1>(t).value + std::get<2>(t).value;
     });
     m.def("copy_tuple", [](std::tuple<CopyOnlyInt, CopyOnlyInt> t) {
         return std::get<0>(t).value + std::get<1>(t).value;
     });
-    m.def("move_copy_nested", [](std::pair<MoveOnlyInt, std::pair<std::tuple<MoveOrCopyInt, CopyOnlyInt, std::tuple<MoveOnlyInt>>, MoveOrCopyInt>> x) {
-        return x.first.value + std::get<0>(x.second.first).value + std::get<1>(x.second.first).value +
-            std::get<0>(std::get<2>(x.second.first)).value + x.second.second.value;
-    });
+    m.def("move_copy_nested",
+          [](std::pair<MoveOnlyInt,
+                       std::pair<std::tuple<MoveOrCopyInt, CopyOnlyInt, std::tuple<MoveOnlyInt>>,
+                                 MoveOrCopyInt>> x) {
+              return x.first.value + std::get<0>(x.second.first).value
+                     + std::get<1>(x.second.first).value
+                     + std::get<0>(std::get<2>(x.second.first)).value + x.second.second.value;
+          });
     m.def("move_and_copy_cstats", []() {
         ConstructorStats::gc();
         // Reset counts to 0 so that previous tests don't affect later ones:
         auto &mc = ConstructorStats::get<MoveOrCopyInt>();
-        mc.move_assignments = mc.move_constructions = mc.copy_assignments = mc.copy_constructions = 0;
+        mc.move_assignments = mc.move_constructions = mc.copy_assignments = mc.copy_constructions
+            = 0;
         auto &mo = ConstructorStats::get<MoveOnlyInt>();
-        mo.move_assignments = mo.move_constructions = mo.copy_assignments = mo.copy_constructions = 0;
+        mo.move_assignments = mo.move_constructions = mo.copy_assignments = mo.copy_constructions
+            = 0;
         auto &co = ConstructorStats::get<CopyOnlyInt>();
-        co.move_assignments = co.move_constructions = co.copy_assignments = co.copy_constructions = 0;
+        co.move_assignments = co.move_constructions = co.copy_assignments = co.copy_constructions
+            = 0;
         py::dict d;
         d["MoveOrCopyInt"] = py::cast(mc, py::return_value_policy::reference);
         d["MoveOnlyInt"] = py::cast(mo, py::return_value_policy::reference);
@@ -188,18 +223,13 @@ TEST_SUBMODULE(copy_move_policies, m) {
 #ifdef PYBIND11_HAS_OPTIONAL
     // test_move_and_copy_load_optional
     m.attr("has_optional") = true;
-    m.def("move_optional", [](std::optional<MoveOnlyInt> o) {
-        return o->value;
-    });
-    m.def("move_or_copy_optional", [](std::optional<MoveOrCopyInt> o) {
-        return o->value;
-    });
-    m.def("copy_optional", [](std::optional<CopyOnlyInt> o) {
-        return o->value;
-    });
-    m.def("move_optional_tuple", [](std::optional<std::tuple<MoveOrCopyInt, MoveOnlyInt, CopyOnlyInt>> x) {
-        return std::get<0>(*x).value + std::get<1>(*x).value + std::get<2>(*x).value;
-    });
+    m.def("move_optional", [](std::optional<MoveOnlyInt> o) { return o->value; });
+    m.def("move_or_copy_optional", [](std::optional<MoveOrCopyInt> o) { return o->value; });
+    m.def("copy_optional", [](std::optional<CopyOnlyInt> o) { return o->value; });
+    m.def("move_optional_tuple",
+          [](std::optional<std::tuple<MoveOrCopyInt, MoveOnlyInt, CopyOnlyInt>> x) {
+              return std::get<0>(*x).value + std::get<1>(*x).value + std::get<2>(*x).value;
+          });
 #else
     m.attr("has_optional") = false;
 #endif
@@ -210,6 +240,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
     // added later.
     struct PrivateOpNew {
         int value = 1;
+
     private:
         void *operator new(size_t bytes) {
             void *ptr = std::malloc(bytes);
@@ -221,10 +252,13 @@ TEST_SUBMODULE(copy_move_policies, m) {
     };
     py::class_<PrivateOpNew>(m, "PrivateOpNew").def_readonly("value", &PrivateOpNew::value);
     m.def("private_op_new_value", []() { return PrivateOpNew(); });
-    m.def("private_op_new_reference", []() -> const PrivateOpNew & {
-        static PrivateOpNew x{};
-        return x;
-    }, py::return_value_policy::reference);
+    m.def(
+        "private_op_new_reference",
+        []() -> const PrivateOpNew & {
+            static PrivateOpNew x{};
+            return x;
+        },
+        py::return_value_policy::reference);
 
     // test_move_fallback
     // #389: rvp::move should fall-through to copy on non-movable objects
@@ -234,16 +268,25 @@ TEST_SUBMODULE(copy_move_policies, m) {
         MoveIssue1(const MoveIssue1 &c) = default;
         MoveIssue1(MoveIssue1 &&) = delete;
     };
-    py::class_<MoveIssue1>(m, "MoveIssue1").def(py::init<int>()).def_readwrite("value", &MoveIssue1::v);
+    py::class_<MoveIssue1>(m, "MoveIssue1")
+        .def(py::init<int>())
+        .def_readwrite("value", &MoveIssue1::v);
 
     struct MoveIssue2 {
         int v;
         explicit MoveIssue2(int v) : v{v} {}
         MoveIssue2(MoveIssue2 &&) = default;
     };
-    py::class_<MoveIssue2>(m, "MoveIssue2").def(py::init<int>()).def_readwrite("value", &MoveIssue2::v);
+    py::class_<MoveIssue2>(m, "MoveIssue2")
+        .def(py::init<int>())
+        .def_readwrite("value", &MoveIssue2::v);
 
-    // #2742: Don't expect ownership of raw pointer to `new`ed object to be transferred with `py::return_value_policy::move`
-    m.def("get_moveissue1", [](int i) { return std::unique_ptr<MoveIssue1>(new MoveIssue1(i)); }, py::return_value_policy::move);
-    m.def("get_moveissue2", [](int i) { return MoveIssue2(i); }, py::return_value_policy::move);
+    // #2742: Don't expect ownership of raw pointer to `new`ed object to be transferred with
+    // `py::return_value_policy::move`
+    m.def(
+        "get_moveissue1",
+        [](int i) { return std::unique_ptr<MoveIssue1>(new MoveIssue1(i)); },
+        py::return_value_policy::move);
+    m.def(
+        "get_moveissue2", [](int i) { return MoveIssue2(i); }, py::return_value_policy::move);
 }
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 48613ee5a1..1d6341582c 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -7,16 +7,23 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
-
+#include "pybind11_tests.h"
 
 // py::arg/py::arg_v testing: these arguments just record their argument when invoked
-class ArgInspector1 { public: std::string arg = "(default arg inspector 1)"; };
-class ArgInspector2 { public: std::string arg = "(default arg inspector 2)"; };
-class ArgAlwaysConverts { };
-namespace pybind11 { namespace detail {
-template <> struct type_caster<ArgInspector1> {
+class ArgInspector1 {
+public:
+    std::string arg = "(default arg inspector 1)";
+};
+class ArgInspector2 {
+public:
+    std::string arg = "(default arg inspector 2)";
+};
+class ArgAlwaysConverts {};
+namespace pybind11 {
+namespace detail {
+template <>
+struct type_caster<ArgInspector1> {
 public:
     // Classic
 #ifdef PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
@@ -26,9 +33,10 @@ template <> struct type_caster<ArgInspector1> {
 #endif
 
     bool load(handle src, bool convert) {
-        value.arg = "loading ArgInspector1 argument " +
-            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
-            "Argument value = " + (std::string) str(src);
+        value.arg = "loading ArgInspector1 argument " + std::string(convert ? "WITH" : "WITHOUT")
+                    + " conversion allowed.  "
+                      "Argument value = "
+                    + (std::string) str(src);
         return true;
     }
 
@@ -36,14 +44,16 @@ template <> struct type_caster<ArgInspector1> {
         return str(src.arg).release();
     }
 };
-template <> struct type_caster<ArgInspector2> {
+template <>
+struct type_caster<ArgInspector2> {
 public:
     PYBIND11_TYPE_CASTER(ArgInspector2, const_name("ArgInspector2"));
 
     bool load(handle src, bool convert) {
-        value.arg = "loading ArgInspector2 argument " +
-            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
-            "Argument value = " + (std::string) str(src);
+        value.arg = "loading ArgInspector2 argument " + std::string(convert ? "WITH" : "WITHOUT")
+                    + " conversion allowed.  "
+                      "Argument value = "
+                    + (std::string) str(src);
         return true;
     }
 
@@ -51,13 +61,12 @@ template <> struct type_caster<ArgInspector2> {
         return str(src.arg).release();
     }
 };
-template <> struct type_caster<ArgAlwaysConverts> {
+template <>
+struct type_caster<ArgAlwaysConverts> {
 public:
     PYBIND11_TYPE_CASTER(ArgAlwaysConverts, const_name("ArgAlwaysConverts"));
 
-    bool load(handle, bool convert) {
-        return convert;
-    }
+    bool load(handle, bool convert) { return convert; }
 
     static handle cast(const ArgAlwaysConverts &, return_value_policy, handle) {
         return py::none().release();
@@ -73,14 +82,19 @@ class DestructionTester {
     ~DestructionTester() { print_destroyed(this); }
     DestructionTester(const DestructionTester &) { print_copy_created(this); }
     DestructionTester(DestructionTester &&) noexcept { print_move_created(this); }
-    DestructionTester &operator=(const DestructionTester &) { print_copy_assigned(this); return *this; }
+    DestructionTester &operator=(const DestructionTester &) {
+        print_copy_assigned(this);
+        return *this;
+    }
     DestructionTester &operator=(DestructionTester &&) noexcept {
         print_move_assigned(this);
         return *this;
     }
 };
-namespace pybind11 { namespace detail {
-template <> struct type_caster<DestructionTester> {
+namespace pybind11 {
+namespace detail {
+template <>
+struct type_caster<DestructionTester> {
     PYBIND11_TYPE_CASTER(DestructionTester, const_name("DestructionTester"));
     bool load(handle, bool) { return true; }
 
@@ -115,9 +129,14 @@ TEST_SUBMODULE(custom_type_casters, m) {
     py::class_<ArgInspector>(m, "ArgInspector")
         .def(py::init<>())
         .def("f", &ArgInspector::f, py::arg(), py::arg() = ArgAlwaysConverts())
-        .def("g", &ArgInspector::g, "a"_a.noconvert(), "b"_a, "c"_a.noconvert()=13, "d"_a=ArgInspector2(), py::arg() = ArgAlwaysConverts())
-        .def_static("h", &ArgInspector::h, py::arg{}.noconvert(), py::arg() = ArgAlwaysConverts())
-        ;
+        .def("g",
+             &ArgInspector::g,
+             "a"_a.noconvert(),
+             "b"_a,
+             "c"_a.noconvert() = 13,
+             "d"_a = ArgInspector2(),
+             py::arg() = ArgAlwaysConverts())
+        .def_static("h", &ArgInspector::h, py::arg{}.noconvert(), py::arg() = ArgAlwaysConverts());
     m.def(
         "arg_inspect_func",
         [](const ArgInspector2 &a, const ArgInspector1 &b, ArgAlwaysConverts) {
@@ -127,20 +146,33 @@ TEST_SUBMODULE(custom_type_casters, m) {
         py::arg_v(nullptr, ArgInspector1()).noconvert(true),
         py::arg() = ArgAlwaysConverts());
 
-    m.def("floats_preferred", [](double f) { return 0.5 * f; }, "f"_a);
-    m.def("floats_only", [](double f) { return 0.5 * f; }, "f"_a.noconvert());
-    m.def("ints_preferred", [](int i) { return i / 2; }, "i"_a);
-    m.def("ints_only", [](int i) { return i / 2; }, "i"_a.noconvert());
+    m.def(
+        "floats_preferred", [](double f) { return 0.5 * f; }, "f"_a);
+    m.def(
+        "floats_only", [](double f) { return 0.5 * f; }, "f"_a.noconvert());
+    m.def(
+        "ints_preferred", [](int i) { return i / 2; }, "i"_a);
+    m.def(
+        "ints_only", [](int i) { return i / 2; }, "i"_a.noconvert());
 
     // test_custom_caster_destruction
     // Test that `take_ownership` works on types with a custom type caster when given a pointer
 
     // default policy: don't take ownership:
-    m.def("custom_caster_no_destroy", []() { static auto *dt = new DestructionTester(); return dt; });
+    m.def("custom_caster_no_destroy", []() {
+        static auto *dt = new DestructionTester();
+        return dt;
+    });
 
-    m.def("custom_caster_destroy", []() { return new DestructionTester(); },
-            py::return_value_policy::take_ownership); // Takes ownership: destroy when finished
-    m.def("custom_caster_destroy_const", []() -> const DestructionTester * { return new DestructionTester(); },
-            py::return_value_policy::take_ownership); // Likewise (const doesn't inhibit destruction)
-    m.def("destruction_tester_cstats", &ConstructorStats::get<DestructionTester>, py::return_value_policy::reference);
+    m.def(
+        "custom_caster_destroy",
+        []() { return new DestructionTester(); },
+        py::return_value_policy::take_ownership); // Takes ownership: destroy when finished
+    m.def(
+        "custom_caster_destroy_const",
+        []() -> const DestructionTester * { return new DestructionTester(); },
+        py::return_value_policy::take_ownership); // Likewise (const doesn't inhibit destruction)
+    m.def("destruction_tester_cstats",
+          &ConstructorStats::get<DestructionTester>,
+          py::return_value_policy::reference);
 }
diff --git a/tests/test_docstring_options.cpp b/tests/test_docstring_options.cpp
index 8a97af55fc..4d44f4e20d 100644
--- a/tests/test_docstring_options.cpp
+++ b/tests/test_docstring_options.cpp
@@ -15,35 +15,52 @@ TEST_SUBMODULE(docstring_options, m) {
         py::options options;
         options.disable_function_signatures();
 
-        m.def("test_function1", [](int, int) {}, py::arg("a"), py::arg("b"));
-        m.def("test_function2", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
-
-        m.def("test_overloaded1", [](int) {}, py::arg("i"), "Overload docstring");
-        m.def("test_overloaded1", [](double) {}, py::arg("d"));
-
-        m.def("test_overloaded2", [](int) {}, py::arg("i"), "overload docstring 1");
-        m.def("test_overloaded2", [](double) {}, py::arg("d"), "overload docstring 2");
-
-        m.def("test_overloaded3", [](int) {}, py::arg("i"));
-        m.def("test_overloaded3", [](double) {}, py::arg("d"), "Overload docstr");
+        m.def(
+            "test_function1", [](int, int) {}, py::arg("a"), py::arg("b"));
+        m.def(
+            "test_function2", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+
+        m.def(
+            "test_overloaded1", [](int) {}, py::arg("i"), "Overload docstring");
+        m.def(
+            "test_overloaded1", [](double) {}, py::arg("d"));
+
+        m.def(
+            "test_overloaded2", [](int) {}, py::arg("i"), "overload docstring 1");
+        m.def(
+            "test_overloaded2", [](double) {}, py::arg("d"), "overload docstring 2");
+
+        m.def(
+            "test_overloaded3", [](int) {}, py::arg("i"));
+        m.def(
+            "test_overloaded3", [](double) {}, py::arg("d"), "Overload docstr");
 
         options.enable_function_signatures();
 
-        m.def("test_function3", [](int, int) {}, py::arg("a"), py::arg("b"));
-        m.def("test_function4", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+        m.def(
+            "test_function3", [](int, int) {}, py::arg("a"), py::arg("b"));
+        m.def(
+            "test_function4", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
 
         options.disable_function_signatures().disable_user_defined_docstrings();
 
-        m.def("test_function5", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+        m.def(
+            "test_function5", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
 
         {
             py::options nested_options;
             nested_options.enable_user_defined_docstrings();
-            m.def("test_function6", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+            m.def(
+                "test_function6",
+                [](int, int) {},
+                py::arg("a"),
+                py::arg("b"),
+                "A custom docstring");
         }
     }
 
-    m.def("test_function7", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+    m.def(
+        "test_function7", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
 
     {
         py::options options;
@@ -63,7 +80,9 @@ TEST_SUBMODULE(docstring_options, m) {
             int getValue() const { return value; }
         };
         py::class_<DocstringTestFoo>(m, "DocstringTestFoo", "This is a class docstring")
-            .def_property("value_prop", &DocstringTestFoo::getValue, &DocstringTestFoo::setValue, "This is a property docstring")
-        ;
+            .def_property("value_prop",
+                          &DocstringTestFoo::getValue,
+                          &DocstringTestFoo::setValue,
+                          "This is a property docstring");
     }
 }
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index d7b62ef784..059843d3da 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -7,27 +7,27 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/eigen.h>
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #if defined(_MSC_VER)
-#if _MSC_VER < 1910  // VS 2015's MSVC
-#  pragma warning(disable: 4127) // C4127: conditional expression is constant
-#endif
-#  pragma warning(disable: 4996) // C4996: std::unary_negation is deprecated
+#    if _MSC_VER < 1910                 // VS 2015's MSVC
+#        pragma warning(disable : 4127) // C4127: conditional expression is constant
+#    endif
+#    pragma warning(disable : 4996) // C4996: std::unary_negation is deprecated
 #endif
 
 #include <Eigen/Cholesky>
 
 using MatrixXdR = Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
 
-
-
 // Sets/resets a testing reference matrix to have values of 10*r + c, where r and c are the
 // (1-based) row/column number.
-template <typename M> void reset_ref(M &x) {
+template <typename M>
+void reset_ref(M &x) {
     for (int i = 0; i < x.rows(); i++) {
         for (int j = 0; j < x.cols(); j++) {
             x(i, j) = 11 + 10 * i + j;
@@ -64,7 +64,8 @@ double get_elem(const Eigen::Ref<const Eigen::MatrixXd> &m) { return m(2, 1); };
 
 // Returns a matrix with 10*r + 100*c added to each matrix element (to help test that the matrix
 // reference is referencing rows/columns correctly).
-template <typename MatrixArgType> Eigen::MatrixXd adjust_matrix(MatrixArgType m) {
+template <typename MatrixArgType>
+Eigen::MatrixXd adjust_matrix(MatrixArgType m) {
     Eigen::MatrixXd ret(m);
     for (int c = 0; c < m.cols(); c++) {
         for (int r = 0; r < m.rows(); r++) {
@@ -97,8 +98,10 @@ TEST_SUBMODULE(eigen, m) {
 
     // various tests
     m.def("double_col", [](const Eigen::VectorXf &x) -> Eigen::VectorXf { return 2.0f * x; });
-    m.def("double_row", [](const Eigen::RowVectorXf &x) -> Eigen::RowVectorXf { return 2.0f * x; });
-    m.def("double_complex", [](const Eigen::VectorXcf &x) -> Eigen::VectorXcf { return 2.0f * x; });
+    m.def("double_row",
+          [](const Eigen::RowVectorXf &x) -> Eigen::RowVectorXf { return 2.0f * x; });
+    m.def("double_complex",
+          [](const Eigen::VectorXcf &x) -> Eigen::VectorXcf { return 2.0f * x; });
     m.def("double_threec", [](py::EigenDRef<Eigen::Vector3f> x) { x *= 2; });
     m.def("double_threer", [](py::EigenDRef<Eigen::RowVector3f> x) { x *= 2; });
     m.def("double_mat_cm", [](const Eigen::MatrixXf &x) -> Eigen::MatrixXf { return 2.0f * x; });
@@ -108,19 +111,22 @@ TEST_SUBMODULE(eigen, m) {
     // Different ways of passing via Eigen::Ref; the first and second are the Eigen-recommended
     m.def("cholesky1",
           [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
-    m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
-    m.def("cholesky3", [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd {
+        return x.llt().matrixL();
+    });
+    m.def("cholesky3",
+          [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky4", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd {
         return x.llt().matrixL();
     });
 
     // test_eigen_ref_mutators
-    // Mutators: these add some value to the given element using Eigen, but Eigen should be mapping into
-    // the numpy array data and so the result should show up there.  There are three versions: one that
-    // works on a contiguous-row matrix (numpy's default), one for a contiguous-column matrix, and one
-    // for any matrix.
-    auto add_rm = [](Eigen::Ref<MatrixXdR> x, int r, int c, double v) { x(r,c) += v; };
-    auto add_cm = [](Eigen::Ref<Eigen::MatrixXd> x, int r, int c, double v) { x(r,c) += v; };
+    // Mutators: these add some value to the given element using Eigen, but Eigen should be mapping
+    // into the numpy array data and so the result should show up there.  There are three versions:
+    // one that works on a contiguous-row matrix (numpy's default), one for a contiguous-column
+    // matrix, and one for any matrix.
+    auto add_rm = [](Eigen::Ref<MatrixXdR> x, int r, int c, double v) { x(r, c) += v; };
+    auto add_cm = [](Eigen::Ref<Eigen::MatrixXd> x, int r, int c, double v) { x(r, c) += v; };
 
     // Mutators (Eigen maps into numpy variables):
     m.def("add_rm", add_rm); // Only takes row-contiguous
@@ -131,7 +137,8 @@ TEST_SUBMODULE(eigen, m) {
     m.def("add2", add_cm);
     m.def("add2", add_rm);
     // This one accepts a matrix of any stride:
-    m.def("add_any", [](py::EigenDRef<Eigen::MatrixXd> x, int r, int c, double v) { x(r,c) += v; });
+    m.def("add_any",
+          [](py::EigenDRef<Eigen::MatrixXd> x, int r, int c, double v) { x(r, c) += v; });
 
     // Return mutable references (numpy maps into eigen variables)
     m.def("get_cm_ref", []() { return Eigen::Ref<Eigen::MatrixXd>(get_cm()); });
@@ -143,45 +150,67 @@ TEST_SUBMODULE(eigen, m) {
     m.def("reset_refs", reset_refs); // Restores get_{cm,rm}_ref to original values
 
     // Increments and returns ref to (same) matrix
-    m.def("incr_matrix", [](Eigen::Ref<Eigen::MatrixXd> m, double v) {
-        m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
-        return m;
-    }, py::return_value_policy::reference);
+    m.def(
+        "incr_matrix",
+        [](Eigen::Ref<Eigen::MatrixXd> m, double v) {
+            m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
+            return m;
+        },
+        py::return_value_policy::reference);
 
     // Same, but accepts a matrix of any strides
-    m.def("incr_matrix_any", [](py::EigenDRef<Eigen::MatrixXd> m, double v) {
-        m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
-        return m;
-    }, py::return_value_policy::reference);
+    m.def(
+        "incr_matrix_any",
+        [](py::EigenDRef<Eigen::MatrixXd> m, double v) {
+            m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
+            return m;
+        },
+        py::return_value_policy::reference);
 
     // Returns an eigen slice of even rows
-    m.def("even_rows", [](py::EigenDRef<Eigen::MatrixXd> m) {
-        return py::EigenDMap<Eigen::MatrixXd>(
-                m.data(), (m.rows() + 1) / 2, m.cols(),
+    m.def(
+        "even_rows",
+        [](py::EigenDRef<Eigen::MatrixXd> m) {
+            return py::EigenDMap<Eigen::MatrixXd>(
+                m.data(),
+                (m.rows() + 1) / 2,
+                m.cols(),
                 py::EigenDStride(m.outerStride(), 2 * m.innerStride()));
-    }, py::return_value_policy::reference);
+        },
+        py::return_value_policy::reference);
 
     // Returns an eigen slice of even columns
-    m.def("even_cols", [](py::EigenDRef<Eigen::MatrixXd> m) {
-        return py::EigenDMap<Eigen::MatrixXd>(
-                m.data(), m.rows(), (m.cols() + 1) / 2,
+    m.def(
+        "even_cols",
+        [](py::EigenDRef<Eigen::MatrixXd> m) {
+            return py::EigenDMap<Eigen::MatrixXd>(
+                m.data(),
+                m.rows(),
+                (m.cols() + 1) / 2,
                 py::EigenDStride(2 * m.outerStride(), m.innerStride()));
-    }, py::return_value_policy::reference);
+        },
+        py::return_value_policy::reference);
 
     // Returns diagonals: a vector-like object with an inner stride != 1
     m.def("diagonal", [](const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.diagonal(); });
-    m.def("diagonal_1", [](const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.diagonal<1>(); });
-    m.def("diagonal_n", [](const Eigen::Ref<const Eigen::MatrixXd> &x, int index) { return x.diagonal(index); });
+    m.def("diagonal_1",
+          [](const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.diagonal<1>(); });
+    m.def("diagonal_n",
+          [](const Eigen::Ref<const Eigen::MatrixXd> &x, int index) { return x.diagonal(index); });
 
     // Return a block of a matrix (gives non-standard strides)
-    m.def("block", [](const Eigen::Ref<const Eigen::MatrixXd> &x, int start_row, int start_col, int block_rows, int block_cols) {
-        return x.block(start_row, start_col, block_rows, block_cols);
-    });
+    m.def("block",
+          [](const Eigen::Ref<const Eigen::MatrixXd> &x,
+             int start_row,
+             int start_col,
+             int block_rows,
+             int block_cols) { return x.block(start_row, start_col, block_rows, block_cols); });
 
     // test_eigen_return_references, test_eigen_keepalive
     // return value referencing/copying tests:
     class ReturnTester {
         Eigen::MatrixXd mat = create();
+
     public:
         ReturnTester() { print_created(this); }
         ~ReturnTester() { print_destroyed(this); }
@@ -194,12 +223,24 @@ TEST_SUBMODULE(eigen, m) {
         const Eigen::MatrixXd *viewPtr() { return &mat; }
         Eigen::Ref<Eigen::MatrixXd> ref() { return mat; }
         Eigen::Ref<const Eigen::MatrixXd> refConst() { return mat; }
-        Eigen::Block<Eigen::MatrixXd> block(int r, int c, int nrow, int ncol) { return mat.block(r, c, nrow, ncol); }
-        Eigen::Block<const Eigen::MatrixXd> blockConst(int r, int c, int nrow, int ncol) const { return mat.block(r, c, nrow, ncol); }
-        py::EigenDMap<Eigen::Matrix2d> corners() { return py::EigenDMap<Eigen::Matrix2d>(mat.data(),
-                    py::EigenDStride(mat.outerStride() * (mat.outerSize()-1), mat.innerStride() * (mat.innerSize()-1))); }
-        py::EigenDMap<const Eigen::Matrix2d> cornersConst() const { return py::EigenDMap<const Eigen::Matrix2d>(mat.data(),
-                    py::EigenDStride(mat.outerStride() * (mat.outerSize()-1), mat.innerStride() * (mat.innerSize()-1))); }
+        Eigen::Block<Eigen::MatrixXd> block(int r, int c, int nrow, int ncol) {
+            return mat.block(r, c, nrow, ncol);
+        }
+        Eigen::Block<const Eigen::MatrixXd> blockConst(int r, int c, int nrow, int ncol) const {
+            return mat.block(r, c, nrow, ncol);
+        }
+        py::EigenDMap<Eigen::Matrix2d> corners() {
+            return py::EigenDMap<Eigen::Matrix2d>(
+                mat.data(),
+                py::EigenDStride(mat.outerStride() * (mat.outerSize() - 1),
+                                 mat.innerStride() * (mat.innerSize() - 1)));
+        }
+        py::EigenDMap<const Eigen::Matrix2d> cornersConst() const {
+            return py::EigenDMap<const Eigen::Matrix2d>(
+                mat.data(),
+                py::EigenDStride(mat.outerStride() * (mat.outerSize() - 1),
+                                 mat.innerStride() * (mat.innerSize() - 1)));
+        }
     };
     using rvp = py::return_value_policy;
     py::class_<ReturnTester>(m, "ReturnTester")
@@ -210,9 +251,9 @@ TEST_SUBMODULE(eigen, m) {
         .def("get_ptr", &ReturnTester::getPtr, rvp::reference_internal)
         .def("view", &ReturnTester::view, rvp::reference_internal)
         .def("view_ptr", &ReturnTester::view, rvp::reference_internal)
-        .def("copy_get", &ReturnTester::get)   // Default rvp: copy
-        .def("copy_view", &ReturnTester::view) //         "
-        .def("ref", &ReturnTester::ref) // Default for Ref is to reference
+        .def("copy_get", &ReturnTester::get)       // Default rvp: copy
+        .def("copy_view", &ReturnTester::view)     //         "
+        .def("ref", &ReturnTester::ref)            // Default for Ref is to reference
         .def("ref_const", &ReturnTester::refConst) // Likewise, but const
         .def("ref_safe", &ReturnTester::ref, rvp::reference_internal)
         .def("ref_const_safe", &ReturnTester::refConst, rvp::reference_internal)
@@ -223,8 +264,7 @@ TEST_SUBMODULE(eigen, m) {
         .def("block_const", &ReturnTester::blockConst, rvp::reference_internal)
         .def("copy_block", &ReturnTester::block, rvp::copy)
         .def("corners", &ReturnTester::corners, rvp::reference_internal)
-        .def("corners_const", &ReturnTester::cornersConst, rvp::reference_internal)
-        ;
+        .def("corners_const", &ReturnTester::cornersConst, rvp::reference_internal);
 
     // test_special_matrix_objects
     // Returns a DiagonalMatrix with diagonal (1,2,3,...)
@@ -237,21 +277,16 @@ TEST_SUBMODULE(eigen, m) {
     });
 
     // Returns a SelfAdjointView referencing the lower triangle of m
-    m.def("symmetric_lower", [](const Eigen::MatrixXi &m) {
-            return m.selfadjointView<Eigen::Lower>();
-    });
+    m.def("symmetric_lower",
+          [](const Eigen::MatrixXi &m) { return m.selfadjointView<Eigen::Lower>(); });
     // Returns a SelfAdjointView referencing the lower triangle of m
-    m.def("symmetric_upper", [](const Eigen::MatrixXi &m) {
-            return m.selfadjointView<Eigen::Upper>();
-    });
+    m.def("symmetric_upper",
+          [](const Eigen::MatrixXi &m) { return m.selfadjointView<Eigen::Upper>(); });
 
     // Test matrix for various functions below.
     Eigen::MatrixXf mat(5, 6);
-    mat << 0,  3,  0,  0,  0, 11,
-           22, 0,  0,  0, 17, 11,
-           7,  5,  0,  1,  0, 11,
-           0,  0,  0,  0,  0, 11,
-           0,  0, 14,  0,  8, 11;
+    mat << 0, 3, 0, 0, 0, 11, 22, 0, 0, 0, 17, 11, 7, 5, 0, 1, 0, 11, 0, 0, 0, 0, 0, 11, 0, 0, 14,
+        0, 8, 11;
 
     // test_fixed, and various other tests
     m.def("fixed_r", [mat]() -> FixedMatrixR { return FixedMatrixR(mat); });
@@ -276,7 +311,8 @@ TEST_SUBMODULE(eigen, m) {
         // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
         return Eigen::SparseView<Eigen::MatrixXf>(mat);
     });
-    m.def("sparse_c", [mat]() -> SparseMatrixC { return Eigen::SparseView<Eigen::MatrixXf>(mat); });
+    m.def("sparse_c",
+          [mat]() -> SparseMatrixC { return Eigen::SparseView<Eigen::MatrixXf>(mat); });
     m.def("sparse_copy_r", [](const SparseMatrixR &m) -> SparseMatrixR { return m; });
     m.def("sparse_copy_c", [](const SparseMatrixC &m) -> SparseMatrixC { return m; });
     // test_partially_fixed
@@ -290,7 +326,8 @@ TEST_SUBMODULE(eigen, m) {
     m.def("cpp_copy", [](py::handle m) { return m.cast<Eigen::MatrixXd>()(1, 0); });
     m.def("cpp_ref_c", [](py::handle m) { return m.cast<Eigen::Ref<Eigen::MatrixXd>>()(1, 0); });
     m.def("cpp_ref_r", [](py::handle m) { return m.cast<Eigen::Ref<MatrixXdR>>()(1, 0); });
-    m.def("cpp_ref_any", [](py::handle m) { return m.cast<py::EigenDRef<Eigen::MatrixXd>>()(1, 0); });
+    m.def("cpp_ref_any",
+          [](py::handle m) { return m.cast<py::EigenDRef<Eigen::MatrixXd>>()(1, 0); });
 
     // [workaround(intel)] ICC 20/21 breaks with py::arg().stuff, using py::arg{}.stuff works.
 
@@ -304,15 +341,23 @@ TEST_SUBMODULE(eigen, m) {
         [](const Eigen::Ref<const Eigen::MatrixXd> &m) -> double { return get_elem(m); },
         py::arg{}.noconvert());
     // Also test a row-major-only no-copy const ref:
-    m.def("get_elem_rm_nocopy", [](Eigen::Ref<const Eigen::Matrix<long, -1, -1, Eigen::RowMajor>> &m) -> long { return m(2, 1); },
-            py::arg{}.noconvert());
+    m.def(
+        "get_elem_rm_nocopy",
+        [](Eigen::Ref<const Eigen::Matrix<long, -1, -1, Eigen::RowMajor>> &m) -> long {
+            return m(2, 1);
+        },
+        py::arg{}.noconvert());
 
     // test_issue738
     // Issue #738: 1xN or Nx1 2D matrices were neither accepted nor properly copied with an
     // incompatible stride value on the length-1 dimension--but that should be allowed (without
     // requiring a copy!) because the stride value can be safely ignored on a size-1 dimension.
-    m.def("iss738_f1", &adjust_matrix<const Eigen::Ref<const Eigen::MatrixXd> &>, py::arg{}.noconvert());
-    m.def("iss738_f2", &adjust_matrix<const Eigen::Ref<const Eigen::Matrix<double, -1, -1, Eigen::RowMajor>> &>, py::arg{}.noconvert());
+    m.def("iss738_f1",
+          &adjust_matrix<const Eigen::Ref<const Eigen::MatrixXd> &>,
+          py::arg{}.noconvert());
+    m.def("iss738_f2",
+          &adjust_matrix<const Eigen::Ref<const Eigen::Matrix<double, -1, -1, Eigen::RowMajor>> &>,
+          py::arg{}.noconvert());
 
     // test_issue1105
     // Issue #1105: when converting from a numpy two-dimensional (Nx1) or (1xN) value into a dense
diff --git a/tests/test_embed/catch.cpp b/tests/test_embed/catch.cpp
index 67a8d51432..96d2e3f92a 100644
--- a/tests/test_embed/catch.cpp
+++ b/tests/test_embed/catch.cpp
@@ -4,14 +4,14 @@
 #include <pybind11/embed.h>
 
 #ifdef _MSC_VER
-// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to catch
-// 2.0.1; this should be fixed in the next catch release after 2.0.1).
-#  pragma warning(disable: 4996)
+// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
+// catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
+#    pragma warning(disable : 4996)
 #endif
 
 // Catch uses _ internally, which breaks gettext style defines
 #ifdef _
-#undef _
+#    undef _
 #endif
 
 #define CATCH_CONFIG_RUNNER
diff --git a/tests/test_embed/external_module.cpp b/tests/test_embed/external_module.cpp
index 4909522993..5c482fe061 100644
--- a/tests/test_embed/external_module.cpp
+++ b/tests/test_embed/external_module.cpp
@@ -13,11 +13,8 @@ PYBIND11_MODULE(external_module, m) {
         int v;
     };
 
-    py::class_<A>(m, "A")
-        .def(py::init<int>())
-        .def_readwrite("value", &A::v);
+    py::class_<A>(m, "A").def(py::init<int>()).def_readwrite("value", &A::v);
 
-    m.def("internals_at", []() {
-        return reinterpret_cast<uintptr_t>(&py::detail::get_internals());
-    });
+    m.def("internals_at",
+          []() { return reinterpret_cast<uintptr_t>(&py::detail::get_internals()); });
 }
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 601a19092f..5782bda618 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -1,13 +1,12 @@
 #include <pybind11/embed.h>
 
 #ifdef _MSC_VER
-// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to catch
-// 2.0.1; this should be fixed in the next catch release after 2.0.1).
-#  pragma warning(disable: 4996)
+// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
+// catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
+#    pragma warning(disable : 4996)
 #endif
 
 #include <catch.hpp>
-
 #include <cstdlib>
 #include <fstream>
 #include <functional>
@@ -62,14 +61,14 @@ PYBIND11_EMBEDDED_MODULE(widget_module, m) {
 }
 
 PYBIND11_EMBEDDED_MODULE(trampoline_module, m) {
-    py::class_<test_override_cache_helper, test_override_cache_helper_trampoline, std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
+    py::class_<test_override_cache_helper,
+               test_override_cache_helper_trampoline,
+               std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
         .def(py::init_alias<>())
         .def("func", &test_override_cache_helper::func);
 }
 
-PYBIND11_EMBEDDED_MODULE(throw_exception, ) {
-    throw std::runtime_error("C++ Error");
-}
+PYBIND11_EMBEDDED_MODULE(throw_exception, ) { throw std::runtime_error("C++ Error"); }
 
 PYBIND11_EMBEDDED_MODULE(throw_error_already_set, ) {
     auto d = py::dict();
@@ -80,11 +79,13 @@ TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
     auto module_ = py::module_::import("test_interpreter");
     REQUIRE(py::hasattr(module_, "DerivedWidget"));
 
-    auto locals = py::dict("hello"_a="Hello, World!", "x"_a=5, **module_.attr("__dict__"));
+    auto locals = py::dict("hello"_a = "Hello, World!", "x"_a = 5, **module_.attr("__dict__"));
     py::exec(R"(
         widget = DerivedWidget("{} - {}".format(hello, x))
         message = widget.the_message
-    )", py::globals(), locals);
+    )",
+             py::globals(),
+             locals);
     REQUIRE(locals["message"].cast<std::string>() == "Hello, World! - 5");
 
     auto py_widget = module_.attr("DerivedWidget")("The question");
@@ -124,20 +125,21 @@ TEST_CASE("Override cache") {
 
 TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
-    REQUIRE_THROWS_WITH(py::module_::import("throw_exception"),
-                        "ImportError: C++ Error");
+    REQUIRE_THROWS_WITH(py::module_::import("throw_exception"), "ImportError: C++ Error");
 #if PY_VERSION_HEX >= 0x03030000
     REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                         Catch::Contains("ImportError: initialization failed"));
 
-    auto locals = py::dict("is_keyerror"_a=false, "message"_a="not set");
+    auto locals = py::dict("is_keyerror"_a = false, "message"_a = "not set");
     py::exec(R"(
         try:
             import throw_error_already_set
         except ImportError as e:
             is_keyerror = type(e.__cause__) == KeyError
             message = str(e.__cause__)
-    )", py::globals(), locals);
+    )",
+             py::globals(),
+             locals);
     REQUIRE(locals["is_keyerror"].cast<bool>() == true);
     REQUIRE(locals["message"].cast<std::string>() == "'missing'");
 #else
@@ -179,11 +181,12 @@ TEST_CASE("Restart the interpreter") {
     REQUIRE(py::module_::import("widget_module").attr("add")(1, 2).cast<int>() == 3);
     REQUIRE(has_pybind11_internals_builtin());
     REQUIRE(has_pybind11_internals_static());
-    REQUIRE(py::module_::import("external_module").attr("A")(123).attr("value").cast<int>() == 123);
+    REQUIRE(py::module_::import("external_module").attr("A")(123).attr("value").cast<int>()
+            == 123);
 
     // local and foreign module internals should point to the same internals:
-    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp()) ==
-            py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
+    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp())
+            == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
 
     // Restart the interpreter.
     py::finalize_interpreter();
@@ -198,16 +201,19 @@ TEST_CASE("Restart the interpreter") {
     pybind11::detail::get_internals();
     REQUIRE(has_pybind11_internals_builtin());
     REQUIRE(has_pybind11_internals_static());
-    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp()) ==
-            py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
+    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp())
+            == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
 
     // Make sure that an interpreter with no get_internals() created until finalize still gets the
     // internals destroyed
     py::finalize_interpreter();
     py::initialize_interpreter();
     bool ran = false;
-    py::module_::import("__main__").attr("internals_destroy_test") =
-        py::capsule(&ran, [](void *ran) { py::detail::get_internals(); *static_cast<bool *>(ran) = true; });
+    py::module_::import("__main__").attr("internals_destroy_test")
+        = py::capsule(&ran, [](void *ran) {
+              py::detail::get_internals();
+              *static_cast<bool *>(ran) = true;
+          });
     REQUIRE_FALSE(has_pybind11_internals_builtin());
     REQUIRE_FALSE(has_pybind11_internals_static());
     REQUIRE_FALSE(ran);
@@ -281,7 +287,7 @@ TEST_CASE("Threads") {
     REQUIRE_FALSE(has_pybind11_internals_static());
 
     constexpr auto num_threads = 10;
-    auto locals = py::dict("count"_a=0);
+    auto locals = py::dict("count"_a = 0);
 
     {
         py::gil_scoped_release gil_release{};
@@ -322,9 +328,8 @@ TEST_CASE("Reload module from file") {
     bool dont_write_bytecode = sys.attr("dont_write_bytecode").cast<bool>();
     sys.attr("dont_write_bytecode") = true;
     // Reset the value at scope exit
-    scope_exit reset_dont_write_bytecode([&]() {
-        sys.attr("dont_write_bytecode") = dont_write_bytecode;
-    });
+    scope_exit reset_dont_write_bytecode(
+        [&]() { sys.attr("dont_write_bytecode") = dont_write_bytecode; });
 
     std::string module_name = "test_module_reload";
     std::string module_file = module_name + ".py";
@@ -335,9 +340,7 @@ TEST_CASE("Reload module from file") {
     test_module << "    return 1\n";
     test_module.close();
     // Delete the file at scope exit
-    scope_exit delete_module_file([&]() {
-        std::remove(module_file.c_str());
-    });
+    scope_exit delete_module_file([&]() { std::remove(module_file.c_str()); });
 
     // Import the module from file
     auto module_ = py::module_::import(module_name.c_str());
diff --git a/tests/test_enum.cpp b/tests/test_enum.cpp
index 40c48d412a..2597b275ef 100644
--- a/tests/test_enum.cpp
+++ b/tests/test_enum.cpp
@@ -11,11 +11,7 @@
 
 TEST_SUBMODULE(enums, m) {
     // test_unscoped_enum
-    enum UnscopedEnum {
-        EOne = 1,
-        ETwo,
-        EThree
-    };
+    enum UnscopedEnum { EOne = 1, ETwo, EThree };
     py::enum_<UnscopedEnum>(m, "UnscopedEnum", py::arithmetic(), "An unscoped enumeration")
         .value("EOne", EOne, "Docstring for EOne")
         .value("ETwo", ETwo, "Docstring for ETwo")
@@ -23,10 +19,7 @@ TEST_SUBMODULE(enums, m) {
         .export_values();
 
     // test_scoped_enum
-    enum class ScopedEnum {
-        Two = 2,
-        Three
-    };
+    enum class ScopedEnum { Two = 2, Three };
     py::enum_<ScopedEnum>(m, "ScopedEnum", py::arithmetic())
         .value("Two", ScopedEnum::Two)
         .value("Three", ScopedEnum::Three);
@@ -36,11 +29,7 @@ TEST_SUBMODULE(enums, m) {
     });
 
     // test_binary_operators
-    enum Flags {
-        Read = 4,
-        Write = 2,
-        Execute = 1
-    };
+    enum Flags { Read = 4, Write = 2, Execute = 1 };
     py::enum_<Flags>(m, "Flags", py::arithmetic())
         .value("Read", Flags::Read)
         .value("Write", Flags::Write)
@@ -50,14 +39,9 @@ TEST_SUBMODULE(enums, m) {
     // test_implicit_conversion
     class ClassWithUnscopedEnum {
     public:
-        enum EMode {
-            EFirstMode = 1,
-            ESecondMode
-        };
-
-        static EMode test_function(EMode mode) {
-            return mode;
-        }
+        enum EMode { EFirstMode = 1, ESecondMode };
+
+        static EMode test_function(EMode mode) { return mode; }
     };
     py::class_<ClassWithUnscopedEnum> exenum_class(m, "ClassWithUnscopedEnum");
     exenum_class.def_static("test_function", &ClassWithUnscopedEnum::test_function);
@@ -67,19 +51,17 @@ TEST_SUBMODULE(enums, m) {
         .export_values();
 
     // test_enum_to_int
-    m.def("test_enum_to_int", [](int) { });
-    m.def("test_enum_to_uint", [](uint32_t) { });
-    m.def("test_enum_to_long_long", [](long long) { });
+    m.def("test_enum_to_int", [](int) {});
+    m.def("test_enum_to_uint", [](uint32_t) {});
+    m.def("test_enum_to_long_long", [](long long) {});
 
     // test_duplicate_enum_name
-    enum SimpleEnum
-    {
-        ONE, TWO, THREE
-    };
+    enum SimpleEnum { ONE, TWO, THREE };
 
     m.def("register_bad_enum", [m]() {
         py::enum_<SimpleEnum>(m, "SimpleEnum")
-            .value("ONE", SimpleEnum::ONE)          //NOTE: all value function calls are called with the same first parameter value
+            .value("ONE", SimpleEnum::ONE) // NOTE: all value function calls are called with the
+                                           // same first parameter value
             .value("ONE", SimpleEnum::TWO)
             .value("ONE", SimpleEnum::THREE)
             .export_values();
@@ -90,33 +72,36 @@ TEST_SUBMODULE(enums, m) {
     enum class ScopedShortEnum : short {};
     enum class ScopedLongEnum : long {};
     enum UnscopedUInt64Enum : std::uint64_t {};
-    static_assert(py::detail::all_of<
-        std::is_same<py::enum_<UnscopedUCharEnum>::Scalar, unsigned char>,
-        std::is_same<py::enum_<ScopedShortEnum>::Scalar, short>,
-        std::is_same<py::enum_<ScopedLongEnum>::Scalar, long>,
-        std::is_same<py::enum_<UnscopedUInt64Enum>::Scalar, std::uint64_t>
-    >::value, "Error during the deduction of enum's scalar type with normal integer underlying");
+    static_assert(
+        py::detail::all_of<
+            std::is_same<py::enum_<UnscopedUCharEnum>::Scalar, unsigned char>,
+            std::is_same<py::enum_<ScopedShortEnum>::Scalar, short>,
+            std::is_same<py::enum_<ScopedLongEnum>::Scalar, long>,
+            std::is_same<py::enum_<UnscopedUInt64Enum>::Scalar, std::uint64_t>>::value,
+        "Error during the deduction of enum's scalar type with normal integer underlying");
 
     // test_enum_scalar_with_char_underlying
-    enum class ScopedCharEnum   : char     { Zero, Positive };
-    enum class ScopedWCharEnum  : wchar_t  { Zero, Positive };
+    enum class ScopedCharEnum : char { Zero, Positive };
+    enum class ScopedWCharEnum : wchar_t { Zero, Positive };
     enum class ScopedChar32Enum : char32_t { Zero, Positive };
     enum class ScopedChar16Enum : char16_t { Zero, Positive };
 
     // test the scalar of char type enums according to chapter 'Character types'
     // from https://en.cppreference.com/w/cpp/language/types
-    static_assert(py::detail::any_of<
-        std::is_same<py::enum_<ScopedCharEnum>::Scalar, signed char>, // e.g. gcc on x86
-        std::is_same<py::enum_<ScopedCharEnum>::Scalar, unsigned char>  // e.g. arm linux
-    >::value, "char should be cast to either signed char or unsigned char");
     static_assert(
-        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 2 ||
-        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 4
-    , "wchar_t should be either 16 bits (Windows) or 32 (everywhere else)");
-    static_assert(py::detail::all_of<
-        std::is_same<py::enum_<ScopedChar32Enum>::Scalar, std::uint_least32_t>,
-        std::is_same<py::enum_<ScopedChar16Enum>::Scalar, std::uint_least16_t>
-    >::value, "char32_t, char16_t (and char8_t)'s size, signedness, and alignment is determined");
+        py::detail::any_of<
+            std::is_same<py::enum_<ScopedCharEnum>::Scalar, signed char>,  // e.g. gcc on x86
+            std::is_same<py::enum_<ScopedCharEnum>::Scalar, unsigned char> // e.g. arm linux
+            >::value,
+        "char should be cast to either signed char or unsigned char");
+    static_assert(sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 2
+                      || sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 4,
+                  "wchar_t should be either 16 bits (Windows) or 32 (everywhere else)");
+    static_assert(
+        py::detail::all_of<
+            std::is_same<py::enum_<ScopedChar32Enum>::Scalar, std::uint_least32_t>,
+            std::is_same<py::enum_<ScopedChar16Enum>::Scalar, std::uint_least16_t>>::value,
+        "char32_t, char16_t (and char8_t)'s size, signedness, and alignment is determined");
 #if defined(PYBIND11_HAS_U8STRING)
     enum class ScopedChar8Enum : char8_t { Zero, Positive };
     static_assert(std::is_same<py::enum_<ScopedChar8Enum>::Scalar, unsigned char>::value);
diff --git a/tests/test_eval.cpp b/tests/test_eval.cpp
index e40dde70ec..cd2903f0ab 100644
--- a/tests/test_eval.cpp
+++ b/tests/test_eval.cpp
@@ -7,10 +7,10 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-
 #include <pybind11/eval.h>
 
 #include "pybind11_tests.h"
+
 #include <utility>
 
 TEST_SUBMODULE(eval_, m) {
@@ -20,16 +20,13 @@ TEST_SUBMODULE(eval_, m) {
 
     m.def("test_eval_statements", [global]() {
         auto local = py::dict();
-        local["call_test"] = py::cpp_function([&]() -> int {
-            return 42;
-        });
+        local["call_test"] = py::cpp_function([&]() -> int { return 42; });
 
         // Regular string literal
-        py::exec(
-            "message = 'Hello World!'\n"
-            "x = call_test()",
-            global, local
-        );
+        py::exec("message = 'Hello World!'\n"
+                 "x = call_test()",
+                 global,
+                 local);
 
         // Multi-line raw string literal
         py::exec(R"(
@@ -37,8 +34,9 @@ TEST_SUBMODULE(eval_, m) {
                 print(message)
             else:
                 raise RuntimeError
-            )", global, local
-        );
+            )",
+                 global,
+                 local);
         auto x = local["x"].cast<int>();
 
         return x == 42;
@@ -53,9 +51,7 @@ TEST_SUBMODULE(eval_, m) {
 
     m.def("test_eval_single_statement", []() {
         auto local = py::dict();
-        local["call_test"] = py::cpp_function([&]() -> int {
-            return 42;
-        });
+        local["call_test"] = py::cpp_function([&]() -> int { return 42; });
 
         auto result = py::eval<py::eval_single_statement>("x = call_test()", py::dict(), local);
         auto x = local["x"].cast<int>();
@@ -114,7 +110,9 @@ TEST_SUBMODULE(eval_, m) {
 
             def func_local():
                 return local_value
-            )", global, local);
+            )",
+                 global,
+                 local);
         return std::make_pair(global, local);
     });
 }
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index ab7dfbf691..f6f93611a2 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -9,8 +9,8 @@
 #include "test_exceptions.h"
 
 #include "local_bindings.h"
-
 #include "pybind11_tests.h"
+
 #include <exception>
 #include <stdexcept>
 #include <utility>
@@ -18,8 +18,9 @@
 // A type that should be raised as an exception in Python
 class MyException : public std::exception {
 public:
-    explicit MyException(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -27,8 +28,9 @@ class MyException : public std::exception {
 // A type that should be translated to a standard Python exception
 class MyException2 : public std::exception {
 public:
-    explicit MyException2(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException2(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -36,13 +38,13 @@ class MyException2 : public std::exception {
 // A type that is not derived from std::exception (and is thus unknown)
 class MyException3 {
 public:
-    explicit MyException3(const char * m) : message{m} {}
-    virtual const char * what() const noexcept {return message.c_str();}
+    explicit MyException3(const char *m) : message{m} {}
+    virtual const char *what() const noexcept { return message.c_str(); }
     // Rule of 5 BEGIN: to preempt compiler warnings.
-    MyException3(const MyException3&) = default;
-    MyException3(MyException3&&) = default;
-    MyException3& operator=(const MyException3&) = default;
-    MyException3& operator=(MyException3&&) = default;
+    MyException3(const MyException3 &) = default;
+    MyException3(MyException3 &&) = default;
+    MyException3 &operator=(const MyException3 &) = default;
+    MyException3 &operator=(MyException3 &&) = default;
     virtual ~MyException3() = default;
     // Rule of 5 END.
 private:
@@ -53,13 +55,13 @@ class MyException3 {
 // and delegated to its exception translator
 class MyException4 : public std::exception {
 public:
-    explicit MyException4(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException4(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
 
-
 // Like the above, but declared via the helper function
 class MyException5 : public std::logic_error {
 public:
@@ -71,17 +73,16 @@ class MyException5_1 : public MyException5 {
     using MyException5::MyException5;
 };
 
-
 // Exception that will be caught via the module local translator.
 class MyException6 : public std::exception {
 public:
-    explicit MyException6(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException6(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
 
-
 struct PythonCallInDestructor {
     explicit PythonCallInDestructor(const py::dict &d) : d(d) {}
     ~PythonCallInDestructor() { d["good"] = true; }
@@ -89,8 +90,6 @@ struct PythonCallInDestructor {
     py::dict d;
 };
 
-
-
 struct PythonAlreadySetInDestructor {
     explicit PythonAlreadySetInDestructor(const py::str &s) : s(s) {}
     ~PythonAlreadySetInDestructor() {
@@ -98,8 +97,7 @@ struct PythonAlreadySetInDestructor {
         try {
             // Assign to a py::object to force read access of nonexistent dict entry
             py::object o = foo["bar"];
-        }
-        catch (py::error_already_set& ex) {
+        } catch (py::error_already_set &ex) {
             ex.discard_as_unraisable(s);
         }
     }
@@ -108,9 +106,8 @@ struct PythonAlreadySetInDestructor {
 };
 
 TEST_SUBMODULE(exceptions, m) {
-    m.def("throw_std_exception", []() {
-        throw std::runtime_error("This exception was intentionally thrown.");
-    });
+    m.def("throw_std_exception",
+          []() { throw std::runtime_error("This exception was intentionally thrown."); });
 
     // make a new custom exception and use it as a translation target
     static py::exception<MyException> ex(m, "MyException");
@@ -157,26 +154,30 @@ TEST_SUBMODULE(exceptions, m) {
     // A slightly more complicated one that declares MyException5_1 as a subclass of MyException5
     py::register_exception<MyException5_1>(m, "MyException5_1", ex5.ptr());
 
-    //py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException")
+    // py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException")
 
     py::register_local_exception_translator([](std::exception_ptr p) {
-      try {
-          if (p) {
-            std::rethrow_exception(p);
-          }
-      } catch (const MyException6 &e) {
-        PyErr_SetString(PyExc_RuntimeError, e.what());
-      }
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const MyException6 &e) {
+            PyErr_SetString(PyExc_RuntimeError, e.what());
+        }
     });
 
     m.def("throws1", []() { throw MyException("this error should go to a custom type"); });
-    m.def("throws2", []() { throw MyException2("this error should go to a standard Python exception"); });
+    m.def("throws2",
+          []() { throw MyException2("this error should go to a standard Python exception"); });
     m.def("throws3", []() { throw MyException3("this error cannot be translated"); });
     m.def("throws4", []() { throw MyException4("this error is rethrown"); });
-    m.def("throws5", []() { throw MyException5("this is a helper-defined translated exception"); });
+    m.def("throws5",
+          []() { throw MyException5("this is a helper-defined translated exception"); });
     m.def("throws5_1", []() { throw MyException5_1("MyException5 subclass"); });
     m.def("throws6", []() { throw MyException6("MyException6 only handled in this module"); });
-    m.def("throws_logic_error", []() { throw std::logic_error("this error should fall through to the standard handler"); });
+    m.def("throws_logic_error", []() {
+        throw std::logic_error("this error should fall through to the standard handler");
+    });
     m.def("throws_overflow_error", []() { throw std::overflow_error(""); });
     m.def("throws_local_error", []() { throw LocalException("never caught"); });
     m.def("throws_local_simple_error", []() { throw LocalSimpleException("this mod"); });
@@ -185,8 +186,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             // Assign to a py::object to force read access of nonexistent dict entry
             py::object o = foo["bar"];
-        }
-        catch (py::error_already_set& ex) {
+        } catch (py::error_already_set &ex) {
             if (!ex.matches(PyExc_KeyError)) {
                 throw;
             }
@@ -199,8 +199,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             // Assign to a py::object to force read access of nonexistent dict entry
             py::object o = foo["bar"];
-        }
-        catch (py::error_already_set &ex) {
+        } catch (py::error_already_set &ex) {
             if (!ex.matches(PyExc_Exception)) {
                 throw;
             }
@@ -212,8 +211,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             // On Python >= 3.6, this raises a ModuleNotFoundError, a subclass of ImportError
             py::module_::import("nonexistent");
-        }
-        catch (py::error_already_set &ex) {
+        } catch (py::error_already_set &ex) {
             if (!ex.matches(PyExc_ImportError)) {
                 throw;
             }
@@ -228,10 +226,9 @@ TEST_SUBMODULE(exceptions, m) {
         }
         try {
             throw py::error_already_set();
-        } catch (const std::runtime_error& e) {
-            if ((err && e.what() != std::string("ValueError: foo")) ||
-                (!err && e.what() != std::string("Unknown internal error occurred")))
-            {
+        } catch (const std::runtime_error &e) {
+            if ((err && e.what() != std::string("ValueError: foo"))
+                || (!err && e.what() != std::string("Unknown internal error occurred"))) {
                 PyErr_Clear();
                 throw std::runtime_error("error message mismatch");
             }
@@ -249,7 +246,7 @@ TEST_SUBMODULE(exceptions, m) {
             PythonCallInDestructor set_dict_in_destructor(d);
             PyErr_SetString(PyExc_ValueError, "foo");
             throw py::error_already_set();
-        } catch (const py::error_already_set&) {
+        } catch (const py::error_already_set &) {
             retval = true;
         }
         return retval;
@@ -275,7 +272,7 @@ TEST_SUBMODULE(exceptions, m) {
           });
 
     // Test repr that cannot be displayed
-    m.def("simple_bool_passthrough", [](bool x) {return x;});
+    m.def("simple_bool_passthrough", [](bool x) { return x; });
 
     m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
 
@@ -291,7 +288,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             PyErr_SetString(PyExc_ValueError, "inner");
             throw py::error_already_set();
-        } catch (py::error_already_set& e) {
+        } catch (py::error_already_set &e) {
             py::raise_from(e, PyExc_ValueError, "outer");
             throw py::error_already_set();
         }
diff --git a/tests/test_exceptions.h b/tests/test_exceptions.h
index 9d428312eb..03684b89fa 100644
--- a/tests/test_exceptions.h
+++ b/tests/test_exceptions.h
@@ -1,5 +1,6 @@
 #pragma once
 #include "pybind11_tests.h"
+
 #include <stdexcept>
 
 // shared exceptions for cross_module_tests
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 455c75d536..81e32f5abe 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -10,6 +10,7 @@
 
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
+
 #include <cmath>
 #include <new>
 #include <utility>
@@ -87,6 +88,7 @@ class TestFactory6 {
 protected:
     int value;
     bool alias = false;
+
 public:
     explicit TestFactory6(int i) : value{i} { print_created(this, i); }
     TestFactory6(TestFactory6 &&f) noexcept {
@@ -133,6 +135,7 @@ class TestFactory7 {
 protected:
     int value;
     bool alias = false;
+
 public:
     explicit TestFactory7(int i) : value{i} { print_created(this, i); }
     TestFactory7(TestFactory7 &&f) noexcept {
@@ -166,14 +169,15 @@ class PyTF7 : public TestFactory7 {
     int get() override { PYBIND11_OVERRIDE(int, TestFactory7, get, /*no args*/); }
 };
 
-
 class TestFactoryHelper {
 public:
     // Non-movable, non-copyable type:
     // Return via pointer:
     static TestFactory1 *construct1() { return new TestFactory1(); }
     // Holder:
-    static std::unique_ptr<TestFactory1> construct1(int a) { return std::unique_ptr<TestFactory1>(new TestFactory1(a)); }
+    static std::unique_ptr<TestFactory1> construct1(int a) {
+        return std::unique_ptr<TestFactory1>(new TestFactory1(a));
+    }
     // pointer again
     static TestFactory1 *construct1_string(std::string a) {
         return new TestFactory1(std::move(a));
@@ -183,7 +187,9 @@ class TestFactoryHelper {
     // pointer:
     static TestFactory2 *construct2() { return new TestFactory2(); }
     // holder:
-    static std::unique_ptr<TestFactory2> construct2(int a) { return std::unique_ptr<TestFactory2>(new TestFactory2(a)); }
+    static std::unique_ptr<TestFactory2> construct2(int a) {
+        return std::unique_ptr<TestFactory2>(new TestFactory2(a));
+    }
     // by value moving:
     static TestFactory2 construct2(std::string a) { return TestFactory2(std::move(a)); }
 
@@ -191,16 +197,18 @@ class TestFactoryHelper {
     // pointer:
     static TestFactory3 *construct3() { return new TestFactory3(); }
     // holder:
-    static std::shared_ptr<TestFactory3> construct3(int a) { return std::shared_ptr<TestFactory3>(new TestFactory3(a)); }
+    static std::shared_ptr<TestFactory3> construct3(int a) {
+        return std::shared_ptr<TestFactory3>(new TestFactory3(a));
+    }
 };
 
 TEST_SUBMODULE(factory_constructors, m) {
 
     // Define various trivial types to allow simpler overload resolution:
     py::module_ m_tag = m.def_submodule("tag");
-#define MAKE_TAG_TYPE(Name) \
-    struct Name##_tag {}; \
-    py::class_<Name##_tag>(m_tag, #Name "_tag").def(py::init<>()); \
+#define MAKE_TAG_TYPE(Name)                                                                       \
+    struct Name##_tag {};                                                                         \
+    py::class_<Name##_tag>(m_tag, #Name "_tag").def(py::init<>());                                \
     m_tag.attr(#Name) = py::cast(Name##_tag{})
     MAKE_TAG_TYPE(pointer);
     MAKE_TAG_TYPE(unique_ptr);
@@ -223,9 +231,9 @@ TEST_SUBMODULE(factory_constructors, m) {
         .def(py::init([](unique_ptr_tag, int v) { return TestFactoryHelper::construct1(v); }))
         .def(py::init(&TestFactoryHelper::construct1_string)) // raw function pointer
         .def(py::init([](pointer_tag) { return TestFactoryHelper::construct1(); }))
-        .def(py::init([](py::handle, int v, py::handle) { return TestFactoryHelper::construct1(v); }))
-        .def_readwrite("value", &TestFactory1::value)
-        ;
+        .def(py::init(
+            [](py::handle, int v, py::handle) { return TestFactoryHelper::construct1(v); }))
+        .def_readwrite("value", &TestFactory1::value);
     py::class_<TestFactory2>(m, "TestFactory2")
         .def(py::init([](pointer_tag, int v) { return TestFactoryHelper::construct2(v); }))
         .def(py::init([](unique_ptr_tag, std::string v) {
@@ -236,7 +244,10 @@ TEST_SUBMODULE(factory_constructors, m) {
 
     // Stateful & reused:
     int c = 1;
-    auto c4a = [c](pointer_tag, TF4_tag, int a) { (void) c; return new TestFactory4(a);};
+    auto c4a = [c](pointer_tag, TF4_tag, int a) {
+        (void) c;
+        return new TestFactory4(a);
+    };
 
     // test_init_factory_basic, test_init_factory_casting
     py::class_<TestFactory3, std::shared_ptr<TestFactory3>> pyTestFactory3(m, "TestFactory3");
@@ -253,16 +264,17 @@ TEST_SUBMODULE(factory_constructors, m) {
         .def(py::init(c4a)) // derived ptr
         .def(py::init([](pointer_tag, TF5_tag, int a) { return new TestFactory5(a); }))
         // derived shared ptr:
-        .def(py::init([](shared_ptr_tag, TF4_tag, int a) { return std::make_shared<TestFactory4>(a); }))
-        .def(py::init([](shared_ptr_tag, TF5_tag, int a) { return std::make_shared<TestFactory5>(a); }))
+        .def(py::init(
+            [](shared_ptr_tag, TF4_tag, int a) { return std::make_shared<TestFactory4>(a); }))
+        .def(py::init(
+            [](shared_ptr_tag, TF5_tag, int a) { return std::make_shared<TestFactory5>(a); }))
 
         // Returns nullptr:
         .def(py::init([](null_ptr_tag) { return (TestFactory3 *) nullptr; }))
         .def(py::init([](null_unique_ptr_tag) { return std::unique_ptr<TestFactory3>(); }))
         .def(py::init([](null_shared_ptr_tag) { return std::shared_ptr<TestFactory3>(); }))
 
-        .def_readwrite("value", &TestFactory3::value)
-        ;
+        .def_readwrite("value", &TestFactory3::value);
 
     // test_init_factory_casting
     py::class_<TestFactory4, TestFactory3, std::shared_ptr<TestFactory4>>(m, "TestFactory4")
@@ -346,9 +358,7 @@ TEST_SUBMODULE(factory_constructors, m) {
     py::class_<NoPlacementNew>(m, "NoPlacementNew")
         .def(py::init<int>())
         .def(py::init([]() { return new NoPlacementNew(100); }))
-        .def_readwrite("i", &NoPlacementNew::i)
-        ;
-
+        .def_readwrite("i", &NoPlacementNew::i);
 
     // test_reallocations
     // Class that has verbose operator_new/operator_delete calls
@@ -358,23 +368,36 @@ TEST_SUBMODULE(factory_constructors, m) {
         explicit NoisyAlloc(double d) { py::print(py::str("NoisyAlloc(double {})").format(d)); }
         ~NoisyAlloc() { py::print("~NoisyAlloc()"); }
 
-        static void *operator new(size_t s) { py::print("noisy new"); return ::operator new(s); }
-        static void *operator new(size_t, void *p) { py::print("noisy placement new"); return p; }
-        static void operator delete(void *p, size_t) { py::print("noisy delete"); ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("noisy new");
+            return ::operator new(s);
+        }
+        static void *operator new(size_t, void *p) {
+            py::print("noisy placement new");
+            return p;
+        }
+        static void operator delete(void *p, size_t) {
+            py::print("noisy delete");
+            ::operator delete(p);
+        }
         static void operator delete(void *, void *) { py::print("noisy placement delete"); }
 #if defined(_MSC_VER) && _MSC_VER < 1910
         // MSVC 2015 bug: the above "noisy delete" isn't invoked (fixed in MSVC 2017)
-        static void operator delete(void *p) { py::print("noisy delete"); ::operator delete(p); }
+        static void operator delete(void *p) {
+            py::print("noisy delete");
+            ::operator delete(p);
+        }
 #endif
     };
 
-
     py::class_<NoisyAlloc> pyNoisyAlloc(m, "NoisyAlloc");
-        // Since these overloads have the same number of arguments, the dispatcher will try each of
-        // them until the arguments convert.  Thus we can get a pre-allocation here when passing a
-        // single non-integer:
+    // Since these overloads have the same number of arguments, the dispatcher will try each of
+    // them until the arguments convert.  Thus we can get a pre-allocation here when passing a
+    // single non-integer:
     ignoreOldStyleInitWarnings([&pyNoisyAlloc]() {
-        pyNoisyAlloc.def("__init__", [](NoisyAlloc *a, int i) { new (a) NoisyAlloc(i); }); // Regular constructor, runs first, requires preallocation
+        pyNoisyAlloc.def("__init__", [](NoisyAlloc *a, int i) {
+            new (a) NoisyAlloc(i);
+        }); // Regular constructor, runs first, requires preallocation
     });
 
     pyNoisyAlloc.def(py::init([](double d) { return new NoisyAlloc(d); }));
@@ -385,7 +408,8 @@ TEST_SUBMODULE(factory_constructors, m) {
     pyNoisyAlloc.def(py::init([](double d, int) { return NoisyAlloc(d); }));
     // Old-style placement new init; requires preallocation
     ignoreOldStyleInitWarnings([&pyNoisyAlloc]() {
-        pyNoisyAlloc.def("__init__", [](NoisyAlloc &a, double d, double) { new (&a) NoisyAlloc(d); });
+        pyNoisyAlloc.def("__init__",
+                         [](NoisyAlloc &a, double d, double) { new (&a) NoisyAlloc(d); });
     });
     // Requires deallocation of previous overload preallocated value:
     pyNoisyAlloc.def(py::init([](int i, double) { return new NoisyAlloc(i); }));
@@ -395,7 +419,8 @@ TEST_SUBMODULE(factory_constructors, m) {
             "__init__", [](NoisyAlloc &a, int i, const std::string &) { new (&a) NoisyAlloc(i); });
     });
 
-    // static_assert testing (the following def's should all fail with appropriate compilation errors):
+    // static_assert testing (the following def's should all fail with appropriate compilation
+    // errors):
 #if 0
     struct BadF1Base {};
     struct BadF1 : BadF1Base {};
diff --git a/tests/test_gil_scoped.cpp b/tests/test_gil_scoped.cpp
index b261085c88..97efdc1616 100644
--- a/tests/test_gil_scoped.cpp
+++ b/tests/test_gil_scoped.cpp
@@ -7,43 +7,41 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/functional.h>
 
+#include "pybind11_tests.h"
 
-class VirtClass  {
+class VirtClass {
 public:
     virtual ~VirtClass() = default;
     VirtClass() = default;
-    VirtClass(const VirtClass&) = delete;
+    VirtClass(const VirtClass &) = delete;
     virtual void virtual_func() {}
     virtual void pure_virtual_func() = 0;
 };
 
 class PyVirtClass : public VirtClass {
-    void virtual_func() override {
-        PYBIND11_OVERRIDE(void, VirtClass, virtual_func,);
-    }
+    void virtual_func() override { PYBIND11_OVERRIDE(void, VirtClass, virtual_func, ); }
     void pure_virtual_func() override {
-        PYBIND11_OVERRIDE_PURE(void, VirtClass, pure_virtual_func,);
+        PYBIND11_OVERRIDE_PURE(void, VirtClass, pure_virtual_func, );
     }
 };
 
 TEST_SUBMODULE(gil_scoped, m) {
-  py::class_<VirtClass, PyVirtClass>(m, "VirtClass")
-      .def(py::init<>())
-      .def("virtual_func", &VirtClass::virtual_func)
-      .def("pure_virtual_func", &VirtClass::pure_virtual_func);
-
-  m.def("test_callback_py_obj", [](py::object &func) { func(); });
-  m.def("test_callback_std_func", [](const std::function<void()> &func) { func(); });
-  m.def("test_callback_virtual_func", [](VirtClass &virt) { virt.virtual_func(); });
-  m.def("test_callback_pure_virtual_func", [](VirtClass &virt) { virt.pure_virtual_func(); });
-  m.def("test_cross_module_gil", []() {
-      auto cm = py::module_::import("cross_module_gil_utils");
-      auto gil_acquire
-          = reinterpret_cast<void (*)()>(PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
-      py::gil_scoped_release gil_release;
-      gil_acquire();
-  });
+    py::class_<VirtClass, PyVirtClass>(m, "VirtClass")
+        .def(py::init<>())
+        .def("virtual_func", &VirtClass::virtual_func)
+        .def("pure_virtual_func", &VirtClass::pure_virtual_func);
+
+    m.def("test_callback_py_obj", [](py::object &func) { func(); });
+    m.def("test_callback_std_func", [](const std::function<void()> &func) { func(); });
+    m.def("test_callback_virtual_func", [](VirtClass &virt) { virt.virtual_func(); });
+    m.def("test_callback_pure_virtual_func", [](VirtClass &virt) { virt.pure_virtual_func(); });
+    m.def("test_cross_module_gil", []() {
+        auto cm = py::module_::import("cross_module_gil_utils");
+        auto gil_acquire = reinterpret_cast<void (*)()>(
+            PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
+        py::gil_scoped_release gil_release;
+        gil_acquire();
+    });
 }
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index ef54b0a1c5..dd0e19e0bd 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -7,12 +7,14 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#if defined(_MSC_VER) && _MSC_VER < 1910  // VS 2015's MSVC
-#  pragma warning(disable: 4702) // unreachable code in system header (xatomic.h(382))
+#if defined(_MSC_VER) && _MSC_VER < 1910 // VS 2015's MSVC
+#    pragma warning(disable : 4702)      // unreachable code in system header (xatomic.h(382))
 #endif
 
 #include <pybind11/iostream.h>
+
 #include "pybind11_tests.h"
+
 #include <atomic>
 #include <iostream>
 #include <mutex>
@@ -51,13 +53,12 @@ struct TestThread {
                     std::cout << "x" << std::flush;
                 }
                 std::this_thread::sleep_for(std::chrono::microseconds(50));
-            } };
+            }
+        };
         t_ = new std::thread(std::move(thread_f));
     }
 
-    ~TestThread() {
-        delete t_;
-    }
+    ~TestThread() { delete t_; }
 
     void stop() { stop_ = true; }
 
@@ -75,7 +76,6 @@ struct TestThread {
     std::atomic<bool> stop_;
 };
 
-
 TEST_SUBMODULE(iostream, m) {
 
     add_ostream_redirect(m);
@@ -92,9 +92,11 @@ TEST_SUBMODULE(iostream, m) {
         std::cout << msg << std::flush;
     });
 
-    m.def("guard_output", &noisy_function,
-            py::call_guard<py::scoped_ostream_redirect>(),
-            py::arg("msg"), py::arg("flush")=true);
+    m.def("guard_output",
+          &noisy_function,
+          py::call_guard<py::scoped_ostream_redirect>(),
+          py::arg("msg"),
+          py::arg("flush") = true);
 
     m.def("captured_err", [](const std::string &msg) {
         py::scoped_ostream_redirect redir(std::cerr, py::module_::import("sys").attr("stderr"));
@@ -103,9 +105,11 @@ TEST_SUBMODULE(iostream, m) {
 
     m.def("noisy_function", &noisy_function, py::arg("msg"), py::arg("flush") = true);
 
-    m.def("dual_guard", &noisy_funct_dual,
-            py::call_guard<py::scoped_ostream_redirect, py::scoped_estream_redirect>(),
-            py::arg("msg"), py::arg("emsg"));
+    m.def("dual_guard",
+          &noisy_funct_dual,
+          py::call_guard<py::scoped_ostream_redirect, py::scoped_estream_redirect>(),
+          py::arg("msg"),
+          py::arg("emsg"));
 
     m.def("raw_output", [](const std::string &msg) { std::cout << msg << std::flush; });
 
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index d09630a8cd..7418afefb4 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -7,39 +7,43 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #include <utility>
 
 TEST_SUBMODULE(kwargs_and_defaults, m) {
-    auto kw_func = [](int x, int y) { return "x=" + std::to_string(x) + ", y=" + std::to_string(y); };
+    auto kw_func
+        = [](int x, int y) { return "x=" + std::to_string(x) + ", y=" + std::to_string(y); };
 
     // test_named_arguments
     m.def("kw_func0", kw_func);
     m.def("kw_func1", kw_func, py::arg("x"), py::arg("y"));
     m.def("kw_func2", kw_func, py::arg("x") = 100, py::arg("y") = 200);
-    m.def("kw_func3", [](const char *) { }, py::arg("data") = std::string("Hello world!"));
+    m.def(
+        "kw_func3", [](const char *) {}, py::arg("data") = std::string("Hello world!"));
 
     /* A fancier default argument */
     std::vector<int> list{{13, 17}};
-    m.def("kw_func4", [](const std::vector<int> &entries) {
-        std::string ret = "{";
-        for (int i : entries) {
-            ret += std::to_string(i) + " ";
-        }
-        ret.back() = '}';
-        return ret;
-    }, py::arg("myList") = list);
+    m.def(
+        "kw_func4",
+        [](const std::vector<int> &entries) {
+            std::string ret = "{";
+            for (int i : entries) {
+                ret += std::to_string(i) + " ";
+            }
+            ret.back() = '}';
+            return ret;
+        },
+        py::arg("myList") = list);
 
-    m.def("kw_func_udl", kw_func, "x"_a, "y"_a=300);
-    m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a=0);
+    m.def("kw_func_udl", kw_func, "x"_a, "y"_a = 300);
+    m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a = 0);
 
     // test_args_and_kwargs
-    m.def("args_function", [](py::args args) -> py::tuple {
-        return std::move(args);
-    });
+    m.def("args_function", [](py::args args) -> py::tuple { return std::move(args); });
     m.def("args_kwargs_function", [](const py::args &args, const py::kwargs &kwargs) {
         return py::make_tuple(args, kwargs);
     });
@@ -54,35 +58,60 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     };
     m.def("mixed_plus_args_kwargs", mixed_plus_both);
 
-    m.def("mixed_plus_args_kwargs_defaults", mixed_plus_both,
-            py::arg("i") = 1, py::arg("j") = 3.14159);
-
-    m.def("args_kwonly",
-            [](int i, double j, const py::args &args, int z) { return py::make_tuple(i, j, args, z); },
-            "i"_a, "j"_a, "z"_a);
-    m.def("args_kwonly_kwargs",
-            [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
-                return py::make_tuple(i, j, args, z, kwargs); },
-            "i"_a, "j"_a, py::kw_only{}, "z"_a);
-    m.def("args_kwonly_kwargs_defaults",
-            [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
-                return py::make_tuple(i, j, args, z, kwargs); },
-            "i"_a = 1, "j"_a = 3.14159, "z"_a = 42);
-    m.def("args_kwonly_full_monty",
-            [](int h, int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
-                return py::make_tuple(h, i, j, args, z, kwargs); },
-            py::arg() = 1, py::arg() = 2, py::pos_only{}, "j"_a = 3.14159, "z"_a = 42);
-
-
-    // test_args_refcount
-    // PyPy needs a garbage collection to get the reference count values to match CPython's behaviour
-    #ifdef PYPY_VERSION
-    #define GC_IF_NEEDED ConstructorStats::gc()
-    #else
-    #define GC_IF_NEEDED
-    #endif
-    m.def("arg_refcount_h", [](py::handle h) { GC_IF_NEEDED; return h.ref_count(); });
-    m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) { GC_IF_NEEDED; return h.ref_count(); });
+    m.def("mixed_plus_args_kwargs_defaults",
+          mixed_plus_both,
+          py::arg("i") = 1,
+          py::arg("j") = 3.14159);
+
+    m.def(
+        "args_kwonly",
+        [](int i, double j, const py::args &args, int z) { return py::make_tuple(i, j, args, z); },
+        "i"_a,
+        "j"_a,
+        "z"_a);
+    m.def(
+        "args_kwonly_kwargs",
+        [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+            return py::make_tuple(i, j, args, z, kwargs);
+        },
+        "i"_a,
+        "j"_a,
+        py::kw_only{},
+        "z"_a);
+    m.def(
+        "args_kwonly_kwargs_defaults",
+        [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+            return py::make_tuple(i, j, args, z, kwargs);
+        },
+        "i"_a = 1,
+        "j"_a = 3.14159,
+        "z"_a = 42);
+    m.def(
+        "args_kwonly_full_monty",
+        [](int h, int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+            return py::make_tuple(h, i, j, args, z, kwargs);
+        },
+        py::arg() = 1,
+        py::arg() = 2,
+        py::pos_only{},
+        "j"_a = 3.14159,
+        "z"_a = 42);
+
+// test_args_refcount
+// PyPy needs a garbage collection to get the reference count values to match CPython's behaviour
+#ifdef PYPY_VERSION
+#    define GC_IF_NEEDED ConstructorStats::gc()
+#else
+#    define GC_IF_NEEDED
+#endif
+    m.def("arg_refcount_h", [](py::handle h) {
+        GC_IF_NEEDED;
+        return h.ref_count();
+    });
+    m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) {
+        GC_IF_NEEDED;
+        return h.ref_count();
+    });
     m.def("arg_refcount_o", [](const py::object &o) {
         GC_IF_NEEDED;
         return o.ref_count();
@@ -109,23 +138,42 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
 
     // pybind11 won't allow these to be bound: args and kwargs, if present, must be at the end.
     // Uncomment these to test that the static_assert is indeed working:
-//    m.def("bad_args1", [](py::args, int) {});
-//    m.def("bad_args2", [](py::kwargs, int) {});
-//    m.def("bad_args3", [](py::kwargs, py::args) {});
-//    m.def("bad_args4", [](py::args, int, py::kwargs) {});
-//    m.def("bad_args5", [](py::args, py::kwargs, int) {});
-//    m.def("bad_args6", [](py::args, py::args) {});
-//    m.def("bad_args7", [](py::kwargs, py::kwargs) {});
+    //    m.def("bad_args1", [](py::args, int) {});
+    //    m.def("bad_args2", [](py::kwargs, int) {});
+    //    m.def("bad_args3", [](py::kwargs, py::args) {});
+    //    m.def("bad_args4", [](py::args, int, py::kwargs) {});
+    //    m.def("bad_args5", [](py::args, py::kwargs, int) {});
+    //    m.def("bad_args6", [](py::args, py::args) {});
+    //    m.def("bad_args7", [](py::kwargs, py::kwargs) {});
 
     // test_keyword_only_args
-    m.def("kw_only_all", [](int i, int j) { return py::make_tuple(i, j); },
-            py::kw_only(), py::arg("i"), py::arg("j"));
-    m.def("kw_only_some", [](int i, int j, int k) { return py::make_tuple(i, j, k); },
-            py::arg(), py::kw_only(), py::arg("j"), py::arg("k"));
-    m.def("kw_only_with_defaults", [](int i, int j, int k, int z) { return py::make_tuple(i, j, k, z); },
-            py::arg() = 3, "j"_a = 4, py::kw_only(), "k"_a = 5, "z"_a);
-    m.def("kw_only_mixed", [](int i, int j) { return py::make_tuple(i, j); },
-            "i"_a, py::kw_only(), "j"_a);
+    m.def(
+        "kw_only_all",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        py::kw_only(),
+        py::arg("i"),
+        py::arg("j"));
+    m.def(
+        "kw_only_some",
+        [](int i, int j, int k) { return py::make_tuple(i, j, k); },
+        py::arg(),
+        py::kw_only(),
+        py::arg("j"),
+        py::arg("k"));
+    m.def(
+        "kw_only_with_defaults",
+        [](int i, int j, int k, int z) { return py::make_tuple(i, j, k, z); },
+        py::arg() = 3,
+        "j"_a = 4,
+        py::kw_only(),
+        "k"_a = 5,
+        "z"_a);
+    m.def(
+        "kw_only_mixed",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        "i"_a,
+        py::kw_only(),
+        "j"_a);
     m.def(
         "kw_only_plus_more",
         [](int i, int j, int k, const py::kwargs &kwargs) {
@@ -137,31 +185,57 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
         py::arg("k") /* kw-only */);
 
     m.def("register_invalid_kw_only", [](py::module_ m) {
-        m.def("bad_kw_only", [](int i, int j) { return py::make_tuple(i, j); },
-                py::kw_only(), py::arg() /* invalid unnamed argument */, "j"_a);
+        m.def(
+            "bad_kw_only",
+            [](int i, int j) { return py::make_tuple(i, j); },
+            py::kw_only(),
+            py::arg() /* invalid unnamed argument */,
+            "j"_a);
     });
 
     // test_positional_only_args
-    m.def("pos_only_all", [](int i, int j) { return py::make_tuple(i, j); },
-            py::arg("i"), py::arg("j"), py::pos_only());
-    m.def("pos_only_mix", [](int i, int j) { return py::make_tuple(i, j); },
-            py::arg("i"), py::pos_only(), py::arg("j"));
-    m.def("pos_kw_only_mix", [](int i, int j, int k) { return py::make_tuple(i, j, k); },
-            py::arg("i"), py::pos_only(), py::arg("j"), py::kw_only(), py::arg("k"));
-    m.def("pos_only_def_mix", [](int i, int j, int k) { return py::make_tuple(i, j, k); },
-            py::arg("i"), py::arg("j") = 2, py::pos_only(), py::arg("k") = 3);
-
+    m.def(
+        "pos_only_all",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        py::arg("i"),
+        py::arg("j"),
+        py::pos_only());
+    m.def(
+        "pos_only_mix",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        py::arg("i"),
+        py::pos_only(),
+        py::arg("j"));
+    m.def(
+        "pos_kw_only_mix",
+        [](int i, int j, int k) { return py::make_tuple(i, j, k); },
+        py::arg("i"),
+        py::pos_only(),
+        py::arg("j"),
+        py::kw_only(),
+        py::arg("k"));
+    m.def(
+        "pos_only_def_mix",
+        [](int i, int j, int k) { return py::make_tuple(i, j, k); },
+        py::arg("i"),
+        py::arg("j") = 2,
+        py::pos_only(),
+        py::arg("k") = 3);
 
     // These should fail to compile:
 #ifdef PYBIND11_NEVER_DEFINED_EVER
     // argument annotations are required when using kw_only
-    m.def("bad_kw_only1", [](int) {}, py::kw_only());
+    m.def(
+        "bad_kw_only1", [](int) {}, py::kw_only());
     // can't specify both `py::kw_only` and a `py::args` argument
-    m.def("bad_kw_only2", [](int i, py::args) {}, py::kw_only(), "i"_a);
+    m.def(
+        "bad_kw_only2", [](int i, py::args) {}, py::kw_only(), "i"_a);
 #endif
 
     // test_function_signatures (along with most of the above)
-    struct KWClass { void foo(int, float) {} };
+    struct KWClass {
+        void foo(int, float) {}
+    };
     py::class_<KWClass>(m, "KWClass")
         .def("foo0", &KWClass::foo)
         .def("foo1", &KWClass::foo, "x"_a, "y"_a);
@@ -182,11 +256,18 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
         .def(py::init([](int) { return first_arg_kw_only(); }),
              py::kw_only(), // This being before any args was broken
              py::arg("i") = 0)
-        .def("method", [](first_arg_kw_only&, int, int) {},
-             py::kw_only(), // and likewise here
-             py::arg("i") = 1, py::arg("j") = 2)
+        .def(
+            "method",
+            [](first_arg_kw_only &, int, int) {},
+            py::kw_only(), // and likewise here
+            py::arg("i") = 1,
+            py::arg("j") = 2)
         // Closely related: pos_only marker didn't show up properly when it was before any other
         // arguments (although that is fairly useless in practice).
-        .def("pos_only", [](first_arg_kw_only&, int, int) {},
-                py::pos_only{}, py::arg("i"), py::arg("j"));
+        .def(
+            "pos_only",
+            [](first_arg_kw_only &, int, int) {},
+            py::pos_only{},
+            py::arg("i"),
+            py::arg("j"));
 }
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index 0fb3ecc19f..1373677447 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -8,12 +8,12 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "local_bindings.h"
-
 #include <pybind11/stl.h>
 #include <pybind11/stl_bind.h>
 
+#include "local_bindings.h"
+#include "pybind11_tests.h"
+
 #include <numeric>
 #include <utility>
 
@@ -24,9 +24,9 @@ TEST_SUBMODULE(local_bindings, m) {
 
     // test_local_bindings
     // Register a class with py::module_local:
-    bind_local<LocalType, -1>(m, "LocalType", py::module_local())
-        .def("get3", [](LocalType &t) { return t.i + 3; })
-        ;
+    bind_local<LocalType, -1>(m, "LocalType", py::module_local()).def("get3", [](LocalType &t) {
+        return t.i + 3;
+    });
 
     m.def("local_value", [](LocalType &l) { return l.i; });
 
@@ -35,14 +35,14 @@ TEST_SUBMODULE(local_bindings, m) {
     // one, in pybind11_cross_module_tests.cpp, is designed to fail):
     bind_local<NonLocalType, 0>(m, "NonLocalType")
         .def(py::init<int>())
-        .def("get", [](LocalType &i) { return i.i; })
-        ;
+        .def("get", [](LocalType &i) { return i.i; });
 
     // test_duplicate_local
-    // py::module_local declarations should be visible across compilation units that get linked together;
-    // this tries to register a duplicate local.  It depends on a definition in test_class.cpp and
-    // should raise a runtime error from the duplicate definition attempt.  If test_class isn't
-    // available it *also* throws a runtime error (with "test_class not enabled" as value).
+    // py::module_local declarations should be visible across compilation units that get linked
+    // together; this tries to register a duplicate local.  It depends on a definition in
+    // test_class.cpp and should raise a runtime error from the duplicate definition attempt.  If
+    // test_class isn't available it *also* throws a runtime error (with "test_class not enabled"
+    // as value).
     m.def("register_local_external", [m]() {
         auto main = py::module_::import("pybind11_tests");
         if (py::hasattr(main, "class_")) {
@@ -79,12 +79,12 @@ TEST_SUBMODULE(local_bindings, m) {
     m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); });
 
     // test_internal_locals_differ
-    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
+    m.def("local_cpp_types_addr",
+          []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
 
     // test_stl_caster_vs_stl_bind
-    m.def("load_vector_via_caster", [](std::vector<int> v) {
-        return std::accumulate(v.begin(), v.end(), 0);
-    });
+    m.def("load_vector_via_caster",
+          [](std::vector<int> v) { return std::accumulate(v.begin(), v.end(), 0); });
 
     // test_cross_module_calls
     m.def("return_self", [](LocalVec *v) { return v; });
@@ -94,11 +94,9 @@ TEST_SUBMODULE(local_bindings, m) {
     public:
         explicit Cat(std::string name) : Pet(std::move(name)) {}
     };
-    py::class_<pets::Pet>(m, "Pet", py::module_local())
-        .def("get_name", &pets::Pet::name);
+    py::class_<pets::Pet>(m, "Pet", py::module_local()).def("get_name", &pets::Pet::name);
     // Binding for local extending class:
-    py::class_<Cat, pets::Pet>(m, "Cat")
-        .def(py::init<std::string>());
+    py::class_<Cat, pets::Pet>(m, "Cat").def(py::init<std::string>());
     m.def("pet_name", [](pets::Pet &p) { return p.name(); });
 
     py::class_<MixGL>(m, "MixGL").def(py::init<int>());
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 9e55452dec..10515e26f9 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -8,8 +8,8 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 
 #if !defined(PYBIND11_OVERLOAD_CAST)
 template <typename... Args>
@@ -27,7 +27,10 @@ class ExampleMandA {
 
     std::string toString() const { return "ExampleMandA[value=" + std::to_string(value) + "]"; }
 
-    void operator=(const ExampleMandA &e) { print_copy_assigned(this); value = e.value; }
+    void operator=(const ExampleMandA &e) {
+        print_copy_assigned(this);
+        value = e.value;
+    }
     void operator=(ExampleMandA &&e) noexcept {
         print_move_assigned(this);
         value = e.value;
@@ -40,37 +43,37 @@ class ExampleMandA {
     void add4(ExampleMandA *other) { value += other->value; }       // passing by pointer
     void add5(const ExampleMandA *other) { value += other->value; } // passing by const pointer
 
-    void add6(int other) { value += other; }                        // passing by value
-    void add7(int &other) { value += other; }                       // passing by reference
-    void add8(const int &other) { value += other; }                 // passing by const reference
+    void add6(int other) { value += other; }        // passing by value
+    void add7(int &other) { value += other; }       // passing by reference
+    void add8(const int &other) { value += other; } // passing by const reference
     // NOLINTNEXTLINE(readability-non-const-parameter) Deliberately non-const for testing
-    void add9(int *other) { value += *other; }                      // passing by pointer
-    void add10(const int *other) { value += *other; }               // passing by const pointer
-
-    void consume_str(std::string&&) {}
-
-    ExampleMandA self1() { return *this; }                          // return by value
-    ExampleMandA &self2() { return *this; }                         // return by reference
-    const ExampleMandA &self3() const { return *this; }             // return by const reference
-    ExampleMandA *self4() { return this; }                          // return by pointer
-    const ExampleMandA *self5() const { return this; }              // return by const pointer
-
-    int internal1() const { return value; }                         // return by value
-    int &internal2() { return value; }                              // return by reference
-    const int &internal3() const { return value; }                  // return by const reference
-    int *internal4() { return &value; }                             // return by pointer
-    const int *internal5() { return &value; }                       // return by const pointer
-
-    py::str overloaded()             { return "()"; }
-    py::str overloaded(int)          { return "(int)"; }
-    py::str overloaded(int, float)   { return "(int, float)"; }
-    py::str overloaded(float, int)   { return "(float, int)"; }
-    py::str overloaded(int, int)     { return "(int, int)"; }
+    void add9(int *other) { value += *other; }        // passing by pointer
+    void add10(const int *other) { value += *other; } // passing by const pointer
+
+    void consume_str(std::string &&) {}
+
+    ExampleMandA self1() { return *this; }              // return by value
+    ExampleMandA &self2() { return *this; }             // return by reference
+    const ExampleMandA &self3() const { return *this; } // return by const reference
+    ExampleMandA *self4() { return this; }              // return by pointer
+    const ExampleMandA *self5() const { return this; }  // return by const pointer
+
+    int internal1() const { return value; }        // return by value
+    int &internal2() { return value; }             // return by reference
+    const int &internal3() const { return value; } // return by const reference
+    int *internal4() { return &value; }            // return by pointer
+    const int *internal5() { return &value; }      // return by const pointer
+
+    py::str overloaded() { return "()"; }
+    py::str overloaded(int) { return "(int)"; }
+    py::str overloaded(int, float) { return "(int, float)"; }
+    py::str overloaded(float, int) { return "(float, int)"; }
+    py::str overloaded(int, int) { return "(int, int)"; }
     py::str overloaded(float, float) { return "(float, float)"; }
-    py::str overloaded(int)          const { return "(int) const"; }
-    py::str overloaded(int, float)   const { return "(int, float) const"; }
-    py::str overloaded(float, int)   const { return "(float, int) const"; }
-    py::str overloaded(int, int)     const { return "(int, int) const"; }
+    py::str overloaded(int) const { return "(int) const"; }
+    py::str overloaded(int, float) const { return "(int, float) const"; }
+    py::str overloaded(float, int) const { return "(float, int) const"; }
+    py::str overloaded(int, int) const { return "(int, int) const"; }
     py::str overloaded(float, float) const { return "(float, float) const"; }
 
     static py::str overloaded(float) { return "static float"; }
@@ -112,7 +115,10 @@ UserType TestPropRVP::sv1(1);
 UserType TestPropRVP::sv2(1);
 
 // Test None-allowed py::arg argument policy
-class NoneTester { public: int answer = 42; };
+class NoneTester {
+public:
+    int answer = 42;
+};
 int none1(const NoneTester &obj) { return obj.answer; }
 int none2(NoneTester *obj) { return obj ? obj->answer : -1; }
 int none3(std::shared_ptr<NoneTester> &obj) { return obj ? obj->answer : -1; }
@@ -134,11 +140,15 @@ struct StrIssue {
     explicit StrIssue(int i) : val{i} {}
 };
 
-// Issues #854, #910: incompatible function args when member function/pointer is in unregistered base class
+// Issues #854, #910: incompatible function args when member function/pointer is in unregistered
+// base class
 class UnregisteredBase {
 public:
     void do_nothing() const {}
-    void increase_value() { rw_value++; ro_value += 0.25; }
+    void increase_value() {
+        rw_value++;
+        ro_value += 0.25;
+    }
     void set_int(int v) { rw_value = v; }
     int get_int() const { return rw_value; }
     double get_double() const { return ro_value; }
@@ -161,10 +171,10 @@ struct RefQualified {
 
 // Test rvalue ref param
 struct RValueRefParam {
-    std::size_t func1(std::string&& s) { return s.size(); }
-    std::size_t func2(std::string&& s) const { return s.size(); }
-    std::size_t func3(std::string&& s) & { return s.size(); }
-    std::size_t func4(std::string&& s) const & { return s.size(); }
+    std::size_t func1(std::string &&s) { return s.size(); }
+    std::size_t func2(std::string &&s) const { return s.size(); }
+    std::size_t func3(std::string &&s) & { return s.size(); }
+    std::size_t func4(std::string &&s) const & { return s.size(); }
 };
 
 TEST_SUBMODULE(methods_and_attributes, m) {
@@ -172,8 +182,8 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     py::class_<ExampleMandA> emna(m, "ExampleMandA");
     emna.def(py::init<>())
         .def(py::init<int>())
-        .def(py::init<std::string&&>())
-        .def(py::init<const ExampleMandA&>())
+        .def(py::init<std::string &&>())
+        .def(py::init<const ExampleMandA &>())
         .def("add1", &ExampleMandA::add1)
         .def("add2", &ExampleMandA::add2)
         .def("add3", &ExampleMandA::add3)
@@ -198,16 +208,20 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 #if defined(PYBIND11_OVERLOAD_CAST)
         .def("overloaded", py::overload_cast<>(&ExampleMandA::overloaded))
         .def("overloaded", py::overload_cast<int>(&ExampleMandA::overloaded))
-        .def("overloaded", py::overload_cast<int,   float>(&ExampleMandA::overloaded))
-        .def("overloaded", py::overload_cast<float,   int>(&ExampleMandA::overloaded))
-        .def("overloaded", py::overload_cast<int,     int>(&ExampleMandA::overloaded))
+        .def("overloaded", py::overload_cast<int, float>(&ExampleMandA::overloaded))
+        .def("overloaded", py::overload_cast<float, int>(&ExampleMandA::overloaded))
+        .def("overloaded", py::overload_cast<int, int>(&ExampleMandA::overloaded))
         .def("overloaded", py::overload_cast<float, float>(&ExampleMandA::overloaded))
         .def("overloaded_float", py::overload_cast<float, float>(&ExampleMandA::overloaded))
-        .def("overloaded_const", py::overload_cast<int         >(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<int,   float>(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<float,   int>(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<int,     int>(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<float, float>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const", py::overload_cast<int>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<int, float>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<float, int>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<int, int>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<float, float>(&ExampleMandA::overloaded, py::const_))
 #else
         // Use both the traditional static_cast method and the C++11 compatible overload_cast_
         .def("overloaded", overload_cast_<>()(&ExampleMandA::overloaded))
@@ -225,16 +239,29 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 #endif
         // test_no_mixed_overloads
         // Raise error if trying to mix static/non-static overloads on the same name:
-        .def_static("add_mixed_overloads1", []() {
-            auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(py::module_::import("pybind11_tests.methods_and_attributes").attr("ExampleMandA"));
-            emna.def       ("overload_mixed1", static_cast<py::str (ExampleMandA::*)(int, int)>(&ExampleMandA::overloaded))
-                .def_static("overload_mixed1", static_cast<py::str (              *)(float   )>(&ExampleMandA::overloaded));
-        })
-        .def_static("add_mixed_overloads2", []() {
-            auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(py::module_::import("pybind11_tests.methods_and_attributes").attr("ExampleMandA"));
-            emna.def_static("overload_mixed2", static_cast<py::str (              *)(float   )>(&ExampleMandA::overloaded))
-                .def       ("overload_mixed2", static_cast<py::str (ExampleMandA::*)(int, int)>(&ExampleMandA::overloaded));
-        })
+        .def_static("add_mixed_overloads1",
+                    []() {
+                        auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(
+                            py::module_::import("pybind11_tests.methods_and_attributes")
+                                .attr("ExampleMandA"));
+                        emna.def("overload_mixed1",
+                                 static_cast<py::str (ExampleMandA::*)(int, int)>(
+                                     &ExampleMandA::overloaded))
+                            .def_static(
+                                "overload_mixed1",
+                                static_cast<py::str (*)(float)>(&ExampleMandA::overloaded));
+                    })
+        .def_static("add_mixed_overloads2",
+                    []() {
+                        auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(
+                            py::module_::import("pybind11_tests.methods_and_attributes")
+                                .attr("ExampleMandA"));
+                        emna.def_static("overload_mixed2",
+                                        static_cast<py::str (*)(float)>(&ExampleMandA::overloaded))
+                            .def("overload_mixed2",
+                                 static_cast<py::str (ExampleMandA::*)(int, int)>(
+                                     &ExampleMandA::overloaded));
+                    })
         .def("__str__", &ExampleMandA::toString)
         .def_readwrite("value", &ExampleMandA::value);
 
@@ -307,7 +334,7 @@ TEST_SUBMODULE(methods_and_attributes, m) {
                                       [](const py::object &) { return UserType(1); });
 
     // test_metaclass_override
-    struct MetaclassOverride { };
+    struct MetaclassOverride {};
     py::class_<MetaclassOverride>(m, "MetaclassOverride", py::metaclass((PyObject *) &PyType_Type))
         .def_property_readonly_static("readonly", [](const py::object &) { return 1; });
 
@@ -315,22 +342,21 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     m.def("overload_order", [](const std::string &) { return 1; });
     m.def("overload_order", [](const std::string &) { return 2; });
     m.def("overload_order", [](int) { return 3; });
-    m.def("overload_order", [](int) { return 4; }, py::prepend{});
+    m.def(
+        "overload_order", [](int) { return 4; }, py::prepend{});
 
 #if !defined(PYPY_VERSION)
     // test_dynamic_attributes
     class DynamicClass {
     public:
         DynamicClass() { print_default_created(this); }
-        DynamicClass(const DynamicClass&) = delete;
+        DynamicClass(const DynamicClass &) = delete;
         ~DynamicClass() { print_destroyed(this); }
     };
-    py::class_<DynamicClass>(m, "DynamicClass", py::dynamic_attr())
-        .def(py::init());
+    py::class_<DynamicClass>(m, "DynamicClass", py::dynamic_attr()).def(py::init());
 
-    class CppDerivedDynamicClass : public DynamicClass { };
-    py::class_<CppDerivedDynamicClass, DynamicClass>(m, "CppDerivedDynamicClass")
-        .def(py::init());
+    class CppDerivedDynamicClass : public DynamicClass {};
+    py::class_<CppDerivedDynamicClass, DynamicClass>(m, "CppDerivedDynamicClass").def(py::init());
 #endif
 
     // test_bad_arg_default
@@ -340,20 +366,27 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 #else
     m.attr("debug_enabled") = false;
 #endif
-    m.def("bad_arg_def_named", []{
+    m.def("bad_arg_def_named", [] {
         auto m = py::module_::import("pybind11_tests");
-        m.def("should_fail", [](int, UnregisteredType) {}, py::arg(), py::arg("a") = UnregisteredType());
+        m.def(
+            "should_fail",
+            [](int, UnregisteredType) {},
+            py::arg(),
+            py::arg("a") = UnregisteredType());
     });
-    m.def("bad_arg_def_unnamed", []{
+    m.def("bad_arg_def_unnamed", [] {
         auto m = py::module_::import("pybind11_tests");
-        m.def("should_fail", [](int, UnregisteredType) {}, py::arg(), py::arg() = UnregisteredType());
+        m.def(
+            "should_fail",
+            [](int, UnregisteredType) {},
+            py::arg(),
+            py::arg() = UnregisteredType());
     });
 
     // [workaround(intel)] ICC 20/21 breaks with py::arg().stuff, using py::arg{}.stuff works.
 
     // test_accepts_none
-    py::class_<NoneTester, std::shared_ptr<NoneTester>>(m, "NoneTester")
-        .def(py::init<>());
+    py::class_<NoneTester, std::shared_ptr<NoneTester>>(m, "NoneTester").def(py::init<>());
     m.def("no_none1", &none1, py::arg{}.none(false));
     m.def("no_none2", &none2, py::arg{}.none(false));
     m.def("no_none3", &none3, py::arg{}.none(false));
@@ -371,21 +404,19 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     // test_casts_none
     // Issue #2778: implicit casting from None to object (not pointer)
     py::class_<NoneCastTester>(m, "NoneCastTester")
-          .def(py::init<>())
-          .def(py::init<int>())
-          .def(py::init([](py::none const&) { return NoneCastTester{}; }));
+        .def(py::init<>())
+        .def(py::init<int>())
+        .def(py::init([](py::none const &) { return NoneCastTester{}; }));
     py::implicitly_convertible<py::none, NoneCastTester>();
-    m.def("ok_obj_or_none", [](NoneCastTester const& foo) { return foo.answer; });
-
+    m.def("ok_obj_or_none", [](NoneCastTester const &foo) { return foo.answer; });
 
     // test_str_issue
     // Issue #283: __str__ called on uninitialized instance when constructor arguments invalid
     py::class_<StrIssue>(m, "StrIssue")
         .def(py::init<int>())
         .def(py::init<>())
-        .def("__str__", [](const StrIssue &si) {
-            return "StrIssue[" + std::to_string(si.val) + "]"; }
-        );
+        .def("__str__",
+             [](const StrIssue &si) { return "StrIssue[" + std::to_string(si.val) + "]"; });
 
     // test_unregistered_base_implementations
     //
@@ -408,7 +439,8 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         // This one is in the registered class:
         .def("sum", &RegisteredDerived::sum);
 
-    using Adapted = decltype(py::method_adaptor<RegisteredDerived>(&RegisteredDerived::do_nothing));
+    using Adapted
+        = decltype(py::method_adaptor<RegisteredDerived>(&RegisteredDerived::do_nothing));
     static_assert(std::is_same<Adapted, void (RegisteredDerived::*)() const>::value, "");
 
     // test_methods_and_attributes
diff --git a/tests/test_modules.cpp b/tests/test_modules.cpp
index ba80a64c9a..8aa2a4bdbd 100644
--- a/tests/test_modules.cpp
+++ b/tests/test_modules.cpp
@@ -8,8 +8,8 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 
 TEST_SUBMODULE(modules, m) {
     // test_nested_modules
@@ -22,23 +22,30 @@ TEST_SUBMODULE(modules, m) {
     public:
         explicit A(int v) : v(v) { print_created(this, v); }
         ~A() { print_destroyed(this); }
-        A(const A&) { print_copy_created(this); }
-        A& operator=(const A &copy) { print_copy_assigned(this); v = copy.v; return *this; }
+        A(const A &) { print_copy_created(this); }
+        A &operator=(const A &copy) {
+            print_copy_assigned(this);
+            v = copy.v;
+            return *this;
+        }
         std::string toString() const { return "A[" + std::to_string(v) + "]"; }
 
     private:
         int v;
     };
-    py::class_<A>(m_sub, "A")
-        .def(py::init<int>())
-        .def("__repr__", &A::toString);
+    py::class_<A>(m_sub, "A").def(py::init<int>()).def("__repr__", &A::toString);
 
     class B {
     public:
         B() { print_default_created(this); }
         ~B() { print_destroyed(this); }
-        B(const B&) { print_copy_created(this); }
-        B& operator=(const B &copy) { print_copy_assigned(this); a1 = copy.a1; a2 = copy.a2; return *this; }
+        B(const B &) { print_copy_created(this); }
+        B &operator=(const B &copy) {
+            print_copy_assigned(this);
+            a1 = copy.a1;
+            a2 = copy.a2;
+            return *this;
+        }
         A &get_a1() { return a1; }
         A &get_a2() { return a2; }
 
@@ -47,10 +54,16 @@ TEST_SUBMODULE(modules, m) {
     };
     py::class_<B>(m_sub, "B")
         .def(py::init<>())
-        .def("get_a1", &B::get_a1, "Return the internal A 1", py::return_value_policy::reference_internal)
-        .def("get_a2", &B::get_a2, "Return the internal A 2", py::return_value_policy::reference_internal)
-        .def_readwrite("a1", &B::a1)  // def_readonly uses an internal
-                                      // reference return policy by default
+        .def("get_a1",
+             &B::get_a1,
+             "Return the internal A 1",
+             py::return_value_policy::reference_internal)
+        .def("get_a2",
+             &B::get_a2,
+             "Return the internal A 2",
+             py::return_value_policy::reference_internal)
+        .def_readwrite("a1", &B::a1) // def_readonly uses an internal
+                                     // reference return policy by default
         .def_readwrite("a2", &B::a2);
 
     // This is intentionally "py::module" to verify it still can be used in place of "py::module_"
@@ -59,13 +72,14 @@ TEST_SUBMODULE(modules, m) {
     // test_duplicate_registration
     // Registering two things with the same name
     m.def("duplicate_registration", []() {
-        class Dupe1 { };
-        class Dupe2 { };
-        class Dupe3 { };
-        class DupeException { };
+        class Dupe1 {};
+        class Dupe2 {};
+        class Dupe3 {};
+        class DupeException {};
 
         // Go ahead and leak, until we have a non-leaking py::module_ constructor
-        auto dm = py::module_::create_extension_module("dummy", nullptr, new py::module_::module_def);
+        auto dm
+            = py::module_::create_extension_module("dummy", nullptr, new py::module_::module_def);
         auto failures = py::list();
 
         py::class_<Dupe1>(dm, "Dupe1");
@@ -76,27 +90,33 @@ TEST_SUBMODULE(modules, m) {
         try {
             py::class_<Dupe1>(dm, "Dupe1");
             failures.append("Dupe1 class");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             dm.def("Dupe1", []() { return Dupe1(); });
             failures.append("Dupe1 function");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             py::class_<Dupe3>(dm, "dupe1_factory");
             failures.append("dupe1_factory");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             py::exception<Dupe3>(dm, "Dupe2");
             failures.append("Dupe2");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             dm.def("DupeException", []() { return 30; });
             failures.append("DupeException1");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             py::class_<DupeException>(dm, "DupeException");
             failures.append("DupeException2");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
 
         return failures;
     });
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index 4689df4e46..5916ae9010 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -8,14 +8,15 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 
 namespace {
 
 // Many bases for testing that multiple inheritance from many classes (i.e. requiring extra
 // space for holder constructed flags) works.
-template <int N> struct BaseN {
+template <int N>
+struct BaseN {
     explicit BaseN(int i) : i(i) {}
     int i;
 };
@@ -57,13 +58,23 @@ struct Base2a {
     int i;
 };
 struct Base12a : Base1a, Base2a {
-    Base12a(int i, int j) : Base1a(i), Base2a(j) { }
+    Base12a(int i, int j) : Base1a(i), Base2a(j) {}
 };
 
 // test_mi_unaligned_base
 // test_mi_base_return
-struct I801B1 { int a = 1; I801B1() = default; I801B1(const I801B1 &) = default; virtual ~I801B1() = default; };
-struct I801B2 { int b = 2; I801B2() = default; I801B2(const I801B2 &) = default; virtual ~I801B2() = default; };
+struct I801B1 {
+    int a = 1;
+    I801B1() = default;
+    I801B1(const I801B1 &) = default;
+    virtual ~I801B1() = default;
+};
+struct I801B2 {
+    int b = 2;
+    I801B2() = default;
+    I801B2(const I801B2 &) = default;
+    virtual ~I801B2() = default;
+};
 struct I801C : I801B1, I801B2 {};
 struct I801D : I801C {}; // Indirect MI
 
@@ -82,8 +93,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         int i;
     };
     py::class_<Base1> b1(m, "Base1");
-    b1.def(py::init<int>())
-      .def("foo", &Base1::foo);
+    b1.def(py::init<int>()).def("foo", &Base1::foo);
 
     struct Base2 {
         explicit Base2(int i) : i(i) {}
@@ -91,42 +101,49 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         int i;
     };
     py::class_<Base2> b2(m, "Base2");
-    b2.def(py::init<int>())
-      .def("bar", &Base2::bar);
-
+    b2.def(py::init<int>()).def("bar", &Base2::bar);
 
     // test_multiple_inheritance_cpp
     struct Base12 : Base1, Base2 {
-        Base12(int i, int j) : Base1(i), Base2(j) { }
+        Base12(int i, int j) : Base1(i), Base2(j) {}
     };
     struct MIType : Base12 {
-        MIType(int i, int j) : Base12(i, j) { }
+        MIType(int i, int j) : Base12(i, j) {}
     };
     py::class_<Base12, Base1, Base2>(m, "Base12");
-    py::class_<MIType, Base12>(m, "MIType")
-        .def(py::init<int, int>());
-
+    py::class_<MIType, Base12>(m, "MIType").def(py::init<int, int>());
 
     // test_multiple_inheritance_python_many_bases
 #define PYBIND11_BASEN(N)                                                                         \
     py::class_<BaseN<(N)>>(m, "BaseN" #N).def(py::init<int>()).def("f" #N, [](BaseN<N> &b) {      \
         return b.i + (N);                                                                         \
     })
-    PYBIND11_BASEN( 1); PYBIND11_BASEN( 2); PYBIND11_BASEN( 3); PYBIND11_BASEN( 4);
-    PYBIND11_BASEN( 5); PYBIND11_BASEN( 6); PYBIND11_BASEN( 7); PYBIND11_BASEN( 8);
-    PYBIND11_BASEN( 9); PYBIND11_BASEN(10); PYBIND11_BASEN(11); PYBIND11_BASEN(12);
-    PYBIND11_BASEN(13); PYBIND11_BASEN(14); PYBIND11_BASEN(15); PYBIND11_BASEN(16);
+    PYBIND11_BASEN(1);
+    PYBIND11_BASEN(2);
+    PYBIND11_BASEN(3);
+    PYBIND11_BASEN(4);
+    PYBIND11_BASEN(5);
+    PYBIND11_BASEN(6);
+    PYBIND11_BASEN(7);
+    PYBIND11_BASEN(8);
+    PYBIND11_BASEN(9);
+    PYBIND11_BASEN(10);
+    PYBIND11_BASEN(11);
+    PYBIND11_BASEN(12);
+    PYBIND11_BASEN(13);
+    PYBIND11_BASEN(14);
+    PYBIND11_BASEN(15);
+    PYBIND11_BASEN(16);
     PYBIND11_BASEN(17);
 
     // Uncommenting this should result in a compile time failure (MI can only be specified via
-    // template parameters because pybind has to know the types involved; see discussion in #742 for
-    // details).
-//    struct Base12v2 : Base1, Base2 {
-//        Base12v2(int i, int j) : Base1(i), Base2(j) { }
-//    };
-//    py::class_<Base12v2>(m, "Base12v2", b1, b2)
-//        .def(py::init<int, int>());
-
+    // template parameters because pybind has to know the types involved; see discussion in #742
+    // for details).
+    //    struct Base12v2 : Base1, Base2 {
+    //        Base12v2(int i, int j) : Base1(i), Base2(j) { }
+    //    };
+    //    py::class_<Base12v2>(m, "Base12v2", b1, b2)
+    //        .def(py::init<int, int>());
 
     // test_multiple_inheritance_virtbase
     // Test the case where not all base classes are specified, and where pybind11 requires the
@@ -139,8 +156,8 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def(py::init<int>())
         .def("bar", &Base2a::bar);
 
-    py::class_<Base12a, /* Base1 missing */ Base2a,
-               std::shared_ptr<Base12a>>(m, "Base12a", py::multiple_inheritance())
+    py::class_<Base12a, /* Base1 missing */ Base2a, std::shared_ptr<Base12a>>(
+        m, "Base12a", py::multiple_inheritance())
         .def(py::init<int, int>());
 
     m.def("bar_base2a", [](Base2a *b) { return b->bar(); });
@@ -150,11 +167,18 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_mi_base_return
     // Issue #801: invalid casting to derived type with MI bases
     // Unregistered classes:
-    struct I801B3 { int c = 3; virtual ~I801B3() = default; };
+    struct I801B3 {
+        int c = 3;
+        virtual ~I801B3() = default;
+    };
     struct I801E : I801B3, I801D {};
 
-    py::class_<I801B1, std::shared_ptr<I801B1>>(m, "I801B1").def(py::init<>()).def_readonly("a", &I801B1::a);
-    py::class_<I801B2, std::shared_ptr<I801B2>>(m, "I801B2").def(py::init<>()).def_readonly("b", &I801B2::b);
+    py::class_<I801B1, std::shared_ptr<I801B1>>(m, "I801B1")
+        .def(py::init<>())
+        .def_readonly("a", &I801B1::a);
+    py::class_<I801B2, std::shared_ptr<I801B2>>(m, "I801B2")
+        .def(py::init<>())
+        .def_readonly("b", &I801B2::b);
     py::class_<I801C, I801B1, I801B2, std::shared_ptr<I801C>>(m, "I801C").def(py::init<>());
     py::class_<I801D, I801C, std::shared_ptr<I801D>>(m, "I801D").def(py::init<>());
 
@@ -179,11 +203,8 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     m.def("i801e_c", []() -> I801C * { return new I801E(); });
     m.def("i801e_b2", []() -> I801B2 * { return new I801E(); });
 
-
     // test_mi_static_properties
-    py::class_<Vanilla>(m, "Vanilla")
-        .def(py::init<>())
-        .def("vanilla", &Vanilla::vanilla);
+    py::class_<Vanilla>(m, "Vanilla").def(py::init<>()).def("vanilla", &Vanilla::vanilla);
 
     py::class_<WithStatic1>(m, "WithStatic1")
         .def(py::init<>())
@@ -195,22 +216,19 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def_static("static_func2", &WithStatic2::static_func2)
         .def_readwrite_static("static_value2", &WithStatic2::static_value2);
 
-    py::class_<VanillaStaticMix1, Vanilla, WithStatic1, WithStatic2>(
-        m, "VanillaStaticMix1")
+    py::class_<VanillaStaticMix1, Vanilla, WithStatic1, WithStatic2>(m, "VanillaStaticMix1")
         .def(py::init<>())
         .def_static("static_func", &VanillaStaticMix1::static_func)
         .def_readwrite_static("static_value", &VanillaStaticMix1::static_value);
 
-    py::class_<VanillaStaticMix2, WithStatic1, Vanilla, WithStatic2>(
-        m, "VanillaStaticMix2")
+    py::class_<VanillaStaticMix2, WithStatic1, Vanilla, WithStatic2>(m, "VanillaStaticMix2")
         .def(py::init<>())
         .def_static("static_func", &VanillaStaticMix2::static_func)
         .def_readwrite_static("static_value", &VanillaStaticMix2::static_value);
 
-
-    struct WithDict { };
-    struct VanillaDictMix1 : Vanilla, WithDict { };
-    struct VanillaDictMix2 : WithDict, Vanilla { };
+    struct WithDict {};
+    struct VanillaDictMix1 : Vanilla, WithDict {};
+    struct VanillaDictMix2 : WithDict, Vanilla {};
     py::class_<WithDict>(m, "WithDict", py::dynamic_attr()).def(py::init<>());
     py::class_<VanillaDictMix1, Vanilla, WithDict>(m, "VanillaDictMix1").def(py::init<>());
     py::class_<VanillaDictMix2, WithDict, Vanilla>(m, "VanillaDictMix2").def(py::init<>());
@@ -218,18 +236,25 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_diamond_inheritance
     // Issue #959: segfault when constructing diamond inheritance instance
     // All of these have int members so that there will be various unequal pointers involved.
-    struct B { int b; B() = default; B(const B&) = default; virtual ~B() = default; };
-    struct C0 : public virtual B { int c0; };
-    struct C1 : public virtual B { int c1; };
-    struct D : public C0, public C1 { int d; };
-    py::class_<B>(m, "B")
-        .def("b", [](B *self) { return self; });
-    py::class_<C0, B>(m, "C0")
-        .def("c0", [](C0 *self) { return self; });
-    py::class_<C1, B>(m, "C1")
-        .def("c1", [](C1 *self) { return self; });
-    py::class_<D, C0, C1>(m, "D")
-        .def(py::init<>());
+    struct B {
+        int b;
+        B() = default;
+        B(const B &) = default;
+        virtual ~B() = default;
+    };
+    struct C0 : public virtual B {
+        int c0;
+    };
+    struct C1 : public virtual B {
+        int c1;
+    };
+    struct D : public C0, public C1 {
+        int d;
+    };
+    py::class_<B>(m, "B").def("b", [](B *self) { return self; });
+    py::class_<C0, B>(m, "C0").def("c0", [](C0 *self) { return self; });
+    py::class_<C1, B>(m, "C1").def("c1", [](C1 *self) { return self; });
+    py::class_<D, C0, C1>(m, "D").def(py::init<>());
 
     // test_pr3635_diamond_*
     // - functions are get_{base}_{var}, return {var}
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 17fc4de2ec..8bc77a33fa 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -7,11 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-
 #include <pybind11/numpy.h>
 #include <pybind11/stl.h>
 
+#include "pybind11_tests.h"
+
 #include <cstdint>
 #include <utility>
 
@@ -22,7 +22,7 @@ struct DtypeCheck {
 };
 
 template <typename T>
-DtypeCheck get_dtype_check(const char* name) {
+DtypeCheck get_dtype_check(const char *name) {
     py::module_ np = py::module_::import("numpy");
     DtypeCheck check{};
     check.numpy = np.attr("dtype")(np.attr(name));
@@ -31,17 +31,15 @@ DtypeCheck get_dtype_check(const char* name) {
 }
 
 std::vector<DtypeCheck> get_concrete_dtype_checks() {
-    return {
-        // Normalization
-        get_dtype_check<std::int8_t>("int8"),
-        get_dtype_check<std::uint8_t>("uint8"),
-        get_dtype_check<std::int16_t>("int16"),
-        get_dtype_check<std::uint16_t>("uint16"),
-        get_dtype_check<std::int32_t>("int32"),
-        get_dtype_check<std::uint32_t>("uint32"),
-        get_dtype_check<std::int64_t>("int64"),
-        get_dtype_check<std::uint64_t>("uint64")
-    };
+    return {// Normalization
+            get_dtype_check<std::int8_t>("int8"),
+            get_dtype_check<std::uint8_t>("uint8"),
+            get_dtype_check<std::int16_t>("int16"),
+            get_dtype_check<std::uint16_t>("uint16"),
+            get_dtype_check<std::int32_t>("int32"),
+            get_dtype_check<std::uint32_t>("uint32"),
+            get_dtype_check<std::int64_t>("int64"),
+            get_dtype_check<std::uint64_t>("uint64")};
 }
 
 struct DtypeSizeCheck {
@@ -80,15 +78,18 @@ using arr = py::array;
 using arr_t = py::array_t<uint16_t, 0>;
 static_assert(std::is_same<arr_t::value_type, uint16_t>::value, "");
 
-template<typename... Ix> arr data(const arr& a, Ix... index) {
+template <typename... Ix>
+arr data(const arr &a, Ix... index) {
     return arr(a.nbytes() - a.offset_at(index...), (const uint8_t *) a.data(index...));
 }
 
-template<typename... Ix> arr data_t(const arr_t& a, Ix... index) {
+template <typename... Ix>
+arr data_t(const arr_t &a, Ix... index) {
     return arr(a.size() - a.index_at(index...), a.data(index...));
 }
 
-template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
+template <typename... Ix>
+arr &mutate_data(arr &a, Ix... index) {
     auto *ptr = (uint8_t *) a.mutable_data(index...);
     for (py::ssize_t i = 0; i < a.nbytes() - a.offset_at(index...); i++) {
         ptr[i] = (uint8_t) (ptr[i] * 2);
@@ -96,7 +97,8 @@ template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
     return a;
 }
 
-template<typename... Ix> arr_t& mutate_data_t(arr_t& a, Ix... index) {
+template <typename... Ix>
+arr_t &mutate_data_t(arr_t &a, Ix... index) {
     auto ptr = a.mutable_data(index...);
     for (py::ssize_t i = 0; i < a.size() - a.index_at(index...); i++) {
         ptr[i]++;
@@ -104,20 +106,40 @@ template<typename... Ix> arr_t& mutate_data_t(arr_t& a, Ix... index) {
     return a;
 }
 
-template<typename... Ix> py::ssize_t index_at(const arr& a, Ix... idx) { return a.index_at(idx...); }
-template<typename... Ix> py::ssize_t index_at_t(const arr_t& a, Ix... idx) { return a.index_at(idx...); }
-template<typename... Ix> py::ssize_t offset_at(const arr& a, Ix... idx) { return a.offset_at(idx...); }
-template<typename... Ix> py::ssize_t offset_at_t(const arr_t& a, Ix... idx) { return a.offset_at(idx...); }
-template<typename... Ix> py::ssize_t at_t(const arr_t& a, Ix... idx) { return a.at(idx...); }
-template<typename... Ix> arr_t& mutate_at_t(arr_t& a, Ix... idx) { a.mutable_at(idx...)++; return a; }
-
-#define def_index_fn(name, type) \
-    sm.def(#name, [](type a) { return name(a); }); \
-    sm.def(#name, [](type a, int i) { return name(a, i); }); \
-    sm.def(#name, [](type a, int i, int j) { return name(a, i, j); }); \
+template <typename... Ix>
+py::ssize_t index_at(const arr &a, Ix... idx) {
+    return a.index_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t index_at_t(const arr_t &a, Ix... idx) {
+    return a.index_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t offset_at(const arr &a, Ix... idx) {
+    return a.offset_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t offset_at_t(const arr_t &a, Ix... idx) {
+    return a.offset_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t at_t(const arr_t &a, Ix... idx) {
+    return a.at(idx...);
+}
+template <typename... Ix>
+arr_t &mutate_at_t(arr_t &a, Ix... idx) {
+    a.mutable_at(idx...)++;
+    return a;
+}
+
+#define def_index_fn(name, type)                                                                  \
+    sm.def(#name, [](type a) { return name(a); });                                                \
+    sm.def(#name, [](type a, int i) { return name(a, i); });                                      \
+    sm.def(#name, [](type a, int i, int j) { return name(a, i, j); });                            \
     sm.def(#name, [](type a, int i, int j, int k) { return name(a, i, j, k); });
 
-template <typename T, typename T2> py::handle auxiliaries(T &&r, T2 &&r2) {
+template <typename T, typename T2>
+py::handle auxiliaries(T &&r, T2 &&r2) {
     if (r.ndim() != 2) {
         throw std::domain_error("error: ndim != 2");
     }
@@ -138,16 +160,18 @@ template <typename T, typename T2> py::handle auxiliaries(T &&r, T2 &&r2) {
 static int data_i = 42;
 
 TEST_SUBMODULE(numpy_array, sm) {
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // test_dtypes
     py::class_<DtypeCheck>(sm, "DtypeCheck")
         .def_readonly("numpy", &DtypeCheck::numpy)
         .def_readonly("pybind11", &DtypeCheck::pybind11)
-        .def("__repr__", [](const DtypeCheck& self) {
-            return py::str("<DtypeCheck numpy={} pybind11={}>").format(
-                self.numpy, self.pybind11);
+        .def("__repr__", [](const DtypeCheck &self) {
+            return py::str("<DtypeCheck numpy={} pybind11={}>").format(self.numpy, self.pybind11);
         });
     sm.def("get_concrete_dtype_checks", &get_concrete_dtype_checks);
 
@@ -155,41 +179,41 @@ TEST_SUBMODULE(numpy_array, sm) {
         .def_readonly("name", &DtypeSizeCheck::name)
         .def_readonly("size_cpp", &DtypeSizeCheck::size_cpp)
         .def_readonly("size_numpy", &DtypeSizeCheck::size_numpy)
-        .def("__repr__", [](const DtypeSizeCheck& self) {
-            return py::str("<DtypeSizeCheck name='{}' size_cpp={} size_numpy={} dtype={}>").format(
-                self.name, self.size_cpp, self.size_numpy, self.dtype);
+        .def("__repr__", [](const DtypeSizeCheck &self) {
+            return py::str("<DtypeSizeCheck name='{}' size_cpp={} size_numpy={} dtype={}>")
+                .format(self.name, self.size_cpp, self.size_numpy, self.dtype);
         });
     sm.def("get_platform_dtype_size_checks", &get_platform_dtype_size_checks);
 
     // test_array_attributes
-    sm.def("ndim", [](const arr& a) { return a.ndim(); });
-    sm.def("shape", [](const arr& a) { return arr(a.ndim(), a.shape()); });
-    sm.def("shape", [](const arr& a, py::ssize_t dim) { return a.shape(dim); });
-    sm.def("strides", [](const arr& a) { return arr(a.ndim(), a.strides()); });
-    sm.def("strides", [](const arr& a, py::ssize_t dim) { return a.strides(dim); });
-    sm.def("writeable", [](const arr& a) { return a.writeable(); });
-    sm.def("size", [](const arr& a) { return a.size(); });
-    sm.def("itemsize", [](const arr& a) { return a.itemsize(); });
-    sm.def("nbytes", [](const arr& a) { return a.nbytes(); });
-    sm.def("owndata", [](const arr& a) { return a.owndata(); });
+    sm.def("ndim", [](const arr &a) { return a.ndim(); });
+    sm.def("shape", [](const arr &a) { return arr(a.ndim(), a.shape()); });
+    sm.def("shape", [](const arr &a, py::ssize_t dim) { return a.shape(dim); });
+    sm.def("strides", [](const arr &a) { return arr(a.ndim(), a.strides()); });
+    sm.def("strides", [](const arr &a, py::ssize_t dim) { return a.strides(dim); });
+    sm.def("writeable", [](const arr &a) { return a.writeable(); });
+    sm.def("size", [](const arr &a) { return a.size(); });
+    sm.def("itemsize", [](const arr &a) { return a.itemsize(); });
+    sm.def("nbytes", [](const arr &a) { return a.nbytes(); });
+    sm.def("owndata", [](const arr &a) { return a.owndata(); });
 
     // test_index_offset
-    def_index_fn(index_at, const arr&);
-    def_index_fn(index_at_t, const arr_t&);
-    def_index_fn(offset_at, const arr&);
-    def_index_fn(offset_at_t, const arr_t&);
+    def_index_fn(index_at, const arr &);
+    def_index_fn(index_at_t, const arr_t &);
+    def_index_fn(offset_at, const arr &);
+    def_index_fn(offset_at_t, const arr_t &);
     // test_data
-    def_index_fn(data, const arr&);
-    def_index_fn(data_t, const arr_t&);
+    def_index_fn(data, const arr &);
+    def_index_fn(data_t, const arr_t &);
     // test_mutate_data, test_mutate_readonly
-    def_index_fn(mutate_data, arr&);
-    def_index_fn(mutate_data_t, arr_t&);
-    def_index_fn(at_t, const arr_t&);
-    def_index_fn(mutate_at_t, arr_t&);
+    def_index_fn(mutate_data, arr &);
+    def_index_fn(mutate_data_t, arr_t &);
+    def_index_fn(at_t, const arr_t &);
+    def_index_fn(mutate_at_t, arr_t &);
 
     // test_make_c_f_array
-    sm.def("make_f_array", [] { return py::array_t<float>({ 2, 2 }, { 4, 8 }); });
-    sm.def("make_c_array", [] { return py::array_t<float>({ 2, 2 }, { 8, 4 }); });
+    sm.def("make_f_array", [] { return py::array_t<float>({2, 2}, {4, 8}); });
+    sm.def("make_c_array", [] { return py::array_t<float>({2, 2}, {8, 4}); });
 
     // test_empty_shaped_array
     sm.def("make_empty_shaped_array", [] { return py::array(py::dtype("f"), {}, {}); });
@@ -198,18 +222,16 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_wrap
     sm.def("wrap", [](const py::array &a) {
-        return py::array(
-            a.dtype(),
-            {a.shape(), a.shape() + a.ndim()},
-            {a.strides(), a.strides() + a.ndim()},
-            a.data(),
-            a
-        );
+        return py::array(a.dtype(),
+                         {a.shape(), a.shape() + a.ndim()},
+                         {a.strides(), a.strides() + a.ndim()},
+                         a.data(),
+                         a);
     });
 
     // test_numpy_view
     struct ArrayClass {
-        int data[2] = { 1, 2 };
+        int data[2] = {1, 2};
         ArrayClass() { py::print("ArrayClass()"); }
         ~ArrayClass() { py::print("~ArrayClass()"); }
     };
@@ -217,13 +239,12 @@ TEST_SUBMODULE(numpy_array, sm) {
         .def(py::init<>())
         .def("numpy_view", [](py::object &obj) {
             py::print("ArrayClass::numpy_view()");
-            auto &a = obj.cast<ArrayClass&>();
+            auto &a = obj.cast<ArrayClass &>();
             return py::array_t<int>({2}, {4}, a.data, obj);
-        }
-    );
+        });
 
     // test_cast_numpy_int64_to_uint64
-    sm.def("function_taking_uint64", [](uint64_t) { });
+    sm.def("function_taking_uint64", [](uint64_t) {});
 
     // test_isinstance
     sm.def("isinstance_untyped", [](py::object yes, py::object no) {
@@ -236,18 +257,14 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_constructors
     sm.def("default_constructors", []() {
-        return py::dict(
-            "array"_a=py::array(),
-            "array_t<int32>"_a=py::array_t<std::int32_t>(),
-            "array_t<double>"_a=py::array_t<double>()
-        );
+        return py::dict("array"_a = py::array(),
+                        "array_t<int32>"_a = py::array_t<std::int32_t>(),
+                        "array_t<double>"_a = py::array_t<double>());
     });
     sm.def("converting_constructors", [](const py::object &o) {
-        return py::dict(
-            "array"_a=py::array(o),
-            "array_t<int32>"_a=py::array_t<std::int32_t>(o),
-            "array_t<double>"_a=py::array_t<double>(o)
-        );
+        return py::dict("array"_a = py::array(o),
+                        "array_t<int32>"_a = py::array_t<std::int32_t>(o),
+                        "array_t<double>"_a = py::array_t<double>(o));
     });
 
     // test_overload_resolution
@@ -294,17 +311,21 @@ TEST_SUBMODULE(numpy_array, sm) {
     sm.def("issue685", [](const py::object &) { return "other"; });
 
     // test_array_unchecked_fixed_dims
-    sm.def("proxy_add2", [](py::array_t<double> a, double v) {
-        auto r = a.mutable_unchecked<2>();
-        for (py::ssize_t i = 0; i < r.shape(0); i++) {
-            for (py::ssize_t j = 0; j < r.shape(1); j++) {
-                r(i, j) += v;
+    sm.def(
+        "proxy_add2",
+        [](py::array_t<double> a, double v) {
+            auto r = a.mutable_unchecked<2>();
+            for (py::ssize_t i = 0; i < r.shape(0); i++) {
+                for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                    r(i, j) += v;
+                }
             }
-        }
-    }, py::arg{}.noconvert(), py::arg());
+        },
+        py::arg{}.noconvert(),
+        py::arg());
 
     sm.def("proxy_init3", [](double start) {
-        py::array_t<double, py::array::c_style> a({ 3, 3, 3 });
+        py::array_t<double, py::array::c_style> a({3, 3, 3});
         auto r = a.mutable_unchecked<3>();
         for (py::ssize_t i = 0; i < r.shape(0); i++) {
             for (py::ssize_t j = 0; j < r.shape(1); j++) {
@@ -316,7 +337,7 @@ TEST_SUBMODULE(numpy_array, sm) {
         return a;
     });
     sm.def("proxy_init3F", [](double start) {
-        py::array_t<double, py::array::f_style> a({ 3, 3, 3 });
+        py::array_t<double, py::array::f_style> a({3, 3, 3});
         auto r = a.mutable_unchecked<3>();
         for (py::ssize_t k = 0; k < r.shape(2); k++) {
             for (py::ssize_t j = 0; j < r.shape(1); j++) {
@@ -356,19 +377,23 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_array_unchecked_dyn_dims
     // Same as the above, but without a compile-time dimensions specification:
-    sm.def("proxy_add2_dyn", [](py::array_t<double> a, double v) {
-        auto r = a.mutable_unchecked();
-        if (r.ndim() != 2) {
-            throw std::domain_error("error: ndim != 2");
-        }
-        for (py::ssize_t i = 0; i < r.shape(0); i++) {
-            for (py::ssize_t j = 0; j < r.shape(1); j++) {
-                r(i, j) += v;
+    sm.def(
+        "proxy_add2_dyn",
+        [](py::array_t<double> a, double v) {
+            auto r = a.mutable_unchecked();
+            if (r.ndim() != 2) {
+                throw std::domain_error("error: ndim != 2");
             }
-        }
-    }, py::arg{}.noconvert(), py::arg());
+            for (py::ssize_t i = 0; i < r.shape(0); i++) {
+                for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                    r(i, j) += v;
+                }
+            }
+        },
+        py::arg{}.noconvert(),
+        py::arg());
     sm.def("proxy_init3_dyn", [](double start) {
-        py::array_t<double, py::array::c_style> a({ 3, 3, 3 });
+        py::array_t<double, py::array::c_style> a({3, 3, 3});
         auto r = a.mutable_unchecked();
         if (r.ndim() != 3) {
             throw std::domain_error("error: ndim != 3");
@@ -386,29 +411,31 @@ TEST_SUBMODULE(numpy_array, sm) {
         return auxiliaries(a.unchecked(), a.mutable_unchecked());
     });
 
-    sm.def("array_auxiliaries2", [](py::array_t<double> a) {
-        return auxiliaries(a, a);
-    });
+    sm.def("array_auxiliaries2", [](py::array_t<double> a) { return auxiliaries(a, a); });
 
     // test_array_failures
-    // Issue #785: Uninformative "Unknown internal error" exception when constructing array from empty object:
+    // Issue #785: Uninformative "Unknown internal error" exception when constructing array from
+    // empty object:
     sm.def("array_fail_test", []() { return py::array(py::object()); });
     sm.def("array_t_fail_test", []() { return py::array_t<double>(py::object()); });
     // Make sure the error from numpy is being passed through:
-    sm.def("array_fail_test_negative_size", []() { int c = 0; return py::array(-1, &c); });
+    sm.def("array_fail_test_negative_size", []() {
+        int c = 0;
+        return py::array(-1, &c);
+    });
 
     // test_initializer_list
     // Issue (unnumbered; reported in #788): regression: initializer lists can be ambiguous
     sm.def("array_initializer_list1", []() { return py::array_t<float>(1); });
     // { 1 } also works for the above, but clang warns about it
-    sm.def("array_initializer_list2", []() { return py::array_t<float>({ 1, 2 }); });
-    sm.def("array_initializer_list3", []() { return py::array_t<float>({ 1, 2, 3 }); });
-    sm.def("array_initializer_list4", []() { return py::array_t<float>({ 1, 2, 3, 4 }); });
+    sm.def("array_initializer_list2", []() { return py::array_t<float>({1, 2}); });
+    sm.def("array_initializer_list3", []() { return py::array_t<float>({1, 2, 3}); });
+    sm.def("array_initializer_list4", []() { return py::array_t<float>({1, 2, 3, 4}); });
 
     // test_array_resize
     // reshape array to 2D without changing size
     sm.def("array_reshape2", [](py::array_t<double> a) {
-        const auto dim_sz = (py::ssize_t)std::sqrt(a.size());
+        const auto dim_sz = (py::ssize_t) std::sqrt(a.size());
         if (dim_sz * dim_sz != a.size()) {
             throw std::domain_error(
                 "array_reshape2: input array total size is not a squared integer");
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index a6566c5c65..dd5b123dc4 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -7,13 +7,14 @@
   BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/numpy.h>
 
+#include "pybind11_tests.h"
+
 #ifdef __GNUC__
-#define PYBIND11_PACKED(cls) cls __attribute__((__packed__))
+#    define PYBIND11_PACKED(cls) cls __attribute__((__packed__))
 #else
-#define PYBIND11_PACKED(cls) __pragma(pack(push, 1)) cls __pragma(pack(pop))
+#    define PYBIND11_PACKED(cls) __pragma(pack(push, 1)) cls __pragma(pack(pop))
 #endif
 
 namespace py = pybind11;
@@ -25,7 +26,7 @@ struct SimpleStruct {
     long double ldbl_;
 };
 
-std::ostream& operator<<(std::ostream& os, const SimpleStruct& v) {
+std::ostream &operator<<(std::ostream &os, const SimpleStruct &v) {
     return os << "s:" << v.bool_ << "," << v.uint_ << "," << v.float_ << "," << v.ldbl_;
 }
 
@@ -43,7 +44,7 @@ PYBIND11_PACKED(struct PackedStruct {
     long double ldbl_;
 });
 
-std::ostream& operator<<(std::ostream& os, const PackedStruct& v) {
+std::ostream &operator<<(std::ostream &os, const PackedStruct &v) {
     return os << "p:" << v.bool_ << "," << v.uint_ << "," << v.float_ << "," << v.ldbl_;
 }
 
@@ -52,7 +53,7 @@ PYBIND11_PACKED(struct NestedStruct {
     PackedStruct b;
 });
 
-std::ostream& operator<<(std::ostream& os, const NestedStruct& v) {
+std::ostream &operator<<(std::ostream &os, const NestedStruct &v) {
     return os << "n:a=" << v.a << ";b=" << v.b;
 }
 
@@ -70,7 +71,7 @@ struct PartialNestedStruct {
     uint64_t dummy2;
 };
 
-struct UnboundStruct { };
+struct UnboundStruct {};
 
 struct StringStruct {
     char a[3];
@@ -82,7 +83,7 @@ struct ComplexStruct {
     std::complex<double> cdbl;
 };
 
-std::ostream& operator<<(std::ostream& os, const ComplexStruct& v) {
+std::ostream &operator<<(std::ostream &os, const ComplexStruct &v) {
     return os << "c:" << v.cflt << "," << v.cdbl;
 }
 
@@ -106,7 +107,7 @@ PYBIND11_PACKED(struct EnumStruct {
     E2 e2;
 });
 
-std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
+std::ostream &operator<<(std::ostream &os, const StringStruct &v) {
     os << "a='";
     for (size_t i = 0; i < 3 && (v.a[i] != 0); i++) {
         os << v.a[i];
@@ -118,7 +119,7 @@ std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
     return os << "'";
 }
 
-std::ostream& operator<<(std::ostream& os, const ArrayStruct& v) {
+std::ostream &operator<<(std::ostream &os, const ArrayStruct &v) {
     os << "a={";
     for (int i = 0; i < 3; i++) {
         if (i > 0) {
@@ -142,15 +143,14 @@ std::ostream& operator<<(std::ostream& os, const ArrayStruct& v) {
     return os << '}';
 }
 
-std::ostream& operator<<(std::ostream& os, const EnumStruct& v) {
+std::ostream &operator<<(std::ostream &os, const EnumStruct &v) {
     return os << "e1=" << (v.e1 == E1::A ? "A" : "B") << ",e2=" << (v.e2 == E2::X ? "X" : "Y");
 }
 
 template <typename T>
 py::array mkarray_via_buffer(size_t n) {
-    return py::array(py::buffer_info(nullptr, sizeof(T),
-                                     py::format_descriptor<T>::format(),
-                                     1, { n }, { sizeof(T) }));
+    return py::array(py::buffer_info(
+        nullptr, sizeof(T), py::format_descriptor<T>::format(), 1, {n}, {sizeof(T)}));
 }
 
 #define SET_TEST_VALS(s, i)                                                                       \
@@ -188,9 +188,9 @@ py::list print_recarray(py::array_t<S, 0> arr) {
 py::array_t<int32_t, 0> test_array_ctors(int i) {
     using arr_t = py::array_t<int32_t, 0>;
 
-    std::vector<int32_t> data { 1, 2, 3, 4, 5, 6 };
-    std::vector<py::ssize_t> shape { 3, 2 };
-    std::vector<py::ssize_t> strides { 8, 4 };
+    std::vector<int32_t> data{1, 2, 3, 4, 5, 6};
+    std::vector<py::ssize_t> shape{3, 2};
+    std::vector<py::ssize_t> strides{8, 4};
 
     auto *ptr = data.data();
     auto *vptr = (void *) ptr;
@@ -210,36 +210,62 @@ py::array_t<int32_t, 0> test_array_ctors(int i) {
     };
 
     switch (i) {
-    // shape: (3, 2)
-    case 10: return arr_t(shape, strides, ptr);
-    case 11: return py::array(shape, strides, ptr);
-    case 12: return py::array(dtype, shape, strides, vptr);
-    case 13: return arr_t(shape, ptr);
-    case 14: return py::array(shape, ptr);
-    case 15: return py::array(dtype, shape, vptr);
-    case 16: return arr_t(buf_ndim2);
-    case 17: return py::array(buf_ndim2);
-    // shape: (3, 2) - post-fill
-    case 20: return fill(arr_t(shape, strides));
-    case 21: return py::array(shape, strides, ptr); // can't have nullptr due to templated ctor
-    case 22: return fill(py::array(dtype, shape, strides));
-    case 23: return fill(arr_t(shape));
-    case 24: return py::array(shape, ptr); // can't have nullptr due to templated ctor
-    case 25: return fill(py::array(dtype, shape));
-    case 26: return fill(arr_t(buf_ndim2_null));
-    case 27: return fill(py::array(buf_ndim2_null));
-    // shape: (6, )
-    case 30: return arr_t(6, ptr);
-    case 31: return py::array(6, ptr);
-    case 32: return py::array(dtype, 6, vptr);
-    case 33: return arr_t(buf_ndim1);
-    case 34: return py::array(buf_ndim1);
-    // shape: (6, )
-    case 40: return fill(arr_t(6));
-    case 41: return py::array(6, ptr);  // can't have nullptr due to templated ctor
-    case 42: return fill(py::array(dtype, 6));
-    case 43: return fill(arr_t(buf_ndim1_null));
-    case 44: return fill(py::array(buf_ndim1_null));
+        // shape: (3, 2)
+        case 10:
+            return arr_t(shape, strides, ptr);
+        case 11:
+            return py::array(shape, strides, ptr);
+        case 12:
+            return py::array(dtype, shape, strides, vptr);
+        case 13:
+            return arr_t(shape, ptr);
+        case 14:
+            return py::array(shape, ptr);
+        case 15:
+            return py::array(dtype, shape, vptr);
+        case 16:
+            return arr_t(buf_ndim2);
+        case 17:
+            return py::array(buf_ndim2);
+        // shape: (3, 2) - post-fill
+        case 20:
+            return fill(arr_t(shape, strides));
+        case 21:
+            return py::array(shape, strides, ptr); // can't have nullptr due to templated ctor
+        case 22:
+            return fill(py::array(dtype, shape, strides));
+        case 23:
+            return fill(arr_t(shape));
+        case 24:
+            return py::array(shape, ptr); // can't have nullptr due to templated ctor
+        case 25:
+            return fill(py::array(dtype, shape));
+        case 26:
+            return fill(arr_t(buf_ndim2_null));
+        case 27:
+            return fill(py::array(buf_ndim2_null));
+        // shape: (6, )
+        case 30:
+            return arr_t(6, ptr);
+        case 31:
+            return py::array(6, ptr);
+        case 32:
+            return py::array(dtype, 6, vptr);
+        case 33:
+            return arr_t(buf_ndim1);
+        case 34:
+            return py::array(buf_ndim1);
+        // shape: (6, )
+        case 40:
+            return fill(arr_t(6));
+        case 41:
+            return py::array(6, ptr); // can't have nullptr due to templated ctor
+        case 42:
+            return fill(py::array(dtype, 6));
+        case 43:
+            return fill(arr_t(buf_ndim1_null));
+        case 44:
+            return fill(py::array(buf_ndim1_null));
     }
     return arr_t();
 }
@@ -251,9 +277,15 @@ py::list test_dtype_ctors() {
     list.append(py::dtype::from_args(py::str("bool")));
     py::list names, offsets, formats;
     py::dict dict;
-    names.append(py::str("a")); names.append(py::str("b")); dict["names"] = names;
-    offsets.append(py::int_(1)); offsets.append(py::int_(10)); dict["offsets"] = offsets;
-    formats.append(py::dtype("int32")); formats.append(py::dtype("float64")); dict["formats"] = formats;
+    names.append(py::str("a"));
+    names.append(py::str("b"));
+    dict["names"] = names;
+    offsets.append(py::int_(1));
+    offsets.append(py::int_(10));
+    dict["offsets"] = offsets;
+    formats.append(py::dtype("int32"));
+    formats.append(py::dtype("float64"));
+    dict["formats"] = formats;
     dict["itemsize"] = py::int_(20);
     list.append(py::dtype::from_args(dict));
     list.append(py::dtype(names, formats, offsets, 20));
@@ -266,8 +298,11 @@ struct A {};
 struct B {};
 
 TEST_SUBMODULE(numpy_dtypes, m) {
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // typeinfo may be registered before the dtype descriptor for scalar casts to work...
     py::class_<SimpleStruct>(m, "SimpleStruct")
@@ -285,11 +320,10 @@ TEST_SUBMODULE(numpy_dtypes, m) {
             if (py::len(tup) != 4) {
                 throw py::cast_error("Invalid size");
             }
-            return SimpleStruct{
-                tup[0].cast<bool>(),
-                tup[1].cast<uint32_t>(),
-                tup[2].cast<float>(),
-                tup[3].cast<long double>()};
+            return SimpleStruct{tup[0].cast<bool>(),
+                                tup[1].cast<uint32_t>(),
+                                tup[2].cast<float>(),
+                                tup[3].cast<long double>()};
         });
 
     PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_);
@@ -311,18 +345,18 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 #ifdef PYBIND11_NEVER_DEFINED_EVER
     // If enabled, this should produce a static_assert failure telling the user that the struct
     // is not a POD type
-    struct NotPOD { std::string v; NotPOD() : v("hi") {}; };
+    struct NotPOD {
+        std::string v;
+        NotPOD() : v("hi"){};
+    };
     PYBIND11_NUMPY_DTYPE(NotPOD, v);
 #endif
 
     // Check that dtypes can be registered programmatically, both from
     // initializer lists of field descriptors and from other containers.
-    py::detail::npy_format_descriptor<A>::register_dtype(
-        {}
-    );
+    py::detail::npy_format_descriptor<A>::register_dtype({});
     py::detail::npy_format_descriptor<B>::register_dtype(
-        std::vector<py::detail::field_descriptor>{}
-    );
+        std::vector<py::detail::field_descriptor>{});
 
     // test_recarray, test_scalar_conversion
     m.def("create_rec_simple", &create_recarray<SimpleStruct>);
@@ -355,17 +389,15 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("get_format_unbound", []() { return py::format_descriptor<UnboundStruct>::format(); });
     m.def("print_format_descriptors", []() {
         py::list l;
-        for (const auto &fmt : {
-            py::format_descriptor<SimpleStruct>::format(),
-            py::format_descriptor<PackedStruct>::format(),
-            py::format_descriptor<NestedStruct>::format(),
-            py::format_descriptor<PartialStruct>::format(),
-            py::format_descriptor<PartialNestedStruct>::format(),
-            py::format_descriptor<StringStruct>::format(),
-            py::format_descriptor<ArrayStruct>::format(),
-            py::format_descriptor<EnumStruct>::format(),
-            py::format_descriptor<ComplexStruct>::format()
-        }) {
+        for (const auto &fmt : {py::format_descriptor<SimpleStruct>::format(),
+                                py::format_descriptor<PackedStruct>::format(),
+                                py::format_descriptor<NestedStruct>::format(),
+                                py::format_descriptor<PartialStruct>::format(),
+                                py::format_descriptor<PartialNestedStruct>::format(),
+                                py::format_descriptor<StringStruct>::format(),
+                                py::format_descriptor<ArrayStruct>::format(),
+                                py::format_descriptor<EnumStruct>::format(),
+                                py::format_descriptor<ComplexStruct>::format()}) {
             l.append(py::cast(fmt));
         }
         return l;
@@ -373,12 +405,9 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 
     // test_dtype
     std::vector<const char *> dtype_names{
-        "byte", "short", "intc", "int_", "longlong",
-        "ubyte", "ushort", "uintc", "uint", "ulonglong",
-        "half", "single", "double", "longdouble",
-        "csingle", "cdouble", "clongdouble",
-        "bool_", "datetime64", "timedelta64", "object_"
-    };
+        "byte",    "short",   "intc",        "int_",  "longlong",   "ubyte",       "ushort",
+        "uintc",   "uint",    "ulonglong",   "half",  "single",     "double",      "longdouble",
+        "csingle", "cdouble", "clongdouble", "bool_", "datetime64", "timedelta64", "object_"};
 
     m.def("print_dtypes", []() {
         py::list l;
@@ -415,9 +444,12 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         py::list list;
         auto dt1 = py::dtype::of<int32_t>();
         auto dt2 = py::dtype::of<SimpleStruct>();
-        list.append(dt1); list.append(dt2);
-        list.append(py::bool_(dt1.has_fields())); list.append(py::bool_(dt2.has_fields()));
-        list.append(py::int_(dt1.itemsize())); list.append(py::int_(dt2.itemsize()));
+        list.append(dt1);
+        list.append(dt2);
+        list.append(py::bool_(dt1.has_fields()));
+        list.append(py::bool_(dt2.has_fields()));
+        list.append(py::int_(dt1.itemsize()));
+        list.append(py::int_(dt2.itemsize()));
         return list;
     });
     struct TrailingPaddingStruct {
@@ -436,14 +468,20 @@ TEST_SUBMODULE(numpy_dtypes, m) {
             for (py::ssize_t i = 0; i < req.size * req.itemsize; i++) {
                 static_cast<char *>(req.ptr)[i] = 0;
             }
-            ptr[1].a[0] = 'a'; ptr[1].b[0] = 'a';
-            ptr[2].a[0] = 'a'; ptr[2].b[0] = 'a';
-            ptr[3].a[0] = 'a'; ptr[3].b[0] = 'a';
-
-            ptr[2].a[1] = 'b'; ptr[2].b[1] = 'b';
-            ptr[3].a[1] = 'b'; ptr[3].b[1] = 'b';
-
-            ptr[3].a[2] = 'c'; ptr[3].b[2] = 'c';
+            ptr[1].a[0] = 'a';
+            ptr[1].b[0] = 'a';
+            ptr[2].a[0] = 'a';
+            ptr[2].b[0] = 'a';
+            ptr[3].a[0] = 'a';
+            ptr[3].b[0] = 'a';
+
+            ptr[2].a[1] = 'b';
+            ptr[2].b[1] = 'b';
+            ptr[3].a[1] = 'b';
+            ptr[3].b[1] = 'b';
+
+            ptr[3].a[2] = 'c';
+            ptr[3].b[2] = 'c';
         }
         return arr;
     });
@@ -513,14 +551,19 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     PYBIND11_NUMPY_DTYPE(CompareStruct, x, y, z);
     m.def("compare_buffer_info", []() {
         py::list list;
-        list.append(py::bool_(py::detail::compare_buffer_info<float>::compare(py::buffer_info(nullptr, sizeof(float), "f", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<unsigned>::compare(py::buffer_info(nullptr, sizeof(int), "I", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(py::buffer_info(nullptr, sizeof(long), "l", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(py::buffer_info(nullptr, sizeof(long), sizeof(long) == sizeof(int) ? "i" : "q", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<CompareStruct>::compare(py::buffer_info(nullptr, sizeof(CompareStruct), "T{?:x:3xI:y:f:z:}", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<float>::compare(
+            py::buffer_info(nullptr, sizeof(float), "f", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<unsigned>::compare(
+            py::buffer_info(nullptr, sizeof(int), "I", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(
+            py::buffer_info(nullptr, sizeof(long), "l", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(
+            py::buffer_info(nullptr, sizeof(long), sizeof(long) == sizeof(int) ? "i" : "q", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<CompareStruct>::compare(
+            py::buffer_info(nullptr, sizeof(CompareStruct), "T{?:x:3xI:y:f:z:}", 1))));
         return list;
     });
-    m.def("buffer_to_dtype", [](py::buffer& buf) { return py::dtype(buf.request()); });
+    m.def("buffer_to_dtype", [](py::buffer &buf) { return py::dtype(buf.request()); });
 
     // test_scalar_conversion
     auto f_simple = [](SimpleStruct s) { return s.uint_ * 10; };
@@ -534,7 +577,8 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("f_simple_pass_thru_vectorized", py::vectorize(f_simple_pass_thru));
 
     // test_register_dtype
-    m.def("register_dtype", []() { PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_); });
+    m.def("register_dtype",
+          []() { PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_); });
 
     // test_str_leak
     m.def("dtype_wrapper", [](py::object d) { return py::dtype::from_args(std::move(d)); });
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index eb5281fb1d..eab08ec0a6 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -8,38 +8,43 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/numpy.h>
 
+#include "pybind11_tests.h"
+
 #include <utility>
 
 double my_func(int x, float y, double z) {
     py::print("my_func(x:int={}, y:float={:.0f}, z:float={:.0f})"_s.format(x, y, z));
-    return (float) x*y*z;
+    return (float) x * y * z;
 }
 
 TEST_SUBMODULE(numpy_vectorize, m) {
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // test_vectorize, test_docs, test_array_collapse
     // Vectorize all arguments of a function (though non-vector arguments are also allowed)
     m.def("vectorized_func", py::vectorize(my_func));
 
-    // Vectorize a lambda function with a capture object (e.g. to exclude some arguments from the vectorization)
+    // Vectorize a lambda function with a capture object (e.g. to exclude some arguments from the
+    // vectorization)
     m.def("vectorized_func2", [](py::array_t<int> x, py::array_t<float> y, float z) {
         return py::vectorize([z](int x, float y) { return my_func(x, y, z); })(std::move(x),
                                                                                std::move(y));
     });
 
     // Vectorize a complex-valued function
-    m.def("vectorized_func3", py::vectorize(
-        [](std::complex<double> c) { return c * std::complex<double>(2.f); }
-    ));
+    m.def("vectorized_func3",
+          py::vectorize([](std::complex<double> c) { return c * std::complex<double>(2.f); }));
 
     // test_type_selection
     // NumPy function which only accepts specific data types
-    // A lot of these no lints could be replaced with const refs, and probably should at some point.
+    // A lot of these no lints could be replaced with const refs, and probably should at some
+    // point.
     m.def("selective_func",
           [](const py::array_t<int, py::array::c_style> &) { return "Int branch taken."; });
     m.def("selective_func",
@@ -49,8 +54,8 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     });
 
     // test_passthrough_arguments
-    // Passthrough test: references and non-pod types should be automatically passed through (in the
-    // function definition below, only `b`, `d`, and `g` are vectorized):
+    // Passthrough test: references and non-pod types should be automatically passed through (in
+    // the function definition below, only `b`, `d`, and `g` are vectorized):
     struct NonPODClass {
         explicit NonPODClass(int v) : value{v} {}
         int value;
@@ -76,8 +81,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
         int value = 0;
     };
     py::class_<VectorizeTestClass> vtc(m, "VectorizeTestClass");
-    vtc .def(py::init<int>())
-        .def_readwrite("value", &VectorizeTestClass::value);
+    vtc.def(py::init<int>()).def_readwrite("value", &VectorizeTestClass::value);
 
     // Automatic vectorizing of methods
     vtc.def("method", py::vectorize(&VectorizeTestClass::method));
@@ -99,5 +103,5 @@ TEST_SUBMODULE(numpy_vectorize, m) {
               return py::detail::broadcast(buffers, ndim, shape);
           });
 
-    m.def("add_to", py::vectorize([](NonPODClass& x, int a) { x.value += a; }));
+    m.def("add_to", py::vectorize([](NonPODClass &x, int a) { x.value += a; }));
 }
diff --git a/tests/test_opaque_types.cpp b/tests/test_opaque_types.cpp
index 2da2457474..0386dba03d 100644
--- a/tests/test_opaque_types.cpp
+++ b/tests/test_opaque_types.cpp
@@ -7,8 +7,10 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/stl.h>
+
+#include "pybind11_tests.h"
+
 #include <vector>
 
 // IMPORTANT: Disable internal pybind11 translation mechanisms for STL data structures
@@ -26,12 +28,13 @@ TEST_SUBMODULE(opaque_types, m) {
         .def(py::init<>())
         .def("pop_back", &StringList::pop_back)
         /* There are multiple versions of push_back(), etc. Select the right ones. */
-        .def("push_back", (void (StringList::*)(const std::string &)) &StringList::push_back)
-        .def("back", (std::string &(StringList::*)()) &StringList::back)
+        .def("push_back", (void(StringList::*)(const std::string &)) & StringList::push_back)
+        .def("back", (std::string & (StringList::*) ()) & StringList::back)
         .def("__len__", [](const StringList &v) { return v.size(); })
-        .def("__iter__", [](StringList &v) {
-           return py::make_iterator(v.begin(), v.end());
-        }, py::keep_alive<0, 1>());
+        .def(
+            "__iter__",
+            [](StringList &v) { return py::make_iterator(v.begin(), v.end()); },
+            py::keep_alive<0, 1>());
 
     class ClassWithSTLVecProperty {
     public:
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index ffa059d5b5..a4b895a897 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -7,11 +7,13 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/operators.h>
+#include <pybind11/stl.h>
+
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
+
 #include <functional>
-#include <pybind11/operators.h>
-#include <pybind11/stl.h>
 
 class Vector2 {
 public:
@@ -21,17 +23,24 @@ class Vector2 {
         print_move_created(this);
         v.x = v.y = 0;
     }
-    Vector2 &operator=(const Vector2 &v) { x = v.x; y = v.y; print_copy_assigned(this); return *this; }
+    Vector2 &operator=(const Vector2 &v) {
+        x = v.x;
+        y = v.y;
+        print_copy_assigned(this);
+        return *this;
+    }
     Vector2 &operator=(Vector2 &&v) noexcept {
-        x   = v.x;
-        y   = v.y;
+        x = v.x;
+        y = v.y;
         v.x = v.y = 0;
         print_move_assigned(this);
         return *this;
     }
     ~Vector2() { print_destroyed(this); }
 
-    std::string toString() const { return "[" + std::to_string(x) + ", " + std::to_string(y) + "]"; }
+    std::string toString() const {
+        return "[" + std::to_string(x) + ", " + std::to_string(y) + "]";
+    }
 
     Vector2 operator-() const { return Vector2(-x, -y); }
     Vector2 operator+(const Vector2 &v) const { return Vector2(x + v.x, y + v.y); }
@@ -42,30 +51,51 @@ class Vector2 {
     Vector2 operator/(float value) const { return Vector2(x / value, y / value); }
     Vector2 operator*(const Vector2 &v) const { return Vector2(x * v.x, y * v.y); }
     Vector2 operator/(const Vector2 &v) const { return Vector2(x / v.x, y / v.y); }
-    Vector2& operator+=(const Vector2 &v) { x += v.x; y += v.y; return *this; }
-    Vector2& operator-=(const Vector2 &v) { x -= v.x; y -= v.y; return *this; }
-    Vector2& operator*=(float v) { x *= v; y *= v; return *this; }
-    Vector2& operator/=(float v) { x /= v; y /= v; return *this; }
-    Vector2& operator*=(const Vector2 &v) { x *= v.x; y *= v.y; return *this; }
-    Vector2& operator/=(const Vector2 &v) { x /= v.x; y /= v.y; return *this; }
+    Vector2 &operator+=(const Vector2 &v) {
+        x += v.x;
+        y += v.y;
+        return *this;
+    }
+    Vector2 &operator-=(const Vector2 &v) {
+        x -= v.x;
+        y -= v.y;
+        return *this;
+    }
+    Vector2 &operator*=(float v) {
+        x *= v;
+        y *= v;
+        return *this;
+    }
+    Vector2 &operator/=(float v) {
+        x /= v;
+        y /= v;
+        return *this;
+    }
+    Vector2 &operator*=(const Vector2 &v) {
+        x *= v.x;
+        y *= v.y;
+        return *this;
+    }
+    Vector2 &operator/=(const Vector2 &v) {
+        x /= v.x;
+        y /= v.y;
+        return *this;
+    }
 
     friend Vector2 operator+(float f, const Vector2 &v) { return Vector2(f + v.x, f + v.y); }
     friend Vector2 operator-(float f, const Vector2 &v) { return Vector2(f - v.x, f - v.y); }
     friend Vector2 operator*(float f, const Vector2 &v) { return Vector2(f * v.x, f * v.y); }
     friend Vector2 operator/(float f, const Vector2 &v) { return Vector2(f / v.x, f / v.y); }
 
-    bool operator==(const Vector2 &v) const {
-        return x == v.x && y == v.y;
-    }
-    bool operator!=(const Vector2 &v) const {
-        return x != v.x || y != v.y;
-    }
+    bool operator==(const Vector2 &v) const { return x == v.x && y == v.y; }
+    bool operator!=(const Vector2 &v) const { return x != v.x || y != v.y; }
+
 private:
     float x, y;
 };
 
-class C1 { };
-class C2 { };
+class C1 {};
+class C2 {};
 
 int operator+(const C1 &, const C1 &) { return 11; }
 int operator+(const C2 &, const C2 &) { return 22; }
@@ -84,43 +114,41 @@ bool operator==(const HashMe &lhs, const HashMe &rhs) { return lhs.member == rhs
 // namespace instead, per this recommendation:
 // https://en.cppreference.com/w/cpp/language/extending_std#Adding_template_specializations
 namespace std {
-    template<>
-    struct hash<Vector2> {
-        // Not a good hash function, but easy to test
-        size_t operator()(const Vector2 &) { return 4; }
-    };
+template <>
+struct hash<Vector2> {
+    // Not a good hash function, but easy to test
+    size_t operator()(const Vector2 &) { return 4; }
+};
 
-    // HashMe has a hash function in C++ but no `__hash__` for Python.
-    template <>
-    struct hash<HashMe> {
-        std::size_t operator()(const HashMe &selector) const {
-            return std::hash<std::string>()(selector.member);
-        }
-    };
+// HashMe has a hash function in C++ but no `__hash__` for Python.
+template <>
+struct hash<HashMe> {
+    std::size_t operator()(const HashMe &selector) const {
+        return std::hash<std::string>()(selector.member);
+    }
+};
 } // namespace std
 
 // Not a good abs function, but easy to test.
-std::string abs(const Vector2&) {
-    return "abs(Vector2)";
-}
+std::string abs(const Vector2 &) { return "abs(Vector2)"; }
 
 // MSVC & Intel warns about unknown pragmas, and warnings are errors.
 #if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-  #pragma GCC diagnostic push
-  // clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
-  // `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
-  // Here, we suppress the warning using `#pragma diagnostic`.
-  // Taken from: https://github.com/RobotLocomotion/drake/commit/aaf84b46
-  // TODO(eric): This could be resolved using a function / functor (e.g. `py::self()`).
-  #if defined(__APPLE__) && defined(__clang__)
-    #if (__clang_major__ >= 10)
-      #pragma GCC diagnostic ignored "-Wself-assign-overloaded"
-    #endif
-  #elif defined(__clang__)
-    #if (__clang_major__ >= 7)
-      #pragma GCC diagnostic ignored "-Wself-assign-overloaded"
-    #endif
-  #endif
+#    pragma GCC diagnostic push
+// clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
+// `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
+// Here, we suppress the warning using `#pragma diagnostic`.
+// Taken from: https://github.com/RobotLocomotion/drake/commit/aaf84b46
+// TODO(eric): This could be resolved using a function / functor (e.g. `py::self()`).
+#    if defined(__APPLE__) && defined(__clang__)
+#        if (__clang_major__ >= 10)
+#            pragma GCC diagnostic ignored "-Wself-assign-overloaded"
+#        endif
+#    elif defined(__clang__)
+#        if (__clang_major__ >= 7)
+#            pragma GCC diagnostic ignored "-Wself-assign-overloaded"
+#        endif
+#    endif
 #endif
 
 TEST_SUBMODULE(operators, m) {
@@ -154,46 +182,52 @@ TEST_SUBMODULE(operators, m) {
         .def(py::hash(py::self))
         // N.B. See warning about usage of `py::detail::abs(py::self)` in
         // `operators.h`.
-        .def("__abs__", [](const Vector2& v) { return abs(v); })
-        ;
+        .def("__abs__", [](const Vector2 &v) { return abs(v); });
 
     m.attr("Vector") = m.attr("Vector2");
 
     // test_operators_notimplemented
     // #393: need to return NotSupported to ensure correct arithmetic operator behavior
-    py::class_<C1>(m, "C1")
-        .def(py::init<>())
-        .def(py::self + py::self);
+    py::class_<C1>(m, "C1").def(py::init<>()).def(py::self + py::self);
 
     py::class_<C2>(m, "C2")
         .def(py::init<>())
         .def(py::self + py::self)
-        .def("__add__", [](const C2& c2, const C1& c1) { return c2 + c1; })
-        .def("__radd__", [](const C2& c2, const C1& c1) { return c1 + c2; });
+        .def("__add__", [](const C2 &c2, const C1 &c1) { return c2 + c1; })
+        .def("__radd__", [](const C2 &c2, const C1 &c1) { return c1 + c2; });
 
     // test_nested
     // #328: first member in a class can't be used in operators
-    struct NestABase { int value = -2; };
+    struct NestABase {
+        int value = -2;
+    };
     py::class_<NestABase>(m, "NestABase")
         .def(py::init<>())
         .def_readwrite("value", &NestABase::value);
 
     struct NestA : NestABase {
         int value = 3;
-        NestA& operator+=(int i) { value += i; return *this; }
+        NestA &operator+=(int i) {
+            value += i;
+            return *this;
+        }
     };
     py::class_<NestA>(m, "NestA")
         .def(py::init<>())
         .def(py::self += int())
-        .def("as_base", [](NestA &a) -> NestABase& {
-            return (NestABase&) a;
-        }, py::return_value_policy::reference_internal);
+        .def(
+            "as_base",
+            [](NestA &a) -> NestABase & { return (NestABase &) a; },
+            py::return_value_policy::reference_internal);
     m.def("get_NestA", [](const NestA &a) { return a.value; });
 
     struct NestB {
         NestA a;
         int value = 4;
-        NestB& operator-=(int i) { value -= i; return *this; }
+        NestB &operator-=(int i) {
+            value -= i;
+            return *this;
+        }
     };
     py::class_<NestB>(m, "NestB")
         .def(py::init<>())
@@ -204,7 +238,10 @@ TEST_SUBMODULE(operators, m) {
     struct NestC {
         NestB b;
         int value = 5;
-        NestC& operator*=(int i) { value *= i; return *this; }
+        NestC &operator*=(int i) {
+            value *= i;
+            return *this;
+        }
     };
     py::class_<NestC>(m, "NestC")
         .def(py::init<>())
@@ -212,16 +249,15 @@ TEST_SUBMODULE(operators, m) {
         .def_readwrite("b", &NestC::b);
     m.def("get_NestC", [](const NestC &c) { return c.value; });
 
-
     // test_overriding_eq_reset_hash
     // #2191 Overriding __eq__ should set __hash__ to None
     struct Comparable {
         int value;
-        bool operator==(const Comparable& rhs) const {return value == rhs.value;}
+        bool operator==(const Comparable &rhs) const { return value == rhs.value; }
     };
 
     struct Hashable : Comparable {
-        explicit Hashable(int value): Comparable{value}{};
+        explicit Hashable(int value) : Comparable{value} {};
         size_t hash() const { return static_cast<size_t>(value); }
     };
 
@@ -229,9 +265,7 @@ TEST_SUBMODULE(operators, m) {
         using Hashable::Hashable;
     };
 
-    py::class_<Comparable>(m, "Comparable")
-        .def(py::init<int>())
-        .def(py::self == py::self);
+    py::class_<Comparable>(m, "Comparable").def(py::init<int>()).def(py::self == py::self);
 
     py::class_<Hashable>(m, "Hashable")
         .def(py::init<int>())
@@ -250,5 +284,5 @@ TEST_SUBMODULE(operators, m) {
     m.def("get_unhashable_HashMe_set", []() { return std::unordered_set<HashMe>{{"one"}}; });
 }
 #if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-  #pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index efe0463df0..bf1ee4671c 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -20,11 +20,11 @@
 namespace exercise_trampoline {
 
 struct SimpleBase {
-    int num               = 0;
+    int num = 0;
     virtual ~SimpleBase() = default;
 
     // For compatibility with old clang versions:
-    SimpleBase()                   = default;
+    SimpleBase() = default;
     SimpleBase(const SimpleBase &) = default;
 };
 
@@ -50,7 +50,7 @@ void wrap(py::module m) {
                 }
                 auto cpp_state = std::unique_ptr<SimpleBase>(new SimpleBaseTrampoline);
                 cpp_state->num = t[0].cast<int>();
-                auto py_state  = t[1].cast<py::dict>();
+                auto py_state = t[1].cast<py::dict>();
                 return std::make_pair(std::move(cpp_state), py_state);
             }));
 
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 196a54c41f..9364cccf69 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -7,22 +7,21 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include <utility>
-
 #include "pybind11_tests.h"
 
+#include <utility>
 
 TEST_SUBMODULE(pytypes, m) {
     // test_bool
-    m.def("get_bool", []{return py::bool_(false);});
+    m.def("get_bool", [] { return py::bool_(false); });
     // test_int
-    m.def("get_int", []{return py::int_(0);});
+    m.def("get_int", [] { return py::int_(0); });
     // test_iterator
-    m.def("get_iterator", []{return py::iterator();});
+    m.def("get_iterator", [] { return py::iterator(); });
     // test_iterable
-    m.def("get_iterable", []{return py::iterable();});
+    m.def("get_iterable", [] { return py::iterable(); });
     // test_float
-    m.def("get_float", []{return py::float_(0.0f);});
+    m.def("get_float", [] { return py::float_(0.0f); });
     // test_list
     m.def("list_no_args", []() { return py::list{}; });
     m.def("list_ssize_t", []() { return py::list{(py::ssize_t) 0}; });
@@ -45,7 +44,7 @@ TEST_SUBMODULE(pytypes, m) {
         }
     });
     // test_none
-    m.def("get_none", []{return py::none();});
+    m.def("get_none", [] { return py::none(); });
     m.def("print_none", [](const py::none &none) { py::print("none: {}"_s.format(none)); });
 
     // test_set
@@ -66,15 +65,15 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("set_contains", [](const py::set &set, const char *key) { return set.contains(key); });
 
     // test_dict
-    m.def("get_dict", []() { return py::dict("key"_a="value"); });
+    m.def("get_dict", []() { return py::dict("key"_a = "value"); });
     m.def("print_dict", [](const py::dict &dict) {
         for (auto item : dict) {
             py::print("key: {}, value={}"_s.format(item.first, item.second));
         }
     });
     m.def("dict_keyword_constructor", []() {
-        auto d1 = py::dict("x"_a=1, "y"_a=2);
-        auto d2 = py::dict("z"_a=3, **d1);
+        auto d1 = py::dict("x"_a = 1, "y"_a = 2);
+        auto d2 = py::dict("z"_a = 3, **d1);
         return d2;
     });
     m.def("dict_contains",
@@ -91,7 +90,8 @@ TEST_SUBMODULE(pytypes, m) {
 #if PY_VERSION_HEX >= 0x03030000
     // test_simple_namespace
     m.def("get_simple_namespace", []() {
-        auto ns = py::module_::import("types").attr("SimpleNamespace")("attr"_a=42, "x"_a="foo", "wrong"_a=1);
+        auto ns = py::module_::import("types").attr("SimpleNamespace")(
+            "attr"_a = 42, "x"_a = "foo", "wrong"_a = 1);
         py::delattr(ns, "wrong");
         py::setattr(ns, "right", py::int_(2));
         return ns;
@@ -103,16 +103,15 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("str_from_char_size_t", []() { return py::str{"blue", (py::size_t) 4}; });
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });
-    m.def("str_from_object", [](const py::object& obj) { return py::str(obj); });
-    m.def("repr_from_object", [](const py::object& obj) { return py::repr(obj); });
+    m.def("str_from_object", [](const py::object &obj) { return py::str(obj); });
+    m.def("repr_from_object", [](const py::object &obj) { return py::repr(obj); });
     m.def("str_from_handle", [](py::handle h) { return py::str(h); });
-    m.def("str_from_string_from_str", [](const py::str& obj) {
-        return py::str(static_cast<std::string>(obj));
-    });
+    m.def("str_from_string_from_str",
+          [](const py::str &obj) { return py::str(static_cast<std::string>(obj)); });
 
     m.def("str_format", []() {
         auto s1 = "{} + {} = {}"_s.format(1, 2, 3);
-        auto s2 = "{a} + {b} = {c}"_s.format("a"_a=1, "b"_a=2, "c"_a=3);
+        auto s2 = "{a} + {b} = {c}"_s.format("a"_a = 1, "b"_a = 2, "c"_a = 3);
         return py::make_tuple(s1, s2);
     });
 
@@ -131,9 +130,7 @@ TEST_SUBMODULE(pytypes, m) {
     // test_capsule
     m.def("return_capsule_with_destructor", []() {
         py::print("creating capsule");
-        return py::capsule([]() {
-            py::print("destructing capsule");
-        });
+        return py::capsule([]() { py::print("destructing capsule"); });
     });
 
     m.def("return_capsule_with_destructor_2", []() {
@@ -148,23 +145,23 @@ TEST_SUBMODULE(pytypes, m) {
             if (ptr) {
                 const auto *name = PyCapsule_GetName(ptr);
                 py::print("destructing capsule ({}, '{}')"_s.format(
-                    (size_t) PyCapsule_GetPointer(ptr, name), name
-                ));
+                    (size_t) PyCapsule_GetPointer(ptr, name), name));
             }
         });
 
         capsule.set_pointer((void *) 1234);
 
         // Using get_pointer<T>()
-        void* contents1 = static_cast<void*>(capsule);
-        void* contents2 = capsule.get_pointer();
-        void* contents3 = capsule.get_pointer<void>();
+        void *contents1 = static_cast<void *>(capsule);
+        void *contents2 = capsule.get_pointer();
+        void *contents3 = capsule.get_pointer<void>();
 
         auto result1 = reinterpret_cast<size_t>(contents1);
         auto result2 = reinterpret_cast<size_t>(contents2);
         auto result3 = reinterpret_cast<size_t>(contents3);
 
-        py::print("created capsule ({}, '{}')"_s.format(result1 & result2 & result3, capsule.name()));
+        py::print(
+            "created capsule ({}, '{}')"_s.format(result1 & result2 & result3, capsule.name()));
         return capsule;
     });
 
@@ -244,51 +241,45 @@ TEST_SUBMODULE(pytypes, m) {
 
     // test_constructors
     m.def("default_constructors", []() {
-        return py::dict(
-            "bytes"_a=py::bytes(),
-            "bytearray"_a=py::bytearray(),
-            "str"_a=py::str(),
-            "bool"_a=py::bool_(),
-            "int"_a=py::int_(),
-            "float"_a=py::float_(),
-            "tuple"_a=py::tuple(),
-            "list"_a=py::list(),
-            "dict"_a=py::dict(),
-            "set"_a=py::set()
-        );
+        return py::dict("bytes"_a = py::bytes(),
+                        "bytearray"_a = py::bytearray(),
+                        "str"_a = py::str(),
+                        "bool"_a = py::bool_(),
+                        "int"_a = py::int_(),
+                        "float"_a = py::float_(),
+                        "tuple"_a = py::tuple(),
+                        "list"_a = py::list(),
+                        "dict"_a = py::dict(),
+                        "set"_a = py::set());
     });
 
     m.def("converting_constructors", [](const py::dict &d) {
-        return py::dict(
-            "bytes"_a=py::bytes(d["bytes"]),
-            "bytearray"_a=py::bytearray(d["bytearray"]),
-            "str"_a=py::str(d["str"]),
-            "bool"_a=py::bool_(d["bool"]),
-            "int"_a=py::int_(d["int"]),
-            "float"_a=py::float_(d["float"]),
-            "tuple"_a=py::tuple(d["tuple"]),
-            "list"_a=py::list(d["list"]),
-            "dict"_a=py::dict(d["dict"]),
-            "set"_a=py::set(d["set"]),
-            "memoryview"_a=py::memoryview(d["memoryview"])
-        );
+        return py::dict("bytes"_a = py::bytes(d["bytes"]),
+                        "bytearray"_a = py::bytearray(d["bytearray"]),
+                        "str"_a = py::str(d["str"]),
+                        "bool"_a = py::bool_(d["bool"]),
+                        "int"_a = py::int_(d["int"]),
+                        "float"_a = py::float_(d["float"]),
+                        "tuple"_a = py::tuple(d["tuple"]),
+                        "list"_a = py::list(d["list"]),
+                        "dict"_a = py::dict(d["dict"]),
+                        "set"_a = py::set(d["set"]),
+                        "memoryview"_a = py::memoryview(d["memoryview"]));
     });
 
     m.def("cast_functions", [](const py::dict &d) {
         // When converting between Python types, obj.cast<T>() should be the same as T(obj)
-        return py::dict(
-            "bytes"_a=d["bytes"].cast<py::bytes>(),
-            "bytearray"_a=d["bytearray"].cast<py::bytearray>(),
-            "str"_a=d["str"].cast<py::str>(),
-            "bool"_a=d["bool"].cast<py::bool_>(),
-            "int"_a=d["int"].cast<py::int_>(),
-            "float"_a=d["float"].cast<py::float_>(),
-            "tuple"_a=d["tuple"].cast<py::tuple>(),
-            "list"_a=d["list"].cast<py::list>(),
-            "dict"_a=d["dict"].cast<py::dict>(),
-            "set"_a=d["set"].cast<py::set>(),
-            "memoryview"_a=d["memoryview"].cast<py::memoryview>()
-        );
+        return py::dict("bytes"_a = d["bytes"].cast<py::bytes>(),
+                        "bytearray"_a = d["bytearray"].cast<py::bytearray>(),
+                        "str"_a = d["str"].cast<py::str>(),
+                        "bool"_a = d["bool"].cast<py::bool_>(),
+                        "int"_a = d["int"].cast<py::int_>(),
+                        "float"_a = d["float"].cast<py::float_>(),
+                        "tuple"_a = d["tuple"].cast<py::tuple>(),
+                        "list"_a = d["list"].cast<py::list>(),
+                        "dict"_a = d["dict"].cast<py::dict>(),
+                        "set"_a = d["set"].cast<py::set>(),
+                        "memoryview"_a = d["memoryview"].cast<py::memoryview>());
     });
 
     m.def("convert_to_pybind11_str", [](const py::object &o) { return py::str(o); });
@@ -341,10 +332,7 @@ TEST_SUBMODULE(pytypes, m) {
         l.append(py::cast(12));
         l.append(py::int_(15));
 
-        return py::dict(
-            "d"_a=d,
-            "l"_a=l
-        );
+        return py::dict("d"_a = d, "l"_a = l);
     });
 
     // test_print
@@ -352,16 +340,17 @@ TEST_SUBMODULE(pytypes, m) {
         py::print("Hello, World!");
         py::print(1, 2.0, "three", true, std::string("-- multiple args"));
         auto args = py::make_tuple("and", "a", "custom", "separator");
-        py::print("*args", *args, "sep"_a="-");
-        py::print("no new line here", "end"_a=" -- ");
+        py::print("*args", *args, "sep"_a = "-");
+        py::print("no new line here", "end"_a = " -- ");
         py::print("next print");
 
         auto py_stderr = py::module_::import("sys").attr("stderr");
-        py::print("this goes to stderr", "file"_a=py_stderr);
+        py::print("this goes to stderr", "file"_a = py_stderr);
 
-        py::print("flush", "flush"_a=true);
+        py::print("flush", "flush"_a = true);
 
-        py::print("{a} + {b} = {c}"_s.format("a"_a="py::print", "b"_a="str.format", "c"_a="this"));
+        py::print(
+            "{a} + {b} = {c}"_s.format("a"_a = "py::print", "b"_a = "str.format", "c"_a = "this"));
     });
 
     m.def("print_failure", []() { py::print(42, UnregisteredType()); });
@@ -406,8 +395,8 @@ TEST_SUBMODULE(pytypes, m) {
           [](const py::buffer &b) { return py::memoryview(b.request()); });
 
     m.def("test_memoryview_from_buffer", [](bool is_unsigned) {
-        static const int16_t si16[] = { 3, 1, 4, 1, 5 };
-        static const uint16_t ui16[] = { 2, 7, 1, 8 };
+        static const int16_t si16[] = {3, 1, 4, 1, 5};
+        static const uint16_t ui16[] = {2, 7, 1, 8};
         if (is_unsigned) {
             return py::memoryview::from_buffer(ui16, {4}, {sizeof(uint16_t)});
         }
@@ -415,32 +404,29 @@ TEST_SUBMODULE(pytypes, m) {
     });
 
     m.def("test_memoryview_from_buffer_nativeformat", []() {
-        static const char* format = "@i";
-        static const int32_t arr[] = { 4, 7, 5 };
-        return py::memoryview::from_buffer(
-            arr, sizeof(int32_t), format, { 3 }, { sizeof(int32_t) });
+        static const char *format = "@i";
+        static const int32_t arr[] = {4, 7, 5};
+        return py::memoryview::from_buffer(arr, sizeof(int32_t), format, {3}, {sizeof(int32_t)});
     });
 
     m.def("test_memoryview_from_buffer_empty_shape", []() {
-        static const char* buf = "";
-        return py::memoryview::from_buffer(buf, 1, "B", { }, { });
+        static const char *buf = "";
+        return py::memoryview::from_buffer(buf, 1, "B", {}, {});
     });
 
     m.def("test_memoryview_from_buffer_invalid_strides", []() {
-        static const char* buf = "\x02\x03\x04";
-        return py::memoryview::from_buffer(buf, 1, "B", { 3 }, { });
+        static const char *buf = "\x02\x03\x04";
+        return py::memoryview::from_buffer(buf, 1, "B", {3}, {});
     });
 
     m.def("test_memoryview_from_buffer_nullptr", []() {
-        return py::memoryview::from_buffer(
-            static_cast<void*>(nullptr), 1, "B", { }, { });
+        return py::memoryview::from_buffer(static_cast<void *>(nullptr), 1, "B", {}, {});
     });
 
 #if PY_MAJOR_VERSION >= 3
     m.def("test_memoryview_from_memory", []() {
-        const char* buf = "\xff\xe1\xab\x37";
-        return py::memoryview::from_memory(
-            buf, static_cast<py::ssize_t>(strlen(buf)));
+        const char *buf = "\xff\xe1\xab\x37";
+        return py::memoryview::from_memory(buf, static_cast<py::ssize_t>(strlen(buf)));
     });
 #endif
 
@@ -461,8 +447,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("pass_to_std_string", [](const std::string &s) { return s.size(); });
 
     // test_weakref
-    m.def("weakref_from_handle",
-          [](py::handle h) { return py::weakref(h); });
+    m.def("weakref_from_handle", [](py::handle h) { return py::weakref(h); });
     m.def("weakref_from_handle_and_function",
           [](py::handle h, py::function f) { return py::weakref(h, std::move(f)); });
     m.def("weakref_from_object", [](const py::object &o) { return py::weakref(o); });
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index 5d4275f36d..addbfe9bb4 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -8,44 +8,52 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/operators.h>
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #include <algorithm>
 #include <utility>
 #include <vector>
 
 #ifdef PYBIND11_HAS_OPTIONAL
-#include <optional>
-#endif  // PYBIND11_HAS_OPTIONAL
-
+#    include <optional>
+#endif // PYBIND11_HAS_OPTIONAL
 
-template<typename T>
+template <typename T>
 class NonZeroIterator {
-    const T* ptr_;
+    const T *ptr_;
+
 public:
     explicit NonZeroIterator(const T *ptr) : ptr_(ptr) {}
-    const T& operator*() const { return *ptr_; }
-    NonZeroIterator& operator++() { ++ptr_; return *this; }
+    const T &operator*() const { return *ptr_; }
+    NonZeroIterator &operator++() {
+        ++ptr_;
+        return *this;
+    }
 };
 
 class NonZeroSentinel {};
 
-template<typename A, typename B>
-bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentinel&) {
+template <typename A, typename B>
+bool operator==(const NonZeroIterator<std::pair<A, B>> &it, const NonZeroSentinel &) {
     return !(*it).first || !(*it).second;
 }
 
 /* Iterator where dereferencing returns prvalues instead of references. */
-template<typename T>
+template <typename T>
 class NonRefIterator {
-    const T* ptr_;
+    const T *ptr_;
+
 public:
     explicit NonRefIterator(const T *ptr) : ptr_(ptr) {}
     T operator*() const { return T(*ptr_); }
-    NonRefIterator& operator++() { ++ptr_; return *this; }
+    NonRefIterator &operator++() {
+        ++ptr_;
+        return *this;
+    }
     bool operator==(const NonRefIterator &other) const { return ptr_ == other.ptr_; }
 };
 
@@ -54,17 +62,18 @@ class NonCopyableInt {
     explicit NonCopyableInt(int value) : value_(value) {}
     NonCopyableInt(const NonCopyableInt &) = delete;
     NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
-        other.value_ = -1;  // detect when an unwanted move occurs
+        other.value_ = -1; // detect when an unwanted move occurs
     }
     NonCopyableInt &operator=(const NonCopyableInt &) = delete;
     NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
         value_ = other.value_;
-        other.value_ = -1;  // detect when an unwanted move occurs
+        other.value_ = -1; // detect when an unwanted move occurs
         return *this;
     }
     int get() const { return value_; }
     void set(int value) { value_ = value; }
     ~NonCopyableInt() = default;
+
 private:
     int value_;
 };
@@ -81,7 +90,9 @@ py::list test_random_access_iterator(PythonType x) {
     auto checks = py::list();
     auto assert_equal = [&checks](py::handle a, py::handle b) {
         auto result = PyObject_RichCompareBool(a.ptr(), b.ptr(), Py_EQ);
-        if (result == -1) { throw py::error_already_set(); }
+        if (result == -1) {
+            throw py::error_already_set();
+        }
         checks.append(result != 0);
     };
 
@@ -116,7 +127,7 @@ py::list test_random_access_iterator(PythonType x) {
 
 TEST_SUBMODULE(sequences_and_iterators, m) {
     // test_sliceable
-    class Sliceable{
+    class Sliceable {
     public:
         explicit Sliceable(int n) : size(n) {}
         int start, stop, step;
@@ -130,18 +141,20 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
                 throw py::error_already_set();
             }
             int istart = static_cast<int>(start);
-            int istop  = static_cast<int>(stop);
-            int istep  = static_cast<int>(step);
+            int istop = static_cast<int>(stop);
+            int istep = static_cast<int>(step);
             return std::make_tuple(istart, istop, istep);
         });
 
     m.def("make_forward_slice_size_t", []() { return py::slice(0, -1, 1); });
-    m.def("make_reversed_slice_object", []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
+    m.def("make_reversed_slice_object",
+          []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
 #ifdef PYBIND11_HAS_OPTIONAL
     m.attr("has_optional") = true;
-    m.def("make_reversed_slice_size_t_optional_verbose", []() { return py::slice(std::nullopt, std::nullopt, -1); });
-    // Warning: The following spelling may still compile if optional<> is not present and give wrong answers.
-    // Please use with caution.
+    m.def("make_reversed_slice_size_t_optional_verbose",
+          []() { return py::slice(std::nullopt, std::nullopt, -1); });
+    // Warning: The following spelling may still compile if optional<> is not present and give
+    // wrong answers. Please use with caution.
     m.def("make_reversed_slice_size_t_optional", []() { return py::slice({}, {}, -1); });
 #else
     m.attr("has_optional") = false;
@@ -166,7 +179,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             print_copy_created(this);
             // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[m_size];
-            memcpy(m_data, s.m_data, sizeof(float)*m_size);
+            memcpy(m_data, s.m_data, sizeof(float) * m_size);
         }
         Sequence(Sequence &&s) noexcept : m_size(s.m_size), m_data(s.m_data) {
             print_move_created(this);
@@ -174,14 +187,17 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             s.m_data = nullptr;
         }
 
-        ~Sequence() { print_destroyed(this); delete[] m_data; }
+        ~Sequence() {
+            print_destroyed(this);
+            delete[] m_data;
+        }
 
         Sequence &operator=(const Sequence &s) {
             if (&s != this) {
                 delete[] m_data;
                 m_size = s.m_size;
                 m_data = new float[m_size];
-                memcpy(m_data, s.m_data, sizeof(float)*m_size);
+                memcpy(m_data, s.m_data, sizeof(float) * m_size);
             }
             print_copy_assigned(this);
             return *this;
@@ -235,7 +251,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         size_t size() const { return m_size; }
 
         const float *begin() const { return m_data; }
-        const float *end() const { return m_data+m_size; }
+        const float *end() const { return m_data + m_size; }
 
     private:
         size_t m_size;
@@ -303,8 +319,8 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         ;
 
     // test_map_iterator
-    // Interface of a map-like object that isn't (directly) an unordered_map, but provides some basic
-    // map-like functionality.
+    // Interface of a map-like object that isn't (directly) an unordered_map, but provides some
+    // basic map-like functionality.
     class StringMap {
     public:
         StringMap() = default;
@@ -314,8 +330,10 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         void set(const std::string &key, std::string val) { map[key] = std::move(val); }
         std::string get(const std::string &key) const { return map.at(key); }
         size_t size() const { return map.size(); }
+
     private:
         std::unordered_map<std::string, std::string> map;
+
     public:
         decltype(map.cbegin()) begin() const { return map.cbegin(); }
         decltype(map.cend()) end() const { return map.cend(); }
@@ -350,90 +368,115 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     class IntPairs {
     public:
         explicit IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
-        const std::pair<int, int>* begin() const { return data_.data(); }
+        const std::pair<int, int> *begin() const { return data_.data(); }
         // .end() only required for py::make_iterator(self) overload
-        const std::pair<int, int>* end() const { return data_.data() + data_.size(); }
+        const std::pair<int, int> *end() const { return data_.data() + data_.size(); }
+
     private:
         std::vector<std::pair<int, int>> data_;
     };
     py::class_<IntPairs>(m, "IntPairs")
         .def(py::init<std::vector<std::pair<int, int>>>())
-        .def("nonzero", [](const IntPairs& s) {
-            return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
-        .def("nonzero_keys", [](const IntPairs& s) {
-            return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
-        .def("nonzero_values", [](const IntPairs& s) {
-            return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
+        .def(
+            "nonzero",
+            [](const IntPairs &s) {
+                return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()),
+                                         NonZeroSentinel());
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonzero_keys",
+            [](const IntPairs &s) {
+                return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()),
+                                             NonZeroSentinel());
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonzero_values",
+            [](const IntPairs &s) {
+                return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()),
+                                               NonZeroSentinel());
+            },
+            py::keep_alive<0, 1>())
 
         // test iterator that returns values instead of references
-        .def("nonref", [](const IntPairs& s) {
-             return py::make_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
-                                      NonRefIterator<std::pair<int, int>>(s.end()));
-        }, py::keep_alive<0, 1>())
-        .def("nonref_keys", [](const IntPairs& s) {
-             return py::make_key_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
-                                          NonRefIterator<std::pair<int, int>>(s.end()));
-        }, py::keep_alive<0, 1>())
-        .def("nonref_values", [](const IntPairs& s) {
-             return py::make_value_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
-                                            NonRefIterator<std::pair<int, int>>(s.end()));
-        }, py::keep_alive<0, 1>())
+        .def(
+            "nonref",
+            [](const IntPairs &s) {
+                return py::make_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                         NonRefIterator<std::pair<int, int>>(s.end()));
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonref_keys",
+            [](const IntPairs &s) {
+                return py::make_key_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                             NonRefIterator<std::pair<int, int>>(s.end()));
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonref_values",
+            [](const IntPairs &s) {
+                return py::make_value_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                               NonRefIterator<std::pair<int, int>>(s.end()));
+            },
+            py::keep_alive<0, 1>())
 
         // test single-argument make_iterator
-        .def("simple_iterator", [](IntPairs& self) {
-            return py::make_iterator(self);
-        }, py::keep_alive<0, 1>())
-        .def("simple_keys", [](IntPairs& self) {
-            return py::make_key_iterator(self);
-        }, py::keep_alive<0, 1>())
-        .def("simple_values", [](IntPairs& self) {
-            return py::make_value_iterator(self);
-        }, py::keep_alive<0, 1>())
+        .def(
+            "simple_iterator",
+            [](IntPairs &self) { return py::make_iterator(self); },
+            py::keep_alive<0, 1>())
+        .def(
+            "simple_keys",
+            [](IntPairs &self) { return py::make_key_iterator(self); },
+            py::keep_alive<0, 1>())
+        .def(
+            "simple_values",
+            [](IntPairs &self) { return py::make_value_iterator(self); },
+            py::keep_alive<0, 1>())
 
         // Test iterator with an Extra (doesn't do anything useful, so not used
         // at runtime, but tests need to be able to compile with the correct
         // overload. See PR #3293.
-        .def("_make_iterator_extras", [](IntPairs& self) {
-            return py::make_iterator(self, py::call_guard<int>());
-        }, py::keep_alive<0, 1>())
-        .def("_make_key_extras", [](IntPairs& self) {
-            return py::make_key_iterator(self, py::call_guard<int>());
-        }, py::keep_alive<0, 1>())
-        .def("_make_value_extras", [](IntPairs& self) {
-            return py::make_value_iterator(self, py::call_guard<int>());
-        }, py::keep_alive<0, 1>())
-        ;
+        .def(
+            "_make_iterator_extras",
+            [](IntPairs &self) { return py::make_iterator(self, py::call_guard<int>()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "_make_key_extras",
+            [](IntPairs &self) { return py::make_key_iterator(self, py::call_guard<int>()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "_make_value_extras",
+            [](IntPairs &self) { return py::make_value_iterator(self, py::call_guard<int>()); },
+            py::keep_alive<0, 1>());
 
     // test_iterater_referencing
     py::class_<NonCopyableInt>(m, "NonCopyableInt")
         .def(py::init<int>())
         .def("set", &NonCopyableInt::set)
-        .def("__int__", &NonCopyableInt::get)
-        ;
+        .def("__int__", &NonCopyableInt::get);
     py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
         .def(py::init<>())
-        .def("append", [](std::vector<NonCopyableInt> &vec, int value) {
-            vec.emplace_back(value);
-        })
+        .def("append",
+             [](std::vector<NonCopyableInt> &vec, int value) { vec.emplace_back(value); })
         .def("__iter__", [](std::vector<NonCopyableInt> &vec) {
             return py::make_iterator(vec.begin(), vec.end());
-        })
-        ;
+        });
     py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
         .def(py::init<>())
-        .def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
-            vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
-        })
-        .def("keys", [](std::vector<NonCopyableIntPair> &vec) {
-            return py::make_key_iterator(vec.begin(), vec.end());
-        })
+        .def("append",
+             [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
+                 vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
+             })
+        .def("keys",
+             [](std::vector<NonCopyableIntPair> &vec) {
+                 return py::make_key_iterator(vec.begin(), vec.end());
+             })
         .def("values", [](std::vector<NonCopyableIntPair> &vec) {
             return py::make_value_iterator(vec.begin(), vec.end());
-        })
-        ;
+        });
 
 #if 0
     // Obsolete: special data structure for exposing custom iterator types to python
@@ -511,7 +554,9 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
 
     // test_iterator_rvp
     // #388: Can't make iterators via make_iterator() with different r/v policies
-    static std::vector<int> list = { 1, 2, 3 };
-    m.def("make_iterator_1", []() { return py::make_iterator<py::return_value_policy::copy>(list); });
-    m.def("make_iterator_2", []() { return py::make_iterator<py::return_value_policy::automatic>(list); });
+    static std::vector<int> list = {1, 2, 3};
+    m.def("make_iterator_1",
+          []() { return py::make_iterator<py::return_value_policy::copy>(list); });
+    m.def("make_iterator_2",
+          []() { return py::make_iterator<py::return_value_policy::automatic>(list); });
 }
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index b2b91a62db..f26c47c305 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -8,21 +8,23 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#if defined(_MSC_VER) && _MSC_VER < 1910  // VS 2015's MSVC
-#  pragma warning(disable: 4702) // unreachable code in system header (xatomic.h(382))
+#if defined(_MSC_VER) && _MSC_VER < 1910 // VS 2015's MSVC
+#    pragma warning(disable : 4702)      // unreachable code in system header (xatomic.h(382))
 #endif
 
-#include "pybind11_tests.h"
 #include "object.h"
+#include "pybind11_tests.h"
 
 namespace {
 
 // This is just a wrapper around unique_ptr, but with extra fields to deliberately bloat up the
-// holder size to trigger the non-simple-layout internal instance layout for single inheritance with
-// large holder type:
-template <typename T> class huge_unique_ptr {
+// holder size to trigger the non-simple-layout internal instance layout for single inheritance
+// with large holder type:
+template <typename T>
+class huge_unique_ptr {
     std::unique_ptr<T> ptr;
     uint64_t padding[10];
+
 public:
     explicit huge_unique_ptr(T *p) : ptr(p) {}
     T *get() { return ptr.get(); }
@@ -32,10 +34,11 @@ template <typename T> class huge_unique_ptr {
 template <typename T>
 class custom_unique_ptr {
     std::unique_ptr<T> impl;
+
 public:
     explicit custom_unique_ptr(T *p) : impl(p) {}
-    T* get() const { return impl.get(); }
-    T* release_ptr() { return impl.release(); }
+    T *get() const { return impl.get(); }
+    T *release_ptr() { return impl.release(); }
 };
 
 // Simple custom holder that works like shared_ptr and has operator& overload
@@ -44,11 +47,12 @@ class custom_unique_ptr {
 template <typename T>
 class shared_ptr_with_addressof_operator {
     std::shared_ptr<T> impl;
+
 public:
-    shared_ptr_with_addressof_operator( ) = default;
+    shared_ptr_with_addressof_operator() = default;
     explicit shared_ptr_with_addressof_operator(T *p) : impl(p) {}
-    T* get() const { return impl.get(); }
-    T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
+    T *get() const { return impl.get(); }
+    T **operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
 };
 
 // Simple custom holder that works like unique_ptr and has operator& overload
@@ -57,12 +61,13 @@ class shared_ptr_with_addressof_operator {
 template <typename T>
 class unique_ptr_with_addressof_operator {
     std::unique_ptr<T> impl;
+
 public:
     unique_ptr_with_addressof_operator() = default;
     explicit unique_ptr_with_addressof_operator(T *p) : impl(p) {}
-    T* get() const { return impl.get(); }
-    T* release_ptr() { return impl.release(); }
-    T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
+    T *get() const { return impl.get(); }
+    T *release_ptr() { return impl.release(); }
+    T **operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
 };
 
 // Custom object with builtin reference counting (see 'object.h' for the implementation)
@@ -70,8 +75,10 @@ class MyObject1 : public Object {
 public:
     explicit MyObject1(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const override { return "MyObject1[" + std::to_string(value) + "]"; }
+
 protected:
     ~MyObject1() override { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -83,6 +90,7 @@ class MyObject2 {
     explicit MyObject2(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject2[" + std::to_string(value) + "]"; }
     virtual ~MyObject2() { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -94,6 +102,7 @@ class MyObject3 : public std::enable_shared_from_this<MyObject3> {
     explicit MyObject3(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject3[" + std::to_string(value) + "]"; }
     virtual ~MyObject3() { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -117,6 +126,7 @@ class MyObject4 {
             delete o;
         }
     }
+
 private:
     ~MyObject4() {
         myobject4_instances.erase(this);
@@ -144,6 +154,7 @@ class MyObject4a {
             delete o;
         }
     }
+
 protected:
     virtual ~MyObject4a() {
         myobject4a_instances.erase(this);
@@ -232,14 +243,14 @@ struct TypeForMoveOnlyHolderWithAddressOf {
 };
 
 // test_smart_ptr_from_default
-struct HeldByDefaultHolder { };
+struct HeldByDefaultHolder {};
 
 // test_shared_ptr_gc
 // #187: issue involving std::shared_ptr<> return value policy & garbage collection
 struct ElementBase {
     virtual ~ElementBase() = default; /* Force creation of virtual table */
     ElementBase() = default;
-    ElementBase(const ElementBase&) = delete;
+    ElementBase(const ElementBase &) = delete;
 };
 
 struct ElementA : ElementBase {
@@ -259,11 +270,12 @@ struct ElementList {
 // It is always possible to construct a ref<T> from an Object* pointer without
 // possible inconsistencies, hence the 'true' argument at the end.
 // Make pybind11 aware of the non-standard getter member function
-namespace pybind11 { namespace detail {
-    template <typename T>
-    struct holder_helper<ref<T>> {
-        static const T *get(const ref<T> &p) { return p.get_ptr(); }
-    };
+namespace pybind11 {
+namespace detail {
+template <typename T>
+struct holder_helper<ref<T>> {
+    static const T *get(const ref<T> &p) { return p.get_ptr(); }
+};
 } // namespace detail
 } // namespace pybind11
 
@@ -287,8 +299,7 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::class_<Object, ref<Object>> obj(m, "Object");
     obj.def("getRefCount", &Object::getRefCount);
 
-    py::class_<MyObject1, ref<MyObject1>>(m, "MyObject1", obj)
-        .def(py::init<int>());
+    py::class_<MyObject1, ref<MyObject1>>(m, "MyObject1", obj).def(py::init<int>());
     py::implicitly_convertible<py::int_, MyObject1>();
 
     m.def("make_object_1", []() -> Object * { return new MyObject1(1); });
@@ -307,25 +318,27 @@ TEST_SUBMODULE(smart_ptr, m) {
     // Expose constructor stats for the ref type
     m.def("cstats_ref", &ConstructorStats::get<ref_tag>);
 
-    py::class_<MyObject2, std::shared_ptr<MyObject2>>(m, "MyObject2")
-        .def(py::init<int>());
+    py::class_<MyObject2, std::shared_ptr<MyObject2>>(m, "MyObject2").def(py::init<int>());
     m.def("make_myobject2_1", []() { return new MyObject2(6); });
     m.def("make_myobject2_2", []() { return std::make_shared<MyObject2>(7); });
     m.def("print_myobject2_1", [](const MyObject2 *obj) { py::print(obj->toString()); });
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("print_myobject2_2", [](std::shared_ptr<MyObject2> obj) { py::print(obj->toString()); });
-    m.def("print_myobject2_3", [](const std::shared_ptr<MyObject2> &obj) { py::print(obj->toString()); });
-    m.def("print_myobject2_4", [](const std::shared_ptr<MyObject2> *obj) { py::print((*obj)->toString()); });
+    m.def("print_myobject2_3",
+          [](const std::shared_ptr<MyObject2> &obj) { py::print(obj->toString()); });
+    m.def("print_myobject2_4",
+          [](const std::shared_ptr<MyObject2> *obj) { py::print((*obj)->toString()); });
 
-    py::class_<MyObject3, std::shared_ptr<MyObject3>>(m, "MyObject3")
-        .def(py::init<int>());
+    py::class_<MyObject3, std::shared_ptr<MyObject3>>(m, "MyObject3").def(py::init<int>());
     m.def("make_myobject3_1", []() { return new MyObject3(8); });
     m.def("make_myobject3_2", []() { return std::make_shared<MyObject3>(9); });
     m.def("print_myobject3_1", [](const MyObject3 *obj) { py::print(obj->toString()); });
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("print_myobject3_2", [](std::shared_ptr<MyObject3> obj) { py::print(obj->toString()); });
-    m.def("print_myobject3_3", [](const std::shared_ptr<MyObject3> &obj) { py::print(obj->toString()); });
-    m.def("print_myobject3_4", [](const std::shared_ptr<MyObject3> *obj) { py::print((*obj)->toString()); });
+    m.def("print_myobject3_3",
+          [](const std::shared_ptr<MyObject3> &obj) { py::print(obj->toString()); });
+    m.def("print_myobject3_4",
+          [](const std::shared_ptr<MyObject3> *obj) { py::print((*obj)->toString()); });
 
     // test_smart_ptr_refcounting
     m.def("test_object1_refcounting", []() {
@@ -421,11 +434,18 @@ TEST_SUBMODULE(smart_ptr, m) {
              [](const HolderWithAddressOf *obj) { py::print((*obj).get()->toString()); });
 
     // test_move_only_holder_with_addressof_operator
-    using MoveOnlyHolderWithAddressOf = unique_ptr_with_addressof_operator<TypeForMoveOnlyHolderWithAddressOf>;
-    py::class_<TypeForMoveOnlyHolderWithAddressOf, MoveOnlyHolderWithAddressOf>(m, "TypeForMoveOnlyHolderWithAddressOf")
-        .def_static("make", []() { return MoveOnlyHolderWithAddressOf(new TypeForMoveOnlyHolderWithAddressOf(0)); })
+    using MoveOnlyHolderWithAddressOf
+        = unique_ptr_with_addressof_operator<TypeForMoveOnlyHolderWithAddressOf>;
+    py::class_<TypeForMoveOnlyHolderWithAddressOf, MoveOnlyHolderWithAddressOf>(
+        m, "TypeForMoveOnlyHolderWithAddressOf")
+        .def_static("make",
+                    []() {
+                        return MoveOnlyHolderWithAddressOf(
+                            new TypeForMoveOnlyHolderWithAddressOf(0));
+                    })
         .def_readwrite("value", &TypeForMoveOnlyHolderWithAddressOf::value)
-        .def("print_object", [](const TypeForMoveOnlyHolderWithAddressOf *obj) { py::print(obj->toString()); });
+        .def("print_object",
+             [](const TypeForMoveOnlyHolderWithAddressOf *obj) { py::print(obj->toString()); });
 
     // test_smart_ptr_from_default
     py::class_<HeldByDefaultHolder, std::unique_ptr<HeldByDefaultHolder>>(m, "HeldByDefaultHolder")
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 77fc9b99b7..44a6eb2e3e 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -7,39 +7,43 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #ifndef PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
-#define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
+#    define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
 #endif
 #include <pybind11/stl/filesystem.h>
 
-#include <vector>
 #include <string>
+#include <vector>
 
 #if defined(PYBIND11_TEST_BOOST)
-#include <boost/optional.hpp>
+#    include <boost/optional.hpp>
 
-namespace pybind11 { namespace detail {
+namespace pybind11 {
+namespace detail {
 template <typename T>
 struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
 
 template <>
 struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
-}} // namespace pybind11::detail
+} // namespace detail
+} // namespace pybind11
 #endif
 
 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
 #if defined(PYBIND11_HAS_VARIANT)
 using std::variant;
 #elif defined(PYBIND11_TEST_BOOST) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
-#  include <boost/variant.hpp>
-#  define PYBIND11_HAS_VARIANT 1
+#    include <boost/variant.hpp>
+#    define PYBIND11_HAS_VARIANT 1
 using boost::variant;
 
-namespace pybind11 { namespace detail {
+namespace pybind11 {
+namespace detail {
 template <typename... Ts>
 struct type_caster<boost::variant<Ts...>> : variant_caster<boost::variant<Ts...>> {};
 
@@ -50,7 +54,8 @@ struct visit_helper<boost::variant> {
         return boost::apply_visitor(args...);
     }
 };
-}} // namespace pybind11::detail
+} // namespace detail
+} // namespace pybind11
 #endif
 
 PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
@@ -63,26 +68,23 @@ struct TplCtorClass {
 };
 
 namespace std {
-    template <>
-    struct hash<TplCtorClass> { size_t operator()(const TplCtorClass &) const { return 0; } };
+template <>
+struct hash<TplCtorClass> {
+    size_t operator()(const TplCtorClass &) const { return 0; }
+};
 } // namespace std
 
-
 template <template <typename> class OptionalImpl, typename T>
-struct OptionalHolder
-{
+struct OptionalHolder {
     // NOLINTNEXTLINE(modernize-use-equals-default): breaks GCC 4.8
-    OptionalHolder() {};
-    bool member_initialized() const {
-        return member && member->initialized;
-    }
+    OptionalHolder(){};
+    bool member_initialized() const { return member && member->initialized; }
     OptionalImpl<T> member = T{};
 };
 
-
 enum class EnumType {
-  kSet = 42,
-  kUnset = 85,
+    kSet = 42,
+    kUnset = 85,
 };
 
 // This is used to test that return-by-ref and return-by-copy policies are
@@ -102,7 +104,7 @@ class OptionalProperties {
         value = EnumType::kUnset;
     }
 
-    OptionalEnumValue& access_by_ref() { return value; }
+    OptionalEnumValue &access_by_ref() { return value; }
     OptionalEnumValue access_by_copy() { return value; }
 
 private:
@@ -122,62 +124,56 @@ class ReferenceSensitiveOptional {
 
     ReferenceSensitiveOptional() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
-    ReferenceSensitiveOptional(const T& value) : storage{value} {}
+    ReferenceSensitiveOptional(const T &value) : storage{value} {}
     // NOLINTNEXTLINE(google-explicit-constructor)
-    ReferenceSensitiveOptional(T&& value) : storage{std::move(value)} {}
-    ReferenceSensitiveOptional& operator=(const T& value) {
+    ReferenceSensitiveOptional(T &&value) : storage{std::move(value)} {}
+    ReferenceSensitiveOptional &operator=(const T &value) {
         storage = {value};
         return *this;
     }
-    ReferenceSensitiveOptional& operator=(T&& value) {
+    ReferenceSensitiveOptional &operator=(T &&value) {
         storage = {std::move(value)};
         return *this;
     }
 
     template <typename... Args>
-    T& emplace(Args&&... args) {
+    T &emplace(Args &&...args) {
         storage.clear();
         storage.emplace_back(std::forward<Args>(args)...);
         return storage.back();
     }
 
-    const T& value() const noexcept {
+    const T &value() const noexcept {
         assert(!storage.empty());
         return storage[0];
     }
 
-    const T& operator*() const noexcept {
-        return value();
-    }
+    const T &operator*() const noexcept { return value(); }
 
-    const T* operator->() const noexcept {
-        return &value();
-    }
+    const T *operator->() const noexcept { return &value(); }
 
-    explicit operator bool() const noexcept {
-        return !storage.empty();
-    }
+    explicit operator bool() const noexcept { return !storage.empty(); }
 
 private:
     std::vector<T> storage;
 };
 
-namespace pybind11 { namespace detail {
+namespace pybind11 {
+namespace detail {
 template <typename T>
-struct type_caster<ReferenceSensitiveOptional<T>> : optional_caster<ReferenceSensitiveOptional<T>> {};
+struct type_caster<ReferenceSensitiveOptional<T>>
+    : optional_caster<ReferenceSensitiveOptional<T>> {};
 } // namespace detail
 } // namespace pybind11
 
-
 TEST_SUBMODULE(stl, m) {
     // test_vector
     m.def("cast_vector", []() { return std::vector<int>{1}; });
     m.def("load_vector", [](const std::vector<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });
     // `std::vector<bool>` is special because it returns proxy objects instead of references
     m.def("cast_bool_vector", []() { return std::vector<bool>{true, false}; });
-    m.def("load_bool_vector", [](const std::vector<bool> &v) {
-        return v.at(0) == true && v.at(1) == false;
-    });
+    m.def("load_bool_vector",
+          [](const std::vector<bool> &v) { return v.at(0) == true && v.at(1) == false; });
     // Unnumbered regression (caused by #936): pointers to stl containers aren't castable
     static std::vector<RValueCaster> lvv{2};
     m.def("cast_ptr_vector", []() { return &lvv; });
@@ -187,12 +183,12 @@ TEST_SUBMODULE(stl, m) {
     m.def("load_deque", [](const std::deque<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });
 
     // test_array
-    m.def("cast_array", []() { return std::array<int, 2> {{1 , 2}}; });
+    m.def("cast_array", []() { return std::array<int, 2>{{1, 2}}; });
     m.def("load_array", [](const std::array<int, 2> &a) { return a[0] == 1 && a[1] == 2; });
 
     // test_valarray
     m.def("cast_valarray", []() { return std::valarray<int>{1, 4, 9}; });
-    m.def("load_valarray", [](const std::valarray<int>& v) {
+    m.def("load_valarray", [](const std::valarray<int> &v) {
         return v.size() == 3 && v[0] == 1 && v[1] == 4 && v[2] == 9;
     });
 
@@ -214,10 +210,12 @@ TEST_SUBMODULE(stl, m) {
     // NB: map and set keys are `const`, so while we technically do move them (as `const Type &&`),
     // casters don't typically do anything with that, which means they fall to the `const Type &`
     // caster.
-    m.def("cast_rv_map", []() { return std::unordered_map<std::string, RValueCaster>{{"a", RValueCaster{}}}; });
+    m.def("cast_rv_map", []() {
+        return std::unordered_map<std::string, RValueCaster>{{"a", RValueCaster{}}};
+    });
     m.def("cast_rv_nested", []() {
         std::vector<std::array<std::list<std::unordered_map<std::string, RValueCaster>>, 2>> v;
-        v.emplace_back(); // add an array
+        v.emplace_back();           // add an array
         v.back()[0].emplace_back(); // add a map to the array
         v.back()[0].back().emplace("b", RValueCaster{});
         v.back()[0].back().emplace("c", RValueCaster{});
@@ -226,13 +224,15 @@ TEST_SUBMODULE(stl, m) {
         return v;
     });
     static std::array<RValueCaster, 2> lva;
-    static std::unordered_map<std::string, RValueCaster> lvm{{"a", RValueCaster{}}, {"b", RValueCaster{}}};
-    static std::unordered_map<std::string, std::vector<std::list<std::array<RValueCaster, 2>>>> lvn;
-    lvn["a"].emplace_back(); // add a list
+    static std::unordered_map<std::string, RValueCaster> lvm{{"a", RValueCaster{}},
+                                                             {"b", RValueCaster{}}};
+    static std::unordered_map<std::string, std::vector<std::list<std::array<RValueCaster, 2>>>>
+        lvn;
+    lvn["a"].emplace_back();        // add a list
     lvn["a"].back().emplace_back(); // add an array
-    lvn["a"].emplace_back(); // another list
+    lvn["a"].emplace_back();        // another list
     lvn["a"].back().emplace_back(); // add an array
-    lvn["b"].emplace_back(); // add a list
+    lvn["b"].emplace_back();        // add a list
     lvn["b"].back().emplace_back(); // add an array
     lvn["b"].back().emplace_back(); // add another array
     m.def("cast_lv_vector", []() -> const decltype(lvv) & { return lvv; });
@@ -253,7 +253,9 @@ TEST_SUBMODULE(stl, m) {
 
     // test_move_out_container
     struct MoveOutContainer {
-        struct Value { int value; };
+        struct Value {
+            int value;
+        };
         std::list<Value> move_list() const { return {{0}, {1}, {2}}; }
     };
     py::class_<MoveOutContainer::Value>(m, "MoveOutContainerValue")
@@ -266,7 +268,7 @@ TEST_SUBMODULE(stl, m) {
     struct NoAssign {
         int value;
 
-        explicit NoAssign(int value = 0) : value(value) { }
+        explicit NoAssign(int value = 0) : value(value) {}
         NoAssign(const NoAssign &) = default;
         NoAssign(NoAssign &&) = default;
 
@@ -277,13 +279,10 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def(py::init<int>());
 
-
-    struct MoveOutDetector
-    {
+    struct MoveOutDetector {
         MoveOutDetector() = default;
-        MoveOutDetector(const MoveOutDetector&) = default;
-        MoveOutDetector(MoveOutDetector&& other) noexcept
-         : initialized(other.initialized) {
+        MoveOutDetector(const MoveOutDetector &) = default;
+        MoveOutDetector(MoveOutDetector &&other) noexcept : initialized(other.initialized) {
             // steal underlying resource
             other.initialized = false;
         }
@@ -293,23 +292,22 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def_readonly("initialized", &MoveOutDetector::initialized);
 
-
 #ifdef PYBIND11_HAS_OPTIONAL
     // test_optional
     m.attr("has_optional") = true;
 
     using opt_int = std::optional<int>;
     using opt_no_assign = std::optional<NoAssign>;
-    m.def("double_or_zero", [](const opt_int& x) -> int {
-        return x.value_or(0) * 2;
-    });
+    m.def("double_or_zero", [](const opt_int &x) -> int { return x.value_or(0) * 2; });
     m.def("half_or_none", [](int x) -> opt_int { return x != 0 ? opt_int(x / 2) : opt_int(); });
-    m.def("test_nullopt", [](opt_int x) {
-        return x.value_or(42);
-    }, py::arg_v("x", std::nullopt, "None"));
-    m.def("test_no_assign", [](const opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", std::nullopt, "None"));
+    m.def(
+        "test_nullopt",
+        [](opt_int x) { return x.value_or(42); },
+        py::arg_v("x", std::nullopt, "None"));
+    m.def(
+        "test_no_assign",
+        [](const opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", std::nullopt, "None"));
 
     m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
     m.def("nodefer_none_optional", [](const py::none &) { return false; });
@@ -333,18 +331,17 @@ TEST_SUBMODULE(stl, m) {
 
     using exp_opt_int = std::experimental::optional<int>;
     using exp_opt_no_assign = std::experimental::optional<NoAssign>;
-    m.def("double_or_zero_exp", [](const exp_opt_int& x) -> int {
-        return x.value_or(0) * 2;
-    });
-    m.def("half_or_none_exp", [](int x) -> exp_opt_int {
-        return x ? exp_opt_int(x / 2) : exp_opt_int();
-    });
-    m.def("test_nullopt_exp", [](exp_opt_int x) {
-        return x.value_or(42);
-    }, py::arg_v("x", std::experimental::nullopt, "None"));
-    m.def("test_no_assign_exp", [](const exp_opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", std::experimental::nullopt, "None"));
+    m.def("double_or_zero_exp", [](const exp_opt_int &x) -> int { return x.value_or(0) * 2; });
+    m.def("half_or_none_exp",
+          [](int x) -> exp_opt_int { return x ? exp_opt_int(x / 2) : exp_opt_int(); });
+    m.def(
+        "test_nullopt_exp",
+        [](exp_opt_int x) { return x.value_or(42); },
+        py::arg_v("x", std::experimental::nullopt, "None"));
+    m.def(
+        "test_no_assign_exp",
+        [](const exp_opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", std::experimental::nullopt, "None"));
 
     using opt_exp_holder = OptionalHolder<std::experimental::optional, MoveOutDetector>;
     py::class_<opt_exp_holder>(m, "OptionalExpHolder", "Class with optional member")
@@ -365,18 +362,17 @@ TEST_SUBMODULE(stl, m) {
 
     using boost_opt_int = boost::optional<int>;
     using boost_opt_no_assign = boost::optional<NoAssign>;
-    m.def("double_or_zero_boost", [](const boost_opt_int& x) -> int {
-        return x.value_or(0) * 2;
-    });
-    m.def("half_or_none_boost", [](int x) -> boost_opt_int {
-        return x != 0 ? boost_opt_int(x / 2) : boost_opt_int();
-    });
-    m.def("test_nullopt_boost", [](boost_opt_int x) {
-        return x.value_or(42);
-    }, py::arg_v("x", boost::none, "None"));
-    m.def("test_no_assign_boost", [](const boost_opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", boost::none, "None"));
+    m.def("double_or_zero_boost", [](const boost_opt_int &x) -> int { return x.value_or(0) * 2; });
+    m.def("half_or_none_boost",
+          [](int x) -> boost_opt_int { return x != 0 ? boost_opt_int(x / 2) : boost_opt_int(); });
+    m.def(
+        "test_nullopt_boost",
+        [](boost_opt_int x) { return x.value_or(42); },
+        py::arg_v("x", boost::none, "None"));
+    m.def(
+        "test_no_assign_boost",
+        [](const boost_opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", boost::none, "None"));
 
     using opt_boost_holder = OptionalHolder<boost::optional, MoveOutDetector>;
     py::class_<opt_boost_holder>(m, "OptionalBoostHolder", "Class with optional member")
@@ -394,9 +390,8 @@ TEST_SUBMODULE(stl, m) {
     // test_refsensitive_optional
     using refsensitive_opt_int = ReferenceSensitiveOptional<int>;
     using refsensitive_opt_no_assign = ReferenceSensitiveOptional<NoAssign>;
-    m.def("double_or_zero_refsensitive", [](const refsensitive_opt_int& x) -> int {
-        return (x ? x.value() : 0) * 2;
-    });
+    m.def("double_or_zero_refsensitive",
+          [](const refsensitive_opt_int &x) -> int { return (x ? x.value() : 0) * 2; });
     m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
         return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
     });
@@ -405,12 +400,14 @@ TEST_SUBMODULE(stl, m) {
         // NOLINTNEXTLINE(performance-unnecessary-value-param)
         [](refsensitive_opt_int x) { return x ? x.value() : 42; },
         py::arg_v("x", refsensitive_opt_int(), "None"));
-    m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", refsensitive_opt_no_assign(), "None"));
+    m.def(
+        "test_no_assign_refsensitive",
+        [](const refsensitive_opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", refsensitive_opt_no_assign(), "None"));
 
     using opt_refsensitive_holder = OptionalHolder<ReferenceSensitiveOptional, MoveOutDetector>;
-    py::class_<opt_refsensitive_holder>(m, "OptionalRefSensitiveHolder", "Class with optional member")
+    py::class_<opt_refsensitive_holder>(
+        m, "OptionalRefSensitiveHolder", "Class with optional member")
         .def(py::init<>())
         .def_readonly("member", &opt_refsensitive_holder::member)
         .def("member_initialized", &opt_refsensitive_holder::member_initialized);
@@ -424,7 +421,7 @@ TEST_SUBMODULE(stl, m) {
 #ifdef PYBIND11_HAS_FILESYSTEM
     // test_fs_path
     m.attr("has_filesystem") = true;
-    m.def("parent_path", [](const std::filesystem::path& p) { return p.parent_path(); });
+    m.def("parent_path", [](const std::filesystem::path &p) { return p.parent_path(); });
 #endif
 
 #ifdef PYBIND11_HAS_VARIANT
@@ -472,13 +469,13 @@ TEST_SUBMODULE(stl, m) {
     // #171: Can't return STL structures containing reference wrapper
     m.def("return_vec_of_reference_wrapper", [](std::reference_wrapper<UserType> p4) {
         static UserType p1{1}, p2{2}, p3{3};
-        return std::vector<std::reference_wrapper<UserType>> {
-            std::ref(p1), std::ref(p2), std::ref(p3), p4
-        };
+        return std::vector<std::reference_wrapper<UserType>>{
+            std::ref(p1), std::ref(p2), std::ref(p3), p4};
     });
 
     // test_stl_pass_by_pointer
-    m.def("stl_pass_by_pointer", [](std::vector<int>* v) { return *v; }, "v"_a=nullptr);
+    m.def(
+        "stl_pass_by_pointer", [](std::vector<int> *v) { return *v; }, "v"_a = nullptr);
 
     // #1258: pybind11/stl.h converts string to vector<string>
     m.def("func_with_string_or_vector_string_arg_overload",
@@ -496,19 +493,24 @@ TEST_SUBMODULE(stl, m) {
     py::class_<Placeholder>(m, "Placeholder");
 
     /// test_stl_vector_ownership
-    m.def("test_stl_ownership",
-          []() {
-              std::vector<Placeholder *> result;
-              result.push_back(new Placeholder());
-              return result;
-          },
-          py::return_value_policy::take_ownership);
+    m.def(
+        "test_stl_ownership",
+        []() {
+            std::vector<Placeholder *> result;
+            result.push_back(new Placeholder());
+            return result;
+        },
+        py::return_value_policy::take_ownership);
 
     m.def("array_cast_sequence", [](std::array<int, 3> x) { return x; });
 
     /// test_issue_1561
-    struct Issue1561Inner { std::string data; };
-    struct Issue1561Outer { std::vector<Issue1561Inner> list; };
+    struct Issue1561Inner {
+        std::string data;
+    };
+    struct Issue1561Outer {
+        std::vector<Issue1561Inner> list;
+    };
 
     py::class_<Issue1561Inner>(m, "Issue1561Inner")
         .def(py::init<std::string>())
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index bf534aec8d..ca9630bd19 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -7,12 +7,13 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/numpy.h>
+#include <pybind11/stl_bind.h>
+
 #include "pybind11_tests.h"
 
-#include <pybind11/stl_bind.h>
-#include <pybind11/numpy.h>
-#include <map>
 #include <deque>
+#include <map>
 #include <unordered_map>
 
 class El {
@@ -23,7 +24,7 @@ class El {
     int a;
 };
 
-std::ostream & operator<<(std::ostream &s, El const&v) {
+std::ostream &operator<<(std::ostream &s, El const &v) {
     s << "El{" << v.a << '}';
     return s;
 }
@@ -40,7 +41,8 @@ class E_nc {
     int value;
 };
 
-template <class Container> Container *one_to_n(int n) {
+template <class Container>
+Container *one_to_n(int n) {
     auto *v = new Container();
     for (int i = 1; i <= n; i++) {
         v->emplace_back(i);
@@ -48,7 +50,8 @@ template <class Container> Container *one_to_n(int n) {
     return v;
 }
 
-template <class Map> Map *times_ten(int n) {
+template <class Map>
+Map *times_ten(int n) {
     auto *m = new Map();
     for (int i = 1; i <= n; i++) {
         m->emplace(int(i), E_nc(10 * i));
@@ -56,7 +59,8 @@ template <class Map> Map *times_ten(int n) {
     return m;
 }
 
-template <class NestMap> NestMap *times_hundred(int n) {
+template <class NestMap>
+NestMap *times_hundred(int n) {
     auto *m = new NestMap();
     for (int i = 1; i <= n; i++) {
         for (int j = 1; j <= n; j++) {
@@ -71,8 +75,7 @@ TEST_SUBMODULE(stl_binders, m) {
     py::bind_vector<std::vector<unsigned int>>(m, "VectorInt", py::buffer_protocol());
 
     // test_vector_custom
-    py::class_<El>(m, "El")
-        .def(py::init<int>());
+    py::class_<El>(m, "El").def(py::init<int>());
     py::bind_vector<std::vector<El>>(m, "VectorEl");
     py::bind_vector<std::vector<std::vector<El>>>(m, "VectorVectorEl");
 
@@ -82,11 +85,10 @@ TEST_SUBMODULE(stl_binders, m) {
 
     // test_map_string_double_const
     py::bind_map<std::map<std::string, double const>>(m, "MapStringDoubleConst");
-    py::bind_map<std::unordered_map<std::string, double const>>(m, "UnorderedMapStringDoubleConst");
+    py::bind_map<std::unordered_map<std::string, double const>>(m,
+                                                                "UnorderedMapStringDoubleConst");
 
-    py::class_<E_nc>(m, "ENC")
-        .def(py::init<int>())
-        .def_readwrite("value", &E_nc::value);
+    py::class_<E_nc>(m, "ENC").def(py::init<int>()).def_readwrite("value", &E_nc::value);
 
     // test_noncopyable_containers
     py::bind_vector<std::vector<E_nc>>(m, "VectorENC");
@@ -116,17 +118,31 @@ TEST_SUBMODULE(stl_binders, m) {
     // test_vector_buffer
     py::bind_vector<std::vector<unsigned char>>(m, "VectorUChar", py::buffer_protocol());
     // no dtype declared for this version:
-    struct VUndeclStruct { bool w; uint32_t x; double y; bool z; };
-    m.def("create_undeclstruct", [m] () mutable {
-        py::bind_vector<std::vector<VUndeclStruct>>(m, "VectorUndeclStruct", py::buffer_protocol());
+    struct VUndeclStruct {
+        bool w;
+        uint32_t x;
+        double y;
+        bool z;
+    };
+    m.def("create_undeclstruct", [m]() mutable {
+        py::bind_vector<std::vector<VUndeclStruct>>(
+            m, "VectorUndeclStruct", py::buffer_protocol());
     });
 
     // The rest depends on numpy:
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // test_vector_buffer_numpy
-    struct VStruct { bool w; uint32_t x; double y; bool z; };
+    struct VStruct {
+        bool w;
+        uint32_t x;
+        double y;
+        bool z;
+    };
     PYBIND11_NUMPY_DTYPE(VStruct, w, x, y, z);
     py::class_<VStruct>(m, "VStruct").def_readwrite("x", &VStruct::x);
     py::bind_vector<std::vector<VStruct>>(m, "VectorStruct", py::buffer_protocol());
diff --git a/tests/test_tagbased_polymorphic.cpp b/tests/test_tagbased_polymorphic.cpp
index d54d1fd325..2807e86ba3 100644
--- a/tests/test_tagbased_polymorphic.cpp
+++ b/tests/test_tagbased_polymorphic.cpp
@@ -7,11 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/stl.h>
 
-struct Animal
-{
+#include "pybind11_tests.h"
+
+struct Animal {
     // Make this type also a "standard" polymorphic type, to confirm that
     // specializing polymorphic_type_hook using enable_if_t still works
     // (https://github.com/pybind/pybind11/pull/2016/).
@@ -20,57 +20,54 @@ struct Animal
     // Enum for tag-based polymorphism.
     enum class Kind {
         Unknown = 0,
-        Dog = 100, Labrador, Chihuahua, LastDog = 199,
-        Cat = 200, Panther, LastCat = 299
+        Dog = 100,
+        Labrador,
+        Chihuahua,
+        LastDog = 199,
+        Cat = 200,
+        Panther,
+        LastCat = 299
     };
-    static const std::type_info* type_of_kind(Kind kind);
+    static const std::type_info *type_of_kind(Kind kind);
     static std::string name_of_kind(Kind kind);
 
     const Kind kind;
     const std::string name;
 
-  protected:
-    Animal(const std::string& _name, Kind _kind)
-        : kind(_kind), name(_name)
-    {}
+protected:
+    Animal(const std::string &_name, Kind _kind) : kind(_kind), name(_name) {}
 };
 
-struct Dog : Animal
-{
+struct Dog : Animal {
     explicit Dog(const std::string &_name, Kind _kind = Kind::Dog) : Animal(_name, _kind) {}
     std::string bark() const { return name_of_kind(kind) + " " + name + " goes " + sound; }
     std::string sound = "WOOF!";
 };
 
-struct Labrador : Dog
-{
+struct Labrador : Dog {
     explicit Labrador(const std::string &_name, int _excitement = 9001)
         : Dog(_name, Kind::Labrador), excitement(_excitement) {}
     int excitement;
 };
 
-struct Chihuahua : Dog
-{
+struct Chihuahua : Dog {
     explicit Chihuahua(const std::string &_name) : Dog(_name, Kind::Chihuahua) {
         sound = "iyiyiyiyiyi";
     }
     std::string bark() const { return Dog::bark() + " and runs in circles"; }
 };
 
-struct Cat : Animal
-{
+struct Cat : Animal {
     explicit Cat(const std::string &_name, Kind _kind = Kind::Cat) : Animal(_name, _kind) {}
     std::string purr() const { return "mrowr"; }
 };
 
-struct Panther : Cat
-{
+struct Panther : Cat {
     explicit Panther(const std::string &_name) : Cat(_name, Kind::Panther) {}
     std::string purr() const { return "mrrrRRRRRR"; }
 };
 
-std::vector<std::unique_ptr<Animal>> create_zoo()
-{
+std::vector<std::unique_ptr<Animal>> create_zoo() {
     std::vector<std::unique_ptr<Animal>> ret;
     ret.emplace_back(new Labrador("Fido", 15000));
 
@@ -85,19 +82,24 @@ std::vector<std::unique_ptr<Animal>> create_zoo()
     return ret;
 }
 
-const std::type_info* Animal::type_of_kind(Kind kind)
-{
+const std::type_info *Animal::type_of_kind(Kind kind) {
     switch (kind) {
         case Kind::Unknown:
-        case Kind::Dog: break;
+        case Kind::Dog:
+            break;
 
-        case Kind::Labrador: return &typeid(Labrador);
-        case Kind::Chihuahua: return &typeid(Chihuahua);
+        case Kind::Labrador:
+            return &typeid(Labrador);
+        case Kind::Chihuahua:
+            return &typeid(Chihuahua);
 
         case Kind::LastDog:
-        case Kind::Cat: break;
-        case Kind::Panther: return &typeid(Panther);
-        case Kind::LastCat: break;
+        case Kind::Cat:
+            break;
+        case Kind::Panther:
+            return &typeid(Panther);
+        case Kind::LastCat:
+            break;
     }
 
     if (kind >= Kind::Dog && kind <= Kind::LastDog) {
@@ -109,25 +111,24 @@ const std::type_info* Animal::type_of_kind(Kind kind)
     return nullptr;
 }
 
-std::string Animal::name_of_kind(Kind kind)
-{
+std::string Animal::name_of_kind(Kind kind) {
     std::string raw_name = type_of_kind(kind)->name();
     py::detail::clean_type_id(raw_name);
     return raw_name;
 }
 
 namespace pybind11 {
-    template <typename itype>
-    struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_base_of<Animal, itype>::value>>
-    {
-        static const void *get(const itype *src, const std::type_info*& type)
-        { type = src ? Animal::type_of_kind(src->kind) : nullptr; return src; }
-    };
+template <typename itype>
+struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_base_of<Animal, itype>::value>> {
+    static const void *get(const itype *src, const std::type_info *&type) {
+        type = src ? Animal::type_of_kind(src->kind) : nullptr;
+        return src;
+    }
+};
 } // namespace pybind11
 
 TEST_SUBMODULE(tagbased_polymorphic, m) {
-    py::class_<Animal>(m, "Animal")
-        .def_readonly("name", &Animal::name);
+    py::class_<Animal>(m, "Animal").def_readonly("name", &Animal::name);
     py::class_<Dog, Animal>(m, "Dog")
         .def(py::init<std::string>())
         .def_readwrite("sound", &Dog::sound)
@@ -138,9 +139,7 @@ TEST_SUBMODULE(tagbased_polymorphic, m) {
     py::class_<Chihuahua, Dog>(m, "Chihuahua")
         .def(py::init<std::string>())
         .def("bark", &Chihuahua::bark);
-    py::class_<Cat, Animal>(m, "Cat")
-        .def(py::init<std::string>())
-        .def("purr", &Cat::purr);
+    py::class_<Cat, Animal>(m, "Cat").def(py::init<std::string>()).def("purr", &Cat::purr);
     py::class_<Panther, Cat>(m, "Panther")
         .def(py::init<std::string>())
         .def("purr", &Panther::purr);
diff --git a/tests/test_thread.cpp b/tests/test_thread.cpp
index 19d91768b3..1536503b6b 100644
--- a/tests/test_thread.cpp
+++ b/tests/test_thread.cpp
@@ -10,20 +10,20 @@
 #include <pybind11/cast.h>
 #include <pybind11/pybind11.h>
 
+#include "pybind11_tests.h"
+
 #include <chrono>
 #include <thread>
 
-#include "pybind11_tests.h"
-
 namespace py = pybind11;
 
 namespace {
 
 struct IntStruct {
-    explicit IntStruct(int v) : value(v) {};
+    explicit IntStruct(int v) : value(v){};
     ~IntStruct() { value = -value; }
-    IntStruct(const IntStruct&) = default;
-    IntStruct& operator=(const IntStruct&) = default;
+    IntStruct(const IntStruct &) = default;
+    IntStruct &operator=(const IntStruct &) = default;
 
     int value;
 };
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 1e47b367d2..0ca83386d5 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -7,13 +7,15 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/functional.h>
+
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #include <thread>
 
 /* This is an example class that we'll want to be able to extend from Python */
-class ExampleVirt  {
+class ExampleVirt {
 public:
     explicit ExampleVirt(int state) : state(state) { print_created(this, state); }
     ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
@@ -25,7 +27,8 @@ class ExampleVirt  {
 
     virtual int run(int value) {
         py::print("Original implementation of "
-                  "ExampleVirt::run(state={}, value={}, str1={}, str2={})"_s.format(state, value, get_string1(), *get_string2()));
+                  "ExampleVirt::run(state={}, value={}, str1={}, str2={})"_s.format(
+                      state, value, get_string1(), *get_string2()));
         return state + value;
     }
 
@@ -33,8 +36,8 @@ class ExampleVirt  {
     virtual void pure_virtual() = 0;
 
     // Returning a reference/pointer to a type converted from python (numbers, strings, etc.) is a
-    // bit trickier, because the actual int& or std::string& or whatever only exists temporarily, so
-    // we have to handle it specially in the trampoline class (see below).
+    // bit trickier, because the actual int& or std::string& or whatever only exists temporarily,
+    // so we have to handle it specially in the trampoline class (see below).
     virtual const std::string &get_string1() { return str1; }
     virtual const std::string *get_string2() { return &str2; }
 
@@ -50,59 +53,53 @@ class PyExampleVirt : public ExampleVirt {
 
     int run(int value) override {
         /* Generate wrapping code that enables native function overloading */
-        PYBIND11_OVERRIDE(
-            int,         /* Return type */
-            ExampleVirt, /* Parent class */
-            run,         /* Name of function */
-            value        /* Argument(s) */
+        PYBIND11_OVERRIDE(int,         /* Return type */
+                          ExampleVirt, /* Parent class */
+                          run,         /* Name of function */
+                          value        /* Argument(s) */
         );
     }
 
     bool run_bool() override {
-        PYBIND11_OVERRIDE_PURE(
-            bool,         /* Return type */
-            ExampleVirt,  /* Parent class */
-            run_bool,     /* Name of function */
-                          /* This function has no arguments. The trailing comma
-                             in the previous line is needed for some compilers */
+        PYBIND11_OVERRIDE_PURE(bool,        /* Return type */
+                               ExampleVirt, /* Parent class */
+                               run_bool,    /* Name of function */
+                                            /* This function has no arguments. The trailing comma
+                                               in the previous line is needed for some compilers */
         );
     }
 
     void pure_virtual() override {
-        PYBIND11_OVERRIDE_PURE(
-            void,         /* Return type */
-            ExampleVirt,  /* Parent class */
-            pure_virtual, /* Name of function */
-                          /* This function has no arguments. The trailing comma
-                             in the previous line is needed for some compilers */
+        PYBIND11_OVERRIDE_PURE(void,         /* Return type */
+                               ExampleVirt,  /* Parent class */
+                               pure_virtual, /* Name of function */
+                                             /* This function has no arguments. The trailing comma
+                                                in the previous line is needed for some compilers */
         );
     }
 
     // We can return reference types for compatibility with C++ virtual interfaces that do so, but
     // note they have some significant limitations (see the documentation).
     const std::string &get_string1() override {
-        PYBIND11_OVERRIDE(
-            const std::string &, /* Return type */
-            ExampleVirt,         /* Parent class */
-            get_string1,         /* Name of function */
-                                 /* (no arguments) */
+        PYBIND11_OVERRIDE(const std::string &, /* Return type */
+                          ExampleVirt,         /* Parent class */
+                          get_string1,         /* Name of function */
+                                               /* (no arguments) */
         );
     }
 
     const std::string *get_string2() override {
-        PYBIND11_OVERRIDE(
-            const std::string *, /* Return type */
-            ExampleVirt,         /* Parent class */
-            get_string2,         /* Name of function */
-                                 /* (no arguments) */
+        PYBIND11_OVERRIDE(const std::string *, /* Return type */
+                          ExampleVirt,         /* Parent class */
+                          get_string2,         /* Name of function */
+                                               /* (no arguments) */
         );
     }
-
 };
 
 class NonCopyable {
 public:
-    NonCopyable(int a, int b) : value{new int(a*b)} { print_created(this, a, b); }
+    NonCopyable(int a, int b) : value{new int(a * b)} { print_created(this, a, b); }
     NonCopyable(NonCopyable &&o) noexcept : value{std::move(o.value)} { print_move_created(this); }
     NonCopyable(const NonCopyable &) = delete;
     NonCopyable() = delete;
@@ -124,11 +121,12 @@ class NonCopyable {
 // when it is not referenced elsewhere, but copied if it is still referenced.
 class Movable {
 public:
-    Movable(int a, int b) : value{a+b} { print_created(this, a, b); }
+    Movable(int a, int b) : value{a + b} { print_created(this, a, b); }
     Movable(const Movable &m) : value{m.value} { print_copy_created(this); }
     Movable(Movable &&m) noexcept : value{m.value} { print_move_created(this); }
     std::string get_value() const { return std::to_string(value); }
     ~Movable() { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -137,7 +135,7 @@ class NCVirt {
 public:
     virtual ~NCVirt() = default;
     NCVirt() = default;
-    NCVirt(const NCVirt&) = delete;
+    NCVirt(const NCVirt &) = delete;
     virtual NonCopyable get_noncopyable(int a, int b) { return NonCopyable(a, b); }
     virtual Movable get_movable(int a, int b) = 0;
 
@@ -160,7 +158,7 @@ struct Base {
     virtual std::string dispatch() const { return {}; };
     virtual ~Base() = default;
     Base() = default;
-    Base(const Base&) = delete;
+    Base(const Base &) = delete;
 };
 
 struct DispatchIssue : Base {
@@ -173,33 +171,33 @@ struct DispatchIssue : Base {
 // objects and send the result to the visitor functor
 struct AdderBase {
     struct Data {};
-    using DataVisitor = std::function<void (const Data&)>;
+    using DataVisitor = std::function<void(const Data &)>;
 
-    virtual void operator()(const Data& first, const Data& second, const DataVisitor& visitor) const = 0;
+    virtual void
+    operator()(const Data &first, const Data &second, const DataVisitor &visitor) const = 0;
     virtual ~AdderBase() = default;
     AdderBase() = default;
-    AdderBase(const AdderBase&) = delete;
+    AdderBase(const AdderBase &) = delete;
 };
 
 struct Adder : AdderBase {
-    void operator()(const Data& first, const Data& second, const DataVisitor& visitor) const override {
-        PYBIND11_OVERRIDE_PURE_NAME(void, AdderBase, "__call__", operator(), first, second, visitor);
+    void
+    operator()(const Data &first, const Data &second, const DataVisitor &visitor) const override {
+        PYBIND11_OVERRIDE_PURE_NAME(
+            void, AdderBase, "__call__", operator(), first, second, visitor);
     }
 };
 
-
 static void test_gil() {
     {
         py::gil_scoped_acquire lock;
         py::print("1st lock acquired");
-
     }
 
     {
         py::gil_scoped_acquire lock;
         py::print("2nd lock acquired");
     }
-
 }
 
 static void test_gil_from_thread() {
@@ -225,12 +223,12 @@ class test_override_cache_helper_trampoline : public test_override_cache_helper
     int func() override { PYBIND11_OVERRIDE(int, test_override_cache_helper, func); }
 };
 
-inline int test_override_cache(std::shared_ptr<test_override_cache_helper> const &instance) { return instance->func(); }
-
-
+inline int test_override_cache(std::shared_ptr<test_override_cache_helper> const &instance) {
+    return instance->func();
+}
 
-// Forward declaration (so that we can put the main tests here; the inherited virtual approaches are
-// rather long).
+// Forward declaration (so that we can put the main tests here; the inherited virtual approaches
+// are rather long).
 void initialize_inherited_virtuals(py::module_ &m);
 
 TEST_SUBMODULE(virtual_functions, m) {
@@ -242,11 +240,9 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def("run_bool", &ExampleVirt::run_bool)
         .def("pure_virtual", &ExampleVirt::pure_virtual);
 
-    py::class_<NonCopyable>(m, "NonCopyable")
-        .def(py::init<int, int>());
+    py::class_<NonCopyable>(m, "NonCopyable").def(py::init<int, int>());
 
-    py::class_<Movable>(m, "Movable")
-        .def(py::init<int, int>());
+    py::class_<Movable>(m, "Movable").def(py::init<int, int>());
 
     // test_move_support
 #if !defined(__INTEL_COMPILER) && !defined(__CUDACC__) && !defined(__PGIC__)
@@ -259,7 +255,7 @@ TEST_SUBMODULE(virtual_functions, m) {
 #endif
 
     m.def("runExampleVirt", [](ExampleVirt *ex, int value) { return ex->run(value); });
-    m.def("runExampleVirtBool", [](ExampleVirt* ex) { return ex->run_bool(); });
+    m.def("runExampleVirtBool", [](ExampleVirt *ex) { return ex->run_bool(); });
     m.def("runExampleVirtVirtual", [](ExampleVirt *ex) { ex->pure_virtual(); });
 
     m.def("cstats_debug", &ConstructorStats::get<ExampleVirt>);
@@ -270,27 +266,25 @@ TEST_SUBMODULE(virtual_functions, m) {
     // that were not extended on the Python side
     struct A {
         A() = default;
-        A(const A&) = delete;
+        A(const A &) = delete;
         virtual ~A() = default;
         virtual void f() { py::print("A.f()"); }
     };
 
     struct PyA : A {
         PyA() { py::print("PyA.PyA()"); }
-        PyA(const PyA&) = delete;
+        PyA(const PyA &) = delete;
         ~PyA() override { py::print("PyA.~PyA()"); }
 
         void f() override {
             py::print("PyA.f()");
-            // This convolution just gives a `void`, but tests that PYBIND11_TYPE() works to protect
-            // a type containing a ,
+            // This convolution just gives a `void`, but tests that PYBIND11_TYPE() works to
+            // protect a type containing a ,
             PYBIND11_OVERRIDE(PYBIND11_TYPE(typename std::enable_if<true, void>::type), A, f);
         }
     };
 
-    py::class_<A, PyA>(m, "A")
-        .def(py::init<>())
-        .def("f", &A::f);
+    py::class_<A, PyA>(m, "A").def(py::init<>()).def("f", &A::f);
 
     m.def("call_f", [](A *a) { a->f(); });
 
@@ -298,14 +292,14 @@ TEST_SUBMODULE(virtual_functions, m) {
     // ... unless we explicitly request it, as in this example:
     struct A2 {
         A2() = default;
-        A2(const A2&) = delete;
+        A2(const A2 &) = delete;
         virtual ~A2() = default;
         virtual void f() { py::print("A2.f()"); }
     };
 
     struct PyA2 : A2 {
         PyA2() { py::print("PyA2.PyA2()"); }
-        PyA2(const PyA2&) = delete;
+        PyA2(const PyA2 &) = delete;
         ~PyA2() override { py::print("PyA2.~PyA2()"); }
         void f() override {
             py::print("PyA2.f()");
@@ -326,7 +320,7 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def(py::init<>())
         .def("dispatch", &Base::dispatch);
 
-    m.def("dispatch_issue_go", [](const Base * b) { return b->dispatch(); });
+    m.def("dispatch_issue_go", [](const Base *b) { return b->dispatch(); });
 
     // test_recursive_dispatch_issue
     // #3357: Recursive dispatch fails to find python function override
@@ -334,31 +328,39 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def(pybind11::init<>())
         .def("__call__", &AdderBase::operator());
 
-    pybind11::class_<AdderBase::Data>(m, "Data")
-        .def(pybind11::init<>());
-
-    m.def("add2", [](const AdderBase::Data& first, const AdderBase::Data& second,
-                     const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
-        adder(first, second, visitor);
-    });
-
-    m.def("add3", [](const AdderBase::Data& first, const AdderBase::Data& second, const AdderBase::Data& third,
-                     const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
-        adder(first, second, [&] (const AdderBase::Data& first_plus_second) {
-            adder(first_plus_second, third, visitor); // NOLINT(readability-suspicious-call-argument)
-        });
-    });
+    pybind11::class_<AdderBase::Data>(m, "Data").def(pybind11::init<>());
+
+    m.def("add2",
+          [](const AdderBase::Data &first,
+             const AdderBase::Data &second,
+             const AdderBase &adder,
+             const AdderBase::DataVisitor &visitor) { adder(first, second, visitor); });
+
+    m.def("add3",
+          [](const AdderBase::Data &first,
+             const AdderBase::Data &second,
+             const AdderBase::Data &third,
+             const AdderBase &adder,
+             const AdderBase::DataVisitor &visitor) {
+              adder(first, second, [&](const AdderBase::Data &first_plus_second) {
+                  adder(first_plus_second,
+                        third,
+                        visitor); // NOLINT(readability-suspicious-call-argument)
+              });
+          });
 
     // test_override_ref
     // #392/397: overriding reference-returning functions
     class OverrideTest {
     public:
-        struct A { std::string value = "hi"; };
+        struct A {
+            std::string value = "hi";
+        };
         std::string v;
         A a;
         explicit OverrideTest(const std::string &v) : v{v} {}
         OverrideTest() = default;
-        OverrideTest(const OverrideTest&) = delete;
+        OverrideTest(const OverrideTest &) = delete;
         virtual std::string str_value() { return v; }
         virtual std::string &str_ref() { return v; }
         virtual A A_value() { return a; }
@@ -369,17 +371,22 @@ TEST_SUBMODULE(virtual_functions, m) {
     class PyOverrideTest : public OverrideTest {
     public:
         using OverrideTest::OverrideTest;
-        std::string str_value() override { PYBIND11_OVERRIDE(std::string, OverrideTest, str_value); }
+        std::string str_value() override {
+            PYBIND11_OVERRIDE(std::string, OverrideTest, str_value);
+        }
         // Not allowed (enabling the below should hit a static_assert failure): we can't get a
         // reference to a python numeric value, since we only copy values in the numeric type
         // caster:
 #ifdef PYBIND11_NEVER_DEFINED_EVER
-        std::string &str_ref() override { PYBIND11_OVERRIDE(std::string &, OverrideTest, str_ref); }
+        std::string &str_ref() override {
+            PYBIND11_OVERRIDE(std::string &, OverrideTest, str_ref);
+        }
 #endif
         // But we can work around it like this:
     private:
         std::string _tmp;
         std::string str_ref_helper() { PYBIND11_OVERRIDE(std::string, OverrideTest, str_ref); }
+
     public:
         std::string &str_ref() override { return _tmp = str_ref_helper(); }
 
@@ -398,14 +405,15 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def("A_value", &OverrideTest::A_value)
         .def("A_ref", &OverrideTest::A_ref);
 
-    py::class_<test_override_cache_helper, test_override_cache_helper_trampoline, std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
+    py::class_<test_override_cache_helper,
+               test_override_cache_helper_trampoline,
+               std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
         .def(py::init_alias<>())
         .def("func", &test_override_cache_helper::func);
 
     m.def("test_override_cache", test_override_cache);
 }
 
-
 // Inheriting virtual methods.  We do two versions here: the repeat-everything version and the
 // templated trampoline versions mentioned in docs/advanced.rst.
 //
@@ -414,83 +422,96 @@ TEST_SUBMODULE(virtual_functions, m) {
 // properly (pybind11, sensibly, doesn't allow us to bind the same C++ class to
 // multiple python classes).
 class A_Repeat {
-#define A_METHODS \
-public: \
-    virtual int unlucky_number() = 0; \
-    virtual std::string say_something(unsigned times) { \
-        std::string s = ""; \
-        for (unsigned i = 0; i < times; ++i) \
-            s += "hi"; \
-        return s; \
-    } \
-    std::string say_everything() { \
-        return say_something(1) + " " + std::to_string(unlucky_number()); \
+#define A_METHODS                                                                                 \
+public:                                                                                           \
+    virtual int unlucky_number() = 0;                                                             \
+    virtual std::string say_something(unsigned times) {                                           \
+        std::string s = "";                                                                       \
+        for (unsigned i = 0; i < times; ++i)                                                      \
+            s += "hi";                                                                            \
+        return s;                                                                                 \
+    }                                                                                             \
+    std::string say_everything() {                                                                \
+        return say_something(1) + " " + std::to_string(unlucky_number());                         \
     }
-A_METHODS
+    A_METHODS
     A_Repeat() = default;
-    A_Repeat(const A_Repeat&) = delete;
+    A_Repeat(const A_Repeat &) = delete;
     virtual ~A_Repeat() = default;
 };
 class B_Repeat : public A_Repeat {
-#define B_METHODS \
-public: \
-    int unlucky_number() override { return 13; } \
-    std::string say_something(unsigned times) override { \
-        return "B says hi " + std::to_string(times) + " times"; \
-    } \
+#define B_METHODS                                                                                 \
+public:                                                                                           \
+    int unlucky_number() override { return 13; }                                                  \
+    std::string say_something(unsigned times) override {                                          \
+        return "B says hi " + std::to_string(times) + " times";                                   \
+    }                                                                                             \
     virtual double lucky_number() { return 7.0; }
-B_METHODS
+    B_METHODS
 };
 class C_Repeat : public B_Repeat {
-#define C_METHODS \
-public: \
-    int unlucky_number() override { return 4444; } \
+#define C_METHODS                                                                                 \
+public:                                                                                           \
+    int unlucky_number() override { return 4444; }                                                \
     double lucky_number() override { return 888; }
-C_METHODS
+    C_METHODS
 };
 class D_Repeat : public C_Repeat {
 #define D_METHODS // Nothing overridden.
-D_METHODS
+    D_METHODS
 };
 
 // Base classes for templated inheritance trampolines.  Identical to the repeat-everything version:
 class A_Tpl {
     A_METHODS;
     A_Tpl() = default;
-    A_Tpl(const A_Tpl&) = delete;
+    A_Tpl(const A_Tpl &) = delete;
     virtual ~A_Tpl() = default;
 };
-class B_Tpl : public A_Tpl { B_METHODS };
-class C_Tpl : public B_Tpl { C_METHODS };
-class D_Tpl : public C_Tpl { D_METHODS };
-
+class B_Tpl : public A_Tpl {
+    B_METHODS
+};
+class C_Tpl : public B_Tpl {
+    C_METHODS
+};
+class D_Tpl : public C_Tpl {
+    D_METHODS
+};
 
 // Inheritance approach 1: each trampoline gets every virtual method (11 in total)
 class PyA_Repeat : public A_Repeat {
 public:
     using A_Repeat::A_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE_PURE(int, A_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, A_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, A_Repeat, say_something, times);
+    }
 };
 class PyB_Repeat : public B_Repeat {
 public:
     using B_Repeat::B_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE(int, B_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, B_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, B_Repeat, say_something, times);
+    }
     double lucky_number() override { PYBIND11_OVERRIDE(double, B_Repeat, lucky_number, ); }
 };
 class PyC_Repeat : public C_Repeat {
 public:
     using C_Repeat::C_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE(int, C_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, C_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, C_Repeat, say_something, times);
+    }
     double lucky_number() override { PYBIND11_OVERRIDE(double, C_Repeat, lucky_number, ); }
 };
 class PyD_Repeat : public D_Repeat {
 public:
     using D_Repeat::D_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE(int, D_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, D_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, D_Repeat, say_something, times);
+    }
     double lucky_number() override { PYBIND11_OVERRIDE(double, D_Repeat, lucky_number, ); }
 };
 
@@ -513,7 +534,9 @@ class PyA_Tpl : public Base {
 public:
     using Base::Base; // Inherit constructors
     int unlucky_number() override { PYBIND11_OVERRIDE_PURE(int, Base, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, Base, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, Base, say_something, times);
+    }
 };
 template <class Base = B_Tpl>
 class PyB_Tpl : public PyA_Tpl<Base> {
@@ -548,10 +571,8 @@ void initialize_inherited_virtuals(py::module_ &m) {
     py::class_<B_Repeat, A_Repeat, PyB_Repeat>(m, "B_Repeat")
         .def(py::init<>())
         .def("lucky_number", &B_Repeat::lucky_number);
-    py::class_<C_Repeat, B_Repeat, PyC_Repeat>(m, "C_Repeat")
-        .def(py::init<>());
-    py::class_<D_Repeat, C_Repeat, PyD_Repeat>(m, "D_Repeat")
-        .def(py::init<>());
+    py::class_<C_Repeat, B_Repeat, PyC_Repeat>(m, "C_Repeat").def(py::init<>());
+    py::class_<D_Repeat, C_Repeat, PyD_Repeat>(m, "D_Repeat").def(py::init<>());
 
     // test_
     // Method 2: Templated trampolines
@@ -563,11 +584,8 @@ void initialize_inherited_virtuals(py::module_ &m) {
     py::class_<B_Tpl, A_Tpl, PyB_Tpl<>>(m, "B_Tpl")
         .def(py::init<>())
         .def("lucky_number", &B_Tpl::lucky_number);
-    py::class_<C_Tpl, B_Tpl, PyB_Tpl<C_Tpl>>(m, "C_Tpl")
-        .def(py::init<>());
-    py::class_<D_Tpl, C_Tpl, PyB_Tpl<D_Tpl>>(m, "D_Tpl")
-        .def(py::init<>());
-
+    py::class_<C_Tpl, B_Tpl, PyB_Tpl<C_Tpl>>(m, "C_Tpl").def(py::init<>());
+    py::class_<D_Tpl, C_Tpl, PyB_Tpl<D_Tpl>>(m, "D_Tpl").def(py::init<>());
 
     // Fix issue #1454 (crash when acquiring/releasing GIL on another thread in Python 2.7)
     m.def("test_gil", &test_gil);

From 46dcd9bc75cd09a24633f2d02eb0adb52e1717e4 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 10 Feb 2022 17:03:33 -0500
Subject: [PATCH 308/638] fix: minor CMake warning fix for unused variable
 (#3718)

---
 tools/FindCatch.cmake | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/FindCatch.cmake b/tools/FindCatch.cmake
index 4d6bffcf68..57bba58b30 100644
--- a/tools/FindCatch.cmake
+++ b/tools/FindCatch.cmake
@@ -9,6 +9,8 @@
 #  CATCH_INCLUDE_DIR      - path to catch.hpp
 #  CATCH_VERSION          - version number
 
+option(DOWNLOAD_CATCH "Download catch2 if not found")
+
 if(NOT Catch_FIND_VERSION)
   message(FATAL_ERROR "A version number must be specified.")
 elseif(Catch_FIND_REQUIRED)

From 6493f496e30c80f004772c906370c8f4db94b6ec Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 10 Feb 2022 18:28:08 -0800
Subject: [PATCH 309/638] Python 2 removal part 1: tests (C++ code is
 intentionally ~untouched) (#3688)

* `#error BYE_BYE_GOLDEN_SNAKE`

* Removing everything related to 2.7 from ci.yml

* Commenting-out Centos7

* Removing `PYTHON: 27` from .appveyor.yml

* "PY2" removal, mainly from tests. C++ code is not touched.

* Systematic removal of `u` prefix from `u"..."` and `u'...'` literals. Collateral cleanup of a couple minor other things.

* Cleaning up around case-insensitive hits for `[^a-z]py.*2` in tests/.

* Removing obsolete Python 2 mention in compiling.rst

* Proper `#error` for Python 2.

* Using PY_VERSION_HEX to guard `#error "PYTHON 2 IS NO LONGER SUPPORTED.`

* chore: bump pre-commit

* style: run pre-commit for pyupgrade 3+

* tests: use sys.version_info, not PY

* chore: more Python 2 removal

* Uncommenting Centos7 block (PR #3691 showed that it is working again).

* Update pre-commit hooks

* Fix pre-commit hook

* refactor: remove Python 2 from CMake

* refactor: remove Python 2 from setup code

* refactor: simplify, better static typing

* feat: fail with nice messages

* refactor: drop Python 2 C++ code

* docs: cleanup for Python 3

* revert: intree

revert: intree

* docs: minor touchup to py2 statement

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 .appveyor.yml                              |   2 -
 .github/workflows/ci.yml                   |  27 ---
 .github/workflows/pip.yml                  |   8 +-
 .pre-commit-config.yaml                    |  33 ++--
 MANIFEST.in                                |   1 -
 README.rst                                 |   6 +-
 docs/Doxyfile                              |   3 +-
 docs/advanced/cast/strings.rst             |  19 +-
 docs/advanced/classes.rst                  |  33 ++--
 docs/advanced/exceptions.rst               |   6 +-
 docs/advanced/pycpp/numpy.rst              |   8 -
 docs/basics.rst                            |   6 +-
 docs/benchmark.py                          |   3 +-
 docs/classes.rst                           |  14 +-
 docs/compiling.rst                         |  14 +-
 docs/conf.py                               |   1 -
 docs/faq.rst                               |  26 +--
 include/pybind11/cast.h                    |  44 +----
 include/pybind11/detail/class.h            |  22 +--
 include/pybind11/detail/common.h           | 121 ++++--------
 include/pybind11/detail/internals.h        |  13 +-
 include/pybind11/detail/type_caster_base.h |  13 --
 include/pybind11/embed.h                   |  55 +-----
 include/pybind11/eval.h                    |  32 +---
 include/pybind11/numpy.h                   |   4 -
 include/pybind11/operators.h               |  19 --
 include/pybind11/pybind11.h                |  41 +----
 include/pybind11/pytypes.h                 |  48 +----
 noxfile.py                                 |   2 +-
 pybind11/__init__.py                       |   7 +-
 pybind11/__main__.py                       |   9 +-
 pybind11/_version.py                       |   4 +-
 pybind11/_version.pyi                      |   6 -
 pybind11/commands.py                       |   7 +-
 pybind11/setup_helpers.py                  | 203 ++++++++++----------
 pybind11/setup_helpers.pyi                 |  63 -------
 pyproject.toml                             |  21 +--
 setup.cfg                                  |  10 +-
 setup.py                                   | 126 ++++++-------
 tests/CMakeLists.txt                       |  16 --
 tests/conftest.py                          |  16 +-
 tests/cross_module_gil_utils.cpp           |  23 +--
 tests/env.py                               |   5 -
 tests/extra_python_package/test_files.py   |   3 -
 tests/extra_setuptools/test_setuphelper.py |  12 +-
 tests/test_async.py                        |   1 -
 tests/test_buffers.py                      |  12 +-
 tests/test_builtin_casters.cpp             |   6 +-
 tests/test_builtin_casters.py              | 205 +++++++++------------
 tests/test_call_policies.py                |   1 -
 tests/test_callbacks.py                    |   1 -
 tests/test_chrono.py                       |   1 -
 tests/test_class.py                        |  10 +-
 tests/test_cmake_build/test.py             |   4 +-
 tests/test_const_name.py                   |   4 +-
 tests/test_constants_and_functions.py      |   1 -
 tests/test_copy_move.py                    |   1 -
 tests/test_custom_type_casters.py          |   7 +-
 tests/test_custom_type_setup.py            |   2 -
 tests/test_docstring_options.py            |   1 -
 tests/test_eigen.py                        |   9 +-
 tests/test_embed/test_interpreter.cpp      |   5 -
 tests/test_embed/test_interpreter.py       |   3 +-
 tests/test_embed/test_trampoline.py        |   2 -
 tests/test_enum.py                         |  12 +-
 tests/test_eval.py                         |   3 +-
 tests/test_eval_call.py                    |   1 -
 tests/test_exceptions.cpp                  |   3 -
 tests/test_exceptions.py                   |  17 +-
 tests/test_factory_constructors.py         |  10 +-
 tests/test_gil_scoped.py                   |   1 -
 tests/test_iostream.py                     |  40 +---
 tests/test_kwargs_and_defaults.py          |  11 +-
 tests/test_local_bindings.py               |   3 +-
 tests/test_methods_and_attributes.py       |  18 +-
 tests/test_modules.py                      |   1 -
 tests/test_multiple_inheritance.py         |  11 +-
 tests/test_numpy_array.py                  |   1 -
 tests/test_numpy_dtypes.py                 |   1 -
 tests/test_numpy_vectorize.py              |   1 -
 tests/test_opaque_types.py                 |   3 +-
 tests/test_operator_overloading.py         |   5 +-
 tests/test_pickling.py                     |   8 +-
 tests/test_pytypes.cpp                     |   4 -
 tests/test_pytypes.py                      | 145 +++++----------
 tests/test_sequences_and_iterators.py      |   1 -
 tests/test_smart_ptr.py                    |   1 -
 tests/test_stl.py                          |   5 +-
 tests/test_stl_binders.py                  |  17 +-
 tests/test_tagbased_polymorphic.py         |   1 -
 tests/test_thread.py                       |   6 +-
 tests/test_union.py                        |   1 -
 tests/test_virtual_functions.py            |  21 +--
 tools/FindPythonLibsNew.cmake              |   2 +-
 tools/libsize.py                           |   3 -
 tools/make_changelog.py                    |   1 -
 tools/pybind11Common.cmake                 |  26 ---
 tools/pybind11Config.cmake.in              |   2 -
 tools/pybind11NewTools.cmake               |  32 +---
 tools/pybind11Tools.cmake                  |   9 +-
 tools/setup_global.py.in                   |   5 -
 tools/setup_main.py.in                     |   2 +-
 102 files changed, 530 insertions(+), 1335 deletions(-)
 delete mode 100644 pybind11/_version.pyi
 delete mode 100644 pybind11/setup_helpers.pyi

diff --git a/.appveyor.yml b/.appveyor.yml
index 85445d41a2..f3bc9cd496 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -11,8 +11,6 @@ environment:
   matrix:
   - PYTHON: 36
     CONFIG: Debug
-  - PYTHON: 27
-    CONFIG: Debug
 install:
 - ps: |
     $env:CMAKE_GENERATOR = "Visual Studio 14 2015"
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b52c306181..07580decd0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,7 +25,6 @@ jobs:
       matrix:
         runs-on: [ubuntu-latest, windows-2022, macos-latest]
         python:
-        - '2.7'
         - '3.5'
         - '3.6'
         - '3.9'
@@ -49,13 +48,9 @@ jobs:
             python: '3.6'
             args: >
               -DPYBIND11_FINDPYTHON=ON
-          - runs-on: macos-latest
-            python: 'pypy-2.7'
           # Inject a couple Windows 2019 runs
           - runs-on: windows-2019
             python: '3.9'
-          - runs-on: windows-2019
-            python: '2.7'
 
     name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • x64 ${{ matrix.args }}"
     runs-on: ${{ matrix.runs-on }}
@@ -168,22 +163,6 @@ jobs:
     - name: Interface test
       run: cmake --build build2 --target test_cmake_build
 
-    # Eventually Microsoft might have an action for setting up
-    # MSVC, but for now, this action works:
-    - name: Prepare compiler environment for Windows 🐍 2.7
-      if: matrix.python == 2.7 && runner.os == 'Windows'
-      uses: ilammy/msvc-dev-cmd@v1.10.0
-      with:
-        arch: x64
-
-    # This makes two environment variables available in the following step(s)
-    - name: Set Windows 🐍 2.7 environment variables
-      if: matrix.python == 2.7 && runner.os == 'Windows'
-      shell: bash
-      run: |
-        echo "DISTUTILS_USE_SDK=1" >> $GITHUB_ENV
-        echo "MSSdk=1" >> $GITHUB_ENV
-
     # This makes sure the setup_helpers module can build packages using
     # setuptools
     - name: Setuptools helpers test
@@ -784,7 +763,6 @@ jobs:
       fail-fast: false
       matrix:
         python:
-          - 2.7
           - 3.6
           - 3.7
           # todo: check/cpptest does not support 3.8+ yet
@@ -832,17 +810,12 @@ jobs:
       fail-fast: false
       matrix:
         python:
-          - 2.7
           - 3.5
           - 3.7
         std:
           - 14
 
         include:
-          - python: 2.7
-            std: 17
-            args: >
-              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR"
           - python: 3.7
             std: 17
             args: >
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index f74b79f0ce..7a5443d14b 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -17,19 +17,19 @@ env:
 
 jobs:
   # This builds the sdists and wheels and makes sure the files are exactly as
-  # expected. Using Windows and Python 2.7, since that is often the most
+  # expected. Using Windows and Python 3.6, since that is often the most
   # challenging matrix element.
   test-packaging:
-    name: 🐍 2.7 • 📦 tests • windows-latest
+    name: 🐍 3.6 • 📦 tests • windows-latest
     runs-on: windows-latest
 
     steps:
     - uses: actions/checkout@v2
 
-    - name: Setup 🐍 2.7
+    - name: Setup 🐍 3.6
       uses: actions/setup-python@v2
       with:
-        python-version: 2.7
+        python-version: 3.6
 
     - name: Prepare env
       run: |
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c31cab71c7..6d44d5e76c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -29,14 +29,15 @@ repos:
   - id: mixed-line-ending
   - id: requirements-txt-fixer
   - id: trailing-whitespace
-  - id: fix-encoding-pragma
-    exclude: ^noxfile.py$
 
+# Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
   rev: v2.31.0
   hooks:
   - id: pyupgrade
+    args: [--py3-plus]
 
+# Nicely sort includes
 - repo: https://github.com/PyCQA/isort
   rev: 5.10.1
   hooks:
@@ -44,20 +45,21 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 21.12b0 # Keep in sync with blacken-docs
+  rev: 22.1.0 # Keep in sync with blacken-docs
   hooks:
   - id: black
 
+# Also code format the docs
 - repo: https://github.com/asottile/blacken-docs
-  rev: v1.12.0
+  rev: v1.12.1
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==21.12b0 # keep in sync with black hook
+    - black==22.1.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: v1.1.10
+  rev: v1.1.11
   hooks:
   - id: remove-tabs
 
@@ -67,12 +69,15 @@ repos:
   hooks:
   - id: pycln
 
+# Checking for common mistakes
 - repo: https://github.com/pre-commit/pygrep-hooks
   rev: v1.9.0
   hooks:
   - id: python-check-blanket-noqa
   - id: python-check-blanket-type-ignore
   - id: python-no-log-warn
+  # Python 3.6
+  # - id: python-use-type-annotations
   - id: rst-backticks
   - id: rst-directive-colons
   - id: rst-inline-touching-normal
@@ -87,6 +92,7 @@ repos:
       - pep8-naming
     exclude: ^(docs/.*|tools/.*)$
 
+# Automatically remove noqa that are not used
 - repo: https://github.com/asottile/yesqa
   rev: v1.3.0
   hooks:
@@ -107,9 +113,9 @@ repos:
   rev: v0.931
   hooks:
   - id: mypy
-    # Running per-file misbehaves a bit, so just run on all files, it's fast
-    pass_filenames: false
-    additional_dependencies: [typed_ast]
+    args: [--show-error-codes]
+    exclude: ^(tests|docs)/
+    additional_dependencies: [nox, rich]
 
 # Checks the manifest for missing files (native support)
 - repo: https://github.com/mgedmin/check-manifest
@@ -120,6 +126,7 @@ repos:
     stages: [manual]
     additional_dependencies: [cmake, ninja]
 
+# Check for spelling
 - repo: https://github.com/codespell-project/codespell
   rev: v2.1.0
   hooks:
@@ -127,20 +134,22 @@ repos:
     exclude: ".supp$"
     args: ["-L", "nd,ot,thist"]
 
+# Check for common shell mistakes
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: v0.8.0.3
+  rev: v0.8.0.4
   hooks:
   - id: shellcheck
 
-# The original pybind11 checks for a few C++ style items
+# Disallow some common capitalization mistakes
 - repo: local
   hooks:
   - id: disallow-caps
     name: Disallow improper capitalization
     language: pygrep
     entry: PyBind|Numpy|Cmake|CCache|PyTest
-    exclude: .pre-commit-config.yaml
+    exclude: ^\.pre-commit-config.yaml$
 
+# Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
   rev: "v13.0.0"
   hooks:
diff --git a/MANIFEST.in b/MANIFEST.in
index aed183e874..033303a74a 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,6 +1,5 @@
 recursive-include pybind11/include/pybind11 *.h
 recursive-include pybind11 *.py
 recursive-include pybind11 py.typed
-recursive-include pybind11 *.pyi
 include pybind11/share/cmake/pybind11/*.cmake
 include LICENSE README.rst pyproject.toml setup.py setup.cfg
diff --git a/README.rst b/README.rst
index 45c4af5a60..6398db4f0b 100644
--- a/README.rst
+++ b/README.rst
@@ -34,7 +34,7 @@ dependency.
 Think of this library as a tiny self-contained version of Boost.Python
 with everything stripped away that isn’t relevant for binding
 generation. Without comments, the core header files only require ~4K
-lines of code and depend on Python (2.7 or 3.5+, or PyPy) and the C++
+lines of code and depend on Python (3.5+, or PyPy) and the C++
 standard library. This compact implementation was possible thanks to
 some of the new C++11 language features (specifically: tuples, lambda
 functions and variadic templates). Since its creation, this library has
@@ -78,8 +78,8 @@ Goodies
 In addition to the core functionality, pybind11 provides some extra
 goodies:
 
-- Python 2.7, 3.5+, and PyPy/PyPy3 7.3 are supported with an
-  implementation-agnostic interface.
+- Python 3.5+, and PyPy3 7.3 are supported with an implementation-agnostic
+  interface (pybind11 2.9 was the last version to support Python 2).
 
 - It is possible to bind C++11 lambda functions with captured
   variables. The lambda capture data is stored inside the resulting
diff --git a/docs/Doxyfile b/docs/Doxyfile
index 62c2675563..09138db364 100644
--- a/docs/Doxyfile
+++ b/docs/Doxyfile
@@ -18,5 +18,4 @@ ALIASES               += "endrst=\endverbatim"
 QUIET                  = YES
 WARNINGS               = YES
 WARN_IF_UNDOCUMENTED   = NO
-PREDEFINED             = PY_MAJOR_VERSION=3 \
-                         PYBIND11_NOINLINE
+PREDEFINED             = PYBIND11_NOINLINE
diff --git a/docs/advanced/cast/strings.rst b/docs/advanced/cast/strings.rst
index cfd7e7b7a5..e246c5219a 100644
--- a/docs/advanced/cast/strings.rst
+++ b/docs/advanced/cast/strings.rst
@@ -1,14 +1,6 @@
 Strings, bytes and Unicode conversions
 ######################################
 
-.. note::
-
-    This section discusses string handling in terms of Python 3 strings. For
-    Python 2.7, replace all occurrences of ``str`` with ``unicode`` and
-    ``bytes`` with ``str``.  Python 2.7 users may find it best to use ``from
-    __future__ import unicode_literals`` to avoid unintentionally using ``str``
-    instead of ``unicode``.
-
 Passing Python strings to C++
 =============================
 
@@ -58,9 +50,9 @@ Passing bytes to C++
 --------------------
 
 A Python ``bytes`` object will be passed to C++ functions that accept
-``std::string`` or ``char*`` *without* conversion.  On Python 3, in order to
-make a function *only* accept ``bytes`` (and not ``str``), declare it as taking
-a ``py::bytes`` argument.
+``std::string`` or ``char*`` *without* conversion.  In order to make a function
+*only* accept ``bytes`` (and not ``str``), declare it as taking a ``py::bytes``
+argument.
 
 
 Returning C++ strings to Python
@@ -204,11 +196,6 @@ decoded to Python ``str``.
         }
     );
 
-.. warning::
-
-    Wide character strings may not work as described on Python 2.7 or Python
-    3.3 compiled with ``--enable-unicode=ucs2``.
-
 Strings in multibyte encodings such as Shift-JIS must transcoded to a
 UTF-8/16/32 before being returned to Python.
 
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index f3339336dc..3e8ba73852 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -133,14 +133,14 @@ a virtual method call.
     >>> from example import *
     >>> d = Dog()
     >>> call_go(d)
-    u'woof! woof! woof! '
+    'woof! woof! woof! '
     >>> class Cat(Animal):
     ...     def go(self, n_times):
     ...         return "meow! " * n_times
     ...
     >>> c = Cat()
     >>> call_go(c)
-    u'meow! meow! meow! '
+    'meow! meow! meow! '
 
 If you are defining a custom constructor in a derived Python class, you *must*
 ensure that you explicitly call the bound C++ constructor using ``__init__``,
@@ -813,26 +813,21 @@ An instance can now be pickled as follows:
 
 .. code-block:: python
 
-    try:
-        import cPickle as pickle  # Use cPickle on Python 2.7
-    except ImportError:
-        import pickle
+    import pickle
 
     p = Pickleable("test_value")
     p.setExtra(15)
-    data = pickle.dumps(p, 2)
+    data = pickle.dumps(p)
 
 
 .. note::
-    Note that only the cPickle module is supported on Python 2.7.
-
-    The second argument to ``dumps`` is also crucial: it selects the pickle
-    protocol version 2, since the older version 1 is not supported. Newer
-    versions are also fine—for instance, specify ``-1`` to always use the
-    latest available version. Beware: failure to follow these instructions
-    will cause important pybind11 memory allocation routines to be skipped
-    during unpickling, which will likely lead to memory corruption and/or
-    segmentation faults.
+    If given, the second argument to ``dumps`` must be 2 or larger - 0 and 1 are
+    not supported. Newer versions are also fine; for instance, specify ``-1`` to
+    always use the latest available version. Beware: failure to follow these
+    instructions will cause important pybind11 memory allocation routines to be
+    skipped during unpickling, which will likely lead to memory corruption
+    and/or segmentation faults. Python defaults to version 3 (Python 3-3.7) and
+    version 4 for Python 3.8+.
 
 .. seealso::
 
@@ -849,11 +844,9 @@ Python normally uses references in assignments. Sometimes a real copy is needed
 to prevent changing all copies. The ``copy`` module [#f5]_ provides these
 capabilities.
 
-On Python 3, a class with pickle support is automatically also (deep)copy
+A class with pickle support is automatically also (deep)copy
 compatible. However, performance can be improved by adding custom
-``__copy__`` and ``__deepcopy__`` methods. With Python 2.7, these custom methods
-are mandatory for (deep)copy compatibility, because pybind11 only supports
-cPickle.
+``__copy__`` and ``__deepcopy__`` methods.
 
 For simple classes (deep)copy can be enabled by using the copy constructor,
 which should look as follows:
diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index 7cd8447b93..2211caf5d3 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -328,8 +328,8 @@ an invalid state.
 Chaining exceptions ('raise from')
 ==================================
 
-In Python 3.3 a mechanism for indicating that exceptions were caused by other
-exceptions was introduced:
+Python has a mechanism for indicating that exceptions were caused by other
+exceptions:
 
 .. code-block:: py
 
@@ -340,7 +340,7 @@ exceptions was introduced:
 
 To do a similar thing in pybind11, you can use the ``py::raise_from`` function. It
 sets the current python error indicator, so to continue propagating the exception
-you should ``throw py::error_already_set()`` (Python 3 only).
+you should ``throw py::error_already_set()``.
 
 .. code-block:: cpp
 
diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index 30daeefff9..dbc48440a6 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -398,8 +398,6 @@ Ellipsis
 Python 3 provides a convenient ``...`` ellipsis notation that is often used to
 slice multidimensional arrays. For instance, the following snippet extracts the
 middle dimensions of a tensor with the first and last index set to zero.
-In Python 2, the syntactic sugar ``...`` is not available, but the singleton
-``Ellipsis`` (of type ``ellipsis``) can still be used directly.
 
 .. code-block:: python
 
@@ -414,8 +412,6 @@ operation on the C++ side:
    py::array a = /* A NumPy array */;
    py::array b = a[py::make_tuple(0, py::ellipsis(), 0)];
 
-.. versionchanged:: 2.6
-   ``py::ellipsis()`` is now also available in Python 2.
 
 Memory view
 ===========
@@ -455,9 +451,5 @@ We can also use ``memoryview::from_memory`` for a simple 1D contiguous buffer:
         );
     })
 
-.. note::
-
-    ``memoryview::from_memory`` is not available in Python 2.
-
 .. versionchanged:: 2.6
     ``memoryview::from_memory`` added.
diff --git a/docs/basics.rst b/docs/basics.rst
index e0479b298d..d40992d386 100644
--- a/docs/basics.rst
+++ b/docs/basics.rst
@@ -166,12 +166,12 @@ load and execute the example:
 .. code-block:: pycon
 
     $ python
-    Python 2.7.10 (default, Aug 22 2015, 20:33:39)
-    [GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.1)] on darwin
+    Python 3.9.10 (main, Jan 15 2022, 11:48:04)
+    [Clang 13.0.0 (clang-1300.0.29.3)] on darwin
     Type "help", "copyright", "credits" or "license" for more information.
     >>> import example
     >>> example.add(1, 2)
-    3L
+    3
     >>>
 
 .. _keyword_args:
diff --git a/docs/benchmark.py b/docs/benchmark.py
index f190793671..a595342926 100644
--- a/docs/benchmark.py
+++ b/docs/benchmark.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import datetime as dt
 import os
 import random
@@ -75,7 +74,7 @@ def generate_dummy_code_boost(nclasses=10):
 for codegen in [generate_dummy_code_pybind11, generate_dummy_code_boost]:
     print("{")
     for i in range(0, 10):
-        nclasses = 2 ** i
+        nclasses = 2**i
         with open("test.cpp", "w") as f:
             f.write(codegen(nclasses))
         n1 = dt.datetime.now()
diff --git a/docs/classes.rst b/docs/classes.rst
index 13fa8b5387..b833bc4ba1 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -48,10 +48,10 @@ interactive Python session demonstrating this example is shown below:
     >>> print(p)
     <example.Pet object at 0x10cd98060>
     >>> p.getName()
-    u'Molly'
+    'Molly'
     >>> p.setName("Charly")
     >>> p.getName()
-    u'Charly'
+    'Charly'
 
 .. seealso::
 
@@ -124,10 +124,10 @@ This makes it possible to write
 
     >>> p = example.Pet("Molly")
     >>> p.name
-    u'Molly'
+    'Molly'
     >>> p.name = "Charly"
     >>> p.name
-    u'Charly'
+    'Charly'
 
 Now suppose that ``Pet::name`` was a private internal variable
 that can only be accessed via setters and getters.
@@ -282,9 +282,9 @@ expose fields and methods of both types:
 
     >>> p = example.Dog("Molly")
     >>> p.name
-    u'Molly'
+    'Molly'
     >>> p.bark()
-    u'woof!'
+    'woof!'
 
 The C++ classes defined above are regular non-polymorphic types with an
 inheritance relationship. This is reflected in Python:
@@ -332,7 +332,7 @@ will automatically recognize this:
     >>> type(p)
     PolymorphicDog  # automatically downcast
     >>> p.bark()
-    u'woof!'
+    'woof!'
 
 Given a pointer to a polymorphic base, pybind11 performs automatic downcasting
 to the actual derived type. Note that this goes beyond the usual situation in
diff --git a/docs/compiling.rst b/docs/compiling.rst
index 25adb9fcf2..f7303fd23f 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -462,11 +462,8 @@ available in all modes. The targets provided are:
    ``pybind11::headers``
      Just the pybind11 headers and minimum compile requirements
 
-   ``pybind11::python2_no_register``
-     Quiets the warning/error when mixing C++14 or higher and Python 2
-
    ``pybind11::pybind11``
-     Python headers + ``pybind11::headers`` + ``pybind11::python2_no_register`` (Python 2 only)
+     Python headers + ``pybind11::headers``
 
    ``pybind11::python_link_helper``
      Just the "linking" part of pybind11:module
@@ -577,21 +574,12 @@ On Linux, you can compile an example such as the one given in
 
     $ c++ -O3 -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)
 
-The flags given here assume that you're using Python 3. For Python 2, just
-change the executable appropriately (to ``python`` or ``python2``).
-
 The ``python3 -m pybind11 --includes`` command fetches the include paths for
 both pybind11 and Python headers. This assumes that pybind11 has been installed
 using ``pip`` or ``conda``. If it hasn't, you can also manually specify
 ``-I <path-to-pybind11>/include`` together with the Python includes path
 ``python3-config --includes``.
 
-Note that Python 2.7 modules don't use a special suffix, so you should simply
-use ``example.so`` instead of ``example$(python3-config --extension-suffix)``.
-Besides, the ``--extension-suffix`` option may or may not be available, depending
-on the distribution; in the latter case, the module extension can be manually
-set to ``.so``.
-
 On macOS: the build command is almost the same but it also requires passing
 the ``-undefined dynamic_lookup`` flag so as to ignore missing symbols when
 building the module:
diff --git a/docs/conf.py b/docs/conf.py
index 092e274e09..99f3be349c 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-# -*- coding: utf-8 -*-
 #
 # pybind11 documentation build configuration file, created by
 # sphinx-quickstart on Sun Oct 11 19:23:48 2015.
diff --git a/docs/faq.rst b/docs/faq.rst
index e2f477b1f5..69c3442e3b 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -8,9 +8,7 @@ Frequently asked questions
 filename of the extension library (without suffixes such as ``.so``).
 
 2. If the above did not fix the issue, you are likely using an incompatible
-version of Python (for instance, the extension library was compiled against
-Python 2, while the interpreter is running on top of some version of Python
-3, or vice versa).
+version of Python that does not match what you compiled with.
 
 "Symbol not found: ``__Py_ZeroStruct`` / ``_PyInstanceMethod_Type``"
 ========================================================================
@@ -289,27 +287,7 @@ Conflicts can arise, however, when using pybind11 in a project that *also* uses
 the CMake Python detection in a system with several Python versions installed.
 
 This difference may cause inconsistencies and errors if *both* mechanisms are
-used in the same project. Consider the following CMake code executed in a
-system with Python 2.7 and 3.x installed:
-
-.. code-block:: cmake
-
-    find_package(PythonInterp)
-    find_package(PythonLibs)
-    find_package(pybind11)
-
-It will detect Python 2.7 and pybind11 will pick it as well.
-
-In contrast this code:
-
-.. code-block:: cmake
-
-    find_package(pybind11)
-    find_package(PythonInterp)
-    find_package(PythonLibs)
-
-will detect Python 3.x for pybind11 and may crash on
-``find_package(PythonLibs)`` afterwards.
+used in the same project.
 
 There are three possible solutions:
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 2622e5819d..b12559ac8b 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -325,7 +325,7 @@ class type_caster<bool> {
                 res = 0; // None is implicitly converted to False
             }
 #if defined(PYPY_VERSION)
-            // On PyPy, check that "__bool__" (or "__nonzero__" on Python 2.7) attr exists
+            // On PyPy, check that "__bool__" attr exists
             else if (hasattr(src, PYBIND11_BOOL_ATTR)) {
                 res = PyObject_IsTrue(src.ptr());
             }
@@ -375,37 +375,16 @@ struct string_caster {
     static constexpr size_t UTF_N = 8 * sizeof(CharT);
 
     bool load(handle src, bool) {
-#if PY_MAJOR_VERSION < 3
-        object temp;
-#endif
         handle load_src = src;
         if (!src) {
             return false;
         }
         if (!PyUnicode_Check(load_src.ptr())) {
-#if PY_MAJOR_VERSION >= 3
             return load_bytes(load_src);
-#else
-            if (std::is_same<CharT, char>::value) {
-                return load_bytes(load_src);
-            }
-
-            // The below is a guaranteed failure in Python 3 when PyUnicode_Check returns false
-            if (!PYBIND11_BYTES_CHECK(load_src.ptr()))
-                return false;
-
-            temp = reinterpret_steal<object>(PyUnicode_FromObject(load_src.ptr()));
-            if (!temp) {
-                PyErr_Clear();
-                return false;
-            }
-            load_src = temp;
-#endif
         }
 
-#if PY_VERSION_HEX >= 0x03030000
-        // On Python >= 3.3, for UTF-8 we avoid the need for a temporary `bytes`
-        // object by using `PyUnicode_AsUTF8AndSize`.
+        // For UTF-8 we avoid the need for a temporary `bytes` object by using
+        // `PyUnicode_AsUTF8AndSize`.
         if (PYBIND11_SILENCE_MSVC_C4127(UTF_N == 8)) {
             Py_ssize_t size = -1;
             const auto *buffer
@@ -417,7 +396,6 @@ struct string_caster {
             value = StringType(buffer, static_cast<size_t>(size));
             return true;
         }
-#endif
 
         auto utfNbytes
             = reinterpret_steal<object>(PyUnicode_AsEncodedString(load_src.ptr(),
@@ -486,7 +464,7 @@ struct string_caster {
     template <typename C = CharT>
     bool load_bytes(enable_if_t<std::is_same<C, char>::value, handle> src) {
         if (PYBIND11_BYTES_CHECK(src.ptr())) {
-            // We were passed a Python 3 raw bytes; accept it into a std::string or char*
+            // We were passed raw bytes; accept it into a std::string or char*
             // without any encoding attempt.
             const char *bytes = PYBIND11_BYTES_AS_STRING(src.ptr());
             if (bytes) {
@@ -922,18 +900,6 @@ struct pyobject_caster {
 
     template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) {
-#if PY_MAJOR_VERSION < 3 && !defined(PYBIND11_STR_LEGACY_PERMISSIVE)
-        // For Python 2, without this implicit conversion, Python code would
-        // need to be cluttered with six.ensure_text() or similar, only to be
-        // un-cluttered later after Python 2 support is dropped.
-        if (PYBIND11_SILENCE_MSVC_C4127(std::is_same<T, str>::value) && isinstance<bytes>(src)) {
-            PyObject *str_from_bytes = PyUnicode_FromEncodedObject(src.ptr(), "utf-8", nullptr);
-            if (!str_from_bytes)
-                throw error_already_set();
-            value = reinterpret_steal<type>(str_from_bytes);
-            return true;
-        }
-#endif
         if (!isinstance<type>(src)) {
             return false;
         }
@@ -1313,7 +1279,7 @@ struct arg_v : arg {
 
 /// \ingroup annotations
 /// Annotation indicating that all following arguments are keyword-only; the is the equivalent of
-/// an unnamed '*' argument (in Python 3)
+/// an unnamed '*' argument
 struct kw_only {};
 
 /// \ingroup annotations
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index ac92ddd632..ebdc07271b 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -15,12 +15,12 @@
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-#if PY_VERSION_HEX >= 0x03030000 && !defined(PYPY_VERSION)
+#if !defined(PYPY_VERSION)
 #    define PYBIND11_BUILTIN_QUALNAME
 #    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
 #else
-// In pre-3.3 Python, we still set __qualname__ so that we can produce reliable function type
-// signatures; in 3.3+ this macro expands to nothing:
+// In PyPy, we still set __qualname__ so that we can produce reliable function type
+// signatures; in CPython this macro expands to nothing:
 #    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)                                             \
         setattr((PyObject *) obj, "__qualname__", nameobj)
 #endif
@@ -155,7 +155,6 @@ extern "C" inline int pybind11_meta_setattro(PyObject *obj, PyObject *name, PyOb
     }
 }
 
-#if PY_MAJOR_VERSION >= 3
 /**
  * Python 3's PyInstanceMethod_Type hides itself via its tp_descr_get, which prevents aliasing
  * methods via cls.attr("m2") = cls.attr("m1"): instead the tp_descr_get returns a plain function,
@@ -170,7 +169,6 @@ extern "C" inline PyObject *pybind11_meta_getattro(PyObject *obj, PyObject *name
     }
     return PyType_Type.tp_getattro(obj, name);
 }
-#endif
 
 /// metaclass `__call__` function that is used to create all pybind11 objects.
 extern "C" inline PyObject *pybind11_meta_call(PyObject *type, PyObject *args, PyObject *kwargs) {
@@ -266,9 +264,7 @@ inline PyTypeObject *make_default_metaclass() {
     type->tp_call = pybind11_meta_call;
 
     type->tp_setattro = pybind11_meta_setattro;
-#if PY_MAJOR_VERSION >= 3
     type->tp_getattro = pybind11_meta_getattro;
-#endif
 
     type->tp_dealloc = pybind11_meta_dealloc;
 
@@ -613,9 +609,6 @@ extern "C" inline void pybind11_releasebuffer(PyObject *, Py_buffer *view) {
 /// Give this type a buffer interface.
 inline void enable_buffer_protocol(PyHeapTypeObject *heap_type) {
     heap_type->ht_type.tp_as_buffer = &heap_type->as_buffer;
-#if PY_MAJOR_VERSION < 3
-    heap_type->ht_type.tp_flags |= Py_TPFLAGS_HAVE_NEWBUFFER;
-#endif
 
     heap_type->as_buffer.bf_getbuffer = pybind11_getbuffer;
     heap_type->as_buffer.bf_releasebuffer = pybind11_releasebuffer;
@@ -628,12 +621,8 @@ inline PyObject *make_new_python_type(const type_record &rec) {
 
     auto qualname = name;
     if (rec.scope && !PyModule_Check(rec.scope.ptr()) && hasattr(rec.scope, "__qualname__")) {
-#if PY_MAJOR_VERSION >= 3
         qualname = reinterpret_steal<object>(
             PyUnicode_FromFormat("%U.%U", rec.scope.attr("__qualname__").ptr(), name.ptr()));
-#else
-        qualname = str(rec.scope.attr("__qualname__").cast<std::string>() + "." + rec.name);
-#endif
     }
 
     object module_;
@@ -697,15 +686,10 @@ inline PyObject *make_new_python_type(const type_record &rec) {
     type->tp_as_number = &heap_type->as_number;
     type->tp_as_sequence = &heap_type->as_sequence;
     type->tp_as_mapping = &heap_type->as_mapping;
-#if PY_VERSION_HEX >= 0x03050000
     type->tp_as_async = &heap_type->as_async;
-#endif
 
     /* Flags */
     type->tp_flags |= Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HEAPTYPE;
-#if PY_MAJOR_VERSION < 3
-    type->tp_flags |= Py_TPFLAGS_CHECKTYPES;
-#endif
     if (!rec.is_final) {
         type->tp_flags |= Py_TPFLAGS_BASETYPE;
     }
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 8aefaa393b..a5d98d71f8 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -211,6 +211,9 @@
 #endif
 
 #include <Python.h>
+#if PY_VERSION_HEX < 0x030500f0
+#    error "PYTHON 2 IS NO LONGER SUPPORTED. pybind11 v2.9 was the last to support Python 2."
+#endif
 #include <frameobject.h>
 #include <pythread.h>
 
@@ -266,69 +269,37 @@
 // If UNDEFINED, pybind11::str can only hold PyUnicodeObject, and
 //               pybind11::isinstance<str>() is true only for pybind11::str.
 //               However, for Python 2 only (!), the pybind11::str caster
-//               implicitly decodes bytes to PyUnicodeObject. This is to ease
+//               implicitly decoded bytes to PyUnicodeObject. This was to ease
 //               the transition from the legacy behavior to the non-permissive
 //               behavior.
 
-#if PY_MAJOR_VERSION >= 3 /// Compatibility macros for various Python versions
-#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
-#    define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
-#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
-#    define PYBIND11_BYTES_CHECK PyBytes_Check
-#    define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
-#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
-#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
-#    define PYBIND11_BYTES_AS_STRING PyBytes_AsString
-#    define PYBIND11_BYTES_SIZE PyBytes_Size
-#    define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
-#    define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
-#    define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
-#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
-#    define PYBIND11_BYTES_NAME "bytes"
-#    define PYBIND11_STRING_NAME "str"
-#    define PYBIND11_SLICE_OBJECT PyObject
-#    define PYBIND11_FROM_STRING PyUnicode_FromString
-#    define PYBIND11_STR_TYPE ::pybind11::str
-#    define PYBIND11_BOOL_ATTR "__bool__"
-#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
-#    define PYBIND11_BUILTINS_MODULE "builtins"
+/// Compatibility macros for Python 2 / Python 3 versions TODO: remove
+#define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
+#define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
+#define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
+#define PYBIND11_BYTES_CHECK PyBytes_Check
+#define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
+#define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
+#define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
+#define PYBIND11_BYTES_AS_STRING PyBytes_AsString
+#define PYBIND11_BYTES_SIZE PyBytes_Size
+#define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
+#define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
+#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
+#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
+#define PYBIND11_BYTES_NAME "bytes"
+#define PYBIND11_STRING_NAME "str"
+#define PYBIND11_SLICE_OBJECT PyObject
+#define PYBIND11_FROM_STRING PyUnicode_FromString
+#define PYBIND11_STR_TYPE ::pybind11::str
+#define PYBIND11_BOOL_ATTR "__bool__"
+#define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
+#define PYBIND11_BUILTINS_MODULE "builtins"
 // Providing a separate declaration to make Clang's -Wmissing-prototypes happy.
 // See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
-        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();               \
-        extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
-
-#else
-#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
-#    define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
-#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
-#    define PYBIND11_BYTES_CHECK PyString_Check
-#    define PYBIND11_BYTES_FROM_STRING PyString_FromString
-#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
-#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
-#    define PYBIND11_BYTES_AS_STRING PyString_AsString
-#    define PYBIND11_BYTES_SIZE PyString_Size
-#    define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
-#    define PYBIND11_LONG_AS_LONGLONG(o)                                                          \
-        (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
-#    define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
-#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
-#    define PYBIND11_BYTES_NAME "str"
-#    define PYBIND11_STRING_NAME "unicode"
-#    define PYBIND11_SLICE_OBJECT PySliceObject
-#    define PYBIND11_FROM_STRING PyString_FromString
-#    define PYBIND11_STR_TYPE ::pybind11::bytes
-#    define PYBIND11_BOOL_ATTR "__nonzero__"
-#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
-#    define PYBIND11_BUILTINS_MODULE "__builtin__"
-// Providing a separate PyInit decl to make Clang's -Wmissing-prototypes happy.
-// See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
-        static PyObject *pybind11_init_wrapper();                                                 \
-        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT void init##name();                       \
-        extern "C" PYBIND11_EXPORT void init##name() { (void) pybind11_init_wrapper(); }          \
-        PyObject *pybind11_init_wrapper()
-#endif
+#define PYBIND11_PLUGIN_IMPL(name)                                                                \
+    extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();                   \
+    extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
 
 #if PY_VERSION_HEX >= 0x03050000 && PY_VERSION_HEX < 0x03050200
 extern "C" {
@@ -362,31 +333,15 @@ PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
         }                                                                                         \
     }
 
-#if PY_VERSION_HEX >= 0x03030000
-
-#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
-        catch (pybind11::error_already_set & e) {                                                 \
-            pybind11::raise_from(e, PyExc_ImportError, "initialization failed");                  \
-            return nullptr;                                                                       \
-        }                                                                                         \
-        catch (const std::exception &e) {                                                         \
-            PyErr_SetString(PyExc_ImportError, e.what());                                         \
-            return nullptr;                                                                       \
-        }
-
-#else
-
-#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
-        catch (pybind11::error_already_set & e) {                                                 \
-            PyErr_SetString(PyExc_ImportError, e.what());                                         \
-            return nullptr;                                                                       \
-        }                                                                                         \
-        catch (const std::exception &e) {                                                         \
-            PyErr_SetString(PyExc_ImportError, e.what());                                         \
-            return nullptr;                                                                       \
-        }
-
-#endif
+#define PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
+    catch (pybind11::error_already_set & e) {                                                     \
+        pybind11::raise_from(e, PyExc_ImportError, "initialization failed");                      \
+        return nullptr;                                                                           \
+    }                                                                                             \
+    catch (const std::exception &e) {                                                             \
+        PyErr_SetString(PyExc_ImportError, e.what());                                             \
+        return nullptr;                                                                           \
+    }
 
 /** \rst
     ***Deprecated in favor of PYBIND11_MODULE***
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 76b4faa8f2..3f83113bd7 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -82,7 +82,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 #    define PYBIND11_TLS_KEY_INIT(var) PYBIND11_TLS_KEY_REF var = 0;
 #    define PYBIND11_TLS_KEY_CREATE(var) (((var) = PyThread_create_key()) != -1)
 #    define PYBIND11_TLS_GET_VALUE(key) PyThread_get_key_value((key))
-#    if PY_MAJOR_VERSION < 3 || defined(PYPY_VERSION)
+#    if defined(PYPY_VERSION)
 // On CPython < 3.4 and on PyPy, `PyThread_set_key_value` strangely does not set
 // the value if it has already been set.  Instead, it must first be deleted and
 // then set again.
@@ -294,7 +294,6 @@ inline internals **&get_internals_pp() {
     return internals_pp;
 }
 
-#if PY_VERSION_HEX >= 0x03030000
 // forward decl
 inline void translate_exception(std::exception_ptr);
 
@@ -318,21 +317,11 @@ bool handle_nested_exception(const T &exc, const std::exception_ptr &p) {
     return false;
 }
 
-#else
-
-template <class T>
-bool handle_nested_exception(const T &, std::exception_ptr &) {
-    return false;
-}
-#endif
-
 inline bool raise_err(PyObject *exc_type, const char *msg) {
-#if PY_VERSION_HEX >= 0x03030000
     if (PyErr_Occurred()) {
         raise_from(exc_type, msg);
         return true;
     }
-#endif
     PyErr_SetString(exc_type, msg);
     return false;
 }
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 134e85b96a..226f7a994f 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -443,17 +443,10 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
         // they default to using pymalloc, which is designed to be efficient for small allocations
         // like the one we're doing here; in earlier versions (and for larger allocations) they are
         // just wrappers around malloc.
-#if PY_VERSION_HEX >= 0x03050000
         nonsimple.values_and_holders = (void **) PyMem_Calloc(space, sizeof(void *));
         if (!nonsimple.values_and_holders) {
             throw std::bad_alloc();
         }
-#else
-        nonsimple.values_and_holders = (void **) PyMem_New(void *, space);
-        if (!nonsimple.values_and_holders)
-            throw std::bad_alloc();
-        std::memset(nonsimple.values_and_holders, 0, space * sizeof(void *));
-#endif
         nonsimple.status
             = reinterpret_cast<std::uint8_t *>(&nonsimple.values_and_holders[flags_at]);
     }
@@ -494,11 +487,9 @@ PYBIND11_NOINLINE std::string error_string() {
 
     PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
 
-#if PY_MAJOR_VERSION >= 3
     if (scope.trace != nullptr) {
         PyException_SetTraceback(scope.value, scope.trace);
     }
-#endif
 
 #if !defined(PYPY_VERSION)
     if (scope.trace) {
@@ -547,10 +538,6 @@ PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_i
 inline PyThreadState *get_thread_state_unchecked() {
 #if defined(PYPY_VERSION)
     return PyThreadState_GET();
-#elif PY_VERSION_HEX < 0x03000000
-    return _PyThreadState_Current;
-#elif PY_VERSION_HEX < 0x03050000
-    return (PyThreadState *) _Py_atomic_load_relaxed(&_PyThreadState_Current);
 #elif PY_VERSION_HEX < 0x03050200
     return (PyThreadState *) _PyThreadState_Current.value;
 #else
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 84e4422212..8e998fc3c6 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -19,15 +19,9 @@
 #    error Embedding the interpreter is not supported with PyPy
 #endif
 
-#if PY_MAJOR_VERSION >= 3
-#    define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                   \
-        extern "C" PyObject *pybind11_init_impl_##name();                                         \
-        extern "C" PyObject *pybind11_init_impl_##name() { return pybind11_init_wrapper_##name(); }
-#else
-#    define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                   \
-        extern "C" void pybind11_init_impl_##name();                                              \
-        extern "C" void pybind11_init_impl_##name() { pybind11_init_wrapper_##name(); }
-#endif
+#define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                       \
+    extern "C" PyObject *pybind11_init_impl_##name();                                             \
+    extern "C" PyObject *pybind11_init_impl_##name() { return pybind11_init_wrapper_##name(); }
 
 /** \rst
     Add a new module to the table of builtins for the interpreter. Must be
@@ -67,11 +61,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
 struct embedded_module {
-#if PY_MAJOR_VERSION >= 3
     using init_t = PyObject *(*) ();
-#else
-    using init_t = void (*)();
-#endif
     embedded_module(const char *name, init_t init) {
         if (Py_IsInitialized() != 0) {
             pybind11_fail("Can't add new modules after the interpreter has been initialized");
@@ -86,42 +76,13 @@ struct embedded_module {
 
 struct wide_char_arg_deleter {
     void operator()(wchar_t *ptr) const {
-#if PY_VERSION_HEX >= 0x030500f0
         // API docs: https://docs.python.org/3/c-api/sys.html#c.Py_DecodeLocale
         PyMem_RawFree(ptr);
-#else
-        delete[] ptr;
-#endif
     }
 };
 
 inline wchar_t *widen_chars(const char *safe_arg) {
-#if PY_VERSION_HEX >= 0x030500f0
     wchar_t *widened_arg = Py_DecodeLocale(safe_arg, nullptr);
-#else
-    wchar_t *widened_arg = nullptr;
-
-// warning C4996: 'mbstowcs': This function or variable may be unsafe.
-#    if defined(_MSC_VER)
-#        pragma warning(push)
-#        pragma warning(disable : 4996)
-#    endif
-
-#    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
-    size_t count = std::strlen(safe_arg);
-#    else
-    size_t count = std::mbstowcs(nullptr, safe_arg, 0);
-#    endif
-    if (count != static_cast<size_t>(-1)) {
-        widened_arg = new wchar_t[count + 1];
-        std::mbstowcs(widened_arg, safe_arg, count + 1);
-    }
-
-#    if defined(_MSC_VER)
-#        pragma warning(pop)
-#    endif
-
-#endif
     return widened_arg;
 }
 
@@ -138,7 +99,6 @@ inline void set_interpreter_argv(int argc, const char *const *argv, bool add_pro
     }
 
     auto argv_size = static_cast<size_t>(argc);
-#if PY_MAJOR_VERSION >= 3
     // SetArgv* on python 3 takes wchar_t, so we have to convert.
     std::unique_ptr<wchar_t *[]> widened_argv(new wchar_t *[argv_size]);
     std::vector<std::unique_ptr<wchar_t[], wide_char_arg_deleter>> widened_argv_entries;
@@ -154,15 +114,6 @@ inline void set_interpreter_argv(int argc, const char *const *argv, bool add_pro
     }
 
     auto *pysys_argv = widened_argv.get();
-#else
-    // python 2.x
-    std::vector<std::string> strings{safe_argv, safe_argv + argv_size};
-    std::vector<char *> char_strings{argv_size};
-    for (std::size_t i = 0; i < argv_size; ++i)
-        char_strings[i] = &strings[i][0];
-    char **pysys_argv = char_strings.data();
-#endif
-
     PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
 }
 
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 731dedd4b1..c157a00957 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -20,10 +20,10 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline void ensure_builtins_in_globals(object &global) {
 #if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
-    // Running exec and eval on Python 2 and 3 adds `builtins` module under
-    // `__builtins__` key to globals if not yet present.
-    // Python 3.8 made PyRun_String behave similarly. Let's also do that for
-    // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
+    // Running exec and eval adds `builtins` module under `__builtins__` key to
+    // globals if not yet present.  Python 3.8 made PyRun_String behave
+    // similarly. Let's also do that for older versions, for consistency. This
+    // was missing from PyPy3.8 7.3.7.
     if (!global.contains("__builtins__"))
         global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
 #else
@@ -94,7 +94,7 @@ void exec(const char (&s)[N], object global = globals(), object local = object()
     eval<eval_statements>(s, global, local);
 }
 
-#if defined(PYPY_VERSION) && PY_VERSION_HEX >= 0x03000000
+#if defined(PYPY_VERSION)
 template <eval_mode mode = eval_statements>
 object eval_file(str, object, object) {
     pybind11_fail("eval_file not supported in PyPy3. Use eval");
@@ -133,40 +133,18 @@ object eval_file(str fname, object global = globals(), object local = object())
 
     int closeFile = 1;
     std::string fname_str = (std::string) fname;
-#    if PY_VERSION_HEX >= 0x03040000
     FILE *f = _Py_fopen_obj(fname.ptr(), "r");
-#    elif PY_VERSION_HEX >= 0x03000000
-    FILE *f = _Py_fopen(fname.ptr(), "r");
-#    else
-    /* No unicode support in open() :( */
-    auto fobj = reinterpret_steal<object>(
-        PyFile_FromString(const_cast<char *>(fname_str.c_str()), const_cast<char *>("r")));
-    FILE *f = nullptr;
-    if (fobj)
-        f = PyFile_AsFile(fobj.ptr());
-    closeFile = 0;
-#    endif
     if (!f) {
         PyErr_Clear();
         pybind11_fail("File \"" + fname_str + "\" could not be opened!");
     }
 
-    // In Python2, this should be encoded by getfilesystemencoding.
-    // We don't boher setting it since Python2 is past EOL anyway.
-    // See PR#3233
-#    if PY_VERSION_HEX >= 0x03000000
     if (!global.contains("__file__")) {
         global["__file__"] = std::move(fname);
     }
-#    endif
 
-#    if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
-    PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(), local.ptr());
-    (void) closeFile;
-#    else
     PyObject *result
         = PyRun_FileEx(f, fname_str.c_str(), start, global.ptr(), local.ptr(), closeFile);
-#    endif
 
     if (!result) {
         throw error_already_set();
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 9f4d516f5f..5e68f60530 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -263,11 +263,7 @@ struct npy_api {
     static npy_api lookup() {
         module_ m = module_::import("numpy.core.multiarray");
         auto c = m.attr("_ARRAY_API");
-#if PY_MAJOR_VERSION >= 3
         void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), NULL);
-#else
-        void **api_ptr = (void **) PyCObject_AsVoidPtr(c.ptr());
-#endif
         npy_api api;
 #define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
         DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
diff --git a/include/pybind11/operators.h b/include/pybind11/operators.h
index 7865d35e10..a0c3b78d65 100644
--- a/include/pybind11/operators.h
+++ b/include/pybind11/operators.h
@@ -91,16 +91,6 @@ struct op_ {
         using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute, is_operator(), extra...);
-#if PY_MAJOR_VERSION < 3
-        if (PYBIND11_SILENCE_MSVC_C4127(id == op_truediv)
-            || PYBIND11_SILENCE_MSVC_C4127(id == op_itruediv))
-            cl.def(id == op_itruediv ? "__idiv__"
-                   : ot == op_l      ? "__div__"
-                                     : "__rdiv__",
-                   &op::execute,
-                   is_operator(),
-                   extra...);
-#endif
     }
     template <typename Class, typename... Extra>
     void execute_cast(Class &cl, const Extra &...extra) const {
@@ -109,15 +99,6 @@ struct op_ {
         using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute_cast, is_operator(), extra...);
-#if PY_MAJOR_VERSION < 3
-        if (id == op_truediv || id == op_itruediv)
-            cl.def(id == op_itruediv ? "__idiv__"
-                   : ot == op_l      ? "__div__"
-                                     : "__rdiv__",
-                   &op::execute,
-                   is_operator(),
-                   extra...);
-#endif
     }
 };
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index b95f31a60e..7b7a1a05dd 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -431,9 +431,8 @@ class cpp_function : public function {
                 }
                 if (auto *tinfo = detail::get_type_info(*t)) {
                     handle th((PyObject *) tinfo->type);
-                    signature += th.attr("__module__").cast<std::string>() + "." +
-                                 // Python 3.3+, but we backport it to earlier versions
-                                 th.attr("__qualname__").cast<std::string>();
+                    signature += th.attr("__module__").cast<std::string>() + "."
+                                 + th.attr("__qualname__").cast<std::string>();
                 } else if (rec->is_new_style_constructor && arg_index == 0) {
                     // A new-style `__init__` takes `self` as `value_and_holder`.
                     // Rewrite it to the proper class type.
@@ -453,15 +452,6 @@ class cpp_function : public function {
             pybind11_fail("Internal error while parsing type signature (2)");
         }
 
-#if PY_MAJOR_VERSION < 3
-        if (std::strcmp(rec->name, "__next__") == 0) {
-            std::free(rec->name);
-            rec->name = guarded_strdup("next");
-        } else if (std::strcmp(rec->name, "__bool__") == 0) {
-            std::free(rec->name);
-            rec->name = guarded_strdup("__nonzero__");
-        }
-#endif
         rec->signature = guarded_strdup(signature.c_str());
         rec->args.shrink_to_fit();
         rec->nargs = (std::uint16_t) args;
@@ -1107,14 +1097,12 @@ class cpp_function : public function {
             }
 
             append_note_if_missing_header_is_suspected(msg);
-#if PY_VERSION_HEX >= 0x03030000
             // Attach additional error info to the exception if supported
             if (PyErr_Occurred()) {
                 // #HelpAppreciated: unit test coverage for this branch.
                 raise_from(PyExc_TypeError, msg.c_str());
                 return nullptr;
             }
-#endif
             PyErr_SetString(PyExc_TypeError, msg.c_str());
             return nullptr;
         }
@@ -1123,13 +1111,11 @@ class cpp_function : public function {
                               "Python type! The signature was\n\t";
             msg += it->signature;
             append_note_if_missing_header_is_suspected(msg);
-#if PY_VERSION_HEX >= 0x03030000
             // Attach additional error info to the exception if supported
             if (PyErr_Occurred()) {
                 raise_from(PyExc_TypeError, msg.c_str());
                 return nullptr;
             }
-#endif
             PyErr_SetString(PyExc_TypeError, msg.c_str());
             return nullptr;
         }
@@ -1149,11 +1135,7 @@ class module_ : public object {
     /// Create a new top-level Python module with the given name and docstring
     PYBIND11_DEPRECATED("Use PYBIND11_MODULE or module_::create_extension_module instead")
     explicit module_(const char *name, const char *doc = nullptr) {
-#if PY_MAJOR_VERSION >= 3
         *this = create_extension_module(name, doc, new PyModuleDef());
-#else
-        *this = create_extension_module(name, doc, nullptr);
-#endif
     }
 
     /** \rst
@@ -1231,20 +1213,14 @@ class module_ : public object {
         PyModule_AddObject(ptr(), name, obj.inc_ref().ptr() /* steals a reference */);
     }
 
-#if PY_MAJOR_VERSION >= 3
     using module_def = PyModuleDef;
-#else
-    struct module_def {};
-#endif
 
     /** \rst
         Create a new top-level module that can be used as the main module of a C extension.
 
-        For Python 3, ``def`` should point to a statically allocated module_def.
-        For Python 2, ``def`` can be a nullptr and is completely ignored.
+        ``def`` should point to a statically allocated module_def.
     \endrst */
     static module_ create_extension_module(const char *name, const char *doc, module_def *def) {
-#if PY_MAJOR_VERSION >= 3
         // module_def is PyModuleDef
         // Placement new (not an allocation).
         def = new (def)
@@ -1258,12 +1234,6 @@ class module_ : public object {
                         /* m_clear */ nullptr,
                         /* m_free */ nullptr};
         auto *m = PyModule_Create(def);
-#else
-        // Ignore module_def *def; only necessary for Python 3
-        (void) def;
-        auto m = Py_InitModule3(
-            name, nullptr, options::show_user_defined_docstrings() ? doc : nullptr);
-#endif
         if (m == nullptr) {
             if (PyErr_Occurred()) {
                 throw error_already_set();
@@ -1290,14 +1260,12 @@ inline dict globals() {
     return reinterpret_borrow<dict>(p ? p : module_::import("__main__").attr("__dict__").ptr());
 }
 
-#if PY_VERSION_HEX >= 0x03030000
 template <typename... Args, typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
 PYBIND11_DEPRECATED("make_simple_namespace should be replaced with "
                     "py::module_::import(\"types\").attr(\"SimpleNamespace\") ")
 object make_simple_namespace(Args &&...args_) {
     return module_::import("types").attr("SimpleNamespace")(std::forward<Args>(args_)...);
 }
-#endif
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 /// Generic support for creating new Python heap types
@@ -2173,9 +2141,6 @@ class enum_ : public class_<Type> {
         def_property_readonly("value", [](Type value) { return (Scalar) value; });
         def("__int__", [](Type value) { return (Scalar) value; });
         def("__index__", [](Type value) { return (Scalar) value; });
-#if PY_MAJOR_VERSION < 3
-        def("__long__", [](Type value) { return (Scalar) value; });
-#endif
         attr("__setstate__") = cpp_function(
             [](detail::value_and_holder &v_h, Scalar arg) {
                 detail::initimpl::setstate<Base>(
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 75ea7de88e..29f70bd5fd 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -434,8 +434,6 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
 #    pragma warning(pop)
 #endif
 
-#if PY_VERSION_HEX >= 0x03030000
-
 /// Replaces the current Python error indicator with the chosen error, performing a
 /// 'raise from' to indicate that the chosen error was caused by the original error.
 inline void raise_from(PyObject *type, const char *message) {
@@ -473,8 +471,6 @@ inline void raise_from(error_already_set &err, PyObject *type, const char *messa
     raise_from(type, message);
 }
 
-#endif
-
 /** \defgroup python_builtins const_name
     Unless stated otherwise, the following C++ functions behave the same
     as their Python counterparts.
@@ -591,12 +587,9 @@ inline ssize_t hash(handle obj) {
 PYBIND11_NAMESPACE_BEGIN(detail)
 inline handle get_function(handle value) {
     if (value) {
-#if PY_MAJOR_VERSION >= 3
         if (PyInstanceMethod_Check(value.ptr())) {
             value = PyInstanceMethod_GET_FUNCTION(value.ptr());
-        } else
-#endif
-            if (PyMethod_Check(value.ptr())) {
+        } else if (PyMethod_Check(value.ptr())) {
             value = PyMethod_GET_FUNCTION(value.ptr());
         }
     }
@@ -608,7 +601,6 @@ inline handle get_function(handle value) {
 
 // copied from cpython _PyDict_GetItemStringWithError
 inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
-#if PY_MAJOR_VERSION >= 3
     PyObject *kv = nullptr, *rv = nullptr;
     kv = PyUnicode_FromString(key);
     if (kv == NULL) {
@@ -621,21 +613,14 @@ inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
         throw error_already_set();
     }
     return rv;
-#else
-    return PyDict_GetItemString(v, key);
-#endif
 }
 
 inline PyObject *dict_getitem(PyObject *v, PyObject *key) {
-#if PY_MAJOR_VERSION >= 3
     PyObject *rv = PyDict_GetItemWithError(v, key);
     if (rv == NULL && PyErr_Occurred()) {
         throw error_already_set();
     }
     return rv;
-#else
-    return PyDict_GetItem(v, key);
-#endif
 }
 
 // Helper aliases/functions to support implicit casting of values given to python
@@ -1273,13 +1258,6 @@ class str : public object {
     /// Return string representation -- always returns a new reference, even if already a str
     static PyObject *raw_str(PyObject *op) {
         PyObject *str_value = PyObject_Str(op);
-#if PY_MAJOR_VERSION < 3
-        if (!str_value)
-            throw error_already_set();
-        PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
-        Py_XDECREF(str_value);
-        str_value = unicode;
-#endif
         return str_value;
     }
 };
@@ -1459,11 +1437,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
 template <typename Unsigned>
 Unsigned as_unsigned(PyObject *o) {
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(Unsigned) <= sizeof(unsigned long))
-#if PY_VERSION_HEX < 0x03000000
-        || PyInt_Check(o)
-#endif
-    ) {
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(Unsigned) <= sizeof(unsigned long))) {
         unsigned long v = PyLong_AsUnsignedLong(o);
         return v == (unsigned long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
     }
@@ -1922,7 +1896,6 @@ class memoryview : public object {
         return memoryview::from_buffer(const_cast<T *>(ptr), shape, strides, true);
     }
 
-#if PY_MAJOR_VERSION >= 3
     /** \rst
         Creates ``memoryview`` from static memory.
 
@@ -1930,8 +1903,6 @@ class memoryview : public object {
         managed by Python. The caller is responsible for managing the lifetime
         of ``mem``, which MUST outlive the memoryview constructed here.
 
-        This method is not available in Python 2.
-
         See also: Python C API documentation for `PyMemoryView_FromBuffer`_.
 
         .. _PyMemoryView_FromMemory:
@@ -1950,12 +1921,10 @@ class memoryview : public object {
         return memoryview::from_memory(const_cast<void *>(mem), size, true);
     }
 
-#    ifdef PYBIND11_HAS_STRING_VIEW
+#ifdef PYBIND11_HAS_STRING_VIEW
     static memoryview from_memory(std::string_view mem) {
         return from_memory(const_cast<char *>(mem.data()), static_cast<ssize_t>(mem.size()), true);
     }
-#    endif
-
 #endif
 };
 
@@ -2010,11 +1979,7 @@ inline size_t len(handle h) {
 /// Get the length hint of a Python object.
 /// Returns 0 when this cannot be determined.
 inline size_t len_hint(handle h) {
-#if PY_VERSION_HEX >= 0x03040000
     ssize_t result = PyObject_LengthHint(h.ptr(), 0);
-#else
-    ssize_t result = PyObject_Length(h.ptr());
-#endif
     if (result < 0) {
         // Sometimes a length can't be determined at all (eg generators)
         // In which case simply return 0
@@ -2029,13 +1994,6 @@ inline str repr(handle h) {
     if (!str_value) {
         throw error_already_set();
     }
-#if PY_MAJOR_VERSION < 3
-    PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
-    Py_XDECREF(str_value);
-    str_value = unicode;
-    if (!str_value)
-        throw error_already_set();
-#endif
     return reinterpret_steal<str>(str_value);
 }
 
diff --git a/noxfile.py b/noxfile.py
index 4adffac2ec..c8ab7441ed 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,7 +2,7 @@
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERISONS = ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+PYTHON_VERISONS = ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
 
 
 @nox.session(reuse_venv=True)
diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index 64e999ba06..faf3892cb6 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -1,4 +1,9 @@
-# -*- coding: utf-8 -*-
+import sys
+
+if sys.version_info < (3, 5):
+    msg = "pybind11 does not support Python < 3.5. 2.9 was the last release supporting older Pythons."
+    raise ImportError(msg)
+
 
 from ._version import __version__, version_info
 from .commands import get_cmake_dir, get_include
diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 3235747bed..645c760420 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -1,6 +1,3 @@
-# -*- coding: utf-8 -*-
-from __future__ import print_function
-
 import argparse
 import sys
 import sysconfig
@@ -8,8 +5,7 @@
 from .commands import get_cmake_dir, get_include
 
 
-def print_includes():
-    # type: () -> None
+def print_includes() -> None:
     dirs = [
         sysconfig.get_path("include"),
         sysconfig.get_path("platinclude"),
@@ -25,8 +21,7 @@ def print_includes():
     print(" ".join("-I" + d for d in unique_dirs))
 
 
-def main():
-    # type: () -> None
+def main() -> None:
 
     parser = argparse.ArgumentParser()
     parser.add_argument(
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 7519ac903b..aee3b1c5b2 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -1,7 +1,7 @@
-# -*- coding: utf-8 -*-
+from typing import Union
 
 
-def _to_int(s):
+def _to_int(s: str) -> Union[int, str]:
     try:
         return int(s)
     except ValueError:
diff --git a/pybind11/_version.pyi b/pybind11/_version.pyi
deleted file mode 100644
index d45e5dc907..0000000000
--- a/pybind11/_version.pyi
+++ /dev/null
@@ -1,6 +0,0 @@
-from typing import Tuple, Union
-
-def _to_int(s: str) -> Union[int, str]: ...
-
-__version__: str
-version_info: Tuple[Union[int, str], ...]
diff --git a/pybind11/commands.py b/pybind11/commands.py
index 11f81d2d6d..84d41478ad 100644
--- a/pybind11/commands.py
+++ b/pybind11/commands.py
@@ -1,18 +1,15 @@
-# -*- coding: utf-8 -*-
 import os
 
 DIR = os.path.abspath(os.path.dirname(__file__))
 
 
-def get_include(user=False):
-    # type: (bool) -> str
+def get_include(user: bool = False) -> str:
     installed_path = os.path.join(DIR, "include")
     source_path = os.path.join(os.path.dirname(DIR), "include")
     return installed_path if os.path.exists(installed_path) else source_path
 
 
-def get_cmake_dir():
-    # type: () -> str
+def get_cmake_dir() -> str:
     cmake_installed_path = os.path.join(DIR, "share", "cmake", "pybind11")
     if os.path.exists(cmake_installed_path):
         return cmake_installed_path
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 5b7c9aab1c..9cbcaa9224 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 """
 This module provides helpers for C++11+ projects using pybind11.
 
@@ -49,6 +47,20 @@
 import tempfile
 import threading
 import warnings
+from functools import lru_cache
+from pathlib import Path
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+    TypeVar,
+    Union,
+)
 
 try:
     from setuptools import Extension as _Extension
@@ -61,7 +73,6 @@
 import distutils.errors
 
 WIN = sys.platform.startswith("win32") and "mingw" not in sysconfig.get_platform()
-PY2 = sys.version_info[0] < 3
 MACOS = sys.platform.startswith("darwin")
 STD_TMPL = "/std:c++{}" if WIN else "-std=c++{}"
 
@@ -73,7 +84,7 @@
 # directory into your path if it sits beside your setup.py.
 
 
-class Pybind11Extension(_Extension):
+class Pybind11Extension(_Extension):  # type: ignore[misc]
     """
     Build a C++11+ Extension module with pybind11. This automatically adds the
     recommended flags when you init the extension and assumes C++ sources - you
@@ -95,21 +106,18 @@ class Pybind11Extension(_Extension):
 
     If you want to add pybind11 headers manually, for example for an exact
     git checkout, then set ``include_pybind11=False``.
-
-    Warning: do not use property-based access to the instance on Python 2 -
-    this is an ugly old-style class due to Distutils.
     """
 
     # flags are prepended, so that they can be further overridden, e.g. by
     # ``extra_compile_args=["-g"]``.
 
-    def _add_cflags(self, flags):
+    def _add_cflags(self, flags: List[str]) -> None:
         self.extra_compile_args[:0] = flags
 
-    def _add_ldflags(self, flags):
+    def _add_ldflags(self, flags: List[str]) -> None:
         self.extra_link_args[:0] = flags
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
 
         self._cxx_level = 0
         cxx_std = kwargs.pop("cxx_std", 0)
@@ -119,9 +127,7 @@ def __init__(self, *args, **kwargs):
 
         include_pybind11 = kwargs.pop("include_pybind11", True)
 
-        # Can't use super here because distutils has old-style classes in
-        # Python 2!
-        _Extension.__init__(self, *args, **kwargs)
+        super().__init__(*args, **kwargs)
 
         # Include the installed package pybind11 headers
         if include_pybind11:
@@ -133,11 +139,10 @@ def __init__(self, *args, **kwargs):
 
                 if pyinc not in self.include_dirs:
                     self.include_dirs.append(pyinc)
-            except ImportError:
+            except ModuleNotFoundError:
                 pass
 
-        # Have to use the accessor manually to support Python 2 distutils
-        Pybind11Extension.cxx_std.__set__(self, cxx_std)
+        self.cxx_std = cxx_std
 
         cflags = []
         ldflags = []
@@ -157,18 +162,18 @@ def __init__(self, *args, **kwargs):
         self._add_ldflags(ldflags)
 
     @property
-    def cxx_std(self):
+    def cxx_std(self) -> int:
         """
-        The CXX standard level. If set, will add the required flags. If left
-        at 0, it will trigger an automatic search when pybind11's build_ext
-        is used. If None, will have no effect.  Besides just the flags, this
-        may add a register warning/error fix for Python 2 or macos-min 10.9
-        or 10.14.
+        The CXX standard level. If set, will add the required flags. If left at
+        0, it will trigger an automatic search when pybind11's build_ext is
+        used. If None, will have no effect.  Besides just the flags, this may
+        add a macos-min 10.9 or 10.14 flag if MACOSX_DEPLOYMENT_TARGET is
+        unset.
         """
         return self._cxx_level
 
     @cxx_std.setter
-    def cxx_std(self, level):
+    def cxx_std(self, level: int) -> None:
 
         if self._cxx_level:
             warnings.warn("You cannot safely change the cxx_level after setting it!")
@@ -195,31 +200,20 @@ def cxx_std(self, level):
             current_macos = tuple(int(x) for x in platform.mac_ver()[0].split(".")[:2])
             desired_macos = (10, 9) if level < 17 else (10, 14)
             macos_string = ".".join(str(x) for x in min(current_macos, desired_macos))
-            macosx_min = "-mmacosx-version-min=" + macos_string
+            macosx_min = "-mmacosx-version-min={}".format(macos_string)
             cflags += [macosx_min]
             ldflags += [macosx_min]
 
-        if PY2:
-            if WIN:
-                # Will be ignored on MSVC 2015, where C++17 is not supported so
-                # this flag is not valid.
-                cflags += ["/wd5033"]
-            elif level >= 17:
-                cflags += ["-Wno-register"]
-            elif level >= 14:
-                cflags += ["-Wno-deprecated-register"]
-
         self._add_cflags(cflags)
         self._add_ldflags(ldflags)
 
 
 # Just in case someone clever tries to multithread
 tmp_chdir_lock = threading.Lock()
-cpp_cache_lock = threading.Lock()
 
 
 @contextlib.contextmanager
-def tmp_chdir():
+def tmp_chdir() -> Iterator[str]:
     "Prepare and enter a temporary directory, cleanup when done"
 
     # Threadsafe
@@ -235,7 +229,7 @@ def tmp_chdir():
 
 
 # cf http://bugs.python.org/issue26689
-def has_flag(compiler, flag):
+def has_flag(compiler: Any, flag: str) -> bool:
     """
     Return the flag if a flag name is supported on the
     specified compiler, otherwise None (can be used as a boolean).
@@ -243,13 +237,12 @@ def has_flag(compiler, flag):
     """
 
     with tmp_chdir():
-        fname = "flagcheck.cpp"
-        with open(fname, "w") as f:
-            # Don't trigger -Wunused-parameter.
-            f.write("int main (int, char **) { return 0; }")
+        fname = Path("flagcheck.cpp")
+        # Don't trigger -Wunused-parameter.
+        fname.write_text("int main (int, char **) { return 0; }")
 
         try:
-            compiler.compile([fname], extra_postargs=[flag])
+            compiler.compile([str(fname)], extra_postargs=[flag])
         except distutils.errors.CompileError:
             return False
         return True
@@ -259,7 +252,8 @@ def has_flag(compiler, flag):
 cpp_flag_cache = None
 
 
-def auto_cpp_level(compiler):
+@lru_cache()
+def auto_cpp_level(compiler: Any) -> Union[str, int]:
     """
     Return the max supported C++ std level (17, 14, or 11). Returns latest on Windows.
     """
@@ -267,48 +261,38 @@ def auto_cpp_level(compiler):
     if WIN:
         return "latest"
 
-    global cpp_flag_cache
-
-    # If this has been previously calculated with the same args, return that
-    with cpp_cache_lock:
-        if cpp_flag_cache:
-            return cpp_flag_cache
-
     levels = [17, 14, 11]
 
     for level in levels:
         if has_flag(compiler, STD_TMPL.format(level)):
-            with cpp_cache_lock:
-                cpp_flag_cache = level
             return level
 
     msg = "Unsupported compiler -- at least C++11 support is needed!"
     raise RuntimeError(msg)
 
 
-class build_ext(_build_ext):  # noqa: N801
+class build_ext(_build_ext):  # type: ignore[misc] # noqa: N801
     """
     Customized build_ext that allows an auto-search for the highest supported
     C++ level for Pybind11Extension. This is only needed for the auto-search
     for now, and is completely optional otherwise.
     """
 
-    def build_extensions(self):
+    def build_extensions(self) -> None:
         """
         Build extensions, injecting C++ std for Pybind11Extension if needed.
         """
 
         for ext in self.extensions:
             if hasattr(ext, "_cxx_level") and ext._cxx_level == 0:
-                # Python 2 syntax - old-style distutils class
-                ext.__class__.cxx_std.__set__(ext, auto_cpp_level(self.compiler))
+                ext.cxx_std = auto_cpp_level(self.compiler)
 
-        # Python 2 doesn't allow super here, since distutils uses old-style
-        # classes!
-        _build_ext.build_extensions(self)
+        super().build_extensions()
 
 
-def intree_extensions(paths, package_dir=None):
+def intree_extensions(
+    paths: Iterable[str], package_dir: Optional[Dict[str, str]] = None
+) -> List[Pybind11Extension]:
     """
     Generate Pybind11Extensions from source files directly located in a Python
     source tree.
@@ -318,6 +302,7 @@ def intree_extensions(paths, package_dir=None):
     not contain an ``__init__.py`` file.
     """
     exts = []
+
     for path in paths:
         if package_dir is None:
             parent, _ = os.path.split(path)
@@ -327,24 +312,25 @@ def intree_extensions(paths, package_dir=None):
             qualified_name = relname.replace(os.path.sep, ".")
             exts.append(Pybind11Extension(qualified_name, [path]))
         else:
-            found = False
             for prefix, parent in package_dir.items():
                 if path.startswith(parent):
-                    found = True
                     relname, _ = os.path.splitext(os.path.relpath(path, parent))
                     qualified_name = relname.replace(os.path.sep, ".")
                     if prefix:
                         qualified_name = prefix + "." + qualified_name
                     exts.append(Pybind11Extension(qualified_name, [path]))
-            if not found:
-                raise ValueError(
-                    "path {} is not a child of any of the directories listed "
-                    "in 'package_dir' ({})".format(path, package_dir)
-                )
+
+    if not exts:
+        msg = (
+            "path {path} is not a child of any of the directories listed "
+            "in 'package_dir' ({package_dir})"
+        ).format(path=path, package_dir=package_dir)
+        raise ValueError(msg)
+
     return exts
 
 
-def naive_recompile(obj, src):
+def naive_recompile(obj: str, src: str) -> bool:
     """
     This will recompile only if the source file changes. It does not check
     header files, so a more advanced function or Ccache is better if you have
@@ -353,7 +339,7 @@ def naive_recompile(obj, src):
     return os.stat(obj).st_mtime < os.stat(src).st_mtime
 
 
-def no_recompile(obg, src):
+def no_recompile(obg: str, src: str) -> bool:
     """
     This is the safest but slowest choice (and is the default) - will always
     recompile sources.
@@ -361,15 +347,33 @@ def no_recompile(obg, src):
     return True
 
 
+S = TypeVar("S", bound="ParallelCompile")
+
+CCompilerMethod = Callable[
+    [
+        distutils.ccompiler.CCompiler,
+        List[str],
+        Optional[str],
+        Optional[Union[Tuple[str], Tuple[str, Optional[str]]]],
+        Optional[List[str]],
+        bool,
+        Optional[List[str]],
+        Optional[List[str]],
+        Optional[List[str]],
+    ],
+    List[str],
+]
+
+
 # Optional parallel compile utility
 # inspired by: http://stackoverflow.com/questions/11013851/speeding-up-build-process-with-distutils
 # and: https://github.com/tbenthompson/cppimport/blob/stable/cppimport/build_module.py
 # and NumPy's parallel distutils module:
 #              https://github.com/numpy/numpy/blob/master/numpy/distutils/ccompiler.py
-class ParallelCompile(object):
+class ParallelCompile:
     """
     Make a parallel compile function. Inspired by
-    numpy.distutils.ccompiler.CCompiler_compile and cppimport.
+    numpy.distutils.ccompiler.CCompiler.compile and cppimport.
 
     This takes several arguments that allow you to customize the compile
     function created:
@@ -404,35 +408,41 @@ class ParallelCompile(object):
 
     __slots__ = ("envvar", "default", "max", "_old", "needs_recompile")
 
-    def __init__(self, envvar=None, default=0, max=0, needs_recompile=no_recompile):
+    def __init__(
+        self,
+        envvar: Optional[str] = None,
+        default: int = 0,
+        max: int = 0,
+        needs_recompile: Callable[[str, str], bool] = no_recompile,
+    ) -> None:
         self.envvar = envvar
         self.default = default
         self.max = max
         self.needs_recompile = needs_recompile
-        self._old = []
+        self._old = []  # type: List[CCompilerMethod]
 
-    def function(self):
+    def function(self) -> CCompilerMethod:
         """
         Builds a function object usable as distutils.ccompiler.CCompiler.compile.
         """
 
         def compile_function(
-            compiler,
-            sources,
-            output_dir=None,
-            macros=None,
-            include_dirs=None,
-            debug=0,
-            extra_preargs=None,
-            extra_postargs=None,
-            depends=None,
-        ):
+            compiler: distutils.ccompiler.CCompiler,
+            sources: List[str],
+            output_dir: Optional[str] = None,
+            macros: Optional[Union[Tuple[str], Tuple[str, Optional[str]]]] = None,
+            include_dirs: Optional[List[str]] = None,
+            debug: bool = False,
+            extra_preargs: Optional[List[str]] = None,
+            extra_postargs: Optional[List[str]] = None,
+            depends: Optional[List[str]] = None,
+        ) -> Any:
 
             # These lines are directly from distutils.ccompiler.CCompiler
-            macros, objects, extra_postargs, pp_opts, build = compiler._setup_compile(
+            macros, objects, extra_postargs, pp_opts, build = compiler._setup_compile(  # type: ignore[attr-defined]
                 output_dir, macros, include_dirs, sources, depends, extra_postargs
             )
-            cc_args = compiler._get_cc_args(pp_opts, debug, extra_preargs)
+            cc_args = compiler._get_cc_args(pp_opts, debug, extra_preargs)  # type: ignore[attr-defined]
 
             # The number of threads; start with default.
             threads = self.default
@@ -441,14 +451,14 @@ def compile_function(
             if self.envvar is not None:
                 threads = int(os.environ.get(self.envvar, self.default))
 
-            def _single_compile(obj):
+            def _single_compile(obj: Any) -> None:
                 try:
                     src, ext = build[obj]
                 except KeyError:
                     return
 
                 if not os.path.exists(obj) or self.needs_recompile(obj, src):
-                    compiler._compile(obj, src, ext, cc_args, extra_postargs, pp_opts)
+                    compiler._compile(obj, src, ext, cc_args, extra_postargs, pp_opts)  # type: ignore[attr-defined]
 
             try:
                 # Importing .synchronize checks for platforms that have some multiprocessing
@@ -466,14 +476,9 @@ def _single_compile(obj):
                     threads = 1
 
             if threads > 1:
-                pool = ThreadPool(threads)
-                # In Python 2, ThreadPool can't be used as a context manager.
-                # Once we are no longer supporting it, this can be 'with pool:'
-                try:
+                with ThreadPool(threads) as pool:
                     for _ in pool.imap_unordered(_single_compile, objects):
                         pass
-                finally:
-                    pool.terminate()
             else:
                 for ob in objects:
                     _single_compile(ob)
@@ -482,13 +487,13 @@ def _single_compile(obj):
 
         return compile_function
 
-    def install(self):
-        distutils.ccompiler.CCompiler.compile = self.function()
+    def install(self: S) -> S:
+        distutils.ccompiler.CCompiler.compile = self.function()  # type: ignore[assignment]
         return self
 
-    def __enter__(self):
+    def __enter__(self: S) -> S:
         self._old.append(distutils.ccompiler.CCompiler.compile)
         return self.install()
 
-    def __exit__(self, *args):
-        distutils.ccompiler.CCompiler.compile = self._old.pop()
+    def __exit__(self, *args: Any) -> None:
+        distutils.ccompiler.CCompiler.compile = self._old.pop()  # type: ignore[assignment]
diff --git a/pybind11/setup_helpers.pyi b/pybind11/setup_helpers.pyi
deleted file mode 100644
index 074744eb82..0000000000
--- a/pybind11/setup_helpers.pyi
+++ /dev/null
@@ -1,63 +0,0 @@
-# IMPORTANT: Should stay in sync with setup_helpers.py (mostly checked by CI /
-# pre-commit).
-
-import contextlib
-import distutils.ccompiler
-from distutils.command.build_ext import build_ext as _build_ext  # type: ignore
-from distutils.extension import Extension as _Extension
-from types import TracebackType
-from typing import Any, Callable, Dict, Iterator, List, Optional, Type, TypeVar, Union
-
-WIN: bool
-PY2: bool
-MACOS: bool
-STD_TMPL: str
-
-class Pybind11Extension(_Extension):
-    def _add_cflags(self, *flags: str) -> None: ...
-    def _add_lflags(self, *flags: str) -> None: ...
-    def __init__(
-        self, *args: Any, cxx_std: int = 0, language: str = "c++", **kwargs: Any
-    ) -> None: ...
-    @property
-    def cxx_std(self) -> int: ...
-    @cxx_std.setter
-    def cxx_std(self, level: int) -> None: ...
-
-@contextlib.contextmanager
-def tmp_chdir() -> Iterator[str]: ...
-def has_flag(compiler: distutils.ccompiler.CCompiler, flag: str) -> bool: ...
-def auto_cpp_level(compiler: distutils.ccompiler.CCompiler) -> Union[int, str]: ...
-
-class build_ext(_build_ext):  # type: ignore
-    def build_extensions(self) -> None: ...
-
-def intree_extensions(
-    paths: Iterator[str], package_dir: Optional[Dict[str, str]] = None
-) -> List[Pybind11Extension]: ...
-def no_recompile(obj: str, src: str) -> bool: ...
-def naive_recompile(obj: str, src: str) -> bool: ...
-
-T = TypeVar("T", bound="ParallelCompile")
-
-class ParallelCompile:
-    envvar: Optional[str]
-    default: int
-    max: int
-    needs_recompile: Callable[[str, str], bool]
-    def __init__(
-        self,
-        envvar: Optional[str] = None,
-        default: int = 0,
-        max: int = 0,
-        needs_recompile: Callable[[str, str], bool] = no_recompile,
-    ) -> None: ...
-    def function(self) -> Any: ...
-    def install(self: T) -> T: ...
-    def __enter__(self: T) -> T: ...
-    def __exit__(
-        self,
-        exc_type: Optional[Type[BaseException]],
-        exc_value: Optional[BaseException],
-        traceback: Optional[TracebackType],
-    ) -> None: ...
diff --git a/pyproject.toml b/pyproject.toml
index 7d7a1c8213..5371c1b33d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -22,20 +22,11 @@ known_first_party = "env,pybind11_cross_module_tests,pybind11_tests,"
 profile = "black"
 
 [tool.mypy]
-files = "pybind11"
-python_version = "2.7"
+files = ["pybind11"]
+python_version = "3.6"
 warn_unused_configs = true
+strict = true
 
-disallow_any_generics = true
-disallow_subclassing_any = true
-disallow_untyped_calls = true
-disallow_untyped_defs = true
-disallow_incomplete_defs = true
-check_untyped_defs = true
-disallow_untyped_decorators = true
-no_implicit_optional = true
-warn_redundant_casts = true
-warn_unused_ignores = true
-warn_return_any = true
-no_implicit_reexport = true
-strict_equality = true
+[[tool.mypy.overrides]]
+module = ["ghapi.*", "setuptools.*"]
+ignore_missing_imports = true
diff --git a/setup.cfg b/setup.cfg
index 317c44bbf6..bd2357e9e8 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -13,8 +13,7 @@ classifiers =
     Topic :: Software Development :: Libraries :: Python Modules
     Topic :: Utilities
     Programming Language :: C++
-    Programming Language :: Python :: 2.7
-    Programming Language :: Python :: 3
+    Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
@@ -39,15 +38,12 @@ project_urls =
     Chat = https://gitter.im/pybind/Lobby
 
 [options]
-python_requires = >=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*
+python_requires = >=3.5
 zip_safe = False
 
-[bdist_wheel]
-universal=1
-
 
 [flake8]
-max-line-length = 99
+max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
 ignore =
diff --git a/setup.py b/setup.py
index f838379190..5b46e0c8d8 100644
--- a/setup.py
+++ b/setup.py
@@ -1,56 +1,52 @@
 #!/usr/bin/env python
-# -*- coding: utf-8 -*-
 
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
 
 import contextlib
-import io
 import os
 import re
 import shutil
 import string
 import subprocess
 import sys
-import tempfile
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from typing import Dict, Iterator, List, Union
 
 import setuptools.command.sdist
 
-DIR = os.path.abspath(os.path.dirname(__file__))
+DIR = Path(__file__).parent.absolute()
 VERSION_REGEX = re.compile(
     r"^\s*#\s*define\s+PYBIND11_VERSION_([A-Z]+)\s+(.*)$", re.MULTILINE
 )
+VERSION_FILE = Path("pybind11/_version.py")
+COMMON_FILE = Path("include/pybind11/detail/common.h")
 
 
-def build_expected_version_hex(matches):
+def build_expected_version_hex(matches: Dict[str, str]) -> str:
     patch_level_serial = matches["PATCH"]
     serial = None
-    try:
-        major = int(matches["MAJOR"])
-        minor = int(matches["MINOR"])
-        flds = patch_level_serial.split(".")
-        if flds:
-            patch = int(flds[0])
-            level = None
-            if len(flds) == 1:
-                level = "0"
-                serial = 0
-            elif len(flds) == 2:
-                level_serial = flds[1]
-                for level in ("a", "b", "c", "dev"):
-                    if level_serial.startswith(level):
-                        serial = int(level_serial[len(level) :])
-                        break
-    except ValueError:
-        pass
+    major = int(matches["MAJOR"])
+    minor = int(matches["MINOR"])
+    flds = patch_level_serial.split(".")
+    if flds:
+        patch = int(flds[0])
+        if len(flds) == 1:
+            level = "0"
+            serial = 0
+        elif len(flds) == 2:
+            level_serial = flds[1]
+            for level in ("a", "b", "c", "dev"):
+                if level_serial.startswith(level):
+                    serial = int(level_serial[len(level) :])
+                    break
     if serial is None:
         msg = 'Invalid PYBIND11_VERSION_PATCH: "{}"'.format(patch_level_serial)
         raise RuntimeError(msg)
-    return (
-        "0x"
-        + "{:02x}{:02x}{:02x}{}{:x}".format(
-            major, minor, patch, level[:1], serial
-        ).upper()
+    version_hex_str = "{:02x}{:02x}{:02x}{}{:x}".format(
+        major, minor, patch, level[:1], serial
     )
+    return "0x{}".format(version_hex_str.upper())
 
 
 # PYBIND11_GLOBAL_SDIST will build a different sdist, with the python-headers
@@ -58,24 +54,25 @@ def build_expected_version_hex(matches):
 
 global_sdist = os.environ.get("PYBIND11_GLOBAL_SDIST", False)
 
-setup_py = "tools/setup_global.py.in" if global_sdist else "tools/setup_main.py.in"
+setup_py = Path(
+    "tools/setup_global.py.in" if global_sdist else "tools/setup_main.py.in"
+)
 extra_cmd = 'cmdclass["sdist"] = SDist\n'
 
 to_src = (
-    ("pyproject.toml", "tools/pyproject.toml"),
-    ("setup.py", setup_py),
+    (Path("pyproject.toml"), Path("tools/pyproject.toml")),
+    (Path("setup.py"), setup_py),
 )
 
+
 # Read the listed version
-with open("pybind11/_version.py") as f:
-    code = compile(f.read(), "pybind11/_version.py", "exec")
-loc = {}
+loc = {}  # type: Dict[str, str]
+code = compile(VERSION_FILE.read_text(encoding="utf-8"), "pybind11/_version.py", "exec")
 exec(code, loc)
 version = loc["__version__"]
 
 # Verify that the version matches the one in C++
-with io.open("include/pybind11/detail/common.h", encoding="utf8") as f:
-    matches = dict(VERSION_REGEX.findall(f.read()))
+matches = dict(VERSION_REGEX.findall(COMMON_FILE.read_text(encoding="utf8")))
 cpp_version = "{MAJOR}.{MINOR}.{PATCH}".format(**matches)
 if version != cpp_version:
     msg = "Python version {} does not match C++ version {}!".format(
@@ -84,56 +81,44 @@ def build_expected_version_hex(matches):
     raise RuntimeError(msg)
 
 version_hex = matches.get("HEX", "MISSING")
-expected_version_hex = build_expected_version_hex(matches)
-if version_hex != expected_version_hex:
+exp_version_hex = build_expected_version_hex(matches)
+if version_hex != exp_version_hex:
     msg = "PYBIND11_VERSION_HEX {} does not match expected value {}!".format(
-        version_hex,
-        expected_version_hex,
+        version_hex, exp_version_hex
     )
     raise RuntimeError(msg)
 
 
-def get_and_replace(filename, binary=False, **opts):
-    with open(filename, "rb" if binary else "r") as f:
-        contents = f.read()
-    # Replacement has to be done on text in Python 3 (both work in Python 2)
+# TODO: use literals & overload (typing extensions or Python 3.8)
+def get_and_replace(
+    filename: Path, binary: bool = False, **opts: str
+) -> Union[bytes, str]:
     if binary:
+        contents = filename.read_bytes()
         return string.Template(contents.decode()).substitute(opts).encode()
-    else:
-        return string.Template(contents).substitute(opts)
+
+    return string.Template(filename.read_text()).substitute(opts)
 
 
 # Use our input files instead when making the SDist (and anything that depends
 # on it, like a wheel)
-class SDist(setuptools.command.sdist.sdist):
-    def make_release_tree(self, base_dir, files):
-        setuptools.command.sdist.sdist.make_release_tree(self, base_dir, files)
+class SDist(setuptools.command.sdist.sdist):  # type: ignore[misc]
+    def make_release_tree(self, base_dir: str, files: List[str]) -> None:
+        super().make_release_tree(base_dir, files)
 
         for to, src in to_src:
             txt = get_and_replace(src, binary=True, version=version, extra_cmd="")
 
-            dest = os.path.join(base_dir, to)
+            dest = Path(base_dir) / to
 
             # This is normally linked, so unlink before writing!
-            os.unlink(dest)
-            with open(dest, "wb") as f:
-                f.write(txt)
-
-
-# Backport from Python 3
-@contextlib.contextmanager
-def TemporaryDirectory():  # noqa: N802
-    "Prepare a temporary directory, cleanup when done"
-    try:
-        tmpdir = tempfile.mkdtemp()
-        yield tmpdir
-    finally:
-        shutil.rmtree(tmpdir)
+            dest.unlink()
+            dest.write_bytes(txt)  # type: ignore[arg-type]
 
 
 # Remove the CMake install directory when done
 @contextlib.contextmanager
-def remove_output(*sources):
+def remove_output(*sources: str) -> Iterator[None]:
     try:
         yield
     finally:
@@ -156,9 +141,14 @@ def remove_output(*sources):
                 if "DCMAKE_INSTALL_PREFIX" not in c
             ]
             cmd += fcommand
-        cmake_opts = dict(cwd=DIR, stdout=sys.stdout, stderr=sys.stderr)
-        subprocess.check_call(cmd, **cmake_opts)
-        subprocess.check_call(["cmake", "--install", tmpdir], **cmake_opts)
+        subprocess.run(cmd, check=True, cwd=DIR, stdout=sys.stdout, stderr=sys.stderr)
+        subprocess.run(
+            ["cmake", "--install", tmpdir],
+            check=True,
+            cwd=DIR,
+            stdout=sys.stdout,
+            stderr=sys.stderr,
+        )
 
     txt = get_and_replace(setup_py, version=version, extra_cmd=extra_cmd)
     code = compile(txt, setup_py, "exec")
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9040cf8c06..bce8cceb1e 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -179,11 +179,6 @@ if(PYBIND11_TEST_FILTER)
   pybind11_filter_tests(PYBIND11_TEST_FILES ${PYBIND11_TEST_FILTER})
 endif()
 
-if(PYTHON_VERSION VERSION_LESS 3.5)
-  pybind11_filter_tests(PYBIND11_TEST_FILES test_async.cpp MESSAGE
-                        "Skipping test_async on Python 2")
-endif()
-
 # Skip tests for CUDA check:
 # /pybind11/tests/test_constants_and_functions.cpp(125):
 #   error: incompatible exception specifications
@@ -388,17 +383,6 @@ function(pybind11_enable_warnings target_name)
           -diag-disable 11074,11076)
     endif()
   endif()
-
-  # Needs to be re-added since the ordering requires these to be after the ones above
-  if(CMAKE_CXX_STANDARD
-     AND CMAKE_CXX_COMPILER_ID MATCHES "Clang"
-     AND PYTHON_VERSION VERSION_LESS 3.0)
-    if(CMAKE_CXX_STANDARD LESS 17)
-      target_compile_options(${target_name} PUBLIC -Wno-deprecated-register)
-    else()
-      target_compile_options(${target_name} PUBLIC -Wno-register)
-    endif()
-  endif()
 endfunction()
 
 set(test_targets pybind11_tests)
diff --git a/tests/conftest.py b/tests/conftest.py
index 362eb80691..e72ec0ef81 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,8 +1,7 @@
-# -*- coding: utf-8 -*-
 """pytest configuration
 
 Extends output capture as needed by pybind11: ignore constructors, optional unordered lines.
-Adds docstring and exceptions message sanitizers: ignore Python 2 vs 3 differences.
+Adds docstring and exceptions message sanitizers.
 """
 
 import contextlib
@@ -13,19 +12,14 @@
 
 import pytest
 
-import env
-
 # Early diagnostic for failed imports
 import pybind11_tests  # noqa: F401
 
-_unicode_marker = re.compile(r"u(\'[^\']*\')")
 _long_marker = re.compile(r"([0-9])L")
 _hexadecimal = re.compile(r"0x[0-9a-fA-F]+")
 
 # Avoid collecting Python3 only files
 collect_ignore = []
-if env.PY2:
-    collect_ignore.append("test_async.py")
 
 
 def _strip_and_dedent(s):
@@ -45,7 +39,7 @@ def _make_explanation(a, b):
     ]
 
 
-class Output(object):
+class Output:
     """Basic output post-processing and comparison"""
 
     def __init__(self, string):
@@ -83,7 +77,7 @@ def __eq__(self, other):
             return False
 
 
-class Capture(object):
+class Capture:
     def __init__(self, capfd):
         self.capfd = capfd
         self.out = ""
@@ -126,7 +120,7 @@ def capture(capsys):
     return Capture(capsys)
 
 
-class SanitizedString(object):
+class SanitizedString:
     def __init__(self, sanitizer):
         self.sanitizer = sanitizer
         self.string = ""
@@ -149,9 +143,7 @@ def __eq__(self, other):
 def _sanitize_general(s):
     s = s.strip()
     s = s.replace("pybind11_tests.", "m.")
-    s = s.replace("unicode", "str")
     s = _long_marker.sub(r"\1", s)
-    s = _unicode_marker.sub(r"\1", s)
     return s
 
 
diff --git a/tests/cross_module_gil_utils.cpp b/tests/cross_module_gil_utils.cpp
index f3aca1561a..2e64da052c 100644
--- a/tests/cross_module_gil_utils.cpp
+++ b/tests/cross_module_gil_utils.cpp
@@ -25,31 +25,14 @@ void gil_acquire() { py::gil_scoped_acquire gil; }
 
 constexpr char kModuleName[] = "cross_module_gil_utils";
 
-#if PY_MAJOR_VERSION >= 3
 struct PyModuleDef moduledef
     = {PyModuleDef_HEAD_INIT, kModuleName, NULL, 0, NULL, NULL, NULL, NULL, NULL};
-#else
-PyMethodDef module_methods[] = {{NULL, NULL, 0, NULL}};
-#endif
 
 } // namespace
 
-extern "C" PYBIND11_EXPORT
-#if PY_MAJOR_VERSION >= 3
-    PyObject *
-    PyInit_cross_module_gil_utils()
-#else
-    void
-    initcross_module_gil_utils()
-#endif
-{
+extern "C" PYBIND11_EXPORT PyObject *PyInit_cross_module_gil_utils() {
 
-    PyObject *m =
-#if PY_MAJOR_VERSION >= 3
-        PyModule_Create(&moduledef);
-#else
-        Py_InitModule(kModuleName, module_methods);
-#endif
+    PyObject *m = PyModule_Create(&moduledef);
 
     if (m != NULL) {
         static_assert(sizeof(&gil_acquire) == sizeof(void *),
@@ -58,7 +41,5 @@ extern "C" PYBIND11_EXPORT
             m, "gil_acquire_funcaddr", PyLong_FromVoidPtr(reinterpret_cast<void *>(&gil_acquire)));
     }
 
-#if PY_MAJOR_VERSION >= 3
     return m;
-#endif
 }
diff --git a/tests/env.py b/tests/env.py
index 6172b451b3..0345df65dc 100644
--- a/tests/env.py
+++ b/tests/env.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import platform
 import sys
 
@@ -11,10 +10,6 @@
 CPYTHON = platform.python_implementation() == "CPython"
 PYPY = platform.python_implementation() == "PyPy"
 
-PY2 = sys.version_info.major == 2
-
-PY = sys.version_info
-
 
 def deprecated_call():
     """
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 337a72dfea..70dcfb987a 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import contextlib
 import os
 import string
@@ -64,11 +63,9 @@
     "__init__.py",
     "__main__.py",
     "_version.py",
-    "_version.pyi",
     "commands.py",
     "py.typed",
     "setup_helpers.py",
-    "setup_helpers.pyi",
 }
 
 headers = main_headers | detail_headers | stl_headers
diff --git a/tests/extra_setuptools/test_setuphelper.py b/tests/extra_setuptools/test_setuphelper.py
index 788f368b14..3a771e558d 100644
--- a/tests/extra_setuptools/test_setuphelper.py
+++ b/tests/extra_setuptools/test_setuphelper.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import os
 import subprocess
 import sys
@@ -19,7 +18,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
 
     (tmpdir / "setup.py").write_text(
         dedent(
-            u"""\
+            """\
             import sys
             sys.path.append({MAIN_DIR!r})
 
@@ -58,7 +57,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
 
     (tmpdir / "main.cpp").write_text(
         dedent(
-            u"""\
+            """\
             #include <pybind11/pybind11.h>
 
             int f(int x) {
@@ -96,7 +95,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
 
     (tmpdir / "test.py").write_text(
         dedent(
-            u"""\
+            """\
             import simple_setup
             assert simple_setup.f(3) == 9
             """
@@ -121,10 +120,11 @@ def test_intree_extensions(monkeypatch, tmpdir):
     subdir.ensure_dir()
     src = subdir / "ext.cpp"
     src.ensure()
-    (ext,) = intree_extensions([src.relto(tmpdir)])
+    relpath = src.relto(tmpdir)
+    (ext,) = intree_extensions([relpath])
     assert ext.name == "ext"
     subdir.ensure("__init__.py")
-    (ext,) = intree_extensions([src.relto(tmpdir)])
+    (ext,) = intree_extensions([relpath])
     assert ext.name == "dir.ext"
 
 
diff --git a/tests/test_async.py b/tests/test_async.py
index df4489c499..b9ff9514d2 100644
--- a/tests/test_async.py
+++ b/tests/test_async.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 asyncio = pytest.importorskip("asyncio")
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index 0d5bf16c3d..8354b68cda 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import ctypes
 import io
 import struct
@@ -93,16 +92,16 @@ def test_pointer_to_member_fn():
 def test_readonly_buffer():
     buf = m.BufferReadOnly(0x64)
     view = memoryview(buf)
-    assert view[0] == b"d" if env.PY2 else 0x64
+    assert view[0] == 0x64
     assert view.readonly
     with pytest.raises(TypeError):
-        view[0] = b"\0" if env.PY2 else 0
+        view[0] = 0
 
 
 def test_selective_readonly_buffer():
     buf = m.BufferReadOnlySelect()
 
-    memoryview(buf)[0] = b"d" if env.PY2 else 0x64
+    memoryview(buf)[0] = 0x64
     assert buf.value == 0x64
 
     io.BytesIO(b"A").readinto(buf)
@@ -110,7 +109,7 @@ def test_selective_readonly_buffer():
 
     buf.readonly = True
     with pytest.raises(TypeError):
-        memoryview(buf)[0] = b"\0" if env.PY2 else 0
+        memoryview(buf)[0] = 0
     with pytest.raises(TypeError):
         io.BytesIO(b"1").readinto(buf)
 
@@ -145,9 +144,6 @@ def test_ctypes_array_2d():
         assert not info.readonly
 
 
-@pytest.mark.skipif(
-    "env.PYPY and env.PY2", reason="PyPy2 bytes buffer not reported as readonly"
-)
 def test_ctypes_from_buffer():
     test_pystr = b"0123456789"
     for pyarray in (test_pystr, bytearray(test_pystr)):
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 320ddd8aa2..7b67515e5e 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -110,8 +110,7 @@ TEST_SUBMODULE(builtin_casters, m) {
                            "def");
     });
     m.def("bad_utf16_string", [=]() { return std::u16string({b16, char16_t(0xd800), z16}); });
-#if PY_MAJOR_VERSION >= 3
-    // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger
+    // Under Python 2.7, invalid unicode UTF-32 characters didn't appear to trigger
     // UnicodeDecodeError
     m.def("bad_utf32_string", [=]() { return std::u32string({a32, char32_t(0xd800), z32}); });
     if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
@@ -119,7 +118,6 @@ TEST_SUBMODULE(builtin_casters, m) {
             return std::wstring({wchar_t(0x61), wchar_t(0xd800)});
         });
     }
-#endif
     m.def("u8_Z", []() -> char { return 'Z'; });
     m.def("u8_eacute", []() -> char { return '\xe9'; });
     m.def("u16_ibang", [=]() -> char16_t { return ib16; });
@@ -198,12 +196,10 @@ TEST_SUBMODULE(builtin_casters, m) {
           []() { return [](py::str s) { return s; }("abc \342\200\275 def"sv); });
     m.def("string_view_from_bytes",
           [](const py::bytes &b) { return [](std::string_view s) { return s; }(b); });
-#    if PY_MAJOR_VERSION >= 3
     m.def("string_view_memoryview", []() {
         static constexpr auto val = "Have some \360\237\216\202"sv;
         return py::memoryview::from_memory(val);
     });
-#    endif
 
 #    ifdef PYBIND11_HAS_U8STRING
     m.def("string_view8_print", [](std::u8string_view s) { py::print(s, s.size()); });
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index b1f1e395a7..74014c9cf4 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -1,4 +1,5 @@
-# -*- coding: utf-8 -*-
+import sys
+
 import pytest
 
 import env
@@ -12,12 +13,12 @@ def test_simple_string():
 
 def test_unicode_conversion():
     """Tests unicode conversion and error reporting."""
-    assert m.good_utf8_string() == u"Say utf8‽ 🎂 𝐀"
-    assert m.good_utf16_string() == u"b‽🎂𝐀z"
-    assert m.good_utf32_string() == u"a𝐀🎂‽z"
-    assert m.good_wchar_string() == u"a⸘𝐀z"
+    assert m.good_utf8_string() == "Say utf8‽ 🎂 𝐀"
+    assert m.good_utf16_string() == "b‽🎂𝐀z"
+    assert m.good_utf32_string() == "a𝐀🎂‽z"
+    assert m.good_wchar_string() == "a⸘𝐀z"
     if hasattr(m, "has_u8string"):
-        assert m.good_utf8_u8string() == u"Say utf8‽ 🎂 𝐀"
+        assert m.good_utf8_u8string() == "Say utf8‽ 🎂 𝐀"
 
     with pytest.raises(UnicodeDecodeError):
         m.bad_utf8_string()
@@ -25,7 +26,7 @@ def test_unicode_conversion():
     with pytest.raises(UnicodeDecodeError):
         m.bad_utf16_string()
 
-    # These are provided only if they actually fail (they don't when 32-bit and under Python 2.7)
+    # These are provided only if they actually fail (they don't when 32-bit)
     if hasattr(m, "bad_utf32_string"):
         with pytest.raises(UnicodeDecodeError):
             m.bad_utf32_string()
@@ -37,10 +38,10 @@ def test_unicode_conversion():
             m.bad_utf8_u8string()
 
     assert m.u8_Z() == "Z"
-    assert m.u8_eacute() == u"é"
-    assert m.u16_ibang() == u"‽"
-    assert m.u32_mathbfA() == u"𝐀"
-    assert m.wchar_heart() == u"♥"
+    assert m.u8_eacute() == "é"
+    assert m.u16_ibang() == "‽"
+    assert m.u32_mathbfA() == "𝐀"
+    assert m.wchar_heart() == "♥"
     if hasattr(m, "has_u8string"):
         assert m.u8_char8_Z() == "Z"
 
@@ -53,68 +54,68 @@ def toobig_message(r):
 
     toolong_message = "Expected a character, but multi-character string found"
 
-    assert m.ord_char(u"a") == 0x61  # simple ASCII
-    assert m.ord_char_lv(u"b") == 0x62
+    assert m.ord_char("a") == 0x61  # simple ASCII
+    assert m.ord_char_lv("b") == 0x62
     assert (
-        m.ord_char(u"é") == 0xE9
+        m.ord_char("é") == 0xE9
     )  # requires 2 bytes in utf-8, but can be stuffed in a char
     with pytest.raises(ValueError) as excinfo:
-        assert m.ord_char(u"Ā") == 0x100  # requires 2 bytes, doesn't fit in a char
+        assert m.ord_char("Ā") == 0x100  # requires 2 bytes, doesn't fit in a char
     assert str(excinfo.value) == toobig_message(0x100)
     with pytest.raises(ValueError) as excinfo:
-        assert m.ord_char(u"ab")
+        assert m.ord_char("ab")
     assert str(excinfo.value) == toolong_message
 
-    assert m.ord_char16(u"a") == 0x61
-    assert m.ord_char16(u"é") == 0xE9
-    assert m.ord_char16_lv(u"ê") == 0xEA
-    assert m.ord_char16(u"Ā") == 0x100
-    assert m.ord_char16(u"‽") == 0x203D
-    assert m.ord_char16(u"♥") == 0x2665
-    assert m.ord_char16_lv(u"♡") == 0x2661
+    assert m.ord_char16("a") == 0x61
+    assert m.ord_char16("é") == 0xE9
+    assert m.ord_char16_lv("ê") == 0xEA
+    assert m.ord_char16("Ā") == 0x100
+    assert m.ord_char16("‽") == 0x203D
+    assert m.ord_char16("♥") == 0x2665
+    assert m.ord_char16_lv("♡") == 0x2661
     with pytest.raises(ValueError) as excinfo:
-        assert m.ord_char16(u"🎂") == 0x1F382  # requires surrogate pair
+        assert m.ord_char16("🎂") == 0x1F382  # requires surrogate pair
     assert str(excinfo.value) == toobig_message(0x10000)
     with pytest.raises(ValueError) as excinfo:
-        assert m.ord_char16(u"aa")
+        assert m.ord_char16("aa")
     assert str(excinfo.value) == toolong_message
 
-    assert m.ord_char32(u"a") == 0x61
-    assert m.ord_char32(u"é") == 0xE9
-    assert m.ord_char32(u"Ā") == 0x100
-    assert m.ord_char32(u"‽") == 0x203D
-    assert m.ord_char32(u"♥") == 0x2665
-    assert m.ord_char32(u"🎂") == 0x1F382
+    assert m.ord_char32("a") == 0x61
+    assert m.ord_char32("é") == 0xE9
+    assert m.ord_char32("Ā") == 0x100
+    assert m.ord_char32("‽") == 0x203D
+    assert m.ord_char32("♥") == 0x2665
+    assert m.ord_char32("🎂") == 0x1F382
     with pytest.raises(ValueError) as excinfo:
-        assert m.ord_char32(u"aa")
+        assert m.ord_char32("aa")
     assert str(excinfo.value) == toolong_message
 
-    assert m.ord_wchar(u"a") == 0x61
-    assert m.ord_wchar(u"é") == 0xE9
-    assert m.ord_wchar(u"Ā") == 0x100
-    assert m.ord_wchar(u"‽") == 0x203D
-    assert m.ord_wchar(u"♥") == 0x2665
+    assert m.ord_wchar("a") == 0x61
+    assert m.ord_wchar("é") == 0xE9
+    assert m.ord_wchar("Ā") == 0x100
+    assert m.ord_wchar("‽") == 0x203D
+    assert m.ord_wchar("♥") == 0x2665
     if m.wchar_size == 2:
         with pytest.raises(ValueError) as excinfo:
-            assert m.ord_wchar(u"🎂") == 0x1F382  # requires surrogate pair
+            assert m.ord_wchar("🎂") == 0x1F382  # requires surrogate pair
         assert str(excinfo.value) == toobig_message(0x10000)
     else:
-        assert m.ord_wchar(u"🎂") == 0x1F382
+        assert m.ord_wchar("🎂") == 0x1F382
     with pytest.raises(ValueError) as excinfo:
-        assert m.ord_wchar(u"aa")
+        assert m.ord_wchar("aa")
     assert str(excinfo.value) == toolong_message
 
     if hasattr(m, "has_u8string"):
-        assert m.ord_char8(u"a") == 0x61  # simple ASCII
-        assert m.ord_char8_lv(u"b") == 0x62
+        assert m.ord_char8("a") == 0x61  # simple ASCII
+        assert m.ord_char8_lv("b") == 0x62
         assert (
-            m.ord_char8(u"é") == 0xE9
+            m.ord_char8("é") == 0xE9
         )  # requires 2 bytes in utf-8, but can be stuffed in a char
         with pytest.raises(ValueError) as excinfo:
-            assert m.ord_char8(u"Ā") == 0x100  # requires 2 bytes, doesn't fit in a char
+            assert m.ord_char8("Ā") == 0x100  # requires 2 bytes, doesn't fit in a char
         assert str(excinfo.value) == toobig_message(0x100)
         with pytest.raises(ValueError) as excinfo:
-            assert m.ord_char8(u"ab")
+            assert m.ord_char8("ab")
         assert str(excinfo.value) == toolong_message
 
 
@@ -123,18 +124,13 @@ def test_bytes_to_string():
     one-way: the only way to return bytes to Python is via the pybind11::bytes class."""
     # Issue #816
 
-    def to_bytes(s):
-        b = s if env.PY2 else s.encode("utf8")
-        assert isinstance(b, bytes)
-        return b
-
-    assert m.strlen(to_bytes("hi")) == 2
-    assert m.string_length(to_bytes("world")) == 5
-    assert m.string_length(to_bytes("a\x00b")) == 3
-    assert m.strlen(to_bytes("a\x00b")) == 1  # C-string limitation
+    assert m.strlen(b"hi") == 2
+    assert m.string_length(b"world") == 5
+    assert m.string_length("a\x00b".encode()) == 3
+    assert m.strlen("a\x00b".encode()) == 1  # C-string limitation
 
     # passing in a utf8 encoded string should work
-    assert m.string_length(u"💩".encode("utf8")) == 4
+    assert m.string_length("💩".encode()) == 4
 
 
 @pytest.mark.skipif(not hasattr(m, "has_string_view"), reason="no <string_view>")
@@ -142,26 +138,26 @@ def test_string_view(capture):
     """Tests support for C++17 string_view arguments and return values"""
     assert m.string_view_chars("Hi") == [72, 105]
     assert m.string_view_chars("Hi 🎂") == [72, 105, 32, 0xF0, 0x9F, 0x8E, 0x82]
-    assert m.string_view16_chars(u"Hi 🎂") == [72, 105, 32, 0xD83C, 0xDF82]
-    assert m.string_view32_chars(u"Hi 🎂") == [72, 105, 32, 127874]
+    assert m.string_view16_chars("Hi 🎂") == [72, 105, 32, 0xD83C, 0xDF82]
+    assert m.string_view32_chars("Hi 🎂") == [72, 105, 32, 127874]
     if hasattr(m, "has_u8string"):
         assert m.string_view8_chars("Hi") == [72, 105]
-        assert m.string_view8_chars(u"Hi 🎂") == [72, 105, 32, 0xF0, 0x9F, 0x8E, 0x82]
+        assert m.string_view8_chars("Hi 🎂") == [72, 105, 32, 0xF0, 0x9F, 0x8E, 0x82]
 
-    assert m.string_view_return() == u"utf8 secret 🎂"
-    assert m.string_view16_return() == u"utf16 secret 🎂"
-    assert m.string_view32_return() == u"utf32 secret 🎂"
+    assert m.string_view_return() == "utf8 secret 🎂"
+    assert m.string_view16_return() == "utf16 secret 🎂"
+    assert m.string_view32_return() == "utf32 secret 🎂"
     if hasattr(m, "has_u8string"):
-        assert m.string_view8_return() == u"utf8 secret 🎂"
+        assert m.string_view8_return() == "utf8 secret 🎂"
 
     with capture:
         m.string_view_print("Hi")
         m.string_view_print("utf8 🎂")
-        m.string_view16_print(u"utf16 🎂")
-        m.string_view32_print(u"utf32 🎂")
+        m.string_view16_print("utf16 🎂")
+        m.string_view32_print("utf32 🎂")
     assert (
         capture
-        == u"""
+        == """
         Hi 2
         utf8 🎂 9
         utf16 🎂 8
@@ -171,10 +167,10 @@ def test_string_view(capture):
     if hasattr(m, "has_u8string"):
         with capture:
             m.string_view8_print("Hi")
-            m.string_view8_print(u"utf8 🎂")
+            m.string_view8_print("utf8 🎂")
         assert (
             capture
-            == u"""
+            == """
             Hi 2
             utf8 🎂 9
         """
@@ -183,11 +179,11 @@ def test_string_view(capture):
     with capture:
         m.string_view_print("Hi, ascii")
         m.string_view_print("Hi, utf8 🎂")
-        m.string_view16_print(u"Hi, utf16 🎂")
-        m.string_view32_print(u"Hi, utf32 🎂")
+        m.string_view16_print("Hi, utf16 🎂")
+        m.string_view32_print("Hi, utf32 🎂")
     assert (
         capture
-        == u"""
+        == """
         Hi, ascii 9
         Hi, utf8 🎂 13
         Hi, utf16 🎂 12
@@ -197,22 +193,21 @@ def test_string_view(capture):
     if hasattr(m, "has_u8string"):
         with capture:
             m.string_view8_print("Hi, ascii")
-            m.string_view8_print(u"Hi, utf8 🎂")
+            m.string_view8_print("Hi, utf8 🎂")
         assert (
             capture
-            == u"""
+            == """
             Hi, ascii 9
             Hi, utf8 🎂 13
         """
         )
 
     assert m.string_view_bytes() == b"abc \x80\x80 def"
-    assert m.string_view_str() == u"abc ‽ def"
-    assert m.string_view_from_bytes(u"abc ‽ def".encode("utf-8")) == u"abc ‽ def"
+    assert m.string_view_str() == "abc ‽ def"
+    assert m.string_view_from_bytes("abc ‽ def".encode()) == "abc ‽ def"
     if hasattr(m, "has_u8string"):
-        assert m.string_view8_str() == u"abc ‽ def"
-    if not env.PY2:
-        assert m.string_view_memoryview() == "Have some 🎂".encode()
+        assert m.string_view8_str() == "abc ‽ def"
+    assert m.string_view_memoryview() == "Have some 🎂".encode()
 
     assert m.bytes_from_type_with_both_operator_string_and_string_view() == b"success"
     assert m.str_from_type_with_both_operator_string_and_string_view() == "success"
@@ -224,20 +219,8 @@ def test_integer_casting():
     assert m.i64_str(-1) == "-1"
     assert m.i32_str(2000000000) == "2000000000"
     assert m.u32_str(2000000000) == "2000000000"
-    if env.PY2:
-        assert m.i32_str(long(-1)) == "-1"  # noqa: F821 undefined name 'long'
-        assert m.i64_str(long(-1)) == "-1"  # noqa: F821 undefined name 'long'
-        assert (
-            m.i64_str(long(-999999999999))  # noqa: F821 undefined name 'long'
-            == "-999999999999"
-        )
-        assert (
-            m.u64_str(long(999999999999))  # noqa: F821 undefined name 'long'
-            == "999999999999"
-        )
-    else:
-        assert m.i64_str(-999999999999) == "-999999999999"
-        assert m.u64_str(999999999999) == "999999999999"
+    assert m.i64_str(-999999999999) == "-999999999999"
+    assert m.u64_str(999999999999) == "999999999999"
 
     with pytest.raises(TypeError) as excinfo:
         m.u32_str(-1)
@@ -252,46 +235,38 @@ def test_integer_casting():
         m.i32_str(3000000000)
     assert "incompatible function arguments" in str(excinfo.value)
 
-    if env.PY2:
-        with pytest.raises(TypeError) as excinfo:
-            m.u32_str(long(-1))  # noqa: F821 undefined name 'long'
-        assert "incompatible function arguments" in str(excinfo.value)
-        with pytest.raises(TypeError) as excinfo:
-            m.u64_str(long(-1))  # noqa: F821 undefined name 'long'
-        assert "incompatible function arguments" in str(excinfo.value)
-
 
 def test_int_convert():
-    class Int(object):
+    class Int:
         def __int__(self):
             return 42
 
-    class NotInt(object):
+    class NotInt:
         pass
 
-    class Float(object):
+    class Float:
         def __float__(self):
             return 41.99999
 
-    class Index(object):
+    class Index:
         def __index__(self):
             return 42
 
-    class IntAndIndex(object):
+    class IntAndIndex:
         def __int__(self):
             return 42
 
         def __index__(self):
             return 0
 
-    class RaisingTypeErrorOnIndex(object):
+    class RaisingTypeErrorOnIndex:
         def __index__(self):
             raise TypeError
 
         def __int__(self):
             return 42
 
-    class RaisingValueErrorOnIndex(object):
+    class RaisingValueErrorOnIndex:
         def __index__(self):
             raise ValueError
 
@@ -311,7 +286,7 @@ def cant_convert(v):
     cant_convert(3.14159)
     # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
     # TODO: PyPy 3.8 does not behave like CPython 3.8 here yet (7.3.7)
-    if (3, 8) <= env.PY < (3, 10) and env.CPYTHON:
+    if (3, 8) <= sys.version_info < (3, 10) and env.CPYTHON:
         with env.deprecated_call():
             assert convert(Int()) == 42
     else:
@@ -348,7 +323,7 @@ def require_implicit(v):
     # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
     # TODO: PyPy 3.8 does not behave like CPython 3.8 here yet (7.3.7)
     # https://github.com/pybind/pybind11/issues/3408
-    if (3, 8) <= env.PY < (3, 10) and env.CPYTHON:
+    if (3, 8) <= sys.version_info < (3, 10) and env.CPYTHON:
         with env.deprecated_call():
             assert convert(np.float32(3.14159)) == 3
     else:
@@ -475,7 +450,7 @@ def cant_convert(v):
     require_implicit(None)
     assert convert(None) is False
 
-    class A(object):
+    class A:
         def __init__(self, x):
             self.x = x
 
@@ -485,7 +460,7 @@ def __nonzero__(self):
         def __bool__(self):
             return self.x
 
-    class B(object):
+    class B:
         pass
 
     # Arbitrary objects are not accepted
@@ -515,17 +490,9 @@ def cant_convert(v):
 
 
 def test_int_long():
-    """In Python 2, a C++ int should return a Python int rather than long
-    if possible: longs are not always accepted where ints are used (such
-    as the argument to sys.exit()). A C++ long long is always a Python
-    long."""
-
-    import sys
-
-    must_be_long = type(getattr(sys, "maxint", 1) + 1)
     assert isinstance(m.int_cast(), int)
     assert isinstance(m.long_cast(), int)
-    assert isinstance(m.longlong_cast(), must_be_long)
+    assert isinstance(m.longlong_cast(), int)
 
 
 def test_void_caster_2():
diff --git a/tests/test_call_policies.py b/tests/test_call_policies.py
index 3599cf81af..6160564123 100644
--- a/tests/test_call_policies.py
+++ b/tests/test_call_policies.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index f41ad86e7f..74aec21e5e 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import time
 from threading import Thread
 
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index fdd73d6908..f419ef387f 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import datetime
 
 import pytest
diff --git a/tests/test_class.py b/tests/test_class.py
index caafe2068d..ff9196f0f2 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -7,7 +6,6 @@
 
 
 def test_repr():
-    # In Python 3.3+, repr() accesses __qualname__
     assert "pybind11_type" in repr(type(UserType))
     assert "UserType" in repr(UserType)
 
@@ -103,8 +101,8 @@ def test_docstrings(doc):
 
 
 def test_qualname(doc):
-    """Tests that a properly qualified name is set in __qualname__ (even in pre-3.3, where we
-    backport the attribute) and that generated docstrings properly use it and the module name"""
+    """Tests that a properly qualified name is set in __qualname__ and that
+    generated docstrings properly use it and the module name"""
     assert m.NestBase.__qualname__ == "NestBase"
     assert m.NestBase.Nested.__qualname__ == "NestBase.Nested"
 
@@ -130,13 +128,13 @@ def test_qualname(doc):
         doc(m.NestBase.Nested.fn)
         == """
         fn(self: m.class_.NestBase.Nested, arg0: int, arg1: m.class_.NestBase, arg2: m.class_.NestBase.Nested) -> None
-    """  # noqa: E501 line too long
+    """
     )
     assert (
         doc(m.NestBase.Nested.fa)
         == """
         fa(self: m.class_.NestBase.Nested, a: int, b: m.class_.NestBase, c: m.class_.NestBase.Nested) -> None
-    """  # noqa: E501 line too long
+    """
     )
     assert m.NestBase.__module__ == "pybind11_tests.class_"
     assert m.NestBase.Nested.__module__ == "pybind11_tests.class_"
diff --git a/tests/test_cmake_build/test.py b/tests/test_cmake_build/test.py
index 972a27bea4..5bf129ea33 100644
--- a/tests/test_cmake_build/test.py
+++ b/tests/test_cmake_build/test.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 import sys
 
 import test_cmake_build
 
-if str is not bytes:  # If not Python2
-    assert isinstance(__file__, str)  # Test this is properly set
+assert isinstance(__file__, str)  # Test this is properly set
 
 assert test_cmake_build.add(1, 2) == 3
 print("{} imports, runs, and adds: 1 + 2 = 3".format(sys.argv[1]))
diff --git a/tests/test_const_name.py b/tests/test_const_name.py
index d4e45e5e98..10b0caee2e 100644
--- a/tests/test_const_name.py
+++ b/tests/test_const_name.py
@@ -1,7 +1,5 @@
-# -*- coding: utf-8 -*-
 import pytest
 
-import env
 from pybind11_tests import const_name as m
 
 
@@ -25,7 +23,7 @@
     ),
 )
 def test_const_name(func, selector, expected):
-    if isinstance(func, type(u"") if env.PY2 else str):
+    if isinstance(func, str):
         pytest.skip(func)
     text = func(selector)
     assert text == expected
diff --git a/tests/test_constants_and_functions.py b/tests/test_constants_and_functions.py
index ff13bd0f26..5da0b84b8e 100644
--- a/tests/test_constants_and_functions.py
+++ b/tests/test_constants_and_functions.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 m = pytest.importorskip("pybind11_tests.constants_and_functions")
diff --git a/tests/test_copy_move.py b/tests/test_copy_move.py
index eb1efddd50..f2c0cdceb1 100644
--- a/tests/test_copy_move.py
+++ b/tests/test_copy_move.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import copy_move_policies as m
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
index a10646ff46..bb47d01bd2 100644
--- a/tests/test_custom_type_casters.py
+++ b/tests/test_custom_type_casters.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import custom_type_casters as m
@@ -19,7 +18,7 @@ def test_noconvert_args(msg):
         loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
         13
         loading ArgInspector2 argument WITH conversion allowed.  Argument value = (default arg inspector 2)
-    """  # noqa: E501 line too long
+    """
     )
     assert (
         msg(a.g("this is a", "this is b", 42))
@@ -28,7 +27,7 @@ def test_noconvert_args(msg):
         loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
         42
         loading ArgInspector2 argument WITH conversion allowed.  Argument value = (default arg inspector 2)
-    """  # noqa: E501 line too long
+    """
     )
     assert (
         msg(a.g("this is a", "this is b", 42, "this is d"))
@@ -76,7 +75,7 @@ def test_noconvert_args(msg):
             1. (i: int) -> int
 
         Invoked with: 4.0
-    """  # noqa: E501 line too long
+    """
     )
 
     assert m.ints_only(4) == 2
diff --git a/tests/test_custom_type_setup.py b/tests/test_custom_type_setup.py
index ef96f08141..19b44c9de2 100644
--- a/tests/test_custom_type_setup.py
+++ b/tests/test_custom_type_setup.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 import gc
 import weakref
 
diff --git a/tests/test_docstring_options.py b/tests/test_docstring_options.py
index 8ee6613884..fcd16b89fd 100644
--- a/tests/test_docstring_options.py
+++ b/tests/test_docstring_options.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from pybind11_tests import docstring_options as m
 
 
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index e53826cbbb..9a94b35f8b 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import ConstructorStats
@@ -201,7 +200,7 @@ def test_negative_stride_from_python(msg):
         double_threer(): incompatible function arguments. The following argument types are supported:
             1. (arg0: numpy.ndarray[numpy.float32[1, 3], flags.writeable]) -> None
 
-        Invoked with: """  # noqa: E501 line too long
+        Invoked with: """
         + repr(np.array([5.0, 4.0, 3.0], dtype="float32"))
     )
 
@@ -213,7 +212,7 @@ def test_negative_stride_from_python(msg):
         double_threec(): incompatible function arguments. The following argument types are supported:
             1. (arg0: numpy.ndarray[numpy.float32[3, 1], flags.writeable]) -> None
 
-        Invoked with: """  # noqa: E501 line too long
+        Invoked with: """
         + repr(np.array([7.0, 4.0, 1.0], dtype="float32"))
     )
 
@@ -724,13 +723,13 @@ def test_sparse_signature(doc):
         doc(m.sparse_copy_r)
         == """
         sparse_copy_r(arg0: scipy.sparse.csr_matrix[numpy.float32]) -> scipy.sparse.csr_matrix[numpy.float32]
-    """  # noqa: E501 line too long
+    """
     )
     assert (
         doc(m.sparse_copy_c)
         == """
         sparse_copy_c(arg0: scipy.sparse.csc_matrix[numpy.float32]) -> scipy.sparse.csc_matrix[numpy.float32]
-    """  # noqa: E501 line too long
+    """
     )
 
 
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 5782bda618..f2f2c29609 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -126,7 +126,6 @@ TEST_CASE("Override cache") {
 TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
     REQUIRE_THROWS_WITH(py::module_::import("throw_exception"), "ImportError: C++ Error");
-#if PY_VERSION_HEX >= 0x03030000
     REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                         Catch::Contains("ImportError: initialization failed"));
 
@@ -142,10 +141,6 @@ TEST_CASE("Import error handling") {
              locals);
     REQUIRE(locals["is_keyerror"].cast<bool>() == true);
     REQUIRE(locals["message"].cast<std::string>() == "'missing'");
-#else
-    REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
-                        Catch::Contains("ImportError: KeyError"));
-#endif
 }
 
 TEST_CASE("There can be only one interpreter") {
diff --git a/tests/test_embed/test_interpreter.py b/tests/test_embed/test_interpreter.py
index 5ab55a4b37..f279449722 100644
--- a/tests/test_embed/test_interpreter.py
+++ b/tests/test_embed/test_interpreter.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import sys
 
 from widget_module import Widget
@@ -6,7 +5,7 @@
 
 class DerivedWidget(Widget):
     def __init__(self, message):
-        super(DerivedWidget, self).__init__(message)
+        super().__init__(message)
 
     def the_answer(self):
         return 42
diff --git a/tests/test_embed/test_trampoline.py b/tests/test_embed/test_trampoline.py
index 87c8fa44c3..8e14e8ef0b 100644
--- a/tests/test_embed/test_trampoline.py
+++ b/tests/test_embed/test_trampoline.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 import trampoline_module
 
 
diff --git a/tests/test_enum.py b/tests/test_enum.py
index 14c754e726..f14a72398f 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -1,7 +1,5 @@
-# -*- coding: utf-8 -*-
 import pytest
 
-import env
 from pybind11_tests import enums as m
 
 
@@ -241,10 +239,7 @@ def test_char_underlying_enum():  # Issue #1331/PR #1334:
     assert type(m.ScopedCharEnum.Positive.__int__()) is int
     assert int(m.ScopedChar16Enum.Zero) == 0
     assert hash(m.ScopedChar32Enum.Positive) == 1
-    if env.PY2:
-        assert m.ScopedCharEnum.Positive.__getstate__() == 1  # long
-    else:
-        assert type(m.ScopedCharEnum.Positive.__getstate__()) is int
+    assert type(m.ScopedCharEnum.Positive.__getstate__()) is int
     assert m.ScopedWCharEnum(1) == m.ScopedWCharEnum.Positive
     with pytest.raises(TypeError):
         # Even if the underlying type is char, only an int can be used to construct the enum:
@@ -255,10 +250,7 @@ def test_bool_underlying_enum():
     assert type(m.ScopedBoolEnum.TRUE.__int__()) is int
     assert int(m.ScopedBoolEnum.FALSE) == 0
     assert hash(m.ScopedBoolEnum.TRUE) == 1
-    if env.PY2:
-        assert m.ScopedBoolEnum.TRUE.__getstate__() == 1  # long
-    else:
-        assert type(m.ScopedBoolEnum.TRUE.__getstate__()) is int
+    assert type(m.ScopedBoolEnum.TRUE.__getstate__()) is int
     assert m.ScopedBoolEnum(1) == m.ScopedBoolEnum.TRUE
     # Enum could construct with a bool
     # (bool is a strict subclass of int, and False will be converted to 0)
diff --git a/tests/test_eval.py b/tests/test_eval.py
index 1bbd991bc0..51b6b796b4 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import os
 
 import pytest
@@ -18,7 +17,7 @@ def test_evals(capture):
     assert m.test_eval_failure()
 
 
-@pytest.mark.xfail("env.PYPY and not env.PY2", raises=RuntimeError)
+@pytest.mark.xfail("env.PYPY", raises=RuntimeError)
 def test_eval_file():
     filename = os.path.join(os.path.dirname(__file__), "test_eval_call.py")
     assert m.test_eval_file(filename)
diff --git a/tests/test_eval_call.py b/tests/test_eval_call.py
index 373b67bac8..fd1da2a5cc 100644
--- a/tests/test_eval_call.py
+++ b/tests/test_eval_call.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # This file is called from 'test_eval.py'
 
 if "call_test2" in locals():
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index f6f93611a2..3e9a3d771e 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -276,8 +276,6 @@ TEST_SUBMODULE(exceptions, m) {
 
     m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
 
-#if PY_VERSION_HEX >= 0x03030000
-
     m.def("raise_from", []() {
         PyErr_SetString(PyExc_ValueError, "inner");
         py::raise_from(PyExc_ValueError, "outer");
@@ -301,5 +299,4 @@ TEST_SUBMODULE(exceptions, m) {
             std::throw_with_nested(std::runtime_error("Outer Exception"));
         }
     });
-#endif
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index d698b1312e..e0da55dfd6 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import sys
 
 import pytest
@@ -24,7 +23,6 @@ def test_error_already_set(msg):
     assert msg(excinfo.value) == "foo"
 
 
-@pytest.mark.skipif("env.PY2")
 def test_raise_from(msg):
     with pytest.raises(ValueError) as excinfo:
         m.raise_from()
@@ -32,7 +30,6 @@ def test_raise_from(msg):
     assert msg(excinfo.value.__cause__) == "inner"
 
 
-@pytest.mark.skipif("env.PY2")
 def test_raise_from_already_set(msg):
     with pytest.raises(ValueError) as excinfo:
         m.raise_from_already_set()
@@ -102,7 +99,7 @@ def ignore_pytest_unraisable_warning(f):
 @ignore_pytest_unraisable_warning
 def test_python_alreadyset_in_destructor(monkeypatch, capsys):
     hooked = False
-    triggered = [False]  # mutable, so Python 2.7 closure can modify it
+    triggered = False
 
     if hasattr(sys, "unraisablehook"):  # Python 3.8+
         hooked = True
@@ -112,7 +109,8 @@ def test_python_alreadyset_in_destructor(monkeypatch, capsys):
         def hook(unraisable_hook_args):
             exc_type, exc_value, exc_tb, err_msg, obj = unraisable_hook_args
             if obj == "already_set demo":
-                triggered[0] = True
+                nonlocal triggered
+                triggered = True
             default_hook(unraisable_hook_args)
             return
 
@@ -121,11 +119,11 @@ def hook(unraisable_hook_args):
 
     assert m.python_alreadyset_in_destructor("already_set demo") is True
     if hooked:
-        assert triggered[0] is True
+        assert triggered is True
 
     _, captured_stderr = capsys.readouterr()
-    # Error message is different in Python 2 and 3, check for words that appear in both
-    assert "ignored" in captured_stderr and "already_set demo" in captured_stderr
+    assert captured_stderr.startswith("Exception ignored in: 'already_set demo'")
+    assert captured_stderr.rstrip().endswith("KeyError: 'bar'")
 
 
 def test_exception_matches():
@@ -239,7 +237,6 @@ def pycatch(exctype, f, *args):
     assert str(excinfo.value) == "this is a helper-defined translated exception"
 
 
-@pytest.mark.skipif("env.PY2")
 def test_throw_nested_exception():
     with pytest.raises(RuntimeError) as excinfo:
         m.throw_nested_exception()
@@ -249,7 +246,7 @@ def test_throw_nested_exception():
 
 # This can often happen if you wrap a pybind11 class in a Python wrapper
 def test_invalid_repr():
-    class MyRepr(object):
+    class MyRepr:
         def __repr__(self):
             raise AttributeError("Example error")
 
diff --git a/tests/test_factory_constructors.py b/tests/test_factory_constructors.py
index 8bc0269852..120a587c45 100644
--- a/tests/test_factory_constructors.py
+++ b/tests/test_factory_constructors.py
@@ -1,9 +1,7 @@
-# -*- coding: utf-8 -*-
 import re
 
 import pytest
 
-import env  # noqa: F401
 from pybind11_tests import ConstructorStats
 from pybind11_tests import factory_constructors as m
 from pybind11_tests.factory_constructors import tag
@@ -82,7 +80,7 @@ def test_init_factory_signature(msg):
             4. m.factory_constructors.TestFactory1(arg0: handle, arg1: int, arg2: handle)
 
         Invoked with: 'invalid', 'constructor', 'arguments'
-    """  # noqa: E501 line too long
+    """
     )
 
     assert (
@@ -465,12 +463,10 @@ def test_reallocation_g(capture, msg):
     )
 
 
-@pytest.mark.skipif("env.PY2")
 def test_invalid_self():
-    """Tests invocation of the pybind-registered base class with an invalid `self` argument.  You
-    can only actually do this on Python 3: Python 2 raises an exception itself if you try."""
+    """Tests invocation of the pybind-registered base class with an invalid `self` argument."""
 
-    class NotPybindDerived(object):
+    class NotPybindDerived:
         pass
 
     # Attempts to initialize with an invalid type passed as `self`:
diff --git a/tests/test_gil_scoped.py b/tests/test_gil_scoped.py
index 0a1d62747d..52374b0cce 100644
--- a/tests/test_gil_scoped.py
+++ b/tests/test_gil_scoped.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import multiprocessing
 import threading
 
diff --git a/tests/test_iostream.py b/tests/test_iostream.py
index 7f18ca65c6..5bbdf6955d 100644
--- a/tests/test_iostream.py
+++ b/tests/test_iostream.py
@@ -1,44 +1,8 @@
-# -*- coding: utf-8 -*-
-import sys
-from contextlib import contextmanager
+from contextlib import redirect_stderr, redirect_stdout
+from io import StringIO
 
 from pybind11_tests import iostream as m
 
-try:
-    # Python 3
-    from io import StringIO
-except ImportError:
-    # Python 2
-    try:
-        from cStringIO import StringIO
-    except ImportError:
-        from StringIO import StringIO
-
-try:
-    # Python 3.4
-    from contextlib import redirect_stdout
-except ImportError:
-
-    @contextmanager
-    def redirect_stdout(target):
-        original = sys.stdout
-        sys.stdout = target
-        yield
-        sys.stdout = original
-
-
-try:
-    # Python 3.5
-    from contextlib import redirect_stderr
-except ImportError:
-
-    @contextmanager
-    def redirect_stderr(target):
-        original = sys.stderr
-        sys.stderr = target
-        yield
-        sys.stderr = original
-
 
 def test_captured(capsys):
     msg = "I've been redirected to Python, I hope!"
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index d61cf2aa58..ab7017886e 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -1,7 +1,5 @@
-# -*- coding: utf-8 -*-
 import pytest
 
-import env  # noqa: F401
 from pybind11_tests import kwargs_and_defaults as m
 
 
@@ -82,7 +80,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (arg0: int, arg1: float, *args) -> tuple
 
         Invoked with: 1
-    """  # noqa: E501 line too long
+    """
     )
     with pytest.raises(TypeError) as excinfo:
         assert mpa()
@@ -93,7 +91,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (arg0: int, arg1: float, *args) -> tuple
 
         Invoked with:
-    """  # noqa: E501 line too long
+    """
     )
 
     assert mpk(-2, 3.5, pi=3.14159, e=2.71828) == (
@@ -127,7 +125,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (i: int = 1, j: float = 3.14159, *args, **kwargs) -> tuple
 
         Invoked with: 1; kwargs: i=1
-    """  # noqa: E501 line too long
+    """
     )
     with pytest.raises(TypeError) as excinfo:
         assert mpakd(1, 2, j=1)
@@ -138,7 +136,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (i: int = 1, j: float = 3.14159, *args, **kwargs) -> tuple
 
         Invoked with: 1, 2; kwargs: j=1
-    """  # noqa: E501 line too long
+    """
     )
 
     # Arguments after a py::args are automatically keyword-only (pybind 2.9+)
@@ -343,7 +341,6 @@ def test_signatures():
     )
 
 
-@pytest.mark.xfail("env.PYPY and env.PY2", reason="PyPy2 doesn't double count")
 def test_args_refcount():
     """Issue/PR #1216 - py::args elements get double-inc_ref()ed when combined with regular
     arguments"""
diff --git a/tests/test_local_bindings.py b/tests/test_local_bindings.py
index 52b1b63358..654d96d490 100644
--- a/tests/test_local_bindings.py
+++ b/tests/test_local_bindings.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -200,7 +199,7 @@ def test_stl_caster_vs_stl_bind(msg):
         1. (arg0: pybind11_cross_module_tests.VectorInt) -> int
 
     Invoked with: [1, 2, 3]
-    """  # noqa: E501 line too long
+    """
     )
 
 
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index fa026f9edd..5a95303e11 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -494,26 +493,17 @@ def test_overload_ordering():
     assert m.overload_order("string") == 1
     assert m.overload_order(0) == 4
 
-    # Different for Python 2 vs. 3
-    uni_name = type(u"").__name__
-
     assert "1. overload_order(arg0: int) -> int" in m.overload_order.__doc__
-    assert (
-        "2. overload_order(arg0: {}) -> int".format(uni_name)
-        in m.overload_order.__doc__
-    )
-    assert (
-        "3. overload_order(arg0: {}) -> int".format(uni_name)
-        in m.overload_order.__doc__
-    )
+    assert "2. overload_order(arg0: str) -> int" in m.overload_order.__doc__
+    assert "3. overload_order(arg0: str) -> int" in m.overload_order.__doc__
     assert "4. overload_order(arg0: int) -> int" in m.overload_order.__doc__
 
     with pytest.raises(TypeError) as err:
         m.overload_order(1.1)
 
     assert "1. (arg0: int) -> int" in str(err.value)
-    assert "2. (arg0: {}) -> int".format(uni_name) in str(err.value)
-    assert "3. (arg0: {}) -> int".format(uni_name) in str(err.value)
+    assert "2. (arg0: str) -> int" in str(err.value)
+    assert "3. (arg0: str) -> int" in str(err.value)
     assert "4. (arg0: int) -> int" in str(err.value)
 
 
diff --git a/tests/test_modules.py b/tests/test_modules.py
index 49e1ea5e30..15db8355ef 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from pybind11_tests import ConstructorStats
 from pybind11_tests import modules as m
 from pybind11_tests.modules import subsubmodule as ms
diff --git a/tests/test_multiple_inheritance.py b/tests/test_multiple_inheritance.py
index abdf25d608..3a1d88d711 100644
--- a/tests/test_multiple_inheritance.py
+++ b/tests/test_multiple_inheritance.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -13,8 +12,7 @@ def test_multiple_inheritance_cpp():
     assert mt.bar() == 4
 
 
-@pytest.mark.skipif("env.PYPY and env.PY2")
-@pytest.mark.xfail("env.PYPY and not env.PY2")
+@pytest.mark.xfail("env.PYPY")
 def test_multiple_inheritance_mix1():
     class Base1:
         def __init__(self, i):
@@ -53,15 +51,14 @@ def __init__(self, i, j):
     assert mt.bar() == 4
 
 
-@pytest.mark.skipif("env.PYPY and env.PY2")
-@pytest.mark.xfail("env.PYPY and not env.PY2")
+@pytest.mark.xfail("env.PYPY")
 def test_multiple_inheritance_python():
     class MI1(m.Base1, m.Base2):
         def __init__(self, i, j):
             m.Base1.__init__(self, i)
             m.Base2.__init__(self, j)
 
-    class B1(object):
+    class B1:
         def v(self):
             return 1
 
@@ -96,7 +93,7 @@ class B2(B1):
         def v(self):
             return 2
 
-    class B3(object):
+    class B3:
         def v(self):
             return 3
 
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index e4138f0239..45be592a84 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 0098eccb87..65fd90d7bc 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import re
 
 import pytest
diff --git a/tests/test_numpy_vectorize.py b/tests/test_numpy_vectorize.py
index de5c9a607d..7e8c015c46 100644
--- a/tests/test_numpy_vectorize.py
+++ b/tests/test_numpy_vectorize.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import numpy_vectorize as m
diff --git a/tests/test_opaque_types.py b/tests/test_opaque_types.py
index 5495cb6b4a..8b9d8f59ce 100644
--- a/tests/test_opaque_types.py
+++ b/tests/test_opaque_types.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import ConstructorStats, UserType
@@ -40,7 +39,7 @@ def test_pointers(msg):
             1. (arg0: capsule) -> int
 
         Invoked with: [1, 2, 3]
-    """  # noqa: E501 line too long
+    """
     )
 
     assert m.return_null_str() is None
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index 8cf375b6da..b228da3cc3 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -1,7 +1,5 @@
-# -*- coding: utf-8 -*-
 import pytest
 
-import env
 from pybind11_tests import ConstructorStats
 from pybind11_tests import operators as m
 
@@ -151,5 +149,4 @@ def test_overriding_eq_reset_hash():
 def test_return_set_of_unhashable():
     with pytest.raises(TypeError) as excinfo:
         m.get_unhashable_HashMe_set()
-    if not env.PY2:
-        assert str(excinfo.value.__cause__).startswith("unhashable type:")
+    assert str(excinfo.value.__cause__).startswith("unhashable type:")
diff --git a/tests/test_pickling.py b/tests/test_pickling.py
index 9f68f37dcf..52802ace86 100644
--- a/tests/test_pickling.py
+++ b/tests/test_pickling.py
@@ -1,14 +1,10 @@
-# -*- coding: utf-8 -*-
+import pickle
+
 import pytest
 
 import env
 from pybind11_tests import pickling as m
 
-try:
-    import cPickle as pickle  # Use cPickle on Python 2.7
-except ImportError:
-    import pickle
-
 
 @pytest.mark.parametrize("cls_name", ["Pickleable", "PickleableNew"])
 def test_roundtrip(cls_name):
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 9364cccf69..1ed237ea21 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -87,7 +87,6 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("tuple_size_t", []() { return py::tuple{(py::size_t) 0}; });
     m.def("get_tuple", []() { return py::make_tuple(42, py::none(), "spam"); });
 
-#if PY_VERSION_HEX >= 0x03030000
     // test_simple_namespace
     m.def("get_simple_namespace", []() {
         auto ns = py::module_::import("types").attr("SimpleNamespace")(
@@ -96,7 +95,6 @@ TEST_SUBMODULE(pytypes, m) {
         py::setattr(ns, "right", py::int_(2));
         return ns;
     });
-#endif
 
     // test_str
     m.def("str_from_char_ssize_t", []() { return py::str{"red", (py::ssize_t) 3}; });
@@ -423,12 +421,10 @@ TEST_SUBMODULE(pytypes, m) {
         return py::memoryview::from_buffer(static_cast<void *>(nullptr), 1, "B", {}, {});
     });
 
-#if PY_MAJOR_VERSION >= 3
     m.def("test_memoryview_from_memory", []() {
         const char *buf = "\xff\xe1\xab\x37";
         return py::memoryview::from_memory(buf, static_cast<py::ssize_t>(strlen(buf)));
     });
-#endif
 
     // test_builtin_functions
     m.def("get_len", [](py::handle h) { return py::len(h); });
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 2cd6c3f03a..f2b1f6b6eb 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -1,11 +1,8 @@
-# -*- coding: utf-8 -*-
-from __future__ import division
-
 import sys
 
 import pytest
 
-import env
+import env  # noqa: F401
 from pybind11_tests import debug_enabled
 from pybind11_tests import pytypes as m
 
@@ -123,7 +120,6 @@ def test_tuple():
     assert m.get_tuple() == (42, None, "spam")
 
 
-@pytest.mark.skipif("env.PY2")
 def test_simple_namespace():
     ns = m.get_simple_namespace()
     assert ns.attr == 42
@@ -140,7 +136,7 @@ def test_str(doc):
 
     assert doc(m.str_from_bytes) == "str_from_bytes() -> str"
 
-    class A(object):
+    class A:
         def __str__(self):
             return "this is a str"
 
@@ -158,24 +154,14 @@ def __repr__(self):
     malformed_utf8 = b"\x80"
     if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE"):
         assert m.str_from_object(malformed_utf8) is malformed_utf8
-    elif env.PY2:
-        with pytest.raises(UnicodeDecodeError):
-            m.str_from_object(malformed_utf8)
     else:
         assert m.str_from_object(malformed_utf8) == "b'\\x80'"
-    if env.PY2:
-        with pytest.raises(UnicodeDecodeError):
-            m.str_from_handle(malformed_utf8)
-    else:
-        assert m.str_from_handle(malformed_utf8) == "b'\\x80'"
+    assert m.str_from_handle(malformed_utf8) == "b'\\x80'"
 
     assert m.str_from_string_from_str("this is a str") == "this is a str"
-    ucs_surrogates_str = u"\udcc3"
-    if env.PY2:
-        assert u"\udcc3" == m.str_from_string_from_str(ucs_surrogates_str)
-    else:
-        with pytest.raises(UnicodeEncodeError):
-            m.str_from_string_from_str(ucs_surrogates_str)
+    ucs_surrogates_str = "\udcc3"
+    with pytest.raises(UnicodeEncodeError):
+        m.str_from_string_from_str(ucs_surrogates_str)
 
 
 def test_bytes(doc):
@@ -184,9 +170,7 @@ def test_bytes(doc):
     assert m.bytes_from_string().decode() == "foo"
     assert m.bytes_from_str().decode() == "bar"
 
-    assert doc(m.bytes_from_str) == "bytes_from_str() -> {}".format(
-        "str" if env.PY2 else "bytes"
-    )
+    assert doc(m.bytes_from_str) == "bytes_from_str() -> bytes"
 
 
 def test_bytearray(doc):
@@ -278,11 +262,6 @@ def test_constructors():
     """C++ default and converting constructors are equivalent to type calls in Python"""
     types = [bytes, bytearray, str, bool, int, float, tuple, list, dict, set]
     expected = {t.__name__: t() for t in types}
-    if env.PY2:
-        # Note that bytes.__name__ == 'str' in Python 2.
-        # pybind11::str is unicode even under Python 2.
-        expected["bytes"] = bytes()
-        expected["str"] = unicode()  # noqa: F821
     assert m.default_constructors() == expected
 
     data = {
@@ -300,11 +279,6 @@ def test_constructors():
     }
     inputs = {k.__name__: v for k, v in data.items()}
     expected = {k.__name__: k(v) for k, v in data.items()}
-    if env.PY2:  # Similar to the above. See comments above.
-        inputs["bytes"] = b"41"
-        inputs["str"] = 42
-        expected["bytes"] = b"41"
-        expected["str"] = u"42"
 
     assert m.converting_constructors(inputs) == expected
     assert m.cast_functions(inputs) == expected
@@ -340,46 +314,39 @@ def test_non_converting_constructors():
 def test_pybind11_str_raw_str():
     # specifically to exercise pybind11::str::raw_str
     cvt = m.convert_to_pybind11_str
-    assert cvt(u"Str") == u"Str"
-    assert cvt(b"Bytes") == u"Bytes" if env.PY2 else "b'Bytes'"
-    assert cvt(None) == u"None"
-    assert cvt(False) == u"False"
-    assert cvt(True) == u"True"
-    assert cvt(42) == u"42"
-    assert cvt(2 ** 65) == u"36893488147419103232"
-    assert cvt(-1.50) == u"-1.5"
-    assert cvt(()) == u"()"
-    assert cvt((18,)) == u"(18,)"
-    assert cvt([]) == u"[]"
-    assert cvt([28]) == u"[28]"
-    assert cvt({}) == u"{}"
-    assert cvt({3: 4}) == u"{3: 4}"
-    assert cvt(set()) == u"set([])" if env.PY2 else "set()"
-    assert cvt({3, 3}) == u"set([3])" if env.PY2 else "{3}"
-
-    valid_orig = u"DZ"
+    assert cvt("Str") == "Str"
+    assert cvt(b"Bytes") == "b'Bytes'"
+    assert cvt(None) == "None"
+    assert cvt(False) == "False"
+    assert cvt(True) == "True"
+    assert cvt(42) == "42"
+    assert cvt(2**65) == "36893488147419103232"
+    assert cvt(-1.50) == "-1.5"
+    assert cvt(()) == "()"
+    assert cvt((18,)) == "(18,)"
+    assert cvt([]) == "[]"
+    assert cvt([28]) == "[28]"
+    assert cvt({}) == "{}"
+    assert cvt({3: 4}) == "{3: 4}"
+    assert cvt(set()) == "set()"
+    assert cvt({3, 3}) == "{3}"
+
+    valid_orig = "DZ"
     valid_utf8 = valid_orig.encode("utf-8")
     valid_cvt = cvt(valid_utf8)
     if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE"):
         assert valid_cvt is valid_utf8
     else:
-        assert type(valid_cvt) is unicode if env.PY2 else str  # noqa: F821
-        if env.PY2:
-            assert valid_cvt == valid_orig
-        else:
-            assert valid_cvt == "b'\\xc7\\xb1'"
+        assert type(valid_cvt) is str
+        assert valid_cvt == "b'\\xc7\\xb1'"
 
     malformed_utf8 = b"\x80"
     if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE"):
         assert cvt(malformed_utf8) is malformed_utf8
     else:
-        if env.PY2:
-            with pytest.raises(UnicodeDecodeError):
-                cvt(malformed_utf8)
-        else:
-            malformed_cvt = cvt(malformed_utf8)
-            assert type(malformed_cvt) is str
-            assert malformed_cvt == "b'\\x80'"
+        malformed_cvt = cvt(malformed_utf8)
+        assert type(malformed_cvt) is str
+        assert malformed_cvt == "b'\\x80'"
 
 
 def test_implicit_casting():
@@ -428,14 +395,14 @@ def test_print(capture):
 
 
 def test_hash():
-    class Hashable(object):
+    class Hashable:
         def __init__(self, value):
             self.value = value
 
         def __hash__(self):
             return self.value
 
-    class Unhashable(object):
+    class Unhashable:
         __hash__ = None
 
     assert m.hash_function(Hashable(42)) == 42
@@ -493,12 +460,7 @@ def test_memoryview(method, args, fmt, expected_view):
     view = method(*args)
     assert isinstance(view, memoryview)
     assert view.format == fmt
-    if isinstance(expected_view, bytes) or not env.PY2:
-        view_as_list = list(view)
-    else:
-        # Using max to pick non-zero byte (big-endian vs little-endian).
-        view_as_list = [max(ord(c) for c in s) for s in view]
-    assert view_as_list == list(expected_view)
+    assert list(view) == list(expected_view)
 
 
 @pytest.mark.xfail("env.PYPY", reason="getrefcount is not available")
@@ -522,12 +484,7 @@ def test_memoryview_from_buffer_empty_shape():
     view = m.test_memoryview_from_buffer_empty_shape()
     assert isinstance(view, memoryview)
     assert view.format == "B"
-    if env.PY2:
-        # Python 2 behavior is weird, but Python 3 (the future) is fine.
-        # PyPy3 has <memoryview, while CPython 2 has <memory
-        assert bytes(view).startswith(b"<memory")
-    else:
-        assert bytes(view) == b""
+    assert bytes(view) == b""
 
 
 def test_test_memoryview_from_buffer_invalid_strides():
@@ -536,14 +493,10 @@ def test_test_memoryview_from_buffer_invalid_strides():
 
 
 def test_test_memoryview_from_buffer_nullptr():
-    if env.PY2:
+    with pytest.raises(ValueError):
         m.test_memoryview_from_buffer_nullptr()
-    else:
-        with pytest.raises(ValueError):
-            m.test_memoryview_from_buffer_nullptr()
 
 
-@pytest.mark.skipif("env.PY2")
 def test_memoryview_from_memory():
     view = m.test_memoryview_from_memory()
     assert isinstance(view, memoryview)
@@ -563,9 +516,9 @@ def test_builtin_functions():
 
 def test_isinstance_string_types():
     assert m.isinstance_pybind11_bytes(b"")
-    assert not m.isinstance_pybind11_bytes(u"")
+    assert not m.isinstance_pybind11_bytes("")
 
-    assert m.isinstance_pybind11_str(u"")
+    assert m.isinstance_pybind11_str("")
     if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE"):
         assert m.isinstance_pybind11_str(b"")
     else:
@@ -575,24 +528,21 @@ def test_isinstance_string_types():
 def test_pass_bytes_or_unicode_to_string_types():
     assert m.pass_to_pybind11_bytes(b"Bytes") == 5
     with pytest.raises(TypeError):
-        m.pass_to_pybind11_bytes(u"Str")
+        m.pass_to_pybind11_bytes("Str")
 
-    if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE") or env.PY2:
+    if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE"):
         assert m.pass_to_pybind11_str(b"Bytes") == 5
     else:
         with pytest.raises(TypeError):
             m.pass_to_pybind11_str(b"Bytes")
-    assert m.pass_to_pybind11_str(u"Str") == 3
+    assert m.pass_to_pybind11_str("Str") == 3
 
     assert m.pass_to_std_string(b"Bytes") == 5
-    assert m.pass_to_std_string(u"Str") == 3
+    assert m.pass_to_std_string("Str") == 3
 
     malformed_utf8 = b"\x80"
     if hasattr(m, "PYBIND11_STR_LEGACY_PERMISSIVE"):
         assert m.pass_to_pybind11_str(malformed_utf8) == 1
-    elif env.PY2:
-        with pytest.raises(UnicodeDecodeError):
-            m.pass_to_pybind11_str(malformed_utf8)
     else:
         with pytest.raises(TypeError):
             m.pass_to_pybind11_str(malformed_utf8)
@@ -609,12 +559,14 @@ def test_weakref(create_weakref, create_weakref_with_callback):
     from weakref import getweakrefcount
 
     # Apparently, you cannot weakly reference an object()
-    class WeaklyReferenced(object):
+    class WeaklyReferenced:
         pass
 
+    callback_called = False
+
     def callback(wr):
-        # No `nonlocal` in Python 2
-        callback.called = True
+        nonlocal callback_called
+        callback_called = True
 
     obj = WeaklyReferenced()
     assert getweakrefcount(obj) == 0
@@ -623,13 +575,12 @@ def callback(wr):
 
     obj = WeaklyReferenced()
     assert getweakrefcount(obj) == 0
-    callback.called = False
     wr = create_weakref_with_callback(obj, callback)  # noqa: F841
     assert getweakrefcount(obj) == 1
-    assert not callback.called
+    assert not callback_called
     del obj
     pytest.gc_collect()
-    assert callback.called
+    assert callback_called
 
 
 def test_cpp_iterators():
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 6985918a11..e1441c07cd 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_smart_ptr.py b/tests/test_smart_ptr.py
index 85f61a3223..4097df28b4 100644
--- a/tests/test_smart_ptr.py
+++ b/tests/test_smart_ptr.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 m = pytest.importorskip("pybind11_tests.smart_ptr")
diff --git a/tests/test_stl.py b/tests/test_stl.py
index e217975944..a3d6866899 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import ConstructorStats, UserType
@@ -283,7 +282,7 @@ def test_stl_pass_by_pointer(msg):
             1. (v: List[int] = None) -> List[int]
 
         Invoked with:
-    """  # noqa: E501 line too long
+    """
     )
 
     with pytest.raises(TypeError) as excinfo:
@@ -295,7 +294,7 @@ def test_stl_pass_by_pointer(msg):
             1. (v: List[int] = None) -> List[int]
 
         Invoked with: None
-    """  # noqa: E501 line too long
+    """
     )
 
     assert m.stl_pass_by_pointer([1, 2, 3]) == [1, 2, 3]
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 59c5ab6b5d..d5e9ccced7 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -1,7 +1,5 @@
-# -*- coding: utf-8 -*-
 import pytest
 
-import env
 from pybind11_tests import stl_binders as m
 
 
@@ -74,18 +72,13 @@ def test_vector_buffer():
     assert v[1] == 2
     v[2] = 5
     mv = memoryview(v)  # We expose the buffer interface
-    if not env.PY2:
-        assert mv[2] == 5
-        mv[2] = 6
-    else:
-        assert mv[2] == "\x05"
-        mv[2] = "\x06"
+    assert mv[2] == 5
+    mv[2] = 6
     assert v[2] == 6
 
-    if not env.PY2:
-        mv = memoryview(b)
-        v = m.VectorUChar(mv[::2])
-        assert v[1] == 3
+    mv = memoryview(b)
+    v = m.VectorUChar(mv[::2])
+    assert v[1] == 3
 
     with pytest.raises(RuntimeError) as excinfo:
         m.create_undeclstruct()  # Undeclared struct contents, no buffer interface
diff --git a/tests/test_tagbased_polymorphic.py b/tests/test_tagbased_polymorphic.py
index 64eb8a3c1b..84f0ea7178 100644
--- a/tests/test_tagbased_polymorphic.py
+++ b/tests/test_tagbased_polymorphic.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from pybind11_tests import tagbased_polymorphic as m
 
 
diff --git a/tests/test_thread.py b/tests/test_thread.py
index f9db1babaf..e89991f9d6 100644
--- a/tests/test_thread.py
+++ b/tests/test_thread.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 import threading
 
 from pybind11_tests import thread as m
@@ -7,7 +5,7 @@
 
 class Thread(threading.Thread):
     def __init__(self, fn):
-        super(Thread, self).__init__()
+        super().__init__()
         self.fn = fn
         self.e = None
 
@@ -19,7 +17,7 @@ def run(self):
             self.e = e
 
     def join(self):
-        super(Thread, self).join()
+        super().join()
         if self.e:
             raise self.e
 
diff --git a/tests/test_union.py b/tests/test_union.py
index 2a2c12fb48..e1866e701d 100644
--- a/tests/test_union.py
+++ b/tests/test_union.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from pybind11_tests import union_ as m
 
 
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index 4f25cac4a3..14a8384a8a 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -10,12 +9,12 @@
 def test_override(capture, msg):
     class ExtendedExampleVirt(m.ExampleVirt):
         def __init__(self, state):
-            super(ExtendedExampleVirt, self).__init__(state + 1)
+            super().__init__(state + 1)
             self.data = "Hello world"
 
         def run(self, value):
             print("ExtendedExampleVirt::run(%i), calling parent.." % value)
-            return super(ExtendedExampleVirt, self).run(value + 1)
+            return super().run(value + 1)
 
         def run_bool(self):
             print("ExtendedExampleVirt::run_bool()")
@@ -29,7 +28,7 @@ def pure_virtual(self):
 
     class ExtendedExampleVirt2(ExtendedExampleVirt):
         def __init__(self, state):
-            super(ExtendedExampleVirt2, self).__init__(state + 1)
+            super().__init__(state + 1)
 
         def get_string2(self):
             return "override2"
@@ -41,7 +40,7 @@ def get_string2(self):
         capture
         == """
         Original implementation of ExampleVirt::run(state=10, value=20, str1=default1, str2=default2)
-    """  # noqa: E501 line too long
+    """
     )
 
     with pytest.raises(RuntimeError) as excinfo:
@@ -59,7 +58,7 @@ def get_string2(self):
         == """
         ExtendedExampleVirt::run(20), calling parent..
         Original implementation of ExampleVirt::run(state=11, value=21, str1=override1, str2=default2)
-    """  # noqa: E501 line too long
+    """
     )
     with capture:
         assert m.runExampleVirtBool(ex12p) is False
@@ -76,7 +75,7 @@ def get_string2(self):
         == """
         ExtendedExampleVirt::run(50), calling parent..
         Original implementation of ExampleVirt::run(state=17, value=51, str1=override1, str2=override2)
-    """  # noqa: E501 line too long
+    """
     )
 
     cstats = ConstructorStats.get(m.ExampleVirt)
@@ -97,7 +96,7 @@ def test_alias_delay_initialization1(capture):
 
     class B(m.A):
         def __init__(self):
-            super(B, self).__init__()
+            super().__init__()
 
         def f(self):
             print("In python f()")
@@ -137,7 +136,7 @@ class such as defining local variables and performing construction/destruction.
 
     class B2(m.A2):
         def __init__(self):
-            super(B2, self).__init__()
+            super().__init__()
 
         def f(self):
             print("In python B2.f()")
@@ -245,7 +244,7 @@ def dispatch(self):
     class PyClass2(m.DispatchIssue):
         def dispatch(self):
             with pytest.raises(RuntimeError) as excinfo:
-                super(PyClass2, self).dispatch()
+                super().dispatch()
             assert (
                 msg(excinfo.value)
                 == 'Tried to call pure virtual function "Base::dispatch"'
@@ -262,7 +261,7 @@ def test_recursive_dispatch_issue(msg):
 
     class Data(m.Data):
         def __init__(self, value):
-            super(Data, self).__init__()
+            super().__init__()
             self.value = value
 
     class Adder(m.Adder):
diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index 3605aebcf3..b3acaaae92 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -92,7 +92,7 @@ endif()
 
 # Use the Python interpreter to find the libs.
 if(NOT PythonLibsNew_FIND_VERSION)
-  set(PythonLibsNew_FIND_VERSION "")
+  set(PythonLibsNew_FIND_VERSION "3.5")
 endif()
 
 find_package(PythonInterp ${PythonLibsNew_FIND_VERSION} ${_pythonlibs_required}
diff --git a/tools/libsize.py b/tools/libsize.py
index 1551477e66..5fb20334d8 100644
--- a/tools/libsize.py
+++ b/tools/libsize.py
@@ -1,6 +1,3 @@
-# -*- coding: utf-8 -*-
-from __future__ import division, print_function
-
 import os
 import sys
 
diff --git a/tools/make_changelog.py b/tools/make_changelog.py
index 629c284d39..839040a938 100755
--- a/tools/make_changelog.py
+++ b/tools/make_changelog.py
@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-# -*- coding: utf-8 -*-
 
 import re
 
diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index df24781213..bbb722ac72 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -8,7 +8,6 @@ Adds the following targets::
     pybind11::lto - Link time optimizations (manual selection)
     pybind11::thin_lto - Link time optimizations (manual selection)
     pybind11::python_link_helper - Adds link to Python libraries
-    pybind11::python2_no_register - Avoid warning/error with Python 2 + C++14/7
     pybind11::windows_extras - MSVC bigobj and mp for building multithreaded
     pybind11::opt_size - avoid optimizations that increase code size
 
@@ -66,31 +65,6 @@ set_property(
   APPEND
   PROPERTY INTERFACE_LINK_LIBRARIES pybind11::pybind11)
 
-# ----------------------- no register ----------------------
-
-# Workaround for Python 2.7 and C++17 (C++14 as a warning) incompatibility
-# This adds the flags -Wno-register and -Wno-deprecated-register if the compiler
-# is Clang 3.9+ or AppleClang and the compile language is CXX, or /wd5033 for MSVC (all languages,
-# since MSVC didn't recognize COMPILE_LANGUAGE until CMake 3.11+).
-
-add_library(pybind11::python2_no_register INTERFACE IMPORTED ${optional_global})
-set(clang_4plus
-    "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
-set(no_register "$<OR:${clang_4plus},$<CXX_COMPILER_ID:AppleClang>>")
-
-if(MSVC AND CMAKE_VERSION VERSION_LESS 3.11)
-  set(cxx_no_register "${no_register}")
-else()
-  set(cxx_no_register "$<AND:$<COMPILE_LANGUAGE:CXX>,${no_register}>")
-endif()
-
-set(msvc "$<CXX_COMPILER_ID:MSVC>")
-
-set_property(
-  TARGET pybind11::python2_no_register
-  PROPERTY INTERFACE_COMPILE_OPTIONS
-           "$<${cxx_no_register}:-Wno-register;-Wno-deprecated-register>" "$<${msvc}:/wd5033>")
-
 # --------------------------- link helper ---------------------------
 
 add_library(pybind11::python_link_helper IMPORTED INTERFACE ${optional_global})
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 262020d14a..6c084d1db8 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -51,8 +51,6 @@ complex applications, and they are available in all modes:
   Python headers too.
 ``pybind11::python_link_helper``
   Just the "linking" part of ``pybind11:module``, for CMake < 3.15.
-``pybind11::python2_no_register``
-  Quiets the warning/error when mixing C++14+ and Python 2, also included in ``pybind11::module``.
 ``pybind11::thin_lto``
   An alternative to ``INTERPROCEDURAL_OPTIMIZATION``.
 ``pybind11::lto``
diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 0b4e21ccef..dbf41e0711 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -22,9 +22,7 @@ else()
   set(_pybind11_quiet "")
 endif()
 
-if(NOT Python_FOUND
-   AND NOT Python3_FOUND
-   AND NOT Python2_FOUND)
+if(NOT Python_FOUND AND NOT Python3_FOUND)
   if(NOT DEFINED Python_FIND_IMPLEMENTATIONS)
     set(Python_FIND_IMPLEMENTATIONS CPython PyPy)
   endif()
@@ -34,7 +32,7 @@ if(NOT Python_FOUND
     set(Python_ROOT_DIR "$ENV{pythonLocation}")
   endif()
 
-  find_package(Python REQUIRED COMPONENTS Interpreter Development ${_pybind11_quiet})
+  find_package(Python 3.5 REQUIRED COMPONENTS Interpreter Development ${_pybind11_quiet})
 
   # If we are in submodule mode, export the Python targets to global targets.
   # If this behavior is not desired, FindPython _before_ pybind11.
@@ -51,19 +49,10 @@ if(Python_FOUND)
   set(_Python
       Python
       CACHE INTERNAL "" FORCE)
-elseif(Python3_FOUND AND NOT Python2_FOUND)
+elseif(Python3_FOUND)
   set(_Python
       Python3
       CACHE INTERNAL "" FORCE)
-elseif(Python2_FOUND AND NOT Python3_FOUND)
-  set(_Python
-      Python2
-      CACHE INTERNAL "" FORCE)
-else()
-  message(AUTHOR_WARNING "Python2 and Python3 both present, pybind11 in "
-                         "PYBIND11_NOPYTHON mode (manually activate to silence warning)")
-  set(_pybind11_nopython ON)
-  return()
 endif()
 
 if(PYBIND11_MASTER_PROJECT)
@@ -137,7 +126,7 @@ if(PYTHON_IS_DEBUG)
     PROPERTY INTERFACE_COMPILE_DEFINITIONS Py_DEBUG)
 endif()
 
-# Check on every access - since Python2 and Python3 could have been used - do nothing in that case.
+# Check on every access - since Python can change - do nothing in that case.
 
 if(DEFINED ${_Python}_INCLUDE_DIRS)
   # Only add Python for build - must be added during the import for config
@@ -159,13 +148,6 @@ if(DEFINED ${_Python}_INCLUDE_DIRS)
       CACHE INTERNAL "Directories where pybind11 and possibly Python headers are located")
 endif()
 
-if(DEFINED ${_Python}_VERSION AND ${_Python}_VERSION VERSION_LESS 3)
-  set_property(
-    TARGET pybind11::pybind11
-    APPEND
-    PROPERTY INTERFACE_LINK_LIBRARIES pybind11::python2_no_register)
-endif()
-
 # In CMake 3.18+, you can find these separately, so include an if
 if(TARGET ${_Python}::Python)
   set_property(
@@ -205,8 +187,6 @@ function(pybind11_add_module target_name)
     python_add_library(${target_name} ${lib_type} ${ARG_UNPARSED_ARGUMENTS})
   elseif("${_Python}" STREQUAL "Python3")
     python3_add_library(${target_name} ${lib_type} ${ARG_UNPARSED_ARGUMENTS})
-  elseif("${_Python}" STREQUAL "Python2")
-    python2_add_library(${target_name} ${lib_type} ${ARG_UNPARSED_ARGUMENTS})
   else()
     message(FATAL_ERROR "Cannot detect FindPython version: ${_Python}")
   endif()
@@ -223,10 +203,6 @@ function(pybind11_add_module target_name)
     target_link_libraries(${target_name} PRIVATE pybind11::windows_extras)
   endif()
 
-  if(DEFINED ${_Python}_VERSION AND ${_Python}_VERSION VERSION_LESS 3)
-    target_link_libraries(${target_name} PRIVATE pybind11::python2_no_register)
-  endif()
-
   # -fvisibility=hidden is required to allow multiple modules compiled against
   # different pybind versions to work properly, and for some features (e.g.
   # py::module_local).  We force it on everything inside the `pybind11`
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index c255e5cfd8..4ee8e52ce9 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -43,7 +43,7 @@ endif()
 
 # A user can set versions manually too
 set(Python_ADDITIONAL_VERSIONS
-    "3.11;3.10;3.9;3.8;3.7;3.6;3.5;3.4"
+    "3.11;3.10;3.9;3.8;3.7;3.6;3.5"
     CACHE INTERNAL "")
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
@@ -122,13 +122,6 @@ set_property(
     INTERFACE_LINK_LIBRARIES pybind11::python_link_helper
     "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
 
-if(PYTHON_VERSION VERSION_LESS 3)
-  set_property(
-    TARGET pybind11::pybind11
-    APPEND
-    PROPERTY INTERFACE_LINK_LIBRARIES pybind11::python2_no_register)
-endif()
-
 set_property(
   TARGET pybind11::embed
   APPEND
diff --git a/tools/setup_global.py.in b/tools/setup_global.py.in
index 8b7e538714..63257447e8 100644
--- a/tools/setup_global.py.in
+++ b/tools/setup_global.py.in
@@ -4,14 +4,9 @@
 # Setup script for pybind11-global (in the sdist or in tools/setup_global.py in the repository)
 # This package is targeted for easy use from CMake.
 
-import contextlib
 import glob
 import os
 import re
-import shutil
-import subprocess
-import sys
-import tempfile
 
 # Setuptools has to be before distutils
 from setuptools import setup
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index 533a75ae71..00d0fd57b3 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -20,7 +20,7 @@ setup(
         "pybind11.share.cmake.pybind11",
     ],
     package_data={
-        "pybind11": ["py.typed", "*.pyi"],
+        "pybind11": ["py.typed"],
         "pybind11.include.pybind11": ["*.h"],
         "pybind11.include.pybind11.detail": ["*.h"],
         "pybind11.include.pybind11.stl": ["*.h"],

From 1a432b426fb9588789450fc4e7a3bf16f9c5d7f1 Mon Sep 17 00:00:00 2001
From: Chris Ohk <utilForever@gmail.com>
Date: Sat, 12 Feb 2022 00:42:48 +0900
Subject: [PATCH 310/638] docs: Correct minor typos (#3721)

---
 noxfile.py                             | 4 ++--
 tests/test_sequences_and_iterators.cpp | 2 +-
 tools/pybind11Config.cmake.in          | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/noxfile.py b/noxfile.py
index c8ab7441ed..cfa84826d2 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,7 +2,7 @@
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERISONS = ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+PYTHON_VERSIONS = ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
 
 
 @nox.session(reuse_venv=True)
@@ -14,7 +14,7 @@ def lint(session: nox.Session) -> None:
     session.run("pre-commit", "run", "-a")
 
 
-@nox.session(python=PYTHON_VERISONS)
+@nox.session(python=PYTHON_VERSIONS)
 def tests(session: nox.Session) -> None:
     """
     Run the tests (requires a compiler).
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index addbfe9bb4..b867f49a25 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -452,7 +452,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             [](IntPairs &self) { return py::make_value_iterator(self, py::call_guard<int>()); },
             py::keep_alive<0, 1>());
 
-    // test_iterater_referencing
+    // test_iterator_referencing
     py::class_<NonCopyableInt>(m, "NonCopyableInt")
         .def(py::init<int>())
         .def("set", &NonCopyableInt::set)
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 6c084d1db8..56e28cf291 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -86,7 +86,7 @@ you can either use the basic targets, or use the FindPython tools:
   set_target_properties(MyModule2 PROPERTIES
                                   INTERPROCEDURAL_OPTIMIZATION ON
                                   CXX_VISIBILITY_PRESET ON
-                                  VISIBLITY_INLINES_HIDDEN ON)
+                                  VISIBILITY_INLINES_HIDDEN ON)
 
 If you build targets yourself, you may be interested in stripping the output
 for reduced size; this is the one other feature that the helper function gives you.

From 522c59ceb27e83750c121d5da3d8b67ac446b754 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 11 Feb 2022 19:06:16 -0500
Subject: [PATCH 311/638] chore: drop Python 3.5 (#3719)

* chore: drop Python 3.5 support

* chore: more fstrings with flynt's help

* ci: drop Python 3.5

* chore: bump dependency versions

* docs: touch up py::args

* tests: remove deprecation warning

* Ban smartquotes

* Very minor tweaks (by-product of reviewing PR #3719).

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 .github/CONTRIBUTING.md                    | 11 +++---
 .github/workflows/ci.yml                   | 15 ++++-----
 .pre-commit-config.yaml                    | 39 ++++++++++++----------
 README.rst                                 | 14 ++++----
 docs/advanced/cast/overview.rst            |  3 +-
 docs/advanced/functions.rst                | 21 ++++++------
 docs/advanced/pycpp/numpy.rst              |  2 +-
 docs/benchmark.py                          | 25 ++++++--------
 docs/changelog.rst                         |  2 +-
 docs/compiling.rst                         |  9 +++--
 docs/conf.py                               |  4 +--
 docs/faq.rst                               |  2 +-
 docs/requirements.txt                      |  8 ++---
 docs/upgrade.rst                           |  2 +-
 include/pybind11/cast.h                    |  2 +-
 include/pybind11/chrono.h                  | 11 ------
 include/pybind11/detail/common.h           | 19 +++--------
 include/pybind11/detail/type_caster_base.h | 11 +++---
 include/pybind11/pybind11.h                |  6 ++--
 include/pybind11/stl/filesystem.h          |  3 +-
 noxfile.py                                 |  2 +-
 pybind11/__init__.py                       |  4 +--
 pybind11/setup_helpers.py                  | 10 +++---
 setup.cfg                                  | 16 ++-------
 setup.py                                   | 20 ++++-------
 tests/extra_python_package/test_files.py   | 18 +++++-----
 tests/extra_setuptools/test_setuphelper.py |  4 +--
 tests/pytest.ini                           |  9 +++--
 tests/requirements.txt                     | 16 ++++-----
 tests/test_builtin_casters.py              |  2 +-
 tests/test_callbacks.py                    | 12 ++-----
 tests/test_chrono.py                       |  2 +-
 tests/test_cmake_build/test.py             |  2 +-
 tests/test_eigen.py                        |  6 ++--
 tests/test_exceptions.py                   |  2 +-
 tests/test_numpy_array.py                  | 13 +++-----
 tests/test_numpy_dtypes.py                 |  4 +--
 tests/test_opaque_types.py                 |  2 +-
 tests/test_pytypes.py                      |  4 +--
 tests/test_sequences_and_iterators.py      | 21 ++++--------
 tests/test_smart_ptr.py                    | 12 +++----
 tests/test_virtual_functions.py            |  4 +--
 tools/FindPythonLibsNew.cmake              |  2 +-
 tools/libsize.py                           |  4 +--
 tools/pybind11Config.cmake.in              |  2 +-
 tools/pybind11NewTools.cmake               |  2 +-
 tools/pybind11Tools.cmake                  |  2 +-
 tools/setup_global.py.in                   |  3 +-
 tools/setup_main.py.in                     |  3 +-
 49 files changed, 171 insertions(+), 241 deletions(-)

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index e8294c83c3..c8ec91ff7a 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -93,11 +93,10 @@ cmake --build build -j4
 
 Tips:
 
-* You can use `virtualenv` (from PyPI) instead of `venv` (which is Python 3
-  only).
+* You can use `virtualenv` (faster, from PyPI) instead of `venv`.
 * You can select any name for your environment folder; if it contains "env" it
   will be ignored by git.
-* If you don’t have CMake 3.14+, just add “cmake” to the pip install command.
+* If you don't have CMake 3.14+, just add "cmake" to the pip install command.
 * You can use `-DPYBIND11_FINDPYTHON=ON` to use FindPython on CMake 3.12+
 * In classic mode, you may need to set `-DPYTHON_EXECUTABLE=/path/to/python`.
   FindPython uses `-DPython_ROOT_DIR=/path/to` or
@@ -105,7 +104,7 @@ Tips:
 
 ### Configuration options
 
-In CMake, configuration options are given with “-D”. Options are stored in the
+In CMake, configuration options are given with "-D". Options are stored in the
 build directory, in the `CMakeCache.txt` file, so they are remembered for each
 build directory. Two selections are special - the generator, given with `-G`,
 and the compiler, which is selected based on environment variables `CXX` and
@@ -115,7 +114,7 @@ after the initial run.
 The valid options are:
 
 * `-DCMAKE_BUILD_TYPE`: Release, Debug, MinSizeRel, RelWithDebInfo
-* `-DPYBIND11_FINDPYTHON=ON`: Use CMake 3.12+’s FindPython instead of the
+* `-DPYBIND11_FINDPYTHON=ON`: Use CMake 3.12+'s FindPython instead of the
   classic, deprecated, custom FindPythonLibs
 * `-DPYBIND11_NOPYTHON=ON`: Disable all Python searching (disables tests)
 * `-DBUILD_TESTING=ON`: Enable the tests
@@ -257,7 +256,7 @@ The report is sent to stderr; you can pipe it into a file if you wish.
 ### Build recipes
 
 This builds with the Intel compiler (assuming it is in your path, along with a
-recent CMake and Python 3):
+recent CMake and Python):
 
 ```bash
 python3 -m venv venv
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 07580decd0..b38d228353 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,6 +15,8 @@ concurrency:
 
 env:
   PIP_ONLY_BINARY: numpy
+  FORCE_COLOR: 3
+  PYTEST_TIMEOUT: 300
 
 jobs:
   # This is the "main" test suite, which tests a large number of different
@@ -25,7 +27,6 @@ jobs:
       matrix:
         runs-on: [ubuntu-latest, windows-2022, macos-latest]
         python:
-        - '3.5'
         - '3.6'
         - '3.9'
         - '3.10'
@@ -167,7 +168,7 @@ jobs:
     # setuptools
     - name: Setuptools helpers test
       run: pytest tests/extra_setuptools
-      if: "!(matrix.python == '3.5' && matrix.runs-on == 'windows-2022')"
+      if: "!(matrix.runs-on == 'windows-2022')"
 
 
   deadsnakes:
@@ -624,9 +625,9 @@ jobs:
 
   # This tests an "install" with the CMake tools
   install-classic:
-    name: "🐍 3.5 • Debian • x86 •  Install"
+    name: "🐍 3.7 • Debian • x86 •  Install"
     runs-on: ubuntu-latest
-    container: i386/debian:stretch
+    container: i386/debian:buster
 
     steps:
     - uses: actions/checkout@v1
@@ -635,7 +636,7 @@ jobs:
       run: |
         apt-get update
         apt-get install -y git make cmake g++ libeigen3-dev python3-dev python3-pip
-        pip3 install "pytest==3.1.*"
+        pip3 install "pytest==6.*"
 
     - name: Configure for install
       run: >
@@ -704,12 +705,10 @@ jobs:
       fail-fast: false
       matrix:
         python:
-        - 3.5
         - 3.6
         - 3.7
         - 3.8
         - 3.9
-        - pypy-3.6
 
         include:
           - python: 3.9
@@ -810,7 +809,7 @@ jobs:
       fail-fast: false
       matrix:
         python:
-          - 3.5
+          - 3.6
           - 3.7
         std:
           - 14
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 6d44d5e76c..564d50042c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,7 +15,7 @@
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: v4.1.0
+  rev: "v4.1.0"
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
@@ -32,26 +32,26 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.31.0
+  rev: "v2.31.0"
   hooks:
   - id: pyupgrade
-    args: [--py3-plus]
+    args: [--py36-plus]
 
 # Nicely sort includes
 - repo: https://github.com/PyCQA/isort
-  rev: 5.10.1
+  rev: "5.10.1"
   hooks:
   - id: isort
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: 22.1.0 # Keep in sync with blacken-docs
+  rev: "22.1.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
 # Also code format the docs
 - repo: https://github.com/asottile/blacken-docs
-  rev: v1.12.1
+  rev: "v1.12.1"
   hooks:
   - id: blacken-docs
     additional_dependencies:
@@ -59,32 +59,37 @@ repos:
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: v1.1.11
+  rev: "v1.1.11"
   hooks:
   - id: remove-tabs
 
+- repo: https://github.com/sirosen/texthooks
+  rev: "0.2.2"
+  hooks:
+  - id: fix-ligatures
+  - id: fix-smartquotes
+
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: v1.1.0
+  rev: "v1.1.0"
   hooks:
   - id: pycln
 
 # Checking for common mistakes
 - repo: https://github.com/pre-commit/pygrep-hooks
-  rev: v1.9.0
+  rev: "v1.9.0"
   hooks:
   - id: python-check-blanket-noqa
   - id: python-check-blanket-type-ignore
   - id: python-no-log-warn
-  # Python 3.6
-  # - id: python-use-type-annotations
+  - id: python-use-type-annotations
   - id: rst-backticks
   - id: rst-directive-colons
   - id: rst-inline-touching-normal
 
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
-  rev: 4.0.1
+  rev: "4.0.1"
   hooks:
   - id: flake8
     additional_dependencies: &flake8_dependencies
@@ -94,14 +99,14 @@ repos:
 
 # Automatically remove noqa that are not used
 - repo: https://github.com/asottile/yesqa
-  rev: v1.3.0
+  rev: "v1.3.0"
   hooks:
   - id: yesqa
     additional_dependencies: *flake8_dependencies
 
 # CMake formatting
 - repo: https://github.com/cheshirekow/cmake-format-precommit
-  rev: v0.6.13
+  rev: "v0.6.13"
   hooks:
   - id: cmake-format
     additional_dependencies: [pyyaml]
@@ -110,7 +115,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.931
+  rev: "v0.931"
   hooks:
   - id: mypy
     args: [--show-error-codes]
@@ -128,7 +133,7 @@ repos:
 
 # Check for spelling
 - repo: https://github.com/codespell-project/codespell
-  rev: v2.1.0
+  rev: "v2.1.0"
   hooks:
   - id: codespell
     exclude: ".supp$"
@@ -136,7 +141,7 @@ repos:
 
 # Check for common shell mistakes
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: v0.8.0.4
+  rev: "v0.8.0.4"
   hooks:
   - id: shellcheck
 
diff --git a/README.rst b/README.rst
index 6398db4f0b..0edcd9179a 100644
--- a/README.rst
+++ b/README.rst
@@ -32,9 +32,9 @@ this heavy machinery has become an excessively large and unnecessary
 dependency.
 
 Think of this library as a tiny self-contained version of Boost.Python
-with everything stripped away that isn’t relevant for binding
+with everything stripped away that isn't relevant for binding
 generation. Without comments, the core header files only require ~4K
-lines of code and depend on Python (3.5+, or PyPy) and the C++
+lines of code and depend on Python (3.6+, or PyPy) and the C++
 standard library. This compact implementation was possible thanks to
 some of the new C++11 language features (specifically: tuples, lambda
 functions and variadic templates). Since its creation, this library has
@@ -78,8 +78,8 @@ Goodies
 In addition to the core functionality, pybind11 provides some extra
 goodies:
 
-- Python 3.5+, and PyPy3 7.3 are supported with an implementation-agnostic
-  interface (pybind11 2.9 was the last version to support Python 2).
+- Python 3.6+, and PyPy3 7.3 are supported with an implementation-agnostic
+  interface (pybind11 2.9 was the last version to support Python 2 and 3.5).
 
 - It is possible to bind C++11 lambda functions with captured
   variables. The lambda capture data is stored inside the resulting
@@ -88,8 +88,8 @@ goodies:
 - pybind11 uses C++11 move constructors and move assignment operators
   whenever possible to efficiently transfer custom data types.
 
-- It’s easy to expose the internal storage of custom data types through
-  Pythons’ buffer protocols. This is handy e.g. for fast conversion
+- It's easy to expose the internal storage of custom data types through
+  Pythons' buffer protocols. This is handy e.g. for fast conversion
   between C++ matrix classes like Eigen and NumPy without expensive
   copy operations.
 
@@ -119,7 +119,7 @@ goodies:
 Supported compilers
 -------------------
 
-1. Clang/LLVM 3.3 or newer (for Apple Xcode’s clang, this is 5.0.0 or
+1. Clang/LLVM 3.3 or newer (for Apple Xcode's clang, this is 5.0.0 or
    newer)
 2. GCC 4.8 or newer
 3. Microsoft Visual Studio 2015 Update 3 or newer
diff --git a/docs/advanced/cast/overview.rst b/docs/advanced/cast/overview.rst
index 6a834a3e51..011bd4c7a3 100644
--- a/docs/advanced/cast/overview.rst
+++ b/docs/advanced/cast/overview.rst
@@ -167,5 +167,4 @@ as arguments and return values, refer to the section on binding :ref:`classes`.
 +------------------------------------+---------------------------+-----------------------------------+
 
 .. [#] ``std::filesystem::path`` is converted to ``pathlib.Path`` and
-   ``os.PathLike`` is converted to ``std::filesystem::path``, but this requires
-   Python 3.6 (for ``__fspath__`` support).
+   ``os.PathLike`` is converted to ``std::filesystem::path``.
diff --git a/docs/advanced/functions.rst b/docs/advanced/functions.rst
index bf5b5fa00d..69e3d8a1df 100644
--- a/docs/advanced/functions.rst
+++ b/docs/advanced/functions.rst
@@ -372,7 +372,7 @@ like so:
 Keyword-only arguments
 ======================
 
-Python 3 introduced keyword-only arguments by specifying an unnamed ``*``
+Python implements keyword-only arguments by specifying an unnamed ``*``
 argument in a function definition:
 
 .. code-block:: python
@@ -395,19 +395,18 @@ argument annotations when registering the function:
     m.def("f", [](int a, int b) { /* ... */ },
           py::arg("a"), py::kw_only(), py::arg("b"));
 
-Note that you currently cannot combine this with a ``py::args`` argument.  This
-feature does *not* require Python 3 to work.
-
 .. versionadded:: 2.6
 
-As of pybind11 2.9, a ``py::args`` argument implies that any following arguments
-are keyword-only, as if ``py::kw_only()`` had been specified in the same
-relative location of the argument list as the ``py::args`` argument.  The
-``py::kw_only()`` may be included to be explicit about this, but is not
-required.  (Prior to 2.9 ``py::args`` may only occur at the end of the argument
-list, or immediately before a ``py::kwargs`` argument at the end).
+A ``py::args`` argument implies that any following arguments are keyword-only,
+as if ``py::kw_only()`` had been specified in the same relative location of the
+argument list as the ``py::args`` argument.  The ``py::kw_only()`` may be
+included to be explicit about this, but is not required.
+
+.. versionchanged:: 2.9
+   This can now be combined with ``py::args``. Before, ``py::args`` could only
+   occur at the end of the argument list, or immediately before a ``py::kwargs``
+   argument at the end.
 
-.. versionadded:: 2.9
 
 Positional-only arguments
 =========================
diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index dbc48440a6..8ad3410045 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -395,7 +395,7 @@ uses of ``py::array``:
 Ellipsis
 ========
 
-Python 3 provides a convenient ``...`` ellipsis notation that is often used to
+Python provides a convenient ``...`` ellipsis notation that is often used to
 slice multidimensional arrays. For instance, the following snippet extracts the
 middle dimensions of a tensor with the first and last index set to zero.
 
diff --git a/docs/benchmark.py b/docs/benchmark.py
index a595342926..2150b6ca78 100644
--- a/docs/benchmark.py
+++ b/docs/benchmark.py
@@ -11,20 +11,20 @@ def generate_dummy_code_pybind11(nclasses=10):
     bindings = ""
 
     for cl in range(nclasses):
-        decl += "class cl%03i;\n" % cl
+        decl += f"class cl{cl:03};\n"
     decl += "\n"
 
     for cl in range(nclasses):
-        decl += "class cl%03i {\n" % cl
+        decl += f"class {cl:03} {{\n"
         decl += "public:\n"
-        bindings += '    py::class_<cl%03i>(m, "cl%03i")\n' % (cl, cl)
+        bindings += f'    py::class_<cl{cl:03}>(m, "cl{cl:03}")\n'
         for fn in range(nfns):
             ret = random.randint(0, nclasses - 1)
             params = [random.randint(0, nclasses - 1) for i in range(nargs)]
-            decl += "    cl%03i *fn_%03i(" % (ret, fn)
-            decl += ", ".join("cl%03i *" % p for p in params)
+            decl += f"    cl{ret:03} *fn_{fn:03}("
+            decl += ", ".join(f"cl{p:03} *" for p in params)
             decl += ");\n"
-            bindings += '        .def("fn_%03i", &cl%03i::fn_%03i)\n' % (fn, cl, fn)
+            bindings += f'        .def("fn_{fn:03}", &cl{cl:03}::fn_{fn:03})\n'
         decl += "};\n\n"
         bindings += "        ;\n"
 
@@ -42,23 +42,20 @@ def generate_dummy_code_boost(nclasses=10):
     bindings = ""
 
     for cl in range(nclasses):
-        decl += "class cl%03i;\n" % cl
+        decl += f"class cl{cl:03};\n"
     decl += "\n"
 
     for cl in range(nclasses):
         decl += "class cl%03i {\n" % cl
         decl += "public:\n"
-        bindings += '    py::class_<cl%03i>("cl%03i")\n' % (cl, cl)
+        bindings += f'    py::class_<cl{cl:03}>("cl{cl:03}")\n'
         for fn in range(nfns):
             ret = random.randint(0, nclasses - 1)
             params = [random.randint(0, nclasses - 1) for i in range(nargs)]
-            decl += "    cl%03i *fn_%03i(" % (ret, fn)
-            decl += ", ".join("cl%03i *" % p for p in params)
+            decl += f"    cl{ret:03} *fn_{fn:03}("
+            decl += ", ".join(f"cl{p:03} *" for p in params)
             decl += ");\n"
-            bindings += (
-                '        .def("fn_%03i", &cl%03i::fn_%03i, py::return_value_policy<py::manage_new_object>())\n'
-                % (fn, cl, fn)
-            )
+            bindings += f'        .def("fn_{fn:03}", &cl{cl:03}::fn_{fn:03}, py::return_value_policy<py::manage_new_object>())\n'
         decl += "};\n\n"
         bindings += "        ;\n"
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 63c7f41d8f..9d7693cddc 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -800,7 +800,7 @@ Packaging / building improvements:
   `#2338 <https://github.com/pybind/pybind11/pull/2338>`_ and
   `#2370 <https://github.com/pybind/pybind11/pull/2370>`_
 
-  * Full integration with CMake’s C++ standard system and compile features
+  * Full integration with CMake's C++ standard system and compile features
     replaces ``PYBIND11_CPP_STANDARD``.
 
   * Generated config file is now portable to different Python/compiler/CMake
diff --git a/docs/compiling.rst b/docs/compiling.rst
index f7303fd23f..4ae9234e15 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -417,10 +417,10 @@ existing targets instead:
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.15...3.19)
+    cmake_minimum_required(VERSION 3.15...3.22)
     project(example LANGUAGES CXX)
 
-    find_package(Python COMPONENTS Interpreter Development REQUIRED)
+    find_package(Python 3.6 COMPONENTS Interpreter Development REQUIRED)
     find_package(pybind11 CONFIG REQUIRED)
     # or add_subdirectory(pybind11)
 
@@ -433,9 +433,8 @@ algorithms from the CMake invocation, with ``-DPYBIND11_FINDPYTHON=ON``.
 
 .. warning::
 
-    If you use FindPython2 and FindPython3 to dual-target Python, use the
-    individual targets listed below, and avoid targets that directly include
-    Python parts.
+    If you use FindPython to multi-target Python versions, use the individual
+    targets listed below, and avoid targets that directly include Python parts.
 
 There are `many ways to hint or force a discovery of a specific Python
 installation <https://cmake.org/cmake/help/latest/module/FindPython.html>`_),
diff --git a/docs/conf.py b/docs/conf.py
index 99f3be349c..00796fbdbe 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -344,9 +344,9 @@ def generate_doxygen_xml(app):
         subprocess.call(["doxygen", "--version"])
         retcode = subprocess.call(["doxygen"], cwd=app.confdir)
         if retcode < 0:
-            sys.stderr.write("doxygen error code: {}\n".format(-retcode))
+            sys.stderr.write(f"doxygen error code: {-retcode}\n")
     except OSError as e:
-        sys.stderr.write("doxygen execution failed: {}\n".format(e))
+        sys.stderr.write(f"doxygen execution failed: {e}\n")
 
 
 def prepare(app):
diff --git a/docs/faq.rst b/docs/faq.rst
index 69c3442e3b..a6b9913126 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -145,7 +145,7 @@ using C++14 template metaprogramming.
 
 .. _`faq:hidden_visibility`:
 
-"‘SomeClass’ declared with greater visibility than the type of its field ‘SomeClass::member’ [-Wattributes]"
+"'SomeClass' declared with greater visibility than the type of its field 'SomeClass::member' [-Wattributes]"
 ============================================================================================================
 
 This error typically indicates that you are compiling without the required
diff --git a/docs/requirements.txt b/docs/requirements.txt
index b2801b1f0d..e452ed261f 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,5 +1,5 @@
-breathe==4.31.0
-sphinx==3.5.4
+breathe==4.32.0
+sphinx==4.4.0
 sphinx_rtd_theme==1.0.0
-sphinxcontrib-moderncmakedomain==3.19
-sphinxcontrib-svg2pdfconverter==1.1.1
+sphinxcontrib-moderncmakedomain==3.21.4
+sphinxcontrib-svg2pdfconverter==1.2.0
diff --git a/docs/upgrade.rst b/docs/upgrade.rst
index d91d51e6f2..6a9db2d08f 100644
--- a/docs/upgrade.rst
+++ b/docs/upgrade.rst
@@ -524,7 +524,7 @@ include a declaration of the form:
 
     PYBIND11_DECLARE_HOLDER_TYPE(T, std::shared_ptr<T>)
 
-Continuing to do so won’t cause an error or even a deprecation warning,
+Continuing to do so won't cause an error or even a deprecation warning,
 but it's completely redundant.
 
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index b12559ac8b..553d7616c1 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1585,7 +1585,7 @@ unpacking_collector<policy> collect_arguments(Args &&...args) {
 template <typename Derived>
 template <return_value_policy policy, typename... Args>
 object object_api<Derived>::operator()(Args &&...args) const {
-#if !defined(NDEBUG) && PY_VERSION_HEX >= 0x03060000
+#ifndef NDEBUG
     if (!PyGILState_Check()) {
         pybind11_fail("pybind11::object_api<>::operator() PyGILState_Check() failure.");
     }
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index ad5e97b024..167ea0e3d1 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -18,17 +18,6 @@
 #include <datetime.h>
 #include <mutex>
 
-// Backport the PyDateTime_DELTA functions from Python3.3 if required
-#ifndef PyDateTime_DELTA_GET_DAYS
-#    define PyDateTime_DELTA_GET_DAYS(o) (((PyDateTime_Delta *) o)->days)
-#endif
-#ifndef PyDateTime_DELTA_GET_SECONDS
-#    define PyDateTime_DELTA_GET_SECONDS(o) (((PyDateTime_Delta *) o)->seconds)
-#endif
-#ifndef PyDateTime_DELTA_GET_MICROSECONDS
-#    define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta *) o)->microseconds)
-#endif
-
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index a5d98d71f8..c1d2de13a7 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -211,8 +211,8 @@
 #endif
 
 #include <Python.h>
-#if PY_VERSION_HEX < 0x030500f0
-#    error "PYTHON 2 IS NO LONGER SUPPORTED. pybind11 v2.9 was the last to support Python 2."
+#if PY_VERSION_HEX < 0x03060000
+#    error "PYTHON < 3.6 IS UNSUPPORTED. pybind11 v2.9 was the last to support Python 2 and 3.5."
 #endif
 #include <frameobject.h>
 #include <pythread.h>
@@ -301,15 +301,6 @@
     extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();                   \
     extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
 
-#if PY_VERSION_HEX >= 0x03050000 && PY_VERSION_HEX < 0x03050200
-extern "C" {
-struct _Py_atomic_address {
-    void *value;
-};
-PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
-}
-#endif
-
 #define PYBIND11_TRY_NEXT_OVERLOAD ((PyObject *) 1) // special failure return code
 #define PYBIND11_STRINGIFY(x) #x
 #define PYBIND11_TOSTRING(x) PYBIND11_STRINGIFY(x)
@@ -438,7 +429,7 @@ enum class return_value_policy : uint8_t {
 
     /** Reference an existing object (i.e. do not create a new copy) and take
         ownership. Python will call the destructor and delete operator when the
-        object’s reference count reaches zero. Undefined behavior ensues when
+        object's reference count reaches zero. Undefined behavior ensues when
         the C++ side does the same.. */
     take_ownership,
 
@@ -454,7 +445,7 @@ enum class return_value_policy : uint8_t {
     move,
 
     /** Reference an existing object, but do not take ownership. The C++ side
-        is responsible for managing the object’s lifetime and deallocating it
+        is responsible for managing the object's lifetime and deallocating it
         when it is no longer used. Warning: undefined behavior will ensue when
         the C++ side deletes an object that is still referenced and used by
         Python. */
@@ -463,7 +454,7 @@ enum class return_value_policy : uint8_t {
     /** This policy only applies to methods and properties. It references the
         object without taking ownership similar to the above
         return_value_policy::reference policy. In contrast to that policy, the
-        function or property’s implicit this argument (called the parent) is
+        function or property's implicit this argument (called the parent) is
         considered to be the the owner of the return value (the child).
         pybind11 then couples the lifetime of the parent to the child via a
         reference relationship that ensures that the parent cannot be garbage
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 226f7a994f..ff7d7cf8c2 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -439,10 +439,11 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
                                         // instance_registered)
 
         // Allocate space for flags, values, and holders, and initialize it to 0 (flags and values,
-        // in particular, need to be 0).  Use Python's memory allocation functions: in Python 3.6
-        // they default to using pymalloc, which is designed to be efficient for small allocations
-        // like the one we're doing here; in earlier versions (and for larger allocations) they are
-        // just wrappers around malloc.
+        // in particular, need to be 0).  Use Python's memory allocation
+        // functions: Python is using pymalloc, which is designed to be
+        // efficient for small allocations like the one we're doing here;
+        // for larger allocations they are just wrappers around malloc.
+        // TODO: is this still true for pure Python 3.6?
         nonsimple.values_and_holders = (void **) PyMem_Calloc(space, sizeof(void *));
         if (!nonsimple.values_and_holders) {
             throw std::bad_alloc();
@@ -538,8 +539,6 @@ PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_i
 inline PyThreadState *get_thread_state_unchecked() {
 #if defined(PYPY_VERSION)
     return PyThreadState_GET();
-#elif PY_VERSION_HEX < 0x03050200
-    return (PyThreadState *) _PyThreadState_Current.value;
 #else
     return _PyThreadState_UncheckedGet();
 #endif
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 7b7a1a05dd..22b629f40d 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1213,7 +1213,7 @@ class module_ : public object {
         PyModule_AddObject(ptr(), name, obj.inc_ref().ptr() /* steals a reference */);
     }
 
-    using module_def = PyModuleDef;
+    using module_def = PyModuleDef; // TODO: Can this be removed (it was needed only for Python 2)?
 
     /** \rst
         Create a new top-level module that can be used as the main module of a C extension.
@@ -1241,8 +1241,8 @@ class module_ : public object {
             pybind11_fail("Internal error in module_::create_extension_module()");
         }
         // TODO: Should be reinterpret_steal for Python 3, but Python also steals it again when
-        // returned from PyInit_...
-        //       For Python 2, reinterpret_borrow is correct.
+        //       returned from PyInit_...
+        //       For Python 2, reinterpret_borrow was correct.
         return reinterpret_borrow<module_>(m);
     }
 };
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 747992f51c..93727424c9 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -13,8 +13,7 @@
 #include <string>
 
 #ifdef __has_include
-#    if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
-      PY_VERSION_HEX >= 0x03060000
+#    if defined(PYBIND11_CPP17) && __has_include(<filesystem>)
 #        include <filesystem>
 #        define PYBIND11_HAS_FILESYSTEM 1
 #    endif
diff --git a/noxfile.py b/noxfile.py
index cfa84826d2..4b6adcfbd7 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,7 +2,7 @@
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERSIONS = ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
 
 
 @nox.session(reuse_venv=True)
diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index faf3892cb6..a1be969819 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -1,7 +1,7 @@
 import sys
 
-if sys.version_info < (3, 5):
-    msg = "pybind11 does not support Python < 3.5. 2.9 was the last release supporting older Pythons."
+if sys.version_info < (3, 6):
+    msg = "pybind11 does not support Python < 3.6. 2.9 was the last release supporting Python 2.7 and 3.5."
     raise ImportError(msg)
 
 
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 9cbcaa9224..e3271ca60d 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -200,7 +200,7 @@ def cxx_std(self, level: int) -> None:
             current_macos = tuple(int(x) for x in platform.mac_ver()[0].split(".")[:2])
             desired_macos = (10, 9) if level < 17 else (10, 14)
             macos_string = ".".join(str(x) for x in min(current_macos, desired_macos))
-            macosx_min = "-mmacosx-version-min={}".format(macos_string)
+            macosx_min = f"-mmacosx-version-min={macos_string}"
             cflags += [macosx_min]
             ldflags += [macosx_min]
 
@@ -322,9 +322,9 @@ def intree_extensions(
 
     if not exts:
         msg = (
-            "path {path} is not a child of any of the directories listed "
-            "in 'package_dir' ({package_dir})"
-        ).format(path=path, package_dir=package_dir)
+            f"path {path} is not a child of any of the directories listed "
+            f"in 'package_dir' ({package_dir})"
+        )
         raise ValueError(msg)
 
     return exts
@@ -419,7 +419,7 @@ def __init__(
         self.default = default
         self.max = max
         self.needs_recompile = needs_recompile
-        self._old = []  # type: List[CCompilerMethod]
+        self._old: List[CCompilerMethod] = []
 
     def function(self) -> CCompilerMethod:
         """
diff --git a/setup.cfg b/setup.cfg
index bd2357e9e8..11b4fde8f3 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -14,7 +14,6 @@ classifiers =
     Topic :: Utilities
     Programming Language :: C++
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
@@ -38,7 +37,7 @@ project_urls =
     Chat = https://gitter.im/pybind/Lobby
 
 [options]
-python_requires = >=3.5
+python_requires = >=3.6
 zip_safe = False
 
 
@@ -46,14 +45,5 @@ zip_safe = False
 max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
-ignore =
-    # required for pretty matrix formatting: multiple spaces after `,` and `[`
-    E201, E241, W504,
-    # camelcase 'cPickle' imported as lowercase 'pickle'
-    N813
-    # Black conflict
-    W503, E203
-
-
-[tool:pytest]
-timeout = 300
+extend-ignore = E203, E722, B950
+select = C,E,F,N,W,B,B9
diff --git a/setup.py b/setup.py
index 5b46e0c8d8..a149755bf6 100644
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
 
@@ -41,12 +41,10 @@ def build_expected_version_hex(matches: Dict[str, str]) -> str:
                     serial = int(level_serial[len(level) :])
                     break
     if serial is None:
-        msg = 'Invalid PYBIND11_VERSION_PATCH: "{}"'.format(patch_level_serial)
+        msg = f'Invalid PYBIND11_VERSION_PATCH: "{patch_level_serial}"'
         raise RuntimeError(msg)
-    version_hex_str = "{:02x}{:02x}{:02x}{}{:x}".format(
-        major, minor, patch, level[:1], serial
-    )
-    return "0x{}".format(version_hex_str.upper())
+    version_hex_str = f"{major:02x}{minor:02x}{patch:02x}{level[:1]}{serial:x}"
+    return f"0x{version_hex_str.upper()}"
 
 
 # PYBIND11_GLOBAL_SDIST will build a different sdist, with the python-headers
@@ -66,7 +64,7 @@ def build_expected_version_hex(matches: Dict[str, str]) -> str:
 
 
 # Read the listed version
-loc = {}  # type: Dict[str, str]
+loc: Dict[str, str] = {}
 code = compile(VERSION_FILE.read_text(encoding="utf-8"), "pybind11/_version.py", "exec")
 exec(code, loc)
 version = loc["__version__"]
@@ -75,17 +73,13 @@ def build_expected_version_hex(matches: Dict[str, str]) -> str:
 matches = dict(VERSION_REGEX.findall(COMMON_FILE.read_text(encoding="utf8")))
 cpp_version = "{MAJOR}.{MINOR}.{PATCH}".format(**matches)
 if version != cpp_version:
-    msg = "Python version {} does not match C++ version {}!".format(
-        version, cpp_version
-    )
+    msg = f"Python version {version} does not match C++ version {cpp_version}!"
     raise RuntimeError(msg)
 
 version_hex = matches.get("HEX", "MISSING")
 exp_version_hex = build_expected_version_hex(matches)
 if version_hex != exp_version_hex:
-    msg = "PYBIND11_VERSION_HEX {} does not match expected value {}!".format(
-        version_hex, exp_version_hex
-    )
+    msg = f"PYBIND11_VERSION_HEX {version_hex} does not match expected value {exp_version_hex}!"
     raise RuntimeError(msg)
 
 
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 70dcfb987a..a6b13bc5f0 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -145,9 +145,9 @@ def test_build_sdist(monkeypatch, tmpdir):
             contents = f.read().decode("utf8")
         assert 'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")' in contents
 
-    files = {"pybind11/{}".format(n) for n in all_files}
+    files = {f"pybind11/{n}" for n in all_files}
     files |= sdist_files
-    files |= {"pybind11{}".format(n) for n in local_sdist_files}
+    files |= {f"pybind11{n}" for n in local_sdist_files}
     files.add("pybind11.egg-info/entry_points.txt")
     files.add("pybind11.egg-info/requires.txt")
     assert simpler == files
@@ -200,9 +200,9 @@ def test_build_global_dist(monkeypatch, tmpdir):
         ) as f:
             pyproject_toml = f.read()
 
-    files = {"pybind11/{}".format(n) for n in all_files}
+    files = {f"pybind11/{n}" for n in all_files}
     files |= sdist_files
-    files |= {"pybind11_global{}".format(n) for n in local_sdist_files}
+    files |= {f"pybind11_global{n}" for n in local_sdist_files}
     assert simpler == files
 
     with open(os.path.join(MAIN_DIR, "tools", "setup_global.py.in"), "rb") as f:
@@ -227,7 +227,7 @@ def tests_build_wheel(monkeypatch, tmpdir):
 
     (wheel,) = tmpdir.visit("*.whl")
 
-    files = {"pybind11/{}".format(n) for n in all_files}
+    files = {f"pybind11/{n}" for n in all_files}
     files |= {
         "dist-info/LICENSE",
         "dist-info/METADATA",
@@ -241,9 +241,7 @@ def tests_build_wheel(monkeypatch, tmpdir):
         names = z.namelist()
 
     trimmed = {n for n in names if "dist-info" not in n}
-    trimmed |= {
-        "dist-info/{}".format(n.split("/", 1)[-1]) for n in names if "dist-info" in n
-    }
+    trimmed |= {f"dist-info/{n.split('/', 1)[-1]}" for n in names if "dist-info" in n}
     assert files == trimmed
 
 
@@ -257,8 +255,8 @@ def tests_build_global_wheel(monkeypatch, tmpdir):
 
     (wheel,) = tmpdir.visit("*.whl")
 
-    files = {"data/data/{}".format(n) for n in src_files}
-    files |= {"data/headers/{}".format(n[8:]) for n in headers}
+    files = {f"data/data/{n}" for n in src_files}
+    files |= {f"data/headers/{n[8:]}" for n in headers}
     files |= {
         "dist-info/LICENSE",
         "dist-info/METADATA",
diff --git a/tests/extra_setuptools/test_setuphelper.py b/tests/extra_setuptools/test_setuphelper.py
index 3a771e558d..d5d3093bf0 100644
--- a/tests/extra_setuptools/test_setuphelper.py
+++ b/tests/extra_setuptools/test_setuphelper.py
@@ -18,7 +18,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
 
     (tmpdir / "setup.py").write_text(
         dedent(
-            """\
+            f"""\
             import sys
             sys.path.append({MAIN_DIR!r})
 
@@ -51,7 +51,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
                 ext_modules=ext_modules,
             )
             """
-        ).format(MAIN_DIR=MAIN_DIR, std=std, parallel=parallel),
+        ),
         encoding="ascii",
     )
 
diff --git a/tests/pytest.ini b/tests/pytest.ini
index a3871d6c3a..792ba361f7 100644
--- a/tests/pytest.ini
+++ b/tests/pytest.ini
@@ -1,12 +1,15 @@
 [pytest]
-minversion = 3.1
+minversion = 3.10
 norecursedirs = test_* extra_*
 xfail_strict = True
 addopts =
-    # show summary of skipped tests
-    -rs
+    # show summary of tests
+    -ra
     # capture only Python print and C++ py::print, but not C output (low-level Python errors)
     --capture=sys
+    # Show local info when a failure occurs
+    --showlocals
+log_cli_level = info
 filterwarnings =
     # make warnings into errors but ignore certain third-party extension issues
     error
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 98ca46d28a..1130c3fd5d 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,12 +1,8 @@
-numpy==1.16.6; python_version<"3.6" and sys_platform!="win32" and platform_python_implementation!="PyPy"
-numpy==1.19.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.6"
-numpy==1.20.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
+numpy==1.21.5; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
 numpy==1.19.3; platform_python_implementation!="PyPy" and python_version=="3.6"
-numpy==1.21.3; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.11"
-py @ git+https://github.com/pytest-dev/py; python_version>="3.11"
-pytest==4.6.9; python_version<"3.5"
-pytest==6.1.2; python_version=="3.5"
-pytest==6.2.4; python_version>="3.6"
+numpy==1.21.5; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.10"
+numpy==1.22.2; platform_python_implementation!="PyPy" and python_version>="3.10" and python_version<"3.11"
+pytest==7.0.0
 pytest-timeout
-scipy==1.2.3; platform_python_implementation!="PyPy" and python_version<"3.6"
-scipy==1.5.4; platform_python_implementation!="PyPy" and python_version>="3.6" and python_version<"3.10"
+scipy==1.5.4; platform_python_implementation!="PyPy" and python_version<"3.10"
+scipy==1.8.0; platform_python_implementation!="PyPy" and python_version=="3.10"
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 74014c9cf4..02207f24fc 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -50,7 +50,7 @@ def test_single_char_arguments():
     """Tests failures for passing invalid inputs to char-accepting functions"""
 
     def toobig_message(r):
-        return "Character code point not in range({:#x})".format(r)
+        return f"Character code point not in range({r:#x})"
 
     toolong_message = "Expected a character, but multi-character string found"
 
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 74aec21e5e..0b1047bbf2 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -17,7 +17,7 @@ def func2(a, b, c, d):
         return "func2", a, b, c, d
 
     def func3(a):
-        return "func3({})".format(a)
+        return f"func3({a})"
 
     assert m.test_callback1(func1) == "func1"
     assert m.test_callback2(func2) == ("func2", "Hello", "x", True, 5)
@@ -188,14 +188,8 @@ def test_callback_num_times():
         if not rep:
             print()
         print(
-            "callback_num_times: {:d} million / {:.3f} seconds = {:.3f} million / second".format(
-                num_millions, td, rate
-            )
+            f"callback_num_times: {num_millions:d} million / {td:.3f} seconds = {rate:.3f} million / second"
         )
     if len(rates) > 1:
         print("Min    Mean   Max")
-        print(
-            "{:6.3f} {:6.3f} {:6.3f}".format(
-                min(rates), sum(rates) / len(rates), max(rates)
-            )
-        )
+        print(f"{min(rates):6.3f} {sum(rates) / len(rates):6.3f} {max(rates):6.3f}")
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index f419ef387f..7f47b37a25 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -100,7 +100,7 @@ def test_chrono_system_clock_roundtrip_date():
 )
 def test_chrono_system_clock_roundtrip_time(time1, tz, monkeypatch):
     if tz is not None:
-        monkeypatch.setenv("TZ", "/usr/share/zoneinfo/{}".format(tz))
+        monkeypatch.setenv("TZ", f"/usr/share/zoneinfo/{tz}")
 
     # Roundtrip the time
     datetime2 = m.test_chrono2(time1)
diff --git a/tests/test_cmake_build/test.py b/tests/test_cmake_build/test.py
index 5bf129ea33..807fd43b4a 100644
--- a/tests/test_cmake_build/test.py
+++ b/tests/test_cmake_build/test.py
@@ -5,4 +5,4 @@
 assert isinstance(__file__, str)  # Test this is properly set
 
 assert test_cmake_build.add(1, 2) == 3
-print("{} imports, runs, and adds: 1 + 2 = 3".format(sys.argv[1]))
+print(f"{sys.argv[1]} imports, runs, and adds: 1 + 2 = 3")
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index 9a94b35f8b..093773a514 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -221,9 +221,7 @@ def test_nonunit_stride_to_python():
     assert np.all(m.diagonal(ref) == ref.diagonal())
     assert np.all(m.diagonal_1(ref) == ref.diagonal(1))
     for i in range(-5, 7):
-        assert np.all(
-            m.diagonal_n(ref, i) == ref.diagonal(i)
-        ), "m.diagonal_n({})".format(i)
+        assert np.all(m.diagonal_n(ref, i) == ref.diagonal(i)), f"m.diagonal_n({i})"
 
     assert np.all(m.block(ref, 2, 1, 3, 3) == ref[2:5, 1:4])
     assert np.all(m.block(ref, 1, 4, 4, 2) == ref[1:, 4:])
@@ -236,7 +234,7 @@ def test_eigen_ref_to_python():
         mymat = chol(np.array([[1.0, 2, 4], [2, 13, 23], [4, 23, 77]]))
         assert np.all(
             mymat == np.array([[1, 0, 0], [2, 3, 0], [4, 5, 6]])
-        ), "cholesky{}".format(i)
+        ), f"cholesky{i}"
 
 
 def assign_both(a1, a2, r, c, v):
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index e0da55dfd6..0be61804a6 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -88,7 +88,7 @@ def test_python_call_in_catch():
 def ignore_pytest_unraisable_warning(f):
     unraisable = "PytestUnraisableExceptionWarning"
     if hasattr(pytest, unraisable):  # Python >= 3.8 and pytest >= 6
-        dec = pytest.mark.filterwarnings("ignore::pytest.{}".format(unraisable))
+        dec = pytest.mark.filterwarnings(f"ignore::pytest.{unraisable}")
         return dec(f)
     else:
         return f
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 45be592a84..504963b166 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -18,9 +18,7 @@ def test_dtypes():
         assert check.numpy == check.pybind11, check
         if check.numpy.num != check.pybind11.num:
             print(
-                "NOTE: typenum mismatch for {}: {} != {}".format(
-                    check, check.numpy.num, check.pybind11.num
-                )
+                f"NOTE: typenum mismatch for {check}: {check.numpy.num} != {check.pybind11.num}"
             )
 
 
@@ -116,9 +114,7 @@ def test_at_fail(arr, dim):
     for func in m.at_t, m.mutate_at_t:
         with pytest.raises(IndexError) as excinfo:
             func(arr, *([0] * dim))
-        assert str(excinfo.value) == "index dimension mismatch: {} (ndim = 2)".format(
-            dim
-        )
+        assert str(excinfo.value) == f"index dimension mismatch: {dim} (ndim = 2)"
 
 
 def test_at(arr):
@@ -192,8 +188,6 @@ def test_make_empty_shaped_array():
 
 def test_wrap():
     def assert_references(a, b, base=None):
-        from distutils.version import LooseVersion
-
         if base is None:
             base = a
         assert a is not b
@@ -204,7 +198,8 @@ def assert_references(a, b, base=None):
         assert a.flags.f_contiguous == b.flags.f_contiguous
         assert a.flags.writeable == b.flags.writeable
         assert a.flags.aligned == b.flags.aligned
-        if LooseVersion(np.__version__) >= LooseVersion("1.14.0"):
+        # 1.13 supported Python 3.6
+        if tuple(int(x) for x in np.__version__.split(".")[:2]) >= (1, 14):
             assert a.flags.writebackifcopy == b.flags.writebackifcopy
         else:
             assert a.flags.updateifcopy == b.flags.updateifcopy
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 65fd90d7bc..7df60583f8 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -14,7 +14,7 @@ def simple_dtype():
     return np.dtype(
         {
             "names": ["bool_", "uint_", "float_", "ldbl_"],
-            "formats": ["?", "u4", "f4", "f{}".format(ld.itemsize)],
+            "formats": ["?", "u4", "f4", f"f{ld.itemsize}"],
             "offsets": [0, 4, 8, (16 if ld.alignment > 4 else 12)],
         }
     )
@@ -125,7 +125,7 @@ def test_dtype(simple_dtype):
     assert [x.replace(" ", "") for x in m.print_dtypes()] == [
         simple_dtype_fmt(),
         packed_dtype_fmt(),
-        "[('a',{}),('b',{})]".format(simple_dtype_fmt(), packed_dtype_fmt()),
+        f"[('a',{simple_dtype_fmt()}),('b',{packed_dtype_fmt()})]",
         partial_dtype_fmt(),
         partial_nested_fmt(),
         "[('a','S3'),('b','S3')]",
diff --git a/tests/test_opaque_types.py b/tests/test_opaque_types.py
index 8b9d8f59ce..5d4f2a1bf4 100644
--- a/tests/test_opaque_types.py
+++ b/tests/test_opaque_types.py
@@ -12,7 +12,7 @@ def test_string_list():
     assert lst.back() == "Element 2"
 
     for i, k in enumerate(lst, start=1):
-        assert k == "Element {}".format(i)
+        assert k == f"Element {i}"
     lst.pop_back()
     assert m.print_opaque_list(lst) == "Opaque list: [Element 1]"
 
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index f2b1f6b6eb..07ace00491 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -305,8 +305,8 @@ def test_non_converting_constructors():
         for move in [True, False]:
             with pytest.raises(TypeError) as excinfo:
                 m.nonconverting_constructor(t, v, move)
-            expected_error = "Object of type '{}' is not an instance of '{}'".format(
-                type(v).__name__, t
+            expected_error = (
+                f"Object of type '{type(v).__name__}' is not an instance of '{t}'"
             )
             assert str(excinfo.value) == expected_error
 
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index e1441c07cd..062e3b3d30 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -1,20 +1,10 @@
 import pytest
+from pytest import approx
 
 from pybind11_tests import ConstructorStats
 from pybind11_tests import sequences_and_iterators as m
 
 
-def isclose(a, b, rel_tol=1e-05, abs_tol=0.0):
-    """Like math.isclose() from Python 3.5"""
-    return abs(a - b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)
-
-
-def allclose(a_list, b_list, rel_tol=1e-05, abs_tol=0.0):
-    return all(
-        isclose(a, b, rel_tol=rel_tol, abs_tol=abs_tol) for a, b in zip(a_list, b_list)
-    )
-
-
 def test_slice_constructors():
     assert m.make_forward_slice_size_t() == slice(0, -1, 1)
     assert m.make_reversed_slice_object() == slice(None, None, -1)
@@ -117,7 +107,8 @@ def test_sequence():
     assert 12.34 not in s
     s[0], s[3] = 12.34, 56.78
     assert 12.34 in s
-    assert isclose(s[0], 12.34) and isclose(s[3], 56.78)
+    assert s[0] == approx(12.34, rel=1e-05)
+    assert s[3] == approx(56.78, rel=1e-05)
 
     rev = reversed(s)
     assert cstats.values() == ["of size", "5"]
@@ -132,14 +123,14 @@ def test_sequence():
     assert cstats.values() == ["of size", "0"]
 
     expected = [0, 56.78, 0, 0, 12.34]
-    assert allclose(rev, expected)
-    assert allclose(rev2, expected)
+    assert rev == approx(expected, rel=1e-05)
+    assert rev2 == approx(expected, rel=1e-05)
     assert rev == rev2
 
     rev[0::2] = m.Sequence([2.0, 2.0, 2.0])
     assert cstats.values() == ["of size", "3", "from std::vector"]
 
-    assert allclose(rev, [2, 56.78, 2, 0, 2])
+    assert rev == approx([2, 56.78, 2, 0, 2], rel=1e-05)
 
     assert cstats.alive() == 4
     del it
diff --git a/tests/test_smart_ptr.py b/tests/test_smart_ptr.py
index 4097df28b4..2f204e01b1 100644
--- a/tests/test_smart_ptr.py
+++ b/tests/test_smart_ptr.py
@@ -15,7 +15,7 @@ def test_smart_ptr(capture):
             m.print_object_2(o)
             m.print_object_3(o)
             m.print_object_4(o)
-        assert capture == "MyObject1[{i}]\n".format(i=i) * 4
+        assert capture == f"MyObject1[{i}]\n" * 4
 
     for i, o in enumerate(
         [m.make_myobject1_1(), m.make_myobject1_2(), m.MyObject1(6), 7], start=4
@@ -33,13 +33,11 @@ def test_smart_ptr(capture):
             m.print_myobject1_4(o)
 
         times = 4 if isinstance(o, int) else 8
-        assert capture == "MyObject1[{i}]\n".format(i=i) * times
+        assert capture == f"MyObject1[{i}]\n" * times
 
     cstats = ConstructorStats.get(m.MyObject1)
     assert cstats.alive() == 0
-    expected_values = ["MyObject1[{}]".format(i) for i in range(1, 7)] + [
-        "MyObject1[7]"
-    ] * 4
+    expected_values = [f"MyObject1[{i}]" for i in range(1, 7)] + ["MyObject1[7]"] * 4
     assert cstats.values() == expected_values
     assert cstats.default_constructions == 0
     assert cstats.copy_constructions == 0
@@ -57,7 +55,7 @@ def test_smart_ptr(capture):
             m.print_myobject2_2(o)
             m.print_myobject2_3(o)
             m.print_myobject2_4(o)
-        assert capture == "MyObject2[{i}]\n".format(i=i) * 4
+        assert capture == f"MyObject2[{i}]\n" * 4
 
     cstats = ConstructorStats.get(m.MyObject2)
     assert cstats.alive() == 1
@@ -80,7 +78,7 @@ def test_smart_ptr(capture):
             m.print_myobject3_2(o)
             m.print_myobject3_3(o)
             m.print_myobject3_4(o)
-        assert capture == "MyObject3[{i}]\n".format(i=i) * 4
+        assert capture == f"MyObject3[{i}]\n" * 4
 
     cstats = ConstructorStats.get(m.MyObject3)
     assert cstats.alive() == 1
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index 14a8384a8a..4d00d3690d 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -13,7 +13,7 @@ def __init__(self, state):
             self.data = "Hello world"
 
         def run(self, value):
-            print("ExtendedExampleVirt::run(%i), calling parent.." % value)
+            print(f"ExtendedExampleVirt::run({value}), calling parent..")
             return super().run(value + 1)
 
         def run_bool(self):
@@ -24,7 +24,7 @@ def get_string1(self):
             return "override1"
 
         def pure_virtual(self):
-            print("ExtendedExampleVirt::pure_virtual(): %s" % self.data)
+            print(f"ExtendedExampleVirt::pure_virtual(): {self.data}")
 
     class ExtendedExampleVirt2(ExtendedExampleVirt):
         def __init__(self, state):
diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index b3acaaae92..7aeffa4412 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -92,7 +92,7 @@ endif()
 
 # Use the Python interpreter to find the libs.
 if(NOT PythonLibsNew_FIND_VERSION)
-  set(PythonLibsNew_FIND_VERSION "3.5")
+  set(PythonLibsNew_FIND_VERSION "3.6")
 endif()
 
 find_package(PythonInterp ${PythonLibsNew_FIND_VERSION} ${_pythonlibs_required}
diff --git a/tools/libsize.py b/tools/libsize.py
index 5fb20334d8..1ac9afbe81 100644
--- a/tools/libsize.py
+++ b/tools/libsize.py
@@ -13,7 +13,7 @@
 save = sys.argv[2]
 
 if not os.path.exists(lib):
-    sys.exit("Error: requested file ({}) does not exist".format(lib))
+    sys.exit(f"Error: requested file ({lib}) does not exist")
 
 libsize = os.path.getsize(lib)
 
@@ -28,7 +28,7 @@
         if change == 0:
             print(" (no change)")
         else:
-            print(" (change of {:+} bytes = {:+.2%})".format(change, change / oldsize))
+            print(f" (change of {change:+} bytes = {change / oldsize:+.2%})")
 else:
     print()
 
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 56e28cf291..9383e8c671 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -193,7 +193,7 @@ Using ``find_package`` with version info is not recommended except for release v
 .. code-block:: cmake
 
   find_package(pybind11 CONFIG)
-  find_package(pybind11 2.0 EXACT CONFIG REQUIRED)
+  find_package(pybind11 2.9 EXACT CONFIG REQUIRED)
 
 #]=============================================================================]
 @PACKAGE_INIT@
diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index dbf41e0711..abba0fe0e2 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -32,7 +32,7 @@ if(NOT Python_FOUND AND NOT Python3_FOUND)
     set(Python_ROOT_DIR "$ENV{pythonLocation}")
   endif()
 
-  find_package(Python 3.5 REQUIRED COMPONENTS Interpreter Development ${_pybind11_quiet})
+  find_package(Python 3.6 REQUIRED COMPONENTS Interpreter Development ${_pybind11_quiet})
 
   # If we are in submodule mode, export the Python targets to global targets.
   # If this behavior is not desired, FindPython _before_ pybind11.
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 4ee8e52ce9..3d1503df86 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -43,7 +43,7 @@ endif()
 
 # A user can set versions manually too
 set(Python_ADDITIONAL_VERSIONS
-    "3.11;3.10;3.9;3.8;3.7;3.6;3.5"
+    "3.11;3.10;3.9;3.8;3.7;3.6"
     CACHE INTERNAL "")
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
diff --git a/tools/setup_global.py.in b/tools/setup_global.py.in
index 63257447e8..8aa3871783 100644
--- a/tools/setup_global.py.in
+++ b/tools/setup_global.py.in
@@ -1,5 +1,4 @@
-#!/usr/bin/env python
-# -*- coding: utf-8 -*-
+#!/usr/bin/env python3
 
 # Setup script for pybind11-global (in the sdist or in tools/setup_global.py in the repository)
 # This package is targeted for easy use from CMake.
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index 00d0fd57b3..738d73faad 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -1,5 +1,4 @@
-#!/usr/bin/env python
-# -*- coding: utf-8 -*-
+#!/usr/bin/env python3
 
 # Setup script (in the sdist or in tools/setup_main.py in the repository)
 

From 44156477a39368c02dcbe19b771f0ab6fe8ae9bf Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 14 Feb 2022 09:29:06 -0800
Subject: [PATCH 312/638] Adding MSVC 2022 C++20 GitHub Action (#3732)

* Trying another way of adding windows-2022 C++20

* ci: try merging 2019 & 2022

* Revert "ci: try merging 2019 & 2022"

This reverts commit b158a1b79f69a43478dce5b89702858ad5952386.

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml | 45 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b38d228353..629879a5bd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -852,6 +852,51 @@ jobs:
     - name: Run all checks
       run: cmake --build build -t check
 
+  windows-2022:
+    strategy:
+      fail-fast: false
+      matrix:
+        python:
+        - 3.9
+
+    name: "🐍 ${{ matrix.python }} • MSVC 2022 C++20 • x64"
+    runs-on: windows-2022
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Python ${{ matrix.python }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+
+    - name: Prepare env
+      run: |
+        python3 -m pip install -r tests/requirements.txt
+
+    - name: Update CMake
+      uses: jwlawson/actions-setup-cmake@v1.12
+
+    - name: Configure C++20
+      run: >
+        cmake -S . -B build
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=OFF
+        -DCMAKE_CXX_STANDARD=20
+
+    - name: Build C++20
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest
+
+    - name: C++20 tests
+      run: cmake --build build --target cpptest -j 2
+
+    - name: Interface test C++20
+      run: cmake --build build --target test_cmake_build
+
   mingw:
     name: "🐍 3 • windows-latest • ${{ matrix.sys }}"
     runs-on: windows-latest

From a97e9d8cacadfddc3ff19790242e335499639168 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 14 Feb 2022 11:36:22 -0800
Subject: [PATCH 313/638] Dropping MSVC 2015 (#3722)

* Changing `_MSC_VER` guard to `< 1910` (dropping MSVC 2015).

* Removing MSVC 2015 from ci.yml, and .appveyor.yml entirely.

* Bringing back .appveyor.yml from master.

* appveyor Visual Studio 2017

* 1st manual pass, builds & tests with unix_clang, before pre-commit.

* After clang-format (via pre-commit).

* Manual pass looking for "2015", builds & tests with unix_clang, before pre-commit.

* Backtracking for include/pybind11 changes in previous commit.

git checkout d07865846c7d31dd61111e6df801864327b65070 include/pybind11/attr.h include/pybind11/detail/common.h include/pybind11/functional.h

--------------------

CI #4160 errors observed:

https://github.com/pybind/pybind11/pull/3722/commits/2a26873727214c5f1e159cba98f5c625b908381a
https://github.com/pybind/pybind11/runs/5168332130?check_suite_focus=true

$ grep ' error C' *.txt | sed 's/2022-02-12[^ ]*//' | sed 's/^[0-9][0-9]*//' | sed 's/^.*\.txt: //' | sort | uniqD:\a\pybind11\pybind11\include\pybind11\cast.h(1364,1): error C2752: 'pybind11::detail::type_caster<Eigen::Ref<Eigen::Vector3f,0,pybind11::EigenDStride>,void>': more than one partial specialization matches the template argument list [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj]

d:\a\pybind11\pybind11\include\pybind11\detail/common.h(1023): error C2737: 'pybind11::overload_cast': 'constexpr' object must be initialized [D:\a\pybind11\pybind11\build\tests\cross_module_gil_utils.vcxproj]
d:\a\pybind11\pybind11\include\pybind11\detail/common.h(1023): error C2737: 'pybind11::overload_cast': 'constexpr' object must be initialized [D:\a\pybind11\pybind11\build\tests\pybind11_cross_module_tests.vcxproj]
d:\a\pybind11\pybind11\include\pybind11\detail/common.h(1023): error C2737: 'pybind11::overload_cast': 'constexpr' object must be initialized [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj]
d:\a\pybind11\pybind11\include\pybind11\detail/common.h(1023): error C2737: 'pybind11::overload_cast': 'constexpr' object must be initialized [D:\a\pybind11\pybind11\build\tests\test_embed\external_module.vcxproj]
D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj]
D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]

$ grep ': error C2737' *.txt | sed 's/^.*MSVC//' | sed 's/___.*//' | sort | uniq

_2017

$ grep ': error C2752' *.txt

3______3.8_____MSVC_2019_____x86_-DCMAKE_CXX_STANDARD=17.txt:2022-02-12T16:12:45.9921122Z D:\a\pybind11\pybind11\include\pybind11\cast.h(1364,1): error C2752: 'pybind11::detail::type_caster<Eigen::Ref<Eigen::Vector3f,0,pybind11::EigenDStride>,void>': more than one partial specialization matches the template argument list [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj]

$ grep ': fatal error C1001:' *.txt

10______pypy-3.8-v7.3.7_____windows-2022_____x64.txt:2022-02-12T16:12:56.3163683Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]
1______3.6_____MSVC_2019_____x86.txt:2022-02-12T16:12:47.6774625Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj]
16______3.6_____windows-latest_____x64_-DPYBIND11_FINDPYTHON=ON.txt:2022-02-12T16:12:27.0556151Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]
17______3.9_____windows-2019_____x64.txt:2022-02-12T16:12:30.3822566Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]
2______3.7_____MSVC_2019_____x86.txt:2022-02-12T16:12:38.7018911Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj]
6______3.6_____windows-2022_____x64.txt:2022-02-12T16:12:00.4513642Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]
7______3.9_____windows-2022_____x64.txt:2022-02-12T16:11:43.6306160Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]
8______3.10_____windows-2022_____x64.txt:2022-02-12T16:11:49.9589644Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]
9______pypy-3.7-v7.3.7_____windows-2022_____x64.txt:2022-02-12T16:11:53.7912112Z D:\a\pybind11\pybind11\include\pybind11\detail/common.h(624): fatal error C1001: Internal compiler error. [D:\a\pybind11\pybind11\tests\pybind11_tests.vcxproj]

* common.h: is_template_base_of

* Re-applying 4 changes from 2a26873727214c5f1e159cba98f5c625b908381a that work universally.

* `overload_cast = {};` only for MSVC 2017 and Clang 5

* Refining condition for using is_template_base_of workaround.

* Undoing MSVC 2015 workaround in test_constants_and_functions.cpp

* CentOS7: silence_unused_warnings

* Tweaks in response to reviews.

* Adding windows-2022 C++20

* Trying another way of adding windows-2022 C++20
---
 .appveyor.yml                          |  4 +-
 .github/workflows/ci.yml               | 47 --------------
 README.rst                             |  2 +-
 docs/advanced/cast/stl.rst             |  2 -
 docs/advanced/classes.rst              |  7 ---
 docs/basics.rst                        |  3 +-
 docs/classes.rst                       |  3 +-
 docs/faq.rst                           | 14 -----
 include/pybind11/attr.h                |  5 +-
 include/pybind11/detail/common.h       | 27 ++++----
 include/pybind11/functional.h          |  3 +-
 tests/pybind11_tests.h                 |  6 --
 tests/test_class.cpp                   | 12 +---
 tests/test_const_name.cpp              | 85 +++++++++++---------------
 tests/test_constants_and_functions.cpp | 15 ++---
 tests/test_eigen.cpp                   |  3 -
 tests/test_factory_constructors.cpp    |  7 ---
 tests/test_iostream.cpp                |  4 --
 tests/test_smart_ptr.cpp               |  4 --
 tests/test_stl.cpp                     |  2 +-
 tests/test_virtual_functions.cpp       |  3 +-
 21 files changed, 65 insertions(+), 193 deletions(-)

diff --git a/.appveyor.yml b/.appveyor.yml
index f3bc9cd496..360760ac8d 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,6 +1,6 @@
 version: 1.0.{build}
 image:
-- Visual Studio 2015
+- Visual Studio 2017
 test: off
 skip_branch_with_pr: true
 build:
@@ -13,7 +13,7 @@ environment:
     CONFIG: Debug
 install:
 - ps: |
-    $env:CMAKE_GENERATOR = "Visual Studio 14 2015"
+    $env:CMAKE_GENERATOR = "Visual Studio 15 2017"
     if ($env:PLATFORM -eq "x64") { $env:PYTHON = "$env:PYTHON-x64" }
     $env:PATH = "C:\Python$env:PYTHON\;C:\Python$env:PYTHON\Scripts\;$env:PATH"
     python -W ignore -m pip install --upgrade pip wheel
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 629879a5bd..6bf56c4e30 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -755,53 +755,6 @@ jobs:
     - name: Python tests
       run: cmake --build build -t pytest
 
-  win32-msvc2015:
-    name: "🐍 ${{ matrix.python }} • MSVC 2015 • x64"
-    runs-on: windows-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        python:
-          - 3.6
-          - 3.7
-          # todo: check/cpptest does not support 3.8+ yet
-
-    steps:
-    - uses: actions/checkout@v2
-
-    - name: Setup 🐍 ${{ matrix.python }}
-      uses: actions/setup-python@v2
-      with:
-        python-version: ${{ matrix.python }}
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
-
-    - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.10.0
-      with:
-        toolset: 14.0
-
-    - name: Prepare env
-      run: |
-        python -m pip install -r tests/requirements.txt
-
-    # First build - C++11 mode and inplace
-    - name: Configure
-      run: >
-        cmake -S . -B build
-        -G "Visual Studio 14 2015" -A x64
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-
-    - name: Build C++14
-      run: cmake --build build -j 2
-
-    - name: Run all checks
-      run: cmake --build build -t check
-
-
   win32-msvc2017:
     name: "🐍 ${{ matrix.python }} • MSVC 2017 • x64"
     runs-on: windows-2016
diff --git a/README.rst b/README.rst
index 0edcd9179a..3c75edb575 100644
--- a/README.rst
+++ b/README.rst
@@ -122,7 +122,7 @@ Supported compilers
 1. Clang/LLVM 3.3 or newer (for Apple Xcode's clang, this is 5.0.0 or
    newer)
 2. GCC 4.8 or newer
-3. Microsoft Visual Studio 2015 Update 3 or newer
+3. Microsoft Visual Studio 2017 or newer
 4. Intel classic C++ compiler 18 or newer (ICC 20.2 tested in CI)
 5. Cygwin/GCC (previously tested on 2.5.1)
 6. NVCC (CUDA 11.0 tested in CI)
diff --git a/docs/advanced/cast/stl.rst b/docs/advanced/cast/stl.rst
index b8622ee095..109763f7aa 100644
--- a/docs/advanced/cast/stl.rst
+++ b/docs/advanced/cast/stl.rst
@@ -87,8 +87,6 @@ included to tell pybind11 how to visit the variant.
 
     pybind11 only supports the modern implementation of ``boost::variant``
     which makes use of variadic templates. This requires Boost 1.56 or newer.
-    Additionally, on Windows, MSVC 2017 is required because ``boost::variant``
-    falls back to the old non-variadic implementation on MSVC 2015.
 
 .. _opaque:
 
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 3e8ba73852..49ddf5c0b1 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -1118,13 +1118,6 @@ described trampoline:
     py::class_<A, Trampoline>(m, "A") // <-- `Trampoline` here
         .def("foo", &Publicist::foo); // <-- `Publicist` here, not `Trampoline`!
 
-.. note::
-
-    MSVC 2015 has a compiler bug (fixed in version 2017) which
-    requires a more explicit function binding in the form of
-    ``.def("foo", static_cast<int (A::*)() const>(&Publicist::foo));``
-    where ``int (A::*)() const`` is the type of ``A::foo``.
-
 Binding final classes
 =====================
 
diff --git a/docs/basics.rst b/docs/basics.rst
index d40992d386..e9b24c7fa7 100644
--- a/docs/basics.rst
+++ b/docs/basics.rst
@@ -32,8 +32,7 @@ The last line will both compile and run the tests.
 Windows
 -------
 
-On Windows, only **Visual Studio 2015** and newer are supported since pybind11 relies
-on various C++11 language features that break older versions of Visual Studio.
+On Windows, only **Visual Studio 2017** and newer are supported.
 
 .. Note::
 
diff --git a/docs/classes.rst b/docs/classes.rst
index b833bc4ba1..0c687b7c53 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -434,8 +434,7 @@ you can use ``py::detail::overload_cast_impl`` with an additional set of parenth
         .def("set", overload_cast_<int>()(&Pet::set), "Set the pet's age")
         .def("set", overload_cast_<const std::string &>()(&Pet::set), "Set the pet's name");
 
-.. [#cpp14] A compiler which supports the ``-std=c++14`` flag
-            or Visual Studio 2015 Update 2 and newer.
+.. [#cpp14] A compiler which supports the ``-std=c++14`` flag.
 
 .. note::
 
diff --git a/docs/faq.rst b/docs/faq.rst
index a6b9913126..28498e7dfc 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -220,20 +220,6 @@ In addition to decreasing binary size, ``-fvisibility=hidden`` also avoids
 potential serious issues when loading multiple modules and is required for
 proper pybind operation.  See the previous FAQ entry for more details.
 
-Working with ancient Visual Studio 2008 builds on Windows
-=========================================================
-
-The official Windows distributions of Python are compiled using truly
-ancient versions of Visual Studio that lack good C++11 support. Some users
-implicitly assume that it would be impossible to load a plugin built with
-Visual Studio 2015 into a Python distribution that was compiled using Visual
-Studio 2008. However, no such issue exists: it's perfectly legitimate to
-interface DLLs that are built with different compilers and/or C libraries.
-Common gotchas to watch out for involve not ``free()``-ing memory region
-that that were ``malloc()``-ed in another shared library, using data
-structures with incompatible ABIs, and so on. pybind11 is very careful not
-to make these types of mistakes.
-
 How can I properly handle Ctrl-C in long-running functions?
 ===========================================================
 
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index de95f89d0f..38139afa32 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -61,7 +61,7 @@ struct base {
 
     PYBIND11_DEPRECATED(
         "base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
-    base() {} // NOLINT(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
+    base() = default;
 };
 
 /// Keep patient alive while nurse lives
@@ -82,8 +82,7 @@ struct metaclass {
     handle value;
 
     PYBIND11_DEPRECATED("py::metaclass() is no longer required. It's turned on by default now.")
-    // NOLINTNEXTLINE(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
-    metaclass() {}
+    metaclass() = default;
 
     /// Override pybind11's default metaclass
     explicit metaclass(handle value) : value(value) {}
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index c1d2de13a7..1070d686ec 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -47,7 +47,7 @@
 // or newer.
 #    if _MSVC_LANG >= 201402L
 #        define PYBIND11_CPP14
-#        if _MSVC_LANG > 201402L && _MSC_VER >= 1910
+#        if _MSVC_LANG > 201402L
 #            define PYBIND11_CPP17
 #            if _MSVC_LANG >= 202002L
 #                define PYBIND11_CPP20
@@ -81,10 +81,8 @@
 #        error pybind11 requires gcc 4.8 or newer
 #    endif
 #elif defined(_MSC_VER)
-// Pybind hits various compiler bugs in 2015u2 and earlier, and also makes use of some stl features
-// (e.g. std::negation) added in 2015u3:
-#    if _MSC_FULL_VER < 190024210
-#        error pybind11 requires MSVC 2015 update 3 or newer
+#    if _MSC_VER < 1910
+#        error pybind11 2.10+ requires MSVC 2017 or newer
 #    endif
 #endif
 
@@ -149,7 +147,7 @@
 
 /* Don't let Python.h #define (v)snprintf as macro because they are implemented
    properly in Visual Studio since 2015. */
-#if defined(_MSC_VER) && _MSC_VER >= 1900
+#if defined(_MSC_VER)
 #    define HAVE_SNPRINTF 1
 #endif
 
@@ -561,7 +559,7 @@ static_assert(std::is_standard_layout<instance>::value,
               "Internal error: `pybind11::detail::instance` is not standard layout!");
 
 /// from __cpp_future__ import (convenient aliases from C++14/17)
-#if defined(PYBIND11_CPP14) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
+#if defined(PYBIND11_CPP14)
 using std::conditional_t;
 using std::enable_if_t;
 using std::remove_cv_t;
@@ -824,10 +822,10 @@ struct is_template_base_of_impl {
 /// Check if a template is the base of a type. For example:
 /// `is_template_base_of<Base, T>` is true if `struct T : Base<U> {}` where U can be anything
 template <template <typename...> class Base, typename T>
-#if !defined(_MSC_VER)
+#if defined(PYBIND11_CPP20) || !defined(_MSC_VER) // Sadly, all MSVC versions incl. 2022 need this.
 using is_template_base_of
     = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr));
-#else // MSVC2015 has trouble with decltype in template aliases
+#else
 struct is_template_base_of
     : decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr)) {
 };
@@ -1002,9 +1000,6 @@ struct nodelete {
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename... Args>
 struct overload_cast_impl {
-    // NOLINTNEXTLINE(modernize-use-equals-default):  MSVC 2015 needs this
-    constexpr overload_cast_impl() {}
-
     template <typename Return>
     constexpr auto operator()(Return (*pf)(Args...)) const noexcept -> decltype(pf) {
         return pf;
@@ -1031,8 +1026,12 @@ PYBIND11_NAMESPACE_END(detail)
 ///  - regular: static_cast<Return (Class::*)(Arg0, Arg1, Arg2)>(&Class::func)
 ///  - sweet:   overload_cast<Arg0, Arg1, Arg2>(&Class::func)
 template <typename... Args>
+#    if (defined(_MSC_VER) && _MSC_VER < 1920) /* MSVC 2017 */                                    \
+        || (defined(__clang__) && __clang_major__ == 5)
 static constexpr detail::overload_cast_impl<Args...> overload_cast = {};
-// MSVC 2015 only accepts this particular initialization syntax for this variable template.
+#    else
+static constexpr detail::overload_cast_impl<Args...> overload_cast;
+#    endif
 #endif
 
 /// Const member function selector for overload_cast
@@ -1118,7 +1117,7 @@ try_get_shared_from_this(std::enable_shared_from_this<T> *holder_value_ptr) {
 
 // For silencing "unused" compiler warnings in special situations.
 template <typename... Args>
-#if defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER < 1920 // MSVC 2017
+#if defined(_MSC_VER) && _MSC_VER < 1920 // MSVC 2017
 constexpr
 #endif
     inline void
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 69cfed5476..23e092e731 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -99,8 +99,7 @@ struct type_caster<std::function<Return(Args...)>> {
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
                 object retval(hfunc.f(std::forward<Args>(args)...));
-                /* Visual studio 2015 parser issue: need parentheses around this expression */
-                return (retval.template cast<Return>());
+                return retval.template cast<Return>();
             }
         };
 
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index 283801a1b7..a7c00c2f9b 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -3,12 +3,6 @@
 #include <pybind11/eval.h>
 #include <pybind11/pybind11.h>
 
-#if defined(_MSC_VER) && _MSC_VER < 1910
-// We get some really long type names here which causes MSVC 2015 to emit warnings
-#    pragma warning(                                                                              \
-        disable : 4503) // NOLINT: warning C4503: decorated name length exceeded, name was truncated
-#endif
-
 namespace py = pybind11;
 using namespace pybind11::literals;
 
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 329c9fe7b6..c8b8071dc9 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -354,13 +354,7 @@ TEST_SUBMODULE(class_, m) {
         using ProtectedA::foo;
     };
 
-    py::class_<ProtectedA>(m, "ProtectedA")
-        .def(py::init<>())
-#if !defined(_MSC_VER) || _MSC_VER >= 1910
-        .def("foo", &PublicistA::foo);
-#else
-        .def("foo", static_cast<int (ProtectedA::*)() const>(&PublicistA::foo));
-#endif
+    py::class_<ProtectedA>(m, "ProtectedA").def(py::init<>()).def("foo", &PublicistA::foo);
 
     class ProtectedB {
     public:
@@ -391,11 +385,7 @@ TEST_SUBMODULE(class_, m) {
 
     py::class_<ProtectedB, TrampolineB>(m, "ProtectedB")
         .def(py::init<>())
-#if !defined(_MSC_VER) || _MSC_VER >= 1910
         .def("foo", &PublicistB::foo);
-#else
-        .def("foo", static_cast<int (ProtectedB::*)() const>(&PublicistB::foo));
-#endif
 
     // test_brace_initialization
     struct BraceInitialization {
diff --git a/tests/test_const_name.cpp b/tests/test_const_name.cpp
index 5cb3d16c14..2ad01e6827 100644
--- a/tests/test_const_name.cpp
+++ b/tests/test_const_name.cpp
@@ -4,65 +4,50 @@
 
 #include "pybind11_tests.h"
 
-#if defined(_MSC_VER) && _MSC_VER < 1910
-
-// MSVC 2015 fails in bizarre ways.
-#    define PYBIND11_SKIP_TEST_CONST_NAME
-
-#else // Only test with MSVC 2017 or newer.
-
 // IUT = Implementation Under Test
-#    define CONST_NAME_TESTS(TEST_FUNC, IUT)                                                      \
-        std::string TEST_FUNC(int selector) {                                                     \
-            switch (selector) {                                                                   \
-                case 0:                                                                           \
-                    return IUT("").text;                                                          \
-                case 1:                                                                           \
-                    return IUT("A").text;                                                         \
-                case 2:                                                                           \
-                    return IUT("Bd").text;                                                        \
-                case 3:                                                                           \
-                    return IUT("Cef").text;                                                       \
-                case 4:                                                                           \
-                    return IUT<int>().text; /*NOLINT(bugprone-macro-parentheses)*/                \
-                case 5:                                                                           \
-                    return IUT<std::string>().text; /*NOLINT(bugprone-macro-parentheses)*/        \
-                case 6:                                                                           \
-                    return IUT<true>("T1", "T2").text; /*NOLINT(bugprone-macro-parentheses)*/     \
-                case 7:                                                                           \
-                    return IUT<false>("U1", "U2").text; /*NOLINT(bugprone-macro-parentheses)*/    \
-                case 8:                                                                           \
-                    /*NOLINTNEXTLINE(bugprone-macro-parentheses)*/                                \
-                    return IUT<true>(IUT("D1"), IUT("D2")).text;                                  \
-                case 9:                                                                           \
-                    /*NOLINTNEXTLINE(bugprone-macro-parentheses)*/                                \
-                    return IUT<false>(IUT("E1"), IUT("E2")).text;                                 \
-                case 10:                                                                          \
-                    return IUT("KeepAtEnd").text;                                                 \
-                default:                                                                          \
-                    break;                                                                        \
-            }                                                                                     \
-            throw std::runtime_error("Invalid selector value.");                                  \
-        }
+#define CONST_NAME_TESTS(TEST_FUNC, IUT)                                                          \
+    std::string TEST_FUNC(int selector) {                                                         \
+        switch (selector) {                                                                       \
+            case 0:                                                                               \
+                return IUT("").text;                                                              \
+            case 1:                                                                               \
+                return IUT("A").text;                                                             \
+            case 2:                                                                               \
+                return IUT("Bd").text;                                                            \
+            case 3:                                                                               \
+                return IUT("Cef").text;                                                           \
+            case 4:                                                                               \
+                return IUT<int>().text; /*NOLINT(bugprone-macro-parentheses)*/                    \
+            case 5:                                                                               \
+                return IUT<std::string>().text; /*NOLINT(bugprone-macro-parentheses)*/            \
+            case 6:                                                                               \
+                return IUT<true>("T1", "T2").text; /*NOLINT(bugprone-macro-parentheses)*/         \
+            case 7:                                                                               \
+                return IUT<false>("U1", "U2").text; /*NOLINT(bugprone-macro-parentheses)*/        \
+            case 8:                                                                               \
+                /*NOLINTNEXTLINE(bugprone-macro-parentheses)*/                                    \
+                return IUT<true>(IUT("D1"), IUT("D2")).text;                                      \
+            case 9:                                                                               \
+                /*NOLINTNEXTLINE(bugprone-macro-parentheses)*/                                    \
+                return IUT<false>(IUT("E1"), IUT("E2")).text;                                     \
+            case 10:                                                                              \
+                return IUT("KeepAtEnd").text;                                                     \
+            default:                                                                              \
+                break;                                                                            \
+        }                                                                                         \
+        throw std::runtime_error("Invalid selector value.");                                      \
+    }
 
 CONST_NAME_TESTS(const_name_tests, py::detail::const_name)
 
-#    ifdef PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
+#ifdef PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
 CONST_NAME_TESTS(underscore_tests, py::detail::_)
-#    endif
-
-#endif // MSVC >= 2017
+#endif
 
 TEST_SUBMODULE(const_name, m) {
-#ifdef PYBIND11_SKIP_TEST_CONST_NAME
-    m.attr("const_name_tests") = "PYBIND11_SKIP_TEST_CONST_NAME";
-#else
     m.def("const_name_tests", const_name_tests);
-#endif
 
-#ifdef PYBIND11_SKIP_TEST_CONST_NAME
-    m.attr("underscore_tests") = "PYBIND11_SKIP_TEST_CONST_NAME";
-#elif defined(PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY)
+#if defined(PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY)
     m.def("underscore_tests", underscore_tests);
 #else
     m.attr("underscore_tests") = "PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY not defined.";
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 7a6dae1a10..873fa1f551 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -137,18 +137,15 @@ TEST_SUBMODULE(constants_and_functions, m) {
     m.def("f4", f4);
 
     // test_function_record_leaks
-    struct LargeCapture {
+    m.def("register_large_capture_with_invalid_arguments", [](py::module_ m) {
         // This should always be enough to trigger the alternative branch
         // where `sizeof(capture) > sizeof(rec->data)`
-        uint64_t zeros[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
-    };
-    m.def("register_large_capture_with_invalid_arguments", [](py::module_ m) {
-        LargeCapture capture; // VS 2015's MSVC is acting up if we create the array here
+        uint64_t capture[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+#if defined(__GNUC__) && __GNUC__ == 4 // CentOS7
+        py::detail::silence_unused_warnings(capture);
+#endif
         m.def(
-            "should_raise",
-            [capture](int) { return capture.zeros[9] + 33; },
-            py::kw_only(),
-            py::arg());
+            "should_raise", [capture](int) { return capture[9] + 33; }, py::kw_only(), py::arg());
     });
     m.def("register_with_raising_repr", [](py::module_ m, const py::object &default_value) {
         m.def(
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index 059843d3da..74e76eb7e0 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -14,9 +14,6 @@
 #include "pybind11_tests.h"
 
 #if defined(_MSC_VER)
-#    if _MSC_VER < 1910                 // VS 2015's MSVC
-#        pragma warning(disable : 4127) // C4127: conditional expression is constant
-#    endif
 #    pragma warning(disable : 4996) // C4996: std::unary_negation is deprecated
 #endif
 
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 81e32f5abe..a387cd2e76 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -381,13 +381,6 @@ TEST_SUBMODULE(factory_constructors, m) {
             ::operator delete(p);
         }
         static void operator delete(void *, void *) { py::print("noisy placement delete"); }
-#if defined(_MSC_VER) && _MSC_VER < 1910
-        // MSVC 2015 bug: the above "noisy delete" isn't invoked (fixed in MSVC 2017)
-        static void operator delete(void *p) {
-            py::print("noisy delete");
-            ::operator delete(p);
-        }
-#endif
     };
 
     py::class_<NoisyAlloc> pyNoisyAlloc(m, "NoisyAlloc");
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index dd0e19e0bd..421eaa2dd8 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -7,10 +7,6 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#if defined(_MSC_VER) && _MSC_VER < 1910 // VS 2015's MSVC
-#    pragma warning(disable : 4702)      // unreachable code in system header (xatomic.h(382))
-#endif
-
 #include <pybind11/iostream.h>
 
 #include "pybind11_tests.h"
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index f26c47c305..2c23a9a197 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -8,10 +8,6 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#if defined(_MSC_VER) && _MSC_VER < 1910 // VS 2015's MSVC
-#    pragma warning(disable : 4702)      // unreachable code in system header (xatomic.h(382))
-#endif
-
 #include "object.h"
 #include "pybind11_tests.h"
 
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 44a6eb2e3e..fd1824beb4 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -37,7 +37,7 @@ struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
 #if defined(PYBIND11_HAS_VARIANT)
 using std::variant;
-#elif defined(PYBIND11_TEST_BOOST) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
+#elif defined(PYBIND11_TEST_BOOST)
 #    include <boost/variant.hpp>
 #    define PYBIND11_HAS_VARIANT 1
 using boost::variant;
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 0ca83386d5..f6d8c5e3c3 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -154,8 +154,7 @@ class NCVirtTrampoline : public NCVirt {
 };
 
 struct Base {
-    /* for some reason MSVC2015 can't compile this if the function is pure virtual */
-    virtual std::string dispatch() const { return {}; };
+    virtual std::string dispatch() const = 0;
     virtual ~Base() = default;
     Base() = default;
     Base(const Base &) = delete;

From a25d40c7bceb4db227aeb4a44fc74e28eb1015f1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 15 Feb 2022 00:32:58 -0500
Subject: [PATCH 314/638] tests: use 'build' in tests instead of running
 setup.py (#3734)

Co-authored-by: Anderson Bravalheri <andersonbravalheri@gmail.com>

Co-authored-by: Anderson Bravalheri <andersonbravalheri@gmail.com>
---
 pyproject.toml                           |  2 +-
 tests/extra_python_package/test_files.py | 26 ++++++++++++------------
 tests/requirements.txt                   |  1 +
 3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 5371c1b33d..31fff8bd6f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools>=42", "wheel", "cmake>=3.18", "ninja"]
+requires = ["setuptools>=42", "cmake>=3.18", "ninja"]
 build-backend = "setuptools.build_meta"
 
 [tool.check-manifest]
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index a6b13bc5f0..ba16b52241 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -108,19 +108,19 @@ def test_build_sdist(monkeypatch, tmpdir):
     out = subprocess.check_output(
         [
             sys.executable,
-            "setup.py",
-            "sdist",
-            "--formats=tar",
-            "--dist-dir",
+            "-m",
+            "build",
+            "--sdist",
+            "--outdir",
             str(tmpdir),
         ]
     )
     if hasattr(out, "decode"):
         out = out.decode()
 
-    (sdist,) = tmpdir.visit("*.tar")
+    (sdist,) = tmpdir.visit("*.tar.gz")
 
-    with tarfile.open(str(sdist)) as tar:
+    with tarfile.open(str(sdist), "r:gz") as tar:
         start = tar.getnames()[0] + "/"
         version = start[9:-1]
         simpler = {n.split("/", 1)[-1] for n in tar.getnames()[1:]}
@@ -169,23 +169,23 @@ def test_build_global_dist(monkeypatch, tmpdir):
 
     monkeypatch.chdir(MAIN_DIR)
     monkeypatch.setenv("PYBIND11_GLOBAL_SDIST", "1")
-
     out = subprocess.check_output(
         [
             sys.executable,
-            "setup.py",
-            "sdist",
-            "--formats=tar",
-            "--dist-dir",
+            "-m",
+            "build",
+            "--sdist",
+            "--outdir",
             str(tmpdir),
         ]
     )
+
     if hasattr(out, "decode"):
         out = out.decode()
 
-    (sdist,) = tmpdir.visit("*.tar")
+    (sdist,) = tmpdir.visit("*.tar.gz")
 
-    with tarfile.open(str(sdist)) as tar:
+    with tarfile.open(str(sdist), "r:gz") as tar:
         start = tar.getnames()[0] + "/"
         version = start[16:-1]
         simpler = {n.split("/", 1)[-1] for n in tar.getnames()[1:]}
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 1130c3fd5d..1159287fa9 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,3 +1,4 @@
+build==0.7.0
 numpy==1.21.5; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
 numpy==1.19.3; platform_python_implementation!="PyPy" and python_version=="3.6"
 numpy==1.21.5; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.10"

From 0986af61824498fbc17aee7c9caae4c40dfd12d8 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 15 Feb 2022 11:27:00 -0500
Subject: [PATCH 315/638] [pre-commit.ci] pre-commit autoupdate (#3672)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/Lucas-C/pre-commit-hooks: v1.1.11 → v1.1.12](https://github.com/Lucas-C/pre-commit-hooks/compare/v1.1.11...v1.1.12)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 564d50042c..8ab7117fef 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -59,7 +59,7 @@ repos:
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.1.11"
+  rev: "v1.1.12"
   hooks:
   - id: remove-tabs
 

From c14170a7878e7ac2f88e11657d629026d1ca31f3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 15 Feb 2022 11:51:17 -0800
Subject: [PATCH 316/638] Removing `// clang-format off` - `on` directives from
 test_pickling.cpp (#3738)

---
 tests/test_pickling.cpp | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index bf1ee4671c..9787bd3001 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -1,4 +1,3 @@
-// clang-format off
 /*
     tests/test_pickling.cpp -- pickle support
 
@@ -11,8 +10,6 @@
 
 #include "pybind11_tests.h"
 
-// clang-format on
-
 #include <memory>
 #include <stdexcept>
 #include <utility>
@@ -63,19 +60,18 @@ void wrap(py::module m) {
 
 } // namespace exercise_trampoline
 
-// clang-format off
-
 TEST_SUBMODULE(pickling, m) {
     // test_roundtrip
     class Pickleable {
     public:
-        explicit Pickleable(const std::string &value) : m_value(value) { }
+        explicit Pickleable(const std::string &value) : m_value(value) {}
         const std::string &value() const { return m_value; }
 
         void setExtra1(int extra1) { m_extra1 = extra1; }
         void setExtra2(int extra2) { m_extra2 = extra2; }
         int extra1() const { return m_extra1; }
         int extra2() const { return m_extra2; }
+
     private:
         std::string m_value;
         int m_extra1 = 0;
@@ -88,8 +84,7 @@ TEST_SUBMODULE(pickling, m) {
     };
 
     py::class_<Pickleable> pyPickleable(m, "Pickleable");
-    pyPickleable
-        .def(py::init<std::string>())
+    pyPickleable.def(py::init<std::string>())
         .def("value", &Pickleable::value)
         .def("extra1", &Pickleable::extra1)
         .def("extra2", &Pickleable::extra2)
@@ -105,7 +100,7 @@ TEST_SUBMODULE(pickling, m) {
         pyPickleable.def("__setstate__", [](Pickleable &p, const py::tuple &t) {
             if (t.size() != 3) {
                 throw std::runtime_error("Invalid state!");
-}
+            }
             /* Invoke the constructor (need to use in-place version) */
             new (&p) Pickleable(t[0].cast<std::string>());
 
@@ -124,7 +119,7 @@ TEST_SUBMODULE(pickling, m) {
             [](const py::tuple &t) {
                 if (t.size() != 3) {
                     throw std::runtime_error("Invalid state!");
-}
+                }
                 auto p = PickleableNew(t[0].cast<std::string>());
 
                 p.setExtra1(t[1].cast<int>());
@@ -136,7 +131,7 @@ TEST_SUBMODULE(pickling, m) {
     // test_roundtrip_with_dict
     class PickleableWithDict {
     public:
-        explicit PickleableWithDict(const std::string &value) : value(value) { }
+        explicit PickleableWithDict(const std::string &value) : value(value) {}
 
         std::string value;
         int extra;
@@ -147,7 +142,8 @@ TEST_SUBMODULE(pickling, m) {
         using PickleableWithDict::PickleableWithDict;
     };
 
-    py::class_<PickleableWithDict> pyPickleableWithDict(m, "PickleableWithDict", py::dynamic_attr());
+    py::class_<PickleableWithDict> pyPickleableWithDict(
+        m, "PickleableWithDict", py::dynamic_attr());
     pyPickleableWithDict.def(py::init<std::string>())
         .def_readwrite("value", &PickleableWithDict::value)
         .def_readwrite("extra", &PickleableWithDict::extra)
@@ -159,7 +155,7 @@ TEST_SUBMODULE(pickling, m) {
         pyPickleableWithDict.def("__setstate__", [](const py::object &self, const py::tuple &t) {
             if (t.size() != 3) {
                 throw std::runtime_error("Invalid state!");
-}
+            }
             /* Cast and construct */
             auto &p = self.cast<PickleableWithDict &>();
             new (&p) PickleableWithDict(t[0].cast<std::string>());
@@ -176,12 +172,13 @@ TEST_SUBMODULE(pickling, m) {
         .def(py::init<std::string>())
         .def(py::pickle(
             [](const py::object &self) {
-                return py::make_tuple(self.attr("value"), self.attr("extra"), self.attr("__dict__"));
+                return py::make_tuple(
+                    self.attr("value"), self.attr("extra"), self.attr("__dict__"));
             },
             [](const py::tuple &t) {
                 if (t.size() != 3) {
                     throw std::runtime_error("Invalid state!");
-}
+                }
 
                 auto cpp_state = PickleableWithDictNew(t[0].cast<std::string>());
                 cpp_state.extra = t[1].cast<int>();

From 4b42c3719113a613ad48b2e9dab218fb18f13f8a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 15 Feb 2022 17:48:33 -0500
Subject: [PATCH 317/638] style: pylint (#3720)

* fix: add pylint and fix issue

* chore: add pylint to pre-commit

* fix: local variable warning surfaced mistake in intree
---
 .gitattributes               |  1 +
 .github/matchers/pylint.json | 32 +++++++++++++++++++++++++++
 .github/workflows/format.yml |  5 +++++
 .pre-commit-config.yaml      | 23 ++++++++++++-------
 noxfile.py                   |  9 ++++++--
 pybind11/__main__.py         |  2 ++
 pybind11/commands.py         | 15 +++++++++----
 pybind11/setup_helpers.py    | 43 ++++++++++++++++++++----------------
 pyproject.toml               | 27 ++++++++++++++++++++++
 9 files changed, 124 insertions(+), 33 deletions(-)
 create mode 100644 .gitattributes
 create mode 100644 .github/matchers/pylint.json

diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000000..d611e1496d
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+docs/*.svg binary
diff --git a/.github/matchers/pylint.json b/.github/matchers/pylint.json
new file mode 100644
index 0000000000..e3a6bd16b0
--- /dev/null
+++ b/.github/matchers/pylint.json
@@ -0,0 +1,32 @@
+{
+  "problemMatcher": [
+    {
+      "severity": "warning",
+      "pattern": [
+        {
+          "regexp": "^([^:]+):(\\d+):(\\d+): ([A-DF-Z]\\d+): \\033\\[[\\d;]+m([^\\033]+).*$",
+          "file": 1,
+          "line": 2,
+          "column": 3,
+          "code": 4,
+          "message": 5
+        }
+      ],
+      "owner": "pylint-warning"
+    },
+    {
+      "severity": "error",
+      "pattern": [
+        {
+          "regexp": "^([^:]+):(\\d+):(\\d+): (E\\d+): \\033\\[[\\d;]+m([^\\033]+).*$",
+          "file": 1,
+          "line": 2,
+          "column": 3,
+          "code": 4,
+          "message": 5
+        }
+      ],
+      "owner": "pylint-error"
+    }
+  ]
+}
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index ab7b40503a..46140fe0c0 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -12,6 +12,9 @@ on:
     - stable
     - "v*"
 
+env:
+  FORCE_COLOR: 3
+
 jobs:
   pre-commit:
     name: Format
@@ -19,6 +22,8 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-python@v2
+    - name: Add matchers
+      run: echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
     - uses: pre-commit/action@v2.0.3
       with:
         # Slow hooks are marked with manual - slow is okay here, run them too
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 8ab7117fef..0ff02f5112 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -87,22 +87,29 @@ repos:
   - id: rst-directive-colons
   - id: rst-inline-touching-normal
 
+# Automatically remove noqa that are not used
+- repo: https://github.com/asottile/yesqa
+  rev: "v1.3.0"
+  hooks:
+  - id: yesqa
+    additional_dependencies: &flake8_dependencies
+      - flake8-bugbear
+      - pep8-naming
+
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
   rev: "4.0.1"
   hooks:
   - id: flake8
-    additional_dependencies: &flake8_dependencies
-      - flake8-bugbear
-      - pep8-naming
     exclude: ^(docs/.*|tools/.*)$
+    additional_dependencies: *flake8_dependencies
 
-# Automatically remove noqa that are not used
-- repo: https://github.com/asottile/yesqa
-  rev: "v1.3.0"
+# PyLint has native support - not always usable, but works for us
+- repo: https://github.com/PyCQA/pylint
+  rev: "v2.12.2"
   hooks:
-  - id: yesqa
-    additional_dependencies: *flake8_dependencies
+  - id: pylint
+    files: ^pybind11
 
 # CMake formatting
 - repo: https://github.com/cheshirekow/cmake-format-precommit
diff --git a/noxfile.py b/noxfile.py
index 4b6adcfbd7..50b7e4ee03 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -1,8 +1,13 @@
+import os
+
 import nox
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+PYTHON_VERISONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "pypy3.7", "pypy3.8"]
+
+if os.environ.get("CI", None):
+    nox.options.error_on_missing_interpreters = True
 
 
 @nox.session(reuse_venv=True)
@@ -14,7 +19,7 @@ def lint(session: nox.Session) -> None:
     session.run("pre-commit", "run", "-a")
 
 
-@nox.session(python=PYTHON_VERSIONS)
+@nox.session(python=PYTHON_VERISONS)
 def tests(session: nox.Session) -> None:
     """
     Run the tests (requires a compiler).
diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 645c760420..22fc4471e7 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -1,3 +1,5 @@
+# pylint: disable=missing-function-docstring
+
 import argparse
 import sys
 import sysconfig
diff --git a/pybind11/commands.py b/pybind11/commands.py
index 84d41478ad..a29c8ca612 100644
--- a/pybind11/commands.py
+++ b/pybind11/commands.py
@@ -3,16 +3,23 @@
 DIR = os.path.abspath(os.path.dirname(__file__))
 
 
-def get_include(user: bool = False) -> str:
+def get_include(user: bool = False) -> str:  # pylint: disable=unused-argument
+    """
+    Return the path to the pybind11 include directory. The historical "user"
+    argument is unused, and may be removed.
+    """
     installed_path = os.path.join(DIR, "include")
     source_path = os.path.join(os.path.dirname(DIR), "include")
     return installed_path if os.path.exists(installed_path) else source_path
 
 
 def get_cmake_dir() -> str:
+    """
+    Return the path to the pybind11 CMake module directory.
+    """
     cmake_installed_path = os.path.join(DIR, "share", "cmake", "pybind11")
     if os.path.exists(cmake_installed_path):
         return cmake_installed_path
-    else:
-        msg = "pybind11 not installed, installation required to access the CMake files"
-        raise ImportError(msg)
+
+    msg = "pybind11 not installed, installation required to access the CMake files"
+    raise ImportError(msg)
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index e3271ca60d..1fd04b9154 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -239,7 +239,7 @@ def has_flag(compiler: Any, flag: str) -> bool:
     with tmp_chdir():
         fname = Path("flagcheck.cpp")
         # Don't trigger -Wunused-parameter.
-        fname.write_text("int main (int, char **) { return 0; }")
+        fname.write_text("int main (int, char **) { return 0; }", encoding="utf-8")
 
         try:
             compiler.compile([str(fname)], extra_postargs=[flag])
@@ -303,29 +303,31 @@ def intree_extensions(
     """
     exts = []
 
-    for path in paths:
-        if package_dir is None:
+    if package_dir is None:
+        for path in paths:
             parent, _ = os.path.split(path)
             while os.path.exists(os.path.join(parent, "__init__.py")):
                 parent, _ = os.path.split(parent)
             relname, _ = os.path.splitext(os.path.relpath(path, parent))
             qualified_name = relname.replace(os.path.sep, ".")
             exts.append(Pybind11Extension(qualified_name, [path]))
+        return exts
+
+    for path in paths:
+        for prefix, parent in package_dir.items():
+            if path.startswith(parent):
+                relname, _ = os.path.splitext(os.path.relpath(path, parent))
+                qualified_name = relname.replace(os.path.sep, ".")
+                if prefix:
+                    qualified_name = prefix + "." + qualified_name
+                exts.append(Pybind11Extension(qualified_name, [path]))
+                break
         else:
-            for prefix, parent in package_dir.items():
-                if path.startswith(parent):
-                    relname, _ = os.path.splitext(os.path.relpath(path, parent))
-                    qualified_name = relname.replace(os.path.sep, ".")
-                    if prefix:
-                        qualified_name = prefix + "." + qualified_name
-                    exts.append(Pybind11Extension(qualified_name, [path]))
-
-    if not exts:
-        msg = (
-            f"path {path} is not a child of any of the directories listed "
-            f"in 'package_dir' ({package_dir})"
-        )
-        raise ValueError(msg)
+            msg = (
+                f"path {path} is not a child of any of the directories listed "
+                f"in 'package_dir' ({package_dir})"
+            )
+            raise ValueError(msg)
 
     return exts
 
@@ -339,7 +341,7 @@ def naive_recompile(obj: str, src: str) -> bool:
     return os.stat(obj).st_mtime < os.stat(src).st_mtime
 
 
-def no_recompile(obg: str, src: str) -> bool:
+def no_recompile(obg: str, src: str) -> bool:  # pylint: disable=unused-argument
     """
     This is the safest but slowest choice (and is the default) - will always
     recompile sources.
@@ -412,7 +414,7 @@ def __init__(
         self,
         envvar: Optional[str] = None,
         default: int = 0,
-        max: int = 0,
+        max: int = 0,  # pylint: disable=redefined-builtin
         needs_recompile: Callable[[str, str], bool] = no_recompile,
     ) -> None:
         self.envvar = envvar
@@ -488,6 +490,9 @@ def _single_compile(obj: Any) -> None:
         return compile_function
 
     def install(self: S) -> S:
+        """
+        Installs the compile function into distutils.ccompiler.CCompiler.compile.
+        """
         distutils.ccompiler.CCompiler.compile = self.function()  # type: ignore[assignment]
         return self
 
diff --git a/pyproject.toml b/pyproject.toml
index 31fff8bd6f..f80cdc1f42 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -30,3 +30,30 @@ strict = true
 [[tool.mypy.overrides]]
 module = ["ghapi.*", "setuptools.*"]
 ignore_missing_imports = true
+
+
+[tool.pytest.ini_options]
+minversion = "6.0"
+addopts = ["-ra", "--showlocals", "--strict-markers", "--strict-config"]
+xfail_strict = true
+filterwarnings = ["error"]
+log_cli_level = "info"
+testpaths = [
+    "tests",
+]
+timeout=300
+
+
+[tool.pylint]
+master.py-version = "3.6"
+reports.output-format = "colorized"
+messages_control.disable = [
+  "design",
+  "fixme",
+  "imports",
+  "line-too-long",
+  "imports",
+  "invalid-name",
+  "protected-access",
+  "missing-module-docstring",
+]

From 009ffc336299f58dcb439fae278eb135150b71c1 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 16 Feb 2022 07:07:53 -0800
Subject: [PATCH 318/638] MSVC C++20 test_eigen (#3741)

* Removing C++20 condition for MSVC is_template_base_of decltype workaround.

* `-DDOWNLOAD_EIGEN=ON` for MSVC 2022 C++20

* `-DDOWNLOAD_EIGEN=ON` for MSVC 2019 C++20

* `-DPYBIND11_WERROR=OFF` for MSVC C++20 (2019, 2020)

* Restoring `defined(PYBIND11_CPP20)` in common.h

* pragma warning(disable : 5054) in eigen.h

* Reverting `-DPYBIND11_WERROR=OFF` changes.
---
 .github/workflows/ci.yml         | 4 ++--
 include/pybind11/detail/common.h | 4 +++-
 include/pybind11/eigen.h         | 4 +++-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6bf56c4e30..bc31281db5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -712,7 +712,7 @@ jobs:
 
         include:
           - python: 3.9
-            args: -DCMAKE_CXX_STANDARD=20 -DDOWNLOAD_EIGEN=OFF
+            args: -DCMAKE_CXX_STANDARD=20
           - python: 3.8
             args: -DCMAKE_CXX_STANDARD=17
 
@@ -835,7 +835,7 @@ jobs:
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=OFF
+        -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=20
 
     - name: Build C++20
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1070d686ec..1d4939bed7 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -822,7 +822,9 @@ struct is_template_base_of_impl {
 /// Check if a template is the base of a type. For example:
 /// `is_template_base_of<Base, T>` is true if `struct T : Base<U> {}` where U can be anything
 template <template <typename...> class Base, typename T>
-#if defined(PYBIND11_CPP20) || !defined(_MSC_VER) // Sadly, all MSVC versions incl. 2022 need this.
+// Sadly, all MSVC versions incl. 2022 need the workaround, even in C++20 mode.
+// See also: https://github.com/pybind/pybind11/pull/3741
+#if !defined(_MSC_VER)
 using is_template_base_of
     = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr));
 #else
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 47820ce895..930c4f7fa8 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -21,10 +21,12 @@
 // make it version specific, or even remove it later, but considering that
 // 1. C4127 is generally far more distracting than useful for modern template code, and
 // 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
-// it is probably best to keep this around indefinitely.
+//    it is probably best to keep this around indefinitely.
 #if defined(_MSC_VER)
 #    pragma warning(push)
 #    pragma warning(disable : 4127) // C4127: conditional expression is constant
+#    pragma warning(disable : 5054) // https://github.com/pybind/pybind11/pull/3741
+//       C5054: operator '&': deprecated between enumerations of different types
 #endif
 
 #include <Eigen/Core>

From 44596bc4ee9e3d82067eb424732ab54aa59dfa63 Mon Sep 17 00:00:00 2001
From: Peter Hawkins <hawkinsp@cs.stanford.edu>
Date: Fri, 18 Feb 2022 14:12:00 -0500
Subject: [PATCH 319/638] Fix exception handling when pybind11::weakref()
 fails. (#3739)

* Clear Python error state if pybind11::weakref() fails.

The weakref() constructor calls pybind11_fail() without clearing any
Python interpreter error state. If a client catches the C++ exception
thrown by pybind11_fail(), the Python interpreter will be left in an
error state.

* Add test case for failing to create weakref

* Add Debug asserts for pybind11 fail

* Make error handling more pythonic

* Does this fix PyPy?

* Adapt test to PyPy differences

* Simplify test to remove redundancy

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/detail/common.h |  2 ++
 include/pybind11/pytypes.h       |  3 +++
 tests/test_pytypes.py            | 28 +++++++++++++++++++++++++++-
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1d4939bed7..ea09bb3fdf 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -936,9 +936,11 @@ PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybin
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
 
 [[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) {
+    assert(!PyErr_Occurred());
     throw std::runtime_error(reason);
 }
 [[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const std::string &reason) {
+    assert(!PyErr_Occurred());
     throw std::runtime_error(reason);
 }
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 29f70bd5fd..dc753d32cd 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1509,6 +1509,9 @@ class weakref : public object {
     explicit weakref(handle obj, handle callback = {})
         : object(PyWeakref_NewRef(obj.ptr(), callback.ptr()), stolen_t{}) {
         if (!m_ptr) {
+            if (PyErr_Occurred()) {
+                throw error_already_set();
+            }
             pybind11_fail("Could not allocate weak reference!");
         }
     }
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 07ace00491..becd1cc8ae 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -1,8 +1,9 @@
+import contextlib
 import sys
 
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import debug_enabled
 from pybind11_tests import pytypes as m
 
@@ -583,6 +584,31 @@ def callback(wr):
     assert callback_called
 
 
+@pytest.mark.parametrize(
+    "create_weakref, has_callback",
+    [
+        (m.weakref_from_handle, False),
+        (m.weakref_from_object, False),
+        (m.weakref_from_handle_and_function, True),
+        (m.weakref_from_object_and_function, True),
+    ],
+)
+def test_weakref_err(create_weakref, has_callback):
+    class C:
+        __slots__ = []
+
+    def callback(_):
+        pass
+
+    ob = C()
+    # Should raise TypeError on CPython
+    with pytest.raises(TypeError) if not env.PYPY else contextlib.nullcontext():
+        if has_callback:
+            _ = create_weakref(ob, callback)
+        else:
+            _ = create_weakref(ob)
+
+
 def test_cpp_iterators():
     assert m.tuple_iterator() == 12
     assert m.dict_iterator() == 305 + 711

From 9aa676d38db4b18d9952c70486412d20c0213f13 Mon Sep 17 00:00:00 2001
From: StarQTius <73899717+StarQTius@users.noreply.github.com>
Date: Sun, 20 Feb 2022 17:00:29 +0100
Subject: [PATCH 320/638] fix: clear local internals after finalizing
 interpreter #2101 (#3744)

* Clear local internals after finalizing interpreter

* Add descriptive comments

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/embed.h              |  4 ++++
 tests/test_embed/test_interpreter.cpp | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 8e998fc3c6..98cc3e4664 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -198,6 +198,10 @@ inline void finalize_interpreter() {
     if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
         internals_ptr_ptr = capsule(builtins[id]);
     }
+    // Local internals contains data managed by the current interpreter, so we must clear them to
+    // avoid undefined behaviors when initializing another interpreter
+    detail::get_local_internals().registered_types_cpp.clear();
+    detail::get_local_internals().registered_exception_translators.clear();
 
     Py_Finalize();
 
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index f2f2c29609..1c45457a05 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -375,3 +375,21 @@ TEST_CASE("sys.argv gets initialized properly") {
     }
     py::initialize_interpreter();
 }
+
+TEST_CASE("make_iterator can be called before then after finalizing an interpreter") {
+    // Reproduction of issue #2101 (https://github.com/pybind/pybind11/issues/2101)
+    py::finalize_interpreter();
+
+    std::vector<int> container;
+    {
+        pybind11::scoped_interpreter g;
+        auto iter = pybind11::make_iterator(container.begin(), container.end());
+    }
+
+    REQUIRE_NOTHROW([&]() {
+        pybind11::scoped_interpreter g;
+        auto iter = pybind11::make_iterator(container.begin(), container.end());
+    }());
+
+    py::initialize_interpreter();
+}

From 91f597be5a606a7063e309776d548e647bf83bf6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Wed, 23 Feb 2022 17:56:41 -0500
Subject: [PATCH 321/638] [pre-commit.ci] pre-commit autoupdate (#3754)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/hadialqattan/pycln: v1.1.0 → v1.2.0](https://github.com/hadialqattan/pycln/compare/v1.1.0...v1.2.0)
- [github.com/pre-commit/mirrors-clang-format: v13.0.0 → v13.0.1](https://github.com/pre-commit/mirrors-clang-format/compare/v13.0.0...v13.0.1)

* Update .pre-commit-config.yaml

* ci: specify which windows image to use

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml | 4 ++--
 .pre-commit-config.yaml  | 5 +++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bc31281db5..e138550aa8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -45,7 +45,7 @@ jobs:
             args: >
               -DPYBIND11_FINDPYTHON=ON
               -DCMAKE_CXX_FLAGS="-D_=1"
-          - runs-on: windows-latest
+          - runs-on: windows-2019
             python: '3.6'
             args: >
               -DPYBIND11_FINDPYTHON=ON
@@ -717,7 +717,7 @@ jobs:
             args: -DCMAKE_CXX_STANDARD=17
 
     name: "🐍 ${{ matrix.python }} • MSVC 2019 • x86 ${{ matrix.args }}"
-    runs-on: windows-latest
+    runs-on: windows-2019
 
     steps:
     - uses: actions/checkout@v2
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0ff02f5112..0524205492 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.1.0"
+  rev: "v1.2.0"
   hooks:
   - id: pycln
 
@@ -163,6 +163,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v13.0.0"
+  rev: "v13.0.1"
   hooks:
   - id: clang-format
+    types_or: [c++, c, cuda]

From da15bb206c21be7180bd428e4e69907756eb70dc Mon Sep 17 00:00:00 2001
From: kururu002 <kururu002@qq.com>
Date: Thu, 24 Feb 2022 07:21:03 +0800
Subject: [PATCH 322/638] Cast bytearray to string  (#3707)

* Add bytearray to string cast, testcase and rename load_bytes to load_raw

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* New bytearray test case and convert failure to pybind11_fail

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix merge comments

* Actually fix merge comments

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Assert early if AsString fails

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Porras Huang <pohuang@jackx-vm-1.nvidia.com>
---
 include/pybind11/cast.h       | 25 ++++++++++++++++++-------
 tests/test_builtin_casters.py |  9 +++++++++
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 553d7616c1..fad65f0fae 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -380,7 +380,7 @@ struct string_caster {
             return false;
         }
         if (!PyUnicode_Check(load_src.ptr())) {
-            return load_bytes(load_src);
+            return load_raw(load_src);
         }
 
         // For UTF-8 we avoid the need for a temporary `bytes` object by using
@@ -458,26 +458,37 @@ struct string_caster {
 #endif
     }
 
-    // When loading into a std::string or char*, accept a bytes object as-is (i.e.
+    // When loading into a std::string or char*, accept a bytes/bytearray object as-is (i.e.
     // without any encoding/decoding attempt).  For other C++ char sizes this is a no-op.
     // which supports loading a unicode from a str, doesn't take this path.
     template <typename C = CharT>
-    bool load_bytes(enable_if_t<std::is_same<C, char>::value, handle> src) {
+    bool load_raw(enable_if_t<std::is_same<C, char>::value, handle> src) {
         if (PYBIND11_BYTES_CHECK(src.ptr())) {
             // We were passed raw bytes; accept it into a std::string or char*
             // without any encoding attempt.
             const char *bytes = PYBIND11_BYTES_AS_STRING(src.ptr());
-            if (bytes) {
-                value = StringType(bytes, (size_t) PYBIND11_BYTES_SIZE(src.ptr()));
-                return true;
+            if (!bytes) {
+                pybind11_fail("Unexpected PYBIND11_BYTES_AS_STRING() failure.");
+            }
+            value = StringType(bytes, (size_t) PYBIND11_BYTES_SIZE(src.ptr()));
+            return true;
+        }
+        if (PyByteArray_Check(src.ptr())) {
+            // We were passed a bytearray; accept it into a std::string or char*
+            // without any encoding attempt.
+            const char *bytearray = PyByteArray_AsString(src.ptr());
+            if (!bytearray) {
+                pybind11_fail("Unexpected PyByteArray_AsString() failure.");
             }
+            value = StringType(bytearray, (size_t) PyByteArray_Size(src.ptr()));
+            return true;
         }
 
         return false;
     }
 
     template <typename C = CharT>
-    bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) {
+    bool load_raw(enable_if_t<!std::is_same<C, char>::value, handle>) {
         return false;
     }
 };
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 02207f24fc..d38ae68028 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -133,6 +133,15 @@ def test_bytes_to_string():
     assert m.string_length("💩".encode()) == 4
 
 
+def test_bytearray_to_string():
+    """Tests the ability to pass bytearray to C++ string-accepting functions"""
+    assert m.string_length(bytearray(b"Hi")) == 2
+    assert m.strlen(bytearray(b"bytearray")) == 9
+    assert m.string_length(bytearray()) == 0
+    assert m.string_length(bytearray("🦜", "utf-8", "strict")) == 4
+    assert m.string_length(bytearray(b"\x80")) == 1
+
+
 @pytest.mark.skipif(not hasattr(m, "has_string_view"), reason="no <string_view>")
 def test_string_view(capture):
     """Tests support for C++17 string_view arguments and return values"""

From f495dfc4339df1454620ac2e7c0f5561959e86af Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Fri, 25 Feb 2022 16:25:23 -0500
Subject: [PATCH 323/638] cast: Qualify symbol usage in PYBIND11_TYPE_CASTER
 (#3758)

* cast: Qualify symbol usage in PYBIND11_TYPE_CASTER

Permits using macro outside of pybind11::detail

* fixup! review
---
 include/pybind11/cast.h            | 14 +++++++++-----
 tests/test_custom_type_casters.cpp | 31 ++++++++++++++++++++++++++++++
 tests/test_custom_type_casters.py  |  4 ++++
 3 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index fad65f0fae..d45b49c52e 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -85,11 +85,15 @@ protected:
                                                                                                   \
 public:                                                                                           \
     static constexpr auto name = py_name;                                                         \
-    template <typename T_, enable_if_t<std::is_same<type, remove_cv_t<T_>>::value, int> = 0>      \
-    static handle cast(T_ *src, return_value_policy policy, handle parent) {                      \
+    template <typename T_,                                                                        \
+              ::pybind11::detail::enable_if_t<                                                    \
+                  std::is_same<type, ::pybind11::detail::remove_cv_t<T_>>::value,                 \
+                  int> = 0>                                                                       \
+    static ::pybind11::handle cast(                                                               \
+        T_ *src, ::pybind11::return_value_policy policy, ::pybind11::handle parent) {             \
         if (!src)                                                                                 \
-            return none().release();                                                              \
-        if (policy == return_value_policy::take_ownership) {                                      \
+            return ::pybind11::none().release();                                                  \
+        if (policy == ::pybind11::return_value_policy::take_ownership) {                          \
             auto h = cast(std::move(*src), policy, parent);                                       \
             delete src;                                                                           \
             return h;                                                                             \
@@ -100,7 +104,7 @@ public:
     operator type &() { return value; }                /* NOLINT(bugprone-macro-parentheses) */   \
     operator type &&() && { return std::move(value); } /* NOLINT(bugprone-macro-parentheses) */   \
     template <typename T_>                                                                        \
-    using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
+    using cast_op_type = ::pybind11::detail::movable_cast_op_type<T_>
 
 template <typename CharT>
 using is_std_char_type = any_of<std::is_same<CharT, char>, /* std::string */
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 1d6341582c..25540e3685 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -20,6 +20,7 @@ class ArgInspector2 {
     std::string arg = "(default arg inspector 2)";
 };
 class ArgAlwaysConverts {};
+
 namespace pybind11 {
 namespace detail {
 template <>
@@ -105,6 +106,34 @@ struct type_caster<DestructionTester> {
 } // namespace detail
 } // namespace pybind11
 
+// Define type caster outside of `pybind11::detail` and then alias it.
+namespace other_lib {
+struct MyType {};
+// Corrupt `py` shorthand alias for surrounding context.
+namespace py {}
+// Corrupt unqualified relative `pybind11` namespace.
+namespace pybind11 {}
+// Correct alias.
+namespace py_ = ::pybind11;
+// Define caster. This is effectively no-op, we only ensure it compiles and we
+// don't have any symbol collision when using macro mixin.
+struct my_caster {
+    PYBIND11_TYPE_CASTER(MyType, py_::detail::const_name("MyType"));
+    bool load(py_::handle, bool) { return true; }
+
+    static py_::handle cast(const MyType &, py_::return_value_policy, py_::handle) {
+        return py_::bool_(true).release();
+    }
+};
+} // namespace other_lib
+// Effectively "alias" it into correct namespace (via inheritance).
+namespace pybind11 {
+namespace detail {
+template <>
+struct type_caster<other_lib::MyType> : public other_lib::my_caster {};
+} // namespace detail
+} // namespace pybind11
+
 TEST_SUBMODULE(custom_type_casters, m) {
     // test_custom_type_casters
 
@@ -175,4 +204,6 @@ TEST_SUBMODULE(custom_type_casters, m) {
     m.def("destruction_tester_cstats",
           &ConstructorStats::get<DestructionTester>,
           py::return_value_policy::reference);
+
+    m.def("other_lib_type", [](other_lib::MyType x) { return x; });
 }
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
index bb47d01bd2..adfa6cf86e 100644
--- a/tests/test_custom_type_casters.py
+++ b/tests/test_custom_type_casters.py
@@ -114,3 +114,7 @@ def test_custom_caster_destruction():
 
     # Make sure we still only have the original object (from ..._no_destroy()) alive:
     assert cstats.alive() == 1
+
+
+def test_custom_caster_other_lib():
+    assert m.other_lib_type(True)

From 061c617707015883b95e11068ffe97fb73d501ec Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 28 Feb 2022 21:35:43 -0500
Subject: [PATCH 324/638] [pre-commit.ci] pre-commit autoupdate (#3765)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/Lucas-C/pre-commit-hooks: v1.1.12 → v1.1.13](https://github.com/Lucas-C/pre-commit-hooks/compare/v1.1.12...v1.1.13)
- [github.com/hadialqattan/pycln: v1.2.0 → v1.2.4](https://github.com/hadialqattan/pycln/compare/v1.2.0...v1.2.4)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0524205492..e9a0e03f2b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -59,7 +59,7 @@ repos:
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.1.12"
+  rev: "v1.1.13"
   hooks:
   - id: remove-tabs
 
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.2.0"
+  rev: "v1.2.4"
   hooks:
   - id: pycln
 

From 5f9b090a915fbaa5904c6bd4a24f888f2ff55db7 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 1 Mar 2022 12:42:52 -0500
Subject: [PATCH 325/638] ci: fix PyPy (#3768)

* chore: minor fixes for newer PyPys

* ci: fix issue with PyPy
---
 .github/workflows/ci.yml        |  4 ++--
 include/pybind11/detail/class.h | 16 ++++++++--------
 include/pybind11/pybind11.h     |  2 +-
 noxfile.py                      |  9 ++++-----
 4 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e138550aa8..179caa9e82 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,8 +30,8 @@ jobs:
         - '3.6'
         - '3.9'
         - '3.10'
-        - 'pypy-3.7-v7.3.7'
-        - 'pypy-3.8-v7.3.7'
+        - 'pypy-3.7'
+        - 'pypy-3.8'
 
         # Items in here will either be added to the build matrix (if not
         # present), or add new keys to an existing matrix element if all the
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index ebdc07271b..e52ec1d3e6 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -101,14 +101,14 @@ inline PyTypeObject *make_static_property_type() {
 inline PyTypeObject *make_static_property_type() {
     auto d = dict();
     PyObject *result = PyRun_String(R"(\
-        class pybind11_static_property(property):
-            def __get__(self, obj, cls):
-                return property.__get__(self, cls, cls)
-
-            def __set__(self, obj, value):
-                cls = obj if isinstance(obj, type) else type(obj)
-                property.__set__(self, cls, value)
-        )",
+class pybind11_static_property(property):
+    def __get__(self, obj, cls):
+        return property.__get__(self, cls, cls)
+
+    def __set__(self, obj, value):
+        cls = obj if isinstance(obj, type) else type(obj)
+        property.__set__(self, cls, value)
+)",
                                     Py_file_input,
                                     d.ptr(),
                                     d.ptr());
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 22b629f40d..1ec6c17c67 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -334,7 +334,7 @@ class cpp_function : public function {
                             const std::type_info *const *types,
                             size_t args) {
         // Do NOT receive `unique_rec` by value. If this function fails to move out the unique_ptr,
-        // we do not want this to destuct the pointer. `initialize` (the caller) still relies on
+        // we do not want this to destruct the pointer. `initialize` (the caller) still relies on
         // the pointee being alive after this call. Only move out if a `capsule` is going to keep
         // it alive.
         auto *rec = unique_rec.get();
diff --git a/noxfile.py b/noxfile.py
index 50b7e4ee03..341d964e95 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,6 +2,7 @@
 
 import nox
 
+nox.needs_version = ">=2022.1.7"
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
 PYTHON_VERISONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "pypy3.7", "pypy3.8"]
@@ -29,14 +30,12 @@ def tests(session: nox.Session) -> None:
     session.install("-r", "tests/requirements.txt")
     session.run(
         "cmake",
-        "-S",
-        ".",
-        "-B",
-        tmpdir,
+        "-S.",
+        f"-B{tmpdir}",
         "-DPYBIND11_WERROR=ON",
         "-DDOWNLOAD_CATCH=ON",
         "-DDOWNLOAD_EIGEN=ON",
-        *session.posargs
+        *session.posargs,
     )
     session.run("cmake", "--build", tmpdir)
     session.run("cmake", "--build", tmpdir, "--config=Release", "--target", "check")

From 465b2e0bd8e25445b8892abfd422457ea275d713 Mon Sep 17 00:00:00 2001
From: Stefano Rivera <github@rivera.za.net>
Date: Tue, 1 Mar 2022 10:47:10 -0800
Subject: [PATCH 326/638] Use sysconfig in Python >= 3.10 (#3764)

* Use sysconfig in Python >= 3.10

Rely on sysconfig for installation paths for Python >= 3.10. distutils
has been deprecated and will be removed.

Fixes: #3677

* Explicitly select the posix_prefix scheme for platinclude on Debian

Debian's default scheme is posix_local, for installing locally-built
packages to /usr/local/.  We want to find the Python headers in /usr/,
so search posix_prefix.
---
 tools/FindPythonLibsNew.cmake | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index 7aeffa4412..6ad5fe1576 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -112,11 +112,24 @@ endif()
 # VERSION. VERSION will typically be like "2.7" on unix, and "27" on windows.
 execute_process(
   COMMAND
-    "${PYTHON_EXECUTABLE}" "-c" "from distutils import sysconfig as s;import sys;import struct;
+    "${PYTHON_EXECUTABLE}" "-c" "
+import sys;import struct;
+import sysconfig as s
+USE_SYSCONFIG = sys.version_info >= (3, 10)
+if not USE_SYSCONFIG:
+    from distutils import sysconfig as ds
 print('.'.join(str(v) for v in sys.version_info));
 print(sys.prefix);
-print(s.get_python_inc(plat_specific=True));
-print(s.get_python_lib(plat_specific=True));
+if USE_SYSCONFIG:
+    scheme = s.get_default_scheme()
+    if scheme == 'posix_local':
+        # Debian's default scheme installs to /usr/local/ but we want to find headers in /usr/
+        scheme = 'posix_prefix'
+    print(s.get_path('platinclude', scheme))
+    print(s.get_path('platlib'))
+else:
+    print(ds.get_python_inc(plat_specific=True));
+    print(ds.get_python_lib(plat_specific=True));
 print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'));
 print(hasattr(sys, 'gettotalrefcount')+0);
 print(struct.calcsize('@P'));

From 42a8e3125348d4e706e46eb410befc1422d42b3f Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 2 Mar 2022 13:17:52 -0500
Subject: [PATCH 327/638] Improve Python 3.11 support (#3694)

* Test out Python 3.11 migration

* Clean up a bit

* Remove todo

* Test workaround

* Fix potential bug uncovered in 3.11

* Try to fix it more

* last ditch fix

* Revert. Tp-traverse isn't the problem

* Test workaround

* Try this hack

* Revert MRO changes

* Use f_back properly

* Qualify auto

* Update include/pybind11/pybind11.h

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Simplify code slightly

* Ensure co_varnames decref if dict_getitem throws

* Eager decref f_code

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/detail/type_caster_base.h | 12 ++++++++++--
 include/pybind11/pybind11.h                | 12 ++++++------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index ff7d7cf8c2..a4154136a6 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -502,9 +502,10 @@ PYBIND11_NOINLINE std::string error_string() {
         }
 
         PyFrameObject *frame = trace->tb_frame;
+        Py_XINCREF(frame);
         errorString += "\n\nAt:\n";
         while (frame) {
-#    if PY_VERSION_HEX >= 0x03090000
+#    if PY_VERSION_HEX >= 0x030900B1
             PyCodeObject *f_code = PyFrame_GetCode(frame);
 #    else
             PyCodeObject *f_code = frame->f_code;
@@ -514,8 +515,15 @@ PYBIND11_NOINLINE std::string error_string() {
             errorString += "  " + handle(f_code->co_filename).cast<std::string>() + "("
                            + std::to_string(lineno)
                            + "): " + handle(f_code->co_name).cast<std::string>() + "\n";
-            frame = frame->f_back;
             Py_DECREF(f_code);
+#    if PY_VERSION_HEX >= 0x030900B1
+            auto *b_frame = PyFrame_GetBack(frame);
+#    else
+            auto *b_frame = frame->f_back;
+            Py_XINCREF(b_frame);
+#    endif
+            Py_DECREF(frame);
+            frame = b_frame;
         }
     }
 #endif
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 1ec6c17c67..4f6b2cdf41 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2636,9 +2636,7 @@ get_type_override(const void *this_ptr, const type_info *this_type, const char *
 
     /* Don't call dispatch code if invoked from overridden function.
        Unfortunately this doesn't work on PyPy. */
-#if !defined(PYPY_VERSION) && PY_VERSION_HEX < 0x030B0000
-    // TODO: Remove PyPy workaround for Python 3.11.
-    // Current API fails on 3.11 since co_varnames can be null.
+#if !defined(PYPY_VERSION)
 #    if PY_VERSION_HEX >= 0x03090000
     PyFrameObject *frame = PyThreadState_GetFrame(PyThreadState_Get());
     if (frame != nullptr) {
@@ -2646,9 +2644,11 @@ get_type_override(const void *this_ptr, const type_info *this_type, const char *
         // f_code is guaranteed to not be NULL
         if ((std::string) str(f_code->co_name) == name && f_code->co_argcount > 0) {
             PyObject *locals = PyEval_GetLocals();
-            if (locals != nullptr && f_code->co_varnames != nullptr) {
-                PyObject *self_caller
-                    = dict_getitem(locals, PyTuple_GET_ITEM(f_code->co_varnames, 0));
+            if (locals != nullptr) {
+                PyObject *co_varnames = PyObject_GetAttrString((PyObject *) f_code, "co_varnames");
+                PyObject *self_arg = PyTuple_GET_ITEM(co_varnames, 0);
+                Py_DECREF(co_varnames);
+                PyObject *self_caller = dict_getitem(locals, self_arg);
                 if (self_caller == self.ptr()) {
                     Py_DECREF(f_code);
                     Py_DECREF(frame);

From af08a95b5666cc1fcb6fc74254fd676940462947 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 2 Mar 2022 14:14:52 -0500
Subject: [PATCH 328/638] fix: potential memory leak in pypy (#3774)

---
 include/pybind11/pybind11.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 4f6b2cdf41..422d534c12 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2694,9 +2694,9 @@ get_type_override(const void *this_ptr, const type_info *this_type, const char *
                        d.ptr());
     if (result == nullptr)
         throw error_already_set();
+    Py_DECREF(result);
     if (d["self"].is_none())
         return function();
-    Py_DECREF(result);
 #endif
 
     return override;

From 2dd52544942be4bef80811ef18c8fcf1d3c7e246 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 2 Mar 2022 15:25:43 -0500
Subject: [PATCH 329/638] fix: missing move in eval.h (#3775)

---
 include/pybind11/eval.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index c157a00957..bd5f981f53 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -82,7 +82,7 @@ template <eval_mode mode = eval_expr, size_t N>
 object eval(const char (&s)[N], object global = globals(), object local = object()) {
     /* Support raw string literals by removing common leading whitespace */
     auto expr = (s[0] == '\n') ? str(module_::import("textwrap").attr("dedent")(s)) : str(s);
-    return eval<mode>(expr, global, local);
+    return eval<mode>(expr, std::move(global), std::move(local));
 }
 
 inline void exec(const str &expr, object global = globals(), object local = object()) {
@@ -91,7 +91,7 @@ inline void exec(const str &expr, object global = globals(), object local = obje
 
 template <size_t N>
 void exec(const char (&s)[N], object global = globals(), object local = object()) {
-    eval<eval_statements>(s, global, local);
+    eval<eval_statements>(s, std::move(global), std::move(local));
 }
 
 #if defined(PYPY_VERSION)

From d75b353694709add8bc31a931e123f7736929c94 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Thu, 10 Mar 2022 10:31:16 -0800
Subject: [PATCH 330/638] CI: MSVC Debug Build (#3784)

---
 .github/workflows/ci.yml | 54 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 179caa9e82..11c93bafc4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -755,6 +755,60 @@ jobs:
     - name: Python tests
       run: cmake --build build -t pytest
 
+  win32-debug:
+    strategy:
+      fail-fast: false
+      matrix:
+        python:
+        - 3.8
+        - 3.9
+
+        include:
+          - python: 3.9
+            args: -DCMAKE_CXX_STANDARD=20
+          - python: 3.8
+            args: -DCMAKE_CXX_STANDARD=17
+
+    name: "🐍 ${{ matrix.python }} • MSVC 2019 (Debug) • x86 ${{ matrix.args }}"
+    runs-on: windows-2019
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Python ${{ matrix.python }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+        architecture: x86
+
+    - name: Update CMake
+      uses: jwlawson/actions-setup-cmake@v1.12
+
+    - name: Prepare MSVC
+      uses: ilammy/msvc-dev-cmd@v1.10.0
+      with:
+        arch: x86
+
+    - name: Prepare env
+      run: |
+        python -m pip install -r tests/requirements.txt
+
+    # First build - C++11 mode and inplace
+    - name: Configure ${{ matrix.args }}
+      run: >
+        cmake -S . -B build
+        -G "Visual Studio 16 2019" -A Win32
+        -DCMAKE_BUILD_TYPE=Debug
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        ${{ matrix.args }}
+    - name: Build C++11
+      run: cmake --build build --config Debug -j 2
+
+    - name: Python tests
+      run: cmake --build build --config Debug -t pytest
+
   win32-msvc2017:
     name: "🐍 ${{ matrix.python }} • MSVC 2017 • x64"
     runs-on: windows-2016

From 91a6e129d9274a0b10943044e5aeae08471e00fe Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <oleksandr.pavlyk@intel.com>
Date: Fri, 11 Mar 2022 14:18:25 -0600
Subject: [PATCH 331/638] PYBIND11_OBJECT_CVT should use namespace for
 error_already_set() (#3797)

* PYBIND11_OBJECT_CVT should use namespace for error_already_set()

This change makes the macro usable outside of pybind11 namespace.

* added test for use of PYBIND11_OBJECT_CVT for classes in external to pybind11 namespaces

* Extended test_pytypes.cpp and test_pytest.py

The added test defines a dummy function that takes a custom-defined class external::float_
that uses PYBIND11_OBJECT_CVT

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fixed issues pointed out by CI

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fixed memory leak in default constructor

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pytypes.h |  4 ++--
 tests/test_pytypes.cpp     | 33 +++++++++++++++++++++++++++++++++
 tests/test_pytypes.py      |  5 +++++
 3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index dc753d32cd..e54941485b 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1038,12 +1038,12 @@ public:
     Name(const object &o)                                                                         \
         : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) {               \
         if (!m_ptr)                                                                               \
-            throw error_already_set();                                                            \
+            throw ::pybind11::error_already_set();                                                \
     }                                                                                             \
     /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
     Name(object &&o) : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) {  \
         if (!m_ptr)                                                                               \
-            throw error_already_set();                                                            \
+            throw ::pybind11::error_already_set();                                                \
     }
 
 #define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun)                           \
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 1ed237ea21..b859497b83 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -11,6 +11,34 @@
 
 #include <utility>
 
+namespace external {
+namespace detail {
+bool check(PyObject *o) { return PyFloat_Check(o) != 0; }
+
+PyObject *conv(PyObject *o) {
+    PyObject *ret = nullptr;
+    if (PyLong_Check(o)) {
+        double v = PyLong_AsDouble(o);
+        if (!(v == -1.0 && PyErr_Occurred())) {
+            ret = PyFloat_FromDouble(v);
+        }
+    } else {
+        PyErr_SetString(PyExc_TypeError, "Unexpected type");
+    }
+    return ret;
+}
+
+PyObject *default_constructed() { return PyFloat_FromDouble(0.0); }
+} // namespace detail
+class float_ : public py::object {
+    PYBIND11_OBJECT_CVT(float_, py::object, external::detail::check, external::detail::conv)
+
+    float_() : py::object(external::detail::default_constructed(), stolen_t{}) {}
+
+    double get_value() const { return PyFloat_AsDouble(this->ptr()); }
+};
+} // namespace external
+
 TEST_SUBMODULE(pytypes, m) {
     // test_bool
     m.def("get_bool", [] { return py::bool_(false); });
@@ -545,4 +573,9 @@ TEST_SUBMODULE(pytypes, m) {
         py::detail::accessor_policies::tuple_item::set(o, (py::size_t) 0, s0);
         return o;
     });
+
+    m.def("square_float_", [](const external::float_ &x) -> double {
+        double v = x.get_value();
+        return v * v;
+    });
 }
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index becd1cc8ae..85afb94232 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -634,3 +634,8 @@ def test_implementation_details():
     assert m.tuple_item_set_ssize_t() == ("emely", "edmond")
     assert m.tuple_item_get_size_t(tup) == 93
     assert m.tuple_item_set_size_t() == ("candy", "cat")
+
+
+def test_external_float_():
+    r1 = m.square_float_(2.0)
+    assert r1 == 4.0

From f8a532a7ded45203cd755d53f0da5f1fadbbea2d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 15 Mar 2022 10:18:12 -0400
Subject: [PATCH 332/638] [pre-commit.ci] pre-commit autoupdate (#3800)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.31.0 → v2.31.1](https://github.com/asottile/pyupgrade/compare/v2.31.0...v2.31.1)
- [github.com/sirosen/texthooks: 0.2.2 → 0.3.1](https://github.com/sirosen/texthooks/compare/0.2.2...0.3.1)
- [github.com/hadialqattan/pycln: v1.2.4 → v1.2.5](https://github.com/hadialqattan/pycln/compare/v1.2.4...v1.2.5)
- [github.com/pre-commit/mirrors-mypy: v0.931 → v0.940](https://github.com/pre-commit/mirrors-mypy/compare/v0.931...v0.940)
- [github.com/mgedmin/check-manifest: 0.47 → 0.48](https://github.com/mgedmin/check-manifest/compare/0.47...0.48)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e9a0e03f2b..c8b5276136 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.31.0"
+  rev: "v2.31.1"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -64,14 +64,14 @@ repos:
   - id: remove-tabs
 
 - repo: https://github.com/sirosen/texthooks
-  rev: "0.2.2"
+  rev: "0.3.1"
   hooks:
   - id: fix-ligatures
   - id: fix-smartquotes
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.2.4"
+  rev: "v1.2.5"
   hooks:
   - id: pycln
 
@@ -122,7 +122,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.931"
+  rev: "v0.940"
   hooks:
   - id: mypy
     args: [--show-error-codes]
@@ -131,7 +131,7 @@ repos:
 
 # Checks the manifest for missing files (native support)
 - repo: https://github.com/mgedmin/check-manifest
-  rev: "0.47"
+  rev: "0.48"
   hooks:
   - id: check-manifest
     # This is a slow hook, so only run this if --hook-stage manual is passed

From a7e7a6e8460767b70f11b375ea564d3856272260 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Thu, 17 Mar 2022 11:21:28 -0700
Subject: [PATCH 333/638] Docs: No Strip in Debug (#3779)

The docs were not 100% the same as we advertise with our
tooling function: most users do not want to strip symbols
in Debug builds.
---
 docs/compiling.rst | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/docs/compiling.rst b/docs/compiling.rst
index 4ae9234e15..2b543be0be 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -505,7 +505,10 @@ You can use these targets to build complex applications. For example, the
     target_link_libraries(example PRIVATE pybind11::module pybind11::lto pybind11::windows_extras)
 
     pybind11_extension(example)
-    pybind11_strip(example)
+    if(NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug|RelWithDebInfo)
+        # Strip unnecessary sections of the binary on Linux/macOS
+        pybind11_strip(example)
+    endif()
 
     set_target_properties(example PROPERTIES CXX_VISIBILITY_PRESET "hidden"
                                              CUDA_VISIBILITY_PRESET "hidden")

From 8b1944d390e9a89f22a1e47d2acbe7c547662aad Mon Sep 17 00:00:00 2001
From: JonTriebenbach <40633432+JonTriebenbach@users.noreply.github.com>
Date: Thu, 17 Mar 2022 14:51:16 -0500
Subject: [PATCH 334/638] Remove idioms in code comments (#3809)

---
 .github/workflows/ci.yml      | 2 +-
 docs/advanced/pycpp/numpy.rst | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 11c93bafc4..3523e82c0d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -667,7 +667,7 @@ jobs:
 
 
   # This verifies that the documentation is not horribly broken, and does a
-  # basic sanity check on the SDist.
+  # basic validation check on the SDist.
   doxygen:
     name: "Documentation build test"
     runs-on: ubuntu-latest
diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index 8ad3410045..b6ef019ed0 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -87,7 +87,7 @@ buffer objects (e.g. a NumPy matrix).
             /* Request a buffer descriptor from Python */
             py::buffer_info info = b.request();
 
-            /* Some sanity checks ... */
+            /* Some basic validation checks ... */
             if (info.format != py::format_descriptor<Scalar>::format())
                 throw std::runtime_error("Incompatible format: expected a double array!");
 

From b3a43d137c6c9ecf271a2a3d51a51b2fd1c3e8f6 Mon Sep 17 00:00:00 2001
From: Laramie Leavitt <laramiel@users.noreply.github.com>
Date: Fri, 18 Mar 2022 11:10:31 -0700
Subject: [PATCH 335/638] Use rvalue reference for std::variant cast_op<T>
 (#3811)

Nearly every call site of cast_op<T> uses an r-value reference.

Except stl.h variant_caster::load_alternative for handling std::variant.

Fix that.
---
 include/pybind11/stl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index b661296887..e3a0614444 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -372,7 +372,7 @@ struct variant_caster<V<Ts...>> {
     bool load_alternative(handle src, bool convert, type_list<U, Us...>) {
         auto caster = make_caster<U>();
         if (caster.load(src, convert)) {
-            value = cast_op<U>(caster);
+            value = cast_op<U>(std::move(caster));
             return true;
         }
         return load_alternative(src, convert, type_list<Us...>{});

From 67089cd3e6ca429faa4d9bf525e4b5ff29ede0d4 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 21 Mar 2022 20:47:02 -0400
Subject: [PATCH 336/638] [pre-commit.ci] pre-commit autoupdate (#3817)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/mirrors-mypy: v0.940 → v0.941](https://github.com/pre-commit/mirrors-mypy/compare/v0.940...v0.941)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c8b5276136..01a21e98d0 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -122,7 +122,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.940"
+  rev: "v0.941"
   hooks:
   - id: mypy
     args: [--show-error-codes]

From b22ee64c7309eb7344031b5e5385e6907d84c7eb Mon Sep 17 00:00:00 2001
From: Laramie Leavitt <laramiel@users.noreply.github.com>
Date: Mon, 21 Mar 2022 22:58:04 -0700
Subject: [PATCH 337/638] Add type_caster<std::monostate> (#3818)

* Add type_caster<std::monostate> for std::variant

Add type_caster<std::monostate>, allowing std::variant<std::monostate, ...>

* Add  variant<std::monostate, ...> test methods

* Add std::monostate tests

* Update test_stl.py

Remove erroneous extra tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update test fn name

* And update the doc() test

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/stl.h |  3 +++
 tests/test_stl.cpp     | 20 ++++++++++++++++++--
 tests/test_stl.py      | 16 ++++++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index e3a0614444..3d1ca7ac23 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -406,6 +406,9 @@ struct variant_caster<V<Ts...>> {
 #if defined(PYBIND11_HAS_VARIANT)
 template <typename... Ts>
 struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> {};
+
+template <>
+struct type_caster<std::monostate> : public void_caster<std::monostate> {};
 #endif
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index fd1824beb4..b56a91953b 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -37,9 +37,10 @@ struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
 #if defined(PYBIND11_HAS_VARIANT)
 using std::variant;
+#    define PYBIND11_TEST_VARIANT 1
 #elif defined(PYBIND11_TEST_BOOST)
 #    include <boost/variant.hpp>
-#    define PYBIND11_HAS_VARIANT 1
+#    define PYBIND11_TEST_VARIANT 1
 using boost::variant;
 
 namespace pybind11 {
@@ -424,7 +425,7 @@ TEST_SUBMODULE(stl, m) {
     m.def("parent_path", [](const std::filesystem::path &p) { return p.parent_path(); });
 #endif
 
-#ifdef PYBIND11_HAS_VARIANT
+#ifdef PYBIND11_TEST_VARIANT
     static_assert(std::is_same<py::detail::variant_caster_visitor::result_type, py::handle>::value,
                   "visitor::result_type is required by boost::variant in C++11 mode");
 
@@ -435,6 +436,9 @@ TEST_SUBMODULE(stl, m) {
         result_type operator()(const std::string &) { return "std::string"; }
         result_type operator()(double) { return "double"; }
         result_type operator()(std::nullptr_t) { return "std::nullptr_t"; }
+#    if defined(PYBIND11_HAS_VARIANT)
+        result_type operator()(std::monostate) { return "std::monostate"; }
+#    endif
     };
 
     // test_variant
@@ -448,6 +452,18 @@ TEST_SUBMODULE(stl, m) {
         using V = variant<int, std::string>;
         return py::make_tuple(V(5), V("Hello"));
     });
+
+#    if defined(PYBIND11_HAS_VARIANT)
+    // std::monostate tests.
+    m.def("load_monostate_variant",
+          [](const variant<std::monostate, int, std::string> &v) -> const char * {
+              return py::detail::visit_helper<variant>::call(visitor(), v);
+          });
+    m.def("cast_monostate_variant", []() {
+        using V = variant<std::monostate, int, std::string>;
+        return py::make_tuple(V{}, V(5), V("Hello"));
+    });
+#    endif
 #endif
 
     // #528: templated constructor
diff --git a/tests/test_stl.py b/tests/test_stl.py
index a3d6866899..3dc55230ab 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -263,6 +263,22 @@ def test_variant(doc):
     )
 
 
+@pytest.mark.skipif(
+    not hasattr(m, "load_monostate_variant"), reason="no std::monostate"
+)
+def test_variant_monostate(doc):
+    assert m.load_monostate_variant(None) == "std::monostate"
+    assert m.load_monostate_variant(1) == "int"
+    assert m.load_monostate_variant("1") == "std::string"
+
+    assert m.cast_monostate_variant() == (None, 5, "Hello")
+
+    assert (
+        doc(m.load_monostate_variant)
+        == "load_monostate_variant(arg0: Union[None, int, str]) -> str"
+    )
+
+
 def test_vec_of_reference_wrapper():
     """#171: Can't return reference wrappers (or STL structures containing them)"""
     assert (

From 47079b9e7b81a4b6d93c46a452115d7d8fd3488f Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 24 Mar 2022 12:57:37 -0400
Subject: [PATCH 338/638] (perf): Add missing move in sp matrix caster and
 microopt char concats (#3823)

* Add missing move in sp matrix caster and microopt char concat

* Remove useless move

* Add a couple more std::move

* Missed one char

* Improve error_string

* Ensure no temp reallocs in errorString concat

* Remove useless move
---
 include/pybind11/detail/type_caster_base.h | 14 +++++++++-----
 include/pybind11/eigen.h                   |  5 +++--
 include/pybind11/numpy.h                   |  6 +++---
 include/pybind11/pybind11.h                | 12 ++++++------
 4 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a4154136a6..5b2ec8e1e4 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -225,8 +225,8 @@ PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
     if (throw_if_missing) {
         std::string tname = tp.name();
         detail::clean_type_id(tname);
-        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname
-                      + "\"");
+        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \""
+                      + std::move(tname) + '"');
     }
     return nullptr;
 }
@@ -512,9 +512,13 @@ PYBIND11_NOINLINE std::string error_string() {
             Py_INCREF(f_code);
 #    endif
             int lineno = PyFrame_GetLineNumber(frame);
-            errorString += "  " + handle(f_code->co_filename).cast<std::string>() + "("
-                           + std::to_string(lineno)
-                           + "): " + handle(f_code->co_name).cast<std::string>() + "\n";
+            errorString += "  ";
+            errorString += handle(f_code->co_filename).cast<std::string>();
+            errorString += '(';
+            errorString += std::to_string(lineno);
+            errorString += "): ";
+            errorString += handle(f_code->co_name).cast<std::string>();
+            errorString += '\n';
             Py_DECREF(f_code);
 #    if PY_VERSION_HEX >= 0x030900B1
             auto *b_frame = PyFrame_GetBack(frame);
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 930c4f7fa8..f658168ded 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -668,7 +668,7 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
                                      Type::Flags &(Eigen::RowMajor | Eigen::ColMajor),
                                      StorageIndex>(shape[0].cast<Index>(),
                                                    shape[1].cast<Index>(),
-                                                   nnz,
+                                                   std::move(nnz),
                                                    outerIndices.mutable_data(),
                                                    innerIndices.mutable_data(),
                                                    values.mutable_data());
@@ -686,7 +686,8 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         array outerIndices((rowMajor ? src.rows() : src.cols()) + 1, src.outerIndexPtr());
         array innerIndices(src.nonZeros(), src.innerIndexPtr());
 
-        return matrix_type(std::make_tuple(data, innerIndices, outerIndices),
+        return matrix_type(std::make_tuple(
+                               std::move(data), std::move(innerIndices), std::move(outerIndices)),
                            std::make_pair(src.rows(), src.cols()))
             .release();
     }
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 5e68f60530..07dea21b4f 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -940,7 +940,7 @@ class array : public buffer {
 
     void fail_dim_check(ssize_t dim, const std::string &msg) const {
         throw index_error(msg + ": " + std::to_string(dim) + " (ndim = " + std::to_string(ndim())
-                          + ")");
+                          + ')');
     }
 
     template <typename... Ix>
@@ -1144,11 +1144,11 @@ struct format_descriptor<T, detail::enable_if_t<detail::is_pod_struct<T>::value>
 
 template <size_t N>
 struct format_descriptor<char[N]> {
-    static std::string format() { return std::to_string(N) + "s"; }
+    static std::string format() { return std::to_string(N) + 's'; }
 };
 template <size_t N>
 struct format_descriptor<std::array<char, N>> {
-    static std::string format() { return std::to_string(N) + "s"; }
+    static std::string format() { return std::to_string(N) + 's'; }
 };
 
 template <typename T>
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 422d534c12..fa018b509d 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -561,14 +561,14 @@ class cpp_function : public function {
         for (auto *it = chain_start; it != nullptr; it = it->next) {
             if (options::show_function_signatures()) {
                 if (index > 0) {
-                    signatures += "\n";
+                    signatures += '\n';
                 }
                 if (chain) {
                     signatures += std::to_string(++index) + ". ";
                 }
                 signatures += rec->name;
                 signatures += it->signature;
-                signatures += "\n";
+                signatures += '\n';
             }
             if (it->doc && it->doc[0] != '\0' && options::show_user_defined_docstrings()) {
                 // If we're appending another docstring, and aren't printing function signatures,
@@ -577,15 +577,15 @@ class cpp_function : public function {
                     if (first_user_def) {
                         first_user_def = false;
                     } else {
-                        signatures += "\n";
+                        signatures += '\n';
                     }
                 }
                 if (options::show_function_signatures()) {
-                    signatures += "\n";
+                    signatures += '\n';
                 }
                 signatures += it->doc;
                 if (options::show_function_signatures()) {
-                    signatures += "\n";
+                    signatures += '\n';
                 }
             }
         }
@@ -1055,7 +1055,7 @@ class cpp_function : public function {
                     msg += it2->signature;
                 }
 
-                msg += "\n";
+                msg += '\n';
             }
             msg += "\nInvoked with: ";
             auto args_ = reinterpret_borrow<tuple>(args_in);

From 146695a904526adc70c97615f7c395c4b3115c18 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 25 Mar 2022 10:55:13 -0400
Subject: [PATCH 339/638] fix: better exception and error handling for capsules
 (#3825)

* Make capsule errors better match python
---
 include/pybind11/numpy.h   |  3 ++-
 include/pybind11/pytypes.h | 32 +++++++++++++++++++-------------
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 07dea21b4f..7624c9fbf4 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1288,7 +1288,8 @@ struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
     static pybind11::dtype dtype() {
         list shape;
         array_info<T>::append_extents(shape);
-        return pybind11::dtype::from_args(pybind11::make_tuple(base_descr::dtype(), shape));
+        return pybind11::dtype::from_args(
+            pybind11::make_tuple(base_descr::dtype(), std::move(shape)));
     }
 };
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index e54941485b..b9ec8af4e1 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1574,7 +1574,7 @@ class capsule : public object {
                      void (*destructor)(PyObject *) = nullptr)
         : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
         if (!m_ptr) {
-            pybind11_fail("Could not allocate capsule object!");
+            throw error_already_set();
         }
     }
 
@@ -1582,34 +1582,42 @@ class capsule : public object {
     capsule(const void *value, void (*destruct)(PyObject *))
         : object(PyCapsule_New(const_cast<void *>(value), nullptr, destruct), stolen_t{}) {
         if (!m_ptr) {
-            pybind11_fail("Could not allocate capsule object!");
+            throw error_already_set();
         }
     }
 
     capsule(const void *value, void (*destructor)(void *)) {
         m_ptr = PyCapsule_New(const_cast<void *>(value), nullptr, [](PyObject *o) {
             auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
+            if (destructor == nullptr) {
+                if (PyErr_Occurred()) {
+                    throw error_already_set();
+                }
+                pybind11_fail("Unable to get capsule context");
+            }
             void *ptr = PyCapsule_GetPointer(o, nullptr);
+            if (ptr == nullptr) {
+                throw error_already_set();
+            }
             destructor(ptr);
         });
 
-        if (!m_ptr) {
-            pybind11_fail("Could not allocate capsule object!");
-        }
-
-        if (PyCapsule_SetContext(m_ptr, (void *) destructor) != 0) {
-            pybind11_fail("Could not set capsule context!");
+        if (!m_ptr || PyCapsule_SetContext(m_ptr, (void *) destructor) != 0) {
+            throw error_already_set();
         }
     }
 
     explicit capsule(void (*destructor)()) {
         m_ptr = PyCapsule_New(reinterpret_cast<void *>(destructor), nullptr, [](PyObject *o) {
             auto destructor = reinterpret_cast<void (*)()>(PyCapsule_GetPointer(o, nullptr));
+            if (destructor == nullptr) {
+                throw error_already_set();
+            }
             destructor();
         });
 
         if (!m_ptr) {
-            pybind11_fail("Could not allocate capsule object!");
+            throw error_already_set();
         }
     }
 
@@ -1624,8 +1632,7 @@ class capsule : public object {
         const auto *name = this->name();
         T *result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
         if (!result) {
-            PyErr_Clear();
-            pybind11_fail("Unable to extract capsule contents!");
+            throw error_already_set();
         }
         return result;
     }
@@ -1633,8 +1640,7 @@ class capsule : public object {
     /// Replaces a capsule's pointer *without* calling the destructor on the existing one.
     void set_pointer(const void *value) {
         if (PyCapsule_SetPointer(m_ptr, const_cast<void *>(value)) != 0) {
-            PyErr_Clear();
-            pybind11_fail("Could not set capsule pointer");
+            throw error_already_set();
         }
     }
 

From 461937d3e545136f48adc08c8cb80dff4c5994cf Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 25 Mar 2022 12:34:32 -0400
Subject: [PATCH 340/638] ci: test pypy 3.9 (#3789)

* ci: test pypy 3.9

* ci: try a use of FindPython with PyPy
---
 .github/workflows/ci.yml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3523e82c0d..78f39b0c19 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -32,6 +32,7 @@ jobs:
         - '3.10'
         - 'pypy-3.7'
         - 'pypy-3.8'
+        - 'pypy-3.9'
 
         # Items in here will either be added to the build matrix (if not
         # present), or add new keys to an existing matrix element if all the
@@ -45,6 +46,10 @@ jobs:
             args: >
               -DPYBIND11_FINDPYTHON=ON
               -DCMAKE_CXX_FLAGS="-D_=1"
+          - runs-on: ubuntu-latest
+            python: 'pypy-3.9'
+            args: >
+              -DPYBIND11_FINDPYTHON=ON
           - runs-on: windows-2019
             python: '3.6'
             args: >

From 7742be02d9d1231c7b541c44a32c4f0921c6f7f9 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 25 Mar 2022 14:54:43 -0400
Subject: [PATCH 341/638] Revert "ci: test pypy 3.9" (#3828)

* Revert "ci: test pypy 3.9 (#3789)"

This reverts commit 461937d3e545136f48adc08c8cb80dff4c5994cf.

* Update ci.yml
---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 78f39b0c19..b2fc52bf20 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,7 +47,7 @@ jobs:
               -DPYBIND11_FINDPYTHON=ON
               -DCMAKE_CXX_FLAGS="-D_=1"
           - runs-on: ubuntu-latest
-            python: 'pypy-3.9'
+            python: 'pypy-3.8'
             args: >
               -DPYBIND11_FINDPYTHON=ON
           - runs-on: windows-2019

From 3a183d4b587841fb868cee23df7bfe0afe893bb8 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 25 Mar 2022 16:01:34 -0400
Subject: [PATCH 342/638] fix: improve str exceptions and consistency with
 python (#3826)

* Improve str exceptions

* Revert macro change just in case

* Make clang-tidy happy

* Fix one more clang-tidy issue

* Refactor duplicate method
---
 include/pybind11/pytypes.h | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index b9ec8af4e1..18cd715805 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1243,8 +1243,8 @@ class str : public object {
         }
         char *buffer = nullptr;
         ssize_t length = 0;
-        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length)) {
-            pybind11_fail("Unable to extract string contents! (invalid type)");
+        if (PyBytes_AsStringAndSize(temp.ptr(), &buffer, &length) != 0) {
+            throw error_already_set();
         }
         return std::string(buffer, (size_t) length);
     }
@@ -1299,14 +1299,7 @@ class bytes : public object {
     explicit bytes(const pybind11::str &s);
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator std::string() const {
-        char *buffer = nullptr;
-        ssize_t length = 0;
-        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length)) {
-            pybind11_fail("Unable to extract bytes contents!");
-        }
-        return std::string(buffer, (size_t) length);
-    }
+    operator std::string() const { return string_op<std::string>(); }
 
 #ifdef PYBIND11_HAS_STRING_VIEW
     // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
@@ -1318,15 +1311,18 @@ class bytes : public object {
     // valid so long as the `bytes` instance remains alive and so generally should not outlive the
     // lifetime of the `bytes` instance.
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator std::string_view() const {
+    operator std::string_view() const { return string_op<std::string_view>(); }
+#endif
+private:
+    template <typename T>
+    T string_op() const {
         char *buffer = nullptr;
         ssize_t length = 0;
-        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length)) {
-            pybind11_fail("Unable to extract bytes contents!");
+        if (PyBytes_AsStringAndSize(m_ptr, &buffer, &length) != 0) {
+            throw error_already_set();
         }
         return {buffer, static_cast<size_t>(length)};
     }
-#endif
 };
 // Note: breathe >= 4.17.0 will fail to build docs if the below two constructors
 // are included in the doxygen group; close here and reopen after as a workaround
@@ -1337,13 +1333,13 @@ inline bytes::bytes(const pybind11::str &s) {
     if (PyUnicode_Check(s.ptr())) {
         temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(s.ptr()));
         if (!temp) {
-            pybind11_fail("Unable to extract string contents! (encoding issue)");
+            throw error_already_set();
         }
     }
     char *buffer = nullptr;
     ssize_t length = 0;
-    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length)) {
-        pybind11_fail("Unable to extract string contents! (invalid type)");
+    if (PyBytes_AsStringAndSize(temp.ptr(), &buffer, &length) != 0) {
+        throw error_already_set();
     }
     auto obj = reinterpret_steal<object>(PYBIND11_BYTES_FROM_STRING_AND_SIZE(buffer, length));
     if (!obj) {
@@ -1355,8 +1351,8 @@ inline bytes::bytes(const pybind11::str &s) {
 inline str::str(const bytes &b) {
     char *buffer = nullptr;
     ssize_t length = 0;
-    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length)) {
-        pybind11_fail("Unable to extract bytes contents!");
+    if (PyBytes_AsStringAndSize(b.ptr(), &buffer, &length) != 0) {
+        throw error_already_set();
     }
     auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, length));
     if (!obj) {

From 42d8593ad4225a634b481cd573f7aeb94de72418 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 28 Mar 2022 17:24:59 -0400
Subject: [PATCH 343/638] style: bump black (#3831)

* style: bump black

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix: pycln broken by typer breakage
---
 .pre-commit-config.yaml | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 01a21e98d0..6a00f2fcee 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -45,7 +45,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "22.1.0" # Keep in sync with blacken-docs
+  rev: "22.3.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -55,7 +55,7 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==22.1.0 # keep in sync with black hook
+    - black==22.3.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
@@ -74,6 +74,8 @@ repos:
   rev: "v1.2.5"
   hooks:
   - id: pycln
+    additional_dependencies: [click<8.1]  # Unpin when typer updates
+    stages: [manual]
 
 # Checking for common mistakes
 - repo: https://github.com/pre-commit/pygrep-hooks
@@ -106,7 +108,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.12.2"
+  rev: "v2.13.2"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -122,7 +124,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.941"
+  rev: "v0.942"
   hooks:
   - id: mypy
     args: [--show-error-codes]

From 65ec5de52fecc974157a0c28490fef61204c39a1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 30 Mar 2022 23:02:00 -0400
Subject: [PATCH 344/638] chore: bump changelog for 2.9.2 (#3834)

* chore: bump changelog for 2.9.2

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update docs/changelog.rst
---
 docs/changelog.rst | 121 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 120 insertions(+), 1 deletion(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 9d7693cddc..67ac79cdd1 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -6,10 +6,129 @@ Changelog
 Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 <http://semver.org>`_ policy.
 
+Changes will be added here periodically from the "Suggested changelog entry"
+block in pull request descriptions.
+
 IN DEVELOPMENT
 --------------
 
-Changes will be added here periodically.
+Removed support for Python 2.7, Python 3.5, and MSVC 2015. Support for MSVC
+2017 is limited due to availability of CI runners; we highly recommend MSVC
+2019 or 2022 be used.
+
+New features:
+
+* ``type_caster<std::monostate>`` was added. ``std::monostate`` is a tag type
+  that allows ``std::variant`` to act as an optional, or allows default
+  construction of a ``std::variant`` holding a non-default constructible type.
+  `#3818 <https://github.com/pybind/pybind11/pull/3818>`_
+
+* Support bytearray casting to string.
+  `#3707 <https://github.com/pybind/pybind11/pull/3707>`_
+
+Changes:
+
+* Python 2 support was removed completely.
+  `#3688 <https://github.com/pybind/pybind11/pull/3688>`_
+
+* The minimum version for MSVC is now 2017.
+  `#3722 <https://github.com/pybind/pybind11/pull/3722>`_
+
+* Improve exception handling in python ``str`` bindings.
+  `#3826 <https://github.com/pybind/pybind11/pull/3826>`_
+
+* The bindings for capsules now have more consistent exception handling.
+  `#3825 <https://github.com/pybind/pybind11/pull/3825>`_
+
+* Fix exception handling when ``pybind11::weakref()`` fails.
+  `#3739 <https://github.com/pybind/pybind11/pull/3739>`_
+
+
+Bug fixes:
+
+* ``PYBIND11_OBJECT_CVT`` and ``PYBIND11_OBJECT_CVT_DEFAULT`` macro can be used
+  to define classes in namespaces other than pybind11.
+  `#3797 <https://github.com/pybind/pybind11/pull/3797>`_
+
+Build system improvements:
+
+* Add MSVC builds in debug mode to CI.
+  `#3784 <https://github.com/pybind/pybind11/pull/3784>`_
+
+* MSVC 2022 C++20 coverage was added to GitHub Actions, including Eigen.
+  `#3732 <https://github.com/pybind/pybind11/pull/3732>`_,
+  `#3741 <https://github.com/pybind/pybind11/pull/3741>`_
+
+* Avoid ``setup.py <command>`` usage in internal tests.
+  `#3734 <https://github.com/pybind/pybind11/pull/3734>`_
+
+
+Backend and tidying up:
+
+* Remove idioms in code comments.  Use inclusive language.
+  `#3809 <https://github.com/pybind/pybind11/pull/3809>`_
+
+
+Version 2.9.2 (Mar 29, 2022)
+----------------------------
+
+Changes:
+
+* Enum now has an ``__index__`` method on Python <3.8 too.
+  `#3700 <https://github.com/pybind/pybind11/pull/3700>`_
+
+* Local internals are now cleared after finalizing the interpreter.
+  `#3744 <https://github.com/pybind/pybind11/pull/3744>`_
+
+Bug fixes:
+
+* Better support for Python 3.11 alphas.
+  `#3694 <https://github.com/pybind/pybind11/pull/3694>`_
+
+* ``PYBIND11_TYPE_CASTER`` now uses fully qualified symbols, so it can be used
+  outside of ``pybind11::detail``.
+  `#3758 <https://github.com/pybind/pybind11/pull/3758>`_
+
+* Some fixes for PyPy 3.9.
+  `#3768 <https://github.com/pybind/pybind11/pull/3768>`_
+
+* Fixed a potential memleak in PyPy in ``get_type_override``.
+  `#3774 <https://github.com/pybind/pybind11/pull/3774>`_
+
+* Fix usage of ``VISIBILITY_INLINES_HIDDEN``.
+  `#3721 <https://github.com/pybind/pybind11/pull/3721>`_
+
+
+Build system improvements:
+
+* Uses ``sysconfig`` module to determine installation locations on Python >=
+  3.10, instead of ``distutils`` which has been deprecated.
+  `#3764 <https://github.com/pybind/pybind11/pull/3764>`_
+
+* Support Catch 2.13.5+ (supporting GLIBC 2.34+).
+  `#3679 <https://github.com/pybind/pybind11/pull/3679>`_
+
+* Fix test failures with numpy 1.22 by ignoring whitespace when comparing
+  ``str()`` of dtypes.
+  `#3682 <https://github.com/pybind/pybind11/pull/3682>`_
+
+
+Backend and tidying up:
+
+* clang-tidy: added ``readability-qualified-auto``,
+  ``readability-braces-around-statements``,
+  ``cppcoreguidelines-prefer-member-initializer``,
+  ``clang-analyzer-optin.performance.Padding``,
+  ``cppcoreguidelines-pro-type-static-cast-downcast``, and
+  ``readability-inconsistent-declaration-parameter-name``.
+  `#3702 <https://github.com/pybind/pybind11/pull/3702>`_,
+  `#3699 <https://github.com/pybind/pybind11/pull/3699>`_,
+  `#3716 <https://github.com/pybind/pybind11/pull/3716>`_,
+  `#3709 <https://github.com/pybind/pybind11/pull/3709>`_
+
+* clang-format was added to the pre-commit actions, and the entire code base
+  automatically reformatted (after several iterations preparing for this leap).
+  `#3713 <https://github.com/pybind/pybind11/pull/3713>`_
 
 
 Version 2.9.1 (Feb 2, 2022)

From b3ebd11d9851007f525e2e41de53b7913b24787c Mon Sep 17 00:00:00 2001
From: "Lonnie L. Souder II" <lonnie2@souderfamily.net>
Date: Fri, 1 Apr 2022 01:16:10 -0400
Subject: [PATCH 345/638] feature: support compilers that use
 std::experimental::filesystem  (#3840)

* feature: support compilers that use std::experimental::filesystem such as gcc7

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* only use this feature if cpp17

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* more specific namespace alias + style

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* move to pybind11 namespace

* no namespace alias

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: Lonnie Souder II <lonnie.souder@g6labs.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/stl/filesystem.h | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 93727424c9..e26f421776 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -13,21 +13,28 @@
 #include <string>
 
 #ifdef __has_include
-#    if defined(PYBIND11_CPP17) && __has_include(<filesystem>)
-#        include <filesystem>
-#        define PYBIND11_HAS_FILESYSTEM 1
+#    if defined(PYBIND11_CPP17)
+#        if __has_include(<filesystem>) && \
+          PY_VERSION_HEX >= 0x03060000
+#            include <filesystem>
+#            define PYBIND11_HAS_FILESYSTEM 1
+#        elif __has_include(<experimental/filesystem>)
+#            include <experimental/filesystem>
+#            define PYBIND11_HAS_EXPERIMENTAL_FILESYSTEM 1
+#        endif
 #    endif
 #endif
 
-#if !defined(PYBIND11_HAS_FILESYSTEM) && !defined(PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL)
+#if !defined(PYBIND11_HAS_FILESYSTEM) && !defined(PYBIND11_HAS_EXPERIMENTAL_FILESYSTEM)           \
+    && !defined(PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL)
 #    error                                                                                        \
-        "#include <filesystem> is not available. (Use -DPYBIND11_HAS_FILESYSTEM_IS_OPTIONAL to ignore.)"
+        "Neither #include <filesystem> nor #include <experimental/filesystem is available. (Use -DPYBIND11_HAS_FILESYSTEM_IS_OPTIONAL to ignore.)"
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-#if defined(PYBIND11_HAS_FILESYSTEM)
+#if defined(PYBIND11_HAS_FILESYSTEM) || defined(PYBIND11_HAS_EXPERIMENTAL_FILESYSTEM)
 template <typename T>
 struct path_caster {
 
@@ -94,9 +101,16 @@ struct path_caster {
     PYBIND11_TYPE_CASTER(T, const_name("os.PathLike"));
 };
 
+#endif // PYBIND11_HAS_FILESYSTEM || defined(PYBIND11_HAS_EXPERIMENTAL_FILESYSTEM)
+
+#if defined(PYBIND11_HAS_FILESYSTEM)
 template <>
 struct type_caster<std::filesystem::path> : public path_caster<std::filesystem::path> {};
-#endif // PYBIND11_HAS_FILESYSTEM
+#elif defined(PYBIND11_HAS_EXPERIMENTAL_FILESYSTEM)
+template <>
+struct type_caster<std::experimental::filesystem::path>
+    : public path_caster<std::experimental::filesystem::path> {};
+#endif
 
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

From f2f0c69096f913f99d59dcde7258ab9c95f08d44 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 4 Apr 2022 17:56:42 -0400
Subject: [PATCH 346/638] [pre-commit.ci] pre-commit autoupdate (#3848)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/pylint: v2.13.2 → v2.13.4](https://github.com/PyCQA/pylint/compare/v2.13.2...v2.13.4)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 6a00f2fcee..9ff2013ed4 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -108,7 +108,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.13.2"
+  rev: "v2.13.4"
   hooks:
   - id: pylint
     files: ^pybind11

From c4e295287b74c0b3f0f8a304cdb746ac2bcb37ad Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 5 Apr 2022 14:36:39 -0400
Subject: [PATCH 347/638] perf: Add more moves and optimize (#3845)

* Make slice constructor consistent

* Add more missing std::move for ref steals

* Add missing perfect forwarding for arg_v ctor

* Add missing move in arg_v constructor

* Revert "Add missing move in arg_v constructor"

This reverts commit 126fc7c524ea7a51b54720defd75de3470d69557.

* Add another missing move in cast.h

* Optimize object move ctor

* Don't do useless move

* Make move ctor same as nb

* Make obj move ctor same as nb

* Revert changes which break MSVC
---
 include/pybind11/cast.h    | 6 +++---
 include/pybind11/numpy.h   | 6 +++---
 include/pybind11/pytypes.h | 9 +++------
 include/pybind11/stl.h     | 2 +-
 4 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index d45b49c52e..07a56e71f7 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1243,8 +1243,8 @@ struct arg_v : arg {
 private:
     template <typename T>
     arg_v(arg &&base, T &&x, const char *descr = nullptr)
-        : arg(base), value(reinterpret_steal<object>(
-                         detail::make_caster<T>::cast(x, return_value_policy::automatic, {}))),
+        : arg(base), value(reinterpret_steal<object>(detail::make_caster<T>::cast(
+                         std::forward<T>(x), return_value_policy::automatic, {}))),
           descr(descr)
 #if !defined(NDEBUG)
           ,
@@ -1491,7 +1491,7 @@ class unpacking_collector {
                                                         type_id<T>());
 #endif
         }
-        args_list.append(o);
+        args_list.append(std::move(o));
     }
 
     void process(list &args_list, detail::args_proxy ap) {
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 7624c9fbf4..d45fe42803 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -640,9 +640,9 @@ class dtype : public object {
 
         list names, formats, offsets;
         for (auto &descr : field_descriptors) {
-            names.append(descr.name);
-            formats.append(descr.format);
-            offsets.append(descr.offset);
+            names.append(std::move(descr.name));
+            formats.append(std::move(descr.format));
+            offsets.append(std::move(descr.offset));
         }
         return dtype(std::move(names), std::move(formats), std::move(offsets), itemsize);
     }
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 18cd715805..ba0fda0a8c 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -268,10 +268,7 @@ class object : public handle {
     /// Copy constructor; always increases the reference count
     object(const object &o) : handle(o) { inc_ref(); }
     /// Move constructor; steals the object from ``other`` and preserves its reference count
-    object(object &&other) noexcept {
-        m_ptr = other.m_ptr;
-        other.m_ptr = nullptr;
-    }
+    object(object &&other) noexcept : handle(other) { other.m_ptr = nullptr; }
     /// Destructor; automatically calls `handle::dec_ref()`
     ~object() { dec_ref(); }
 
@@ -1519,8 +1516,8 @@ class weakref : public object {
 class slice : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(slice, object, PySlice_Check)
-    slice(handle start, handle stop, handle step) {
-        m_ptr = PySlice_New(start.ptr(), stop.ptr(), step.ptr());
+    slice(handle start, handle stop, handle step)
+        : object(PySlice_New(start.ptr(), stop.ptr(), step.ptr()), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate slice object!");
         }
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 3d1ca7ac23..51b57a92ba 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -79,7 +79,7 @@ struct set_caster {
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(
                 key_conv::cast(forward_like<T>(value), policy, parent));
-            if (!value_ || !s.add(value_)) {
+            if (!value_ || !s.add(std::move(value_))) {
                 return handle();
             }
         }

From ab59f45d2ee05b1df299021b62ab1f59a768e285 Mon Sep 17 00:00:00 2001
From: Laramie Leavitt <laramiel@users.noreply.github.com>
Date: Mon, 11 Apr 2022 10:36:24 -0700
Subject: [PATCH 348/638] Prefer make_caster<T> to type_caster<T> (#3859)

---
 include/pybind11/cast.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 07a56e71f7..bead97f914 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -514,7 +514,7 @@ struct type_caster<std::basic_string_view<CharT, Traits>,
 template <typename CharT>
 struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
     using StringType = std::basic_string<CharT>;
-    using StringCaster = type_caster<StringType>;
+    using StringCaster = make_caster<StringType>;
     StringCaster str_caster;
     bool none = false;
     CharT one_char = 0;

From 1b27b744c151bfa2db60566112b4d8307cb05104 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 11 Apr 2022 13:53:30 -0400
Subject: [PATCH 349/638] chore: Make stl_bind take slice as const_ref (#3852)

* Make stl_bind take slice as const_ref

* Change eval order if

* Silence MSVC warning
---
 include/pybind11/pybind11.h | 3 ++-
 include/pybind11/stl_bind.h | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index fa018b509d..797c769d78 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1817,7 +1817,8 @@ class class_ : public detail::generic_type {
         if (holder_ptr) {
             init_holder_from_existing(v_h, holder_ptr, std::is_copy_constructible<holder_type>());
             v_h.set_holder_constructed();
-        } else if (inst->owned || detail::always_construct_holder<holder_type>::value) {
+        } else if (PYBIND11_SILENCE_MSVC_C4127(detail::always_construct_holder<holder_type>::value)
+                   || inst->owned) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(v_h.value_ptr<type>());
             v_h.set_holder_constructed();
         }
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 3a3e54dd48..22a29b476f 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -232,7 +232,7 @@ void vector_modifiers(
     /// Slicing protocol
     cl.def(
         "__getitem__",
-        [](const Vector &v, slice slice) -> Vector * {
+        [](const Vector &v, const slice &slice) -> Vector * {
             size_t start = 0, stop = 0, step = 0, slicelength = 0;
 
             if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
@@ -253,7 +253,7 @@ void vector_modifiers(
 
     cl.def(
         "__setitem__",
-        [](Vector &v, slice slice, const Vector &value) {
+        [](Vector &v, const slice &slice, const Vector &value) {
             size_t start = 0, stop = 0, step = 0, slicelength = 0;
             if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
                 throw error_already_set();
@@ -281,7 +281,7 @@ void vector_modifiers(
 
     cl.def(
         "__delitem__",
-        [](Vector &v, slice slice) {
+        [](Vector &v, const slice &slice) {
             size_t start = 0, stop = 0, step = 0, slicelength = 0;
 
             if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {

From e3aa215b020886d648add951186052c619c3cf9d Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 11 Apr 2022 14:03:43 -0400
Subject: [PATCH 350/638] Add perfect forwarding to make_iterator calls (#3860)

---
 include/pybind11/pybind11.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 797c769d78..97275e40a8 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2403,7 +2403,8 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Type,
           typename... Extra>
 iterator make_iterator(Type &value, Extra &&...extra) {
-    return make_iterator<Policy>(std::begin(value), std::end(value), extra...);
+    return make_iterator<Policy>(
+        std::begin(value), std::end(value), std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over the keys (`.first`) of a stl map-like container supporting
@@ -2412,7 +2413,8 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Type,
           typename... Extra>
 iterator make_key_iterator(Type &value, Extra &&...extra) {
-    return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
+    return make_key_iterator<Policy>(
+        std::begin(value), std::end(value), std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over the values (`.second`) of a stl map-like container supporting
@@ -2421,7 +2423,8 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Type,
           typename... Extra>
 iterator make_value_iterator(Type &value, Extra &&...extra) {
-    return make_value_iterator<Policy>(std::begin(value), std::end(value), extra...);
+    return make_value_iterator<Policy>(
+        std::begin(value), std::end(value), std::forward<Extra>(extra)...);
 }
 
 template <typename InputType, typename OutputType>

From 088ad4f2987d3da4b1ffab376b2b4812fd7634ef Mon Sep 17 00:00:00 2001
From: Laramie Leavitt <laramiel@users.noreply.github.com>
Date: Mon, 11 Apr 2022 11:57:05 -0700
Subject: [PATCH 351/638] Cleanup cast_safe<void> specialization (#3861)

* Cleanup cast_safe<void> specialization

Replace explicit specialization of cast_safe<void> with SFINAE.
It's better for SFINAE cases to cover all type-sets rather than mixing SFINAE and explicit specialization.

Extracted from #3674

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update cast.h

Use detail::none_of<> as suggested

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update cast.h

Reorder:
If TEMP_REF
If VOID
if (!VOID && !TEMP_REF)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/cast.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index bead97f914..e8128710e2 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1155,15 +1155,18 @@ enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&,
 // static_assert, even though if it's in dead code, so we provide a "trampoline" to pybind11::cast
 // that only does anything in cases where pybind11::cast is valid.
 template <typename T>
-enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&o) {
-    return pybind11::cast<T>(std::move(o));
-}
-template <typename T>
 enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&) {
     pybind11_fail("Internal error: cast_safe fallback invoked");
 }
-template <>
-inline void cast_safe<void>(object &&) {}
+template <typename T>
+enable_if_t<std::is_same<void, intrinsic_t<T>>::value, void> cast_safe(object &&) {}
+template <typename T>
+enable_if_t<detail::none_of<cast_is_temporary_value_reference<T>,
+                            std::is_same<void, intrinsic_t<T>>>::value,
+            T>
+cast_safe(object &&o) {
+    return pybind11::cast<T>(std::move(o));
+}
 
 PYBIND11_NAMESPACE_END(detail)
 

From 9969f3b5b5ccad5524a9dab237b551c0ea6359f4 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 11 Apr 2022 16:54:33 -0400
Subject: [PATCH 352/638] ci: drop win2016 (#3854)

* ci: drop dead windows CI jobs

* chore: touch up pre-commit

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update configure.yml

* Update configure.yml
---
 .github/workflows/ci.yml        | 49 ---------------------------------
 .github/workflows/configure.yml | 10 ++-----
 .pre-commit-config.yaml         |  3 +-
 pyproject.toml                  |  4 ++-
 4 files changed, 7 insertions(+), 59 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b2fc52bf20..0e018fb7ff 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -814,55 +814,6 @@ jobs:
     - name: Python tests
       run: cmake --build build --config Debug -t pytest
 
-  win32-msvc2017:
-    name: "🐍 ${{ matrix.python }} • MSVC 2017 • x64"
-    runs-on: windows-2016
-    strategy:
-      fail-fast: false
-      matrix:
-        python:
-          - 3.6
-          - 3.7
-        std:
-          - 14
-
-        include:
-          - python: 3.7
-            std: 17
-            args: >
-              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR"
-
-    steps:
-    - uses: actions/checkout@v2
-
-    - name: Setup 🐍 ${{ matrix.python }}
-      uses: actions/setup-python@v2
-      with:
-        python-version: ${{ matrix.python }}
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
-
-    - name: Prepare env
-      run: |
-        python -m pip install -r tests/requirements.txt
-
-    # First build - C++11 mode and inplace
-    - name: Configure
-      run: >
-        cmake -S . -B build
-        -G "Visual Studio 15 2017" -A x64
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-        ${{ matrix.args }}
-
-    - name: Build ${{ matrix.std }}
-      run: cmake --build build -j 2
-
-    - name: Run all checks
-      run: cmake --build build -t check
 
   windows-2022:
     strategy:
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 66ab0e3d78..55be5bd349 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -18,7 +18,7 @@ jobs:
       matrix:
         runs-on: [ubuntu-latest, macos-latest, windows-latest]
         arch: [x64]
-        cmake: ["3.21"]
+        cmake: ["3.23"]
 
         include:
         - runs-on: ubuntu-latest
@@ -29,12 +29,8 @@ jobs:
           arch: x64
           cmake: 3.7
 
-        - runs-on: windows-2016
-          arch: x86
-          cmake: 3.8
-
-        - runs-on: windows-2016
-          arch: x86
+        - runs-on: windows-2019
+          arch: x64 # x86 compilers seem to be missing on 2019 image
           cmake: 3.18
 
     name: 🐍 3.7 • CMake ${{ matrix.cmake }} • ${{ matrix.runs-on }}
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 9ff2013ed4..2bfd699a60 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -74,7 +74,6 @@ repos:
   rev: "v1.2.5"
   hooks:
   - id: pycln
-    additional_dependencies: [click<8.1]  # Unpin when typer updates
     stages: [manual]
 
 # Checking for common mistakes
@@ -127,7 +126,7 @@ repos:
   rev: "v0.942"
   hooks:
   - id: mypy
-    args: [--show-error-codes]
+    args: []
     exclude: ^(tests|docs)/
     additional_dependencies: [nox, rich]
 
diff --git a/pyproject.toml b/pyproject.toml
index f80cdc1f42..3ba1b4b22f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,8 +24,10 @@ profile = "black"
 [tool.mypy]
 files = ["pybind11"]
 python_version = "3.6"
-warn_unused_configs = true
 strict = true
+show_error_codes = true
+enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
+warn_unreachable = true
 
 [[tool.mypy.overrides]]
 module = ["ghapi.*", "setuptools.*"]

From ad0de0f5a6bebbebbeb7f8f2f15c0c1430f34268 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 11 Apr 2022 19:50:42 -0400
Subject: [PATCH 353/638] [pre-commit.ci] pre-commit autoupdate (#3863)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/pre-commit-hooks: v4.1.0 → v4.2.0](https://github.com/pre-commit/pre-commit-hooks/compare/v4.1.0...v4.2.0)
- [github.com/asottile/pyupgrade: v2.31.1 → v2.32.0](https://github.com/asottile/pyupgrade/compare/v2.31.1...v2.32.0)
- [github.com/PyCQA/pylint: v2.13.4 → v2.13.5](https://github.com/PyCQA/pylint/compare/v2.13.4...v2.13.5)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2bfd699a60..9cfcef21fd 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,7 +15,7 @@
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: "v4.1.0"
+  rev: "v4.2.0"
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.31.1"
+  rev: "v2.32.0"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -107,7 +107,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.13.4"
+  rev: "v2.13.5"
   hooks:
   - id: pylint
     files: ^pybind11

From fa98804a07982cef41d554ff96f71334bac92445 Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <oleksandr.pavlyk@intel.com>
Date: Thu, 14 Apr 2022 09:51:27 -0500
Subject: [PATCH 354/638] Adds set_name method of pybind11::capsule class
 (#3866)

* Adds set_name method of pybind11::capsule class

This calls PyCapsule_SetName on the underlying capsule object.

modified destructors to query capsules's Name

[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Handle possible exception thrown by PyCapsule_GetName

Also removed accidentally reintroduced use of `const char *&`.

[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Fixed function name

* Introduced private static function to reuse get_name_or_throw

* added tests for capsule renaming

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* handle python error in flight

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Initialized PyObject * variables to nullptr

* use write-unraisable if PyCapsule_GetName raises

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* get_name_or_throw->get_name_no_throw

If PyCapsule_GetName raises an error we should write as unraisable
to consume it and notify user, and then restore the error in flight if any.
This way this method called from destructor would not modify interpreter
error state.

* used error_scope struct

* Renamed get_name_no_throw->get_name_in_error_scope

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pytypes.h | 34 +++++++++++++++++++++++++++++++---
 tests/test_pytypes.cpp     | 20 ++++++++++++++++++++
 tests/test_pytypes.py      | 26 ++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index ba0fda0a8c..7d52774c8b 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1588,7 +1588,8 @@ class capsule : public object {
                 }
                 pybind11_fail("Unable to get capsule context");
             }
-            void *ptr = PyCapsule_GetPointer(o, nullptr);
+            const char *name = get_name_in_error_scope(o);
+            void *ptr = PyCapsule_GetPointer(o, name);
             if (ptr == nullptr) {
                 throw error_already_set();
             }
@@ -1602,7 +1603,8 @@ class capsule : public object {
 
     explicit capsule(void (*destructor)()) {
         m_ptr = PyCapsule_New(reinterpret_cast<void *>(destructor), nullptr, [](PyObject *o) {
-            auto destructor = reinterpret_cast<void (*)()>(PyCapsule_GetPointer(o, nullptr));
+            const char *name = get_name_in_error_scope(o);
+            auto destructor = reinterpret_cast<void (*)()>(PyCapsule_GetPointer(o, name));
             if (destructor == nullptr) {
                 throw error_already_set();
             }
@@ -1637,7 +1639,33 @@ class capsule : public object {
         }
     }
 
-    const char *name() const { return PyCapsule_GetName(m_ptr); }
+    const char *name() const {
+        const char *name = PyCapsule_GetName(m_ptr);
+        if ((name == nullptr) && PyErr_Occurred()) {
+            throw error_already_set();
+        }
+        return name;
+    }
+
+    /// Replaces a capsule's name *without* calling the destructor on the existing one.
+    void set_name(const char *new_name) {
+        if (PyCapsule_SetName(m_ptr, new_name) != 0) {
+            throw error_already_set();
+        }
+    }
+
+private:
+    static const char *get_name_in_error_scope(PyObject *o) {
+        error_scope error_guard;
+
+        const char *name = PyCapsule_GetName(o);
+        if ((name == nullptr) && PyErr_Occurred()) {
+            // write out and consume error raised by call to PyCapsule_GetName
+            PyErr_WriteUnraisable(o);
+        }
+
+        return name;
+    }
 };
 
 class tuple : public object {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index b859497b83..d1e9b81a73 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -159,6 +159,15 @@ TEST_SUBMODULE(pytypes, m) {
         return py::capsule([]() { py::print("destructing capsule"); });
     });
 
+    m.def("return_renamed_capsule_with_destructor", []() {
+        py::print("creating capsule");
+        auto cap = py::capsule([]() { py::print("destructing capsule"); });
+        static const char *capsule_name = "test_name1";
+        py::print("renaming capsule");
+        cap.set_name(capsule_name);
+        return cap;
+    });
+
     m.def("return_capsule_with_destructor_2", []() {
         py::print("creating capsule");
         return py::capsule((void *) 1234, [](void *ptr) {
@@ -166,6 +175,17 @@ TEST_SUBMODULE(pytypes, m) {
         });
     });
 
+    m.def("return_renamed_capsule_with_destructor_2", []() {
+        py::print("creating capsule");
+        auto cap = py::capsule((void *) 1234, [](void *ptr) {
+            py::print("destructing capsule: {}"_s.format((size_t) ptr));
+        });
+        static const char *capsule_name = "test_name2";
+        py::print("renaming capsule");
+        cap.set_name(capsule_name);
+        return cap;
+    });
+
     m.def("return_capsule_with_name_and_destructor", []() {
         auto capsule = py::capsule((void *) 12345, "pointer type description", [](PyObject *ptr) {
             if (ptr) {
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 85afb94232..5c715ada6b 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -195,6 +195,19 @@ def test_capsule(capture):
     """
     )
 
+    with capture:
+        a = m.return_renamed_capsule_with_destructor()
+        del a
+        pytest.gc_collect()
+    assert (
+        capture.unordered
+        == """
+        creating capsule
+        renaming capsule
+        destructing capsule
+    """
+    )
+
     with capture:
         a = m.return_capsule_with_destructor_2()
         del a
@@ -207,6 +220,19 @@ def test_capsule(capture):
     """
     )
 
+    with capture:
+        a = m.return_renamed_capsule_with_destructor_2()
+        del a
+        pytest.gc_collect()
+    assert (
+        capture.unordered
+        == """
+        creating capsule
+        renaming capsule
+        destructing capsule: 1234
+    """
+    )
+
     with capture:
         a = m.return_capsule_with_name_and_destructor()
         del a

From ba7a0fac739554a4e24d2c4bcb836922a50314a0 Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <oleksandr.pavlyk@intel.com>
Date: Thu, 14 Apr 2022 09:53:16 -0500
Subject: [PATCH 355/638] Expand dtype accessors (#3868)

* Added constructor based on typenum, based on PyArray_DescrFromType

Added accessors for typenum, alignment, byteorder and flags fields of
PyArray_Descr struct.

* Added tests for new py::dtype constructor, and for accessors

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fixed the comment for alignment method

* Update include/pybind11/numpy.h

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/numpy.h    | 24 ++++++++++++++++++++++++
 tests/test_numpy_dtypes.cpp | 29 +++++++++++++++++++++++++++++
 tests/test_numpy_dtypes.py  |  8 +++++++-
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index d45fe42803..d71f089073 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -562,6 +562,13 @@ class dtype : public object {
         m_ptr = from_args(std::move(args)).release().ptr();
     }
 
+    explicit dtype(int typenum)
+        : object(detail::npy_api::get().PyArray_DescrFromType_(typenum), stolen_t{}) {
+        if (m_ptr == nullptr) {
+            throw error_already_set();
+        }
+    }
+
     /// This is essentially the same as calling numpy.dtype(args) in Python.
     static dtype from_args(object args) {
         PyObject *ptr = nullptr;
@@ -596,6 +603,23 @@ class dtype : public object {
         return detail::array_descriptor_proxy(m_ptr)->type;
     }
 
+    /// type number of dtype.
+    ssize_t num() const {
+        // Note: The signature, `dtype::num` follows the naming of NumPy's public
+        // Python API (i.e., ``dtype.num``), rather than its internal
+        // C API (``PyArray_Descr::type_num``).
+        return detail::array_descriptor_proxy(m_ptr)->type_num;
+    }
+
+    /// Single character for byteorder
+    char byteorder() const { return detail::array_descriptor_proxy(m_ptr)->byteorder; }
+
+    /// Alignment of the data type
+    int alignment() const { return detail::array_descriptor_proxy(m_ptr)->alignment; }
+
+    /// Flags for the array descriptor
+    char flags() const { return detail::array_descriptor_proxy(m_ptr)->flags; }
+
 private:
     static object _dtype_from_pep3118() {
         static PyObject *obj = module_::import("numpy.core._internal")
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index dd5b123dc4..7de36f2fe8 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -291,6 +291,7 @@ py::list test_dtype_ctors() {
     list.append(py::dtype(names, formats, offsets, 20));
     list.append(py::dtype(py::buffer_info((void *) 0, sizeof(unsigned int), "I", 1)));
     list.append(py::dtype(py::buffer_info((void *) 0, 0, "T{i:a:f:b:}", 1)));
+    list.append(py::dtype(py::detail::npy_api::NPY_DOUBLE_));
     return list;
 }
 
@@ -440,6 +441,34 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         }
         return list;
     });
+    m.def("test_dtype_num", [dtype_names]() {
+        py::list list;
+        for (const auto &dt_name : dtype_names) {
+            list.append(py::dtype(dt_name).num());
+        }
+        return list;
+    });
+    m.def("test_dtype_byteorder", [dtype_names]() {
+        py::list list;
+        for (const auto &dt_name : dtype_names) {
+            list.append(py::dtype(dt_name).byteorder());
+        }
+        return list;
+    });
+    m.def("test_dtype_alignment", [dtype_names]() {
+        py::list list;
+        for (const auto &dt_name : dtype_names) {
+            list.append(py::dtype(dt_name).alignment());
+        }
+        return list;
+    });
+    m.def("test_dtype_flags", [dtype_names]() {
+        py::list list;
+        for (const auto &dt_name : dtype_names) {
+            list.append(py::dtype(dt_name).flags());
+        }
+        return list;
+    });
     m.def("test_dtype_methods", []() {
         py::list list;
         auto dt1 = py::dtype::of<int32_t>();
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 7df60583f8..fcfd587b18 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -160,6 +160,7 @@ def test_dtype(simple_dtype):
         d1,
         np.dtype("uint32"),
         d2,
+        np.dtype("d"),
     ]
 
     assert m.test_dtype_methods() == [
@@ -175,8 +176,13 @@ def test_dtype(simple_dtype):
         np.zeros(1, m.trailing_padding_dtype())
     )
 
+    expected_chars = "bhilqBHILQefdgFDG?MmO"
     assert m.test_dtype_kind() == list("iiiiiuuuuuffffcccbMmO")
-    assert m.test_dtype_char_() == list("bhilqBHILQefdgFDG?MmO")
+    assert m.test_dtype_char_() == list(expected_chars)
+    assert m.test_dtype_num() == [np.dtype(ch).num for ch in expected_chars]
+    assert m.test_dtype_byteorder() == [np.dtype(ch).byteorder for ch in expected_chars]
+    assert m.test_dtype_alignment() == [np.dtype(ch).alignment for ch in expected_chars]
+    assert m.test_dtype_flags() == [chr(np.dtype(ch).flags) for ch in expected_chars]
 
 
 def test_recarray(simple_dtype, packed_dtype):

From 45164c1fcb7b4af1c5f8263f37c16beea1aabb98 Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <oleksandr.pavlyk@intel.com>
Date: Thu, 14 Apr 2022 11:16:58 -0500
Subject: [PATCH 356/638] Added deleted copy constructor for error_scope to
 comply with rule of 3. (#3870)

* Added deleted copy constructor for error_scope to comply with rule of 3.
---
 include/pybind11/detail/common.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index ea09bb3fdf..b49313e445 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -992,6 +992,7 @@ constexpr const char
 struct error_scope {
     PyObject *type, *value, *trace;
     error_scope() { PyErr_Fetch(&type, &value, &trace); }
+    error_scope(const error_scope &) = delete;
     ~error_scope() { PyErr_Restore(type, value, trace); }
 };
 

From 3829b7624c644c2691a5675130acb12a55d30934 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 14 Apr 2022 17:12:44 -0400
Subject: [PATCH 357/638] chore: simplify numpy dtype ctor (#3869)

* Simplify numpy dtype ctor

* Simplify c_str ctor

* Remove compat macro for str in numpy
---
 include/pybind11/numpy.h | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index d71f089073..d06ddfa11d 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -540,18 +540,16 @@ class dtype : public object {
     PYBIND11_OBJECT_DEFAULT(dtype, object, detail::npy_api::get().PyArrayDescr_Check_);
 
     explicit dtype(const buffer_info &info) {
-        dtype descr(_dtype_from_pep3118()(PYBIND11_STR_TYPE(info.format)));
+        dtype descr(_dtype_from_pep3118()(pybind11::str(info.format)));
         // If info.itemsize == 0, use the value calculated from the format string
         m_ptr = descr.strip_padding(info.itemsize != 0 ? info.itemsize : descr.itemsize())
                     .release()
                     .ptr();
     }
 
-    explicit dtype(const std::string &format) {
-        m_ptr = from_args(pybind11::str(format)).release().ptr();
-    }
+    explicit dtype(const std::string &format) : dtype(from_args(pybind11::str(format))) {}
 
-    explicit dtype(const char *format) : dtype(std::string(format)) {}
+    explicit dtype(const char *format) : dtype(from_args(pybind11::str(format))) {}
 
     dtype(list names, list formats, list offsets, ssize_t itemsize) {
         dict args;
@@ -638,7 +636,7 @@ class dtype : public object {
         }
 
         struct field_descr {
-            PYBIND11_STR_TYPE name;
+            pybind11::str name;
             object format;
             pybind11::int_ offset;
         };
@@ -653,7 +651,7 @@ class dtype : public object {
                 continue;
             }
             field_descriptors.push_back(
-                {(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
+                {(pybind11::str) name, format.strip_padding(format.itemsize()), offset});
         }
 
         std::sort(field_descriptors.begin(),
@@ -1359,7 +1357,7 @@ PYBIND11_NOINLINE void register_structured_dtype(any_container<field_descriptor>
             pybind11_fail(std::string("NumPy: unsupported field dtype: `") + field.name + "` @ "
                           + tinfo.name());
         }
-        names.append(PYBIND11_STR_TYPE(field.name));
+        names.append(pybind11::str(field.name));
         formats.append(field.descr);
         offsets.append(pybind11::int_(field.offset));
     }

From 30716c67a16fca836c447a263a87025ba080a6f2 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 15 Apr 2022 11:44:48 -0700
Subject: [PATCH 358/638] Also add error_scope assignment operator to complete
 the rule-of-3 (follow-on to PR #3870). (#3872)

---
 include/pybind11/detail/common.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index b49313e445..a130ebea08 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -993,6 +993,7 @@ struct error_scope {
     PyObject *type, *value, *trace;
     error_scope() { PyErr_Fetch(&type, &value, &trace); }
     error_scope(const error_scope &) = delete;
+    error_scope &operator=(const error_scope &) = delete;
     ~error_scope() { PyErr_Restore(type, value, trace); }
 };
 

From fbcde3f0af59c5ae26561a774046623e1cc8a7c9 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 18 Apr 2022 11:09:45 -0400
Subject: [PATCH 359/638] chore: enable clang-tidy check modernize-use-nullptr
 (#3881)

* Enable clang-tidy check modernize-use-nullptr

* Sort clang-tidy

* Sorted again
---
 .clang-tidy                      | 5 +++--
 include/pybind11/numpy.h         | 4 ++--
 include/pybind11/pybind11.h      | 2 +-
 include/pybind11/pytypes.h       | 6 +++---
 tests/cross_module_gil_utils.cpp | 6 +++---
 tests/test_numpy_dtypes.cpp      | 4 ++--
 6 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index d01ca352cc..e82443c4ca 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -25,11 +25,12 @@ modernize-replace-random-shuffle,
 modernize-shrink-to-fit,
 modernize-use-auto,
 modernize-use-bool-literals,
+modernize-use-default-member-init,
 modernize-use-equals-default,
 modernize-use-equals-delete,
-modernize-use-default-member-init,
-modernize-use-noexcept,
 modernize-use-emplace,
+modernize-use-noexcept,
+modernize-use-nullptr,
 modernize-use-override,
 modernize-use-using,
 *performance*,
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index d06ddfa11d..335b78ff17 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -263,7 +263,7 @@ struct npy_api {
     static npy_api lookup() {
         module_ m = module_::import("numpy.core.multiarray");
         auto c = m.attr("_ARRAY_API");
-        void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), NULL);
+        void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), nullptr);
         npy_api api;
 #define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
         DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
@@ -1549,7 +1549,7 @@ class common_iterator {
     void *data() const { return p_ptr; }
 
 private:
-    char *p_ptr{0};
+    char *p_ptr{nullptr};
     container_type m_strides;
 };
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 97275e40a8..ce05b6e4e6 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2489,7 +2489,7 @@ class exception : public object {
     exception(handle scope, const char *name, handle base = PyExc_Exception) {
         std::string full_name
             = scope.attr("__name__").cast<std::string>() + std::string(".") + name;
-        m_ptr = PyErr_NewException(const_cast<char *>(full_name.c_str()), base.ptr(), NULL);
+        m_ptr = PyErr_NewException(const_cast<char *>(full_name.c_str()), base.ptr(), nullptr);
         if (hasattr(scope, "__dict__") && scope.attr("__dict__").contains(name)) {
             pybind11_fail("Error during initialization: multiple incompatible "
                           "definitions with name \""
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 7d52774c8b..26d9025c51 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -600,13 +600,13 @@ inline handle get_function(handle value) {
 inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
     PyObject *kv = nullptr, *rv = nullptr;
     kv = PyUnicode_FromString(key);
-    if (kv == NULL) {
+    if (kv == nullptr) {
         throw error_already_set();
     }
 
     rv = PyDict_GetItemWithError(v, kv);
     Py_DECREF(kv);
-    if (rv == NULL && PyErr_Occurred()) {
+    if (rv == nullptr && PyErr_Occurred()) {
         throw error_already_set();
     }
     return rv;
@@ -614,7 +614,7 @@ inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
 
 inline PyObject *dict_getitem(PyObject *v, PyObject *key) {
     PyObject *rv = PyDict_GetItemWithError(v, key);
-    if (rv == NULL && PyErr_Occurred()) {
+    if (rv == nullptr && PyErr_Occurred()) {
         throw error_already_set();
     }
     return rv;
diff --git a/tests/cross_module_gil_utils.cpp b/tests/cross_module_gil_utils.cpp
index 2e64da052c..1436c35d6e 100644
--- a/tests/cross_module_gil_utils.cpp
+++ b/tests/cross_module_gil_utils.cpp
@@ -25,8 +25,8 @@ void gil_acquire() { py::gil_scoped_acquire gil; }
 
 constexpr char kModuleName[] = "cross_module_gil_utils";
 
-struct PyModuleDef moduledef
-    = {PyModuleDef_HEAD_INIT, kModuleName, NULL, 0, NULL, NULL, NULL, NULL, NULL};
+struct PyModuleDef moduledef = {
+    PyModuleDef_HEAD_INIT, kModuleName, nullptr, 0, nullptr, nullptr, nullptr, nullptr, nullptr};
 
 } // namespace
 
@@ -34,7 +34,7 @@ extern "C" PYBIND11_EXPORT PyObject *PyInit_cross_module_gil_utils() {
 
     PyObject *m = PyModule_Create(&moduledef);
 
-    if (m != NULL) {
+    if (m != nullptr) {
         static_assert(sizeof(&gil_acquire) == sizeof(void *),
                       "Function pointer must have the same size as void*");
         PyModule_AddObject(
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index 7de36f2fe8..38f2afa07d 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -289,8 +289,8 @@ py::list test_dtype_ctors() {
     dict["itemsize"] = py::int_(20);
     list.append(py::dtype::from_args(dict));
     list.append(py::dtype(names, formats, offsets, 20));
-    list.append(py::dtype(py::buffer_info((void *) 0, sizeof(unsigned int), "I", 1)));
-    list.append(py::dtype(py::buffer_info((void *) 0, 0, "T{i:a:f:b:}", 1)));
+    list.append(py::dtype(py::buffer_info((void *) nullptr, sizeof(unsigned int), "I", 1)));
+    list.append(py::dtype(py::buffer_info((void *) nullptr, 0, "T{i:a:f:b:}", 1)));
     list.append(py::dtype(py::detail::npy_api::NPY_DOUBLE_));
     return list;
 }

From 1c636f4dce8414d458fee3a00df72ed769b7f79a Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 18 Apr 2022 11:11:24 -0400
Subject: [PATCH 360/638] chore: Change numpy dtype from_args call sig to const
 ref (#3878)

* Change numpy from_args call signature to avoid copy

* Reorder ctors

* Rename arg

* Fix unnecessary move

* Fix clang-tidy and Add a few missing moves to memory_view pytype
---
 include/pybind11/numpy.h    | 10 ++++++----
 include/pybind11/pytypes.h  |  7 ++++---
 tests/test_numpy_dtypes.cpp |  2 +-
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 335b78ff17..2713e13a86 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -547,9 +547,11 @@ class dtype : public object {
                     .ptr();
     }
 
-    explicit dtype(const std::string &format) : dtype(from_args(pybind11::str(format))) {}
+    explicit dtype(const pybind11::str &format) : dtype(from_args(format)) {}
 
-    explicit dtype(const char *format) : dtype(from_args(pybind11::str(format))) {}
+    explicit dtype(const std::string &format) : dtype(pybind11::str(format)) {}
+
+    explicit dtype(const char *format) : dtype(pybind11::str(format)) {}
 
     dtype(list names, list formats, list offsets, ssize_t itemsize) {
         dict args;
@@ -557,7 +559,7 @@ class dtype : public object {
         args["formats"] = std::move(formats);
         args["offsets"] = std::move(offsets);
         args["itemsize"] = pybind11::int_(itemsize);
-        m_ptr = from_args(std::move(args)).release().ptr();
+        m_ptr = from_args(args).release().ptr();
     }
 
     explicit dtype(int typenum)
@@ -568,7 +570,7 @@ class dtype : public object {
     }
 
     /// This is essentially the same as calling numpy.dtype(args) in Python.
-    static dtype from_args(object args) {
+    static dtype from_args(const object &args) {
         PyObject *ptr = nullptr;
         if ((detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) == 0) || !ptr) {
             throw error_already_set();
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 26d9025c51..324fa932f1 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1914,8 +1914,8 @@ class memoryview : public object {
         return memoryview::from_buffer(reinterpret_cast<void *>(ptr),
                                        sizeof(T),
                                        format_descriptor<T>::value,
-                                       shape,
-                                       strides,
+                                       std::move(shape),
+                                       std::move(strides),
                                        readonly);
     }
 
@@ -1923,7 +1923,8 @@ class memoryview : public object {
     static memoryview from_buffer(const T *ptr,
                                   detail::any_container<ssize_t> shape,
                                   detail::any_container<ssize_t> strides) {
-        return memoryview::from_buffer(const_cast<T *>(ptr), shape, strides, true);
+        return memoryview::from_buffer(
+            const_cast<T *>(ptr), std::move(shape), std::move(strides), true);
     }
 
     /** \rst
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index 38f2afa07d..c25bc042b8 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -610,5 +610,5 @@ TEST_SUBMODULE(numpy_dtypes, m) {
           []() { PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_); });
 
     // test_str_leak
-    m.def("dtype_wrapper", [](py::object d) { return py::dtype::from_args(std::move(d)); });
+    m.def("dtype_wrapper", [](const py::object &d) { return py::dtype::from_args(d); });
 }

From e8e229fa0b486118bf91321b923f8158055c053c Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 18 Apr 2022 17:44:01 -0400
Subject: [PATCH 361/638] [pre-commit.ci] pre-commit autoupdate (#3885)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/hadialqattan/pycln: v1.2.5 → v1.3.1](https://github.com/hadialqattan/pycln/compare/v1.2.5...v1.3.1)
- [github.com/pre-commit/mirrors-clang-format: v13.0.1 → v14.0.1](https://github.com/pre-commit/mirrors-clang-format/compare/v13.0.1...v14.0.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 9cfcef21fd..099f0dc26e 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.2.5"
+  rev: "v1.3.1"
   hooks:
   - id: pycln
     stages: [manual]
@@ -164,7 +164,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v13.0.1"
+  rev: "v14.0.1"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From 1a8603e4792315d1eabcbaaa4b286a3a98963b0d Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sun, 24 Apr 2022 13:50:29 -0400
Subject: [PATCH 362/638] ci: dependabot major versions for official actions
 (#3888)

* ci: dependabot major versions for official actions

* style: use extend-select for flake8
---
 .github/dependabot.yml | 9 ++-------
 setup.cfg              | 2 +-
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 73273365c0..d8d1eed8c3 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -7,10 +7,5 @@ updates:
       interval: "daily"
     ignore:
       # Official actions have moving tags like v1
-      # that are used, so they don't need updates here
-      - dependency-name: "actions/checkout"
-      - dependency-name: "actions/setup-python"
-      - dependency-name: "actions/cache"
-      - dependency-name: "actions/upload-artifact"
-      - dependency-name: "actions/download-artifact"
-      - dependency-name: "actions/labeler"
+      - dependency-name: "actions/*"
+        update-types: ["version-update:semver-minor", "version-update:semver-patch"]
diff --git a/setup.cfg b/setup.cfg
index 11b4fde8f3..4fd1e7a6fa 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -46,4 +46,4 @@ max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
 extend-ignore = E203, E722, B950
-select = C,E,F,N,W,B,B9
+extend-select = B9

From b58b772b4632dca24014fee0dc193c41a448ae5d Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 24 Apr 2022 14:40:58 -0400
Subject: [PATCH 363/638] chore(deps): bump actions/setup-python from 2 to 3
 (#3895)

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 2 to 3.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](https://github.com/actions/setup-python/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 10 +++++-----
 .github/workflows/configure.yml |  2 +-
 .github/workflows/format.yml    |  2 +-
 .github/workflows/pip.yml       |  6 +++---
 .github/workflows/upstream.yml  |  2 +-
 5 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0e018fb7ff..14e8adea7c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -65,7 +65,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: ${{ matrix.python }}
 
@@ -680,7 +680,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v3
 
     - name: Install Doxygen
       run: sudo apt-get install -y doxygen librsvg2-bin # Changed to rsvg-convert in 20.04
@@ -728,7 +728,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: ${{ matrix.python }}
         architecture: x86
@@ -781,7 +781,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: ${{ matrix.python }}
         architecture: x86
@@ -829,7 +829,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: ${{ matrix.python }}
 
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 55be5bd349..23cc283762 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -40,7 +40,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup Python 3.7
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: 3.7
         architecture: ${{ matrix.arch }}
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 46140fe0c0..d46f81442e 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v3
     - name: Add matchers
       run: echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
     - uses: pre-commit/action@v2.0.3
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 7a5443d14b..b76d0c8bdf 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -27,7 +27,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup 🐍 3.6
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: 3.6
 
@@ -49,7 +49,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup 🐍 3.8
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: 3.8
 
@@ -90,7 +90,7 @@ jobs:
     needs: [packaging]
 
     steps:
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v3
 
     # Downloads all to directories matching the artifact names
     - uses: actions/download-artifact@v2
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 138c9ad292..8dc860f2bb 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -22,7 +22,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Setup Python 3.11
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v3
       with:
         python-version: "3.11-dev"
 

From e79293cf2fd68578ce63c08a8663397b3af9d807 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 24 Apr 2022 14:41:09 -0400
Subject: [PATCH 364/638] chore(deps): bump actions/cache from 2 to 3 (#3898)

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 3.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](https://github.com/actions/cache/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 14e8adea7c..9a99be3bba 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -83,7 +83,7 @@ jobs:
 
     - name: Cache wheels
       if: runner.os == 'macOS'
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         # This path is specific to macOS - we really only need it for PyPy NumPy wheels
         # See https://github.com/actions/cache/blob/master/examples.md#python---pip
@@ -205,7 +205,7 @@ jobs:
 
     - name: Valgrind cache
       if: matrix.valgrind
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       id: cache-valgrind
       with:
         path: valgrind

From 2a7cb008acbf7a1942a6270b014bdf86886ed6f1 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 24 Apr 2022 14:41:23 -0400
Subject: [PATCH 365/638] chore(deps): bump actions/download-artifact from 2 to
 3 (#3897)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 2 to 3.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index b76d0c8bdf..7b0a73a635 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -93,7 +93,7 @@ jobs:
     - uses: actions/setup-python@v3
 
     # Downloads all to directories matching the artifact names
-    - uses: actions/download-artifact@v2
+    - uses: actions/download-artifact@v3
 
     - name: Publish standard package
       uses: pypa/gh-action-pypi-publish@v1.5.0

From 82455a41fdc9cabf6a0eeba2071dc8a0c8cac4c1 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sun, 24 Apr 2022 14:46:39 -0400
Subject: [PATCH 366/638] Minor opt to cache tuple casting (#3894)

---
 include/pybind11/numpy.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 2713e13a86..b8ba2259ff 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -647,8 +647,9 @@ class dtype : public object {
         for (auto field : attr("fields").attr("items")()) {
             auto spec = field.cast<tuple>();
             auto name = spec[0].cast<pybind11::str>();
-            auto format = spec[1].cast<tuple>()[0].cast<dtype>();
-            auto offset = spec[1].cast<tuple>()[1].cast<pybind11::int_>();
+            auto spec_fo = spec[1].cast<tuple>();
+            auto format = spec_fo[0].cast<dtype>();
+            auto offset = spec_fo[1].cast<pybind11::int_>();
             if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
             }

From be4a634c675fc55db6da595c322f2ca947096862 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 24 Apr 2022 16:49:13 -0400
Subject: [PATCH 367/638] chore(deps): bump actions/checkout from 2 to 3
 (#3896)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 30 +++++++++++++++---------------
 .github/workflows/configure.yml |  2 +-
 .github/workflows/format.yml    |  4 ++--
 .github/workflows/pip.yml       |  4 ++--
 .github/workflows/upstream.yml  |  2 +-
 5 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9a99be3bba..aeceaee2c8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -62,7 +62,7 @@ jobs:
     runs-on: ${{ matrix.runs-on }}
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
       uses: actions/setup-python@v3
@@ -192,7 +192,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python-version }} (deadsnakes)
       uses: deadsnakes/action@v2.1.1
@@ -285,7 +285,7 @@ jobs:
     container: "silkeh/clang:${{ matrix.clang }}"
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Add wget and python3
       run: apt-get update && apt-get install -y python3-dev python3-numpy python3-pytest libeigen3-dev
@@ -319,7 +319,7 @@ jobs:
     container: nvidia/cuda:11.0-devel-ubuntu20.04
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     # tzdata will try to ask for the timezone, so set the DEBIAN_FRONTEND
     - name: Install 🐍 3
@@ -343,7 +343,7 @@ jobs:
 #    container: centos:8
 #
 #    steps:
-#    - uses: actions/checkout@v2
+#    - uses: actions/checkout@v3
 #
 #    - name: Add Python 3 and a few requirements
 #      run: yum update -y && yum install -y git python3-devel python3-numpy python3-pytest make environment-modules
@@ -386,7 +386,7 @@ jobs:
     container: centos:7
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Add Python 3 and a few requirements
       run: yum update -y && yum install -y epel-release && yum install -y git python3-devel make environment-modules cmake3
@@ -447,7 +447,7 @@ jobs:
     container: "gcc:${{ matrix.gcc }}"
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v3
 
     - name: Add Python 3
       run: apt-get update; apt-get install -y python3-dev python3-numpy python3-pytest python3-pip libeigen3-dev
@@ -489,7 +489,7 @@ jobs:
     name: "🐍 3 • ICC latest • x64"
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Add apt repo
       run: |
@@ -592,7 +592,7 @@ jobs:
     container: "quay.io/centos/centos:${{ matrix.centos }}"
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Add Python 3
       run: yum update -y && yum install -y python3-devel gcc-c++ make git
@@ -635,7 +635,7 @@ jobs:
     container: i386/debian:buster
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v3
 
     - name: Install requirements
       run: |
@@ -678,7 +678,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - uses: actions/setup-python@v3
 
@@ -725,7 +725,7 @@ jobs:
     runs-on: windows-2019
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
       uses: actions/setup-python@v3
@@ -778,7 +778,7 @@ jobs:
     runs-on: windows-2019
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
       uses: actions/setup-python@v3
@@ -826,7 +826,7 @@ jobs:
     runs-on: windows-2022
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
       uses: actions/setup-python@v3
@@ -889,7 +889,7 @@ jobs:
           mingw-w64-${{matrix.env}}-boost
           mingw-w64-${{matrix.env}}-catch
 
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Configure C++11
       # LTO leads to many undefined reference like
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 23cc283762..aa2485ac08 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -37,7 +37,7 @@ jobs:
     runs-on: ${{ matrix.runs-on }}
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python 3.7
       uses: actions/setup-python@v3
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index d46f81442e..5eb228a707 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -20,7 +20,7 @@ jobs:
     name: Format
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: actions/setup-python@v3
     - name: Add matchers
       run: echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
@@ -36,7 +36,7 @@ jobs:
     runs-on: ubuntu-latest
     container: silkeh/clang:12
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Install requirements
       run: apt-get update && apt-get install -y python3-dev python3-pytest
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 7b0a73a635..6e7afa3859 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -24,7 +24,7 @@ jobs:
     runs-on: windows-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup 🐍 3.6
       uses: actions/setup-python@v3
@@ -46,7 +46,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup 🐍 3.8
       uses: actions/setup-python@v3
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 8dc860f2bb..174dc24965 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -19,7 +19,7 @@ jobs:
     if: "contains(github.event.pull_request.labels.*.name, 'python dev')"
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python 3.11
       uses: actions/setup-python@v3

From 03252067db057777db75c2e5bcf0e69013b919ec Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 24 Apr 2022 16:49:41 -0400
Subject: [PATCH 368/638] chore(deps): bump actions/upload-artifact from 2 to 3
 (#3899)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 2 to 3.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](https://github.com/actions/upload-artifact/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 6e7afa3859..1d9a35604e 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -69,13 +69,13 @@ jobs:
       run: twine check dist/*
 
     - name: Save standard package
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v3
       with:
         name: standard
         path: dist/pybind11-*
 
     - name: Save global package
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v3
       with:
         name: global
         path: dist/pybind11_global-*

From 9bc270443068c90298c0220cd866fbf9ea1bb589 Mon Sep 17 00:00:00 2001
From: Ed Catmur <ed@catmur.uk>
Date: Sun, 24 Apr 2022 22:39:47 +0100
Subject: [PATCH 369/638] Add tests for cast from tuple to sequence containers
 (#3900)

We already test that tuple can cast to std::vector and std::deque; add tests for std::vector<bool>, std::list and
std::valarray.

Extracted from #3886.
---
 tests/test_stl.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tests/test_stl.py b/tests/test_stl.py
index 3dc55230ab..975860b85a 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -14,6 +14,7 @@ def test_vector(doc):
 
     assert m.cast_bool_vector() == [True, False]
     assert m.load_bool_vector([True, False])
+    assert m.load_bool_vector(tuple([True, False]))
 
     assert doc(m.cast_vector) == "cast_vector() -> List[int]"
     assert doc(m.load_vector) == "load_vector(arg0: List[int]) -> bool"
@@ -36,6 +37,7 @@ def test_array(doc):
     lst = m.cast_array()
     assert lst == [1, 2]
     assert m.load_array(lst)
+    assert m.load_array(tuple(lst))
 
     assert doc(m.cast_array) == "cast_array() -> List[int[2]]"
     assert doc(m.load_array) == "load_array(arg0: List[int[2]]) -> bool"
@@ -46,6 +48,7 @@ def test_valarray(doc):
     lst = m.cast_valarray()
     assert lst == [1, 4, 9]
     assert m.load_valarray(lst)
+    assert m.load_valarray(tuple(lst))
 
     assert doc(m.cast_valarray) == "cast_valarray() -> List[int]"
     assert doc(m.load_valarray) == "load_valarray(arg0: List[int]) -> bool"

From 75007dda72ad4508064c1f080394eae50d3a61ee Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 26 Apr 2022 15:49:24 -0400
Subject: [PATCH 370/638] chore: rule of 3 for strdup guard (#3905)

---
 include/pybind11/pybind11.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ce05b6e4e6..e828f725dd 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -312,6 +312,10 @@ class cpp_function : public function {
     // along the way.
     class strdup_guard {
     public:
+        strdup_guard() = default;
+        strdup_guard(const strdup_guard &) = delete;
+        strdup_guard &operator=(const strdup_guard &) = delete;
+
         ~strdup_guard() {
             for (auto *s : strings) {
                 std::free(s);

From f0b9f755e465532f90ae6e696bdd7fa4e9d589ce Mon Sep 17 00:00:00 2001
From: Michael Voznesensky <voznesenskym@gmail.com>
Date: Mon, 2 May 2022 12:30:19 -0700
Subject: [PATCH 371/638] Replace error printing code gated by NDEBUG with a
 new flag: PYBIND11_DETAILED_ERROR_MESSAGES  (#3913)

* Update cast.h

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Move definition to detail/common, change name, apply everywhere

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Rename debug_enabled in tests to detailed_error_messages_enabled
---
 include/pybind11/attr.h                    |  6 ++-
 include/pybind11/cast.h                    | 51 ++++++++++++----------
 include/pybind11/detail/common.h           |  7 +++
 include/pybind11/detail/type_caster_base.h | 31 +++++++------
 include/pybind11/gil.h                     |  6 +--
 include/pybind11/pybind11.h                |  9 ++--
 tests/pybind11_tests.cpp                   |  6 +--
 tests/test_methods_and_attributes.cpp      |  6 +--
 tests/test_methods_and_attributes.py       | 20 ++++-----
 tests/test_pytypes.py                      |  6 +--
 10 files changed, 82 insertions(+), 66 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 38139afa32..14600e9bb0 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -10,6 +10,7 @@
 
 #pragma once
 
+#include "detail/common.h"
 #include "cast.h"
 
 #include <functional>
@@ -477,7 +478,7 @@ struct process_attribute<arg_v> : process_attribute_default<arg_v> {
         }
 
         if (!a.value) {
-#if !defined(NDEBUG)
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             std::string descr("'");
             if (a.name) {
                 descr += std::string(a.name) + ": ";
@@ -498,7 +499,8 @@ struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 #else
             pybind11_fail("arg(): could not convert default argument "
                           "into a Python object (type not registered yet?). "
-                          "Compile in debug mode for more information.");
+                          "#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for "
+                          "more information.");
 #endif
         }
         r->args.emplace_back(a.name, a.descr, a.value.inc_ref(), !a.flag_noconvert, a.flag_none);
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index e8128710e2..22d2dba4ca 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -777,8 +777,9 @@ struct copyable_holder_caster : public type_caster_base<type> {
             return true;
         }
         throw cast_error("Unable to cast from non-held to held instance (T& to Holder<T>) "
-#if defined(NDEBUG)
-                         "(compile in debug mode for type information)");
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+                         "(#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for "
+                         "type information)");
 #else
                          "of type '"
                          + type_id<holder_type>() + "''");
@@ -1001,9 +1002,9 @@ struct return_value_policy_override<
 template <typename T, typename SFINAE>
 type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
     if (!conv.load(handle, true)) {
-#if defined(NDEBUG)
-        throw cast_error(
-            "Unable to cast Python instance to C++ type (compile in debug mode for details)");
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+        throw cast_error("Unable to cast Python instance to C++ type (#define "
+                         "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
         throw cast_error("Unable to cast Python instance of type "
                          + (std::string) str(type::handle_of(handle)) + " to C++ type '"
@@ -1068,10 +1069,10 @@ inline void handle::cast() const {
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         throw cast_error(
             "Unable to cast Python instance to C++ rvalue: instance has multiple references"
-            " (compile in debug mode for details)");
+            " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
         throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj))
                          + " instance to C++ " + type_id<T>()
@@ -1172,10 +1173,10 @@ PYBIND11_NAMESPACE_END(detail)
 
 // The overloads could coexist, i.e. the #if is not strictly speaking needed,
 // but it is an easy minor optimization.
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
 inline cast_error cast_error_unable_to_convert_call_arg() {
-    return cast_error(
-        "Unable to convert call argument to Python object (compile in debug mode for details)");
+    return cast_error("Unable to convert call argument to Python object (#define "
+                      "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 }
 #else
 inline cast_error cast_error_unable_to_convert_call_arg(const std::string &name,
@@ -1197,7 +1198,7 @@ tuple make_tuple(Args &&...args_) {
         detail::make_caster<Args>::cast(std::forward<Args>(args_), policy, nullptr))...}};
     for (size_t i = 0; i < args.size(); i++) {
         if (!args[i]) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             throw cast_error_unable_to_convert_call_arg();
 #else
             std::array<std::string, size> argtypes{{type_id<Args>()...}};
@@ -1249,7 +1250,7 @@ struct arg_v : arg {
         : arg(base), value(reinterpret_steal<object>(detail::make_caster<T>::cast(
                          std::forward<T>(x), return_value_policy::automatic, {}))),
           descr(descr)
-#if !defined(NDEBUG)
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
           ,
           type(type_id<T>())
 #endif
@@ -1289,7 +1290,7 @@ struct arg_v : arg {
     object value;
     /// The (optional) description of the default value
     const char *descr;
-#if !defined(NDEBUG)
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
     /// The C++ type name of the default value (only available when compiled in debug mode)
     std::string type;
 #endif
@@ -1487,7 +1488,7 @@ class unpacking_collector {
         auto o = reinterpret_steal<object>(
             detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
         if (!o) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             throw cast_error_unable_to_convert_call_arg();
 #else
             throw cast_error_unable_to_convert_call_arg(std::to_string(args_list.size()),
@@ -1505,21 +1506,21 @@ class unpacking_collector {
 
     void process(list & /*args_list*/, arg_v a) {
         if (!a.name) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             nameless_argument_error();
 #else
             nameless_argument_error(a.type);
 #endif
         }
         if (m_kwargs.contains(a.name)) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             multiple_values_error();
 #else
             multiple_values_error(a.name);
 #endif
         }
         if (!a.value) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             throw cast_error_unable_to_convert_call_arg();
 #else
             throw cast_error_unable_to_convert_call_arg(a.name, a.type);
@@ -1534,7 +1535,7 @@ class unpacking_collector {
         }
         for (auto k : reinterpret_borrow<dict>(kp)) {
             if (m_kwargs.contains(k.first)) {
-#if defined(NDEBUG)
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
                 multiple_values_error();
 #else
                 multiple_values_error(str(k.first));
@@ -1545,9 +1546,10 @@ class unpacking_collector {
     }
 
     [[noreturn]] static void nameless_argument_error() {
-        throw type_error("Got kwargs without a name; only named arguments "
-                         "may be passed via py::arg() to a python function call. "
-                         "(compile in debug mode for details)");
+        throw type_error(
+            "Got kwargs without a name; only named arguments "
+            "may be passed via py::arg() to a python function call. "
+            "(#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
     }
     [[noreturn]] static void nameless_argument_error(const std::string &type) {
         throw type_error("Got kwargs without a name of type '" + type
@@ -1555,8 +1557,9 @@ class unpacking_collector {
                            "arguments may be passed via py::arg() to a python function call. ");
     }
     [[noreturn]] static void multiple_values_error() {
-        throw type_error("Got multiple values for keyword argument "
-                         "(compile in debug mode for details)");
+        throw type_error(
+            "Got multiple values for keyword argument "
+            "(#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
     }
 
     [[noreturn]] static void multiple_values_error(const std::string &name) {
@@ -1603,7 +1606,7 @@ unpacking_collector<policy> collect_arguments(Args &&...args) {
 template <typename Derived>
 template <return_value_policy policy, typename... Args>
 object object_api<Derived>::operator()(Args &&...args) const {
-#ifndef NDEBUG
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
     if (!PyGILState_Check()) {
         pybind11_fail("pybind11::object_api<>::operator() PyGILState_Check() failure.");
     }
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index a130ebea08..9355ecfda0 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -1157,5 +1157,12 @@ constexpr inline bool silence_msvc_c4127(bool cond) { return cond; }
 #    define PYBIND11_SILENCE_MSVC_C4127(...) __VA_ARGS__
 #endif
 
+// Pybind offers detailed error messages by default for all builts that are debug (through the
+// negation of ndebug). This can also be manually enabled by users, for any builds, through
+// defining PYBIND11_DETAILED_ERROR_MESSAGES.
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES) && !defined(NDEBUG)
+#    define PYBIND11_DETAILED_ERROR_MESSAGES
+#endif
+
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 5b2ec8e1e4..a7b9771326 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -394,15 +394,16 @@ instance::get_value_and_holder(const type_info *find_type /*= nullptr default in
         return value_and_holder();
     }
 
-#if defined(NDEBUG)
-    pybind11_fail("pybind11::detail::instance::get_value_and_holder: "
-                  "type is not a pybind11 base of the given instance "
-                  "(compile in debug mode for type details)");
-#else
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
     pybind11_fail("pybind11::detail::instance::get_value_and_holder: `"
                   + get_fully_qualified_tp_name(find_type->type)
                   + "' is not a pybind11 base of the given `"
                   + get_fully_qualified_tp_name(Py_TYPE(this)) + "' instance");
+#else
+    pybind11_fail(
+        "pybind11::detail::instance::get_value_and_holder: "
+        "type is not a pybind11 base of the given instance "
+        "(#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for type details)");
 #endif
 }
 
@@ -612,14 +613,15 @@ class type_caster_generic {
                 if (copy_constructor) {
                     valueptr = copy_constructor(src);
                 } else {
-#if defined(NDEBUG)
-                    throw cast_error("return_value_policy = copy, but type is "
-                                     "non-copyable! (compile in debug mode for details)");
-#else
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
                     std::string type_name(tinfo->cpptype->name());
                     detail::clean_type_id(type_name);
                     throw cast_error("return_value_policy = copy, but type " + type_name
                                      + " is non-copyable!");
+#else
+                    throw cast_error("return_value_policy = copy, but type is "
+                                     "non-copyable! (#define PYBIND11_DETAILED_ERROR_MESSAGES or "
+                                     "compile in debug mode for details)");
 #endif
                 }
                 wrapper->owned = true;
@@ -631,15 +633,16 @@ class type_caster_generic {
                 } else if (copy_constructor) {
                     valueptr = copy_constructor(src);
                 } else {
-#if defined(NDEBUG)
-                    throw cast_error("return_value_policy = move, but type is neither "
-                                     "movable nor copyable! "
-                                     "(compile in debug mode for details)");
-#else
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
                     std::string type_name(tinfo->cpptype->name());
                     detail::clean_type_id(type_name);
                     throw cast_error("return_value_policy = move, but type " + type_name
                                      + " is neither movable nor copyable!");
+#else
+                    throw cast_error("return_value_policy = move, but type is neither "
+                                     "movable nor copyable! "
+                                     "(#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in "
+                                     "debug mode for details)");
 #endif
                 }
                 wrapper->owned = true;
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 446f4620b2..a0b5de1514 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -62,7 +62,7 @@ class gil_scoped_acquire {
 
         if (!tstate) {
             tstate = PyThreadState_New(internals.istate);
-#    if !defined(NDEBUG)
+#    if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             if (!tstate) {
                 pybind11_fail("scoped_acquire: could not create thread state!");
             }
@@ -84,7 +84,7 @@ class gil_scoped_acquire {
 
     PYBIND11_NOINLINE void dec_ref() {
         --tstate->gilstate_counter;
-#    if !defined(NDEBUG)
+#    if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         if (detail::get_thread_state_unchecked() != tstate) {
             pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
         }
@@ -93,7 +93,7 @@ class gil_scoped_acquire {
         }
 #    endif
         if (tstate->gilstate_counter == 0) {
-#    if !defined(NDEBUG)
+#    if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             if (!release) {
                 pybind11_fail("scoped_acquire::dec_ref(): internal error!");
             }
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index e828f725dd..cd86152e57 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -370,7 +370,7 @@ class cpp_function : public function {
         rec->is_constructor = (std::strcmp(rec->name, "__init__") == 0)
                               || (std::strcmp(rec->name, "__setstate__") == 0);
 
-#if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
             const auto class_name
                 = detail::get_fully_qualified_tp_name((PyTypeObject *) rec->scope.ptr());
@@ -518,8 +518,9 @@ class cpp_function : public function {
             if (chain->is_method != rec->is_method) {
                 pybind11_fail(
                     "overloading a method with both static and instance methods is not supported; "
-#if defined(NDEBUG)
-                    "compile in debug mode for more details"
+#if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+                    "#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for more "
+                    "details"
 #else
                     "error while attempting to bind "
                     + std::string(rec->is_method ? "instance" : "static") + " method "
@@ -906,7 +907,7 @@ class cpp_function : public function {
 
 // 5. Put everything in a vector.  Not technically step 5, we've been building it
 // in `call.args` all along.
-#if !defined(NDEBUG)
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
                 if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs) {
                     pybind11_fail("Internal error: function call dispatcher inserted wrong number "
                                   "of arguments!");
diff --git a/tests/pybind11_tests.cpp b/tests/pybind11_tests.cpp
index d9b88fcc24..3c04699157 100644
--- a/tests/pybind11_tests.cpp
+++ b/tests/pybind11_tests.cpp
@@ -67,10 +67,10 @@ PYBIND11_MODULE(pybind11_tests, m) {
 
     bind_ConstructorStats(m);
 
-#if !defined(NDEBUG)
-    m.attr("debug_enabled") = true;
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+    m.attr("detailed_error_messages_enabled") = true;
 #else
-    m.attr("debug_enabled") = false;
+    m.attr("detailed_error_messages_enabled") = false;
 #endif
 
     py::class_<UserType>(m, "UserType", "A `py::class_` type for testing")
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 10515e26f9..815dd5e98a 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -361,10 +361,10 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 
     // test_bad_arg_default
     // Issue/PR #648: bad arg default debugging output
-#if !defined(NDEBUG)
-    m.attr("debug_enabled") = true;
+#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+    m.attr("detailed_error_messages_enabled") = true;
 #else
-    m.attr("debug_enabled") = false;
+    m.attr("detailed_error_messages_enabled") = false;
 #endif
     m.def("bad_arg_def_named", [] {
         auto m = py::module_::import("pybind11_tests");
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 5a95303e11..54597fa788 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -216,15 +216,15 @@ def test_metaclass_override():
 
 
 def test_no_mixed_overloads():
-    from pybind11_tests import debug_enabled
+    from pybind11_tests import detailed_error_messages_enabled
 
     with pytest.raises(RuntimeError) as excinfo:
         m.ExampleMandA.add_mixed_overloads1()
     assert str(
         excinfo.value
     ) == "overloading a method with both static and instance methods is not supported; " + (
-        "compile in debug mode for more details"
-        if not debug_enabled
+        "#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for more details"
+        if not detailed_error_messages_enabled
         else "error while attempting to bind static method ExampleMandA.overload_mixed1"
         "(arg0: float) -> str"
     )
@@ -234,8 +234,8 @@ def test_no_mixed_overloads():
     assert str(
         excinfo.value
     ) == "overloading a method with both static and instance methods is not supported; " + (
-        "compile in debug mode for more details"
-        if not debug_enabled
+        "#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for more details"
+        if not detailed_error_messages_enabled
         else "error while attempting to bind instance method ExampleMandA.overload_mixed2"
         "(self: pybind11_tests.methods_and_attributes.ExampleMandA, arg0: int, arg1: int)"
         " -> str"
@@ -344,16 +344,16 @@ def test_cyclic_gc():
 
 
 def test_bad_arg_default(msg):
-    from pybind11_tests import debug_enabled
+    from pybind11_tests import detailed_error_messages_enabled
 
     with pytest.raises(RuntimeError) as excinfo:
         m.bad_arg_def_named()
     assert msg(excinfo.value) == (
         "arg(): could not convert default argument 'a: UnregisteredType' in function "
         "'should_fail' into a Python object (type not registered yet?)"
-        if debug_enabled
+        if detailed_error_messages_enabled
         else "arg(): could not convert default argument into a Python object (type not registered "
-        "yet?). Compile in debug mode for more information."
+        "yet?). #define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for more information."
     )
 
     with pytest.raises(RuntimeError) as excinfo:
@@ -361,9 +361,9 @@ def test_bad_arg_default(msg):
     assert msg(excinfo.value) == (
         "arg(): could not convert default argument 'UnregisteredType' in function "
         "'should_fail' into a Python object (type not registered yet?)"
-        if debug_enabled
+        if detailed_error_messages_enabled
         else "arg(): could not convert default argument into a Python object (type not registered "
-        "yet?). Compile in debug mode for more information."
+        "yet?). #define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for more information."
     )
 
 
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 5c715ada6b..c740414aee 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -4,7 +4,7 @@
 import pytest
 
 import env
-from pybind11_tests import debug_enabled
+from pybind11_tests import detailed_error_messages_enabled
 from pybind11_tests import pytypes as m
 
 
@@ -416,8 +416,8 @@ def test_print(capture):
         m.print_failure()
     assert str(excinfo.value) == "Unable to convert call argument " + (
         "'1' of type 'UnregisteredType' to Python object"
-        if debug_enabled
-        else "to Python object (compile in debug mode for details)"
+        if detailed_error_messages_enabled
+        else "to Python object (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
     )
 
 

From 287e4f233dcaea92398810b7ff95b7137a96f5a2 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 2 May 2022 12:39:36 -0700
Subject: [PATCH 372/638] Test pickling a simple callable (does not work).
 (#3906)

* Test pickling a simple callable (does not work).

Currently only documents that it does not work. Starting point for future fix.

* Use re.search to accommodate variations of the TypeError message.

* PyPy: exercise full dumps/loads cycle.

* Adding explicit "broken" comment.
---
 tests/test_pickling.cpp |  2 ++
 tests/test_pickling.py  | 15 +++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index 9787bd3001..e154bc483c 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -61,6 +61,8 @@ void wrap(py::module m) {
 } // namespace exercise_trampoline
 
 TEST_SUBMODULE(pickling, m) {
+    m.def("simple_callable", []() { return 20220426; });
+
     // test_roundtrip
     class Pickleable {
     public:
diff --git a/tests/test_pickling.py b/tests/test_pickling.py
index 52802ace86..12361a661e 100644
--- a/tests/test_pickling.py
+++ b/tests/test_pickling.py
@@ -1,4 +1,5 @@
 import pickle
+import re
 
 import pytest
 
@@ -6,6 +7,20 @@
 from pybind11_tests import pickling as m
 
 
+def test_pickle_simple_callable():
+    assert m.simple_callable() == 20220426
+    if env.PYPY:
+        serialized = pickle.dumps(m.simple_callable)
+        deserialized = pickle.loads(serialized)
+        assert deserialized() == 20220426
+    else:
+        # To document broken behavior: currently it fails universally with
+        # all C Python versions.
+        with pytest.raises(TypeError) as excinfo:
+            pickle.dumps(m.simple_callable)
+        assert re.search("can.*t pickle .*PyCapsule.* object", str(excinfo.value))
+
+
 @pytest.mark.parametrize("cls_name", ["Pickleable", "PickleableNew"])
 def test_roundtrip(cls_name):
     cls = getattr(m, cls_name)

From bdc7dd8c31ee5ab4ec59bbadb0fa64e8059c93b0 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 4 May 2022 13:02:07 -0400
Subject: [PATCH 373/638] chore: update NVIDIA-PGI CI workflow (#3922)

* Update PGI workflow

* Remove copy paste typo

* ci: fix debian image

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index aeceaee2c8..2f295614e1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -382,17 +382,17 @@ jobs:
   # Testing on CentOS 7 + PGI compilers, which seems to require more workarounds
   centos-nvhpc7:
     runs-on: ubuntu-latest
-    name: "🐍 3 • CentOS7 / PGI 20.9 • x64"
+    name: "🐍 3 • CentOS7 / PGI 22.3 • x64"
     container: centos:7
 
     steps:
     - uses: actions/checkout@v3
 
     - name: Add Python 3 and a few requirements
-      run: yum update -y && yum install -y epel-release && yum install -y git python3-devel make environment-modules cmake3
+      run: yum update -y && yum install -y epel-release && yum install -y git python3-devel make environment-modules cmake3 yum-utils
 
     - name: Install NVidia HPC SDK
-      run:  yum -y install https://developer.download.nvidia.com/hpc-sdk/20.9/nvhpc-20-9-20.9-1.x86_64.rpm https://developer.download.nvidia.com/hpc-sdk/20.9/nvhpc-2020-20.9-1.x86_64.rpm
+      run: yum-config-manager --add-repo https://developer.download.nvidia.com/hpc-sdk/rhel/nvhpc.repo && yum -y install nvhpc-22.3
 
     # On CentOS 7, we have to filter a few tests (compiler internal error)
     # and allow deeper template recursion (not needed on CentOS 8 with a newer
@@ -402,7 +402,7 @@ jobs:
       shell: bash
       run: |
         source /etc/profile.d/modules.sh
-        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/20.9
+        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/22.3
         cmake3 -S . -B build -DDOWNLOAD_CATCH=ON \
                             -DCMAKE_CXX_STANDARD=11 \
                             -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
@@ -635,7 +635,7 @@ jobs:
     container: i386/debian:buster
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v1  # Required to run inside docker
 
     - name: Install requirements
       run: |

From f306012b55beccf93ffa5ce63d3a21450620eb61 Mon Sep 17 00:00:00 2001
From: HaarigerHarald <haarigerharald@gmx.at>
Date: Wed, 4 May 2022 19:12:33 +0200
Subject: [PATCH 374/638] fix: file extension on windows with cp36 and cp37
 (#3919)

---
 tools/FindPythonLibsNew.cmake | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index 6ad5fe1576..a035428f83 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -127,10 +127,11 @@ if USE_SYSCONFIG:
         scheme = 'posix_prefix'
     print(s.get_path('platinclude', scheme))
     print(s.get_path('platlib'))
+    print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'))
 else:
     print(ds.get_python_inc(plat_specific=True));
     print(ds.get_python_lib(plat_specific=True));
-print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'));
+    print(ds.get_config_var('EXT_SUFFIX') or ds.get_config_var('SO'));
 print(hasattr(sys, 'gettotalrefcount')+0);
 print(struct.calcsize('@P'));
 print(s.get_config_var('LDVERSION') or s.get_config_var('VERSION'));

From 9a16e55ad226b5e387c1f3cf65f8d82e9b62e3c4 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 5 May 2022 15:02:16 -0400
Subject: [PATCH 375/638] [pre-commit.ci] pre-commit autoupdate (#3903)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/hadialqattan/pycln: v1.3.1 → v1.3.2](https://github.com/hadialqattan/pycln/compare/v1.3.1...v1.3.2)
- [github.com/PyCQA/pylint: v2.13.5 → v2.13.8](https://github.com/PyCQA/pylint/compare/v2.13.5...v2.13.8)
- [github.com/pre-commit/mirrors-mypy: v0.942 → v0.950](https://github.com/pre-commit/mirrors-mypy/compare/v0.942...v0.950)
---
 .pre-commit-config.yaml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 099f0dc26e..2a7dd01cf6 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.3.1"
+  rev: "v1.3.2"
   hooks:
   - id: pycln
     stages: [manual]
@@ -107,7 +107,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.13.5"
+  rev: "v2.13.8"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -123,7 +123,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.942"
+  rev: "v0.950"
   hooks:
   - id: mypy
     args: []

From 68a0b2dfd8cb3f5ac1846f22b6a8d0d539cb493c Mon Sep 17 00:00:00 2001
From: Ed Catmur <ed@catmur.uk>
Date: Thu, 5 May 2022 20:09:56 +0100
Subject: [PATCH 376/638] Add anyset & frozenset, enable copying (cast) to
 std::set (#3901)

* Add frozenset, and allow it cast to std::set

For the reverse direction, std::set still casts to set. This is in concordance with the behavior for sequence containers, where e.g. tuple casts to std::vector but std::vector casts to list.

Extracted from #3886.

* Rename set_base to any_set to match Python C API

since this will be part of pybind11 public API

* PR: static_cast, anyset

* Add tests for frozenset

and rename anyset methods

* Remove frozenset default ctor, add tests

Making frozenset non-default constructible means that we need to adjust pyobject_caster to not require that its value is default constructible, by initializing value to a nil handle.  This also allows writing C++ functions taking anyset, and is arguably a performance improvement, since there is no need to allocate an object that will just be replaced by load.

Add some more tests, including anyset::empty, anyset::size, set::add and set::clear.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add rationale to `pyobject_caster` default ctor

* Remove ineffectual protected: access control

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/cast.h    |  8 +++++++
 include/pybind11/pytypes.h | 28 +++++++++++++++--------
 include/pybind11/stl.h     |  4 ++--
 tests/test_pytypes.cpp     | 24 +++++++++++++++----
 tests/test_pytypes.py      | 47 ++++++++++++++++++++++++++++++++------
 tests/test_stl.py          |  1 +
 6 files changed, 89 insertions(+), 23 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 22d2dba4ca..376a679544 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -908,6 +908,14 @@ struct handle_type_name<kwargs> {
 
 template <typename type>
 struct pyobject_caster {
+    template <typename T = type, enable_if_t<std::is_same<T, handle>::value, int> = 0>
+    pyobject_caster() : value() {}
+
+    // `type` may not be default constructible (e.g. frozenset, anyset).  Initializing `value`
+    // to a nil handle is safe since it will only be accessed if `load` succeeds.
+    template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
+    pyobject_caster() : value(reinterpret_steal<type>(handle())) {}
+
     template <typename T = type, enable_if_t<std::is_same<T, handle>::value, int> = 0>
     bool load(handle src, bool /* convert */) {
         value = src;
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 324fa932f1..256a2441b1 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1784,25 +1784,35 @@ class kwargs : public dict {
     PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)
 };
 
-class set : public object {
+class anyset : public object {
 public:
-    PYBIND11_OBJECT_CVT(set, object, PySet_Check, PySet_New)
-    set() : object(PySet_New(nullptr), stolen_t{}) {
+    PYBIND11_OBJECT(anyset, object, PyAnySet_Check)
+    size_t size() const { return static_cast<size_t>(PySet_Size(m_ptr)); }
+    bool empty() const { return size() == 0; }
+    template <typename T>
+    bool contains(T &&val) const {
+        return PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 1;
+    }
+};
+
+class set : public anyset {
+public:
+    PYBIND11_OBJECT_CVT(set, anyset, PySet_Check, PySet_New)
+    set() : anyset(PySet_New(nullptr), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate set object!");
         }
     }
-    size_t size() const { return (size_t) PySet_Size(m_ptr); }
-    bool empty() const { return size() == 0; }
     template <typename T>
     bool add(T &&val) /* py-non-const */ {
         return PySet_Add(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 0;
     }
     void clear() /* py-non-const */ { PySet_Clear(m_ptr); }
-    template <typename T>
-    bool contains(T &&val) const {
-        return PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 1;
-    }
+};
+
+class frozenset : public anyset {
+public:
+    PYBIND11_OBJECT_CVT(frozenset, anyset, PyFrozenSet_Check, PyFrozenSet_New)
 };
 
 class function : public object {
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 51b57a92ba..625fb210fc 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -55,10 +55,10 @@ struct set_caster {
     using key_conv = make_caster<Key>;
 
     bool load(handle src, bool convert) {
-        if (!isinstance<pybind11::set>(src)) {
+        if (!isinstance<anyset>(src)) {
             return false;
         }
-        auto s = reinterpret_borrow<pybind11::set>(src);
+        auto s = reinterpret_borrow<anyset>(src);
         value.clear();
         for (auto entry : s) {
             key_conv conv;
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index d1e9b81a73..8d296f655a 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -75,7 +75,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("get_none", [] { return py::none(); });
     m.def("print_none", [](const py::none &none) { py::print("none: {}"_s.format(none)); });
 
-    // test_set
+    // test_set, test_frozenset
     m.def("get_set", []() {
         py::set set;
         set.add(py::str("key1"));
@@ -83,14 +83,26 @@ TEST_SUBMODULE(pytypes, m) {
         set.add(std::string("key3"));
         return set;
     });
-    m.def("print_set", [](const py::set &set) {
+    m.def("get_frozenset", []() {
+        py::set set;
+        set.add(py::str("key1"));
+        set.add("key2");
+        set.add(std::string("key3"));
+        return py::frozenset(set);
+    });
+    m.def("print_anyset", [](const py::anyset &set) {
         for (auto item : set) {
             py::print("key:", item);
         }
     });
-    m.def("set_contains",
-          [](const py::set &set, const py::object &key) { return set.contains(key); });
-    m.def("set_contains", [](const py::set &set, const char *key) { return set.contains(key); });
+    m.def("anyset_size", [](const py::anyset &set) { return set.size(); });
+    m.def("anyset_empty", [](const py::anyset &set) { return set.empty(); });
+    m.def("anyset_contains",
+          [](const py::anyset &set, const py::object &key) { return set.contains(key); });
+    m.def("anyset_contains",
+          [](const py::anyset &set, const char *key) { return set.contains(key); });
+    m.def("set_add", [](py::set &set, const py::object &key) { set.add(key); });
+    m.def("set_clear", [](py::set &set) { set.clear(); });
 
     // test_dict
     m.def("get_dict", []() { return py::dict("key"_a = "value"); });
@@ -310,6 +322,7 @@ TEST_SUBMODULE(pytypes, m) {
                         "list"_a = py::list(d["list"]),
                         "dict"_a = py::dict(d["dict"]),
                         "set"_a = py::set(d["set"]),
+                        "frozenset"_a = py::frozenset(d["frozenset"]),
                         "memoryview"_a = py::memoryview(d["memoryview"]));
     });
 
@@ -325,6 +338,7 @@ TEST_SUBMODULE(pytypes, m) {
                         "list"_a = d["list"].cast<py::list>(),
                         "dict"_a = d["dict"].cast<py::dict>(),
                         "set"_a = d["set"].cast<py::set>(),
+                        "frozenset"_a = d["frozenset"].cast<py::frozenset>(),
                         "memoryview"_a = d["memoryview"].cast<py::memoryview>());
     });
 
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index c740414aee..9afe62f424 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -66,11 +66,12 @@ def test_none(capture, doc):
 
 def test_set(capture, doc):
     s = m.get_set()
+    assert isinstance(s, set)
     assert s == {"key1", "key2", "key3"}
 
+    s.add("key4")
     with capture:
-        s.add("key4")
-        m.print_set(s)
+        m.print_anyset(s)
     assert (
         capture.unordered
         == """
@@ -81,12 +82,43 @@ def test_set(capture, doc):
     """
     )
 
-    assert not m.set_contains(set(), 42)
-    assert m.set_contains({42}, 42)
-    assert m.set_contains({"foo"}, "foo")
+    m.set_add(s, "key5")
+    assert m.anyset_size(s) == 5
 
-    assert doc(m.get_list) == "get_list() -> list"
-    assert doc(m.print_list) == "print_list(arg0: list) -> None"
+    m.set_clear(s)
+    assert m.anyset_empty(s)
+
+    assert not m.anyset_contains(set(), 42)
+    assert m.anyset_contains({42}, 42)
+    assert m.anyset_contains({"foo"}, "foo")
+
+    assert doc(m.get_set) == "get_set() -> set"
+    assert doc(m.print_anyset) == "print_anyset(arg0: anyset) -> None"
+
+
+def test_frozenset(capture, doc):
+    s = m.get_frozenset()
+    assert isinstance(s, frozenset)
+    assert s == frozenset({"key1", "key2", "key3"})
+
+    with capture:
+        m.print_anyset(s)
+    assert (
+        capture.unordered
+        == """
+        key: key1
+        key: key2
+        key: key3
+    """
+    )
+    assert m.anyset_size(s) == 3
+    assert not m.anyset_empty(s)
+
+    assert not m.anyset_contains(frozenset(), 42)
+    assert m.anyset_contains(frozenset({42}), 42)
+    assert m.anyset_contains(frozenset({"foo"}), "foo")
+
+    assert doc(m.get_frozenset) == "get_frozenset() -> frozenset"
 
 
 def test_dict(capture, doc):
@@ -302,6 +334,7 @@ def test_constructors():
         list: range(3),
         dict: [("two", 2), ("one", 1), ("three", 3)],
         set: [4, 4, 5, 6, 6, 6],
+        frozenset: [4, 4, 5, 6, 6, 6],
         memoryview: b"abc",
     }
     inputs = {k.__name__: v for k, v in data.items()}
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 975860b85a..d30c382113 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -73,6 +73,7 @@ def test_set(doc):
     assert s == {"key1", "key2"}
     s.add("key3")
     assert m.load_set(s)
+    assert m.load_set(frozenset(s))
 
     assert doc(m.cast_set) == "cast_set() -> Set[str]"
     assert doc(m.load_set) == "load_set(arg0: Set[str]) -> bool"

From 2e331308d38a521c087e7fc0cfee227cd29f3f71 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 6 May 2022 16:57:39 -0400
Subject: [PATCH 377/638] chore: remove unused include from stl.h (#3928)

* change iostream include to ostream include
---
 include/pybind11/stl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 625fb210fc..597bce61d5 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -13,9 +13,9 @@
 #include "detail/common.h"
 
 #include <deque>
-#include <iostream>
 #include <list>
 #include <map>
+#include <ostream>
 #include <set>
 #include <unordered_map>
 #include <unordered_set>

From ad146b2a1877e8ba3803f94a7837969835a297a7 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 9 May 2022 18:44:21 -0400
Subject: [PATCH 378/638] [pre-commit.ci] pre-commit autoupdate (#3933)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.32.0 → v2.32.1](https://github.com/asottile/pyupgrade/compare/v2.32.0...v2.32.1)
- [github.com/pre-commit/mirrors-clang-format: v14.0.1 → v14.0.3](https://github.com/pre-commit/mirrors-clang-format/compare/v14.0.1...v14.0.3)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2a7dd01cf6..03f829c251 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.32.0"
+  rev: "v2.32.1"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -164,7 +164,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v14.0.1"
+  rev: "v14.0.3"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From 5621ab853a60ad48bce08487cc6e220930178b79 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 16 May 2022 04:26:35 -0700
Subject: [PATCH 379/638] Do we have a unit test for the traceback code in
 error_string()?

---
 include/pybind11/detail/type_caster_base.h | 40 ----------------------
 1 file changed, 40 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a7b9771326..36d56e23c4 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -493,46 +493,6 @@ PYBIND11_NOINLINE std::string error_string() {
         PyException_SetTraceback(scope.value, scope.trace);
     }
 
-#if !defined(PYPY_VERSION)
-    if (scope.trace) {
-        auto *trace = (PyTracebackObject *) scope.trace;
-
-        /* Get the deepest trace possible */
-        while (trace->tb_next) {
-            trace = trace->tb_next;
-        }
-
-        PyFrameObject *frame = trace->tb_frame;
-        Py_XINCREF(frame);
-        errorString += "\n\nAt:\n";
-        while (frame) {
-#    if PY_VERSION_HEX >= 0x030900B1
-            PyCodeObject *f_code = PyFrame_GetCode(frame);
-#    else
-            PyCodeObject *f_code = frame->f_code;
-            Py_INCREF(f_code);
-#    endif
-            int lineno = PyFrame_GetLineNumber(frame);
-            errorString += "  ";
-            errorString += handle(f_code->co_filename).cast<std::string>();
-            errorString += '(';
-            errorString += std::to_string(lineno);
-            errorString += "): ";
-            errorString += handle(f_code->co_name).cast<std::string>();
-            errorString += '\n';
-            Py_DECREF(f_code);
-#    if PY_VERSION_HEX >= 0x030900B1
-            auto *b_frame = PyFrame_GetBack(frame);
-#    else
-            auto *b_frame = frame->f_back;
-            Py_XINCREF(b_frame);
-#    endif
-            Py_DECREF(frame);
-            frame = b_frame;
-        }
-    }
-#endif
-
     return errorString;
 }
 

From 48c7be4a5643cdf48a1228de05f6279ec95e99d3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 16 May 2022 04:30:10 -0700
Subject: [PATCH 380/638] Undoing previous accidental commit. Sorry I forgot to
 git branch.

---
 include/pybind11/detail/type_caster_base.h | 40 ++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 36d56e23c4..a7b9771326 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -493,6 +493,46 @@ PYBIND11_NOINLINE std::string error_string() {
         PyException_SetTraceback(scope.value, scope.trace);
     }
 
+#if !defined(PYPY_VERSION)
+    if (scope.trace) {
+        auto *trace = (PyTracebackObject *) scope.trace;
+
+        /* Get the deepest trace possible */
+        while (trace->tb_next) {
+            trace = trace->tb_next;
+        }
+
+        PyFrameObject *frame = trace->tb_frame;
+        Py_XINCREF(frame);
+        errorString += "\n\nAt:\n";
+        while (frame) {
+#    if PY_VERSION_HEX >= 0x030900B1
+            PyCodeObject *f_code = PyFrame_GetCode(frame);
+#    else
+            PyCodeObject *f_code = frame->f_code;
+            Py_INCREF(f_code);
+#    endif
+            int lineno = PyFrame_GetLineNumber(frame);
+            errorString += "  ";
+            errorString += handle(f_code->co_filename).cast<std::string>();
+            errorString += '(';
+            errorString += std::to_string(lineno);
+            errorString += "): ";
+            errorString += handle(f_code->co_name).cast<std::string>();
+            errorString += '\n';
+            Py_DECREF(f_code);
+#    if PY_VERSION_HEX >= 0x030900B1
+            auto *b_frame = PyFrame_GetBack(frame);
+#    else
+            auto *b_frame = frame->f_back;
+            Py_XINCREF(b_frame);
+#    endif
+            Py_DECREF(frame);
+            frame = b_frame;
+        }
+    }
+#endif
+
     return errorString;
 }
 

From 72eea20afd51e363fe115265043c2b2b6bcc523a Mon Sep 17 00:00:00 2001
From: Maarten Baert <maarten-baert@hotmail.com>
Date: Mon, 16 May 2022 22:51:01 +0200
Subject: [PATCH 381/638] Fix py::cast from pytype rvalue to pytype (#3949)

* Fix py::cast from pytype rvalue to pytype

Previously, py::cast blindly assumed that the destination type was a C++
type rather than a python type when the source type was an rvalue.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/cast.h  | 17 ++++++++++++++---
 tests/test_copy_move.cpp |  3 +++
 tests/test_copy_move.py  |  7 +++++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 376a679544..9a971704e4 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1009,6 +1009,8 @@ struct return_value_policy_override<
 // Basic python -> C++ casting; throws if casting fails
 template <typename T, typename SFINAE>
 type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
+    static_assert(!detail::is_pyobject<T>::value,
+                  "Internal error: type_caster should only be used for C++ types");
     if (!conv.load(handle, true)) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         throw cast_error("Unable to cast Python instance to C++ type (#define "
@@ -1099,21 +1101,30 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
 // - If both movable and copyable, check ref count: if 1, move; otherwise copy
 // - Otherwise (not movable), copy.
 template <typename T>
-detail::enable_if_t<detail::move_always<T>::value, T> cast(object &&object) {
+detail::enable_if_t<!detail::is_pyobject<T>::value && detail::move_always<T>::value, T>
+cast(object &&object) {
     return move<T>(std::move(object));
 }
 template <typename T>
-detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
+detail::enable_if_t<!detail::is_pyobject<T>::value && detail::move_if_unreferenced<T>::value, T>
+cast(object &&object) {
     if (object.ref_count() > 1) {
         return cast<T>(object);
     }
     return move<T>(std::move(object));
 }
 template <typename T>
-detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
+detail::enable_if_t<!detail::is_pyobject<T>::value && detail::move_never<T>::value, T>
+cast(object &&object) {
     return cast<T>(object);
 }
 
+// pytype rvalue -> pytype (calls converting constructor)
+template <typename T>
+detail::enable_if_t<detail::is_pyobject<T>::value, T> cast(object &&object) {
+    return T(std::move(object));
+}
+
 template <typename T>
 T object::cast() const & {
     return pybind11::cast<T>(*this);
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 6e1bdd8568..28c2445644 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -289,4 +289,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
         py::return_value_policy::move);
     m.def(
         "get_moveissue2", [](int i) { return MoveIssue2(i); }, py::return_value_policy::move);
+
+    // Make sure that cast from pytype rvalue to other pytype works
+    m.def("get_pytype_rvalue_castissue", [](double i) { return py::float_(i).cast<py::int_>(); });
 }
diff --git a/tests/test_copy_move.py b/tests/test_copy_move.py
index f2c0cdceb1..9fef089339 100644
--- a/tests/test_copy_move.py
+++ b/tests/test_copy_move.py
@@ -123,3 +123,10 @@ def test_move_fallback():
     assert m1.value == 1
     m2 = m.get_moveissue2(2)
     assert m2.value == 2
+
+
+def test_pytype_rvalue_cast():
+    """Make sure that cast from pytype rvalue to other pytype works"""
+
+    value = m.get_pytype_rvalue_castissue(1.0)
+    assert value == 1

From 1a7b12983e09f698be3007b5868bfdf931d9a4d1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 16 May 2022 17:27:19 -0400
Subject: [PATCH 382/638] ci: fix cuda issue & MSVC spurious warning (#3950)

* ci: fix cuda issue

* ci: cuda 11.3-11.4 produce warnings -> errors

* tests: ignore unused warning for MSVC

* Update tests/CMakeLists.txt
---
 .github/workflows/ci.yml | 4 ++--
 tests/CMakeLists.txt     | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2f295614e1..8b537e6e1e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -315,8 +315,8 @@ jobs:
   # Testing NVCC; forces sources to behave like .cu files
   cuda:
     runs-on: ubuntu-latest
-    name: "🐍 3.8 • CUDA 11 • Ubuntu 20.04"
-    container: nvidia/cuda:11.0-devel-ubuntu20.04
+    name: "🐍 3.8 • CUDA 11.2 • Ubuntu 20.04"
+    container: nvidia/cuda:11.2.2-devel-ubuntu20.04
 
     steps:
     - uses: actions/checkout@v3
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index bce8cceb1e..a14b520a5f 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -351,7 +351,7 @@ endif()
 # Compile with compiler warnings turned on
 function(pybind11_enable_warnings target_name)
   if(MSVC)
-    target_compile_options(${target_name} PRIVATE /W4)
+    target_compile_options(${target_name} PRIVATE /W4 /wd4189)
   elseif(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Intel|Clang)" AND NOT PYBIND11_CUDA_TESTS)
     target_compile_options(
       ${target_name}

From dff6fa0554bf6efe98a8da3f932b749cff4d76a8 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 16 May 2022 23:45:54 -0400
Subject: [PATCH 383/638] fix(cmake): avoid issue with NVCC + Windows (#3947)

---
 tools/pybind11Common.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index bbb722ac72..e1fb601acc 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -96,7 +96,7 @@ if(MSVC) # That's also clang-cl
   set_property(
     TARGET pybind11::windows_extras
     APPEND
-    PROPERTY INTERFACE_COMPILE_OPTIONS /bigobj)
+    PROPERTY INTERFACE_COMPILE_OPTIONS $<$<COMPILE_LANGUAGE:CXX>:/bigobj>)
 
   # /MP enables multithreaded builds (relevant when there are many files) for MSVC
   if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC") # no Clang no Intel

From a8b3ff30f9649459021adc80f98a945d3ac675a5 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 17 May 2022 11:29:49 -0400
Subject: [PATCH 384/638] chore: add a couple of moves in pybind11.h (#3941)

* Add missing std::moves in enum_base methods

* Remove useless move

* Add one more std::move in print

* Further optimize print

* Some more misc optimizations
---
 include/pybind11/pybind11.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index cd86152e57..ca94aaeb3a 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1926,7 +1926,8 @@ struct enum_base {
             [](const object &arg) -> str {
                 handle type = type::handle_of(arg);
                 object type_name = type.attr("__name__");
-                return pybind11::str("<{}.{}: {}>").format(type_name, enum_name(arg), int_(arg));
+                return pybind11::str("<{}.{}: {}>")
+                    .format(std::move(type_name), enum_name(arg), int_(arg));
             },
             name("__repr__"),
             is_method(m_base));
@@ -1936,7 +1937,7 @@ struct enum_base {
         m_base.attr("__str__") = cpp_function(
             [](handle arg) -> str {
                 object type_name = type::handle_of(arg).attr("__name__");
-                return pybind11::str("{}.{}").format(type_name, enum_name(arg));
+                return pybind11::str("{}.{}").format(std::move(type_name), enum_name(arg));
             },
             name("name"),
             is_method(m_base));
@@ -2576,8 +2577,8 @@ PYBIND11_NOINLINE void print(const tuple &args, const dict &kwargs) {
     for (size_t i = 0; i < args.size(); ++i) {
         strings[i] = str(args[i]);
     }
-    auto sep = kwargs.contains("sep") ? kwargs["sep"] : cast(" ");
-    auto line = sep.attr("join")(strings);
+    auto sep = kwargs.contains("sep") ? kwargs["sep"] : str(" ");
+    auto line = sep.attr("join")(std::move(strings));
 
     object file;
     if (kwargs.contains("file")) {
@@ -2596,7 +2597,7 @@ PYBIND11_NOINLINE void print(const tuple &args, const dict &kwargs) {
 
     auto write = file.attr("write");
     write(line);
-    write(kwargs.contains("end") ? kwargs["end"] : cast("\n"));
+    write(kwargs.contains("end") ? kwargs["end"] : str("\n"));
 
     if (kwargs.contains("flush") && kwargs["flush"].cast<bool>()) {
         file.attr("flush")();
@@ -2639,7 +2640,7 @@ get_type_override(const void *this_ptr, const type_info *this_type, const char *
 
     function override = getattr(self, name, function());
     if (override.is_cpp_function()) {
-        cache.insert(key);
+        cache.insert(std::move(key));
         return function();
     }
 

From 1e4bd22bdca5068188d2d46136b79d18a1d1f647 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 18 May 2022 23:19:33 -0400
Subject: [PATCH 385/638] fix(cmake): support release and debug at the same
 time (#3948)

---
 tools/pybind11Tools.cmake | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 3d1503df86..5535e872f3 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -115,17 +115,32 @@ if(PYTHON_IS_DEBUG)
     PROPERTY INTERFACE_COMPILE_DEFINITIONS Py_DEBUG)
 endif()
 
-set_property(
-  TARGET pybind11::module
-  APPEND
-  PROPERTY
-    INTERFACE_LINK_LIBRARIES pybind11::python_link_helper
-    "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
+if(CMAKE_VERSION VERSION_LESS 3.11)
+  set_property(
+    TARGET pybind11::module
+    APPEND
+    PROPERTY
+      INTERFACE_LINK_LIBRARIES
+      pybind11::python_link_helper
+      "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>"
+  )
 
-set_property(
-  TARGET pybind11::embed
-  APPEND
-  PROPERTY INTERFACE_LINK_LIBRARIES pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+  set_property(
+    TARGET pybind11::embed
+    APPEND
+    PROPERTY INTERFACE_LINK_LIBRARIES pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+else()
+  target_link_libraries(
+    pybind11::module
+    INTERFACE
+      pybind11::python_link_helper
+      "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>"
+  )
+
+  target_link_libraries(pybind11::embed INTERFACE pybind11::pybind11
+                                                  $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+
+endif()
 
 function(pybind11_extension name)
   # The prefix and extension are provided by FindPythonLibsNew.cmake

From 918d4481a4f69c7a4cbb4282acbabd28e2433039 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 20 May 2022 09:38:29 -0400
Subject: [PATCH 386/638] fix(cmake): support cross-compiles with classic
 Python (#3959)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 tools/FindPythonLibsNew.cmake | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index a035428f83..a5a628fd7a 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -151,26 +151,36 @@ if(NOT _PYTHON_SUCCESS MATCHES 0)
   return()
 endif()
 
+# Can manually set values when cross-compiling
+macro(_PYBIND11_GET_IF_UNDEF lst index name)
+  if(NOT DEFINED "${name}")
+    list(GET "${lst}" "${index}" "${name}")
+  endif()
+endmacro()
+
 # Convert the process output into a list
 if(WIN32)
   string(REGEX REPLACE "\\\\" "/" _PYTHON_VALUES ${_PYTHON_VALUES})
 endif()
 string(REGEX REPLACE ";" "\\\\;" _PYTHON_VALUES ${_PYTHON_VALUES})
 string(REGEX REPLACE "\n" ";" _PYTHON_VALUES ${_PYTHON_VALUES})
-list(GET _PYTHON_VALUES 0 _PYTHON_VERSION_LIST)
-list(GET _PYTHON_VALUES 1 PYTHON_PREFIX)
-list(GET _PYTHON_VALUES 2 PYTHON_INCLUDE_DIR)
-list(GET _PYTHON_VALUES 3 PYTHON_SITE_PACKAGES)
-list(GET _PYTHON_VALUES 4 PYTHON_MODULE_EXTENSION)
-list(GET _PYTHON_VALUES 5 PYTHON_IS_DEBUG)
-list(GET _PYTHON_VALUES 6 PYTHON_SIZEOF_VOID_P)
-list(GET _PYTHON_VALUES 7 PYTHON_LIBRARY_SUFFIX)
-list(GET _PYTHON_VALUES 8 PYTHON_LIBDIR)
-list(GET _PYTHON_VALUES 9 PYTHON_MULTIARCH)
+_pybind11_get_if_undef(_PYTHON_VALUES 0 _PYTHON_VERSION_LIST)
+_pybind11_get_if_undef(_PYTHON_VALUES 1 PYTHON_PREFIX)
+_pybind11_get_if_undef(_PYTHON_VALUES 2 PYTHON_INCLUDE_DIR)
+_pybind11_get_if_undef(_PYTHON_VALUES 3 PYTHON_SITE_PACKAGES)
+_pybind11_get_if_undef(_PYTHON_VALUES 4 PYTHON_MODULE_EXTENSION)
+_pybind11_get_if_undef(_PYTHON_VALUES 5 PYTHON_IS_DEBUG)
+_pybind11_get_if_undef(_PYTHON_VALUES 6 PYTHON_SIZEOF_VOID_P)
+_pybind11_get_if_undef(_PYTHON_VALUES 7 PYTHON_LIBRARY_SUFFIX)
+_pybind11_get_if_undef(_PYTHON_VALUES 8 PYTHON_LIBDIR)
+_pybind11_get_if_undef(_PYTHON_VALUES 9 PYTHON_MULTIARCH)
 
 # Make sure the Python has the same pointer-size as the chosen compiler
 # Skip if CMAKE_SIZEOF_VOID_P is not defined
-if(CMAKE_SIZEOF_VOID_P AND (NOT "${PYTHON_SIZEOF_VOID_P}" STREQUAL "${CMAKE_SIZEOF_VOID_P}"))
+# This should be skipped for (non-Apple) cross-compiles (like EMSCRIPTEN)
+if(NOT CMAKE_CROSSCOMPILING
+   AND CMAKE_SIZEOF_VOID_P
+   AND (NOT "${PYTHON_SIZEOF_VOID_P}" STREQUAL "${CMAKE_SIZEOF_VOID_P}"))
   if(PythonLibsNew_FIND_REQUIRED)
     math(EXPR _PYTHON_BITS "${PYTHON_SIZEOF_VOID_P} * 8")
     math(EXPR _CMAKE_BITS "${CMAKE_SIZEOF_VOID_P} * 8")

From c42414db86d393aaea8b450d987f0f56c2c66bca Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 23 May 2022 12:26:53 -0400
Subject: [PATCH 387/638] (perf): use a rvalue cast in func_wrapper (#3966)

* (perf): use an rvalue cast in func_wrapper

* Try to clarify comment

* Fix comment typo
---
 include/pybind11/functional.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 23e092e731..f2a752e9d6 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -98,8 +98,8 @@ struct type_caster<std::function<Return(Args...)>> {
             explicit func_wrapper(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
-                object retval(hfunc.f(std::forward<Args>(args)...));
-                return retval.template cast<Return>();
+                // casts the returned object as a rvalue to the return type
+                return object(hfunc.f(std::forward<Args>(args)...)).template cast<Return>();
             }
         };
 

From 4624e8e16433f56c315abc9bfc49c449fdfe137f Mon Sep 17 00:00:00 2001
From: Maarten Baert <maarten-baert@hotmail.com>
Date: Tue, 24 May 2022 19:46:31 +0200
Subject: [PATCH 388/638] Don't return pointers to static objects with
 return_value_policy::take_ownership. (#3946)

* Don't return pointers to static objects with return_value_policy::take_ownership.

This fixes -Wfree-nonheap-object warnings produced by GCC.

* Use return value policy fix instead

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 tests/test_builtin_casters.cpp | 3 ++-
 tests/test_stl.cpp             | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 7b67515e5e..6529f47d05 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -267,7 +267,8 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("lvalue_nested", []() -> const decltype(lvnested) & { return lvnested; });
 
     static std::pair<int, std::string> int_string_pair{2, "items"};
-    m.def("int_string_pair", []() { return &int_string_pair; });
+    m.def(
+        "int_string_pair", []() { return &int_string_pair; }, py::return_value_policy::reference);
 
     // test_builtins_cast_return_none
     m.def("return_none_string", []() -> std::string * { return nullptr; });
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index b56a91953b..38d32fda93 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -177,7 +177,8 @@ TEST_SUBMODULE(stl, m) {
           [](const std::vector<bool> &v) { return v.at(0) == true && v.at(1) == false; });
     // Unnumbered regression (caused by #936): pointers to stl containers aren't castable
     static std::vector<RValueCaster> lvv{2};
-    m.def("cast_ptr_vector", []() { return &lvv; });
+    m.def(
+        "cast_ptr_vector", []() { return &lvv; }, py::return_value_policy::reference);
 
     // test_deque
     m.def("cast_deque", []() { return std::deque<int>{1}; });

From 2d4a20c8cb1009bdc47079581759230a202579e8 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 25 May 2022 12:14:07 -0400
Subject: [PATCH 389/638] chore: add missing moves for buffer_func and
 staticmethod in pybind11.h (#3969)

* Use move converting ctor when making class staticmethod

* Add missing caster move in buffer func

* fix use after move

* add back move to staticmethod

* avoid shadowing with varname
---
 include/pybind11/pybind11.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ca94aaeb3a..4c392713c9 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1566,7 +1566,8 @@ class class_ : public detail::generic_type {
                         scope(*this),
                         sibling(getattr(*this, name_, none())),
                         extra...);
-        attr(cf.name()) = staticmethod(cf);
+        auto cf_name = cf.name();
+        attr(std::move(cf_name)) = staticmethod(std::move(cf));
         return *this;
     }
 
@@ -1620,7 +1621,7 @@ class class_ : public detail::generic_type {
                 if (!caster.load(obj, false)) {
                     return nullptr;
                 }
-                return new buffer_info(((capture *) ptr)->func(caster));
+                return new buffer_info(((capture *) ptr)->func(std::move(caster)));
             },
             ptr);
         weakref(m_ptr, cpp_function([ptr](handle wr) {

From 2c549eb7aa16bf1297af337e1b022e9ed2a4dc52 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 25 May 2022 21:44:55 -0700
Subject: [PATCH 390/638] Move `PyErr_NormalizeException()` up a few lines
 (#3971)

* Add error_already_set_what what tests, asserting the status quo.

* Move PyErr_NormalizeException() up a few lines.

* @pytest.mark.skipif("env.PYPY") from PR #1895 is required even for this much simpler PR

* Move PyException_SetTraceback() with PyErr_NormalizeException() as suggested by @skylion007

* Insert a std::move() as suggested by @skylion007
---
 include/pybind11/detail/type_caster_base.h | 11 +++--
 tests/test_exceptions.cpp                  |  8 ++++
 tests/test_exceptions.py                   | 50 ++++++++++++++++++++++
 3 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index a7b9771326..14561759b6 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -478,6 +478,11 @@ PYBIND11_NOINLINE std::string error_string() {
 
     error_scope scope; // Preserve error state
 
+    PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
+    if (scope.trace != nullptr) {
+        PyException_SetTraceback(scope.value, scope.trace);
+    }
+
     std::string errorString;
     if (scope.type) {
         errorString += handle(scope.type).attr("__name__").cast<std::string>();
@@ -487,12 +492,6 @@ PYBIND11_NOINLINE std::string error_string() {
         errorString += (std::string) str(scope.value);
     }
 
-    PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
-
-    if (scope.trace != nullptr) {
-        PyException_SetTraceback(scope.value, scope.trace);
-    }
-
 #if !defined(PYPY_VERSION)
     if (scope.trace) {
         auto *trace = (PyTracebackObject *) scope.trace;
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 3e9a3d771e..d7b31cf744 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -299,4 +299,12 @@ TEST_SUBMODULE(exceptions, m) {
             std::throw_with_nested(std::runtime_error("Outer Exception"));
         }
     });
+
+    m.def("error_already_set_what", [](const py::object &exc_type, const py::object &exc_value) {
+        PyErr_SetObject(exc_type.ptr(), exc_value.ptr());
+        std::string what = py::error_already_set().what();
+        bool py_err_set_after_what = (PyErr_Occurred() != nullptr);
+        PyErr_Clear();
+        return py::make_tuple(std::move(what), py_err_set_after_what);
+    });
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 0be61804a6..dc75941134 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -270,3 +270,53 @@ def test_local_translator(msg):
         m.throws_local_simple_error()
     assert not isinstance(excinfo.value, cm.LocalSimpleException)
     assert msg(excinfo.value) == "this mod"
+
+
+class FlakyException(Exception):
+    def __init__(self, failure_point):
+        if failure_point == "failure_point_init":
+            raise ValueError("triggered_failure_point_init")
+        self.failure_point = failure_point
+
+    def __str__(self):
+        if self.failure_point == "failure_point_str":
+            raise ValueError("triggered_failure_point_str")
+        return "FlakyException.__str__"
+
+
+@pytest.mark.parametrize(
+    "exc_type, exc_value, expected_what",
+    (
+        (ValueError, "plain_str", "ValueError: plain_str"),
+        (ValueError, ("tuple_elem",), "ValueError: tuple_elem"),
+        (FlakyException, ("happy",), "FlakyException: FlakyException.__str__"),
+    ),
+)
+def test_error_already_set_what_with_happy_exceptions(
+    exc_type, exc_value, expected_what
+):
+    what, py_err_set_after_what = m.error_already_set_what(exc_type, exc_value)
+    assert not py_err_set_after_what
+    assert what == expected_what
+
+
+@pytest.mark.skipif("env.PYPY", reason="PyErr_NormalizeException Segmentation fault")
+def test_flaky_exception_failure_point_init():
+    what, py_err_set_after_what = m.error_already_set_what(
+        FlakyException, ("failure_point_init",)
+    )
+    assert not py_err_set_after_what
+    lines = what.splitlines()
+    # PyErr_NormalizeException replaces the original FlakyException with ValueError:
+    assert lines[:3] == ["ValueError: triggered_failure_point_init", "", "At:"]
+    # Checking the first two lines of the traceback as formatted in error_string():
+    assert "test_exceptions.py(" in lines[3]
+    assert lines[3].endswith("): __init__")
+    assert lines[4].endswith("): test_flaky_exception_failure_point_init")
+
+
+def test_flaky_exception_failure_point_str():
+    # The error_already_set ctor fails due to a ValueError in error_string():
+    with pytest.raises(ValueError) as excinfo:
+        m.error_already_set_what(FlakyException, ("failure_point_str",))
+    assert str(excinfo.value) == "triggered_failure_point_str"

From 8d14e666e3aab5c958169e23b619ae8b17b09ea6 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 26 May 2022 08:07:40 -0700
Subject: [PATCH 391/638] fix: avoid `catch (...)` for expected `import numpy`
 failures (#3974)

* Replace import numpy catch (...) with catch (error_already_set)

* Add missing const (not sure how those got lost).
---
 tests/test_numpy_array.cpp     | 2 +-
 tests/test_numpy_dtypes.cpp    | 2 +-
 tests/test_numpy_vectorize.cpp | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 8bc77a33fa..69ddbe1ef2 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -162,7 +162,7 @@ static int data_i = 42;
 TEST_SUBMODULE(numpy_array, sm) {
     try {
         py::module_::import("numpy");
-    } catch (...) {
+    } catch (const py::error_already_set &) {
         return;
     }
 
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index c25bc042b8..6654f9ed8f 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -301,7 +301,7 @@ struct B {};
 TEST_SUBMODULE(numpy_dtypes, m) {
     try {
         py::module_::import("numpy");
-    } catch (...) {
+    } catch (const py::error_already_set &) {
         return;
     }
 
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index eab08ec0a6..dcc4c6ac25 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -22,7 +22,7 @@ double my_func(int x, float y, double z) {
 TEST_SUBMODULE(numpy_vectorize, m) {
     try {
         py::module_::import("numpy");
-    } catch (...) {
+    } catch (const py::error_already_set &) {
         return;
     }
 

From 68f80105007a574f114cfe899243bb3d96272a2e Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 27 May 2022 14:32:57 -0400
Subject: [PATCH 392/638] chore: add err guard to capsule destructor and add a
 move to iostream (#3958)

* Add err guard to capsule destructor

* only uses ostream currently

* can these be noexcept

* Add back header

* fix for older compilers

* This should at least be noexcept

* Add missing move

* Apparently not noexcept for old llvm
---
 include/pybind11/iostream.h | 2 +-
 include/pybind11/pytypes.h  | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 12e1f19f0c..1878089e31 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -100,7 +100,7 @@ class pythonbuf : public std::streambuf {
 
             if (size > remainder) {
                 str line(pbase(), size - remainder);
-                pywrite(line);
+                pywrite(std::move(line));
                 pyflush();
             }
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 256a2441b1..5b1c60e337 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1581,6 +1581,8 @@ class capsule : public object {
 
     capsule(const void *value, void (*destructor)(void *)) {
         m_ptr = PyCapsule_New(const_cast<void *>(value), nullptr, [](PyObject *o) {
+            // guard if destructor called while err indicator is set
+            error_scope error_guard;
             auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
             if (destructor == nullptr) {
                 if (PyErr_Occurred()) {

From 748ae2270b333d7024d9ef7ffb7f2ca947b2491f Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 28 May 2022 16:40:57 -0700
Subject: [PATCH 393/638] Add missing error handling to
 `module_::def_submodule` (#3973)

* Add missing error handling to module_::def_submodule

* Add test_def_submodule_failures

* PyPy only: Skip test with trigger for PyModule_GetName() failure.

* Reapply minor fix that accidentally got lost in transfer from PR #3964
---
 include/pybind11/pybind11.h | 13 ++++++++++---
 tests/test_modules.cpp      |  2 ++
 tests/test_modules.py       | 30 ++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 4c392713c9..ea97ed072f 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1173,9 +1173,16 @@ class module_ : public object {
             py::module_ m3 = m2.def_submodule("subsub", "A submodule of 'example.sub'");
     \endrst */
     module_ def_submodule(const char *name, const char *doc = nullptr) {
-        std::string full_name
-            = std::string(PyModule_GetName(m_ptr)) + std::string(".") + std::string(name);
-        auto result = reinterpret_borrow<module_>(PyImport_AddModule(full_name.c_str()));
+        const char *this_name = PyModule_GetName(m_ptr);
+        if (this_name == nullptr) {
+            throw error_already_set();
+        }
+        std::string full_name = std::string(this_name) + '.' + name;
+        handle submodule = PyImport_AddModule(full_name.c_str());
+        if (!submodule) {
+            throw error_already_set();
+        }
+        auto result = reinterpret_borrow<module_>(submodule);
         if (doc && options::show_user_defined_docstrings()) {
             result.attr("__doc__") = pybind11::str(doc);
         }
diff --git a/tests/test_modules.cpp b/tests/test_modules.cpp
index 8aa2a4bdbd..18a7ec74cc 100644
--- a/tests/test_modules.cpp
+++ b/tests/test_modules.cpp
@@ -120,4 +120,6 @@ TEST_SUBMODULE(modules, m) {
 
         return failures;
     });
+
+    m.def("def_submodule", [](py::module_ m, const char *name) { return m.def_submodule(name); });
 }
diff --git a/tests/test_modules.py b/tests/test_modules.py
index 15db8355ef..e11d68e78e 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -1,3 +1,6 @@
+import pytest
+
+import env
 from pybind11_tests import ConstructorStats
 from pybind11_tests import modules as m
 from pybind11_tests.modules import subsubmodule as ms
@@ -89,3 +92,30 @@ def test_builtin_key_type():
         keys = __builtins__.__dict__.keys()
 
     assert {type(k) for k in keys} == {str}
+
+
+@pytest.mark.xfail("env.PYPY", reason="PyModule_GetName()")
+def test_def_submodule_failures():
+    sm = m.def_submodule(m, b"ScratchSubModuleName")  # Using bytes to show it works.
+    assert sm.__name__ == m.__name__ + "." + "ScratchSubModuleName"
+    malformed_utf8 = b"\x80"
+    if env.PYPY:
+        # It is not worth the effort finding a trigger for a failure when running with PyPy.
+        pytest.skip("Sufficiently exercised on platforms other than PyPy.")
+    else:
+        # Meant to trigger PyModule_GetName() failure:
+        sm_name_orig = sm.__name__
+        sm.__name__ = malformed_utf8
+        try:
+            with pytest.raises(Exception):
+                # Seen with Python 3.9: SystemError: nameless module
+                # But we do not want to exercise the internals of PyModule_GetName(), which could
+                # change in future versions of Python, but a bad __name__ is very likely to cause
+                # some kind of failure indefinitely.
+                m.def_submodule(sm, b"SubSubModuleName")
+        finally:
+            # Clean up to ensure nothing gets upset by a module with an invalid __name__.
+            sm.__name__ = sm_name_orig  # Purely precautionary.
+    # Meant to trigger PyImport_AddModule() failure:
+    with pytest.raises(UnicodeDecodeError):
+        m.def_submodule(sm, malformed_utf8)

From 8da58da53996e9aa40d051b3b84cb3220fdbbb58 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sat, 28 May 2022 19:58:15 -0400
Subject: [PATCH 394/638] chore: perfectly forward all make_iterator args
 (#3980)

* Perfectly forward all make_iterator args

* Try emplace back
---
 include/pybind11/pybind11.h | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ea97ed072f..be206e1a6b 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2333,7 +2333,7 @@ template <typename Access,
           typename Sentinel,
           typename ValueType,
           typename... Extra>
-iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&...extra) {
+iterator make_iterator_impl(Iterator &&first, Sentinel &&last, Extra &&...extra) {
     using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
     // TODO: state captures only the types of Extra, not the values
 
@@ -2359,7 +2359,7 @@ iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&...extra) {
                 Policy);
     }
 
-    return cast(state{first, last, true});
+    return cast(state{std::forward<Iterator>(first), std::forward<Sentinel>(last), true});
 }
 
 PYBIND11_NAMESPACE_END(detail)
@@ -2370,13 +2370,15 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename ValueType = typename detail::iterator_access<Iterator>::result_type,
           typename... Extra>
-iterator make_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+iterator make_iterator(Iterator &&first, Sentinel &&last, Extra &&...extra) {
     return detail::make_iterator_impl<detail::iterator_access<Iterator>,
                                       Policy,
                                       Iterator,
                                       Sentinel,
                                       ValueType,
-                                      Extra...>(first, last, std::forward<Extra>(extra)...);
+                                      Extra...>(std::forward<Iterator>(first),
+                                                std::forward<Sentinel>(last),
+                                                std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
@@ -2386,13 +2388,15 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
           typename... Extra>
-iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+iterator make_key_iterator(Iterator &&first, Sentinel &&last, Extra &&...extra) {
     return detail::make_iterator_impl<detail::iterator_key_access<Iterator>,
                                       Policy,
                                       Iterator,
                                       Sentinel,
                                       KeyType,
-                                      Extra...>(first, last, std::forward<Extra>(extra)...);
+                                      Extra...>(std::forward<Iterator>(first),
+                                                std::forward<Sentinel>(last),
+                                                std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
@@ -2402,13 +2406,15 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
           typename... Extra>
-iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+iterator make_value_iterator(Iterator &&first, Sentinel &&last, Extra &&...extra) {
     return detail::make_iterator_impl<detail::iterator_value_access<Iterator>,
                                       Policy,
                                       Iterator,
                                       Sentinel,
                                       ValueType,
-                                      Extra...>(first, last, std::forward<Extra>(extra)...);
+                                      Extra...>(std::forward<Iterator>(first),
+                                                std::forward<Sentinel>(last),
+                                                std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
@@ -2467,7 +2473,7 @@ void implicitly_convertible() {
     };
 
     if (auto *tinfo = detail::get_type_info(typeid(OutputType))) {
-        tinfo->implicit_conversions.push_back(implicit_caster);
+        tinfo->implicit_conversions.emplace_back(std::move(implicit_caster));
     } else {
         pybind11_fail("implicitly_convertible: Unable to find type " + type_id<OutputType>());
     }

From de4ba92c9fe1d5d225f39cbc251e7f2616f3b58d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 31 May 2022 11:51:13 -0700
Subject: [PATCH 395/638] Add `error_scope` to `detail::get_internals()`
 (#3981)

* Add `error_scope` to `detail::get_internals()`

* Adjust test to tolerate macOS PyPy behavior.
---
 include/pybind11/detail/internals.h           |  1 +
 tests/CMakeLists.txt                          |  1 +
 ...s_module_interleaved_error_already_set.cpp | 51 +++++++++++++++++++
 tests/test_exceptions.cpp                     |  7 +++
 tests/test_exceptions.py                      |  9 ++++
 5 files changed, 69 insertions(+)
 create mode 100644 tests/cross_module_interleaved_error_already_set.cpp

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 3f83113bd7..6ca5e1482f 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -415,6 +415,7 @@ PYBIND11_NOINLINE internals &get_internals() {
         ~gil_scoped_acquire_local() { PyGILState_Release(state); }
         const PyGILState_STATE state;
     } gil;
+    error_scope err_scope;
 
     PYBIND11_STR_TYPE id(PYBIND11_INTERNALS_ID);
     auto builtins = handle(PyEval_GetBuiltins());
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index a14b520a5f..7296cd1b81 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -215,6 +215,7 @@ tests_extra_targets("test_exceptions.py;test_local_bindings.py;test_stl.py;test_
                     "pybind11_cross_module_tests")
 
 # And add additional targets for other tests.
+tests_extra_targets("test_exceptions.py" "cross_module_interleaved_error_already_set")
 tests_extra_targets("test_gil_scoped.py" "cross_module_gil_utils")
 
 set(PYBIND11_EIGEN_REPO
diff --git a/tests/cross_module_interleaved_error_already_set.cpp b/tests/cross_module_interleaved_error_already_set.cpp
new file mode 100644
index 0000000000..fdd9939e45
--- /dev/null
+++ b/tests/cross_module_interleaved_error_already_set.cpp
@@ -0,0 +1,51 @@
+/*
+    Copyright (c) 2022 Google LLC
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/pybind11.h>
+
+// This file mimics a DSO that makes pybind11 calls but does not define a PYBIND11_MODULE,
+// so that the first call of cross_module_error_already_set() triggers the first call of
+// pybind11::detail::get_internals().
+
+namespace {
+
+namespace py = pybind11;
+
+void interleaved_error_already_set() {
+    PyErr_SetString(PyExc_RuntimeError, "1st error.");
+    try {
+        throw py::error_already_set();
+    } catch (const py::error_already_set &) {
+        // The 2nd error could be conditional in a real application.
+        PyErr_SetString(PyExc_RuntimeError, "2nd error.");
+    } // Here the 1st error is destroyed before the 2nd error is fetched.
+    // The error_already_set dtor triggers a pybind11::detail::get_internals()
+    // call via pybind11::gil_scoped_acquire.
+    if (PyErr_Occurred()) {
+        throw py::error_already_set();
+    }
+}
+
+constexpr char kModuleName[] = "cross_module_interleaved_error_already_set";
+
+struct PyModuleDef moduledef = {
+    PyModuleDef_HEAD_INIT, kModuleName, nullptr, 0, nullptr, nullptr, nullptr, nullptr, nullptr};
+
+} // namespace
+
+extern "C" PYBIND11_EXPORT PyObject *PyInit_cross_module_interleaved_error_already_set() {
+    PyObject *m = PyModule_Create(&moduledef);
+    if (m != nullptr) {
+        static_assert(sizeof(&interleaved_error_already_set) == sizeof(void *),
+                      "Function pointer must have the same size as void *");
+        PyModule_AddObject(
+            m,
+            "funcaddr",
+            PyLong_FromVoidPtr(reinterpret_cast<void *>(&interleaved_error_already_set)));
+    }
+    return m;
+}
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index d7b31cf744..8c74d70299 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -307,4 +307,11 @@ TEST_SUBMODULE(exceptions, m) {
         PyErr_Clear();
         return py::make_tuple(std::move(what), py_err_set_after_what);
     });
+
+    m.def("test_cross_module_interleaved_error_already_set", []() {
+        auto cm = py::module_::import("cross_module_interleaved_error_already_set");
+        auto interleaved_error_already_set
+            = reinterpret_cast<void (*)()>(PyLong_AsVoidPtr(cm.attr("funcaddr").ptr()));
+        interleaved_error_already_set();
+    });
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index dc75941134..4320ad181a 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -320,3 +320,12 @@ def test_flaky_exception_failure_point_str():
     with pytest.raises(ValueError) as excinfo:
         m.error_already_set_what(FlakyException, ("failure_point_str",))
     assert str(excinfo.value) == "triggered_failure_point_str"
+
+
+def test_cross_module_interleaved_error_already_set():
+    with pytest.raises(RuntimeError) as excinfo:
+        m.test_cross_module_interleaved_error_already_set()
+    assert str(excinfo.value) in (
+        "2nd error.",  # Almost all platforms.
+        "RuntimeError: 2nd error.",  # Some PyPy builds (seen under macOS).
+    )

From b24c5ed204f4e2b9599106c879106594ea3ef8c3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 31 May 2022 11:54:33 -0700
Subject: [PATCH 396/638] Replace "Unknown internal error occurred" with a more
 helpful message. (#3982)

---
 include/pybind11/detail/type_caster_base.h | 14 ++++++++------
 include/pybind11/pytypes.h                 | 20 ++++++++++++++------
 tests/test_exceptions.cpp                  |  5 ++++-
 tests/test_exceptions.py                   |  5 ++++-
 4 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 14561759b6..dd8d03751e 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -470,14 +470,16 @@ PYBIND11_NOINLINE bool isinstance_generic(handle obj, const std::type_info &tp)
     return isinstance(obj, type);
 }
 
-PYBIND11_NOINLINE std::string error_string() {
-    if (!PyErr_Occurred()) {
-        PyErr_SetString(PyExc_RuntimeError, "Unknown internal error occurred");
-        return "Unknown internal error occurred";
+PYBIND11_NOINLINE std::string error_string(const char *called) {
+    error_scope scope; // Fetch error state (will be restored when this function returns).
+    if (scope.type == nullptr) {
+        if (called == nullptr) {
+            called = "pybind11::detail::error_string()";
+        }
+        pybind11_fail("Internal error: " + std::string(called)
+                      + " called while Python error indicator not set.");
     }
 
-    error_scope scope; // Preserve error state
-
     PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
     if (scope.trace != nullptr) {
         PyException_SetTraceback(scope.value, scope.trace);
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 5b1c60e337..c71f1b2e90 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -360,7 +360,7 @@ T reinterpret_steal(handle h) {
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-std::string error_string();
+std::string error_string(const char *called = nullptr);
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
@@ -375,20 +375,27 @@ PYBIND11_NAMESPACE_END(detail)
 /// python).
 class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
 public:
-    /// Constructs a new exception from the current Python error indicator, if any.  The current
+    /// Constructs a new exception from the current Python error indicator.  The current
     /// Python error indicator will be cleared.
-    error_already_set() : std::runtime_error(detail::error_string()) {
+    error_already_set() : std::runtime_error(detail::error_string("pybind11::error_already_set")) {
         PyErr_Fetch(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
     }
 
+    /// WARNING: The GIL must be held when this copy constructor is invoked!
     error_already_set(const error_already_set &) = default;
     error_already_set(error_already_set &&) = default;
 
+    /// WARNING: This destructor needs to acquire the Python GIL. This can lead to
+    ///          crashes (undefined behavior) if the Python interpreter is finalizing.
     inline ~error_already_set() override;
 
-    /// Give the currently-held error back to Python, if any.  If there is currently a Python error
-    /// already set it is cleared first.  After this call, the current object no longer stores the
-    /// error variables (but the `.what()` string is still available).
+    /// Restores the currently-held Python error (which will clear the Python error indicator first
+    /// if already set). After this call, the current object no longer stores the error variables.
+    /// NOTE: Any copies of this object may still store the error variables. Currently there is no
+    //        protection against calling restore() from multiple copies.
+    /// NOTE: This member function will always restore the normalized exception, which may or may
+    ///       not be the original Python exception.
+    /// WARNING: The GIL must be held when this member function is called!
     void restore() {
         PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr());
     }
@@ -405,6 +412,7 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
     }
     /// An alternate version of `discard_as_unraisable()`, where a string provides information on
     /// the location of the error. For example, `__func__` could be helpful.
+    /// WARNING: The GIL must be held when this member function is called!
     void discard_as_unraisable(const char *err_context) {
         discard_as_unraisable(reinterpret_steal<object>(PYBIND11_FROM_STRING(err_context)));
     }
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 8c74d70299..9469b86724 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -228,7 +228,10 @@ TEST_SUBMODULE(exceptions, m) {
             throw py::error_already_set();
         } catch (const std::runtime_error &e) {
             if ((err && e.what() != std::string("ValueError: foo"))
-                || (!err && e.what() != std::string("Unknown internal error occurred"))) {
+                || (!err
+                    && e.what()
+                           != std::string("Internal error: pybind11::error_already_set called "
+                                          "while Python error indicator not set."))) {
                 PyErr_Clear();
                 throw std::runtime_error("error message mismatch");
             }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 4320ad181a..4dcbb83a36 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -16,7 +16,10 @@ def test_std_exception(msg):
 def test_error_already_set(msg):
     with pytest.raises(RuntimeError) as excinfo:
         m.throw_already_set(False)
-    assert msg(excinfo.value) == "Unknown internal error occurred"
+    assert (
+        msg(excinfo.value)
+        == "Internal error: pybind11::error_already_set called while Python error indicator not set."
+    )
 
     with pytest.raises(ValueError) as excinfo:
         m.throw_already_set(True)

From 9f7b3f735aae417838001b338c9970710e9cee82 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 31 May 2022 12:59:19 -0700
Subject: [PATCH 397/638] addl unit tests for PR #3970 (#3977)

* Add test_perf_accessors (to be merged into test_pytypes).

* Python < 3.8 f-string compatibility

* Use thread_local in inc_ref_counter()

* Intentional breakage, brute-force way to quickly find out how many platforms reach the PYBIND11_HANDLE_REF_DEBUG code, with and without threads.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Remove Intentional breakage

* Drop perf test, move inc_refs tests to test_pytypes

* Fold in PR #3970 with `#ifdef`s

* Complete test coverage for all newly added code.

* Condense new unit tests via a simple local helper macro.

* Remove PYBIND11_PR3970 define. See https://github.com/pybind/pybind11/pull/3977#issuecomment-1142526417

* Move static keyword first (fixes silly oversight).

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pytypes.h | 19 +++++++++++++++
 tests/test_pytypes.cpp     | 49 ++++++++++++++++++++++++++++++++++++++
 tests/test_pytypes.py      |  9 +++++++
 3 files changed, 77 insertions(+)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index c71f1b2e90..0c56900648 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -180,6 +180,10 @@ class object_api : public pyobject_tag {
 
 PYBIND11_NAMESPACE_END(detail)
 
+#if !defined(PYBIND11_HANDLE_REF_DEBUG) && !defined(NDEBUG)
+#    define PYBIND11_HANDLE_REF_DEBUG
+#endif
+
 /** \rst
     Holds a reference to a Python object (no reference counting)
 
@@ -209,6 +213,9 @@ class handle : public detail::object_api<handle> {
         this function automatically. Returns a reference to itself.
     \endrst */
     const handle &inc_ref() const & {
+#ifdef PYBIND11_HANDLE_REF_DEBUG
+        inc_ref_counter(1);
+#endif
         Py_XINCREF(m_ptr);
         return *this;
     }
@@ -244,6 +251,18 @@ class handle : public detail::object_api<handle> {
 
 protected:
     PyObject *m_ptr = nullptr;
+
+#ifdef PYBIND11_HANDLE_REF_DEBUG
+private:
+    static std::size_t inc_ref_counter(std::size_t add) {
+        thread_local std::size_t counter = 0;
+        counter += add;
+        return counter;
+    }
+
+public:
+    static std::size_t inc_ref_counter() { return inc_ref_counter(0); }
+#endif
 };
 
 /** \rst
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 8d296f655a..ef214acc3b 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -297,6 +297,55 @@ TEST_SUBMODULE(pytypes, m) {
         return d;
     });
 
+    m.def("accessor_moves", []() { // See PR #3970
+        py::list return_list;
+#ifdef PYBIND11_HANDLE_REF_DEBUG
+        py::int_ py_int_0(0);
+        py::int_ py_int_42(42);
+        py::str py_str_count("count");
+
+        auto tup = py::make_tuple(0);
+
+        py::sequence seq(tup);
+
+        py::list lst;
+        lst.append(0);
+
+#    define PYBIND11_LOCAL_DEF(...)                                                               \
+        {                                                                                         \
+            std::size_t inc_refs = py::handle::inc_ref_counter();                                 \
+            __VA_ARGS__;                                                                          \
+            inc_refs = py::handle::inc_ref_counter() - inc_refs;                                  \
+            return_list.append(inc_refs);                                                         \
+        }
+
+        PYBIND11_LOCAL_DEF(tup[py_int_0])    // l-value (to have a control)
+        PYBIND11_LOCAL_DEF(tup[py::int_(0)]) // r-value
+
+        PYBIND11_LOCAL_DEF(tup.attr(py_str_count))     // l-value
+        PYBIND11_LOCAL_DEF(tup.attr(py::str("count"))) // r-value
+
+        PYBIND11_LOCAL_DEF(seq[py_int_0])    // l-value
+        PYBIND11_LOCAL_DEF(seq[py::int_(0)]) // r-value
+
+        PYBIND11_LOCAL_DEF(seq.attr(py_str_count))     // l-value
+        PYBIND11_LOCAL_DEF(seq.attr(py::str("count"))) // r-value
+
+        PYBIND11_LOCAL_DEF(lst[py_int_0])    // l-value
+        PYBIND11_LOCAL_DEF(lst[py::int_(0)]) // r-value
+
+        PYBIND11_LOCAL_DEF(lst.attr(py_str_count))     // l-value
+        PYBIND11_LOCAL_DEF(lst.attr(py::str("count"))) // r-value
+
+        auto lst_acc = lst[py::int_(0)];
+        lst_acc = py::int_(42);                    // Detaches lst_acc from lst.
+        PYBIND11_LOCAL_DEF(lst_acc = py_int_42)    // l-value
+        PYBIND11_LOCAL_DEF(lst_acc = py::int_(42)) // r-value
+#    undef PYBIND11_LOCAL_DEF
+#endif
+        return return_list;
+    });
+
     // test_constructors
     m.def("default_constructors", []() {
         return py::dict("bytes"_a = py::bytes(),
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 9afe62f424..b91a7e1564 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -317,6 +317,15 @@ def func(self, x, *args):
     assert d["var"] == 99
 
 
+def test_accessor_moves():
+    inc_refs = m.accessor_moves()
+    if inc_refs:
+        # To be changed in PR #3970: [1, 0, 1, 0, ...]
+        assert inc_refs == [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
+    else:
+        pytest.skip("Not defined: PYBIND11_HANDLE_REF_DEBUG")
+
+
 def test_constructors():
     """C++ default and converting constructors are equivalent to type calls in Python"""
     types = [bytes, bytearray, str, bool, int, float, tuple, list, dict, set]

From 58802de41bc9c78425b66c3b6f22392241aac8de Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 1 Jun 2022 15:19:13 -0400
Subject: [PATCH 398/638] perf: Add object rvalue overload for accessors.
 Enables reference stealing (#3970)

* Add object rvalue overload for accessors. Enables reference stealing

* Fix comments

* Fix more comment typos

* Fix bug

* reorder declarations for clarity

* fix another perf bug

* should be static

* future proof operator overloads

* Fix perfect forwarding

* Add a couple of tests

* Remove errant include

* Improve test documentation

* Add dict test

* add object attr tests

* Optimize STL map caster and cleanup enum

* Reorder to match declarations

* adjust increfs

* Remove comment

* revert value change

* add missing move
---
 include/pybind11/pybind11.h |  6 +++---
 include/pybind11/pytypes.h  | 36 ++++++++++++++++++++++++++++++------
 include/pybind11/stl.h      |  2 +-
 tests/test_pytypes.cpp      | 34 ++++++++++++++++++++++++++++++++++
 tests/test_pytypes.py       | 31 +++++++++++++++++++++++++++++--
 5 files changed, 97 insertions(+), 12 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index be206e1a6b..cfa4420679 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2069,12 +2069,12 @@ struct enum_base {
         str name(name_);
         if (entries.contains(name)) {
             std::string type_name = (std::string) str(m_base.attr("__name__"));
-            throw value_error(type_name + ": element \"" + std::string(name_)
+            throw value_error(std::move(type_name) + ": element \"" + std::string(name_)
                               + "\" already exists!");
         }
 
         entries[name] = std::make_pair(value, doc);
-        m_base.attr(name) = value;
+        m_base.attr(std::move(name)) = std::move(value);
     }
 
     PYBIND11_NOINLINE void export_values() {
@@ -2610,7 +2610,7 @@ PYBIND11_NOINLINE void print(const tuple &args, const dict &kwargs) {
     }
 
     auto write = file.attr("write");
-    write(line);
+    write(std::move(line));
     write(kwargs.contains("end") ? kwargs["end"] : str("\n"));
 
     if (kwargs.contains("flush") && kwargs["flush"].cast<bool>()) {
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 0c56900648..27807953b7 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -85,7 +85,9 @@ class object_api : public pyobject_tag {
         or `object` subclass causes a call to ``__setitem__``.
     \endrst */
     item_accessor operator[](handle key) const;
-    /// See above (the only difference is that they key is provided as a string literal)
+    /// See above (the only difference is that the key's reference is stolen)
+    item_accessor operator[](object &&key) const;
+    /// See above (the only difference is that the key is provided as a string literal)
     item_accessor operator[](const char *key) const;
 
     /** \rst
@@ -95,7 +97,9 @@ class object_api : public pyobject_tag {
         or `object` subclass causes a call to ``setattr``.
     \endrst */
     obj_attr_accessor attr(handle key) const;
-    /// See above (the only difference is that they key is provided as a string literal)
+    /// See above (the only difference is that the key's reference is stolen)
+    obj_attr_accessor attr(object &&key) const;
+    /// See above (the only difference is that the key is provided as a string literal)
     str_attr_accessor attr(const char *key) const;
 
     /** \rst
@@ -684,7 +688,7 @@ class accessor : public object_api<accessor<Policy>> {
     }
     template <typename T>
     void operator=(T &&value) & {
-        get_cache() = reinterpret_borrow<object>(object_or_cast(std::forward<T>(value)));
+        get_cache() = ensure_object(object_or_cast(std::forward<T>(value)));
     }
 
     template <typename T = Policy>
@@ -712,6 +716,9 @@ class accessor : public object_api<accessor<Policy>> {
     }
 
 private:
+    static object ensure_object(object &&o) { return std::move(o); }
+    static object ensure_object(handle h) { return reinterpret_borrow<object>(h); }
+
     object &get_cache() const {
         if (!cache) {
             cache = Policy::get(obj, key);
@@ -1711,7 +1718,10 @@ class tuple : public object {
     size_t size() const { return (size_t) PyTuple_Size(m_ptr); }
     bool empty() const { return size() == 0; }
     detail::tuple_accessor operator[](size_t index) const { return {*this, index}; }
-    detail::item_accessor operator[](handle h) const { return object::operator[](h); }
+    template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
+    detail::item_accessor operator[](T &&o) const {
+        return object::operator[](std::forward<T>(o));
+    }
     detail::tuple_iterator begin() const { return {*this, 0}; }
     detail::tuple_iterator end() const { return {*this, PyTuple_GET_SIZE(m_ptr)}; }
 };
@@ -1771,7 +1781,10 @@ class sequence : public object {
     }
     bool empty() const { return size() == 0; }
     detail::sequence_accessor operator[](size_t index) const { return {*this, index}; }
-    detail::item_accessor operator[](handle h) const { return object::operator[](h); }
+    template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
+    detail::item_accessor operator[](T &&o) const {
+        return object::operator[](std::forward<T>(o));
+    }
     detail::sequence_iterator begin() const { return {*this, 0}; }
     detail::sequence_iterator end() const { return {*this, PySequence_Size(m_ptr)}; }
 };
@@ -1790,7 +1803,10 @@ class list : public object {
     size_t size() const { return (size_t) PyList_Size(m_ptr); }
     bool empty() const { return size() == 0; }
     detail::list_accessor operator[](size_t index) const { return {*this, index}; }
-    detail::item_accessor operator[](handle h) const { return object::operator[](h); }
+    template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
+    detail::item_accessor operator[](T &&o) const {
+        return object::operator[](std::forward<T>(o));
+    }
     detail::list_iterator begin() const { return {*this, 0}; }
     detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
     template <typename T>
@@ -2090,6 +2106,10 @@ item_accessor object_api<D>::operator[](handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
 }
 template <typename D>
+item_accessor object_api<D>::operator[](object &&key) const {
+    return {derived(), std::move(key)};
+}
+template <typename D>
 item_accessor object_api<D>::operator[](const char *key) const {
     return {derived(), pybind11::str(key)};
 }
@@ -2098,6 +2118,10 @@ obj_attr_accessor object_api<D>::attr(handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
 }
 template <typename D>
+obj_attr_accessor object_api<D>::attr(object &&key) const {
+    return {derived(), std::move(key)};
+}
+template <typename D>
 str_attr_accessor object_api<D>::attr(const char *key) const {
     return {derived(), key};
 }
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 597bce61d5..ab30ecac0b 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -128,7 +128,7 @@ struct map_caster {
             if (!key || !value) {
                 return handle();
             }
-            d[key] = value;
+            d[std::move(key)] = std::move(value);
         }
         return d.release();
     }
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index ef214acc3b..cb81007c37 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -661,4 +661,38 @@ TEST_SUBMODULE(pytypes, m) {
         double v = x.get_value();
         return v * v;
     });
+
+    m.def("tuple_rvalue_getter", [](const py::tuple &tup) {
+        // tests accessing tuple object with rvalue int
+        for (size_t i = 0; i < tup.size(); i++) {
+            auto o = py::handle(tup[py::int_(i)]);
+            if (!o) {
+                throw py::value_error("tuple is malformed");
+            }
+        }
+        return tup;
+    });
+    m.def("list_rvalue_getter", [](const py::list &l) {
+        // tests accessing list with rvalue int
+        for (size_t i = 0; i < l.size(); i++) {
+            auto o = py::handle(l[py::int_(i)]);
+            if (!o) {
+                throw py::value_error("list is malformed");
+            }
+        }
+        return l;
+    });
+    m.def("populate_dict_rvalue", [](int population) {
+        auto d = py::dict();
+        for (int i = 0; i < population; i++) {
+            d[py::int_(i)] = py::int_(i);
+        }
+        return d;
+    });
+    m.def("populate_obj_str_attrs", [](py::object &o, int population) {
+        for (int i = 0; i < population; i++) {
+            o.attr(py::str(py::int_(i))) = py::str(py::int_(i));
+        }
+        return o;
+    });
 }
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index b91a7e1564..3e9d51a27c 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -1,5 +1,6 @@
 import contextlib
 import sys
+import types
 
 import pytest
 
@@ -320,8 +321,7 @@ def func(self, x, *args):
 def test_accessor_moves():
     inc_refs = m.accessor_moves()
     if inc_refs:
-        # To be changed in PR #3970: [1, 0, 1, 0, ...]
-        assert inc_refs == [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
+        assert inc_refs == [1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0]
     else:
         pytest.skip("Not defined: PYBIND11_HANDLE_REF_DEBUG")
 
@@ -707,3 +707,30 @@ def test_implementation_details():
 def test_external_float_():
     r1 = m.square_float_(2.0)
     assert r1 == 4.0
+
+
+def test_tuple_rvalue_getter():
+    pop = 1000
+    tup = tuple(range(pop))
+    m.tuple_rvalue_getter(tup)
+
+
+def test_list_rvalue_getter():
+    pop = 1000
+    my_list = list(range(pop))
+    m.list_rvalue_getter(my_list)
+
+
+def test_populate_dict_rvalue():
+    pop = 1000
+    my_dict = {i: i for i in range(pop)}
+    assert m.populate_dict_rvalue(pop) == my_dict
+
+
+def test_populate_obj_str_attrs():
+    pop = 1000
+    o = types.SimpleNamespace(**{str(i): i for i in range(pop)})
+    new_o = m.populate_obj_str_attrs(o, pop)
+    new_attrs = {k: v for k, v in new_o.__dict__.items() if not k.startswith("_")}
+    assert all(isinstance(v, str) for v in new_attrs.values())
+    assert len(new_attrs) == pop

From a05bc3d2359d12840ef2329d68f613f1a7df9c5d Mon Sep 17 00:00:00 2001
From: Sergei Lebedev <185856+superbobry@users.noreply.github.com>
Date: Fri, 3 Jun 2022 00:17:38 +0100
Subject: [PATCH 399/638] error_already_set::what() is now constructed lazily
 (#1895)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* error_already_set::what() is now constructed lazily

Prior to this commit throwing error_already_set was expensive due to the
eager construction of the error string (which required traversing the
Python stack). See #1853 for more context and an alternative take on the
issue.

Note that error_already_set no longer inherits from std::runtime_error
because the latter has no default constructor.

* Do not attempt to normalize if no exception occurred

This is not supported on PyPy-2.7 5.8.0.

* Extract exception name via tp_name

This is faster than dynamically looking up __name__ via GetAttrString.
Note though that the runtime of the code throwing an error_already_set
will be dominated by stack unwinding so the improvement will not be
noticeable.

Before:

396 ns ± 0.913 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

After:

277 ns ± 0.549 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

Benchmark:

const std::string foo() {
    PyErr_SetString(PyExc_KeyError, "");
    const std::string &s = py::detail::error_string();
    PyErr_Clear();
    return s;
}

PYBIND11_MODULE(foo, m) {
    m.def("foo", &::foo);
}

* Reverted error_already_set to subclass std::runtime_error

* Revert "Extract exception name via tp_name"

The implementation of __name__ is slightly more complex than that.
It handles the module name prefix, and heap-allocated types. We could
port it to pybind11 later on but for now it seems like an overkill.

This reverts commit f1435c7e6b068a1ed13ebd3db597ea3bb15aa398.

* Cosmit following @YannickJadoul's comments

Note that detail::error_string() no longer calls PyException_SetTraceback
as it is unncessary for pretty-printing the exception.

* Fixed PyPy build

* Moved normalization to error_already_set ctor

* Fix merge bugs

* Fix more merge errors

* Improve formatting

* Improve error message in rare case

* Revert back if statements

* Fix clang-tidy

* Try removing mutable

* Does build_mode release fix it

* Set to Debug to expose segfault

* Fix remove set error string

* Do not run error_string() more than once

* Trying setting the tracebackk to the value

* guard if m_type is null

* Try to debug PGI

* One last try for PGI

* Does reverting this fix PyPy

* Reviewer suggestions

* Remove unnecessary initialization

* Add noexcept move and explicit fail throw

* Optimize error_string creation

* Fix typo

* Revert noexcept

* Fix merge conflict error

* Abuse assignment operator

* Revert operator abuse

* See if we still need debug

* Remove unnecessary mutable

* Report "FATAL failure building pybind11::error_already_set error_string" and terminate process.

* Try specifying noexcept again

* Try explicit ctor

* default ctor is noexcept too

* Apply reviewer suggestions, simplify code, and make helper method private

* Remove unnecessary include

* Clang-Tidy fix

* detail::obj_class_name(), fprintf with [STDERR], [STDOUT] tags, polish comments

* consistently check m_lazy_what.empty() also in production builds

* Make a comment slightly less ambiguous.

* Bug fix: Remove `what();` from `restore()`.

It sure would need to be guarded by `if (m_type)`, otherwise `what()` fails and masks that no error was set (see update unit test). But since `error_already_set` is copyable, there is no point in releasing m_type, m_value, m_trace, therefore we can just as well avoid the runtime overhead of force-building `m_lazy_what`, it may never be used.

* Replace extremely opaque (unhelpful) error message with a truthful reflection of what we know.

* Fix clang-tidy error [performance-move-constructor-init].

* Make expected error message less specific.

* Various changes.

* bug fix: error_string(PyObject **, ...)

* Putting back the two eager PyErr_NormalizeException() calls.

* Change error_already_set() to call pybind11_fail() if the Python error indicator not set. The net result is that a std::runtime_error is thrown instead of error_already_set, but all tests pass as is.

* Remove mutable (fixes oversight in the previous commit).

* Normalize the exception only locally in error_string(). Python 3.6 & 3.7 test failures expected. This is meant for benchmarking, to determine if it is worth the trouble looking into the failures.

* clang-tidy: use auto

* Use `gil_scoped_acquire_local` in `error_already_set` destructor. See long comment.

* For Python < 3.8: `PyErr_NormalizeException` before `PyErr_WriteUnraisable`

* Go back to replacing the held Python exception with then normalized exception, if & when needed. Consistently document the side-effect.

* Slightly rewording comment. (There were also other failures.)

* Add 1-line comment for obj_class_name()

* Benchmark code, with results in this commit message.

          function                   #calls  test time [s]  μs / call
master    pure_unwind                729540      1.061      14.539876
          err_set_unwind_err_clear   681476      1.040      15.260282
          err_set_error_already_set  508038      1.049      20.640525
          error_already_set_restore  555578      1.052      18.933288
          pr1895_original_foo        244113      1.050      43.018168
                                                                       PR / master
PR #1895  pure_unwind                736981      1.054      14.295685       98.32%
          err_set_unwind_err_clear   685820      1.045      15.237399       99.85%
          err_set_error_already_set  661374      1.046      15.811879       76.61%
          error_already_set_restore  669881      1.048      15.645176       82.63%
          pr1895_original_foo        318243      1.059      33.290806       77.39%

master @ commit ad146b2a1877e8ba3803f94a7837969835a297a7

Running tests in directory "/usr/local/google/home/rwgk/forked/pybind11/tests":
============================= test session starts ==============================
platform linux -- Python 3.9.10, pytest-6.2.3, py-1.10.0, pluggy-0.13.1 -- /usr/bin/python3
cachedir: .pytest_cache
rootdir: /usr/local/google/home/rwgk/forked/pybind11/tests, configfile: pytest.ini
collecting ... collected 5 items

test_perf_error_already_set.py::test_perf[pure_unwind]
PERF pure_unwind,729540,1.061,14.539876
PASSED
test_perf_error_already_set.py::test_perf[err_set_unwind_err_clear]
PERF err_set_unwind_err_clear,681476,1.040,15.260282
PASSED
test_perf_error_already_set.py::test_perf[err_set_error_already_set]
PERF err_set_error_already_set,508038,1.049,20.640525
PASSED
test_perf_error_already_set.py::test_perf[error_already_set_restore]
PERF error_already_set_restore,555578,1.052,18.933288
PASSED
test_perf_error_already_set.py::test_perf[pr1895_original_foo]
PERF pr1895_original_foo,244113,1.050,43.018168
PASSED

============================== 5 passed in 12.38s ==============================

pr1895 @ commit 8dff51d12e4af11aff415ee966070368fe606664

Running tests in directory "/usr/local/google/home/rwgk/forked/pybind11/tests":
============================= test session starts ==============================
platform linux -- Python 3.9.10, pytest-6.2.3, py-1.10.0, pluggy-0.13.1 -- /usr/bin/python3
cachedir: .pytest_cache
rootdir: /usr/local/google/home/rwgk/forked/pybind11/tests, configfile: pytest.ini
collecting ... collected 5 items

test_perf_error_already_set.py::test_perf[pure_unwind]
PERF pure_unwind,736981,1.054,14.295685
PASSED
test_perf_error_already_set.py::test_perf[err_set_unwind_err_clear]
PERF err_set_unwind_err_clear,685820,1.045,15.237399
PASSED
test_perf_error_already_set.py::test_perf[err_set_error_already_set]
PERF err_set_error_already_set,661374,1.046,15.811879
PASSED
test_perf_error_already_set.py::test_perf[error_already_set_restore]
PERF error_already_set_restore,669881,1.048,15.645176
PASSED
test_perf_error_already_set.py::test_perf[pr1895_original_foo]
PERF pr1895_original_foo,318243,1.059,33.290806
PASSED

============================== 5 passed in 12.40s ==============================

clang++ -o pybind11/tests/test_perf_error_already_set.os -c -std=c++17 -fPIC -fvisibility=hidden -Os -flto -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated -Wnon-virtual-dtor -Wunused-result -isystem /usr/include/python3.9 -isystem /usr/include/eigen3 -DPYBIND11_STRICT_ASSERTS_CLASS_HOLDER_VS_TYPE_CASTER_MIX -DPYBIND11_TEST_BOOST -Ipybind11/include -I/usr/local/google/home/rwgk/forked/pybind11/include -I/usr/local/google/home/rwgk/clone/pybind11/include /usr/local/google/home/rwgk/forked/pybind11/tests/test_perf_error_already_set.cpp

clang++ -o lib/pybind11_tests.so -shared -fPIC -Os -flto -shared ...

Debian clang version 13.0.1-3+build2
Target: x86_64-pc-linux-gnu
Thread model: posix

* Changing call_repetitions_target_elapsed_secs to 0.1 for regular unit testing.

* Adding in `recursion_depth`

* Optimized ctor

* Fix silly bug in recurse_first_then_call()

* Add tests that have equivalent PyErr_Fetch(), PyErr_Restore() but no try-catch.

* Add call_error_string to tests. Sample only recursion_depth 0, 100.

* Show lazy-what speed-up in percent.

* Include real_work in benchmarks.

* Replace all PyErr_SetString() with generate_python_exception_with_traceback()

* Better organization of test loops.

* Add test_error_already_set_copy_move

* Fix bug in newly added test (discovered by clang-tidy): actually use move ctor

* MSVC detects the unreachable return

* change test_perf_error_already_set.py back to quick mode

* Inherit from std::exception (instead of std::runtime_error, which does not make sense anymore with the lazy what)

* Special handling under Windows.

* print with leading newline

* Removing test_perf_error_already_set (copies are under https://github.com/rwgk/rwgk_tbx/commit/7765113fbb659e1ea004c5ba24fb578244bc6cfd).

* Avoid gil and scope overhead if there is nothing to release.

* Restore default move ctor. "member function" instead of "function" (note that "method" is Python terminology).

* Delete error_already_set copy ctor.

* Make restore() non-const again to resolve clang-tidy failure (still experimenting).

* Bring back error_already_set copy ctor, to see if that resolves the 4 MSVC test failures.

* Add noexcept to error_already_set copy & move ctors (as suggested by @skylion007 IIUC).

* Trying one-by-one noexcept copy ctor for old compilers.

* Add back test covering copy ctor. Add another simple test that exercises the copy ctor.

* Exclude more older compilers from using the noexcept = default ctors. (The tests in the previous commit exposed that those are broken.)

* Factor out & reuse gil_scoped_acquire_local as gil_scoped_acquire_simple

* Guard gil_scoped_acquire_simple by _Py_IsFinalizing() check.

* what() GIL safety

* clang-tidy & Python 3.6 fixes

* Use `gil_scoped_acquire` in dtor, copy ctor, `what()`. Remove `_Py_IsFinalizing()` checks (they are racy: https://github.com/python/cpython/pull/28525).

* Remove error_scope from copy ctor.

* Add `error_scope` to `get_internals()`, to cover the situation that `get_internals()` is called from the `error_already_set` dtor while a new Python error is in flight already. Also backing out `gil_scoped_acquire_simple` change.

* Add `FlakyException` tests with failure triggers in `__init__` and `__str__`

THIS IS STILL A WORK IN PROGRESS. This commit is only an important resting point.

This commit is a first attempt at addressing the observation that `PyErr_NormalizeException()` completely replaces the original exception if `__init__` fails. This can be very confusing even in small applications, and extremely confusing in large ones.

* Tweaks to resolve Py 3.6 and PyPy CI failures.

* Normalize Python exception immediately in error_already_set ctor.

For background see: https://github.com/pybind/pybind11/pull/1895#issuecomment-1135304081

* Fix oversights based on CI failures (copy & move ctor initialization).

* Move @pytest.mark.xfail("env.PYPY") after @pytest.mark.parametrize(...)

* Use @pytest.mark.skipif (xfail does not work for segfaults, of course).

* Remove unused obj_class_name_or() function (it was added only under this PR).

* Remove already obsolete C++ comments and code that were added only under this PR.

* Slightly better (newly added) comments.

* Factor out detail::error_fetch_and_normalize. Preparation for producing identical results from error_already_set::what() and detail::error_string(). Note that this is a very conservative refactoring. It would be much better to first move detail::error_string into detail/error_string.h

* Copy most of error_string() code to new error_fetch_and_normalize::complete_lazy_error_string()

* Remove all error_string() code from detail/type_caster_base.h. Note that this commit includes a subtle bug fix: previously error_string() restored the Python error, which will upset pybind11_fail(). This never was a problem in practice because the two PyType_Ready() calls in detail/class.h do not usually fail.

* Return const std::string& instead of const char * and move error_string() to pytypes.h

* Remove gil_scope_acquire from error_fetch_and_normalize, add back to error_already_set

* Better handling of FlakyException __str__ failure.

* Move error_fetch_and_normalize::complete_lazy_error_string() implementation from pybind11.h to pytypes.h

* Add error_fetch_and_normalize::release_py_object_references() and use from error_already_set dtor.

* Use shared_ptr for m_fetched_error => 1. non-racy, copy ctor that does not need the GIL; 2. enables guard against duplicate restore() calls.

* Add comments.

* Trivial renaming of a newly introduced member function.

* Workaround for PyPy

* Bug fix (oversight). Only valgrind got this one.

* Use shared_ptr custom deleter for m_fetched_error in error_already_set. This enables removing the dtor, copy ctor, move ctor completely.

* Further small simplification. With the GIL held, simply deleting the raw_ptr takes care of everything.

* IWYU cleanup

```
iwyu version: include-what-you-use 0.17 based on Debian clang version 13.0.1-3+build2
```

Command used:

```
iwyu -c -std=c++17 -DPYBIND11_TEST_BOOST -Iinclude/pybind11 -I/usr/include/python3.9 -I/usr/include/eigen3 include/pybind11/pytypes.cpp
```

pytypes.cpp is a temporary file: `#include "pytypes.h"`

The raw output is very long and noisy.

I decided to use `#include <cstddef>` instead of `#include <cstdio>` for `std::size_t` (iwyu sticks to the manual choice).

I ignored all iwyu suggestions that are indirectly covered by `#include <Python.h>`.

I manually verified that all added includes are actually needed.

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/detail/class.h            |   6 +-
 include/pybind11/detail/type_caster_base.h |  67 ------
 include/pybind11/pybind11.h                |  20 +-
 include/pybind11/pytypes.h                 | 232 ++++++++++++++++++---
 tests/test_exceptions.cpp                  |  19 +-
 tests/test_exceptions.py                   |  48 ++++-
 6 files changed, 272 insertions(+), 120 deletions(-)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index e52ec1d3e6..1ddf1393bb 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -455,6 +455,8 @@ extern "C" inline void pybind11_object_dealloc(PyObject *self) {
 #endif
 }
 
+std::string error_string();
+
 /** Create the type which can be used as a common base for all classes.  This is
     needed in order to satisfy Python's requirements for multiple inheritance.
     Return value: New reference. */
@@ -490,7 +492,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
     type->tp_weaklistoffset = offsetof(instance, weakrefs);
 
     if (PyType_Ready(type) < 0) {
-        pybind11_fail("PyType_Ready failed in make_object_base_type():" + error_string());
+        pybind11_fail("PyType_Ready failed in make_object_base_type(): " + error_string());
     }
 
     setattr((PyObject *) type, "__module__", str("pybind11_builtins"));
@@ -707,7 +709,7 @@ inline PyObject *make_new_python_type(const type_record &rec) {
     }
 
     if (PyType_Ready(type) < 0) {
-        pybind11_fail(std::string(rec.name) + ": PyType_Ready failed (" + error_string() + ")!");
+        pybind11_fail(std::string(rec.name) + ": PyType_Ready failed: " + error_string());
     }
 
     assert(!rec.dynamic_attr || PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC));
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index dd8d03751e..21f69c289f 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -470,73 +470,6 @@ PYBIND11_NOINLINE bool isinstance_generic(handle obj, const std::type_info &tp)
     return isinstance(obj, type);
 }
 
-PYBIND11_NOINLINE std::string error_string(const char *called) {
-    error_scope scope; // Fetch error state (will be restored when this function returns).
-    if (scope.type == nullptr) {
-        if (called == nullptr) {
-            called = "pybind11::detail::error_string()";
-        }
-        pybind11_fail("Internal error: " + std::string(called)
-                      + " called while Python error indicator not set.");
-    }
-
-    PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
-    if (scope.trace != nullptr) {
-        PyException_SetTraceback(scope.value, scope.trace);
-    }
-
-    std::string errorString;
-    if (scope.type) {
-        errorString += handle(scope.type).attr("__name__").cast<std::string>();
-        errorString += ": ";
-    }
-    if (scope.value) {
-        errorString += (std::string) str(scope.value);
-    }
-
-#if !defined(PYPY_VERSION)
-    if (scope.trace) {
-        auto *trace = (PyTracebackObject *) scope.trace;
-
-        /* Get the deepest trace possible */
-        while (trace->tb_next) {
-            trace = trace->tb_next;
-        }
-
-        PyFrameObject *frame = trace->tb_frame;
-        Py_XINCREF(frame);
-        errorString += "\n\nAt:\n";
-        while (frame) {
-#    if PY_VERSION_HEX >= 0x030900B1
-            PyCodeObject *f_code = PyFrame_GetCode(frame);
-#    else
-            PyCodeObject *f_code = frame->f_code;
-            Py_INCREF(f_code);
-#    endif
-            int lineno = PyFrame_GetLineNumber(frame);
-            errorString += "  ";
-            errorString += handle(f_code->co_filename).cast<std::string>();
-            errorString += '(';
-            errorString += std::to_string(lineno);
-            errorString += "): ";
-            errorString += handle(f_code->co_name).cast<std::string>();
-            errorString += '\n';
-            Py_DECREF(f_code);
-#    if PY_VERSION_HEX >= 0x030900B1
-            auto *b_frame = PyFrame_GetBack(frame);
-#    else
-            auto *b_frame = frame->f_back;
-            Py_XINCREF(b_frame);
-#    endif
-            Py_DECREF(frame);
-            frame = b_frame;
-        }
-    }
-#endif
-
-    return errorString;
-}
-
 PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_info *type) {
     auto &instances = get_internals().registered_instances;
     auto range = instances.equal_range(ptr);
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index cfa4420679..d61dcd5c7e 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2625,17 +2625,21 @@ void print(Args &&...args) {
     detail::print(c.args(), c.kwargs());
 }
 
-error_already_set::~error_already_set() {
-    if (m_type) {
-        gil_scoped_acquire gil;
-        error_scope scope;
-        m_type.release().dec_ref();
-        m_value.release().dec_ref();
-        m_trace.release().dec_ref();
-    }
+inline void
+error_already_set::m_fetched_error_deleter(detail::error_fetch_and_normalize *raw_ptr) {
+    gil_scoped_acquire gil;
+    error_scope scope;
+    delete raw_ptr;
+}
+
+inline const char *error_already_set::what() const noexcept {
+    gil_scoped_acquire gil;
+    error_scope scope;
+    return m_fetched_error->error_string().c_str();
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
+
 inline function
 get_type_override(const void *this_ptr, const type_info *this_type, const char *name) {
     handle self = get_object_handle(this_ptr, this_type);
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 27807953b7..f9625e77ea 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -12,7 +12,15 @@
 #include "detail/common.h"
 #include "buffer_info.h"
 
+#include <assert.h>
+#include <cstddef>
+#include <exception>
+#include <frameobject.h>
+#include <iterator>
+#include <memory>
+#include <string>
 #include <type_traits>
+#include <typeinfo>
 #include <utility>
 
 #if defined(PYBIND11_HAS_OPTIONAL)
@@ -383,7 +391,175 @@ T reinterpret_steal(handle h) {
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-std::string error_string(const char *called = nullptr);
+
+// Equivalent to obj.__class__.__name__ (or obj.__name__ if obj is a class).
+inline const char *obj_class_name(PyObject *obj) {
+    if (Py_TYPE(obj) == &PyType_Type) {
+        return reinterpret_cast<PyTypeObject *>(obj)->tp_name;
+    }
+    return Py_TYPE(obj)->tp_name;
+}
+
+std::string error_string();
+
+struct error_fetch_and_normalize {
+    // Immediate normalization is long-established behavior (starting with
+    // https://github.com/pybind/pybind11/commit/135ba8deafb8bf64a15b24d1513899eb600e2011
+    // from Sep 2016) and safest. Normalization could be deferred, but this could mask
+    // errors elsewhere, the performance gain is very minor in typical situations
+    // (usually the dominant bottleneck is EH unwinding), and the implementation here
+    // would be more complex.
+    explicit error_fetch_and_normalize(const char *called) {
+        PyErr_Fetch(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
+        if (!m_type) {
+            pybind11_fail("Internal error: " + std::string(called)
+                          + " called while "
+                            "Python error indicator not set.");
+        }
+        const char *exc_type_name_orig = detail::obj_class_name(m_type.ptr());
+        if (exc_type_name_orig == nullptr) {
+            pybind11_fail("Internal error: " + std::string(called)
+                          + " failed to obtain the name "
+                            "of the original active exception type.");
+        }
+        m_lazy_error_string = exc_type_name_orig;
+        // PyErr_NormalizeException() may change the exception type if there are cascading
+        // failures. This can potentially be extremely confusing.
+        PyErr_NormalizeException(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
+        if (m_type.ptr() == nullptr) {
+            pybind11_fail("Internal error: " + std::string(called)
+                          + " failed to normalize the "
+                            "active exception.");
+        }
+        const char *exc_type_name_norm = detail::obj_class_name(m_type.ptr());
+        if (exc_type_name_orig == nullptr) {
+            pybind11_fail("Internal error: " + std::string(called)
+                          + " failed to obtain the name "
+                            "of the normalized active exception type.");
+        }
+        if (exc_type_name_norm != m_lazy_error_string) {
+            std::string msg = std::string(called)
+                              + ": MISMATCH of original and normalized "
+                                "active exception types: ";
+            msg += "ORIGINAL ";
+            msg += m_lazy_error_string;
+            msg += " REPLACED BY ";
+            msg += exc_type_name_norm;
+            msg += ": " + format_value_and_trace();
+            pybind11_fail(msg);
+        }
+    }
+
+    error_fetch_and_normalize(const error_fetch_and_normalize &) = delete;
+    error_fetch_and_normalize(error_fetch_and_normalize &&) = delete;
+
+    std::string format_value_and_trace() const {
+        std::string result;
+        std::string message_error_string;
+        if (m_value) {
+            auto value_str = reinterpret_steal<object>(PyObject_Str(m_value.ptr()));
+            if (!value_str) {
+                message_error_string = detail::error_string();
+                result = "<MESSAGE UNAVAILABLE DUE TO ANOTHER EXCEPTION>";
+            } else {
+                result = value_str.cast<std::string>();
+            }
+        } else {
+            result = "<MESSAGE UNAVAILABLE>";
+        }
+        if (result.empty()) {
+            result = "<EMPTY MESSAGE>";
+        }
+
+        bool have_trace = false;
+        if (m_trace) {
+#if !defined(PYPY_VERSION)
+            auto *tb = reinterpret_cast<PyTracebackObject *>(m_trace.ptr());
+
+            // Get the deepest trace possible.
+            while (tb->tb_next) {
+                tb = tb->tb_next;
+            }
+
+            PyFrameObject *frame = tb->tb_frame;
+            Py_XINCREF(frame);
+            result += "\n\nAt:\n";
+            while (frame) {
+#    if PY_VERSION_HEX >= 0x030900B1
+                PyCodeObject *f_code = PyFrame_GetCode(frame);
+#    else
+                PyCodeObject *f_code = frame->f_code;
+                Py_INCREF(f_code);
+#    endif
+                int lineno = PyFrame_GetLineNumber(frame);
+                result += "  ";
+                result += handle(f_code->co_filename).cast<std::string>();
+                result += '(';
+                result += std::to_string(lineno);
+                result += "): ";
+                result += handle(f_code->co_name).cast<std::string>();
+                result += '\n';
+                Py_DECREF(f_code);
+#    if PY_VERSION_HEX >= 0x030900B1
+                auto *b_frame = PyFrame_GetBack(frame);
+#    else
+                auto *b_frame = frame->f_back;
+                Py_XINCREF(b_frame);
+#    endif
+                Py_DECREF(frame);
+                frame = b_frame;
+            }
+
+            have_trace = true;
+#endif //! defined(PYPY_VERSION)
+        }
+
+        if (!message_error_string.empty()) {
+            if (!have_trace) {
+                result += '\n';
+            }
+            result += "\nMESSAGE UNAVAILABLE DUE TO EXCEPTION: " + message_error_string;
+        }
+
+        return result;
+    }
+
+    std::string const &error_string() const {
+        if (!m_lazy_error_string_completed) {
+            m_lazy_error_string += ": " + format_value_and_trace();
+            m_lazy_error_string_completed = true;
+        }
+        return m_lazy_error_string;
+    }
+
+    void restore() {
+        if (m_restore_called) {
+            pybind11_fail("Internal error: pybind11::detail::error_fetch_and_normalize::restore() "
+                          "called a second time. ORIGINAL ERROR: "
+                          + error_string());
+        }
+        PyErr_Restore(m_type.inc_ref().ptr(), m_value.inc_ref().ptr(), m_trace.inc_ref().ptr());
+        m_restore_called = true;
+    }
+
+    bool matches(handle exc) const {
+        return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
+    }
+
+    // Not protecting these for simplicity.
+    object m_type, m_value, m_trace;
+
+private:
+    // Only protecting invariants.
+    mutable std::string m_lazy_error_string;
+    mutable bool m_lazy_error_string_completed = false;
+    mutable bool m_restore_called = false;
+};
+
+inline std::string error_string() {
+    return error_fetch_and_normalize("pybind11::detail::error_string").error_string();
+}
+
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
@@ -396,39 +572,30 @@ PYBIND11_NAMESPACE_END(detail)
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
 /// else falls back to the function dispatcher (which then raises the captured error back to
 /// python).
-class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
+class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::exception {
 public:
-    /// Constructs a new exception from the current Python error indicator.  The current
-    /// Python error indicator will be cleared.
-    error_already_set() : std::runtime_error(detail::error_string("pybind11::error_already_set")) {
-        PyErr_Fetch(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
-    }
-
-    /// WARNING: The GIL must be held when this copy constructor is invoked!
-    error_already_set(const error_already_set &) = default;
-    error_already_set(error_already_set &&) = default;
-
-    /// WARNING: This destructor needs to acquire the Python GIL. This can lead to
+    /// Fetches the current Python exception (using PyErr_Fetch()), which will clear the
+    /// current Python error indicator.
+    error_already_set()
+        : m_fetched_error{new detail::error_fetch_and_normalize("pybind11::error_already_set"),
+                          m_fetched_error_deleter} {}
+
+    /// The what() result is built lazily on demand.
+    /// WARNING: This member function needs to acquire the Python GIL. This can lead to
     ///          crashes (undefined behavior) if the Python interpreter is finalizing.
-    inline ~error_already_set() override;
+    const char *what() const noexcept override;
 
     /// Restores the currently-held Python error (which will clear the Python error indicator first
-    /// if already set). After this call, the current object no longer stores the error variables.
-    /// NOTE: Any copies of this object may still store the error variables. Currently there is no
-    //        protection against calling restore() from multiple copies.
+    /// if already set).
     /// NOTE: This member function will always restore the normalized exception, which may or may
     ///       not be the original Python exception.
     /// WARNING: The GIL must be held when this member function is called!
-    void restore() {
-        PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr());
-    }
+    void restore() { m_fetched_error->restore(); }
 
     /// If it is impossible to raise the currently-held error, such as in a destructor, we can
     /// write it out using Python's unraisable hook (`sys.unraisablehook`). The error context
     /// should be some object whose `repr()` helps identify the location of the error. Python
-    /// already knows the type and value of the error, so there is no need to repeat that. After
-    /// this call, the current object no longer stores the error variables, and neither does
-    /// Python.
+    /// already knows the type and value of the error, so there is no need to repeat that.
     void discard_as_unraisable(object err_context) {
         restore();
         PyErr_WriteUnraisable(err_context.ptr());
@@ -447,16 +614,18 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
     /// Check if the currently trapped error type matches the given Python exception class (or a
     /// subclass thereof).  May also be passed a tuple to search for any exception class matches in
     /// the given tuple.
-    bool matches(handle exc) const {
-        return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
-    }
+    bool matches(handle exc) const { return m_fetched_error->matches(exc); }
 
-    const object &type() const { return m_type; }
-    const object &value() const { return m_value; }
-    const object &trace() const { return m_trace; }
+    const object &type() const { return m_fetched_error->m_type; }
+    const object &value() const { return m_fetched_error->m_value; }
+    const object &trace() const { return m_fetched_error->m_trace; }
 
 private:
-    object m_type, m_value, m_trace;
+    std::shared_ptr<detail::error_fetch_and_normalize> m_fetched_error;
+
+    /// WARNING: This custom deleter needs to acquire the Python GIL. This can lead to
+    ///          crashes (undefined behavior) if the Python interpreter is finalizing.
+    static void m_fetched_error_deleter(detail::error_fetch_and_normalize *raw_ptr);
 };
 #if defined(_MSC_VER)
 #    pragma warning(pop)
@@ -492,8 +661,7 @@ inline void raise_from(PyObject *type, const char *message) {
 
 /// Sets the current Python error indicator with the chosen error, performing a 'raise from'
 /// from the error contained in error_already_set to indicate that the chosen error was
-/// caused by the original error. After this function is called error_already_set will
-/// no longer contain an error.
+/// caused by the original error.
 inline void raise_from(error_already_set &err, PyObject *type, const char *message) {
     err.restore();
     raise_from(type, message);
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 9469b86724..3ec999d1dc 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -105,6 +105,11 @@ struct PythonAlreadySetInDestructor {
     py::str s;
 };
 
+std::string error_already_set_what(const py::object &exc_type, const py::object &exc_value) {
+    PyErr_SetObject(exc_type.ptr(), exc_value.ptr());
+    return py::error_already_set().what();
+}
+
 TEST_SUBMODULE(exceptions, m) {
     m.def("throw_std_exception",
           []() { throw std::runtime_error("This exception was intentionally thrown."); });
@@ -269,7 +274,9 @@ TEST_SUBMODULE(exceptions, m) {
                   if (ex.matches(exc_type)) {
                       py::print(ex.what());
                   } else {
-                      throw;
+                      // Simply `throw;` also works and is better, but using `throw ex;`
+                      // here to cover that situation (as observed in the wild).
+                      throw ex; // Invokes the copy ctor.
                   }
               }
           });
@@ -317,4 +324,14 @@ TEST_SUBMODULE(exceptions, m) {
             = reinterpret_cast<void (*)()>(PyLong_AsVoidPtr(cm.attr("funcaddr").ptr()));
         interleaved_error_already_set();
     });
+
+    m.def("test_error_already_set_double_restore", [](bool dry_run) {
+        PyErr_SetString(PyExc_ValueError, "Random error.");
+        py::error_already_set e;
+        e.restore();
+        PyErr_Clear();
+        if (!dry_run) {
+            e.restore();
+        }
+    });
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 4dcbb83a36..a5984a142f 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -305,13 +305,16 @@ def test_error_already_set_what_with_happy_exceptions(
 
 @pytest.mark.skipif("env.PYPY", reason="PyErr_NormalizeException Segmentation fault")
 def test_flaky_exception_failure_point_init():
-    what, py_err_set_after_what = m.error_already_set_what(
-        FlakyException, ("failure_point_init",)
-    )
-    assert not py_err_set_after_what
-    lines = what.splitlines()
+    with pytest.raises(RuntimeError) as excinfo:
+        m.error_already_set_what(FlakyException, ("failure_point_init",))
+    lines = str(excinfo.value).splitlines()
     # PyErr_NormalizeException replaces the original FlakyException with ValueError:
-    assert lines[:3] == ["ValueError: triggered_failure_point_init", "", "At:"]
+    assert lines[:3] == [
+        "pybind11::error_already_set: MISMATCH of original and normalized active exception types:"
+        " ORIGINAL FlakyException REPLACED BY ValueError: triggered_failure_point_init",
+        "",
+        "At:",
+    ]
     # Checking the first two lines of the traceback as formatted in error_string():
     assert "test_exceptions.py(" in lines[3]
     assert lines[3].endswith("): __init__")
@@ -319,10 +322,25 @@ def test_flaky_exception_failure_point_init():
 
 
 def test_flaky_exception_failure_point_str():
-    # The error_already_set ctor fails due to a ValueError in error_string():
-    with pytest.raises(ValueError) as excinfo:
-        m.error_already_set_what(FlakyException, ("failure_point_str",))
-    assert str(excinfo.value) == "triggered_failure_point_str"
+    what, py_err_set_after_what = m.error_already_set_what(
+        FlakyException, ("failure_point_str",)
+    )
+    assert not py_err_set_after_what
+    lines = what.splitlines()
+    if env.PYPY and len(lines) == 3:
+        n = 3  # Traceback is missing.
+    else:
+        n = 5
+    assert (
+        lines[:n]
+        == [
+            "FlakyException: <MESSAGE UNAVAILABLE DUE TO ANOTHER EXCEPTION>",
+            "",
+            "MESSAGE UNAVAILABLE DUE TO EXCEPTION: ValueError: triggered_failure_point_str",
+            "",
+            "At:",
+        ][:n]
+    )
 
 
 def test_cross_module_interleaved_error_already_set():
@@ -332,3 +350,13 @@ def test_cross_module_interleaved_error_already_set():
         "2nd error.",  # Almost all platforms.
         "RuntimeError: 2nd error.",  # Some PyPy builds (seen under macOS).
     )
+
+
+def test_error_already_set_double_restore():
+    m.test_error_already_set_double_restore(True)  # dry_run
+    with pytest.raises(RuntimeError) as excinfo:
+        m.test_error_already_set_double_restore(False)
+    assert str(excinfo.value) == (
+        "Internal error: pybind11::detail::error_fetch_and_normalize::restore()"
+        " called a second time. ORIGINAL ERROR: ValueError: Random error."
+    )

From 42a41bf3e70b5aa87945813f7bb722c2c75c14a8 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 3 Jun 2022 15:18:06 -0400
Subject: [PATCH 400/638] remove useless ctor (#3989)

---
 include/pybind11/functional.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index f2a752e9d6..4034990d89 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -99,7 +99,7 @@ struct type_caster<std::function<Return(Args...)>> {
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
                 // casts the returned object as a rvalue to the return type
-                return object(hfunc.f(std::forward<Args>(args)...)).template cast<Return>();
+                return hfunc.f(std::forward<Args>(args)...).template cast<Return>();
             }
         };
 

From 554c0453776db915d09f679bd11201d8eb07e147 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 6 Jun 2022 12:15:45 -0400
Subject: [PATCH 401/638] enable two new clang-tidy checks (#3988)

* enable two new clang-tidy checks

* Use better loop var for char
---
 .clang-tidy                            | 4 ++++
 tests/test_constants_and_functions.cpp | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index e82443c4ca..ddee835c15 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -10,6 +10,7 @@ cppcoreguidelines-pro-type-static-cast-downcast,
 cppcoreguidelines-slicing,
 google-explicit-constructor,
 llvm-namespace-comment,
+misc-definitions-in-headers,
 misc-misplaced-const,
 misc-non-copyable-objects,
 misc-static-assert,
@@ -17,6 +18,7 @@ misc-throw-by-value-catch-by-reference,
 misc-uniqueptr-reset-release,
 misc-unused-parameters,
 modernize-avoid-bind,
+modernize-loop-convert,
 modernize-make-shared,
 modernize-redundant-void-arg,
 modernize-replace-auto-ptr,
@@ -63,6 +65,8 @@ readability-uniqueptr-delete-release,
 CheckOptions:
 - key:             performance-for-range-copy.WarnOnAllAutoCopies
   value:           true
+- key:             performance-inefficient-string-concatenation.StrictMode
+  value:           true
 - key:             performance-unnecessary-value-param.AllowedTypes
   value:           'exception_ptr$;'
 - key:             readability-implicit-bool-conversion.AllowPointerConditions
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 873fa1f551..1918a429c8 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -31,8 +31,8 @@ py::bytes return_bytes() {
 std::string print_bytes(const py::bytes &bytes) {
     std::string ret = "bytes[";
     const auto value = static_cast<std::string>(bytes);
-    for (size_t i = 0; i < value.length(); ++i) {
-        ret += std::to_string(static_cast<int>(value[i])) + " ";
+    for (char c : value) {
+        ret += std::to_string(static_cast<int>(c)) + ' ';
     }
     ret.back() = ']';
     return ret;

From c5fa3436c66ddc8e4a14b79e7c40f16182409d6e Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 6 Jun 2022 17:56:18 -0400
Subject: [PATCH 402/638] [pre-commit.ci] pre-commit autoupdate (#3951)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.32.1 → v2.33.0](https://github.com/asottile/pyupgrade/compare/v2.32.1...v2.33.0)
- [github.com/Lucas-C/pre-commit-hooks: v1.1.13 → v1.2.0](https://github.com/Lucas-C/pre-commit-hooks/compare/v1.1.13...v1.2.0)
- [github.com/hadialqattan/pycln: v1.3.2 → v1.3.3](https://github.com/hadialqattan/pycln/compare/v1.3.2...v1.3.3)
- [github.com/PyCQA/pylint: v2.13.8 → v2.14.1](https://github.com/PyCQA/pylint/compare/v2.13.8...v2.14.1)
- [github.com/pre-commit/mirrors-mypy: v0.950 → v0.960](https://github.com/pre-commit/mirrors-mypy/compare/v0.950...v0.960)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 03f829c251..e71944875b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.32.1"
+  rev: "v2.33.0"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -59,7 +59,7 @@ repos:
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.1.13"
+  rev: "v1.2.0"
   hooks:
   - id: remove-tabs
 
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.3.2"
+  rev: "v1.3.3"
   hooks:
   - id: pycln
     stages: [manual]
@@ -107,7 +107,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.13.8"
+  rev: "v2.14.1"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -123,7 +123,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.950"
+  rev: "v0.960"
   hooks:
   - id: mypy
     args: []

From 918892b97e21a4feca42cd5501c98c5b3aa8bb3f Mon Sep 17 00:00:00 2001
From: Maarten Baert <maarten-baert@hotmail.com>
Date: Tue, 7 Jun 2022 01:41:38 +0200
Subject: [PATCH 403/638] Make dtype::num() return type consistent with other
 functions (#3995)

---
 include/pybind11/numpy.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index b8ba2259ff..0c77a98ddf 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -604,7 +604,7 @@ class dtype : public object {
     }
 
     /// type number of dtype.
-    ssize_t num() const {
+    int num() const {
         // Note: The signature, `dtype::num` follows the naming of NumPy's public
         // Python API (i.e., ``dtype.num``), rather than its internal
         // C API (``PyArray_Descr::type_num``).

From e2dcd95407d5202019cecd2bb2827ee6a4a8f9f3 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 6 Jun 2022 22:33:28 -0400
Subject: [PATCH 404/638] chore: optimize dictionary access in strip_padding
 numpy (#3994)

* emplace field descriptors

* reserve sufficient capacity

* remove std::move

* properly iterate through dict

* make handle casting more explicit

* Revert to old dict api
---
 include/pybind11/numpy.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 0c77a98ddf..43784f8e9e 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -641,10 +641,14 @@ class dtype : public object {
             pybind11::str name;
             object format;
             pybind11::int_ offset;
+            field_descr(pybind11::str &&name, object &&format, pybind11::int_ &&offset)
+                : name{std::move(name)}, format{std::move(format)}, offset{std::move(offset)} {};
         };
+        auto field_dict = attr("fields").cast<dict>();
         std::vector<field_descr> field_descriptors;
+        field_descriptors.reserve(field_dict.size());
 
-        for (auto field : attr("fields").attr("items")()) {
+        for (auto field : field_dict.attr("items")()) {
             auto spec = field.cast<tuple>();
             auto name = spec[0].cast<pybind11::str>();
             auto spec_fo = spec[1].cast<tuple>();
@@ -653,8 +657,8 @@ class dtype : public object {
             if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
             }
-            field_descriptors.push_back(
-                {(pybind11::str) name, format.strip_padding(format.itemsize()), offset});
+            field_descriptors.emplace_back(
+                std::move(name), format.strip_padding(format.itemsize()), std::move(offset));
         }
 
         std::sort(field_descriptors.begin(),

From 0e956a2e4f7838fc26f42a6399bc358ae7248134 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 8 Jun 2022 09:22:57 -0400
Subject: [PATCH 405/638] chore(deps): bump pre-commit/action from 2.0.3 to
 3.0.0 (#3992)

Bumps [pre-commit/action](https://github.com/pre-commit/action) from 2.0.3 to 3.0.0.
- [Release notes](https://github.com/pre-commit/action/releases)
- [Commits](https://github.com/pre-commit/action/compare/v2.0.3...v3.0.0)

---
updated-dependencies:
- dependency-name: pre-commit/action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/format.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 5eb228a707..70e3ddfa4b 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -24,7 +24,7 @@ jobs:
     - uses: actions/setup-python@v3
     - name: Add matchers
       run: echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
-    - uses: pre-commit/action@v2.0.3
+    - uses: pre-commit/action@v3.0.0
       with:
         # Slow hooks are marked with manual - slow is okay here, run them too
         extra_args: --hook-stage manual --all-files

From 21f0e72b0f29cc3b631b888447454b9a21642c22 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 13 Jun 2022 21:02:25 -0400
Subject: [PATCH 406/638] [pre-commit.ci] pre-commit autoupdate (#4003)

---
 .pre-commit-config.yaml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e71944875b..3b4c90656e 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,7 +15,7 @@
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: "v4.2.0"
+  rev: "v4.3.0"
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.33.0"
+  rev: "v2.34.0"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -123,7 +123,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.960"
+  rev: "v0.961"
   hooks:
   - id: mypy
     args: []
@@ -164,7 +164,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v14.0.3"
+  rev: "v14.0.4-1"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From 0964a9093a728dbf67b9b98c6371752b1a346f25 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Tue, 14 Jun 2022 14:20:26 -0400
Subject: [PATCH 407/638] Add a missing std::move in numpy.h (#4005)

---
 include/pybind11/numpy.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 43784f8e9e..0291b02d0b 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1409,7 +1409,7 @@ PYBIND11_NOINLINE void register_structured_dtype(any_container<field_descriptor>
     }
 
     auto tindex = std::type_index(tinfo);
-    numpy_internals.registered_dtypes[tindex] = {dtype_ptr, format_str};
+    numpy_internals.registered_dtypes[tindex] = {dtype_ptr, std::move(format_str)};
     get_internals().direct_conversions[tindex].push_back(direct_converter);
 }
 

From 2ad974c9455c2ed46c3704df11852cf0a5462b22 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 21 Jun 2022 14:36:49 -0400
Subject: [PATCH 408/638] [pre-commit.ci] pre-commit autoupdate (#4021)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/pylint: v2.14.1 → v2.14.3](https://github.com/PyCQA/pylint/compare/v2.14.1...v2.14.3)
- [github.com/pre-commit/mirrors-clang-format: v14.0.4-1 → v14.0.5](https://github.com/pre-commit/mirrors-clang-format/compare/v14.0.4-1...v14.0.5)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3b4c90656e..fc91dfe541 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -107,7 +107,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.14.1"
+  rev: "v2.14.3"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -164,7 +164,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v14.0.4-1"
+  rev: "v14.0.5"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From c3e9173f0f6da05a8463db093c4bc85934872c84 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 21 Jun 2022 14:55:49 -0400
Subject: [PATCH 409/638] ci: use almalinux instead of centos, add 9 (#4020)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8b537e6e1e..cb7966839a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -584,19 +584,25 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        centos:
-          - centos7  # GCC 4.8
-          - stream8
+        container:
+          - "centos:7"  # GCC 4.8
+          - "almalinux:8"
+          - "almalinux:9"
 
-    name: "🐍 3 • CentOS ${{ matrix.centos }} • x64"
-    container: "quay.io/centos/centos:${{ matrix.centos }}"
+    name: "🐍 3 • ${{ matrix.container }} • x64"
+    container: "${{ matrix.container }}"
 
     steps:
     - uses: actions/checkout@v3
 
-    - name: Add Python 3
+    - name: Add Python 3 (RHEL 7)
+      if: matrix.container == 'centos:7'
       run: yum update -y && yum install -y python3-devel gcc-c++ make git
 
+    - name: Add Python 3 (RHEL 8+)
+      if: matrix.container != 'centos:7'
+      run: dnf update -y && dnf install -y python3-devel gcc-c++ make git
+
     - name: Update pip
       run: python3 -m pip install --upgrade pip
 

From dd3bf7fd128177b9bf17b397cff64f56190a567b Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 27 Jun 2022 19:39:19 -0400
Subject: [PATCH 410/638] [pre-commit.ci] pre-commit autoupdate (#4030)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/hadialqattan/pycln: v1.3.3 → v1.3.5](https://github.com/hadialqattan/pycln/compare/v1.3.3...v1.3.5)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index fc91dfe541..e4880830fe 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.3.3"
+  rev: "v1.3.5"
   hooks:
   - id: pycln
     stages: [manual]

From 374a5b000af0b334979ce0cffdff46689b9fe27f Mon Sep 17 00:00:00 2001
From: Masaki Kozuki <masaki.kozuki.2014@gmail.com>
Date: Tue, 28 Jun 2022 12:38:37 -0700
Subject: [PATCH 411/638] [docs] Fix "Enumerations and internal types" example
 (#4034)

* Fix binding of `Pet::Attributes`

* omit `attributes` as it's not needed

Signed-off-by: Masaki Kozuki <mkozuki@nvidia.com>
---
 docs/classes.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/classes.rst b/docs/classes.rst
index 0c687b7c53..c0c53135b8 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -482,7 +482,7 @@ The binding code for this example looks as follows:
         .value("Cat", Pet::Kind::Cat)
         .export_values();
 
-    py::class_<Pet::Attributes> attributes(pet, "Attributes")
+    py::class_<Pet::Attributes>(pet, "Attributes")
         .def(py::init<>())
         .def_readwrite("age", &Pet::Attributes::age);
 

From 479e9a50f38cfa8e525a697d7f5d850f851223b5 Mon Sep 17 00:00:00 2001
From: Matthew Woehlke <matthew.woehlke@kitware.com>
Date: Wed, 29 Jun 2022 14:37:16 -0400
Subject: [PATCH 412/638] Fix arrays with zero-size dimensions (#4038)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When converting an array to an Eigen matrix, ignore the strides if any
dimension size is 0. If the array is empty, the strides aren't relevant,
and especially numpy ≥ 1.23 explicitly sets the strides to 0 in this
case. (See numpy commit dd5ab7b11520.)

Update tests to verify that this works, and continues to work.
---
 include/pybind11/eigen.h | 14 ++++++++++----
 tests/test_eigen.cpp     |  7 +++++--
 tests/test_eigen.py      |  7 +++++++
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index f658168ded..71df3eb8bd 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -111,10 +111,16 @@ struct EigenConformable {
     bool stride_compatible() const {
         // To have compatible strides, we need (on both dimensions) one of fully dynamic strides,
         // matching strides, or a dimension size of 1 (in which case the stride value is
-        // irrelevant)
-        return !negativestrides
-               && (props::inner_stride == Eigen::Dynamic || props::inner_stride == stride.inner()
-                   || (EigenRowMajor ? cols : rows) == 1)
+        // irrelevant). Alternatively, if any dimension size is 0, the strides are not relevant
+        // (and numpy ≥ 1.23 sets the strides to 0 in that case, so we need to check explicitly).
+        if (negativestrides) {
+            return false;
+        }
+        if (rows == 0 || cols == 0) {
+            return true;
+        }
+        return (props::inner_stride == Eigen::Dynamic || props::inner_stride == stride.inner()
+                || (EigenRowMajor ? cols : rows) == 1)
                && (props::outer_stride == Eigen::Dynamic || props::outer_stride == stride.outer()
                    || (EigenRowMajor ? rows : cols) == 1);
     }
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index 74e76eb7e0..591dacc624 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -345,10 +345,13 @@ TEST_SUBMODULE(eigen, m) {
         },
         py::arg{}.noconvert());
 
-    // test_issue738
-    // Issue #738: 1xN or Nx1 2D matrices were neither accepted nor properly copied with an
+    // test_issue738, test_zero_length
+    // Issue #738: 1×N or N×1 2D matrices were neither accepted nor properly copied with an
     // incompatible stride value on the length-1 dimension--but that should be allowed (without
     // requiring a copy!) because the stride value can be safely ignored on a size-1 dimension.
+    // Similarly, 0×N or N×0 matrices were not accepted--again, these should be allowed since
+    // they contain no data. This particularly affects numpy ≥ 1.23, which sets the strides to
+    // 0 if any dimension size is 0.
     m.def("iss738_f1",
           &adjust_matrix<const Eigen::Ref<const Eigen::MatrixXd> &>,
           py::arg{}.noconvert());
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index 093773a514..a1c114aede 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -744,6 +744,13 @@ def test_issue738():
     )
 
 
+@pytest.mark.parametrize("func", [m.iss738_f1, m.iss738_f2])
+@pytest.mark.parametrize("sizes", [(0, 2), (2, 0)])
+def test_zero_length(func, sizes):
+    """Ignore strides on a length-0 dimension (even if they would be incompatible length > 1)"""
+    assert np.all(func(np.zeros(sizes)) == np.zeros(sizes))
+
+
 def test_issue1105():
     """Issue 1105: 1xN or Nx1 input arrays weren't accepted for eigen
     compile-time row vectors or column vector"""

From 5a3a1e34152edceb0a23bd53e0ceb77de8c3ea12 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 4 Jul 2022 10:24:34 -0400
Subject: [PATCH 413/638] chore: simpler dependabot (#4035)

Ignores no longer needed after April 2022. Dependabot keeps the same style pinning now.
---
 .github/dependabot.yml | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index d8d1eed8c3..2c7d170839 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -5,7 +5,3 @@ updates:
     directory: "/"
     schedule:
       interval: "daily"
-    ignore:
-      # Official actions have moving tags like v1
-      - dependency-name: "actions/*"
-        update-types: ["version-update:semver-minor", "version-update:semver-patch"]

From bc1f9f9ba63a1fd5928c6d8a97260cb07fcc0e17 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 4 Jul 2022 10:24:55 -0400
Subject: [PATCH 414/638] chore(deps): bump actions/setup-python from 3 to 4
 (#3999)

* chore(deps): bump actions/setup-python from 3 to 4

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 3 to 4.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](https://github.com/actions/setup-python/compare/v3...v4)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* Apply suggestions from code review

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml        | 12 +++++++-----
 .github/workflows/configure.yml |  2 +-
 .github/workflows/format.yml    |  4 +++-
 .github/workflows/pip.yml       |  8 +++++---
 .github/workflows/upstream.yml  |  2 +-
 5 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cb7966839a..9a69438bd8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -65,7 +65,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python }}
 
@@ -686,7 +686,9 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
-    - uses: actions/setup-python@v3
+    - uses: actions/setup-python@v4
+      with:
+        python-version: "3.x"
 
     - name: Install Doxygen
       run: sudo apt-get install -y doxygen librsvg2-bin # Changed to rsvg-convert in 20.04
@@ -734,7 +736,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python }}
         architecture: x86
@@ -787,7 +789,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python }}
         architecture: x86
@@ -835,7 +837,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python }}
 
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index aa2485ac08..edcad4198b 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -40,7 +40,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python 3.7
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: 3.7
         architecture: ${{ matrix.arch }}
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 70e3ddfa4b..a54a727341 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -21,7 +21,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-    - uses: actions/setup-python@v3
+    - uses: actions/setup-python@v4
+      with:
+        python-version: "3.x"
     - name: Add matchers
       run: echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
     - uses: pre-commit/action@v3.0.0
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 1d9a35604e..2c16735e1e 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -27,7 +27,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup 🐍 3.6
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: 3.6
 
@@ -49,7 +49,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup 🐍 3.8
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: 3.8
 
@@ -90,7 +90,9 @@ jobs:
     needs: [packaging]
 
     steps:
-    - uses: actions/setup-python@v3
+    - uses: actions/setup-python@v4
+      with:
+        python-version: "3.x"
 
     # Downloads all to directories matching the artifact names
     - uses: actions/download-artifact@v3
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 174dc24965..424fce79c4 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -22,7 +22,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python 3.11
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: "3.11-dev"
 

From c42e3ab793f17b2aeecc69e11561708506877e56 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 4 Jul 2022 22:21:59 -0400
Subject: [PATCH 415/638] [pre-commit.ci] pre-commit autoupdate (#4041)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/psf/black: 22.3.0 → 22.6.0](https://github.com/psf/black/compare/22.3.0...22.6.0)
- [github.com/Lucas-C/pre-commit-hooks: v1.2.0 → v1.3.0](https://github.com/Lucas-C/pre-commit-hooks/compare/v1.2.0...v1.3.0)
- [github.com/PyCQA/pylint: v2.14.3 → v2.14.4](https://github.com/PyCQA/pylint/compare/v2.14.3...v2.14.4)
- [github.com/pre-commit/mirrors-clang-format: v14.0.5 → v14.0.6](https://github.com/pre-commit/mirrors-clang-format/compare/v14.0.5...v14.0.6)

* Update blacken-docs

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 .pre-commit-config.yaml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e4880830fe..4b9681984a 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -45,7 +45,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "22.3.0" # Keep in sync with blacken-docs
+  rev: "22.6.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -55,11 +55,11 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==22.3.0 # keep in sync with black hook
+    - black==22.6.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.2.0"
+  rev: "v1.3.0"
   hooks:
   - id: remove-tabs
 
@@ -107,7 +107,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.14.3"
+  rev: "v2.14.4"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -164,7 +164,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v14.0.5"
+  rev: "v14.0.6"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From 2af163d9c7d5c0276b7b2385034c1dd9181b187c Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 6 Jul 2022 16:35:12 -0400
Subject: [PATCH 416/638] Fix: 3.11 beta support (#3923)

* Placeholder commit for 3.11 testing

* Does this fix it?

* Try suggestion

* Placeholder commit for 3.11 testing

* Does this fix it?

* Try suggestion

* fix: try using modern init for embedded interp

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix: error message changed in 3.11

* fix: apply logic in Python manually

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix autodetect dynamic attrs in 3.11

* fix: include error message if possible in error

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* ci: enable standard Python 3.11 testing

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Make dynamic attrs condtiion exclusive to ver.

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml             |  5 +-
 .github/workflows/upstream.yml       |  2 +-
 include/pybind11/attr.h              |  8 ++-
 include/pybind11/detail/class.h      |  4 ++
 include/pybind11/embed.h             | 88 ++++++++++++++++++----------
 setup.cfg                            |  1 +
 tests/requirements.txt               |  2 +-
 tests/test_methods_and_attributes.py | 30 +++++++---
 8 files changed, 92 insertions(+), 48 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9a69438bd8..787fa3c507 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,6 +30,7 @@ jobs:
         - '3.6'
         - '3.9'
         - '3.10'
+        - '3.11-dev'
         - 'pypy-3.7'
         - 'pypy-3.8'
         - 'pypy-3.9'
@@ -185,8 +186,8 @@ jobs:
         - python-version: "3.9"
           python-debug: true
           valgrind: true
-      # - python-version: "3.11-dev"
-      #   python-debug: false
+        - python-version: "3.11-dev"
+          python-debug: false
 
     name: "🐍 ${{ matrix.python-version }}${{ matrix.python-debug && '-dbg' || '' }} (deadsnakes)${{ matrix.valgrind && ' • Valgrind' || '' }} • x64"
     runs-on: ubuntu-latest
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 424fce79c4..a40a6c7d78 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -14,7 +14,7 @@ env:
 
 jobs:
   standard:
-    name: "🐍 3.11 dev • ubuntu-latest • x64"
+    name: "🐍 3.11 latest internals • ubuntu-latest • x64"
     runs-on: ubuntu-latest
     if: "contains(github.event.pull_request.labels.*.name, 'python dev')"
 
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 14600e9bb0..db7cd8efff 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -345,9 +345,11 @@ struct type_record {
 
         bases.append((PyObject *) base_info->type);
 
-        if (base_info->type->tp_dictoffset != 0) {
-            dynamic_attr = true;
-        }
+#if PY_VERSION_HEX < 0x030B0000
+        dynamic_attr |= base_info->type->tp_dictoffset != 0;
+#else
+        dynamic_attr |= (base_info->type->tp_flags & Py_TPFLAGS_MANAGED_DICT) != 0;
+#endif
 
         if (caster) {
             base_info->implicit_casts.emplace_back(type, caster);
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 1ddf1393bb..c09f70ef04 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -545,8 +545,12 @@ extern "C" inline int pybind11_clear(PyObject *self) {
 inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
     auto *type = &heap_type->ht_type;
     type->tp_flags |= Py_TPFLAGS_HAVE_GC;
+#if PY_VERSION_HEX < 0x030B0000
     type->tp_dictoffset = type->tp_basicsize;           // place dict at the end
     type->tp_basicsize += (ssize_t) sizeof(PyObject *); // and allocate enough space for it
+#else
+    type->tp_flags |= Py_TPFLAGS_MANAGED_DICT;
+#endif
     type->tp_traverse = pybind11_traverse;
     type->tp_clear = pybind11_clear;
 
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 98cc3e4664..d6999cd779 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -86,37 +86,6 @@ inline wchar_t *widen_chars(const char *safe_arg) {
     return widened_arg;
 }
 
-/// Python 2.x/3.x-compatible version of `PySys_SetArgv`
-inline void set_interpreter_argv(int argc, const char *const *argv, bool add_program_dir_to_path) {
-    // Before it was special-cased in python 3.8, passing an empty or null argv
-    // caused a segfault, so we have to reimplement the special case ourselves.
-    bool special_case = (argv == nullptr || argc <= 0);
-
-    const char *const empty_argv[]{"\0"};
-    const char *const *safe_argv = special_case ? empty_argv : argv;
-    if (special_case) {
-        argc = 1;
-    }
-
-    auto argv_size = static_cast<size_t>(argc);
-    // SetArgv* on python 3 takes wchar_t, so we have to convert.
-    std::unique_ptr<wchar_t *[]> widened_argv(new wchar_t *[argv_size]);
-    std::vector<std::unique_ptr<wchar_t[], wide_char_arg_deleter>> widened_argv_entries;
-    widened_argv_entries.reserve(argv_size);
-    for (size_t ii = 0; ii < argv_size; ++ii) {
-        widened_argv_entries.emplace_back(widen_chars(safe_argv[ii]));
-        if (!widened_argv_entries.back()) {
-            // A null here indicates a character-encoding failure or the python
-            // interpreter out of memory. Give up.
-            return;
-        }
-        widened_argv[ii] = widened_argv_entries.back().get();
-    }
-
-    auto *pysys_argv = widened_argv.get();
-    PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
-}
-
 PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
@@ -146,9 +115,64 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
         pybind11_fail("The interpreter is already running");
     }
 
+#if PY_VERSION_HEX < 0x030B0000
+
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
 
-    detail::set_interpreter_argv(argc, argv, add_program_dir_to_path);
+    // Before it was special-cased in python 3.8, passing an empty or null argv
+    // caused a segfault, so we have to reimplement the special case ourselves.
+    bool special_case = (argv == nullptr || argc <= 0);
+
+    const char *const empty_argv[]{"\0"};
+    const char *const *safe_argv = special_case ? empty_argv : argv;
+    if (special_case) {
+        argc = 1;
+    }
+
+    auto argv_size = static_cast<size_t>(argc);
+    // SetArgv* on python 3 takes wchar_t, so we have to convert.
+    std::unique_ptr<wchar_t *[]> widened_argv(new wchar_t *[argv_size]);
+    std::vector<std::unique_ptr<wchar_t[], detail::wide_char_arg_deleter>> widened_argv_entries;
+    widened_argv_entries.reserve(argv_size);
+    for (size_t ii = 0; ii < argv_size; ++ii) {
+        widened_argv_entries.emplace_back(detail::widen_chars(safe_argv[ii]));
+        if (!widened_argv_entries.back()) {
+            // A null here indicates a character-encoding failure or the python
+            // interpreter out of memory. Give up.
+            return;
+        }
+        widened_argv[ii] = widened_argv_entries.back().get();
+    }
+
+    auto *pysys_argv = widened_argv.get();
+
+    PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
+#else
+    PyConfig config;
+    PyConfig_InitIsolatedConfig(&config);
+    config.install_signal_handlers = init_signal_handlers ? 1 : 0;
+
+    PyStatus status = PyConfig_SetBytesArgv(&config, argc, const_cast<char *const *>(argv));
+    if (PyStatus_Exception(status)) {
+        // A failure here indicates a character-encoding failure or the python
+        // interpreter out of memory. Give up.
+        PyConfig_Clear(&config);
+        throw std::runtime_error(PyStatus_IsError(status) ? status.err_msg
+                                                          : "Failed to prepare CPython");
+    }
+    status = Py_InitializeFromConfig(&config);
+    PyConfig_Clear(&config);
+    if (PyStatus_Exception(status)) {
+        throw std::runtime_error(PyStatus_IsError(status) ? status.err_msg
+                                                          : "Failed to init CPython");
+    }
+    if (add_program_dir_to_path) {
+        PyRun_SimpleString("import sys, os.path; "
+                           "sys.path.insert(0, "
+                           "os.path.abspath(os.path.dirname(sys.argv[0])) "
+                           "if sys.argv and os.path.exists(sys.argv[0]) else '')");
+    }
+#endif
 }
 
 /** \rst
diff --git a/setup.cfg b/setup.cfg
index 4fd1e7a6fa..36fbfed4f3 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -19,6 +19,7 @@ classifiers =
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
+    Programming Language :: Python :: 3.11
     License :: OSI Approved :: BSD License
     Programming Language :: Python :: Implementation :: PyPy
     Programming Language :: Python :: Implementation :: CPython
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 1159287fa9..04aafa8cf9 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,4 +1,4 @@
-build==0.7.0
+build==0.8.0
 numpy==1.21.5; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
 numpy==1.19.3; platform_python_implementation!="PyPy" and python_version=="3.6"
 numpy==1.21.5; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.10"
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 54597fa788..0a2ae1239a 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -1,9 +1,21 @@
+import sys
+
 import pytest
 
 import env  # noqa: F401
 from pybind11_tests import ConstructorStats
 from pybind11_tests import methods_and_attributes as m
 
+NO_GETTER_MSG = (
+    "unreadable attribute" if sys.version_info < (3, 11) else "object has no getter"
+)
+NO_SETTER_MSG = (
+    "can't set attribute" if sys.version_info < (3, 11) else "object has no setter"
+)
+NO_DELETER_MSG = (
+    "can't delete attribute" if sys.version_info < (3, 11) else "object has no deleter"
+)
+
 
 def test_methods_and_attributes():
     instance1 = m.ExampleMandA()
@@ -102,32 +114,32 @@ def test_properties():
 
     with pytest.raises(AttributeError) as excinfo:
         dummy = instance.def_property_writeonly  # unused var
-    assert "unreadable attribute" in str(excinfo.value)
+    assert NO_GETTER_MSG in str(excinfo.value)
 
     instance.def_property_writeonly = 4
     assert instance.def_property_readonly == 4
 
     with pytest.raises(AttributeError) as excinfo:
         dummy = instance.def_property_impossible  # noqa: F841 unused var
-    assert "unreadable attribute" in str(excinfo.value)
+    assert NO_GETTER_MSG in str(excinfo.value)
 
     with pytest.raises(AttributeError) as excinfo:
         instance.def_property_impossible = 5
-    assert "can't set attribute" in str(excinfo.value)
+    assert NO_SETTER_MSG in str(excinfo.value)
 
 
 def test_static_properties():
     assert m.TestProperties.def_readonly_static == 1
     with pytest.raises(AttributeError) as excinfo:
         m.TestProperties.def_readonly_static = 2
-    assert "can't set attribute" in str(excinfo.value)
+    assert NO_SETTER_MSG in str(excinfo.value)
 
     m.TestProperties.def_readwrite_static = 2
     assert m.TestProperties.def_readwrite_static == 2
 
     with pytest.raises(AttributeError) as excinfo:
         dummy = m.TestProperties.def_writeonly_static  # unused var
-    assert "unreadable attribute" in str(excinfo.value)
+    assert NO_GETTER_MSG in str(excinfo.value)
 
     m.TestProperties.def_writeonly_static = 3
     assert m.TestProperties.def_readonly_static == 3
@@ -135,14 +147,14 @@ def test_static_properties():
     assert m.TestProperties.def_property_readonly_static == 3
     with pytest.raises(AttributeError) as excinfo:
         m.TestProperties.def_property_readonly_static = 99
-    assert "can't set attribute" in str(excinfo.value)
+    assert NO_SETTER_MSG in str(excinfo.value)
 
     m.TestProperties.def_property_static = 4
     assert m.TestProperties.def_property_static == 4
 
     with pytest.raises(AttributeError) as excinfo:
         dummy = m.TestProperties.def_property_writeonly_static
-    assert "unreadable attribute" in str(excinfo.value)
+    assert NO_GETTER_MSG in str(excinfo.value)
 
     m.TestProperties.def_property_writeonly_static = 5
     assert m.TestProperties.def_property_static == 5
@@ -160,7 +172,7 @@ def test_static_properties():
 
     with pytest.raises(AttributeError) as excinfo:
         dummy = instance.def_property_writeonly_static  # noqa: F841 unused var
-    assert "unreadable attribute" in str(excinfo.value)
+    assert NO_GETTER_MSG in str(excinfo.value)
 
     instance.def_property_writeonly_static = 4
     assert instance.def_property_static == 4
@@ -180,7 +192,7 @@ def test_static_properties():
     properties_override = m.TestPropertiesOverride()
     with pytest.raises(AttributeError) as excinfo:
         del properties_override.def_readonly
-    assert "can't delete attribute" in str(excinfo.value)
+    assert NO_DELETER_MSG in str(excinfo.value)
 
 
 def test_static_cls():

From 0ab1fcfb1c6c696422cc072ba7b9f50a11ed23c2 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 6 Jul 2022 16:36:05 -0400
Subject: [PATCH 417/638] docs: update changelog (#4042)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst | 149 +++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 137 insertions(+), 12 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 67ac79cdd1..9d0f217ad4 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -14,44 +14,164 @@ IN DEVELOPMENT
 
 Removed support for Python 2.7, Python 3.5, and MSVC 2015. Support for MSVC
 2017 is limited due to availability of CI runners; we highly recommend MSVC
-2019 or 2022 be used.
+2019 or 2022 be used. Initial support added for Python 3.11.
+
 
 New features:
 
+* ``py::anyset`` & ``py::frozenset`` were added, with copying (cast) to
+  ``std::set`` (similar to ``set``).
+  `#3901 <https://github.com/pybind/pybind11/pull/3901>`_
+
+* Support bytearray casting to string.
+  `#3707 <https://github.com/pybind/pybind11/pull/3707>`_
+
 * ``type_caster<std::monostate>`` was added. ``std::monostate`` is a tag type
   that allows ``std::variant`` to act as an optional, or allows default
   construction of a ``std::variant`` holding a non-default constructible type.
   `#3818 <https://github.com/pybind/pybind11/pull/3818>`_
 
-* Support bytearray casting to string.
-  `#3707 <https://github.com/pybind/pybind11/pull/3707>`_
+* ``pybind11::capsule::set_name`` added to mutate the name of the capsule instance.
+  `#3866 <https://github.com/pybind/pybind11/pull/3866>`_
+
+* NumPy: dtype constructor from type number added, accessors corresponding to
+  Python API ``dtype.num``, ``dtype.byteorder``, ``dtype.flags`` and
+  ``dtype.alignment`` added.
+  `#3868 <https://github.com/pybind/pybind11/pull/3868>`_
+
 
 Changes:
 
-* Python 2 support was removed completely.
+* Python 3.6 is now the minimum supported version.
   `#3688 <https://github.com/pybind/pybind11/pull/3688>`_
+  `#3719 <https://github.com/pybind/pybind11/pull/3719>`_
 
 * The minimum version for MSVC is now 2017.
   `#3722 <https://github.com/pybind/pybind11/pull/3722>`_
 
+* Fix issues with CPython 3.11 betas and add to supported test matrix.
+  `#3923 <https://github.com/pybind/pybind11/pull/3923>`_
+
+* ``error_already_set`` is now safer and more performant, especially for
+  exceptions with long tracebacks, by delaying computation.
+  `#1895 <https://github.com/pybind/pybind11/pull/1895>`_
+
 * Improve exception handling in python ``str`` bindings.
   `#3826 <https://github.com/pybind/pybind11/pull/3826>`_
 
 * The bindings for capsules now have more consistent exception handling.
   `#3825 <https://github.com/pybind/pybind11/pull/3825>`_
 
+* ``PYBIND11_OBJECT_CVT`` and ``PYBIND11_OBJECT_CVT_DEFAULT`` macro can now be
+  used to define classes in namespaces other than pybind11.
+  `#3797 <https://github.com/pybind/pybind11/pull/3797>`_
+
+* Error printing code now uses ``PYBIND11_DETAILED_ERROR_MESSAGES`` instead of
+  requiring ``NDEBUG``, allowing use with release builds if desired.
+  `#3913 <https://github.com/pybind/pybind11/pull/3913>`_
+
+
+Bug fixes:
+
 * Fix exception handling when ``pybind11::weakref()`` fails.
   `#3739 <https://github.com/pybind/pybind11/pull/3739>`_
 
+* ``module_::def_submodule`` was missing proper error handling. This is fixed now.
+  `#3973 <https://github.com/pybind/pybind11/pull/3973>`_
 
-Bug fixes:
+* The behavior or ``error_already_set`` was made safer and the highly opaque
+  "Unknown internal error occurred" message was replaced with a more helpful
+  message.
+  `#3982 <https://github.com/pybind/pybind11/pull/3982>`_
+
+* ``error_already_set::what()`` now handles non-normalized exceptions correctly.
+  `#3971 <https://github.com/pybind/pybind11/pull/3971>`_
+
+* Support older C++ compilers where filesystem is not yet part of the standard
+  library and is instead included in ``std::experimental::filesystem``.
+  `#3840 <https://github.com/pybind/pybind11/pull/3840>`_
+
+* Fix ``-Wfree-nonheap-object`` warnings produced by GCC by avoiding returning
+  pointers to static objects with ``return_value_policy::take_ownership``.
+  `#3946 <https://github.com/pybind/pybind11/pull/3946>`_
+
+* Fix cast from pytype rvalue to another pytype.
+  `#3949 <https://github.com/pybind/pybind11/pull/3949>`_
+
+* ``pybind11::detail::get_internals()`` is now resilient to in-flight Python
+  exceptions.
+  `#3981 <https://github.com/pybind/pybind11/pull/3981>`_
+
+* Arrays with a dimension of size 0 are now properly converted to dynamic Eigen
+  matrices (more common in NumPy 1.23).
+  `#4038 <https://github.com/pybind/pybind11/pull/4038>`_
+
+* Avoid catching unrelated errors when importing NumPy.
+  `#3974 <https://github.com/pybind/pybind11/pull/3974>`_
+
+Performance and style:
+
+* Added an accessor overload of ``(object &&key)`` to reference steal the
+  object when using python types as keys. This prevents unnecessary reference
+  count overhead for attr, dictionary, tuple, and sequence look ups. Added
+  additional regression tests. Fixed a performance bug the caused accessor
+  assignments to potentially perform unnecessary copies.
+  `#3970 <https://github.com/pybind/pybind11/pull/3970>`_
+
+* Perfect forward all args of ``make_iterator``.
+  `#3980 <https://github.com/pybind/pybind11/pull/3980>`_
+
+* Avoid potential bug in pycapsule destructor by adding an ``error_guard`` to
+  one of the dtors.
+  `#3958 <https://github.com/pybind/pybind11/pull/3958>`_
+
+* Optimize dictionary access in ``strip_padding`` for numpy.
+  `#3994 <https://github.com/pybind/pybind11/pull/3994>`_
+
+* ``stl_bind.h`` bindings now take slice args as a const-ref.
+  `#3852 <https://github.com/pybind/pybind11/pull/3852>`_
+
+* Made slice constructor more consistent, and improve performance of some
+  casters by allowing reference stealing.
+  `#3845 <https://github.com/pybind/pybind11/pull/3845>`_
+
+* Change numpy dtype from_args method to use const ref.
+  `#3878 <https://github.com/pybind/pybind11/pull/3878>`_
+
+* Follow rule of three to ensure ``PyErr_Restore`` is called only once.
+  `#3872 <https://github.com/pybind/pybind11/pull/3872>`_
+
+* Added missing perfect forwarding for ``make_iterator`` functions.
+  `#3860 <https://github.com/pybind/pybind11/pull/3860>`_
+
+* Optimize c++ to python function casting by using the rvalue caster.
+  `#3966 <https://github.com/pybind/pybind11/pull/3966>`_
+
+* Avoid potential implicit copy/assignment constructors causing double free in
+  ``strdup_gaurd``.
+  `#3905 <https://github.com/pybind/pybind11/pull/3905>`_
+
+* Enable clang-tidy checks ``misc-definitions-in-headers``,
+  ``modernize-loop-convert``, and ``modernize-use-nullptr``.
+  `#3881 <https://github.com/pybind/pybind11/pull/3881>`_
+  `#3988 <https://github.com/pybind/pybind11/pull/3988>`_
 
-* ``PYBIND11_OBJECT_CVT`` and ``PYBIND11_OBJECT_CVT_DEFAULT`` macro can be used
-  to define classes in namespaces other than pybind11.
-  `#3797 <https://github.com/pybind/pybind11/pull/3797>`_
 
 Build system improvements:
 
+* CMake: Fix file extension on Windows with cp36 and cp37 using FindPython.
+  `#3919 <https://github.com/pybind/pybind11/pull/3919>`_
+
+* CMake: Support multiple Python targets (such as on vcpkg).
+  `#3948 <https://github.com/pybind/pybind11/pull/3948>`_
+
+* CMake: Fix issue with NVCC on Windows.
+  `#3947 <https://github.com/pybind/pybind11/pull/3947>`_
+
+* CMake: Drop the bitness check on cross compiles (like targeting WebAssembly
+  via Emscripten).
+  `#3959 <https://github.com/pybind/pybind11/pull/3959>`_
+
 * Add MSVC builds in debug mode to CI.
   `#3784 <https://github.com/pybind/pybind11/pull/3784>`_
 
@@ -59,15 +179,20 @@ Build system improvements:
   `#3732 <https://github.com/pybind/pybind11/pull/3732>`_,
   `#3741 <https://github.com/pybind/pybind11/pull/3741>`_
 
-* Avoid ``setup.py <command>`` usage in internal tests.
-  `#3734 <https://github.com/pybind/pybind11/pull/3734>`_
-
 
 Backend and tidying up:
 
-* Remove idioms in code comments.  Use inclusive language.
+* Remove idioms in code comments.  Use more inclusive language.
   `#3809 <https://github.com/pybind/pybind11/pull/3809>`_
 
+* ``#include <iostream>`` was removed from the ``pybind11/stl.h`` header. Your
+  project may break if it has a transitive dependency on this include. The fix
+  is to "Include What You Use".
+  `#3928 <https://github.com/pybind/pybind11/pull/3928>`_
+
+* Avoid ``setup.py <command>`` usage in internal tests.
+  `#3734 <https://github.com/pybind/pybind11/pull/3734>`_
+
 
 Version 2.9.2 (Mar 29, 2022)
 ----------------------------

From cd08869df14d02afd55519ea92c79b42b8e48c1c Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 6 Jul 2022 14:29:20 -0700
Subject: [PATCH 418/638] PYBIND11_NAMESPACE consistency fixes. (#4043)

---
 include/pybind11/cast.h        | 8 ++++----
 include/pybind11/detail/init.h | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 9a971704e4..782fb20d46 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -846,7 +846,7 @@ struct always_construct_holder {
 
 /// Create a specialization for custom holder types (silently ignores std::shared_ptr)
 #define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type, ...)                                      \
-    namespace pybind11 {                                                                          \
+    PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)                                                  \
     namespace detail {                                                                            \
     template <typename type>                                                                      \
     struct always_construct_holder<holder_type> : always_construct_holder<void, ##__VA_ARGS__> {  \
@@ -855,7 +855,7 @@ struct always_construct_holder {
     class type_caster<holder_type, enable_if_t<!is_shared_ptr<holder_type>::value>>               \
         : public type_caster_holder<type, holder_type> {};                                        \
     }                                                                                             \
-    }
+    PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 // PYBIND11_DECLARE_HOLDER_TYPE holder types:
 template <typename base, typename holder>
@@ -1650,12 +1650,12 @@ handle type::handle_of() {
 }
 
 #define PYBIND11_MAKE_OPAQUE(...)                                                                 \
-    namespace pybind11 {                                                                          \
+    PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)                                                  \
     namespace detail {                                                                            \
     template <>                                                                                   \
     class type_caster<__VA_ARGS__> : public type_caster_base<__VA_ARGS__> {};                     \
     }                                                                                             \
-    }
+    PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 /// Lets you pass a type containing a `,` through a macro parameter without needing a separate
 /// typedef, e.g.:
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index e1e665a69b..05f4fe54aa 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -425,4 +425,4 @@ struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
 
 PYBIND11_NAMESPACE_END(initimpl)
 PYBIND11_NAMESPACE_END(detail)
-PYBIND11_NAMESPACE_END(pybind11)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

From 85bc088441bcf4047ee9bdcfa22e5448f445a565 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 7 Jul 2022 17:51:44 -0700
Subject: [PATCH 419/638] Report `C++ Info:` via `pytest_report_header()`
 (#4046)

* Report `C++ Info:` from `pytest_configure()`

* Use pytest_report_header() as suggested by @skylion007
---
 include/pybind11/detail/common.h |  1 +
 tests/conftest.py                | 15 ++++++++++++++-
 tests/pybind11_tests.cpp         | 25 +++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 9355ecfda0..e52507a9e8 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -38,6 +38,7 @@
 #            define PYBIND11_CPP17
 #            if __cplusplus >= 202002L
 #                define PYBIND11_CPP20
+// Please update tests/pybind11_tests.cpp `cpp_std()` when adding a macro here.
 #            endif
 #        endif
 #    endif
diff --git a/tests/conftest.py b/tests/conftest.py
index e72ec0ef81..02ce263afc 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -13,7 +13,7 @@
 import pytest
 
 # Early diagnostic for failed imports
-import pybind11_tests  # noqa: F401
+import pybind11_tests
 
 _long_marker = re.compile(r"([0-9])L")
 _hexadecimal = re.compile(r"0x[0-9a-fA-F]+")
@@ -198,3 +198,16 @@ def gc_collect():
 def pytest_configure():
     pytest.suppress = suppress
     pytest.gc_collect = gc_collect
+
+
+def pytest_report_header(config):
+    del config  # Unused.
+    assert (
+        pybind11_tests.compiler_info is not None
+    ), "Please update pybind11_tests.cpp if this assert fails."
+    return (
+        "C++ Info:"
+        f" {pybind11_tests.compiler_info}"
+        f" {pybind11_tests.cpp_std}"
+        f" {pybind11_tests.PYBIND11_INTERNALS_ID}"
+    )
diff --git a/tests/pybind11_tests.cpp b/tests/pybind11_tests.cpp
index 3c04699157..aa3095594b 100644
--- a/tests/pybind11_tests.cpp
+++ b/tests/pybind11_tests.cpp
@@ -62,9 +62,34 @@ void bind_ConstructorStats(py::module_ &m) {
         });
 }
 
+const char *cpp_std() {
+    return
+#if defined(PYBIND11_CPP20)
+        "C++20";
+#elif defined(PYBIND11_CPP17)
+        "C++17";
+#elif defined(PYBIND11_CPP14)
+        "C++14";
+#else
+        "C++11";
+#endif
+}
+
 PYBIND11_MODULE(pybind11_tests, m) {
     m.doc() = "pybind11 test module";
 
+    // Intentionally kept minimal to not create a maintenance chore
+    // ("just enough" to be conclusive).
+#if defined(_MSC_FULL_VER)
+    m.attr("compiler_info") = "MSVC " PYBIND11_TOSTRING(_MSC_FULL_VER);
+#elif defined(__VERSION__)
+    m.attr("compiler_info") = __VERSION__;
+#else
+    m.attr("compiler_info") = py::none();
+#endif
+    m.attr("cpp_std") = cpp_std();
+    m.attr("PYBIND11_INTERNALS_ID") = PYBIND11_INTERNALS_ID;
+
     bind_ConstructorStats(m);
 
 #if defined(PYBIND11_DETAILED_ERROR_MESSAGES)

From 432bc5cfb5c696044e93dfc78b2fa822dfd1dc4e Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 7 Jul 2022 19:08:10 -0700
Subject: [PATCH 420/638] Add `std::string clean_type_id(const char
 *typeid_name)` overload (in namespace detail). (#4049)

Very minor refactoring to ease development and debugging.

Having to declare a local `std::string` has bugged me many times. Nice to get this little nuisance out of the way.

Extracted from PR #4022, where it is used like this:

```
    std::fprintf(stdout,
                 "\nTYPE_CASTER_ODR_GUARD_IMPL %s %s\n",
                 clean_type_id(intrinsic_type_info.name()).c_str(),
                 source_file_line_from_sloc.c_str());
```
---
 include/pybind11/detail/typeid.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/detail/typeid.h b/include/pybind11/detail/typeid.h
index 8d99fc0286..a67b52135b 100644
--- a/include/pybind11/detail/typeid.h
+++ b/include/pybind11/detail/typeid.h
@@ -20,6 +20,7 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
+
 /// Erase all occurrences of a substring
 inline void erase_all(std::string &string, const std::string &search) {
     for (size_t pos = 0;;) {
@@ -46,14 +47,19 @@ PYBIND11_NOINLINE void clean_type_id(std::string &name) {
 #endif
     detail::erase_all(name, "pybind11::");
 }
+
+inline std::string clean_type_id(const char *typeid_name) {
+    std::string name(typeid_name);
+    detail::clean_type_id(name);
+    return name;
+}
+
 PYBIND11_NAMESPACE_END(detail)
 
 /// Return a string representation of a C++ type
 template <typename T>
 static std::string type_id() {
-    std::string name(typeid(T).name());
-    detail::clean_type_id(name);
-    return name;
+    return detail::clean_type_id(typeid(T).name());
 }
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

From f9f00495a3f0ef6037c215c42bd2d919590ff11f Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sun, 10 Jul 2022 00:43:53 -0400
Subject: [PATCH 421/638] Properly visit self in >=3.9 traverse (#4051)

* Properly visit self in >=3.9 traverse

* Add comment about 3.9 behavior
---
 include/pybind11/detail/class.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index c09f70ef04..42720f844d 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -531,6 +531,10 @@ extern "C" inline int pybind11_set_dict(PyObject *self, PyObject *new_dict, void
 extern "C" inline int pybind11_traverse(PyObject *self, visitproc visit, void *arg) {
     PyObject *&dict = *_PyObject_GetDictPtr(self);
     Py_VISIT(dict);
+// https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_traverse
+#if PY_VERSION_HEX >= 0x03090000
+    Py_VISIT(Py_TYPE(self));
+#endif
     return 0;
 }
 

From 790241bce25bb0bd60996fcd5750eef1dff9b658 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 11 Jul 2022 22:31:54 -0400
Subject: [PATCH 422/638] [pre-commit.ci] pre-commit autoupdate (#4058)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.34.0 → v2.37.1](https://github.com/asottile/pyupgrade/compare/v2.34.0...v2.37.1)
- [github.com/hadialqattan/pycln: v1.3.5 → v2.0.1](https://github.com/hadialqattan/pycln/compare/v1.3.5...v2.0.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4b9681984a..ba9955a316 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.34.0"
+  rev: "v2.37.1"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v1.3.5"
+  rev: "v2.0.1"
   hooks:
   - id: pycln
     stages: [manual]

From 023b3f32c83a0faab1a6702cba7fd7bc30589d31 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 12 Jul 2022 12:02:20 -0700
Subject: [PATCH 423/638] Undo accidental one-line change under PR #3913
 (#4060)

---
 include/pybind11/cast.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 782fb20d46..a0e32281bc 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1625,7 +1625,7 @@ unpacking_collector<policy> collect_arguments(Args &&...args) {
 template <typename Derived>
 template <return_value_policy policy, typename... Args>
 object object_api<Derived>::operator()(Args &&...args) const {
-#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+#ifndef NDEBUG
     if (!PyGILState_Check()) {
         pybind11_fail("pybind11::object_api<>::operator() PyGILState_Check() failure.");
     }

From 7c3a0317664c406e483342631558406c8a9e31e3 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 13 Jul 2022 09:06:32 -0500
Subject: [PATCH 424/638] chore: bump clang-tidy to 13 (#3997)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .clang-tidy                      | 124 +++++++++++++++----------------
 .github/CONTRIBUTING.md          |   8 +-
 .github/workflows/ci.yml         |   2 +
 .github/workflows/format.yml     |   4 +-
 tests/test_embed/CMakeLists.txt  |   2 +-
 tests/test_virtual_functions.cpp |   5 +-
 6 files changed, 73 insertions(+), 72 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index ddee835c15..d945a4a27d 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,66 +1,66 @@
 FormatStyle: file
 
-Checks: '
-*bugprone*,
-clang-analyzer-optin.performance.Padding,
-clang-analyzer-optin.cplusplus.VirtualCall,
-cppcoreguidelines-init-variables,
-cppcoreguidelines-prefer-member-initializer,
-cppcoreguidelines-pro-type-static-cast-downcast,
-cppcoreguidelines-slicing,
-google-explicit-constructor,
-llvm-namespace-comment,
-misc-definitions-in-headers,
-misc-misplaced-const,
-misc-non-copyable-objects,
-misc-static-assert,
-misc-throw-by-value-catch-by-reference,
-misc-uniqueptr-reset-release,
-misc-unused-parameters,
-modernize-avoid-bind,
-modernize-loop-convert,
-modernize-make-shared,
-modernize-redundant-void-arg,
-modernize-replace-auto-ptr,
-modernize-replace-disallow-copy-and-assign-macro,
-modernize-replace-random-shuffle,
-modernize-shrink-to-fit,
-modernize-use-auto,
-modernize-use-bool-literals,
-modernize-use-default-member-init,
-modernize-use-equals-default,
-modernize-use-equals-delete,
-modernize-use-emplace,
-modernize-use-noexcept,
-modernize-use-nullptr,
-modernize-use-override,
-modernize-use-using,
-*performance*,
-readability-avoid-const-params-in-decls,
-readability-braces-around-statements,
-readability-const-return-type,
-readability-container-size-empty,
-readability-delete-null-pointer,
-readability-else-after-return,
-readability-implicit-bool-conversion,
-readability-inconsistent-declaration-parameter-name,
-readability-make-member-function-const,
-readability-misplaced-array-index,
-readability-non-const-parameter,
-readability-qualified-auto,
-readability-redundant-function-ptr-dereference,
-readability-redundant-smartptr-get,
-readability-redundant-string-cstr,
-readability-simplify-subscript-expr,
-readability-static-accessed-through-instance,
-readability-static-definition-in-anonymous-namespace,
-readability-string-compare,
-readability-suspicious-call-argument,
-readability-uniqueptr-delete-release,
--bugprone-exception-escape,
--bugprone-reserved-identifier,
--bugprone-unused-raii,
-'
+Checks: |
+  *bugprone*,
+  *performance*,
+  clang-analyzer-optin.cplusplus.VirtualCall,
+  clang-analyzer-optin.performance.Padding,
+  cppcoreguidelines-init-variables,
+  cppcoreguidelines-prefer-member-initializer,
+  cppcoreguidelines-pro-type-static-cast-downcast,
+  cppcoreguidelines-slicing,
+  google-explicit-constructor,
+  llvm-namespace-comment,
+  misc-definitions-in-headers,
+  misc-misplaced-const,
+  misc-non-copyable-objects,
+  misc-static-assert,
+  misc-throw-by-value-catch-by-reference,
+  misc-uniqueptr-reset-release,
+  misc-unused-parameters,
+  modernize-avoid-bind,
+  modernize-loop-convert,
+  modernize-make-shared,
+  modernize-redundant-void-arg,
+  modernize-replace-auto-ptr,
+  modernize-replace-disallow-copy-and-assign-macro,
+  modernize-replace-random-shuffle,
+  modernize-shrink-to-fit,
+  modernize-use-auto,
+  modernize-use-bool-literals,
+  modernize-use-default-member-init,
+  modernize-use-emplace,
+  modernize-use-equals-default,
+  modernize-use-equals-delete,
+  modernize-use-noexcept,
+  modernize-use-nullptr,
+  modernize-use-override,
+  modernize-use-using,
+  readability-avoid-const-params-in-decls,
+  readability-braces-around-statements,
+  readability-const-return-type,
+  readability-container-size-empty,
+  readability-delete-null-pointer,
+  readability-else-after-return,
+  readability-implicit-bool-conversion,
+  readability-inconsistent-declaration-parameter-name,
+  readability-make-member-function-const,
+  readability-misplaced-array-index,
+  readability-non-const-parameter,
+  readability-qualified-auto,
+  readability-redundant-function-ptr-dereference,
+  readability-redundant-smartptr-get,
+  readability-redundant-string-cstr,
+  readability-simplify-subscript-expr,
+  readability-static-accessed-through-instance,
+  readability-static-definition-in-anonymous-namespace,
+  readability-string-compare,
+  readability-suspicious-call-argument,
+  readability-uniqueptr-delete-release,
+  -bugprone-easily-swappable-parameters,
+  -bugprone-exception-escape,
+  -bugprone-reserved-identifier,
+  -bugprone-unused-raii,
 
 CheckOptions:
 - key:             performance-for-range-copy.WarnOnAllAutoCopies
@@ -73,5 +73,3 @@ CheckOptions:
   value:           true
 
 HeaderFilterRegex: 'pybind11/.*h'
-
-WarningsAsErrors: '*'
diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index c8ec91ff7a..00b1fea4cf 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -235,12 +235,14 @@ directory inside your pybind11 git clone. Files will be modified in place,
 so you can use git to monitor the changes.
 
 ```bash
-docker run --rm -v $PWD:/mounted_pybind11 -it silkeh/clang:12
+docker run --rm -v $PWD:/mounted_pybind11 -it silkeh/clang:13
 apt-get update && apt-get install -y python3-dev python3-pytest
-cmake -S /mounted_pybind11/ -B build -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);-fix" -DDOWNLOAD_EIGEN=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=17
-cmake --build build -j 2 -- --keep-going
+cmake -S /mounted_pybind11/ -B build -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);--use-color" -DDOWNLOAD_EIGEN=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=17
+cmake --build build -j 2
 ```
 
+You can add `--fix` to the options list if you want.
+
 ### Include what you use
 
 To run include what you use, install (`brew install include-what-you-use` on
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 787fa3c507..412282a4f2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -281,6 +281,8 @@ jobs:
             std: 20
           - clang: 10
             std: 17
+          - clang: 14
+            std: 20
 
     name: "🐍 3 • Clang ${{ matrix.clang }} • C++${{ matrix.std }} • x64"
     container: "silkeh/clang:${{ matrix.clang }}"
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index a54a727341..31d893c479 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -36,7 +36,7 @@ jobs:
     # in .github/CONTRIBUTING.md and update as needed.
     name: Clang-Tidy
     runs-on: ubuntu-latest
-    container: silkeh/clang:12
+    container: silkeh/clang:13
     steps:
     - uses: actions/checkout@v3
 
@@ -46,7 +46,7 @@ jobs:
     - name: Configure
       run: >
         cmake -S . -B build
-        -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy)"
+        -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);--use-color;--warnings-as-errors=*"
         -DDOWNLOAD_EIGEN=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=17
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 69c33bbd54..09a3693999 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -7,7 +7,7 @@ if("${PYTHON_MODULE_EXTENSION}" MATCHES "pypy" OR "${Python_INTERPRETER_ID}" STR
   return()
 endif()
 
-find_package(Catch 2.13.5)
+find_package(Catch 2.13.9)
 
 if(CATCH_FOUND)
   message(STATUS "Building interpreter tests using Catch v${CATCH_VERSION}")
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index f6d8c5e3c3..323aa0d22d 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -342,9 +342,8 @@ TEST_SUBMODULE(virtual_functions, m) {
              const AdderBase &adder,
              const AdderBase::DataVisitor &visitor) {
               adder(first, second, [&](const AdderBase::Data &first_plus_second) {
-                  adder(first_plus_second,
-                        third,
-                        visitor); // NOLINT(readability-suspicious-call-argument)
+                  // NOLINTNEXTLINE(readability-suspicious-call-argument)
+                  adder(first_plus_second, third, visitor);
               });
           });
 

From 6b60d97d301c180badb16329aee5d19f3289c43c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 13 Jul 2022 10:13:35 -0500
Subject: [PATCH 425/638] docs: use Furo (#3109)

* docs: try using Furo

* docs: darker output

* docs: improve logo for dark background

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/_static/css/custom.css      |   3 +++
 docs/_static/theme_overrides.css |  11 -----------
 docs/conf.py                     |  23 ++++++-----------------
 docs/pybind11-logo.png           | Bin 58510 -> 61034 bytes
 docs/requirements.txt            |   7 ++++---
 noxfile.py                       |   4 ++--
 6 files changed, 15 insertions(+), 33 deletions(-)
 create mode 100644 docs/_static/css/custom.css
 delete mode 100644 docs/_static/theme_overrides.css

diff --git a/docs/_static/css/custom.css b/docs/_static/css/custom.css
new file mode 100644
index 0000000000..7a49a6ac4f
--- /dev/null
+++ b/docs/_static/css/custom.css
@@ -0,0 +1,3 @@
+.highlight .go {
+  color: #707070;
+}
diff --git a/docs/_static/theme_overrides.css b/docs/_static/theme_overrides.css
deleted file mode 100644
index 1071809fa0..0000000000
--- a/docs/_static/theme_overrides.css
+++ /dev/null
@@ -1,11 +0,0 @@
-.wy-table-responsive table td,
-.wy-table-responsive table th {
-    white-space: initial !important;
-}
-.rst-content table.docutils td {
-    vertical-align: top !important;
-}
-div[class^='highlight'] pre {
-    white-space: pre;
-    white-space: pre-wrap;
-}
diff --git a/docs/conf.py b/docs/conf.py
index 00796fbdbe..2da6773f4f 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -35,6 +35,7 @@
 # ones.
 extensions = [
     "breathe",
+    "sphinx_copybutton",
     "sphinxcontrib.rsvgconverter",
     "sphinxcontrib.moderncmakedomain",
 ]
@@ -125,23 +126,7 @@
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 
-on_rtd = os.environ.get("READTHEDOCS", None) == "True"
-
-if not on_rtd:  # only import and set the theme if we're building docs locally
-    import sphinx_rtd_theme
-
-    html_theme = "sphinx_rtd_theme"
-    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
-
-    html_context = {"css_files": ["_static/theme_overrides.css"]}
-else:
-    html_context = {
-        "css_files": [
-            "//media.readthedocs.org/css/sphinx_rtd_theme.css",
-            "//media.readthedocs.org/css/readthedocs-doc-embed.css",
-            "_static/theme_overrides.css",
-        ]
-    }
+html_theme = "furo"
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
@@ -172,6 +157,10 @@
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ["_static"]
 
+html_css_files = [
+    "css/custom.css",
+]
+
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied
 # directly to the root of the documentation.
diff --git a/docs/pybind11-logo.png b/docs/pybind11-logo.png
index 4cbad54f797d3ced04d4048f282df5e4336d4af4..2d633a4d0c129d6bdd94b4134c9516fdc92bb192 100644
GIT binary patch
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diff --git a/docs/requirements.txt b/docs/requirements.txt
index e452ed261f..d2a9ae1645 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,5 +1,6 @@
-breathe==4.32.0
-sphinx==4.4.0
-sphinx_rtd_theme==1.0.0
+breathe==4.34.0
+furo==2022.6.21
+sphinx==5.0.2
+sphinx-copybutton==0.5.0
 sphinxcontrib-moderncmakedomain==3.21.4
 sphinxcontrib-svg2pdfconverter==1.2.0
diff --git a/noxfile.py b/noxfile.py
index 341d964e95..fe36d70fe0 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -61,10 +61,10 @@ def docs(session: nox.Session) -> None:
     session.chdir("docs")
 
     if "pdf" in session.posargs:
-        session.run("sphinx-build", "-b", "latexpdf", ".", "_build")
+        session.run("sphinx-build", "-M", "latexpdf", ".", "_build")
         return
 
-    session.run("sphinx-build", "-b", "html", ".", "_build")
+    session.run("sphinx-build", "-M", "html", ".", "_build")
 
     if "serve" in session.posargs:
         session.log("Launching docs at http://localhost:8000/ - use Ctrl-C to quit")

From bc9315fe380138ac9b547dd01ac1394ccaf197ce Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 13 Jul 2022 19:27:00 -0400
Subject: [PATCH 426/638] chore: optimize sparse matrix casting with python
 tuple (#4064)

* optimize casting of sparse Eigen arrays

* move array

* Revert for safety
---
 include/pybind11/eigen.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 71df3eb8bd..4d221b3d75 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -692,9 +692,9 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         array outerIndices((rowMajor ? src.rows() : src.cols()) + 1, src.outerIndexPtr());
         array innerIndices(src.nonZeros(), src.innerIndexPtr());
 
-        return matrix_type(std::make_tuple(
+        return matrix_type(pybind11::make_tuple(
                                std::move(data), std::move(innerIndices), std::move(outerIndices)),
-                           std::make_pair(src.rows(), src.cols()))
+                           pybind11::make_tuple(src.rows(), src.cols()))
             .release();
     }
 

From 1d811910777491ddf40660a2324a3a862dfc5e04 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 14 Jul 2022 09:53:39 -0700
Subject: [PATCH 427/638] Disable implicit conversion of `0` to
 `pybind11::handle`. (#4008)

* Disable implicit conversion from `0` to `pybind11::handle`.

* Reverse or-ed condition in an attempt to resolve GCC 8.3.0 errors (i386/debian:buster).

* Trying the simpler `std::is_same<T, PyObject *>`

* Add implicit_conversion_from_pytorch_THPObjectPtr_to_handle test.

* Accommodate types with implicit conversions to `PyObject *`, other than `handle` & `handle` subclasses, or integral types.

* Fix copy-paste mishap (picked wrong name).

* Revamp SFINAE construct to actually fix the pytorch issue (already validated against pytorch proper).

The first version of the reduced pytorch code was critically missing the move ctor. The first version of the accompanying test was meaningless.

Note: It turns out the `!std::is_arithmetic<T>` condition is not needed: `int` is not in general implicitly convertible to `PyObject *`, only the literal `0` is.

* Use `NOLINT(performance-noexcept-move-constructor)` for reduced code from the wild (rather than changing the code).

* Use any_of, all_of, negation. It turns out to clang-format nicer.

* Clean up comments for changed code.

* Reduce pytorch situation further, add test for operator ... const.

* Use `none_of` as suggested by @skylion007

* Add `pure_compile_tests_for_handle_from_PyObject_pointers()`

* Fix inconsequential oversight (retested).

* Factor our `is_pyobj_ptr_or_nullptr_t` to make the SFINAE conditions more readable.

* Remove stray line (oversight).

* Make the `pure_compile_tests_for_handle_from_PyObject_pointers()` "rhs-const-complete", too.

* Remove the temporary PYBIND11_UNDO_PR4008 `#ifdef`.
---
 include/pybind11/pytypes.h | 23 ++++++++++++--
 tests/test_pytypes.cpp     | 61 ++++++++++++++++++++++++++++++++++++++
 tests/test_pytypes.py      |  5 ++++
 3 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f9625e77ea..339b0961eb 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -190,6 +190,11 @@ class object_api : public pyobject_tag {
     bool rich_compare(object_api const &other, int value) const;
 };
 
+template <typename T>
+using is_pyobj_ptr_or_nullptr_t = detail::any_of<std::is_same<T, PyObject *>,
+                                                 std::is_same<T, PyObject *const>,
+                                                 std::is_same<T, std::nullptr_t>>;
+
 PYBIND11_NAMESPACE_END(detail)
 
 #if !defined(PYBIND11_HANDLE_REF_DEBUG) && !defined(NDEBUG)
@@ -211,9 +216,23 @@ class handle : public detail::object_api<handle> {
 public:
     /// The default constructor creates a handle with a ``nullptr``-valued pointer
     handle() = default;
-    /// Creates a ``handle`` from the given raw Python object pointer
+
+    /// Enable implicit conversion from ``PyObject *`` and ``nullptr``.
+    /// Not using ``handle(PyObject *ptr)`` to avoid implicit conversion from ``0``.
+    template <typename T,
+              detail::enable_if_t<detail::is_pyobj_ptr_or_nullptr_t<T>::value, int> = 0>
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    handle(T ptr) : m_ptr(ptr) {}
+
+    /// Enable implicit conversion through ``T::operator PyObject *()``.
+    template <
+        typename T,
+        detail::enable_if_t<detail::all_of<detail::none_of<std::is_base_of<handle, T>,
+                                                           detail::is_pyobj_ptr_or_nullptr_t<T>>,
+                                           std::is_convertible<T, PyObject *>>::value,
+                            int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    handle(PyObject *ptr) : m_ptr(ptr) {} // Allow implicit conversion from PyObject*
+    handle(T &obj) : m_ptr(obj) {}
 
     /// Return the underlying ``PyObject *`` pointer
     PyObject *ptr() const { return m_ptr; }
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index cb81007c37..f532e26085 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -39,7 +39,68 @@ class float_ : public py::object {
 };
 } // namespace external
 
+namespace implicit_conversion_from_0_to_handle {
+// Uncomment to trigger compiler error. Note: Before PR #4008 this used to compile successfully.
+// void expected_to_trigger_compiler_error() { py::handle(0); }
+} // namespace implicit_conversion_from_0_to_handle
+
+// Used to validate systematically that PR #4008 does/did NOT change the behavior.
+void pure_compile_tests_for_handle_from_PyObject_pointers() {
+    {
+        PyObject *ptr = Py_None;
+        py::handle{ptr};
+    }
+    {
+        PyObject *const ptr = Py_None;
+        py::handle{ptr};
+    }
+    // Uncomment to trigger compiler errors.
+    // PyObject const *               ptr = Py_None; py::handle{ptr};
+    // PyObject const *const          ptr = Py_None; py::handle{ptr};
+    // PyObject volatile *            ptr = Py_None; py::handle{ptr};
+    // PyObject volatile *const       ptr = Py_None; py::handle{ptr};
+    // PyObject const volatile *      ptr = Py_None; py::handle{ptr};
+    // PyObject const volatile *const ptr = Py_None; py::handle{ptr};
+}
+
+namespace handle_from_move_only_type_with_operator_PyObject {
+
+// Reduced from
+// https://github.com/pytorch/pytorch/blob/279634f384662b7c3a9f8bf7ccc3a6afd2f05657/torch/csrc/utils/object_ptr.h
+struct operator_ncnst {
+    operator_ncnst() = default;
+    operator_ncnst(operator_ncnst &&) = default;
+    operator PyObject *() /* */ { return Py_None; } // NOLINT(google-explicit-constructor)
+};
+
+struct operator_const {
+    operator_const() = default;
+    operator_const(operator_const &&) = default;
+    operator PyObject *() const { return Py_None; } // NOLINT(google-explicit-constructor)
+};
+
+bool from_ncnst() {
+    operator_ncnst obj;
+    auto h = py::handle(obj);  // Critical part of test: does this compile?
+    return h.ptr() == Py_None; // Just something.
+}
+
+bool from_const() {
+    operator_const obj;
+    auto h = py::handle(obj);  // Critical part of test: does this compile?
+    return h.ptr() == Py_None; // Just something.
+}
+
+void m_defs(py::module_ &m) {
+    m.def("handle_from_move_only_type_with_operator_PyObject_ncnst", from_ncnst);
+    m.def("handle_from_move_only_type_with_operator_PyObject_const", from_const);
+}
+
+} // namespace handle_from_move_only_type_with_operator_PyObject
+
 TEST_SUBMODULE(pytypes, m) {
+    handle_from_move_only_type_with_operator_PyObject::m_defs(m);
+
     // test_bool
     m.def("get_bool", [] { return py::bool_(false); });
     // test_int
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 3e9d51a27c..7a0a8b4aba 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -9,6 +9,11 @@
 from pybind11_tests import pytypes as m
 
 
+def test_handle_from_move_only_type_with_operator_PyObject():  # noqa: N802
+    assert m.handle_from_move_only_type_with_operator_PyObject_ncnst()
+    assert m.handle_from_move_only_type_with_operator_PyObject_const()
+
+
 def test_bool(doc):
     assert doc(m.get_bool) == "get_bool() -> bool"
 

From 87f64c4321e01f3290dc925e59ce38c20ff1924b Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 15 Jul 2022 13:45:16 -0500
Subject: [PATCH 428/638] docs: update changelog for 2.10.0 (#4066)

---
 docs/changelog.rst | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 9d0f217ad4..b926b27afa 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -9,14 +9,13 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 Changes will be added here periodically from the "Suggested changelog entry"
 block in pull request descriptions.
 
-IN DEVELOPMENT
---------------
+Version 2.10.0 (Jul 15, 2022)
+-----------------------------
 
 Removed support for Python 2.7, Python 3.5, and MSVC 2015. Support for MSVC
 2017 is limited due to availability of CI runners; we highly recommend MSVC
 2019 or 2022 be used. Initial support added for Python 3.11.
 
-
 New features:
 
 * ``py::anyset`` & ``py::frozenset`` were added, with copying (cast) to
@@ -70,6 +69,9 @@ Changes:
   requiring ``NDEBUG``, allowing use with release builds if desired.
   `#3913 <https://github.com/pybind/pybind11/pull/3913>`_
 
+* Implicit conversion of the literal ``0`` to ``pybind11::handle`` is now disabled.
+  `#4008 <https://github.com/pybind/pybind11/pull/4008>`_
+
 
 Bug fixes:
 
@@ -98,6 +100,14 @@ Bug fixes:
 * Fix cast from pytype rvalue to another pytype.
   `#3949 <https://github.com/pybind/pybind11/pull/3949>`_
 
+* Ensure proper behavior when garbage collecting classes with dynamic attributes in Python >=3.9.
+  `#4051 <https://github.com/pybind/pybind11/pull/4051>`_
+
+* A couple long-standing ``PYBIND11_NAMESPACE``
+  ``__attribute__((visibility("hidden")))`` inconsistencies are now fixed
+  (affects only unusual environments).
+  `#4043 <https://github.com/pybind/pybind11/pull/4043>`_
+
 * ``pybind11::detail::get_internals()`` is now resilient to in-flight Python
   exceptions.
   `#3981 <https://github.com/pybind/pybind11/pull/3981>`_
@@ -147,6 +157,9 @@ Performance and style:
 * Optimize c++ to python function casting by using the rvalue caster.
   `#3966 <https://github.com/pybind/pybind11/pull/3966>`_
 
+* Optimize Eigen sparse matrix casting by removing unnecessary temporary.
+  `#4064 <https://github.com/pybind/pybind11/pull/4064>`_
+
 * Avoid potential implicit copy/assignment constructors causing double free in
   ``strdup_gaurd``.
   `#3905 <https://github.com/pybind/pybind11/pull/3905>`_
@@ -182,6 +195,9 @@ Build system improvements:
 
 Backend and tidying up:
 
+* New theme for the documentation.
+  `#3109 <https://github.com/pybind/pybind11/pull/3109>`_
+
 * Remove idioms in code comments.  Use more inclusive language.
   `#3809 <https://github.com/pybind/pybind11/pull/3809>`_
 

From aa304c9c7d725ffb9d10af08a3b34cb372307020 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 15 Jul 2022 15:47:47 -0500
Subject: [PATCH 429/638] chore: preapre for 2.10.0 release (#4068)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 include/pybind11/detail/common.h | 4 ++--
 pybind11/_version.py             | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index e52507a9e8..1da323f317 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 10
-#define PYBIND11_VERSION_PATCH 0.dev1
+#define PYBIND11_VERSION_PATCH 0
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020A00D1
+#define PYBIND11_VERSION_HEX 0x020A0000
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index aee3b1c5b2..b78d5963d5 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.10.0.dev1"
+__version__ = "2.10.0"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 8d82f298871c8222a922d0c8992a200012750659 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 15 Jul 2022 21:40:33 -0500
Subject: [PATCH 430/638] chore: back to work

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst               | 7 +++++++
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index b926b27afa..9c8ff423f4 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -9,6 +9,13 @@ Starting with version 1.8.0, pybind11 releases use a `semantic versioning
 Changes will be added here periodically from the "Suggested changelog entry"
 block in pull request descriptions.
 
+
+
+IN DEVELOPMENT
+--------------
+
+Changes will be summarized here periodically.
+
 Version 2.10.0 (Jul 15, 2022)
 -----------------------------
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1da323f317..05370108fb 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 10
-#define PYBIND11_VERSION_PATCH 0
+#define PYBIND11_VERSION_MINOR 11
+#define PYBIND11_VERSION_PATCH 0.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020A0000
+#define PYBIND11_VERSION_HEX 0x020B00D1
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
diff --git a/pybind11/_version.py b/pybind11/_version.py
index b78d5963d5..1cb51fc5c2 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.10.0"
+__version__ = "2.11.0.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 5116a629e9819aeb6d142e7d94c1feb365adae98 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 15 Jul 2022 21:03:51 -0500
Subject: [PATCH 431/638] fix(spelling): PYTHON_VERSIONS

---
 noxfile.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/noxfile.py b/noxfile.py
index fe36d70fe0..2639cdd3aa 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -5,7 +5,7 @@
 nox.needs_version = ">=2022.1.7"
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERISONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "pypy3.7", "pypy3.8"]
+PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "pypy3.7", "pypy3.8"]
 
 if os.environ.get("CI", None):
     nox.options.error_on_missing_interpreters = True
@@ -20,7 +20,7 @@ def lint(session: nox.Session) -> None:
     session.run("pre-commit", "run", "-a")
 
 
-@nox.session(python=PYTHON_VERISONS)
+@nox.session(python=PYTHON_VERSIONS)
 def tests(session: nox.Session) -> None:
     """
     Run the tests (requires a compiler).

From 59f03ee389c283cde65bd800c8f32ea690daf3fd Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 15 Jul 2022 21:43:27 -0500
Subject: [PATCH 432/638] tests: include pypy3.9 in nox if present

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 noxfile.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/noxfile.py b/noxfile.py
index 2639cdd3aa..7be1f25440 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -5,7 +5,17 @@
 nox.needs_version = ">=2022.1.7"
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "pypy3.7", "pypy3.8"]
+PYTHON_VERSIONS = [
+    "3.6",
+    "3.7",
+    "3.8",
+    "3.9",
+    "3.10",
+    "3.11",
+    "pypy3.7",
+    "pypy3.8",
+    "pypy3.9",
+]
 
 if os.environ.get("CI", None):
     nox.options.error_on_missing_interpreters = True

From ef7d971e036e4675ca266b2c990f0fd65c99e360 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 18 Jul 2022 19:39:10 -0500
Subject: [PATCH 433/638] [pre-commit.ci] pre-commit autoupdate (#4082)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/hadialqattan/pycln: v2.0.1 → v2.0.4](https://github.com/hadialqattan/pycln/compare/v2.0.1...v2.0.4)
- [github.com/PyCQA/pylint: v2.14.4 → v2.14.5](https://github.com/PyCQA/pylint/compare/v2.14.4...v2.14.5)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index ba9955a316..cc0df85f3f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v2.0.1"
+  rev: "v2.0.4"
   hooks:
   - id: pycln
     stages: [manual]
@@ -107,7 +107,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.14.4"
+  rev: "v2.14.5"
   hooks:
   - id: pylint
     files: ^pybind11

From f47f1edfe8a4842e2a723f024aae19d70ed426aa Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 20 Jul 2022 11:42:24 -0400
Subject: [PATCH 434/638] Fix #3812 and fix const of inplace assignments
 (#4065)

* Fix #3812 and fix const of inplace assignments

* Fix missing tests

* Revert operator overloading changes

* calculate answer first for tests

* Simplify tests

* Add more tests

* Add a couple more tests

* Add test_inplace_lshift, test_inplace_rshift for completeness.

* Update tests

* Shortcircuit on self assigment and address reviewer comment

* broaden skip for self assignment

* One more reviewer comment

* Document opt behavior and make consistent

* Revert unnecessary change

* Clarify comment

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/pytypes.h | 74 +++++++++++++++++++++++++-------------
 tests/test_pytypes.cpp     | 34 ++++++++++++++++++
 tests/test_pytypes.py      | 72 +++++++++++++++++++++++++++++++++++++
 3 files changed, 156 insertions(+), 24 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 339b0961eb..ad5edfed9f 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -155,23 +155,23 @@ class object_api : public pyobject_tag {
     object operator-() const;
     object operator~() const;
     object operator+(object_api const &other) const;
-    object operator+=(object_api const &other) const;
+    object operator+=(object_api const &other);
     object operator-(object_api const &other) const;
-    object operator-=(object_api const &other) const;
+    object operator-=(object_api const &other);
     object operator*(object_api const &other) const;
-    object operator*=(object_api const &other) const;
+    object operator*=(object_api const &other);
     object operator/(object_api const &other) const;
-    object operator/=(object_api const &other) const;
+    object operator/=(object_api const &other);
     object operator|(object_api const &other) const;
-    object operator|=(object_api const &other) const;
+    object operator|=(object_api const &other);
     object operator&(object_api const &other) const;
-    object operator&=(object_api const &other) const;
+    object operator&=(object_api const &other);
     object operator^(object_api const &other) const;
-    object operator^=(object_api const &other) const;
+    object operator^=(object_api const &other);
     object operator<<(object_api const &other) const;
-    object operator<<=(object_api const &other) const;
+    object operator<<=(object_api const &other);
     object operator>>(object_api const &other) const;
-    object operator>>=(object_api const &other) const;
+    object operator>>=(object_api const &other);
 
     PYBIND11_DEPRECATED("Use py::str(obj) instead")
     pybind11::str str() const;
@@ -334,12 +334,15 @@ class object : public handle {
     }
 
     object &operator=(const object &other) {
-        other.inc_ref();
-        // Use temporary variable to ensure `*this` remains valid while
-        // `Py_XDECREF` executes, in case `*this` is accessible from Python.
-        handle temp(m_ptr);
-        m_ptr = other.m_ptr;
-        temp.dec_ref();
+        // Skip inc_ref and dec_ref if both objects are the same
+        if (!this->is(other)) {
+            other.inc_ref();
+            // Use temporary variable to ensure `*this` remains valid while
+            // `Py_XDECREF` executes, in case `*this` is accessible from Python.
+            handle temp(m_ptr);
+            m_ptr = other.m_ptr;
+            temp.dec_ref();
+        }
         return *this;
     }
 
@@ -353,6 +356,20 @@ class object : public handle {
         return *this;
     }
 
+#define PYBIND11_INPLACE_OP(iop)                                                                  \
+    object iop(object_api const &other) { return operator=(handle::iop(other)); }
+
+    PYBIND11_INPLACE_OP(operator+=)
+    PYBIND11_INPLACE_OP(operator-=)
+    PYBIND11_INPLACE_OP(operator*=)
+    PYBIND11_INPLACE_OP(operator/=)
+    PYBIND11_INPLACE_OP(operator|=)
+    PYBIND11_INPLACE_OP(operator&=)
+    PYBIND11_INPLACE_OP(operator^=)
+    PYBIND11_INPLACE_OP(operator<<=)
+    PYBIND11_INPLACE_OP(operator>>=)
+#undef PYBIND11_INPLACE_OP
+
     // Calling cast() on an object lvalue just copies (via handle::cast)
     template <typename T>
     T cast() const &;
@@ -2364,26 +2381,35 @@ bool object_api<D>::rich_compare(object_api const &other, int value) const {
         return result;                                                                            \
     }
 
+#define PYBIND11_MATH_OPERATOR_BINARY_INPLACE(iop, fn)                                            \
+    template <typename D>                                                                         \
+    object object_api<D>::iop(object_api const &other) {                                          \
+        object result = reinterpret_steal<object>(fn(derived().ptr(), other.derived().ptr()));    \
+        if (!result.ptr())                                                                        \
+            throw error_already_set();                                                            \
+        return result;                                                                            \
+    }
+
 PYBIND11_MATH_OPERATOR_UNARY(operator~, PyNumber_Invert)
 PYBIND11_MATH_OPERATOR_UNARY(operator-, PyNumber_Negative)
 PYBIND11_MATH_OPERATOR_BINARY(operator+, PyNumber_Add)
-PYBIND11_MATH_OPERATOR_BINARY(operator+=, PyNumber_InPlaceAdd)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator+=, PyNumber_InPlaceAdd)
 PYBIND11_MATH_OPERATOR_BINARY(operator-, PyNumber_Subtract)
-PYBIND11_MATH_OPERATOR_BINARY(operator-=, PyNumber_InPlaceSubtract)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator-=, PyNumber_InPlaceSubtract)
 PYBIND11_MATH_OPERATOR_BINARY(operator*, PyNumber_Multiply)
-PYBIND11_MATH_OPERATOR_BINARY(operator*=, PyNumber_InPlaceMultiply)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator*=, PyNumber_InPlaceMultiply)
 PYBIND11_MATH_OPERATOR_BINARY(operator/, PyNumber_TrueDivide)
-PYBIND11_MATH_OPERATOR_BINARY(operator/=, PyNumber_InPlaceTrueDivide)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator/=, PyNumber_InPlaceTrueDivide)
 PYBIND11_MATH_OPERATOR_BINARY(operator|, PyNumber_Or)
-PYBIND11_MATH_OPERATOR_BINARY(operator|=, PyNumber_InPlaceOr)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator|=, PyNumber_InPlaceOr)
 PYBIND11_MATH_OPERATOR_BINARY(operator&, PyNumber_And)
-PYBIND11_MATH_OPERATOR_BINARY(operator&=, PyNumber_InPlaceAnd)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator&=, PyNumber_InPlaceAnd)
 PYBIND11_MATH_OPERATOR_BINARY(operator^, PyNumber_Xor)
-PYBIND11_MATH_OPERATOR_BINARY(operator^=, PyNumber_InPlaceXor)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator^=, PyNumber_InPlaceXor)
 PYBIND11_MATH_OPERATOR_BINARY(operator<<, PyNumber_Lshift)
-PYBIND11_MATH_OPERATOR_BINARY(operator<<=, PyNumber_InPlaceLshift)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator<<=, PyNumber_InPlaceLshift)
 PYBIND11_MATH_OPERATOR_BINARY(operator>>, PyNumber_Rshift)
-PYBIND11_MATH_OPERATOR_BINARY(operator>>=, PyNumber_InPlaceRshift)
+PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator>>=, PyNumber_InPlaceRshift)
 
 #undef PYBIND11_MATH_OPERATOR_UNARY
 #undef PYBIND11_MATH_OPERATOR_BINARY
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index f532e26085..81387fd9f5 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -756,4 +756,38 @@ TEST_SUBMODULE(pytypes, m) {
         }
         return o;
     });
+
+    // testing immutable object augmented assignment: #issue 3812
+    m.def("inplace_append", [](py::object &a, const py::object &b) {
+        a += b;
+        return a;
+    });
+    m.def("inplace_subtract", [](py::object &a, const py::object &b) {
+        a -= b;
+        return a;
+    });
+    m.def("inplace_multiply", [](py::object &a, const py::object &b) {
+        a *= b;
+        return a;
+    });
+    m.def("inplace_divide", [](py::object &a, const py::object &b) {
+        a /= b;
+        return a;
+    });
+    m.def("inplace_or", [](py::object &a, const py::object &b) {
+        a |= b;
+        return a;
+    });
+    m.def("inplace_and", [](py::object &a, const py::object &b) {
+        a &= b;
+        return a;
+    });
+    m.def("inplace_lshift", [](py::object &a, const py::object &b) {
+        a <<= b;
+        return a;
+    });
+    m.def("inplace_rshift", [](py::object &a, const py::object &b) {
+        a >>= b;
+        return a;
+    });
 }
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 7a0a8b4aba..bde8317386 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -739,3 +739,75 @@ def test_populate_obj_str_attrs():
     new_attrs = {k: v for k, v in new_o.__dict__.items() if not k.startswith("_")}
     assert all(isinstance(v, str) for v in new_attrs.values())
     assert len(new_attrs) == pop
+
+
+@pytest.mark.parametrize(
+    "a,b", [("foo", "bar"), (1, 2), (1.0, 2.0), (list(range(3)), list(range(3, 6)))]
+)
+def test_inplace_append(a, b):
+    expected = a + b
+    assert m.inplace_append(a, b) == expected
+
+
+@pytest.mark.parametrize("a,b", [(3, 2), (3.0, 2.0), (set(range(3)), set(range(2)))])
+def test_inplace_subtract(a, b):
+    expected = a - b
+    assert m.inplace_subtract(a, b) == expected
+
+
+@pytest.mark.parametrize("a,b", [(3, 2), (3.0, 2.0), ([1], 3)])
+def test_inplace_multiply(a, b):
+    expected = a * b
+    assert m.inplace_multiply(a, b) == expected
+
+
+@pytest.mark.parametrize("a,b", [(6, 3), (6.0, 3.0)])
+def test_inplace_divide(a, b):
+    expected = a / b
+    assert m.inplace_divide(a, b) == expected
+
+
+@pytest.mark.parametrize(
+    "a,b",
+    [
+        (False, True),
+        (
+            set(),
+            {
+                1,
+            },
+        ),
+    ],
+)
+def test_inplace_or(a, b):
+    expected = a | b
+    assert m.inplace_or(a, b) == expected
+
+
+@pytest.mark.parametrize(
+    "a,b",
+    [
+        (True, False),
+        (
+            {1, 2, 3},
+            {
+                1,
+            },
+        ),
+    ],
+)
+def test_inplace_and(a, b):
+    expected = a & b
+    assert m.inplace_and(a, b) == expected
+
+
+@pytest.mark.parametrize("a,b", [(8, 1), (-3, 2)])
+def test_inplace_lshift(a, b):
+    expected = a << b
+    assert m.inplace_lshift(a, b) == expected
+
+
+@pytest.mark.parametrize("a,b", [(8, 1), (-2, 2)])
+def test_inplace_rshift(a, b):
+    expected = a >> b
+    assert m.inplace_rshift(a, b) == expected

From 42b54507eaa23b265e8de144aeacb2455a837486 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 20 Jul 2022 12:02:20 -0400
Subject: [PATCH 435/638] chore: use explicit defaulting in pyobject macros
 (#4017)

* Use equals default in pyobject macros

* Remove extra semicolon

* Update clang-tidy equals-default rule to not ignore macros

* Fix formatting

* One last formatting change
---
 .clang-tidy                | 2 ++
 include/pybind11/numpy.h   | 2 +-
 include/pybind11/pytypes.h | 4 ++--
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index d945a4a27d..23018386c1 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -63,6 +63,8 @@ Checks: |
   -bugprone-unused-raii,
 
 CheckOptions:
+- key:             modernize-use-equals-default.IgnoreMacros
+  value:           false
 - key:             performance-for-range-copy.WarnOnAllAutoCopies
   value:           true
 - key:             performance-inefficient-string-concatenation.StrictMode
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 0291b02d0b..4f82f1ec3f 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -537,7 +537,7 @@ PYBIND11_NAMESPACE_END(detail)
 
 class dtype : public object {
 public:
-    PYBIND11_OBJECT_DEFAULT(dtype, object, detail::npy_api::get().PyArrayDescr_Check_);
+    PYBIND11_OBJECT_DEFAULT(dtype, object, detail::npy_api::get().PyArrayDescr_Check_)
 
     explicit dtype(const buffer_info &info) {
         dtype descr(_dtype_from_pep3118()(pybind11::str(info.format)));
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index ad5edfed9f..7a731e22a5 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1283,7 +1283,7 @@ public:
 
 #define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun)                           \
     PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                       \
-    Name() : Parent() {}
+    Name() = default;
 
 #define PYBIND11_OBJECT_CHECK_FAILED(Name, o_ptr)                                                 \
     ::pybind11::type_error("Object of type '"                                                     \
@@ -1306,7 +1306,7 @@ public:
 
 #define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun)                                           \
     PYBIND11_OBJECT(Name, Parent, CheckFun)                                                       \
-    Name() : Parent() {}
+    Name() = default;
 
 /// \addtogroup pytypes
 /// @{

From cb35a3c1432a5e0441aab4a62593fed82664abed Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 21 Jul 2022 06:38:00 -0700
Subject: [PATCH 436/638] For PyPy only, re-enable old behavior (runs the risk
 of masking bugs) (#4079)

* For PyPy only, re-enable old behavior (likely to mask bugs), to avoid segfault with unknown root cause.

Change prompted by https://github.com/pybind/pybind11/issues/4075

* Undo the change in tests/test_exceptions.py

I turns out (I forgot) that PyPy segfaults in `test_flaky_exception_failure_point_init` already before the `MISMATCH` code path is reached:

https://github.com/pybind/pybind11/runs/7383663596

```
RPython traceback:
test_exceptions.py .......X.........Error in cpyext, CPython compatibility layer:
  File "pypy_module_cpyext.c", line 14052, in wrapper_second_level__star_3_1
  File "pypy_module_cpyext_1.c", line 35750, in not_supposed_to_fail
Fatal Python error: Segmentation fault
Stack (most recent call first, approximate line numbers):
  File "/home/runner/work/pybind11/pybind11/tests/test_exceptions.py", line 306 in test_flaky_exception_failure_point_init
The function PyErr_NormalizeException was not supposed to fail
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/python.py", line 185 in pytest_pyfunc_call
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_callers.py", line 9 in _multicall
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_manager.py", line 77 in _hookexec
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_hooks.py", line 244 in __call__
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/python.py", line 1716 in runtest
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 159 in pytest_runtest_call
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_callers.py", line 9 in _multicall
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_manager.py", line 77 in _hookexec
Fatal error in cpyext, CPython compatibility layer, calling PyErr_NormalizeException
Either report a bug or consider not using this particular extension
<SystemError object at 0x7fcc8cea6868>
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_hooks.py", line 244 in __call__
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 261 in <lambda>
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 317 in from_call
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 246 in call_runtest_hook
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 218 in call_and_report
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 118 in runtestprotocol
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/runner.py", line 110 in pytest_runtest_protocol
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_callers.py", line 9 in _multicall
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_manager.py", line 77 in _hookexec
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_hooks.py", line 244 in __call__
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/main.py", line 335 in pytest_runtestloop
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_callers.py", line 9 in _multicall
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_manager.py", line 77 in _hookexec
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_hooks.py", line 244 in __call__
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/main.py", line 318 in _main
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/main.py", line 255 in wrap_session
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/main.py", line 314 in pytest_cmdline_main
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_callers.py", line 9 in _multicall
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_manager.py", line 77 in _hookexec
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pluggy/_hooks.py", line 244 in __call__
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/config/__init__.py", line 133 in main
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/_pytest/config/__init__.py", line 181 in console_main
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/site-packages/pytest/__main__.py", line 1 in <module>
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/lib-python/3/runpy.py", line 62 in _run_code
  File "/opt/hostedtoolcache/PyPy/3.7.13/x64/lib-python/3/runpy.py", line 170 in _run_module_as_main
  File "<builtin>/app_main.py", line 109 in run_toplevel
  File "<builtin>/app_main.py", line 652 in run_command_line
  File "<builtin>/app_main.py", line 996 in entry_point
Segmentation fault (core dumped)
```

* Add test_pypy_oserror_normalization

* Disable new `PYPY_VERSION` `#if`, to verify that the new test actually fails.

* Restore PYPY_VERSION workaround and update comment to reflect what was learned.

* [ci skip] Fix trivial oversight in comment.
---
 include/pybind11/pytypes.h |  7 +++++++
 tests/test_exceptions.cpp  | 10 ++++++++++
 tests/test_exceptions.py   |  6 ++++++
 3 files changed, 23 insertions(+)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 7a731e22a5..a837fb9fa6 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -473,6 +473,12 @@ struct error_fetch_and_normalize {
                           + " failed to obtain the name "
                             "of the normalized active exception type.");
         }
+#if defined(PYPY_VERSION)
+        // This behavior runs the risk of masking errors in the error handling, but avoids a
+        // conflict with PyPy, which relies on the normalization here to change OSError to
+        // FileNotFoundError (https://github.com/pybind/pybind11/issues/4075).
+        m_lazy_error_string = exc_type_name_norm;
+#else
         if (exc_type_name_norm != m_lazy_error_string) {
             std::string msg = std::string(called)
                               + ": MISMATCH of original and normalized "
@@ -484,6 +490,7 @@ struct error_fetch_and_normalize {
             msg += ": " + format_value_and_trace();
             pybind11_fail(msg);
         }
+#endif
     }
 
     error_fetch_and_normalize(const error_fetch_and_normalize &) = delete;
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 3ec999d1dc..3583f22a50 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -334,4 +334,14 @@ TEST_SUBMODULE(exceptions, m) {
             e.restore();
         }
     });
+
+    // https://github.com/pybind/pybind11/issues/4075
+    m.def("test_pypy_oserror_normalization", []() {
+        try {
+            py::module_::import("io").attr("open")("this_filename_must_not_exist", "r");
+        } catch (const py::error_already_set &e) {
+            return py::str(e.what()); // str must be built before e goes out of scope.
+        }
+        return py::str("UNEXPECTED");
+    });
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index a5984a142f..5e3beeedbc 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -360,3 +360,9 @@ def test_error_already_set_double_restore():
         "Internal error: pybind11::detail::error_fetch_and_normalize::restore()"
         " called a second time. ORIGINAL ERROR: ValueError: Random error."
     )
+
+
+def test_pypy_oserror_normalization():
+    # https://github.com/pybind/pybind11/issues/4075
+    what = m.test_pypy_oserror_normalization()
+    assert "this_filename_must_not_exist" in what

From 9a2963734de309a6d3f4ffb3e43bb56713a7ccae Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 21 Jul 2022 06:40:34 -0700
Subject: [PATCH 437/638] More systematic gcc & clang coverage (#4083)

* More systematic gcc coverage, based on https://github.com/pybind/pybind11/pull/4074#issuecomment-1188385580

* Fix complete fail.

* Resolve GCC 11 & 12 "redundant move in return statement" warnings.

* Also add clang 11, 12, 13 (to gather info for warning suppressions).

* Add & use `PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING`
---
 .github/workflows/ci.yml           | 20 +++++++++++++-------
 include/pybind11/detail/common.h   | 18 ++++++++++++++++++
 include/pybind11/numpy.h           | 11 +++++++++--
 tests/test_kwargs_and_defaults.cpp | 11 ++++++++++-
 4 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 412282a4f2..5a24ad6abd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -281,6 +281,12 @@ jobs:
             std: 20
           - clang: 10
             std: 17
+          - clang: 11
+            std: 20
+          - clang: 12
+            std: 20
+          - clang: 13
+            std: 20
           - clang: 14
             std: 20
 
@@ -437,14 +443,14 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        gcc:
-          - 7
-          - latest
-        std:
-          - 11
         include:
-          - gcc: 10
-            std: 20
+          - { gcc: 7, std: 11 }
+          - { gcc: 7, std: 17 }
+          - { gcc: 8, std: 14 }
+          - { gcc: 8, std: 17 }
+          - { gcc: 10, std: 17 }
+          - { gcc: 11, std: 20 }
+          - { gcc: 12, std: 20 }
 
     name: "🐍 3 • GCC ${{ matrix.gcc }} • C++${{ matrix.std }}• x64"
     container: "gcc:${{ matrix.gcc }}"
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 05370108fb..9e6947daa3 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -1158,6 +1158,24 @@ constexpr inline bool silence_msvc_c4127(bool cond) { return cond; }
 #    define PYBIND11_SILENCE_MSVC_C4127(...) __VA_ARGS__
 #endif
 
+#if defined(__clang__)                                                                            \
+    && (defined(__apple_build_version__) /* AppleClang 13.0.0.13000029 was the only data point    \
+                                            available. */                                         \
+        || (__clang_major__ >= 7                                                                  \
+            && __clang_major__ <= 12) /* Clang 3, 5, 13, 14, 15 do not generate the warning. */   \
+    )
+#    define PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
+// Example:
+// tests/test_kwargs_and_defaults.cpp:46:68: error: local variable 'args' will be copied despite
+// being returned by name [-Werror,-Wreturn-std-move]
+//     m.def("args_function", [](py::args args) -> py::tuple { return args; });
+//                                                                    ^~~~
+// test_kwargs_and_defaults.cpp:46:68: note: call 'std::move' explicitly to avoid copying
+//     m.def("args_function", [](py::args args) -> py::tuple { return args; });
+//                                                                    ^~~~
+//                                                                    std::move(args)
+#endif
+
 // Pybind offers detailed error messages by default for all builts that are debug (through the
 // negation of ndebug). This can also be manually enabled by users, for any builds, through
 // defining PYBIND11_DETAILED_ERROR_MESSAGES.
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 4f82f1ec3f..56e5edc5a4 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1865,9 +1865,13 @@ struct vectorize_helper {
         }
 
         auto result = returned_array::create(trivial, shape);
+#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
+#    pragma clang diagnostic push
+#    pragma clang diagnostic ignored "-Wreturn-std-move"
+#endif
 
         if (size == 0) {
-            return std::move(result);
+            return result;
         }
 
         /* Call the function */
@@ -1878,7 +1882,10 @@ struct vectorize_helper {
             apply_trivial(buffers, params, mutable_data, size, i_seq, vi_seq, bi_seq);
         }
 
-        return std::move(result);
+        return result;
+#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
+#    pragma clang diagnostic pop
+#endif
     }
 
     template <size_t... Index, size_t... VIndex, size_t... BIndex>
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 7418afefb4..2f3cabaf0f 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -43,7 +43,16 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a = 0);
 
     // test_args_and_kwargs
-    m.def("args_function", [](py::args args) -> py::tuple { return std::move(args); });
+    m.def("args_function", [](py::args args) -> py::tuple {
+#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
+#    pragma clang diagnostic push
+#    pragma clang diagnostic ignored "-Wreturn-std-move"
+#endif
+        return args;
+#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
+#    pragma clang diagnostic pop
+#endif
+    });
     m.def("args_kwargs_function", [](const py::args &args, const py::kwargs &kwargs) {
         return py::make_tuple(args, kwargs);
     });

From b07975f492c2eed0409a18353fa23c9969e83e42 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Fri, 22 Jul 2022 11:52:01 -0400
Subject: [PATCH 438/638] Fix missing undef in pytypes (#4087)

---
 include/pybind11/pytypes.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index a837fb9fa6..6ba1f5f201 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -2420,6 +2420,7 @@ PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator>>=, PyNumber_InPlaceRshift)
 
 #undef PYBIND11_MATH_OPERATOR_UNARY
 #undef PYBIND11_MATH_OPERATOR_BINARY
+#undef PYBIND11_MATH_OPERATOR_BINARY_INPLACE
 
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

From d70f54b073d9961a4b9eebd151e721a1172ecada Mon Sep 17 00:00:00 2001
From: Hyunwook Choi <danichoi737@gmail.com>
Date: Thu, 28 Jul 2022 02:41:57 +0900
Subject: [PATCH 439/638] docs: Missing semicolons (#4094)

Add semicolons to Memory view sample code
---
 docs/advanced/pycpp/numpy.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index b6ef019ed0..07c969305d 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -433,7 +433,7 @@ following:
             { 2, 4 },                                  // shape (rows, cols)
             { sizeof(uint8_t) * 4, sizeof(uint8_t) }   // strides in bytes
         );
-    })
+    });
 
 This approach is meant for providing a ``memoryview`` for a C/C++ buffer not
 managed by Python. The user is responsible for managing the lifetime of the
@@ -449,7 +449,7 @@ We can also use ``memoryview::from_memory`` for a simple 1D contiguous buffer:
             buffer,               // buffer pointer
             sizeof(uint8_t) * 8   // buffer size
         );
-    })
+    });
 
 .. versionchanged:: 2.6
     ``memoryview::from_memory`` added.

From 1e3400b6742288429f2069aaf5febf92d0662dae Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 28 Jul 2022 21:37:47 -0400
Subject: [PATCH 440/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.5.0 to 1.5.1 (#4091)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.5.0 to 1.5.1.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.5.0...v1.5.1)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 2c16735e1e..f03a397019 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.5.0
+      uses: pypa/gh-action-pypi-publish@v1.5.1
       with:
         password: ${{ secrets.pypi_password }}
         packages_dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.5.0
+      uses: pypa/gh-action-pypi-publish@v1.5.1
       with:
         password: ${{ secrets.pypi_password_global }}
         packages_dir: global/

From 3665530264bbfeb9ec7623635d7cc644a70116b3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 1 Aug 2022 06:18:48 -0700
Subject: [PATCH 441/638] Add `-DPYBIND11_WERROR=ON` to mingw cmake commands
 (#4073)

* Add `-DPYBIND11_WERROR=ON` to mingw cmake commands (and `-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON`).

* Using no-destructor idiom to side-step overzealous MINGW warning.

* Add __MINGW32__ pragma GCC diagnostic ignored in eigen.h

* Add another no-destructor workaround.

* Temporarily add -k (keep-going) flags to hopefully speed up finding all warnings.

* Revert "Temporarily add -k (keep-going) flags to hopefully speed up finding all warnings."

This reverts commit f36b0af8f93e9f6f16c969fb5b646e116f5eaf0f.

* Very minor shuffle to avoid MSVC warnings.

* Remove all `:BOOL` as suggested by @henryiii
---
 .github/workflows/ci.yml       |  6 +++---
 include/pybind11/eigen.h       |  5 +++++
 tests/test_builtin_casters.cpp |  9 +++++++--
 tests/test_stl.cpp             | 10 ++++++++--
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5a24ad6abd..ac6c536ced 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -911,7 +911,7 @@ jobs:
     - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DDOWNLOAD_CATCH=ON -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build
 
     - name: Build C++11
       run: cmake --build build -j 2
@@ -929,7 +929,7 @@ jobs:
       run: git clean -fdx
 
     - name: Configure C++14
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DDOWNLOAD_CATCH=ON -S . -B build2
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build2
 
     - name: Build C++14
       run: cmake --build build2 -j 2
@@ -947,7 +947,7 @@ jobs:
       run: git clean -fdx
 
     - name: Configure C++17
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DDOWNLOAD_CATCH=ON -S . -B build3
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build3
 
     - name: Build C++17
       run: cmake --build build3 -j 2
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 4d221b3d75..8316252294 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -27,6 +27,9 @@
 #    pragma warning(disable : 4127) // C4127: conditional expression is constant
 #    pragma warning(disable : 5054) // https://github.com/pybind/pybind11/pull/3741
 //       C5054: operator '&': deprecated between enumerations of different types
+#elif defined(__MINGW32__)
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
 #endif
 
 #include <Eigen/Core>
@@ -34,6 +37,8 @@
 
 #if defined(_MSC_VER)
 #    pragma warning(pop)
+#elif defined(__MINGW32__)
+#    pragma GCC diagnostic pop
 #endif
 
 // Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 6529f47d05..6ff63edfc6 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -266,9 +266,14 @@ TEST_SUBMODULE(builtin_casters, m) {
     });
     m.def("lvalue_nested", []() -> const decltype(lvnested) & { return lvnested; });
 
-    static std::pair<int, std::string> int_string_pair{2, "items"};
     m.def(
-        "int_string_pair", []() { return &int_string_pair; }, py::return_value_policy::reference);
+        "int_string_pair",
+        []() {
+            // Using no-destructor idiom to side-step warnings from overzealous compilers.
+            static auto *int_string_pair = new std::pair<int, std::string>{2, "items"};
+            return int_string_pair;
+        },
+        py::return_value_policy::reference);
 
     // test_builtins_cast_return_none
     m.def("return_none_string", []() -> std::string * { return nullptr; });
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 38d32fda93..dcc92c3f0d 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -176,9 +176,14 @@ TEST_SUBMODULE(stl, m) {
     m.def("load_bool_vector",
           [](const std::vector<bool> &v) { return v.at(0) == true && v.at(1) == false; });
     // Unnumbered regression (caused by #936): pointers to stl containers aren't castable
-    static std::vector<RValueCaster> lvv{2};
     m.def(
-        "cast_ptr_vector", []() { return &lvv; }, py::return_value_policy::reference);
+        "cast_ptr_vector",
+        []() {
+            // Using no-destructor idiom to side-step warnings from overzealous compilers.
+            static auto *v = new std::vector<RValueCaster>{2};
+            return v;
+        },
+        py::return_value_policy::reference);
 
     // test_deque
     m.def("cast_deque", []() { return std::deque<int>{1}; });
@@ -237,6 +242,7 @@ TEST_SUBMODULE(stl, m) {
     lvn["b"].emplace_back();        // add a list
     lvn["b"].back().emplace_back(); // add an array
     lvn["b"].back().emplace_back(); // add another array
+    static std::vector<RValueCaster> lvv{2};
     m.def("cast_lv_vector", []() -> const decltype(lvv) & { return lvv; });
     m.def("cast_lv_array", []() -> const decltype(lva) & { return lva; });
     m.def("cast_lv_map", []() -> const decltype(lvm) & { return lvm; });

From aa953710c180fb9da5178c47b4dadcad945119f7 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 1 Aug 2022 12:18:42 -0400
Subject: [PATCH 442/638] [pre-commit.ci] pre-commit autoupdate (#4090)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.37.1 → v2.37.2](https://github.com/asottile/pyupgrade/compare/v2.37.1...v2.37.2)
- [github.com/pre-commit/mirrors-mypy: v0.961 → v0.971](https://github.com/pre-commit/mirrors-mypy/compare/v0.961...v0.971)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index cc0df85f3f..c2c098c5a9 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.37.1"
+  rev: "v2.37.2"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -123,7 +123,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.961"
+  rev: "v0.971"
   hooks:
   - id: mypy
     args: []

From f8e8403b858d11f3d2102e66c06178ab204fd3d6 Mon Sep 17 00:00:00 2001
From: Thomas Eding <thomaseding@users.noreply.github.com>
Date: Mon, 1 Aug 2022 11:31:31 -0700
Subject: [PATCH 443/638] Open pybind11 namespace with consistent visility.
 (#4098)

---
 docs/advanced/cast/custom.rst       |  4 ++--
 docs/advanced/cast/stl.rst          |  6 +++---
 docs/advanced/classes.rst           |  4 ++--
 docs/advanced/smart_ptrs.rst        |  2 +-
 tests/test_custom_type_casters.cpp  | 14 +++++++-------
 tests/test_smart_ptr.cpp            |  4 ++--
 tests/test_stl.cpp                  | 12 ++++++------
 tests/test_tagbased_polymorphic.cpp |  4 ++--
 8 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/docs/advanced/cast/custom.rst b/docs/advanced/cast/custom.rst
index 1df4d3e14b..8138cac619 100644
--- a/docs/advanced/cast/custom.rst
+++ b/docs/advanced/cast/custom.rst
@@ -38,7 +38,7 @@ type is explicitly allowed.
 
 .. code-block:: cpp
 
-    namespace pybind11 { namespace detail {
+    namespace PYBIND11_NAMESPACE { namespace detail {
         template <> struct type_caster<inty> {
         public:
             /**
@@ -78,7 +78,7 @@ type is explicitly allowed.
                 return PyLong_FromLong(src.long_value);
             }
         };
-    }} // namespace pybind11::detail
+    }} // namespace PYBIND11_NAMESPACE::detail
 
 .. note::
 
diff --git a/docs/advanced/cast/stl.rst b/docs/advanced/cast/stl.rst
index 109763f7aa..03d49b2950 100644
--- a/docs/advanced/cast/stl.rst
+++ b/docs/advanced/cast/stl.rst
@@ -42,7 +42,7 @@ types:
 .. code-block:: cpp
 
     // `boost::optional` as an example -- can be any `std::optional`-like container
-    namespace pybind11 { namespace detail {
+    namespace PYBIND11_NAMESPACE { namespace detail {
         template <typename T>
         struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
     }}
@@ -54,7 +54,7 @@ for custom variant types:
 .. code-block:: cpp
 
     // `boost::variant` as an example -- can be any `std::variant`-like container
-    namespace pybind11 { namespace detail {
+    namespace PYBIND11_NAMESPACE { namespace detail {
         template <typename... Ts>
         struct type_caster<boost::variant<Ts...>> : variant_caster<boost::variant<Ts...>> {};
 
@@ -66,7 +66,7 @@ for custom variant types:
                 return boost::apply_visitor(args...);
             }
         };
-    }} // namespace pybind11::detail
+    }} // namespace PYBIND11_NAMESPACE::detail
 
 The ``visit_helper`` specialization is not required if your ``name::variant`` provides
 a ``name::visit()`` function. For any other function name, the specialization must be
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 49ddf5c0b1..01a490b721 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -1228,7 +1228,7 @@ whether a downcast is safe, you can proceed by specializing the
         std::string bark() const { return sound; }
     };
 
-    namespace pybind11 {
+    namespace PYBIND11_NAMESPACE {
         template<> struct polymorphic_type_hook<Pet> {
             static const void *get(const Pet *src, const std::type_info*& type) {
                 // note that src may be nullptr
@@ -1239,7 +1239,7 @@ whether a downcast is safe, you can proceed by specializing the
                 return src;
             }
         };
-    } // namespace pybind11
+    } // namespace PYBIND11_NAMESPACE
 
 When pybind11 wants to convert a C++ pointer of type ``Base*`` to a
 Python object, it calls ``polymorphic_type_hook<Base>::get()`` to
diff --git a/docs/advanced/smart_ptrs.rst b/docs/advanced/smart_ptrs.rst
index 5a22201095..3c40ce1237 100644
--- a/docs/advanced/smart_ptrs.rst
+++ b/docs/advanced/smart_ptrs.rst
@@ -157,7 +157,7 @@ specialized:
     PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>);
 
     // Only needed if the type's `.get()` goes by another name
-    namespace pybind11 { namespace detail {
+    namespace PYBIND11_NAMESPACE { namespace detail {
         template <typename T>
         struct holder_helper<SmartPtr<T>> { // <-- specialization
             static const T *get(const SmartPtr<T> &p) { return p.getPointer(); }
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 25540e3685..b4af02a452 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -21,7 +21,7 @@ class ArgInspector2 {
 };
 class ArgAlwaysConverts {};
 
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <>
 struct type_caster<ArgInspector1> {
@@ -74,7 +74,7 @@ struct type_caster<ArgAlwaysConverts> {
     }
 };
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 
 // test_custom_caster_destruction
 class DestructionTester {
@@ -92,7 +92,7 @@ class DestructionTester {
         return *this;
     }
 };
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <>
 struct type_caster<DestructionTester> {
@@ -104,7 +104,7 @@ struct type_caster<DestructionTester> {
     }
 };
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 
 // Define type caster outside of `pybind11::detail` and then alias it.
 namespace other_lib {
@@ -112,7 +112,7 @@ struct MyType {};
 // Corrupt `py` shorthand alias for surrounding context.
 namespace py {}
 // Corrupt unqualified relative `pybind11` namespace.
-namespace pybind11 {}
+namespace PYBIND11_NAMESPACE {}
 // Correct alias.
 namespace py_ = ::pybind11;
 // Define caster. This is effectively no-op, we only ensure it compiles and we
@@ -127,12 +127,12 @@ struct my_caster {
 };
 } // namespace other_lib
 // Effectively "alias" it into correct namespace (via inheritance).
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <>
 struct type_caster<other_lib::MyType> : public other_lib::my_caster {};
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 
 TEST_SUBMODULE(custom_type_casters, m) {
     // test_custom_type_casters
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 2c23a9a197..6d9efcedce 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -266,14 +266,14 @@ struct ElementList {
 // It is always possible to construct a ref<T> from an Object* pointer without
 // possible inconsistencies, hence the 'true' argument at the end.
 // Make pybind11 aware of the non-standard getter member function
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <typename T>
 struct holder_helper<ref<T>> {
     static const T *get(const ref<T> &p) { return p.get_ptr(); }
 };
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 
 // Make pybind aware of the ref-counted wrapper type (s):
 PYBIND11_DECLARE_HOLDER_TYPE(T, ref<T>, true);
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index dcc92c3f0d..d45465d681 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -23,7 +23,7 @@
 #if defined(PYBIND11_TEST_BOOST)
 #    include <boost/optional.hpp>
 
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <typename T>
 struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
@@ -31,7 +31,7 @@ struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
 template <>
 struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 #endif
 
 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
@@ -43,7 +43,7 @@ using std::variant;
 #    define PYBIND11_TEST_VARIANT 1
 using boost::variant;
 
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <typename... Ts>
 struct type_caster<boost::variant<Ts...>> : variant_caster<boost::variant<Ts...>> {};
@@ -56,7 +56,7 @@ struct visit_helper<boost::variant> {
     }
 };
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 #endif
 
 PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
@@ -159,13 +159,13 @@ class ReferenceSensitiveOptional {
     std::vector<T> storage;
 };
 
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 namespace detail {
 template <typename T>
 struct type_caster<ReferenceSensitiveOptional<T>>
     : optional_caster<ReferenceSensitiveOptional<T>> {};
 } // namespace detail
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 
 TEST_SUBMODULE(stl, m) {
     // test_vector
diff --git a/tests/test_tagbased_polymorphic.cpp b/tests/test_tagbased_polymorphic.cpp
index 2807e86ba3..12ba6532f3 100644
--- a/tests/test_tagbased_polymorphic.cpp
+++ b/tests/test_tagbased_polymorphic.cpp
@@ -117,7 +117,7 @@ std::string Animal::name_of_kind(Kind kind) {
     return raw_name;
 }
 
-namespace pybind11 {
+namespace PYBIND11_NAMESPACE {
 template <typename itype>
 struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_base_of<Animal, itype>::value>> {
     static const void *get(const itype *src, const std::type_info *&type) {
@@ -125,7 +125,7 @@ struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_base_of<Animal,
         return src;
     }
 };
-} // namespace pybind11
+} // namespace PYBIND11_NAMESPACE
 
 TEST_SUBMODULE(tagbased_polymorphic, m) {
     py::class_<Animal>(m, "Animal").def_readonly("name", &Animal::name);

From 88a1bb926085dc2298cd7bbfc330f232362c793d Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 1 Aug 2022 15:48:44 -0400
Subject: [PATCH 444/638] chore: remove unnecessary temporary std::pair (#4103)

---
 include/pybind11/pybind11.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index d61dcd5c7e..c889dc4169 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2073,7 +2073,7 @@ struct enum_base {
                               + "\" already exists!");
         }
 
-        entries[name] = std::make_pair(value, doc);
+        entries[name] = pybind11::make_tuple(value, doc);
         m_base.attr(std::move(name)) = std::move(value);
     }
 

From ba5ccd845a2261e538df651e3d528dc1bece094d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Wed, 3 Aug 2022 11:38:07 -0400
Subject: [PATCH 445/638] [pre-commit.ci] pre-commit autoupdate (#4104)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/asottile/pyupgrade: v2.37.2 → v2.37.3](https://github.com/asottile/pyupgrade/compare/v2.37.2...v2.37.3)
- [github.com/hadialqattan/pycln: v2.0.4 → v2.1.1](https://github.com/hadialqattan/pycln/compare/v2.0.4...v2.1.1)
- [github.com/PyCQA/flake8: 4.0.1 → 5.0.2](https://github.com/PyCQA/flake8/compare/4.0.1...5.0.2)

* fix: minor touchups for flake8

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .pre-commit-config.yaml  | 6 +++---
 setup.cfg                | 2 +-
 tests/test_exceptions.py | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c2c098c5a9..e41480d054 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -32,7 +32,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.37.2"
+  rev: "v2.37.3"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -71,7 +71,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v2.0.4"
+  rev: "v2.1.1"
   hooks:
   - id: pycln
     stages: [manual]
@@ -99,7 +99,7 @@ repos:
 
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
-  rev: "4.0.1"
+  rev: "5.0.2"
   hooks:
   - id: flake8
     exclude: ^(docs/.*|tools/.*)$
diff --git a/setup.cfg b/setup.cfg
index 36fbfed4f3..9af50ea483 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -46,5 +46,5 @@ zip_safe = False
 max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
-extend-ignore = E203, E722, B950
+extend-ignore = E203, E722, B903, B950
 extend-select = B9
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 5e3beeedbc..70b6ffea95 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -185,8 +185,8 @@ def test_custom(msg):
     with pytest.raises(m.MyException5) as excinfo:
         try:
             m.throws5()
-        except m.MyException5_1:
-            raise RuntimeError("Exception error: caught child from parent")
+        except m.MyException5_1 as err:
+            raise RuntimeError("Exception error: caught child from parent") from err
     assert msg(excinfo.value) == "this is a helper-defined translated exception"
 
 

From 29f4940cd4aa4e954a16d2f20897b458e3098588 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 5 Aug 2022 08:05:40 -0700
Subject: [PATCH 446/638] Fix copy-paste oversight (#4118)

---
 .github/workflows/upstream.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index a40a6c7d78..95ff4cb83d 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -104,7 +104,7 @@ jobs:
       run: cmake --build build3 --target pytest
 
     - name: Interface test
-      run: cmake --build build2 --target test_cmake_build
+      run: cmake --build build3 --target test_cmake_build
 
     # This makes sure the setup_helpers module can build packages using
     # setuptools

From 8a4bca8216f94f64d9582997db5e7eaf2e4660b3 Mon Sep 17 00:00:00 2001
From: Daniel Dinu <daniel@danieldinu.com>
Date: Mon, 8 Aug 2022 07:01:39 -0700
Subject: [PATCH 447/638] fix(cmake): use case-insensitive CMAKE_BUILD_TYPE
 comparisons (#4078)

---
 tools/pybind11NewTools.cmake | 4 +++-
 tools/pybind11Tools.cmake    | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index abba0fe0e2..9e13daf1a1 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -233,7 +233,9 @@ function(pybind11_add_module target_name)
     endif()
   endif()
 
-  if(NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug|RelWithDebInfo)
+  # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
+  string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+  if(NOT MSVC AND NOT ${uppercase_CMAKE_BUILD_TYPE} MATCHES DEBUG|RELWITHDEBINFO)
     # Strip unnecessary sections of the binary on Linux/macOS
     pybind11_strip(${target_name})
   endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 5535e872f3..1b6045b70e 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -208,7 +208,9 @@ function(pybind11_add_module target_name)
     endif()
   endif()
 
-  if(NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug|RelWithDebInfo)
+  # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
+  string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+  if(NOT MSVC AND NOT ${uppercase_CMAKE_BUILD_TYPE} MATCHES DEBUG|RELWITHDEBINFO)
     pybind11_strip(${target_name})
   endif()
 

From 6abb7de6cd12d7a3b6d3afbdf98f3795639466a3 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 8 Aug 2022 14:28:33 -0400
Subject: [PATCH 448/638] chore: Use PyObject_GenericGetDict and
 PyObject_GenericSetDict functions (#4106)

* Try to update getset_dict APIs for 3.11

* Update API for all Python versions

* Test ifdef for forward explicit forward compat

* Fix ifdef
---
 include/pybind11/detail/class.h | 39 ++++++++++-----------------------
 1 file changed, 11 insertions(+), 28 deletions(-)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 42720f844d..a98e5e5414 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -502,31 +502,6 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass) {
     return (PyObject *) heap_type;
 }
 
-/// dynamic_attr: Support for `d = instance.__dict__`.
-extern "C" inline PyObject *pybind11_get_dict(PyObject *self, void *) {
-    PyObject *&dict = *_PyObject_GetDictPtr(self);
-    if (!dict) {
-        dict = PyDict_New();
-    }
-    Py_XINCREF(dict);
-    return dict;
-}
-
-/// dynamic_attr: Support for `instance.__dict__ = dict()`.
-extern "C" inline int pybind11_set_dict(PyObject *self, PyObject *new_dict, void *) {
-    if (!PyDict_Check(new_dict)) {
-        PyErr_Format(PyExc_TypeError,
-                     "__dict__ must be set to a dictionary, not a '%.200s'",
-                     get_fully_qualified_tp_name(Py_TYPE(new_dict)).c_str());
-        return -1;
-    }
-    PyObject *&dict = *_PyObject_GetDictPtr(self);
-    Py_INCREF(new_dict);
-    Py_CLEAR(dict);
-    dict = new_dict;
-    return 0;
-}
-
 /// dynamic_attr: Allow the garbage collector to traverse the internal instance `__dict__`.
 extern "C" inline int pybind11_traverse(PyObject *self, visitproc visit, void *arg) {
     PyObject *&dict = *_PyObject_GetDictPtr(self);
@@ -558,9 +533,17 @@ inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
     type->tp_traverse = pybind11_traverse;
     type->tp_clear = pybind11_clear;
 
-    static PyGetSetDef getset[] = {
-        {const_cast<char *>("__dict__"), pybind11_get_dict, pybind11_set_dict, nullptr, nullptr},
-        {nullptr, nullptr, nullptr, nullptr, nullptr}};
+    static PyGetSetDef getset[] = {{
+#if PY_VERSION_HEX < 0x03070000
+                                       const_cast<char *>("__dict__"),
+#else
+                                       "__dict__",
+#endif
+                                       PyObject_GenericGetDict,
+                                       PyObject_GenericSetDict,
+                                       nullptr,
+                                       nullptr},
+                                   {nullptr, nullptr, nullptr, nullptr, nullptr}};
     type->tp_getset = getset;
 }
 

From 14c84654f8674b78a4c0462f0520b8fab93bc80c Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 8 Aug 2022 21:15:43 -0400
Subject: [PATCH 449/638] [pre-commit.ci] pre-commit autoupdate (#4126)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/yesqa: v1.3.0 → v1.4.0](https://github.com/asottile/yesqa/compare/v1.3.0...v1.4.0)
- [github.com/PyCQA/flake8: 5.0.2 → 5.0.4](https://github.com/PyCQA/flake8/compare/5.0.2...5.0.4)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e41480d054..94359ab62d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -90,7 +90,7 @@ repos:
 
 # Automatically remove noqa that are not used
 - repo: https://github.com/asottile/yesqa
-  rev: "v1.3.0"
+  rev: "v1.4.0"
   hooks:
   - id: yesqa
     additional_dependencies: &flake8_dependencies
@@ -99,7 +99,7 @@ repos:
 
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
-  rev: "5.0.2"
+  rev: "5.0.4"
   hooks:
   - id: flake8
     exclude: ^(docs/.*|tools/.*)$

From 5bdd3d59becf82d77e3da81226c1f4f869bfaf64 Mon Sep 17 00:00:00 2001
From: Eli Schwartz <eschwartz93@gmail.com>
Date: Tue, 9 Aug 2022 00:02:45 -0400
Subject: [PATCH 450/638] feat(cmake): add installation support for pkg-config
 dependency detection (#4077)

* add installation support for pkg-config dependency detection

pkg-config is a buildsystem-agnostic alternative to
`pybind11Config.cmake` that can be used from build systems other than
cmake.

Fixes #230

* tests: add test for pkg config

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .pre-commit-config.yaml                  |   3 +
 CMakeLists.txt                           |  13 +++
 noxfile.py                               |   4 +-
 pybind11/__init__.py                     |   3 +-
 pybind11/__main__.py                     |   9 +-
 pybind11/commands.py                     |  12 +++
 setup.py                                 |   1 +
 tests/extra_python_package/test_files.py | 126 ++++++++++++-----------
 tools/JoinPaths.cmake                    |  23 +++++
 tools/pybind11.pc.in                     |   7 ++
 tools/setup_global.py.in                 |   2 +
 tools/setup_main.py.in                   |   2 +
 12 files changed, 143 insertions(+), 62 deletions(-)
 create mode 100644 tools/JoinPaths.cmake
 create mode 100644 tools/pybind11.pc.in

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 94359ab62d..a962f8b798 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -12,6 +12,9 @@
 #
 # See https://github.com/pre-commit/pre-commit
 
+# third-party content
+exclude: ^tools/JoinPaths.cmake$
+
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3787982cbd..ee0975bc1f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -198,6 +198,9 @@ else()
 endif()
 
 include("${CMAKE_CURRENT_SOURCE_DIR}/tools/pybind11Common.cmake")
+# https://github.com/jtojnar/cmake-snips/#concatenating-paths-when-building-pkg-config-files
+# TODO: cmake 3.20 adds the cmake_path() function, which obsoletes this snippet
+include("${CMAKE_CURRENT_SOURCE_DIR}/tools/JoinPaths.cmake")
 
 # Relative directory setting
 if(USE_PYTHON_INCLUDE_DIR AND DEFINED Python_INCLUDE_DIRS)
@@ -262,6 +265,16 @@ if(PYBIND11_INSTALL)
     NAMESPACE "pybind11::"
     DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
 
+  # pkg-config support
+  if(NOT prefix_for_pc_file)
+    set(prefix_for_pc_file "${CMAKE_INSTALL_PREFIX}")
+  endif()
+  join_paths(includedir_for_pc_file "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}")
+  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/tools/pybind11.pc.in"
+                 "${CMAKE_CURRENT_BINARY_DIR}/pybind11.pc" @ONLY)
+  install(FILES "${CMAKE_CURRENT_BINARY_DIR}/pybind11.pc"
+          DESTINATION "${CMAKE_INSTALL_DATAROOTDIR}/pkgconfig/")
+
   # Uninstall target
   if(PYBIND11_MASTER_PROJECT)
     configure_file("${CMAKE_CURRENT_SOURCE_DIR}/tools/cmake_uninstall.cmake.in"
diff --git a/noxfile.py b/noxfile.py
index 7be1f25440..021ced2453 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -27,7 +27,7 @@ def lint(session: nox.Session) -> None:
     Lint the codebase (except for clang-format/tidy).
     """
     session.install("pre-commit")
-    session.run("pre-commit", "run", "-a")
+    session.run("pre-commit", "run", "-a", *session.posargs)
 
 
 @nox.session(python=PYTHON_VERSIONS)
@@ -58,7 +58,7 @@ def tests_packaging(session: nox.Session) -> None:
     """
 
     session.install("-r", "tests/requirements.txt", "--prefer-binary")
-    session.run("pytest", "tests/extra_python_package")
+    session.run("pytest", "tests/extra_python_package", *session.posargs)
 
 
 @nox.session(reuse_venv=True)
diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index a1be969819..4fbb17079f 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -6,11 +6,12 @@
 
 
 from ._version import __version__, version_info
-from .commands import get_cmake_dir, get_include
+from .commands import get_cmake_dir, get_include, get_pkgconfig_dir
 
 __all__ = (
     "version_info",
     "__version__",
     "get_include",
     "get_cmake_dir",
+    "get_pkgconfig_dir",
 )
diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 22fc4471e7..8c89533843 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -4,7 +4,7 @@
 import sys
 import sysconfig
 
-from .commands import get_cmake_dir, get_include
+from .commands import get_cmake_dir, get_include, get_pkgconfig_dir
 
 
 def print_includes() -> None:
@@ -36,6 +36,11 @@ def main() -> None:
         action="store_true",
         help="Print the CMake module directory, ideal for setting -Dpybind11_ROOT in CMake.",
     )
+    parser.add_argument(
+        "--pkgconfigdir",
+        action="store_true",
+        help="Print the pkgconfig directory, ideal for setting $PKG_CONFIG_PATH.",
+    )
     args = parser.parse_args()
     if not sys.argv[1:]:
         parser.print_help()
@@ -43,6 +48,8 @@ def main() -> None:
         print_includes()
     if args.cmakedir:
         print(get_cmake_dir())
+    if args.pkgconfigdir:
+        print(get_pkgconfig_dir())
 
 
 if __name__ == "__main__":
diff --git a/pybind11/commands.py b/pybind11/commands.py
index a29c8ca612..152fa20ce7 100644
--- a/pybind11/commands.py
+++ b/pybind11/commands.py
@@ -23,3 +23,15 @@ def get_cmake_dir() -> str:
 
     msg = "pybind11 not installed, installation required to access the CMake files"
     raise ImportError(msg)
+
+
+def get_pkgconfig_dir() -> str:
+    """
+    Return the path to the pybind11 pkgconfig directory.
+    """
+    pkgconfig_installed_path = os.path.join(DIR, "share", "pkgconfig")
+    if os.path.exists(pkgconfig_installed_path):
+        return pkgconfig_installed_path
+
+    msg = "pybind11 not installed, installation required to access the pkgconfig files"
+    raise ImportError(msg)
diff --git a/setup.py b/setup.py
index a149755bf6..68573519c1 100644
--- a/setup.py
+++ b/setup.py
@@ -127,6 +127,7 @@ def remove_output(*sources: str) -> Iterator[None]:
             "-DCMAKE_INSTALL_PREFIX=pybind11",
             "-DBUILD_TESTING=OFF",
             "-DPYBIND11_NOPYTHON=ON",
+            "-Dprefix_for_pc_file=${pcfiledir}/../../",
         ]
         if "CMAKE_ARGS" in os.environ:
             fcommand = [
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index ba16b52241..8e1ddd8508 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -12,6 +12,16 @@
 DIR = os.path.abspath(os.path.dirname(__file__))
 MAIN_DIR = os.path.dirname(os.path.dirname(DIR))
 
+PKGCONFIG = """\
+prefix=${{pcfiledir}}/../../
+includedir=${{prefix}}/include
+
+Name: pybind11
+Description: Seamless operability between C++11 and Python
+Version: {VERSION}
+Cflags: -I${{includedir}}
+"""
+
 
 main_headers = {
     "include/pybind11/attr.h",
@@ -59,6 +69,10 @@
     "share/cmake/pybind11/pybind11Tools.cmake",
 }
 
+pkgconfig_files = {
+    "share/pkgconfig/pybind11.pc",
+}
+
 py_files = {
     "__init__.py",
     "__main__.py",
@@ -69,7 +83,7 @@
 }
 
 headers = main_headers | detail_headers | stl_headers
-src_files = headers | cmake_files
+src_files = headers | cmake_files | pkgconfig_files
 all_files = src_files | py_files
 
 
@@ -82,6 +96,7 @@
     "pybind11/share",
     "pybind11/share/cmake",
     "pybind11/share/cmake/pybind11",
+    "pybind11/share/pkgconfig",
     "pyproject.toml",
     "setup.cfg",
     "setup.py",
@@ -101,22 +116,25 @@
 }
 
 
+def read_tz_file(tar: tarfile.TarFile, name: str) -> bytes:
+    start = tar.getnames()[0] + "/"
+    inner_file = tar.extractfile(tar.getmember(f"{start}{name}"))
+    assert inner_file
+    with contextlib.closing(inner_file) as f:
+        return f.read()
+
+
+def normalize_line_endings(value: bytes) -> bytes:
+    return value.replace(os.linesep.encode("utf-8"), b"\n")
+
+
 def test_build_sdist(monkeypatch, tmpdir):
 
     monkeypatch.chdir(MAIN_DIR)
 
-    out = subprocess.check_output(
-        [
-            sys.executable,
-            "-m",
-            "build",
-            "--sdist",
-            "--outdir",
-            str(tmpdir),
-        ]
+    subprocess.run(
+        [sys.executable, "-m", "build", "--sdist", f"--outdir={tmpdir}"], check=True
     )
-    if hasattr(out, "decode"):
-        out = out.decode()
 
     (sdist,) = tmpdir.visit("*.tar.gz")
 
@@ -125,25 +143,17 @@ def test_build_sdist(monkeypatch, tmpdir):
         version = start[9:-1]
         simpler = {n.split("/", 1)[-1] for n in tar.getnames()[1:]}
 
-        with contextlib.closing(
-            tar.extractfile(tar.getmember(start + "setup.py"))
-        ) as f:
-            setup_py = f.read()
-
-        with contextlib.closing(
-            tar.extractfile(tar.getmember(start + "pyproject.toml"))
-        ) as f:
-            pyproject_toml = f.read()
-
-        with contextlib.closing(
-            tar.extractfile(
-                tar.getmember(
-                    start + "pybind11/share/cmake/pybind11/pybind11Config.cmake"
-                )
-            )
-        ) as f:
-            contents = f.read().decode("utf8")
-        assert 'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")' in contents
+        setup_py = read_tz_file(tar, "setup.py")
+        pyproject_toml = read_tz_file(tar, "pyproject.toml")
+        pkgconfig = read_tz_file(tar, "pybind11/share/pkgconfig/pybind11.pc")
+        cmake_cfg = read_tz_file(
+            tar, "pybind11/share/cmake/pybind11/pybind11Config.cmake"
+        )
+
+    assert (
+        'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")'
+        in cmake_cfg.decode("utf-8")
+    )
 
     files = {f"pybind11/{n}" for n in all_files}
     files |= sdist_files
@@ -154,9 +164,9 @@ def test_build_sdist(monkeypatch, tmpdir):
 
     with open(os.path.join(MAIN_DIR, "tools", "setup_main.py.in"), "rb") as f:
         contents = (
-            string.Template(f.read().decode())
+            string.Template(f.read().decode("utf-8"))
             .substitute(version=version, extra_cmd="")
-            .encode()
+            .encode("utf-8")
         )
     assert setup_py == contents
 
@@ -164,25 +174,19 @@ def test_build_sdist(monkeypatch, tmpdir):
         contents = f.read()
     assert pyproject_toml == contents
 
+    simple_version = ".".join(version.split(".")[:3])
+    pkgconfig_expected = PKGCONFIG.format(VERSION=simple_version).encode("utf-8")
+    assert normalize_line_endings(pkgconfig) == pkgconfig_expected
+
 
 def test_build_global_dist(monkeypatch, tmpdir):
 
     monkeypatch.chdir(MAIN_DIR)
     monkeypatch.setenv("PYBIND11_GLOBAL_SDIST", "1")
-    out = subprocess.check_output(
-        [
-            sys.executable,
-            "-m",
-            "build",
-            "--sdist",
-            "--outdir",
-            str(tmpdir),
-        ]
+    subprocess.run(
+        [sys.executable, "-m", "build", "--sdist", "--outdir", str(tmpdir)], check=True
     )
 
-    if hasattr(out, "decode"):
-        out = out.decode()
-
     (sdist,) = tmpdir.visit("*.tar.gz")
 
     with tarfile.open(str(sdist), "r:gz") as tar:
@@ -190,15 +194,17 @@ def test_build_global_dist(monkeypatch, tmpdir):
         version = start[16:-1]
         simpler = {n.split("/", 1)[-1] for n in tar.getnames()[1:]}
 
-        with contextlib.closing(
-            tar.extractfile(tar.getmember(start + "setup.py"))
-        ) as f:
-            setup_py = f.read()
+        setup_py = read_tz_file(tar, "setup.py")
+        pyproject_toml = read_tz_file(tar, "pyproject.toml")
+        pkgconfig = read_tz_file(tar, "pybind11/share/pkgconfig/pybind11.pc")
+        cmake_cfg = read_tz_file(
+            tar, "pybind11/share/cmake/pybind11/pybind11Config.cmake"
+        )
 
-        with contextlib.closing(
-            tar.extractfile(tar.getmember(start + "pyproject.toml"))
-        ) as f:
-            pyproject_toml = f.read()
+    assert (
+        'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")'
+        in cmake_cfg.decode("utf-8")
+    )
 
     files = {f"pybind11/{n}" for n in all_files}
     files |= sdist_files
@@ -209,7 +215,7 @@ def test_build_global_dist(monkeypatch, tmpdir):
         contents = (
             string.Template(f.read().decode())
             .substitute(version=version, extra_cmd="")
-            .encode()
+            .encode("utf-8")
         )
         assert setup_py == contents
 
@@ -217,12 +223,16 @@ def test_build_global_dist(monkeypatch, tmpdir):
         contents = f.read()
         assert pyproject_toml == contents
 
+    simple_version = ".".join(version.split(".")[:3])
+    pkgconfig_expected = PKGCONFIG.format(VERSION=simple_version).encode("utf-8")
+    assert normalize_line_endings(pkgconfig) == pkgconfig_expected
+
 
 def tests_build_wheel(monkeypatch, tmpdir):
     monkeypatch.chdir(MAIN_DIR)
 
-    subprocess.check_output(
-        [sys.executable, "-m", "pip", "wheel", ".", "-w", str(tmpdir)]
+    subprocess.run(
+        [sys.executable, "-m", "pip", "wheel", ".", "-w", str(tmpdir)], check=True
     )
 
     (wheel,) = tmpdir.visit("*.whl")
@@ -249,8 +259,8 @@ def tests_build_global_wheel(monkeypatch, tmpdir):
     monkeypatch.chdir(MAIN_DIR)
     monkeypatch.setenv("PYBIND11_GLOBAL_SDIST", "1")
 
-    subprocess.check_output(
-        [sys.executable, "-m", "pip", "wheel", ".", "-w", str(tmpdir)]
+    subprocess.run(
+        [sys.executable, "-m", "pip", "wheel", ".", "-w", str(tmpdir)], check=True
     )
 
     (wheel,) = tmpdir.visit("*.whl")
diff --git a/tools/JoinPaths.cmake b/tools/JoinPaths.cmake
new file mode 100644
index 0000000000..c68d91b84d
--- /dev/null
+++ b/tools/JoinPaths.cmake
@@ -0,0 +1,23 @@
+# This module provides function for joining paths
+# known from most languages
+#
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()
diff --git a/tools/pybind11.pc.in b/tools/pybind11.pc.in
new file mode 100644
index 0000000000..402f0b357d
--- /dev/null
+++ b/tools/pybind11.pc.in
@@ -0,0 +1,7 @@
+prefix=@prefix_for_pc_file@
+includedir=@includedir_for_pc_file@
+
+Name: @PROJECT_NAME@
+Description: Seamless operability between C++11 and Python
+Version: @PROJECT_VERSION@
+Cflags: -I${includedir}
diff --git a/tools/setup_global.py.in b/tools/setup_global.py.in
index 8aa3871783..d91468c10c 100644
--- a/tools/setup_global.py.in
+++ b/tools/setup_global.py.in
@@ -29,6 +29,7 @@ main_headers = glob.glob("pybind11/include/pybind11/*.h")
 detail_headers = glob.glob("pybind11/include/pybind11/detail/*.h")
 stl_headers = glob.glob("pybind11/include/pybind11/stl/*.h")
 cmake_files = glob.glob("pybind11/share/cmake/pybind11/*.cmake")
+pkgconfig_files = glob.glob("pybind11/share/pkgconfig/*.pc")
 headers = main_headers + detail_headers + stl_headers
 
 cmdclass = {"install_headers": InstallHeadersNested}
@@ -51,6 +52,7 @@ setup(
     headers=headers,
     data_files=[
         (base + "share/cmake/pybind11", cmake_files),
+        (base + "share/pkgconfig", pkgconfig_files),
         (base + "include/pybind11", main_headers),
         (base + "include/pybind11/detail", detail_headers),
         (base + "include/pybind11/stl", stl_headers),
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index 738d73faad..65198bdb66 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -17,6 +17,7 @@ setup(
         "pybind11.include.pybind11.detail",
         "pybind11.include.pybind11.stl",
         "pybind11.share.cmake.pybind11",
+        "pybind11.share.pkgconfig",
     ],
     package_data={
         "pybind11": ["py.typed"],
@@ -24,6 +25,7 @@ setup(
         "pybind11.include.pybind11.detail": ["*.h"],
         "pybind11.include.pybind11.stl": ["*.h"],
         "pybind11.share.cmake.pybind11": ["*.cmake"],
+        "pybind11.share.pkgconfig": ["*.pc"],
     },
     extras_require={
         "global": ["pybind11_global==$version"]

From bbb89da152a0e4f63a4fecc0d4db44f0ad855fdf Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 9 Aug 2022 00:03:36 -0400
Subject: [PATCH 451/638] fix(cmake): support vcpkg, try 2 (#4123)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 tools/pybind11Tools.cmake | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 1b6045b70e..0dc61d3996 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -115,6 +115,7 @@ if(PYTHON_IS_DEBUG)
     PROPERTY INTERFACE_COMPILE_DEFINITIONS Py_DEBUG)
 endif()
 
+# The <3.11 code here does not support release/debug builds at the same time, like on vcpkg
 if(CMAKE_VERSION VERSION_LESS 3.11)
   set_property(
     TARGET pybind11::module
@@ -130,16 +131,19 @@ if(CMAKE_VERSION VERSION_LESS 3.11)
     APPEND
     PROPERTY INTERFACE_LINK_LIBRARIES pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
 else()
+  # The IMPORTED INTERFACE library here is to ensure that "debug" and "release" get processed outside
+  # of a generator expression - https://gitlab.kitware.com/cmake/cmake/-/issues/18424, as they are
+  # target_link_library keywords rather than real libraries.
+  add_library(pybind11::_ClassicPythonLibraries IMPORTED INTERFACE)
+  target_link_libraries(pybind11::_ClassicPythonLibraries INTERFACE ${PYTHON_LIBRARIES})
   target_link_libraries(
     pybind11::module
     INTERFACE
       pybind11::python_link_helper
-      "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>"
-  )
+      "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:pybind11::_ClassicPythonLibraries>")
 
   target_link_libraries(pybind11::embed INTERFACE pybind11::pybind11
-                                                  $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
-
+                                                  pybind11::_ClassicPythonLibraries)
 endif()
 
 function(pybind11_extension name)

From b884b9dc6b99e41f08322dc198e62717770ea916 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Thu, 11 Aug 2022 16:14:17 -0400
Subject: [PATCH 452/638] chore: Add pytests for constructing pytypes from
 iterable (#4138)

* Add some additional pytests

* Reorder tests

* Further reorder tests

* remove stray lines

* remove unused fixtures
---
 tests/test_pytypes.cpp |  5 +++++
 tests/test_pytypes.py  | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 81387fd9f5..da0dc8f6ba 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -109,6 +109,11 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("get_iterator", [] { return py::iterator(); });
     // test_iterable
     m.def("get_iterable", [] { return py::iterable(); });
+    m.def("get_frozenset_from_iterable",
+          [](const py::iterable &iter) { return py::frozenset(iter); });
+    m.def("get_list_from_iterable", [](const py::iterable &iter) { return py::list(iter); });
+    m.def("get_set_from_iterable", [](const py::iterable &iter) { return py::set(iter); });
+    m.def("get_tuple_from_iterable", [](const py::iterable &iter) { return py::tuple(iter); });
     // test_float
     m.def("get_float", [] { return py::float_(0.0f); });
     // test_list
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index bde8317386..a34eaa59e8 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -26,6 +26,22 @@ def test_iterator(doc):
     assert doc(m.get_iterator) == "get_iterator() -> Iterator"
 
 
+@pytest.mark.parametrize(
+    "pytype, from_iter_func",
+    [
+        (frozenset, m.get_frozenset_from_iterable),
+        (list, m.get_list_from_iterable),
+        (set, m.get_set_from_iterable),
+        (tuple, m.get_tuple_from_iterable),
+    ],
+)
+def test_from_iterable(pytype, from_iter_func):
+    my_iter = iter(range(10))
+    s = from_iter_func(my_iter)
+    assert type(s) == pytype
+    assert s == pytype(range(10))
+
+
 def test_iterable(doc):
     assert doc(m.get_iterable) == "get_iterable() -> Iterable"
 

From 2d59b43cbf8793119fb92726ce8eb33441469e3e Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Thu, 11 Aug 2022 21:19:39 -0700
Subject: [PATCH 453/638] Qualify detail::forward_like to avoid conflict.
 (#4136)

C++23 feature: P2445R1 forward_like()
---
 include/pybind11/stl.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index ab30ecac0b..6426bff083 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -78,7 +78,7 @@ struct set_caster {
         pybind11::set s;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(
-                key_conv::cast(forward_like<T>(value), policy, parent));
+                key_conv::cast(detail::forward_like<T>(value), policy, parent));
             if (!value_ || !s.add(std::move(value_))) {
                 return handle();
             }
@@ -122,9 +122,9 @@ struct map_caster {
         }
         for (auto &&kv : src) {
             auto key = reinterpret_steal<object>(
-                key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
+                key_conv::cast(detail::forward_like<T>(kv.first), policy_key, parent));
             auto value = reinterpret_steal<object>(
-                value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
+                value_conv::cast(detail::forward_like<T>(kv.second), policy_value, parent));
             if (!key || !value) {
                 return handle();
             }
@@ -178,7 +178,7 @@ struct list_caster {
         ssize_t index = 0;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(
-                value_conv::cast(forward_like<T>(value), policy, parent));
+                value_conv::cast(detail::forward_like<T>(value), policy, parent));
             if (!value_) {
                 return handle();
             }
@@ -242,7 +242,7 @@ struct array_caster {
         ssize_t index = 0;
         for (auto &&value : src) {
             auto value_ = reinterpret_steal<object>(
-                value_conv::cast(forward_like<T>(value), policy, parent));
+                value_conv::cast(detail::forward_like<T>(value), policy, parent));
             if (!value_) {
                 return handle();
             }

From 81f35d29c621ce2ba8a82eebeb6ad97f842983c0 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sat, 20 Aug 2022 17:05:07 -0400
Subject: [PATCH 454/638] chore: Mark detail:forward_like as constexpr (#4147)

---
 include/pybind11/stl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 6426bff083..48031c2a60 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -45,7 +45,7 @@ using forwarded_type = conditional_t<std::is_lvalue_reference<T>::value,
 /// Forwards a value U as rvalue or lvalue according to whether T is rvalue or lvalue; typically
 /// used for forwarding a container's elements.
 template <typename T, typename U>
-forwarded_type<T, U> forward_like(U &&u) {
+constexpr forwarded_type<T, U> forward_like(U &&u) {
     return std::forward<detail::forwarded_type<T, U>>(std::forward<U>(u));
 }
 

From 68e6fdaa90fc93979e6d5d1e9f788f464593e8f2 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgkio@gmail.com>
Date: Sun, 21 Aug 2022 09:44:01 -0700
Subject: [PATCH 455/638] embed.h Python 3.11 `config.use_environment=1` +
 `PYTHONPATH` test (#4119)

* Add debug fprintf to test_interpreter.cpp

* Update `sys.path` from `PYTHONPATH` in Python >= 3.11 branch of `initialize_interpreter()`

* Use `config.isolated = 0; config.use_environment = 1;`

As suggsted by @vstinner here: https://github.com/pybind/pybind11/pull/4119#issuecomment-1219442853

* Add `TEST_CASE("PYTHONPATH is used to update sys.path")`

* Fix clang-tidy error.

* Use `_putenv_s()` under Windows.

* Fix clang-tidy error: argument name ... in comment does not match parameter name

* Remove slash from PYTHONPATH addition, to work around Windows slash-vs-backslash issue.

* Use `py::str(...)` instead of `.attr("__str__")` as suggested by @skylion007

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
---
 include/pybind11/embed.h              |  2 ++
 tests/test_embed/catch.cpp            | 18 ++++++++++++++++++
 tests/test_embed/test_interpreter.cpp |  7 +++++++
 3 files changed, 27 insertions(+)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index d6999cd779..0ac609e0f1 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -150,6 +150,8 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
 #else
     PyConfig config;
     PyConfig_InitIsolatedConfig(&config);
+    config.isolated = 0;
+    config.use_environment = 1;
     config.install_signal_handlers = init_signal_handlers ? 1 : 0;
 
     PyStatus status = PyConfig_SetBytesArgv(&config, argc, const_cast<char *const *>(argv));
diff --git a/tests/test_embed/catch.cpp b/tests/test_embed/catch.cpp
index 96d2e3f92a..a03a8b37c4 100644
--- a/tests/test_embed/catch.cpp
+++ b/tests/test_embed/catch.cpp
@@ -20,7 +20,25 @@
 namespace py = pybind11;
 
 int main(int argc, char *argv[]) {
+    // Setup for TEST_CASE in test_interpreter.cpp, tagging on a large random number:
+    std::string updated_pythonpath("pybind11_test_embed_PYTHONPATH_2099743835476552");
+    const char *preexisting_pythonpath = getenv("PYTHONPATH");
+    if (preexisting_pythonpath != nullptr) {
+#if defined(_WIN32)
+        updated_pythonpath += ';';
+#else
+        updated_pythonpath += ':';
+#endif
+        updated_pythonpath += preexisting_pythonpath;
+    }
+#if defined(_WIN32)
+    _putenv_s("PYTHONPATH", updated_pythonpath.c_str());
+#else
+    setenv("PYTHONPATH", updated_pythonpath.c_str(), /*replace=*/1);
+#endif
+
     py::scoped_interpreter guard{};
+
     auto result = Catch::Session().run(argc, argv);
 
     return result < 0xff ? result : 0xff;
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 1c45457a05..6299293b91 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -75,6 +75,13 @@ PYBIND11_EMBEDDED_MODULE(throw_error_already_set, ) {
     d["missing"].cast<py::object>();
 }
 
+TEST_CASE("PYTHONPATH is used to update sys.path") {
+    // The setup for this TEST_CASE is in catch.cpp!
+    auto sys_path = py::str(py::module_::import("sys").attr("path")).cast<std::string>();
+    REQUIRE_THAT(sys_path,
+                 Catch::Matchers::Contains("pybind11_test_embed_PYTHONPATH_2099743835476552"));
+}
+
 TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
     auto module_ = py::module_::import("test_interpreter");
     REQUIRE(py::hasattr(module_, "DerivedWidget"));

From a48ec3e8820064511aac5fab71706166bdd590d3 Mon Sep 17 00:00:00 2001
From: Brad Messer <messerb5467@gmail.com>
Date: Wed, 24 Aug 2022 10:34:31 -0400
Subject: [PATCH 456/638] Words matter updates (#4155)

* Remove sanity check from code base.

* Use main over master.

* Better alternative that doesn't collide with language keywords/frequent usage words.
---
 include/pybind11/numpy.h |  2 +-
 tests/test_eigen.py      | 68 ++++++++++++++++++++--------------------
 2 files changed, 35 insertions(+), 35 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 56e5edc5a4..369e18649b 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1401,7 +1401,7 @@ PYBIND11_NOINLINE void register_structured_dtype(any_container<field_descriptor>
     oss << '}';
     auto format_str = oss.str();
 
-    // Sanity check: verify that NumPy properly parses our buffer format string
+    // Smoke test: verify that NumPy properly parses our buffer format string
     auto &api = npy_api::get();
     auto arr = array(buffer_info(nullptr, itemsize, format_str, 1));
     if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr())) {
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index a1c114aede..9c6485de3c 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -251,14 +251,14 @@ def array_copy_but_one(a, r, c, v):
 def test_eigen_return_references():
     """Tests various ways of returning references and non-referencing copies"""
 
-    master = np.ones((10, 10))
+    primary = np.ones((10, 10))
     a = m.ReturnTester()
     a_get1 = a.get()
     assert not a_get1.flags.owndata and a_get1.flags.writeable
-    assign_both(a_get1, master, 3, 3, 5)
+    assign_both(a_get1, primary, 3, 3, 5)
     a_get2 = a.get_ptr()
     assert not a_get2.flags.owndata and a_get2.flags.writeable
-    assign_both(a_get1, master, 2, 3, 6)
+    assign_both(a_get1, primary, 2, 3, 6)
 
     a_view1 = a.view()
     assert not a_view1.flags.owndata and not a_view1.flags.writeable
@@ -271,25 +271,25 @@ def test_eigen_return_references():
 
     a_copy1 = a.copy_get()
     assert a_copy1.flags.owndata and a_copy1.flags.writeable
-    np.testing.assert_array_equal(a_copy1, master)
+    np.testing.assert_array_equal(a_copy1, primary)
     a_copy1[7, 7] = -44  # Shouldn't affect anything else
-    c1want = array_copy_but_one(master, 7, 7, -44)
+    c1want = array_copy_but_one(primary, 7, 7, -44)
     a_copy2 = a.copy_view()
     assert a_copy2.flags.owndata and a_copy2.flags.writeable
-    np.testing.assert_array_equal(a_copy2, master)
+    np.testing.assert_array_equal(a_copy2, primary)
     a_copy2[4, 4] = -22  # Shouldn't affect anything else
-    c2want = array_copy_but_one(master, 4, 4, -22)
+    c2want = array_copy_but_one(primary, 4, 4, -22)
 
     a_ref1 = a.ref()
     assert not a_ref1.flags.owndata and a_ref1.flags.writeable
-    assign_both(a_ref1, master, 1, 1, 15)
+    assign_both(a_ref1, primary, 1, 1, 15)
     a_ref2 = a.ref_const()
     assert not a_ref2.flags.owndata and not a_ref2.flags.writeable
     with pytest.raises(ValueError):
         a_ref2[5, 5] = 33
     a_ref3 = a.ref_safe()
     assert not a_ref3.flags.owndata and a_ref3.flags.writeable
-    assign_both(a_ref3, master, 0, 7, 99)
+    assign_both(a_ref3, primary, 0, 7, 99)
     a_ref4 = a.ref_const_safe()
     assert not a_ref4.flags.owndata and not a_ref4.flags.writeable
     with pytest.raises(ValueError):
@@ -297,23 +297,23 @@ def test_eigen_return_references():
 
     a_copy3 = a.copy_ref()
     assert a_copy3.flags.owndata and a_copy3.flags.writeable
-    np.testing.assert_array_equal(a_copy3, master)
+    np.testing.assert_array_equal(a_copy3, primary)
     a_copy3[8, 1] = 11
-    c3want = array_copy_but_one(master, 8, 1, 11)
+    c3want = array_copy_but_one(primary, 8, 1, 11)
     a_copy4 = a.copy_ref_const()
     assert a_copy4.flags.owndata and a_copy4.flags.writeable
-    np.testing.assert_array_equal(a_copy4, master)
+    np.testing.assert_array_equal(a_copy4, primary)
     a_copy4[8, 4] = 88
-    c4want = array_copy_but_one(master, 8, 4, 88)
+    c4want = array_copy_but_one(primary, 8, 4, 88)
 
     a_block1 = a.block(3, 3, 2, 2)
     assert not a_block1.flags.owndata and a_block1.flags.writeable
     a_block1[0, 0] = 55
-    master[3, 3] = 55
+    primary[3, 3] = 55
     a_block2 = a.block_safe(2, 2, 3, 2)
     assert not a_block2.flags.owndata and a_block2.flags.writeable
     a_block2[2, 1] = -123
-    master[4, 3] = -123
+    primary[4, 3] = -123
     a_block3 = a.block_const(6, 7, 4, 3)
     assert not a_block3.flags.owndata and not a_block3.flags.writeable
     with pytest.raises(ValueError):
@@ -321,18 +321,18 @@ def test_eigen_return_references():
 
     a_copy5 = a.copy_block(2, 2, 2, 3)
     assert a_copy5.flags.owndata and a_copy5.flags.writeable
-    np.testing.assert_array_equal(a_copy5, master[2:4, 2:5])
+    np.testing.assert_array_equal(a_copy5, primary[2:4, 2:5])
     a_copy5[1, 1] = 777
-    c5want = array_copy_but_one(master[2:4, 2:5], 1, 1, 777)
+    c5want = array_copy_but_one(primary[2:4, 2:5], 1, 1, 777)
 
     a_corn1 = a.corners()
     assert not a_corn1.flags.owndata and a_corn1.flags.writeable
     a_corn1 *= 50
     a_corn1[1, 1] = 999
-    master[0, 0] = 50
-    master[0, 9] = 50
-    master[9, 0] = 50
-    master[9, 9] = 999
+    primary[0, 0] = 50
+    primary[0, 9] = 50
+    primary[9, 0] = 50
+    primary[9, 9] = 999
     a_corn2 = a.corners_const()
     assert not a_corn2.flags.owndata and not a_corn2.flags.writeable
     with pytest.raises(ValueError):
@@ -340,22 +340,22 @@ def test_eigen_return_references():
 
     # All of the changes made all the way along should be visible everywhere
     # now (except for the copies, of course)
-    np.testing.assert_array_equal(a_get1, master)
-    np.testing.assert_array_equal(a_get2, master)
-    np.testing.assert_array_equal(a_view1, master)
-    np.testing.assert_array_equal(a_view2, master)
-    np.testing.assert_array_equal(a_ref1, master)
-    np.testing.assert_array_equal(a_ref2, master)
-    np.testing.assert_array_equal(a_ref3, master)
-    np.testing.assert_array_equal(a_ref4, master)
-    np.testing.assert_array_equal(a_block1, master[3:5, 3:5])
-    np.testing.assert_array_equal(a_block2, master[2:5, 2:4])
-    np.testing.assert_array_equal(a_block3, master[6:10, 7:10])
+    np.testing.assert_array_equal(a_get1, primary)
+    np.testing.assert_array_equal(a_get2, primary)
+    np.testing.assert_array_equal(a_view1, primary)
+    np.testing.assert_array_equal(a_view2, primary)
+    np.testing.assert_array_equal(a_ref1, primary)
+    np.testing.assert_array_equal(a_ref2, primary)
+    np.testing.assert_array_equal(a_ref3, primary)
+    np.testing.assert_array_equal(a_ref4, primary)
+    np.testing.assert_array_equal(a_block1, primary[3:5, 3:5])
+    np.testing.assert_array_equal(a_block2, primary[2:5, 2:4])
+    np.testing.assert_array_equal(a_block3, primary[6:10, 7:10])
     np.testing.assert_array_equal(
-        a_corn1, master[0 :: master.shape[0] - 1, 0 :: master.shape[1] - 1]
+        a_corn1, primary[0 :: primary.shape[0] - 1, 0 :: primary.shape[1] - 1]
     )
     np.testing.assert_array_equal(
-        a_corn2, master[0 :: master.shape[0] - 1, 0 :: master.shape[1] - 1]
+        a_corn2, primary[0 :: primary.shape[0] - 1, 0 :: primary.shape[1] - 1]
     )
 
     np.testing.assert_array_equal(a_copy1, c1want)

From fac23b6f65e6d0b9aa8525712936b036e372eae1 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 24 Aug 2022 13:08:24 -0700
Subject: [PATCH 457/638] `error_fetch_and_normalize`: PyPy 7.3.10+ does not
 need the PR #4079 workaround anymore. (#4154)

---
 include/pybind11/pytypes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 6ba1f5f201..f4ba459f20 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -473,7 +473,7 @@ struct error_fetch_and_normalize {
                           + " failed to obtain the name "
                             "of the normalized active exception type.");
         }
-#if defined(PYPY_VERSION)
+#if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00
         // This behavior runs the risk of masking errors in the error handling, but avoids a
         // conflict with PyPy, which relies on the normalization here to change OSError to
         // FileNotFoundError (https://github.com/pybind/pybind11/issues/4075).

From 0b4c1bc2865cf89abc751809e72a184bde671678 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Mon, 29 Aug 2022 20:25:01 -0700
Subject: [PATCH 458/638] test: ConstructorStats newline (PyPy) (#4167)

This looks like it lacks a newline.
---
 tests/constructor_stats.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/constructor_stats.h b/tests/constructor_stats.h
index a3835c21e6..937f6c233b 100644
--- a/tests/constructor_stats.h
+++ b/tests/constructor_stats.h
@@ -115,7 +115,7 @@ class ConstructorStats {
 #if defined(PYPY_VERSION)
         PyObject *globals = PyEval_GetGlobals();
         PyObject *result = PyRun_String("import gc\n"
-                                        "for i in range(2):"
+                                        "for i in range(2):\n"
                                         "    gc.collect()\n",
                                         Py_file_input,
                                         globals,

From 283f10dc55636e495bc2114c6b5baf7cd7064a0f Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 29 Aug 2022 23:26:53 -0400
Subject: [PATCH 459/638] chore(deps): bump ilammy/msvc-dev-cmd from 1.10.0 to
 1.11.0 (#4161)

Bumps [ilammy/msvc-dev-cmd](https://github.com/ilammy/msvc-dev-cmd) from 1.10.0 to 1.11.0.
- [Release notes](https://github.com/ilammy/msvc-dev-cmd/releases)
- [Commits](https://github.com/ilammy/msvc-dev-cmd/compare/v1.10.0...v1.11.0)

---
updated-dependencies:
- dependency-name: ilammy/msvc-dev-cmd
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ac6c536ced..213c690050 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -754,7 +754,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.10.0
+      uses: ilammy/msvc-dev-cmd@v1.11.0
       with:
         arch: x86
 
@@ -807,7 +807,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.12
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.10.0
+      uses: ilammy/msvc-dev-cmd@v1.11.0
       with:
         arch: x86
 

From 8756f16ed842e40406018df901f3219b231e2105 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 29 Aug 2022 21:59:48 -0700
Subject: [PATCH 460/638] [pre-commit.ci] pre-commit autoupdate (#4151)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/Lucas-C/pre-commit-hooks: v1.3.0 → v1.3.1](https://github.com/Lucas-C/pre-commit-hooks/compare/v1.3.0...v1.3.1)
- [github.com/sirosen/texthooks: 0.3.1 → 0.4.0](https://github.com/sirosen/texthooks/compare/0.3.1...0.4.0)
- [github.com/PyCQA/pylint: v2.14.5 → v2.15.0](https://github.com/PyCQA/pylint/compare/v2.14.5...v2.15.0)
- [github.com/codespell-project/codespell: v2.1.0 → v2.2.1](https://github.com/codespell-project/codespell/compare/v2.1.0...v2.2.1)

* Introduce .codespell-ignore-lines for safer (line-based instead of word-based) suppressions.

* Fix two issues: 1. ensure sort order; 2. remove duplicates

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 .codespell-ignore-lines                     | 24 ++++++++++++++
 .pre-commit-config.yaml                     | 12 ++++---
 tools/codespell_ignore_lines_from_errors.py | 35 +++++++++++++++++++++
 3 files changed, 66 insertions(+), 5 deletions(-)
 create mode 100644 .codespell-ignore-lines
 create mode 100644 tools/codespell_ignore_lines_from_errors.py

diff --git a/.codespell-ignore-lines b/.codespell-ignore-lines
new file mode 100644
index 0000000000..2a01d63ebb
--- /dev/null
+++ b/.codespell-ignore-lines
@@ -0,0 +1,24 @@
+template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t>
+    template <typename ThisT>
+        auto &this_ = static_cast<ThisT &>(*this);
+                if (load_impl<ThisT>(temp, false)) {
+        ssize_t nd = 0;
+        auto trivial = broadcast(buffers, nd, shape);
+        auto ndim = (size_t) nd;
+    int nd;
+    ssize_t ndim() const { return detail::array_proxy(m_ptr)->nd; }
+        using op = op_impl<id, ot, Base, L_type, R_type>;
+template <op_id id, op_type ot, typename L, typename R>
+    template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
+    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
+    class_ &def_cast(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
+@pytest.mark.parametrize("access", ["ro", "rw", "static_ro", "static_rw"])
+struct IntStruct {
+    explicit IntStruct(int v) : value(v){};
+    ~IntStruct() { value = -value; }
+    IntStruct(const IntStruct &) = default;
+    IntStruct &operator=(const IntStruct &) = default;
+    py::class_<IntStruct>(m, "IntStruct").def(py::init([](const int i) { return IntStruct(i); }));
+    py::implicitly_convertible<int, IntStruct>();
+    m.def("test", [](int expected, const IntStruct &in) {
+        [](int expected, const IntStruct &in) {
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index a962f8b798..bced50caf1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -62,12 +62,12 @@ repos:
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.3.0"
+  rev: "v1.3.1"
   hooks:
   - id: remove-tabs
 
 - repo: https://github.com/sirosen/texthooks
-  rev: "0.3.1"
+  rev: "0.4.0"
   hooks:
   - id: fix-ligatures
   - id: fix-smartquotes
@@ -110,7 +110,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.14.5"
+  rev: "v2.15.0"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -143,12 +143,14 @@ repos:
     additional_dependencies: [cmake, ninja]
 
 # Check for spelling
+# Use tools/codespell_ignore_lines_from_errors.py
+# to rebuild .codespell-ignore-lines
 - repo: https://github.com/codespell-project/codespell
-  rev: "v2.1.0"
+  rev: "v2.2.1"
   hooks:
   - id: codespell
     exclude: ".supp$"
-    args: ["-L", "nd,ot,thist"]
+    args: ["-x", ".codespell-ignore-lines"]
 
 # Check for common shell mistakes
 - repo: https://github.com/shellcheck-py/shellcheck-py
diff --git a/tools/codespell_ignore_lines_from_errors.py b/tools/codespell_ignore_lines_from_errors.py
new file mode 100644
index 0000000000..5403ec3ad0
--- /dev/null
+++ b/tools/codespell_ignore_lines_from_errors.py
@@ -0,0 +1,35 @@
+"""Simple script for rebuilding .codespell-ignore-lines
+
+Usage:
+
+cat < /dev/null > .codespell-ignore-lines
+pre-commit run --all-files codespell >& /tmp/codespell_errors.txt
+python3 tools/codespell_ignore_lines_from_errors.py /tmp/codespell_errors.txt > .codespell-ignore-lines
+
+git diff to review changes, then commit, push.
+"""
+
+import sys
+from typing import List
+
+
+def run(args: List[str]) -> None:
+    assert len(args) == 1, "codespell_errors.txt"
+    cache = {}
+    done = set()
+    for line in sorted(open(args[0]).read().splitlines()):
+        i = line.find(" ==> ")
+        if i > 0:
+            flds = line[:i].split(":")
+            if len(flds) >= 2:
+                filename, line_num = flds[:2]
+                if filename not in cache:
+                    cache[filename] = open(filename).read().splitlines()
+                supp = cache[filename][int(line_num) - 1]
+                if supp not in done:
+                    print(supp)
+                    done.add(supp)
+
+
+if __name__ == "__main__":
+    run(args=sys.argv[1:])

From aa8f8baa4e402885e5c89f5dc42a579932c33790 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Wed, 7 Sep 2022 09:19:02 -0400
Subject: [PATCH 461/638] [pre-commit.ci] pre-commit autoupdate (#4171)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/psf/black: 22.6.0 → 22.8.0](https://github.com/psf/black/compare/22.6.0...22.8.0)

* Update .pre-commit-config.yaml

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index bced50caf1..b230306471 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -48,7 +48,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "22.6.0" # Keep in sync with blacken-docs
+  rev: "22.8.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -58,7 +58,7 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==22.6.0 # keep in sync with black hook
+    - black==22.8.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks

From 64f7281874c3b439dc0102b6ad6cfc7586f17651 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 12 Sep 2022 20:04:44 -0400
Subject: [PATCH 462/638] [pre-commit.ci] pre-commit autoupdate (#4178)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/pylint: v2.15.0 → v2.15.2](https://github.com/PyCQA/pylint/compare/v2.15.0...v2.15.2)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b230306471..5d794a7496 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -110,7 +110,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.15.0"
+  rev: "v2.15.2"
   hooks:
   - id: pylint
     files: ^pybind11

From 8524b20c3caf8a5e868dbbf76b39927c45b41f72 Mon Sep 17 00:00:00 2001
From: Sergei Izmailov <sergei.a.izmailov@gmail.com>
Date: Thu, 15 Sep 2022 05:56:40 +0900
Subject: [PATCH 463/638] fix: Python-3.12 compatibility (#4168)

* fix: Python-3.12 compatibility

Enable dynamic attributes for `pybind11_static_property`

* Add future-notice comment
---
 include/pybind11/detail/class.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index a98e5e5414..528e716f78 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -55,6 +55,9 @@ extern "C" inline int pybind11_static_set(PyObject *self, PyObject *obj, PyObjec
     return PyProperty_Type.tp_descr_set(self, cls, value);
 }
 
+// Forward declaration to use in `make_static_property_type()`
+inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type);
+
 /** A `static_property` is the same as a `property` but the `__get__()` and `__set__()`
     methods are modified to always use the object type instead of a concrete instance.
     Return value: New reference. */
@@ -87,6 +90,13 @@ inline PyTypeObject *make_static_property_type() {
         pybind11_fail("make_static_property_type(): failure in PyType_Ready()!");
     }
 
+#    if PY_VERSION_HEX >= 0x030C0000
+    // PRE 3.12 FEATURE FREEZE. PLEASE REVIEW AFTER FREEZE.
+    // Since Python-3.12 property-derived types are required to
+    // have dynamic attributes (to set `__doc__`)
+    enable_dynamic_attributes(heap_type);
+#    endif
+
     setattr((PyObject *) type, "__module__", str("pybind11_builtins"));
     PYBIND11_SET_OLDPY_QUALNAME(type, name_obj);
 

From 1874f8fa8767179ab8f8c645a6e8c8c4e4a7c486 Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Wed, 14 Sep 2022 17:00:27 -0400
Subject: [PATCH 464/638] Clarify GIL documentation (#4057)

---
 docs/advanced/misc.rst | 40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/docs/advanced/misc.rst b/docs/advanced/misc.rst
index edab15fcb7..71960b803d 100644
--- a/docs/advanced/misc.rst
+++ b/docs/advanced/misc.rst
@@ -39,15 +39,42 @@ The ``PYBIND11_MAKE_OPAQUE`` macro does *not* require the above workarounds.
 Global Interpreter Lock (GIL)
 =============================
 
-When calling a C++ function from Python, the GIL is always held.
+The Python C API dictates that the Global Interpreter Lock (GIL) must always
+be held by the current thread to safely access Python objects. As a result,
+when Python calls into C++ via pybind11 the GIL must be held, and pybind11
+will never implicitly release the GIL.
+
+.. code-block:: cpp
+
+    void my_function() {
+        /* GIL is held when this function is called from Python */
+    }
+
+    PYBIND11_MODULE(example, m) {
+        m.def("my_function", &my_function);
+    }
+
+pybind11 will ensure that the GIL is held when it knows that it is calling
+Python code. For example, if a Python callback is passed to C++ code via
+``std::function``, when C++ code calls the function the built-in wrapper
+will acquire the GIL before calling the Python callback. Similarly, the
+``PYBIND11_OVERRIDE`` family of macros will acquire the GIL before calling
+back into Python.
+
+When writing C++ code that is called from other C++ code, if that code accesses
+Python state, it must explicitly acquire and release the GIL.
+
 The classes :class:`gil_scoped_release` and :class:`gil_scoped_acquire` can be
 used to acquire and release the global interpreter lock in the body of a C++
 function call. In this way, long-running C++ code can be parallelized using
-multiple Python threads. Taking :ref:`overriding_virtuals` as an example, this
+multiple Python threads, **but great care must be taken** when any
+:class:`gil_scoped_release` appear: if there is any way that the C++ code
+can access Python objects, :class:`gil_scoped_acquire` should be used to
+reacquire the GIL. Taking :ref:`overriding_virtuals` as an example, this
 could be realized as follows (important changes highlighted):
 
 .. code-block:: cpp
-    :emphasize-lines: 8,9,31,32
+    :emphasize-lines: 8,30,31
 
     class PyAnimal : public Animal {
     public:
@@ -56,9 +83,7 @@ could be realized as follows (important changes highlighted):
 
         /* Trampoline (need one for each virtual function) */
         std::string go(int n_times) {
-            /* Acquire GIL before calling Python code */
-            py::gil_scoped_acquire acquire;
-
+            /* PYBIND11_OVERRIDE_PURE will acquire the GIL before accessing Python state */
             PYBIND11_OVERRIDE_PURE(
                 std::string, /* Return type */
                 Animal,      /* Parent class */
@@ -78,7 +103,8 @@ could be realized as follows (important changes highlighted):
             .def(py::init<>());
 
         m.def("call_go", [](Animal *animal) -> std::string {
-            /* Release GIL before calling into (potentially long-running) C++ code */
+            // GIL is held when called from Python code. Release GIL before
+            // calling into (potentially long-running) C++ code
             py::gil_scoped_release release;
             return call_go(animal);
         });

From 9c04c7b0f1210a5f6ca7cc2e975606a1eaf21316 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 19 Sep 2022 12:56:31 -0400
Subject: [PATCH 465/638] chore: Delete copy ctor/assign for GIL RAIIs (#4183)

* chore: Delete copy ctor/assign for GIL RAIIs

* Fix typo

* Delete copy ops for local gil scoped acquire
---
 include/pybind11/detail/internals.h |  2 ++
 include/pybind11/gil.h              | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 6ca5e1482f..86991955b5 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -412,6 +412,8 @@ PYBIND11_NOINLINE internals &get_internals() {
     // Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
     struct gil_scoped_acquire_local {
         gil_scoped_acquire_local() : state(PyGILState_Ensure()) {}
+        gil_scoped_acquire_local(const gil_scoped_acquire_local &) = delete;
+        gil_scoped_acquire_local &operator=(const gil_scoped_acquire_local &) = delete;
         ~gil_scoped_acquire_local() { PyGILState_Release(state); }
         const PyGILState_STATE state;
     } gil;
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index a0b5de1514..1ef5f0a8c8 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -80,6 +80,9 @@ class gil_scoped_acquire {
         inc_ref();
     }
 
+    gil_scoped_acquire(const gil_scoped_acquire &) = delete;
+    gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
+
     void inc_ref() { ++tstate->gilstate_counter; }
 
     PYBIND11_NOINLINE void dec_ref() {
@@ -144,6 +147,9 @@ class gil_scoped_release {
         }
     }
 
+    gil_scoped_release(const gil_scoped_acquire &) = delete;
+    gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
+
     /// This method will disable the PyThreadState_DeleteCurrent call and the
     /// GIL won't be acquired. This method should be used if the interpreter
     /// could be shutting down when this is called, as thread deletion is not
@@ -178,6 +184,8 @@ class gil_scoped_acquire {
 
 public:
     gil_scoped_acquire() { state = PyGILState_Ensure(); }
+    gil_scoped_acquire(const gil_scoped_acquire &) = delete;
+    gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
     ~gil_scoped_acquire() { PyGILState_Release(state); }
     void disarm() {}
 };
@@ -187,6 +195,8 @@ class gil_scoped_release {
 
 public:
     gil_scoped_release() { state = PyEval_SaveThread(); }
+    gil_scoped_release(const gil_scoped_release &) = delete;
+    gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
     ~gil_scoped_release() { PyEval_RestoreThread(state); }
     void disarm() {}
 };

From d02f219fb9b9012ce7b27f34c5ee9feb55da08ec Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 19 Sep 2022 21:11:57 -0400
Subject: [PATCH 466/638] [pre-commit.ci] pre-commit autoupdate (#4189)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.37.3 → v2.38.0](https://github.com/asottile/pyupgrade/compare/v2.37.3...v2.38.0)
- [github.com/PyCQA/pylint: v2.15.2 → v2.15.3](https://github.com/PyCQA/pylint/compare/v2.15.2...v2.15.3)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 5d794a7496..508b3ea6e1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -35,7 +35,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.37.3"
+  rev: "v2.38.0"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -110,7 +110,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.15.2"
+  rev: "v2.15.3"
   hooks:
   - id: pylint
     files: ^pybind11

From 424ac4fe1bde46894a56775e78a702199a03137b Mon Sep 17 00:00:00 2001
From: Jan Iwaszkiewicz <jiwaszkiewicz6@gmail.com>
Date: Tue, 20 Sep 2022 19:03:57 +0200
Subject: [PATCH 467/638] fix: Windows compiler, missing object initializer
 (#4188)

* Fix for windows compiler, missing object initializer

* Removal of if-else macro for MSVC
---
 include/pybind11/detail/common.h | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 9e6947daa3..6da7ef859c 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -1033,12 +1033,7 @@ PYBIND11_NAMESPACE_END(detail)
 ///  - regular: static_cast<Return (Class::*)(Arg0, Arg1, Arg2)>(&Class::func)
 ///  - sweet:   overload_cast<Arg0, Arg1, Arg2>(&Class::func)
 template <typename... Args>
-#    if (defined(_MSC_VER) && _MSC_VER < 1920) /* MSVC 2017 */                                    \
-        || (defined(__clang__) && __clang_major__ == 5)
-static constexpr detail::overload_cast_impl<Args...> overload_cast = {};
-#    else
-static constexpr detail::overload_cast_impl<Args...> overload_cast;
-#    endif
+static constexpr detail::overload_cast_impl<Args...> overload_cast{};
 #endif
 
 /// Const member function selector for overload_cast

From 95d0e71a652992bcdc0c54844c4c6e5282247c6b Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Wed, 21 Sep 2022 11:20:07 -0400
Subject: [PATCH 468/638] test C++14 on MSVC (#4191)

---
 .github/workflows/ci.yml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 213c690050..fe57e7ce90 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -737,6 +737,9 @@ jobs:
             args: -DCMAKE_CXX_STANDARD=20
           - python: 3.8
             args: -DCMAKE_CXX_STANDARD=17
+          - python: 3.7
+            args: -DCMAKE_CXX_STANDARD=14
+
 
     name: "🐍 ${{ matrix.python }} • MSVC 2019 • x86 ${{ matrix.args }}"
     runs-on: windows-2019

From f743bdf8e61b2dc4a8995a0485111bedd9c2cbb1 Mon Sep 17 00:00:00 2001
From: bogdan-lab <60753036+bogdan-lab@users.noreply.github.com>
Date: Wed, 21 Sep 2022 21:50:31 +0300
Subject: [PATCH 469/638] Avoid local_internals destruction (#4192)

* Avoid local_internals destruction

It allows to avoid possible static deinitialization fiasco.

* Add link to relevant google style guide discussion
---
 include/pybind11/detail/internals.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 86991955b5..d47084e263 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -514,8 +514,13 @@ struct local_internals {
 
 /// Works like `get_internals`, but for things which are locally registered.
 inline local_internals &get_local_internals() {
-    static local_internals locals;
-    return locals;
+    // Current static can be created in the interpreter finalization routine. If the later will be
+    // destroyed in another static variable destructor, creation of this static there will cause
+    // static deinitialization fiasco. In order to avoid it we avoid destruction of the
+    // local_internals static. One can read more about the problem and current solution here:
+    // https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables
+    static auto *locals = new local_internals();
+    return *locals;
 }
 
 /// Constructs a std::string with the given arguments, stores it in `internals`, and returns its

From 5aa0fad5def3fc4d48f29998b6f65e74bacafd19 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Sun, 25 Sep 2022 16:10:57 -0400
Subject: [PATCH 470/638] perf: call reserve method in set and map casters
 (#4194)

* Call reserve method in set and map casters too

* Refactor template logic into has_reserve_method

* Adjust comment for reviews

* Rearrange reserve_maybe to not be underneath macro
---
 include/pybind11/stl.h | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 48031c2a60..8f243502ef 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -49,17 +49,31 @@ constexpr forwarded_type<T, U> forward_like(U &&u) {
     return std::forward<detail::forwarded_type<T, U>>(std::forward<U>(u));
 }
 
+// Checks if a container has a STL style reserve method.
+// This will only return true for a `reserve()` with a `void` return.
+template <typename C>
+using has_reserve_method = std::is_same<decltype(std::declval<C>().reserve(0)), void>;
+
 template <typename Type, typename Key>
 struct set_caster {
     using type = Type;
     using key_conv = make_caster<Key>;
 
+private:
+    template <typename T = Type, enable_if_t<has_reserve_method<T>::value, int> = 0>
+    void reserve_maybe(const anyset &s, Type *) {
+        value.reserve(s.size());
+    }
+    void reserve_maybe(const anyset &, void *) {}
+
+public:
     bool load(handle src, bool convert) {
         if (!isinstance<anyset>(src)) {
             return false;
         }
         auto s = reinterpret_borrow<anyset>(src);
         value.clear();
+        reserve_maybe(s, &value);
         for (auto entry : s) {
             key_conv conv;
             if (!conv.load(entry, convert)) {
@@ -94,12 +108,21 @@ struct map_caster {
     using key_conv = make_caster<Key>;
     using value_conv = make_caster<Value>;
 
+private:
+    template <typename T = Type, enable_if_t<has_reserve_method<T>::value, int> = 0>
+    void reserve_maybe(const dict &d, Type *) {
+        value.reserve(d.size());
+    }
+    void reserve_maybe(const dict &, void *) {}
+
+public:
     bool load(handle src, bool convert) {
         if (!isinstance<dict>(src)) {
             return false;
         }
         auto d = reinterpret_borrow<dict>(src);
         value.clear();
+        reserve_maybe(d, &value);
         for (auto it : d) {
             key_conv kconv;
             value_conv vconv;
@@ -160,9 +183,7 @@ struct list_caster {
     }
 
 private:
-    template <
-        typename T = Type,
-        enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
+    template <typename T = Type, enable_if_t<has_reserve_method<T>::value, int> = 0>
     void reserve_maybe(const sequence &s, Type *) {
         value.reserve(s.size());
     }

From da8c730a62a7f9654433f5e2206bd1135a8b57d8 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 26 Sep 2022 20:44:19 -0400
Subject: [PATCH 471/638] [pre-commit.ci] pre-commit autoupdate (#4197)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.38.0 → v2.38.2](https://github.com/asottile/pyupgrade/compare/v2.38.0...v2.38.2)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 508b3ea6e1..2c317ea7a2 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -35,7 +35,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.38.0"
+  rev: "v2.38.2"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]

From c78dfe6964579c69692eb8b5e57cbed26e409f6e Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 3 Oct 2022 13:44:09 -0400
Subject: [PATCH 472/638] bugfix: Add error checking to list append and insert
 (#4208)

---
 include/pybind11/pytypes.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f4ba459f20..565df4375b 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -2022,14 +2022,20 @@ class list : public object {
     detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
     template <typename T>
     void append(T &&val) /* py-non-const */ {
-        PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
+        if (PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) != 0) {
+            throw error_already_set();
+        }
     }
     template <typename IdxType,
               typename ValType,
               detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     void insert(const IdxType &index, ValType &&val) /* py-non-const */ {
-        PyList_Insert(
-            m_ptr, ssize_t_cast(index), detail::object_or_cast(std::forward<ValType>(val)).ptr());
+        if (PyList_Insert(m_ptr,
+                          ssize_t_cast(index),
+                          detail::object_or_cast(std::forward<ValType>(val)).ptr())
+            != 0) {
+            throw error_already_set();
+        }
     }
 };
 

From 600d697648f4eda8c88a6884472bd1d2ec0a68ad Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 3 Oct 2022 21:25:46 -0400
Subject: [PATCH 473/638] [pre-commit.ci] pre-commit autoupdate (#4210)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/mirrors-mypy: v0.971 → v0.981](https://github.com/pre-commit/mirrors-mypy/compare/v0.971...v0.981)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2c317ea7a2..ad07577eb5 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -126,7 +126,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.971"
+  rev: "v0.981"
   hooks:
   - id: mypy
     args: []

From 8275b769129816f97c7665f64c88a0e05d8987df Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 4 Oct 2022 14:01:26 -0400
Subject: [PATCH 474/638] ci: update pre-commit schedule (#4212)

---
 .pre-commit-config.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index ad07577eb5..742e7a30aa 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -12,6 +12,12 @@
 #
 # See https://github.com/pre-commit/pre-commit
 
+
+ci:
+  autoupdate_commit_msg: "chore(deps): update pre-commit hooks"
+  autofix_commit_msg: "style: pre-commit fixes"
+  autoupdate_schedule: monthly
+
 # third-party content
 exclude: ^tools/JoinPaths.cmake$
 

From 864ed1120c704bf27d6ad5ab40645262d0d1e955 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Thu, 6 Oct 2022 16:11:34 -0400
Subject: [PATCH 475/638] chore: steal arg_v.value from copied arg in
 unpacking_collector (#4219)

---
 include/pybind11/cast.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index a0e32281bc..b89e4946ad 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1545,7 +1545,7 @@ class unpacking_collector {
             throw cast_error_unable_to_convert_call_arg(a.name, a.type);
 #endif
         }
-        m_kwargs[a.name] = a.value;
+        m_kwargs[a.name] = std::move(a.value);
     }
 
     void process(list & /*args_list*/, detail::kwargs_proxy kp) {

From 6cb214748d6ec3a61fdc35ee27f9a90d170dd242 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Thu, 6 Oct 2022 21:02:57 -0700
Subject: [PATCH 476/638] fix: NVCC 11.4.0 - 11.8.0 host bug workaround (#4220)

* Work-Around: NVCC 11.4.0 - 11.8.0

Adds a targeted NVCC work around for limited number of CUDA
releases. Fixed in NVCC development.

* style: pre-commit fixes

* CI: Bump CTK Version 11.2 -> 11.7

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml    |  4 ++--
 include/pybind11/pybind11.h | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fe57e7ce90..99caabf097 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -324,8 +324,8 @@ jobs:
   # Testing NVCC; forces sources to behave like .cu files
   cuda:
     runs-on: ubuntu-latest
-    name: "🐍 3.8 • CUDA 11.2 • Ubuntu 20.04"
-    container: nvidia/cuda:11.2.2-devel-ubuntu20.04
+    name: "🐍 3.10 • CUDA 11.7 • Ubuntu 22.04"
+    container: nvidia/cuda:11.7.0-devel-ubuntu22.04
 
     steps:
     - uses: actions/checkout@v3
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index c889dc4169..3f6e27b751 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1578,6 +1578,22 @@ class class_ : public detail::generic_type {
         return *this;
     }
 
+// Nvidia's NVCC is broken between 11.4.0 and 11.8.0
+//   https://github.com/pybind/pybind11/issues/4193
+#if defined(__CUDACC__) && (__CUDACC_VER_MAJOR__ == 11) && (__CUDACC_VER_MINOR__ >= 4)            \
+    && (__CUDACC_VER_MINOR__ <= 8)
+    template <typename T, typename... Extra>
+    class_ &def(const T &op, const Extra &...extra) {
+        op.execute(*this, extra...);
+        return *this;
+    }
+
+    template <typename T, typename... Extra>
+    class_ &def_cast(const T &op, const Extra &...extra) {
+        op.execute_cast(*this, extra...);
+        return *this;
+    }
+#else
     template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
     class_ &def(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
         op.execute(*this, extra...);
@@ -1589,6 +1605,7 @@ class class_ : public detail::generic_type {
         op.execute_cast(*this, extra...);
         return *this;
     }
+#endif
 
     template <typename... Args, typename... Extra>
     class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra &...extra) {

From 4a4215620920ee659145cd34597e14f0553a73f1 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 7 Oct 2022 09:20:38 -0700
Subject: [PATCH 477/638] test_eigen.py test_nonunit_stride_to_python bug fix
 (ASAN failure) (#4217)

* Disable test triggering ASAN failure (to pin-point where the problem is).

* Fix unsafe "block" implementation in test_eigen.cpp

* Undo changes (i.e. revert back to master).

* Detect "type_caster for Eigen::Ref made a copy."

This is achieved without
* reaching into internals,
* making test_eigen.cpp depend on pybind11/numpy.h.

* Add comment pointing to PR, for easy reference.
---
 tests/test_eigen.cpp | 39 ++++++++++++++++++++++++++++++++++-----
 tests/test_eigen.py  | 15 ++++++++++++---
 2 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index 591dacc624..b0c7bdb48a 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -197,11 +197,40 @@ TEST_SUBMODULE(eigen, m) {
 
     // Return a block of a matrix (gives non-standard strides)
     m.def("block",
-          [](const Eigen::Ref<const Eigen::MatrixXd> &x,
-             int start_row,
-             int start_col,
-             int block_rows,
-             int block_cols) { return x.block(start_row, start_col, block_rows, block_cols); });
+          [m](const py::object &x_obj,
+              int start_row,
+              int start_col,
+              int block_rows,
+              int block_cols) {
+              return m.attr("_block")(x_obj, x_obj, start_row, start_col, block_rows, block_cols);
+          });
+
+    m.def(
+        "_block",
+        [](const py::object &x_obj,
+           const Eigen::Ref<const Eigen::MatrixXd> &x,
+           int start_row,
+           int start_col,
+           int block_rows,
+           int block_cols) {
+            // See PR #4217 for background. This test is a bit over the top, but might be useful
+            // as a concrete example to point to when explaining the dangling reference trap.
+            auto i0 = py::make_tuple(0, 0);
+            auto x0_orig = x_obj[*i0].cast<double>();
+            if (x(0, 0) != x0_orig) {
+                throw std::runtime_error(
+                    "Something in the type_caster for Eigen::Ref is terribly wrong.");
+            }
+            double x0_mod = x0_orig + 1;
+            x_obj[*i0] = x0_mod;
+            auto copy_detected = (x(0, 0) != x0_mod);
+            x_obj[*i0] = x0_orig;
+            if (copy_detected) {
+                throw std::runtime_error("type_caster for Eigen::Ref made a copy.");
+            }
+            return x.block(start_row, start_col, block_rows, block_cols);
+        },
+        py::keep_alive<0, 1>());
 
     // test_eigen_return_references, test_eigen_keepalive
     // return value referencing/copying tests:
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index 9c6485de3c..713432a815 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -217,15 +217,24 @@ def test_negative_stride_from_python(msg):
     )
 
 
+def test_block_runtime_error_type_caster_eigen_ref_made_a_copy():
+    with pytest.raises(RuntimeError) as excinfo:
+        m.block(ref, 0, 0, 0, 0)
+    assert str(excinfo.value) == "type_caster for Eigen::Ref made a copy."
+
+
 def test_nonunit_stride_to_python():
     assert np.all(m.diagonal(ref) == ref.diagonal())
     assert np.all(m.diagonal_1(ref) == ref.diagonal(1))
     for i in range(-5, 7):
         assert np.all(m.diagonal_n(ref, i) == ref.diagonal(i)), f"m.diagonal_n({i})"
 
-    assert np.all(m.block(ref, 2, 1, 3, 3) == ref[2:5, 1:4])
-    assert np.all(m.block(ref, 1, 4, 4, 2) == ref[1:, 4:])
-    assert np.all(m.block(ref, 1, 4, 3, 2) == ref[1:4, 4:])
+    # Must be order="F", otherwise the type_caster will make a copy and
+    # m.block() will return a dangling reference (heap-use-after-free).
+    rof = np.asarray(ref, order="F")
+    assert np.all(m.block(rof, 2, 1, 3, 3) == rof[2:5, 1:4])
+    assert np.all(m.block(rof, 1, 4, 4, 2) == rof[1:, 4:])
+    assert np.all(m.block(rof, 1, 4, 3, 2) == rof[1:4, 4:])
 
 
 def test_eigen_ref_to_python():

From 7c6f2f80a73e330642226138ae3ddaf448a4f672 Mon Sep 17 00:00:00 2001
From: Daniel Galvez <galv@users.noreply.github.com>
Date: Fri, 7 Oct 2022 12:27:54 -0700
Subject: [PATCH 478/638] fix: PyCapsule_GetDestructor is allowed to return a
 nullptr destructor (#4221)

* fix: PyCapsule_GetDestructor is allowed to return a nullptr destructor

Previously, this code would error out if the destructor happened to be
a nullptr. This is incorrect. nullptrs are allowed for capsule
destructors.

"It is legal for a capsule to have a NULL destructor. This makes a
NULL return code somewhat ambiguous; use PyCapsule_IsValid() or
PyErr_Occurred() to disambiguate."

See:

https://docs.python.org/3/c-api/capsule.html#c.PyCapsule_GetDestructor

I noticed this while working on a type caster related to #3858 DLPack
happens to allow the destructor not to be defined on a capsule, and I
encountered such a case. See:

https://github.com/dmlc/dlpack/blob/e2bdd3bee8cb6501558042633fa59144cc8b7f5f/include/dlpack/dlpack.h#L219

* Add test for the fix.

* Update tests/test_pytypes.cpp

I tried this locally and it works!
I never knew that there are cases where `reinterpret_cast` does not work but `static_cast` does. Let's see if all compilers are happy with this.

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* style: pre-commit fixes

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgkio@gmail.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pytypes.h | 12 ++++++------
 tests/test_pytypes.cpp     |  6 ++++++
 tests/test_pytypes.py      | 11 +++++++++++
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 565df4375b..29506b7eaf 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1829,18 +1829,18 @@ class capsule : public object {
             // guard if destructor called while err indicator is set
             error_scope error_guard;
             auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
-            if (destructor == nullptr) {
-                if (PyErr_Occurred()) {
-                    throw error_already_set();
-                }
-                pybind11_fail("Unable to get capsule context");
+            if (PyErr_Occurred()) {
+                throw error_already_set();
             }
             const char *name = get_name_in_error_scope(o);
             void *ptr = PyCapsule_GetPointer(o, name);
             if (ptr == nullptr) {
                 throw error_already_set();
             }
-            destructor(ptr);
+
+            if (destructor != nullptr) {
+                destructor(ptr);
+            }
         });
 
         if (!m_ptr || PyCapsule_SetContext(m_ptr, (void *) destructor) != 0) {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index da0dc8f6ba..c95ff8230a 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -289,6 +289,12 @@ TEST_SUBMODULE(pytypes, m) {
         return capsule;
     });
 
+    m.def("return_capsule_with_explicit_nullptr_dtor", []() {
+        py::print("creating capsule with explicit nullptr dtor");
+        return py::capsule(reinterpret_cast<void *>(1234),
+                           static_cast<void (*)(void *)>(nullptr)); // PR #4221
+    });
+
     // test_accessors
     m.def("accessor_api", [](const py::object &o) {
         auto d = py::dict();
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index a34eaa59e8..070849fc55 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -299,6 +299,17 @@ def test_capsule(capture):
     """
     )
 
+    with capture:
+        a = m.return_capsule_with_explicit_nullptr_dtor()
+        del a
+        pytest.gc_collect()
+    assert (
+        capture.unordered
+        == """
+        creating capsule with explicit nullptr dtor
+    """
+    )
+
 
 def test_accessors():
     class SubTestObject:

From da104a9efd0357b5c144c67eb641ae0b9e23012d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 9 Oct 2022 21:50:35 -0700
Subject: [PATCH 479/638] Reproducer and fix for issue encountered in
 smart_holder update. (#4228)

* Reproducer for issue encountered in smart_holder update.

* clang-tidy compatibility (untested).

* Add `enable_if_t` to workaround.

* Bug fix: Move `PYBIND11_USING_WORKAROUND_FOR_CUDA_11_4_THROUGH_8` determination to detail/common.h

So that it actually is defined in pybind11.h

* Try using the workaround (which is nicer than the original code) universally.

* Reduce reproducer for CUDA 11.7 issue encountered in smart_holder update.

This commit tested in isolation on top of current master + first version of reproducer (62311eb431849d135a5db84f6c75ec390f2ede7c).

Succeeds with Debian Clang 14.0.6 C++17 (and probably all other compilers).

Fails for CUDA 11.7:

```
cd /build/tests && /usr/local/cuda/bin/nvcc -forward-unknown-to-host-compiler -Dpybind11_tests_EXPORTS -I/mounted_pybind11/include -isystem=/usr/include/python3.10 -g --generate-code=arch=compute_52,code=[compute_52,sm_52] -Xcompiler=-fPIC -Xcompiler=-fvisibility=hidden -Werror all-warnings -std=c++17 -MD -MT tests/CMakeFiles/pybind11_tests.dir/test_class.cpp.o -MF CMakeFiles/pybind11_tests.dir/test_class.cpp.o.d -x cu -c /mounted_pybind11/tests/test_class.cpp -o CMakeFiles/pybind11_tests.dir/test_class.cpp.o
/mounted_pybind11/tests/test_class.cpp(53): error: more than one instance of overloaded function "pybind11::class_<type_, options...>::def [with type_=test_class::pr4220_tripped_over_this::Empty0, options=<>]" matches the argument list:
            function template "pybind11::class_<test_class::pr4220_tripped_over_this::Empty0> &pybind11::class_<type_, options...>::def(const char *, Func &&, const Extra &...) [with type_=test_class::pr4220_tripped_over_this::Empty0, options=<>]"
/mounted_pybind11/include/pybind11/pybind11.h(1557): here
            function template "pybind11::class_<test_class::pr4220_tripped_over_this::Empty0> &pybind11::class_<type_, options...>::def(const T &, const Extra &...) [with type_=test_class::pr4220_tripped_over_this::Empty0, options=<>]"
/mounted_pybind11/include/pybind11/pybind11.h(1586): here
            argument types are: (const char [8], <unknown-type>)
            object type is: pybind11::class_<test_class::pr4220_tripped_over_this::Empty0>

1 error detected in the compilation of "/mounted_pybind11/tests/test_class.cpp".
```
---
 include/pybind11/operators.h |  1 +
 include/pybind11/pybind11.h  | 21 ++-------------------
 tests/test_class.cpp         | 22 ++++++++++++++++++++++
 tests/test_class.py          |  7 +++++++
 4 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/include/pybind11/operators.h b/include/pybind11/operators.h
index a0c3b78d65..16a88ae171 100644
--- a/include/pybind11/operators.h
+++ b/include/pybind11/operators.h
@@ -84,6 +84,7 @@ struct op_impl {};
 /// Operator implementation generator
 template <op_id id, op_type ot, typename L, typename R>
 struct op_ {
+    static constexpr bool op_enable_if_hook = true;
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) const {
         using Base = typename Class::type;
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 3f6e27b751..fb4b7578d9 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1578,34 +1578,17 @@ class class_ : public detail::generic_type {
         return *this;
     }
 
-// Nvidia's NVCC is broken between 11.4.0 and 11.8.0
-//   https://github.com/pybind/pybind11/issues/4193
-#if defined(__CUDACC__) && (__CUDACC_VER_MAJOR__ == 11) && (__CUDACC_VER_MINOR__ >= 4)            \
-    && (__CUDACC_VER_MINOR__ <= 8)
-    template <typename T, typename... Extra>
+    template <typename T, typename... Extra, detail::enable_if_t<T::op_enable_if_hook, int> = 0>
     class_ &def(const T &op, const Extra &...extra) {
         op.execute(*this, extra...);
         return *this;
     }
 
-    template <typename T, typename... Extra>
+    template <typename T, typename... Extra, detail::enable_if_t<T::op_enable_if_hook, int> = 0>
     class_ &def_cast(const T &op, const Extra &...extra) {
         op.execute_cast(*this, extra...);
         return *this;
     }
-#else
-    template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
-    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
-        op.execute(*this, extra...);
-        return *this;
-    }
-
-    template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
-    class_ &def_cast(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
-        op.execute_cast(*this, extra...);
-        return *this;
-    }
-#endif
 
     template <typename... Args, typename... Extra>
     class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra &...extra) {
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index c8b8071dc9..18c8d358bb 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -36,6 +36,26 @@ struct NoBraceInitialization {
     std::vector<int> vec;
 };
 
+namespace test_class {
+namespace pr4220_tripped_over_this { // PR #4227
+
+template <int>
+struct SoEmpty {};
+
+template <typename T>
+std::string get_msg(const T &) {
+    return "This is really only meant to exercise successful compilation.";
+}
+
+using Empty0 = SoEmpty<0x0>;
+
+void bind_empty0(py::module_ &m) {
+    py::class_<Empty0>(m, "Empty0").def(py::init<>()).def("get_msg", get_msg<Empty0>);
+}
+
+} // namespace pr4220_tripped_over_this
+} // namespace test_class
+
 TEST_SUBMODULE(class_, m) {
     // test_instance
     struct NoConstructor {
@@ -517,6 +537,8 @@ TEST_SUBMODULE(class_, m) {
         py::class_<OtherDuplicateNested>(gt, "OtherDuplicateNested");
         py::class_<OtherDuplicateNested>(gt, "YetAnotherDuplicateNested");
     });
+
+    test_class::pr4220_tripped_over_this::bind_empty0(m);
 }
 
 template <int N>
diff --git a/tests/test_class.py b/tests/test_class.py
index ff9196f0f2..47ba450fc2 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -469,3 +469,10 @@ class ClassScope:
         m.register_duplicate_nested_class_type(ClassScope)
     expected = 'generic_type: type "YetAnotherDuplicateNested" is already registered!'
     assert str(exc_info.value) == expected
+
+
+def test_pr4220_tripped_over_this():
+    assert (
+        m.Empty0().get_msg()
+        == "This is really only meant to exercise successful compilation."
+    )

From ff7b69714d76c312b0bcc45e4a8b854783f6dbc5 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Tue, 11 Oct 2022 00:50:40 -0400
Subject: [PATCH 480/638] chore(deps): bump jwlawson/actions-setup-cmake from
 1.12 to 1.13 (#4233)

Bumps [jwlawson/actions-setup-cmake](https://github.com/jwlawson/actions-setup-cmake) from 1.12 to 1.13.
- [Release notes](https://github.com/jwlawson/actions-setup-cmake/releases)
- [Commits](https://github.com/jwlawson/actions-setup-cmake/compare/v1.12...v1.13)

---
updated-dependencies:
- dependency-name: jwlawson/actions-setup-cmake
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 12 ++++++------
 .github/workflows/configure.yml |  2 +-
 .github/workflows/upstream.yml  |  2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 99caabf097..38694bcfa4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -80,7 +80,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -202,7 +202,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -465,7 +465,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Configure
       shell: bash
@@ -754,7 +754,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.11.0
@@ -807,7 +807,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.11.0
@@ -858,7 +858,7 @@ jobs:
         python3 -m pip install -r tests/requirements.txt
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Configure C++20
       run: >
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index edcad4198b..5ec0dd462f 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -51,7 +51,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
       with:
         cmake-version: ${{ matrix.cmake }}
 
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 95ff4cb83d..366284acf4 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -31,7 +31,7 @@ jobs:
       run: sudo apt-get install libboost-dev
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.12
+      uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare env
       run: |

From 0927c4d19e33687b463346ecb7d194493ee53b4c Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Tue, 11 Oct 2022 16:07:42 -0400
Subject: [PATCH 481/638] chore: Improve PyCapsule exception handling (#4232)

* Improve pycapsule error handling corner cases

* Handle another corner case

* Simplify err handling code
---
 include/pybind11/pytypes.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 29506b7eaf..2e6b755caf 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1829,7 +1829,7 @@ class capsule : public object {
             // guard if destructor called while err indicator is set
             error_scope error_guard;
             auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
-            if (PyErr_Occurred()) {
+            if (destructor == nullptr && PyErr_Occurred()) {
                 throw error_already_set();
             }
             const char *name = get_name_in_error_scope(o);
@@ -1843,7 +1843,7 @@ class capsule : public object {
             }
         });
 
-        if (!m_ptr || PyCapsule_SetContext(m_ptr, (void *) destructor) != 0) {
+        if (!m_ptr || PyCapsule_SetContext(m_ptr, reinterpret_cast<void *>(destructor)) != 0) {
             throw error_already_set();
         }
     }

From 8781daf6e6c2a80524d787110094584a28619f2a Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Wed, 12 Oct 2022 16:46:40 -0400
Subject: [PATCH 482/638] chore: Optimize iterator advance() call (#4237)

---
 include/pybind11/pytypes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 2e6b755caf..0dda48145a 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1382,7 +1382,7 @@ class iterator : public object {
 private:
     void advance() {
         value = reinterpret_steal<object>(PyIter_Next(m_ptr));
-        if (PyErr_Occurred()) {
+        if (value.ptr() == nullptr && PyErr_Occurred()) {
             throw error_already_set();
         }
     }

From 964c49978f7e7227f2968c359f4f05255d2b54f4 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 12 Oct 2022 15:43:43 -0700
Subject: [PATCH 483/638] Minor `py::capsule` cleanup. No functional change.
 (#4238)

Use `PyCapsule_Destructor` (part of the stable Python ABI) instead of spelling out the C `typedef`.

The deprecation message is misleading. Replace with a message pointing to another existing ctor.

Background: According to @wjakob the original motivation for deprecating the ctor (in PR #752) was to hide Python C API details, but PR #902 brought those back with a new ctor, it cannot be avoided. Having a `PyCapsule_Destructor` or a `void (*destructor)(void *)` are two separate and valid use cases.
---
 include/pybind11/pytypes.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 0dda48145a..4b93d20182 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1809,16 +1809,16 @@ class capsule : public object {
 
     explicit capsule(const void *value,
                      const char *name = nullptr,
-                     void (*destructor)(PyObject *) = nullptr)
+                     PyCapsule_Destructor destructor = nullptr)
         : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
         if (!m_ptr) {
             throw error_already_set();
         }
     }
 
-    PYBIND11_DEPRECATED("Please pass a destructor that takes a void pointer as input")
-    capsule(const void *value, void (*destruct)(PyObject *))
-        : object(PyCapsule_New(const_cast<void *>(value), nullptr, destruct), stolen_t{}) {
+    PYBIND11_DEPRECATED("Please use the ctor with value, name, destructor args")
+    capsule(const void *value, PyCapsule_Destructor destructor)
+        : object(PyCapsule_New(const_cast<void *>(value), nullptr, destructor), stolen_t{}) {
         if (!m_ptr) {
             throw error_already_set();
         }

From 5b5547bc1bcfdf58ff4febbb3a08f1764ac4ec7e Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 17 Oct 2022 17:57:55 -0400
Subject: [PATCH 484/638] chore(deps): bump ilammy/msvc-dev-cmd from 1.11.0 to
 1.12.0 (#4242)

Bumps [ilammy/msvc-dev-cmd](https://github.com/ilammy/msvc-dev-cmd) from 1.11.0 to 1.12.0.
- [Release notes](https://github.com/ilammy/msvc-dev-cmd/releases)
- [Commits](https://github.com/ilammy/msvc-dev-cmd/compare/v1.11.0...v1.12.0)

---
updated-dependencies:
- dependency-name: ilammy/msvc-dev-cmd
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 38694bcfa4..bc7175d829 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -757,7 +757,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.11.0
+      uses: ilammy/msvc-dev-cmd@v1.12.0
       with:
         arch: x86
 
@@ -810,7 +810,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.11.0
+      uses: ilammy/msvc-dev-cmd@v1.12.0
       with:
         arch: x86
 

From b926396bdf42ef1e5f1f67f9d42277ce0c88adb8 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 17 Oct 2022 19:15:08 -0400
Subject: [PATCH 485/638] bugfix: py contains raises errors when appropiate
 (#4209)

* bugfix: contains now throws an exception if the key is not hashable

* Fix tests and improve robustness

* Remove todo

* Workaround PyPy corner case

* PyPy xfail

* Fix typo

* fix xfail

* Make clang-tidy happy

* Remove redundant exc checking
---
 include/pybind11/pytypes.h | 12 ++++++++++--
 tests/test_pytypes.cpp     |  5 ++++-
 tests/test_pytypes.py      | 25 +++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 4b93d20182..37fc49a0e1 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1967,7 +1967,11 @@ class dict : public object {
     void clear() /* py-non-const */ { PyDict_Clear(ptr()); }
     template <typename T>
     bool contains(T &&key) const {
-        return PyDict_Contains(m_ptr, detail::object_or_cast(std::forward<T>(key)).ptr()) == 1;
+        auto result = PyDict_Contains(m_ptr, detail::object_or_cast(std::forward<T>(key)).ptr());
+        if (result == -1) {
+            throw error_already_set();
+        }
+        return result == 1;
     }
 
 private:
@@ -2053,7 +2057,11 @@ class anyset : public object {
     bool empty() const { return size() == 0; }
     template <typename T>
     bool contains(T &&val) const {
-        return PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 1;
+        auto result = PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
+        if (result == -1) {
+            throw error_already_set();
+        }
+        return result == 1;
     }
 };
 
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index c95ff8230a..99237ccef7 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -183,7 +183,7 @@ TEST_SUBMODULE(pytypes, m) {
         return d2;
     });
     m.def("dict_contains",
-          [](const py::dict &dict, py::object val) { return dict.contains(val); });
+          [](const py::dict &dict, const py::object &val) { return dict.contains(val); });
     m.def("dict_contains",
           [](const py::dict &dict, const char *val) { return dict.contains(val); });
 
@@ -538,6 +538,9 @@ TEST_SUBMODULE(pytypes, m) {
 
     m.def("hash_function", [](py::object obj) { return py::hash(std::move(obj)); });
 
+    m.def("obj_contains",
+          [](py::object &obj, const py::object &key) { return obj.contains(key); });
+
     m.def("test_number_protocol", [](const py::object &a, const py::object &b) {
         py::list l;
         l.append(a.equal(b));
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 070849fc55..3ed7b9c946 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -168,6 +168,31 @@ def test_dict(capture, doc):
     assert m.dict_keyword_constructor() == {"x": 1, "y": 2, "z": 3}
 
 
+class CustomContains:
+    d = {"key": None}
+
+    def __contains__(self, m):
+        return m in self.d
+
+
+@pytest.mark.parametrize(
+    "arg,func",
+    [
+        (set(), m.anyset_contains),
+        (dict(), m.dict_contains),
+        (CustomContains(), m.obj_contains),
+    ],
+)
+@pytest.mark.xfail("env.PYPY and sys.pypy_version_info < (7, 3, 10)", strict=False)
+def test_unhashable_exceptions(arg, func):
+    class Unhashable:
+        __hash__ = None
+
+    with pytest.raises(TypeError) as exc_info:
+        func(arg, Unhashable())
+    assert "unhashable type:" in str(exc_info.value)
+
+
 def test_tuple():
     assert m.tuple_no_args() == ()
     assert m.tuple_ssize_t() == ()

From fab1eebe2c4c52e0abac249f3d058787bc83b5ec Mon Sep 17 00:00:00 2001
From: Lalaland <ethan.steinberg@gmail.com>
Date: Tue, 18 Oct 2022 16:54:16 -0700
Subject: [PATCH 486/638] First draft of Eigen::Tensor support (#4201)

* First draft of Eigen::Tensor support

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix build errors

* Weird allocator stuff?

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Remove unused + additional allocator junk

* Disable warning

* Use constexpr

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* clang tidy fixes

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Resolve comments

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Remove auto constexpr function

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Try again for older C++

* Oops forgot constexpr

* Move to new files as suggested

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix weird tests

* Fix nits

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Oops, forgot import

* Fix clang 3.6 bug

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* More comprehensive test suite

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Refactor allocators to make things more clear

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Switch to std::copy

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Switch to DSizes instead of array

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Address feedback

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix python + dummy c++ change to trigger build

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Alignment

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add include guard

* Forgot inline

* Fix compiler warning

* Remove bad test

* Better type signatures

* Add guards to make compiler requirements more explicit

* style: pre-commit fixes

* Force rerun of tests due to flake

* style: pre-commit fixes

* Keep pragmas & all related comments together, add PLEASE KEEP IN SYNC

* Move headers out of detail

* style: pre-commit fixes

* Fix cmake

* Improve casting

* style: pre-commit fixes

* Add a ton more tests + refactor

* Improve names

* style: pre-commit fixes

* Update include/pybind11/eigen/tensor.h

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* Fix tests

* style: pre-commit fixes

* Update

* Add a test to verify that strange numpy arrays work

* Fix dumb compiler warning

* Better tests

* Better tests

* Fix tests

* style: pre-commit fixes

* More test fixes

* style: pre-commit fixes

* A ton more test coverage

* Fix tests

* style: pre-commit fixes

* style: pre-commit fixes

* Add back constexpr

* Another test

* style: pre-commit fixes

* Improve tests

* Whoops

* Less magic numbers

* Update tests/test_eigen_tensor.py

Co-authored-by: Sergiu Deitsch <sergiud@users.noreply.github.com>

* Update tests/test_eigen_tensor.py

Co-authored-by: Sergiu Deitsch <sergiud@users.noreply.github.com>

* style: pre-commit fixes

* Fix tests

* style: pre-commit fixes

* Fix memory leak

* style: pre-commit fixes

* Fix order

* style: pre-commit fixes

* Add test to make sure unsafe casts fail

* Minor bug fix to work on 32 bit machines

* Implement convert flag

* style: pre-commit fixes

* Switch to correct TensorMap const use

* style: pre-commit fixes

* Support older versions of eigen

* Weird c++ compilers

* Fix Eigen bug

* Fix another eigen bug

* Yet another eigen bug

* Potential flakes?

* style: pre-commit fixes

* Rerun tests with dummy exception to find out what is going on

* Another dummy test run

* Ablate more

* Found the broken test?

* One step closer

* one step further

* Double check

* one thing at a time

* Give up and disable the test

* Clang lies about being gcc

* Oops, fix matrix test

* style: pre-commit fixes

* Add tests to verify scalar conversions

* style: pre-commit fixes

* Fix nits

* Support no_array

* Fix tests

* style: pre-commit fixes

* Silence compiler warning

* Improve build system for ancient compilers

* Make clang happy

* Make gcc happy

* Implement Skylion's suggestions

* Fix warning

* Inline const pointer check

* Implement suggestions

* style: pre-commit fixes

* Improve tests

* Typo

* style: pre-commit fixes

* Support Google's build environment

* style: pre-commit fixes

* Update include/pybind11/eigen/tensor.h

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* style: pre-commit fixes

* Test cleanup per Skylion

* Switch to remvove_cv_t

* Cleaner test

* style: pre-commit fixes

* Remove tensor from eigen.h, update tests

* style: pre-commit fixes

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
Co-authored-by: Aaron Gokaslan <aaronGokaslan@gmail.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Sergiu Deitsch <sergiud@users.noreply.github.com>
---
 .gitignore                                    |   1 +
 CMakeLists.txt                                |   2 +
 include/pybind11/eigen.h                      | 703 +----------------
 include/pybind11/eigen/matrix.h               | 713 ++++++++++++++++++
 include/pybind11/eigen/tensor.h               | 518 +++++++++++++
 tests/CMakeLists.txt                          |  36 +-
 tests/extra_python_package/test_files.py      |   8 +-
 .../{test_eigen.cpp => test_eigen_matrix.cpp} |   4 +-
 tests/{test_eigen.py => test_eigen_matrix.py} |   2 +-
 tests/test_eigen_tensor.cpp                   |  16 +
 tests/test_eigen_tensor.inl                   | 333 ++++++++
 tests/test_eigen_tensor.py                    | 288 +++++++
 tests/test_eigen_tensor_avoid_stl_array.cpp   |  16 +
 tests/test_numpy_array.cpp                    |   2 +
 tests/test_numpy_array.py                     |   6 +
 tools/setup_global.py.in                      |   4 +-
 tools/setup_main.py.in                        |   2 +
 17 files changed, 1944 insertions(+), 710 deletions(-)
 create mode 100644 include/pybind11/eigen/matrix.h
 create mode 100644 include/pybind11/eigen/tensor.h
 rename tests/{test_eigen.cpp => test_eigen_matrix.cpp} (99%)
 rename tests/{test_eigen.py => test_eigen_matrix.py} (99%)
 create mode 100644 tests/test_eigen_tensor.cpp
 create mode 100644 tests/test_eigen_tensor.inl
 create mode 100644 tests/test_eigen_tensor.py
 create mode 100644 tests/test_eigen_tensor_avoid_stl_array.cpp

diff --git a/.gitignore b/.gitignore
index 3cf4fbbda0..43d5094c96 100644
--- a/.gitignore
+++ b/.gitignore
@@ -43,3 +43,4 @@ pybind11Targets.cmake
 /pybind11/share/*
 /docs/_build/*
 .ipynb_checkpoints/
+tests/main.cpp
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ee0975bc1f..3284e21eb4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -120,6 +120,8 @@ set(PYBIND11_HEADERS
     include/pybind11/complex.h
     include/pybind11/options.h
     include/pybind11/eigen.h
+    include/pybind11/eigen/matrix.h
+    include/pybind11/eigen/tensor.h
     include/pybind11/embed.h
     include/pybind11/eval.h
     include/pybind11/gil.h
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 8316252294..273b9c9308 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -9,705 +9,4 @@
 
 #pragma once
 
-/* HINT: To suppress warnings originating from the Eigen headers, use -isystem.
-   See also:
-       https://stackoverflow.com/questions/2579576/i-dir-vs-isystem-dir
-       https://stackoverflow.com/questions/1741816/isystem-for-ms-visual-studio-c-compiler
-*/
-
-#include "numpy.h"
-
-// The C4127 suppression was introduced for Eigen 3.4.0. In theory we could
-// make it version specific, or even remove it later, but considering that
-// 1. C4127 is generally far more distracting than useful for modern template code, and
-// 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
-//    it is probably best to keep this around indefinitely.
-#if defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning(disable : 4127) // C4127: conditional expression is constant
-#    pragma warning(disable : 5054) // https://github.com/pybind/pybind11/pull/3741
-//       C5054: operator '&': deprecated between enumerations of different types
-#elif defined(__MINGW32__)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
-#endif
-
-#include <Eigen/Core>
-#include <Eigen/SparseCore>
-
-#if defined(_MSC_VER)
-#    pragma warning(pop)
-#elif defined(__MINGW32__)
-#    pragma GCC diagnostic pop
-#endif
-
-// Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
-// move constructors that break things.  We could detect this an explicitly copy, but an extra copy
-// of matrices seems highly undesirable.
-static_assert(EIGEN_VERSION_AT_LEAST(3, 2, 7),
-              "Eigen support in pybind11 requires Eigen >= 3.2.7");
-
-PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-
-// Provide a convenience alias for easier pass-by-ref usage with fully dynamic strides:
-using EigenDStride = Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic>;
-template <typename MatrixType>
-using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
-template <typename MatrixType>
-using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
-
-PYBIND11_NAMESPACE_BEGIN(detail)
-
-#if EIGEN_VERSION_AT_LEAST(3, 3, 0)
-using EigenIndex = Eigen::Index;
-template <typename Scalar, int Flags, typename StorageIndex>
-using EigenMapSparseMatrix = Eigen::Map<Eigen::SparseMatrix<Scalar, Flags, StorageIndex>>;
-#else
-using EigenIndex = EIGEN_DEFAULT_DENSE_INDEX_TYPE;
-template <typename Scalar, int Flags, typename StorageIndex>
-using EigenMapSparseMatrix = Eigen::MappedSparseMatrix<Scalar, Flags, StorageIndex>;
-#endif
-
-// Matches Eigen::Map, Eigen::Ref, blocks, etc:
-template <typename T>
-using is_eigen_dense_map = all_of<is_template_base_of<Eigen::DenseBase, T>,
-                                  std::is_base_of<Eigen::MapBase<T, Eigen::ReadOnlyAccessors>, T>>;
-template <typename T>
-using is_eigen_mutable_map = std::is_base_of<Eigen::MapBase<T, Eigen::WriteAccessors>, T>;
-template <typename T>
-using is_eigen_dense_plain
-    = all_of<negation<is_eigen_dense_map<T>>, is_template_base_of<Eigen::PlainObjectBase, T>>;
-template <typename T>
-using is_eigen_sparse = is_template_base_of<Eigen::SparseMatrixBase, T>;
-// Test for objects inheriting from EigenBase<Derived> that aren't captured by the above.  This
-// basically covers anything that can be assigned to a dense matrix but that don't have a typical
-// matrix data layout that can be copied from their .data().  For example, DiagonalMatrix and
-// SelfAdjointView fall into this category.
-template <typename T>
-using is_eigen_other
-    = all_of<is_template_base_of<Eigen::EigenBase, T>,
-             negation<any_of<is_eigen_dense_map<T>, is_eigen_dense_plain<T>, is_eigen_sparse<T>>>>;
-
-// Captures numpy/eigen conformability status (returned by EigenProps::conformable()):
-template <bool EigenRowMajor>
-struct EigenConformable {
-    bool conformable = false;
-    EigenIndex rows = 0, cols = 0;
-    EigenDStride stride{0, 0};    // Only valid if negativestrides is false!
-    bool negativestrides = false; // If true, do not use stride!
-
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    EigenConformable(bool fits = false) : conformable{fits} {}
-    // Matrix type:
-    EigenConformable(EigenIndex r, EigenIndex c, EigenIndex rstride, EigenIndex cstride)
-        : conformable{true}, rows{r}, cols{c},
-          // TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity.
-          // http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
-          stride{EigenRowMajor ? (rstride > 0 ? rstride : 0)
-                               : (cstride > 0 ? cstride : 0) /* outer stride */,
-                 EigenRowMajor ? (cstride > 0 ? cstride : 0)
-                               : (rstride > 0 ? rstride : 0) /* inner stride */},
-          negativestrides{rstride < 0 || cstride < 0} {}
-    // Vector type:
-    EigenConformable(EigenIndex r, EigenIndex c, EigenIndex stride)
-        : EigenConformable(r, c, r == 1 ? c * stride : stride, c == 1 ? r : r * stride) {}
-
-    template <typename props>
-    bool stride_compatible() const {
-        // To have compatible strides, we need (on both dimensions) one of fully dynamic strides,
-        // matching strides, or a dimension size of 1 (in which case the stride value is
-        // irrelevant). Alternatively, if any dimension size is 0, the strides are not relevant
-        // (and numpy ≥ 1.23 sets the strides to 0 in that case, so we need to check explicitly).
-        if (negativestrides) {
-            return false;
-        }
-        if (rows == 0 || cols == 0) {
-            return true;
-        }
-        return (props::inner_stride == Eigen::Dynamic || props::inner_stride == stride.inner()
-                || (EigenRowMajor ? cols : rows) == 1)
-               && (props::outer_stride == Eigen::Dynamic || props::outer_stride == stride.outer()
-                   || (EigenRowMajor ? rows : cols) == 1);
-    }
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    operator bool() const { return conformable; }
-};
-
-template <typename Type>
-struct eigen_extract_stride {
-    using type = Type;
-};
-template <typename PlainObjectType, int MapOptions, typename StrideType>
-struct eigen_extract_stride<Eigen::Map<PlainObjectType, MapOptions, StrideType>> {
-    using type = StrideType;
-};
-template <typename PlainObjectType, int Options, typename StrideType>
-struct eigen_extract_stride<Eigen::Ref<PlainObjectType, Options, StrideType>> {
-    using type = StrideType;
-};
-
-// Helper struct for extracting information from an Eigen type
-template <typename Type_>
-struct EigenProps {
-    using Type = Type_;
-    using Scalar = typename Type::Scalar;
-    using StrideType = typename eigen_extract_stride<Type>::type;
-    static constexpr EigenIndex rows = Type::RowsAtCompileTime, cols = Type::ColsAtCompileTime,
-                                size = Type::SizeAtCompileTime;
-    static constexpr bool row_major = Type::IsRowMajor,
-                          vector
-                          = Type::IsVectorAtCompileTime, // At least one dimension has fixed size 1
-        fixed_rows = rows != Eigen::Dynamic, fixed_cols = cols != Eigen::Dynamic,
-                          fixed = size != Eigen::Dynamic, // Fully-fixed size
-        dynamic = !fixed_rows && !fixed_cols;             // Fully-dynamic size
-
-    template <EigenIndex i, EigenIndex ifzero>
-    using if_zero = std::integral_constant<EigenIndex, i == 0 ? ifzero : i>;
-    static constexpr EigenIndex inner_stride
-        = if_zero<StrideType::InnerStrideAtCompileTime, 1>::value,
-        outer_stride = if_zero < StrideType::OuterStrideAtCompileTime,
-        vector      ? size
-        : row_major ? cols
-                    : rows > ::value;
-    static constexpr bool dynamic_stride
-        = inner_stride == Eigen::Dynamic && outer_stride == Eigen::Dynamic;
-    static constexpr bool requires_row_major
-        = !dynamic_stride && !vector && (row_major ? inner_stride : outer_stride) == 1;
-    static constexpr bool requires_col_major
-        = !dynamic_stride && !vector && (row_major ? outer_stride : inner_stride) == 1;
-
-    // Takes an input array and determines whether we can make it fit into the Eigen type.  If
-    // the array is a vector, we attempt to fit it into either an Eigen 1xN or Nx1 vector
-    // (preferring the latter if it will fit in either, i.e. for a fully dynamic matrix type).
-    static EigenConformable<row_major> conformable(const array &a) {
-        const auto dims = a.ndim();
-        if (dims < 1 || dims > 2) {
-            return false;
-        }
-
-        if (dims == 2) { // Matrix type: require exact match (or dynamic)
-
-            EigenIndex np_rows = a.shape(0), np_cols = a.shape(1),
-                       np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
-                       np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
-            if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows)
-                || (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols)) {
-                return false;
-            }
-
-            return {np_rows, np_cols, np_rstride, np_cstride};
-        }
-
-        // Otherwise we're storing an n-vector.  Only one of the strides will be used, but
-        // whichever is used, we want the (single) numpy stride value.
-        const EigenIndex n = a.shape(0),
-                         stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
-
-        if (vector) { // Eigen type is a compile-time vector
-            if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n) {
-                return false; // Vector size mismatch
-            }
-            return {rows == 1 ? 1 : n, cols == 1 ? 1 : n, stride};
-        }
-        if (fixed) {
-            // The type has a fixed size, but is not a vector: abort
-            return false;
-        }
-        if (fixed_cols) {
-            // Since this isn't a vector, cols must be != 1.  We allow this only if it exactly
-            // equals the number of elements (rows is Dynamic, and so 1 row is allowed).
-            if (cols != n) {
-                return false;
-            }
-            return {1, n, stride};
-        } // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
-        if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) {
-            return false;
-        }
-        return {n, 1, stride};
-    }
-
-    static constexpr bool show_writeable
-        = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
-    static constexpr bool show_order = is_eigen_dense_map<Type>::value;
-    static constexpr bool show_c_contiguous = show_order && requires_row_major;
-    static constexpr bool show_f_contiguous
-        = !show_c_contiguous && show_order && requires_col_major;
-
-    static constexpr auto descriptor
-        = const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name + const_name("[")
-          + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) + const_name(", ")
-          + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) + const_name("]")
-          +
-          // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to
-          // be satisfied: writeable=True (for a mutable reference), and, depending on the map's
-          // stride options, possibly f_contiguous or c_contiguous.  We include them in the
-          // descriptor output to provide some hint as to why a TypeError is occurring (otherwise
-          // it can be confusing to see that a function accepts a 'numpy.ndarray[float64[3,2]]' and
-          // an error message that you *gave* a numpy.ndarray of the right type and dimensions.
-          const_name<show_writeable>(", flags.writeable", "")
-          + const_name<show_c_contiguous>(", flags.c_contiguous", "")
-          + const_name<show_f_contiguous>(", flags.f_contiguous", "") + const_name("]");
-};
-
-// Casts an Eigen type to numpy array.  If given a base, the numpy array references the src data,
-// otherwise it'll make a copy.  writeable lets you turn off the writeable flag for the array.
-template <typename props>
-handle
-eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
-    constexpr ssize_t elem_size = sizeof(typename props::Scalar);
-    array a;
-    if (props::vector) {
-        a = array({src.size()}, {elem_size * src.innerStride()}, src.data(), base);
-    } else {
-        a = array({src.rows(), src.cols()},
-                  {elem_size * src.rowStride(), elem_size * src.colStride()},
-                  src.data(),
-                  base);
-    }
-
-    if (!writeable) {
-        array_proxy(a.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
-    }
-
-    return a.release();
-}
-
-// Takes an lvalue ref to some Eigen type and a (python) base object, creating a numpy array that
-// reference the Eigen object's data with `base` as the python-registered base class (if omitted,
-// the base will be set to None, and lifetime management is up to the caller).  The numpy array is
-// non-writeable if the given type is const.
-template <typename props, typename Type>
-handle eigen_ref_array(Type &src, handle parent = none()) {
-    // none here is to get past array's should-we-copy detection, which currently always
-    // copies when there is no base.  Setting the base to None should be harmless.
-    return eigen_array_cast<props>(src, parent, !std::is_const<Type>::value);
-}
-
-// Takes a pointer to some dense, plain Eigen type, builds a capsule around it, then returns a
-// numpy array that references the encapsulated data with a python-side reference to the capsule to
-// tie its destruction to that of any dependent python objects.  Const-ness is determined by
-// whether or not the Type of the pointer given is const.
-template <typename props, typename Type, typename = enable_if_t<is_eigen_dense_plain<Type>::value>>
-handle eigen_encapsulate(Type *src) {
-    capsule base(src, [](void *o) { delete static_cast<Type *>(o); });
-    return eigen_ref_array<props>(*src, base);
-}
-
-// Type caster for regular, dense matrix types (e.g. MatrixXd), but not maps/refs/etc. of dense
-// types.
-template <typename Type>
-struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
-    using Scalar = typename Type::Scalar;
-    using props = EigenProps<Type>;
-
-    bool load(handle src, bool convert) {
-        // If we're in no-convert mode, only load if given an array of the correct type
-        if (!convert && !isinstance<array_t<Scalar>>(src)) {
-            return false;
-        }
-
-        // Coerce into an array, but don't do type conversion yet; the copy below handles it.
-        auto buf = array::ensure(src);
-
-        if (!buf) {
-            return false;
-        }
-
-        auto dims = buf.ndim();
-        if (dims < 1 || dims > 2) {
-            return false;
-        }
-
-        auto fits = props::conformable(buf);
-        if (!fits) {
-            return false;
-        }
-
-        // Allocate the new type, then build a numpy reference into it
-        value = Type(fits.rows, fits.cols);
-        auto ref = reinterpret_steal<array>(eigen_ref_array<props>(value));
-        if (dims == 1) {
-            ref = ref.squeeze();
-        } else if (ref.ndim() == 1) {
-            buf = buf.squeeze();
-        }
-
-        int result = detail::npy_api::get().PyArray_CopyInto_(ref.ptr(), buf.ptr());
-
-        if (result < 0) { // Copy failed!
-            PyErr_Clear();
-            return false;
-        }
-
-        return true;
-    }
-
-private:
-    // Cast implementation
-    template <typename CType>
-    static handle cast_impl(CType *src, return_value_policy policy, handle parent) {
-        switch (policy) {
-            case return_value_policy::take_ownership:
-            case return_value_policy::automatic:
-                return eigen_encapsulate<props>(src);
-            case return_value_policy::move:
-                return eigen_encapsulate<props>(new CType(std::move(*src)));
-            case return_value_policy::copy:
-                return eigen_array_cast<props>(*src);
-            case return_value_policy::reference:
-            case return_value_policy::automatic_reference:
-                return eigen_ref_array<props>(*src);
-            case return_value_policy::reference_internal:
-                return eigen_ref_array<props>(*src, parent);
-            default:
-                throw cast_error("unhandled return_value_policy: should not happen!");
-        };
-    }
-
-public:
-    // Normal returned non-reference, non-const value:
-    static handle cast(Type &&src, return_value_policy /* policy */, handle parent) {
-        return cast_impl(&src, return_value_policy::move, parent);
-    }
-    // If you return a non-reference const, we mark the numpy array readonly:
-    static handle cast(const Type &&src, return_value_policy /* policy */, handle parent) {
-        return cast_impl(&src, return_value_policy::move, parent);
-    }
-    // lvalue reference return; default (automatic) becomes copy
-    static handle cast(Type &src, return_value_policy policy, handle parent) {
-        if (policy == return_value_policy::automatic
-            || policy == return_value_policy::automatic_reference) {
-            policy = return_value_policy::copy;
-        }
-        return cast_impl(&src, policy, parent);
-    }
-    // const lvalue reference return; default (automatic) becomes copy
-    static handle cast(const Type &src, return_value_policy policy, handle parent) {
-        if (policy == return_value_policy::automatic
-            || policy == return_value_policy::automatic_reference) {
-            policy = return_value_policy::copy;
-        }
-        return cast(&src, policy, parent);
-    }
-    // non-const pointer return
-    static handle cast(Type *src, return_value_policy policy, handle parent) {
-        return cast_impl(src, policy, parent);
-    }
-    // const pointer return
-    static handle cast(const Type *src, return_value_policy policy, handle parent) {
-        return cast_impl(src, policy, parent);
-    }
-
-    static constexpr auto name = props::descriptor;
-
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type *() { return &value; }
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type &() { return value; }
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type &&() && { return std::move(value); }
-    template <typename T>
-    using cast_op_type = movable_cast_op_type<T>;
-
-private:
-    Type value;
-};
-
-// Base class for casting reference/map/block/etc. objects back to python.
-template <typename MapType>
-struct eigen_map_caster {
-private:
-    using props = EigenProps<MapType>;
-
-public:
-    // Directly referencing a ref/map's data is a bit dangerous (whatever the map/ref points to has
-    // to stay around), but we'll allow it under the assumption that you know what you're doing
-    // (and have an appropriate keep_alive in place).  We return a numpy array pointing directly at
-    // the ref's data (The numpy array ends up read-only if the ref was to a const matrix type.)
-    // Note that this means you need to ensure you don't destroy the object in some other way (e.g.
-    // with an appropriate keep_alive, or with a reference to a statically allocated matrix).
-    static handle cast(const MapType &src, return_value_policy policy, handle parent) {
-        switch (policy) {
-            case return_value_policy::copy:
-                return eigen_array_cast<props>(src);
-            case return_value_policy::reference_internal:
-                return eigen_array_cast<props>(src, parent, is_eigen_mutable_map<MapType>::value);
-            case return_value_policy::reference:
-            case return_value_policy::automatic:
-            case return_value_policy::automatic_reference:
-                return eigen_array_cast<props>(src, none(), is_eigen_mutable_map<MapType>::value);
-            default:
-                // move, take_ownership don't make any sense for a ref/map:
-                pybind11_fail("Invalid return_value_policy for Eigen Map/Ref/Block type");
-        }
-    }
-
-    static constexpr auto name = props::descriptor;
-
-    // Explicitly delete these: support python -> C++ conversion on these (i.e. these can be return
-    // types but not bound arguments).  We still provide them (with an explicitly delete) so that
-    // you end up here if you try anyway.
-    bool load(handle, bool) = delete;
-    operator MapType() = delete;
-    template <typename>
-    using cast_op_type = MapType;
-};
-
-// We can return any map-like object (but can only load Refs, specialized next):
-template <typename Type>
-struct type_caster<Type, enable_if_t<is_eigen_dense_map<Type>::value>> : eigen_map_caster<Type> {};
-
-// Loader for Ref<...> arguments.  See the documentation for info on how to make this work without
-// copying (it requires some extra effort in many cases).
-template <typename PlainObjectType, typename StrideType>
-struct type_caster<
-    Eigen::Ref<PlainObjectType, 0, StrideType>,
-    enable_if_t<is_eigen_dense_map<Eigen::Ref<PlainObjectType, 0, StrideType>>::value>>
-    : public eigen_map_caster<Eigen::Ref<PlainObjectType, 0, StrideType>> {
-private:
-    using Type = Eigen::Ref<PlainObjectType, 0, StrideType>;
-    using props = EigenProps<Type>;
-    using Scalar = typename props::Scalar;
-    using MapType = Eigen::Map<PlainObjectType, 0, StrideType>;
-    using Array
-        = array_t<Scalar,
-                  array::forcecast
-                      | ((props::row_major ? props::inner_stride : props::outer_stride) == 1
-                             ? array::c_style
-                         : (props::row_major ? props::outer_stride : props::inner_stride) == 1
-                             ? array::f_style
-                             : 0)>;
-    static constexpr bool need_writeable = is_eigen_mutable_map<Type>::value;
-    // Delay construction (these have no default constructor)
-    std::unique_ptr<MapType> map;
-    std::unique_ptr<Type> ref;
-    // Our array.  When possible, this is just a numpy array pointing to the source data, but
-    // sometimes we can't avoid copying (e.g. input is not a numpy array at all, has an
-    // incompatible layout, or is an array of a type that needs to be converted).  Using a numpy
-    // temporary (rather than an Eigen temporary) saves an extra copy when we need both type
-    // conversion and storage order conversion.  (Note that we refuse to use this temporary copy
-    // when loading an argument for a Ref<M> with M non-const, i.e. a read-write reference).
-    Array copy_or_ref;
-
-public:
-    bool load(handle src, bool convert) {
-        // First check whether what we have is already an array of the right type.  If not, we
-        // can't avoid a copy (because the copy is also going to do type conversion).
-        bool need_copy = !isinstance<Array>(src);
-
-        EigenConformable<props::row_major> fits;
-        if (!need_copy) {
-            // We don't need a converting copy, but we also need to check whether the strides are
-            // compatible with the Ref's stride requirements
-            auto aref = reinterpret_borrow<Array>(src);
-
-            if (aref && (!need_writeable || aref.writeable())) {
-                fits = props::conformable(aref);
-                if (!fits) {
-                    return false; // Incompatible dimensions
-                }
-                if (!fits.template stride_compatible<props>()) {
-                    need_copy = true;
-                } else {
-                    copy_or_ref = std::move(aref);
-                }
-            } else {
-                need_copy = true;
-            }
-        }
-
-        if (need_copy) {
-            // We need to copy: If we need a mutable reference, or we're not supposed to convert
-            // (either because we're in the no-convert overload pass, or because we're explicitly
-            // instructed not to copy (via `py::arg().noconvert()`) we have to fail loading.
-            if (!convert || need_writeable) {
-                return false;
-            }
-
-            Array copy = Array::ensure(src);
-            if (!copy) {
-                return false;
-            }
-            fits = props::conformable(copy);
-            if (!fits || !fits.template stride_compatible<props>()) {
-                return false;
-            }
-            copy_or_ref = std::move(copy);
-            loader_life_support::add_patient(copy_or_ref);
-        }
-
-        ref.reset();
-        map.reset(new MapType(data(copy_or_ref),
-                              fits.rows,
-                              fits.cols,
-                              make_stride(fits.stride.outer(), fits.stride.inner())));
-        ref.reset(new Type(*map));
-
-        return true;
-    }
-
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type *() { return ref.get(); }
-    // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type &() { return *ref; }
-    template <typename _T>
-    using cast_op_type = pybind11::detail::cast_op_type<_T>;
-
-private:
-    template <typename T = Type, enable_if_t<is_eigen_mutable_map<T>::value, int> = 0>
-    Scalar *data(Array &a) {
-        return a.mutable_data();
-    }
-
-    template <typename T = Type, enable_if_t<!is_eigen_mutable_map<T>::value, int> = 0>
-    const Scalar *data(Array &a) {
-        return a.data();
-    }
-
-    // Attempt to figure out a constructor of `Stride` that will work.
-    // If both strides are fixed, use a default constructor:
-    template <typename S>
-    using stride_ctor_default = bool_constant<S::InnerStrideAtCompileTime != Eigen::Dynamic
-                                              && S::OuterStrideAtCompileTime != Eigen::Dynamic
-                                              && std::is_default_constructible<S>::value>;
-    // Otherwise, if there is a two-index constructor, assume it is (outer,inner) like
-    // Eigen::Stride, and use it:
-    template <typename S>
-    using stride_ctor_dual
-        = bool_constant<!stride_ctor_default<S>::value
-                        && std::is_constructible<S, EigenIndex, EigenIndex>::value>;
-    // Otherwise, if there is a one-index constructor, and just one of the strides is dynamic, use
-    // it (passing whichever stride is dynamic).
-    template <typename S>
-    using stride_ctor_outer
-        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
-                        && S::OuterStrideAtCompileTime == Eigen::Dynamic
-                        && S::InnerStrideAtCompileTime != Eigen::Dynamic
-                        && std::is_constructible<S, EigenIndex>::value>;
-    template <typename S>
-    using stride_ctor_inner
-        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
-                        && S::InnerStrideAtCompileTime == Eigen::Dynamic
-                        && S::OuterStrideAtCompileTime != Eigen::Dynamic
-                        && std::is_constructible<S, EigenIndex>::value>;
-
-    template <typename S = StrideType, enable_if_t<stride_ctor_default<S>::value, int> = 0>
-    static S make_stride(EigenIndex, EigenIndex) {
-        return S();
-    }
-    template <typename S = StrideType, enable_if_t<stride_ctor_dual<S>::value, int> = 0>
-    static S make_stride(EigenIndex outer, EigenIndex inner) {
-        return S(outer, inner);
-    }
-    template <typename S = StrideType, enable_if_t<stride_ctor_outer<S>::value, int> = 0>
-    static S make_stride(EigenIndex outer, EigenIndex) {
-        return S(outer);
-    }
-    template <typename S = StrideType, enable_if_t<stride_ctor_inner<S>::value, int> = 0>
-    static S make_stride(EigenIndex, EigenIndex inner) {
-        return S(inner);
-    }
-};
-
-// type_caster for special matrix types (e.g. DiagonalMatrix), which are EigenBase, but not
-// EigenDense (i.e. they don't have a data(), at least not with the usual matrix layout).
-// load() is not supported, but we can cast them into the python domain by first copying to a
-// regular Eigen::Matrix, then casting that.
-template <typename Type>
-struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
-protected:
-    using Matrix
-        = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
-    using props = EigenProps<Matrix>;
-
-public:
-    static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
-        handle h = eigen_encapsulate<props>(new Matrix(src));
-        return h;
-    }
-    static handle cast(const Type *src, return_value_policy policy, handle parent) {
-        return cast(*src, policy, parent);
-    }
-
-    static constexpr auto name = props::descriptor;
-
-    // Explicitly delete these: support python -> C++ conversion on these (i.e. these can be return
-    // types but not bound arguments).  We still provide them (with an explicitly delete) so that
-    // you end up here if you try anyway.
-    bool load(handle, bool) = delete;
-    operator Type() = delete;
-    template <typename>
-    using cast_op_type = Type;
-};
-
-template <typename Type>
-struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
-    using Scalar = typename Type::Scalar;
-    using StorageIndex = remove_reference_t<decltype(*std::declval<Type>().outerIndexPtr())>;
-    using Index = typename Type::Index;
-    static constexpr bool rowMajor = Type::IsRowMajor;
-
-    bool load(handle src, bool) {
-        if (!src) {
-            return false;
-        }
-
-        auto obj = reinterpret_borrow<object>(src);
-        object sparse_module = module_::import("scipy.sparse");
-        object matrix_type = sparse_module.attr(rowMajor ? "csr_matrix" : "csc_matrix");
-
-        if (!type::handle_of(obj).is(matrix_type)) {
-            try {
-                obj = matrix_type(obj);
-            } catch (const error_already_set &) {
-                return false;
-            }
-        }
-
-        auto values = array_t<Scalar>((object) obj.attr("data"));
-        auto innerIndices = array_t<StorageIndex>((object) obj.attr("indices"));
-        auto outerIndices = array_t<StorageIndex>((object) obj.attr("indptr"));
-        auto shape = pybind11::tuple((pybind11::object) obj.attr("shape"));
-        auto nnz = obj.attr("nnz").cast<Index>();
-
-        if (!values || !innerIndices || !outerIndices) {
-            return false;
-        }
-
-        value = EigenMapSparseMatrix<Scalar,
-                                     Type::Flags &(Eigen::RowMajor | Eigen::ColMajor),
-                                     StorageIndex>(shape[0].cast<Index>(),
-                                                   shape[1].cast<Index>(),
-                                                   std::move(nnz),
-                                                   outerIndices.mutable_data(),
-                                                   innerIndices.mutable_data(),
-                                                   values.mutable_data());
-
-        return true;
-    }
-
-    static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
-        const_cast<Type &>(src).makeCompressed();
-
-        object matrix_type
-            = module_::import("scipy.sparse").attr(rowMajor ? "csr_matrix" : "csc_matrix");
-
-        array data(src.nonZeros(), src.valuePtr());
-        array outerIndices((rowMajor ? src.rows() : src.cols()) + 1, src.outerIndexPtr());
-        array innerIndices(src.nonZeros(), src.innerIndexPtr());
-
-        return matrix_type(pybind11::make_tuple(
-                               std::move(data), std::move(innerIndices), std::move(outerIndices)),
-                           pybind11::make_tuple(src.rows(), src.cols()))
-            .release();
-    }
-
-    PYBIND11_TYPE_CASTER(Type,
-                         const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[",
-                                                             "scipy.sparse.csc_matrix[")
-                             + npy_format_descriptor<Scalar>::name + const_name("]"));
-};
-
-PYBIND11_NAMESPACE_END(detail)
-PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
+#include "eigen/matrix.h"
diff --git a/include/pybind11/eigen/matrix.h b/include/pybind11/eigen/matrix.h
new file mode 100644
index 0000000000..5f5ad3867b
--- /dev/null
+++ b/include/pybind11/eigen/matrix.h
@@ -0,0 +1,713 @@
+/*
+    pybind11/eigen/matrix.h: Transparent conversion for dense and sparse Eigen matrices
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "../numpy.h"
+
+// Similar to comments & pragma block in eigen_tensor.h. PLEASE KEEP IN SYNC.
+/* HINT: To suppress warnings originating from the Eigen headers, use -isystem.
+   See also:
+       https://stackoverflow.com/questions/2579576/i-dir-vs-isystem-dir
+       https://stackoverflow.com/questions/1741816/isystem-for-ms-visual-studio-c-compiler
+*/
+// The C4127 suppression was introduced for Eigen 3.4.0. In theory we could
+// make it version specific, or even remove it later, but considering that
+// 1. C4127 is generally far more distracting than useful for modern template code, and
+// 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
+//    it is probably best to keep this around indefinitely.
+#if defined(_MSC_VER)
+#    pragma warning(push)
+#    pragma warning(disable : 4127) // C4127: conditional expression is constant
+#    pragma warning(disable : 5054) // https://github.com/pybind/pybind11/pull/3741
+//       C5054: operator '&': deprecated between enumerations of different types
+#elif defined(__MINGW32__)
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
+
+#include <Eigen/Core>
+#include <Eigen/SparseCore>
+
+#if defined(_MSC_VER)
+#    pragma warning(pop)
+#elif defined(__MINGW32__)
+#    pragma GCC diagnostic pop
+#endif
+
+// Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
+// move constructors that break things.  We could detect this an explicitly copy, but an extra copy
+// of matrices seems highly undesirable.
+static_assert(EIGEN_VERSION_AT_LEAST(3, 2, 7),
+              "Eigen matrix support in pybind11 requires Eigen >= 3.2.7");
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+// Provide a convenience alias for easier pass-by-ref usage with fully dynamic strides:
+using EigenDStride = Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic>;
+template <typename MatrixType>
+using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
+template <typename MatrixType>
+using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
+
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+#if EIGEN_VERSION_AT_LEAST(3, 3, 0)
+using EigenIndex = Eigen::Index;
+template <typename Scalar, int Flags, typename StorageIndex>
+using EigenMapSparseMatrix = Eigen::Map<Eigen::SparseMatrix<Scalar, Flags, StorageIndex>>;
+#else
+using EigenIndex = EIGEN_DEFAULT_DENSE_INDEX_TYPE;
+template <typename Scalar, int Flags, typename StorageIndex>
+using EigenMapSparseMatrix = Eigen::MappedSparseMatrix<Scalar, Flags, StorageIndex>;
+#endif
+
+// Matches Eigen::Map, Eigen::Ref, blocks, etc:
+template <typename T>
+using is_eigen_dense_map = all_of<is_template_base_of<Eigen::DenseBase, T>,
+                                  std::is_base_of<Eigen::MapBase<T, Eigen::ReadOnlyAccessors>, T>>;
+template <typename T>
+using is_eigen_mutable_map = std::is_base_of<Eigen::MapBase<T, Eigen::WriteAccessors>, T>;
+template <typename T>
+using is_eigen_dense_plain
+    = all_of<negation<is_eigen_dense_map<T>>, is_template_base_of<Eigen::PlainObjectBase, T>>;
+template <typename T>
+using is_eigen_sparse = is_template_base_of<Eigen::SparseMatrixBase, T>;
+// Test for objects inheriting from EigenBase<Derived> that aren't captured by the above.  This
+// basically covers anything that can be assigned to a dense matrix but that don't have a typical
+// matrix data layout that can be copied from their .data().  For example, DiagonalMatrix and
+// SelfAdjointView fall into this category.
+template <typename T>
+using is_eigen_other
+    = all_of<is_template_base_of<Eigen::EigenBase, T>,
+             negation<any_of<is_eigen_dense_map<T>, is_eigen_dense_plain<T>, is_eigen_sparse<T>>>>;
+
+// Captures numpy/eigen conformability status (returned by EigenProps::conformable()):
+template <bool EigenRowMajor>
+struct EigenConformable {
+    bool conformable = false;
+    EigenIndex rows = 0, cols = 0;
+    EigenDStride stride{0, 0};    // Only valid if negativestrides is false!
+    bool negativestrides = false; // If true, do not use stride!
+
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    EigenConformable(bool fits = false) : conformable{fits} {}
+    // Matrix type:
+    EigenConformable(EigenIndex r, EigenIndex c, EigenIndex rstride, EigenIndex cstride)
+        : conformable{true}, rows{r}, cols{c},
+          // TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity.
+          // http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
+          stride{EigenRowMajor ? (rstride > 0 ? rstride : 0)
+                               : (cstride > 0 ? cstride : 0) /* outer stride */,
+                 EigenRowMajor ? (cstride > 0 ? cstride : 0)
+                               : (rstride > 0 ? rstride : 0) /* inner stride */},
+          negativestrides{rstride < 0 || cstride < 0} {}
+    // Vector type:
+    EigenConformable(EigenIndex r, EigenIndex c, EigenIndex stride)
+        : EigenConformable(r, c, r == 1 ? c * stride : stride, c == 1 ? r : r * stride) {}
+
+    template <typename props>
+    bool stride_compatible() const {
+        // To have compatible strides, we need (on both dimensions) one of fully dynamic strides,
+        // matching strides, or a dimension size of 1 (in which case the stride value is
+        // irrelevant). Alternatively, if any dimension size is 0, the strides are not relevant
+        // (and numpy ≥ 1.23 sets the strides to 0 in that case, so we need to check explicitly).
+        if (negativestrides) {
+            return false;
+        }
+        if (rows == 0 || cols == 0) {
+            return true;
+        }
+        return (props::inner_stride == Eigen::Dynamic || props::inner_stride == stride.inner()
+                || (EigenRowMajor ? cols : rows) == 1)
+               && (props::outer_stride == Eigen::Dynamic || props::outer_stride == stride.outer()
+                   || (EigenRowMajor ? rows : cols) == 1);
+    }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator bool() const { return conformable; }
+};
+
+template <typename Type>
+struct eigen_extract_stride {
+    using type = Type;
+};
+template <typename PlainObjectType, int MapOptions, typename StrideType>
+struct eigen_extract_stride<Eigen::Map<PlainObjectType, MapOptions, StrideType>> {
+    using type = StrideType;
+};
+template <typename PlainObjectType, int Options, typename StrideType>
+struct eigen_extract_stride<Eigen::Ref<PlainObjectType, Options, StrideType>> {
+    using type = StrideType;
+};
+
+// Helper struct for extracting information from an Eigen type
+template <typename Type_>
+struct EigenProps {
+    using Type = Type_;
+    using Scalar = typename Type::Scalar;
+    using StrideType = typename eigen_extract_stride<Type>::type;
+    static constexpr EigenIndex rows = Type::RowsAtCompileTime, cols = Type::ColsAtCompileTime,
+                                size = Type::SizeAtCompileTime;
+    static constexpr bool row_major = Type::IsRowMajor,
+                          vector
+                          = Type::IsVectorAtCompileTime, // At least one dimension has fixed size 1
+        fixed_rows = rows != Eigen::Dynamic, fixed_cols = cols != Eigen::Dynamic,
+                          fixed = size != Eigen::Dynamic, // Fully-fixed size
+        dynamic = !fixed_rows && !fixed_cols;             // Fully-dynamic size
+
+    template <EigenIndex i, EigenIndex ifzero>
+    using if_zero = std::integral_constant<EigenIndex, i == 0 ? ifzero : i>;
+    static constexpr EigenIndex inner_stride
+        = if_zero<StrideType::InnerStrideAtCompileTime, 1>::value,
+        outer_stride = if_zero < StrideType::OuterStrideAtCompileTime,
+        vector      ? size
+        : row_major ? cols
+                    : rows > ::value;
+    static constexpr bool dynamic_stride
+        = inner_stride == Eigen::Dynamic && outer_stride == Eigen::Dynamic;
+    static constexpr bool requires_row_major
+        = !dynamic_stride && !vector && (row_major ? inner_stride : outer_stride) == 1;
+    static constexpr bool requires_col_major
+        = !dynamic_stride && !vector && (row_major ? outer_stride : inner_stride) == 1;
+
+    // Takes an input array and determines whether we can make it fit into the Eigen type.  If
+    // the array is a vector, we attempt to fit it into either an Eigen 1xN or Nx1 vector
+    // (preferring the latter if it will fit in either, i.e. for a fully dynamic matrix type).
+    static EigenConformable<row_major> conformable(const array &a) {
+        const auto dims = a.ndim();
+        if (dims < 1 || dims > 2) {
+            return false;
+        }
+
+        if (dims == 2) { // Matrix type: require exact match (or dynamic)
+
+            EigenIndex np_rows = a.shape(0), np_cols = a.shape(1),
+                       np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
+                       np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
+            if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows)
+                || (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols)) {
+                return false;
+            }
+
+            return {np_rows, np_cols, np_rstride, np_cstride};
+        }
+
+        // Otherwise we're storing an n-vector.  Only one of the strides will be used, but
+        // whichever is used, we want the (single) numpy stride value.
+        const EigenIndex n = a.shape(0),
+                         stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
+
+        if (vector) { // Eigen type is a compile-time vector
+            if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n) {
+                return false; // Vector size mismatch
+            }
+            return {rows == 1 ? 1 : n, cols == 1 ? 1 : n, stride};
+        }
+        if (fixed) {
+            // The type has a fixed size, but is not a vector: abort
+            return false;
+        }
+        if (fixed_cols) {
+            // Since this isn't a vector, cols must be != 1.  We allow this only if it exactly
+            // equals the number of elements (rows is Dynamic, and so 1 row is allowed).
+            if (cols != n) {
+                return false;
+            }
+            return {1, n, stride};
+        } // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
+        if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) {
+            return false;
+        }
+        return {n, 1, stride};
+    }
+
+    static constexpr bool show_writeable
+        = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
+    static constexpr bool show_order = is_eigen_dense_map<Type>::value;
+    static constexpr bool show_c_contiguous = show_order && requires_row_major;
+    static constexpr bool show_f_contiguous
+        = !show_c_contiguous && show_order && requires_col_major;
+
+    static constexpr auto descriptor
+        = const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name + const_name("[")
+          + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) + const_name(", ")
+          + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) + const_name("]")
+          +
+          // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to
+          // be satisfied: writeable=True (for a mutable reference), and, depending on the map's
+          // stride options, possibly f_contiguous or c_contiguous.  We include them in the
+          // descriptor output to provide some hint as to why a TypeError is occurring (otherwise
+          // it can be confusing to see that a function accepts a 'numpy.ndarray[float64[3,2]]' and
+          // an error message that you *gave* a numpy.ndarray of the right type and dimensions.
+          const_name<show_writeable>(", flags.writeable", "")
+          + const_name<show_c_contiguous>(", flags.c_contiguous", "")
+          + const_name<show_f_contiguous>(", flags.f_contiguous", "") + const_name("]");
+};
+
+// Casts an Eigen type to numpy array.  If given a base, the numpy array references the src data,
+// otherwise it'll make a copy.  writeable lets you turn off the writeable flag for the array.
+template <typename props>
+handle
+eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
+    constexpr ssize_t elem_size = sizeof(typename props::Scalar);
+    array a;
+    if (props::vector) {
+        a = array({src.size()}, {elem_size * src.innerStride()}, src.data(), base);
+    } else {
+        a = array({src.rows(), src.cols()},
+                  {elem_size * src.rowStride(), elem_size * src.colStride()},
+                  src.data(),
+                  base);
+    }
+
+    if (!writeable) {
+        array_proxy(a.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
+    }
+
+    return a.release();
+}
+
+// Takes an lvalue ref to some Eigen type and a (python) base object, creating a numpy array that
+// reference the Eigen object's data with `base` as the python-registered base class (if omitted,
+// the base will be set to None, and lifetime management is up to the caller).  The numpy array is
+// non-writeable if the given type is const.
+template <typename props, typename Type>
+handle eigen_ref_array(Type &src, handle parent = none()) {
+    // none here is to get past array's should-we-copy detection, which currently always
+    // copies when there is no base.  Setting the base to None should be harmless.
+    return eigen_array_cast<props>(src, parent, !std::is_const<Type>::value);
+}
+
+// Takes a pointer to some dense, plain Eigen type, builds a capsule around it, then returns a
+// numpy array that references the encapsulated data with a python-side reference to the capsule to
+// tie its destruction to that of any dependent python objects.  Const-ness is determined by
+// whether or not the Type of the pointer given is const.
+template <typename props, typename Type, typename = enable_if_t<is_eigen_dense_plain<Type>::value>>
+handle eigen_encapsulate(Type *src) {
+    capsule base(src, [](void *o) { delete static_cast<Type *>(o); });
+    return eigen_ref_array<props>(*src, base);
+}
+
+// Type caster for regular, dense matrix types (e.g. MatrixXd), but not maps/refs/etc. of dense
+// types.
+template <typename Type>
+struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
+    using Scalar = typename Type::Scalar;
+    using props = EigenProps<Type>;
+
+    bool load(handle src, bool convert) {
+        // If we're in no-convert mode, only load if given an array of the correct type
+        if (!convert && !isinstance<array_t<Scalar>>(src)) {
+            return false;
+        }
+
+        // Coerce into an array, but don't do type conversion yet; the copy below handles it.
+        auto buf = array::ensure(src);
+
+        if (!buf) {
+            return false;
+        }
+
+        auto dims = buf.ndim();
+        if (dims < 1 || dims > 2) {
+            return false;
+        }
+
+        auto fits = props::conformable(buf);
+        if (!fits) {
+            return false;
+        }
+
+        // Allocate the new type, then build a numpy reference into it
+        value = Type(fits.rows, fits.cols);
+        auto ref = reinterpret_steal<array>(eigen_ref_array<props>(value));
+        if (dims == 1) {
+            ref = ref.squeeze();
+        } else if (ref.ndim() == 1) {
+            buf = buf.squeeze();
+        }
+
+        int result = detail::npy_api::get().PyArray_CopyInto_(ref.ptr(), buf.ptr());
+
+        if (result < 0) { // Copy failed!
+            PyErr_Clear();
+            return false;
+        }
+
+        return true;
+    }
+
+private:
+    // Cast implementation
+    template <typename CType>
+    static handle cast_impl(CType *src, return_value_policy policy, handle parent) {
+        switch (policy) {
+            case return_value_policy::take_ownership:
+            case return_value_policy::automatic:
+                return eigen_encapsulate<props>(src);
+            case return_value_policy::move:
+                return eigen_encapsulate<props>(new CType(std::move(*src)));
+            case return_value_policy::copy:
+                return eigen_array_cast<props>(*src);
+            case return_value_policy::reference:
+            case return_value_policy::automatic_reference:
+                return eigen_ref_array<props>(*src);
+            case return_value_policy::reference_internal:
+                return eigen_ref_array<props>(*src, parent);
+            default:
+                throw cast_error("unhandled return_value_policy: should not happen!");
+        };
+    }
+
+public:
+    // Normal returned non-reference, non-const value:
+    static handle cast(Type &&src, return_value_policy /* policy */, handle parent) {
+        return cast_impl(&src, return_value_policy::move, parent);
+    }
+    // If you return a non-reference const, we mark the numpy array readonly:
+    static handle cast(const Type &&src, return_value_policy /* policy */, handle parent) {
+        return cast_impl(&src, return_value_policy::move, parent);
+    }
+    // lvalue reference return; default (automatic) becomes copy
+    static handle cast(Type &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast_impl(&src, policy, parent);
+    }
+    // const lvalue reference return; default (automatic) becomes copy
+    static handle cast(const Type &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast(&src, policy, parent);
+    }
+    // non-const pointer return
+    static handle cast(Type *src, return_value_policy policy, handle parent) {
+        return cast_impl(src, policy, parent);
+    }
+    // const pointer return
+    static handle cast(const Type *src, return_value_policy policy, handle parent) {
+        return cast_impl(src, policy, parent);
+    }
+
+    static constexpr auto name = props::descriptor;
+
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator Type *() { return &value; }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator Type &() { return value; }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator Type &&() && { return std::move(value); }
+    template <typename T>
+    using cast_op_type = movable_cast_op_type<T>;
+
+private:
+    Type value;
+};
+
+// Base class for casting reference/map/block/etc. objects back to python.
+template <typename MapType>
+struct eigen_map_caster {
+private:
+    using props = EigenProps<MapType>;
+
+public:
+    // Directly referencing a ref/map's data is a bit dangerous (whatever the map/ref points to has
+    // to stay around), but we'll allow it under the assumption that you know what you're doing
+    // (and have an appropriate keep_alive in place).  We return a numpy array pointing directly at
+    // the ref's data (The numpy array ends up read-only if the ref was to a const matrix type.)
+    // Note that this means you need to ensure you don't destroy the object in some other way (e.g.
+    // with an appropriate keep_alive, or with a reference to a statically allocated matrix).
+    static handle cast(const MapType &src, return_value_policy policy, handle parent) {
+        switch (policy) {
+            case return_value_policy::copy:
+                return eigen_array_cast<props>(src);
+            case return_value_policy::reference_internal:
+                return eigen_array_cast<props>(src, parent, is_eigen_mutable_map<MapType>::value);
+            case return_value_policy::reference:
+            case return_value_policy::automatic:
+            case return_value_policy::automatic_reference:
+                return eigen_array_cast<props>(src, none(), is_eigen_mutable_map<MapType>::value);
+            default:
+                // move, take_ownership don't make any sense for a ref/map:
+                pybind11_fail("Invalid return_value_policy for Eigen Map/Ref/Block type");
+        }
+    }
+
+    static constexpr auto name = props::descriptor;
+
+    // Explicitly delete these: support python -> C++ conversion on these (i.e. these can be return
+    // types but not bound arguments).  We still provide them (with an explicitly delete) so that
+    // you end up here if you try anyway.
+    bool load(handle, bool) = delete;
+    operator MapType() = delete;
+    template <typename>
+    using cast_op_type = MapType;
+};
+
+// We can return any map-like object (but can only load Refs, specialized next):
+template <typename Type>
+struct type_caster<Type, enable_if_t<is_eigen_dense_map<Type>::value>> : eigen_map_caster<Type> {};
+
+// Loader for Ref<...> arguments.  See the documentation for info on how to make this work without
+// copying (it requires some extra effort in many cases).
+template <typename PlainObjectType, typename StrideType>
+struct type_caster<
+    Eigen::Ref<PlainObjectType, 0, StrideType>,
+    enable_if_t<is_eigen_dense_map<Eigen::Ref<PlainObjectType, 0, StrideType>>::value>>
+    : public eigen_map_caster<Eigen::Ref<PlainObjectType, 0, StrideType>> {
+private:
+    using Type = Eigen::Ref<PlainObjectType, 0, StrideType>;
+    using props = EigenProps<Type>;
+    using Scalar = typename props::Scalar;
+    using MapType = Eigen::Map<PlainObjectType, 0, StrideType>;
+    using Array
+        = array_t<Scalar,
+                  array::forcecast
+                      | ((props::row_major ? props::inner_stride : props::outer_stride) == 1
+                             ? array::c_style
+                         : (props::row_major ? props::outer_stride : props::inner_stride) == 1
+                             ? array::f_style
+                             : 0)>;
+    static constexpr bool need_writeable = is_eigen_mutable_map<Type>::value;
+    // Delay construction (these have no default constructor)
+    std::unique_ptr<MapType> map;
+    std::unique_ptr<Type> ref;
+    // Our array.  When possible, this is just a numpy array pointing to the source data, but
+    // sometimes we can't avoid copying (e.g. input is not a numpy array at all, has an
+    // incompatible layout, or is an array of a type that needs to be converted).  Using a numpy
+    // temporary (rather than an Eigen temporary) saves an extra copy when we need both type
+    // conversion and storage order conversion.  (Note that we refuse to use this temporary copy
+    // when loading an argument for a Ref<M> with M non-const, i.e. a read-write reference).
+    Array copy_or_ref;
+
+public:
+    bool load(handle src, bool convert) {
+        // First check whether what we have is already an array of the right type.  If not, we
+        // can't avoid a copy (because the copy is also going to do type conversion).
+        bool need_copy = !isinstance<Array>(src);
+
+        EigenConformable<props::row_major> fits;
+        if (!need_copy) {
+            // We don't need a converting copy, but we also need to check whether the strides are
+            // compatible with the Ref's stride requirements
+            auto aref = reinterpret_borrow<Array>(src);
+
+            if (aref && (!need_writeable || aref.writeable())) {
+                fits = props::conformable(aref);
+                if (!fits) {
+                    return false; // Incompatible dimensions
+                }
+                if (!fits.template stride_compatible<props>()) {
+                    need_copy = true;
+                } else {
+                    copy_or_ref = std::move(aref);
+                }
+            } else {
+                need_copy = true;
+            }
+        }
+
+        if (need_copy) {
+            // We need to copy: If we need a mutable reference, or we're not supposed to convert
+            // (either because we're in the no-convert overload pass, or because we're explicitly
+            // instructed not to copy (via `py::arg().noconvert()`) we have to fail loading.
+            if (!convert || need_writeable) {
+                return false;
+            }
+
+            Array copy = Array::ensure(src);
+            if (!copy) {
+                return false;
+            }
+            fits = props::conformable(copy);
+            if (!fits || !fits.template stride_compatible<props>()) {
+                return false;
+            }
+            copy_or_ref = std::move(copy);
+            loader_life_support::add_patient(copy_or_ref);
+        }
+
+        ref.reset();
+        map.reset(new MapType(data(copy_or_ref),
+                              fits.rows,
+                              fits.cols,
+                              make_stride(fits.stride.outer(), fits.stride.inner())));
+        ref.reset(new Type(*map));
+
+        return true;
+    }
+
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator Type *() { return ref.get(); }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator Type &() { return *ref; }
+    template <typename _T>
+    using cast_op_type = pybind11::detail::cast_op_type<_T>;
+
+private:
+    template <typename T = Type, enable_if_t<is_eigen_mutable_map<T>::value, int> = 0>
+    Scalar *data(Array &a) {
+        return a.mutable_data();
+    }
+
+    template <typename T = Type, enable_if_t<!is_eigen_mutable_map<T>::value, int> = 0>
+    const Scalar *data(Array &a) {
+        return a.data();
+    }
+
+    // Attempt to figure out a constructor of `Stride` that will work.
+    // If both strides are fixed, use a default constructor:
+    template <typename S>
+    using stride_ctor_default = bool_constant<S::InnerStrideAtCompileTime != Eigen::Dynamic
+                                              && S::OuterStrideAtCompileTime != Eigen::Dynamic
+                                              && std::is_default_constructible<S>::value>;
+    // Otherwise, if there is a two-index constructor, assume it is (outer,inner) like
+    // Eigen::Stride, and use it:
+    template <typename S>
+    using stride_ctor_dual
+        = bool_constant<!stride_ctor_default<S>::value
+                        && std::is_constructible<S, EigenIndex, EigenIndex>::value>;
+    // Otherwise, if there is a one-index constructor, and just one of the strides is dynamic, use
+    // it (passing whichever stride is dynamic).
+    template <typename S>
+    using stride_ctor_outer
+        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
+                        && S::OuterStrideAtCompileTime == Eigen::Dynamic
+                        && S::InnerStrideAtCompileTime != Eigen::Dynamic
+                        && std::is_constructible<S, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_inner
+        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
+                        && S::InnerStrideAtCompileTime == Eigen::Dynamic
+                        && S::OuterStrideAtCompileTime != Eigen::Dynamic
+                        && std::is_constructible<S, EigenIndex>::value>;
+
+    template <typename S = StrideType, enable_if_t<stride_ctor_default<S>::value, int> = 0>
+    static S make_stride(EigenIndex, EigenIndex) {
+        return S();
+    }
+    template <typename S = StrideType, enable_if_t<stride_ctor_dual<S>::value, int> = 0>
+    static S make_stride(EigenIndex outer, EigenIndex inner) {
+        return S(outer, inner);
+    }
+    template <typename S = StrideType, enable_if_t<stride_ctor_outer<S>::value, int> = 0>
+    static S make_stride(EigenIndex outer, EigenIndex) {
+        return S(outer);
+    }
+    template <typename S = StrideType, enable_if_t<stride_ctor_inner<S>::value, int> = 0>
+    static S make_stride(EigenIndex, EigenIndex inner) {
+        return S(inner);
+    }
+};
+
+// type_caster for special matrix types (e.g. DiagonalMatrix), which are EigenBase, but not
+// EigenDense (i.e. they don't have a data(), at least not with the usual matrix layout).
+// load() is not supported, but we can cast them into the python domain by first copying to a
+// regular Eigen::Matrix, then casting that.
+template <typename Type>
+struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
+protected:
+    using Matrix
+        = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
+    using props = EigenProps<Matrix>;
+
+public:
+    static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
+        handle h = eigen_encapsulate<props>(new Matrix(src));
+        return h;
+    }
+    static handle cast(const Type *src, return_value_policy policy, handle parent) {
+        return cast(*src, policy, parent);
+    }
+
+    static constexpr auto name = props::descriptor;
+
+    // Explicitly delete these: support python -> C++ conversion on these (i.e. these can be return
+    // types but not bound arguments).  We still provide them (with an explicitly delete) so that
+    // you end up here if you try anyway.
+    bool load(handle, bool) = delete;
+    operator Type() = delete;
+    template <typename>
+    using cast_op_type = Type;
+};
+
+template <typename Type>
+struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
+    using Scalar = typename Type::Scalar;
+    using StorageIndex = remove_reference_t<decltype(*std::declval<Type>().outerIndexPtr())>;
+    using Index = typename Type::Index;
+    static constexpr bool rowMajor = Type::IsRowMajor;
+
+    bool load(handle src, bool) {
+        if (!src) {
+            return false;
+        }
+
+        auto obj = reinterpret_borrow<object>(src);
+        object sparse_module = module_::import("scipy.sparse");
+        object matrix_type = sparse_module.attr(rowMajor ? "csr_matrix" : "csc_matrix");
+
+        if (!type::handle_of(obj).is(matrix_type)) {
+            try {
+                obj = matrix_type(obj);
+            } catch (const error_already_set &) {
+                return false;
+            }
+        }
+
+        auto values = array_t<Scalar>((object) obj.attr("data"));
+        auto innerIndices = array_t<StorageIndex>((object) obj.attr("indices"));
+        auto outerIndices = array_t<StorageIndex>((object) obj.attr("indptr"));
+        auto shape = pybind11::tuple((pybind11::object) obj.attr("shape"));
+        auto nnz = obj.attr("nnz").cast<Index>();
+
+        if (!values || !innerIndices || !outerIndices) {
+            return false;
+        }
+
+        value = EigenMapSparseMatrix<Scalar,
+                                     Type::Flags &(Eigen::RowMajor | Eigen::ColMajor),
+                                     StorageIndex>(shape[0].cast<Index>(),
+                                                   shape[1].cast<Index>(),
+                                                   std::move(nnz),
+                                                   outerIndices.mutable_data(),
+                                                   innerIndices.mutable_data(),
+                                                   values.mutable_data());
+
+        return true;
+    }
+
+    static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
+        const_cast<Type &>(src).makeCompressed();
+
+        object matrix_type
+            = module_::import("scipy.sparse").attr(rowMajor ? "csr_matrix" : "csc_matrix");
+
+        array data(src.nonZeros(), src.valuePtr());
+        array outerIndices((rowMajor ? src.rows() : src.cols()) + 1, src.outerIndexPtr());
+        array innerIndices(src.nonZeros(), src.innerIndexPtr());
+
+        return matrix_type(pybind11::make_tuple(
+                               std::move(data), std::move(innerIndices), std::move(outerIndices)),
+                           pybind11::make_tuple(src.rows(), src.cols()))
+            .release();
+    }
+
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[",
+                                                             "scipy.sparse.csc_matrix[")
+                             + npy_format_descriptor<Scalar>::name + const_name("]"));
+};
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
new file mode 100644
index 0000000000..a823c0f397
--- /dev/null
+++ b/include/pybind11/eigen/tensor.h
@@ -0,0 +1,518 @@
+/*
+    pybind11/eigen/tensor.h: Transparent conversion for Eigen tensors
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "../numpy.h"
+
+#if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+static_assert(__GNUC__ > 5, "Eigen Tensor support in pybind11 requires GCC > 5.0");
+#endif
+
+#if defined(_MSC_VER)
+#    pragma warning(push)
+#    pragma warning(disable : 4554) // Tensor.h warning
+#    pragma warning(disable : 4127) // Tensor.h warning
+#elif defined(__MINGW32__)
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
+
+#include <unsupported/Eigen/CXX11/Tensor>
+
+#if defined(_MSC_VER)
+#    pragma warning(pop)
+#elif defined(__MINGW32__)
+#    pragma GCC diagnostic pop
+#endif
+
+static_assert(EIGEN_VERSION_AT_LEAST(3, 3, 0),
+              "Eigen Tensor support in pybind11 requires Eigen >= 3.3.0");
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+inline bool is_tensor_aligned(const void *data) {
+    return (reinterpret_cast<std::size_t>(data) % EIGEN_DEFAULT_ALIGN_BYTES) == 0;
+}
+
+template <typename T>
+constexpr int compute_array_flag_from_tensor() {
+    static_assert((static_cast<int>(T::Layout) == static_cast<int>(Eigen::RowMajor))
+                      || (static_cast<int>(T::Layout) == static_cast<int>(Eigen::ColMajor)),
+                  "Layout must be row or column major");
+    return (static_cast<int>(T::Layout) == static_cast<int>(Eigen::RowMajor)) ? array::c_style
+                                                                              : array::f_style;
+}
+
+template <typename T>
+struct eigen_tensor_helper {};
+
+template <typename Scalar_, int NumIndices_, int Options_, typename IndexType>
+struct eigen_tensor_helper<Eigen::Tensor<Scalar_, NumIndices_, Options_, IndexType>> {
+    using Type = Eigen::Tensor<Scalar_, NumIndices_, Options_, IndexType>;
+    using ValidType = void;
+
+    static Eigen::DSizes<typename Type::Index, Type::NumIndices> get_shape(const Type &f) {
+        return f.dimensions();
+    }
+
+    static constexpr bool
+    is_correct_shape(const Eigen::DSizes<typename Type::Index, Type::NumIndices> & /*shape*/) {
+        return true;
+    }
+
+    template <typename T>
+    struct helper {};
+
+    template <size_t... Is>
+    struct helper<index_sequence<Is...>> {
+        static constexpr auto value = concat(const_name(((void) Is, "?"))...);
+    };
+
+    static constexpr auto dimensions_descriptor
+        = helper<decltype(make_index_sequence<Type::NumIndices>())>::value;
+
+    template <typename... Args>
+    static Type *alloc(Args &&...args) {
+        return new Type(std::forward<Args>(args)...);
+    }
+
+    static void free(Type *tensor) { delete tensor; }
+};
+
+template <typename Scalar_, typename std::ptrdiff_t... Indices, int Options_, typename IndexType>
+struct eigen_tensor_helper<
+    Eigen::TensorFixedSize<Scalar_, Eigen::Sizes<Indices...>, Options_, IndexType>> {
+    using Type = Eigen::TensorFixedSize<Scalar_, Eigen::Sizes<Indices...>, Options_, IndexType>;
+    using ValidType = void;
+
+    static constexpr Eigen::DSizes<typename Type::Index, Type::NumIndices>
+    get_shape(const Type & /*f*/) {
+        return get_shape();
+    }
+
+    static constexpr Eigen::DSizes<typename Type::Index, Type::NumIndices> get_shape() {
+        return Eigen::DSizes<typename Type::Index, Type::NumIndices>(Indices...);
+    }
+
+    static bool
+    is_correct_shape(const Eigen::DSizes<typename Type::Index, Type::NumIndices> &shape) {
+        return get_shape() == shape;
+    }
+
+    static constexpr auto dimensions_descriptor = concat(const_name<Indices>()...);
+
+    template <typename... Args>
+    static Type *alloc(Args &&...args) {
+        Eigen::aligned_allocator<Type> allocator;
+        return ::new (allocator.allocate(1)) Type(std::forward<Args>(args)...);
+    }
+
+    static void free(Type *tensor) {
+        Eigen::aligned_allocator<Type> allocator;
+        tensor->~Type();
+        allocator.deallocate(tensor, 1);
+    }
+};
+
+template <typename Type, bool ShowDetails, bool NeedsWriteable = false>
+struct get_tensor_descriptor {
+    static constexpr auto details
+        = const_name<NeedsWriteable>(", flags.writeable", "")
+          + const_name<static_cast<int>(Type::Layout) == static_cast<int>(Eigen::RowMajor)>(
+              ", flags.c_contiguous", ", flags.f_contiguous");
+    static constexpr auto value
+        = const_name("numpy.ndarray[") + npy_format_descriptor<typename Type::Scalar>::name
+          + const_name("[") + eigen_tensor_helper<remove_cv_t<Type>>::dimensions_descriptor
+          + const_name("]") + const_name<ShowDetails>(details, const_name("")) + const_name("]");
+};
+
+// When EIGEN_AVOID_STL_ARRAY is defined, Eigen::DSizes<T, 0> does not have the begin() member
+// function. Falling back to a simple loop works around this issue.
+//
+// We need to disable the type-limits warning for the inner loop when size = 0.
+
+#if defined(__GNUC__)
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wtype-limits"
+#endif
+
+template <typename T, int size>
+std::vector<T> convert_dsizes_to_vector(const Eigen::DSizes<T, size> &arr) {
+    std::vector<T> result(size);
+
+    for (size_t i = 0; i < size; i++) {
+        result[i] = arr[i];
+    }
+
+    return result;
+}
+
+template <typename T, int size>
+Eigen::DSizes<T, size> get_shape_for_array(const array &arr) {
+    Eigen::DSizes<T, size> result;
+    const T *shape = arr.shape();
+    for (size_t i = 0; i < size; i++) {
+        result[i] = shape[i];
+    }
+
+    return result;
+}
+
+#if defined(__GNUC__)
+#    pragma GCC diagnostic pop
+#endif
+
+template <typename Type>
+struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
+    using Helper = eigen_tensor_helper<Type>;
+    static constexpr auto temp_name = get_tensor_descriptor<Type, false>::value;
+    PYBIND11_TYPE_CASTER(Type, temp_name);
+
+    bool load(handle src, bool convert) {
+        if (!convert) {
+            if (!isinstance<array>(src)) {
+                return false;
+            }
+            array temp = array::ensure(src);
+            if (!temp) {
+                return false;
+            }
+
+            if (!convert && !temp.dtype().is(dtype::of<typename Type::Scalar>())) {
+                return false;
+            }
+        }
+
+        array_t<typename Type::Scalar, compute_array_flag_from_tensor<Type>()> arr(
+            reinterpret_borrow<object>(src));
+
+        if (arr.ndim() != Type::NumIndices) {
+            return false;
+        }
+        auto shape = get_shape_for_array<typename Type::Index, Type::NumIndices>(arr);
+
+        if (!Helper::is_correct_shape(shape)) {
+            return false;
+        }
+
+#if EIGEN_VERSION_AT_LEAST(3, 4, 0)
+        auto data_pointer = arr.data();
+#else
+        // Handle Eigen bug
+        auto data_pointer = const_cast<typename Type::Scalar *>(arr.data());
+#endif
+
+        if (is_tensor_aligned(arr.data())) {
+            value = Eigen::TensorMap<const Type, Eigen::Aligned>(data_pointer, shape);
+        } else {
+            value = Eigen::TensorMap<const Type>(data_pointer, shape);
+        }
+
+        return true;
+    }
+
+    static handle cast(Type &&src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::reference
+            || policy == return_value_policy::reference_internal) {
+            pybind11_fail("Cannot use a reference return value policy for an rvalue");
+        }
+        return cast_impl(&src, return_value_policy::move, parent);
+    }
+
+    static handle cast(const Type &&src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::reference
+            || policy == return_value_policy::reference_internal) {
+            pybind11_fail("Cannot use a reference return value policy for an rvalue");
+        }
+        return cast_impl(&src, return_value_policy::move, parent);
+    }
+
+    static handle cast(Type &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(const Type &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast(&src, policy, parent);
+    }
+
+    static handle cast(Type *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    static handle cast(const Type *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    template <typename C>
+    static handle cast_impl(C *src, return_value_policy policy, handle parent) {
+        object parent_object;
+        bool writeable = false;
+        switch (policy) {
+            case return_value_policy::move:
+                if (std::is_const<C>::value) {
+                    pybind11_fail("Cannot move from a constant reference");
+                }
+
+                src = Helper::alloc(std::move(*src));
+
+                parent_object
+                    = capsule(src, [](void *ptr) { Helper::free(reinterpret_cast<Type *>(ptr)); });
+                writeable = true;
+                break;
+
+            case return_value_policy::take_ownership:
+                if (std::is_const<C>::value) {
+                    // This cast is ugly, and might be UB in some cases, but we don't have an
+                    // alterantive here as we must free that memory
+                    Helper::free(const_cast<Type *>(src));
+                    pybind11_fail("Cannot take ownership of a const reference");
+                }
+
+                parent_object
+                    = capsule(src, [](void *ptr) { Helper::free(reinterpret_cast<Type *>(ptr)); });
+                writeable = true;
+                break;
+
+            case return_value_policy::copy:
+                writeable = true;
+                break;
+
+            case return_value_policy::reference:
+                parent_object = none();
+                writeable = !std::is_const<C>::value;
+                break;
+
+            case return_value_policy::reference_internal:
+                // Default should do the right thing
+                if (!parent) {
+                    pybind11_fail("Cannot use reference internal when there is no parent");
+                }
+                parent_object = reinterpret_borrow<object>(parent);
+                writeable = !std::is_const<C>::value;
+                break;
+
+            default:
+                pybind11_fail("pybind11 bug in eigen.h, please file a bug report");
+        }
+
+        auto result = array_t<typename Type::Scalar, compute_array_flag_from_tensor<Type>()>(
+            convert_dsizes_to_vector(Helper::get_shape(*src)), src->data(), parent_object);
+
+        if (!writeable) {
+            array_proxy(result.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
+        }
+
+        return result.release();
+    }
+};
+
+template <typename StoragePointerType,
+          bool needs_writeable,
+          enable_if_t<!needs_writeable, bool> = true>
+StoragePointerType get_array_data_for_type(array &arr) {
+#if EIGEN_VERSION_AT_LEAST(3, 4, 0)
+    return reinterpret_cast<StoragePointerType>(arr.data());
+#else
+    // Handle Eigen bug
+    return reinterpret_cast<StoragePointerType>(const_cast<void *>(arr.data()));
+#endif
+}
+
+template <typename StoragePointerType,
+          bool needs_writeable,
+          enable_if_t<needs_writeable, bool> = true>
+StoragePointerType get_array_data_for_type(array &arr) {
+    return reinterpret_cast<StoragePointerType>(arr.mutable_data());
+}
+
+template <typename T, typename = void>
+struct get_storage_pointer_type;
+
+template <typename MapType>
+struct get_storage_pointer_type<MapType, void_t<typename MapType::StoragePointerType>> {
+    using SPT = typename MapType::StoragePointerType;
+};
+
+template <typename MapType>
+struct get_storage_pointer_type<MapType, void_t<typename MapType::PointerArgType>> {
+    using SPT = typename MapType::PointerArgType;
+};
+
+template <typename Type, int Options>
+struct type_caster<Eigen::TensorMap<Type, Options>,
+                   typename eigen_tensor_helper<remove_cv_t<Type>>::ValidType> {
+    using MapType = Eigen::TensorMap<Type, Options>;
+    using Helper = eigen_tensor_helper<remove_cv_t<Type>>;
+
+    bool load(handle src, bool /*convert*/) {
+        // Note that we have a lot more checks here as we want to make sure to avoid copies
+        if (!isinstance<array>(src)) {
+            return false;
+        }
+        auto arr = reinterpret_borrow<array>(src);
+        if ((arr.flags() & compute_array_flag_from_tensor<Type>()) == 0) {
+            return false;
+        }
+
+        if (!arr.dtype().is(dtype::of<typename Type::Scalar>())) {
+            return false;
+        }
+
+        if (arr.ndim() != Type::NumIndices) {
+            return false;
+        }
+
+        constexpr bool is_aligned = (Options & Eigen::Aligned) != 0;
+
+        if (PYBIND11_SILENCE_MSVC_C4127(is_aligned) && !is_tensor_aligned(arr.data())) {
+            return false;
+        }
+
+        auto shape = get_shape_for_array<typename Type::Index, Type::NumIndices>(arr);
+
+        if (!Helper::is_correct_shape(shape)) {
+            return false;
+        }
+
+        if (PYBIND11_SILENCE_MSVC_C4127(needs_writeable) && !arr.writeable()) {
+            return false;
+        }
+
+        auto result = get_array_data_for_type<typename get_storage_pointer_type<MapType>::SPT,
+                                              needs_writeable>(arr);
+
+        value.reset(new MapType(std::move(result), std::move(shape)));
+
+        return true;
+    }
+
+    static handle cast(MapType &&src, return_value_policy policy, handle parent) {
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(const MapType &&src, return_value_policy policy, handle parent) {
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(MapType &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(const MapType &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast(&src, policy, parent);
+    }
+
+    static handle cast(MapType *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    static handle cast(const MapType *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    template <typename C>
+    static handle cast_impl(C *src, return_value_policy policy, handle parent) {
+        object parent_object;
+        constexpr bool writeable = !std::is_const<C>::value;
+        switch (policy) {
+            case return_value_policy::reference:
+                parent_object = none();
+                break;
+
+            case return_value_policy::reference_internal:
+                // Default should do the right thing
+                if (!parent) {
+                    pybind11_fail("Cannot use reference internal when there is no parent");
+                }
+                parent_object = reinterpret_borrow<object>(parent);
+                break;
+
+            case return_value_policy::take_ownership:
+                delete src;
+                // fallthrough
+            default:
+                // move, take_ownership don't make any sense for a ref/map:
+                pybind11_fail("Invalid return_value_policy for Eigen Map type, must be either "
+                              "reference or reference_internal");
+        }
+
+        auto result = array_t<typename Type::Scalar, compute_array_flag_from_tensor<Type>()>(
+            convert_dsizes_to_vector(Helper::get_shape(*src)),
+            src->data(),
+            std::move(parent_object));
+
+        if (!writeable) {
+            array_proxy(result.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
+        }
+
+        return result.release();
+    }
+
+#if EIGEN_VERSION_AT_LEAST(3, 4, 0)
+
+    static constexpr bool needs_writeable = !std::is_const<typename std::remove_pointer<
+        typename get_storage_pointer_type<MapType>::SPT>::type>::value;
+#else
+    // Handle Eigen bug
+    static constexpr bool needs_writeable = !std::is_const<Type>::value;
+#endif
+
+protected:
+    // TODO: Move to std::optional once std::optional has more support
+    std::unique_ptr<MapType> value;
+
+public:
+    static constexpr auto name = get_tensor_descriptor<Type, true, needs_writeable>::value;
+    explicit operator MapType *() { return value.get(); }
+    explicit operator MapType &() { return *value; }
+    explicit operator MapType &&() && { return std::move(*value); }
+
+    template <typename T_>
+    using cast_op_type = ::pybind11::detail::movable_cast_op_type<T_>;
+};
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 7296cd1b81..491f215cef 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -128,7 +128,9 @@ set(PYBIND11_TEST_FILES
     test_custom_type_casters
     test_custom_type_setup
     test_docstring_options
-    test_eigen
+    test_eigen_matrix
+    test_eigen_tensor
+    test_eigen_tensor_avoid_stl_array.cpp
     test_enum
     test_eval
     test_exceptions
@@ -233,7 +235,10 @@ list(GET PYBIND11_EIGEN_VERSION_AND_HASH 1 PYBIND11_EIGEN_VERSION_HASH)
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
 # skip message).
-list(FIND PYBIND11_TEST_FILES test_eigen.cpp PYBIND11_TEST_FILES_EIGEN_I)
+list(FIND PYBIND11_TEST_FILES test_eigen_matrix.cpp PYBIND11_TEST_FILES_EIGEN_I)
+if(PYBIND11_TEST_FILES_EIGEN_I EQUAL -1)
+  list(FIND PYBIND11_TEST_FILES test_eigen_tensor.cpp PYBIND11_TEST_FILES_EIGEN_I)
+endif()
 if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
   # Try loading via newer Eigen's Eigen3Config first (bypassing tools/FindEigen3.cmake).
   # Eigen 3.3.1+ exports a cmake 3.0+ target for handling dependency requirements, but also
@@ -289,12 +294,37 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     endif()
     message(STATUS "Building tests with Eigen v${EIGEN3_VERSION}")
   else()
-    list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    list(FIND PYBIND11_TEST_FILES test_eigen_matrix.cpp PYBIND11_TEST_FILES_EIGEN_I)
+    if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+      list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    endif()
+
+    list(FIND PYBIND11_TEST_FILES test_eigen_tensor.cpp PYBIND11_TEST_FILES_EIGEN_I)
+    if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+      list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    endif()
+    list(FIND PYBIND11_TEST_FILES test_eigen_tensor_avoid_stl_array.cpp
+         PYBIND11_TEST_FILES_EIGEN_I)
+    if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+      list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    endif()
     message(
       STATUS "Building tests WITHOUT Eigen, use -DDOWNLOAD_EIGEN=ON on CMake 3.11+ to download")
   endif()
 endif()
 
+# Some code doesn't support gcc 4
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
+  list(FIND PYBIND11_TEST_FILES test_eigen_tensor.cpp PYBIND11_TEST_FILES_EIGEN_I)
+  if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+    list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+  endif()
+  list(FIND PYBIND11_TEST_FILES test_eigen_tensor_avoid_stl_array.cpp PYBIND11_TEST_FILES_EIGEN_I)
+  if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+    list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+  endif()
+endif()
+
 # Optional dependency for some tests (boost::variant is only supported with version >= 1.56)
 find_package(Boost 1.56)
 
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 8e1ddd8508..9a9bb1556a 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -55,6 +55,11 @@
     "include/pybind11/detail/typeid.h",
 }
 
+eigen_headers = {
+    "include/pybind11/eigen/matrix.h",
+    "include/pybind11/eigen/tensor.h",
+}
+
 stl_headers = {
     "include/pybind11/stl/filesystem.h",
 }
@@ -82,7 +87,7 @@
     "setup_helpers.py",
 }
 
-headers = main_headers | detail_headers | stl_headers
+headers = main_headers | detail_headers | eigen_headers | stl_headers
 src_files = headers | cmake_files | pkgconfig_files
 all_files = src_files | py_files
 
@@ -92,6 +97,7 @@
     "pybind11/include",
     "pybind11/include/pybind11",
     "pybind11/include/pybind11/detail",
+    "pybind11/include/pybind11/eigen",
     "pybind11/include/pybind11/stl",
     "pybind11/share",
     "pybind11/share/cmake",
diff --git a/tests/test_eigen.cpp b/tests/test_eigen_matrix.cpp
similarity index 99%
rename from tests/test_eigen.cpp
rename to tests/test_eigen_matrix.cpp
index b0c7bdb48a..71e41d198a 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen_matrix.cpp
@@ -7,7 +7,7 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include <pybind11/eigen.h>
+#include <pybind11/eigen/matrix.h>
 #include <pybind11/stl.h>
 
 #include "constructor_stats.h"
@@ -81,7 +81,7 @@ struct CustomOperatorNew {
     EIGEN_MAKE_ALIGNED_OPERATOR_NEW;
 };
 
-TEST_SUBMODULE(eigen, m) {
+TEST_SUBMODULE(eigen_matrix, m) {
     using FixedMatrixR = Eigen::Matrix<float, 5, 6, Eigen::RowMajor>;
     using FixedMatrixC = Eigen::Matrix<float, 5, 6>;
     using DenseMatrixR = Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
diff --git a/tests/test_eigen.py b/tests/test_eigen_matrix.py
similarity index 99%
rename from tests/test_eigen.py
rename to tests/test_eigen_matrix.py
index 713432a815..4407fa6aee 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen_matrix.py
@@ -3,7 +3,7 @@
 from pybind11_tests import ConstructorStats
 
 np = pytest.importorskip("numpy")
-m = pytest.importorskip("pybind11_tests.eigen")
+m = pytest.importorskip("pybind11_tests.eigen_matrix")
 
 
 ref = np.array(
diff --git a/tests/test_eigen_tensor.cpp b/tests/test_eigen_tensor.cpp
new file mode 100644
index 0000000000..40b4940053
--- /dev/null
+++ b/tests/test_eigen_tensor.cpp
@@ -0,0 +1,16 @@
+/*
+    tests/eigen_tensor.cpp -- automatic conversion of Eigen Tensor
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+constexpr const char *test_eigen_tensor_module_name = "eigen_tensor";
+
+#define PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE eigen_tensor
+
+#ifdef EIGEN_AVOID_STL_ARRAY
+#    undef EIGEN_AVOID_STL_ARRAY
+#endif
+
+#include "test_eigen_tensor.inl"
diff --git a/tests/test_eigen_tensor.inl b/tests/test_eigen_tensor.inl
new file mode 100644
index 0000000000..09b35fa134
--- /dev/null
+++ b/tests/test_eigen_tensor.inl
@@ -0,0 +1,333 @@
+/*
+    tests/eigen_tensor.cpp -- automatic conversion of Eigen Tensor
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/eigen/tensor.h>
+
+#include "pybind11_tests.h"
+
+namespace PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE {
+
+template <typename M>
+void reset_tensor(M &x) {
+    for (int i = 0; i < x.dimension(0); i++) {
+        for (int j = 0; j < x.dimension(1); j++) {
+            for (int k = 0; k < x.dimension(2); k++) {
+                x(i, j, k) = i * (5 * 2) + j * 2 + k;
+            }
+        }
+    }
+}
+
+template <typename M>
+bool check_tensor(M &x) {
+    for (int i = 0; i < x.dimension(0); i++) {
+        for (int j = 0; j < x.dimension(1); j++) {
+            for (int k = 0; k < x.dimension(2); k++) {
+                if (x(i, j, k) != (i * (5 * 2) + j * 2 + k)) {
+                    return false;
+                }
+            }
+        }
+    }
+    return true;
+}
+
+template <int Options>
+Eigen::Tensor<double, 3, Options> &get_tensor() {
+    static Eigen::Tensor<double, 3, Options> *x;
+
+    if (!x) {
+        x = new Eigen::Tensor<double, 3, Options>(3, 5, 2);
+        reset_tensor(*x);
+    }
+
+    return *x;
+}
+
+template <int Options>
+Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> &get_tensor_map() {
+    static Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> *x;
+
+    if (!x) {
+        x = new Eigen::TensorMap<Eigen::Tensor<double, 3, Options>>(get_tensor<Options>());
+    }
+
+    return *x;
+}
+
+template <int Options>
+Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options> &get_fixed_tensor() {
+    static Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options> *x;
+
+    if (!x) {
+        Eigen::aligned_allocator<Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options>>
+            allocator;
+        x = new (allocator.allocate(1))
+            Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options>();
+        reset_tensor(*x);
+    }
+
+    return *x;
+}
+
+template <int Options>
+const Eigen::Tensor<double, 3, Options> &get_const_tensor() {
+    return get_tensor<Options>();
+}
+
+template <int Options>
+struct CustomExample {
+    CustomExample() : member(get_tensor<Options>()), view_member(member) {}
+
+    Eigen::Tensor<double, 3, Options> member;
+    Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> view_member;
+};
+
+template <int Options>
+void init_tensor_module(pybind11::module &m) {
+    const char *needed_options = "";
+    if (PYBIND11_SILENCE_MSVC_C4127(Options == Eigen::ColMajor)) {
+        needed_options = "F";
+    } else {
+        needed_options = "C";
+    }
+    m.attr("needed_options") = needed_options;
+
+    m.def("setup", []() {
+        reset_tensor(get_tensor<Options>());
+        reset_tensor(get_fixed_tensor<Options>());
+    });
+
+    m.def("is_ok", []() {
+        return check_tensor(get_tensor<Options>()) && check_tensor(get_fixed_tensor<Options>());
+    });
+
+    py::class_<CustomExample<Options>>(m, "CustomExample")
+        .def(py::init<>())
+        .def_readonly(
+            "member", &CustomExample<Options>::member, py::return_value_policy::reference_internal)
+        .def_readonly("member_view",
+                      &CustomExample<Options>::view_member,
+                      py::return_value_policy::reference_internal);
+
+    m.def(
+        "copy_fixed_tensor",
+        []() { return &get_fixed_tensor<Options>(); },
+        py::return_value_policy::copy);
+
+    m.def(
+        "copy_tensor", []() { return &get_tensor<Options>(); }, py::return_value_policy::copy);
+
+    m.def(
+        "copy_const_tensor",
+        []() { return &get_const_tensor<Options>(); },
+        py::return_value_policy::copy);
+
+    m.def(
+        "move_fixed_tensor_copy",
+        []() -> Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options> {
+            return get_fixed_tensor<Options>();
+        },
+        py::return_value_policy::move);
+
+    m.def(
+        "move_tensor_copy",
+        []() -> Eigen::Tensor<double, 3, Options> { return get_tensor<Options>(); },
+        py::return_value_policy::move);
+
+    m.def(
+        "move_const_tensor",
+        []() -> const Eigen::Tensor<double, 3, Options> & { return get_const_tensor<Options>(); },
+        py::return_value_policy::move);
+
+    m.def(
+        "take_fixed_tensor",
+
+        []() {
+            Eigen::aligned_allocator<
+                Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options>>
+                allocator;
+            return new (allocator.allocate(1))
+                Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options>(
+                    get_fixed_tensor<Options>());
+        },
+        py::return_value_policy::take_ownership);
+
+    m.def(
+        "take_tensor",
+        []() { return new Eigen::Tensor<double, 3, Options>(get_tensor<Options>()); },
+        py::return_value_policy::take_ownership);
+
+    m.def(
+        "take_const_tensor",
+        []() -> const Eigen::Tensor<double, 3, Options> * {
+            return new Eigen::Tensor<double, 3, Options>(get_tensor<Options>());
+        },
+        py::return_value_policy::take_ownership);
+
+    m.def(
+        "take_view_tensor",
+        []() -> const Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> * {
+            return new Eigen::TensorMap<Eigen::Tensor<double, 3, Options>>(get_tensor<Options>());
+        },
+        py::return_value_policy::take_ownership);
+
+    m.def(
+        "reference_tensor",
+        []() { return &get_tensor<Options>(); },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_tensor_v2",
+        []() -> Eigen::Tensor<double, 3, Options> & { return get_tensor<Options>(); },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_tensor_internal",
+        []() { return &get_tensor<Options>(); },
+        py::return_value_policy::reference_internal);
+
+    m.def(
+        "reference_fixed_tensor",
+        []() { return &get_tensor<Options>(); },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_const_tensor",
+        []() { return &get_const_tensor<Options>(); },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_const_tensor_v2",
+        []() -> const Eigen::Tensor<double, 3, Options> & { return get_const_tensor<Options>(); },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_tensor",
+        []() -> Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> {
+            return get_tensor_map<Options>();
+        },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_tensor_v2",
+        // NOLINTNEXTLINE(readability-const-return-type)
+        []() -> const Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> {
+            return get_tensor_map<Options>(); // NOLINT(readability-const-return-type)
+        },                                    // NOLINT(readability-const-return-type)
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_tensor_v3",
+        []() -> Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> * {
+            return &get_tensor_map<Options>();
+        },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_tensor_v4",
+        []() -> const Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> * {
+            return &get_tensor_map<Options>();
+        },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_tensor_v5",
+        []() -> Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> & {
+            return get_tensor_map<Options>();
+        },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_tensor_v6",
+        []() -> const Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> & {
+            return get_tensor_map<Options>();
+        },
+        py::return_value_policy::reference);
+
+    m.def(
+        "reference_view_of_fixed_tensor",
+        []() {
+            return Eigen::TensorMap<
+                Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options>>(
+                get_fixed_tensor<Options>());
+        },
+        py::return_value_policy::reference);
+
+    m.def("round_trip_tensor",
+          [](const Eigen::Tensor<double, 3, Options> &tensor) { return tensor; });
+
+    m.def(
+        "round_trip_tensor_noconvert",
+        [](const Eigen::Tensor<double, 3, Options> &tensor) { return tensor; },
+        py::arg("tensor").noconvert());
+
+    m.def("round_trip_tensor2",
+          [](const Eigen::Tensor<int32_t, 3, Options> &tensor) { return tensor; });
+
+    m.def("round_trip_fixed_tensor",
+          [](const Eigen::TensorFixedSize<double, Eigen::Sizes<3, 5, 2>, Options> &tensor) {
+              return tensor;
+          });
+
+    m.def(
+        "round_trip_view_tensor",
+        [](Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> view) { return view; },
+        py::return_value_policy::reference);
+
+    m.def(
+        "round_trip_view_tensor_ref",
+        [](Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> &view) { return view; },
+        py::return_value_policy::reference);
+
+    m.def(
+        "round_trip_view_tensor_ptr",
+        [](Eigen::TensorMap<Eigen::Tensor<double, 3, Options>> *view) { return view; },
+        py::return_value_policy::reference);
+
+    m.def(
+        "round_trip_aligned_view_tensor",
+        [](Eigen::TensorMap<Eigen::Tensor<double, 3, Options>, Eigen::Aligned> view) {
+            return view;
+        },
+        py::return_value_policy::reference);
+
+    m.def(
+        "round_trip_const_view_tensor",
+        [](Eigen::TensorMap<const Eigen::Tensor<double, 3, Options>> view) {
+            return Eigen::Tensor<double, 3, Options>(view);
+        },
+        py::return_value_policy::move);
+
+    m.def(
+        "round_trip_rank_0",
+        [](const Eigen::Tensor<double, 0, Options> &tensor) { return tensor; },
+        py::return_value_policy::move);
+
+    m.def(
+        "round_trip_rank_0_noconvert",
+        [](const Eigen::Tensor<double, 0, Options> &tensor) { return tensor; },
+        py::arg("tensor").noconvert(),
+        py::return_value_policy::move);
+
+    m.def(
+        "round_trip_rank_0_view",
+        [](Eigen::TensorMap<Eigen::Tensor<double, 0, Options>> &tensor) { return tensor; },
+        py::return_value_policy::reference);
+}
+
+void test_module(py::module_ &);
+test_initializer name(test_eigen_tensor_module_name, test_module);
+void test_module(py::module_ &m) {
+    auto f_style = m.def_submodule("f_style");
+    auto c_style = m.def_submodule("c_style");
+
+    init_tensor_module<Eigen::ColMajor>(f_style);
+    init_tensor_module<Eigen::RowMajor>(c_style);
+}
+
+} // namespace PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE
diff --git a/tests/test_eigen_tensor.py b/tests/test_eigen_tensor.py
new file mode 100644
index 0000000000..5ee5fa01b2
--- /dev/null
+++ b/tests/test_eigen_tensor.py
@@ -0,0 +1,288 @@
+import sys
+
+import pytest
+
+np = pytest.importorskip("numpy")
+eigen_tensor = pytest.importorskip("pybind11_tests.eigen_tensor")
+submodules = [eigen_tensor.c_style, eigen_tensor.f_style]
+try:
+    from pybind11_tests import eigen_tensor_avoid_stl_array as avoid
+
+    submodules += [avoid.c_style, avoid.f_style]
+except ImportError:
+    pass
+
+tensor_ref = np.empty((3, 5, 2), dtype=np.int64)
+
+for i in range(tensor_ref.shape[0]):
+    for j in range(tensor_ref.shape[1]):
+        for k in range(tensor_ref.shape[2]):
+            tensor_ref[i, j, k] = i * (5 * 2) + j * 2 + k
+
+indices = (2, 3, 1)
+
+
+@pytest.fixture(autouse=True)
+def cleanup():
+    for module in submodules:
+        module.setup()
+
+    yield
+
+    for module in submodules:
+        assert module.is_ok()
+
+
+def test_import_avoid_stl_array():
+    pytest.importorskip("pybind11_tests.eigen_tensor_avoid_stl_array")
+    assert len(submodules) == 4
+
+
+def assert_equal_tensor_ref(mat, writeable=True, modified=None):
+    assert mat.flags.writeable == writeable
+
+    copy = np.array(tensor_ref)
+    if modified is not None:
+        copy[indices] = modified
+
+    np.testing.assert_array_equal(mat, copy)
+
+
+@pytest.mark.parametrize("m", submodules)
+@pytest.mark.parametrize("member_name", ["member", "member_view"])
+def test_reference_internal(m, member_name):
+
+    if not hasattr(sys, "getrefcount"):
+        pytest.skip("No reference counting")
+    foo = m.CustomExample()
+    counts = sys.getrefcount(foo)
+    mem = getattr(foo, member_name)
+    assert_equal_tensor_ref(mem, writeable=False)
+    new_counts = sys.getrefcount(foo)
+    assert new_counts == counts + 1
+    assert_equal_tensor_ref(mem, writeable=False)
+    del mem
+    assert sys.getrefcount(foo) == counts
+
+
+assert_equal_funcs = [
+    "copy_tensor",
+    "copy_fixed_tensor",
+    "copy_const_tensor",
+    "move_tensor_copy",
+    "move_fixed_tensor_copy",
+    "take_tensor",
+    "take_fixed_tensor",
+    "reference_tensor",
+    "reference_tensor_v2",
+    "reference_fixed_tensor",
+    "reference_view_of_tensor",
+    "reference_view_of_tensor_v3",
+    "reference_view_of_tensor_v5",
+    "reference_view_of_fixed_tensor",
+]
+
+assert_equal_const_funcs = [
+    "reference_view_of_tensor_v2",
+    "reference_view_of_tensor_v4",
+    "reference_view_of_tensor_v6",
+    "reference_const_tensor",
+    "reference_const_tensor_v2",
+]
+
+
+@pytest.mark.parametrize("m", submodules)
+@pytest.mark.parametrize("func_name", assert_equal_funcs + assert_equal_const_funcs)
+def test_convert_tensor_to_py(m, func_name):
+    writeable = func_name in assert_equal_funcs
+    assert_equal_tensor_ref(getattr(m, func_name)(), writeable=writeable)
+
+
+@pytest.mark.parametrize("m", submodules)
+def test_bad_cpp_to_python_casts(m):
+
+    with pytest.raises(
+        RuntimeError, match="Cannot use reference internal when there is no parent"
+    ):
+        m.reference_tensor_internal()
+
+    with pytest.raises(RuntimeError, match="Cannot move from a constant reference"):
+        m.move_const_tensor()
+
+    with pytest.raises(
+        RuntimeError, match="Cannot take ownership of a const reference"
+    ):
+        m.take_const_tensor()
+
+    with pytest.raises(
+        RuntimeError,
+        match="Invalid return_value_policy for Eigen Map type, must be either reference or reference_internal",
+    ):
+        m.take_view_tensor()
+
+
+@pytest.mark.parametrize("m", submodules)
+def test_bad_python_to_cpp_casts(m):
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_tensor\(\): incompatible function arguments"
+    ):
+        m.round_trip_tensor(np.zeros((2, 3)))
+
+    with pytest.raises(TypeError, match=r"^Cannot cast array data from dtype"):
+        m.round_trip_tensor(np.zeros(dtype=np.str_, shape=(2, 3, 1)))
+
+    with pytest.raises(
+        TypeError,
+        match=r"^round_trip_tensor_noconvert\(\): incompatible function arguments",
+    ):
+        m.round_trip_tensor_noconvert(tensor_ref)
+
+    assert_equal_tensor_ref(
+        m.round_trip_tensor_noconvert(tensor_ref.astype(np.float64))
+    )
+
+    if m.needed_options == "F":
+        bad_options = "C"
+    else:
+        bad_options = "F"
+    # Shape, dtype and the order need to be correct for a TensorMap cast
+    with pytest.raises(
+        TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
+    ):
+        m.round_trip_view_tensor(
+            np.zeros((3, 5, 2), dtype=np.float64, order=bad_options)
+        )
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
+    ):
+        m.round_trip_view_tensor(
+            np.zeros((3, 5, 2), dtype=np.float32, order=m.needed_options)
+        )
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
+    ):
+        m.round_trip_view_tensor(
+            np.zeros((3, 5), dtype=np.float64, order=m.needed_options)
+        )
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
+    ):
+        temp = np.zeros((3, 5, 2), dtype=np.float64, order=m.needed_options)
+        m.round_trip_view_tensor(
+            temp[:, ::-1, :],
+        )
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
+    ):
+        temp = np.zeros((3, 5, 2), dtype=np.float64, order=m.needed_options)
+        temp.setflags(write=False)
+        m.round_trip_view_tensor(temp)
+
+
+@pytest.mark.parametrize("m", submodules)
+def test_references_actually_refer(m):
+
+    a = m.reference_tensor()
+    temp = a[indices]
+    a[indices] = 100
+    assert_equal_tensor_ref(m.copy_const_tensor(), modified=100)
+    a[indices] = temp
+    assert_equal_tensor_ref(m.copy_const_tensor())
+
+    a = m.reference_view_of_tensor()
+    a[indices] = 100
+    assert_equal_tensor_ref(m.copy_const_tensor(), modified=100)
+    a[indices] = temp
+    assert_equal_tensor_ref(m.copy_const_tensor())
+
+
+@pytest.mark.parametrize("m", submodules)
+def test_round_trip(m):
+
+    assert_equal_tensor_ref(m.round_trip_tensor(tensor_ref))
+
+    with pytest.raises(TypeError, match="^Cannot cast array data from"):
+        assert_equal_tensor_ref(m.round_trip_tensor2(tensor_ref))
+
+    assert_equal_tensor_ref(m.round_trip_tensor2(np.array(tensor_ref, dtype=np.int32)))
+    assert_equal_tensor_ref(m.round_trip_fixed_tensor(tensor_ref))
+    assert_equal_tensor_ref(m.round_trip_aligned_view_tensor(m.reference_tensor()))
+
+    copy = np.array(tensor_ref, dtype=np.float64, order=m.needed_options)
+    assert_equal_tensor_ref(m.round_trip_view_tensor(copy))
+    assert_equal_tensor_ref(m.round_trip_view_tensor_ref(copy))
+    assert_equal_tensor_ref(m.round_trip_view_tensor_ptr(copy))
+    copy.setflags(write=False)
+    assert_equal_tensor_ref(m.round_trip_const_view_tensor(copy))
+
+    np.testing.assert_array_equal(
+        tensor_ref[:, ::-1, :], m.round_trip_tensor(tensor_ref[:, ::-1, :])
+    )
+
+    assert m.round_trip_rank_0(np.float64(3.5)) == 3.5
+    assert m.round_trip_rank_0(3.5) == 3.5
+
+    with pytest.raises(
+        TypeError,
+        match=r"^round_trip_rank_0_noconvert\(\): incompatible function arguments",
+    ):
+        m.round_trip_rank_0_noconvert(np.float64(3.5))
+
+    with pytest.raises(
+        TypeError,
+        match=r"^round_trip_rank_0_noconvert\(\): incompatible function arguments",
+    ):
+        m.round_trip_rank_0_noconvert(3.5)
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_rank_0_view\(\): incompatible function arguments"
+    ):
+        m.round_trip_rank_0_view(np.float64(3.5))
+
+    with pytest.raises(
+        TypeError, match=r"^round_trip_rank_0_view\(\): incompatible function arguments"
+    ):
+        m.round_trip_rank_0_view(3.5)
+
+
+@pytest.mark.parametrize("m", submodules)
+def test_round_trip_references_actually_refer(m):
+
+    # Need to create a copy that matches the type on the C side
+    copy = np.array(tensor_ref, dtype=np.float64, order=m.needed_options)
+    a = m.round_trip_view_tensor(copy)
+    temp = a[indices]
+    a[indices] = 100
+    assert_equal_tensor_ref(copy, modified=100)
+    a[indices] = temp
+    assert_equal_tensor_ref(copy)
+
+
+@pytest.mark.parametrize("m", submodules)
+def test_doc_string(m, doc):
+    assert (
+        doc(m.copy_tensor) == "copy_tensor() -> numpy.ndarray[numpy.float64[?, ?, ?]]"
+    )
+    assert (
+        doc(m.copy_fixed_tensor)
+        == "copy_fixed_tensor() -> numpy.ndarray[numpy.float64[3, 5, 2]]"
+    )
+    assert (
+        doc(m.reference_const_tensor)
+        == "reference_const_tensor() -> numpy.ndarray[numpy.float64[?, ?, ?]]"
+    )
+
+    order_flag = f"flags.{m.needed_options.lower()}_contiguous"
+    assert doc(m.round_trip_view_tensor) == (
+        f"round_trip_view_tensor(arg0: numpy.ndarray[numpy.float64[?, ?, ?], flags.writeable, {order_flag}])"
+        + f" -> numpy.ndarray[numpy.float64[?, ?, ?], flags.writeable, {order_flag}]"
+    )
+    assert doc(m.round_trip_const_view_tensor) == (
+        f"round_trip_const_view_tensor(arg0: numpy.ndarray[numpy.float64[?, ?, ?], {order_flag}])"
+        + " -> numpy.ndarray[numpy.float64[?, ?, ?]]"
+    )
diff --git a/tests/test_eigen_tensor_avoid_stl_array.cpp b/tests/test_eigen_tensor_avoid_stl_array.cpp
new file mode 100644
index 0000000000..58bedf62dd
--- /dev/null
+++ b/tests/test_eigen_tensor_avoid_stl_array.cpp
@@ -0,0 +1,16 @@
+/*
+    tests/eigen_tensor.cpp -- automatic conversion of Eigen Tensor
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+constexpr const char *test_eigen_tensor_module_name = "eigen_tensor_avoid_stl_array";
+
+#ifndef EIGEN_AVOID_STL_ARRAY
+#    define EIGEN_AVOID_STL_ARRAY
+#endif
+
+#define PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE eigen_tensor_avoid_stl_array
+
+#include "test_eigen_tensor.inl"
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 69ddbe1ef2..b118e2c6cc 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -521,4 +521,6 @@ TEST_SUBMODULE(numpy_array, sm) {
     sm.def("test_fmt_desc_double", [](const py::array_t<double> &) {});
     sm.def("test_fmt_desc_const_float", [](const py::array_t<const float> &) {});
     sm.def("test_fmt_desc_const_double", [](const py::array_t<const double> &) {});
+
+    sm.def("round_trip_float", [](double d) { return d; });
 }
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 504963b166..cdec9ad60b 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -585,3 +585,9 @@ def test_dtype_refcount_leak():
     m.ndim(a)
     after = getrefcount(dtype)
     assert after == before
+
+
+def test_round_trip_float():
+    arr = np.zeros((), np.float64)
+    arr[()] = 37.2
+    assert m.round_trip_float(arr) == 37.2
diff --git a/tools/setup_global.py.in b/tools/setup_global.py.in
index d91468c10c..885ac5c725 100644
--- a/tools/setup_global.py.in
+++ b/tools/setup_global.py.in
@@ -27,10 +27,11 @@ class InstallHeadersNested(install_headers):
 
 main_headers = glob.glob("pybind11/include/pybind11/*.h")
 detail_headers = glob.glob("pybind11/include/pybind11/detail/*.h")
+eigen_headers = glob.glob("pybind11/include/pybind11/eigen/*.h")
 stl_headers = glob.glob("pybind11/include/pybind11/stl/*.h")
 cmake_files = glob.glob("pybind11/share/cmake/pybind11/*.cmake")
 pkgconfig_files = glob.glob("pybind11/share/pkgconfig/*.pc")
-headers = main_headers + detail_headers + stl_headers
+headers = main_headers + detail_headers + stl_headers + eigen_headers
 
 cmdclass = {"install_headers": InstallHeadersNested}
 $extra_cmd
@@ -55,6 +56,7 @@ setup(
         (base + "share/pkgconfig", pkgconfig_files),
         (base + "include/pybind11", main_headers),
         (base + "include/pybind11/detail", detail_headers),
+        (base + "include/pybind11/eigen", eigen_headers),
         (base + "include/pybind11/stl", stl_headers),
     ],
     cmdclass=cmdclass,
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index 65198bdb66..6358cc7b9b 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -15,6 +15,7 @@ setup(
         "pybind11",
         "pybind11.include.pybind11",
         "pybind11.include.pybind11.detail",
+        "pybind11.include.pybind11.eigen",
         "pybind11.include.pybind11.stl",
         "pybind11.share.cmake.pybind11",
         "pybind11.share.pkgconfig",
@@ -23,6 +24,7 @@ setup(
         "pybind11": ["py.typed"],
         "pybind11.include.pybind11": ["*.h"],
         "pybind11.include.pybind11.detail": ["*.h"],
+        "pybind11.include.pybind11.eigen": ["*.h"],
         "pybind11.include.pybind11.stl": ["*.h"],
         "pybind11.share.cmake.pybind11": ["*.cmake"],
         "pybind11.share.pkgconfig": ["*.pc"],

From 17c68091658f036eb6aed05cebabfc9265407a5b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 20 Oct 2022 05:49:52 -0700
Subject: [PATCH 487/638] ci: update PGI build (old one no longer signed)
 (#4260)

* Simply replace "22.3" with "22.9" to see what happens.

* Remove PYBIND11_TEST_FILTER to see what happens.

* Revert "Remove PYBIND11_TEST_FILTER to see what happens."

This reverts commit 0cba2cef0c5c5bcbf57cad219c7d5dfb0cda241c.

* Remove only test_smart_ptr.cpp to see what happens.

* Revert "Remove only test_smart_ptr.cpp to see what happens."

This reverts commit 8e9df22c85292003abcab50260393e547567fc18.

* Remove only test_virtual_functions.cpp to see what happens.
---
 .github/workflows/ci.yml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bc7175d829..2951a0ad19 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -391,7 +391,7 @@ jobs:
   # Testing on CentOS 7 + PGI compilers, which seems to require more workarounds
   centos-nvhpc7:
     runs-on: ubuntu-latest
-    name: "🐍 3 • CentOS7 / PGI 22.3 • x64"
+    name: "🐍 3 • CentOS7 / PGI 22.9 • x64"
     container: centos:7
 
     steps:
@@ -401,7 +401,7 @@ jobs:
       run: yum update -y && yum install -y epel-release && yum install -y git python3-devel make environment-modules cmake3 yum-utils
 
     - name: Install NVidia HPC SDK
-      run: yum-config-manager --add-repo https://developer.download.nvidia.com/hpc-sdk/rhel/nvhpc.repo && yum -y install nvhpc-22.3
+      run: yum-config-manager --add-repo https://developer.download.nvidia.com/hpc-sdk/rhel/nvhpc.repo && yum -y install nvhpc-22.9
 
     # On CentOS 7, we have to filter a few tests (compiler internal error)
     # and allow deeper template recursion (not needed on CentOS 8 with a newer
@@ -411,12 +411,12 @@ jobs:
       shell: bash
       run: |
         source /etc/profile.d/modules.sh
-        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/22.3
+        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/22.9
         cmake3 -S . -B build -DDOWNLOAD_CATCH=ON \
                             -DCMAKE_CXX_STANDARD=11 \
                             -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
                             -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0" \
-                            -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp;test_virtual_functions.cpp"
+                            -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp"
 
     # Building before installing Pip should produce a warning but not an error
     - name: Build

From c3854682e6644c60ff4f99f81595636f582b04f5 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 20 Oct 2022 09:39:19 -0400
Subject: [PATCH 488/638] ci(fix): don't label weekly dep updates & ci fixes
 (#4264)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/labeler.yml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/labeler.yml b/.github/workflows/labeler.yml
index d2b5979681..5152cebca2 100644
--- a/.github/workflows/labeler.yml
+++ b/.github/workflows/labeler.yml
@@ -10,7 +10,10 @@ jobs:
     steps:
 
     - uses: actions/labeler@main
-      if: github.event.pull_request.merged == true
+      if: >
+        github.event.pull_request.merged == true &&
+        !startsWith(github.event.pull_request.title, 'chore(deps):') &&
+        !startsWith(github.event.plul_request.title, 'ci(fix):'
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         configuration-path: .github/labeler_merged.yml

From 1d4a65e2f145a25b66e44e9d5edae9ec11abbc73 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 20 Oct 2022 10:35:18 -0400
Subject: [PATCH 489/638] feat: add entrypoint for cmake modules dir (#4258)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 setup.py                                 | 2 ++
 tests/extra_python_package/test_files.py | 2 ++
 tools/setup_main.py.in                   | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/setup.py b/setup.py
index 68573519c1..9097440bfe 100644
--- a/setup.py
+++ b/setup.py
@@ -144,6 +144,8 @@ def remove_output(*sources: str) -> Iterator[None]:
             stdout=sys.stdout,
             stderr=sys.stderr,
         )
+        if not global_sdist:
+            Path("pybind11/share/cmake/pybind11/__init__.py").touch()
 
     txt = get_and_replace(setup_py, version=version, extra_cmd=extra_cmd)
     code = compile(txt, setup_py, "exec")
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 9a9bb1556a..ae69e56d3a 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -166,6 +166,7 @@ def test_build_sdist(monkeypatch, tmpdir):
     files |= {f"pybind11{n}" for n in local_sdist_files}
     files.add("pybind11.egg-info/entry_points.txt")
     files.add("pybind11.egg-info/requires.txt")
+    files.add("pybind11/share/cmake/pybind11/__init__.py")
     assert simpler == files
 
     with open(os.path.join(MAIN_DIR, "tools", "setup_main.py.in"), "rb") as f:
@@ -252,6 +253,7 @@ def tests_build_wheel(monkeypatch, tmpdir):
         "dist-info/entry_points.txt",
         "dist-info/top_level.txt",
     }
+    files.add("pybind11/share/cmake/pybind11/__init__.py")
 
     with zipfile.ZipFile(str(wheel)) as z:
         names = z.namelist()
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index 6358cc7b9b..b3681bba8c 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -38,6 +38,9 @@ setup(
         ],
         "pipx.run": [
              "pybind11 = pybind11.__main__:main",
+        ],
+        "cmake.modules": [
+            "pybind11 = pybind11.share.cmake.pybind11",
         ]
     },
     cmdclass=cmdclass

From 128d988ef183cfb6334714f0bcf8b8e7b7e2e95b Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 20 Oct 2022 10:37:12 -0400
Subject: [PATCH 490/638] ci: fix labeler

---
 .github/workflows/labeler.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/labeler.yml b/.github/workflows/labeler.yml
index 5152cebca2..165a2fd87b 100644
--- a/.github/workflows/labeler.yml
+++ b/.github/workflows/labeler.yml
@@ -13,7 +13,8 @@ jobs:
       if: >
         github.event.pull_request.merged == true &&
         !startsWith(github.event.pull_request.title, 'chore(deps):') &&
-        !startsWith(github.event.plul_request.title, 'ci(fix):'
+        !startsWith(github.event.pull_request.title, 'ci(fix):') &&
+        !startsWith(github.event.pull_request.title, 'docs(changelog):')
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         configuration-path: .github/labeler_merged.yml

From 36ccb08b0d8f007f674ce373095b4b278689fc10 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 20 Oct 2022 10:58:04 -0400
Subject: [PATCH 491/638] docs: update changelog (#4265)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst | 101 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 9c8ff423f4..1199ecdedf 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -16,6 +16,107 @@ IN DEVELOPMENT
 
 Changes will be summarized here periodically.
 
+Version 2.10.1 (Oct 2?, 2022)
+-----------------------------
+
+
+Changes:
+
+
+* Allow ``pybind11::capsule`` constructor to take null destructor pointers.
+  `#4221 <https://github.com/pybind/pybind11/pull/4221>`_
+
+* ``embed.h`` was changed so that ``PYTHONPATH`` is used also with Python 3.11
+  (established behavior).
+  `#4119 <https://github.com/pybind/pybind11/pull/4119>`_
+
+Bug fixes:
+
+* Fix MSVC 2019 v.1924 & C++14 mode error for ``overload_cast``.
+  `#4188 <https://github.com/pybind/pybind11/pull/4188>`_
+
+* Make augmented assignment operators non-const for the object-api. Behavior
+  was previously broken for augmented assignment operators.
+  `#4065 <https://github.com/pybind/pybind11/pull/4065>`_
+
+* Add proper error checking to C++ bindings for Python list append and insert.
+  `#4208 <https://github.com/pybind/pybind11/pull/4208>`_
+
+* Work-around for Nvidia's CUDA nvcc compiler in versions 11.4.0 - 11.8.0.
+  `#4220 <https://github.com/pybind/pybind11/pull/4220>`_
+
+* A workaround for PyPy was added in the ``py::error_already_set``
+  implementation, related to PR `#1895 <https://github.com/pybind/pybind11/pull/1895>`_
+  released with v2.10.0.
+  `#4079 <https://github.com/pybind/pybind11/pull/4079>`_
+
+* Fixed compiler errors when C++23 ``std::forward_like`` is available.
+  `#4136 <https://github.com/pybind/pybind11/pull/4136>`_
+
+* Properly raise exceptions in contains methods (like when an object in unhashable).
+  `#4209 <https://github.com/pybind/pybind11/pull/4209>`_
+
+* Further improve another error in exception handling.
+  `#4232 <https://github.com/pybind/pybind11/pull/4232>`_
+
+* ``get_local_internals()`` was made compatible with
+  ``finalize_interpreter()``, fixing potential freezes during interpreter
+  finalization.
+  `#4192 <https://github.com/pybind/pybind11/pull/4192>`_
+
+
+Performance and style:
+
+* Reserve space in set and STL map casters if possible. This will prevent
+  unnecessary rehashing / resizing by knowing the number of keys ahead of time
+  for Python to C++ casting. This improvement will greatly speed up the casting
+  of large unordered maps and sets.
+  `#4194 <https://github.com/pybind/pybind11/pull/4194>`_
+
+* GIL RAII scopes are non-copyable to avoid potential bugs.
+  `#4183 <https://github.com/pybind/pybind11/pull/4183>`_
+
+* Explicitly default all relevant ctors for pytypes in the ``PYBIND11_OBJECT``
+  macros and enforce the clang-tidy checks ``modernize-use-equals-default`` in
+  macros as well.
+  `#4017 <https://github.com/pybind/pybind11/pull/4017>`_
+
+* Optimize iterator advancement in C++ bindings.
+  `#4237 <https://github.com/pybind/pybind11/pull/4237>`_
+
+* Use the modern ``PyObject_GenericGetDict`` and ``PyObject_GenericSetDict``
+  for handling dynamic attribute dictionaries.
+  `#4106 <https://github.com/pybind/pybind11/pull/4106>`_
+
+* Document that users should use ``PYBIND11_NAMESPACE`` instead of using ``pybind11`` when
+  opening namespaces. Using namespace declarations and namespace qualification
+  remain the same as ``pybind11``. This is done to ensure consistent symbol
+  visibility.
+  `#4098 <https://github.com/pybind/pybind11/pull/4098>`_
+
+* Mark ``detail::forward_like`` as constexpr.
+  `#4147 <https://github.com/pybind/pybind11/pull/4147>`_
+
+* Optimize unpacking_collector when processing ``arg_v`` arguments.
+  `#4219 <https://github.com/pybind/pybind11/pull/4219>`_
+
+
+Build system improvements:
+
+* Experimental support for ``cmake.modules`` entrypoint.
+  `#4258 <https://github.com/pybind/pybind11/pull/4258>`_
+
+* Include a pkg-config file when installing pybind11, such as in the Python
+  package.
+  `#4077 <https://github.com/pybind/pybind11/pull/4077>`_
+
+* Avoid stripping debug symbols when ``CMAKE_BUILD_TYPE`` is set to ``DEBUG``
+  instead of ``Debug``.
+  `#4078 <https://github.com/pybind/pybind11/pull/4078>`_
+
+* Followup to `#3948 <https://github.com/pybind/pybind11/pull/3948>`_, fixing vcpkg again.
+  `#4123 <https://github.com/pybind/pybind11/pull/4123>`_
+
 Version 2.10.0 (Jul 15, 2022)
 -----------------------------
 

From 2ce76f783373b1dd34e94c8283598af3051ef3d7 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Fri, 21 Oct 2022 12:51:26 -0400
Subject: [PATCH 492/638] Cleanup casters to release none() to avoid ref
 counting (#4269)

---
 include/pybind11/cast.h       | 6 +++---
 include/pybind11/functional.h | 2 +-
 include/pybind11/stl.h        | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index b89e4946ad..5699d4fb00 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -248,7 +248,7 @@ struct void_caster {
         return false;
     }
     static handle cast(T, return_value_policy /* policy */, handle /* parent */) {
-        return none().inc_ref();
+        return none().release();
     }
     PYBIND11_TYPE_CASTER(T, const_name("None"));
 };
@@ -291,7 +291,7 @@ class type_caster<void> : public type_caster<void_type> {
         if (ptr) {
             return capsule(ptr).release();
         }
-        return none().inc_ref();
+        return none().release();
     }
 
     template <typename T>
@@ -537,7 +537,7 @@ struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
 
     static handle cast(const CharT *src, return_value_policy policy, handle parent) {
         if (src == nullptr) {
-            return pybind11::none().inc_ref();
+            return pybind11::none().release();
         }
         return StringCaster::cast(StringType(src), policy, parent);
     }
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 4034990d89..102d1a938b 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -110,7 +110,7 @@ struct type_caster<std::function<Return(Args...)>> {
     template <typename Func>
     static handle cast(Func &&f_, return_value_policy policy, handle /* parent */) {
         if (!f_) {
-            return none().inc_ref();
+            return none().release();
         }
 
         auto result = f_.template target<function_type>();
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 8f243502ef..2d144b598b 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -311,7 +311,7 @@ struct optional_caster {
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
         if (!src) {
-            return none().inc_ref();
+            return none().release();
         }
         if (!std::is_lvalue_reference<T>::value) {
             policy = return_value_policy_override<Value>::policy(policy);

From 91cfb7702280d3176e56a6667d8a091d9731a779 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 21 Oct 2022 17:25:53 -0400
Subject: [PATCH 493/638] Revert "feat: add entrypoint for cmake modules dir"
 (#4270)

* Revert "feat: add entrypoint for cmake modules dir (#4258)"

This reverts commit 1d4a65e2f145a25b66e44e9d5edae9ec11abbc73.

* docs: revert changelog mention too
---
 docs/changelog.rst                       | 3 ---
 setup.py                                 | 2 --
 tests/extra_python_package/test_files.py | 2 --
 tools/setup_main.py.in                   | 3 ---
 4 files changed, 10 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 1199ecdedf..df3181c524 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -103,9 +103,6 @@ Performance and style:
 
 Build system improvements:
 
-* Experimental support for ``cmake.modules`` entrypoint.
-  `#4258 <https://github.com/pybind/pybind11/pull/4258>`_
-
 * Include a pkg-config file when installing pybind11, such as in the Python
   package.
   `#4077 <https://github.com/pybind/pybind11/pull/4077>`_
diff --git a/setup.py b/setup.py
index 9097440bfe..68573519c1 100644
--- a/setup.py
+++ b/setup.py
@@ -144,8 +144,6 @@ def remove_output(*sources: str) -> Iterator[None]:
             stdout=sys.stdout,
             stderr=sys.stderr,
         )
-        if not global_sdist:
-            Path("pybind11/share/cmake/pybind11/__init__.py").touch()
 
     txt = get_and_replace(setup_py, version=version, extra_cmd=extra_cmd)
     code = compile(txt, setup_py, "exec")
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index ae69e56d3a..9a9bb1556a 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -166,7 +166,6 @@ def test_build_sdist(monkeypatch, tmpdir):
     files |= {f"pybind11{n}" for n in local_sdist_files}
     files.add("pybind11.egg-info/entry_points.txt")
     files.add("pybind11.egg-info/requires.txt")
-    files.add("pybind11/share/cmake/pybind11/__init__.py")
     assert simpler == files
 
     with open(os.path.join(MAIN_DIR, "tools", "setup_main.py.in"), "rb") as f:
@@ -253,7 +252,6 @@ def tests_build_wheel(monkeypatch, tmpdir):
         "dist-info/entry_points.txt",
         "dist-info/top_level.txt",
     }
-    files.add("pybind11/share/cmake/pybind11/__init__.py")
 
     with zipfile.ZipFile(str(wheel)) as z:
         names = z.namelist()
diff --git a/tools/setup_main.py.in b/tools/setup_main.py.in
index b3681bba8c..6358cc7b9b 100644
--- a/tools/setup_main.py.in
+++ b/tools/setup_main.py.in
@@ -38,9 +38,6 @@ setup(
         ],
         "pipx.run": [
              "pybind11 = pybind11.__main__:main",
-        ],
-        "cmake.modules": [
-            "pybind11 = pybind11.share.cmake.pybind11",
         ]
     },
     cmdclass=cmdclass

From 17c1e27b3d202aaab6d5443b1800124bbf24d9ca Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Fri, 21 Oct 2022 18:04:01 -0400
Subject: [PATCH 494/638] fix: Revert pfect args make iterator (#4234)

* Revert "chore: perfectly forward all make_iterator args (#3980)"

This reverts commit 8da58da53996e9aa40d051b3b84cb3220fdbbb58.

* Redo unrelated optimization in commit

* Add tests for ambiguous overloads
---
 include/pybind11/pybind11.h            | 22 ++++++++--------------
 tests/test_sequences_and_iterators.cpp | 19 +++++++++++++++++++
 tests/test_sequences_and_iterators.py  |  8 ++++++++
 3 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index fb4b7578d9..e662236d01 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2333,7 +2333,7 @@ template <typename Access,
           typename Sentinel,
           typename ValueType,
           typename... Extra>
-iterator make_iterator_impl(Iterator &&first, Sentinel &&last, Extra &&...extra) {
+iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&...extra) {
     using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
     // TODO: state captures only the types of Extra, not the values
 
@@ -2359,7 +2359,7 @@ iterator make_iterator_impl(Iterator &&first, Sentinel &&last, Extra &&...extra)
                 Policy);
     }
 
-    return cast(state{std::forward<Iterator>(first), std::forward<Sentinel>(last), true});
+    return cast(state{first, last, true});
 }
 
 PYBIND11_NAMESPACE_END(detail)
@@ -2370,15 +2370,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename ValueType = typename detail::iterator_access<Iterator>::result_type,
           typename... Extra>
-iterator make_iterator(Iterator &&first, Sentinel &&last, Extra &&...extra) {
+iterator make_iterator(Iterator first, Sentinel last, Extra &&...extra) {
     return detail::make_iterator_impl<detail::iterator_access<Iterator>,
                                       Policy,
                                       Iterator,
                                       Sentinel,
                                       ValueType,
-                                      Extra...>(std::forward<Iterator>(first),
-                                                std::forward<Sentinel>(last),
-                                                std::forward<Extra>(extra)...);
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
@@ -2388,15 +2386,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
           typename... Extra>
-iterator make_key_iterator(Iterator &&first, Sentinel &&last, Extra &&...extra) {
+iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
     return detail::make_iterator_impl<detail::iterator_key_access<Iterator>,
                                       Policy,
                                       Iterator,
                                       Sentinel,
                                       KeyType,
-                                      Extra...>(std::forward<Iterator>(first),
-                                                std::forward<Sentinel>(last),
-                                                std::forward<Extra>(extra)...);
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
@@ -2406,15 +2402,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
           typename... Extra>
-iterator make_value_iterator(Iterator &&first, Sentinel &&last, Extra &&...extra) {
+iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
     return detail::make_iterator_impl<detail::iterator_value_access<Iterator>,
                                       Policy,
                                       Iterator,
                                       Sentinel,
                                       ValueType,
-                                      Extra...>(std::forward<Iterator>(first),
-                                                std::forward<Sentinel>(last),
-                                                std::forward<Extra>(extra)...);
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index b867f49a25..1de65edbf2 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -559,4 +559,23 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
           []() { return py::make_iterator<py::return_value_policy::copy>(list); });
     m.def("make_iterator_2",
           []() { return py::make_iterator<py::return_value_policy::automatic>(list); });
+
+    // test_iterator on c arrays
+    // #4100: ensure lvalue required as increment operand
+    class CArrayHolder {
+    public:
+        CArrayHolder(double x, double y, double z) {
+            values[0] = x;
+            values[1] = y;
+            values[2] = z;
+        };
+        double values[3];
+    };
+
+    py::class_<CArrayHolder>(m, "CArrayHolder")
+        .def(py::init<double, double, double>())
+        .def(
+            "__iter__",
+            [](const CArrayHolder &v) { return py::make_iterator(v.values, v.values + 3); },
+            py::keep_alive<0, 1>());
 }
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index 062e3b3d30..de486e3e8e 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -241,3 +241,11 @@ def test_iterator_rvp():
     assert list(m.make_iterator_1()) == [1, 2, 3]
     assert list(m.make_iterator_2()) == [1, 2, 3]
     assert not isinstance(m.make_iterator_1(), type(m.make_iterator_2()))
+
+
+def test_carray_iterator():
+    """#4100: Check for proper iterator overload with C-Arrays"""
+    args_gt = list(float(i) for i in range(3))
+    arr_h = m.CArrayHolder(*args_gt)
+    args = list(arr_h)
+    assert args_gt == args

From 8ea75ab4d754305676d1bff5e324df2d9470dec7 Mon Sep 17 00:00:00 2001
From: Lalaland <ethan.steinberg@gmail.com>
Date: Sat, 22 Oct 2022 16:52:35 -0700
Subject: [PATCH 495/638] Fix casts to void* (#4275)

* Fix casts to void*

* Improve tests

* style: pre-commit fixes

* remove c style cast

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <aaronGokaslan@gmail.com>
---
 include/pybind11/cast.h |  6 ++----
 tests/test_class.cpp    | 18 +++++++++++++++++-
 tests/test_class.py     |  2 ++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 5699d4fb00..430c62f357 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1179,11 +1179,9 @@ enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&)
     pybind11_fail("Internal error: cast_safe fallback invoked");
 }
 template <typename T>
-enable_if_t<std::is_same<void, intrinsic_t<T>>::value, void> cast_safe(object &&) {}
+enable_if_t<std::is_void<T>::value, void> cast_safe(object &&) {}
 template <typename T>
-enable_if_t<detail::none_of<cast_is_temporary_value_reference<T>,
-                            std::is_same<void, intrinsic_t<T>>>::value,
-            T>
+enable_if_t<detail::none_of<cast_is_temporary_value_reference<T>, std::is_void<T>>::value, T>
 cast_safe(object &&o) {
     return pybind11::cast<T>(std::move(o));
 }
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 18c8d358bb..fc1c17b179 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -384,6 +384,8 @@ TEST_SUBMODULE(class_, m) {
 
     protected:
         virtual int foo() const { return value; }
+        virtual void *void_foo() { return static_cast<void *>(&value); }
+        virtual void *get_self() { return static_cast<void *>(this); }
 
     private:
         int value = 42;
@@ -392,6 +394,8 @@ TEST_SUBMODULE(class_, m) {
     class TrampolineB : public ProtectedB {
     public:
         int foo() const override { PYBIND11_OVERRIDE(int, ProtectedB, foo, ); }
+        void *void_foo() override { PYBIND11_OVERRIDE(void *, ProtectedB, void_foo, ); }
+        void *get_self() override { PYBIND11_OVERRIDE(void *, ProtectedB, get_self, ); }
     };
 
     class PublicistB : public ProtectedB {
@@ -401,11 +405,23 @@ TEST_SUBMODULE(class_, m) {
         // (in Debug builds only, tested with icpc (ICC) 2021.1 Beta 20200827)
         ~PublicistB() override{}; // NOLINT(modernize-use-equals-default)
         using ProtectedB::foo;
+        using ProtectedB::get_self;
+        using ProtectedB::void_foo;
     };
 
+    m.def("read_foo", [](const void *original) {
+        const int *ptr = reinterpret_cast<const int *>(original);
+        return *ptr;
+    });
+
+    m.def("pointers_equal",
+          [](const void *original, const void *comparison) { return original == comparison; });
+
     py::class_<ProtectedB, TrampolineB>(m, "ProtectedB")
         .def(py::init<>())
-        .def("foo", &PublicistB::foo);
+        .def("foo", &PublicistB::foo)
+        .def("void_foo", &PublicistB::void_foo)
+        .def("get_self", &PublicistB::get_self);
 
     // test_brace_initialization
     struct BraceInitialization {
diff --git a/tests/test_class.py b/tests/test_class.py
index 47ba450fc2..7c1ed20608 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -313,6 +313,8 @@ def test_bind_protected_functions():
 
     b = m.ProtectedB()
     assert b.foo() == 42
+    assert m.read_foo(b.void_foo()) == 42
+    assert m.pointers_equal(b.get_self(), b)
 
     class C(m.ProtectedB):
         def __init__(self):

From 4fe905d4f01ce47bdea5fdcbcb6037acc9e2596c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sun, 23 Oct 2022 00:32:17 -0400
Subject: [PATCH 496/638] fix: add flag for overriding classic Python search
 values (#4195)

* fix: PyPy needs to overrite broken FindPythonInterp values

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix: add flag to opt-in to new (cross-compile) behavior

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Apply suggestions from code review

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 tools/FindPythonLibsNew.cmake | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index a5a628fd7a..bbbd9f9ec1 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -151,9 +151,13 @@ if(NOT _PYTHON_SUCCESS MATCHES 0)
   return()
 endif()
 
+option(
+  PYBIND11_PYTHONLIBS_OVERWRITE
+  "Overwrite cached values read from Python library (classic search). Turn off if cross-compiling and manually setting these values."
+  ON)
 # Can manually set values when cross-compiling
 macro(_PYBIND11_GET_IF_UNDEF lst index name)
-  if(NOT DEFINED "${name}")
+  if(PYBIND11_PYTHONLIBS_OVERWRITE OR NOT DEFINED "${name}")
     list(GET "${lst}" "${index}" "${name}")
   endif()
 endmacro()

From d1c31e9aa0b8f7594b4c816b8745493272791c27 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sun, 23 Oct 2022 08:08:00 -0400
Subject: [PATCH 497/638] chore: improve issue template (#4276)

---
 .github/ISSUE_TEMPLATE/bug-report.yml | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/.github/ISSUE_TEMPLATE/bug-report.yml b/.github/ISSUE_TEMPLATE/bug-report.yml
index bd6a9a8e22..e6494ba6a0 100644
--- a/.github/ISSUE_TEMPLATE/bug-report.yml
+++ b/.github/ISSUE_TEMPLATE/bug-report.yml
@@ -6,7 +6,8 @@ body:
   - type: markdown
     attributes:
       value: |
-        Maintainers will only make a best effort to triage PRs. Please do your best to make the issue as easy to act on as possible, and only open if clearly a problem with pybind11 (ask first if unsure).
+        Please do your best to make the issue as easy to act on as possible, and only submit here if there is clearly a problem with pybind11 (ask first if unsure). **Note that a reproducer in a PR is much more likely to get immediate attention.**
+
   - type: checkboxes
     id: steps
     attributes:
@@ -20,6 +21,12 @@ body:
         - label: Consider asking first in the [Gitter chat room](https://gitter.im/pybind/Lobby) or in a [Discussion](https:/pybind/pybind11/discussions/new).
           required: false
 
+  - type: Input
+    id: version
+    attributes:
+      label: What version (or hash if on master) of pybind11 are you using?
+      required: true
+
   - type: textarea
     id: description
     attributes:
@@ -40,6 +47,14 @@ body:
         The code should be minimal, have no external dependencies, isolate the
         function(s) that cause breakage. Submit matched and complete C++ and
         Python snippets that can be easily compiled and run to diagnose the
-        issue. If possible, make a PR with a new, failing test to give us a
-        starting point to work on!
+        issue. — Note that a reproducer in a PR is much more likely to get
+        immediate attention: failing tests in the pybind11 CI are the best
+        starting point for working out fixes.
       render: text
+
+  - type: Input
+    id: regression
+    attributes:
+      label: Is this a regression? Put the last known working version here if it is.
+      description: Put the last known working version here if this is a regression.
+      value: Not a regression

From 07a61aa1c0a331431165103d49e1848e69373d62 Mon Sep 17 00:00:00 2001
From: Vemund Handeland <vehandel@online.no>
Date: Sun, 23 Oct 2022 20:57:45 +0200
Subject: [PATCH 498/638] Fix char8_t support (#4278)

Standard library macro __cpp_lib_char8_t is only available
after including standard header
---
 include/pybind11/detail/common.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 6da7ef859c..b43100b95a 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -205,10 +205,6 @@
 #    endif
 #endif
 
-#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
-#    define PYBIND11_HAS_U8STRING
-#endif
-
 #include <Python.h>
 #if PY_VERSION_HEX < 0x03060000
 #    error "PYTHON < 3.6 IS UNSUPPORTED. pybind11 v2.9 was the last to support Python 2 and 3.5."
@@ -259,6 +255,11 @@
 #    endif
 #endif
 
+// Must be after including <version> or one of the other headers specified by the standard
+#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
+#    define PYBIND11_HAS_U8STRING
+#endif
+
 // #define PYBIND11_STR_LEGACY_PERMISSIVE
 // If DEFINED, pybind11::str can hold PyUnicodeObject or PyBytesObject
 //             (probably surprising and never documented, but this was the

From fcb5554d9fdd4ad3150bf12cb8be04099cb4976e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 26 Oct 2022 10:41:51 -0400
Subject: [PATCH 499/638] ci: move to final release of 3.11 (#4286)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2951a0ad19..b56e8f447f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,7 +30,7 @@ jobs:
         - '3.6'
         - '3.9'
         - '3.10'
-        - '3.11-dev'
+        - '3.11'
         - 'pypy-3.7'
         - 'pypy-3.8'
         - 'pypy-3.9'
@@ -119,7 +119,7 @@ jobs:
 
     - name: C++11 tests
       # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11-dev' || matrix.python == 'pypy-3.8'))"
+      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11' || matrix.python == 'pypy-3.8'))"
       run: cmake --build .  --target cpptest -j 2
 
     - name: Interface test C++11
@@ -146,7 +146,7 @@ jobs:
 
     - name: C++ tests
       # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11-dev' || matrix.python == 'pypy-3.8'))"
+      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11' || matrix.python == 'pypy-3.8'))"
       run: cmake --build build2 --target cpptest
 
     # Third build - C++17 mode with unstable ABI
@@ -186,7 +186,7 @@ jobs:
         - python-version: "3.9"
           python-debug: true
           valgrind: true
-        - python-version: "3.11-dev"
+        - python-version: "3.11"
           python-debug: false
 
     name: "🐍 ${{ matrix.python-version }}${{ matrix.python-debug && '-dbg' || '' }} (deadsnakes)${{ matrix.valgrind && ' • Valgrind' || '' }} • x64"

From b07223fa693f65da81e17c12858d636569947f98 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Sat, 29 Oct 2022 11:12:24 -0400
Subject: [PATCH 500/638] fix: improve bytes to str decoding error handling
 (#4294)

* (bugfix): Improve bytes to str decoding error handling

* regroup test

* Further broaden tests

* Add another decode error test

* Fix bug in tests

* Reviewer suggestions
---
 include/pybind11/pytypes.h |  9 +++++++++
 tests/test_pytypes.cpp     |  5 +++++
 tests/test_pytypes.py      | 14 ++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 37fc49a0e1..80a2e2228e 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1432,6 +1432,9 @@ class str : public object {
     str(const char *c, const SzType &n)
         : object(PyUnicode_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
         if (!m_ptr) {
+            if (PyErr_Occurred()) {
+                throw error_already_set();
+            }
             pybind11_fail("Could not allocate string object!");
         }
     }
@@ -1441,6 +1444,9 @@ class str : public object {
     // NOLINTNEXTLINE(google-explicit-constructor)
     str(const char *c = "") : object(PyUnicode_FromString(c), stolen_t{}) {
         if (!m_ptr) {
+            if (PyErr_Occurred()) {
+                throw error_already_set();
+            }
             pybind11_fail("Could not allocate string object!");
         }
     }
@@ -1598,6 +1604,9 @@ inline str::str(const bytes &b) {
     }
     auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, length));
     if (!obj) {
+        if (PyErr_Occurred()) {
+            throw error_already_set();
+        }
         pybind11_fail("Could not allocate string object!");
     }
     m_ptr = obj.release().ptr();
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 99237ccef7..ea8d03958b 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -206,7 +206,12 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("str_from_char_ssize_t", []() { return py::str{"red", (py::ssize_t) 3}; });
     m.def("str_from_char_size_t", []() { return py::str{"blue", (py::size_t) 4}; });
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
+    m.def("str_from_std_string_input", [](const std::string &stri) { return py::str(stri); });
+    m.def("str_from_cstr_input", [](const char *c_str) { return py::str(c_str); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });
+    m.def("str_from_bytes_input",
+          [](const py::bytes &encoded_str) { return py::str(encoded_str); });
+
     m.def("str_from_object", [](const py::object &obj) { return py::str(obj); });
     m.def("repr_from_object", [](const py::object &obj) { return py::repr(obj); });
     m.def("str_from_handle", [](py::handle h) { return py::str(h); });
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 3ed7b9c946..079ee7ca50 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -244,6 +244,20 @@ def __repr__(self):
         m.str_from_string_from_str(ucs_surrogates_str)
 
 
+@pytest.mark.parametrize(
+    "func",
+    [
+        m.str_from_bytes_input,
+        m.str_from_cstr_input,
+        m.str_from_std_string_input,
+    ],
+)
+def test_surrogate_pairs_unicode_error(func):
+    input_str = "\ud83d\ude4f".encode("utf-8", "surrogatepass")
+    with pytest.raises(UnicodeDecodeError):
+        func(input_str)
+
+
 def test_bytes(doc):
     assert m.bytes_from_char_ssize_t().decode() == "green"
     assert m.bytes_from_char_size_t().decode() == "purple"

From b07d08f6009a52050bb588a3e6fb0489c98af85e Mon Sep 17 00:00:00 2001
From: Chekov2k <arnimbalzer@gmail.com>
Date: Sun, 30 Oct 2022 15:57:23 +0000
Subject: [PATCH 501/638] Add `PYBIND11_SIMPLE_GIL_MANAGEMENT` option (cmake,
 C++ define) (#4216)

* Add option to force the use of the PYPY GIL scoped acquire/release logic to support nested gil access, see https://github.com/pybind/pybind11/issues/1276 and https://github.com/pytorch/pytorch/issues/83101

* Apply suggestions from code review

* Update CMakeLists.txt

* docs: update upgrade guide

* Update docs/upgrade.rst

* All bells & whistles.

* Add Reminder to common.h, so that we will not forget to purge `!WITH_THREAD` branches when dropping Python 3.6

* New sentence instead of semicolon.

* Temporarily pull in snapshot of PR #4246

* Add `test_release_acquire`

* Add more unit tests for nested gil locking

* Add test_report_builtins_internals_keys

* Very minor enhancement: sort list only after filtering.

* Revert change in docs/upgrade.rst

* Add test_multi_acquire_release_cross_module, while also forcing unique PYBIND11_INTERNALS_VERSION for cross_module_gil_utils.cpp

* Hopefully fix apparently new ICC error.

```
2022-10-28T07:57:54.5187728Z -- The CXX compiler identification is Intel 2021.7.0.20220726
...
2022-10-28T07:58:53.6758994Z icpc: remark #10441: The Intel(R) C++ Compiler Classic (ICC) is deprecated and will be removed from product release in the second half of 2023. The Intel(R) oneAPI DPC++/C++ Compiler (ICX) is the recommended compiler moving forward. Please transition to use this compiler. Use '-diag-disable=10441' to disable this message.
2022-10-28T07:58:54.5801597Z In file included from /home/runner/work/pybind11/pybind11/include/pybind11/detail/../detail/type_caster_base.h(15),
2022-10-28T07:58:54.5803794Z                  from /home/runner/work/pybind11/pybind11/include/pybind11/detail/../cast.h(15),
2022-10-28T07:58:54.5805740Z                  from /home/runner/work/pybind11/pybind11/include/pybind11/detail/../attr.h(14),
2022-10-28T07:58:54.5809556Z                  from /home/runner/work/pybind11/pybind11/include/pybind11/detail/class.h(12),
2022-10-28T07:58:54.5812154Z                  from /home/runner/work/pybind11/pybind11/include/pybind11/pybind11.h(13),
2022-10-28T07:58:54.5948523Z                  from /home/runner/work/pybind11/pybind11/tests/cross_module_gil_utils.cpp(13):
2022-10-28T07:58:54.5949009Z /home/runner/work/pybind11/pybind11/include/pybind11/detail/../detail/internals.h(177): error #2282: unrecognized GCC pragma
2022-10-28T07:58:54.5949374Z       PYBIND11_TLS_KEY_INIT(tstate)
2022-10-28T07:58:54.5949579Z       ^
2022-10-28T07:58:54.5949695Z
```

* clang-tidy fixes

* Workaround for PYPY WIN exitcode None

* Revert "Temporarily pull in snapshot of PR #4246"

This reverts commit 23ac16e859150f27fda25ca865cabcb4444e0770.

* Another workaround for PYPY WIN exitcode None

* Clean up how the tests are run "run in process" Part 1: uniformity

* Clean up how the tests are run "run in process" Part 2: use `@pytest.mark.parametrize` and clean up the naming.

* Skip some tests `#if defined(THREAD_SANITIZER)` (tested with TSAN using the Google-internal toolchain).

* Run all tests again but ignore ThreadSanitizer exitcode 66 (this is less likely to mask unrelated ThreadSanitizer issues in the future).

* bug fix: missing common.h include before using `PYBIND11_SIMPLE_GIL_MANAGEMENT`

For the tests in the github CI this does not matter, because
`PYBIND11_SIMPLE_GIL_MANAGEMENT` is always defined from the command line,
but when monkey-patching common.h locally, it matters.

* if process.exitcode is None: assert t_delta > 9.9

* More sophisiticated `_run_in_process()` implementation, clearly reporting `DEADLOCK`, additionally exercised via added `intentional_deadlock()`

* Wrap m.intentional_deadlock in a Python function, for `ForkingPickler` compatibility.

```
>       ForkingPickler(file, protocol).dump(obj)
E       TypeError: cannot pickle 'PyCapsule' object
```

Observed with all Windows builds including mingw but not PyPy, and macos-latest with Python 3.9, 3.10, 3.11 but not 3.6.

* Add link to potential solution for WOULD-BE-NICE-TO-HAVE feature.

* Add `SKIP_IF_DEADLOCK = True` option, to not pollute the CI results with expected `DEADLOCK` failures while we figure out what to do about them.

* Add COPY-PASTE-THIS: gdb ... command (to be used for debugging the detected deadlock)

* style: pre-commit fixes

* Do better than automatic pre-commit fixes.

* Add `PYBIND11_SIMPLE_GIL_MANAGEMENT` to `pytest_report_header()` (so that we can easily know when harvesting deadlock information from the CI logs).

Co-authored-by: Arnim Balzer <arnim@seechange.ai>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml              |   4 +
 CMakeLists.txt                        |   6 +
 include/pybind11/detail/common.h      |   5 +
 include/pybind11/detail/internals.h   |  16 +-
 include/pybind11/gil.h                |  53 ++++--
 tests/conftest.py                     |   1 +
 tests/cross_module_gil_utils.cpp      |  67 +++++++-
 tests/pybind11_tests.cpp              |   6 +
 tests/test_embed/test_interpreter.cpp |   1 -
 tests/test_gil_scoped.cpp             | 107 +++++++++++-
 tests/test_gil_scoped.py              | 227 +++++++++++++++++++++-----
 11 files changed, 433 insertions(+), 60 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b56e8f447f..a11cae1ab0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -102,10 +102,12 @@ jobs:
       run: python -m pip install pytest-github-actions-annotate-failures
 
     # First build - C++11 mode and inplace
+    # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON here.
     - name: Configure C++11 ${{ matrix.args }}
       run: >
         cmake -S . -B .
         -DPYBIND11_WERROR=ON
+        -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
@@ -129,10 +131,12 @@ jobs:
       run: git clean -fdx
 
     # Second build - C++17 mode and in a build directory
+    # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF here.
     - name: Configure C++17
       run: >
         cmake -S . -B build2
         -DPYBIND11_WERROR=ON
+        -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3284e21eb4..0d93203881 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -91,10 +91,16 @@ endif()
 option(PYBIND11_INSTALL "Install pybind11 header files?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_TEST "Build pybind11 test suite?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_NOPYTHON "Disable search for Python" OFF)
+option(PYBIND11_SIMPLE_GIL_MANAGEMENT
+       "Use simpler GIL management logic that does not support disassociation" OFF)
 set(PYBIND11_INTERNALS_VERSION
     ""
     CACHE STRING "Override the ABI version, may be used to enable the unstable ABI.")
 
+if(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+  add_compile_definitions(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+endif()
+
 cmake_dependent_option(
   USE_PYTHON_INCLUDE_DIR
   "Install pybind11 headers in Python include directory instead of default installation prefix"
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index b43100b95a..a3e0bc9b37 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -206,6 +206,7 @@
 #endif
 
 #include <Python.h>
+// Reminder: WITH_THREAD is always defined if PY_VERSION_HEX >= 0x03070000
 #if PY_VERSION_HEX < 0x03060000
 #    error "PYTHON < 3.6 IS UNSUPPORTED. pybind11 v2.9 was the last to support Python 2 and 3.5."
 #endif
@@ -229,6 +230,10 @@
 #    undef copysign
 #endif
 
+#if defined(PYPY_VERSION) && !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#    define PYBIND11_SIMPLE_GIL_MANAGEMENT
+#endif
+
 #if defined(_MSC_VER)
 #    if defined(PYBIND11_DEBUG_MARKER)
 #        define _DEBUG
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index d47084e263..7de7794344 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -9,6 +9,12 @@
 
 #pragma once
 
+#include "common.h"
+
+#if defined(WITH_THREAD) && defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#    include "../gil.h"
+#endif
+
 #include "../pytypes.h"
 
 #include <exception>
@@ -49,7 +55,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 // `Py_LIMITED_API` anyway.
 #    if PYBIND11_INTERNALS_VERSION > 4
 #        define PYBIND11_TLS_KEY_REF Py_tss_t &
-#        ifdef __GNUC__
+#        if defined(__GNUC__) && !defined(__INTEL_COMPILER)
 // Clang on macOS warns due to `Py_tss_NEEDS_INIT` not specifying an initializer
 // for every field.
 #            define PYBIND11_TLS_KEY_INIT(var)                                                    \
@@ -169,10 +175,12 @@ struct internals {
     PyTypeObject *default_metaclass;
     PyObject *instance_base;
 #if defined(WITH_THREAD)
+    // Unused if PYBIND11_SIMPLE_GIL_MANAGEMENT is defined:
     PYBIND11_TLS_KEY_INIT(tstate)
 #    if PYBIND11_INTERNALS_VERSION > 4
     PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
 #    endif // PYBIND11_INTERNALS_VERSION > 4
+    // Unused if PYBIND11_SIMPLE_GIL_MANAGEMENT is defined:
     PyInterpreterState *istate = nullptr;
     ~internals() {
 #    if PYBIND11_INTERNALS_VERSION > 4
@@ -408,6 +416,10 @@ PYBIND11_NOINLINE internals &get_internals() {
         return **internals_pp;
     }
 
+#if defined(WITH_THREAD)
+#    if defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+    gil_scoped_acquire gil;
+#    else
     // Ensure that the GIL is held since we will need to make Python calls.
     // Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
     struct gil_scoped_acquire_local {
@@ -417,6 +429,8 @@ PYBIND11_NOINLINE internals &get_internals() {
         ~gil_scoped_acquire_local() { PyGILState_Release(state); }
         const PyGILState_STATE state;
     } gil;
+#    endif
+#endif
     error_scope err_scope;
 
     PYBIND11_STR_TYPE id(PYBIND11_INTERNALS_ID);
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 1ef5f0a8c8..cb0028d505 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -10,7 +10,10 @@
 #pragma once
 
 #include "detail/common.h"
-#include "detail/internals.h"
+
+#if defined(WITH_THREAD) && !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#    include "detail/internals.h"
+#endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
@@ -21,7 +24,9 @@ PyThreadState *get_thread_state_unchecked();
 
 PYBIND11_NAMESPACE_END(detail)
 
-#if defined(WITH_THREAD) && !defined(PYPY_VERSION)
+#if defined(WITH_THREAD)
+
+#    if !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
 
 /* The functions below essentially reproduce the PyGILState_* API using a RAII
  * pattern, but there are a few important differences:
@@ -62,11 +67,11 @@ class gil_scoped_acquire {
 
         if (!tstate) {
             tstate = PyThreadState_New(internals.istate);
-#    if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+#        if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             if (!tstate) {
                 pybind11_fail("scoped_acquire: could not create thread state!");
             }
-#    endif
+#        endif
             tstate->gilstate_counter = 0;
             PYBIND11_TLS_REPLACE_VALUE(internals.tstate, tstate);
         } else {
@@ -87,20 +92,20 @@ class gil_scoped_acquire {
 
     PYBIND11_NOINLINE void dec_ref() {
         --tstate->gilstate_counter;
-#    if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+#        if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         if (detail::get_thread_state_unchecked() != tstate) {
             pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
         }
         if (tstate->gilstate_counter < 0) {
             pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
         }
-#    endif
+#        endif
         if (tstate->gilstate_counter == 0) {
-#    if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+#        if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             if (!release) {
                 pybind11_fail("scoped_acquire::dec_ref(): internal error!");
             }
-#    endif
+#        endif
             PyThreadState_Clear(tstate);
             if (active) {
                 PyThreadState_DeleteCurrent();
@@ -178,12 +183,14 @@ class gil_scoped_release {
     bool disassoc;
     bool active = true;
 };
-#elif defined(PYPY_VERSION)
+
+#    else // PYBIND11_SIMPLE_GIL_MANAGEMENT
+
 class gil_scoped_acquire {
     PyGILState_STATE state;
 
 public:
-    gil_scoped_acquire() { state = PyGILState_Ensure(); }
+    gil_scoped_acquire() : state{PyGILState_Ensure()} {}
     gil_scoped_acquire(const gil_scoped_acquire &) = delete;
     gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
     ~gil_scoped_acquire() { PyGILState_Release(state); }
@@ -194,19 +201,39 @@ class gil_scoped_release {
     PyThreadState *state;
 
 public:
-    gil_scoped_release() { state = PyEval_SaveThread(); }
+    gil_scoped_release() : state{PyEval_SaveThread()} {}
     gil_scoped_release(const gil_scoped_release &) = delete;
     gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
     ~gil_scoped_release() { PyEval_RestoreThread(state); }
     void disarm() {}
 };
-#else
+
+#    endif // PYBIND11_SIMPLE_GIL_MANAGEMENT
+
+#else // WITH_THREAD
+
 class gil_scoped_acquire {
+public:
+    gil_scoped_acquire() {
+        // Trick to suppress `unused variable` error messages (at call sites).
+        (void) (this != (this + 1));
+    }
+    gil_scoped_acquire(const gil_scoped_acquire &) = delete;
+    gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
     void disarm() {}
 };
+
 class gil_scoped_release {
+public:
+    gil_scoped_release() {
+        // Trick to suppress `unused variable` error messages (at call sites).
+        (void) (this != (this + 1));
+    }
+    gil_scoped_release(const gil_scoped_release &) = delete;
+    gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
     void disarm() {}
 };
-#endif
+
+#endif // WITH_THREAD
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/tests/conftest.py b/tests/conftest.py
index 02ce263afc..f5ddb9f129 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -210,4 +210,5 @@ def pytest_report_header(config):
         f" {pybind11_tests.compiler_info}"
         f" {pybind11_tests.cpp_std}"
         f" {pybind11_tests.PYBIND11_INTERNALS_ID}"
+        f" PYBIND11_SIMPLE_GIL_MANAGEMENT={pybind11_tests.PYBIND11_SIMPLE_GIL_MANAGEMENT}"
     )
diff --git a/tests/cross_module_gil_utils.cpp b/tests/cross_module_gil_utils.cpp
index 1436c35d6e..7c20849dd9 100644
--- a/tests/cross_module_gil_utils.cpp
+++ b/tests/cross_module_gil_utils.cpp
@@ -6,9 +6,15 @@
     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
 */
+#if defined(PYBIND11_INTERNALS_VERSION)
+#    undef PYBIND11_INTERNALS_VERSION
+#endif
+#define PYBIND11_INTERNALS_VERSION 21814642 // Ensure this module has its own `internals` instance.
 #include <pybind11/pybind11.h>
 
 #include <cstdint>
+#include <string>
+#include <thread>
 
 // This file mimics a DSO that makes pybind11 calls but does not define a
 // PYBIND11_MODULE. The purpose is to test that such a DSO can create a
@@ -21,8 +27,54 @@
 namespace {
 
 namespace py = pybind11;
+
 void gil_acquire() { py::gil_scoped_acquire gil; }
 
+std::string gil_multi_acquire_release(unsigned bits) {
+    if ((bits & 0x1u) != 0u) {
+        py::gil_scoped_acquire gil;
+    }
+    if ((bits & 0x2u) != 0u) {
+        py::gil_scoped_release gil;
+    }
+    if ((bits & 0x4u) != 0u) {
+        py::gil_scoped_acquire gil;
+    }
+    if ((bits & 0x8u) != 0u) {
+        py::gil_scoped_release gil;
+    }
+    return PYBIND11_INTERNALS_ID;
+}
+
+struct CustomAutoGIL {
+    CustomAutoGIL() : gstate(PyGILState_Ensure()) {}
+    ~CustomAutoGIL() { PyGILState_Release(gstate); }
+
+    PyGILState_STATE gstate;
+};
+struct CustomAutoNoGIL {
+    CustomAutoNoGIL() : save(PyEval_SaveThread()) {}
+    ~CustomAutoNoGIL() { PyEval_RestoreThread(save); }
+
+    PyThreadState *save;
+};
+
+template <typename Acquire, typename Release>
+void gil_acquire_inner() {
+    Acquire acquire_outer;
+    Acquire acquire_inner;
+    Release release;
+}
+
+template <typename Acquire, typename Release>
+void gil_acquire_nested() {
+    Acquire acquire_outer;
+    Acquire acquire_inner;
+    Release release;
+    auto thread = std::thread(&gil_acquire_inner<Acquire, Release>);
+    thread.join();
+}
+
 constexpr char kModuleName[] = "cross_module_gil_utils";
 
 struct PyModuleDef moduledef = {
@@ -30,6 +82,9 @@ struct PyModuleDef moduledef = {
 
 } // namespace
 
+#define ADD_FUNCTION(Name, ...)                                                                   \
+    PyModule_AddObject(m, Name, PyLong_FromVoidPtr(reinterpret_cast<void *>(&__VA_ARGS__)));
+
 extern "C" PYBIND11_EXPORT PyObject *PyInit_cross_module_gil_utils() {
 
     PyObject *m = PyModule_Create(&moduledef);
@@ -37,8 +92,16 @@ extern "C" PYBIND11_EXPORT PyObject *PyInit_cross_module_gil_utils() {
     if (m != nullptr) {
         static_assert(sizeof(&gil_acquire) == sizeof(void *),
                       "Function pointer must have the same size as void*");
-        PyModule_AddObject(
-            m, "gil_acquire_funcaddr", PyLong_FromVoidPtr(reinterpret_cast<void *>(&gil_acquire)));
+        ADD_FUNCTION("gil_acquire_funcaddr", gil_acquire)
+        ADD_FUNCTION("gil_multi_acquire_release_funcaddr", gil_multi_acquire_release)
+        ADD_FUNCTION("gil_acquire_inner_custom_funcaddr",
+                     gil_acquire_inner<CustomAutoGIL, CustomAutoNoGIL>)
+        ADD_FUNCTION("gil_acquire_nested_custom_funcaddr",
+                     gil_acquire_nested<CustomAutoGIL, CustomAutoNoGIL>)
+        ADD_FUNCTION("gil_acquire_inner_pybind11_funcaddr",
+                     gil_acquire_inner<py::gil_scoped_acquire, py::gil_scoped_release>)
+        ADD_FUNCTION("gil_acquire_nested_pybind11_funcaddr",
+                     gil_acquire_nested<py::gil_scoped_acquire, py::gil_scoped_release>)
     }
 
     return m;
diff --git a/tests/pybind11_tests.cpp b/tests/pybind11_tests.cpp
index aa3095594b..6240346487 100644
--- a/tests/pybind11_tests.cpp
+++ b/tests/pybind11_tests.cpp
@@ -89,6 +89,12 @@ PYBIND11_MODULE(pybind11_tests, m) {
 #endif
     m.attr("cpp_std") = cpp_std();
     m.attr("PYBIND11_INTERNALS_ID") = PYBIND11_INTERNALS_ID;
+    m.attr("PYBIND11_SIMPLE_GIL_MANAGEMENT") =
+#if defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+        true;
+#else
+        false;
+#endif
 
     bind_ConstructorStats(m);
 
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 6299293b91..44dcd1fdb0 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -293,7 +293,6 @@ TEST_CASE("Threads") {
 
     {
         py::gil_scoped_release gil_release{};
-        REQUIRE(has_pybind11_internals_static());
 
         auto threads = std::vector<std::thread>();
         for (auto i = 0; i < num_threads; ++i) {
diff --git a/tests/test_gil_scoped.cpp b/tests/test_gil_scoped.cpp
index 97efdc1616..f136086e84 100644
--- a/tests/test_gil_scoped.cpp
+++ b/tests/test_gil_scoped.cpp
@@ -11,6 +11,13 @@
 
 #include "pybind11_tests.h"
 
+#include <string>
+#include <thread>
+
+#define CROSS_MODULE(Function)                                                                    \
+    auto cm = py::module_::import("cross_module_gil_utils");                                      \
+    auto target = reinterpret_cast<void (*)()>(PyLong_AsVoidPtr(cm.attr(Function).ptr()));
+
 class VirtClass {
 public:
     virtual ~VirtClass() = default;
@@ -28,6 +35,16 @@ class PyVirtClass : public VirtClass {
 };
 
 TEST_SUBMODULE(gil_scoped, m) {
+    m.attr("defined_THREAD_SANITIZER") =
+#if defined(THREAD_SANITIZER)
+        true;
+#else
+        false;
+#endif
+
+    m.def("intentional_deadlock",
+          []() { std::thread([]() { py::gil_scoped_acquire gil_acquired; }).join(); });
+
     py::class_<VirtClass, PyVirtClass>(m, "VirtClass")
         .def(py::init<>())
         .def("virtual_func", &VirtClass::virtual_func)
@@ -37,11 +54,91 @@ TEST_SUBMODULE(gil_scoped, m) {
     m.def("test_callback_std_func", [](const std::function<void()> &func) { func(); });
     m.def("test_callback_virtual_func", [](VirtClass &virt) { virt.virtual_func(); });
     m.def("test_callback_pure_virtual_func", [](VirtClass &virt) { virt.pure_virtual_func(); });
-    m.def("test_cross_module_gil", []() {
-        auto cm = py::module_::import("cross_module_gil_utils");
-        auto gil_acquire = reinterpret_cast<void (*)()>(
-            PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
+    m.def("test_cross_module_gil_released", []() {
+        CROSS_MODULE("gil_acquire_funcaddr")
+        py::gil_scoped_release gil_release;
+        target();
+    });
+    m.def("test_cross_module_gil_acquired", []() {
+        CROSS_MODULE("gil_acquire_funcaddr")
+        py::gil_scoped_acquire gil_acquire;
+        target();
+    });
+    m.def("test_cross_module_gil_inner_custom_released", []() {
+        CROSS_MODULE("gil_acquire_inner_custom_funcaddr")
+        py::gil_scoped_release gil_release;
+        target();
+    });
+    m.def("test_cross_module_gil_inner_custom_acquired", []() {
+        CROSS_MODULE("gil_acquire_inner_custom_funcaddr")
+        py::gil_scoped_acquire gil_acquire;
+        target();
+    });
+    m.def("test_cross_module_gil_inner_pybind11_released", []() {
+        CROSS_MODULE("gil_acquire_inner_pybind11_funcaddr")
         py::gil_scoped_release gil_release;
-        gil_acquire();
+        target();
+    });
+    m.def("test_cross_module_gil_inner_pybind11_acquired", []() {
+        CROSS_MODULE("gil_acquire_inner_pybind11_funcaddr")
+        py::gil_scoped_acquire gil_acquire;
+        target();
+    });
+    m.def("test_cross_module_gil_nested_custom_released", []() {
+        CROSS_MODULE("gil_acquire_nested_custom_funcaddr")
+        py::gil_scoped_release gil_release;
+        target();
+    });
+    m.def("test_cross_module_gil_nested_custom_acquired", []() {
+        CROSS_MODULE("gil_acquire_nested_custom_funcaddr")
+        py::gil_scoped_acquire gil_acquire;
+        target();
+    });
+    m.def("test_cross_module_gil_nested_pybind11_released", []() {
+        CROSS_MODULE("gil_acquire_nested_pybind11_funcaddr")
+        py::gil_scoped_release gil_release;
+        target();
+    });
+    m.def("test_cross_module_gil_nested_pybind11_acquired", []() {
+        CROSS_MODULE("gil_acquire_nested_pybind11_funcaddr")
+        py::gil_scoped_acquire gil_acquire;
+        target();
+    });
+    m.def("test_release_acquire", [](const py::object &obj) {
+        py::gil_scoped_release gil_released;
+        py::gil_scoped_acquire gil_acquired;
+        return py::str(obj);
+    });
+    m.def("test_nested_acquire", [](const py::object &obj) {
+        py::gil_scoped_release gil_released;
+        py::gil_scoped_acquire gil_acquired_outer;
+        py::gil_scoped_acquire gil_acquired_inner;
+        return py::str(obj);
+    });
+    m.def("test_multi_acquire_release_cross_module", [](unsigned bits) {
+        py::set internals_ids;
+        internals_ids.add(PYBIND11_INTERNALS_ID);
+        {
+            py::gil_scoped_release gil_released;
+            auto thread_f = [bits, &internals_ids]() {
+                py::gil_scoped_acquire gil_acquired;
+                auto cm = py::module_::import("cross_module_gil_utils");
+                auto target = reinterpret_cast<std::string (*)(unsigned)>(
+                    PyLong_AsVoidPtr(cm.attr("gil_multi_acquire_release_funcaddr").ptr()));
+                std::string cm_internals_id = target(bits >> 3);
+                internals_ids.add(cm_internals_id);
+            };
+            if ((bits & 0x1u) != 0u) {
+                thread_f();
+            }
+            if ((bits & 0x2u) != 0u) {
+                std::thread non_python_thread(thread_f);
+                non_python_thread.join();
+            }
+            if ((bits & 0x4u) != 0u) {
+                thread_f();
+            }
+        }
+        return internals_ids;
     });
 }
diff --git a/tests/test_gil_scoped.py b/tests/test_gil_scoped.py
index 52374b0cce..e890a7b0c8 100644
--- a/tests/test_gil_scoped.py
+++ b/tests/test_gil_scoped.py
@@ -1,45 +1,199 @@
 import multiprocessing
+import sys
 import threading
+import time
+
+import pytest
 
 from pybind11_tests import gil_scoped as m
 
 
+class ExtendedVirtClass(m.VirtClass):
+    def virtual_func(self):
+        pass
+
+    def pure_virtual_func(self):
+        pass
+
+
+def test_callback_py_obj():
+    m.test_callback_py_obj(lambda: None)
+
+
+def test_callback_std_func():
+    m.test_callback_std_func(lambda: None)
+
+
+def test_callback_virtual_func():
+    extended = ExtendedVirtClass()
+    m.test_callback_virtual_func(extended)
+
+
+def test_callback_pure_virtual_func():
+    extended = ExtendedVirtClass()
+    m.test_callback_pure_virtual_func(extended)
+
+
+def test_cross_module_gil_released():
+    """Makes sure that the GIL can be acquired by another module from a GIL-released state."""
+    m.test_cross_module_gil_released()  # Should not raise a SIGSEGV
+
+
+def test_cross_module_gil_acquired():
+    """Makes sure that the GIL can be acquired by another module from a GIL-acquired state."""
+    m.test_cross_module_gil_acquired()  # Should not raise a SIGSEGV
+
+
+def test_cross_module_gil_inner_custom_released():
+    """Makes sure that the GIL can be acquired/released by another module
+    from a GIL-released state using custom locking logic."""
+    m.test_cross_module_gil_inner_custom_released()
+
+
+def test_cross_module_gil_inner_custom_acquired():
+    """Makes sure that the GIL can be acquired/acquired by another module
+    from a GIL-acquired state using custom locking logic."""
+    m.test_cross_module_gil_inner_custom_acquired()
+
+
+def test_cross_module_gil_inner_pybind11_released():
+    """Makes sure that the GIL can be acquired/released by another module
+    from a GIL-released state using pybind11 locking logic."""
+    m.test_cross_module_gil_inner_pybind11_released()
+
+
+def test_cross_module_gil_inner_pybind11_acquired():
+    """Makes sure that the GIL can be acquired/acquired by another module
+    from a GIL-acquired state using pybind11 locking logic."""
+    m.test_cross_module_gil_inner_pybind11_acquired()
+
+
+def test_cross_module_gil_nested_custom_released():
+    """Makes sure that the GIL can be nested acquired/released by another module
+    from a GIL-released state using custom locking logic."""
+    m.test_cross_module_gil_nested_custom_released()
+
+
+def test_cross_module_gil_nested_custom_acquired():
+    """Makes sure that the GIL can be nested acquired/acquired by another module
+    from a GIL-acquired state using custom locking logic."""
+    m.test_cross_module_gil_nested_custom_acquired()
+
+
+def test_cross_module_gil_nested_pybind11_released():
+    """Makes sure that the GIL can be nested acquired/released by another module
+    from a GIL-released state using pybind11 locking logic."""
+    m.test_cross_module_gil_nested_pybind11_released()
+
+
+def test_cross_module_gil_nested_pybind11_acquired():
+    """Makes sure that the GIL can be nested acquired/acquired by another module
+    from a GIL-acquired state using pybind11 locking logic."""
+    m.test_cross_module_gil_nested_pybind11_acquired()
+
+
+def test_release_acquire():
+    assert m.test_release_acquire(0xAB) == "171"
+
+
+def test_nested_acquire():
+    assert m.test_nested_acquire(0xAB) == "171"
+
+
+def test_multi_acquire_release_cross_module():
+    for bits in range(16 * 8):
+        internals_ids = m.test_multi_acquire_release_cross_module(bits)
+        assert len(internals_ids) == 2 if bits % 8 else 1
+
+
+# Intentionally putting human review in the loop here, to guard against accidents.
+VARS_BEFORE_ALL_BASIC_TESTS = dict(vars())  # Make a copy of the dict (critical).
+ALL_BASIC_TESTS = (
+    test_callback_py_obj,
+    test_callback_std_func,
+    test_callback_virtual_func,
+    test_callback_pure_virtual_func,
+    test_cross_module_gil_released,
+    test_cross_module_gil_acquired,
+    test_cross_module_gil_inner_custom_released,
+    test_cross_module_gil_inner_custom_acquired,
+    test_cross_module_gil_inner_pybind11_released,
+    test_cross_module_gil_inner_pybind11_acquired,
+    test_cross_module_gil_nested_custom_released,
+    test_cross_module_gil_nested_custom_acquired,
+    test_cross_module_gil_nested_pybind11_released,
+    test_cross_module_gil_nested_pybind11_acquired,
+    test_release_acquire,
+    test_nested_acquire,
+    test_multi_acquire_release_cross_module,
+)
+
+
+def test_all_basic_tests_completeness():
+    num_found = 0
+    for key, value in VARS_BEFORE_ALL_BASIC_TESTS.items():
+        if not key.startswith("test_"):
+            continue
+        assert value in ALL_BASIC_TESTS
+        num_found += 1
+    assert len(ALL_BASIC_TESTS) == num_found
+
+
+def _intentional_deadlock():
+    m.intentional_deadlock()
+
+
+ALL_BASIC_TESTS_PLUS_INTENTIONAL_DEADLOCK = ALL_BASIC_TESTS + (_intentional_deadlock,)
+SKIP_IF_DEADLOCK = True  # See PR #4216
+
+
 def _run_in_process(target, *args, **kwargs):
-    """Runs target in process and returns its exitcode after 10s (None if still alive)."""
+    if len(args) == 0:
+        test_fn = target
+    else:
+        test_fn = args[0]
+    # Do not need to wait much, 10s should be more than enough.
+    timeout = 0.1 if test_fn is _intentional_deadlock else 10
     process = multiprocessing.Process(target=target, args=args, kwargs=kwargs)
     process.daemon = True
     try:
+        t_start = time.time()
         process.start()
-        # Do not need to wait much, 10s should be more than enough.
-        process.join(timeout=10)
+        if timeout >= 100:  # For debugging.
+            print(
+                "\nprocess.pid STARTED", process.pid, (sys.argv, target, args, kwargs)
+            )
+            print(f"COPY-PASTE-THIS: gdb {sys.argv[0]} -p {process.pid}", flush=True)
+        process.join(timeout=timeout)
+        if timeout >= 100:
+            print("\nprocess.pid JOINED", process.pid, flush=True)
+        t_delta = time.time() - t_start
+        if process.exitcode == 66 and m.defined_THREAD_SANITIZER:  # Issue #2754
+            # WOULD-BE-NICE-TO-HAVE: Check that the message below is actually in the output.
+            # Maybe this could work:
+            # https://gist.github.com/alexeygrigorev/01ce847f2e721b513b42ea4a6c96905e
+            pytest.skip(
+                "ThreadSanitizer: starting new threads after multi-threaded fork is not supported."
+            )
+        elif test_fn is _intentional_deadlock:
+            assert process.exitcode is None
+            return 0
+        elif process.exitcode is None:
+            assert t_delta > 0.9 * timeout
+            msg = "DEADLOCK, most likely, exactly what this test is meant to detect."
+            if SKIP_IF_DEADLOCK:
+                pytest.skip(msg)
+            raise RuntimeError(msg)
         return process.exitcode
     finally:
         if process.is_alive():
             process.terminate()
 
 
-def _python_to_cpp_to_python():
-    """Calls different C++ functions that come back to Python."""
-
-    class ExtendedVirtClass(m.VirtClass):
-        def virtual_func(self):
-            pass
-
-        def pure_virtual_func(self):
-            pass
-
-    extended = ExtendedVirtClass()
-    m.test_callback_py_obj(lambda: None)
-    m.test_callback_std_func(lambda: None)
-    m.test_callback_virtual_func(extended)
-    m.test_callback_pure_virtual_func(extended)
-
-
-def _python_to_cpp_to_python_from_threads(num_threads, parallel=False):
-    """Calls different C++ functions that come back to Python, from Python threads."""
+def _run_in_threads(test_fn, num_threads, parallel):
     threads = []
     for _ in range(num_threads):
-        thread = threading.Thread(target=_python_to_cpp_to_python)
+        thread = threading.Thread(target=test_fn)
         thread.daemon = True
         thread.start()
         if parallel:
@@ -51,43 +205,40 @@ def _python_to_cpp_to_python_from_threads(num_threads, parallel=False):
 
 
 # TODO: FIXME, sometimes returns -11 (segfault) instead of 0 on macOS Python 3.9
-def test_python_to_cpp_to_python_from_thread():
+@pytest.mark.parametrize("test_fn", ALL_BASIC_TESTS_PLUS_INTENTIONAL_DEADLOCK)
+def test_run_in_process_one_thread(test_fn):
     """Makes sure there is no GIL deadlock when running in a thread.
 
     It runs in a separate process to be able to stop and assert if it deadlocks.
     """
-    assert _run_in_process(_python_to_cpp_to_python_from_threads, 1) == 0
+    assert _run_in_process(_run_in_threads, test_fn, num_threads=1, parallel=False) == 0
 
 
 # TODO: FIXME on macOS Python 3.9
-def test_python_to_cpp_to_python_from_thread_multiple_parallel():
+@pytest.mark.parametrize("test_fn", ALL_BASIC_TESTS_PLUS_INTENTIONAL_DEADLOCK)
+def test_run_in_process_multiple_threads_parallel(test_fn):
     """Makes sure there is no GIL deadlock when running in a thread multiple times in parallel.
 
     It runs in a separate process to be able to stop and assert if it deadlocks.
     """
-    assert _run_in_process(_python_to_cpp_to_python_from_threads, 8, parallel=True) == 0
+    assert _run_in_process(_run_in_threads, test_fn, num_threads=8, parallel=True) == 0
 
 
 # TODO: FIXME on macOS Python 3.9
-def test_python_to_cpp_to_python_from_thread_multiple_sequential():
+@pytest.mark.parametrize("test_fn", ALL_BASIC_TESTS_PLUS_INTENTIONAL_DEADLOCK)
+def test_run_in_process_multiple_threads_sequential(test_fn):
     """Makes sure there is no GIL deadlock when running in a thread multiple times sequentially.
 
     It runs in a separate process to be able to stop and assert if it deadlocks.
     """
-    assert (
-        _run_in_process(_python_to_cpp_to_python_from_threads, 8, parallel=False) == 0
-    )
+    assert _run_in_process(_run_in_threads, test_fn, num_threads=8, parallel=False) == 0
 
 
 # TODO: FIXME on macOS Python 3.9
-def test_python_to_cpp_to_python_from_process():
+@pytest.mark.parametrize("test_fn", ALL_BASIC_TESTS_PLUS_INTENTIONAL_DEADLOCK)
+def test_run_in_process_direct(test_fn):
     """Makes sure there is no GIL deadlock when using processes.
 
     This test is for completion, but it was never an issue.
     """
-    assert _run_in_process(_python_to_cpp_to_python) == 0
-
-
-def test_cross_module_gil():
-    """Makes sure that the GIL can be acquired by another module from a GIL-released state."""
-    m.test_cross_module_gil()  # Should not raise a SIGSEGV
+    assert _run_in_process(test_fn) == 0

From 5bc0943ed96836f46489f53961f6c438d2935357 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 30 Oct 2022 13:24:41 -0700
Subject: [PATCH 502/638] Ensure config, build, toolchain, spelling, etc.
 issues are not masked. (#4255)

---
 include/pybind11/eigen/matrix.h |  1 -
 tests/test_eigen_tensor.py      | 12 ++++++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/eigen/matrix.h b/include/pybind11/eigen/matrix.h
index 5f5ad3867b..c30dac2411 100644
--- a/include/pybind11/eigen/matrix.h
+++ b/include/pybind11/eigen/matrix.h
@@ -11,7 +11,6 @@
 
 #include "../numpy.h"
 
-// Similar to comments & pragma block in eigen_tensor.h. PLEASE KEEP IN SYNC.
 /* HINT: To suppress warnings originating from the Eigen headers, use -isystem.
    See also:
        https://stackoverflow.com/questions/2579576/i-dir-vs-isystem-dir
diff --git a/tests/test_eigen_tensor.py b/tests/test_eigen_tensor.py
index 5ee5fa01b2..653c9f288d 100644
--- a/tests/test_eigen_tensor.py
+++ b/tests/test_eigen_tensor.py
@@ -9,8 +9,16 @@
     from pybind11_tests import eigen_tensor_avoid_stl_array as avoid
 
     submodules += [avoid.c_style, avoid.f_style]
-except ImportError:
-    pass
+except ImportError as e:
+    # Ensure config, build, toolchain, etc. issues are not masked here:
+    raise RuntimeError(
+        "import pybind11_tests.eigen_tensor_avoid_stl_array FAILED, while "
+        "import pybind11_tests.eigen_tensor succeeded. "
+        "Please ensure that "
+        "test_eigen_tensor.cpp & "
+        "test_eigen_tensor_avoid_stl_array.cpp "
+        "are built together (or both are not built if Eigen is not available)."
+    ) from e
 
 tensor_ref = np.empty((3, 5, 2), dtype=np.int64)
 

From 3a2c96bd6f95f6b183c342380558238583415ab1 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 31 Oct 2022 09:18:05 -0700
Subject: [PATCH 503/638] fix: unicode surrogate character in Python exception
 message. (#4297)

* Fix & test for issue #4288 (unicode surrogate character in Python exception message).

* DRY `message_unavailable_exc`

* fix: add a constexpr

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* style: pre-commit fixes

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/pytypes.h | 22 ++++++++++++++++++++--
 tests/test_exceptions.cpp  |  5 -----
 tests/test_exceptions.py   | 14 ++++++++++++++
 3 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 80a2e2228e..91cbaaba28 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -501,11 +501,29 @@ struct error_fetch_and_normalize {
         std::string message_error_string;
         if (m_value) {
             auto value_str = reinterpret_steal<object>(PyObject_Str(m_value.ptr()));
+            constexpr const char *message_unavailable_exc
+                = "<MESSAGE UNAVAILABLE DUE TO ANOTHER EXCEPTION>";
             if (!value_str) {
                 message_error_string = detail::error_string();
-                result = "<MESSAGE UNAVAILABLE DUE TO ANOTHER EXCEPTION>";
+                result = message_unavailable_exc;
             } else {
-                result = value_str.cast<std::string>();
+                // Not using `value_str.cast<std::string>()`, to not potentially throw a secondary
+                // error_already_set that will then result in process termination (#4288).
+                auto value_bytes = reinterpret_steal<object>(
+                    PyUnicode_AsEncodedString(value_str.ptr(), "utf-8", "backslashreplace"));
+                if (!value_bytes) {
+                    message_error_string = detail::error_string();
+                    result = message_unavailable_exc;
+                } else {
+                    char *buffer = nullptr;
+                    Py_ssize_t length = 0;
+                    if (PyBytes_AsStringAndSize(value_bytes.ptr(), &buffer, &length) == -1) {
+                        message_error_string = detail::error_string();
+                        result = message_unavailable_exc;
+                    } else {
+                        result = std::string(buffer, static_cast<std::size_t>(length));
+                    }
+                }
             }
         } else {
             result = "<MESSAGE UNAVAILABLE>";
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index 3583f22a50..f57e095068 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -105,11 +105,6 @@ struct PythonAlreadySetInDestructor {
     py::str s;
 };
 
-std::string error_already_set_what(const py::object &exc_type, const py::object &exc_value) {
-    PyErr_SetObject(exc_type.ptr(), exc_value.ptr());
-    return py::error_already_set().what();
-}
-
 TEST_SUBMODULE(exceptions, m) {
     m.def("throw_std_exception",
           []() { throw std::runtime_error("This exception was intentionally thrown."); });
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 70b6ffea95..7eb1a9d62c 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -275,6 +275,20 @@ def test_local_translator(msg):
     assert msg(excinfo.value) == "this mod"
 
 
+def test_error_already_set_message_with_unicode_surrogate():  # Issue #4288
+    assert m.error_already_set_what(RuntimeError, "\ud927") == (
+        "RuntimeError: \\ud927",
+        False,
+    )
+
+
+def test_error_already_set_message_with_malformed_utf8():
+    assert m.error_already_set_what(RuntimeError, b"\x80") == (
+        "RuntimeError: b'\\x80'",
+        False,
+    )
+
+
 class FlakyException(Exception):
     def __init__(self, failure_point):
         if failure_point == "failure_point_init":

From b1bd7f2600d650bf59c88800c637703dd89317f3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 31 Oct 2022 10:36:26 -0700
Subject: [PATCH 504/638] fix: define (non-empty) `PYBIND11_EXPORT_EXCEPTION`
 only under macOS. (#4298)

Background: #2999, #4105, #4283, #4284

In a nutshell:

* Only macOS actually needs `PYBIND11_EXPORT_EXCEPTION` (#4284).

* Evidently (#4283), under macOS `PYBIND11_EXPORT_EXCEPTION` does not run the risk of introducing ODR violations,

* but evidently (#4283) under Linux it does, in the presumably rare/unusual situation that `RTLD_GLOBAL` is used.

* Windows does no have the equivalent of `RTLD_GLOBAL`, therefore `PYBIND11_EXPORT_EXCEPTION` has no practical benefit, on the contrary, noisy warning suppression pragmas are needed, therefore it is best left empty.
---
 docs/advanced/exceptions.rst     |  9 ++++++---
 include/pybind11/detail/common.h | 18 +++---------------
 include/pybind11/pytypes.h       |  9 ---------
 3 files changed, 9 insertions(+), 27 deletions(-)

diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst
index 2211caf5d3..53981dc08f 100644
--- a/docs/advanced/exceptions.rst
+++ b/docs/advanced/exceptions.rst
@@ -177,9 +177,12 @@ section.
     may be explicitly (re-)thrown to delegate it to the other,
     previously-declared existing exception translators.
 
-    Note that ``libc++`` and ``libstdc++`` `behave differently <https://stackoverflow.com/questions/19496643/using-clang-fvisibility-hidden-and-typeinfo-and-type-erasure/28827430>`_
-    with ``-fvisibility=hidden``. Therefore exceptions that are used across ABI boundaries need to be explicitly exported, as exercised in ``tests/test_exceptions.h``.
-    See also: "Problems with C++ exceptions" under `GCC Wiki <https://gcc.gnu.org/wiki/Visibility>`_.
+    Note that ``libc++`` and ``libstdc++`` `behave differently under macOS
+    <https://stackoverflow.com/questions/19496643/using-clang-fvisibility-hidden-and-typeinfo-and-type-erasure/28827430>`_
+    with ``-fvisibility=hidden``. Therefore exceptions that are used across ABI
+    boundaries need to be explicitly exported, as exercised in
+    ``tests/test_exceptions.h``. See also:
+    "Problems with C++ exceptions" under `GCC Wiki <https://gcc.gnu.org/wiki/Visibility>`_.
 
 
 Local vs Global Exception Translators
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index a3e0bc9b37..9b74323f67 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -96,13 +96,10 @@
 #endif
 
 #if !defined(PYBIND11_EXPORT_EXCEPTION)
-#    ifdef __MINGW32__
-// workaround for:
-// error: 'dllexport' implies default visibility, but xxx has already been declared with a
-// different visibility
-#        define PYBIND11_EXPORT_EXCEPTION
-#    else
+#    if defined(__apple_build_version__)
 #        define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
+#    else
+#        define PYBIND11_EXPORT_EXCEPTION
 #    endif
 #endif
 
@@ -904,12 +901,6 @@ using expand_side_effects = bool[];
 
 PYBIND11_NAMESPACE_END(detail)
 
-#if defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning(disable : 4275)
-//     warning C4275: An exported class was derived from a class that wasn't exported.
-//     Can be ignored when derived from a STL class.
-#endif
 /// C++ bindings of builtin Python exceptions
 class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
 public:
@@ -917,9 +908,6 @@ class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
     /// Set the error using the Python C API
     virtual void set_error() const = 0;
 };
-#if defined(_MSC_VER)
-#    pragma warning(pop)
-#endif
 
 #define PYBIND11_RUNTIME_EXCEPTION(name, type)                                                    \
     class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception {                             \
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 91cbaaba28..80b49ec397 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -623,12 +623,6 @@ inline std::string error_string() {
 
 PYBIND11_NAMESPACE_END(detail)
 
-#if defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning(disable : 4275 4251)
-//     warning C4275: An exported class was derived from a class that wasn't exported.
-//     Can be ignored when derived from a STL class.
-#endif
 /// Fetch and hold an error which was already set in Python.  An instance of this is typically
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
 /// else falls back to the function dispatcher (which then raises the captured error back to
@@ -688,9 +682,6 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::exception {
     ///          crashes (undefined behavior) if the Python interpreter is finalizing.
     static void m_fetched_error_deleter(detail::error_fetch_and_normalize *raw_ptr);
 };
-#if defined(_MSC_VER)
-#    pragma warning(pop)
-#endif
 
 /// Replaces the current Python error indicator with the chosen error, performing a
 /// 'raise from' to indicate that the chosen error was caused by the original error.

From 252ed8fb52e46eb3ec3e3b8c621ca9f79b53b26a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 31 Oct 2022 14:11:23 -0400
Subject: [PATCH 505/638] docs: prepare for 2.10.1 release (#4279)

* docs: prepare for 2.10.1 release

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update changelog.rst

* docs: update changelog with final list of PRs

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update docs/changelog.rst

* chore: one more changelog bump

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst | 43 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index df3181c524..7d6d0c0f56 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,19 +10,18 @@ Changes will be added here periodically from the "Suggested changelog entry"
 block in pull request descriptions.
 
 
-
 IN DEVELOPMENT
 --------------
 
 Changes will be summarized here periodically.
 
-Version 2.10.1 (Oct 2?, 2022)
+Version 2.10.1 (Oct 31, 2022)
 -----------------------------
 
+This is the first version to fully support embedding the newly released Python 3.11.
 
 Changes:
 
-
 * Allow ``pybind11::capsule`` constructor to take null destructor pointers.
   `#4221 <https://github.com/pybind/pybind11/pull/4221>`_
 
@@ -30,8 +29,40 @@ Changes:
   (established behavior).
   `#4119 <https://github.com/pybind/pybind11/pull/4119>`_
 
+* A ``PYBIND11_SIMPLE_GIL_MANAGEMENT`` option was added (cmake, C++ define),
+  along with many additional tests in ``test_gil_scoped.py``. The option may be
+  useful to try when debugging GIL-related issues, to determine if the more
+  complex default implementation is or is not to blame. See #4216 for
+  background. WARNING: Please be careful to not create ODR violations when
+  using the option: everything that is linked together with mutual symbol
+  visibility needs to be rebuilt.
+  `#4216 <https://github.com/pybind/pybind11/pull/4216>`_
+
+* ``PYBIND11_EXPORT_EXCEPTION`` was made non-empty only under macOS. This makes
+  Linux builds safer, and enables the removal of warning suppression pragmas for
+  Windows.
+  `#4298 <https://github.com/pybind/pybind11/pull/4298>`_
+
 Bug fixes:
 
+* Fixed a bug where ``UnicodeDecodeError`` was not propagated from various
+  ``py::str`` ctors when decoding surrogate utf characters.
+  `#4294 <https://github.com/pybind/pybind11/pull/4294>`_
+
+* Revert perfect forwarding for ``make_iterator``. This broke at least one
+  valid use case. May revisit later.
+  `#4234 <https://github.com/pybind/pybind11/pull/4234>`_
+
+* Fix support for safe casts to ``void*`` (regression in 2.10.0).
+  `#4275 <https://github.com/pybind/pybind11/pull/4275>`_
+
+* Fix ``char8_t`` support (regression in 2.9).
+  `#4278 <https://github.com/pybind/pybind11/pull/4278>`_
+
+* Unicode surrogate character in Python exception message leads to process
+  termination in ``error_already_set::what()``.
+  `#4297 <https://github.com/pybind/pybind11/pull/4297>`_
+
 * Fix MSVC 2019 v.1924 & C++14 mode error for ``overload_cast``.
   `#4188 <https://github.com/pybind/pybind11/pull/4188>`_
 
@@ -100,9 +131,15 @@ Performance and style:
 * Optimize unpacking_collector when processing ``arg_v`` arguments.
   `#4219 <https://github.com/pybind/pybind11/pull/4219>`_
 
+* Optimize casting C++ object to ``None``.
+  `#4269 <https://github.com/pybind/pybind11/pull/4269>`_
+
 
 Build system improvements:
 
+* CMake: revert overwrite behavior, now opt-in with ``PYBIND11_PYTHONLIBS_OVERRWRITE OFF``.
+  `#4195 <https://github.com/pybind/pybind11/pull/4195>`_
+
 * Include a pkg-config file when installing pybind11, such as in the Python
   package.
   `#4077 <https://github.com/pybind/pybind11/pull/4077>`_

From 2441d25b26af3e7b89d521a218694b604ec716e8 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 1 Nov 2022 00:10:13 -0400
Subject: [PATCH 506/638] chore(deps): update pre-commit hooks (#4302)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v2.38.2 → v3.2.0](https://github.com/asottile/pyupgrade/compare/v2.38.2...v3.2.0)
- [github.com/psf/black: 22.8.0 → 22.10.0](https://github.com/psf/black/compare/22.8.0...22.10.0)
- [github.com/PyCQA/pylint: v2.15.3 → v2.15.5](https://github.com/PyCQA/pylint/compare/v2.15.3...v2.15.5)
- [github.com/pre-commit/mirrors-mypy: v0.981 → v0.982](https://github.com/pre-commit/mirrors-mypy/compare/v0.981...v0.982)
- [github.com/codespell-project/codespell: v2.2.1 → v2.2.2](https://github.com/codespell-project/codespell/compare/v2.2.1...v2.2.2)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 742e7a30aa..a60d84f22f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -41,7 +41,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v2.38.2"
+  rev: "v3.2.0"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -54,7 +54,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "22.8.0" # Keep in sync with blacken-docs
+  rev: "22.10.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -116,7 +116,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.15.3"
+  rev: "v2.15.5"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -132,7 +132,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.981"
+  rev: "v0.982"
   hooks:
   - id: mypy
     args: []
@@ -152,7 +152,7 @@ repos:
 # Use tools/codespell_ignore_lines_from_errors.py
 # to rebuild .codespell-ignore-lines
 - repo: https://github.com/codespell-project/codespell
-  rev: "v2.2.1"
+  rev: "v2.2.2"
   hooks:
   - id: codespell
     exclude: ".supp$"

From 0176632e8cef72a4223f2df54d6dfb9e552ec71f Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Tue, 1 Nov 2022 12:19:34 -0400
Subject: [PATCH 507/638] chore: sync blacken-docs hook with black (#4304)

---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index a60d84f22f..fd079dd037 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -64,7 +64,7 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==22.8.0 # keep in sync with black hook
+    - black==22.10.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks

From ee2b5226295d67b690faddd446a329bb2840a1a8 Mon Sep 17 00:00:00 2001
From: Ethan Steinberg <ethan.steinberg@gmail.com>
Date: Wed, 2 Nov 2022 11:32:53 -0700
Subject: [PATCH 508/638] Fix functional.h bug + introduce test to verify that
 it is fixed (#4254)

* Illustrate bug in functional.h

* style: pre-commit fixes

* Make functional casting more robust / add workaround

* Make function_record* casting even more robust

* See if this fixes PyPy issue

* It still fails on PyPy sadly

* Do not make new CTOR just yet

* Fix test

* Add name to ensure correctness

* style: pre-commit fixes

* Clean up tests + remove ifdef guards

* Add comments

* Improve comments, error handling, and safety

* Fix compile error

* Fix magic logic

* Extract helper function

* Fix func signature

* move to local internals

* style: pre-commit fixes

* Switch to simpler design

* style: pre-commit fixes

* Move to function_record

* style: pre-commit fixes

* Switch to internals, update tests and docs

* Fix lint

* Oops, forgot to resolve last comment

* Fix typo

* Update in response to comments

* Implement suggestion to improve test

* Update comment

* Simple fixes

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Aaron Gokaslan <aaronGokaslan@gmail.com>
---
 include/pybind11/detail/internals.h | 31 ++++++++++++++++++++
 include/pybind11/functional.h       | 11 ++++++--
 include/pybind11/pybind11.h         | 44 ++++++++++++++++++++++-------
 tests/test_callbacks.cpp            | 37 ++++++++++++++++++++++++
 tests/test_callbacks.py             | 13 +++++++++
 5 files changed, 124 insertions(+), 12 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 7de7794344..6fd61098c4 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -43,6 +43,8 @@ using ExceptionTranslator = void (*)(std::exception_ptr);
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
+constexpr const char *internals_function_record_capsule_name = "pybind11_function_record_capsule";
+
 // Forward declarations
 inline PyTypeObject *make_static_property_type();
 inline PyTypeObject *make_default_metaclass();
@@ -182,6 +184,16 @@ struct internals {
 #    endif // PYBIND11_INTERNALS_VERSION > 4
     // Unused if PYBIND11_SIMPLE_GIL_MANAGEMENT is defined:
     PyInterpreterState *istate = nullptr;
+
+#    if PYBIND11_INTERNALS_VERSION > 4
+    // Note that we have to use a std::string to allocate memory to ensure a unique address
+    // We want unique addresses since we use pointer equality to compare function records
+    std::string function_record_capsule_name = internals_function_record_capsule_name;
+#    endif
+
+    internals() = default;
+    internals(const internals &other) = delete;
+    internals &operator=(const internals &other) = delete;
     ~internals() {
 #    if PYBIND11_INTERNALS_VERSION > 4
         PYBIND11_TLS_FREE(loader_life_support_tls_key);
@@ -548,6 +560,25 @@ const char *c_str(Args &&...args) {
     return strings.front().c_str();
 }
 
+inline const char *get_function_record_capsule_name() {
+#if PYBIND11_INTERNALS_VERSION > 4
+    return get_internals().function_record_capsule_name.c_str();
+#else
+    return nullptr;
+#endif
+}
+
+// Determine whether or not the following capsule contains a pybind11 function record.
+// Note that we use `internals` to make sure that only ABI compatible records are touched.
+//
+// This check is currently used in two places:
+// - An important optimization in functional.h to avoid overhead in C++ -> Python -> C++
+// - The sibling feature of cpp_function to allow overloads
+inline bool is_function_record_capsule(const capsule &cap) {
+    // Pointer equality as we rely on internals() to ensure unique pointers
+    return cap.name() == get_function_record_capsule_name();
+}
+
 PYBIND11_NAMESPACE_END(detail)
 
 /// Returns a named pointer that is shared among all extension modules (using the same
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 102d1a938b..87ec4d10cb 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -48,9 +48,16 @@ struct type_caster<std::function<Return(Args...)>> {
          */
         if (auto cfunc = func.cpp_function()) {
             auto *cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
-            if (isinstance<capsule>(cfunc_self)) {
+            if (cfunc_self == nullptr) {
+                PyErr_Clear();
+            } else if (isinstance<capsule>(cfunc_self)) {
                 auto c = reinterpret_borrow<capsule>(cfunc_self);
-                auto *rec = (function_record *) c;
+
+                function_record *rec = nullptr;
+                // Check that we can safely reinterpret the capsule into a function_record
+                if (detail::is_function_record_capsule(c)) {
+                    rec = c.get_pointer<function_record>();
+                }
 
                 while (rec != nullptr) {
                     if (rec->is_stateless
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index e662236d01..76d6eadcae 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -468,13 +468,20 @@ class cpp_function : public function {
         if (rec->sibling) {
             if (PyCFunction_Check(rec->sibling.ptr())) {
                 auto *self = PyCFunction_GET_SELF(rec->sibling.ptr());
-                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self)
-                                                                : capsule(self);
-                chain = (detail::function_record *) rec_capsule;
-                /* Never append a method to an overload chain of a parent class;
-                   instead, hide the parent's overloads in this case */
-                if (!chain->scope.is(rec->scope)) {
+                if (!isinstance<capsule>(self)) {
                     chain = nullptr;
+                } else {
+                    auto rec_capsule = reinterpret_borrow<capsule>(self);
+                    if (detail::is_function_record_capsule(rec_capsule)) {
+                        chain = rec_capsule.get_pointer<detail::function_record>();
+                        /* Never append a method to an overload chain of a parent class;
+                           instead, hide the parent's overloads in this case */
+                        if (!chain->scope.is(rec->scope)) {
+                            chain = nullptr;
+                        }
+                    } else {
+                        chain = nullptr;
+                    }
                 }
             }
             // Don't trigger for things like the default __init__, which are wrapper_descriptors
@@ -496,6 +503,7 @@ class cpp_function : public function {
 
             capsule rec_capsule(unique_rec.release(),
                                 [](void *ptr) { destruct((detail::function_record *) ptr); });
+            rec_capsule.set_name(detail::get_function_record_capsule_name());
             guarded_strdup.release();
 
             object scope_module;
@@ -661,10 +669,13 @@ class cpp_function : public function {
     /// Main dispatch logic for calls to functions bound using pybind11
     static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) {
         using namespace detail;
+        assert(isinstance<capsule>(self));
 
         /* Iterator over the list of potentially admissible overloads */
-        const function_record *overloads = (function_record *) PyCapsule_GetPointer(self, nullptr),
+        const function_record *overloads = reinterpret_cast<function_record *>(
+                                  PyCapsule_GetPointer(self, get_function_record_capsule_name())),
                               *it = overloads;
+        assert(overloads != nullptr);
 
         /* Need to know how many arguments + keyword arguments there are to pick the right
            overload */
@@ -1871,9 +1882,22 @@ class class_ : public detail::generic_type {
 
     static detail::function_record *get_function_record(handle h) {
         h = detail::get_function(h);
-        return h ? (detail::function_record *) reinterpret_borrow<capsule>(
-                   PyCFunction_GET_SELF(h.ptr()))
-                 : nullptr;
+        if (!h) {
+            return nullptr;
+        }
+
+        handle func_self = PyCFunction_GET_SELF(h.ptr());
+        if (!func_self) {
+            throw error_already_set();
+        }
+        if (!isinstance<capsule>(func_self)) {
+            return nullptr;
+        }
+        auto cap = reinterpret_borrow<capsule>(func_self);
+        if (!detail::is_function_record_capsule(cap)) {
+            return nullptr;
+        }
+        return cap.get_pointer<detail::function_record>();
     }
 };
 
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 92b8053de4..2fd05dec72 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -240,4 +240,41 @@ TEST_SUBMODULE(callbacks, m) {
             f();
         }
     });
+
+    auto *custom_def = []() {
+        static PyMethodDef def;
+        def.ml_name = "example_name";
+        def.ml_doc = "Example doc";
+        def.ml_meth = [](PyObject *, PyObject *args) -> PyObject * {
+            if (PyTuple_Size(args) != 1) {
+                throw std::runtime_error("Invalid number of arguments for example_name");
+            }
+            PyObject *first = PyTuple_GetItem(args, 0);
+            if (!PyLong_Check(first)) {
+                throw std::runtime_error("Invalid argument to example_name");
+            }
+            auto result = py::cast(PyLong_AsLong(first) * 9);
+            return result.release().ptr();
+        };
+        def.ml_flags = METH_VARARGS;
+        return &def;
+    }();
+
+    // rec_capsule with name that has the same value (but not pointer) as our internal one
+    // This capsule should be detected by our code as foreign and not inspected as the pointers
+    // shouldn't match
+    constexpr const char *rec_capsule_name
+        = pybind11::detail::internals_function_record_capsule_name;
+    py::capsule rec_capsule(std::malloc(1), [](void *data) { std::free(data); });
+    rec_capsule.set_name(rec_capsule_name);
+    m.add_object("custom_function", PyCFunction_New(custom_def, rec_capsule.ptr()));
+
+    // This test requires a new ABI version to pass
+#if PYBIND11_INTERNALS_VERSION > 4
+    // rec_capsule with nullptr name
+    py::capsule rec_capsule2(std::malloc(1), [](void *data) { std::free(data); });
+    m.add_object("custom_function2", PyCFunction_New(custom_def, rec_capsule2.ptr()));
+#else
+    m.add_object("custom_function2", py::none());
+#endif
 }
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 0b1047bbf2..57b6599880 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -193,3 +193,16 @@ def test_callback_num_times():
     if len(rates) > 1:
         print("Min    Mean   Max")
         print(f"{min(rates):6.3f} {sum(rates) / len(rates):6.3f} {max(rates):6.3f}")
+
+
+def test_custom_func():
+    assert m.custom_function(4) == 36
+    assert m.roundtrip(m.custom_function)(4) == 36
+
+
+@pytest.mark.skipif(
+    m.custom_function2 is None, reason="Current PYBIND11_INTERNALS_VERSION too low"
+)
+def test_custom_func2():
+    assert m.custom_function2(3) == 27
+    assert m.roundtrip(m.custom_function2)(3) == 27

From 1f04cc7062e33481c62c78231e9561b318bca67b Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 10 Nov 2022 08:33:26 -0800
Subject: [PATCH 509/638] Add windows_clang to ci.yml (#4323)

* Add windows_clang to ci.yml (previously tested under PRs #4321, #4319)

* Add `pip install --upgrade pip`, Show env, cosmetic changes

Already tested under PR #4321
---
 .github/workflows/ci.yml | 70 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a11cae1ab0..adbbf626f1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -967,3 +967,73 @@ jobs:
 
     - name: Interface test C++17
       run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build3 --target test_cmake_build
+
+  windows_clang:
+
+    strategy:
+      matrix:
+        os: [windows-latest]
+        python: ['3.10']
+
+    runs-on: "${{ matrix.os }}"
+
+    name: "🐍 ${{ matrix.python }} • ${{ matrix.os }} • clang-latest"
+
+    steps:
+      - name: Show env
+        run: env
+
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Set up Clang
+        uses: egor-tensin/setup-clang@v1
+
+      - name: Setup Python ${{ matrix.python }}
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python }}
+
+      - name: Update CMake
+        uses: jwlawson/actions-setup-cmake@v1.13
+
+      - name: Install ninja-build tool
+        uses: seanmiddleditch/gha-setup-ninja@v3
+
+      - name: Run pip installs
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -r tests/requirements.txt
+
+      - name: Show Clang++ version
+        run: clang++ --version
+
+      - name: Show CMake version
+        run: cmake --version
+
+      # TODO: WERROR=ON
+      - name: Configure Clang
+        run: >
+          cmake -G Ninja -S . -B .
+          -DCMAKE_VERBOSE_MAKEFILE=ON
+          -DPYBIND11_WERROR=OFF
+          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
+          -DDOWNLOAD_CATCH=ON
+          -DDOWNLOAD_EIGEN=ON
+          -DCMAKE_CXX_COMPILER=clang++
+          -DCMAKE_CXX_STANDARD=17
+
+      - name: Build
+        run: cmake --build . -j 2
+
+      - name: Python tests
+        run: cmake --build . --target pytest -j 2
+
+      - name: C++ tests
+        run: cmake --build . --target cpptest -j 2
+
+      - name: Interface test
+        run: cmake --build . --target test_cmake_build -j 2
+
+      - name: Clean directory
+        run: git clean -fdx

From 88b019a8a5e116d7e4a4ffae6399a426364d4bcd Mon Sep 17 00:00:00 2001
From: gitartpiano <51239761+gitartpiano@users.noreply.github.com>
Date: Fri, 11 Nov 2022 19:52:57 -0600
Subject: [PATCH 510/638] fix pybind11Tools.cmake typo causing Unknown
 arguments (#4327)

* fix pybind11Tools.cmake typo causing Unknown arguments

CMake Error at pybind11/tools/pybind11Tools.cmake:217 (if):
  if given arguments:
    "NOT" "MSVC" "AND" "NOT" "TEST" "MATCHES" "DEBUG|RELWITHDEBINFO"
  Unknown arguments specified
https://github.com/pybind/pybind11/issues/4325

* Apply the same fix in tools/pybind11NewTools.cmake

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 tools/pybind11NewTools.cmake | 2 +-
 tools/pybind11Tools.cmake    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 9e13daf1a1..5a6a0cb8be 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -235,7 +235,7 @@ function(pybind11_add_module target_name)
 
   # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
   string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
-  if(NOT MSVC AND NOT ${uppercase_CMAKE_BUILD_TYPE} MATCHES DEBUG|RELWITHDEBINFO)
+  if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
     # Strip unnecessary sections of the binary on Linux/macOS
     pybind11_strip(${target_name})
   endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 0dc61d3996..66ad00a478 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -214,7 +214,7 @@ function(pybind11_add_module target_name)
 
   # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
   string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
-  if(NOT MSVC AND NOT ${uppercase_CMAKE_BUILD_TYPE} MATCHES DEBUG|RELWITHDEBINFO)
+  if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
     pybind11_strip(${target_name})
   endif()
 

From 296615ad34f9d8f680efbab22553881ad9843063 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 12 Nov 2022 12:24:19 -0800
Subject: [PATCH 511/638] Add macos_brew_install_llvm to ci.yml (#4326)

* Add macos_brew_install_llvm to ci.yml

Added block transferred from PR #4324

* `test_cross_module_exception_translator` xfail 'Homebrew Clang'

* Add `pip install numpy scipy` (tested already under PR #4324).
---
 .github/workflows/ci.yml | 67 ++++++++++++++++++++++++++++++++++++++++
 tests/test_exceptions.py |  5 +--
 2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index adbbf626f1..bd99ddd338 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1037,3 +1037,70 @@ jobs:
 
       - name: Clean directory
         run: git clean -fdx
+
+  macos_brew_install_llvm:
+    name: "macos-latest • brew install llvm"
+    runs-on: macos-latest
+
+    env:
+      # https://apple.stackexchange.com/questions/227026/how-to-install-recent-clang-with-homebrew
+      LDFLAGS: '-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib'
+
+    steps:
+      - name: Update PATH
+        run: echo "/usr/local/opt/llvm/bin" >> $GITHUB_PATH
+
+      - name: Show env
+        run: env
+
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Show Clang++ version before brew install llvm
+        run: clang++ --version
+
+      - name: brew install llvm
+        run: brew install llvm
+
+      - name: Show Clang++ version after brew install llvm
+        run: clang++ --version
+
+      - name: Update CMake
+        uses: jwlawson/actions-setup-cmake@v1.13
+
+      - name: Run pip installs
+        run: |
+          python3 -m pip install --upgrade pip
+          python3 -m pip install -r tests/requirements.txt
+          python3 -m pip install numpy
+          python3 -m pip install scipy
+
+      - name: Show CMake version
+        run: cmake --version
+
+      - name: CMake Configure
+        run: >
+          cmake -S . -B .
+          -DCMAKE_VERBOSE_MAKEFILE=ON
+          -DPYBIND11_WERROR=ON
+          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
+          -DDOWNLOAD_CATCH=ON
+          -DDOWNLOAD_EIGEN=ON
+          -DCMAKE_CXX_COMPILER=clang++
+          -DCMAKE_CXX_STANDARD=17
+          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+
+      - name: Build
+        run: cmake --build . -j 2
+
+      - name: Python tests
+        run: cmake --build . --target pytest -j 2
+
+      - name: C++ tests
+        run: cmake --build . --target cpptest -j 2
+
+      - name: Interface test
+        run: cmake --build . --target test_cmake_build -j 2
+
+      - name: Clean directory
+        run: git clean -fdx
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 7eb1a9d62c..0d2c808143 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -4,6 +4,7 @@
 
 import env
 import pybind11_cross_module_tests as cm
+import pybind11_tests  # noqa: F401
 from pybind11_tests import exceptions as m
 
 
@@ -72,9 +73,9 @@ def test_cross_module_exceptions(msg):
 
 # TODO: FIXME
 @pytest.mark.xfail(
-    "env.PYPY and env.MACOS",
+    "env.MACOS and (env.PYPY or pybind11_tests.compiler_info.startswith('Homebrew Clang'))",
     raises=RuntimeError,
-    reason="Expected failure with PyPy and libc++ (Issue #2847 & PR #2999)",
+    reason="See Issue #2847, PR #2999, PR #4324",
 )
 def test_cross_module_exception_translator():
     with pytest.raises(KeyError):

From 48949222c637da9fc72b0ed6526ae1b40bb55237 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 22 Nov 2022 15:14:49 -0800
Subject: [PATCH 512/638] Use `PyEval_InitThreads()` as intended (#4350)

* Use `PyEval_InitThreads()` as intended (actually matters only for Python 3.6).

* Add `if defined(WITH_THREAD)` condition.

https://docs.python.org/3.6/c-api/init.html#c.PyEval_InitThreads

> This function is not available when thread support is disabled at compile time.

* Fix oversight pointed out by @EricCousineau-TRI: Remove condition that is always false.
---
 include/pybind11/detail/internals.h | 3 ---
 include/pybind11/embed.h            | 3 +++
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 6fd61098c4..ef1849fbea 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -468,9 +468,6 @@ PYBIND11_NOINLINE internals &get_internals() {
         internals_ptr = new internals();
 #if defined(WITH_THREAD)
 
-#    if PY_VERSION_HEX < 0x03090000
-        PyEval_InitThreads();
-#    endif
         PyThreadState *tstate = PyThreadState_Get();
         if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->tstate)) {
             pybind11_fail("get_internals: could not successfully initialize the tstate TSS key!");
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 0ac609e0f1..5b77594b35 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -118,6 +118,9 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
 #if PY_VERSION_HEX < 0x030B0000
 
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
+#    if defined(WITH_THREAD) && PY_VERSION_HEX < 0x03070000
+    PyEval_InitThreads();
+#    endif
 
     // Before it was special-cased in python 3.8, passing an empty or null argv
     // caused a segfault, so we have to reimplement the special case ourselves.

From 9c18a74e377dece2f2acd22c2c6e63ecb2a59c77 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 22 Nov 2022 17:17:02 -0800
Subject: [PATCH 513/638] Use `multiprocessing` `start_method` `"forkserver"`
 (#4306)

* Use `multiprocessing` `start_method` `"forkserver"`

Alternative to PR #4305

* Add link to comment under PR #4105

* Unconditionally `pytest.skip("DEADLOCK")` for PyPy Windows

* Remove `SKIP_IF_DEADLOCK` entirely, for simplicity. Hopefully this PR will resolve the deadlocks for good.

* Add "In a nutshell" comment, in response to request by @EricCousineau-TRI
---
 tests/conftest.py        | 12 ++++++++++++
 tests/test_gil_scoped.py |  4 ++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/tests/conftest.py b/tests/conftest.py
index f5ddb9f129..96dffc81cc 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -7,6 +7,8 @@
 import contextlib
 import difflib
 import gc
+import multiprocessing
+import os
 import re
 import textwrap
 
@@ -15,6 +17,16 @@
 # Early diagnostic for failed imports
 import pybind11_tests
 
+if os.name != "nt":
+    # Full background: https://github.com/pybind/pybind11/issues/4105#issuecomment-1301004592
+    # In a nutshell: fork() after starting threads == flakiness in the form of deadlocks.
+    # It is actually a well-known pitfall, unfortunately without guard rails.
+    # "forkserver" is more performant than "spawn" (~9s vs ~13s for tests/test_gil_scoped.py,
+    # visit the issuecomment link above for details).
+    # Windows does not have fork() and the associated pitfall, therefore it is best left
+    # running with defaults.
+    multiprocessing.set_start_method("forkserver")
+
 _long_marker = re.compile(r"([0-9])L")
 _hexadecimal = re.compile(r"0x[0-9a-fA-F]+")
 
diff --git a/tests/test_gil_scoped.py b/tests/test_gil_scoped.py
index e890a7b0c8..6af6a472d5 100644
--- a/tests/test_gil_scoped.py
+++ b/tests/test_gil_scoped.py
@@ -5,6 +5,7 @@
 
 import pytest
 
+import env
 from pybind11_tests import gil_scoped as m
 
 
@@ -144,7 +145,6 @@ def _intentional_deadlock():
 
 
 ALL_BASIC_TESTS_PLUS_INTENTIONAL_DEADLOCK = ALL_BASIC_TESTS + (_intentional_deadlock,)
-SKIP_IF_DEADLOCK = True  # See PR #4216
 
 
 def _run_in_process(target, *args, **kwargs):
@@ -181,7 +181,7 @@ def _run_in_process(target, *args, **kwargs):
         elif process.exitcode is None:
             assert t_delta > 0.9 * timeout
             msg = "DEADLOCK, most likely, exactly what this test is meant to detect."
-            if SKIP_IF_DEADLOCK:
+            if env.PYPY and env.WIN:
                 pytest.skip(msg)
             raise RuntimeError(msg)
         return process.exitcode

From 9907bedce517ea291c70c6a7b5dfec9e594f41df Mon Sep 17 00:00:00 2001
From: Xuehai Pan <XuehaiPan@outlook.com>
Date: Sat, 26 Nov 2022 07:15:54 +0800
Subject: [PATCH 514/638] fix(.github): fix bug-report issue template (#4363)

---
 .github/ISSUE_TEMPLATE/bug-report.yml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/.github/ISSUE_TEMPLATE/bug-report.yml b/.github/ISSUE_TEMPLATE/bug-report.yml
index e6494ba6a0..4f1e78f33c 100644
--- a/.github/ISSUE_TEMPLATE/bug-report.yml
+++ b/.github/ISSUE_TEMPLATE/bug-report.yml
@@ -21,10 +21,11 @@ body:
         - label: Consider asking first in the [Gitter chat room](https://gitter.im/pybind/Lobby) or in a [Discussion](https:/pybind/pybind11/discussions/new).
           required: false
 
-  - type: Input
+  - type: input
     id: version
     attributes:
       label: What version (or hash if on master) of pybind11 are you using?
+    validations:
       required: true
 
   - type: textarea
@@ -52,7 +53,7 @@ body:
         starting point for working out fixes.
       render: text
 
-  - type: Input
+  - type: input
     id: regression
     attributes:
       label: Is this a regression? Put the last known working version here if it is.

From 06003e82b3ff48337b71b310b46c3d8b15ca6d5a Mon Sep 17 00:00:00 2001
From: Ethan Steinberg <ethan.steinberg@gmail.com>
Date: Mon, 28 Nov 2022 07:39:38 -0800
Subject: [PATCH 515/638] Introduce a new style of warning suppression based on
 push/pop (#4285)

* Introduce a new warning suppression system

* Switch to better name

* Nits
---
 include/pybind11/cast.h                | 11 ++--
 include/pybind11/detail/common.h       | 82 +++++++++++++++++++++-----
 include/pybind11/detail/init.h         |  9 ++-
 include/pybind11/eigen/matrix.h        | 31 +++-------
 include/pybind11/eigen/tensor.h        | 35 ++++-------
 include/pybind11/numpy.h               | 15 ++---
 include/pybind11/pybind11.h            | 38 +++++-------
 include/pybind11/pytypes.h             | 16 +++--
 tests/test_builtin_casters.cpp         |  9 ++-
 tests/test_class.cpp                   |  4 +-
 tests/test_constants_and_functions.cpp | 34 ++++-------
 tests/test_eigen_matrix.cpp            |  4 +-
 tests/test_eigen_tensor.inl            |  8 ++-
 tests/test_embed/catch.cpp             |  4 +-
 tests/test_embed/test_interpreter.cpp  |  4 +-
 tests/test_kwargs_and_defaults.cpp     |  9 ++-
 tests/test_operator_overloading.cpp    | 23 +++-----
 17 files changed, 173 insertions(+), 163 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 430c62f357..8f92df8ab3 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -29,6 +29,9 @@
 #include <vector>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <typename type, typename SFINAE = void>
@@ -389,7 +392,7 @@ struct string_caster {
 
         // For UTF-8 we avoid the need for a temporary `bytes` object by using
         // `PyUnicode_AsUTF8AndSize`.
-        if (PYBIND11_SILENCE_MSVC_C4127(UTF_N == 8)) {
+        if (UTF_N == 8) {
             Py_ssize_t size = -1;
             const auto *buffer
                 = reinterpret_cast<const CharT *>(PyUnicode_AsUTF8AndSize(load_src.ptr(), &size));
@@ -416,7 +419,7 @@ struct string_caster {
             = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
         size_t length = (size_t) PYBIND11_BYTES_SIZE(utfNbytes.ptr()) / sizeof(CharT);
         // Skip BOM for UTF-16/32
-        if (PYBIND11_SILENCE_MSVC_C4127(UTF_N > 8)) {
+        if (UTF_N > 8) {
             buffer++;
             length--;
         }
@@ -572,7 +575,7 @@ struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
         // figure out how long the first encoded character is in bytes to distinguish between these
         // two errors.  We also allow want to allow unicode characters U+0080 through U+00FF, as
         // those can fit into a single char value.
-        if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 8) && str_len > 1 && str_len <= 4) {
+        if (StringCaster::UTF_N == 8 && str_len > 1 && str_len <= 4) {
             auto v0 = static_cast<unsigned char>(value[0]);
             // low bits only: 0-127
             // 0b110xxxxx - start of 2-byte sequence
@@ -598,7 +601,7 @@ struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
         // UTF-16 is much easier: we can only have a surrogate pair for values above U+FFFF, thus a
         // surrogate pair with total length 2 instantly indicates a range error (but not a "your
         // string was too long" error).
-        else if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 16) && str_len == 2) {
+        else if (StringCaster::UTF_N == 16 && str_len == 2) {
             one_char = static_cast<CharT>(value[0]);
             if (one_char >= 0xD800 && one_char < 0xE000) {
                 throw value_error("Character code point not in range(0x10000)");
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 9b74323f67..b58dc3afa7 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -17,8 +17,69 @@
 // Additional convention: 0xD = dev
 #define PYBIND11_VERSION_HEX 0x020B00D1
 
-#define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
-#define PYBIND11_NAMESPACE_END(name) }
+// Define some generic pybind11 helper macros for warning management.
+//
+// Note that compiler-specific push/pop pairs are baked into the
+// PYBIND11_NAMESPACE_BEGIN/PYBIND11_NAMESPACE_END pair of macros. Therefore manual
+// PYBIND11_WARNING_PUSH/PYBIND11_WARNING_POP are usually only needed in `#include` sections.
+//
+// If you find you need to suppress a warning, please try to make the suppression as local as
+// possible using these macros. Please also be sure to push/pop with the pybind11 macros. Please
+// only use compiler specifics if you need to check specific versions, e.g. Apple Clang vs. vanilla
+// Clang.
+#if defined(_MSC_VER)
+#    define PYBIND11_COMPILER_MSVC
+#    define PYBIND11_PRAGMA(...) __pragma(__VA_ARGS__)
+#    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(warning(push))
+#    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(warning(pop))
+#elif defined(__INTEL_COMPILER)
+#    define PYBIND11_COMPILER_INTEL
+#    define PYBIND11_PRAGMA(...) _Pragma(#    __VA_ARGS__)
+#    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(warning push)
+#    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(warning pop)
+#elif defined(__clang__)
+#    define PYBIND11_COMPILER_CLANG
+#    define PYBIND11_PRAGMA(...) _Pragma(#    __VA_ARGS__)
+#    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(clang diagnostic push)
+#    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(clang diagnostic push)
+#elif defined(__GNUC__)
+#    define PYBIND11_COMPILER_GCC
+#    define PYBIND11_PRAGMA(...) _Pragma(#    __VA_ARGS__)
+#    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(GCC diagnostic push)
+#    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(GCC diagnostic pop)
+#endif
+
+#ifdef PYBIND11_COMPILER_MSVC
+#    define PYBIND11_WARNING_DISABLE_MSVC(name) PYBIND11_PRAGMA(warning(disable : name))
+#else
+#    define PYBIND11_WARNING_DISABLE_MSVC(name)
+#endif
+
+#ifdef PYBIND11_COMPILER_CLANG
+#    define PYBIND11_WARNING_DISABLE_CLANG(name) PYBIND11_PRAGMA(clang diagnostic ignored name)
+#else
+#    define PYBIND11_WARNING_DISABLE_CLANG(name)
+#endif
+
+#ifdef PYBIND11_COMPILER_GCC
+#    define PYBIND11_WARNING_DISABLE_GCC(name) PYBIND11_PRAGMA(GCC diagnostic ignored name)
+#else
+#    define PYBIND11_WARNING_DISABLE_GCC(name)
+#endif
+
+#ifdef PYBIND11_COMPILER_INTEL
+#    define PYBIND11_WARNING_DISABLE_INTEL(name) PYBIND11_PRAGMA(warning disable name)
+#else
+#    define PYBIND11_WARNING_DISABLE_INTEL(name)
+#endif
+
+#define PYBIND11_NAMESPACE_BEGIN(name)                                                            \
+    namespace name {                                                                              \
+    PYBIND11_WARNING_PUSH
+
+#define PYBIND11_NAMESPACE_END(name)                                                              \
+    PYBIND11_WARNING_POP                                                                          \
+    }
 
 // Robust support for some features and loading modules compiled against different pybind versions
 // requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute
@@ -151,9 +212,9 @@
 
 /// Include Python header, disable linking to pythonX_d.lib on Windows in debug mode
 #if defined(_MSC_VER)
-#    pragma warning(push)
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_MSVC(4505)
 // C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
-#    pragma warning(disable : 4505)
 #    if defined(_DEBUG) && !defined(Py_DEBUG)
 // Workaround for a VS 2022 issue.
 // NOTE: This workaround knowingly violates the Python.h include order requirement:
@@ -236,7 +297,7 @@
 #        define _DEBUG
 #        undef PYBIND11_DEBUG_MARKER
 #    endif
-#    pragma warning(pop)
+PYBIND11_WARNING_POP
 #endif
 
 #include <cstddef>
@@ -1136,17 +1197,6 @@ constexpr
 #    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)
 #endif
 
-#if defined(_MSC_VER) // All versions (as of July 2021).
-
-// warning C4127: Conditional expression is constant
-constexpr inline bool silence_msvc_c4127(bool cond) { return cond; }
-
-#    define PYBIND11_SILENCE_MSVC_C4127(...) ::pybind11::detail::silence_msvc_c4127(__VA_ARGS__)
-
-#else
-#    define PYBIND11_SILENCE_MSVC_C4127(...) __VA_ARGS__
-#endif
-
 #if defined(__clang__)                                                                            \
     && (defined(__apple_build_version__) /* AppleClang 13.0.0.13000029 was the only data point    \
                                             available. */                                         \
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 05f4fe54aa..0938c9bdeb 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -12,6 +12,9 @@
 #include "class.h"
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <>
@@ -115,7 +118,7 @@ template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> *ptr, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     no_nullptr(ptr);
-    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr)) {
+    if (Class::has_alias && need_alias && !is_alias<Class>(ptr)) {
         // We're going to try to construct an alias by moving the cpp type.  Whether or not
         // that succeeds, we still need to destroy the original cpp pointer (either the
         // moved away leftover, if the alias construction works, or the value itself if we
@@ -156,7 +159,7 @@ void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
     auto *ptr = holder_helper<Holder<Class>>::get(holder);
     no_nullptr(ptr);
     // If we need an alias, check that the held pointer is actually an alias instance
-    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr)) {
+    if (Class::has_alias && need_alias && !is_alias<Class>(ptr)) {
         throw type_error("pybind11::init(): construction failed: returned holder-wrapped instance "
                          "is not an alias instance");
     }
@@ -174,7 +177,7 @@ void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
                   "pybind11::init() return-by-value factory function requires a movable class");
-    if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias) {
+    if (Class::has_alias && need_alias) {
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
     } else {
         v_h.value_ptr() = new Cpp<Class>(std::move(result));
diff --git a/include/pybind11/eigen/matrix.h b/include/pybind11/eigen/matrix.h
index c30dac2411..34fe329a82 100644
--- a/include/pybind11/eigen/matrix.h
+++ b/include/pybind11/eigen/matrix.h
@@ -16,29 +16,15 @@
        https://stackoverflow.com/questions/2579576/i-dir-vs-isystem-dir
        https://stackoverflow.com/questions/1741816/isystem-for-ms-visual-studio-c-compiler
 */
-// The C4127 suppression was introduced for Eigen 3.4.0. In theory we could
-// make it version specific, or even remove it later, but considering that
-// 1. C4127 is generally far more distracting than useful for modern template code, and
-// 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
-//    it is probably best to keep this around indefinitely.
-#if defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning(disable : 4127) // C4127: conditional expression is constant
-#    pragma warning(disable : 5054) // https://github.com/pybind/pybind11/pull/3741
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_MSVC(5054) // https://github.com/pybind/pybind11/pull/3741
 //       C5054: operator '&': deprecated between enumerations of different types
-#elif defined(__MINGW32__)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
-#endif
+PYBIND11_WARNING_DISABLE_GCC("-Wmaybe-uninitialized")
 
 #include <Eigen/Core>
 #include <Eigen/SparseCore>
 
-#if defined(_MSC_VER)
-#    pragma warning(pop)
-#elif defined(__MINGW32__)
-#    pragma GCC diagnostic pop
-#endif
+PYBIND11_WARNING_POP
 
 // Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
 // move constructors that break things.  We could detect this an explicitly copy, but an extra copy
@@ -48,6 +34,8 @@ static_assert(EIGEN_VERSION_AT_LEAST(3, 2, 7),
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 // Provide a convenience alias for easier pass-by-ref usage with fully dynamic strides:
 using EigenDStride = Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic>;
 template <typename MatrixType>
@@ -189,8 +177,7 @@ struct EigenProps {
             EigenIndex np_rows = a.shape(0), np_cols = a.shape(1),
                        np_rstride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar)),
                        np_cstride = a.strides(1) / static_cast<ssize_t>(sizeof(Scalar));
-            if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows)
-                || (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols)) {
+            if ((fixed_rows && np_rows != rows) || (fixed_cols && np_cols != cols)) {
                 return false;
             }
 
@@ -203,7 +190,7 @@ struct EigenProps {
                          stride = a.strides(0) / static_cast<ssize_t>(sizeof(Scalar));
 
         if (vector) { // Eigen type is a compile-time vector
-            if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n) {
+            if (fixed && size != n) {
                 return false; // Vector size mismatch
             }
             return {rows == 1 ? 1 : n, cols == 1 ? 1 : n, stride};
@@ -220,7 +207,7 @@ struct EigenProps {
             }
             return {1, n, stride};
         } // Otherwise it's either fully dynamic, or column dynamic; both become a column vector
-        if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) {
+        if (fixed_rows && rows != n) {
             return false;
         }
         return {n, 1, stride};
diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
index a823c0f397..a129f99292 100644
--- a/include/pybind11/eigen/tensor.h
+++ b/include/pybind11/eigen/tensor.h
@@ -13,28 +13,23 @@
 static_assert(__GNUC__ > 5, "Eigen Tensor support in pybind11 requires GCC > 5.0");
 #endif
 
-#if defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning(disable : 4554) // Tensor.h warning
-#    pragma warning(disable : 4127) // Tensor.h warning
-#elif defined(__MINGW32__)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
-#endif
+// Disable warnings for Eigen
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_MSVC(4554)
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+PYBIND11_WARNING_DISABLE_GCC("-Wmaybe-uninitialized")
 
 #include <unsupported/Eigen/CXX11/Tensor>
 
-#if defined(_MSC_VER)
-#    pragma warning(pop)
-#elif defined(__MINGW32__)
-#    pragma GCC diagnostic pop
-#endif
+PYBIND11_WARNING_POP
 
 static_assert(EIGEN_VERSION_AT_LEAST(3, 3, 0),
               "Eigen Tensor support in pybind11 requires Eigen >= 3.3.0");
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline bool is_tensor_aligned(const void *data) {
@@ -138,10 +133,8 @@ struct get_tensor_descriptor {
 //
 // We need to disable the type-limits warning for the inner loop when size = 0.
 
-#if defined(__GNUC__)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wtype-limits"
-#endif
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_GCC("-Wtype-limits")
 
 template <typename T, int size>
 std::vector<T> convert_dsizes_to_vector(const Eigen::DSizes<T, size> &arr) {
@@ -165,9 +158,7 @@ Eigen::DSizes<T, size> get_shape_for_array(const array &arr) {
     return result;
 }
 
-#if defined(__GNUC__)
-#    pragma GCC diagnostic pop
-#endif
+PYBIND11_WARNING_POP
 
 template <typename Type>
 struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
@@ -389,7 +380,7 @@ struct type_caster<Eigen::TensorMap<Type, Options>,
 
         constexpr bool is_aligned = (Options & Eigen::Aligned) != 0;
 
-        if (PYBIND11_SILENCE_MSVC_C4127(is_aligned) && !is_tensor_aligned(arr.data())) {
+        if (is_aligned && !is_tensor_aligned(arr.data())) {
             return false;
         }
 
@@ -399,7 +390,7 @@ struct type_caster<Eigen::TensorMap<Type, Options>,
             return false;
         }
 
-        if (PYBIND11_SILENCE_MSVC_C4127(needs_writeable) && !arr.writeable()) {
+        if (needs_writeable && !arr.writeable()) {
             return false;
         }
 
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 369e18649b..ea64aa7e7e 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -36,6 +36,8 @@ static_assert(std::is_signed<Py_intptr_t>::value, "Py_intptr_t must be signed");
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 class array; // Forward declaration
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -875,7 +877,7 @@ class array : public buffer {
      */
     template <typename T, ssize_t Dims = -1>
     detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
-        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
+        if (Dims >= 0 && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
@@ -893,7 +895,7 @@ class array : public buffer {
      */
     template <typename T, ssize_t Dims = -1>
     detail::unchecked_reference<T, Dims> unchecked() const & {
-        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
+        if (Dims >= 0 && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
@@ -1865,9 +1867,10 @@ struct vectorize_helper {
         }
 
         auto result = returned_array::create(trivial, shape);
+
+        PYBIND11_WARNING_PUSH
 #ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
-#    pragma clang diagnostic push
-#    pragma clang diagnostic ignored "-Wreturn-std-move"
+        PYBIND11_WARNING_DISABLE_CLANG("-Wreturn-std-move")
 #endif
 
         if (size == 0) {
@@ -1883,9 +1886,7 @@ struct vectorize_helper {
         }
 
         return result;
-#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
-#    pragma clang diagnostic pop
-#endif
+        PYBIND11_WARNING_POP
     }
 
     template <size_t... Index, size_t... VIndex, size_t... BIndex>
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 76d6eadcae..10b27254eb 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -35,6 +35,8 @@
 #    include <cxxabi.h>
 #endif
 
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
 /* https://stackoverflow.com/questions/46798456/handling-gccs-noexcept-type-warning
    This warning is about ABI compatibility, not code health.
    It is only actually needed in a couple places, but apparently GCC 7 "generates this warning if
@@ -43,11 +45,10 @@
    No other GCC version generates this warning.
  */
 #if defined(__GNUC__) && __GNUC__ == 7
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wnoexcept-type"
+PYBIND11_WARNING_DISABLE_GCC("-Wnoexcept-type")
 #endif
 
-PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_WARNING_DISABLE_MSVC(4127)
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
@@ -177,22 +178,22 @@ class cpp_function : public function {
         auto *rec = unique_rec.get();
 
         /* Store the capture object directly in the function record if there is enough space */
-        if (PYBIND11_SILENCE_MSVC_C4127(sizeof(capture) <= sizeof(rec->data))) {
+        if (sizeof(capture) <= sizeof(rec->data)) {
             /* Without these pragmas, GCC warns that there might not be
                enough space to use the placement new operator. However, the
                'if' statement above ensures that this is the case. */
-#if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wplacement-new"
+            PYBIND11_WARNING_PUSH
+
+#if defined(__GNUG__) && __GNUC__ >= 6
+            PYBIND11_WARNING_DISABLE_GCC("-Wplacement-new")
 #endif
+
             new ((capture *) &rec->data) capture{std::forward<Func>(f)};
-#if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
-#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wstrict-aliasing"
+
+#if !PYBIND11_HAS_STD_LAUNDER
+            PYBIND11_WARNING_DISABLE_GCC("-Wstrict-aliasing")
 #endif
+
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
             if (!std::is_trivially_destructible<capture>::value) {
@@ -202,9 +203,7 @@ class cpp_function : public function {
                     data->~capture();
                 };
             }
-#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
+            PYBIND11_WARNING_POP
         } else {
             rec->data[0] = new capture{std::forward<Func>(f)};
             rec->free_data = [](function_record *r) { delete ((capture *) r->data[0]); };
@@ -1841,8 +1840,7 @@ class class_ : public detail::generic_type {
         if (holder_ptr) {
             init_holder_from_existing(v_h, holder_ptr, std::is_copy_constructible<holder_type>());
             v_h.set_holder_constructed();
-        } else if (PYBIND11_SILENCE_MSVC_C4127(detail::always_construct_holder<holder_type>::value)
-                   || inst->owned) {
+        } else if (detail::always_construct_holder<holder_type>::value || inst->owned) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(v_h.value_ptr<type>());
             v_h.set_holder_constructed();
         }
@@ -2876,7 +2874,3 @@ inline function get_overload(const T *this_ptr, const char *name) {
     PYBIND11_OVERRIDE_PURE(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), fn, __VA_ARGS__);
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
-
-#if defined(__GNUC__) && __GNUC__ == 7
-#    pragma GCC diagnostic pop // -Wnoexcept-type
-#endif
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 80b49ec397..f913565d36 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -33,6 +33,8 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 /* A few forward declarations */
 class handle;
 class object;
@@ -884,10 +886,8 @@ object object_or_cast(T &&o);
 // Match a PyObject*, which we want to convert directly to handle via its converting constructor
 inline handle object_or_cast(PyObject *ptr) { return ptr; }
 
-#if defined(_MSC_VER) && _MSC_VER < 1920
-#    pragma warning(push)
-#    pragma warning(disable : 4522) // warning C4522: multiple assignment operators specified
-#endif
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_MSVC(4522) // warning C4522: multiple assignment operators specified
 template <typename Policy>
 class accessor : public object_api<accessor<Policy>> {
     using key_type = typename Policy::key_type;
@@ -951,9 +951,7 @@ class accessor : public object_api<accessor<Policy>> {
     key_type key;
     mutable object cache;
 };
-#if defined(_MSC_VER) && _MSC_VER < 1920
-#    pragma warning(pop)
-#endif
+PYBIND11_WARNING_POP
 
 PYBIND11_NAMESPACE_BEGIN(accessor_policies)
 struct obj_attr {
@@ -1693,7 +1691,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
 template <typename Unsigned>
 Unsigned as_unsigned(PyObject *o) {
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(Unsigned) <= sizeof(unsigned long))) {
+    if (sizeof(Unsigned) <= sizeof(unsigned long)) {
         unsigned long v = PyLong_AsUnsignedLong(o);
         return v == (unsigned long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
     }
@@ -1710,7 +1708,7 @@ class int_ : public object {
     template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     int_(T value) {
-        if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
+        if (sizeof(T) <= sizeof(long)) {
             if (std::is_signed<T>::value) {
                 m_ptr = PyLong_FromLong((long) value);
             } else {
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index 6ff63edfc6..0623b85dc9 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -73,6 +73,9 @@ PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
 
 TEST_SUBMODULE(builtin_casters, m) {
+    PYBIND11_WARNING_PUSH
+    PYBIND11_WARNING_DISABLE_MSVC(4127)
+
     // test_simple_string
     m.def("string_roundtrip", [](const char *s) { return s; });
 
@@ -86,7 +89,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     std::wstring wstr;
     wstr.push_back(0x61);   // a
     wstr.push_back(0x2e18); // ⸘
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+    if (sizeof(wchar_t) == 2) {
         wstr.push_back(mathbfA16_1);
         wstr.push_back(mathbfA16_2);
     } // 𝐀, utf16
@@ -113,7 +116,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     // Under Python 2.7, invalid unicode UTF-32 characters didn't appear to trigger
     // UnicodeDecodeError
     m.def("bad_utf32_string", [=]() { return std::u32string({a32, char32_t(0xd800), z32}); });
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+    if (sizeof(wchar_t) == 2) {
         m.def("bad_wchar_string", [=]() {
             return std::wstring({wchar_t(0x61), wchar_t(0xd800)});
         });
@@ -384,4 +387,6 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("takes_const_ref", [](const ConstRefCasted &x) { return x.tag; });
     m.def("takes_const_ref_wrap",
           [](std::reference_wrapper<const ConstRefCasted> x) { return x.get().tag; });
+
+    PYBIND11_WARNING_POP
 }
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index fc1c17b179..9ea10fae1e 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -22,10 +22,8 @@
 
 #include <utility>
 
-#if defined(_MSC_VER)
-#    pragma warning(disable : 4324)
+PYBIND11_WARNING_DISABLE_MSVC(4324)
 //     warning C4324: structure was padded due to alignment specifier
-#endif
 
 // test_brace_initialization
 struct NoBraceInitialization {
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 1918a429c8..922375c5ea 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -52,15 +52,12 @@ int f1(int x) noexcept { return x + 1; }
 #endif
 int f2(int x) noexcept(true) { return x + 2; }
 int f3(int x) noexcept(false) { return x + 3; }
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wdeprecated"
-#endif
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_GCC("-Wdeprecated")
+PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated")
 // NOLINTNEXTLINE(modernize-use-noexcept)
 int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
+PYBIND11_WARNING_POP
 struct C {
     int m1(int x) noexcept { return x - 1; }
     int m2(int x) const noexcept { return x - 2; }
@@ -68,17 +65,14 @@ struct C {
     int m4(int x) const noexcept(true) { return x - 4; }
     int m5(int x) noexcept(false) { return x - 5; }
     int m6(int x) const noexcept(false) { return x - 6; }
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wdeprecated"
-#endif
+    PYBIND11_WARNING_PUSH
+    PYBIND11_WARNING_DISABLE_GCC("-Wdeprecated")
+    PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated")
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m7(int x) throw() { return x - 7; }
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m8(int x) const throw() { return x - 8; }
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
+    PYBIND11_WARNING_POP
 };
 } // namespace test_exc_sp
 
@@ -126,14 +120,12 @@ TEST_SUBMODULE(constants_and_functions, m) {
         .def("m8", &C::m8);
     m.def("f1", f1);
     m.def("f2", f2);
-#if defined(__INTEL_COMPILER)
-#    pragma warning push
-#    pragma warning disable 878 // incompatible exception specifications
-#endif
+
+    PYBIND11_WARNING_PUSH
+    PYBIND11_WARNING_DISABLE_INTEL(878) // incompatible exception specifications
     m.def("f3", f3);
-#if defined(__INTEL_COMPILER)
-#    pragma warning pop
-#endif
+    PYBIND11_WARNING_POP
+
     m.def("f4", f4);
 
     // test_function_record_leaks
diff --git a/tests/test_eigen_matrix.cpp b/tests/test_eigen_matrix.cpp
index 71e41d198a..554cc4d7f8 100644
--- a/tests/test_eigen_matrix.cpp
+++ b/tests/test_eigen_matrix.cpp
@@ -13,9 +13,7 @@
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
 
-#if defined(_MSC_VER)
-#    pragma warning(disable : 4996) // C4996: std::unary_negation is deprecated
-#endif
+PYBIND11_WARNING_DISABLE_MSVC(4996)
 
 #include <Eigen/Cholesky>
 
diff --git a/tests/test_eigen_tensor.inl b/tests/test_eigen_tensor.inl
index 09b35fa134..f46eb1803a 100644
--- a/tests/test_eigen_tensor.inl
+++ b/tests/test_eigen_tensor.inl
@@ -9,7 +9,9 @@
 
 #include "pybind11_tests.h"
 
-namespace PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE {
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE)
+
+PYBIND11_WARNING_DISABLE_MSVC(4127)
 
 template <typename M>
 void reset_tensor(M &x) {
@@ -90,7 +92,7 @@ struct CustomExample {
 template <int Options>
 void init_tensor_module(pybind11::module &m) {
     const char *needed_options = "";
-    if (PYBIND11_SILENCE_MSVC_C4127(Options == Eigen::ColMajor)) {
+    if (Options == Eigen::ColMajor) {
         needed_options = "F";
     } else {
         needed_options = "C";
@@ -330,4 +332,4 @@ void test_module(py::module_ &m) {
     init_tensor_module<Eigen::RowMajor>(c_style);
 }
 
-} // namespace PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE
+PYBIND11_NAMESPACE_END(PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE)
diff --git a/tests/test_embed/catch.cpp b/tests/test_embed/catch.cpp
index a03a8b37c4..558a7a35e5 100644
--- a/tests/test_embed/catch.cpp
+++ b/tests/test_embed/catch.cpp
@@ -3,11 +3,9 @@
 
 #include <pybind11/embed.h>
 
-#ifdef _MSC_VER
 // Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
 // catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
-#    pragma warning(disable : 4996)
-#endif
+PYBIND11_WARNING_DISABLE_MSVC(4996)
 
 // Catch uses _ internally, which breaks gettext style defines
 #ifdef _
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 44dcd1fdb0..8cfd13fe52 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -1,10 +1,8 @@
 #include <pybind11/embed.h>
 
-#ifdef _MSC_VER
 // Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
 // catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
-#    pragma warning(disable : 4996)
-#endif
+PYBIND11_WARNING_DISABLE_MSVC(4996)
 
 #include <catch.hpp>
 #include <cstdlib>
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 2f3cabaf0f..77e72c0c70 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -44,14 +44,13 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
 
     // test_args_and_kwargs
     m.def("args_function", [](py::args args) -> py::tuple {
+        PYBIND11_WARNING_PUSH
+
 #ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
-#    pragma clang diagnostic push
-#    pragma clang diagnostic ignored "-Wreturn-std-move"
+        PYBIND11_WARNING_DISABLE_CLANG("-Wreturn-std-move")
 #endif
         return args;
-#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
-#    pragma clang diagnostic pop
-#endif
+        PYBIND11_WARNING_POP
     });
     m.def("args_kwargs_function", [](const py::args &args, const py::kwargs &kwargs) {
         return py::make_tuple(args, kwargs);
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index a4b895a897..112a363b4b 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -132,22 +132,18 @@ struct hash<HashMe> {
 // Not a good abs function, but easy to test.
 std::string abs(const Vector2 &) { return "abs(Vector2)"; }
 
-// MSVC & Intel warns about unknown pragmas, and warnings are errors.
-#if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
 // clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
 // `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
-// Here, we suppress the warning using `#pragma diagnostic`.
+// Here, we suppress the warning
 // Taken from: https://github.com/RobotLocomotion/drake/commit/aaf84b46
 // TODO(eric): This could be resolved using a function / functor (e.g. `py::self()`).
-#    if defined(__APPLE__) && defined(__clang__)
-#        if (__clang_major__ >= 10)
-#            pragma GCC diagnostic ignored "-Wself-assign-overloaded"
-#        endif
-#    elif defined(__clang__)
-#        if (__clang_major__ >= 7)
-#            pragma GCC diagnostic ignored "-Wself-assign-overloaded"
-#        endif
+#if defined(__APPLE__) && defined(__clang__)
+#    if (__clang_major__ >= 10)
+PYBIND11_WARNING_DISABLE_CLANG("-Wself-assign-overloaded")
+#    endif
+#elif defined(__clang__)
+#    if (__clang_major__ >= 7)
+PYBIND11_WARNING_DISABLE_CLANG("-Wself-assign-overloaded")
 #    endif
 #endif
 
@@ -283,6 +279,3 @@ TEST_SUBMODULE(operators, m) {
 
     m.def("get_unhashable_HashMe_set", []() { return std::unordered_set<HashMe>{{"one"}}; });
 }
-#if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif

From 88699849264150f513dafb98d9ec1bb31a7fa904 Mon Sep 17 00:00:00 2001
From: Arman <arm.nov@ya.ru>
Date: Thu, 1 Dec 2022 07:17:59 +0200
Subject: [PATCH 516/638] scoped_interpreter. overloaded constructor: PyConfig
 param (#4330)

* scoped_interpreter overloaded ctor: PyConfig param

* style: pre-commit fixes

* refact: some logics extracted into funcs (precheck_interpreter, _initialize_interpreter); config_guard

* style: pre-commit fixes

* refact: scoped_config, some funcs hidden in detail ns

* refact: macro PYBIND11_PYCONFIG_SUPPORT_PY_VERSION + undef

* feat: PYBIND11_PYCONFIG_SUPPORT_PY_VERSION set to 3.8

* tests: Custom PyConfig

* ci: python 3.6 -> 3.8

* ci: reverted py 38 back  to 36; refact: initialize_interpreter overloads

* style: pre-commit fixes

* fix: readability-implicit-bool-conversion

* refact: each initialize_interpreter overloads in pybind11 ns

* Move `initialize_interpreter_pre_pyconfig()` into the `detail` namespace.

Move the `PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX` define down to where it is used for the first time, and check if it is defined already, so that it is possible to customize from the compilation command line, just in case there is some unforeseen issue for Python 3.8, 3.9, 3.10.

* tests: Add program dir to path, Custom PyConfig with argv

* refact: clang-formatted

* tests: Add-program-dir-to-path covers both scoped_interpreter overloads

* tests: Add-program-dir-to-path fixed

* tests: Add-program-dir-to-path py_version dependant validation

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/embed.h              | 119 +++++++++++++++++---------
 tests/test_embed/test_interpreter.cpp |  66 ++++++++++++++
 2 files changed, 143 insertions(+), 42 deletions(-)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 5b77594b35..749c75beb6 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -86,37 +86,22 @@ inline wchar_t *widen_chars(const char *safe_arg) {
     return widened_arg;
 }
 
-PYBIND11_NAMESPACE_END(detail)
-
-/** \rst
-    Initialize the Python interpreter. No other pybind11 or CPython API functions can be
-    called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
-    optional `init_signal_handlers` parameter can be used to skip the registration of
-    signal handlers (see the `Python documentation`_ for details). Calling this function
-    again after the interpreter has already been initialized is a fatal error.
-
-    If initializing the Python interpreter fails, then the program is terminated.  (This
-    is controlled by the CPython runtime and is an exception to pybind11's normal behavior
-    of throwing exceptions on errors.)
-
-    The remaining optional parameters, `argc`, `argv`, and `add_program_dir_to_path` are
-    used to populate ``sys.argv`` and ``sys.path``.
-    See the |PySys_SetArgvEx documentation|_ for details.
-
-    .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
-    .. |PySys_SetArgvEx documentation| replace:: ``PySys_SetArgvEx`` documentation
-    .. _PySys_SetArgvEx documentation: https://docs.python.org/3/c-api/init.html#c.PySys_SetArgvEx
- \endrst */
-inline void initialize_interpreter(bool init_signal_handlers = true,
-                                   int argc = 0,
-                                   const char *const *argv = nullptr,
-                                   bool add_program_dir_to_path = true) {
+inline void precheck_interpreter() {
     if (Py_IsInitialized() != 0) {
         pybind11_fail("The interpreter is already running");
     }
+}
 
-#if PY_VERSION_HEX < 0x030B0000
+#if !defined(PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX)
+#    define PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX (0x03080000)
+#endif
 
+#if PY_VERSION_HEX < PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+inline void initialize_interpreter_pre_pyconfig(bool init_signal_handlers,
+                                                int argc,
+                                                const char *const *argv,
+                                                bool add_program_dir_to_path) {
+    detail::precheck_interpreter();
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
 #    if defined(WITH_THREAD) && PY_VERSION_HEX < 0x03070000
     PyEval_InitThreads();
@@ -150,26 +135,30 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
     auto *pysys_argv = widened_argv.get();
 
     PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
-#else
-    PyConfig config;
-    PyConfig_InitIsolatedConfig(&config);
-    config.isolated = 0;
-    config.use_environment = 1;
-    config.install_signal_handlers = init_signal_handlers ? 1 : 0;
+}
+#endif
 
-    PyStatus status = PyConfig_SetBytesArgv(&config, argc, const_cast<char *const *>(argv));
-    if (PyStatus_Exception(status)) {
+PYBIND11_NAMESPACE_END(detail)
+
+#if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+inline void initialize_interpreter(PyConfig *config,
+                                   int argc = 0,
+                                   const char *const *argv = nullptr,
+                                   bool add_program_dir_to_path = true) {
+    detail::precheck_interpreter();
+    PyStatus status = PyConfig_SetBytesArgv(config, argc, const_cast<char *const *>(argv));
+    if (PyStatus_Exception(status) != 0) {
         // A failure here indicates a character-encoding failure or the python
         // interpreter out of memory. Give up.
-        PyConfig_Clear(&config);
-        throw std::runtime_error(PyStatus_IsError(status) ? status.err_msg
-                                                          : "Failed to prepare CPython");
+        PyConfig_Clear(config);
+        throw std::runtime_error(PyStatus_IsError(status) != 0 ? status.err_msg
+                                                               : "Failed to prepare CPython");
     }
-    status = Py_InitializeFromConfig(&config);
-    PyConfig_Clear(&config);
-    if (PyStatus_Exception(status)) {
-        throw std::runtime_error(PyStatus_IsError(status) ? status.err_msg
-                                                          : "Failed to init CPython");
+    status = Py_InitializeFromConfig(config);
+    if (PyStatus_Exception(status) != 0) {
+        PyConfig_Clear(config);
+        throw std::runtime_error(PyStatus_IsError(status) != 0 ? status.err_msg
+                                                               : "Failed to init CPython");
     }
     if (add_program_dir_to_path) {
         PyRun_SimpleString("import sys, os.path; "
@@ -177,6 +166,43 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
                            "os.path.abspath(os.path.dirname(sys.argv[0])) "
                            "if sys.argv and os.path.exists(sys.argv[0]) else '')");
     }
+    PyConfig_Clear(config);
+}
+#endif
+
+/** \rst
+    Initialize the Python interpreter. No other pybind11 or CPython API functions can be
+    called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
+    optional `init_signal_handlers` parameter can be used to skip the registration of
+    signal handlers (see the `Python documentation`_ for details). Calling this function
+    again after the interpreter has already been initialized is a fatal error.
+
+    If initializing the Python interpreter fails, then the program is terminated.  (This
+    is controlled by the CPython runtime and is an exception to pybind11's normal behavior
+    of throwing exceptions on errors.)
+
+    The remaining optional parameters, `argc`, `argv`, and `add_program_dir_to_path` are
+    used to populate ``sys.argv`` and ``sys.path``.
+    See the |PySys_SetArgvEx documentation|_ for details.
+
+    .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
+    .. |PySys_SetArgvEx documentation| replace:: ``PySys_SetArgvEx`` documentation
+    .. _PySys_SetArgvEx documentation: https://docs.python.org/3/c-api/init.html#c.PySys_SetArgvEx
+ \endrst */
+inline void initialize_interpreter(bool init_signal_handlers = true,
+                                   int argc = 0,
+                                   const char *const *argv = nullptr,
+                                   bool add_program_dir_to_path = true) {
+#if PY_VERSION_HEX < PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+    detail::initialize_interpreter_pre_pyconfig(
+        init_signal_handlers, argc, argv, add_program_dir_to_path);
+#else
+    PyConfig config;
+    PyConfig_InitIsolatedConfig(&config);
+    config.isolated = 0;
+    config.use_environment = 1;
+    config.install_signal_handlers = init_signal_handlers ? 1 : 0;
+    initialize_interpreter(&config, argc, argv, add_program_dir_to_path);
 #endif
 }
 
@@ -264,6 +290,15 @@ class scoped_interpreter {
         initialize_interpreter(init_signal_handlers, argc, argv, add_program_dir_to_path);
     }
 
+#if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+    explicit scoped_interpreter(PyConfig *config,
+                                int argc = 0,
+                                const char *const *argv = nullptr,
+                                bool add_program_dir_to_path = true) {
+        initialize_interpreter(config, argc, argv, add_program_dir_to_path);
+    }
+#endif
+
     scoped_interpreter(const scoped_interpreter &) = delete;
     scoped_interpreter(scoped_interpreter &&other) noexcept { other.is_valid = false; }
     scoped_interpreter &operator=(const scoped_interpreter &) = delete;
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 8cfd13fe52..5c306d3637 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -166,6 +166,72 @@ TEST_CASE("There can be only one interpreter") {
     py::initialize_interpreter();
 }
 
+#if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+TEST_CASE("Custom PyConfig") {
+    py::finalize_interpreter();
+    PyConfig config;
+    PyConfig_InitPythonConfig(&config);
+    REQUIRE_NOTHROW(py::scoped_interpreter{&config});
+    {
+        py::scoped_interpreter p{&config};
+        REQUIRE(py::module_::import("widget_module").attr("add")(1, 41).cast<int>() == 42);
+    }
+    py::initialize_interpreter();
+}
+
+TEST_CASE("Custom PyConfig with argv") {
+    py::finalize_interpreter();
+    {
+        PyConfig config;
+        PyConfig_InitIsolatedConfig(&config);
+        char *argv[] = {strdup("a.out")};
+        py::scoped_interpreter argv_scope{&config, 1, argv};
+        std::free(argv[0]);
+        auto module = py::module::import("test_interpreter");
+        auto py_widget = module.attr("DerivedWidget")("The question");
+        const auto &cpp_widget = py_widget.cast<const Widget &>();
+        REQUIRE(cpp_widget.argv0() == "a.out");
+    }
+    py::initialize_interpreter();
+}
+#endif
+
+TEST_CASE("Add program dir to path") {
+    static auto get_sys_path_size = []() -> size_t {
+        auto sys_path = py::module::import("sys").attr("path");
+        return py::len(sys_path);
+    };
+    static auto validate_path_len = [](size_t default_len) {
+#if PY_VERSION_HEX < 0x030A0000
+        // It seems a value remains in sys.path
+        // left by the previous call of scoped_interpreter ctor.
+        REQUIRE(get_sys_path_size() > default_len);
+#else
+        REQUIRE(get_sys_path_size() == default_len + 1);
+#endif
+    };
+    py::finalize_interpreter();
+
+    size_t sys_path_default_size = 0;
+    {
+        py::scoped_interpreter scoped_interp{true, 0, nullptr, false};
+        sys_path_default_size = get_sys_path_size();
+    }
+    {
+        py::scoped_interpreter scoped_interp{}; // expected to append some to sys.path
+        validate_path_len(sys_path_default_size);
+    }
+#if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+    {
+        PyConfig config;
+        PyConfig_InitPythonConfig(&config);
+        py::scoped_interpreter scoped_interp{&config}; // expected to append some to sys.path
+        validate_path_len(sys_path_default_size);
+    }
+#endif
+    py::initialize_interpreter();
+}
+
 bool has_pybind11_internals_builtin() {
     auto builtins = py::handle(PyEval_GetBuiltins());
     return builtins.contains(PYBIND11_INTERNALS_ID);

From b14d58b6151b3cc7a9d9b2bf90d636940935db5c Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 30 Nov 2022 23:30:36 -0800
Subject: [PATCH 517/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.5.1 to 1.5.2 (#4370)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.5.1 to 1.5.2.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.5.1...v1.5.2)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index f03a397019..b787187ee0 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.5.1
+      uses: pypa/gh-action-pypi-publish@v1.5.2
       with:
         password: ${{ secrets.pypi_password }}
         packages_dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.5.1
+      uses: pypa/gh-action-pypi-publish@v1.5.2
       with:
         password: ${{ secrets.pypi_password_global }}
         packages_dir: global/

From 358ba459d2f05321a15555c3b57c606fe2597ec7 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 1 Dec 2022 09:25:30 -0800
Subject: [PATCH 518/638] Fix test added with PR #4330 (#4372)

---
 tests/test_embed/test_interpreter.cpp | 47 ++++++++++++++-------------
 1 file changed, 25 insertions(+), 22 deletions(-)

diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 5c306d3637..10b20f3715 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -14,6 +14,11 @@ PYBIND11_WARNING_DISABLE_MSVC(4996)
 namespace py = pybind11;
 using namespace py::literals;
 
+size_t get_sys_path_size() {
+    auto sys_path = py::module::import("sys").attr("path");
+    return py::len(sys_path);
+}
+
 class Widget {
 public:
     explicit Widget(std::string message) : message(std::move(message)) {}
@@ -196,41 +201,39 @@ TEST_CASE("Custom PyConfig with argv") {
 }
 #endif
 
-TEST_CASE("Add program dir to path") {
-    static auto get_sys_path_size = []() -> size_t {
-        auto sys_path = py::module::import("sys").attr("path");
-        return py::len(sys_path);
-    };
-    static auto validate_path_len = [](size_t default_len) {
-#if PY_VERSION_HEX < 0x030A0000
-        // It seems a value remains in sys.path
-        // left by the previous call of scoped_interpreter ctor.
-        REQUIRE(get_sys_path_size() > default_len);
-#else
-        REQUIRE(get_sys_path_size() == default_len + 1);
-#endif
-    };
+TEST_CASE("Add program dir to path pre-PyConfig") {
     py::finalize_interpreter();
-
-    size_t sys_path_default_size = 0;
+    size_t path_size_add_program_dir_to_path_false = 0;
     {
         py::scoped_interpreter scoped_interp{true, 0, nullptr, false};
-        sys_path_default_size = get_sys_path_size();
+        path_size_add_program_dir_to_path_false = get_sys_path_size();
     }
     {
-        py::scoped_interpreter scoped_interp{}; // expected to append some to sys.path
-        validate_path_len(sys_path_default_size);
+        py::scoped_interpreter scoped_interp{};
+        REQUIRE(get_sys_path_size() == path_size_add_program_dir_to_path_false + 1);
     }
+    py::initialize_interpreter();
+}
+
 #if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+TEST_CASE("Add program dir to path using PyConfig") {
+    py::finalize_interpreter();
+    size_t path_size_add_program_dir_to_path_false = 0;
     {
         PyConfig config;
         PyConfig_InitPythonConfig(&config);
-        py::scoped_interpreter scoped_interp{&config}; // expected to append some to sys.path
-        validate_path_len(sys_path_default_size);
+        py::scoped_interpreter scoped_interp{&config, 0, nullptr, false};
+        path_size_add_program_dir_to_path_false = get_sys_path_size();
+    }
+    {
+        PyConfig config;
+        PyConfig_InitPythonConfig(&config);
+        py::scoped_interpreter scoped_interp{&config};
+        REQUIRE(get_sys_path_size() == path_size_add_program_dir_to_path_false + 1);
     }
-#endif
     py::initialize_interpreter();
 }
+#endif
 
 bool has_pybind11_internals_builtin() {
     auto builtins = py::handle(PyEval_GetBuiltins());

From e133c33d5c6b19acab55fb1d6c10331d918bd830 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Thu, 1 Dec 2022 15:15:47 -0500
Subject: [PATCH 519/638] chore: Convert direct
 multiprocessing.set_start_method("forkserver") call to a pytest fixture.
 (#4377)

* chore: convert multiprocessing set_spawn to fixture in pytest

* Switch to early return
---
 tests/conftest.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tests/conftest.py b/tests/conftest.py
index 96dffc81cc..402fd4b25b 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -17,7 +17,12 @@
 # Early diagnostic for failed imports
 import pybind11_tests
 
-if os.name != "nt":
+
+@pytest.fixture(scope="session", autouse=True)
+def always_forkserver_on_unix():
+    if os.name == "nt":
+        return
+
     # Full background: https://github.com/pybind/pybind11/issues/4105#issuecomment-1301004592
     # In a nutshell: fork() after starting threads == flakiness in the form of deadlocks.
     # It is actually a well-known pitfall, unfortunately without guard rails.
@@ -27,6 +32,7 @@
     # running with defaults.
     multiprocessing.set_start_method("forkserver")
 
+
 _long_marker = re.compile(r"([0-9])L")
 _hexadecimal = re.compile(r"0x[0-9a-fA-F]+")
 

From 5b55f8fe8261dc50397e26b08435cd27a9e1f89c Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 4 Dec 2022 19:39:25 -0800
Subject: [PATCH 520/638] Replace `ubuntu-latest` with `ubuntu-22.04` (#4382)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Replace 🐍 3.6 • ubuntu-latest • x64 -DPYBIND11_FINDPYTHON=ON -DCMAKE_CXX_FLAGS="-D_=1" with 3.9

* Revert "Replace 🐍 3.6 • ubuntu-latest • x64 -DPYBIND11_FINDPYTHON=ON -DCMAKE_CXX_FLAGS="-D_=1" with 3.9"

This reverts commit 3ec984e1ed7265ac152e6760c68a0bad97d5a2bd.

* Systematically change all active ubuntu-latest to ubuntu-20.04, except in upstream.yml

* Revert "Systematically change all active ubuntu-latest to ubuntu-20.04, except in upstream.yml"

This reverts commit cdfd99526a9d3c172691685ac17054bfe76590fc.

* Change only some ubuntu-latest to ubuntu-20.04
---
 .github/workflows/ci.yml        | 8 ++++----
 .github/workflows/configure.yml | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bd99ddd338..a6f2624dba 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,7 +25,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        runs-on: [ubuntu-latest, windows-2022, macos-latest]
+        runs-on: [ubuntu-20.04, windows-2022, macos-latest]
         python:
         - '3.6'
         - '3.9'
@@ -42,12 +42,12 @@ jobs:
         # We support an optional key: args, for cmake args
         include:
           # Just add a key
-          - runs-on: ubuntu-latest
+          - runs-on: ubuntu-20.04
             python: '3.6'
             args: >
               -DPYBIND11_FINDPYTHON=ON
               -DCMAKE_CXX_FLAGS="-D_=1"
-          - runs-on: ubuntu-latest
+          - runs-on: ubuntu-20.04
             python: 'pypy-3.8'
             args: >
               -DPYBIND11_FINDPYTHON=ON
@@ -194,7 +194,7 @@ jobs:
           python-debug: false
 
     name: "🐍 ${{ matrix.python-version }}${{ matrix.python-debug && '-dbg' || '' }} (deadsnakes)${{ matrix.valgrind && ' • Valgrind' || '' }} • x64"
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 5ec0dd462f..05e972c754 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -16,12 +16,12 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        runs-on: [ubuntu-latest, macos-latest, windows-latest]
+        runs-on: [ubuntu-20.04, macos-latest, windows-latest]
         arch: [x64]
         cmake: ["3.23"]
 
         include:
-        - runs-on: ubuntu-latest
+        - runs-on: ubuntu-20.04
           arch: x64
           cmake: 3.4
 

From 6a1023e3e9ba32f7a9c4f59dfa8ea3f9e8dec341 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 5 Dec 2022 01:01:45 -0800
Subject: [PATCH 521/638] chore(deps): bump deadsnakes/action from 2.1.1 to
 3.0.0 (#4383)

Bumps [deadsnakes/action](https://github.com/deadsnakes/action) from 2.1.1 to 3.0.0.
- [Release notes](https://github.com/deadsnakes/action/releases)
- [Commits](https://github.com/deadsnakes/action/compare/v2.1.1...v3.0.0)

---
updated-dependencies:
- dependency-name: deadsnakes/action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a6f2624dba..1c6a63f409 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -200,7 +200,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python-version }} (deadsnakes)
-      uses: deadsnakes/action@v2.1.1
+      uses: deadsnakes/action@v3.0.0
       with:
         python-version: ${{ matrix.python-version }}
         debug: ${{ matrix.python-debug }}

From a6e75e4d8af51151587c13236fdc8570023fb57c Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 5 Dec 2022 01:03:05 -0800
Subject: [PATCH 522/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.5.2 to 1.6.1 (#4384)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.5.2 to 1.6.1.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.5.2...v1.6.1)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index b787187ee0..1f4422d138 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.5.2
+      uses: pypa/gh-action-pypi-publish@v1.6.1
       with:
         password: ${{ secrets.pypi_password }}
         packages_dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.5.2
+      uses: pypa/gh-action-pypi-publish@v1.6.1
       with:
         password: ${{ secrets.pypi_password_global }}
         packages_dir: global/

From a672de7cc88c053b77da0ae48f0f1a9b3afb86bb Mon Sep 17 00:00:00 2001
From: luzpaz <luzpaz@users.noreply.github.com>
Date: Tue, 6 Dec 2022 12:54:15 -0500
Subject: [PATCH 523/638] Fix source comment typo (#4388)

---
 include/pybind11/eigen/tensor.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
index a129f99292..568c641a2d 100644
--- a/include/pybind11/eigen/tensor.h
+++ b/include/pybind11/eigen/tensor.h
@@ -279,7 +279,7 @@ struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
             case return_value_policy::take_ownership:
                 if (std::is_const<C>::value) {
                     // This cast is ugly, and might be UB in some cases, but we don't have an
-                    // alterantive here as we must free that memory
+                    // alternative here as we must free that memory
                     Helper::free(const_cast<Type *>(src));
                     pybind11_fail("Cannot take ownership of a const reference");
                 }

From 4768a6f8f5e1abe106b4e3c9899d5866d88d77f6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 6 Dec 2022 10:10:48 -0800
Subject: [PATCH 524/638] chore(deps): update pre-commit hooks (#4386)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* chore(deps): update pre-commit hooks

updates:
- [github.com/pre-commit/pre-commit-hooks: v4.3.0 → v4.4.0](https://github.com/pre-commit/pre-commit-hooks/compare/v4.3.0...v4.4.0)
- [github.com/asottile/pyupgrade: v3.2.0 → v3.3.0](https://github.com/asottile/pyupgrade/compare/v3.2.0...v3.3.0)
- [github.com/hadialqattan/pycln: v2.1.1 → v2.1.2](https://github.com/hadialqattan/pycln/compare/v2.1.1...v2.1.2)
- [github.com/PyCQA/flake8: 5.0.4 → 6.0.0](https://github.com/PyCQA/flake8/compare/5.0.4...6.0.0)
- [github.com/PyCQA/pylint: v2.15.5 → v2.15.8](https://github.com/PyCQA/pylint/compare/v2.15.5...v2.15.8)
- [github.com/pre-commit/mirrors-mypy: v0.982 → v0.991](https://github.com/pre-commit/mirrors-mypy/compare/v0.982...v0.991)
- [github.com/mgedmin/check-manifest: 0.48 → 0.49](https://github.com/mgedmin/check-manifest/compare/0.48...0.49)
- [github.com/pre-commit/mirrors-clang-format: v14.0.6 → v15.0.4](https://github.com/pre-commit/mirrors-clang-format/compare/v14.0.6...v15.0.4)

* style: pre-commit fixes

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml          | 16 ++++++++--------
 include/pybind11/cast.h          |  3 ++-
 include/pybind11/detail/common.h |  6 +++---
 include/pybind11/detail/init.h   | 27 +++++++++++++++------------
 include/pybind11/numpy.h         |  2 +-
 include/pybind11/pybind11.h      |  6 +++---
 include/pybind11/pytypes.h       |  3 ++-
 tests/test_virtual_functions.cpp |  3 ++-
 8 files changed, 36 insertions(+), 30 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index fd079dd037..4e80fbad15 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -24,7 +24,7 @@ exclude: ^tools/JoinPaths.cmake$
 repos:
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: "v4.3.0"
+  rev: "v4.4.0"
   hooks:
   - id: check-added-large-files
   - id: check-case-conflict
@@ -41,7 +41,7 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v3.2.0"
+  rev: "v3.3.0"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
@@ -80,7 +80,7 @@ repos:
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v2.1.1"
+  rev: "v2.1.2"
   hooks:
   - id: pycln
     stages: [manual]
@@ -108,7 +108,7 @@ repos:
 
 # Flake8 also supports pre-commit natively (same author)
 - repo: https://github.com/PyCQA/flake8
-  rev: "5.0.4"
+  rev: "6.0.0"
   hooks:
   - id: flake8
     exclude: ^(docs/.*|tools/.*)$
@@ -116,7 +116,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.15.5"
+  rev: "v2.15.8"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -132,7 +132,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.982"
+  rev: "v0.991"
   hooks:
   - id: mypy
     args: []
@@ -141,7 +141,7 @@ repos:
 
 # Checks the manifest for missing files (native support)
 - repo: https://github.com/mgedmin/check-manifest
-  rev: "0.48"
+  rev: "0.49"
   hooks:
   - id: check-manifest
     # This is a slow hook, so only run this if --hook-stage manual is passed
@@ -175,7 +175,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v14.0.6"
+  rev: "v15.0.4"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 8f92df8ab3..3a40460276 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -91,7 +91,8 @@ public:
     template <typename T_,                                                                        \
               ::pybind11::detail::enable_if_t<                                                    \
                   std::is_same<type, ::pybind11::detail::remove_cv_t<T_>>::value,                 \
-                  int> = 0>                                                                       \
+                  int>                                                                            \
+              = 0>                                                                                \
     static ::pybind11::handle cast(                                                               \
         T_ *src, ::pybind11::return_value_policy policy, ::pybind11::handle parent) {             \
         if (!src)                                                                                 \
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index b58dc3afa7..6e295fd2f8 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -34,17 +34,17 @@
 #    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(warning(pop))
 #elif defined(__INTEL_COMPILER)
 #    define PYBIND11_COMPILER_INTEL
-#    define PYBIND11_PRAGMA(...) _Pragma(#    __VA_ARGS__)
+#    define PYBIND11_PRAGMA(...) _Pragma(#__VA_ARGS__)
 #    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(warning push)
 #    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(warning pop)
 #elif defined(__clang__)
 #    define PYBIND11_COMPILER_CLANG
-#    define PYBIND11_PRAGMA(...) _Pragma(#    __VA_ARGS__)
+#    define PYBIND11_PRAGMA(...) _Pragma(#__VA_ARGS__)
 #    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(clang diagnostic push)
 #    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(clang diagnostic push)
 #elif defined(__GNUC__)
 #    define PYBIND11_COMPILER_GCC
-#    define PYBIND11_PRAGMA(...) _Pragma(#    __VA_ARGS__)
+#    define PYBIND11_PRAGMA(...) _Pragma(#__VA_ARGS__)
 #    define PYBIND11_WARNING_PUSH PYBIND11_PRAGMA(GCC diagnostic push)
 #    define PYBIND11_WARNING_POP PYBIND11_PRAGMA(GCC diagnostic pop)
 #endif
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 0938c9bdeb..9f71278c26 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -209,10 +209,11 @@ struct constructor {
             extra...);
     }
 
-    template <typename Class,
-              typename... Extra,
-              enable_if_t<Class::has_alias && std::is_constructible<Cpp<Class>, Args...>::value,
-                          int> = 0>
+    template <
+        typename Class,
+        typename... Extra,
+        enable_if_t<Class::has_alias && std::is_constructible<Cpp<Class>, Args...>::value, int>
+        = 0>
     static void execute(Class &cl, const Extra &...extra) {
         cl.def(
             "__init__",
@@ -229,10 +230,11 @@ struct constructor {
             extra...);
     }
 
-    template <typename Class,
-              typename... Extra,
-              enable_if_t<Class::has_alias && !std::is_constructible<Cpp<Class>, Args...>::value,
-                          int> = 0>
+    template <
+        typename Class,
+        typename... Extra,
+        enable_if_t<Class::has_alias && !std::is_constructible<Cpp<Class>, Args...>::value, int>
+        = 0>
     static void execute(Class &cl, const Extra &...extra) {
         cl.def(
             "__init__",
@@ -248,10 +250,11 @@ struct constructor {
 // Implementing class for py::init_alias<...>()
 template <typename... Args>
 struct alias_constructor {
-    template <typename Class,
-              typename... Extra,
-              enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value,
-                          int> = 0>
+    template <
+        typename Class,
+        typename... Extra,
+        enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value, int>
+        = 0>
     static void execute(Class &cl, const Extra &...extra) {
         cl.def(
             "__init__",
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index ea64aa7e7e..8f072af267 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1471,7 +1471,7 @@ struct npy_format_descriptor {
         }
 
 // Extract name, offset and format descriptor for a struct field
-#    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #    Field)
+#    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
 
 // The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
 // (C) William Swanson, Paul Fultz
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 10b27254eb..a7310dfd4d 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1426,9 +1426,9 @@ template <typename T, enable_if_t<has_operator_delete<T>::value, int> = 0>
 void call_operator_delete(T *p, size_t, size_t) {
     T::operator delete(p);
 }
-template <
-    typename T,
-    enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
+template <typename T,
+          enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int>
+          = 0>
 void call_operator_delete(T *p, size_t s, size_t) {
     T::operator delete(p, s);
 }
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f913565d36..3282879312 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -232,7 +232,8 @@ class handle : public detail::object_api<handle> {
         detail::enable_if_t<detail::all_of<detail::none_of<std::is_base_of<handle, T>,
                                                            detail::is_pyobj_ptr_or_nullptr_t<T>>,
                                            std::is_convertible<T, PyObject *>>::value,
-                            int> = 0>
+                            int>
+        = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     handle(T &obj) : m_ptr(obj) {}
 
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 323aa0d22d..93b136ad3c 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -173,7 +173,8 @@ struct AdderBase {
     using DataVisitor = std::function<void(const Data &)>;
 
     virtual void
-    operator()(const Data &first, const Data &second, const DataVisitor &visitor) const = 0;
+    operator()(const Data &first, const Data &second, const DataVisitor &visitor) const
+        = 0;
     virtual ~AdderBase() = default;
     AdderBase() = default;
     AdderBase(const AdderBase &) = delete;

From 65cc9d2a291c983c289b35afe970bdda5710d706 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Tue, 6 Dec 2022 23:36:11 -0500
Subject: [PATCH 525/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.6.1 to 1.6.4 (#4389)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.6.1 to 1.6.4.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.6.1...v1.6.4)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 1f4422d138..7c6fc67a3e 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.6.1
+      uses: pypa/gh-action-pypi-publish@v1.6.4
       with:
         password: ${{ secrets.pypi_password }}
         packages_dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.6.1
+      uses: pypa/gh-action-pypi-publish@v1.6.4
       with:
         password: ${{ secrets.pypi_password_global }}
         packages_dir: global/

From 65374c8e62488c557dccf70c9276e3f9fe04b007 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 8 Dec 2022 22:06:51 -0800
Subject: [PATCH 526/638] `pybind11::handle` `inc_ref()` & `dec_ref()`
 `PyGILState_Check()` **excluding** `nullptr` (#4246)

* pybind11/pytypes.h `inc_ref()`, `dec_ref()` `PyGILState_Check()` **excluding** `nullptr`

Guarded by `PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF`

* Disable `PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF` for PyPy under Windows.

* Add reference to PR #4268 (PyPy Windows)
---
 include/pybind11/detail/common.h |  9 +++++++++
 include/pybind11/pytypes.h       | 10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 6e295fd2f8..9acf104668 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -323,6 +323,15 @@ PYBIND11_WARNING_POP
 #    define PYBIND11_HAS_U8STRING
 #endif
 
+// See description of PR #4246:
+#if !defined(NDEBUG) && !defined(PY_ASSERT_GIL_HELD_INCREF_DECREF)                                \
+    && !(defined(PYPY_VERSION)                                                                    \
+         && defined(_MSC_VER)) /* PyPy Windows: pytest hangs indefinitely at the end of the       \
+                                  process (see PR #4268) */                                       \
+    && !defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+#    define PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
+#endif
+
 // #define PYBIND11_STR_LEGACY_PERMISSIVE
 // If DEFINED, pybind11::str can hold PyUnicodeObject or PyBytesObject
 //             (probably surprising and never documented, but this was the
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 3282879312..56e0423ac4 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -249,6 +249,11 @@ class handle : public detail::object_api<handle> {
     const handle &inc_ref() const & {
 #ifdef PYBIND11_HANDLE_REF_DEBUG
         inc_ref_counter(1);
+#endif
+#if defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+        if (m_ptr != nullptr && !PyGILState_Check()) {
+            throw std::runtime_error("pybind11::handle::inc_ref() PyGILState_Check() failure.");
+        }
 #endif
         Py_XINCREF(m_ptr);
         return *this;
@@ -260,6 +265,11 @@ class handle : public detail::object_api<handle> {
         this function automatically. Returns a reference to itself.
     \endrst */
     const handle &dec_ref() const & {
+#if defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+        if (m_ptr != nullptr && !PyGILState_Check()) {
+            throw std::runtime_error("pybind11::handle::dec_ref() PyGILState_Check() failure.");
+        }
+#endif
         Py_XDECREF(m_ptr);
         return *this;
     }

From 00126859a550d10fb9f5bc0d4fdf86988c2012f4 Mon Sep 17 00:00:00 2001
From: Frank <frank-stettner@gmx.net>
Date: Fri, 9 Dec 2022 08:10:10 +0100
Subject: [PATCH 527/638] Add option for enable/disable enum members in
 docstring. (#2768)

* Add option for enable/disable enum members in docstring

* Add tests for disable enum members docstring option

* Add docstring options to documentation

* style: pre-commit fixes

* Fix typos in documentation

* Improve documentation wording

* Apply suggestions by @Skylion007

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 docs/advanced/misc.rst           |  9 ++++++
 include/pybind11/options.h       | 16 ++++++++++
 include/pybind11/pybind11.h      | 50 +++++++++++++++++-------------
 tests/test_docstring_options.cpp | 53 ++++++++++++++++++++++++++++++++
 tests/test_docstring_options.py  | 23 ++++++++++++++
 5 files changed, 129 insertions(+), 22 deletions(-)

diff --git a/docs/advanced/misc.rst b/docs/advanced/misc.rst
index 71960b803d..35a6ebcd60 100644
--- a/docs/advanced/misc.rst
+++ b/docs/advanced/misc.rst
@@ -324,6 +324,15 @@ The class ``options`` allows you to selectively suppress auto-generated signatur
         m.def("add", [](int a, int b) { return a + b; }, "A function which adds two numbers");
     }
 
+pybind11 also appends all members of an enum to the resulting enum docstring.
+This default behavior can be disabled by using the ``disable_enum_members_docstring()``
+function of the ``options`` class.
+
+With ``disable_user_defined_docstrings()`` all user defined docstrings of
+``module_::def()``, ``class_::def()`` and ``enum_()`` are disabled, but the
+function signatures and enum members are included in the docstring, unless they
+are disabled separately.
+
 Note that changes to the settings affect only function bindings created during the
 lifetime of the ``options`` instance. When it goes out of scope at the end of the module's init function,
 the default settings are restored to prevent unwanted side effects.
diff --git a/include/pybind11/options.h b/include/pybind11/options.h
index 1e493bdcc4..1b2122522d 100644
--- a/include/pybind11/options.h
+++ b/include/pybind11/options.h
@@ -47,6 +47,16 @@ class options {
         return *this;
     }
 
+    options &disable_enum_members_docstring() & {
+        global_state().show_enum_members_docstring = false;
+        return *this;
+    }
+
+    options &enable_enum_members_docstring() & {
+        global_state().show_enum_members_docstring = true;
+        return *this;
+    }
+
     // Getter methods (return the global state):
 
     static bool show_user_defined_docstrings() {
@@ -55,6 +65,10 @@ class options {
 
     static bool show_function_signatures() { return global_state().show_function_signatures; }
 
+    static bool show_enum_members_docstring() {
+        return global_state().show_enum_members_docstring;
+    }
+
     // This type is not meant to be allocated on the heap.
     void *operator new(size_t) = delete;
 
@@ -63,6 +77,8 @@ class options {
         bool show_user_defined_docstrings = true; //< Include user-supplied texts in docstrings.
         bool show_function_signatures = true;     //< Include auto-generated function signatures
                                                   //  in docstrings.
+        bool show_enum_members_docstring = true;  //< Include auto-generated member list in enum
+                                                  //  docstrings.
     };
 
     static state &global_state() {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index a7310dfd4d..6205effd61 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1972,29 +1972,35 @@ struct enum_base {
             name("name"),
             is_method(m_base));
 
-        m_base.attr("__doc__") = static_property(
-            cpp_function(
-                [](handle arg) -> std::string {
-                    std::string docstring;
-                    dict entries = arg.attr("__entries");
-                    if (((PyTypeObject *) arg.ptr())->tp_doc) {
-                        docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
-                    }
-                    docstring += "Members:";
-                    for (auto kv : entries) {
-                        auto key = std::string(pybind11::str(kv.first));
-                        auto comment = kv.second[int_(1)];
-                        docstring += "\n\n  " + key;
-                        if (!comment.is_none()) {
-                            docstring += " : " + (std::string) pybind11::str(comment);
+        if (options::show_enum_members_docstring()) {
+            m_base.attr("__doc__") = static_property(
+                cpp_function(
+                    [](handle arg) -> std::string {
+                        std::string docstring;
+                        dict entries = arg.attr("__entries");
+                        if (((PyTypeObject *) arg.ptr())->tp_doc) {
+                            docstring += std::string(
+                                reinterpret_cast<PyTypeObject *>(arg.ptr())->tp_doc);
+                            docstring += "\n\n";
                         }
-                    }
-                    return docstring;
-                },
-                name("__doc__")),
-            none(),
-            none(),
-            "");
+                        docstring += "Members:";
+                        for (auto kv : entries) {
+                            auto key = std::string(pybind11::str(kv.first));
+                            auto comment = kv.second[int_(1)];
+                            docstring += "\n\n  ";
+                            docstring += key;
+                            if (!comment.is_none()) {
+                                docstring += " : ";
+                                docstring += pybind11::str(comment).cast<std::string>();
+                            }
+                        }
+                        return docstring;
+                    },
+                    name("__doc__")),
+                none(),
+                none(),
+                "");
+        }
 
         m_base.attr("__members__") = static_property(cpp_function(
                                                          [](handle arg) -> dict {
diff --git a/tests/test_docstring_options.cpp b/tests/test_docstring_options.cpp
index 4d44f4e20d..dda1cf6e41 100644
--- a/tests/test_docstring_options.cpp
+++ b/tests/test_docstring_options.cpp
@@ -85,4 +85,57 @@ TEST_SUBMODULE(docstring_options, m) {
                           &DocstringTestFoo::setValue,
                           "This is a property docstring");
     }
+
+    {
+        enum class DocstringTestEnum1 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum1>(m, "DocstringTestEnum1", "Enum docstring")
+            .value("Member1", DocstringTestEnum1::Member1)
+            .value("Member2", DocstringTestEnum1::Member2);
+    }
+
+    {
+        py::options options;
+        options.enable_enum_members_docstring();
+
+        enum class DocstringTestEnum2 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum2>(m, "DocstringTestEnum2", "Enum docstring")
+            .value("Member1", DocstringTestEnum2::Member1)
+            .value("Member2", DocstringTestEnum2::Member2);
+    }
+
+    {
+        py::options options;
+        options.disable_enum_members_docstring();
+
+        enum class DocstringTestEnum3 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum3>(m, "DocstringTestEnum3", "Enum docstring")
+            .value("Member1", DocstringTestEnum3::Member1)
+            .value("Member2", DocstringTestEnum3::Member2);
+    }
+
+    {
+        py::options options;
+        options.disable_user_defined_docstrings();
+
+        enum class DocstringTestEnum4 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum4>(m, "DocstringTestEnum4", "Enum docstring")
+            .value("Member1", DocstringTestEnum4::Member1)
+            .value("Member2", DocstringTestEnum4::Member2);
+    }
+
+    {
+        py::options options;
+        options.disable_user_defined_docstrings();
+        options.disable_enum_members_docstring();
+
+        enum class DocstringTestEnum5 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum5>(m, "DocstringTestEnum5", "Enum docstring")
+            .value("Member1", DocstringTestEnum5::Member1)
+            .value("Member2", DocstringTestEnum5::Member2);
+    }
 }
diff --git a/tests/test_docstring_options.py b/tests/test_docstring_options.py
index fcd16b89fd..e6f5a9d987 100644
--- a/tests/test_docstring_options.py
+++ b/tests/test_docstring_options.py
@@ -39,3 +39,26 @@ def test_docstring_options():
     # Suppression of user-defined docstrings for non-function objects
     assert not m.DocstringTestFoo.__doc__
     assert not m.DocstringTestFoo.value_prop.__doc__
+
+    # Check existig behaviour of enum docstings
+    assert (
+        m.DocstringTestEnum1.__doc__
+        == "Enum docstring\n\nMembers:\n\n  Member1\n\n  Member2"
+    )
+
+    # options.enable_enum_members_docstring()
+    assert (
+        m.DocstringTestEnum2.__doc__
+        == "Enum docstring\n\nMembers:\n\n  Member1\n\n  Member2"
+    )
+
+    # options.disable_enum_members_docstring()
+    assert m.DocstringTestEnum3.__doc__ == "Enum docstring"
+
+    # options.disable_user_defined_docstrings()
+    assert m.DocstringTestEnum4.__doc__ == "Members:\n\n  Member1\n\n  Member2"
+
+    # options.disable_user_defined_docstrings()
+    # options.disable_enum_members_docstring()
+    # When all options are disabled, no docstring (instead of an empty one) should be generated
+    assert m.DocstringTestEnum5.__doc__ is None

From 9db988013ceb54ab15fb775b229ac9180fd08fbe Mon Sep 17 00:00:00 2001
From: aimir <48388610+aimir@users.noreply.github.com>
Date: Fri, 9 Dec 2022 09:15:11 +0200
Subject: [PATCH 528/638] Correct class names for KeysView, ValuesView and
 ItemsView in bind_map (#4353)

* Create templated abstract classes KeysView, ValuesView and ItemsView, and implement them on-the-fly when wrapping any specific map type

* We don't want to wrap different ValuesView objects for double values and const double, for example, as both wrappers will be named ValuesView[float]

* Fallback to C++ names if key or values types are not wrapped

* Added a test for .keys(), .values() and .items() returning the same types for similarly-typed maps

* Fixed wrong use of auto in a declarator list: the two descriptions might have different types

* Fixes for clang-tidy issues: explicit single-argument constructor, using the 'override' keyword when overriding functions

* Bugfix for old versions of clang++, which seem to have trouble with the struct being defined inside a module, which was also needlessly ugly anyway

* Bugfix for clang++, which doesn't have some of the names in runtime uness they are specified to be static

* A fix for clang-tidy performance-inefficient-string-concatenation issues - I personally think this looks uglier, but it's probably worth it for clang-tidy to be happy

* Possible fix for clang++ linking issues - make the descriptions static constexpr to make sure they are known before linking

* Correct names for previously-wrapped types as keys/values of maps

* Bugfix - typo in type info names which caused things to segfault

* Apply suggestions from code review

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* Use detail::remove_cvref_t instead of doing remove_cv and remove_reference separately

* Avoid names with double underscore, as they are reserved

* Improved testing for KeysView, ValuesView and ItemsView: check type names + stricter asserts

* Moved description logic to helper function in type_caster_base.h

* style: pre-commit fixes

* Fix a clang-tidy issue: do not use 'else' after 'return'

* Apply suggestion by @Skylion007, with additional trivial simplification.

Co-authored-by: Amir <aimir@local>
Co-authored-by: aimir <aimir@localhost>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 include/pybind11/detail/type_caster_base.h |   9 ++
 include/pybind11/stl_bind.h                | 154 ++++++++++++++-------
 tests/test_stl_binders.py                  |  26 ++++
 3 files changed, 142 insertions(+), 47 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 21f69c289f..0b710d7e4c 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -1006,5 +1006,14 @@ class type_caster_base : public type_caster_generic {
     static Constructor make_move_constructor(...) { return nullptr; }
 };
 
+PYBIND11_NOINLINE std::string type_info_description(const std::type_info &ti) {
+    if (auto *type_data = get_type_info(ti)) {
+        handle th((PyObject *) type_data->type);
+        return th.attr("__module__").cast<std::string>() + '.'
+               + th.attr("__qualname__").cast<std::string>();
+    }
+    return clean_type_id(ti.name());
+}
+
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 22a29b476f..0c634597ec 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -10,10 +10,13 @@
 #pragma once
 
 #include "detail/common.h"
+#include "detail/type_caster_base.h"
+#include "cast.h"
 #include "operators.h"
 
 #include <algorithm>
 #include <sstream>
+#include <type_traits>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -636,18 +639,52 @@ auto map_if_insertion_operator(Class_ &cl, std::string const &name)
         "Return the canonical string representation of this map.");
 }
 
-template <typename Map>
+template <typename KeyType>
 struct keys_view {
-    Map &map;
+    virtual size_t len() = 0;
+    virtual iterator iter() = 0;
+    virtual bool contains(const KeyType &k) = 0;
+    virtual bool contains(const object &k) = 0;
+    virtual ~keys_view() = default;
 };
 
-template <typename Map>
+template <typename MappedType>
 struct values_view {
-    Map &map;
+    virtual size_t len() = 0;
+    virtual iterator iter() = 0;
+    virtual ~values_view() = default;
 };
 
-template <typename Map>
+template <typename KeyType, typename MappedType>
 struct items_view {
+    virtual size_t len() = 0;
+    virtual iterator iter() = 0;
+    virtual ~items_view() = default;
+};
+
+template <typename Map, typename KeysView>
+struct KeysViewImpl : public KeysView {
+    explicit KeysViewImpl(Map &map) : map(map) {}
+    size_t len() override { return map.size(); }
+    iterator iter() override { return make_key_iterator(map.begin(), map.end()); }
+    bool contains(const typename Map::key_type &k) override { return map.find(k) != map.end(); }
+    bool contains(const object &) override { return false; }
+    Map &map;
+};
+
+template <typename Map, typename ValuesView>
+struct ValuesViewImpl : public ValuesView {
+    explicit ValuesViewImpl(Map &map) : map(map) {}
+    size_t len() override { return map.size(); }
+    iterator iter() override { return make_value_iterator(map.begin(), map.end()); }
+    Map &map;
+};
+
+template <typename Map, typename ItemsView>
+struct ItemsViewImpl : public ItemsView {
+    explicit ItemsViewImpl(Map &map) : map(map) {}
+    size_t len() override { return map.size(); }
+    iterator iter() override { return make_iterator(map.begin(), map.end()); }
     Map &map;
 };
 
@@ -657,9 +694,11 @@ template <typename Map, typename holder_type = std::unique_ptr<Map>, typename...
 class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&...args) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
-    using KeysView = detail::keys_view<Map>;
-    using ValuesView = detail::values_view<Map>;
-    using ItemsView = detail::items_view<Map>;
+    using StrippedKeyType = detail::remove_cvref_t<KeyType>;
+    using StrippedMappedType = detail::remove_cvref_t<MappedType>;
+    using KeysView = detail::keys_view<StrippedKeyType>;
+    using ValuesView = detail::values_view<StrippedMappedType>;
+    using ItemsView = detail::items_view<StrippedKeyType, StrippedMappedType>;
     using Class_ = class_<Map, holder_type>;
 
     // If either type is a non-module-local bound type then make the map binding non-local as well;
@@ -673,12 +712,57 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
     }
 
     Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
-    class_<KeysView> keys_view(
-        scope, ("KeysView[" + name + "]").c_str(), pybind11::module_local(local));
-    class_<ValuesView> values_view(
-        scope, ("ValuesView[" + name + "]").c_str(), pybind11::module_local(local));
-    class_<ItemsView> items_view(
-        scope, ("ItemsView[" + name + "]").c_str(), pybind11::module_local(local));
+    static constexpr auto key_type_descr = detail::make_caster<KeyType>::name;
+    static constexpr auto mapped_type_descr = detail::make_caster<MappedType>::name;
+    std::string key_type_name(key_type_descr.text), mapped_type_name(mapped_type_descr.text);
+
+    // If key type isn't properly wrapped, fall back to C++ names
+    if (key_type_name == "%") {
+        key_type_name = detail::type_info_description(typeid(KeyType));
+    }
+    // Similarly for value type:
+    if (mapped_type_name == "%") {
+        mapped_type_name = detail::type_info_description(typeid(MappedType));
+    }
+
+    // Wrap KeysView[KeyType] if it wasn't already wrapped
+    if (!detail::get_type_info(typeid(KeysView))) {
+        class_<KeysView> keys_view(
+            scope, ("KeysView[" + key_type_name + "]").c_str(), pybind11::module_local(local));
+        keys_view.def("__len__", &KeysView::len);
+        keys_view.def("__iter__",
+                      &KeysView::iter,
+                      keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+        );
+        keys_view.def("__contains__",
+                      static_cast<bool (KeysView::*)(const KeyType &)>(&KeysView::contains));
+        // Fallback for when the object is not of the key type
+        keys_view.def("__contains__",
+                      static_cast<bool (KeysView::*)(const object &)>(&KeysView::contains));
+    }
+    // Similarly for ValuesView:
+    if (!detail::get_type_info(typeid(ValuesView))) {
+        class_<ValuesView> values_view(scope,
+                                       ("ValuesView[" + mapped_type_name + "]").c_str(),
+                                       pybind11::module_local(local));
+        values_view.def("__len__", &ValuesView::len);
+        values_view.def("__iter__",
+                        &ValuesView::iter,
+                        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+        );
+    }
+    // Similarly for ItemsView:
+    if (!detail::get_type_info(typeid(ItemsView))) {
+        class_<ItemsView> items_view(
+            scope,
+            ("ItemsView[" + key_type_name + ", ").append(mapped_type_name + "]").c_str(),
+            pybind11::module_local(local));
+        items_view.def("__len__", &ItemsView::len);
+        items_view.def("__iter__",
+                       &ItemsView::iter,
+                       keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+        );
+    }
 
     cl.def(init<>());
 
@@ -698,19 +782,25 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
 
     cl.def(
         "keys",
-        [](Map &m) { return KeysView{m}; },
+        [](Map &m) {
+            return std::unique_ptr<KeysView>(new detail::KeysViewImpl<Map, KeysView>(m));
+        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def(
         "values",
-        [](Map &m) { return ValuesView{m}; },
+        [](Map &m) {
+            return std::unique_ptr<ValuesView>(new detail::ValuesViewImpl<Map, ValuesView>(m));
+        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def(
         "items",
-        [](Map &m) { return ItemsView{m}; },
+        [](Map &m) {
+            return std::unique_ptr<ItemsView>(new detail::ItemsViewImpl<Map, ItemsView>(m));
+        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
@@ -749,36 +839,6 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
 
     cl.def("__len__", &Map::size);
 
-    keys_view.def("__len__", [](KeysView &view) { return view.map.size(); });
-    keys_view.def(
-        "__iter__",
-        [](KeysView &view) { return make_key_iterator(view.map.begin(), view.map.end()); },
-        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
-    );
-    keys_view.def("__contains__", [](KeysView &view, const KeyType &k) -> bool {
-        auto it = view.map.find(k);
-        if (it == view.map.end()) {
-            return false;
-        }
-        return true;
-    });
-    // Fallback for when the object is not of the key type
-    keys_view.def("__contains__", [](KeysView &, const object &) -> bool { return false; });
-
-    values_view.def("__len__", [](ValuesView &view) { return view.map.size(); });
-    values_view.def(
-        "__iter__",
-        [](ValuesView &view) { return make_value_iterator(view.map.begin(), view.map.end()); },
-        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
-    );
-
-    items_view.def("__len__", [](ItemsView &view) { return view.map.size(); });
-    items_view.def(
-        "__iter__",
-        [](ItemsView &view) { return make_iterator(view.map.begin(), view.map.end()); },
-        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
-    );
-
     return cl;
 }
 
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index d5e9ccced7..9eb906f065 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -309,3 +309,29 @@ def test_map_delitem():
     del um["ua"]
     assert sorted(list(um)) == ["ub"]
     assert sorted(list(um.items())) == [("ub", 2.6)]
+
+
+def test_map_view_types():
+    map_string_double = m.MapStringDouble()
+    unordered_map_string_double = m.UnorderedMapStringDouble()
+    map_string_double_const = m.MapStringDoubleConst()
+    unordered_map_string_double_const = m.UnorderedMapStringDoubleConst()
+
+    assert map_string_double.keys().__class__.__name__ == "KeysView[str]"
+    assert map_string_double.values().__class__.__name__ == "ValuesView[float]"
+    assert map_string_double.items().__class__.__name__ == "ItemsView[str, float]"
+
+    keys_type = type(map_string_double.keys())
+    assert type(unordered_map_string_double.keys()) is keys_type
+    assert type(map_string_double_const.keys()) is keys_type
+    assert type(unordered_map_string_double_const.keys()) is keys_type
+
+    values_type = type(map_string_double.values())
+    assert type(unordered_map_string_double.values()) is values_type
+    assert type(map_string_double_const.values()) is values_type
+    assert type(unordered_map_string_double_const.values()) is values_type
+
+    items_type = type(map_string_double.items())
+    assert type(unordered_map_string_double.items()) is items_type
+    assert type(map_string_double_const.items()) is items_type
+    assert type(unordered_map_string_double_const.items()) is items_type

From 663b86c26ca07c51f2981681ba79e2595e17fbb9 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 9 Dec 2022 10:53:03 -0800
Subject: [PATCH 529/638] Add flake8 `B905` to `extend-ignore` in setup.cfg
 (#4391)

* Add flake8 `--ignore=B905,N818,W503`

* Add B905 to `extend-ignore` in setup.cfg (thanks @Skylion007), leave .pre-commit-config.yaml as-is on master.
---
 setup.cfg | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/setup.cfg b/setup.cfg
index 9af50ea483..16479ab000 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -46,5 +46,5 @@ zip_safe = False
 max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
-extend-ignore = E203, E722, B903, B950
+extend-ignore = E203, E722, B903, B905, B950
 extend-select = B9

From 9727dcdae5b723a01ec04bec5eb1a5a681cbb0fd Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 9 Dec 2022 23:18:36 -0500
Subject: [PATCH 530/638] chore: future safe bugbear opinionated warnings
 (#4393)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 setup.cfg | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/setup.cfg b/setup.cfg
index 16479ab000..8b3361981a 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -46,5 +46,5 @@ zip_safe = False
 max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
-extend-ignore = E203, E722, B903, B905, B950
-extend-select = B9
+extend-ignore = E203, E722
+extend-select = B902, B904

From ff42f5254a2f1315d3b56e2692590f1ce10b8193 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 13 Dec 2022 11:04:05 -0800
Subject: [PATCH 531/638] Systematically add `-DCMAKE_VERBOSE_MAKEFILE=ON` to
 obtain full command lines related to `-Wodr` (#4398)

---
 .github/workflows/ci.yml | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1c6a63f409..cd0f33d279 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -106,6 +106,7 @@ jobs:
     - name: Configure C++11 ${{ matrix.args }}
       run: >
         cmake -S . -B .
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON
         -DDOWNLOAD_CATCH=ON
@@ -135,6 +136,7 @@ jobs:
     - name: Configure C++17
       run: >
         cmake -S . -B build2
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
         -DDOWNLOAD_CATCH=ON
@@ -157,6 +159,7 @@ jobs:
     - name: Configure (unstable ABI)
       run: >
         cmake -S . -B build3
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
@@ -243,6 +246,7 @@ jobs:
         SETUPTOOLS_USE_DISTUTILS: stdlib
       run: >
         cmake -S . -B build
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DCMAKE_BUILD_TYPE=Debug
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -307,6 +311,7 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -339,7 +344,7 @@ jobs:
       run: apt-get update && DEBIAN_FRONTEND="noninteractive" apt-get install -y cmake git python3-dev python3-pytest python3-numpy
 
     - name: Configure
-      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
+      run: cmake -S . -B build -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
 
     - name: Build
       run: cmake --build build -j2 --verbose
@@ -377,7 +382,7 @@ jobs:
 #      run: |
 #        source /etc/profile.d/modules.sh
 #        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/20.11
-#        cmake -S . -B build -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=14 -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+#        cmake -S . -B build -DCMAKE_VERBOSE_MAKEFILE=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=14 -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 #
 #    - name: Build
 #      run: cmake --build build -j 2 --verbose
@@ -475,6 +480,7 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -529,6 +535,7 @@ jobs:
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         cmake -S . -B build-11     \
+        -DCMAKE_VERBOSE_MAKEFILE=ON \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
@@ -561,6 +568,7 @@ jobs:
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         cmake -S . -B build-17     \
+        -DCMAKE_VERBOSE_MAKEFILE=ON \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
@@ -627,6 +635,7 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DCMAKE_BUILD_TYPE=MinSizeRel
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -774,6 +783,7 @@ jobs:
       run: >
         cmake -S . -B build
         -G "Visual Studio 16 2019" -A Win32
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
@@ -827,6 +837,7 @@ jobs:
       run: >
         cmake -S . -B build
         -G "Visual Studio 16 2019" -A Win32
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DCMAKE_BUILD_TYPE=Debug
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -867,6 +878,7 @@ jobs:
     - name: Configure C++20
       run: >
         cmake -S . -B build
+        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON

From 89c3561d9a217f494900e82cd35723402c7d3e7c Mon Sep 17 00:00:00 2001
From: Martin Blanchard <49144287+mablanchard@users.noreply.github.com>
Date: Wed, 14 Dec 2022 20:03:37 +0100
Subject: [PATCH 532/638] Fix multi-context new Python linking mode (#4401)

Allow CMake find_package() from multiple directories.

https://github.com/pybind/pybind11/issues/4400

Co-authored-by: Martin Blanchard <martin.blanchard@siemens.com>
---
 tools/pybind11NewTools.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 5a6a0cb8be..7d7424a790 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -9,7 +9,7 @@ if(CMAKE_VERSION VERSION_LESS 3.12)
   message(FATAL_ERROR "You cannot use the new FindPython module with CMake < 3.12")
 endif()
 
-include_guard(GLOBAL)
+include_guard(DIRECTORY)
 
 get_property(
   is_config

From ece1206b8ae4d1fc350d6f8129f7a098d223519d Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 15 Dec 2022 13:19:13 -0800
Subject: [PATCH 533/638] ci: set `env: VERBOSE: 1` (#4405)

* Revert "Systematically add `-DCMAKE_VERBOSE_MAKEFILE=ON` to obtain full command lines related to `-Wodr` (#4398)"

This reverts commit ff42f5254a2f1315d3b56e2692590f1ce10b8193.

* Set `env: VERBOSE: 1` as suggested by @henryiii

* Set `env: VERBOSE: 1` also in all other .yml files using cmake
---
 .github/workflows/ci.yml        | 26 +++++++-------------------
 .github/workflows/configure.yml |  4 ++++
 .github/workflows/format.yml    |  2 ++
 .github/workflows/upstream.yml  |  2 ++
 4 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cd0f33d279..af5a29d627 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,6 +17,8 @@ env:
   PIP_ONLY_BINARY: numpy
   FORCE_COLOR: 3
   PYTEST_TIMEOUT: 300
+  # For cmake:
+  VERBOSE: 1
 
 jobs:
   # This is the "main" test suite, which tests a large number of different
@@ -106,7 +108,6 @@ jobs:
     - name: Configure C++11 ${{ matrix.args }}
       run: >
         cmake -S . -B .
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON
         -DDOWNLOAD_CATCH=ON
@@ -136,7 +137,6 @@ jobs:
     - name: Configure C++17
       run: >
         cmake -S . -B build2
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
         -DDOWNLOAD_CATCH=ON
@@ -159,7 +159,6 @@ jobs:
     - name: Configure (unstable ABI)
       run: >
         cmake -S . -B build3
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
@@ -246,7 +245,6 @@ jobs:
         SETUPTOOLS_USE_DISTUTILS: stdlib
       run: >
         cmake -S . -B build
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DCMAKE_BUILD_TYPE=Debug
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -311,7 +309,6 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -344,7 +341,7 @@ jobs:
       run: apt-get update && DEBIAN_FRONTEND="noninteractive" apt-get install -y cmake git python3-dev python3-pytest python3-numpy
 
     - name: Configure
-      run: cmake -S . -B build -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
+      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
 
     - name: Build
       run: cmake --build build -j2 --verbose
@@ -382,7 +379,7 @@ jobs:
 #      run: |
 #        source /etc/profile.d/modules.sh
 #        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/20.11
-#        cmake -S . -B build -DCMAKE_VERBOSE_MAKEFILE=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=14 -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+#        cmake -S . -B build -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=14 -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 #
 #    - name: Build
 #      run: cmake --build build -j 2 --verbose
@@ -480,7 +477,6 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -535,7 +531,6 @@ jobs:
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         cmake -S . -B build-11     \
-        -DCMAKE_VERBOSE_MAKEFILE=ON \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
@@ -568,7 +563,6 @@ jobs:
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         cmake -S . -B build-17     \
-        -DCMAKE_VERBOSE_MAKEFILE=ON \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
@@ -635,7 +629,6 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DCMAKE_BUILD_TYPE=MinSizeRel
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -783,7 +776,6 @@ jobs:
       run: >
         cmake -S . -B build
         -G "Visual Studio 16 2019" -A Win32
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
@@ -837,7 +829,6 @@ jobs:
       run: >
         cmake -S . -B build
         -G "Visual Studio 16 2019" -A Win32
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DCMAKE_BUILD_TYPE=Debug
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -878,7 +869,6 @@ jobs:
     - name: Configure C++20
       run: >
         cmake -S . -B build
-        -DCMAKE_VERBOSE_MAKEFILE=ON
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
@@ -930,7 +920,7 @@ jobs:
     - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build
 
     - name: Build C++11
       run: cmake --build build -j 2
@@ -948,7 +938,7 @@ jobs:
       run: git clean -fdx
 
     - name: Configure C++14
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build2
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build2
 
     - name: Build C++14
       run: cmake --build build2 -j 2
@@ -966,7 +956,7 @@ jobs:
       run: git clean -fdx
 
     - name: Configure C++17
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DCMAKE_VERBOSE_MAKEFILE=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build3
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -S . -B build3
 
     - name: Build C++17
       run: cmake --build build3 -j 2
@@ -1027,7 +1017,6 @@ jobs:
       - name: Configure Clang
         run: >
           cmake -G Ninja -S . -B .
-          -DCMAKE_VERBOSE_MAKEFILE=ON
           -DPYBIND11_WERROR=OFF
           -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
           -DDOWNLOAD_CATCH=ON
@@ -1093,7 +1082,6 @@ jobs:
       - name: CMake Configure
         run: >
           cmake -S . -B .
-          -DCMAKE_VERBOSE_MAKEFILE=ON
           -DPYBIND11_WERROR=ON
           -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
           -DDOWNLOAD_CATCH=ON
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 05e972c754..29b041168e 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -9,6 +9,10 @@ on:
       - stable
       - v*
 
+env:
+  # For cmake:
+  VERBOSE: 1
+
 jobs:
   # This tests various versions of CMake in various combinations, to make sure
   # the configure step passes.
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 31d893c479..b18474bc3d 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -14,6 +14,8 @@ on:
 
 env:
   FORCE_COLOR: 3
+  # For cmake:
+  VERBOSE: 1
 
 jobs:
   pre-commit:
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 366284acf4..a15861ee47 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -11,6 +11,8 @@ concurrency:
 
 env:
   PIP_ONLY_BINARY: numpy
+  # For cmake:
+  VERBOSE: 1
 
 jobs:
   standard:

From 09db6445d8da6e918c2d2be3aa4e7b0ddd8077c7 Mon Sep 17 00:00:00 2001
From: Martin Blanchard <49144287+mablanchard@users.noreply.github.com>
Date: Fri, 16 Dec 2022 06:10:46 +0100
Subject: [PATCH 534/638] IPO/LTO support for ICX (IntelLLVM) compiler (#4402)

* IPO/LTO support for ICX (IntelLLVM) compiler

https://github.com/pybind/pybind11/issues/4080

* style: pre-commit fixes

* Add WARNING/HELP WANTED comment.

Co-authored-by: Martin Blanchard <martin.blanchard@siemens.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 tools/pybind11Common.cmake | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index e1fb601acc..0c985bc8e5 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -311,6 +311,16 @@ function(_pybind11_generate_lto target prefer_thin_lto)
         HAS_FLTO "-flto${cxx_append}" "-flto${linker_append}" PYBIND11_LTO_CXX_FLAGS
         PYBIND11_LTO_LINKER_FLAGS)
     endif()
+  elseif(CMAKE_CXX_COMPILER_ID MATCHES "IntelLLVM")
+    # IntelLLVM equivalent to LTO is called IPO; also IntelLLVM is WIN32/UNIX
+    # WARNING/HELP WANTED: This block of code is currently not covered by pybind11 GitHub Actions!
+    if(WIN32)
+      _pybind11_return_if_cxx_and_linker_flags_work(
+        HAS_INTEL_IPO "-Qipo" "-Qipo" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+    else()
+      _pybind11_return_if_cxx_and_linker_flags_work(
+        HAS_INTEL_IPO "-ipo" "-ipo" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+    endif()
   elseif(CMAKE_CXX_COMPILER_ID MATCHES "Intel")
     # Intel equivalent to LTO is called IPO
     _pybind11_return_if_cxx_and_linker_flags_work(HAS_INTEL_IPO "-ipo" "-ipo"

From a97c4d220ed8f10b6f2a67b0382887699a5ecf07 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Mon, 19 Dec 2022 14:36:39 -0500
Subject: [PATCH 535/638] fix(cmake): support Windows ARM cross-compilation
 (#4406)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 tools/FindPythonLibsNew.cmake | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index bbbd9f9ec1..ce558d4ece 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -208,7 +208,9 @@ string(REGEX REPLACE "\\\\" "/" PYTHON_PREFIX "${PYTHON_PREFIX}")
 string(REGEX REPLACE "\\\\" "/" PYTHON_INCLUDE_DIR "${PYTHON_INCLUDE_DIR}")
 string(REGEX REPLACE "\\\\" "/" PYTHON_SITE_PACKAGES "${PYTHON_SITE_PACKAGES}")
 
-if(CMAKE_HOST_WIN32)
+if(DEFINED PYTHON_LIBRARY)
+  # Don't write to PYTHON_LIBRARY if it's already set
+elseif(CMAKE_HOST_WIN32)
   set(PYTHON_LIBRARY "${PYTHON_PREFIX}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
 
   # when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
@@ -274,7 +276,7 @@ if(NOT PYTHON_DEBUG_LIBRARY)
 endif()
 set(PYTHON_DEBUG_LIBRARIES "${PYTHON_DEBUG_LIBRARY}")
 
-find_package_message(PYTHON "Found PythonLibs: ${PYTHON_LIBRARY}"
+find_package_message(PYTHON "Found PythonLibs: ${PYTHON_LIBRARIES}"
                      "${PYTHON_EXECUTABLE}${PYTHON_VERSION_STRING}")
 
 set(PYTHONLIBS_FOUND TRUE)

From ee4b9f5d7b43383c1d4344dd11caf3dd5b066695 Mon Sep 17 00:00:00 2001
From: Ethan Steinberg <ethan.steinberg@gmail.com>
Date: Tue, 20 Dec 2022 05:34:00 -0800
Subject: [PATCH 536/638] Fix ODR violations in our Eigen Tensor tests (#4412)

* First

* Fix centos 7 again :(

* Fix minor nits
---
 tests/CMakeLists.txt                              | 15 +++++----------
 ...array.cpp => eigen_tensor_avoid_stl_array.cpp} |  6 ++----
 tests/test_eigen_tensor.cpp                       |  6 ++++--
 tests/test_eigen_tensor.inl                       | 10 ++++------
 tests/test_eigen_tensor.py                        |  8 ++++----
 5 files changed, 19 insertions(+), 26 deletions(-)
 rename tests/{test_eigen_tensor_avoid_stl_array.cpp => eigen_tensor_avoid_stl_array.cpp} (65%)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 491f215cef..9beb268ed7 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -130,7 +130,6 @@ set(PYBIND11_TEST_FILES
     test_docstring_options
     test_eigen_matrix
     test_eigen_tensor
-    test_eigen_tensor_avoid_stl_array.cpp
     test_enum
     test_eval
     test_exceptions
@@ -293,6 +292,11 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
       set(EIGEN3_VERSION ${EIGEN3_VERSION_STRING})
     endif()
     message(STATUS "Building tests with Eigen v${EIGEN3_VERSION}")
+
+    if(NOT (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0))
+      tests_extra_targets("test_eigen_tensor.py" "eigen_tensor_avoid_stl_array")
+    endif()
+
   else()
     list(FIND PYBIND11_TEST_FILES test_eigen_matrix.cpp PYBIND11_TEST_FILES_EIGEN_I)
     if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
@@ -303,11 +307,6 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
       list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
     endif()
-    list(FIND PYBIND11_TEST_FILES test_eigen_tensor_avoid_stl_array.cpp
-         PYBIND11_TEST_FILES_EIGEN_I)
-    if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
-      list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
-    endif()
     message(
       STATUS "Building tests WITHOUT Eigen, use -DDOWNLOAD_EIGEN=ON on CMake 3.11+ to download")
   endif()
@@ -319,10 +318,6 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_L
   if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
   endif()
-  list(FIND PYBIND11_TEST_FILES test_eigen_tensor_avoid_stl_array.cpp PYBIND11_TEST_FILES_EIGEN_I)
-  if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
-    list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
-  endif()
 endif()
 
 # Optional dependency for some tests (boost::variant is only supported with version >= 1.56)
diff --git a/tests/test_eigen_tensor_avoid_stl_array.cpp b/tests/eigen_tensor_avoid_stl_array.cpp
similarity index 65%
rename from tests/test_eigen_tensor_avoid_stl_array.cpp
rename to tests/eigen_tensor_avoid_stl_array.cpp
index 58bedf62dd..eacc9e9bd6 100644
--- a/tests/test_eigen_tensor_avoid_stl_array.cpp
+++ b/tests/eigen_tensor_avoid_stl_array.cpp
@@ -5,12 +5,10 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-constexpr const char *test_eigen_tensor_module_name = "eigen_tensor_avoid_stl_array";
-
 #ifndef EIGEN_AVOID_STL_ARRAY
 #    define EIGEN_AVOID_STL_ARRAY
 #endif
 
-#define PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE eigen_tensor_avoid_stl_array
-
 #include "test_eigen_tensor.inl"
+
+PYBIND11_MODULE(eigen_tensor_avoid_stl_array, m) { eigen_tensor_test::test_module(m); }
diff --git a/tests/test_eigen_tensor.cpp b/tests/test_eigen_tensor.cpp
index 40b4940053..503c69c7d3 100644
--- a/tests/test_eigen_tensor.cpp
+++ b/tests/test_eigen_tensor.cpp
@@ -5,8 +5,6 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-constexpr const char *test_eigen_tensor_module_name = "eigen_tensor";
-
 #define PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE eigen_tensor
 
 #ifdef EIGEN_AVOID_STL_ARRAY
@@ -14,3 +12,7 @@ constexpr const char *test_eigen_tensor_module_name = "eigen_tensor";
 #endif
 
 #include "test_eigen_tensor.inl"
+
+#include "pybind11_tests.h"
+
+test_initializer egien_tensor("eigen_tensor", eigen_tensor_test::test_module);
diff --git a/tests/test_eigen_tensor.inl b/tests/test_eigen_tensor.inl
index f46eb1803a..d864ce7379 100644
--- a/tests/test_eigen_tensor.inl
+++ b/tests/test_eigen_tensor.inl
@@ -7,9 +7,9 @@
 
 #include <pybind11/eigen/tensor.h>
 
-#include "pybind11_tests.h"
+PYBIND11_NAMESPACE_BEGIN(eigen_tensor_test)
 
-PYBIND11_NAMESPACE_BEGIN(PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE)
+namespace py = pybind11;
 
 PYBIND11_WARNING_DISABLE_MSVC(4127)
 
@@ -108,7 +108,7 @@ void init_tensor_module(pybind11::module &m) {
         return check_tensor(get_tensor<Options>()) && check_tensor(get_fixed_tensor<Options>());
     });
 
-    py::class_<CustomExample<Options>>(m, "CustomExample")
+    py::class_<CustomExample<Options>>(m, "CustomExample", py::module_local())
         .def(py::init<>())
         .def_readonly(
             "member", &CustomExample<Options>::member, py::return_value_policy::reference_internal)
@@ -322,8 +322,6 @@ void init_tensor_module(pybind11::module &m) {
         py::return_value_policy::reference);
 }
 
-void test_module(py::module_ &);
-test_initializer name(test_eigen_tensor_module_name, test_module);
 void test_module(py::module_ &m) {
     auto f_style = m.def_submodule("f_style");
     auto c_style = m.def_submodule("c_style");
@@ -332,4 +330,4 @@ void test_module(py::module_ &m) {
     init_tensor_module<Eigen::RowMajor>(c_style);
 }
 
-PYBIND11_NAMESPACE_END(PYBIND11_TEST_EIGEN_TENSOR_NAMESPACE)
+PYBIND11_NAMESPACE_END(eigen_tensor_test)
diff --git a/tests/test_eigen_tensor.py b/tests/test_eigen_tensor.py
index 653c9f288d..dc8aa4643e 100644
--- a/tests/test_eigen_tensor.py
+++ b/tests/test_eigen_tensor.py
@@ -6,17 +6,17 @@
 eigen_tensor = pytest.importorskip("pybind11_tests.eigen_tensor")
 submodules = [eigen_tensor.c_style, eigen_tensor.f_style]
 try:
-    from pybind11_tests import eigen_tensor_avoid_stl_array as avoid
+    import eigen_tensor_avoid_stl_array as avoid
 
     submodules += [avoid.c_style, avoid.f_style]
 except ImportError as e:
     # Ensure config, build, toolchain, etc. issues are not masked here:
     raise RuntimeError(
-        "import pybind11_tests.eigen_tensor_avoid_stl_array FAILED, while "
+        "import eigen_tensor_avoid_stl_array FAILED, while "
         "import pybind11_tests.eigen_tensor succeeded. "
         "Please ensure that "
         "test_eigen_tensor.cpp & "
-        "test_eigen_tensor_avoid_stl_array.cpp "
+        "eigen_tensor_avoid_stl_array.cpp "
         "are built together (or both are not built if Eigen is not available)."
     ) from e
 
@@ -42,7 +42,7 @@ def cleanup():
 
 
 def test_import_avoid_stl_array():
-    pytest.importorskip("pybind11_tests.eigen_tensor_avoid_stl_array")
+    pytest.importorskip("eigen_tensor_avoid_stl_array")
     assert len(submodules) == 4
 
 

From 3fd1520de294035325469a7fcb3d60a2d818a85b Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 20 Dec 2022 14:47:41 -0500
Subject: [PATCH 537/638] docs: changelog for next version (#4413)

* docs: changelog for next version

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* docs: address feedback

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst | 55 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 7d6d0c0f56..9ff7281bc6 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -15,6 +15,60 @@ IN DEVELOPMENT
 
 Changes will be summarized here periodically.
 
+Version 2.10.2 (Dec 20, 2022)
+-----------------------------
+
+Changes:
+
+* ``scoped_interpreter`` constructor taking ``PyConfig``.
+  `#4330 <https://github.com/pybind/pybind11/pull/4330>`_
+
+* ``pybind11/eigen/tensor.h`` adds converters to and from ``Eigen::Tensor`` and
+  ``Eigen::TensorMap``.
+  `#4201 <https://github.com/pybind/pybind11/pull/4201>`_
+
+* ``PyGILState_Check()``'s  were integrated to ``pybind11::handle``
+  ``inc_ref()`` & ``dec_ref()``. The added GIL checks are guarded by
+  ``PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF``, which is the default only if
+  ``NDEBUG`` is not defined.
+  `#4246 <https://github.com/pybind/pybind11/pull/4246>`_
+
+* Add option for enable/disable enum members in docstring.
+  `#2768 <https://github.com/pybind/pybind11/pull/2768>`_
+
+* Fixed typing of ``KeysView``, ``ValuesView`` and ``ItemsView`` in ``bind_map``.
+  `#4353 <https://github.com/pybind/pybind11/pull/4353>`_
+
+Bug fixes:
+
+* Bug fix affecting only Python 3.6 under very specific, uncommon conditions:
+  move ``PyEval_InitThreads()`` call to the correct location.
+  `#4350 <https://github.com/pybind/pybind11/pull/4350>`_
+
+* Fix segfault bug when passing foreign native functions to functional.h.
+  `#4254 <https://github.com/pybind/pybind11/pull/4254>`_
+
+Build system improvements:
+
+* Support setting PYTHON_LIBRARIES manually for Windows ARM cross-compilation
+  (classic mode).
+  `#4406 <https://github.com/pybind/pybind11/pull/4406>`_
+
+* Extend IPO/LTO detection for ICX (a.k.a IntelLLVM) compiler.
+  `#4402 <https://github.com/pybind/pybind11/pull/4402>`_
+
+* Allow calling ``find_package(pybind11 CONFIG)`` multiple times from separate
+  directories in the same CMake project and properly link Python (new mode).
+  `#4401 <https://github.com/pybind/pybind11/pull/4401>`_
+
+* ``multiprocessing_set_spawn`` in pytest fixture for added safety.
+  `#4377 <https://github.com/pybind/pybind11/pull/4377>`_
+
+* Fixed a bug in two pybind11/tools cmake scripts causing "Unknown arguments specified" errors.
+  `#4327 <https://github.com/pybind/pybind11/pull/4327>`_
+
+
+
 Version 2.10.1 (Oct 31, 2022)
 -----------------------------
 
@@ -95,7 +149,6 @@ Bug fixes:
   finalization.
   `#4192 <https://github.com/pybind/pybind11/pull/4192>`_
 
-
 Performance and style:
 
 * Reserve space in set and STL map casters if possible. This will prevent

From 0694ec6a15863bff2e0ea5efe07c78de39b9a33c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 20 Dec 2022 17:57:47 -0500
Subject: [PATCH 538/638] chore: preapre for 2.10.2 release (#4414)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 9acf104668..068ae0137a 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 11
-#define PYBIND11_VERSION_PATCH 0.dev1
+#define PYBIND11_VERSION_MINOR 10
+#define PYBIND11_VERSION_PATCH 2
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020B00D1
+#define PYBIND11_VERSION_HEX 0x020A0200
 
 // Define some generic pybind11 helper macros for warning management.
 //
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 1cb51fc5c2..4c814edfac 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.11.0.dev1"
+__version__ = "2.10.2"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 7f23e9f3a47cb6b6373467c18962c16dfdd82fe7 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Tue, 27 Dec 2022 15:14:10 -0500
Subject: [PATCH 539/638] chore: update clang-tidy to 15 (#4387)

* chore: update clang-tidy to 15

* Add git

* Add NOLINTNEXTLINE for assignment in if

* Update CONTRIBUTING.md

* Add NOLINTNEXTLINE where needed

* Add one more NOLINTNEXTLINE

* stl_bind: make more readable

* Another missing NOLINTNEXTLINE

* Match style elsewhere

* Apply reviewer suggestion. Mark false positive
---
 .github/CONTRIBUTING.md             |  4 ++--
 .github/workflows/format.yml        |  4 ++--
 include/pybind11/detail/internals.h |  3 +++
 include/pybind11/stl.h              |  1 +
 include/pybind11/stl_bind.h         | 12 ++++++++----
 5 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 00b1fea4cf..ad79743953 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -235,8 +235,8 @@ directory inside your pybind11 git clone. Files will be modified in place,
 so you can use git to monitor the changes.
 
 ```bash
-docker run --rm -v $PWD:/mounted_pybind11 -it silkeh/clang:13
-apt-get update && apt-get install -y python3-dev python3-pytest
+docker run --rm -v $PWD:/mounted_pybind11 -it silkeh/clang:15-bullseye
+apt-get update && apt-get install -y git python3-dev python3-pytest
 cmake -S /mounted_pybind11/ -B build -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);--use-color" -DDOWNLOAD_EIGEN=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=17
 cmake --build build -j 2
 ```
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index b18474bc3d..46489feb31 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -38,12 +38,12 @@ jobs:
     # in .github/CONTRIBUTING.md and update as needed.
     name: Clang-Tidy
     runs-on: ubuntu-latest
-    container: silkeh/clang:13
+    container: silkeh/clang:15-bullseye
     steps:
     - uses: actions/checkout@v3
 
     - name: Install requirements
-      run: apt-get update && apt-get install -y python3-dev python3-pytest
+      run: apt-get update && apt-get install -y git python3-dev python3-pytest
 
     - name: Configure
       run: >
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index ef1849fbea..05e36ad18b 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -469,12 +469,14 @@ PYBIND11_NOINLINE internals &get_internals() {
 #if defined(WITH_THREAD)
 
         PyThreadState *tstate = PyThreadState_Get();
+        // NOLINTNEXTLINE(bugprone-assignment-in-if-condition)
         if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->tstate)) {
             pybind11_fail("get_internals: could not successfully initialize the tstate TSS key!");
         }
         PYBIND11_TLS_REPLACE_VALUE(internals_ptr->tstate, tstate);
 
 #    if PYBIND11_INTERNALS_VERSION > 4
+        // NOLINTNEXTLINE(bugprone-assignment-in-if-condition)
         if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->loader_life_support_tls_key)) {
             pybind11_fail("get_internals: could not successfully initialize the "
                           "loader_life_support TSS key!");
@@ -514,6 +516,7 @@ struct local_internals {
     struct shared_loader_life_support_data {
         PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
         shared_loader_life_support_data() {
+            // NOLINTNEXTLINE(bugprone-assignment-in-if-condition)
             if (!PYBIND11_TLS_KEY_CREATE(loader_life_support_tls_key)) {
                 pybind11_fail("local_internals: could not successfully initialize the "
                               "loader_life_support TLS key!");
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 2d144b598b..84c5171081 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -316,6 +316,7 @@ struct optional_caster {
         if (!std::is_lvalue_reference<T>::value) {
             policy = return_value_policy_override<Value>::policy(policy);
         }
+        // NOLINTNEXTLINE(bugprone-unchecked-optional-access)
         return value_conv::cast(*std::forward<T>(src), policy, parent);
     }
 
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 0c634597ec..7cfd996dda 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -355,13 +355,17 @@ void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl)
     using DiffType = typename Vector::difference_type;
     using ItType = typename Vector::iterator;
     cl.def("__getitem__", [](const Vector &v, DiffType i) -> T {
-        if (i < 0 && (i += v.size()) < 0) {
-            throw index_error();
+        if (i < 0) {
+            i += v.size();
+            if (i < 0) {
+                throw index_error();
+            }
         }
-        if ((SizeType) i >= v.size()) {
+        auto i_st = static_cast<SizeType>(i);
+        if (i_st >= v.size()) {
             throw index_error();
         }
-        return v[(SizeType) i];
+        return v[i_st];
     });
 
     cl.def(

From 70af9873c26ea46cf97d66444f4d80c4af79dd7a Mon Sep 17 00:00:00 2001
From: kajananchinniah <kajananchinniah@gmail.com>
Date: Wed, 28 Dec 2022 12:49:57 -0500
Subject: [PATCH 540/638] docs: fixed typo in spelling of first (#4428)

---
 include/pybind11/detail/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 068ae0137a..421cbe192f 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -436,7 +436,7 @@ PYBIND11_WARNING_POP
 
 /** \rst
     This macro creates the entry point that will be invoked when the Python interpreter
-    imports an extension module. The module name is given as the fist argument and it
+    imports an extension module. The module name is given as the first argument and it
     should not be in quotes. The second macro argument defines a variable of type
     `py::module_` which can be used to initialize the module.
 

From 60f02f5f663829c9fd2d7d52c03d4064129e38df Mon Sep 17 00:00:00 2001
From: Ethan Steinberg <ethan.steinberg@gmail.com>
Date: Fri, 30 Dec 2022 10:46:55 -0800
Subject: [PATCH 541/638] fix: improve the error reporting for inc_ref GIL
 failures (#4427)

* First

* Fixs

* Improve

* Additional assertions comment

* Improve docs
---
 docs/advanced/misc.rst     | 28 ++++++++++++++++++++++++++++
 include/pybind11/pytypes.h | 30 +++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/docs/advanced/misc.rst b/docs/advanced/misc.rst
index 35a6ebcd60..805ec838fc 100644
--- a/docs/advanced/misc.rst
+++ b/docs/advanced/misc.rst
@@ -118,6 +118,34 @@ The ``call_go`` wrapper can also be simplified using the ``call_guard`` policy
     m.def("call_go", &call_go, py::call_guard<py::gil_scoped_release>());
 
 
+Common Sources Of Global Interpreter Lock Errors
+==================================================================
+
+Failing to properly hold the Global Interpreter Lock (GIL) is one of the
+more common sources of bugs within code that uses pybind11. If you are
+running into GIL related errors, we highly recommend you consult the
+following checklist.
+
+- Do you have any global variables that are pybind11 objects or invoke
+  pybind11 functions in either their constructor or destructor? You are generally
+  not allowed to invoke any Python function in a global static context. We recommend
+  using lazy initialization and then intentionally leaking at the end of the program.
+
+- Do you have any pybind11 objects that are members of other C++ structures? One
+  commonly overlooked requirement is that pybind11 objects have to increase their reference count
+  whenever their copy constructor is called. Thus, you need to be holding the GIL to invoke
+  the copy constructor of any C++ class that has a pybind11 member. This can sometimes be very
+  tricky to track for complicated programs Think carefully when you make a pybind11 object
+  a member in another struct.
+
+- C++ destructors that invoke Python functions can be particularly troublesome as
+  destructors can sometimes get invoked in weird and unexpected circumstances as a result
+  of exceptions.
+
+- You should try running your code in a debug build. That will enable additional assertions
+  within pybind11 that will throw exceptions on certain GIL handling errors
+  (reference counting operations).
+
 Binding sequence data types, iterators, the slicing protocol, etc.
 ==================================================================
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 56e0423ac4..3660c180d9 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -250,9 +250,9 @@ class handle : public detail::object_api<handle> {
 #ifdef PYBIND11_HANDLE_REF_DEBUG
         inc_ref_counter(1);
 #endif
-#if defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+#ifdef PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
         if (m_ptr != nullptr && !PyGILState_Check()) {
-            throw std::runtime_error("pybind11::handle::inc_ref() PyGILState_Check() failure.");
+            throw_gilstate_error("pybind11::handle::inc_ref()");
         }
 #endif
         Py_XINCREF(m_ptr);
@@ -265,9 +265,9 @@ class handle : public detail::object_api<handle> {
         this function automatically. Returns a reference to itself.
     \endrst */
     const handle &dec_ref() const & {
-#if defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+#ifdef PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
         if (m_ptr != nullptr && !PyGILState_Check()) {
-            throw std::runtime_error("pybind11::handle::dec_ref() PyGILState_Check() failure.");
+            throw_gilstate_error("pybind11::handle::dec_ref()");
         }
 #endif
         Py_XDECREF(m_ptr);
@@ -296,8 +296,28 @@ class handle : public detail::object_api<handle> {
 protected:
     PyObject *m_ptr = nullptr;
 
-#ifdef PYBIND11_HANDLE_REF_DEBUG
 private:
+#ifdef PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
+    void throw_gilstate_error(const std::string &function_name) const {
+        fprintf(
+            stderr,
+            "%s is being called while the GIL is either not held or invalid. Please see "
+            "https://pybind11.readthedocs.io/en/stable/advanced/"
+            "misc.html#common-sources-of-global-interpreter-lock-errors for debugging advice.\n",
+            function_name.c_str());
+        fflush(stderr);
+        if (Py_TYPE(m_ptr)->tp_name != nullptr) {
+            fprintf(stderr,
+                    "The failing %s call was triggered on a %s object.\n",
+                    function_name.c_str(),
+                    Py_TYPE(m_ptr)->tp_name);
+            fflush(stderr);
+        }
+        throw std::runtime_error(function_name + " PyGILState_Check() failure.");
+    }
+#endif
+
+#ifdef PYBIND11_HANDLE_REF_DEBUG
     static std::size_t inc_ref_counter(std::size_t add) {
         thread_local std::size_t counter = 0;
         counter += add;

From f12e098f1d68d9e7445f84d9bf94ce7d0908c531 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 2 Jan 2023 03:46:17 -0800
Subject: [PATCH 542/638] Fix `detail::obj_class_name()` to work correctly for
 meta classes. (#4436)

* Fix `detail::obj_class_name()` to work correctly for meta classes.

* Adjust expected name for PyPy
---
 include/pybind11/pytypes.h |  2 +-
 tests/test_class.cpp       |  2 ++
 tests/test_class.py        | 11 ++++++++++-
 tests/test_pytypes.cpp     |  2 ++
 tests/test_pytypes.py      |  6 ++++++
 5 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 3660c180d9..a2824a0e01 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -463,7 +463,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Equivalent to obj.__class__.__name__ (or obj.__name__ if obj is a class).
 inline const char *obj_class_name(PyObject *obj) {
-    if (Py_TYPE(obj) == &PyType_Type) {
+    if (PyType_Check(obj)) {
         return reinterpret_cast<PyTypeObject *>(obj)->tp_name;
     }
     return Py_TYPE(obj)->tp_name;
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 9ea10fae1e..ca925917e6 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -55,6 +55,8 @@ void bind_empty0(py::module_ &m) {
 } // namespace test_class
 
 TEST_SUBMODULE(class_, m) {
+    m.def("obj_class_name", [](py::handle obj) { return py::detail::obj_class_name(obj.ptr()); });
+
     // test_instance
     struct NoConstructor {
         NoConstructor() = default;
diff --git a/tests/test_class.py b/tests/test_class.py
index 7c1ed20608..9c964e001b 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -1,10 +1,19 @@
 import pytest
 
-import env  # noqa: F401
+import env
 from pybind11_tests import ConstructorStats, UserType
 from pybind11_tests import class_ as m
 
 
+def test_obj_class_name():
+    if env.PYPY:
+        expected_name = "UserType"
+    else:
+        expected_name = "pybind11_tests.UserType"
+    assert m.obj_class_name(UserType(1)) == expected_name
+    assert m.obj_class_name(UserType) == expected_name
+
+
 def test_repr():
     assert "pybind11_type" in repr(type(UserType))
     assert "UserType" in repr(UserType)
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index ea8d03958b..1028bb58e8 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -99,6 +99,8 @@ void m_defs(py::module_ &m) {
 } // namespace handle_from_move_only_type_with_operator_PyObject
 
 TEST_SUBMODULE(pytypes, m) {
+    m.def("obj_class_name", [](py::handle obj) { return py::detail::obj_class_name(obj.ptr()); });
+
     handle_from_move_only_type_with_operator_PyObject::m_defs(m);
 
     // test_bool
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 079ee7ca50..8f9f2987e9 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -9,6 +9,12 @@
 from pybind11_tests import pytypes as m
 
 
+def test_obj_class_name():
+    assert m.obj_class_name(None) == "NoneType"
+    assert m.obj_class_name(list) == "list"
+    assert m.obj_class_name([]) == "list"
+
+
 def test_handle_from_move_only_type_with_operator_PyObject():  # noqa: N802
     assert m.handle_from_move_only_type_with_operator_PyObject_ncnst()
     assert m.handle_from_move_only_type_with_operator_PyObject_const()

From 6da268a5c58b76c0577d0d7b223a78edd6a34bea Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 3 Jan 2023 05:46:55 -0800
Subject: [PATCH 543/638] ci: remove clang 10 C++20 (it broke recently) (#4438)

* Remove clang 10 C++20 (it broke recently), add clang 15 C++20 while we are at it.

* No luck trying clang15: Error response from daemon: manifest for silkeh/clang:15 not found: manifest unknown: manifest unknown. Giving up, this needs to be a separate PR.
---
 .github/workflows/ci.yml | 2 --
 1 file changed, 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index af5a29d627..b36bbfe1b9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -283,8 +283,6 @@ jobs:
         include:
           - clang: 5
             std: 14
-          - clang: 10
-            std: 20
           - clang: 10
             std: 17
           - clang: 11

From e3e24f3f656841142ef5897e33a0aabc2b34fd07 Mon Sep 17 00:00:00 2001
From: cyy <cyyever@outlook.com>
Date: Tue, 3 Jan 2023 23:20:39 +0800
Subject: [PATCH 544/638] fix: issuses detected by static analyzer (#4440)

* fix incorrect variable check

* remove duplicated check

* remove unneeded const cast
---
 include/pybind11/attr.h         | 2 +-
 include/pybind11/eigen/tensor.h | 2 +-
 include/pybind11/pytypes.h      | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index db7cd8efff..b5e3b7b22c 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -399,7 +399,7 @@ struct process_attribute<doc> : process_attribute_default<doc> {
 template <>
 struct process_attribute<const char *> : process_attribute_default<const char *> {
     static void init(const char *d, function_record *r) { r->doc = const_cast<char *>(d); }
-    static void init(const char *d, type_record *r) { r->doc = const_cast<char *>(d); }
+    static void init(const char *d, type_record *r) { r->doc = d; }
 };
 template <>
 struct process_attribute<char *> : process_attribute<const char *> {};
diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
index 568c641a2d..0877da8953 100644
--- a/include/pybind11/eigen/tensor.h
+++ b/include/pybind11/eigen/tensor.h
@@ -176,7 +176,7 @@ struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
                 return false;
             }
 
-            if (!convert && !temp.dtype().is(dtype::of<typename Type::Scalar>())) {
+            if (!temp.dtype().is(dtype::of<typename Type::Scalar>())) {
                 return false;
             }
         }
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index a2824a0e01..f11ed5da78 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -501,7 +501,7 @@ struct error_fetch_and_normalize {
                             "active exception.");
         }
         const char *exc_type_name_norm = detail::obj_class_name(m_type.ptr());
-        if (exc_type_name_orig == nullptr) {
+        if (exc_type_name_norm == nullptr) {
             pybind11_fail("Internal error: " + std::string(called)
                           + " failed to obtain the name "
                             "of the normalized active exception type.");

From 769fd3b889fef6cddb060f2a0be26aee62b4da05 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 3 Jan 2023 10:21:05 -0500
Subject: [PATCH 545/638] chore(deps): update pre-commit hooks (#4439)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/asottile/pyupgrade: v3.3.0 → v3.3.1](https://github.com/asottile/pyupgrade/compare/v3.3.0...v3.3.1)
- [github.com/PyCQA/isort: 5.10.1 → 5.11.4](https://github.com/PyCQA/isort/compare/5.10.1...5.11.4)
- [github.com/psf/black: 22.10.0 → 22.12.0](https://github.com/psf/black/compare/22.10.0...22.12.0)
- [github.com/PyCQA/pylint: v2.15.8 → v2.15.9](https://github.com/PyCQA/pylint/compare/v2.15.8...v2.15.9)
- [github.com/shellcheck-py/shellcheck-py: v0.8.0.4 → v0.9.0.2](https://github.com/shellcheck-py/shellcheck-py/compare/v0.8.0.4...v0.9.0.2)
- [github.com/pre-commit/mirrors-clang-format: v15.0.4 → v15.0.6](https://github.com/pre-commit/mirrors-clang-format/compare/v15.0.4...v15.0.6)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4e80fbad15..d625d5726b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -41,20 +41,20 @@ repos:
 
 # Upgrade old Python syntax
 - repo: https://github.com/asottile/pyupgrade
-  rev: "v3.3.0"
+  rev: "v3.3.1"
   hooks:
   - id: pyupgrade
     args: [--py36-plus]
 
 # Nicely sort includes
 - repo: https://github.com/PyCQA/isort
-  rev: "5.10.1"
+  rev: "5.11.4"
   hooks:
   - id: isort
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "22.10.0" # Keep in sync with blacken-docs
+  rev: "22.12.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -116,7 +116,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.15.8"
+  rev: "v2.15.9"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -160,7 +160,7 @@ repos:
 
 # Check for common shell mistakes
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: "v0.8.0.4"
+  rev: "v0.9.0.2"
   hooks:
   - id: shellcheck
 
@@ -175,7 +175,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v15.0.4"
+  rev: "v15.0.6"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From b2d7ad72c24ee8d2acc22a4ce39fa38a1e9d77b8 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 3 Jan 2023 11:34:22 -0500
Subject: [PATCH 546/638] chore: prepare for 2.10.3 (#4437)

* docs: update changelog for v2.10.3

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore: bump versions for 2.10.3

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore: fix make changelog script with entry is empty

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst               | 35 +++++++++++++++++++++++++++++++-
 include/pybind11/detail/common.h |  4 ++--
 pybind11/_version.py             |  2 +-
 tools/make_changelog.py          |  9 ++++----
 4 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 9ff7281bc6..bb111c5f26 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -15,6 +15,39 @@ IN DEVELOPMENT
 
 Changes will be summarized here periodically.
 
+Changes:
+
+* ``PyGILState_Check()``'s in ``pybind11::handle``'s ``inc_ref()`` &
+  ``dec_ref()`` are now enabled by default again.
+  `#4246 <https://github.com/pybind/pybind11/pull/4246>`_
+
+Build system improvements:
+
+* Update clang-tidy to 15 in CI.
+  `#4387 <https://github.com/pybind/pybind11/pull/4387>`_
+
+
+Version 2.10.3 (Jan 3, 2023)
+----------------------------
+
+Changes:
+
+* Temporarily made our GIL status assertions (added in 2.10.2) disabled by
+  default (re-enable manually by defining
+  ``PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF``, will be enabled in 2.11).
+  `#4432 <https://github.com/pybind/pybind11/pull/4432>`_
+
+* Improved error messages when ``inc_ref``/``dec_ref`` are called with an
+  invalid GIL state.
+  `#4427 <https://github.com/pybind/pybind11/pull/4427>`_
+  `#4436 <https://github.com/pybind/pybind11/pull/4436>`_
+
+Bug Fixes:
+
+* Some minor touchups found by static analyzers.
+  `#4440 <https://github.com/pybind/pybind11/pull/4440>`_
+
+
 Version 2.10.2 (Dec 20, 2022)
 -----------------------------
 
@@ -30,7 +63,7 @@ Changes:
 * ``PyGILState_Check()``'s  were integrated to ``pybind11::handle``
   ``inc_ref()`` & ``dec_ref()``. The added GIL checks are guarded by
   ``PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF``, which is the default only if
-  ``NDEBUG`` is not defined.
+  ``NDEBUG`` is not defined. (Made non-default in 2.10.3, will be active in 2.11)
   `#4246 <https://github.com/pybind/pybind11/pull/4246>`_
 
 * Add option for enable/disable enum members in docstring.
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 421cbe192f..fc7e50776c 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 10
-#define PYBIND11_VERSION_PATCH 2
+#define PYBIND11_VERSION_PATCH 3
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020A0200
+#define PYBIND11_VERSION_HEX 0x020A0300
 
 // Define some generic pybind11 helper macros for warning management.
 //
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 4c814edfac..63078bbe67 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.10.2"
+__version__ = "2.10.3"
 version_info = tuple(_to_int(s) for s in __version__.split("."))
diff --git a/tools/make_changelog.py b/tools/make_changelog.py
index 839040a938..b5bd832940 100755
--- a/tools/make_changelog.py
+++ b/tools/make_changelog.py
@@ -31,8 +31,10 @@
 missing = []
 
 for issue in issues:
-    changelog = ENTRY.findall(issue.body)
-    if changelog:
+    changelog = ENTRY.findall(issue.body or "")
+    if not changelog or not changelog[0]:
+        missing.append(issue)
+    else:
         (msg,) = changelog
         if not msg.startswith("* "):
             msg = "* " + msg
@@ -44,9 +46,6 @@
         print(Syntax(msg, "rst", theme="ansi_light", word_wrap=True))
         print()
 
-    else:
-        missing.append(issue)
-
 if missing:
     print()
     print("[blue]" + "-" * 30)

From a34596bfe1947b4a6b0bcc4218e1f72d0c2e9b4c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 3 Jan 2023 14:23:36 -0500
Subject: [PATCH 547/638] chore: back to work

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 include/pybind11/detail/common.h | 6 +++---
 pybind11/_version.py             | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index fc7e50776c..0fc81e0534 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -10,12 +10,12 @@
 #pragma once
 
 #define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 10
-#define PYBIND11_VERSION_PATCH 3
+#define PYBIND11_VERSION_MINOR 11
+#define PYBIND11_VERSION_PATCH 0.dev1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020A0300
+#define PYBIND11_VERSION_HEX 0x020B00D1
 
 // Define some generic pybind11 helper macros for warning management.
 //
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 63078bbe67..1cb51fc5c2 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.10.3"
+__version__ = "2.11.0.dev1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From d821788bb62fa911bb9797550b8d06ca41462455 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 12 Jan 2023 17:50:28 -0800
Subject: [PATCH 548/638] Add clang15 C++20 job (#4443)

---
 .github/workflows/ci.yml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b36bbfe1b9..7c5fcb43ac 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -280,6 +280,8 @@ jobs:
           - dev
         std:
           - 11
+        container_suffix:
+          - ""
         include:
           - clang: 5
             std: 14
@@ -293,9 +295,12 @@ jobs:
             std: 20
           - clang: 14
             std: 20
+          - clang: 15
+            std: 20
+            container_suffix: "-bullseye"
 
     name: "🐍 3 • Clang ${{ matrix.clang }} • C++${{ matrix.std }} • x64"
-    container: "silkeh/clang:${{ matrix.clang }}"
+    container: "silkeh/clang:${{ matrix.clang }}${{ matrix.container_suffix }}"
 
     steps:
     - uses: actions/checkout@v3

From e53d58af6c0ade85fa6edce6a228ad2aeace55ee Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 14 Jan 2023 13:47:56 -0800
Subject: [PATCH 549/638] Ensure `import pybind11_tests` traceback is shown.
 (#4455)

---
 tests/conftest.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tests/conftest.py b/tests/conftest.py
index 402fd4b25b..c24d51d4d1 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -11,11 +11,17 @@
 import os
 import re
 import textwrap
+import traceback
 
 import pytest
 
 # Early diagnostic for failed imports
-import pybind11_tests
+try:
+    import pybind11_tests
+except Exception:
+    # pytest does not show the traceback without this.
+    traceback.print_exc()
+    raise
 
 
 @pytest.fixture(scope="session", autouse=True)

From c709d2a83e06aaec06987aa9761d0ebbfefbecd7 Mon Sep 17 00:00:00 2001
From: albanD <desmaison.alban@gmail.com>
Date: Wed, 18 Jan 2023 21:11:26 +0100
Subject: [PATCH 550/638] Make sure to properly untrack gc objects before
 freeing them (#4461)

* Make sure to properly untrack gc objects before freeing them

* style: pre-commit fixes

* Fix lint

* Add comment about where the original track comes from

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/detail/class.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 528e716f78..bc2b40c50a 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -445,9 +445,17 @@ inline void clear_instance(PyObject *self) {
 /// Instance destructor function for all pybind11 types. It calls `type_info.dealloc`
 /// to destroy the C++ object itself, while the rest is Python bookkeeping.
 extern "C" inline void pybind11_object_dealloc(PyObject *self) {
+    auto *type = Py_TYPE(self);
+
+    // If this is a GC tracked object, untrack it first
+    // Note that the track call is implicitly done by the
+    // default tp_alloc, which we never override.
+    if (PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC) != 0) {
+        PyObject_GC_UnTrack(self);
+    }
+
     clear_instance(self);
 
-    auto *type = Py_TYPE(self);
     type->tp_free(self);
 
 #if PY_VERSION_HEX < 0x03080000

From a500f439d06d220ee2c680cdd2c8828eac8e7dfc Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 19 Jan 2023 10:48:46 -0800
Subject: [PATCH 551/638] Resolve new flake8 error (#4462)

* Resolve flake8 error by replacing `pytest.raises(Exception)` with `SystemError`

* Also remove the obsolete comment.

* Tweak comment instead of removing it.
---
 tests/test_modules.py | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tests/test_modules.py b/tests/test_modules.py
index e11d68e78e..c3e8cea6e1 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -107,11 +107,10 @@ def test_def_submodule_failures():
         sm_name_orig = sm.__name__
         sm.__name__ = malformed_utf8
         try:
-            with pytest.raises(Exception):
-                # Seen with Python 3.9: SystemError: nameless module
-                # But we do not want to exercise the internals of PyModule_GetName(), which could
-                # change in future versions of Python, but a bad __name__ is very likely to cause
-                # some kind of failure indefinitely.
+            # We want to assert that a bad __name__ causes some kind of failure, although we do not want to exercise
+            # the internals of PyModule_GetName(). Currently all supported Python versions raise SystemError. If that
+            # changes in future Python versions, simply add the new expected exception types here.
+            with pytest.raises(SystemError):
                 m.def_submodule(sm, b"SubSubModuleName")
         finally:
             # Clean up to ensure nothing gets upset by a module with an invalid __name__.

From c71e3af73f80140023ee399a982678a8b968b5c5 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 31 Jan 2023 22:44:18 -0800
Subject: [PATCH 552/638] Bump isort version to 5.12.0 (#4480)

---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index d625d5726b..9ec31ae997 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -48,7 +48,7 @@ repos:
 
 # Nicely sort includes
 - repo: https://github.com/PyCQA/isort
-  rev: "5.11.4"
+  rev: "5.12.0"
   hooks:
   - id: isort
 

From 44e936822252df9e6420b42dc2520d622f430bc3 Mon Sep 17 00:00:00 2001
From: Daniel Jacobs <44678615+danielcjacobs@users.noreply.github.com>
Date: Wed, 1 Feb 2023 02:42:05 -0500
Subject: [PATCH 553/638] Use PyConfig_InitPythonConfig instead of
 PyConfig_InitIsolatedConfig (#4473)

* Use PyConfig_InitPythonConfig instead of PyConfig_InitIsolatedConfig

* add unit test for default python configuration

---------

Co-authored-by: Daniel Jacobs <daniel.jacobs@is4s.com>
---
 include/pybind11/embed.h              |  7 ++++---
 tests/test_embed/test_interpreter.cpp | 22 +++++++++++++++++++++-
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 749c75beb6..5a175b1341 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -198,9 +198,10 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
         init_signal_handlers, argc, argv, add_program_dir_to_path);
 #else
     PyConfig config;
-    PyConfig_InitIsolatedConfig(&config);
-    config.isolated = 0;
-    config.use_environment = 1;
+    PyConfig_InitPythonConfig(&config);
+    // See PR #4473 for background
+    config.parse_argv = 0;
+
     config.install_signal_handlers = init_signal_handlers ? 1 : 0;
     initialize_interpreter(&config, argc, argv, add_program_dir_to_path);
 #endif
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 10b20f3715..e54e822708 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -184,7 +184,7 @@ TEST_CASE("Custom PyConfig") {
     py::initialize_interpreter();
 }
 
-TEST_CASE("Custom PyConfig with argv") {
+TEST_CASE("scoped_interpreter with PyConfig_InitIsolatedConfig and argv") {
     py::finalize_interpreter();
     {
         PyConfig config;
@@ -199,6 +199,26 @@ TEST_CASE("Custom PyConfig with argv") {
     }
     py::initialize_interpreter();
 }
+
+TEST_CASE("scoped_interpreter with PyConfig_InitPythonConfig and argv") {
+    py::finalize_interpreter();
+    {
+        PyConfig config;
+        PyConfig_InitPythonConfig(&config);
+
+        // `initialize_interpreter() overrides the default value for config.parse_argv (`1`) by
+        // changing it to `0`. This test exercises `scoped_interpreter` with the default config.
+        char *argv[] = {strdup("a.out"), strdup("arg1")};
+        py::scoped_interpreter argv_scope(&config, 2, argv);
+        std::free(argv[0]);
+        std::free(argv[1]);
+        auto module = py::module::import("test_interpreter");
+        auto py_widget = module.attr("DerivedWidget")("The question");
+        const auto &cpp_widget = py_widget.cast<const Widget &>();
+        REQUIRE(cpp_widget.argv0() == "arg1");
+    }
+    py::initialize_interpreter();
+}
 #endif
 
 TEST_CASE("Add program dir to path pre-PyConfig") {

From 3efe9d4cb5d7314faee722205e560b8b932aed9e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 1 Feb 2023 14:23:37 -0500
Subject: [PATCH 554/638] chore: update to black 23 (#4482)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .pre-commit-config.yaml                  | 18 +++++++++---------
 docs/conf.py                             |  1 -
 pybind11/__main__.py                     |  1 -
 pybind11/setup_helpers.py                |  3 ---
 tests/extra_python_package/test_files.py |  2 --
 tests/test_chrono.py                     |  4 ----
 tests/test_class.py                      |  1 -
 tests/test_custom_type_casters.py        |  3 ++-
 tests/test_eigen_tensor.py               |  6 ------
 tests/test_local_bindings.py             |  3 ++-
 tests/test_operator_overloading.py       |  1 -
 11 files changed, 13 insertions(+), 30 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 9ec31ae997..363ac71c6f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -54,40 +54,40 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "22.12.0" # Keep in sync with blacken-docs
+  rev: "23.1.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
 # Also code format the docs
 - repo: https://github.com/asottile/blacken-docs
-  rev: "v1.12.1"
+  rev: "1.13.0"
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==22.10.0 # keep in sync with black hook
+    - black==23.1.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.3.1"
+  rev: "v1.4.2"
   hooks:
   - id: remove-tabs
 
 - repo: https://github.com/sirosen/texthooks
-  rev: "0.4.0"
+  rev: "0.5.0"
   hooks:
   - id: fix-ligatures
   - id: fix-smartquotes
 
 # Autoremoves unused imports
 - repo: https://github.com/hadialqattan/pycln
-  rev: "v2.1.2"
+  rev: "v2.1.3"
   hooks:
   - id: pycln
     stages: [manual]
 
 # Checking for common mistakes
 - repo: https://github.com/pre-commit/pygrep-hooks
-  rev: "v1.9.0"
+  rev: "v1.10.0"
   hooks:
   - id: python-check-blanket-noqa
   - id: python-check-blanket-type-ignore
@@ -116,7 +116,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.15.9"
+  rev: "v2.16.0"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -175,7 +175,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v15.0.6"
+  rev: "v15.0.7"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]
diff --git a/docs/conf.py b/docs/conf.py
index 2da6773f4f..cdb9f63069 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -358,7 +358,6 @@ def clean_up(app, exception):
 
 
 def setup(app):
-
     # Add hook for building doxygen xml when needed
     app.connect("builder-inited", generate_doxygen_xml)
 
diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 8c89533843..e87b16beb4 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -24,7 +24,6 @@ def print_includes() -> None:
 
 
 def main() -> None:
-
     parser = argparse.ArgumentParser()
     parser.add_argument(
         "--includes",
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 1fd04b9154..1db4795327 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -118,7 +118,6 @@ def _add_ldflags(self, flags: List[str]) -> None:
         self.extra_link_args[:0] = flags
 
     def __init__(self, *args: Any, **kwargs: Any) -> None:
-
         self._cxx_level = 0
         cxx_std = kwargs.pop("cxx_std", 0)
 
@@ -174,7 +173,6 @@ def cxx_std(self) -> int:
 
     @cxx_std.setter
     def cxx_std(self, level: int) -> None:
-
         if self._cxx_level:
             warnings.warn("You cannot safely change the cxx_level after setting it!")
 
@@ -439,7 +437,6 @@ def compile_function(
             extra_postargs: Optional[List[str]] = None,
             depends: Optional[List[str]] = None,
         ) -> Any:
-
             # These lines are directly from distutils.ccompiler.CCompiler
             macros, objects, extra_postargs, pp_opts, build = compiler._setup_compile(  # type: ignore[attr-defined]
                 output_dir, macros, include_dirs, sources, depends, extra_postargs
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 9a9bb1556a..dd6393bf0b 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -135,7 +135,6 @@ def normalize_line_endings(value: bytes) -> bytes:
 
 
 def test_build_sdist(monkeypatch, tmpdir):
-
     monkeypatch.chdir(MAIN_DIR)
 
     subprocess.run(
@@ -186,7 +185,6 @@ def test_build_sdist(monkeypatch, tmpdir):
 
 
 def test_build_global_dist(monkeypatch, tmpdir):
-
     monkeypatch.chdir(MAIN_DIR)
     monkeypatch.setenv("PYBIND11_GLOBAL_SDIST", "1")
     subprocess.run(
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index 7f47b37a25..a29316c38d 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -7,7 +7,6 @@
 
 
 def test_chrono_system_clock():
-
     # Get the time from both c++ and datetime
     date0 = datetime.datetime.today()
     date1 = m.test_chrono1()
@@ -122,7 +121,6 @@ def test_chrono_system_clock_roundtrip_time(time1, tz, monkeypatch):
 
 
 def test_chrono_duration_roundtrip():
-
     # Get the difference between two times (a timedelta)
     date1 = datetime.datetime.today()
     date2 = datetime.datetime.today()
@@ -143,7 +141,6 @@ def test_chrono_duration_roundtrip():
 
 
 def test_chrono_duration_subtraction_equivalence():
-
     date1 = datetime.datetime.today()
     date2 = datetime.datetime.today()
 
@@ -154,7 +151,6 @@ def test_chrono_duration_subtraction_equivalence():
 
 
 def test_chrono_duration_subtraction_equivalence_date():
-
     date1 = datetime.date.today()
     date2 = datetime.date.today()
 
diff --git a/tests/test_class.py b/tests/test_class.py
index 9c964e001b..64abac133c 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -185,7 +185,6 @@ def test_inheritance(msg):
 
 
 def test_inheritance_init(msg):
-
     # Single base
     class Python(m.Pet):
         def __init__(self):
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
index adfa6cf86e..731380e46a 100644
--- a/tests/test_custom_type_casters.py
+++ b/tests/test_custom_type_casters.py
@@ -94,7 +94,8 @@ def test_noconvert_args(msg):
 
 def test_custom_caster_destruction():
     """Tests that returning a pointer to a type that gets converted with a custom type caster gets
-    destroyed when the function has py::return_value_policy::take_ownership policy applied."""
+    destroyed when the function has py::return_value_policy::take_ownership policy applied.
+    """
 
     cstats = m.destruction_tester_cstats()
     # This one *doesn't* have take_ownership: the pointer should be used but not destroyed:
diff --git a/tests/test_eigen_tensor.py b/tests/test_eigen_tensor.py
index dc8aa4643e..cd54efa069 100644
--- a/tests/test_eigen_tensor.py
+++ b/tests/test_eigen_tensor.py
@@ -59,7 +59,6 @@ def assert_equal_tensor_ref(mat, writeable=True, modified=None):
 @pytest.mark.parametrize("m", submodules)
 @pytest.mark.parametrize("member_name", ["member", "member_view"])
 def test_reference_internal(m, member_name):
-
     if not hasattr(sys, "getrefcount"):
         pytest.skip("No reference counting")
     foo = m.CustomExample()
@@ -108,7 +107,6 @@ def test_convert_tensor_to_py(m, func_name):
 
 @pytest.mark.parametrize("m", submodules)
 def test_bad_cpp_to_python_casts(m):
-
     with pytest.raises(
         RuntimeError, match="Cannot use reference internal when there is no parent"
     ):
@@ -131,7 +129,6 @@ def test_bad_cpp_to_python_casts(m):
 
 @pytest.mark.parametrize("m", submodules)
 def test_bad_python_to_cpp_casts(m):
-
     with pytest.raises(
         TypeError, match=r"^round_trip_tensor\(\): incompatible function arguments"
     ):
@@ -194,7 +191,6 @@ def test_bad_python_to_cpp_casts(m):
 
 @pytest.mark.parametrize("m", submodules)
 def test_references_actually_refer(m):
-
     a = m.reference_tensor()
     temp = a[indices]
     a[indices] = 100
@@ -211,7 +207,6 @@ def test_references_actually_refer(m):
 
 @pytest.mark.parametrize("m", submodules)
 def test_round_trip(m):
-
     assert_equal_tensor_ref(m.round_trip_tensor(tensor_ref))
 
     with pytest.raises(TypeError, match="^Cannot cast array data from"):
@@ -260,7 +255,6 @@ def test_round_trip(m):
 
 @pytest.mark.parametrize("m", submodules)
 def test_round_trip_references_actually_refer(m):
-
     # Need to create a copy that matches the type on the C side
     copy = np.array(tensor_ref, dtype=np.float64, order=m.needed_options)
     a = m.round_trip_view_tensor(copy)
diff --git a/tests/test_local_bindings.py b/tests/test_local_bindings.py
index 654d96d490..d641877396 100644
--- a/tests/test_local_bindings.py
+++ b/tests/test_local_bindings.py
@@ -130,7 +130,8 @@ def test_stl_bind_global():
 def test_mixed_local_global():
     """Local types take precedence over globally registered types: a module with a `module_local`
     type can be registered even if the type is already registered globally.  With the module,
-    casting will go to the local type; outside the module casting goes to the global type."""
+    casting will go to the local type; outside the module casting goes to the global type.
+    """
     import pybind11_cross_module_tests as cm
 
     m.register_mixed_global()
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index b228da3cc3..9fde305a03 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -130,7 +130,6 @@ def test_nested():
 
 
 def test_overriding_eq_reset_hash():
-
     assert m.Comparable(15) is not m.Comparable(15)
     assert m.Comparable(15) == m.Comparable(15)
 

From 08a89fac3a11c5cb5498d76cfde3ba3988368d3a Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Sat, 4 Feb 2023 13:40:13 -0500
Subject: [PATCH 555/638] bugfix: delete proper ctors in gil.h (#4490)

---
 include/pybind11/gil.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index cb0028d505..570a5581d5 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -152,8 +152,8 @@ class gil_scoped_release {
         }
     }
 
-    gil_scoped_release(const gil_scoped_acquire &) = delete;
-    gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
+    gil_scoped_release(const gil_scoped_release &) = delete;
+    gil_scoped_release &operator=(const gil_scoped_release &) = delete;
 
     /// This method will disable the PyThreadState_DeleteCurrent call and the
     /// GIL won't be acquired. This method should be used if the interpreter
@@ -203,7 +203,7 @@ class gil_scoped_release {
 public:
     gil_scoped_release() : state{PyEval_SaveThread()} {}
     gil_scoped_release(const gil_scoped_release &) = delete;
-    gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
+    gil_scoped_release &operator=(const gil_scoped_release &) = delete;
     ~gil_scoped_release() { PyEval_RestoreThread(state); }
     void disarm() {}
 };
@@ -230,7 +230,7 @@ class gil_scoped_release {
         (void) (this != (this + 1));
     }
     gil_scoped_release(const gil_scoped_release &) = delete;
-    gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
+    gil_scoped_release &operator=(const gil_scoped_release &) = delete;
     void disarm() {}
 };
 

From 9ef65cee0e780e6443fa0813122712c9ae4bdcc7 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 6 Feb 2023 00:16:52 -0500
Subject: [PATCH 556/638] chore(deps): bump ilammy/msvc-dev-cmd from 1.12.0 to
 1.12.1 (#4493)

Bumps [ilammy/msvc-dev-cmd](https://github.com/ilammy/msvc-dev-cmd) from 1.12.0 to 1.12.1.
- [Release notes](https://github.com/ilammy/msvc-dev-cmd/releases)
- [Commits](https://github.com/ilammy/msvc-dev-cmd/compare/v1.12.0...v1.12.1)

---
updated-dependencies:
- dependency-name: ilammy/msvc-dev-cmd
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7c5fcb43ac..8befccdbc2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -766,7 +766,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.12.0
+      uses: ilammy/msvc-dev-cmd@v1.12.1
       with:
         arch: x86
 
@@ -819,7 +819,7 @@ jobs:
       uses: jwlawson/actions-setup-cmake@v1.13
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.12.0
+      uses: ilammy/msvc-dev-cmd@v1.12.1
       with:
         arch: x86
 

From b2c1978caaa6627095e3326f7ecba84b43037869 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 6 Feb 2023 11:36:05 -0500
Subject: [PATCH 557/638] bugfix: Keep registered types until after
 Py_Finalize(). Fix #4459 (#4486)

* Keep registered types until after Py_Finalize(). Fix #4459

* Address reviewer comments
---
 include/pybind11/embed.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 5a175b1341..8450d53589 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -254,13 +254,16 @@ inline void finalize_interpreter() {
     if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
         internals_ptr_ptr = capsule(builtins[id]);
     }
+
+    Py_Finalize();
+
     // Local internals contains data managed by the current interpreter, so we must clear them to
     // avoid undefined behaviors when initializing another interpreter
+    // Must be cleared only after Py_Finalize() so atexit and other hooks can still use
+    // registered_types
     detail::get_local_internals().registered_types_cpp.clear();
     detail::get_local_internals().registered_exception_translators.clear();
 
-    Py_Finalize();
-
     if (internals_ptr_ptr) {
         delete *internals_ptr_ptr;
         *internals_ptr_ptr = nullptr;

From 8a90b36772f36da577c485bd450130c8318c8111 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 7 Feb 2023 01:16:25 -0500
Subject: [PATCH 558/638] chore(deps): update pre-commit hooks (#4495)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/PyCQA/pylint: v2.16.0 → v2.16.1](https://github.com/PyCQA/pylint/compare/v2.16.0...v2.16.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 363ac71c6f..27474f2f73 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -116,7 +116,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.16.0"
+  rev: "v2.16.1"
   hooks:
   - id: pylint
     files: ^pybind11

From f8713ec43e6833033b43126c8b55de97242ab4dd Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 7 Feb 2023 16:55:00 -0800
Subject: [PATCH 559/638] Revert "bugfix: Keep registered types until after
 Py_Finalize(). Fix #4459 (#4486)" (#4501)

This reverts commit b2c1978caaa6627095e3326f7ecba84b43037869.

See #4500 for background.
---
 include/pybind11/embed.h | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 8450d53589..5a175b1341 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -254,16 +254,13 @@ inline void finalize_interpreter() {
     if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
         internals_ptr_ptr = capsule(builtins[id]);
     }
-
-    Py_Finalize();
-
     // Local internals contains data managed by the current interpreter, so we must clear them to
     // avoid undefined behaviors when initializing another interpreter
-    // Must be cleared only after Py_Finalize() so atexit and other hooks can still use
-    // registered_types
     detail::get_local_internals().registered_types_cpp.clear();
     detail::get_local_internals().registered_exception_translators.clear();
 
+    Py_Finalize();
+
     if (internals_ptr_ptr) {
         delete *internals_ptr_ptr;
         *internals_ptr_ptr = nullptr;

From b8f28551cc3a98ea9fbfc15c05b513c8f2d23e84 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 7 Feb 2023 20:19:33 -0800
Subject: [PATCH 560/638] Go back to CMake 3.25.2 (#4496)

---
 .github/workflows/ci.yml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8befccdbc2..5d93d42b17 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -83,6 +83,9 @@ jobs:
 
     - name: Update CMake
       uses: jwlawson/actions-setup-cmake@v1.13
+      # TEMPORARILY pin version because 3.26.0-rc1 is failing under macOS:
+      with:
+        cmake-version: '3.25.2'
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -1071,6 +1074,9 @@ jobs:
 
       - name: Update CMake
         uses: jwlawson/actions-setup-cmake@v1.13
+        # TEMPORARILY pin version because 3.26.0-rc1 is failing under macOS:
+        with:
+          cmake-version: '3.25.2'
 
       - name: Run pip installs
         run: |

From 531144dddc8abf05612523a83ff575f6834fd611 Mon Sep 17 00:00:00 2001
From: Mike Essenmacher <112431871+mikeessen@users.noreply.github.com>
Date: Thu, 9 Feb 2023 13:11:01 -0500
Subject: [PATCH 561/638] Replace "whitelist" with "allowlist" (#4506)

---
 tests/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9beb268ed7..b1cb222b4a 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -169,7 +169,7 @@ if(PYBIND11_TEST_OVERRIDE)
   # This allows the override to be done with extensions, preserving backwards compatibility.
   foreach(test_name ${TEST_FILES_NO_EXT})
     if(NOT ${test_name} IN_LIST TEST_OVERRIDE_NO_EXT
-    )# If not in the whitelist, add to be filtered out.
+    )# If not in the allowlist, add to be filtered out.
       list(APPEND PYBIND11_TEST_FILTER ${test_name})
     endif()
   endforeach()

From 8dcced29ae4c7654c25bc50742a72556ee3ae36c Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Fri, 10 Feb 2023 00:21:17 -0500
Subject: [PATCH 562/638] Always display python type information in cast errors
 (#4463)

* Always display python type information in cast errors

* Address comments

* Update comment
---
 include/pybind11/cast.h          | 33 ++++++++++++++++++--------------
 include/pybind11/detail/common.h |  5 +++--
 tests/test_callbacks.py          | 14 ++++++++++++--
 tests/test_exceptions.cpp        |  5 +++++
 tests/test_exceptions.py         |  9 +++++++++
 tests/test_pytypes.py            |  2 +-
 6 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 3a40460276..9b013bc39f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1017,11 +1017,14 @@ type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &ha
                   "Internal error: type_caster should only be used for C++ types");
     if (!conv.load(handle, true)) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
-        throw cast_error("Unable to cast Python instance to C++ type (#define "
-                         "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
+        throw cast_error(
+            "Unable to cast Python instance of type "
+            + str(type::handle_of(handle)).cast<std::string>()
+            + " to C++ type '?' (#define "
+              "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
         throw cast_error("Unable to cast Python instance of type "
-                         + (std::string) str(type::handle_of(handle)) + " to C++ type '"
+                         + str(type::handle_of(handle)).cast<std::string>() + " to C++ type '"
                          + type_id<T>() + "'");
 #endif
     }
@@ -1085,12 +1088,13 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         throw cast_error(
-            "Unable to cast Python instance to C++ rvalue: instance has multiple references"
-            " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
+            "Unable to cast Python " + str(type::handle_of(obj)).cast<std::string>()
+            + " instance to C++ rvalue: instance has multiple references"
+              " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
-        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj))
-                         + " instance to C++ " + type_id<T>()
-                         + " instance: instance has multiple references");
+        throw cast_error("Unable to move from Python "
+                         + str(type::handle_of(obj)).cast<std::string>() + " instance to C++ "
+                         + type_id<T>() + " instance: instance has multiple references");
 #endif
     }
 
@@ -1195,9 +1199,10 @@ PYBIND11_NAMESPACE_END(detail)
 // The overloads could coexist, i.e. the #if is not strictly speaking needed,
 // but it is an easy minor optimization.
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
-inline cast_error cast_error_unable_to_convert_call_arg() {
-    return cast_error("Unable to convert call argument to Python object (#define "
-                      "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
+inline cast_error cast_error_unable_to_convert_call_arg(const std::string &name) {
+    return cast_error("Unable to convert call argument '" + name
+                      + "' to Python object (#define "
+                        "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 }
 #else
 inline cast_error cast_error_unable_to_convert_call_arg(const std::string &name,
@@ -1220,7 +1225,7 @@ tuple make_tuple(Args &&...args_) {
     for (size_t i = 0; i < args.size(); i++) {
         if (!args[i]) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
-            throw cast_error_unable_to_convert_call_arg();
+            throw cast_error_unable_to_convert_call_arg(std::to_string(i));
 #else
             std::array<std::string, size> argtypes{{type_id<Args>()...}};
             throw cast_error_unable_to_convert_call_arg(std::to_string(i), argtypes[i]);
@@ -1510,7 +1515,7 @@ class unpacking_collector {
             detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
         if (!o) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
-            throw cast_error_unable_to_convert_call_arg();
+            throw cast_error_unable_to_convert_call_arg(std::to_string(args_list.size()));
 #else
             throw cast_error_unable_to_convert_call_arg(std::to_string(args_list.size()),
                                                         type_id<T>());
@@ -1542,7 +1547,7 @@ class unpacking_collector {
         }
         if (!a.value) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
-            throw cast_error_unable_to_convert_call_arg();
+            throw cast_error_unable_to_convert_call_arg(a.name);
 #else
             throw cast_error_unable_to_convert_call_arg(a.name, a.type);
 #endif
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 0fc81e0534..1032293d21 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -1225,8 +1225,9 @@ constexpr
 #endif
 
 // Pybind offers detailed error messages by default for all builts that are debug (through the
-// negation of ndebug). This can also be manually enabled by users, for any builds, through
-// defining PYBIND11_DETAILED_ERROR_MESSAGES.
+// negation of NDEBUG). This can also be manually enabled by users, for any builds, through
+// defining PYBIND11_DETAILED_ERROR_MESSAGES. This information is primarily useful for those
+// who are writing (as opposed to merely using) libraries that use pybind11.
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES) && !defined(NDEBUG)
 #    define PYBIND11_DETAILED_ERROR_MESSAGES
 #endif
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 57b6599880..4a652f53e8 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -5,6 +5,7 @@
 
 import env  # noqa: F401
 from pybind11_tests import callbacks as m
+from pybind11_tests import detailed_error_messages_enabled
 
 
 def test_callbacks():
@@ -70,11 +71,20 @@ def f(*args, **kwargs):
 
     with pytest.raises(RuntimeError) as excinfo:
         m.test_arg_conversion_error1(f)
-    assert "Unable to convert call argument" in str(excinfo.value)
+    assert str(excinfo.value) == "Unable to convert call argument " + (
+        "'1' of type 'UnregisteredType' to Python object"
+        if detailed_error_messages_enabled
+        else "'1' to Python object (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
+    )
 
     with pytest.raises(RuntimeError) as excinfo:
         m.test_arg_conversion_error2(f)
-    assert "Unable to convert call argument" in str(excinfo.value)
+    assert str(excinfo.value) == "Unable to convert call argument " + (
+        "'expected_name' of type 'UnregisteredType' to Python object"
+        if detailed_error_messages_enabled
+        else "'expected_name' to Python object "
+        "(#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
+    )
 
 
 def test_lambda_closure_cleanup():
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index f57e095068..854c7e6f76 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -339,4 +339,9 @@ TEST_SUBMODULE(exceptions, m) {
         }
         return py::str("UNEXPECTED");
     });
+
+    m.def("test_fn_cast_int", [](const py::function &fn) {
+        // function returns None instead of int, should give a useful error message
+        fn().cast<int>();
+    });
 }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 0d2c808143..8bcefe3de6 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -381,3 +381,12 @@ def test_pypy_oserror_normalization():
     # https://github.com/pybind/pybind11/issues/4075
     what = m.test_pypy_oserror_normalization()
     assert "this_filename_must_not_exist" in what
+
+
+def test_fn_cast_int_exception():
+    with pytest.raises(RuntimeError) as excinfo:
+        m.test_fn_cast_int(lambda: None)
+
+    assert str(excinfo.value).startswith(
+        "Unable to cast Python instance of type <class 'NoneType'> to C++ type"
+    )
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 8f9f2987e9..a1a80a2933 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -536,7 +536,7 @@ def test_print(capture):
     assert str(excinfo.value) == "Unable to convert call argument " + (
         "'1' of type 'UnregisteredType' to Python object"
         if detailed_error_messages_enabled
-        else "to Python object (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
+        else "'1' to Python object (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
     )
 
 

From 535f81a1c0f60f39aaf0f7661f2a1ac2a3a0af16 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 16 Feb 2023 06:54:27 -0800
Subject: [PATCH 563/638] fix: tests dir has started to show up in packaging
 (#4510)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 MANIFEST.in | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MANIFEST.in b/MANIFEST.in
index 033303a74a..31632acc33 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,3 +1,4 @@
+prune tests
 recursive-include pybind11/include/pybind11 *.h
 recursive-include pybind11 *.py
 recursive-include pybind11 py.typed

From 08a4a47a6c0a8e8ca99a86c23c9b6ac843837395 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 16 Feb 2023 07:54:57 -0800
Subject: [PATCH 564/638] Revert "Go back to CMake 3.25.2 (#4496)" (#4503)

* Revert "Go back to CMake 3.25.2 (#4496)"

This reverts commit b8f28551cc3a98ea9fbfc15c05b513c8f2d23e84.

* Apply patch provided by @bradking (with pre-commit cmake-format auto fixes).

https://github.com/pybind/pybind11/pull/4503#issuecomment-1424768172
---
 .github/workflows/ci.yml | 6 ------
 tools/FindCatch.cmake    | 8 ++++++--
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5d93d42b17..8befccdbc2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -83,9 +83,6 @@ jobs:
 
     - name: Update CMake
       uses: jwlawson/actions-setup-cmake@v1.13
-      # TEMPORARILY pin version because 3.26.0-rc1 is failing under macOS:
-      with:
-        cmake-version: '3.25.2'
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -1074,9 +1071,6 @@ jobs:
 
       - name: Update CMake
         uses: jwlawson/actions-setup-cmake@v1.13
-        # TEMPORARILY pin version because 3.26.0-rc1 is failing under macOS:
-        with:
-          cmake-version: '3.25.2'
 
       - name: Run pip installs
         run: |
diff --git a/tools/FindCatch.cmake b/tools/FindCatch.cmake
index 57bba58b30..5d3fcbfb13 100644
--- a/tools/FindCatch.cmake
+++ b/tools/FindCatch.cmake
@@ -36,10 +36,14 @@ endfunction()
 function(_download_catch version destination_dir)
   message(STATUS "Downloading catch v${version}...")
   set(url https://github.com/philsquared/Catch/releases/download/v${version}/catch.hpp)
-  file(DOWNLOAD ${url} "${destination_dir}/catch.hpp" STATUS status)
+  file(
+    DOWNLOAD ${url} "${destination_dir}/catch.hpp"
+    STATUS status
+    LOG log)
   list(GET status 0 error)
   if(error)
-    message(FATAL_ERROR "Could not download ${url}")
+    string(REPLACE "\n" "\n  " log "  ${log}")
+    message(FATAL_ERROR "Could not download URL:\n" "  ${url}\n" "Log:\n" "${log}")
   endif()
   set(CATCH_INCLUDE_DIR
       "${destination_dir}"

From d1956eabb50d93428097a8a564cef4fc8b0ded82 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 17 Feb 2023 12:31:08 -0800
Subject: [PATCH 565/638] Appease new flake8 B028 error: (#4513)

```
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

pybind11/setup_helpers.py:177:13: B028 No explicit stacklevel keyword argument found. The warn method from the warnings module uses a stacklevel of 1 by default. This will only show a stack trace for the line on which the warn method is called. It is therefore recommended to use a stacklevel of 2 or greater to provide more information to the user.
            warnings.warn("You cannot safely change the cxx_level after setting it!")
            ^
```
---
 pybind11/setup_helpers.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 1db4795327..4c14498f6f 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -174,7 +174,9 @@ def cxx_std(self) -> int:
     @cxx_std.setter
     def cxx_std(self, level: int) -> None:
         if self._cxx_level:
-            warnings.warn("You cannot safely change the cxx_level after setting it!")
+            warnings.warn(
+                "You cannot safely change the cxx_level after setting it!", stacklevel=1
+            )
 
         # MSVC 2015 Update 3 and later only have 14 (and later 17) modes, so
         # force a valid flag here.

From 6a5e6007cdfa9441fc05a589d7b819c6c37eb489 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 17 Feb 2023 12:58:35 -0800
Subject: [PATCH 566/638] Make warning suppressions MINGW-specific again.
 (#4515)

Background: https://github.com/pybind/pybind11/pull/4285#issuecomment-1435066554
---
 include/pybind11/eigen/matrix.h | 2 ++
 include/pybind11/eigen/tensor.h | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/pybind11/eigen/matrix.h b/include/pybind11/eigen/matrix.h
index 34fe329a82..bd533bed37 100644
--- a/include/pybind11/eigen/matrix.h
+++ b/include/pybind11/eigen/matrix.h
@@ -19,7 +19,9 @@
 PYBIND11_WARNING_PUSH
 PYBIND11_WARNING_DISABLE_MSVC(5054) // https://github.com/pybind/pybind11/pull/3741
 //       C5054: operator '&': deprecated between enumerations of different types
+#if defined(__MINGW32__)
 PYBIND11_WARNING_DISABLE_GCC("-Wmaybe-uninitialized")
+#endif
 
 #include <Eigen/Core>
 #include <Eigen/SparseCore>
diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
index 0877da8953..de7dcba89d 100644
--- a/include/pybind11/eigen/tensor.h
+++ b/include/pybind11/eigen/tensor.h
@@ -17,7 +17,9 @@ static_assert(__GNUC__ > 5, "Eigen Tensor support in pybind11 requires GCC > 5.0
 PYBIND11_WARNING_PUSH
 PYBIND11_WARNING_DISABLE_MSVC(4554)
 PYBIND11_WARNING_DISABLE_MSVC(4127)
+#if defined(__MINGW32__)
 PYBIND11_WARNING_DISABLE_GCC("-Wmaybe-uninitialized")
+#endif
 
 #include <unsupported/Eigen/CXX11/Tensor>
 

From 68211d41c1ef94fa65ef27ea2a6cdd8677996635 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Fri, 17 Feb 2023 14:13:29 -0800
Subject: [PATCH 567/638] fix: nicer stack level for warning (#4516)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 pybind11/setup_helpers.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 4c14498f6f..b9b433b656 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -175,7 +175,7 @@ def cxx_std(self) -> int:
     def cxx_std(self, level: int) -> None:
         if self._cxx_level:
             warnings.warn(
-                "You cannot safely change the cxx_level after setting it!", stacklevel=1
+                "You cannot safely change the cxx_level after setting it!", stacklevel=2
             )
 
         # MSVC 2015 Update 3 and later only have 14 (and later 17) modes, so

From a19daeac16685877fd0b5ffcadce4b9f60d90f7b Mon Sep 17 00:00:00 2001
From: xkszltl <xkszltl@gmail.com>
Date: Tue, 21 Feb 2023 06:58:37 +0800
Subject: [PATCH 568/638] Inconsistent comments between 2 templates of
 `unchecked()`. (#4519)

This comment is unrelated to having T in tparam or not.
Probably a typo.
Copied the correct one here.

Resolve https://github.com/pybind/pybind11/issues/4518
---
 include/pybind11/numpy.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 8f072af267..854d6e87fa 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -1121,10 +1121,10 @@ class array_t : public array {
 
     /**
      * Returns a proxy object that provides const access to the array's data without bounds or
-     * dimensionality checking.  Unlike `unchecked()`, this does not require that the underlying
-     * array have the `writable` flag.  Use with care: the array must not be destroyed or reshaped
-     * for the duration of the returned object, and the caller must take care not to access invalid
-     * dimensions or dimension indices.
+     * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
+     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed
+     * or reshaped for the duration of the returned object, and the caller must take care not to
+     * access invalid dimensions or dimension indices.
      */
     template <ssize_t Dims = -1>
     detail::unchecked_reference<T, Dims> unchecked() const & {

From 438034c5b8a6a8bf82dda7a195e3c00cafe575e0 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 22 Feb 2023 06:18:55 -0800
Subject: [PATCH 569/638] chore: move to Ruff and add rules (#4483)

---
 .pre-commit-config.yaml                     | 44 ++--------
 docs/conf.py                                |  2 +-
 pybind11/__init__.py                        |  2 +-
 pybind11/commands.py                        |  2 +-
 pybind11/setup_helpers.py                   |  2 +-
 pyproject.toml                              | 46 ++++++++--
 setup.cfg                                   |  8 --
 tests/conftest.py                           | 50 ++++-------
 tests/env.py                                |  3 +-
 tests/test_async.py                         |  4 +-
 tests/test_buffers.py                       |  3 +-
 tests/test_builtin_casters.py               | 10 ++-
 tests/test_class.py                         | 11 +--
 tests/test_const_name.py                    |  4 +-
 tests/test_custom_type_casters.py           |  3 +-
 tests/test_custom_type_setup.py             |  2 +-
 tests/test_eigen_matrix.py                  | 93 +++++++++++++--------
 tests/test_eigen_tensor.py                  | 20 ++---
 tests/test_enum.py                          |  2 +
 tests/test_exceptions.py                    | 18 ++--
 tests/test_factory_constructors.py          |  2 +-
 tests/test_gil_scoped.py                    |  8 +-
 tests/test_iostream.py                      | 20 ++---
 tests/test_kwargs_and_defaults.py           | 31 ++++---
 tests/test_methods_and_attributes.py        |  9 +-
 tests/test_modules.py                       |  9 +-
 tests/test_numpy_array.py                   | 18 ++--
 tests/test_numpy_dtypes.py                  | 28 +++----
 tests/test_numpy_vectorize.py               |  2 +-
 tests/test_pytypes.py                       | 48 +++++------
 tests/test_sequences_and_iterators.py       |  7 +-
 tests/test_stl.py                           |  7 +-
 tests/test_stl_binders.py                   | 12 +--
 tests/test_virtual_functions.py             |  7 +-
 tools/codespell_ignore_lines_from_errors.py |  8 +-
 35 files changed, 266 insertions(+), 279 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 27474f2f73..2255f2e4d5 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -39,19 +39,6 @@ repos:
   - id: requirements-txt-fixer
   - id: trailing-whitespace
 
-# Upgrade old Python syntax
-- repo: https://github.com/asottile/pyupgrade
-  rev: "v3.3.1"
-  hooks:
-  - id: pyupgrade
-    args: [--py36-plus]
-
-# Nicely sort includes
-- repo: https://github.com/PyCQA/isort
-  rev: "5.12.0"
-  hooks:
-  - id: isort
-
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
   rev: "23.1.0" # Keep in sync with blacken-docs
@@ -72,47 +59,28 @@ repos:
   hooks:
   - id: remove-tabs
 
+# Avoid directional quotes
 - repo: https://github.com/sirosen/texthooks
   rev: "0.5.0"
   hooks:
   - id: fix-ligatures
   - id: fix-smartquotes
 
-# Autoremoves unused imports
-- repo: https://github.com/hadialqattan/pycln
-  rev: "v2.1.3"
+# Ruff, the Python auto-correcting linter written in Rust
+- repo: https://github.com/charliermarsh/ruff-pre-commit
+  rev: v0.0.251
   hooks:
-  - id: pycln
-    stages: [manual]
+  - id: ruff
+    args: ["--fix", "--show-fixes"]
 
 # Checking for common mistakes
 - repo: https://github.com/pre-commit/pygrep-hooks
   rev: "v1.10.0"
   hooks:
-  - id: python-check-blanket-noqa
-  - id: python-check-blanket-type-ignore
-  - id: python-no-log-warn
-  - id: python-use-type-annotations
   - id: rst-backticks
   - id: rst-directive-colons
   - id: rst-inline-touching-normal
 
-# Automatically remove noqa that are not used
-- repo: https://github.com/asottile/yesqa
-  rev: "v1.4.0"
-  hooks:
-  - id: yesqa
-    additional_dependencies: &flake8_dependencies
-      - flake8-bugbear
-      - pep8-naming
-
-# Flake8 also supports pre-commit natively (same author)
-- repo: https://github.com/PyCQA/flake8
-  rev: "6.0.0"
-  hooks:
-  - id: flake8
-    exclude: ^(docs/.*|tools/.*)$
-    additional_dependencies: *flake8_dependencies
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
diff --git a/docs/conf.py b/docs/conf.py
index cdb9f63069..6e24751e9e 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -353,7 +353,7 @@ def prepare(app):
         f.write(contents)
 
 
-def clean_up(app, exception):
+def clean_up(app, exception):  # noqa: ARG001
     (DIR / "readme.rst").unlink()
 
 
diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index 4fbb17079f..7c10b30578 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -1,6 +1,6 @@
 import sys
 
-if sys.version_info < (3, 6):
+if sys.version_info < (3, 6):  # noqa: UP036
     msg = "pybind11 does not support Python < 3.6. 2.9 was the last release supporting Python 2.7 and 3.5."
     raise ImportError(msg)
 
diff --git a/pybind11/commands.py b/pybind11/commands.py
index 152fa20ce7..b11690f46b 100644
--- a/pybind11/commands.py
+++ b/pybind11/commands.py
@@ -3,7 +3,7 @@
 DIR = os.path.abspath(os.path.dirname(__file__))
 
 
-def get_include(user: bool = False) -> str:  # pylint: disable=unused-argument
+def get_include(user: bool = False) -> str:  # noqa: ARG001
     """
     Return the path to the pybind11 include directory. The historical "user"
     argument is unused, and may be removed.
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index b9b433b656..0fb4679e49 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -341,7 +341,7 @@ def naive_recompile(obj: str, src: str) -> bool:
     return os.stat(obj).st_mtime < os.stat(src).st_mtime
 
 
-def no_recompile(obg: str, src: str) -> bool:  # pylint: disable=unused-argument
+def no_recompile(obg: str, src: str) -> bool:  # noqa: ARG001
     """
     This is the safest but slowest choice (and is the default) - will always
     recompile sources.
diff --git a/pyproject.toml b/pyproject.toml
index 3ba1b4b22f..96cf842650 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,12 +15,6 @@ ignore = [
     "noxfile.py",
 ]
 
-[tool.isort]
-# Needs the compiled .so modules and env.py from tests
-known_first_party = "env,pybind11_cross_module_tests,pybind11_tests,"
-# For black compatibility
-profile = "black"
-
 [tool.mypy]
 files = ["pybind11"]
 python_version = "3.6"
@@ -58,4 +52,44 @@ messages_control.disable = [
   "invalid-name",
   "protected-access",
   "missing-module-docstring",
+  "unused-argument",  # covered by Ruff ARG
+]
+
+[tool.ruff]
+select = [
+  "E", "F", "W", # flake8
+  "B",  "B904",  # flake8-bugbear
+  "I",           # isort
+  "N",           # pep8-naming
+  "ARG",         # flake8-unused-arguments
+  "C4",          # flake8-comprehensions
+  "EM",          # flake8-errmsg
+  "ICN",         # flake8-import-conventions
+  "ISC",         # flake8-implicit-str-concat
+  "PGH",         # pygrep-hooks
+  "PIE",         # flake8-pie
+  "PL",          # pylint
+  "PT",          # flake8-pytest-style
+  "RET",         # flake8-return
+  "RUF100",      # Ruff-specific
+  "SIM",         # flake8-simplify
+  "UP",          # pyupgrade
+  "YTT",         # flake8-2020
 ]
+ignore = [
+  "PLR",   # Design related pylint
+  "E501",  # Line too long (Black is enough)
+  "PT011", # Too broad with raises in pytest
+  "PT004", # Fixture that doesn't return needs underscore (no, it is fine)
+  "SIM118",# iter(x) is not always the same as iter(x.keys())
+]
+target-version = "py37"
+typing-modules = ["scikit_build_core._compat.typing"]
+src = ["src"]
+unfixable = ["T20"]
+exclude = []
+line-length = 120
+isort.known-first-party = ["env", "pybind11_cross_module_tests", "pybind11_tests"]
+
+[tool.ruff.per-file-ignores]
+"tests/**" = ["EM", "N"]
diff --git a/setup.cfg b/setup.cfg
index 8b3361981a..c35dd07ae6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -40,11 +40,3 @@ project_urls =
 [options]
 python_requires = >=3.6
 zip_safe = False
-
-
-[flake8]
-max-line-length = 120
-show_source = True
-exclude = .git, __pycache__, build, dist, docs, tools, venv
-extend-ignore = E203, E722
-extend-select = B902, B904
diff --git a/tests/conftest.py b/tests/conftest.py
index c24d51d4d1..b60d3c956b 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -83,9 +83,8 @@ def __eq__(self, other):
         b = _strip_and_dedent(other).splitlines()
         if a == b:
             return True
-        else:
-            self.explanation = _make_explanation(a, b)
-            return False
+        self.explanation = _make_explanation(a, b)
+        return False
 
 
 class Unordered(Output):
@@ -96,9 +95,8 @@ def __eq__(self, other):
         b = _split_and_sort(other)
         if a == b:
             return True
-        else:
-            self.explanation = _make_explanation(a, b)
-            return False
+        self.explanation = _make_explanation(a, b)
+        return False
 
 
 class Capture:
@@ -119,9 +117,8 @@ def __eq__(self, other):
         b = other
         if a == b:
             return True
-        else:
-            self.explanation = a.explanation
-            return False
+        self.explanation = a.explanation
+        return False
 
     def __str__(self):
         return self.out
@@ -138,7 +135,7 @@ def stderr(self):
         return Output(self.err)
 
 
-@pytest.fixture
+@pytest.fixture()
 def capture(capsys):
     """Extended `capsys` with context manager and custom equality operators"""
     return Capture(capsys)
@@ -159,25 +156,22 @@ def __eq__(self, other):
         b = _strip_and_dedent(other)
         if a == b:
             return True
-        else:
-            self.explanation = _make_explanation(a.splitlines(), b.splitlines())
-            return False
+        self.explanation = _make_explanation(a.splitlines(), b.splitlines())
+        return False
 
 
 def _sanitize_general(s):
     s = s.strip()
     s = s.replace("pybind11_tests.", "m.")
-    s = _long_marker.sub(r"\1", s)
-    return s
+    return _long_marker.sub(r"\1", s)
 
 
 def _sanitize_docstring(thing):
     s = thing.__doc__
-    s = _sanitize_general(s)
-    return s
+    return _sanitize_general(s)
 
 
-@pytest.fixture
+@pytest.fixture()
 def doc():
     """Sanitize docstrings and add custom failure explanation"""
     return SanitizedString(_sanitize_docstring)
@@ -186,30 +180,20 @@ def doc():
 def _sanitize_message(thing):
     s = str(thing)
     s = _sanitize_general(s)
-    s = _hexadecimal.sub("0", s)
-    return s
+    return _hexadecimal.sub("0", s)
 
 
-@pytest.fixture
+@pytest.fixture()
 def msg():
     """Sanitize messages and add custom failure explanation"""
     return SanitizedString(_sanitize_message)
 
 
-# noinspection PyUnusedLocal
-def pytest_assertrepr_compare(op, left, right):
+def pytest_assertrepr_compare(op, left, right):  # noqa: ARG001
     """Hook to insert custom failure explanation"""
     if hasattr(left, "explanation"):
         return left.explanation
-
-
-@contextlib.contextmanager
-def suppress(exception):
-    """Suppress the desired exception"""
-    try:
-        yield
-    except exception:
-        pass
+    return None
 
 
 def gc_collect():
@@ -220,7 +204,7 @@ def gc_collect():
 
 
 def pytest_configure():
-    pytest.suppress = suppress
+    pytest.suppress = contextlib.suppress
     pytest.gc_collect = gc_collect
 
 
diff --git a/tests/env.py b/tests/env.py
index 0345df65dc..7eea5a3b3b 100644
--- a/tests/env.py
+++ b/tests/env.py
@@ -24,5 +24,4 @@ def deprecated_call():
     pytest_major_minor = (int(pieces[0]), int(pieces[1]))
     if pytest_major_minor < (3, 9):
         return pytest.warns((DeprecationWarning, PendingDeprecationWarning))
-    else:
-        return pytest.deprecated_call()
+    return pytest.deprecated_call()
diff --git a/tests/test_async.py b/tests/test_async.py
index b9ff9514d2..83a4c5036a 100644
--- a/tests/test_async.py
+++ b/tests/test_async.py
@@ -4,7 +4,7 @@
 m = pytest.importorskip("pybind11_tests.async_module")
 
 
-@pytest.fixture
+@pytest.fixture()
 def event_loop():
     loop = asyncio.new_event_loop()
     yield loop
@@ -16,7 +16,7 @@ async def get_await_result(x):
 
 
 def test_await(event_loop):
-    assert 5 == event_loop.run_until_complete(get_await_result(m.SupportsAsync()))
+    assert event_loop.run_until_complete(get_await_result(m.SupportsAsync())) == 5
 
 
 def test_await_missing(event_loop):
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index 8354b68cda..eb58c4675e 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -54,7 +54,8 @@ def test_to_python():
     mat2 = np.array(mat, copy=False)
     assert mat2.shape == (5, 4)
     assert abs(mat2).sum() == 11
-    assert mat2[2, 3] == 4 and mat2[3, 2] == 7
+    assert mat2[2, 3] == 4
+    assert mat2[3, 2] == 7
     mat2[2, 3] = 5
     assert mat2[2, 3] == 5
 
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index d38ae68028..b1f57bdd98 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -126,8 +126,8 @@ def test_bytes_to_string():
 
     assert m.strlen(b"hi") == 2
     assert m.string_length(b"world") == 5
-    assert m.string_length("a\x00b".encode()) == 3
-    assert m.strlen("a\x00b".encode()) == 1  # C-string limitation
+    assert m.string_length(b"a\x00b") == 3
+    assert m.strlen(b"a\x00b") == 1  # C-string limitation
 
     # passing in a utf8 encoded string should work
     assert m.string_length("💩".encode()) == 4
@@ -421,13 +421,15 @@ def test_reference_wrapper():
     a2 = m.refwrap_list(copy=True)
     assert [x.value for x in a1] == [2, 3]
     assert [x.value for x in a2] == [2, 3]
-    assert not a1[0] is a2[0] and not a1[1] is a2[1]
+    assert a1[0] is not a2[0]
+    assert a1[1] is not a2[1]
 
     b1 = m.refwrap_list(copy=False)
     b2 = m.refwrap_list(copy=False)
     assert [x.value for x in b1] == [1, 2]
     assert [x.value for x in b2] == [1, 2]
-    assert b1[0] is b2[0] and b1[1] is b2[1]
+    assert b1[0] is b2[0]
+    assert b1[1] is b2[1]
 
     assert m.refwrap_iiw(IncType(5)) == 5
     assert m.refwrap_call_iiw(IncType(10), m.refwrap_iiw) == [10, 10, 10, 10]
diff --git a/tests/test_class.py b/tests/test_class.py
index 64abac133c..ee7467cf8b 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -6,10 +6,7 @@
 
 
 def test_obj_class_name():
-    if env.PYPY:
-        expected_name = "UserType"
-    else:
-        expected_name = "pybind11_tests.UserType"
+    expected_name = "UserType" if env.PYPY else "pybind11_tests.UserType"
     assert m.obj_class_name(UserType(1)) == expected_name
     assert m.obj_class_name(UserType) == expected_name
 
@@ -32,7 +29,7 @@ def test_instance(msg):
     assert cstats.alive() == 0
 
 
-def test_instance_new(msg):
+def test_instance_new():
     instance = m.NoConstructorNew()  # .__new__(m.NoConstructor.__class__)
     cstats = ConstructorStats.get(m.NoConstructorNew)
     assert cstats.alive() == 1
@@ -221,7 +218,7 @@ def test_automatic_upcasting():
 
 
 def test_isinstance():
-    objects = [tuple(), dict(), m.Pet("Polly", "parrot")] + [m.Dog("Molly")] * 4
+    objects = [(), {}, m.Pet("Polly", "parrot")] + [m.Dog("Molly")] * 4
     expected = (True, True, True, True, True, False, False)
     assert m.check_instances(objects) == expected
 
@@ -427,7 +424,7 @@ def test_exception_rvalue_abort():
 
 
 # https://github.com/pybind/pybind11/issues/1568
-def test_multiple_instances_with_same_pointer(capture):
+def test_multiple_instances_with_same_pointer():
     n = 100
     instances = [m.SamePointer() for _ in range(n)]
     for i in range(n):
diff --git a/tests/test_const_name.py b/tests/test_const_name.py
index 10b0caee2e..a145f0bbb5 100644
--- a/tests/test_const_name.py
+++ b/tests/test_const_name.py
@@ -3,9 +3,9 @@
 from pybind11_tests import const_name as m
 
 
-@pytest.mark.parametrize("func", (m.const_name_tests, m.underscore_tests))
+@pytest.mark.parametrize("func", [m.const_name_tests, m.underscore_tests])
 @pytest.mark.parametrize(
-    "selector, expected",
+    ("selector", "expected"),
     enumerate(
         (
             "",
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
index 731380e46a..3a00ea964b 100644
--- a/tests/test_custom_type_casters.py
+++ b/tests/test_custom_type_casters.py
@@ -100,7 +100,8 @@ def test_custom_caster_destruction():
     cstats = m.destruction_tester_cstats()
     # This one *doesn't* have take_ownership: the pointer should be used but not destroyed:
     z = m.custom_caster_no_destroy()
-    assert cstats.alive() == 1 and cstats.default_constructions == 1
+    assert cstats.alive() == 1
+    assert cstats.default_constructions == 1
     assert z
 
     # take_ownership applied: this constructs a new object, casts it, then destroys it:
diff --git a/tests/test_custom_type_setup.py b/tests/test_custom_type_setup.py
index 19b44c9de2..e63ff5758e 100644
--- a/tests/test_custom_type_setup.py
+++ b/tests/test_custom_type_setup.py
@@ -7,7 +7,7 @@
 from pybind11_tests import custom_type_setup as m
 
 
-@pytest.fixture
+@pytest.fixture()
 def gc_tester():
     """Tests that an object is garbage collected.
 
diff --git a/tests/test_eigen_matrix.py b/tests/test_eigen_matrix.py
index 4407fa6aee..b2e76740b1 100644
--- a/tests/test_eigen_matrix.py
+++ b/tests/test_eigen_matrix.py
@@ -263,79 +263,96 @@ def test_eigen_return_references():
     primary = np.ones((10, 10))
     a = m.ReturnTester()
     a_get1 = a.get()
-    assert not a_get1.flags.owndata and a_get1.flags.writeable
+    assert not a_get1.flags.owndata
+    assert a_get1.flags.writeable
     assign_both(a_get1, primary, 3, 3, 5)
     a_get2 = a.get_ptr()
-    assert not a_get2.flags.owndata and a_get2.flags.writeable
+    assert not a_get2.flags.owndata
+    assert a_get2.flags.writeable
     assign_both(a_get1, primary, 2, 3, 6)
 
     a_view1 = a.view()
-    assert not a_view1.flags.owndata and not a_view1.flags.writeable
+    assert not a_view1.flags.owndata
+    assert not a_view1.flags.writeable
     with pytest.raises(ValueError):
         a_view1[2, 3] = 4
     a_view2 = a.view_ptr()
-    assert not a_view2.flags.owndata and not a_view2.flags.writeable
+    assert not a_view2.flags.owndata
+    assert not a_view2.flags.writeable
     with pytest.raises(ValueError):
         a_view2[2, 3] = 4
 
     a_copy1 = a.copy_get()
-    assert a_copy1.flags.owndata and a_copy1.flags.writeable
+    assert a_copy1.flags.owndata
+    assert a_copy1.flags.writeable
     np.testing.assert_array_equal(a_copy1, primary)
     a_copy1[7, 7] = -44  # Shouldn't affect anything else
     c1want = array_copy_but_one(primary, 7, 7, -44)
     a_copy2 = a.copy_view()
-    assert a_copy2.flags.owndata and a_copy2.flags.writeable
+    assert a_copy2.flags.owndata
+    assert a_copy2.flags.writeable
     np.testing.assert_array_equal(a_copy2, primary)
     a_copy2[4, 4] = -22  # Shouldn't affect anything else
     c2want = array_copy_but_one(primary, 4, 4, -22)
 
     a_ref1 = a.ref()
-    assert not a_ref1.flags.owndata and a_ref1.flags.writeable
+    assert not a_ref1.flags.owndata
+    assert a_ref1.flags.writeable
     assign_both(a_ref1, primary, 1, 1, 15)
     a_ref2 = a.ref_const()
-    assert not a_ref2.flags.owndata and not a_ref2.flags.writeable
+    assert not a_ref2.flags.owndata
+    assert not a_ref2.flags.writeable
     with pytest.raises(ValueError):
         a_ref2[5, 5] = 33
     a_ref3 = a.ref_safe()
-    assert not a_ref3.flags.owndata and a_ref3.flags.writeable
+    assert not a_ref3.flags.owndata
+    assert a_ref3.flags.writeable
     assign_both(a_ref3, primary, 0, 7, 99)
     a_ref4 = a.ref_const_safe()
-    assert not a_ref4.flags.owndata and not a_ref4.flags.writeable
+    assert not a_ref4.flags.owndata
+    assert not a_ref4.flags.writeable
     with pytest.raises(ValueError):
         a_ref4[7, 0] = 987654321
 
     a_copy3 = a.copy_ref()
-    assert a_copy3.flags.owndata and a_copy3.flags.writeable
+    assert a_copy3.flags.owndata
+    assert a_copy3.flags.writeable
     np.testing.assert_array_equal(a_copy3, primary)
     a_copy3[8, 1] = 11
     c3want = array_copy_but_one(primary, 8, 1, 11)
     a_copy4 = a.copy_ref_const()
-    assert a_copy4.flags.owndata and a_copy4.flags.writeable
+    assert a_copy4.flags.owndata
+    assert a_copy4.flags.writeable
     np.testing.assert_array_equal(a_copy4, primary)
     a_copy4[8, 4] = 88
     c4want = array_copy_but_one(primary, 8, 4, 88)
 
     a_block1 = a.block(3, 3, 2, 2)
-    assert not a_block1.flags.owndata and a_block1.flags.writeable
+    assert not a_block1.flags.owndata
+    assert a_block1.flags.writeable
     a_block1[0, 0] = 55
     primary[3, 3] = 55
     a_block2 = a.block_safe(2, 2, 3, 2)
-    assert not a_block2.flags.owndata and a_block2.flags.writeable
+    assert not a_block2.flags.owndata
+    assert a_block2.flags.writeable
     a_block2[2, 1] = -123
     primary[4, 3] = -123
     a_block3 = a.block_const(6, 7, 4, 3)
-    assert not a_block3.flags.owndata and not a_block3.flags.writeable
+    assert not a_block3.flags.owndata
+    assert not a_block3.flags.writeable
     with pytest.raises(ValueError):
         a_block3[2, 2] = -44444
 
     a_copy5 = a.copy_block(2, 2, 2, 3)
-    assert a_copy5.flags.owndata and a_copy5.flags.writeable
+    assert a_copy5.flags.owndata
+    assert a_copy5.flags.writeable
     np.testing.assert_array_equal(a_copy5, primary[2:4, 2:5])
     a_copy5[1, 1] = 777
     c5want = array_copy_but_one(primary[2:4, 2:5], 1, 1, 777)
 
     a_corn1 = a.corners()
-    assert not a_corn1.flags.owndata and a_corn1.flags.writeable
+    assert not a_corn1.flags.owndata
+    assert a_corn1.flags.writeable
     a_corn1 *= 50
     a_corn1[1, 1] = 999
     primary[0, 0] = 50
@@ -343,7 +360,8 @@ def test_eigen_return_references():
     primary[9, 0] = 50
     primary[9, 9] = 999
     a_corn2 = a.corners_const()
-    assert not a_corn2.flags.owndata and not a_corn2.flags.writeable
+    assert not a_corn2.flags.owndata
+    assert not a_corn2.flags.writeable
     with pytest.raises(ValueError):
         a_corn2[1, 0] = 51
 
@@ -503,10 +521,14 @@ def test_numpy_ref_mutators():
 
     assert [zc[1, 2], zcro[1, 2], zr[1, 2], zrro[1, 2]] == [23] * 4
 
-    assert not zc.flags.owndata and zc.flags.writeable
-    assert not zr.flags.owndata and zr.flags.writeable
-    assert not zcro.flags.owndata and not zcro.flags.writeable
-    assert not zrro.flags.owndata and not zrro.flags.writeable
+    assert not zc.flags.owndata
+    assert zc.flags.writeable
+    assert not zr.flags.owndata
+    assert zr.flags.writeable
+    assert not zcro.flags.owndata
+    assert not zcro.flags.writeable
+    assert not zrro.flags.owndata
+    assert not zrro.flags.writeable
 
     zc[1, 2] = 99
     expect = np.array([[11.0, 12, 13], [21, 22, 99], [31, 32, 33]])
@@ -530,7 +552,8 @@ def test_numpy_ref_mutators():
     # the const should drop away)
     y1 = np.array(m.get_cm_const_ref())
 
-    assert y1.flags.owndata and y1.flags.writeable
+    assert y1.flags.owndata
+    assert y1.flags.writeable
     # We should get copies of the eigen data, which was modified above:
     assert y1[1, 2] == 99
     y1[1, 2] += 12
@@ -603,38 +626,38 @@ def test_nocopy_wrapper():
     # All but the second should fail with m.get_elem_nocopy:
     with pytest.raises(TypeError) as excinfo:
         m.get_elem_nocopy(int_matrix_colmajor)
-    assert "get_elem_nocopy(): incompatible function arguments." in str(
-        excinfo.value
-    ) and ", flags.f_contiguous" in str(excinfo.value)
+    assert "get_elem_nocopy(): incompatible function arguments." in str(excinfo.value)
+    assert ", flags.f_contiguous" in str(excinfo.value)
     assert m.get_elem_nocopy(dbl_matrix_colmajor) == 8
     with pytest.raises(TypeError) as excinfo:
         m.get_elem_nocopy(int_matrix_rowmajor)
-    assert "get_elem_nocopy(): incompatible function arguments." in str(
-        excinfo.value
-    ) and ", flags.f_contiguous" in str(excinfo.value)
+    assert "get_elem_nocopy(): incompatible function arguments." in str(excinfo.value)
+    assert ", flags.f_contiguous" in str(excinfo.value)
     with pytest.raises(TypeError) as excinfo:
         m.get_elem_nocopy(dbl_matrix_rowmajor)
-    assert "get_elem_nocopy(): incompatible function arguments." in str(
-        excinfo.value
-    ) and ", flags.f_contiguous" in str(excinfo.value)
+    assert "get_elem_nocopy(): incompatible function arguments." in str(excinfo.value)
+    assert ", flags.f_contiguous" in str(excinfo.value)
 
     # For the row-major test, we take a long matrix in row-major, so only the third is allowed:
     with pytest.raises(TypeError) as excinfo:
         m.get_elem_rm_nocopy(int_matrix_colmajor)
     assert "get_elem_rm_nocopy(): incompatible function arguments." in str(
         excinfo.value
-    ) and ", flags.c_contiguous" in str(excinfo.value)
+    )
+    assert ", flags.c_contiguous" in str(excinfo.value)
     with pytest.raises(TypeError) as excinfo:
         m.get_elem_rm_nocopy(dbl_matrix_colmajor)
     assert "get_elem_rm_nocopy(): incompatible function arguments." in str(
         excinfo.value
-    ) and ", flags.c_contiguous" in str(excinfo.value)
+    )
+    assert ", flags.c_contiguous" in str(excinfo.value)
     assert m.get_elem_rm_nocopy(int_matrix_rowmajor) == 8
     with pytest.raises(TypeError) as excinfo:
         m.get_elem_rm_nocopy(dbl_matrix_rowmajor)
     assert "get_elem_rm_nocopy(): incompatible function arguments." in str(
         excinfo.value
-    ) and ", flags.c_contiguous" in str(excinfo.value)
+    )
+    assert ", flags.c_contiguous" in str(excinfo.value)
 
 
 def test_eigen_ref_life_support():
diff --git a/tests/test_eigen_tensor.py b/tests/test_eigen_tensor.py
index cd54efa069..3e7ee6b7f2 100644
--- a/tests/test_eigen_tensor.py
+++ b/tests/test_eigen_tensor.py
@@ -11,14 +11,15 @@
     submodules += [avoid.c_style, avoid.f_style]
 except ImportError as e:
     # Ensure config, build, toolchain, etc. issues are not masked here:
-    raise RuntimeError(
+    msg = (
         "import eigen_tensor_avoid_stl_array FAILED, while "
         "import pybind11_tests.eigen_tensor succeeded. "
         "Please ensure that "
         "test_eigen_tensor.cpp & "
         "eigen_tensor_avoid_stl_array.cpp "
         "are built together (or both are not built if Eigen is not available)."
-    ) from e
+    )
+    raise RuntimeError(msg) from e
 
 tensor_ref = np.empty((3, 5, 2), dtype=np.int64)
 
@@ -147,10 +148,7 @@ def test_bad_python_to_cpp_casts(m):
         m.round_trip_tensor_noconvert(tensor_ref.astype(np.float64))
     )
 
-    if m.needed_options == "F":
-        bad_options = "C"
-    else:
-        bad_options = "F"
+    bad_options = "C" if m.needed_options == "F" else "F"
     # Shape, dtype and the order need to be correct for a TensorMap cast
     with pytest.raises(
         TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
@@ -173,19 +171,19 @@ def test_bad_python_to_cpp_casts(m):
             np.zeros((3, 5), dtype=np.float64, order=m.needed_options)
         )
 
+    temp = np.zeros((3, 5, 2), dtype=np.float64, order=m.needed_options)
     with pytest.raises(
         TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
     ):
-        temp = np.zeros((3, 5, 2), dtype=np.float64, order=m.needed_options)
         m.round_trip_view_tensor(
             temp[:, ::-1, :],
         )
 
+    temp = np.zeros((3, 5, 2), dtype=np.float64, order=m.needed_options)
+    temp.setflags(write=False)
     with pytest.raises(
         TypeError, match=r"^round_trip_view_tensor\(\): incompatible function arguments"
     ):
-        temp = np.zeros((3, 5, 2), dtype=np.float64, order=m.needed_options)
-        temp.setflags(write=False)
         m.round_trip_view_tensor(temp)
 
 
@@ -282,9 +280,9 @@ def test_doc_string(m, doc):
     order_flag = f"flags.{m.needed_options.lower()}_contiguous"
     assert doc(m.round_trip_view_tensor) == (
         f"round_trip_view_tensor(arg0: numpy.ndarray[numpy.float64[?, ?, ?], flags.writeable, {order_flag}])"
-        + f" -> numpy.ndarray[numpy.float64[?, ?, ?], flags.writeable, {order_flag}]"
+        f" -> numpy.ndarray[numpy.float64[?, ?, ?], flags.writeable, {order_flag}]"
     )
     assert doc(m.round_trip_const_view_tensor) == (
         f"round_trip_const_view_tensor(arg0: numpy.ndarray[numpy.float64[?, ?, ?], {order_flag}])"
-        + " -> numpy.ndarray[numpy.float64[?, ?, ?]]"
+        " -> numpy.ndarray[numpy.float64[?, ?, ?]]"
     )
diff --git a/tests/test_enum.py b/tests/test_enum.py
index f14a72398f..4e85d29c31 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -1,3 +1,5 @@
+# ruff: noqa: SIM201 SIM300 SIM202
+
 import pytest
 
 from pybind11_tests import enums as m
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 8bcefe3de6..7f80a5da56 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -94,8 +94,7 @@ def ignore_pytest_unraisable_warning(f):
     if hasattr(pytest, unraisable):  # Python >= 3.8 and pytest >= 6
         dec = pytest.mark.filterwarnings(f"ignore::pytest.{unraisable}")
         return dec(f)
-    else:
-        return f
+    return f
 
 
 # TODO: find out why this fails on PyPy, https://foss.heptapod.net/pypy/pypy/-/issues/3583
@@ -183,7 +182,7 @@ def test_custom(msg):
         m.throws5_1()
     assert msg(excinfo.value) == "MyException5 subclass"
 
-    with pytest.raises(m.MyException5) as excinfo:
+    with pytest.raises(m.MyException5) as excinfo:  # noqa: PT012
         try:
             m.throws5()
         except m.MyException5_1 as err:
@@ -212,7 +211,7 @@ def throw_myex5():
         m.try_catch(m.MyException5, throw_myex)
     assert str(excinfo.value) == "nested error"
 
-    def pycatch(exctype, f, *args):
+    def pycatch(exctype, f, *args):  # noqa: ARG001
         try:
             f(*args)
         except m.MyException as e:
@@ -303,12 +302,12 @@ def __str__(self):
 
 
 @pytest.mark.parametrize(
-    "exc_type, exc_value, expected_what",
-    (
+    ("exc_type", "exc_value", "expected_what"),
+    [
         (ValueError, "plain_str", "ValueError: plain_str"),
         (ValueError, ("tuple_elem",), "ValueError: tuple_elem"),
         (FlakyException, ("happy",), "FlakyException: FlakyException.__str__"),
-    ),
+    ],
 )
 def test_error_already_set_what_with_happy_exceptions(
     exc_type, exc_value, expected_what
@@ -342,10 +341,7 @@ def test_flaky_exception_failure_point_str():
     )
     assert not py_err_set_after_what
     lines = what.splitlines()
-    if env.PYPY and len(lines) == 3:
-        n = 3  # Traceback is missing.
-    else:
-        n = 5
+    n = 3 if env.PYPY and len(lines) == 3 else 5
     assert (
         lines[:n]
         == [
diff --git a/tests/test_factory_constructors.py b/tests/test_factory_constructors.py
index 120a587c45..04df80260d 100644
--- a/tests/test_factory_constructors.py
+++ b/tests/test_factory_constructors.py
@@ -96,7 +96,7 @@ def test_init_factory_signature(msg):
         3. __init__(self: m.factory_constructors.TestFactory1, arg0: m.factory_constructors.tag.pointer_tag) -> None
 
         4. __init__(self: m.factory_constructors.TestFactory1, arg0: handle, arg1: int, arg2: handle) -> None
-    """  # noqa: E501 line too long
+    """
     )
 
 
diff --git a/tests/test_gil_scoped.py b/tests/test_gil_scoped.py
index 6af6a472d5..fc8af9b77c 100644
--- a/tests/test_gil_scoped.py
+++ b/tests/test_gil_scoped.py
@@ -148,10 +148,7 @@ def _intentional_deadlock():
 
 
 def _run_in_process(target, *args, **kwargs):
-    if len(args) == 0:
-        test_fn = target
-    else:
-        test_fn = args[0]
+    test_fn = target if len(args) == 0 else args[0]
     # Do not need to wait much, 10s should be more than enough.
     timeout = 0.1 if test_fn is _intentional_deadlock else 10
     process = multiprocessing.Process(target=target, args=args, kwargs=kwargs)
@@ -178,7 +175,8 @@ def _run_in_process(target, *args, **kwargs):
         elif test_fn is _intentional_deadlock:
             assert process.exitcode is None
             return 0
-        elif process.exitcode is None:
+
+        if process.exitcode is None:
             assert t_delta > 0.9 * timeout
             msg = "DEADLOCK, most likely, exactly what this test is meant to detect."
             if env.PYPY and env.WIN:
diff --git a/tests/test_iostream.py b/tests/test_iostream.py
index 5bbdf6955d..79b2a2b8cc 100644
--- a/tests/test_iostream.py
+++ b/tests/test_iostream.py
@@ -224,9 +224,8 @@ def test_redirect(capfd):
     assert stream.getvalue() == ""
 
     stream = StringIO()
-    with redirect_stdout(stream):
-        with m.ostream_redirect():
-            m.raw_output(msg)
+    with redirect_stdout(stream), m.ostream_redirect():
+        m.raw_output(msg)
     stdout, stderr = capfd.readouterr()
     assert stdout == ""
     assert stream.getvalue() == msg
@@ -244,10 +243,9 @@ def test_redirect_err(capfd):
     msg2 = "StdErr"
 
     stream = StringIO()
-    with redirect_stderr(stream):
-        with m.ostream_redirect(stdout=False):
-            m.raw_output(msg)
-            m.raw_err(msg2)
+    with redirect_stderr(stream), m.ostream_redirect(stdout=False):
+        m.raw_output(msg)
+        m.raw_err(msg2)
     stdout, stderr = capfd.readouterr()
     assert stdout == msg
     assert stderr == ""
@@ -260,11 +258,9 @@ def test_redirect_both(capfd):
 
     stream = StringIO()
     stream2 = StringIO()
-    with redirect_stdout(stream):
-        with redirect_stderr(stream2):
-            with m.ostream_redirect():
-                m.raw_output(msg)
-                m.raw_err(msg2)
+    with redirect_stdout(stream), redirect_stderr(stream2), m.ostream_redirect():
+        m.raw_output(msg)
+        m.raw_err(msg2)
     stdout, stderr = capfd.readouterr()
     assert stdout == ""
     assert stderr == ""
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index ab7017886e..7174726fce 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -25,7 +25,7 @@ def test_function_signatures(doc):
     )
 
 
-def test_named_arguments(msg):
+def test_named_arguments():
     assert m.kw_func0(5, 10) == "x=5, y=10"
 
     assert m.kw_func1(5, 10) == "x=5, y=10"
@@ -43,8 +43,7 @@ def test_named_arguments(msg):
         # noinspection PyArgumentList
         m.kw_func2(x=5, y=10, z=12)
     assert excinfo.match(
-        r"(?s)^kw_func2\(\): incompatible.*Invoked with: kwargs: ((x=5|y=10|z=12)(, |$))"
-        + "{3}$"
+        r"(?s)^kw_func2\(\): incompatible.*Invoked with: kwargs: ((x=5|y=10|z=12)(, |$)){3}$"
     )
 
     assert m.kw_func4() == "{13 17}"
@@ -59,7 +58,7 @@ def test_arg_and_kwargs():
     assert m.args_function(*args) == args
 
     args = "a1", "a2"
-    kwargs = dict(arg3="a3", arg4=4)
+    kwargs = {"arg3": "a3", "arg4": 4}
     assert m.args_kwargs_function(*args, **kwargs) == (args, kwargs)
 
 
@@ -177,7 +176,7 @@ def test_mixed_args_and_kwargs(msg):
 
     assert (
         m.args_kwonly_kwargs_defaults.__doc__
-        == "args_kwonly_kwargs_defaults(i: int = 1, j: float = 3.14159, *args, z: int = 42, **kwargs) -> tuple\n"  # noqa: E501 line too long
+        == "args_kwonly_kwargs_defaults(i: int = 1, j: float = 3.14159, *args, z: int = 42, **kwargs) -> tuple\n"
     )
     assert m.args_kwonly_kwargs_defaults() == (1, 3.14159, (), 42, {})
     assert m.args_kwonly_kwargs_defaults(2) == (2, 3.14159, (), 42, {})
@@ -233,15 +232,15 @@ def test_keyword_only_args(msg):
     x.method(i=1, j=2)
     assert (
         m.first_arg_kw_only.__init__.__doc__
-        == "__init__(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, *, i: int = 0) -> None\n"  # noqa: E501 line too long
+        == "__init__(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, *, i: int = 0) -> None\n"
     )
     assert (
         m.first_arg_kw_only.method.__doc__
-        == "method(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, *, i: int = 1, j: int = 2) -> None\n"  # noqa: E501 line too long
+        == "method(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, *, i: int = 1, j: int = 2) -> None\n"
     )
 
 
-def test_positional_only_args(msg):
+def test_positional_only_args():
     assert m.pos_only_all(1, 2) == (1, 2)
     assert m.pos_only_all(2, 1) == (2, 1)
 
@@ -283,7 +282,7 @@ def test_positional_only_args(msg):
     # Mix it with args and kwargs:
     assert (
         m.args_kwonly_full_monty.__doc__
-        == "args_kwonly_full_monty(arg0: int = 1, arg1: int = 2, /, j: float = 3.14159, *args, z: int = 42, **kwargs) -> tuple\n"  # noqa: E501 line too long
+        == "args_kwonly_full_monty(arg0: int = 1, arg1: int = 2, /, j: float = 3.14159, *args, z: int = 42, **kwargs) -> tuple\n"
     )
     assert m.args_kwonly_full_monty() == (1, 2, 3.14159, (), 42, {})
     assert m.args_kwonly_full_monty(8) == (8, 2, 3.14159, (), 42, {})
@@ -326,18 +325,18 @@ def test_positional_only_args(msg):
     # https://github.com/pybind/pybind11/pull/3402#issuecomment-963341987
     assert (
         m.first_arg_kw_only.pos_only.__doc__
-        == "pos_only(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, /, i: int, j: int) -> None\n"  # noqa: E501 line too long
+        == "pos_only(self: pybind11_tests.kwargs_and_defaults.first_arg_kw_only, /, i: int, j: int) -> None\n"
     )
 
 
 def test_signatures():
-    assert "kw_only_all(*, i: int, j: int) -> tuple\n" == m.kw_only_all.__doc__
-    assert "kw_only_mixed(i: int, *, j: int) -> tuple\n" == m.kw_only_mixed.__doc__
-    assert "pos_only_all(i: int, j: int, /) -> tuple\n" == m.pos_only_all.__doc__
-    assert "pos_only_mix(i: int, /, j: int) -> tuple\n" == m.pos_only_mix.__doc__
+    assert m.kw_only_all.__doc__ == "kw_only_all(*, i: int, j: int) -> tuple\n"
+    assert m.kw_only_mixed.__doc__ == "kw_only_mixed(i: int, *, j: int) -> tuple\n"
+    assert m.pos_only_all.__doc__ == "pos_only_all(i: int, j: int, /) -> tuple\n"
+    assert m.pos_only_mix.__doc__ == "pos_only_mix(i: int, /, j: int) -> tuple\n"
     assert (
-        "pos_kw_only_mix(i: int, /, j: int, *, k: int) -> tuple\n"
-        == m.pos_kw_only_mix.__doc__
+        m.pos_kw_only_mix.__doc__
+        == "pos_kw_only_mix(i: int, /, j: int, *, k: int) -> tuple\n"
     )
 
 
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 0a2ae1239a..a854685750 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -183,9 +183,9 @@ def test_static_properties():
 
     # Only static attributes can be deleted
     del m.TestPropertiesOverride.def_readonly_static
+    assert hasattr(m.TestPropertiesOverride, "def_readonly_static")
     assert (
-        hasattr(m.TestPropertiesOverride, "def_readonly_static")
-        and m.TestPropertiesOverride.def_readonly_static
+        m.TestPropertiesOverride.def_readonly_static
         is m.TestProperties.def_readonly_static
     )
     assert "def_readonly_static" not in m.TestPropertiesOverride.__dict__
@@ -256,10 +256,7 @@ def test_no_mixed_overloads():
 
 @pytest.mark.parametrize("access", ["ro", "rw", "static_ro", "static_rw"])
 def test_property_return_value_policies(access):
-    if not access.startswith("static"):
-        obj = m.TestPropRVP()
-    else:
-        obj = m.TestPropRVP
+    obj = m.TestPropRVP() if not access.startswith("static") else m.TestPropRVP
 
     ref = getattr(obj, access + "_ref")
     assert ref.value == 1
diff --git a/tests/test_modules.py b/tests/test_modules.py
index c3e8cea6e1..3d73e3fbd2 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -1,3 +1,5 @@
+import builtins
+
 import pytest
 
 import env
@@ -86,12 +88,7 @@ def test_builtin_key_type():
 
     Previous versions of pybind11 would add a unicode key in python 2.
     """
-    if hasattr(__builtins__, "keys"):
-        keys = __builtins__.keys()
-    else:  # this is to make pypy happy since builtins is different there.
-        keys = __builtins__.__dict__.keys()
-
-    assert {type(k) for k in keys} == {str}
+    assert all(type(k) == str for k in dir(builtins))
 
 
 @pytest.mark.xfail("env.PYPY", reason="PyModule_GetName()")
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index cdec9ad60b..070813d3a2 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -22,7 +22,7 @@ def test_dtypes():
             )
 
 
-@pytest.fixture(scope="function")
+@pytest.fixture()
 def arr():
     return np.array([[1, 2, 3], [4, 5, 6]], "=u2")
 
@@ -67,7 +67,7 @@ def test_array_attributes():
 
 
 @pytest.mark.parametrize(
-    "args, ret", [([], 0), ([0], 0), ([1], 3), ([0, 1], 1), ([1, 2], 5)]
+    ("args", "ret"), [([], 0), ([0], 0), ([1], 3), ([0, 1], 1), ([1, 2], 5)]
 )
 def test_index_offset(arr, args, ret):
     assert m.index_at(arr, *args) == ret
@@ -93,7 +93,7 @@ def test_dim_check_fail(arr):
 
 
 @pytest.mark.parametrize(
-    "args, ret",
+    ("args", "ret"),
     [
         ([], [1, 2, 3, 4, 5, 6]),
         ([1], [4, 5, 6]),
@@ -211,12 +211,14 @@ def assert_references(a, b, base=None):
             assert b[0, 0] == 1234
 
     a1 = np.array([1, 2], dtype=np.int16)
-    assert a1.flags.owndata and a1.base is None
+    assert a1.flags.owndata
+    assert a1.base is None
     a2 = m.wrap(a1)
     assert_references(a1, a2)
 
     a1 = np.array([[1, 2], [3, 4]], dtype=np.float32, order="F")
-    assert a1.flags.owndata and a1.base is None
+    assert a1.flags.owndata
+    assert a1.base is None
     a2 = m.wrap(a1)
     assert_references(a1, a2)
 
@@ -451,13 +453,15 @@ def test_array_resize():
     try:
         m.array_resize3(a, 3, True)
     except ValueError as e:
-        assert str(e).startswith("cannot resize an array")
+        assert str(e).startswith("cannot resize an array")  # noqa: PT017
     # transposed array doesn't own data
     b = a.transpose()
     try:
         m.array_resize3(b, 3, False)
     except ValueError as e:
-        assert str(e).startswith("cannot resize this array: it does not own its data")
+        assert str(e).startswith(  # noqa: PT017
+            "cannot resize this array: it does not own its data"
+        )
     # ... but reshape should be fine
     m.array_reshape2(b)
     assert b.shape == (8, 8)
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index fcfd587b18..d10457eeb2 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -130,14 +130,10 @@ def test_dtype(simple_dtype):
         partial_nested_fmt(),
         "[('a','S3'),('b','S3')]",
         (
-            "{{'names':['a','b','c','d'],"
-            + "'formats':[('S4',(3,)),('"
-            + e
-            + "i4',(2,)),('u1',(3,)),('"
-            + e
-            + "f4',(4,2))],"
-            + "'offsets':[0,12,20,24],'itemsize':56}}"
-        ).format(e=e),
+            "{'names':['a','b','c','d'],"
+            f"'formats':[('S4',(3,)),('{e}i4',(2,)),('u1',(3,)),('{e}f4',(4,2))],"
+            "'offsets':[0,12,20,24],'itemsize':56}"
+        ),
         "[('e1','" + e + "i8'),('e2','u1')]",
         "[('x','i1'),('y','" + e + "u8')]",
         "[('cflt','" + e + "c8'),('cdbl','" + e + "c16')]",
@@ -291,19 +287,17 @@ def test_array_array():
 
     arr = m.create_array_array(3)
     assert str(arr.dtype).replace(" ", "") == (
-        "{{'names':['a','b','c','d'],"
-        + "'formats':[('S4',(3,)),('"
-        + e
-        + "i4',(2,)),('u1',(3,)),('{e}f4',(4,2))],"
-        + "'offsets':[0,12,20,24],'itemsize':56}}"
-    ).format(e=e)
+        "{'names':['a','b','c','d'],"
+        f"'formats':[('S4',(3,)),('{e}i4',(2,)),('u1',(3,)),('{e}f4',(4,2))],"
+        "'offsets':[0,12,20,24],'itemsize':56}"
+    )
     assert m.print_array_array(arr) == [
         "a={{A,B,C,D},{K,L,M,N},{U,V,W,X}},b={0,1},"
-        + "c={0,1,2},d={{0,1},{10,11},{20,21},{30,31}}",
+        "c={0,1,2},d={{0,1},{10,11},{20,21},{30,31}}",
         "a={{W,X,Y,Z},{G,H,I,J},{Q,R,S,T}},b={1000,1001},"
-        + "c={10,11,12},d={{100,101},{110,111},{120,121},{130,131}}",
+        "c={10,11,12},d={{100,101},{110,111},{120,121},{130,131}}",
         "a={{S,T,U,V},{C,D,E,F},{M,N,O,P}},b={2000,2001},"
-        + "c={20,21,22},d={{200,201},{210,211},{220,221},{230,231}}",
+        "c={20,21,22},d={{200,201},{210,211},{220,221},{230,231}}",
     ]
     assert arr["a"].tolist() == [
         [b"ABCD", b"KLMN", b"UVWX"],
diff --git a/tests/test_numpy_vectorize.py b/tests/test_numpy_vectorize.py
index 7e8c015c46..f1e8b62540 100644
--- a/tests/test_numpy_vectorize.py
+++ b/tests/test_numpy_vectorize.py
@@ -149,7 +149,7 @@ def test_docs(doc):
         doc(m.vectorized_func)
         == """
         vectorized_func(arg0: numpy.ndarray[numpy.int32], arg1: numpy.ndarray[numpy.float32], arg2: numpy.ndarray[numpy.float64]) -> object
-    """  # noqa: E501 line too long
+    """
     )
 
 
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index a1a80a2933..946b941402 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -15,7 +15,7 @@ def test_obj_class_name():
     assert m.obj_class_name([]) == "list"
 
 
-def test_handle_from_move_only_type_with_operator_PyObject():  # noqa: N802
+def test_handle_from_move_only_type_with_operator_PyObject():
     assert m.handle_from_move_only_type_with_operator_PyObject_ncnst()
     assert m.handle_from_move_only_type_with_operator_PyObject_const()
 
@@ -33,7 +33,7 @@ def test_iterator(doc):
 
 
 @pytest.mark.parametrize(
-    "pytype, from_iter_func",
+    ("pytype", "from_iter_func"),
     [
         (frozenset, m.get_frozenset_from_iterable),
         (list, m.get_list_from_iterable),
@@ -87,7 +87,7 @@ def test_list(capture, doc):
     assert doc(m.print_list) == "print_list(arg0: list) -> None"
 
 
-def test_none(capture, doc):
+def test_none(doc):
     assert doc(m.get_none) == "get_none() -> None"
     assert doc(m.print_none) == "print_none(arg0: None) -> None"
 
@@ -182,10 +182,10 @@ def __contains__(self, m):
 
 
 @pytest.mark.parametrize(
-    "arg,func",
+    ("arg", "func"),
     [
         (set(), m.anyset_contains),
-        (dict(), m.dict_contains),
+        ({}, m.dict_contains),
         (CustomContains(), m.obj_contains),
     ],
 )
@@ -273,7 +273,7 @@ def test_bytes(doc):
     assert doc(m.bytes_from_str) == "bytes_from_str() -> bytes"
 
 
-def test_bytearray(doc):
+def test_bytearray():
     assert m.bytearray_from_char_ssize_t().decode() == "$%"
     assert m.bytearray_from_char_size_t().decode() == "@$!"
     assert m.bytearray_from_string().decode() == "foo"
@@ -385,7 +385,7 @@ def func(self, x, *args):
     assert d["implicit_list"] == [1, 2, 3]
     assert all(x in TestObject.__dict__ for x in d["implicit_dict"])
 
-    assert m.tuple_accessor(tuple()) == (0, 1, 2)
+    assert m.tuple_accessor(()) == (0, 1, 2)
 
     d = m.accessor_assignment()
     assert d["get"] == 0
@@ -593,7 +593,7 @@ def test_issue2361():
 
 
 @pytest.mark.parametrize(
-    "method, args, fmt, expected_view",
+    ("method", "args", "fmt", "expected_view"),
     [
         (m.test_memoryview_object, (b"red",), "B", b"red"),
         (m.test_memoryview_buffer_info, (b"green",), "B", b"green"),
@@ -651,7 +651,7 @@ def test_memoryview_from_memory():
 
 
 def test_builtin_functions():
-    assert m.get_len([i for i in range(42)]) == 42
+    assert m.get_len(list(range(42))) == 42
     with pytest.raises(TypeError) as exc_info:
         m.get_len(i for i in range(42))
     assert str(exc_info.value) in [
@@ -695,7 +695,7 @@ def test_pass_bytes_or_unicode_to_string_types():
 
 
 @pytest.mark.parametrize(
-    "create_weakref, create_weakref_with_callback",
+    ("create_weakref", "create_weakref_with_callback"),
     [
         (m.weakref_from_handle, m.weakref_from_handle_and_function),
         (m.weakref_from_object, m.weakref_from_object_and_function),
@@ -710,7 +710,7 @@ class WeaklyReferenced:
 
     callback_called = False
 
-    def callback(wr):
+    def callback(_):
         nonlocal callback_called
         callback_called = True
 
@@ -730,7 +730,7 @@ def callback(wr):
 
 
 @pytest.mark.parametrize(
-    "create_weakref, has_callback",
+    ("create_weakref", "has_callback"),
     [
         (m.weakref_from_handle, False),
         (m.weakref_from_object, False),
@@ -748,10 +748,7 @@ def callback(_):
     ob = C()
     # Should raise TypeError on CPython
     with pytest.raises(TypeError) if not env.PYPY else contextlib.nullcontext():
-        if has_callback:
-            _ = create_weakref(ob, callback)
-        else:
-            _ = create_weakref(ob)
+        _ = create_weakref(ob, callback) if has_callback else create_weakref(ob)
 
 
 def test_cpp_iterators():
@@ -814,33 +811,36 @@ def test_populate_obj_str_attrs():
 
 
 @pytest.mark.parametrize(
-    "a,b", [("foo", "bar"), (1, 2), (1.0, 2.0), (list(range(3)), list(range(3, 6)))]
+    ("a", "b"),
+    [("foo", "bar"), (1, 2), (1.0, 2.0), (list(range(3)), list(range(3, 6)))],
 )
 def test_inplace_append(a, b):
     expected = a + b
     assert m.inplace_append(a, b) == expected
 
 
-@pytest.mark.parametrize("a,b", [(3, 2), (3.0, 2.0), (set(range(3)), set(range(2)))])
+@pytest.mark.parametrize(
+    ("a", "b"), [(3, 2), (3.0, 2.0), (set(range(3)), set(range(2)))]
+)
 def test_inplace_subtract(a, b):
     expected = a - b
     assert m.inplace_subtract(a, b) == expected
 
 
-@pytest.mark.parametrize("a,b", [(3, 2), (3.0, 2.0), ([1], 3)])
+@pytest.mark.parametrize(("a", "b"), [(3, 2), (3.0, 2.0), ([1], 3)])
 def test_inplace_multiply(a, b):
     expected = a * b
     assert m.inplace_multiply(a, b) == expected
 
 
-@pytest.mark.parametrize("a,b", [(6, 3), (6.0, 3.0)])
+@pytest.mark.parametrize(("a", "b"), [(6, 3), (6.0, 3.0)])
 def test_inplace_divide(a, b):
     expected = a / b
     assert m.inplace_divide(a, b) == expected
 
 
 @pytest.mark.parametrize(
-    "a,b",
+    ("a", "b"),
     [
         (False, True),
         (
@@ -857,7 +857,7 @@ def test_inplace_or(a, b):
 
 
 @pytest.mark.parametrize(
-    "a,b",
+    ("a", "b"),
     [
         (True, False),
         (
@@ -873,13 +873,13 @@ def test_inplace_and(a, b):
     assert m.inplace_and(a, b) == expected
 
 
-@pytest.mark.parametrize("a,b", [(8, 1), (-3, 2)])
+@pytest.mark.parametrize(("a", "b"), [(8, 1), (-3, 2)])
 def test_inplace_lshift(a, b):
     expected = a << b
     assert m.inplace_lshift(a, b) == expected
 
 
-@pytest.mark.parametrize("a,b", [(8, 1), (-2, 2)])
+@pytest.mark.parametrize(("a", "b"), [(8, 1), (-2, 2)])
 def test_inplace_rshift(a, b):
     expected = a >> b
     assert m.inplace_rshift(a, b) == expected
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index de486e3e8e..dc129f2bff 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -1,5 +1,5 @@
 import pytest
-from pytest import approx
+from pytest import approx  # noqa: PT013
 
 from pybind11_tests import ConstructorStats
 from pybind11_tests import sequences_and_iterators as m
@@ -103,7 +103,8 @@ def test_sequence():
 
     assert "Sequence" in repr(s)
     assert len(s) == 5
-    assert s[0] == 0 and s[3] == 0
+    assert s[0] == 0
+    assert s[3] == 0
     assert 12.34 not in s
     s[0], s[3] = 12.34, 56.78
     assert 12.34 in s
@@ -245,7 +246,7 @@ def test_iterator_rvp():
 
 def test_carray_iterator():
     """#4100: Check for proper iterator overload with C-Arrays"""
-    args_gt = list(float(i) for i in range(3))
+    args_gt = [float(i) for i in range(3)]
     arr_h = m.CArrayHolder(*args_gt)
     args = list(arr_h)
     assert args_gt == args
diff --git a/tests/test_stl.py b/tests/test_stl.py
index d30c382113..b7a0d1c0d5 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -14,7 +14,7 @@ def test_vector(doc):
 
     assert m.cast_bool_vector() == [True, False]
     assert m.load_bool_vector([True, False])
-    assert m.load_bool_vector(tuple([True, False]))
+    assert m.load_bool_vector((True, False))
 
     assert doc(m.cast_vector) == "cast_vector() -> List[int]"
     assert doc(m.load_vector) == "load_vector(arg0: List[int]) -> bool"
@@ -23,7 +23,7 @@ def test_vector(doc):
     assert m.cast_ptr_vector() == ["lvalue", "lvalue"]
 
 
-def test_deque(doc):
+def test_deque():
     """std::deque <-> list"""
     lst = m.cast_deque()
     assert lst == [1]
@@ -95,7 +95,8 @@ def test_recursive_casting():
 
     # Issue #853 test case:
     z = m.cast_unique_ptr_vector()
-    assert z[0].value == 7 and z[1].value == 42
+    assert z[0].value == 7
+    assert z[1].value == 42
 
 
 def test_move_out_container():
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 9eb906f065..7dca742a9e 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -186,9 +186,9 @@ def test_map_string_double():
     um["ua"] = 1.1
     um["ub"] = 2.6
 
-    assert sorted(list(um)) == ["ua", "ub"]
+    assert sorted(um) == ["ua", "ub"]
     assert list(um.keys()) == list(um)
-    assert sorted(list(um.items())) == [("ua", 1.1), ("ub", 2.6)]
+    assert sorted(um.items()) == [("ua", 1.1), ("ub", 2.6)]
     assert list(zip(um.keys(), um.values())) == list(um.items())
     assert "UnorderedMapStringDouble" in str(um)
 
@@ -304,11 +304,11 @@ def test_map_delitem():
     um["ua"] = 1.1
     um["ub"] = 2.6
 
-    assert sorted(list(um)) == ["ua", "ub"]
-    assert sorted(list(um.items())) == [("ua", 1.1), ("ub", 2.6)]
+    assert sorted(um) == ["ua", "ub"]
+    assert sorted(um.items()) == [("ua", 1.1), ("ub", 2.6)]
     del um["ua"]
-    assert sorted(list(um)) == ["ub"]
-    assert sorted(list(um.items())) == [("ub", 2.6)]
+    assert sorted(um) == ["ub"]
+    assert sorted(um.items()) == [("ub", 2.6)]
 
 
 def test_map_view_types():
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index 4d00d3690d..c17af7df58 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -192,8 +192,7 @@ def test_move_support():
     class NCVirtExt(m.NCVirt):
         def get_noncopyable(self, a, b):
             # Constructs and returns a new instance:
-            nc = m.NonCopyable(a * a, b * b)
-            return nc
+            return m.NonCopyable(a * a, b * b)
 
         def get_movable(self, a, b):
             # Return a referenced copy
@@ -256,7 +255,7 @@ def dispatch(self):
     assert m.dispatch_issue_go(b) == "Yay.."
 
 
-def test_recursive_dispatch_issue(msg):
+def test_recursive_dispatch_issue():
     """#3357: Recursive dispatch fails to find python function override"""
 
     class Data(m.Data):
@@ -269,7 +268,7 @@ def __call__(self, first, second, visitor):
             # lambda is a workaround, which adds extra frame to the
             # current CPython thread. Removing lambda reveals the bug
             # [https://github.com/pybind/pybind11/issues/3357]
-            (lambda: visitor(Data(first.value + second.value)))()
+            (lambda: visitor(Data(first.value + second.value)))()  # noqa: PLC3002
 
     class StoreResultVisitor:
         def __init__(self):
diff --git a/tools/codespell_ignore_lines_from_errors.py b/tools/codespell_ignore_lines_from_errors.py
index 5403ec3ad0..4ec9add12d 100644
--- a/tools/codespell_ignore_lines_from_errors.py
+++ b/tools/codespell_ignore_lines_from_errors.py
@@ -17,14 +17,18 @@ def run(args: List[str]) -> None:
     assert len(args) == 1, "codespell_errors.txt"
     cache = {}
     done = set()
-    for line in sorted(open(args[0]).read().splitlines()):
+    with open(args[0]) as f:
+        lines = f.read().splitlines()
+
+    for line in sorted(lines):
         i = line.find(" ==> ")
         if i > 0:
             flds = line[:i].split(":")
             if len(flds) >= 2:
                 filename, line_num = flds[:2]
                 if filename not in cache:
-                    cache[filename] = open(filename).read().splitlines()
+                    with open(filename) as f:
+                        cache[filename] = f.read().splitlines()
                 supp = cache[filename][int(line_num) - 1]
                 if supp not in done:
                     print(supp)

From 3cc7e4258c15a6a19ba5e0b62a220b1a6196d4eb Mon Sep 17 00:00:00 2001
From: Eli Schwartz <eschwartz93@gmail.com>
Date: Thu, 23 Feb 2023 00:59:14 -0500
Subject: [PATCH 570/638] add --version option to pybind11-config (#4526)

Without this, it's impossible to get feature parity between detection
mechanisms. Both the pkg-config file and the cmake config set their
versions, but the python probe script didn't provide an option for this.

So you could print the compiler flags for using it, but you could not
check what you got.
---
 pybind11/__main__.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index e87b16beb4..180665c23c 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -4,6 +4,7 @@
 import sys
 import sysconfig
 
+from ._version import __version__
 from .commands import get_cmake_dir, get_include, get_pkgconfig_dir
 
 
@@ -25,6 +26,12 @@ def print_includes() -> None:
 
 def main() -> None:
     parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--version",
+        action="version",
+        version=__version__,
+        help="Print the version and exit.",
+    )
     parser.add_argument(
         "--includes",
         action="store_true",

From cbb876cc7b02c5f57e715cbc2c46ead3d1fbcf79 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 7 Mar 2023 00:34:41 -0500
Subject: [PATCH 571/638] chore(deps): update pre-commit hooks (#4552)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/charliermarsh/ruff-pre-commit: v0.0.251 → v0.0.254](https://github.com/charliermarsh/ruff-pre-commit/compare/v0.0.251...v0.0.254)
- [github.com/PyCQA/pylint: v2.16.1 → v2.16.4](https://github.com/PyCQA/pylint/compare/v2.16.1...v2.16.4)
- [github.com/pre-commit/mirrors-mypy: v0.991 → v1.0.1](https://github.com/pre-commit/mirrors-mypy/compare/v0.991...v1.0.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2255f2e4d5..7c43161921 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -68,7 +68,7 @@ repos:
 
 # Ruff, the Python auto-correcting linter written in Rust
 - repo: https://github.com/charliermarsh/ruff-pre-commit
-  rev: v0.0.251
+  rev: v0.0.254
   hooks:
   - id: ruff
     args: ["--fix", "--show-fixes"]
@@ -84,7 +84,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.16.1"
+  rev: "v2.16.4"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -100,7 +100,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v0.991"
+  rev: "v1.0.1"
   hooks:
   - id: mypy
     args: []

From 442261da585536521ff459b1457b2904895f23b4 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 9 Mar 2023 13:02:34 -0800
Subject: [PATCH 572/638] Remove test code that does not exercise anything in
 pybind11, but breaks between Python 3.12alpha3 (still working) and 3.12alpha6
 (broken): (#4559)

```
str(OrderedDict([(1, "a"), (2, "b")]))
```

Old:
```
OrderedDict([(1, 'a'), (2, 'b')])
```

New:
```
OrderedDict({1: 'a', 2: 'b'})
```

See also: https://github.com/python/cpython/issues/101446
---
 tests/test_modules.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/test_modules.py b/tests/test_modules.py
index 3d73e3fbd2..2f6d825b79 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -63,7 +63,6 @@ def test_importing():
     from pybind11_tests.modules import OD
 
     assert OD is OrderedDict
-    assert str(OD([(1, "a"), (2, "b")])) == "OrderedDict([(1, 'a'), (2, 'b')])"
 
 
 def test_pydoc():

From 04ef4e422980ce1406a76358cbb74e7e3fd23a21 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 16 Mar 2023 18:18:44 +0000
Subject: [PATCH 573/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.6.4 to 1.8.1 (#4576)

---
 .github/workflows/pip.yml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 7c6fc67a3e..3d4d2c6548 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.6.4
+      uses: pypa/gh-action-pypi-publish@v1.8.1
       with:
         password: ${{ secrets.pypi_password }}
-        packages_dir: standard/
+        packages-dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.6.4
+      uses: pypa/gh-action-pypi-publish@v1.8.1
       with:
         password: ${{ secrets.pypi_password_global }}
-        packages_dir: global/
+        packages-dir: global/

From c4c15d4b109b7870319818d0f17fc0b4357ff631 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 16 Mar 2023 13:01:28 -0700
Subject: [PATCH 574/638] docs: changelog for 2.10.4 (#4532)

* docs: changelog for 2.10.4

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Apply suggestions from code review

* Update docs/changelog.rst

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index bb111c5f26..58cc409839 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -21,11 +21,47 @@ Changes:
   ``dec_ref()`` are now enabled by default again.
   `#4246 <https://github.com/pybind/pybind11/pull/4246>`_
 
+* ``py::initialize_interpreter()`` using ``PyConfig_InitPythonConfig()``
+  instead of ``PyConfig_InitIsolatedConfig()``, to obtain complete
+  ``sys.path``.
+  `#4473 <https://github.com/pybind/pybind11/pull/4473>`_
+
+* Cast errors now always include Python type information, even if
+  ``PYBIND11_DETAILED_ERROR_MESSAGES`` is not defined. This increases binary
+  sizes slightly (~1.5%) but the error messages are much more informative.
+  `#4463 <https://github.com/pybind/pybind11/pull/4463>`_
+
+
 Build system improvements:
 
 * Update clang-tidy to 15 in CI.
   `#4387 <https://github.com/pybind/pybind11/pull/4387>`_
 
+* Moved the linting framework over to Ruff.
+  `#4483 <https://github.com/pybind/pybind11/pull/4483>`_
+
+Version 2.10.4 (Mar 16, 2023)
+----------------------------
+
+Changes:
+
+* ``python3 -m pybind11`` gained a ``--version`` option (prints the version and
+  exits).
+  `#4526 <https://github.com/pybind/pybind11/pull/4526>`_
+
+Bug Fixes:
+
+* Fix a warning when pydebug is enabled on Python 3.11.
+  `#4461 <https://github.com/pybind/pybind11/pull/4461>`_
+
+* Ensure ``gil_scoped_release`` RAII is non-copyable.
+  `#4490 <https://github.com/pybind/pybind11/pull/4490>`_
+
+* Ensure the tests dir does not show up with new versions of setuptools.
+  `#4510 <https://github.com/pybind/pybind11/pull/4510>`_
+
+* Better stacklevel for a warning in setuptools helpers.
+  `#4516 <https://github.com/pybind/pybind11/pull/4516>`_
 
 Version 2.10.3 (Jan 3, 2023)
 ----------------------------

From cf7d2e6f15be7622515a77466e84bd9414737680 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 16 Mar 2023 14:33:34 -0700
Subject: [PATCH 575/638] Change `always_forkserver_on_unix()` to
 `use_multiprocessing_forkserver_on_linux()` (#4577)

---
 tests/conftest.py | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tests/conftest.py b/tests/conftest.py
index b60d3c956b..ad5b47b4b3 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -8,8 +8,8 @@
 import difflib
 import gc
 import multiprocessing
-import os
 import re
+import sys
 import textwrap
 import traceback
 
@@ -25,8 +25,9 @@
 
 
 @pytest.fixture(scope="session", autouse=True)
-def always_forkserver_on_unix():
-    if os.name == "nt":
+def use_multiprocessing_forkserver_on_linux():
+    if sys.platform != "linux":
+        # The default on Windows and macOS is "spawn": If it's not broken, don't fix it.
         return
 
     # Full background: https://github.com/pybind/pybind11/issues/4105#issuecomment-1301004592
@@ -34,8 +35,6 @@ def always_forkserver_on_unix():
     # It is actually a well-known pitfall, unfortunately without guard rails.
     # "forkserver" is more performant than "spawn" (~9s vs ~13s for tests/test_gil_scoped.py,
     # visit the issuecomment link above for details).
-    # Windows does not have fork() and the associated pitfall, therefore it is best left
-    # running with defaults.
     multiprocessing.set_start_method("forkserver")
 
 

From 286873ecf72f03df3a177a45d9dd4e9c678b2bdf Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Thu, 23 Mar 2023 10:23:52 -0400
Subject: [PATCH 576/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.8.1 to 1.8.3 (#4584)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.8.1 to 1.8.3.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.8.1...v1.8.3)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 3d4d2c6548..d5427c7961 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.8.1
+      uses: pypa/gh-action-pypi-publish@v1.8.3
       with:
         password: ${{ secrets.pypi_password }}
         packages-dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.8.1
+      uses: pypa/gh-action-pypi-publish@v1.8.3
       with:
         password: ${{ secrets.pypi_password_global }}
         packages-dir: global/

From 5bbcba548a27baf8d6bfb7993e814da24b432dbf Mon Sep 17 00:00:00 2001
From: Konstantin Bespalov <kos5tya@yandex.ru>
Date: Fri, 24 Mar 2023 06:01:09 +0100
Subject: [PATCH 577/638] use C++17 syntax to get rid of recursive template
 instantiations for concatenating type signatures (#4587)

---
 include/pybind11/detail/descr.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index e7a5e2c145..85259d488e 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -143,11 +143,24 @@ constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) {
     return descr;
 }
 
+#if defined(PYBIND11_CPP17)
+template <size_t N1, size_t N2, typename... Ts1, typename... Ts2>
+constexpr descr<N1 + N2 + 2, Ts1..., Ts2...> operator,(const descr<N1, Ts1...> &a,
+                                                       const descr<N2, Ts2...> &b) {
+    return a + const_name(", ") + b;
+}
+
+template <size_t N, typename... Ts, typename... Args>
+constexpr auto concat(const descr<N, Ts...> &d, const Args &...args) {
+    return (d, ..., args);
+}
+#else
 template <size_t N, typename... Ts, typename... Args>
 constexpr auto concat(const descr<N, Ts...> &d, const Args &...args)
     -> decltype(std::declval<descr<N + 2, Ts...>>() + concat(args...)) {
     return d + const_name(", ") + concat(args...);
 }
+#endif
 
 template <size_t N, typename... Ts>
 constexpr descr<N + 2, Ts...> type_descr(const descr<N, Ts...> &descr) {

From 66f12df03b33a3ea32c82b0d0af7c303cf17d50e Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 27 Mar 2023 10:59:56 -0400
Subject: [PATCH 578/638] chore: make #4587 use proper cpp17 feature macro
 (#4592)

---
 include/pybind11/detail/descr.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 85259d488e..635614b0d6 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -143,7 +143,7 @@ constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) {
     return descr;
 }
 
-#if defined(PYBIND11_CPP17)
+#ifdef __cpp_fold_expressions
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2>
 constexpr descr<N1 + N2 + 2, Ts1..., Ts2...> operator,(const descr<N1, Ts1...> &a,
                                                        const descr<N2, Ts2...> &b) {

From 1e8b52a9acea1aa7a322fe6a87049c4828e439f9 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Mon, 27 Mar 2023 20:21:06 -0400
Subject: [PATCH 579/638] bugfix: allow noexcept lambdas in C++17. Fix #4565
 (#4593)

* bugfix: allow noexcept lambdas in CPP17. Fix #4565

* Remove unused code from test case

* Fix clang-tidy error

* Address reviewer comment
---
 include/pybind11/detail/common.h       | 11 ++++++++++-
 tests/test_constants_and_functions.cpp |  3 +++
 tests/test_constants_and_functions.py  |  4 ++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1032293d21..129039252f 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -754,7 +754,16 @@ template <typename C, typename R, typename... A>
 struct remove_class<R (C::*)(A...) const> {
     using type = R(A...);
 };
-
+#ifdef __cpp_noexcept_function_type
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...) noexcept> {
+    using type = R(A...);
+};
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...) const noexcept> {
+    using type = R(A...);
+};
+#endif
 /// Helper template to strip away type modifiers
 template <typename T>
 struct intrinsic_type {
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index 922375c5ea..312edca9e0 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -148,4 +148,7 @@ TEST_SUBMODULE(constants_and_functions, m) {
             py::arg_v("y", 42, "<the answer>"),
             py::arg_v("z", default_value));
     });
+
+    // test noexcept(true) lambda (#4565)
+    m.def("l1", []() noexcept(true) { return 0; });
 }
diff --git a/tests/test_constants_and_functions.py b/tests/test_constants_and_functions.py
index 5da0b84b8e..a1142461c0 100644
--- a/tests/test_constants_and_functions.py
+++ b/tests/test_constants_and_functions.py
@@ -50,3 +50,7 @@ def __repr__(self):
         m.register_large_capture_with_invalid_arguments(m)
     with pytest.raises(RuntimeError):
         m.register_with_raising_repr(m, RaisingRepr())
+
+
+def test_noexcept_lambda():
+    assert m.l1() == 0

From 654fe92652e6dc0eec80b1877b531aaab3a3e56c Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 27 Mar 2023 17:52:57 -0700
Subject: [PATCH 580/638] Introduce `get_python_state_dict()` for Python 3.12
 compatibility. (#4570)

* Introduce `get_python_state_dict()`

* Conditional version bump for Python 3.12+

* Shuffle subexpressions to make the condition easier to understand (no change to logic).

* Make pybind11 ABI version 5 the minimum for Python 3.12+ (as suggested by @Lalaland)

* Add back condition for PYPY_VERSION, but keep it open for future PyPy versions.

* Fall back to simple `|| defined(PYPY_VERSION)`. `PY_VERSION_HEX` does not appear to be meaningful with PyPy.
---
 include/pybind11/detail/internals.h   | 57 +++++++++++++++++++++++----
 include/pybind11/embed.h              | 10 ++---
 tests/test_embed/test_interpreter.cpp | 22 +++++------
 3 files changed, 64 insertions(+), 25 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 05e36ad18b..8364ebd1e0 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -34,9 +34,18 @@
 /// further ABI-incompatible changes may be made before the ABI is officially
 /// changed to the new version.
 #ifndef PYBIND11_INTERNALS_VERSION
-#    define PYBIND11_INTERNALS_VERSION 4
+#    if PY_VERSION_HEX >= 0x030C0000
+// Version bump for Python 3.12+, before first 3.12 beta release.
+#        define PYBIND11_INTERNALS_VERSION 5
+#    else
+#        define PYBIND11_INTERNALS_VERSION 4
+#    endif
 #endif
 
+// This requirement is mainly to reduce the support burden (see PR #4570).
+static_assert(PY_VERSION_HEX < 0x030C0000 || PYBIND11_INTERNALS_VERSION >= 5,
+              "pybind11 ABI version 5 is the minimum for Python 3.12+");
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 using ExceptionTranslator = void (*)(std::exception_ptr);
@@ -421,6 +430,38 @@ inline void translate_local_exception(std::exception_ptr p) {
 }
 #endif
 
+inline object get_python_state_dict() {
+    object state_dict;
+#if PYBIND11_INTERNALS_VERSION <= 4 || PY_VERSION_HEX < 0x03080000 || defined(PYPY_VERSION)
+    state_dict = reinterpret_borrow<object>(PyEval_GetBuiltins());
+#else
+#    if PY_VERSION_HEX < 0x03090000
+    PyInterpreterState *istate = _PyInterpreterState_Get();
+#    else
+    PyInterpreterState *istate = PyInterpreterState_Get();
+#    endif
+    if (istate) {
+        state_dict = reinterpret_borrow<object>(PyInterpreterState_GetDict(istate));
+    }
+#endif
+    if (!state_dict) {
+        raise_from(PyExc_SystemError, "pybind11::detail::get_python_state_dict() FAILED");
+    }
+    return state_dict;
+}
+
+inline object get_internals_obj_from_state_dict(handle state_dict) {
+    return reinterpret_borrow<object>(dict_getitemstring(state_dict.ptr(), PYBIND11_INTERNALS_ID));
+}
+
+inline internals **get_internals_pp_from_capsule(handle obj) {
+    void *raw_ptr = PyCapsule_GetPointer(obj.ptr(), /*name=*/nullptr);
+    if (raw_ptr == nullptr) {
+        raise_from(PyExc_SystemError, "pybind11::detail::get_internals_pp_from_capsule() FAILED");
+    }
+    return static_cast<internals **>(raw_ptr);
+}
+
 /// Return a reference to the current `internals` data
 PYBIND11_NOINLINE internals &get_internals() {
     auto **&internals_pp = get_internals_pp();
@@ -445,12 +486,12 @@ PYBIND11_NOINLINE internals &get_internals() {
 #endif
     error_scope err_scope;
 
-    PYBIND11_STR_TYPE id(PYBIND11_INTERNALS_ID);
-    auto builtins = handle(PyEval_GetBuiltins());
-    if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
-        internals_pp = static_cast<internals **>(capsule(builtins[id]));
-
-        // We loaded builtins through python's builtins, which means that our `error_already_set`
+    dict state_dict = get_python_state_dict();
+    if (object internals_obj = get_internals_obj_from_state_dict(state_dict)) {
+        internals_pp = get_internals_pp_from_capsule(internals_obj);
+    }
+    if (internals_pp && *internals_pp) {
+        // We loaded the internals through `state_dict`, which means that our `error_already_set`
         // and `builtin_exception` may be different local classes than the ones set up in the
         // initial exception translator, below, so add another for our local exception classes.
         //
@@ -484,7 +525,7 @@ PYBIND11_NOINLINE internals &get_internals() {
 #    endif
         internals_ptr->istate = tstate->interp;
 #endif
-        builtins[id] = capsule(internals_pp);
+        state_dict[PYBIND11_INTERNALS_ID] = capsule(internals_pp);
         internals_ptr->registered_exception_translators.push_front(&translate_exception);
         internals_ptr->static_property_type = make_static_property_type();
         internals_ptr->default_metaclass = make_default_metaclass();
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 5a175b1341..caa14f4a05 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -243,16 +243,14 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
 
  \endrst */
 inline void finalize_interpreter() {
-    handle builtins(PyEval_GetBuiltins());
-    const char *id = PYBIND11_INTERNALS_ID;
-
     // Get the internals pointer (without creating it if it doesn't exist).  It's possible for the
     // internals to be created during Py_Finalize() (e.g. if a py::capsule calls `get_internals()`
     // during destruction), so we get the pointer-pointer here and check it after Py_Finalize().
     detail::internals **internals_ptr_ptr = detail::get_internals_pp();
-    // It could also be stashed in builtins, so look there too:
-    if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
-        internals_ptr_ptr = capsule(builtins[id]);
+    // It could also be stashed in state_dict, so look there too:
+    if (object internals_obj
+        = get_internals_obj_from_state_dict(detail::get_python_state_dict())) {
+        internals_ptr_ptr = detail::get_internals_pp_from_capsule(internals_obj);
     }
     // Local internals contains data managed by the current interpreter, so we must clear them to
     // avoid undefined behaviors when initializing another interpreter
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index e54e822708..c6c8a22d98 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -255,10 +255,10 @@ TEST_CASE("Add program dir to path using PyConfig") {
 }
 #endif
 
-bool has_pybind11_internals_builtin() {
-    auto builtins = py::handle(PyEval_GetBuiltins());
-    return builtins.contains(PYBIND11_INTERNALS_ID);
-};
+bool has_state_dict_internals_obj() {
+    return bool(
+        py::detail::get_internals_obj_from_state_dict(py::detail::get_python_state_dict()));
+}
 
 bool has_pybind11_internals_static() {
     auto **&ipp = py::detail::get_internals_pp();
@@ -268,7 +268,7 @@ bool has_pybind11_internals_static() {
 TEST_CASE("Restart the interpreter") {
     // Verify pre-restart state.
     REQUIRE(py::module_::import("widget_module").attr("add")(1, 2).cast<int>() == 3);
-    REQUIRE(has_pybind11_internals_builtin());
+    REQUIRE(has_state_dict_internals_obj());
     REQUIRE(has_pybind11_internals_static());
     REQUIRE(py::module_::import("external_module").attr("A")(123).attr("value").cast<int>()
             == 123);
@@ -285,10 +285,10 @@ TEST_CASE("Restart the interpreter") {
     REQUIRE(Py_IsInitialized() == 1);
 
     // Internals are deleted after a restart.
-    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_state_dict_internals_obj());
     REQUIRE_FALSE(has_pybind11_internals_static());
     pybind11::detail::get_internals();
-    REQUIRE(has_pybind11_internals_builtin());
+    REQUIRE(has_state_dict_internals_obj());
     REQUIRE(has_pybind11_internals_static());
     REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp())
             == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
@@ -303,13 +303,13 @@ TEST_CASE("Restart the interpreter") {
               py::detail::get_internals();
               *static_cast<bool *>(ran) = true;
           });
-    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_state_dict_internals_obj());
     REQUIRE_FALSE(has_pybind11_internals_static());
     REQUIRE_FALSE(ran);
     py::finalize_interpreter();
     REQUIRE(ran);
     py::initialize_interpreter();
-    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_state_dict_internals_obj());
     REQUIRE_FALSE(has_pybind11_internals_static());
 
     // C++ modules can be reloaded.
@@ -331,7 +331,7 @@ TEST_CASE("Subinterpreter") {
 
         REQUIRE(m.attr("add")(1, 2).cast<int>() == 3);
     }
-    REQUIRE(has_pybind11_internals_builtin());
+    REQUIRE(has_state_dict_internals_obj());
     REQUIRE(has_pybind11_internals_static());
 
     /// Create and switch to a subinterpreter.
@@ -341,7 +341,7 @@ TEST_CASE("Subinterpreter") {
     // Subinterpreters get their own copy of builtins. detail::get_internals() still
     // works by returning from the static variable, i.e. all interpreters share a single
     // global pybind11::internals;
-    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_state_dict_internals_obj());
     REQUIRE(has_pybind11_internals_static());
 
     // Modules tags should be gone.

From 4ce05175d51a4685232452bdc1e9cbb13a240a65 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Thu, 30 Mar 2023 07:29:25 -0700
Subject: [PATCH 581/638] ci: Python 3.12 optional test job (#4575)

* ci: Python 3.12 optional testing

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Skip test_flaky_exception_failure_point_init() for Python 3.12.0a6 (similar to https://github.com/google/pywrapcc/commit/af5c6536aba77b1db99bb16995d3a684351efb93#diff-f46006e3f43ffb1dd5d6862005427f6620f4dcfb1fa2f883d8482550069eeecc).

* Disable tests/test_embed/test_interpreter.cpp (broken with Python 3.12.0alpha6)

```
free(): invalid pointer

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test_embed is a Catch v2.13.9 host application.
Run with -? for options

-------------------------------------------------------------------------------
Custom PyConfig
-------------------------------------------------------------------------------
/home/runner/work/pybind11/pybind11/tests/test_embed/test_interpreter.cpp:175
...............................................................................

/home/runner/work/pybind11/pybind11/tests/test_embed/test_interpreter.cpp:179: FAILED:
  {Unknown expression after the reported line}
due to a fatal error condition:
  SIGABRT - Abort (abnormal termination) signal

===============================================================================
test cases:    6 |    5 passed | 1 failed
assertions: 1518 | 1517 passed | 1 failed
```

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 .github/workflows/upstream.yml | 60 ++++++++++++++++------------------
 tests/test_exceptions.py       |  5 +++
 2 files changed, 34 insertions(+), 31 deletions(-)

diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index a15861ee47..b7e14f72e8 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -10,103 +10,101 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  PIP_ONLY_BINARY: numpy
+  PIP_ONLY_BINARY: ":all:"
   # For cmake:
   VERBOSE: 1
 
 jobs:
   standard:
-    name: "🐍 3.11 latest internals • ubuntu-latest • x64"
+    name: "🐍 3.12 latest • ubuntu-latest • x64"
     runs-on: ubuntu-latest
+    # Only runs when the  'python dev' label is selected
     if: "contains(github.event.pull_request.labels.*.name, 'python dev')"
 
     steps:
     - uses: actions/checkout@v3
 
-    - name: Setup Python 3.11
+    - name: Setup Python 3.12
       uses: actions/setup-python@v4
       with:
-        python-version: "3.11-dev"
+        python-version: "3.12-dev"
 
-    - name: Setup Boost (Linux)
-      if: runner.os == 'Linux'
+    - name: Setup Boost
       run: sudo apt-get install libboost-dev
 
     - name: Update CMake
       uses: jwlawson/actions-setup-cmake@v1.13
 
-    - name: Prepare env
+    - name: Run pip installs
       run: |
+        python -m pip install --upgrade pip
         python -m pip install -r tests/requirements.txt
 
-    - name: Setup annotations on Linux
-      if: runner.os == 'Linux'
-      run: python -m pip install pytest-github-actions-annotate-failures
+    - name: Show platform info
+      run: |
+        python -m platform
+        cmake --version
+        pip list
 
     # First build - C++11 mode and inplace
     - name: Configure C++11
       run: >
-        cmake -S . -B .
+        cmake -S . -B build11
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
+        -DCMAKE_BUILD_TYPE=Debug
 
     - name: Build C++11
-      run: cmake --build . -j 2
+      run: cmake --build build11 -j 2
 
     - name: Python tests C++11
-      run: cmake --build . --target pytest -j 2
+      run: cmake --build build11 --target pytest -j 2
 
-    - name: C++11 tests
-      run: cmake --build .  --target cpptest -j 2
+    # - name: C++11 tests
+    #   run: cmake --build build11  --target cpptest -j 2
 
     - name: Interface test C++11
-      run: cmake --build . --target test_cmake_build
-
-    - name: Clean directory
-      run: git clean -fdx
+      run: cmake --build build11 --target test_cmake_build
 
     # Second build - C++17 mode and in a build directory
     - name: Configure C++17
       run: >
-        cmake -S . -B build2
+        cmake -S . -B build17
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
-        ${{ matrix.args }}
-        ${{ matrix.args2 }}
 
     - name: Build
-      run: cmake --build build2 -j 2
+      run: cmake --build build17 -j 2
 
     - name: Python tests
-      run: cmake --build build2 --target pytest
+      run: cmake --build build17 --target pytest
 
-    - name: C++ tests
-      run: cmake --build build2 --target cpptest
+    # - name: C++ tests
+    #   run: cmake --build build17 --target cpptest
 
     # Third build - C++17 mode with unstable ABI
     - name: Configure (unstable ABI)
       run: >
-        cmake -S . -B build3
+        cmake -S . -B build17max
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         -DPYBIND11_INTERNALS_VERSION=10000000
         "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
-        ${{ matrix.args }}
 
     - name: Build (unstable ABI)
-      run: cmake --build build3 -j 2
+      run: cmake --build build17max -j 2
 
     - name: Python tests (unstable ABI)
-      run: cmake --build build3 --target pytest
+      run: cmake --build build17max --target pytest
 
     - name: Interface test
-      run: cmake --build build3 --target test_cmake_build
+      run: cmake --build build17max --target test_cmake_build
 
     # This makes sure the setup_helpers module can build packages using
     # setuptools
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 7f80a5da56..1b4c89add1 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -317,6 +317,11 @@ def test_error_already_set_what_with_happy_exceptions(
     assert what == expected_what
 
 
+@pytest.mark.skipif(
+    # Intentionally very specific:
+    "sys.version_info == (3, 12, 0, 'alpha', 6)",
+    reason="WIP: https://github.com/python/cpython/issues/102594",
+)
 @pytest.mark.skipif("env.PYPY", reason="PyErr_NormalizeException Segmentation fault")
 def test_flaky_exception_failure_point_init():
     with pytest.raises(RuntimeError) as excinfo:

From 7ab88d2e4fbb7fb21473f87b17b68a1f0e51cb4e Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 3 Apr 2023 10:18:53 -0400
Subject: [PATCH 582/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.8.3 to 1.8.4 (#4602)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.8.3 to 1.8.4.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.8.3...v1.8.4)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index d5427c7961..8ca6fd69ea 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.8.3
+      uses: pypa/gh-action-pypi-publish@v1.8.4
       with:
         password: ${{ secrets.pypi_password }}
         packages-dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.8.3
+      uses: pypa/gh-action-pypi-publish@v1.8.4
       with:
         password: ${{ secrets.pypi_password_global }}
         packages-dir: global/

From ed466da571fbc1d711351eb818e4bf82adb99eca Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Fri, 7 Apr 2023 15:52:41 -0400
Subject: [PATCH 583/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.8.4 to 1.8.5 (#4604)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.8.4 to 1.8.5.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.8.4...v1.8.5)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 8ca6fd69ea..7f686b13f9 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.8.4
+      uses: pypa/gh-action-pypi-publish@v1.8.5
       with:
         password: ${{ secrets.pypi_password }}
         packages-dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.8.4
+      uses: pypa/gh-action-pypi-publish@v1.8.5
       with:
         password: ${{ secrets.pypi_password_global }}
         packages-dir: global/

From 071f35ab85aa5d8d91ee3c5735a601fd3221d783 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sun, 23 Apr 2023 12:32:35 -0400
Subject: [PATCH 584/638] chore(deps): bump jwlawson/actions-setup-cmake from
 1.13 to 1.14 (#4632)

Bumps [jwlawson/actions-setup-cmake](https://github.com/jwlawson/actions-setup-cmake) from 1.13 to 1.14.
- [Release notes](https://github.com/jwlawson/actions-setup-cmake/releases)
- [Commits](https://github.com/jwlawson/actions-setup-cmake/compare/v1.13...v1.14)

---
updated-dependencies:
- dependency-name: jwlawson/actions-setup-cmake
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/ci.yml        | 16 ++++++++--------
 .github/workflows/configure.yml |  2 +-
 .github/workflows/upstream.yml  |  2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8befccdbc2..a6a9a16fa6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -82,7 +82,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -208,7 +208,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -474,7 +474,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Configure
       shell: bash
@@ -763,7 +763,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.12.1
@@ -816,7 +816,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.12.1
@@ -867,7 +867,7 @@ jobs:
         python3 -m pip install -r tests/requirements.txt
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Configure C++20
       run: >
@@ -1000,7 +1000,7 @@ jobs:
           python-version: ${{ matrix.python }}
 
       - name: Update CMake
-        uses: jwlawson/actions-setup-cmake@v1.13
+        uses: jwlawson/actions-setup-cmake@v1.14
 
       - name: Install ninja-build tool
         uses: seanmiddleditch/gha-setup-ninja@v3
@@ -1070,7 +1070,7 @@ jobs:
         run: clang++ --version
 
       - name: Update CMake
-        uses: jwlawson/actions-setup-cmake@v1.13
+        uses: jwlawson/actions-setup-cmake@v1.14
 
       - name: Run pip installs
         run: |
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 29b041168e..b469a69d11 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -55,7 +55,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
       with:
         cmake-version: ${{ matrix.cmake }}
 
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index b7e14f72e8..be3cd40502 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -33,7 +33,7 @@ jobs:
       run: sudo apt-get install libboost-dev
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.13
+      uses: jwlawson/actions-setup-cmake@v1.14
 
     - name: Run pip installs
       run: |

From 07725c28c0b1d68e044ccbc7820920c15c1f21e3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 24 Apr 2023 00:19:21 -0700
Subject: [PATCH 585/638] Introduce `pybind11::detail::is_move_constructible`
 (#4631)

To support the use case captured in the new test_vector_unique_ptr_member.cpp
---
 include/pybind11/cast.h                    |  4 +-
 include/pybind11/detail/init.h             |  4 +-
 include/pybind11/detail/type_caster_base.h |  5 +-
 tests/CMakeLists.txt                       |  1 +
 tests/test_vector_unique_ptr_member.cpp    | 56 ++++++++++++++++++++++
 tests/test_vector_unique_ptr_member.py     | 14 ++++++
 6 files changed, 79 insertions(+), 5 deletions(-)
 create mode 100644 tests/test_vector_unique_ptr_member.cpp
 create mode 100644 tests/test_vector_unique_ptr_member.py

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 9b013bc39f..9d1ce15d48 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -964,7 +964,7 @@ struct move_always<
     enable_if_t<
         all_of<move_is_plain_type<T>,
                negation<is_copy_constructible<T>>,
-               std::is_move_constructible<T>,
+               is_move_constructible<T>,
                std::is_same<decltype(std::declval<make_caster<T>>().operator T &()), T &>>::value>>
     : std::true_type {};
 template <typename T, typename SFINAE = void>
@@ -975,7 +975,7 @@ struct move_if_unreferenced<
     enable_if_t<
         all_of<move_is_plain_type<T>,
                negation<move_always<T>>,
-               std::is_move_constructible<T>,
+               is_move_constructible<T>,
                std::is_same<decltype(std::declval<make_caster<T>>().operator T &()), T &>>::value>>
     : std::true_type {};
 template <typename T>
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index 9f71278c26..e21171688c 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -175,7 +175,7 @@ void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
 template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
-    static_assert(std::is_move_constructible<Cpp<Class>>::value,
+    static_assert(is_move_constructible<Cpp<Class>>::value,
                   "pybind11::init() return-by-value factory function requires a movable class");
     if (Class::has_alias && need_alias) {
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
@@ -190,7 +190,7 @@ void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
 template <typename Class>
 void construct(value_and_holder &v_h, Alias<Class> &&result, bool) {
     static_assert(
-        std::is_move_constructible<Alias<Class>>::value,
+        is_move_constructible<Alias<Class>>::value,
         "pybind11::init() return-by-alias-value factory function requires a movable alias class");
     v_h.value_ptr() = new Alias<Class>(std::move(result));
 }
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 0b710d7e4c..34dcd26ce5 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -827,6 +827,9 @@ using movable_cast_op_type
 template <typename T, typename SFINAE = void>
 struct is_copy_constructible : std::is_copy_constructible<T> {};
 
+template <typename T, typename SFINAE = void>
+struct is_move_constructible : std::is_move_constructible<T> {};
+
 // Specialization for types that appear to be copy constructible but also look like stl containers
 // (we specifically check for: has `value_type` and `reference` with `reference = value_type&`): if
 // so, copy constructability depends on whether the value_type is copy constructible.
@@ -994,7 +997,7 @@ class type_caster_base : public type_caster_generic {
         return [](const void *arg) -> void * { return new T(*reinterpret_cast<const T *>(arg)); };
     }
 
-    template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
+    template <typename T, typename = enable_if_t<is_move_constructible<T>::value>>
     static auto make_move_constructor(const T *)
         -> decltype(new T(std::declval<T &&>()), Constructor{}) {
         return [](const void *arg) -> void * {
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b1cb222b4a..1d0eb27c0d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -155,6 +155,7 @@ set(PYBIND11_TEST_FILES
     test_tagbased_polymorphic
     test_thread
     test_union
+    test_vector_unique_ptr_member
     test_virtual_functions)
 
 # Invoking cmake with something like:
diff --git a/tests/test_vector_unique_ptr_member.cpp b/tests/test_vector_unique_ptr_member.cpp
new file mode 100644
index 0000000000..657743e4dd
--- /dev/null
+++ b/tests/test_vector_unique_ptr_member.cpp
@@ -0,0 +1,56 @@
+#include "pybind11_tests.h"
+
+#include <cstddef>
+#include <memory>
+#include <vector>
+
+namespace pybind11_tests {
+namespace vector_unique_ptr_member {
+
+struct DataType {};
+
+// Reduced from a use case in the wild.
+struct VectorOwner {
+    static std::unique_ptr<VectorOwner> Create(std::size_t num_elems) {
+        return std::unique_ptr<VectorOwner>(
+            new VectorOwner(std::vector<std::unique_ptr<DataType>>(num_elems)));
+    }
+
+    std::size_t data_size() const { return data_.size(); }
+
+private:
+    explicit VectorOwner(std::vector<std::unique_ptr<DataType>> data) : data_(std::move(data)) {}
+
+    const std::vector<std::unique_ptr<DataType>> data_;
+};
+
+} // namespace vector_unique_ptr_member
+} // namespace pybind11_tests
+
+namespace pybind11 {
+namespace detail {
+
+template <>
+struct is_copy_constructible<pybind11_tests::vector_unique_ptr_member::VectorOwner>
+    : std::false_type {};
+
+template <>
+struct is_move_constructible<pybind11_tests::vector_unique_ptr_member::VectorOwner>
+    : std::false_type {};
+
+} // namespace detail
+} // namespace pybind11
+
+using namespace pybind11_tests::vector_unique_ptr_member;
+
+py::object py_cast_VectorOwner_ptr(VectorOwner *ptr) { return py::cast(ptr); }
+
+// PYBIND11_SMART_HOLDER_TYPE_CASTERS(VectorOwner)
+
+TEST_SUBMODULE(vector_unique_ptr_member, m) {
+    py::class_<VectorOwner>(m, "VectorOwner")
+        .def_static("Create", &VectorOwner::Create)
+        .def("data_size", &VectorOwner::data_size);
+
+    m.def("py_cast_VectorOwner_ptr", py_cast_VectorOwner_ptr);
+}
diff --git a/tests/test_vector_unique_ptr_member.py b/tests/test_vector_unique_ptr_member.py
new file mode 100644
index 0000000000..2da3d97c37
--- /dev/null
+++ b/tests/test_vector_unique_ptr_member.py
@@ -0,0 +1,14 @@
+import pytest
+
+from pybind11_tests import vector_unique_ptr_member as m
+
+
+@pytest.mark.parametrize("num_elems", range(3))
+def test_create(num_elems):
+    vo = m.VectorOwner.Create(num_elems)
+    assert vo.data_size() == num_elems
+
+
+def test_cast():
+    vo = m.VectorOwner.Create(0)
+    assert m.py_cast_VectorOwner_ptr(vo) is vo

From ff7f5dfca32224b65524a9cebe3daa8f2d328a35 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 25 Apr 2023 10:25:57 -0700
Subject: [PATCH 586/638] 1. Fully test unstable ABI (#4635)

2. Selectively exercise cmake `-DPYBIND11_TEST_OVERRIDE`: ubuntu, macos, windows

Extra work added to quick jobs, based on timings below, to not increase the GHA start-to-last-job-finished time.

```
Duration
^              Number of pytest runs
^              ^ Job identifier
^              ^ ^
0:03:48.024227 1 1___3___Clang_3.6___C++11___x64.txt
0:03:58.992814 1 2___3___Clang_3.7___C++11___x64.txt
0:04:25.758942 1 1___3.7___Debian___x86____Install.txt
0:04:50.148276 1 4___3___Clang_7___C++11___x64.txt
0:04:55.784558 1 13___3___Clang_15___C++20___x64.txt
0:04:57.048754 1 6___3___Clang_dev___C++11___x64.txt
0:05:00.485181 1 7___3___Clang_5___C++14___x64.txt
0:05:03.744964 1 2___3___almalinux8___x64.txt
0:05:06.222752 1 5___3___Clang_9___C++11___x64.txt
0:05:11.767022 1 2___3___GCC_7___C++17__x64.txt
0:05:18.634930 1 2___3.11__deadsnakes____x64.txt
0:05:22.810995 1 1___3___GCC_7___C++11__x64.txt
0:05:25.275317 1 12___3___Clang_14___C++20___x64.txt
0:05:32.058174 1 5___3___GCC_10___C++17__x64.txt
0:05:39.381351 1 7___3___GCC_12___C++20__x64.txt
0:05:40.502252 1 8___3___Clang_10___C++17___x64.txt
0:05:59.344905 1 3___3___Clang_3.9___C++11___x64.txt
0:06:10.825147 1 6___3___GCC_11___C++20__x64.txt
0:06:20.655443 1 3___3___almalinux9___x64.txt
0:06:22.472061 1 3___3___GCC_8___C++14__x64.txt
0:06:42.647406 1 11___3___Clang_13___C++20___x64.txt
0:06:53.352720 1 1___3.10___CUDA_11.7___Ubuntu_22.04.txt
0:07:07.357801 1 2___3.7___MSVC_2019___x86_-DCMAKE_CXX_STANDARD=14.txt
0:07:09.057603 1 1___3___centos7___x64.txt
0:07:15.546282 1 1___3.8___MSVC_2019__Debug____x86_-DCMAKE_CXX_STANDARD=17.txt
0:07:22.566022 1 4___3___GCC_8___C++17__x64.txt
0:08:13.592674 1 2___3.9___MSVC_2019__Debug____x86_-DCMAKE_CXX_STANDARD=20.txt
0:08:16.422768 1 9___3___Clang_11___C++20___x64.txt
0:08:21.168457 1 3___3.8___MSVC_2019___x86_-DCMAKE_CXX_STANDARD=17.txt
0:08:27.129468 1 10___3___Clang_12___C++20___x64.txt
0:09:35.045470 1 1___3.10___windows-latest___clang-latest.txt
0:09:57.361843 1 1___3.9___MSVC_2022_C++20___x64.txt
0:10:35.187767 1 1___3.6___MSVC_2019___x86.txt
0:11:14.691200 4 2___3.9___ubuntu-20.04___x64.txt
0:11:37.701167 1 1_macos-latest___brew_install_llvm.txt
0:11:38.688299 4 4___3.11___ubuntu-20.04___x64.txt
0:11:52.720216 1 4___3.9___MSVC_2019___x86_-DCMAKE_CXX_STANDARD=20.txt
0:13:23.456591 4 6___pypy-3.8___ubuntu-20.04___x64_-DPYBIND11_FINDPYTHON=ON.txt
0:13:25.863592 2 1___3___ICC_latest___x64.txt
0:13:32.411758 3 9___3.9___windows-2022___x64.txt
0:13:45.473377 4 3___3.10___ubuntu-20.04___x64.txt
0:13:55.366447 4 5___pypy-3.7___ubuntu-20.04___x64.txt
0:13:57.969502 3 10___3.10___windows-2022___x64.txt
0:14:19.837475 3 11___3.11___windows-2022___x64.txt
0:14:33.316770 4 1___3.6___ubuntu-20.04___x64_-DPYBIND11_FINDPYTHON=ON_-DCMA.txt
0:15:34.449278 4 22___3.6___windows-2019___x64_-DPYBIND11_FINDPYTHON=ON.txt
0:16:25.189055 2 1___3.9-dbg__deadsnakes____Valgrind___x64.txt
0:17:20.956667 4 15___3.6___macos-latest___x64.txt
0:17:27.513891 4 23___3.9___windows-2019___x64.txt
0:17:58.783286 3 8___3.6___windows-2022___x64.txt
0:18:25.917828 4 7___pypy-3.9___ubuntu-20.04___x64.txt
0:19:17.399820 3 13___pypy-3.8___windows-2022___x64.txt
0:19:45.002122 3 12___pypy-3.7___windows-2022___x64.txt
0:20:03.201926 4 16___3.9___macos-latest___x64.txt
0:20:15.415178 4 17___3.10___macos-latest___x64.txt
0:20:20.263216 4 20___pypy-3.8___macos-latest___x64.txt
0:20:31.998226 3 1___3___windows-latest___mingw64.txt
0:20:40.812286 4 18___3.11___macos-latest___x64.txt
0:22:47.714749 4 19___pypy-3.7___macos-latest___x64.txt
0:23:04.435859 3 2___3___windows-latest___mingw32.txt
0:25:48.719597 3 14___pypy-3.9___windows-2022___x64.txt
0:26:01.211688 4 21___pypy-3.9___macos-latest___x64.txt
0:28:19.971015 1 1___3___CentOS7__PGI_22.9___x64.txt
```
---
 .github/workflows/ci.yml | 52 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a6a9a16fa6..c88f0797f2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -164,7 +164,6 @@ jobs:
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         -DPYBIND11_INTERNALS_VERSION=10000000
-        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
         ${{ matrix.args }}
 
     - name: Build (unstable ABI)
@@ -497,6 +496,24 @@ jobs:
     - name: Interface test
       run: cmake --build build --target test_cmake_build
 
+    - name: Configure - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+      if: matrix.gcc == '12'
+      shell: bash
+      run: >
+        cmake -S . -B build_partial
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DCMAKE_CXX_STANDARD=${{ matrix.std }}
+        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
+
+    - name: Build - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+      if: matrix.gcc == '12'
+      run: cmake --build build_partial -j 2
+
+    - name: Python tests - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+      if: matrix.gcc == '12'
+      run: cmake --build build_partial --target pytest
 
   # Testing on ICC using the oneAPI apt repo
   icc:
@@ -889,6 +906,21 @@ jobs:
     - name: Interface test C++20
       run: cmake --build build --target test_cmake_build
 
+    - name: Configure C++20 - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+      run: >
+        cmake -S . -B build_partial
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=20
+        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
+
+    - name: Build C++20 - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+      run: cmake --build build_partial -j 2
+
+    - name: Python tests - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+      run: cmake --build build_partial --target pytest
+
   mingw:
     name: "🐍 3 • windows-latest • ${{ matrix.sys }}"
     runs-on: windows-latest
@@ -1105,5 +1137,23 @@ jobs:
       - name: Interface test
         run: cmake --build . --target test_cmake_build -j 2
 
+      - name: CMake Configure - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+        run: >
+          cmake -S . -B build_partial
+          -DPYBIND11_WERROR=ON
+          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
+          -DDOWNLOAD_CATCH=ON
+          -DDOWNLOAD_EIGEN=ON
+          -DCMAKE_CXX_COMPILER=clang++
+          -DCMAKE_CXX_STANDARD=17
+          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+          "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
+
+      - name: Build - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+        run: cmake --build build_partial -j 2
+
+      - name: Python tests - Exercise cmake -DPYBIND11_TEST_OVERRIDE
+        run: cmake --build build_partial --target pytest -j 2
+
       - name: Clean directory
         run: git clean -fdx

From 6de6191a0c56a9b0d31ac1c32778081a9e2b0311 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 25 Apr 2023 14:03:24 -0700
Subject: [PATCH 587/638] Use `std::hash<std::type_index>`,
 `std::equal_to<std::type_index>` everywhere **except when libc++ is in use**
 (#4319)

* Try using `std::hash<std::type_index>`, `std::equal_to<std::type_index>` everywhere.

From PR #4316 we know that types in the unnamed namespace in different translation units do not compare equal, as desired.

But do types in named namespaces compare equal, as desired?

* Revert "Try using `std::hash<std::type_index>`, `std::equal_to<std::type_index>` everywhere."

This reverts commit a06949a9265014b3c581396c4f37c45ccc03dea6.

* Use "our own name-based hash and equality functions" for `std::type_index` only under macOS, based on results shown under https://github.com/pybind/pybind11/pull/4316#issuecomment-1305097879

* Patch in PR #4313: Minimal reproducer for clash when binding types defined in the unnamed namespace.

* test_unnamed_namespace_b xfail for clang

* `PYBIND11_INTERNALS_VERSION 5`

* Add a note to docs/classes.rst

* For compatibility with Google-internal testing, test_unnamed_namespace_a & test_unnamed_namespace_b need to work when imported in any order.

* Trying "__GLIBCXX__ or Windows", based on observations from Google-internal testing.

* Try _LIBCPP_VERSION

* Account for libc++ behavior in tests and documentation.

* Adjust expectations for Windows Clang (and make code less redundant).

* Add WindowsClang to ci.yml

Added block transferred from PR #4321

* Add clang-latest to name that appears in the GitHub Actions web view.

* Tweak the note in classes.rst again.

* Add `pip install --upgrade pip`, Show env, cosmetic changes

Already tested under PR #4321

* Add macos_brew_install_llvm to ci.yml

Added block transferred from PR #4324

* `test_cross_module_exception_translator` xfail 'Homebrew Clang'

* Revert back to base version of .github/workflows/ci.yml (the ci.yml changes were merged under #4323 and #4326)

* Fixes for ruff

* Make updated condition in internals.h dependent on ABI version.

* Remove PYBIND11_TEST_OVERRIDE when testing with PYBIND11_INTERNALS_VERSION=10000000

* Selectively exercise cmake `-DPYBIND11_TEST_OVERRIDE`: ubuntu, macos, windows

Extra work added to quick jobs, based on timings below, to not increase the GHA start-to-last-job-finished time.

```
Duration
^              Number of pytest runs
^              ^ Job identifier
^              ^ ^
0:03:48.024227 1 1___3___Clang_3.6___C++11___x64.txt
0:03:58.992814 1 2___3___Clang_3.7___C++11___x64.txt
0:04:25.758942 1 1___3.7___Debian___x86____Install.txt
0:04:50.148276 1 4___3___Clang_7___C++11___x64.txt
0:04:55.784558 1 13___3___Clang_15___C++20___x64.txt
0:04:57.048754 1 6___3___Clang_dev___C++11___x64.txt
0:05:00.485181 1 7___3___Clang_5___C++14___x64.txt
0:05:03.744964 1 2___3___almalinux8___x64.txt
0:05:06.222752 1 5___3___Clang_9___C++11___x64.txt
0:05:11.767022 1 2___3___GCC_7___C++17__x64.txt
0:05:18.634930 1 2___3.11__deadsnakes____x64.txt
0:05:22.810995 1 1___3___GCC_7___C++11__x64.txt
0:05:25.275317 1 12___3___Clang_14___C++20___x64.txt
0:05:32.058174 1 5___3___GCC_10___C++17__x64.txt
0:05:39.381351 1 7___3___GCC_12___C++20__x64.txt
0:05:40.502252 1 8___3___Clang_10___C++17___x64.txt
0:05:59.344905 1 3___3___Clang_3.9___C++11___x64.txt
0:06:10.825147 1 6___3___GCC_11___C++20__x64.txt
0:06:20.655443 1 3___3___almalinux9___x64.txt
0:06:22.472061 1 3___3___GCC_8___C++14__x64.txt
0:06:42.647406 1 11___3___Clang_13___C++20___x64.txt
0:06:53.352720 1 1___3.10___CUDA_11.7___Ubuntu_22.04.txt
0:07:07.357801 1 2___3.7___MSVC_2019___x86_-DCMAKE_CXX_STANDARD=14.txt
0:07:09.057603 1 1___3___centos7___x64.txt
0:07:15.546282 1 1___3.8___MSVC_2019__Debug____x86_-DCMAKE_CXX_STANDARD=17.txt
0:07:22.566022 1 4___3___GCC_8___C++17__x64.txt
0:08:13.592674 1 2___3.9___MSVC_2019__Debug____x86_-DCMAKE_CXX_STANDARD=20.txt
0:08:16.422768 1 9___3___Clang_11___C++20___x64.txt
0:08:21.168457 1 3___3.8___MSVC_2019___x86_-DCMAKE_CXX_STANDARD=17.txt
0:08:27.129468 1 10___3___Clang_12___C++20___x64.txt
0:09:35.045470 1 1___3.10___windows-latest___clang-latest.txt
0:09:57.361843 1 1___3.9___MSVC_2022_C++20___x64.txt
0:10:35.187767 1 1___3.6___MSVC_2019___x86.txt
0:11:14.691200 4 2___3.9___ubuntu-20.04___x64.txt
0:11:37.701167 1 1_macos-latest___brew_install_llvm.txt
0:11:38.688299 4 4___3.11___ubuntu-20.04___x64.txt
0:11:52.720216 1 4___3.9___MSVC_2019___x86_-DCMAKE_CXX_STANDARD=20.txt
0:13:23.456591 4 6___pypy-3.8___ubuntu-20.04___x64_-DPYBIND11_FINDPYTHON=ON.txt
0:13:25.863592 2 1___3___ICC_latest___x64.txt
0:13:32.411758 3 9___3.9___windows-2022___x64.txt
0:13:45.473377 4 3___3.10___ubuntu-20.04___x64.txt
0:13:55.366447 4 5___pypy-3.7___ubuntu-20.04___x64.txt
0:13:57.969502 3 10___3.10___windows-2022___x64.txt
0:14:19.837475 3 11___3.11___windows-2022___x64.txt
0:14:33.316770 4 1___3.6___ubuntu-20.04___x64_-DPYBIND11_FINDPYTHON=ON_-DCMA.txt
0:15:34.449278 4 22___3.6___windows-2019___x64_-DPYBIND11_FINDPYTHON=ON.txt
0:16:25.189055 2 1___3.9-dbg__deadsnakes____Valgrind___x64.txt
0:17:20.956667 4 15___3.6___macos-latest___x64.txt
0:17:27.513891 4 23___3.9___windows-2019___x64.txt
0:17:58.783286 3 8___3.6___windows-2022___x64.txt
0:18:25.917828 4 7___pypy-3.9___ubuntu-20.04___x64.txt
0:19:17.399820 3 13___pypy-3.8___windows-2022___x64.txt
0:19:45.002122 3 12___pypy-3.7___windows-2022___x64.txt
0:20:03.201926 4 16___3.9___macos-latest___x64.txt
0:20:15.415178 4 17___3.10___macos-latest___x64.txt
0:20:20.263216 4 20___pypy-3.8___macos-latest___x64.txt
0:20:31.998226 3 1___3___windows-latest___mingw64.txt
0:20:40.812286 4 18___3.11___macos-latest___x64.txt
0:22:47.714749 4 19___pypy-3.7___macos-latest___x64.txt
0:23:04.435859 3 2___3___windows-latest___mingw32.txt
0:25:48.719597 3 14___pypy-3.9___windows-2022___x64.txt
0:26:01.211688 4 21___pypy-3.9___macos-latest___x64.txt
0:28:19.971015 1 1___3___CentOS7__PGI_22.9___x64.txt
```

* Update skipif for Python 3.12a7 (the WIP needs to be handled in a separate PR).
---
 .github/workflows/upstream.yml      |  1 -
 docs/classes.rst                    | 10 ++++++++
 include/pybind11/detail/internals.h |  3 ++-
 tests/CMakeLists.txt                |  2 ++
 tests/test_exceptions.py            |  2 +-
 tests/test_unnamed_namespace_a.cpp  | 38 +++++++++++++++++++++++++++++
 tests/test_unnamed_namespace_a.py   | 34 ++++++++++++++++++++++++++
 tests/test_unnamed_namespace_b.cpp  | 13 ++++++++++
 tests/test_unnamed_namespace_b.py   |  5 ++++
 9 files changed, 105 insertions(+), 3 deletions(-)
 create mode 100644 tests/test_unnamed_namespace_a.cpp
 create mode 100644 tests/test_unnamed_namespace_a.py
 create mode 100644 tests/test_unnamed_namespace_b.cpp
 create mode 100644 tests/test_unnamed_namespace_b.py

diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index be3cd40502..be643ddfdb 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -95,7 +95,6 @@ jobs:
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         -DPYBIND11_INTERNALS_VERSION=10000000
-        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
 
     - name: Build (unstable ABI)
       run: cmake --build build17max -j 2
diff --git a/docs/classes.rst b/docs/classes.rst
index c0c53135b8..52cd52da3f 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -58,6 +58,16 @@ interactive Python session demonstrating this example is shown below:
     Static member functions can be bound in the same way using
     :func:`class_::def_static`.
 
+.. note::
+
+    Binding C++ types in unnamed namespaces (also known as anonymous namespaces)
+    works reliably on many platforms, but not all. The `XFAIL_CONDITION` in
+    tests/test_unnamed_namespace_a.py encodes the currently known conditions.
+    For background see `#4319 <https://github.com/pybind/pybind11/pull/4319>`_.
+    If portability is a concern, it is therefore not recommended to bind C++
+    types in unnamed namespaces. It will be safest to manually pick unique
+    namespace names.
+
 Keyword and default arguments
 =============================
 It is possible to specify keyword and default arguments using the syntax
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 8364ebd1e0..aaa7f8686e 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -123,7 +123,8 @@ inline void tls_replace_value(PYBIND11_TLS_KEY_REF key, void *value) {
 // libstdc++, this doesn't happen: equality and the type_index hash are based on the type name,
 // which works.  If not under a known-good stl, provide our own name-based hash and equality
 // functions that use the type name.
-#if defined(__GLIBCXX__)
+#if (PYBIND11_INTERNALS_VERSION <= 4 && defined(__GLIBCXX__))                                     \
+    || (PYBIND11_INTERNALS_VERSION >= 5 && !defined(_LIBCPP_VERSION))
 inline bool same_type(const std::type_info &lhs, const std::type_info &rhs) { return lhs == rhs; }
 using type_hash = std::hash<std::type_index>;
 using type_equal_to = std::equal_to<std::type_index>;
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 1d0eb27c0d..11ac2215b3 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -155,6 +155,8 @@ set(PYBIND11_TEST_FILES
     test_tagbased_polymorphic
     test_thread
     test_union
+    test_unnamed_namespace_a
+    test_unnamed_namespace_b
     test_vector_unique_ptr_member
     test_virtual_functions)
 
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 1b4c89add1..a92ab59a34 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -319,7 +319,7 @@ def test_error_already_set_what_with_happy_exceptions(
 
 @pytest.mark.skipif(
     # Intentionally very specific:
-    "sys.version_info == (3, 12, 0, 'alpha', 6)",
+    "sys.version_info == (3, 12, 0, 'alpha', 7)",
     reason="WIP: https://github.com/python/cpython/issues/102594",
 )
 @pytest.mark.skipif("env.PYPY", reason="PyErr_NormalizeException Segmentation fault")
diff --git a/tests/test_unnamed_namespace_a.cpp b/tests/test_unnamed_namespace_a.cpp
new file mode 100644
index 0000000000..2152e64bd7
--- /dev/null
+++ b/tests/test_unnamed_namespace_a.cpp
@@ -0,0 +1,38 @@
+#include "pybind11_tests.h"
+
+namespace {
+struct any_struct {};
+} // namespace
+
+TEST_SUBMODULE(unnamed_namespace_a, m) {
+    if (py::detail::get_type_info(typeid(any_struct)) == nullptr) {
+        py::class_<any_struct>(m, "unnamed_namespace_a_any_struct");
+    } else {
+        m.attr("unnamed_namespace_a_any_struct") = py::none();
+    }
+    m.attr("PYBIND11_INTERNALS_VERSION") = PYBIND11_INTERNALS_VERSION;
+    m.attr("defined_WIN32_or__WIN32") =
+#if defined(WIN32) || defined(_WIN32)
+        true;
+#else
+        false;
+#endif
+    m.attr("defined___clang__") =
+#if defined(__clang__)
+        true;
+#else
+        false;
+#endif
+    m.attr("defined__LIBCPP_VERSION") =
+#if defined(_LIBCPP_VERSION)
+        true;
+#else
+        false;
+#endif
+    m.attr("defined___GLIBCXX__") =
+#if defined(__GLIBCXX__)
+        true;
+#else
+        false;
+#endif
+}
diff --git a/tests/test_unnamed_namespace_a.py b/tests/test_unnamed_namespace_a.py
new file mode 100644
index 0000000000..9d9856c5a4
--- /dev/null
+++ b/tests/test_unnamed_namespace_a.py
@@ -0,0 +1,34 @@
+import pytest
+
+from pybind11_tests import unnamed_namespace_a as m
+from pybind11_tests import unnamed_namespace_b as mb
+
+XFAIL_CONDITION = (
+    "(m.PYBIND11_INTERNALS_VERSION <= 4 and (m.defined___clang__ or not m.defined___GLIBCXX__))"
+    " or "
+    "(m.PYBIND11_INTERNALS_VERSION >= 5 and not m.defined_WIN32_or__WIN32"
+    " and "
+    "(m.defined___clang__ or m.defined__LIBCPP_VERSION))"
+)
+XFAIL_REASON = "Known issues: https://github.com/pybind/pybind11/pull/4319"
+
+
+@pytest.mark.xfail(XFAIL_CONDITION, reason=XFAIL_REASON, strict=False)
+@pytest.mark.parametrize(
+    "any_struct", [m.unnamed_namespace_a_any_struct, mb.unnamed_namespace_b_any_struct]
+)
+def test_have_class_any_struct(any_struct):
+    assert any_struct is not None
+
+
+def test_have_at_least_one_class_any_struct():
+    assert (
+        m.unnamed_namespace_a_any_struct is not None
+        or mb.unnamed_namespace_b_any_struct is not None
+    )
+
+
+@pytest.mark.xfail(XFAIL_CONDITION, reason=XFAIL_REASON, strict=True)
+def test_have_both_class_any_struct():
+    assert m.unnamed_namespace_a_any_struct is not None
+    assert mb.unnamed_namespace_b_any_struct is not None
diff --git a/tests/test_unnamed_namespace_b.cpp b/tests/test_unnamed_namespace_b.cpp
new file mode 100644
index 0000000000..f97757a7de
--- /dev/null
+++ b/tests/test_unnamed_namespace_b.cpp
@@ -0,0 +1,13 @@
+#include "pybind11_tests.h"
+
+namespace {
+struct any_struct {};
+} // namespace
+
+TEST_SUBMODULE(unnamed_namespace_b, m) {
+    if (py::detail::get_type_info(typeid(any_struct)) == nullptr) {
+        py::class_<any_struct>(m, "unnamed_namespace_b_any_struct");
+    } else {
+        m.attr("unnamed_namespace_b_any_struct") = py::none();
+    }
+}
diff --git a/tests/test_unnamed_namespace_b.py b/tests/test_unnamed_namespace_b.py
new file mode 100644
index 0000000000..4bcaa7a6c5
--- /dev/null
+++ b/tests/test_unnamed_namespace_b.py
@@ -0,0 +1,5 @@
+from pybind11_tests import unnamed_namespace_b as m
+
+
+def test_have_attr_any_struct():
+    assert hasattr(m, "unnamed_namespace_b_any_struct")

From 3f366ff888c846a3bc39af36615f99dc9e424e51 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 27 Apr 2023 07:24:48 -0700
Subject: [PATCH 588/638] Remove stray comment. (Oversight in PR #4631. Noticed
 by chance.) (#4641)

---
 tests/test_vector_unique_ptr_member.cpp | 2 --
 1 file changed, 2 deletions(-)

diff --git a/tests/test_vector_unique_ptr_member.cpp b/tests/test_vector_unique_ptr_member.cpp
index 657743e4dd..680cf9a6d8 100644
--- a/tests/test_vector_unique_ptr_member.cpp
+++ b/tests/test_vector_unique_ptr_member.cpp
@@ -45,8 +45,6 @@ using namespace pybind11_tests::vector_unique_ptr_member;
 
 py::object py_cast_VectorOwner_ptr(VectorOwner *ptr) { return py::cast(ptr); }
 
-// PYBIND11_SMART_HOLDER_TYPE_CASTERS(VectorOwner)
-
 TEST_SUBMODULE(vector_unique_ptr_member, m) {
     py::class_<VectorOwner>(m, "VectorOwner")
         .def_static("Create", &VectorOwner::Create)

From 5e946c2fa5b3c3170d702f57311492a8f838444e Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 28 Apr 2023 14:32:32 -0400
Subject: [PATCH 589/638] chore(deps): update pre-commit hooks (#4605)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* chore(deps): update pre-commit hooks

updates:
- [github.com/psf/black: 23.1.0 → 23.3.0](https://github.com/psf/black/compare/23.1.0...23.3.0)
- [github.com/Lucas-C/pre-commit-hooks: v1.4.2 → v1.5.1](https://github.com/Lucas-C/pre-commit-hooks/compare/v1.4.2...v1.5.1)
- [github.com/charliermarsh/ruff-pre-commit: v0.0.254 → v0.0.260](https://github.com/charliermarsh/ruff-pre-commit/compare/v0.0.254...v0.0.260)
- [github.com/PyCQA/pylint: v2.16.4 → v3.0.0a6](https://github.com/PyCQA/pylint/compare/v2.16.4...v3.0.0a6)
- [github.com/pre-commit/mirrors-mypy: v1.0.1 → v1.1.1](https://github.com/pre-commit/mirrors-mypy/compare/v1.0.1...v1.1.1)
- [github.com/codespell-project/codespell: v2.2.2 → v2.2.4](https://github.com/codespell-project/codespell/compare/v2.2.2...v2.2.4)
- [github.com/pre-commit/mirrors-clang-format: v15.0.7 → v16.0.0](https://github.com/pre-commit/mirrors-clang-format/compare/v15.0.7...v16.0.0)

* style: pre-commit fixes

* style: fix issues

* Update tests/test_call_policies.py

* Update tests/test_call_policies.py

* fix: ignore code in file

* style: pre-commit fixes

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .pre-commit-config.yaml                    | 18 +++----
 include/pybind11/detail/type_caster_base.h |  6 +--
 pyproject.toml                             |  1 +
 tests/test_iostream.py                     | 58 +++++++++++-----------
 tests/test_stl.py                          |  2 +-
 5 files changed, 43 insertions(+), 42 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7c43161921..51b6f0a41b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -41,7 +41,7 @@ repos:
 
 # Black, the code formatter, natively supports pre-commit
 - repo: https://github.com/psf/black
-  rev: "23.1.0" # Keep in sync with blacken-docs
+  rev: "23.3.0" # Keep in sync with blacken-docs
   hooks:
   - id: black
 
@@ -51,11 +51,11 @@ repos:
   hooks:
   - id: blacken-docs
     additional_dependencies:
-    - black==23.1.0 # keep in sync with black hook
+    - black==23.3.0 # keep in sync with black hook
 
 # Changes tabs to spaces
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: "v1.4.2"
+  rev: "v1.5.1"
   hooks:
   - id: remove-tabs
 
@@ -68,7 +68,7 @@ repos:
 
 # Ruff, the Python auto-correcting linter written in Rust
 - repo: https://github.com/charliermarsh/ruff-pre-commit
-  rev: v0.0.254
+  rev: v0.0.263
   hooks:
   - id: ruff
     args: ["--fix", "--show-fixes"]
@@ -84,7 +84,7 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v2.16.4"
+  rev: "v3.0.0a6"
   hooks:
   - id: pylint
     files: ^pybind11
@@ -100,7 +100,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v1.0.1"
+  rev: "v1.1.1"
   hooks:
   - id: mypy
     args: []
@@ -120,11 +120,11 @@ repos:
 # Use tools/codespell_ignore_lines_from_errors.py
 # to rebuild .codespell-ignore-lines
 - repo: https://github.com/codespell-project/codespell
-  rev: "v2.2.2"
+  rev: "v2.2.4"
   hooks:
   - id: codespell
     exclude: ".supp$"
-    args: ["-x", ".codespell-ignore-lines"]
+    args: ["-x.codespell-ignore-lines", "-Lccompiler"]
 
 # Check for common shell mistakes
 - repo: https://github.com/shellcheck-py/shellcheck-py
@@ -143,7 +143,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v15.0.7"
+  rev: "v16.0.0"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 34dcd26ce5..8f3d0f3791 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -258,9 +258,9 @@ struct value_and_holder {
 
     // Main constructor for a found value/holder:
     value_and_holder(instance *i, const detail::type_info *type, size_t vpos, size_t index)
-        : inst{i}, index{index}, type{type}, vh{inst->simple_layout
-                                                    ? inst->simple_value_holder
-                                                    : &inst->nonsimple.values_and_holders[vpos]} {}
+        : inst{i}, index{index}, type{type},
+          vh{inst->simple_layout ? inst->simple_value_holder
+                                 : &inst->nonsimple.values_and_holders[vpos]} {}
 
     // Default constructor (used to signal a value-and-holder not found by get_value_and_holder())
     value_and_holder() = default;
diff --git a/pyproject.toml b/pyproject.toml
index 96cf842650..e3655aca74 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -93,3 +93,4 @@ isort.known-first-party = ["env", "pybind11_cross_module_tests", "pybind11_tests
 
 [tool.ruff.per-file-ignores]
 "tests/**" = ["EM", "N"]
+"tests/test_call_policies.py" = ["PLC1901"]
diff --git a/tests/test_iostream.py b/tests/test_iostream.py
index 79b2a2b8cc..d283eb1520 100644
--- a/tests/test_iostream.py
+++ b/tests/test_iostream.py
@@ -9,16 +9,16 @@ def test_captured(capsys):
     m.captured_output(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
     m.captured_err(msg)
     stdout, stderr = capsys.readouterr()
-    assert stdout == ""
+    assert not stdout
     assert stderr == msg
 
 
@@ -30,7 +30,7 @@ def test_captured_large_string(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_2byte_offset0(capsys):
@@ -40,7 +40,7 @@ def test_captured_utf8_2byte_offset0(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_2byte_offset1(capsys):
@@ -50,7 +50,7 @@ def test_captured_utf8_2byte_offset1(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_3byte_offset0(capsys):
@@ -60,7 +60,7 @@ def test_captured_utf8_3byte_offset0(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_3byte_offset1(capsys):
@@ -70,7 +70,7 @@ def test_captured_utf8_3byte_offset1(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_3byte_offset2(capsys):
@@ -80,7 +80,7 @@ def test_captured_utf8_3byte_offset2(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_4byte_offset0(capsys):
@@ -90,7 +90,7 @@ def test_captured_utf8_4byte_offset0(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_4byte_offset1(capsys):
@@ -100,7 +100,7 @@ def test_captured_utf8_4byte_offset1(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_4byte_offset2(capsys):
@@ -110,7 +110,7 @@ def test_captured_utf8_4byte_offset2(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_captured_utf8_4byte_offset3(capsys):
@@ -120,7 +120,7 @@ def test_captured_utf8_4byte_offset3(capsys):
     m.captured_output_default(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_guard_capture(capsys):
@@ -128,7 +128,7 @@ def test_guard_capture(capsys):
     m.guard_output(msg)
     stdout, stderr = capsys.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
 
 
 def test_series_captured(capture):
@@ -145,7 +145,7 @@ def test_flush(capfd):
     with m.ostream_redirect():
         m.noisy_function(msg, flush=False)
         stdout, stderr = capfd.readouterr()
-        assert stdout == ""
+        assert not stdout
 
         m.noisy_function(msg2, flush=True)
         stdout, stderr = capfd.readouterr()
@@ -164,15 +164,15 @@ def test_not_captured(capfd):
         m.raw_output(msg)
     stdout, stderr = capfd.readouterr()
     assert stdout == msg
-    assert stderr == ""
-    assert stream.getvalue() == ""
+    assert not stderr
+    assert not stream.getvalue()
 
     stream = StringIO()
     with redirect_stdout(stream):
         m.captured_output(msg)
     stdout, stderr = capfd.readouterr()
-    assert stdout == ""
-    assert stderr == ""
+    assert not stdout
+    assert not stderr
     assert stream.getvalue() == msg
 
 
@@ -182,16 +182,16 @@ def test_err(capfd):
     with redirect_stderr(stream):
         m.raw_err(msg)
     stdout, stderr = capfd.readouterr()
-    assert stdout == ""
+    assert not stdout
     assert stderr == msg
-    assert stream.getvalue() == ""
+    assert not stream.getvalue()
 
     stream = StringIO()
     with redirect_stderr(stream):
         m.captured_err(msg)
     stdout, stderr = capfd.readouterr()
-    assert stdout == ""
-    assert stderr == ""
+    assert not stdout
+    assert not stderr
     assert stream.getvalue() == msg
 
 
@@ -221,13 +221,13 @@ def test_redirect(capfd):
         m.raw_output(msg)
     stdout, stderr = capfd.readouterr()
     assert stdout == msg
-    assert stream.getvalue() == ""
+    assert not stream.getvalue()
 
     stream = StringIO()
     with redirect_stdout(stream), m.ostream_redirect():
         m.raw_output(msg)
     stdout, stderr = capfd.readouterr()
-    assert stdout == ""
+    assert not stdout
     assert stream.getvalue() == msg
 
     stream = StringIO()
@@ -235,7 +235,7 @@ def test_redirect(capfd):
         m.raw_output(msg)
     stdout, stderr = capfd.readouterr()
     assert stdout == msg
-    assert stream.getvalue() == ""
+    assert not stream.getvalue()
 
 
 def test_redirect_err(capfd):
@@ -248,7 +248,7 @@ def test_redirect_err(capfd):
         m.raw_err(msg2)
     stdout, stderr = capfd.readouterr()
     assert stdout == msg
-    assert stderr == ""
+    assert not stderr
     assert stream.getvalue() == msg2
 
 
@@ -262,8 +262,8 @@ def test_redirect_both(capfd):
         m.raw_output(msg)
         m.raw_err(msg2)
     stdout, stderr = capfd.readouterr()
-    assert stdout == ""
-    assert stderr == ""
+    assert not stdout
+    assert not stderr
     assert stream.getvalue() == msg
     assert stream2.getvalue() == msg2
 
diff --git a/tests/test_stl.py b/tests/test_stl.py
index b7a0d1c0d5..2d9dcc89f1 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -367,7 +367,7 @@ def test_issue_1561():
     """check fix for issue #1561"""
     bar = m.Issue1561Outer()
     bar.list = [m.Issue1561Inner("bar")]
-    bar.list
+    assert bar.list
     assert bar.list[0].data == "bar"
 
 

From 956390a87f6e2ee6ea20438f3faa05222415018f Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sat, 29 Apr 2023 10:15:45 -0400
Subject: [PATCH 590/638] fix(cmake): only define lto if CMAKE's IPO setting is
 unset (#4643)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 tools/pybind11Common.cmake | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index 0c985bc8e5..e4ff1e4080 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -5,8 +5,8 @@ Adds the following targets::
     pybind11::pybind11 - link to headers and pybind11
     pybind11::module - Adds module links
     pybind11::embed - Adds embed links
-    pybind11::lto - Link time optimizations (manual selection)
-    pybind11::thin_lto - Link time optimizations (manual selection)
+    pybind11::lto - Link time optimizations (only if CMAKE_INTERPROCEDURAL_OPTIMIZATION is not set)
+    pybind11::thin_lto - Link time optimizations (only if CMAKE_INTERPROCEDURAL_OPTIMIZATION is not set)
     pybind11::python_link_helper - Adds link to Python libraries
     pybind11::windows_extras - MSVC bigobj and mp for building multithreaded
     pybind11::opt_size - avoid optimizations that increase code size
@@ -20,7 +20,7 @@ Adds the following functions::
 
 # CMake 3.10 has an include_guard command, but we can't use that yet
 # include_guard(global) (pre-CMake 3.10)
-if(TARGET pybind11::lto)
+if(TARGET pybind11::pybind11)
   return()
 endif()
 
@@ -372,11 +372,13 @@ function(_pybind11_generate_lto target prefer_thin_lto)
   endif()
 endfunction()
 
-add_library(pybind11::lto IMPORTED INTERFACE ${optional_global})
-_pybind11_generate_lto(pybind11::lto FALSE)
+if(NOT DEFINED CMAKE_INTERPROCEDURAL_OPTIMIZATION)
+  add_library(pybind11::lto IMPORTED INTERFACE ${optional_global})
+  _pybind11_generate_lto(pybind11::lto FALSE)
 
-add_library(pybind11::thin_lto IMPORTED INTERFACE ${optional_global})
-_pybind11_generate_lto(pybind11::thin_lto TRUE)
+  add_library(pybind11::thin_lto IMPORTED INTERFACE ${optional_global})
+  _pybind11_generate_lto(pybind11::thin_lto TRUE)
+endif()
 
 # ---------------------- pybind11_strip -----------------------------
 

From da91926295638b2b1c0c85a568a2d66ca3646565 Mon Sep 17 00:00:00 2001
From: biergaizi <biergaizi@users.noreply.github.com>
Date: Mon, 1 May 2023 14:14:52 +0000
Subject: [PATCH 591/638] fix: remove -stdlib=libc++ from setup helpers, not
 needed on modern Pythons (#4639)

* Inject -stdlib=libc++ on macOS only when it's supported, close #4637.

On macOS, by default, pybind11 currently unconditionally set the compiler
flag "-stdlib=libc++" in Pybind11Extension.__init__(), regardless of which
compiler is used. This flag is required for clang, but is invalid for GCC.
If GCC is used, it causes compilation failures in all Python projects that
use pybind11, with the error message:

    arm64-apple-darwin22-gcc: error: unrecognized command-line option -stdlib=libc++.

This commit uses has_flag() to detect whether "-stdlib=libc++" on macOS,
and injects this flag from build_ext.build_extensions(), rather than
setting it unconditionally.

Signed-off-by: Yifeng Li <tomli@tomli.me>

* revert: just remove flags

---------

Signed-off-by: Yifeng Li <tomli@tomli.me>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 pybind11/setup_helpers.py | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index 0fb4679e49..cb279f27e0 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -144,7 +144,6 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
         self.cxx_std = cxx_std
 
         cflags = []
-        ldflags = []
         if WIN:
             cflags += ["/EHsc", "/bigobj"]
         else:
@@ -154,11 +153,7 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
             c_cpp_flags = shlex.split(env_cflags) + shlex.split(env_cppflags)
             if not any(opt.startswith("-g") for opt in c_cpp_flags):
                 cflags += ["-g0"]
-            if MACOS:
-                cflags += ["-stdlib=libc++"]
-                ldflags += ["-stdlib=libc++"]
         self._add_cflags(cflags)
-        self._add_ldflags(ldflags)
 
     @property
     def cxx_std(self) -> int:

From dff75a62bd33ff35312aedf696c17f0300301b89 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 3 May 2023 00:34:51 -0400
Subject: [PATCH 592/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.8.5 to 1.8.6 (#4650)

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.8.5 to 1.8.6.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.8.5...v1.8.6)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 7f686b13f9..6d9be3b1d4 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -98,13 +98,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.8.5
+      uses: pypa/gh-action-pypi-publish@v1.8.6
       with:
         password: ${{ secrets.pypi_password }}
         packages-dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.8.5
+      uses: pypa/gh-action-pypi-publish@v1.8.6
       with:
         password: ${{ secrets.pypi_password_global }}
         packages-dir: global/

From b3e88ecf894269b6b3fe822a7551c95247a3c47e Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Wed, 3 May 2023 00:35:21 -0400
Subject: [PATCH 593/638] chore(deps): update pre-commit hooks (#4648)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/mirrors-mypy: v1.1.1 → v1.2.0](https://github.com/pre-commit/mirrors-mypy/compare/v1.1.1...v1.2.0)
- [github.com/pre-commit/mirrors-clang-format: v16.0.0 → v16.0.2](https://github.com/pre-commit/mirrors-clang-format/compare/v16.0.0...v16.0.2)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 .pre-commit-config.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 51b6f0a41b..aca9b3ca2e 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -100,7 +100,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v1.1.1"
+  rev: "v1.2.0"
   hooks:
   - id: mypy
     args: []
@@ -143,7 +143,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v16.0.0"
+  rev: "v16.0.2"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]

From f70165463328c218d118204efc13aac93783d17b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franz=20P=C3=B6schel?= <franz.poeschel@gmail.com>
Date: Fri, 5 May 2023 07:39:05 +0200
Subject: [PATCH 594/638] Introduce recursive_container_traits (#4623)

* Testing

* Similar fix for std::vector

* Fix infinite recursion check:

1) Apply to is_copy_assignable additionally
2) Check infinite recursion for map-like types

* style: pre-commit fixes

* Optional commit that demonstrates the limitations of this PR

* Fix positioning of container bindings

The bindings were previously in a block that was only activated if numpy
was available.

* Suggestions from code review: API side

* Suggestions from code review: Test side

* Suggestions from code review

1) Renaming: is_recursive_container and
   MutuallyRecursiveContainerPair(MV|VM)
2) Avoid ambiguous specializations of is_recursive_container

* Some little fixes

* Reordering of structs

* Add recursive checks for is_move_constructible

* Static testing for pybind11 type traits

* More precise checking of recursive types

Instead of a trait `is_recursive_container`, use a trait
`recursive_container_traits` with dependent type
`recursive_container_traits::type_to_check_recursively`.
So, instead of just checking if a type is recursive and then trying to
somehow deal with it, recursively-defined traits such as
is_move_constructible can now directly ask this trait where the
recursion should proceed.

* Review suggestions

1. Use std::conditional
2. Fix typo

* Remove leftover include from test

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/detail/type_caster_base.h | 203 +++++++++++++++---
 include/pybind11/stl_bind.h                |   8 +-
 tests/test_copy_move.cpp                   | 238 +++++++++++++++++++++
 tests/test_stl_binders.cpp                 |  44 ++++
 tests/test_stl_binders.py                  |  18 ++
 5 files changed, 484 insertions(+), 27 deletions(-)

diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index 8f3d0f3791..16387506cf 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -822,26 +822,179 @@ using movable_cast_op_type
                                   typename std::add_rvalue_reference<intrinsic_t<T>>::type,
                                   typename std::add_lvalue_reference<intrinsic_t<T>>::type>>;
 
-// std::is_copy_constructible isn't quite enough: it lets std::vector<T> (and similar) through when
-// T is non-copyable, but code containing such a copy constructor fails to actually compile.
-template <typename T, typename SFINAE = void>
-struct is_copy_constructible : std::is_copy_constructible<T> {};
+// Does the container have a mapped type and is it recursive?
+// Implemented by specializations below.
+template <typename Container, typename SFINAE = void>
+struct container_mapped_type_traits {
+    static constexpr bool has_mapped_type = false;
+    static constexpr bool has_recursive_mapped_type = false;
+};
+
+template <typename Container>
+struct container_mapped_type_traits<
+    Container,
+    typename std::enable_if<
+        std::is_same<typename Container::mapped_type, Container>::value>::type> {
+    static constexpr bool has_mapped_type = true;
+    static constexpr bool has_recursive_mapped_type = true;
+};
+
+template <typename Container>
+struct container_mapped_type_traits<
+    Container,
+    typename std::enable_if<
+        negation<std::is_same<typename Container::mapped_type, Container>>::value>::type> {
+    static constexpr bool has_mapped_type = true;
+    static constexpr bool has_recursive_mapped_type = false;
+};
+
+// Does the container have a value type and is it recursive?
+// Implemented by specializations below.
+template <typename Container, typename SFINAE = void>
+struct container_value_type_traits : std::false_type {
+    static constexpr bool has_value_type = false;
+    static constexpr bool has_recursive_value_type = false;
+};
+
+template <typename Container>
+struct container_value_type_traits<
+    Container,
+    typename std::enable_if<
+        std::is_same<typename Container::value_type, Container>::value>::type> {
+    static constexpr bool has_value_type = true;
+    static constexpr bool has_recursive_value_type = true;
+};
+
+template <typename Container>
+struct container_value_type_traits<
+    Container,
+    typename std::enable_if<
+        negation<std::is_same<typename Container::value_type, Container>>::value>::type> {
+    static constexpr bool has_value_type = true;
+    static constexpr bool has_recursive_value_type = false;
+};
+
+/*
+ * Tag to be used for representing the bottom of recursively defined types.
+ * Define this tag so we don't have to use void.
+ */
+struct recursive_bottom {};
+
+/*
+ * Implementation detail of `recursive_container_traits` below.
+ * `T` is the `value_type` of the container, which might need to be modified to
+ * avoid recursive types and const types.
+ */
+template <typename T, bool is_this_a_map>
+struct impl_type_to_check_recursively {
+    /*
+     * If the container is recursive, then no further recursion should be done.
+     */
+    using if_recursive = recursive_bottom;
+    /*
+     * Otherwise yield `T` unchanged.
+     */
+    using if_not_recursive = T;
+};
+
+/*
+ * For pairs - only as value type of a map -, the first type should remove the `const`.
+ * Also, if the map is recursive, then the recursive checking should consider
+ * the first type only.
+ */
+template <typename A, typename B>
+struct impl_type_to_check_recursively<std::pair<A, B>, /* is_this_a_map = */ true> {
+    using if_recursive = typename std::remove_const<A>::type;
+    using if_not_recursive = std::pair<typename std::remove_const<A>::type, B>;
+};
 
-template <typename T, typename SFINAE = void>
-struct is_move_constructible : std::is_move_constructible<T> {};
+/*
+ * Implementation of `recursive_container_traits` below.
+ */
+template <typename Container, typename SFINAE = void>
+struct impl_recursive_container_traits {
+    using type_to_check_recursively = recursive_bottom;
+};
 
-// Specialization for types that appear to be copy constructible but also look like stl containers
-// (we specifically check for: has `value_type` and `reference` with `reference = value_type&`): if
-// so, copy constructability depends on whether the value_type is copy constructible.
 template <typename Container>
-struct is_copy_constructible<
+struct impl_recursive_container_traits<
     Container,
-    enable_if_t<
-        all_of<std::is_copy_constructible<Container>,
-               std::is_same<typename Container::value_type &, typename Container::reference>,
-               // Avoid infinite recursion
-               negation<std::is_same<Container, typename Container::value_type>>>::value>>
-    : is_copy_constructible<typename Container::value_type> {};
+    typename std::enable_if<container_value_type_traits<Container>::has_value_type>::type> {
+    static constexpr bool is_recursive
+        = container_mapped_type_traits<Container>::has_recursive_mapped_type
+          || container_value_type_traits<Container>::has_recursive_value_type;
+    /*
+     * This member dictates which type Pybind11 should check recursively in traits
+     * such as `is_move_constructible`, `is_copy_constructible`, `is_move_assignable`, ...
+     * Direct access to `value_type` should be avoided:
+     * 1. `value_type` might recursively contain the type again
+     * 2. `value_type` of STL map types is `std::pair<A const, B>`, the `const`
+     *    should be removed.
+     *
+     */
+    using type_to_check_recursively = typename std::conditional<
+        is_recursive,
+        typename impl_type_to_check_recursively<
+            typename Container::value_type,
+            container_mapped_type_traits<Container>::has_mapped_type>::if_recursive,
+        typename impl_type_to_check_recursively<
+            typename Container::value_type,
+            container_mapped_type_traits<Container>::has_mapped_type>::if_not_recursive>::type;
+};
+
+/*
+ * This trait defines the `type_to_check_recursively` which is needed to properly
+ * handle recursively defined traits such as `is_move_constructible` without going
+ * into an infinite recursion.
+ * Should be used instead of directly accessing the `value_type`.
+ * It cancels the recursion by returning the `recursive_bottom` tag.
+ *
+ * The default definition of `type_to_check_recursively` is as follows:
+ *
+ * 1. By default, it is `recursive_bottom`, so that the recursion is canceled.
+ * 2. If the type is non-recursive and defines a `value_type`, then the `value_type` is used.
+ *    If the `value_type` is a pair and a `mapped_type` is defined,
+ *    then the `const` is removed from the first type.
+ * 3. If the type is recursive and `value_type` is not a pair, then `recursive_bottom` is returned.
+ * 4. If the type is recursive and `value_type` is a pair and a `mapped_type` is defined,
+ *    then `const` is removed from the first type and the first type is returned.
+ *
+ * This behavior can be extended by the user as seen in test_stl_binders.cpp.
+ *
+ * This struct is exactly the same as impl_recursive_container_traits.
+ * The duplication achieves that user-defined specializations don't compete
+ * with internal specializations, but take precedence.
+ */
+template <typename Container, typename SFINAE = void>
+struct recursive_container_traits : impl_recursive_container_traits<Container> {};
+
+template <typename T>
+struct is_move_constructible
+    : all_of<std::is_move_constructible<T>,
+             is_move_constructible<
+                 typename recursive_container_traits<T>::type_to_check_recursively>> {};
+
+template <>
+struct is_move_constructible<recursive_bottom> : std::true_type {};
+
+// Likewise for std::pair
+// (after C++17 it is mandatory that the move constructor not exist when the two types aren't
+// themselves move constructible, but this can not be relied upon when T1 or T2 are themselves
+// containers).
+template <typename T1, typename T2>
+struct is_move_constructible<std::pair<T1, T2>>
+    : all_of<is_move_constructible<T1>, is_move_constructible<T2>> {};
+
+// std::is_copy_constructible isn't quite enough: it lets std::vector<T> (and similar) through when
+// T is non-copyable, but code containing such a copy constructor fails to actually compile.
+template <typename T>
+struct is_copy_constructible
+    : all_of<std::is_copy_constructible<T>,
+             is_copy_constructible<
+                 typename recursive_container_traits<T>::type_to_check_recursively>> {};
+
+template <>
+struct is_copy_constructible<recursive_bottom> : std::true_type {};
 
 // Likewise for std::pair
 // (after C++17 it is mandatory that the copy constructor not exist when the two types aren't
@@ -852,14 +1005,16 @@ struct is_copy_constructible<std::pair<T1, T2>>
     : all_of<is_copy_constructible<T1>, is_copy_constructible<T2>> {};
 
 // The same problems arise with std::is_copy_assignable, so we use the same workaround.
-template <typename T, typename SFINAE = void>
-struct is_copy_assignable : std::is_copy_assignable<T> {};
-template <typename Container>
-struct is_copy_assignable<Container,
-                          enable_if_t<all_of<std::is_copy_assignable<Container>,
-                                             std::is_same<typename Container::value_type &,
-                                                          typename Container::reference>>::value>>
-    : is_copy_assignable<typename Container::value_type> {};
+template <typename T>
+struct is_copy_assignable
+    : all_of<
+          std::is_copy_assignable<T>,
+          is_copy_assignable<typename recursive_container_traits<T>::type_to_check_recursively>> {
+};
+
+template <>
+struct is_copy_assignable<recursive_bottom> : std::true_type {};
+
 template <typename T1, typename T2>
 struct is_copy_assignable<std::pair<T1, T2>>
     : all_of<is_copy_assignable<T1>, is_copy_assignable<T2>> {};
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 7cfd996dda..49f1b77821 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -61,9 +61,11 @@ struct is_comparable<
 /* For a vector/map data structure, recursively check the value type
    (which is std::pair for maps) */
 template <typename T>
-struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
-    static constexpr const bool value = is_comparable<typename T::value_type>::value;
-};
+struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>>
+    : is_comparable<typename recursive_container_traits<T>::type_to_check_recursively> {};
+
+template <>
+struct is_comparable<recursive_bottom> : std::true_type {};
 
 /* For pairs, recursively check the two data types */
 template <typename T>
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 28c2445644..f54733550a 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -13,6 +13,8 @@
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
 
+#include <type_traits>
+
 template <typename derived>
 struct empty {
     static const derived &get_one() { return instance_; }
@@ -293,3 +295,239 @@ TEST_SUBMODULE(copy_move_policies, m) {
     // Make sure that cast from pytype rvalue to other pytype works
     m.def("get_pytype_rvalue_castissue", [](double i) { return py::float_(i).cast<py::int_>(); });
 }
+
+/*
+ * Rest of the file:
+ * static_assert based tests for pybind11 adaptations of
+ * std::is_move_constructible, std::is_copy_constructible and
+ * std::is_copy_assignable (no adaptation of std::is_move_assignable).
+ * Difference between pybind11 and std traits: pybind11 traits will also check
+ * the contained value_types.
+ */
+
+struct NotMovable {
+    NotMovable() = default;
+    NotMovable(NotMovable const &) = default;
+    NotMovable(NotMovable &&) = delete;
+    NotMovable &operator=(NotMovable const &) = default;
+    NotMovable &operator=(NotMovable &&) = delete;
+};
+static_assert(!std::is_move_constructible<NotMovable>::value,
+              "!std::is_move_constructible<NotMovable>::value");
+static_assert(std::is_copy_constructible<NotMovable>::value,
+              "std::is_copy_constructible<NotMovable>::value");
+static_assert(!pybind11::detail::is_move_constructible<NotMovable>::value,
+              "!pybind11::detail::is_move_constructible<NotMovable>::value");
+static_assert(pybind11::detail::is_copy_constructible<NotMovable>::value,
+              "pybind11::detail::is_copy_constructible<NotMovable>::value");
+static_assert(!std::is_move_assignable<NotMovable>::value,
+              "!std::is_move_assignable<NotMovable>::value");
+static_assert(std::is_copy_assignable<NotMovable>::value,
+              "std::is_copy_assignable<NotMovable>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotMovable>::value,
+//               "!pybind11::detail::is_move_assignable<NotMovable>::value");
+static_assert(pybind11::detail::is_copy_assignable<NotMovable>::value,
+              "pybind11::detail::is_copy_assignable<NotMovable>::value");
+
+struct NotCopyable {
+    NotCopyable() = default;
+    NotCopyable(NotCopyable const &) = delete;
+    NotCopyable(NotCopyable &&) = default;
+    NotCopyable &operator=(NotCopyable const &) = delete;
+    NotCopyable &operator=(NotCopyable &&) = default;
+};
+static_assert(std::is_move_constructible<NotCopyable>::value,
+              "std::is_move_constructible<NotCopyable>::value");
+static_assert(!std::is_copy_constructible<NotCopyable>::value,
+              "!std::is_copy_constructible<NotCopyable>::value");
+static_assert(pybind11::detail::is_move_constructible<NotCopyable>::value,
+              "pybind11::detail::is_move_constructible<NotCopyable>::value");
+static_assert(!pybind11::detail::is_copy_constructible<NotCopyable>::value,
+              "!pybind11::detail::is_copy_constructible<NotCopyable>::value");
+static_assert(std::is_move_assignable<NotCopyable>::value,
+              "std::is_move_assignable<NotCopyable>::value");
+static_assert(!std::is_copy_assignable<NotCopyable>::value,
+              "!std::is_copy_assignable<NotCopyable>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotCopyable>::value,
+//               "!pybind11::detail::is_move_assignable<NotCopyable>::value");
+static_assert(!pybind11::detail::is_copy_assignable<NotCopyable>::value,
+              "!pybind11::detail::is_copy_assignable<NotCopyable>::value");
+
+struct NotCopyableNotMovable {
+    NotCopyableNotMovable() = default;
+    NotCopyableNotMovable(NotCopyableNotMovable const &) = delete;
+    NotCopyableNotMovable(NotCopyableNotMovable &&) = delete;
+    NotCopyableNotMovable &operator=(NotCopyableNotMovable const &) = delete;
+    NotCopyableNotMovable &operator=(NotCopyableNotMovable &&) = delete;
+};
+static_assert(!std::is_move_constructible<NotCopyableNotMovable>::value,
+              "!std::is_move_constructible<NotCopyableNotMovable>::value");
+static_assert(!std::is_copy_constructible<NotCopyableNotMovable>::value,
+              "!std::is_copy_constructible<NotCopyableNotMovable>::value");
+static_assert(!pybind11::detail::is_move_constructible<NotCopyableNotMovable>::value,
+              "!pybind11::detail::is_move_constructible<NotCopyableNotMovable>::value");
+static_assert(!pybind11::detail::is_copy_constructible<NotCopyableNotMovable>::value,
+              "!pybind11::detail::is_copy_constructible<NotCopyableNotMovable>::value");
+static_assert(!std::is_move_assignable<NotCopyableNotMovable>::value,
+              "!std::is_move_assignable<NotCopyableNotMovable>::value");
+static_assert(!std::is_copy_assignable<NotCopyableNotMovable>::value,
+              "!std::is_copy_assignable<NotCopyableNotMovable>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotCopyableNotMovable>::value,
+//               "!pybind11::detail::is_move_assignable<NotCopyableNotMovable>::value");
+static_assert(!pybind11::detail::is_copy_assignable<NotCopyableNotMovable>::value,
+              "!pybind11::detail::is_copy_assignable<NotCopyableNotMovable>::value");
+
+struct NotMovableVector : std::vector<NotMovable> {};
+static_assert(std::is_move_constructible<NotMovableVector>::value,
+              "std::is_move_constructible<NotMovableVector>::value");
+static_assert(std::is_copy_constructible<NotMovableVector>::value,
+              "std::is_copy_constructible<NotMovableVector>::value");
+static_assert(!pybind11::detail::is_move_constructible<NotMovableVector>::value,
+              "!pybind11::detail::is_move_constructible<NotMovableVector>::value");
+static_assert(pybind11::detail::is_copy_constructible<NotMovableVector>::value,
+              "pybind11::detail::is_copy_constructible<NotMovableVector>::value");
+static_assert(std::is_move_assignable<NotMovableVector>::value,
+              "std::is_move_assignable<NotMovableVector>::value");
+static_assert(std::is_copy_assignable<NotMovableVector>::value,
+              "std::is_copy_assignable<NotMovableVector>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotMovableVector>::value,
+//               "!pybind11::detail::is_move_assignable<NotMovableVector>::value");
+static_assert(pybind11::detail::is_copy_assignable<NotMovableVector>::value,
+              "pybind11::detail::is_copy_assignable<NotMovableVector>::value");
+
+struct NotCopyableVector : std::vector<NotCopyable> {};
+static_assert(std::is_move_constructible<NotCopyableVector>::value,
+              "std::is_move_constructible<NotCopyableVector>::value");
+static_assert(std::is_copy_constructible<NotCopyableVector>::value,
+              "std::is_copy_constructible<NotCopyableVector>::value");
+static_assert(pybind11::detail::is_move_constructible<NotCopyableVector>::value,
+              "pybind11::detail::is_move_constructible<NotCopyableVector>::value");
+static_assert(!pybind11::detail::is_copy_constructible<NotCopyableVector>::value,
+              "!pybind11::detail::is_copy_constructible<NotCopyableVector>::value");
+static_assert(std::is_move_assignable<NotCopyableVector>::value,
+              "std::is_move_assignable<NotCopyableVector>::value");
+static_assert(std::is_copy_assignable<NotCopyableVector>::value,
+              "std::is_copy_assignable<NotCopyableVector>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotCopyableVector>::value,
+//               "!pybind11::detail::is_move_assignable<NotCopyableVector>::value");
+static_assert(!pybind11::detail::is_copy_assignable<NotCopyableVector>::value,
+              "!pybind11::detail::is_copy_assignable<NotCopyableVector>::value");
+
+struct NotCopyableNotMovableVector : std::vector<NotCopyableNotMovable> {};
+static_assert(std::is_move_constructible<NotCopyableNotMovableVector>::value,
+              "std::is_move_constructible<NotCopyableNotMovableVector>::value");
+static_assert(std::is_copy_constructible<NotCopyableNotMovableVector>::value,
+              "std::is_copy_constructible<NotCopyableNotMovableVector>::value");
+static_assert(!pybind11::detail::is_move_constructible<NotCopyableNotMovableVector>::value,
+              "!pybind11::detail::is_move_constructible<NotCopyableNotMovableVector>::value");
+static_assert(!pybind11::detail::is_copy_constructible<NotCopyableNotMovableVector>::value,
+              "!pybind11::detail::is_copy_constructible<NotCopyableNotMovableVector>::value");
+static_assert(std::is_move_assignable<NotCopyableNotMovableVector>::value,
+              "std::is_move_assignable<NotCopyableNotMovableVector>::value");
+static_assert(std::is_copy_assignable<NotCopyableNotMovableVector>::value,
+              "std::is_copy_assignable<NotCopyableNotMovableVector>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotCopyableNotMovableVector>::value,
+//               "!pybind11::detail::is_move_assignable<NotCopyableNotMovableVector>::value");
+static_assert(!pybind11::detail::is_copy_assignable<NotCopyableNotMovableVector>::value,
+              "!pybind11::detail::is_copy_assignable<NotCopyableNotMovableVector>::value");
+
+struct NotMovableMap : std::map<int, NotMovable> {};
+static_assert(std::is_move_constructible<NotMovableMap>::value,
+              "std::is_move_constructible<NotMovableMap>::value");
+static_assert(std::is_copy_constructible<NotMovableMap>::value,
+              "std::is_copy_constructible<NotMovableMap>::value");
+static_assert(!pybind11::detail::is_move_constructible<NotMovableMap>::value,
+              "!pybind11::detail::is_move_constructible<NotMovableMap>::value");
+static_assert(pybind11::detail::is_copy_constructible<NotMovableMap>::value,
+              "pybind11::detail::is_copy_constructible<NotMovableMap>::value");
+static_assert(std::is_move_assignable<NotMovableMap>::value,
+              "std::is_move_assignable<NotMovableMap>::value");
+static_assert(std::is_copy_assignable<NotMovableMap>::value,
+              "std::is_copy_assignable<NotMovableMap>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotMovableMap>::value,
+//               "!pybind11::detail::is_move_assignable<NotMovableMap>::value");
+static_assert(pybind11::detail::is_copy_assignable<NotMovableMap>::value,
+              "pybind11::detail::is_copy_assignable<NotMovableMap>::value");
+
+struct NotCopyableMap : std::map<int, NotCopyable> {};
+static_assert(std::is_move_constructible<NotCopyableMap>::value,
+              "std::is_move_constructible<NotCopyableMap>::value");
+static_assert(std::is_copy_constructible<NotCopyableMap>::value,
+              "std::is_copy_constructible<NotCopyableMap>::value");
+static_assert(pybind11::detail::is_move_constructible<NotCopyableMap>::value,
+              "pybind11::detail::is_move_constructible<NotCopyableMap>::value");
+static_assert(!pybind11::detail::is_copy_constructible<NotCopyableMap>::value,
+              "!pybind11::detail::is_copy_constructible<NotCopyableMap>::value");
+static_assert(std::is_move_assignable<NotCopyableMap>::value,
+              "std::is_move_assignable<NotCopyableMap>::value");
+static_assert(std::is_copy_assignable<NotCopyableMap>::value,
+              "std::is_copy_assignable<NotCopyableMap>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotCopyableMap>::value,
+//               "!pybind11::detail::is_move_assignable<NotCopyableMap>::value");
+static_assert(!pybind11::detail::is_copy_assignable<NotCopyableMap>::value,
+              "!pybind11::detail::is_copy_assignable<NotCopyableMap>::value");
+
+struct NotCopyableNotMovableMap : std::map<int, NotCopyableNotMovable> {};
+static_assert(std::is_move_constructible<NotCopyableNotMovableMap>::value,
+              "std::is_move_constructible<NotCopyableNotMovableMap>::value");
+static_assert(std::is_copy_constructible<NotCopyableNotMovableMap>::value,
+              "std::is_copy_constructible<NotCopyableNotMovableMap>::value");
+static_assert(!pybind11::detail::is_move_constructible<NotCopyableNotMovableMap>::value,
+              "!pybind11::detail::is_move_constructible<NotCopyableNotMovableMap>::value");
+static_assert(!pybind11::detail::is_copy_constructible<NotCopyableNotMovableMap>::value,
+              "!pybind11::detail::is_copy_constructible<NotCopyableNotMovableMap>::value");
+static_assert(std::is_move_assignable<NotCopyableNotMovableMap>::value,
+              "std::is_move_assignable<NotCopyableNotMovableMap>::value");
+static_assert(std::is_copy_assignable<NotCopyableNotMovableMap>::value,
+              "std::is_copy_assignable<NotCopyableNotMovableMap>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<NotCopyableNotMovableMap>::value,
+//               "!pybind11::detail::is_move_assignable<NotCopyableNotMovableMap>::value");
+static_assert(!pybind11::detail::is_copy_assignable<NotCopyableNotMovableMap>::value,
+              "!pybind11::detail::is_copy_assignable<NotCopyableNotMovableMap>::value");
+
+struct RecursiveVector : std::vector<RecursiveVector> {};
+static_assert(std::is_move_constructible<RecursiveVector>::value,
+              "std::is_move_constructible<RecursiveVector>::value");
+static_assert(std::is_copy_constructible<RecursiveVector>::value,
+              "std::is_copy_constructible<RecursiveVector>::value");
+static_assert(pybind11::detail::is_move_constructible<RecursiveVector>::value,
+              "pybind11::detail::is_move_constructible<RecursiveVector>::value");
+static_assert(pybind11::detail::is_copy_constructible<RecursiveVector>::value,
+              "pybind11::detail::is_copy_constructible<RecursiveVector>::value");
+static_assert(std::is_move_assignable<RecursiveVector>::value,
+              "std::is_move_assignable<RecursiveVector>::value");
+static_assert(std::is_copy_assignable<RecursiveVector>::value,
+              "std::is_copy_assignable<RecursiveVector>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<RecursiveVector>::value,
+//               "!pybind11::detail::is_move_assignable<RecursiveVector>::value");
+static_assert(pybind11::detail::is_copy_assignable<RecursiveVector>::value,
+              "pybind11::detail::is_copy_assignable<RecursiveVector>::value");
+
+struct RecursiveMap : std::map<int, RecursiveMap> {};
+static_assert(std::is_move_constructible<RecursiveMap>::value,
+              "std::is_move_constructible<RecursiveMap>::value");
+static_assert(std::is_copy_constructible<RecursiveMap>::value,
+              "std::is_copy_constructible<RecursiveMap>::value");
+static_assert(pybind11::detail::is_move_constructible<RecursiveMap>::value,
+              "pybind11::detail::is_move_constructible<RecursiveMap>::value");
+static_assert(pybind11::detail::is_copy_constructible<RecursiveMap>::value,
+              "pybind11::detail::is_copy_constructible<RecursiveMap>::value");
+static_assert(std::is_move_assignable<RecursiveMap>::value,
+              "std::is_move_assignable<RecursiveMap>::value");
+static_assert(std::is_copy_assignable<RecursiveMap>::value,
+              "std::is_copy_assignable<RecursiveMap>::value");
+// pybind11 does not have this
+// static_assert(!pybind11::detail::is_move_assignable<RecursiveMap>::value,
+//               "!pybind11::detail::is_move_assignable<RecursiveMap>::value");
+static_assert(pybind11::detail::is_copy_assignable<RecursiveMap>::value,
+              "pybind11::detail::is_copy_assignable<RecursiveMap>::value");
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index ca9630bd19..1681760aa8 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -70,6 +70,44 @@ NestMap *times_hundred(int n) {
     return m;
 }
 
+/*
+ * Recursive data structures as test for issue #4623
+ */
+struct RecursiveVector : std::vector<RecursiveVector> {
+    using Parent = std::vector<RecursiveVector>;
+    using Parent::Parent;
+};
+
+struct RecursiveMap : std::map<int, RecursiveMap> {
+    using Parent = std::map<int, RecursiveMap>;
+    using Parent::Parent;
+};
+
+/*
+ * Pybind11 does not catch more complicated recursion schemes, such as mutual
+ * recursion.
+ * In that case custom recursive_container_traits specializations need to be added,
+ * thus manually telling pybind11 about the recursion.
+ */
+struct MutuallyRecursiveContainerPairMV;
+struct MutuallyRecursiveContainerPairVM;
+
+struct MutuallyRecursiveContainerPairMV : std::map<int, MutuallyRecursiveContainerPairVM> {};
+struct MutuallyRecursiveContainerPairVM : std::vector<MutuallyRecursiveContainerPairMV> {};
+
+namespace pybind11 {
+namespace detail {
+template <typename SFINAE>
+struct recursive_container_traits<MutuallyRecursiveContainerPairMV, SFINAE> {
+    using type_to_check_recursively = recursive_bottom;
+};
+template <typename SFINAE>
+struct recursive_container_traits<MutuallyRecursiveContainerPairVM, SFINAE> {
+    using type_to_check_recursively = recursive_bottom;
+};
+} // namespace detail
+} // namespace pybind11
+
 TEST_SUBMODULE(stl_binders, m) {
     // test_vector_int
     py::bind_vector<std::vector<unsigned int>>(m, "VectorInt", py::buffer_protocol());
@@ -129,6 +167,12 @@ TEST_SUBMODULE(stl_binders, m) {
             m, "VectorUndeclStruct", py::buffer_protocol());
     });
 
+    // Bind recursive container types
+    py::bind_vector<RecursiveVector>(m, "RecursiveVector");
+    py::bind_map<RecursiveMap>(m, "RecursiveMap");
+    py::bind_map<MutuallyRecursiveContainerPairMV>(m, "MutuallyRecursiveContainerPairMV");
+    py::bind_vector<MutuallyRecursiveContainerPairVM>(m, "MutuallyRecursiveContainerPairVM");
+
     // The rest depends on numpy:
     try {
         py::module_::import("numpy");
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 7dca742a9e..e002f5b678 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -335,3 +335,21 @@ def test_map_view_types():
     assert type(unordered_map_string_double.items()) is items_type
     assert type(map_string_double_const.items()) is items_type
     assert type(unordered_map_string_double_const.items()) is items_type
+
+
+def test_recursive_vector():
+    recursive_vector = m.RecursiveVector()
+    recursive_vector.append(m.RecursiveVector())
+    recursive_vector[0].append(m.RecursiveVector())
+    recursive_vector[0].append(m.RecursiveVector())
+    # Can't use len() since test_stl_binders.cpp does not include stl.h,
+    # so the necessary conversion is missing
+    assert recursive_vector[0].count(m.RecursiveVector()) == 2
+
+
+def test_recursive_map():
+    recursive_map = m.RecursiveMap()
+    recursive_map[100] = m.RecursiveMap()
+    recursive_map[100][101] = m.RecursiveMap()
+    recursive_map[100][102] = m.RecursiveMap()
+    assert list(recursive_map[100].keys()) == [101, 102]

From 90312a6ee8de69f582e165b25338ead4f1a6ccc2 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 7 May 2023 10:15:53 -0700
Subject: [PATCH 595/638] Add `type_caster<PyObject>` (#4601)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Add `type_caster<PyObject>` (tests are still incomplete).

* Fix oversight (`const PyObject *`).

* Ensure `type_caster<PyObject>` only works for `PyObject *`

* Move `is_same_ignoring_cvref` into `detail` namespace.

* Add test_cast_nullptr

* Change is_same_ignoring_cvref from variable template to using.

```
test_type_caster_pyobject_ptr.cpp:8:23: error: variable templates only available with ‘-std=c++14’ or ‘-std=gnu++14’ [-Werror]
    8 | static constexpr bool is_same_ignoring_cvref = std::is_same<detail::remove_cvref_t<T>, U>::value;
      |                       ^~~~~~~~~~~~~~~~~~~~~~
```

* Remove `return_value_policy::reference_internal` `keep_alive` feature (because of doubts about it actually being useful).

* Add missing test, fix bug (missing `throw error_already_set();`), various cosmetic changes.

* Move `type_caster<PyObject>` from test to new include (pybind11/type_caster_pyobject_ptr.h)

* Add new header file to CMakeLists.txt and tests/extra_python_package/test_files.py

* Backport changes from https://github.com/google/pywrapcc/pull/30021 to https://github.com/pybind/pybind11/pull/4601

* Fix oversight in test (to resolve a valgrind leak detection error) and add a related comment in cast.h.

No production code changes.

Make tests more sensitive by using `ValueHolder` instead of empty tuples and dicts.

Manual leak checks with `while True:` & top command repeated for all tests.

* Add tests for interop with stl.h `list_caster`

(No production code changes.)

* Bug fix in test. Minor comment enhancements.

* Change `type_caster<PyObject>::name` to `object`, as suggested by @Skylion007

* Expand comment for the new `T cast(const handle &handle)` [`T` = `PyObject *`]

* Add `T cast(object &&obj)` overload as suggested by @Skylion007

The original suggestion leads to `error: call to 'cast' is ambiguous` (full error message below), therefore SFINAE guarding is needed.

```
clang++ -o pybind11/tests/test_type_caster_pyobject_ptr.os -c -std=c++17 -fPIC -fvisibility=hidden -O0 -g -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated -Wundef -Wnon-virtual-dtor -Wunused-result -Werror -isystem /usr/include/python3.10 -isystem /usr/include/eigen3 -DPYBIND11_STRICT_ASSERTS_CLASS_HOLDER_VS_TYPE_CASTER_MIX -DPYBIND11_ENABLE_TYPE_CASTER_ODR_GUARD_IF_AVAILABLE -DPYBIND11_TEST_BOOST -Ipybind11/include -I/usr/local/google/home/rwgk/forked/pybind11/include -I/usr/local/google/home/rwgk/clone/pybind11/include /usr/local/google/home/rwgk/forked/pybind11/tests/test_type_caster_pyobject_ptr.cpp
In file included from /usr/local/google/home/rwgk/forked/pybind11/tests/test_type_caster_pyobject_ptr.cpp:1:
In file included from /usr/local/google/home/rwgk/forked/pybind11/include/pybind11/functional.h:12:
In file included from /usr/local/google/home/rwgk/forked/pybind11/include/pybind11/pybind11.h:13:
In file included from /usr/local/google/home/rwgk/forked/pybind11/include/pybind11/detail/class.h:12:
In file included from /usr/local/google/home/rwgk/forked/pybind11/include/pybind11/attr.h:14:
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/cast.h:1165:12: error: call to 'cast' is ambiguous
    return pybind11::cast<T>(std::move(*this));
           ^~~~~~~~~~~~~~~~~
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/functional.h:109:70: note: in instantiation of function template specialization 'pybind11::object::cast<_object *>' requested here
                return hfunc.f(std::forward<Args>(args)...).template cast<Return>();
                                                                     ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/functional.h:103:16: note: in instantiation of member function 'pybind11::detail::type_caster<std::function<_object *(int)>>::load(pybind11::handle, bool)::func_wrapper::operator()' requested here
        struct func_wrapper {
               ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/cast.h:1456:47: note: in instantiation of member function 'pybind11::detail::type_caster<std::function<_object *(int)>>::load' requested here
        if ((... || !std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is]))) {
                                              ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/cast.h:1434:50: note: in instantiation of function template specialization 'pybind11::detail::argument_loader<const std::function<_object *(int)> &, int>::load_impl_sequence<0UL, 1UL>' requested here
    bool load_args(function_call &call) { return load_impl_sequence(call, indices{}); }
                                                 ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/pybind11.h:227:33: note: in instantiation of member function 'pybind11::detail::argument_loader<const std::function<_object *(int)> &, int>::load_args' requested here
            if (!args_converter.load_args(call)) {
                                ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/pybind11.h:101:9: note: in instantiation of function template specialization 'pybind11::cpp_function::initialize<(lambda at /usr/local/google/home/rwgk/forked/pybind11/tests/test_type_caster_pyobject_ptr.cpp:50:9), _object *, const std::function<_object *(int)> &, int, pybind11::name, pybind11::scope, pybind11::sibling, pybind11::return_value_policy>' requested here
        initialize(
        ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/pybind11.h:1163:22: note: in instantiation of function template specialization 'pybind11::cpp_function::cpp_function<(lambda at /usr/local/google/home/rwgk/forked/pybind11/tests/test_type_caster_pyobject_ptr.cpp:50:9), pybind11::name, pybind11::scope, pybind11::sibling, pybind11::return_value_policy, void>' requested here
        cpp_function func(std::forward<Func>(f),
                     ^
/usr/local/google/home/rwgk/forked/pybind11/tests/test_type_caster_pyobject_ptr.cpp:48:7: note: in instantiation of function template specialization 'pybind11::module_::def<(lambda at /usr/local/google/home/rwgk/forked/pybind11/tests/test_type_caster_pyobject_ptr.cpp:50:9), pybind11::return_value_policy>' requested here
    m.def(
      ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/cast.h:1077:3: note: candidate function [with T = _object *, $1 = 0]
T cast(object &&obj) {
  ^
/usr/local/google/home/rwgk/forked/pybind11/include/pybind11/cast.h:1149:1: note: candidate function [with T = _object *]
cast(object &&object) {
^
1 error generated.
```
---
 CMakeLists.txt                              |   3 +-
 include/pybind11/cast.h                     |  34 ++++-
 include/pybind11/detail/common.h            |   4 +
 include/pybind11/type_caster_pyobject_ptr.h |  61 +++++++++
 tests/CMakeLists.txt                        |   1 +
 tests/extra_python_package/test_files.py    |   1 +
 tests/test_type_caster_pyobject_ptr.cpp     | 130 ++++++++++++++++++++
 tests/test_type_caster_pyobject_ptr.py      | 104 ++++++++++++++++
 8 files changed, 336 insertions(+), 2 deletions(-)
 create mode 100644 include/pybind11/type_caster_pyobject_ptr.h
 create mode 100644 tests/test_type_caster_pyobject_ptr.cpp
 create mode 100644 tests/test_type_caster_pyobject_ptr.py

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0d93203881..25a7d14984 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -139,7 +139,8 @@ set(PYBIND11_HEADERS
     include/pybind11/pytypes.h
     include/pybind11/stl.h
     include/pybind11/stl_bind.h
-    include/pybind11/stl/filesystem.h)
+    include/pybind11/stl/filesystem.h
+    include/pybind11/type_caster_pyobject_ptr.h)
 
 # Compare with grep and warn if mismatched
 if(PYBIND11_MASTER_PROJECT AND NOT CMAKE_VERSION VERSION_LESS 3.12)
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 9d1ce15d48..db39341180 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1041,7 +1041,11 @@ make_caster<T> load_type(const handle &handle) {
 PYBIND11_NAMESPACE_END(detail)
 
 // pytype -> C++ type
-template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
+template <typename T,
+          detail::enable_if_t<!detail::is_pyobject<T>::value
+                                  && !detail::is_same_ignoring_cvref<T, PyObject *>::value,
+                              int>
+          = 0>
 T cast(const handle &handle) {
     using namespace detail;
     static_assert(!cast_is_temporary_value_reference<T>::value,
@@ -1055,6 +1059,34 @@ T cast(const handle &handle) {
     return T(reinterpret_borrow<object>(handle));
 }
 
+// Note that `cast<PyObject *>(obj)` increments the reference count of `obj`.
+// This is necessary for the case that `obj` is a temporary, and could
+// not possibly be different, given
+// 1. the established convention that the passed `handle` is borrowed, and
+// 2. we don't want to force all generic code using `cast<T>()` to special-case
+//    handling of `T` = `PyObject *` (to increment the reference count there).
+// It is the responsibility of the caller to ensure that the reference count
+// is decremented.
+template <typename T,
+          typename Handle,
+          detail::enable_if_t<detail::is_same_ignoring_cvref<T, PyObject *>::value
+                                  && detail::is_same_ignoring_cvref<Handle, handle>::value,
+                              int>
+          = 0>
+T cast(Handle &&handle) {
+    return handle.inc_ref().ptr();
+}
+// To optimize way an inc_ref/dec_ref cycle:
+template <typename T,
+          typename Object,
+          detail::enable_if_t<detail::is_same_ignoring_cvref<T, PyObject *>::value
+                                  && detail::is_same_ignoring_cvref<Object, object>::value,
+                              int>
+          = 0>
+T cast(Object &&obj) {
+    return obj.release().ptr();
+}
+
 // C++ type -> py::object
 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
 object cast(T &&value,
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 129039252f..1ff0df09fe 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -661,6 +661,10 @@ template <class T>
 using remove_cvref_t = typename remove_cvref<T>::type;
 #endif
 
+/// Example usage: is_same_ignoring_cvref<T, PyObject *>::value
+template <typename T, typename U>
+using is_same_ignoring_cvref = std::is_same<detail::remove_cvref_t<T>, U>;
+
 /// Index sequences
 #if defined(PYBIND11_CPP14)
 using std::index_sequence;
diff --git a/include/pybind11/type_caster_pyobject_ptr.h b/include/pybind11/type_caster_pyobject_ptr.h
new file mode 100644
index 0000000000..aa914f9e15
--- /dev/null
+++ b/include/pybind11/type_caster_pyobject_ptr.h
@@ -0,0 +1,61 @@
+// Copyright (c) 2023 The pybind Community.
+
+#pragma once
+
+#include "detail/common.h"
+#include "detail/descr.h"
+#include "cast.h"
+#include "pytypes.h"
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+template <>
+class type_caster<PyObject> {
+public:
+    static constexpr auto name = const_name("object"); // See discussion under PR #4601.
+
+    // This overload is purely to guard against accidents.
+    template <typename T,
+              detail::enable_if_t<!is_same_ignoring_cvref<T, PyObject *>::value, int> = 0>
+    static handle cast(T &&, return_value_policy, handle /*parent*/) {
+        static_assert(is_same_ignoring_cvref<T, PyObject *>::value,
+                      "Invalid C++ type T for to-Python conversion (type_caster<PyObject>).");
+        return nullptr; // Unreachable.
+    }
+
+    static handle cast(PyObject *src, return_value_policy policy, handle /*parent*/) {
+        if (src == nullptr) {
+            throw error_already_set();
+        }
+        if (PyErr_Occurred()) {
+            raise_from(PyExc_SystemError, "src != nullptr but PyErr_Occurred()");
+            throw error_already_set();
+        }
+        if (policy == return_value_policy::take_ownership) {
+            return src;
+        }
+        if (policy == return_value_policy::reference
+            || policy == return_value_policy::automatic_reference) {
+            return handle(src).inc_ref();
+        }
+        pybind11_fail("type_caster<PyObject>::cast(): unsupported return_value_policy: "
+                      + std::to_string(static_cast<int>(policy)));
+    }
+
+    bool load(handle src, bool) {
+        value = reinterpret_borrow<object>(src);
+        return true;
+    }
+
+    template <typename T>
+    using cast_op_type = PyObject *;
+
+    explicit operator PyObject *() { return value.ptr(); }
+
+private:
+    object value;
+};
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 11ac2215b3..5574663b63 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -154,6 +154,7 @@ set(PYBIND11_TEST_FILES
     test_stl_binders
     test_tagbased_polymorphic
     test_thread
+    test_type_caster_pyobject_ptr
     test_union
     test_unnamed_namespace_a
     test_unnamed_namespace_b
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index dd6393bf0b..e5982f962e 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -43,6 +43,7 @@
     "include/pybind11/pytypes.h",
     "include/pybind11/stl.h",
     "include/pybind11/stl_bind.h",
+    "include/pybind11/type_caster_pyobject_ptr.h",
 }
 
 detail_headers = {
diff --git a/tests/test_type_caster_pyobject_ptr.cpp b/tests/test_type_caster_pyobject_ptr.cpp
new file mode 100644
index 0000000000..1667ea1266
--- /dev/null
+++ b/tests/test_type_caster_pyobject_ptr.cpp
@@ -0,0 +1,130 @@
+#include <pybind11/functional.h>
+#include <pybind11/stl.h>
+#include <pybind11/type_caster_pyobject_ptr.h>
+
+#include "pybind11_tests.h"
+
+#include <cstddef>
+#include <vector>
+
+namespace {
+
+std::vector<PyObject *> make_vector_pyobject_ptr(const py::object &ValueHolder) {
+    std::vector<PyObject *> vec_obj;
+    for (int i = 1; i < 3; i++) {
+        vec_obj.push_back(ValueHolder(i * 93).release().ptr());
+    }
+    // This vector now owns the refcounts.
+    return vec_obj;
+}
+
+} // namespace
+
+TEST_SUBMODULE(type_caster_pyobject_ptr, m) {
+    m.def("cast_from_pyobject_ptr", []() {
+        PyObject *ptr = PyLong_FromLongLong(6758L);
+        return py::cast(ptr, py::return_value_policy::take_ownership);
+    });
+    m.def("cast_handle_to_pyobject_ptr", [](py::handle obj) {
+        auto rc1 = obj.ref_count();
+        auto *ptr = py::cast<PyObject *>(obj);
+        auto rc2 = obj.ref_count();
+        if (rc2 != rc1 + 1) {
+            return -1;
+        }
+        return 100 - py::reinterpret_steal<py::object>(ptr).attr("value").cast<int>();
+    });
+    m.def("cast_object_to_pyobject_ptr", [](py::object obj) {
+        py::handle hdl = obj;
+        auto rc1 = hdl.ref_count();
+        auto *ptr = py::cast<PyObject *>(std::move(obj));
+        auto rc2 = hdl.ref_count();
+        if (rc2 != rc1) {
+            return -1;
+        }
+        return 300 - py::reinterpret_steal<py::object>(ptr).attr("value").cast<int>();
+    });
+    m.def("cast_list_to_pyobject_ptr", [](py::list lst) {
+        // This is to cover types implicitly convertible to object.
+        py::handle hdl = lst;
+        auto rc1 = hdl.ref_count();
+        auto *ptr = py::cast<PyObject *>(std::move(lst));
+        auto rc2 = hdl.ref_count();
+        if (rc2 != rc1) {
+            return -1;
+        }
+        return 400 - static_cast<int>(py::len(py::reinterpret_steal<py::list>(ptr)));
+    });
+
+    m.def(
+        "return_pyobject_ptr",
+        []() { return PyLong_FromLongLong(2314L); },
+        py::return_value_policy::take_ownership);
+    m.def("pass_pyobject_ptr", [](PyObject *ptr) {
+        return 200 - py::reinterpret_borrow<py::object>(ptr).attr("value").cast<int>();
+    });
+
+    m.def("call_callback_with_object_return",
+          [](const std::function<py::object(int)> &cb, int value) { return cb(value); });
+    m.def(
+        "call_callback_with_pyobject_ptr_return",
+        [](const std::function<PyObject *(int)> &cb, int value) { return cb(value); },
+        py::return_value_policy::take_ownership);
+    m.def(
+        "call_callback_with_pyobject_ptr_arg",
+        [](const std::function<int(PyObject *)> &cb, py::handle obj) { return cb(obj.ptr()); },
+        py::arg("cb"), // This triggers return_value_policy::automatic_reference
+        py::arg("obj"));
+
+    m.def("cast_to_pyobject_ptr_nullptr", [](bool set_error) {
+        if (set_error) {
+            PyErr_SetString(PyExc_RuntimeError, "Reflective of healthy error handling.");
+        }
+        PyObject *ptr = nullptr;
+        py::cast(ptr);
+    });
+
+    m.def("cast_to_pyobject_ptr_non_nullptr_with_error_set", []() {
+        PyErr_SetString(PyExc_RuntimeError, "Reflective of unhealthy error handling.");
+        py::cast(Py_None);
+    });
+
+    m.def("pass_list_pyobject_ptr", [](const std::vector<PyObject *> &vec_obj) {
+        int acc = 0;
+        for (const auto &ptr : vec_obj) {
+            acc = acc * 1000 + py::reinterpret_borrow<py::object>(ptr).attr("value").cast<int>();
+        }
+        return acc;
+    });
+
+    m.def("return_list_pyobject_ptr_take_ownership",
+          make_vector_pyobject_ptr,
+          // Ownership is transferred one-by-one when the vector is converted to a Python list.
+          py::return_value_policy::take_ownership);
+
+    m.def("return_list_pyobject_ptr_reference",
+          make_vector_pyobject_ptr,
+          // Ownership is not transferred.
+          py::return_value_policy::reference);
+
+    m.def("dec_ref_each_pyobject_ptr", [](const std::vector<PyObject *> &vec_obj) {
+        std::size_t i = 0;
+        for (; i < vec_obj.size(); i++) {
+            py::handle h(vec_obj[i]);
+            if (static_cast<std::size_t>(h.ref_count()) < 2) {
+                break; // Something is badly wrong.
+            }
+            h.dec_ref();
+        }
+        return i;
+    });
+
+    m.def("pass_pyobject_ptr_and_int", [](PyObject *, int) {});
+
+#ifdef PYBIND11_NO_COMPILE_SECTION // Change to ifndef for manual testing.
+    {
+        PyObject *ptr = nullptr;
+        (void) py::cast(*ptr);
+    }
+#endif
+}
diff --git a/tests/test_type_caster_pyobject_ptr.py b/tests/test_type_caster_pyobject_ptr.py
new file mode 100644
index 0000000000..1f1ece2baf
--- /dev/null
+++ b/tests/test_type_caster_pyobject_ptr.py
@@ -0,0 +1,104 @@
+import pytest
+
+from pybind11_tests import type_caster_pyobject_ptr as m
+
+
+# For use as a temporary user-defined object, to maximize sensitivity of the tests below.
+class ValueHolder:
+    def __init__(self, value):
+        self.value = value
+
+
+def test_cast_from_pyobject_ptr():
+    assert m.cast_from_pyobject_ptr() == 6758
+
+
+def test_cast_handle_to_pyobject_ptr():
+    assert m.cast_handle_to_pyobject_ptr(ValueHolder(24)) == 76
+
+
+def test_cast_object_to_pyobject_ptr():
+    assert m.cast_object_to_pyobject_ptr(ValueHolder(43)) == 257
+
+
+def test_cast_list_to_pyobject_ptr():
+    assert m.cast_list_to_pyobject_ptr([1, 2, 3, 4, 5]) == 395
+
+
+def test_return_pyobject_ptr():
+    assert m.return_pyobject_ptr() == 2314
+
+
+def test_pass_pyobject_ptr():
+    assert m.pass_pyobject_ptr(ValueHolder(82)) == 118
+
+
+@pytest.mark.parametrize(
+    "call_callback",
+    [
+        m.call_callback_with_object_return,
+        m.call_callback_with_pyobject_ptr_return,
+    ],
+)
+def test_call_callback_with_object_return(call_callback):
+    def cb(value):
+        if value < 0:
+            raise ValueError("Raised from cb")
+        return ValueHolder(1000 - value)
+
+    assert call_callback(cb, 287).value == 713
+
+    with pytest.raises(ValueError, match="^Raised from cb$"):
+        call_callback(cb, -1)
+
+
+def test_call_callback_with_pyobject_ptr_arg():
+    def cb(obj):
+        return 300 - obj.value
+
+    assert m.call_callback_with_pyobject_ptr_arg(cb, ValueHolder(39)) == 261
+
+
+@pytest.mark.parametrize("set_error", [True, False])
+def test_cast_to_python_nullptr(set_error):
+    expected = {
+        True: r"^Reflective of healthy error handling\.$",
+        False: (
+            r"^Internal error: pybind11::error_already_set called "
+            r"while Python error indicator not set\.$"
+        ),
+    }[set_error]
+    with pytest.raises(RuntimeError, match=expected):
+        m.cast_to_pyobject_ptr_nullptr(set_error)
+
+
+def test_cast_to_python_non_nullptr_with_error_set():
+    with pytest.raises(SystemError) as excinfo:
+        m.cast_to_pyobject_ptr_non_nullptr_with_error_set()
+    assert str(excinfo.value) == "src != nullptr but PyErr_Occurred()"
+    assert str(excinfo.value.__cause__) == "Reflective of unhealthy error handling."
+
+
+def test_pass_list_pyobject_ptr():
+    acc = m.pass_list_pyobject_ptr([ValueHolder(842), ValueHolder(452)])
+    assert acc == 842452
+
+
+def test_return_list_pyobject_ptr_take_ownership():
+    vec_obj = m.return_list_pyobject_ptr_take_ownership(ValueHolder)
+    assert [e.value for e in vec_obj] == [93, 186]
+
+
+def test_return_list_pyobject_ptr_reference():
+    vec_obj = m.return_list_pyobject_ptr_reference(ValueHolder)
+    assert [e.value for e in vec_obj] == [93, 186]
+    # Commenting out the next `assert` will leak the Python references.
+    # An easy way to see evidence of the leaks:
+    # Insert `while True:` as the first line of this function and monitor the
+    # process RES (Resident Memory Size) with the Unix top command.
+    assert m.dec_ref_each_pyobject_ptr(vec_obj) == 2
+
+
+def test_type_caster_name_via_incompatible_function_arguments_type_error():
+    with pytest.raises(TypeError, match=r"1\. \(arg0: object, arg1: int\) -> None"):
+        m.pass_pyobject_ptr_and_int(ValueHolder(101), ValueHolder(202))

From e9b961d9b913575c07ba28c038c3706731768da6 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 8 May 2023 10:13:54 -0700
Subject: [PATCH 596/638] Elide to-python conversion of setter return values
 (#4621)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Reproducer for property setter with return type that is not wrapped.

* Use `py::class_<OptionsBase>()` to work around the return value conversion issue.

* WIP drop_return_value

* Remove struct drop_return_value

* Introduce `return_value_policy::return_none` for use by setters.

* Add `is_setter` to attr.h and use from `.def_property()`

* Merge the new test into test_methods_and_attributes

* Remove return_none return_value_policy again.

* Fix oversight (NOLINTNEXTLINE placement).

* Simplification (for the better) found while searching for a way to resolve GCC build failures.

Example of failure resolved by this change:

g++ (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0

```
cd /build/tests && /usr/bin/c++ -DPYBIND11_TEST_EIGEN -Dpybind11_tests_EXPORTS -I/mounted_pybind11/include -isystem /usr/include/python3.8 -isystem /build/_deps/eigen-src -g -std=c++17 -fPIC -fvisibility=hidden -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated -Wundef -Wnon-virtual-dtor -MD -MT tests/CMakeFiles/pybind11_tests.dir/test_buffers.cpp.o -MF CMakeFiles/pybind11_tests.dir/test_buffers.cpp.o.d -o CMakeFiles/pybind11_tests.dir/test_buffers.cpp.o -c /mounted_pybind11/tests/test_buffers.cpp
In file included from /mounted_pybind11/include/pybind11/stl.h:12,
                 from /mounted_pybind11/tests/test_buffers.cpp:10:
/mounted_pybind11/include/pybind11/pybind11.h: In instantiation of ‘pybind11::class_<type_, options>& pybind11::class_<type_, options>::def_property(const char*, const Getter&, const Setter&, const Extra& ...) [with Getter = pybind11::cpp_function; Setter = std::nullptr_t; Extra = {pybind11::return_value_policy}; type_ = pybind11::buffer_info; options = {}]’:
/mounted_pybind11/include/pybind11/pybind11.h:1716:58:   required from ‘pybind11::class_<type_, options>& pybind11::class_<type_, options>::def_property_readonly(const char*, const pybind11::cpp_function&, const Extra& ...) [with Extra = {pybind11::return_value_policy}; type_ = pybind11::buffer_info; options = {}]’
/mounted_pybind11/include/pybind11/pybind11.h:1684:9:   required from ‘pybind11::class_<type_, options>& pybind11::class_<type_, options>::def_readonly(const char*, const D C::*, const Extra& ...) [with C = pybind11::buffer_info; D = long int; Extra = {}; type_ = pybind11::buffer_info; options = {}]’
/mounted_pybind11/tests/test_buffers.cpp:209:61:   required from here
/mounted_pybind11/include/pybind11/pybind11.h:1740:25: error: call of overloaded ‘cpp_function(std::nullptr_t&, pybind11::is_setter)’ is ambiguous
 1740 |             name, fget, cpp_function(method_adaptor<type>(fset), is_setter()), extra...);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/mounted_pybind11/include/pybind11/pybind11.h:101:5: note: candidate: ‘pybind11::cpp_function::cpp_function(Func&&, const Extra& ...) [with Func = std::nullptr_t&; Extra = {pybind11::is_setter}; <template-parameter-1-3> = void]’
  101 |     cpp_function(Func &&f, const Extra &...extra) {
      |     ^~~~~~~~~~~~
In file included from /mounted_pybind11/include/pybind11/stl.h:12,
                 from /mounted_pybind11/tests/test_buffers.cpp:10:
/mounted_pybind11/include/pybind11/pybind11.h:87:5: note: candidate: ‘pybind11::cpp_function::cpp_function(std::nullptr_t, const Extra& ...) [with Extra = {pybind11::is_setter}; std::nullptr_t = std::nullptr_t]’
   87 |     cpp_function(std::nullptr_t, const Extra &...) {}
      |     ^~~~~~~~~~~~
```

* Bug fix: obvious in hindsight. I thought the original version was incrementing the reference count for None, but no.

Discovered via many failing tests in the wild (10s of thousands).

It is very tricky to construct a meaningful unit test for this bug specifically. It's unlikely to come back, because 10s of thousands of tests will fail again.
---
 include/pybind11/attr.h               | 16 +++++++++++--
 include/pybind11/pybind11.h           | 18 ++++++++++----
 tests/test_methods_and_attributes.cpp | 34 +++++++++++++++++++++++++++
 tests/test_methods_and_attributes.py  |  9 +++++++
 4 files changed, 70 insertions(+), 7 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index b5e3b7b22c..1044db94d9 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -26,6 +26,9 @@ struct is_method {
     explicit is_method(const handle &c) : class_(c) {}
 };
 
+/// Annotation for setters
+struct is_setter {};
+
 /// Annotation for operators
 struct is_operator {};
 
@@ -188,8 +191,8 @@ struct argument_record {
 struct function_record {
     function_record()
         : is_constructor(false), is_new_style_constructor(false), is_stateless(false),
-          is_operator(false), is_method(false), has_args(false), has_kwargs(false),
-          prepend(false) {}
+          is_operator(false), is_method(false), is_setter(false), has_args(false),
+          has_kwargs(false), prepend(false) {}
 
     /// Function name
     char *name = nullptr; /* why no C++ strings? They generate heavier code.. */
@@ -230,6 +233,9 @@ struct function_record {
     /// True if this is a method
     bool is_method : 1;
 
+    /// True if this is a setter
+    bool is_setter : 1;
+
     /// True if the function has a '*args' argument
     bool has_args : 1;
 
@@ -426,6 +432,12 @@ struct process_attribute<is_method> : process_attribute_default<is_method> {
     }
 };
 
+/// Process an attribute which indicates that this function is a setter
+template <>
+struct process_attribute<is_setter> : process_attribute_default<is_setter> {
+    static void init(const is_setter &, function_record *r) { r->is_setter = true; }
+};
+
 /// Process an attribute which indicates the parent scope of a method
 template <>
 struct process_attribute<scope> : process_attribute_default<scope> {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 6205effd61..28ebc22297 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -84,6 +84,7 @@ class cpp_function : public function {
     cpp_function() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
     cpp_function(std::nullptr_t) {}
+    cpp_function(std::nullptr_t, const is_setter &) {}
 
     /// Construct a cpp_function from a vanilla function pointer
     template <typename Return, typename... Args, typename... Extra>
@@ -244,10 +245,16 @@ class cpp_function : public function {
             using Guard = extract_guard_t<Extra...>;
 
             /* Perform the function call */
-            handle result
-                = cast_out::cast(std::move(args_converter).template call<Return, Guard>(cap->f),
-                                 policy,
-                                 call.parent);
+            handle result;
+            if (call.func.is_setter) {
+                (void) std::move(args_converter).template call<Return, Guard>(cap->f);
+                result = none().release();
+            } else {
+                result = cast_out::cast(
+                    std::move(args_converter).template call<Return, Guard>(cap->f),
+                    policy,
+                    call.parent);
+            }
 
             /* Invoke call policy post-call hook */
             process_attributes<Extra...>::postcall(call, result);
@@ -1729,7 +1736,8 @@ class class_ : public detail::generic_type {
     template <typename Getter, typename Setter, typename... Extra>
     class_ &
     def_property(const char *name, const Getter &fget, const Setter &fset, const Extra &...extra) {
-        return def_property(name, fget, cpp_function(method_adaptor<type>(fset)), extra...);
+        return def_property(
+            name, fget, cpp_function(method_adaptor<type>(fset), is_setter()), extra...);
     }
     template <typename Getter, typename... Extra>
     class_ &def_property(const char *name,
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 815dd5e98a..31d46eb7ed 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -177,6 +177,38 @@ struct RValueRefParam {
     std::size_t func4(std::string &&s) const & { return s.size(); }
 };
 
+namespace pybind11_tests {
+namespace exercise_is_setter {
+
+struct FieldBase {
+    int int_value() const { return int_value_; }
+
+    FieldBase &SetIntValue(int int_value) {
+        int_value_ = int_value;
+        return *this;
+    }
+
+private:
+    int int_value_ = -99;
+};
+
+struct Field : FieldBase {};
+
+void add_bindings(py::module &m) {
+    py::module sm = m.def_submodule("exercise_is_setter");
+    // NOTE: FieldBase is not wrapped, therefore ...
+    py::class_<Field>(sm, "Field")
+        .def(py::init<>())
+        .def_property(
+            "int_value",
+            &Field::int_value,
+            &Field::SetIntValue // ... the `FieldBase &` return value here cannot be converted.
+        );
+}
+
+} // namespace exercise_is_setter
+} // namespace pybind11_tests
+
 TEST_SUBMODULE(methods_and_attributes, m) {
     // test_methods_and_attributes
     py::class_<ExampleMandA> emna(m, "ExampleMandA");
@@ -456,4 +488,6 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def("func2", &RValueRefParam::func2)
         .def("func3", &RValueRefParam::func3)
         .def("func4", &RValueRefParam::func4);
+
+    pybind11_tests::exercise_is_setter::add_bindings(m);
 }
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index a854685750..955a85f67c 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -522,3 +522,12 @@ def test_rvalue_ref_param():
     assert r.func2("1234") == 4
     assert r.func3("12345") == 5
     assert r.func4("123456") == 6
+
+
+def test_is_setter():
+    fld = m.exercise_is_setter.Field()
+    assert fld.int_value == -99
+    setter_return = fld.int_value = 100
+    assert isinstance(setter_return, int)
+    assert setter_return == 100
+    assert fld.int_value == 100

From cca4c51ca463ea02fa504331ff21bc313c80c7f3 Mon Sep 17 00:00:00 2001
From: Tim Stumbaugh <anabus.maximus@gmail.com>
Date: Tue, 9 May 2023 08:04:20 -0600
Subject: [PATCH 597/638] Update errors in string "Explicit conversions" docs
 (#4658)

`PyUnicode_DecodeLatin1` requires you to pass in the `error`
parameter. The code as it is in the docs didn't compile.

There is a reference leak in the example
code. `PyUnicode_DecodeLatin1` returns a new reference. Calling
`py::str(PyObject*)` calls `PyObject_Str`, which also returns a new
reference. That reference is managed by the `py::str`
constructor (which correctly steals the reference, using the
`stolen_t` constructor), but the original reference returned by
`PyUnicode_DecodeLatin1` is never decref'd: it never makes it into an
`object`, and it's never manually decremented.

This fixes both of those issues. The code compiles, and I viewed the
sphinx docs locally.
---
 docs/advanced/cast/strings.rst | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/docs/advanced/cast/strings.rst b/docs/advanced/cast/strings.rst
index e246c5219a..271716b4b3 100644
--- a/docs/advanced/cast/strings.rst
+++ b/docs/advanced/cast/strings.rst
@@ -101,8 +101,11 @@ conversion has the same overhead as implicit conversion.
     m.def("str_output",
         []() {
             std::string s = "Send your r\xe9sum\xe9 to Alice in HR"; // Latin-1
-            py::str py_s = PyUnicode_DecodeLatin1(s.data(), s.length());
-            return py_s;
+            py::handle py_s = PyUnicode_DecodeLatin1(s.data(), s.length(), nullptr);
+            if (!py_s) {
+                throw py::error_already_set();
+            }
+            return py::reinterpret_steal<py::str>(py_s);
         }
     );
 
@@ -113,7 +116,8 @@ conversion has the same overhead as implicit conversion.
 
 The `Python C API
 <https://docs.python.org/3/c-api/unicode.html#built-in-codecs>`_ provides
-several built-in codecs.
+several built-in codecs. Note that these all return *new* references, so
+use :cpp:func:`reinterpret_steal` when converting them to a :cpp:class:`str`.
 
 
 One could also use a third party encoding library such as libiconv to transcode

From d72ffb448c58b4ffb08b5ad629bc788646e2d59e Mon Sep 17 00:00:00 2001
From: Joyce <joycebrum@google.com>
Date: Mon, 15 May 2023 14:02:25 -0300
Subject: [PATCH 598/638] ci: set minimal permissions to github workflows
 (#4665)

* set ci.yml minimal permissions

Signed-off-by: Joyce <joycebrum@google.com>

* set configure.yml minimal permissions

Signed-off-by: Joyce <joycebrum@google.com>

* set format.yml minimal permissions

Signed-off-by: Joyce <joycebrum@google.com>

* set pip.yml minimal permissions

Signed-off-by: Joyce <joycebrum@google.com>

* set upstream.yml minimal permissions

Signed-off-by: Joyce <joycebrum@google.com>

* set labeler.yml minimal permissions

Signed-off-by: Joyce <joycebrum@google.com>

* Update ci.yml to read all

Signed-off-by: Joyce <joycebrum@google.com>

* test labeler.yml

Signed-off-by: Joyce <joycebrum@google.com>

* restore the if at labeler.yml

Signed-off-by: Joyce <joycebrum@google.com>

---------

Signed-off-by: Joyce <joycebrum@google.com>
---
 .github/workflows/ci.yml        | 2 ++
 .github/workflows/configure.yml | 3 +++
 .github/workflows/format.yml    | 3 +++
 .github/workflows/labeler.yml   | 5 +++++
 .github/workflows/pip.yml       | 3 +++
 .github/workflows/upstream.yml  | 3 +++
 6 files changed, 19 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c88f0797f2..8c2aba343a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,6 +9,8 @@ on:
       - stable
       - v*
 
+permissions: read-all
+
 concurrency:
   group: test-${{ github.ref }}
   cancel-in-progress: true
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index b469a69d11..4ae22281c6 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -9,6 +9,9 @@ on:
       - stable
       - v*
 
+permissions:
+  contents: read
+
 env:
   # For cmake:
   VERBOSE: 1
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 46489feb31..b8242ee52c 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -12,6 +12,9 @@ on:
     - stable
     - "v*"
 
+permissions:
+  contents: read
+
 env:
   FORCE_COLOR: 3
   # For cmake:
diff --git a/.github/workflows/labeler.yml b/.github/workflows/labeler.yml
index 165a2fd87b..858a4a0e26 100644
--- a/.github/workflows/labeler.yml
+++ b/.github/workflows/labeler.yml
@@ -3,10 +3,15 @@ on:
   pull_request_target:
     types: [closed]
 
+permissions: {}
+
 jobs:
   label:
     name: Labeler
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
     steps:
 
     - uses: actions/labeler@main
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 6d9be3b1d4..c1feb6fe10 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -12,6 +12,9 @@ on:
     types:
     - published
 
+permissions:
+  contents: read
+
 env:
   PIP_ONLY_BINARY: numpy
 
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index be643ddfdb..4acfbfce75 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -5,6 +5,9 @@ on:
   workflow_dispatch:
   pull_request:
 
+permissions:
+  contents: read
+
 concurrency:
   group: upstream-${{ github.ref }}
   cancel-in-progress: true

From 19816f0db7b89468104f5ed284c0ec9d7e312c44 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 22 May 2023 13:44:03 -0700
Subject: [PATCH 599/638] chore: update changelog, with target date for v2.11.0
 release (#4677)

* Remove .dev1 from version number.

* [skip ci] Update changelog.rst

* [ci skip] Fix pre-commit: rst ``code`` is two backticks

* Apply fix suggested by @henryiii

* [ci skip] Set target date for the release to June 2, 2023

* [ci skip] Apply more fixes suggested by @henryiii (I missed those before).

* [ci skip] Revert "Remove .dev1 from version number."

This reverts commit afc80134cb1035be2913fd8153a16a864181c52c.
---
 docs/changelog.rst | 54 ++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 50 insertions(+), 4 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 58cc409839..32f6606aad 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,10 +10,25 @@ Changes will be added here periodically from the "Suggested changelog entry"
 block in pull request descriptions.
 
 
-IN DEVELOPMENT
---------------
+Version 2.11.0 (June 2, 2023)
+-----------------------------
+
+New features:
+
+* ``pybind11::detail::is_move_constructible`` can now be specialized for cases
+   in which ``std::is_move_constructible`` does not work as needed. This is
+   very similar to the long-established
+   ``pybind11::detail::is_copy_constructible``.
+  `#4631 <https://github.com/pybind/pybind11/pull/4631>`_
 
-Changes will be summarized here periodically.
+* Introduce ``recursive_container_traits``.
+  `#4623 <https://github.com/pybind/pybind11/pull/4623>`_
+
+* ``pybind11/type_caster_pyobject_ptr.h`` was added to support automatic
+  wrapping of APIs that make use of ``PyObject *``. This header needs to
+  included explicitly (i.e. it is not included implicitly
+  with ``pybind/pybind11.h``).
+  `#4601 <https://github.com/pybind/pybind11/pull/4601>`_
 
 Changes:
 
@@ -31,6 +46,28 @@ Changes:
   sizes slightly (~1.5%) but the error messages are much more informative.
   `#4463 <https://github.com/pybind/pybind11/pull/4463>`_
 
+* Setter return values (which are inaccessible for all practical purposes) are
+  no longer converted to Python (only to be discarded).
+  `#4621 <https://github.com/pybind/pybind11/pull/4621>`_
+
+* Allow lambda specified to function definition to be ``noexcept(true)``
+  in C++17.
+  `#4593 <https://github.com/pybind/pybind11/pull/4593>`_
+
+* Get rid of recursive template instantiations for concatenating type
+  signatures on C++17 and higher.
+  `#4587 <https://github.com/pybind/pybind11/pull/4587>`_
+
+* Compatibility with Python 3.12 (alpha). Note that the minimum pybind11
+  ABI version for Python 3.12 is version 5. (The default ABI version
+  for Python versions up to and including 3.11 is still version 4.).
+  `#4570 <https://github.com/pybind/pybind11/pull/4570>`_
+
+* With ``PYBIND11_INTERNALS_VERSION 5`` (default for Python 3.12+), MSVC builds
+  use ``std::hash<std::type_index>`` and ``std::equal_to<std::type_index>``
+  instead of string-based type comparisons. This resolves issues when binding
+  types defined in the unnamed namespace.
+  `#4319 <https://github.com/pybind/pybind11/pull/4319>`_
 
 Build system improvements:
 
@@ -40,8 +77,17 @@ Build system improvements:
 * Moved the linting framework over to Ruff.
   `#4483 <https://github.com/pybind/pybind11/pull/4483>`_
 
+* Skip lto checks and target generation when
+  ``CMAKE_INTERPROCEDURAL_OPTIMIZATION`` is defined.
+  `#4643 <https://github.com/pybind/pybind11/pull/4643>`_
+
+* No longer inject ``-stdlib=libc++``, not needed for modern Pythons
+  (macOS 10.9+).
+  `#4639 <https://github.com/pybind/pybind11/pull/4639>`_
+
+
 Version 2.10.4 (Mar 16, 2023)
-----------------------------
+-----------------------------
 
 Changes:
 

From ce9bbc0a213bfb21b77ada8de5346be5e350e3c4 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 23 May 2023 10:03:33 -0700
Subject: [PATCH 600/638] Python 3.11+: Add `__notes__` to
 `error_already_set::what()` output. (#4678)

* First version adding `__notes__` to `error_already_set::what()` output.

* Fix trivial oversight (missing adjustment in existing test).

* Minor enhancements of new code.

* Re-enable `cmake --target cpptest -j 2`

* Revert "Re-enable `cmake --target cpptest -j 2`"

This reverts commit 60816285e9e7b95b7d33a60805888b80b2bec641.

* Add general comment explaining why the `error_fetch_and_normalize` code is so unusual.
---
 include/pybind11/pytypes.h | 70 +++++++++++++++++++++++++++++++++-----
 tests/test_exceptions.py   | 36 +++++++++++++++-----
 2 files changed, 90 insertions(+), 16 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f11ed5da78..f5d3f34f38 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -471,13 +471,24 @@ inline const char *obj_class_name(PyObject *obj) {
 
 std::string error_string();
 
+// The code in this struct is very unusual, to minimize the chances of
+// masking bugs (elsewhere) by errors during the error handling (here).
+// This is meant to be a lifeline for troubleshooting long-running processes
+// that crash under conditions that are virtually impossible to reproduce.
+// Low-level implementation alternatives are preferred to higher-level ones
+// that might raise cascading exceptions. Last-ditch-kind-of attempts are made
+// to report as much of the original error as possible, even if there are
+// secondary issues obtaining some of the details.
 struct error_fetch_and_normalize {
-    // Immediate normalization is long-established behavior (starting with
-    // https://github.com/pybind/pybind11/commit/135ba8deafb8bf64a15b24d1513899eb600e2011
-    // from Sep 2016) and safest. Normalization could be deferred, but this could mask
-    // errors elsewhere, the performance gain is very minor in typical situations
-    // (usually the dominant bottleneck is EH unwinding), and the implementation here
-    // would be more complex.
+    // This comment only applies to Python <= 3.11:
+    //     Immediate normalization is long-established behavior (starting with
+    //     https://github.com/pybind/pybind11/commit/135ba8deafb8bf64a15b24d1513899eb600e2011
+    //     from Sep 2016) and safest. Normalization could be deferred, but this could mask
+    //     errors elsewhere, the performance gain is very minor in typical situations
+    //     (usually the dominant bottleneck is EH unwinding), and the implementation here
+    //     would be more complex.
+    // Starting with Python 3.12, PyErr_Fetch() normalizes exceptions immediately.
+    // Any errors during normalization are tracked under __notes__.
     explicit error_fetch_and_normalize(const char *called) {
         PyErr_Fetch(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
         if (!m_type) {
@@ -492,6 +503,14 @@ struct error_fetch_and_normalize {
                             "of the original active exception type.");
         }
         m_lazy_error_string = exc_type_name_orig;
+#if PY_VERSION_HEX >= 0x030C0000
+        // The presence of __notes__ is likely due to exception normalization
+        // errors, although that is not necessarily true, therefore insert a
+        // hint only:
+        if (PyObject_HasAttrString(m_value.ptr(), "__notes__")) {
+            m_lazy_error_string += "[WITH __notes__]";
+        }
+#else
         // PyErr_NormalizeException() may change the exception type if there are cascading
         // failures. This can potentially be extremely confusing.
         PyErr_NormalizeException(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
@@ -506,12 +525,12 @@ struct error_fetch_and_normalize {
                           + " failed to obtain the name "
                             "of the normalized active exception type.");
         }
-#if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00
+#    if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00
         // This behavior runs the risk of masking errors in the error handling, but avoids a
         // conflict with PyPy, which relies on the normalization here to change OSError to
         // FileNotFoundError (https://github.com/pybind/pybind11/issues/4075).
         m_lazy_error_string = exc_type_name_norm;
-#else
+#    else
         if (exc_type_name_norm != m_lazy_error_string) {
             std::string msg = std::string(called)
                               + ": MISMATCH of original and normalized "
@@ -523,6 +542,7 @@ struct error_fetch_and_normalize {
             msg += ": " + format_value_and_trace();
             pybind11_fail(msg);
         }
+#    endif
 #endif
     }
 
@@ -558,6 +578,40 @@ struct error_fetch_and_normalize {
                     }
                 }
             }
+#if PY_VERSION_HEX >= 0x030B0000
+            auto notes
+                = reinterpret_steal<object>(PyObject_GetAttrString(m_value.ptr(), "__notes__"));
+            if (!notes) {
+                PyErr_Clear(); // No notes is good news.
+            } else {
+                auto len_notes = PyList_Size(notes.ptr());
+                if (len_notes < 0) {
+                    result += "\nFAILURE obtaining len(__notes__): " + detail::error_string();
+                } else {
+                    result += "\n__notes__ (len=" + std::to_string(len_notes) + "):";
+                    for (ssize_t i = 0; i < len_notes; i++) {
+                        PyObject *note = PyList_GET_ITEM(notes.ptr(), i);
+                        auto note_bytes = reinterpret_steal<object>(
+                            PyUnicode_AsEncodedString(note, "utf-8", "backslashreplace"));
+                        if (!note_bytes) {
+                            result += "\nFAILURE obtaining __notes__[" + std::to_string(i)
+                                      + "]: " + detail::error_string();
+                        } else {
+                            char *buffer = nullptr;
+                            Py_ssize_t length = 0;
+                            if (PyBytes_AsStringAndSize(note_bytes.ptr(), &buffer, &length)
+                                == -1) {
+                                result += "\nFAILURE formatting __notes__[" + std::to_string(i)
+                                          + "]: " + detail::error_string();
+                            } else {
+                                result += '\n';
+                                result += std::string(buffer, static_cast<std::size_t>(length));
+                            }
+                        }
+                    }
+                }
+            }
+#endif
         } else {
             result = "<MESSAGE UNAVAILABLE>";
         }
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index a92ab59a34..ccac4536d6 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -317,13 +317,7 @@ def test_error_already_set_what_with_happy_exceptions(
     assert what == expected_what
 
 
-@pytest.mark.skipif(
-    # Intentionally very specific:
-    "sys.version_info == (3, 12, 0, 'alpha', 7)",
-    reason="WIP: https://github.com/python/cpython/issues/102594",
-)
-@pytest.mark.skipif("env.PYPY", reason="PyErr_NormalizeException Segmentation fault")
-def test_flaky_exception_failure_point_init():
+def _test_flaky_exception_failure_point_init_before_py_3_12():
     with pytest.raises(RuntimeError) as excinfo:
         m.error_already_set_what(FlakyException, ("failure_point_init",))
     lines = str(excinfo.value).splitlines()
@@ -337,7 +331,33 @@ def test_flaky_exception_failure_point_init():
     # Checking the first two lines of the traceback as formatted in error_string():
     assert "test_exceptions.py(" in lines[3]
     assert lines[3].endswith("): __init__")
-    assert lines[4].endswith("): test_flaky_exception_failure_point_init")
+    assert lines[4].endswith(
+        "): _test_flaky_exception_failure_point_init_before_py_3_12"
+    )
+
+
+def _test_flaky_exception_failure_point_init_py_3_12():
+    # Behavior change in Python 3.12: https://github.com/python/cpython/issues/102594
+    what, py_err_set_after_what = m.error_already_set_what(
+        FlakyException, ("failure_point_init",)
+    )
+    assert not py_err_set_after_what
+    lines = what.splitlines()
+    assert lines[0].endswith("ValueError[WITH __notes__]: triggered_failure_point_init")
+    assert lines[1] == "__notes__ (len=1):"
+    assert "Normalization failed:" in lines[2]
+    assert "FlakyException" in lines[2]
+
+
+@pytest.mark.skipif(
+    "env.PYPY and sys.version_info[:2] < (3, 12)",
+    reason="PyErr_NormalizeException Segmentation fault",
+)
+def test_flaky_exception_failure_point_init():
+    if sys.version_info[:2] < (3, 12):
+        _test_flaky_exception_failure_point_init_before_py_3_12()
+    else:
+        _test_flaky_exception_failure_point_init_py_3_12()
 
 
 def test_flaky_exception_failure_point_str():

From 6e6bcca5b28461cd16b2af70bba837a4b24482c0 Mon Sep 17 00:00:00 2001
From: Joyce <joycebrum@google.com>
Date: Tue, 23 May 2023 14:05:25 -0300
Subject: [PATCH 601/638] Create s Security Policy (#4671)

* Create SECURITY.md

* Update test_files.py to include SECURITY.md file

* Update MANIFEST.in to include SECURITY.md file
---
 MANIFEST.in                              |  2 +-
 SECURITY.md                              | 13 +++++++++++++
 tests/extra_python_package/test_files.py |  1 +
 3 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 SECURITY.md

diff --git a/MANIFEST.in b/MANIFEST.in
index 31632acc33..7ce83c5527 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -3,4 +3,4 @@ recursive-include pybind11/include/pybind11 *.h
 recursive-include pybind11 *.py
 recursive-include pybind11 py.typed
 include pybind11/share/cmake/pybind11/*.cmake
-include LICENSE README.rst pyproject.toml setup.py setup.cfg
+include LICENSE README.rst SECURITY.md pyproject.toml setup.py setup.cfg
diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000000..3d74611f2d
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,13 @@
+# Security Policy
+
+## Supported Versions
+
+Security updates are applied only to the latest release.
+
+## Reporting a Vulnerability
+
+If you have discovered a security vulnerability in this project, please report it privately. **Do not disclose it as a public issue.** This gives us time to work with you to fix the issue before public exposure, reducing the chance that the exploit will be used before a patch is released.
+
+Please disclose it at [security advisory](https://github.com/pybind/pybind11/security/advisories/new).
+
+This project is maintained by a team of volunteers on a reasonable-effort basis. As such, please give us at least 90 days to work on a fix before public exposure.
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index e5982f962e..5b9e145694 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -111,6 +111,7 @@
     "MANIFEST.in",
     "README.rst",
     "PKG-INFO",
+    "SECURITY.md",
 }
 
 local_sdist_files = {

From 8e1f9d5c40f74632799c8a44287d32d18a6c8630 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 23 May 2023 10:49:32 -0700
Subject: [PATCH 602/638] Add `format_descriptor<>` & `npy_format_descriptor<>`
 `PyObject *` specializations. (#4674)

* Add `npy_format_descriptor<PyObject *>` to enable `py::array_t<PyObject *>` to/from-python conversions.

* resolve clang-tidy warning

* Use existing constructor instead of adding a static method. Thanks @Skylion007 for pointing out.

* Add `format_descriptor<PyObject *>`

Trivial addition, but still in search for a meaningful test.

* Add test_format_descriptor_format

* Ensure the Eigen `type_caster`s do not segfault when loading arrays with dtype=object

* Use `static_assert()` `!std::is_pointer<>` to replace runtime guards.

* Add comments to explain how to check for ref-count bugs. (NO code changes.)

* Make the "Pointer types ... are not supported" message Eigen-specific, as suggested by @Lalaland. Move to new pybind11/eigen/common.h header.

* Change "format_descriptor_format" implementation as suggested by @Lalaland. Additional tests meant to ensure consistency between py::format_descriptor<>, np.array, np.format_parser turn out to be useful only to highlight long-standing inconsistencies.

* resolve clang-tidy warning

* Account for np.float128, np.complex256 not being available on Windows, in a future-proof way.

* Fully address i|q|l ambiguity (hopefully).

* Remove the new `np.format_parser()`-based test, it's much more distracting than useful.

* Use bi.itemsize to disambiguate "l" or "L"

* Use `py::detail::compare_buffer_info<T>::compare()` to validate the `format_descriptor<T>::format()` strings.

* Add `buffer_info::compare<T>` to make `detail::compare_buffer_info<T>::compare` more visible & accessible.

* silence clang-tidy warning

* pytest-compatible access to np.float128, np.complex256

* Revert "pytest-compatible access to np.float128, np.complex256"

This reverts commit e9a289c50fc07199806d14ded644215ab6f03afa.

* Use `sizeof(long double) == sizeof(double)` instead of `std::is_same<>`

* Report skipped `long double` tests.

* Change the name of the new `buffer_info` member function to `item_type_is_equivalent_to`. Add comment defining "equivalent" by example.

* Change `item_type_is_equivalent_to<>()` from `static` function to member function, as suggested by @Lalaland
---
 CMakeLists.txt                           |  1 +
 include/pybind11/buffer_info.h           | 17 +++++-
 include/pybind11/detail/common.h         |  9 +++
 include/pybind11/eigen/common.h          |  9 +++
 include/pybind11/eigen/matrix.h          | 13 +++++
 include/pybind11/eigen/tensor.h          |  5 ++
 include/pybind11/numpy.h                 | 18 ++++--
 tests/extra_python_package/test_files.py |  1 +
 tests/test_buffers.cpp                   | 35 ++++++++++++
 tests/test_buffers.py                    | 57 +++++++++++++++++++
 tests/test_numpy_array.cpp               | 26 +++++++++
 tests/test_numpy_array.py                | 71 ++++++++++++++++++++++++
 12 files changed, 255 insertions(+), 7 deletions(-)
 create mode 100644 include/pybind11/eigen/common.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 25a7d14984..0ad74db2bb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -126,6 +126,7 @@ set(PYBIND11_HEADERS
     include/pybind11/complex.h
     include/pybind11/options.h
     include/pybind11/eigen.h
+    include/pybind11/eigen/common.h
     include/pybind11/eigen/matrix.h
     include/pybind11/eigen/tensor.h
     include/pybind11/embed.h
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 06120d5563..b99ee8bef4 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -37,6 +37,9 @@ inline std::vector<ssize_t> f_strides(const std::vector<ssize_t> &shape, ssize_t
     return strides;
 }
 
+template <typename T, typename SFINAE = void>
+struct compare_buffer_info;
+
 PYBIND11_NAMESPACE_END(detail)
 
 /// Information record describing a Python buffer object
@@ -150,6 +153,17 @@ struct buffer_info {
     Py_buffer *view() const { return m_view; }
     Py_buffer *&view() { return m_view; }
 
+    /* True if the buffer item type is equivalent to `T`. */
+    // To define "equivalent" by example:
+    // `buffer_info::item_type_is_equivalent_to<int>(b)` and
+    // `buffer_info::item_type_is_equivalent_to<long>(b)` may both be true
+    // on some platforms, but `int` and `unsigned` will never be equivalent.
+    // For the ground truth, please inspect `detail::compare_buffer_info<>`.
+    template <typename T>
+    bool item_type_is_equivalent_to() const {
+        return detail::compare_buffer_info<T>::compare(*this);
+    }
+
 private:
     struct private_ctr_tag {};
 
@@ -170,9 +184,10 @@ struct buffer_info {
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T, typename SFINAE = void>
+template <typename T, typename SFINAE>
 struct compare_buffer_info {
     static bool compare(const buffer_info &b) {
+        // NOLINTNEXTLINE(bugprone-sizeof-expression) Needed for `PyObject *`
         return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
     }
 };
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 1ff0df09fe..c2e6f9ec89 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -1025,6 +1025,15 @@ PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used in
 template <typename T, typename SFINAE = void>
 struct format_descriptor {};
 
+template <typename T>
+struct format_descriptor<
+    T,
+    detail::enable_if_t<detail::is_same_ignoring_cvref<T, PyObject *>::value>> {
+    static constexpr const char c = 'O';
+    static constexpr const char value[2] = {c, '\0'};
+    static std::string format() { return std::string(1, c); }
+};
+
 PYBIND11_NAMESPACE_BEGIN(detail)
 // Returns the index of the given type in the type char array below, and in the list in numpy.h
 // The order here is: bool; 8 ints ((signed,unsigned)x(8,16,32,64)bits); float,double,long double;
diff --git a/include/pybind11/eigen/common.h b/include/pybind11/eigen/common.h
new file mode 100644
index 0000000000..24f56d1584
--- /dev/null
+++ b/include/pybind11/eigen/common.h
@@ -0,0 +1,9 @@
+// Copyright (c) 2023 The pybind Community.
+
+#pragma once
+
+// Common message for `static_assert()`s, which are useful to easily
+// preempt much less obvious errors.
+#define PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED                                    \
+    "Pointer types (in particular `PyObject *`) are not supported as scalar types for Eigen "     \
+    "types."
diff --git a/include/pybind11/eigen/matrix.h b/include/pybind11/eigen/matrix.h
index bd533bed37..8d4342f81b 100644
--- a/include/pybind11/eigen/matrix.h
+++ b/include/pybind11/eigen/matrix.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "../numpy.h"
+#include "common.h"
 
 /* HINT: To suppress warnings originating from the Eigen headers, use -isystem.
    See also:
@@ -287,6 +288,8 @@ handle eigen_encapsulate(Type *src) {
 template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     using Scalar = typename Type::Scalar;
+    static_assert(!std::is_pointer<Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using props = EigenProps<Type>;
 
     bool load(handle src, bool convert) {
@@ -405,6 +408,9 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
 // Base class for casting reference/map/block/etc. objects back to python.
 template <typename MapType>
 struct eigen_map_caster {
+    static_assert(!std::is_pointer<typename MapType::Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+
 private:
     using props = EigenProps<MapType>;
 
@@ -457,6 +463,8 @@ struct type_caster<
     using Type = Eigen::Ref<PlainObjectType, 0, StrideType>;
     using props = EigenProps<Type>;
     using Scalar = typename props::Scalar;
+    static_assert(!std::is_pointer<Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using MapType = Eigen::Map<PlainObjectType, 0, StrideType>;
     using Array
         = array_t<Scalar,
@@ -604,6 +612,9 @@ struct type_caster<
 // regular Eigen::Matrix, then casting that.
 template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
+    static_assert(!std::is_pointer<typename Type::Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+
 protected:
     using Matrix
         = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
@@ -632,6 +643,8 @@ struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
 template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
     using Scalar = typename Type::Scalar;
+    static_assert(!std::is_pointer<Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using StorageIndex = remove_reference_t<decltype(*std::declval<Type>().outerIndexPtr())>;
     using Index = typename Type::Index;
     static constexpr bool rowMajor = Type::IsRowMajor;
diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
index de7dcba89d..25d12baca1 100644
--- a/include/pybind11/eigen/tensor.h
+++ b/include/pybind11/eigen/tensor.h
@@ -8,6 +8,7 @@
 #pragma once
 
 #include "../numpy.h"
+#include "common.h"
 
 #if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 static_assert(__GNUC__ > 5, "Eigen Tensor support in pybind11 requires GCC > 5.0");
@@ -164,6 +165,8 @@ PYBIND11_WARNING_POP
 
 template <typename Type>
 struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
+    static_assert(!std::is_pointer<typename Type::Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using Helper = eigen_tensor_helper<Type>;
     static constexpr auto temp_name = get_tensor_descriptor<Type, false>::value;
     PYBIND11_TYPE_CASTER(Type, temp_name);
@@ -359,6 +362,8 @@ struct get_storage_pointer_type<MapType, void_t<typename MapType::PointerArgType
 template <typename Type, int Options>
 struct type_caster<Eigen::TensorMap<Type, Options>,
                    typename eigen_tensor_helper<remove_cv_t<Type>>::ValidType> {
+    static_assert(!std::is_pointer<typename Type::Scalar>::value,
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using MapType = Eigen::TensorMap<Type, Options>;
     using Helper = eigen_tensor_helper<remove_cv_t<Type>>;
 
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 854d6e87fa..36077ec04d 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -564,6 +564,8 @@ class dtype : public object {
         m_ptr = from_args(args).release().ptr();
     }
 
+    /// Return dtype for the given typenum (one of the NPY_TYPES).
+    /// https://numpy.org/devdocs/reference/c-api/array.html#c.PyArray_DescrFromType
     explicit dtype(int typenum)
         : object(detail::npy_api::get().PyArray_DescrFromType_(typenum), stolen_t{}) {
         if (m_ptr == nullptr) {
@@ -1283,12 +1285,16 @@ struct npy_format_descriptor<
 public:
     static constexpr int value = values[detail::is_fmt_numeric<T>::index];
 
-    static pybind11::dtype dtype() {
-        if (auto *ptr = npy_api::get().PyArray_DescrFromType_(value)) {
-            return reinterpret_steal<pybind11::dtype>(ptr);
-        }
-        pybind11_fail("Unsupported buffer format!");
-    }
+    static pybind11::dtype dtype() { return pybind11::dtype(/*typenum*/ value); }
+};
+
+template <typename T>
+struct npy_format_descriptor<T, enable_if_t<is_same_ignoring_cvref<T, PyObject *>::value>> {
+    static constexpr auto name = const_name("object");
+
+    static constexpr int value = npy_api::NPY_OBJECT_;
+
+    static pybind11::dtype dtype() { return pybind11::dtype(/*typenum*/ value); }
 };
 
 #define PYBIND11_DECL_CHAR_FMT                                                                    \
diff --git a/tests/extra_python_package/test_files.py b/tests/extra_python_package/test_files.py
index 5b9e145694..57387dd8bc 100644
--- a/tests/extra_python_package/test_files.py
+++ b/tests/extra_python_package/test_files.py
@@ -57,6 +57,7 @@
 }
 
 eigen_headers = {
+    "include/pybind11/eigen/common.h",
     "include/pybind11/eigen/matrix.h",
     "include/pybind11/eigen/tensor.h",
 }
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 6b6e8cba7f..b5b8c355b3 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -7,12 +7,47 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/complex.h>
 #include <pybind11/stl.h>
 
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
 
 TEST_SUBMODULE(buffers, m) {
+    m.attr("long_double_and_double_have_same_size") = (sizeof(long double) == sizeof(double));
+
+    m.def("format_descriptor_format_buffer_info_equiv",
+          [](const std::string &cpp_name, const py::buffer &buffer) {
+              // https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables
+              static auto *format_table = new std::map<std::string, std::string>;
+              static auto *equiv_table
+                  = new std::map<std::string, bool (py::buffer_info::*)() const>;
+              if (format_table->empty()) {
+#define PYBIND11_ASSIGN_HELPER(...)                                                               \
+    (*format_table)[#__VA_ARGS__] = py::format_descriptor<__VA_ARGS__>::format();                 \
+    (*equiv_table)[#__VA_ARGS__] = &py::buffer_info::item_type_is_equivalent_to<__VA_ARGS__>;
+                  PYBIND11_ASSIGN_HELPER(PyObject *)
+                  PYBIND11_ASSIGN_HELPER(bool)
+                  PYBIND11_ASSIGN_HELPER(std::int8_t)
+                  PYBIND11_ASSIGN_HELPER(std::uint8_t)
+                  PYBIND11_ASSIGN_HELPER(std::int16_t)
+                  PYBIND11_ASSIGN_HELPER(std::uint16_t)
+                  PYBIND11_ASSIGN_HELPER(std::int32_t)
+                  PYBIND11_ASSIGN_HELPER(std::uint32_t)
+                  PYBIND11_ASSIGN_HELPER(std::int64_t)
+                  PYBIND11_ASSIGN_HELPER(std::uint64_t)
+                  PYBIND11_ASSIGN_HELPER(float)
+                  PYBIND11_ASSIGN_HELPER(double)
+                  PYBIND11_ASSIGN_HELPER(long double)
+                  PYBIND11_ASSIGN_HELPER(std::complex<float>)
+                  PYBIND11_ASSIGN_HELPER(std::complex<double>)
+                  PYBIND11_ASSIGN_HELPER(std::complex<long double>)
+#undef PYBIND11_ASSIGN_HELPER
+              }
+              return std::pair<std::string, bool>(
+                  (*format_table)[cpp_name], (buffer.request().*((*equiv_table)[cpp_name]))());
+          });
+
     // test_from_python / test_to_python:
     class Matrix {
     public:
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index eb58c4675e..63d9d869fd 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -10,6 +10,63 @@
 
 np = pytest.importorskip("numpy")
 
+if m.long_double_and_double_have_same_size:
+    # Determined by the compiler used to build the pybind11 tests
+    # (e.g. MSVC gets here, but MinGW might not).
+    np_float128 = None
+    np_complex256 = None
+else:
+    # Determined by the compiler used to build numpy (e.g. MinGW).
+    np_float128 = getattr(np, *["float128"] * 2)
+    np_complex256 = getattr(np, *["complex256"] * 2)
+
+CPP_NAME_FORMAT_NP_DTYPE_TABLE = [
+    ("PyObject *", "O", object),
+    ("bool", "?", np.bool_),
+    ("std::int8_t", "b", np.int8),
+    ("std::uint8_t", "B", np.uint8),
+    ("std::int16_t", "h", np.int16),
+    ("std::uint16_t", "H", np.uint16),
+    ("std::int32_t", "i", np.int32),
+    ("std::uint32_t", "I", np.uint32),
+    ("std::int64_t", "q", np.int64),
+    ("std::uint64_t", "Q", np.uint64),
+    ("float", "f", np.float32),
+    ("double", "d", np.float64),
+    ("long double", "g", np_float128),
+    ("std::complex<float>", "Zf", np.complex64),
+    ("std::complex<double>", "Zd", np.complex128),
+    ("std::complex<long double>", "Zg", np_complex256),
+]
+CPP_NAME_FORMAT_TABLE = [
+    (cpp_name, format)
+    for cpp_name, format, np_dtype in CPP_NAME_FORMAT_NP_DTYPE_TABLE
+    if np_dtype is not None
+]
+CPP_NAME_NP_DTYPE_TABLE = [
+    (cpp_name, np_dtype) for cpp_name, _, np_dtype in CPP_NAME_FORMAT_NP_DTYPE_TABLE
+]
+
+
+@pytest.mark.parametrize(("cpp_name", "np_dtype"), CPP_NAME_NP_DTYPE_TABLE)
+def test_format_descriptor_format_buffer_info_equiv(cpp_name, np_dtype):
+    if np_dtype is None:
+        pytest.skip(
+            f"cpp_name=`{cpp_name}`: `long double` and `double` have same size."
+        )
+    if isinstance(np_dtype, str):
+        pytest.skip(f"np.{np_dtype} does not exist.")
+    np_array = np.array([], dtype=np_dtype)
+    for other_cpp_name, expected_format in CPP_NAME_FORMAT_TABLE:
+        format, np_array_is_matching = m.format_descriptor_format_buffer_info_equiv(
+            other_cpp_name, np_array
+        )
+        assert format == expected_format
+        if other_cpp_name == cpp_name:
+            assert np_array_is_matching
+        else:
+            assert not np_array_is_matching
+
 
 def test_from_python():
     with pytest.raises(RuntimeError) as excinfo:
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index b118e2c6cc..8c122a8658 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -523,4 +523,30 @@ TEST_SUBMODULE(numpy_array, sm) {
     sm.def("test_fmt_desc_const_double", [](const py::array_t<const double> &) {});
 
     sm.def("round_trip_float", [](double d) { return d; });
+
+    sm.def("pass_array_pyobject_ptr_return_sum_str_values",
+           [](const py::array_t<PyObject *> &objs) {
+               std::string sum_str_values;
+               for (const auto &obj : objs) {
+                   sum_str_values += py::str(obj.attr("value"));
+               }
+               return sum_str_values;
+           });
+
+    sm.def("pass_array_pyobject_ptr_return_as_list",
+           [](const py::array_t<PyObject *> &objs) -> py::list { return objs; });
+
+    sm.def("return_array_pyobject_ptr_cpp_loop", [](const py::list &objs) {
+        py::size_t arr_size = py::len(objs);
+        py::array_t<PyObject *> arr_from_list(static_cast<py::ssize_t>(arr_size));
+        PyObject **data = arr_from_list.mutable_data();
+        for (py::size_t i = 0; i < arr_size; i++) {
+            assert(data[i] == nullptr);
+            data[i] = py::cast<PyObject *>(objs[i].attr("value"));
+        }
+        return arr_from_list;
+    });
+
+    sm.def("return_array_pyobject_ptr_from_list",
+           [](const py::list &objs) -> py::array_t<PyObject *> { return objs; });
 }
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 070813d3a2..12e7d17d15 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -595,3 +595,74 @@ def test_round_trip_float():
     arr = np.zeros((), np.float64)
     arr[()] = 37.2
     assert m.round_trip_float(arr) == 37.2
+
+
+# HINT: An easy and robust way (although only manual unfortunately) to check for
+#       ref-count leaks in the test_.*pyobject_ptr.* functions below is to
+#           * temporarily insert `while True:` (one-by-one),
+#           * run this test, and
+#           * run the Linux `top` command in another shell to visually monitor
+#             `RES` for a minute or two.
+#       If there is a leak, it is usually evident in seconds because the `RES`
+#       value increases without bounds. (Don't forget to Ctrl-C the test!)
+
+
+# For use as a temporary user-defined object, to maximize sensitivity of the tests below:
+#     * Ref-count leaks will be immediately evident.
+#     * Sanitizers are much more likely to detect heap-use-after-free due to
+#       other ref-count bugs.
+class PyValueHolder:
+    def __init__(self, value):
+        self.value = value
+
+
+def WrapWithPyValueHolder(*values):
+    return [PyValueHolder(v) for v in values]
+
+
+def UnwrapPyValueHolder(vhs):
+    return [vh.value for vh in vhs]
+
+
+def test_pass_array_pyobject_ptr_return_sum_str_values_ndarray():
+    # Intentionally all temporaries, do not change.
+    assert (
+        m.pass_array_pyobject_ptr_return_sum_str_values(
+            np.array(WrapWithPyValueHolder(-3, "four", 5.0), dtype=object)
+        )
+        == "-3four5.0"
+    )
+
+
+def test_pass_array_pyobject_ptr_return_sum_str_values_list():
+    # Intentionally all temporaries, do not change.
+    assert (
+        m.pass_array_pyobject_ptr_return_sum_str_values(
+            WrapWithPyValueHolder(2, "three", -4.0)
+        )
+        == "2three-4.0"
+    )
+
+
+def test_pass_array_pyobject_ptr_return_as_list():
+    # Intentionally all temporaries, do not change.
+    assert UnwrapPyValueHolder(
+        m.pass_array_pyobject_ptr_return_as_list(
+            np.array(WrapWithPyValueHolder(-1, "two", 3.0), dtype=object)
+        )
+    ) == [-1, "two", 3.0]
+
+
+@pytest.mark.parametrize(
+    ("return_array_pyobject_ptr", "unwrap"),
+    [
+        (m.return_array_pyobject_ptr_cpp_loop, list),
+        (m.return_array_pyobject_ptr_from_list, UnwrapPyValueHolder),
+    ],
+)
+def test_return_array_pyobject_ptr_cpp_loop(return_array_pyobject_ptr, unwrap):
+    # Intentionally all temporaries, do not change.
+    arr_from_list = return_array_pyobject_ptr(WrapWithPyValueHolder(6, "seven", -8.0))
+    assert isinstance(arr_from_list, np.ndarray)
+    assert arr_from_list.dtype == np.dtype("O")
+    assert unwrap(arr_from_list) == [6, "seven", -8.0]

From d0232b119f5f0cf2bf6cecacaf099c301c811ca8 Mon Sep 17 00:00:00 2001
From: "T.Yamada" <cielartisan@gmail.com>
Date: Thu, 25 May 2023 13:39:36 +0900
Subject: [PATCH 603/638] Use annotated for array (#4679)

* use Annotated for std::array docstring

* add tests

* fix test

* style: pre-commit fixes

* fix valarray annotation

* style: pre-commit fixes

* refix test

* add FixedSize

* style: pre-commit fixes

* Update test_stl.py

* style: pre-commit fixes

---------

Co-authored-by: Taiju Yamada <taiju.yamada@mujin.co.jp>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/stl.h | 8 ++++----
 tests/test_stl.py      | 7 +++++--
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 84c5171081..f39f44f7c9 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -273,11 +273,11 @@ struct array_caster {
     }
 
     PYBIND11_TYPE_CASTER(ArrayType,
-                         const_name("List[") + value_conv::name
+                         const_name<Resizable>(const_name(""), const_name("Annotated["))
+                             + const_name("List[") + value_conv::name + const_name("]")
                              + const_name<Resizable>(const_name(""),
-                                                     const_name("[") + const_name<Size>()
-                                                         + const_name("]"))
-                             + const_name("]"));
+                                                     const_name(", FixedSize(")
+                                                         + const_name<Size>() + const_name(")]")));
 };
 
 template <typename Type, size_t Size>
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 2d9dcc89f1..8a614f8b87 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -39,8 +39,11 @@ def test_array(doc):
     assert m.load_array(lst)
     assert m.load_array(tuple(lst))
 
-    assert doc(m.cast_array) == "cast_array() -> List[int[2]]"
-    assert doc(m.load_array) == "load_array(arg0: List[int[2]]) -> bool"
+    assert doc(m.cast_array) == "cast_array() -> Annotated[List[int], FixedSize(2)]"
+    assert (
+        doc(m.load_array)
+        == "load_array(arg0: Annotated[List[int], FixedSize(2)]) -> bool"
+    )
 
 
 def test_valarray(doc):

From 29487dee8f86c984605570c298b21c79ea3bada3 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 7 Jun 2023 12:00:37 -0700
Subject: [PATCH 604/638] =?UTF-8?q?Disable=20=F0=9F=90=8D=203=20=E2=80=A2?=
 =?UTF-8?q?=20CentOS7=20/=20PGI=2022.9=20=E2=80=A2=20x64=20(#4691)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .github/workflows/ci.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8c2aba343a..91144241f4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -400,6 +400,7 @@ jobs:
 
   # Testing on CentOS 7 + PGI compilers, which seems to require more workarounds
   centos-nvhpc7:
+    if: ${{ false }}  # JOB DISABLED (NEEDS WORK): https://github.com/pybind/pybind11/issues/4690
     runs-on: ubuntu-latest
     name: "🐍 3 • CentOS7 / PGI 22.9 • x64"
     container: centos:7

From 3617f3554aa5096e2148281c14be99afe9c138e6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Wed, 7 Jun 2023 12:57:38 -0700
Subject: [PATCH 605/638] chore(deps): update pre-commit hooks (#4689)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* chore(deps): update pre-commit hooks

updates:
- [github.com/charliermarsh/ruff-pre-commit: v0.0.263 → v0.0.270](https://github.com/charliermarsh/ruff-pre-commit/compare/v0.0.263...v0.0.270)
- [github.com/pre-commit/mirrors-mypy: v1.2.0 → v1.3.0](https://github.com/pre-commit/mirrors-mypy/compare/v1.2.0...v1.3.0)
- [github.com/shellcheck-py/shellcheck-py: v0.9.0.2 → v0.9.0.5](https://github.com/shellcheck-py/shellcheck-py/compare/v0.9.0.2...v0.9.0.5)
- [github.com/pre-commit/mirrors-clang-format: v16.0.2 → v16.0.4](https://github.com/pre-commit/mirrors-clang-format/compare/v16.0.2...v16.0.4)

* Resolve new ruff error:

```
tests/test_pytypes.py:478:20: PLW0130 Duplicate value `3` in set
```

The reduction from `{3, 3}` to `{3}` never happened in pybind11 code, therefore this change is essentially a no-op for the purpose of unit-testing pybind11.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 .pre-commit-config.yaml | 8 ++++----
 tests/test_pytypes.py   | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index aca9b3ca2e..bcc3f27232 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -68,7 +68,7 @@ repos:
 
 # Ruff, the Python auto-correcting linter written in Rust
 - repo: https://github.com/charliermarsh/ruff-pre-commit
-  rev: v0.0.263
+  rev: v0.0.270
   hooks:
   - id: ruff
     args: ["--fix", "--show-fixes"]
@@ -100,7 +100,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v1.2.0"
+  rev: "v1.3.0"
   hooks:
   - id: mypy
     args: []
@@ -128,7 +128,7 @@ repos:
 
 # Check for common shell mistakes
 - repo: https://github.com/shellcheck-py/shellcheck-py
-  rev: "v0.9.0.2"
+  rev: "v0.9.0.5"
   hooks:
   - id: shellcheck
 
@@ -143,7 +143,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v16.0.2"
+  rev: "v16.0.4"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 946b941402..afb7a1ce8a 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -475,7 +475,7 @@ def test_pybind11_str_raw_str():
     assert cvt({}) == "{}"
     assert cvt({3: 4}) == "{3: 4}"
     assert cvt(set()) == "set()"
-    assert cvt({3, 3}) == "{3}"
+    assert cvt({3}) == "{3}"
 
     valid_orig = "DZ"
     valid_utf8 = valid_orig.encode("utf-8")

From c679a9209557ef0324a19f4618c556b60e251009 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 7 Jun 2023 13:49:14 -0700
Subject: [PATCH 606/638] chore(deps): bump deadsnakes/action from 3.0.0 to
 3.0.1 (#4687)

Bumps [deadsnakes/action](https://github.com/deadsnakes/action) from 3.0.0 to 3.0.1.
- [Release notes](https://github.com/deadsnakes/action/releases)
- [Commits](https://github.com/deadsnakes/action/compare/v3.0.0...v3.0.1)

---
updated-dependencies:
- dependency-name: deadsnakes/action
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 91144241f4..b844d81336 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -203,7 +203,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python-version }} (deadsnakes)
-      uses: deadsnakes/action@v3.0.0
+      uses: deadsnakes/action@v3.0.1
       with:
         python-version: ${{ matrix.python-version }}
         debug: ${{ matrix.python-debug }}

From 0e43fcc75e6b7429e3511dfb44343ec05a0ab843 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 10 Jun 2023 10:14:08 -0700
Subject: [PATCH 607/638] Python 3.12b2 testing (#4695)

* Uncomment `Interface test` sections (test_embed)

* fix: setuptools has been removed from default installs in 3.12

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml       |  6 +++---
 .github/workflows/upstream.yml | 19 ++++++++++---------
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b844d81336..45a6738f75 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -180,7 +180,9 @@ jobs:
     # This makes sure the setup_helpers module can build packages using
     # setuptools
     - name: Setuptools helpers test
-      run: pytest tests/extra_setuptools
+      run: |
+        pip install setuptools
+        pytest tests/extra_setuptools
       if: "!(matrix.runs-on == 'windows-2022')"
 
 
@@ -242,8 +244,6 @@ jobs:
         python -m pip install -r tests/requirements.txt
 
     - name: Configure
-      env:
-        SETUPTOOLS_USE_DISTUTILS: stdlib
       run: >
         cmake -S . -B build
         -DCMAKE_BUILD_TYPE=Debug
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 4acfbfce75..d4220be228 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -1,4 +1,3 @@
-
 name: Upstream
 
 on:
@@ -65,8 +64,8 @@ jobs:
     - name: Python tests C++11
       run: cmake --build build11 --target pytest -j 2
 
-    # - name: C++11 tests
-    #   run: cmake --build build11  --target cpptest -j 2
+    - name: C++11 tests
+      run: cmake --build build11  --target cpptest -j 2
 
     - name: Interface test C++11
       run: cmake --build build11 --target test_cmake_build
@@ -80,14 +79,14 @@ jobs:
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
 
-    - name: Build
+    - name: Build C++17
       run: cmake --build build17 -j 2
 
-    - name: Python tests
+    - name: Python tests C++17
       run: cmake --build build17 --target pytest
 
-    # - name: C++ tests
-    #   run: cmake --build build17 --target cpptest
+    - name: C++17 tests
+      run: cmake --build build17 --target cpptest
 
     # Third build - C++17 mode with unstable ABI
     - name: Configure (unstable ABI)
@@ -105,10 +104,12 @@ jobs:
     - name: Python tests (unstable ABI)
       run: cmake --build build17max --target pytest
 
-    - name: Interface test
+    - name: Interface test (unstable ABI)
       run: cmake --build build17max --target test_cmake_build
 
     # This makes sure the setup_helpers module can build packages using
     # setuptools
     - name: Setuptools helpers test
-      run: pytest tests/extra_setuptools
+      run: |
+        pip install setuptools
+        pytest tests/extra_setuptools

From 86f60a0c072e5bd5cab79233f712c321fe8deca7 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 16 Jun 2023 14:09:40 -0700
Subject: [PATCH 608/638] pre-commit markdown-it-py<3 (for Python 3.7
 compatibility) (#4704)

* markdown-it-py dropped Python 3.7 support, but we are type checking for Python 3.7 from a newer version of Python. Keep using markdown-it-py<3 as long as we support Python 3.7.

* Shuffle order of pre-commit checks for better agility.
---
 .pre-commit-config.yaml | 91 +++++++++++++++++++++--------------------
 1 file changed, 47 insertions(+), 44 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index bcc3f27232..2d508276e1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -22,6 +22,48 @@ ci:
 exclude: ^tools/JoinPaths.cmake$
 
 repos:
+
+# Clang format the codebase automatically
+- repo: https://github.com/pre-commit/mirrors-clang-format
+  rev: "v16.0.4"
+  hooks:
+  - id: clang-format
+    types_or: [c++, c, cuda]
+
+# Black, the code formatter, natively supports pre-commit
+- repo: https://github.com/psf/black
+  rev: "23.3.0" # Keep in sync with blacken-docs
+  hooks:
+  - id: black
+
+# Ruff, the Python auto-correcting linter written in Rust
+- repo: https://github.com/charliermarsh/ruff-pre-commit
+  rev: v0.0.270
+  hooks:
+  - id: ruff
+    args: ["--fix", "--show-fixes"]
+
+# Check static types with mypy
+- repo: https://github.com/pre-commit/mirrors-mypy
+  rev: "v1.3.0"
+  hooks:
+  - id: mypy
+    args: []
+    exclude: ^(tests|docs)/
+    additional_dependencies:
+    - markdown-it-py<3 # Drop this together with dropping Python 3.7 support.
+    - nox
+    - rich
+
+# CMake formatting
+- repo: https://github.com/cheshirekow/cmake-format-precommit
+  rev: "v0.6.13"
+  hooks:
+  - id: cmake-format
+    additional_dependencies: [pyyaml]
+    types: [file]
+    files: (\.cmake|CMakeLists.txt)(.in)?$
+
 # Standard hooks
 - repo: https://github.com/pre-commit/pre-commit-hooks
   rev: "v4.4.0"
@@ -39,12 +81,6 @@ repos:
   - id: requirements-txt-fixer
   - id: trailing-whitespace
 
-# Black, the code formatter, natively supports pre-commit
-- repo: https://github.com/psf/black
-  rev: "23.3.0" # Keep in sync with blacken-docs
-  hooks:
-  - id: black
-
 # Also code format the docs
 - repo: https://github.com/asottile/blacken-docs
   rev: "1.13.0"
@@ -66,13 +102,6 @@ repos:
   - id: fix-ligatures
   - id: fix-smartquotes
 
-# Ruff, the Python auto-correcting linter written in Rust
-- repo: https://github.com/charliermarsh/ruff-pre-commit
-  rev: v0.0.270
-  hooks:
-  - id: ruff
-    args: ["--fix", "--show-fixes"]
-
 # Checking for common mistakes
 - repo: https://github.com/pre-commit/pygrep-hooks
   rev: "v1.10.0"
@@ -81,32 +110,6 @@ repos:
   - id: rst-directive-colons
   - id: rst-inline-touching-normal
 
-
-# PyLint has native support - not always usable, but works for us
-- repo: https://github.com/PyCQA/pylint
-  rev: "v3.0.0a6"
-  hooks:
-  - id: pylint
-    files: ^pybind11
-
-# CMake formatting
-- repo: https://github.com/cheshirekow/cmake-format-precommit
-  rev: "v0.6.13"
-  hooks:
-  - id: cmake-format
-    additional_dependencies: [pyyaml]
-    types: [file]
-    files: (\.cmake|CMakeLists.txt)(.in)?$
-
-# Check static types with mypy
-- repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v1.3.0"
-  hooks:
-  - id: mypy
-    args: []
-    exclude: ^(tests|docs)/
-    additional_dependencies: [nox, rich]
-
 # Checks the manifest for missing files (native support)
 - repo: https://github.com/mgedmin/check-manifest
   rev: "0.49"
@@ -141,9 +144,9 @@ repos:
     entry: PyBind|Numpy|Cmake|CCache|PyTest
     exclude: ^\.pre-commit-config.yaml$
 
-# Clang format the codebase automatically
-- repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v16.0.4"
+# PyLint has native support - not always usable, but works for us
+- repo: https://github.com/PyCQA/pylint
+  rev: "v3.0.0a6"
   hooks:
-  - id: clang-format
-    types_or: [c++, c, cuda]
+  - id: pylint
+    files: ^pybind11

From 849322806cd4b3697ad1d35eedd6d0352c5f267a Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 17 Jun 2023 07:02:23 -0700
Subject: [PATCH 609/638] Systematically add `PIP_BREAK_SYSTEM_PACKAGES` to all
 .yml files from which pip is called. (#4705)

* Systematically add PIP_BREAK_SYSTEM_PACKAGES to all .yml files from which pip is called.

* Try gcc:10-bullseye (because gcc:10 is broken: https://github.com/docker-library/gcc/issues/95)

* bug fix (matrix did not work as hoped)
---
 .github/workflows/ci.yml        | 17 +++++++++--------
 .github/workflows/configure.yml |  1 +
 .github/workflows/pip.yml       |  1 +
 .github/workflows/upstream.yml  |  1 +
 4 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 45a6738f75..1d5d502b00 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,6 +16,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
+  PIP_BREAK_SYSTEM_PACKAGES: 1
   PIP_ONLY_BINARY: numpy
   FORCE_COLOR: 3
   PYTEST_TIMEOUT: 300
@@ -455,16 +456,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { gcc: 7, std: 11 }
-          - { gcc: 7, std: 17 }
-          - { gcc: 8, std: 14 }
-          - { gcc: 8, std: 17 }
-          - { gcc: 10, std: 17 }
-          - { gcc: 11, std: 20 }
-          - { gcc: 12, std: 20 }
+          - { gcc: 7, std: 11, container_suffix: "" }
+          - { gcc: 7, std: 17, container_suffix: "" }
+          - { gcc: 8, std: 14, container_suffix: "" }
+          - { gcc: 8, std: 17, container_suffix: "" }
+          - { gcc: 10, std: 17, container_suffix: "-bullseye" }
+          - { gcc: 11, std: 20, container_suffix: "" }
+          - { gcc: 12, std: 20, container_suffix: "" }
 
     name: "🐍 3 • GCC ${{ matrix.gcc }} • C++${{ matrix.std }}• x64"
-    container: "gcc:${{ matrix.gcc }}"
+    container: "gcc:${{ matrix.gcc }}${{ matrix.container_suffix }}"
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 4ae22281c6..82a4939004 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -13,6 +13,7 @@ permissions:
   contents: read
 
 env:
+  PIP_BREAK_SYSTEM_PACKAGES: 1
   # For cmake:
   VERBOSE: 1
 
diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index c1feb6fe10..04d95a28c5 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -16,6 +16,7 @@ permissions:
   contents: read
 
 env:
+  PIP_BREAK_SYSTEM_PACKAGES: 1
   PIP_ONLY_BINARY: numpy
 
 jobs:
diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index d4220be228..dd8a1c9606 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -12,6 +12,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
+  PIP_BREAK_SYSTEM_PACKAGES: 1
   PIP_ONLY_BINARY: ":all:"
   # For cmake:
   VERBOSE: 1

From bc1bcf7c05b6097c2f0c993a776a975d7332f279 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 21 Jun 2023 13:25:10 -0400
Subject: [PATCH 610/638] chore: 3.12 + cleanup (#4713)

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/ci.yml  |  2 ++
 .pre-commit-config.yaml   |  1 +
 pybind11/setup_helpers.py |  8 ++++----
 pyproject.toml            | 18 ++++++++++--------
 setup.cfg                 |  1 +
 setup.py                  |  2 +-
 6 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1d5d502b00..1d61ad6a9c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -36,6 +36,7 @@ jobs:
         - '3.9'
         - '3.10'
         - '3.11'
+        - '3.12'
         - 'pypy-3.7'
         - 'pypy-3.8'
         - 'pypy-3.9'
@@ -74,6 +75,7 @@ jobs:
       uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python }}
+        allow-prereleases: true
 
     - name: Setup Boost (Linux)
       # Can't use boost + define _
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2d508276e1..9a829d72b1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -54,6 +54,7 @@ repos:
     - markdown-it-py<3 # Drop this together with dropping Python 3.7 support.
     - nox
     - rich
+    - types-setuptools
 
 # CMake formatting
 - repo: https://github.com/cheshirekow/cmake-format-precommit
diff --git a/pybind11/setup_helpers.py b/pybind11/setup_helpers.py
index cb279f27e0..aeeee9dcfa 100644
--- a/pybind11/setup_helpers.py
+++ b/pybind11/setup_helpers.py
@@ -66,8 +66,8 @@
     from setuptools import Extension as _Extension
     from setuptools.command.build_ext import build_ext as _build_ext
 except ImportError:
-    from distutils.command.build_ext import build_ext as _build_ext
-    from distutils.extension import Extension as _Extension
+    from distutils.command.build_ext import build_ext as _build_ext  # type: ignore[assignment]
+    from distutils.extension import Extension as _Extension  # type: ignore[assignment]
 
 import distutils.ccompiler
 import distutils.errors
@@ -84,7 +84,7 @@
 # directory into your path if it sits beside your setup.py.
 
 
-class Pybind11Extension(_Extension):  # type: ignore[misc]
+class Pybind11Extension(_Extension):
     """
     Build a C++11+ Extension module with pybind11. This automatically adds the
     recommended flags when you init the extension and assumes C++ sources - you
@@ -266,7 +266,7 @@ def auto_cpp_level(compiler: Any) -> Union[str, int]:
     raise RuntimeError(msg)
 
 
-class build_ext(_build_ext):  # type: ignore[misc] # noqa: N801
+class build_ext(_build_ext):  # noqa: N801
     """
     Customized build_ext that allows an auto-search for the highest supported
     C++ level for Pybind11Extension. This is only needed for the auto-search
diff --git a/pyproject.toml b/pyproject.toml
index e3655aca74..59c15ea636 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -2,6 +2,7 @@
 requires = ["setuptools>=42", "cmake>=3.18", "ninja"]
 build-backend = "setuptools.build_meta"
 
+
 [tool.check-manifest]
 ignore = [
     "tests/**",
@@ -15,6 +16,7 @@ ignore = [
     "noxfile.py",
 ]
 
+
 [tool.mypy]
 files = ["pybind11"]
 python_version = "3.6"
@@ -24,7 +26,7 @@ enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
 warn_unreachable = true
 
 [[tool.mypy.overrides]]
-module = ["ghapi.*", "setuptools.*"]
+module = ["ghapi.*"]
 ignore_missing_imports = true
 
 
@@ -55,10 +57,11 @@ messages_control.disable = [
   "unused-argument",  # covered by Ruff ARG
 ]
 
+
 [tool.ruff]
 select = [
   "E", "F", "W", # flake8
-  "B",  "B904",  # flake8-bugbear
+  "B",           # flake8-bugbear
   "I",           # isort
   "N",           # pep8-naming
   "ARG",         # flake8-unused-arguments
@@ -77,14 +80,13 @@ select = [
   "YTT",         # flake8-2020
 ]
 ignore = [
-  "PLR",   # Design related pylint
-  "E501",  # Line too long (Black is enough)
-  "PT011", # Too broad with raises in pytest
-  "PT004", # Fixture that doesn't return needs underscore (no, it is fine)
-  "SIM118",# iter(x) is not always the same as iter(x.keys())
+  "PLR",    # Design related pylint
+  "E501",   # Line too long (Black is enough)
+  "PT011",  # Too broad with raises in pytest
+  "PT004",  # Fixture that doesn't return needs underscore (no, it is fine)
+  "SIM118", # iter(x) is not always the same as iter(x.keys())
 ]
 target-version = "py37"
-typing-modules = ["scikit_build_core._compat.typing"]
 src = ["src"]
 unfixable = ["T20"]
 exclude = []
diff --git a/setup.cfg b/setup.cfg
index c35dd07ae6..92e6c953a9 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -20,6 +20,7 @@ classifiers =
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
+    Programming Language :: Python :: 3.12
     License :: OSI Approved :: BSD License
     Programming Language :: Python :: Implementation :: PyPy
     Programming Language :: Python :: Implementation :: CPython
diff --git a/setup.py b/setup.py
index 68573519c1..9fea7d35c7 100644
--- a/setup.py
+++ b/setup.py
@@ -96,7 +96,7 @@ def get_and_replace(
 
 # Use our input files instead when making the SDist (and anything that depends
 # on it, like a wheel)
-class SDist(setuptools.command.sdist.sdist):  # type: ignore[misc]
+class SDist(setuptools.command.sdist.sdist):
     def make_release_tree(self, base_dir: str, files: List[str]) -> None:
         super().make_release_tree(base_dir, files)
 

From e10da79b6ee2554be364ef14df1c988f94df02ea Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sat, 24 Jun 2023 12:12:35 -0700
Subject: [PATCH 611/638] Undo ci.yml gcc10 workaround after
 docker-library/gcc#95 was resolved. (#4717)

The gcc10 workaround was introduced with PR #4705.
---
 .github/workflows/ci.yml | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1d61ad6a9c..0d64014123 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -458,16 +458,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { gcc: 7, std: 11, container_suffix: "" }
-          - { gcc: 7, std: 17, container_suffix: "" }
-          - { gcc: 8, std: 14, container_suffix: "" }
-          - { gcc: 8, std: 17, container_suffix: "" }
-          - { gcc: 10, std: 17, container_suffix: "-bullseye" }
-          - { gcc: 11, std: 20, container_suffix: "" }
-          - { gcc: 12, std: 20, container_suffix: "" }
+          - { gcc: 7, std: 11 }
+          - { gcc: 7, std: 17 }
+          - { gcc: 8, std: 14 }
+          - { gcc: 8, std: 17 }
+          - { gcc: 10, std: 17 }
+          - { gcc: 11, std: 20 }
+          - { gcc: 12, std: 20 }
 
     name: "🐍 3 • GCC ${{ matrix.gcc }} • C++${{ matrix.std }}• x64"
-    container: "gcc:${{ matrix.gcc }}${{ matrix.container_suffix }}"
+    container: "gcc:${{ matrix.gcc }}"
 
     steps:
     - uses: actions/checkout@v3

From 2fb3d7cbde264a0b3f921e802f287195387e8263 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Tue, 27 Jun 2023 15:08:32 -0700
Subject: [PATCH 612/638] Trivial refactoring to make the capsule API more user
 friendly. (#4720)

* Trivial refactoring to make the capsule API more user friendly.

* Use new API in production code. Thanks @Lalaland for pointing this out.
---
 include/pybind11/pybind11.h |  2 +-
 include/pybind11/pytypes.h  | 51 ++++++++++++++++++++++---------------
 tests/test_pytypes.cpp      |  9 +++++++
 tests/test_pytypes.py       | 13 ++++++++++
 4 files changed, 54 insertions(+), 21 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 28ebc22297..3bce1a01ba 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -508,8 +508,8 @@ class cpp_function : public function {
             rec->def->ml_flags = METH_VARARGS | METH_KEYWORDS;
 
             capsule rec_capsule(unique_rec.release(),
+                                detail::get_function_record_capsule_name(),
                                 [](void *ptr) { destruct((detail::function_record *) ptr); });
-            rec_capsule.set_name(detail::get_function_record_capsule_name());
             guarded_strdup.release();
 
             object scope_module;
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index f5d3f34f38..c93e3d3b92 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1925,28 +1925,13 @@ class capsule : public object {
         }
     }
 
+    /// Capsule name is nullptr.
     capsule(const void *value, void (*destructor)(void *)) {
-        m_ptr = PyCapsule_New(const_cast<void *>(value), nullptr, [](PyObject *o) {
-            // guard if destructor called while err indicator is set
-            error_scope error_guard;
-            auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
-            if (destructor == nullptr && PyErr_Occurred()) {
-                throw error_already_set();
-            }
-            const char *name = get_name_in_error_scope(o);
-            void *ptr = PyCapsule_GetPointer(o, name);
-            if (ptr == nullptr) {
-                throw error_already_set();
-            }
-
-            if (destructor != nullptr) {
-                destructor(ptr);
-            }
-        });
+        initialize_with_void_ptr_destructor(value, nullptr, destructor);
+    }
 
-        if (!m_ptr || PyCapsule_SetContext(m_ptr, reinterpret_cast<void *>(destructor)) != 0) {
-            throw error_already_set();
-        }
+    capsule(const void *value, const char *name, void (*destructor)(void *)) {
+        initialize_with_void_ptr_destructor(value, name, destructor);
     }
 
     explicit capsule(void (*destructor)()) {
@@ -2014,6 +1999,32 @@ class capsule : public object {
 
         return name;
     }
+
+    void initialize_with_void_ptr_destructor(const void *value,
+                                             const char *name,
+                                             void (*destructor)(void *)) {
+        m_ptr = PyCapsule_New(const_cast<void *>(value), name, [](PyObject *o) {
+            // guard if destructor called while err indicator is set
+            error_scope error_guard;
+            auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
+            if (destructor == nullptr && PyErr_Occurred()) {
+                throw error_already_set();
+            }
+            const char *name = get_name_in_error_scope(o);
+            void *ptr = PyCapsule_GetPointer(o, name);
+            if (ptr == nullptr) {
+                throw error_already_set();
+            }
+
+            if (destructor != nullptr) {
+                destructor(ptr);
+            }
+        });
+
+        if (!m_ptr || PyCapsule_SetContext(m_ptr, reinterpret_cast<void *>(destructor)) != 0) {
+            throw error_already_set();
+        }
+    }
 };
 
 class tuple : public object {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 1028bb58e8..b4ee642891 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -260,6 +260,15 @@ TEST_SUBMODULE(pytypes, m) {
         });
     });
 
+    m.def("return_capsule_with_destructor_3", []() {
+        py::print("creating capsule");
+        auto cap = py::capsule((void *) 1233, "oname", [](void *ptr) {
+            py::print("destructing capsule: {}"_s.format((size_t) ptr));
+        });
+        py::print("original name: {}"_s.format(cap.name()));
+        return cap;
+    });
+
     m.def("return_renamed_capsule_with_destructor_2", []() {
         py::print("creating capsule");
         auto cap = py::capsule((void *) 1234, [](void *ptr) {
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index afb7a1ce8a..eda7a20a9d 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -319,6 +319,19 @@ def test_capsule(capture):
     """
     )
 
+    with capture:
+        a = m.return_capsule_with_destructor_3()
+        del a
+        pytest.gc_collect()
+    assert (
+        capture.unordered
+        == """
+        creating capsule
+        destructing capsule: 1233
+        original name: oname
+    """
+    )
+
     with capture:
         a = m.return_renamed_capsule_with_destructor_2()
         del a

From 5ccb9e412d8974e8eeac1b061d9077ac0bd365e1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Tue, 4 Jul 2023 08:38:14 -0400
Subject: [PATCH 613/638] chore: ruff moved to astral-sh (#4726)

* chore: ruff moved to astral-sh

Committed via https://github.com/asottile/all-repos

* ci: bump CUDA version
---
 .github/workflows/ci.yml | 4 ++--
 .pre-commit-config.yaml  | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0d64014123..39b4c237e8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -337,8 +337,8 @@ jobs:
   # Testing NVCC; forces sources to behave like .cu files
   cuda:
     runs-on: ubuntu-latest
-    name: "🐍 3.10 • CUDA 11.7 • Ubuntu 22.04"
-    container: nvidia/cuda:11.7.0-devel-ubuntu22.04
+    name: "🐍 3.10 • CUDA 12.2 • Ubuntu 22.04"
+    container: nvidia/cuda:12.2.0-devel-ubuntu22.04
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 9a829d72b1..d406624f3c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -37,7 +37,7 @@ repos:
   - id: black
 
 # Ruff, the Python auto-correcting linter written in Rust
-- repo: https://github.com/charliermarsh/ruff-pre-commit
+- repo: https://github.com/astral-sh/ruff-pre-commit
   rev: v0.0.270
   hooks:
   - id: ruff

From 782b6281a2aec358fb54dc1badc4b8ae1988bd41 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Sun, 9 Jul 2023 09:40:47 -0700
Subject: [PATCH 614/638] Drop PyPy 3.7 from GitHub Actions (ci.yml) (#4728)

* Remove `pypy-3.7` from ci.yml

* Update .github/workflows/ci.yml

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 39b4c237e8..48f7c5e934 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,9 +37,9 @@ jobs:
         - '3.10'
         - '3.11'
         - '3.12'
-        - 'pypy-3.7'
         - 'pypy-3.8'
         - 'pypy-3.9'
+        - 'pypy-3.10'
 
         # Items in here will either be added to the build matrix (if not
         # present), or add new keys to an existing matrix element if all the

From d462dd91a58116a043974b198462864a527e84ca Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 10 Jul 2023 10:43:20 -0700
Subject: [PATCH 615/638] chore(deps): bump scipy from 1.8.0 to 1.10.0 in
 /tests (#4731)

Bumps [scipy](https://github.com/scipy/scipy) from 1.8.0 to 1.10.0.
- [Release notes](https://github.com/scipy/scipy/releases)
- [Commits](https://github.com/scipy/scipy/compare/v1.8.0...v1.10.0)

---
updated-dependencies:
- dependency-name: scipy
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 tests/requirements.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/requirements.txt b/tests/requirements.txt
index 04aafa8cf9..4ba1011196 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -6,4 +6,4 @@ numpy==1.22.2; platform_python_implementation!="PyPy" and python_version>="3.10"
 pytest==7.0.0
 pytest-timeout
 scipy==1.5.4; platform_python_implementation!="PyPy" and python_version<"3.10"
-scipy==1.8.0; platform_python_implementation!="PyPy" and python_version=="3.10"
+scipy==1.10.0; platform_python_implementation!="PyPy" and python_version=="3.10"

From 47dc0c4bd16b7a97edb2072e93e6960647c3872f Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 11 Jul 2023 10:31:43 -0700
Subject: [PATCH 616/638] chore(deps): update pre-commit hooks (#4727)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

updates:
- [github.com/pre-commit/mirrors-clang-format: v16.0.4 → v16.0.6](https://github.com/pre-commit/mirrors-clang-format/compare/v16.0.4...v16.0.6)
- https://github.com/charliermarsh/ruff-pre-commit → https://github.com/astral-sh/ruff-pre-commit
- [github.com/astral-sh/ruff-pre-commit: v0.0.270 → v0.0.276](https://github.com/astral-sh/ruff-pre-commit/compare/v0.0.270...v0.0.276)
- [github.com/pre-commit/mirrors-mypy: v1.3.0 → v1.4.1](https://github.com/pre-commit/mirrors-mypy/compare/v1.3.0...v1.4.1)
- [github.com/asottile/blacken-docs: 1.13.0 → 1.14.0](https://github.com/asottile/blacken-docs/compare/1.13.0...1.14.0)
- [github.com/codespell-project/codespell: v2.2.4 → v2.2.5](https://github.com/codespell-project/codespell/compare/v2.2.4...v2.2.5)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .pre-commit-config.yaml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index d406624f3c..86ac965d96 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -25,7 +25,7 @@ repos:
 
 # Clang format the codebase automatically
 - repo: https://github.com/pre-commit/mirrors-clang-format
-  rev: "v16.0.4"
+  rev: "v16.0.6"
   hooks:
   - id: clang-format
     types_or: [c++, c, cuda]
@@ -38,14 +38,14 @@ repos:
 
 # Ruff, the Python auto-correcting linter written in Rust
 - repo: https://github.com/astral-sh/ruff-pre-commit
-  rev: v0.0.270
+  rev: v0.0.276
   hooks:
   - id: ruff
     args: ["--fix", "--show-fixes"]
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v1.3.0"
+  rev: "v1.4.1"
   hooks:
   - id: mypy
     args: []
@@ -84,7 +84,7 @@ repos:
 
 # Also code format the docs
 - repo: https://github.com/asottile/blacken-docs
-  rev: "1.13.0"
+  rev: "1.14.0"
   hooks:
   - id: blacken-docs
     additional_dependencies:
@@ -124,7 +124,7 @@ repos:
 # Use tools/codespell_ignore_lines_from_errors.py
 # to rebuild .codespell-ignore-lines
 - repo: https://github.com/codespell-project/codespell
-  rev: "v2.2.4"
+  rev: "v2.2.5"
   hooks:
   - id: codespell
     exclude: ".supp$"

From b2732c6e1a96eb97e79359c049871c41e2cd34c8 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 12 Jul 2023 08:55:18 -0700
Subject: [PATCH 617/638] chore(deps): bump pypa/gh-action-pypi-publish from
 1.8.6 to 1.8.7 (#4718)

* chore(deps): bump pypa/gh-action-pypi-publish from 1.8.6 to 1.8.7

Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.8.6 to 1.8.7.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.8.6...v1.8.7)

---
updated-dependencies:
- dependency-name: pypa/gh-action-pypi-publish
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

* Apply suggestions from code review

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .github/workflows/pip.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 04d95a28c5..d6687b441c 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -102,13 +102,13 @@ jobs:
     - uses: actions/download-artifact@v3
 
     - name: Publish standard package
-      uses: pypa/gh-action-pypi-publish@v1.8.6
+      uses: pypa/gh-action-pypi-publish@release/v1
       with:
         password: ${{ secrets.pypi_password }}
         packages-dir: standard/
 
     - name: Publish global package
-      uses: pypa/gh-action-pypi-publish@v1.8.6
+      uses: pypa/gh-action-pypi-publish@release/v1
       with:
         password: ${{ secrets.pypi_password_global }}
         packages-dir: global/

From 6d22dba82f1789f11a8eb2c2debbcbd4d2d8a969 Mon Sep 17 00:00:00 2001
From: Luc de Jonckheere <lsdejonckheere@gmail.com>
Date: Wed, 12 Jul 2023 17:56:40 +0200
Subject: [PATCH 618/638] Warning on comparing wrapper enums with is (#4732)

* Warning on comparing wrapper enums with is

* backticks for quoting and link to related issue

---------

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 docs/classes.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/docs/classes.rst b/docs/classes.rst
index 52cd52da3f..4f2167dac1 100644
--- a/docs/classes.rst
+++ b/docs/classes.rst
@@ -549,3 +549,7 @@ The ``name`` property returns the name of the enum value as a unicode string.
            ...
 
     By default, these are omitted to conserve space.
+
+.. warning::
+
+    Contrary to Python customs, enum values from the wrappers should not be compared using ``is``, but with ``==`` (see `#1177 <https://github.com/pybind/pybind11/issues/1177>`_ for background).

From 2e5f5c4cf8efdd62acbeb4632e8988b2148f6caf Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Wed, 12 Jul 2023 13:10:24 -0500
Subject: [PATCH 619/638] fix: support CMake 3.27, drop 3.4 (#4719)

* fix: support CMake 3.27, drop 3.4

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update upgrade.rst

* Update upgrade.rst

* Update upgrade.rst

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 .github/workflows/configure.yml                    | 12 ++++++++----
 CMakeLists.txt                                     |  8 ++++----
 docs/advanced/embedding.rst                        |  2 +-
 docs/compiling.rst                                 |  9 ++++++---
 docs/faq.rst                                       |  3 ++-
 docs/upgrade.rst                                   | 14 ++++++++++++++
 tests/CMakeLists.txt                               | 11 ++++-------
 tests/test_cmake_build/CMakeLists.txt              |  3 ---
 .../installed_embed/CMakeLists.txt                 |  8 ++++----
 .../installed_function/CMakeLists.txt              |  8 ++++----
 .../installed_target/CMakeLists.txt                |  8 ++++----
 .../subdirectory_embed/CMakeLists.txt              |  8 ++++----
 .../subdirectory_function/CMakeLists.txt           |  8 ++++----
 .../subdirectory_target/CMakeLists.txt             |  8 ++++----
 tools/pybind11Common.cmake                         | 10 +++++++++-
 tools/pybind11Config.cmake.in                      |  4 +++-
 16 files changed, 75 insertions(+), 49 deletions(-)

diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index 82a4939004..ec7cd612de 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -26,20 +26,24 @@ jobs:
       matrix:
         runs-on: [ubuntu-20.04, macos-latest, windows-latest]
         arch: [x64]
-        cmake: ["3.23"]
+        cmake: ["3.26"]
 
         include:
         - runs-on: ubuntu-20.04
           arch: x64
-          cmake: 3.4
+          cmake: "3.5"
+
+        - runs-on: ubuntu-20.04
+          arch: x64
+          cmake: "3.27"
 
         - runs-on: macos-latest
           arch: x64
-          cmake: 3.7
+          cmake: "3.7"
 
         - runs-on: windows-2019
           arch: x64 # x86 compilers seem to be missing on 2019 image
-          cmake: 3.18
+          cmake: "3.18"
 
     name: 🐍 3.7 • CMake ${{ matrix.cmake }} • ${{ matrix.runs-on }}
     runs-on: ${{ matrix.runs-on }}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0ad74db2bb..87ec103468 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,15 +5,15 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.22)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.22)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.22)
+  cmake_policy(VERSION 3.26)
 endif()
 
 # Avoid infinite recursion if tests include this as a subdirectory
diff --git a/docs/advanced/embedding.rst b/docs/advanced/embedding.rst
index dd980d483a..e6a1686f87 100644
--- a/docs/advanced/embedding.rst
+++ b/docs/advanced/embedding.rst
@@ -18,7 +18,7 @@ information, see :doc:`/compiling`.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.4)
+    cmake_minimum_required(VERSION 3.5...3.26)
     project(example)
 
     find_package(pybind11 REQUIRED)  # or `add_subdirectory(pybind11)`
diff --git a/docs/compiling.rst b/docs/compiling.rst
index 2b543be0be..1fd098bec4 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -241,7 +241,7 @@ extension module can be created with just a few lines of code:
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.4...3.18)
+    cmake_minimum_required(VERSION 3.5...3.26)
     project(example LANGUAGES CXX)
 
     add_subdirectory(pybind11)
@@ -261,6 +261,9 @@ PyPI integration, can be found in the [cmake_example]_  repository.
 .. versionchanged:: 2.6
    CMake 3.4+ is required.
 
+.. versionchanged:: 2.11
+   CMake 3.5+ is required.
+
 Further information can be found at :doc:`cmake/index`.
 
 pybind11_add_module
@@ -495,7 +498,7 @@ You can use these targets to build complex applications. For example, the
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.4)
+    cmake_minimum_required(VERSION 3.5...3.26)
     project(example LANGUAGES CXX)
 
     find_package(pybind11 REQUIRED)  # or add_subdirectory(pybind11)
@@ -553,7 +556,7 @@ information about usage in C++, see :doc:`/advanced/embedding`.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.4...3.18)
+    cmake_minimum_required(VERSION 3.5...3.26)
     project(example LANGUAGES CXX)
 
     find_package(pybind11 REQUIRED)  # or add_subdirectory(pybind11)
diff --git a/docs/faq.rst b/docs/faq.rst
index 28498e7dfc..1eb00efada 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -284,7 +284,8 @@ There are three possible solutions:
    COMPONENTS Interpreter Development)`` on modern CMake (3.12+, 3.15+ better,
    3.18.2+ best). Pybind11 in these cases uses the new CMake FindPython instead
    of the old, deprecated search tools, and these modules are much better at
-   finding the correct Python.
+   finding the correct Python. If FindPythonLibs/Interp are not available
+   (CMake 3.27+), then this will be ignored and FindPython will be used.
 3. Set ``PYBIND11_NOPYTHON`` to ``TRUE``. Pybind11 will not search for Python.
    However, you will have to use the target-based system, and do more setup
    yourself, because it does not know about or include things that depend on
diff --git a/docs/upgrade.rst b/docs/upgrade.rst
index 6a9db2d08f..b13d21f5ec 100644
--- a/docs/upgrade.rst
+++ b/docs/upgrade.rst
@@ -8,6 +8,20 @@ to a new version. But it goes into more detail. This includes things like
 deprecated APIs and their replacements, build system changes, general code
 modernization and other useful information.
 
+.. _upgrade-guide-2.11:
+
+v2.11
+=====
+
+* The minimum version of CMake is now 3.5. A future version will likely move to
+  requiring something like CMake 3.15. Note that CMake 3.27 is removing the
+  long-deprecated support for ``FindPythonInterp`` if you set 3.27 as the
+  minimum or maximum supported version. To prepare for that future, CMake 3.15+
+  using ``FindPython`` or setting ``PYBIND11_FINDPYTHON`` is highly recommended,
+  otherwise pybind11 will automatically switch to using ``FindPython`` if
+  ``FindPythonInterp`` is not available.
+
+
 .. _upgrade-guide-2.9:
 
 v2.9
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 5574663b63..80ee9c1f11 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -5,20 +5,17 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.21)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.21)
+  cmake_policy(VERSION 3.26)
 endif()
 
-# Only needed for CMake < 3.5 support
-include(CMakeParseArguments)
-
 # Filter out items; print an optional message if any items filtered. This ignores extensions.
 #
 # Usage:
diff --git a/tests/test_cmake_build/CMakeLists.txt b/tests/test_cmake_build/CMakeLists.txt
index 8bfaa386ae..e5aa975cfc 100644
--- a/tests/test_cmake_build/CMakeLists.txt
+++ b/tests/test_cmake_build/CMakeLists.txt
@@ -1,6 +1,3 @@
-# Built-in in CMake 3.5+
-include(CMakeParseArguments)
-
 add_custom_target(test_cmake_build)
 
 function(pybind11_add_build_test name)
diff --git a/tests/test_cmake_build/installed_embed/CMakeLists.txt b/tests/test_cmake_build/installed_embed/CMakeLists.txt
index f7d6939982..d9dcb45e42 100644
--- a/tests/test_cmake_build/installed_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_embed/CMakeLists.txt
@@ -1,12 +1,12 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.26)
 endif()
 
 project(test_installed_embed CXX)
diff --git a/tests/test_cmake_build/installed_function/CMakeLists.txt b/tests/test_cmake_build/installed_function/CMakeLists.txt
index d7ca4db55d..2f4f642753 100644
--- a/tests/test_cmake_build/installed_function/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_function/CMakeLists.txt
@@ -1,13 +1,13 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 project(test_installed_module CXX)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.26)
 endif()
 
 project(test_installed_function CXX)
diff --git a/tests/test_cmake_build/installed_target/CMakeLists.txt b/tests/test_cmake_build/installed_target/CMakeLists.txt
index bc5e101f1d..a981e236f5 100644
--- a/tests/test_cmake_build/installed_target/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_target/CMakeLists.txt
@@ -1,12 +1,12 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.26)
 endif()
 
 project(test_installed_target CXX)
diff --git a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
index 58cdd7cfd1..f286746b95 100644
--- a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
@@ -1,12 +1,12 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.26)
 endif()
 
 project(test_subdirectory_embed CXX)
diff --git a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
index 01557c439a..275a75c0b5 100644
--- a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
@@ -1,12 +1,12 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.26)
 endif()
 
 project(test_subdirectory_function CXX)
diff --git a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
index ba82fdee2e..37bb2c56e7 100644
--- a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
@@ -1,12 +1,12 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.18)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.26)
 endif()
 
 project(test_subdirectory_target CXX)
diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index e4ff1e4080..308d1b70d1 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -163,11 +163,19 @@ endif()
 
 # --------------------- Python specifics -------------------------
 
+# CMake 3.27 removes the classic FindPythonInterp if CMP0148 is NEW
+if(CMAKE_VERSION VERSION_LESS "3.27")
+  set(_pybind11_missing_old_python "OLD")
+else()
+  cmake_policy(GET CMP0148 _pybind11_missing_old_python)
+endif()
+
 # Check to see which Python mode we are in, new, old, or no python
 if(PYBIND11_NOPYTHON)
   set(_pybind11_nopython ON)
 elseif(
-  PYBIND11_FINDPYTHON
+  _pybind11_missing_old_python STREQUAL "NEW"
+  OR PYBIND11_FINDPYTHON
   OR Python_FOUND
   OR Python2_FOUND
   OR Python3_FOUND)
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 9383e8c671..5734f437b3 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -63,7 +63,9 @@ Modes
 
 There are two modes provided; classic, which is built on the old Python
 discovery packages in CMake, or the new FindPython mode, which uses FindPython
-from 3.12+ forward (3.15+ _highly_ recommended).
+from 3.12+ forward (3.15+ _highly_ recommended). If you set the minimum or
+maximum version of CMake to 3.27+, then FindPython is the default (since
+FindPythonInterp/FindPythonLibs has been removed via policy `CMP0148`).
 
 New FindPython mode
 ^^^^^^^^^^^^^^^^^^^

From b33d06f61543878a81a433ed2d472b61d3fca0ca Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Wed, 12 Jul 2023 16:20:08 -0400
Subject: [PATCH 620/638] bugfix: fixes a test suite bug in the __new__ example
 (#4698)

* bugfix: fixes a test suite bug in the __new__ example

* See https://github.com/pybind/pybind11/pull/4698#discussion_r1227107682

---------

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
---
 tests/test_class.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index ca925917e6..7241bc8818 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -85,7 +85,7 @@ TEST_SUBMODULE(class_, m) {
         .def_static("new_instance", &NoConstructor::new_instance, "Return an instance");
 
     py::class_<NoConstructorNew>(m, "NoConstructorNew")
-        .def(py::init([](const NoConstructorNew &self) { return self; })) // Need a NOOP __init__
+        .def(py::init([]() { return nullptr; })) // Need a NOOP __init__
         .def_static("__new__",
                     [](const py::object &) { return NoConstructorNew::new_instance(); });
 

From 1a917f1852eb7819b671fc3fa862840f4c491a07 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Fri, 14 Jul 2023 08:20:38 -0700
Subject: [PATCH 621/638] docs: preparation for v2.11.0 release (#4744)

* Remove .dev1 from version number.

* Update Changelog (starting from `nox -s make_changelog` output)

* Miscellaneous minor fixes from proofreading in GitHub web view.

* docs: minor changelog updates

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/changelog.rst               | 47 +++++++++++++++++++++++++++-----
 docs/release.rst                 | 10 ++++---
 include/pybind11/detail/common.h |  4 +--
 pybind11/_version.py             |  2 +-
 4 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 32f6606aad..7bb115b90f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,15 +10,15 @@ Changes will be added here periodically from the "Suggested changelog entry"
 block in pull request descriptions.
 
 
-Version 2.11.0 (June 2, 2023)
+Version 2.11.0 (July 14, 2023)
 -----------------------------
 
 New features:
 
-* ``pybind11::detail::is_move_constructible`` can now be specialized for cases
-   in which ``std::is_move_constructible`` does not work as needed. This is
-   very similar to the long-established
-   ``pybind11::detail::is_copy_constructible``.
+* The newly added ``pybind11::detail::is_move_constructible`` trait can be
+  specialized for cases in which ``std::is_move_constructible`` does not work
+  as needed. This is very similar to the long-established
+  ``pybind11::detail::is_copy_constructible``.
   `#4631 <https://github.com/pybind/pybind11/pull/4631>`_
 
 * Introduce ``recursive_container_traits``.
@@ -30,6 +30,19 @@ New features:
   with ``pybind/pybind11.h``).
   `#4601 <https://github.com/pybind/pybind11/pull/4601>`_
 
+* ``format_descriptor<>`` & ``npy_format_descriptor<>`` ``PyObject *``
+  specializations were added. The latter enables ``py::array_t<PyObject *>``
+  to/from-python conversions.
+  `#4674 <https://github.com/pybind/pybind11/pull/4674>`_
+
+* ``buffer_info`` gained an ``item_type_is_equivalent_to<T>()`` member
+  function.
+  `#4674 <https://github.com/pybind/pybind11/pull/4674>`_
+
+* The ``capsule`` API gained a user-friendly constructor
+  (``py::capsule(ptr, "name", dtor)``).
+  `#4720 <https://github.com/pybind/pybind11/pull/4720>`_
+
 Changes:
 
 * ``PyGILState_Check()``'s in ``pybind11::handle``'s ``inc_ref()`` &
@@ -46,6 +59,12 @@ Changes:
   sizes slightly (~1.5%) but the error messages are much more informative.
   `#4463 <https://github.com/pybind/pybind11/pull/4463>`_
 
+* The docstring generation for the ``std::array``-list caster was fixed.
+  Previously, signatures included the size of the list in a non-standard,
+  non-spec compliant way. The new format conforms to PEP 593.
+  **Tooling for processing the docstrings may need to be updated accordingly.**
+  `#4679 <https://github.com/pybind/pybind11/pull/4679>`_
+
 * Setter return values (which are inaccessible for all practical purposes) are
   no longer converted to Python (only to be discarded).
   `#4621 <https://github.com/pybind/pybind11/pull/4621>`_
@@ -58,7 +77,7 @@ Changes:
   signatures on C++17 and higher.
   `#4587 <https://github.com/pybind/pybind11/pull/4587>`_
 
-* Compatibility with Python 3.12 (alpha). Note that the minimum pybind11
+* Compatibility with Python 3.12 (beta). Note that the minimum pybind11
   ABI version for Python 3.12 is version 5. (The default ABI version
   for Python versions up to and including 3.11 is still version 4.).
   `#4570 <https://github.com/pybind/pybind11/pull/4570>`_
@@ -69,15 +88,23 @@ Changes:
   types defined in the unnamed namespace.
   `#4319 <https://github.com/pybind/pybind11/pull/4319>`_
 
+* Python exception ``__notes__`` (introduced with Python 3.11) are now added to
+  the ``error_already_set::what()`` output.
+  `#4678 <https://github.com/pybind/pybind11/pull/4678>`_
+
 Build system improvements:
 
+* CMake 3.27 support was added, CMake 3.4 support was dropped.
+  FindPython will be used if ``FindPythonInterp`` is not present.
+  `#4719 <https://github.com/pybind/pybind11/pull/4719>`_
+
 * Update clang-tidy to 15 in CI.
   `#4387 <https://github.com/pybind/pybind11/pull/4387>`_
 
 * Moved the linting framework over to Ruff.
   `#4483 <https://github.com/pybind/pybind11/pull/4483>`_
 
-* Skip lto checks and target generation when
+* Skip ``lto`` checks and target generation when
   ``CMAKE_INTERPROCEDURAL_OPTIMIZATION`` is defined.
   `#4643 <https://github.com/pybind/pybind11/pull/4643>`_
 
@@ -85,6 +112,12 @@ Build system improvements:
   (macOS 10.9+).
   `#4639 <https://github.com/pybind/pybind11/pull/4639>`_
 
+* PyPy 3.10 support was added, PyPy 3.7 support was dropped.
+  `#4728 <https://github.com/pybind/pybind11/pull/4728>`_
+
+* Testing with Python 3.12 beta releases was added.
+  `#4713 <https://github.com/pybind/pybind11/pull/4713>`_
+
 
 Version 2.10.4 (Mar 16, 2023)
 -----------------------------
diff --git a/docs/release.rst b/docs/release.rst
index e761cdf7a6..4950c3b887 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -33,10 +33,12 @@ If you don't have nox, you should either use ``pipx run nox`` instead, or use
     - Run ``nox -s tests_packaging`` to ensure this was done correctly.
     - Ensure that all the information in ``setup.cfg`` is up-to-date, like
       supported Python versions.
-    - Add release date in ``docs/changelog.rst``.
-          - Check to make sure
-            `needs-changelog <https://github.com/pybind/pybind11/pulls?q=is%3Apr+is%3Aclosed+label%3A%22needs+changelog%22>`_
-            issues are entered in the changelog (clear the label when done).
+    - Add release date in ``docs/changelog.rst`` and integrate the output of
+      ``nox -s make_changelog``.
+          - Note that the ``make_changelog`` command inspects
+            `needs changelog <https://github.com/pybind/pybind11/pulls?q=is%3Apr+is%3Aclosed+label%3A%22needs+changelog%22>`_.
+          - Manually clear the ``needs changelog`` labels using the GitHub web
+            interface (very easy: start by clicking the link above).
     - ``git add`` and ``git commit``, ``git push``. **Ensure CI passes**. (If it
       fails due to a known flake issue, either ignore or restart CI.)
 - Add a release branch if this is a new minor version, or update the existing release branch if it is a patch version
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index c2e6f9ec89..27c426db5b 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 11
-#define PYBIND11_VERSION_PATCH 0.dev1
+#define PYBIND11_VERSION_PATCH 0
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020B00D1
+#define PYBIND11_VERSION_HEX 0x020B0000
 
 // Define some generic pybind11 helper macros for warning management.
 //
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 1cb51fc5c2..1c310e0c95 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.11.0.dev1"
+__version__ = "2.11.0"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 2965fa8de3cf9e82c789f906a525a76197b186c1 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 17 Jul 2023 09:50:35 -0700
Subject: [PATCH 622/638] Preparation for v2.11.1 patch release (#4752)

* Update README.rst - Add missing comma in the list of acknowlegements (#4750)

* Disable `PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF` generally for PyPy (not just PyPy Windows). (#4751)

* Update changelog

* Provide `PYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF` as an option (#4753)

* Remove GIL checks

* Update common.h

* Add flag

* style: pre-commit fixes

* Update pytypes.h

* style: pre-commit fixes

* Update common.h

* style: pre-commit fixes

* Update pytypes.h

* style: pre-commit fixes

* Update common.h

* style: pre-commit fixes

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

* Update changelog: PR #4753

---------

Co-authored-by: bzaar <slepov@gmail.com>
Co-authored-by: Ethan Steinberg <ethan.steinberg@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 README.rst                       |  2 +-
 docs/changelog.rst               | 15 +++++++++++++++
 include/pybind11/detail/common.h |  7 ++-----
 include/pybind11/pytypes.h       |  7 ++++++-
 4 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/README.rst b/README.rst
index 3c75edb575..80213a4062 100644
--- a/README.rst
+++ b/README.rst
@@ -135,7 +135,7 @@ This project was created by `Wenzel
 Jakob <http://rgl.epfl.ch/people/wjakob>`_. Significant features and/or
 improvements to the code were contributed by Jonas Adler, Lori A. Burns,
 Sylvain Corlay, Eric Cousineau, Aaron Gokaslan, Ralf Grosse-Kunstleve, Trent Houliston, Axel
-Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov Johan Mabille, Tomasz Miąsko,
+Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov, Johan Mabille, Tomasz Miąsko,
 Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling, Pim
 Schellart, Henry Schreiner, Ivan Smirnov, Boris Staletic, and Patrick Stewart.
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 7bb115b90f..add3fd66b6 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,6 +10,21 @@ Changes will be added here periodically from the "Suggested changelog entry"
 block in pull request descriptions.
 
 
+Version 2.11.1 (July 17, 2023)
+-----------------------------
+
+Changes:
+
+* ``PYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF`` is now provided as an option
+  for disabling the default-on ``PyGILState_Check()``'s in
+  ``pybind11::handle``'s ``inc_ref()`` & ``dec_ref()``.
+  `#4753 <https://github.com/pybind/pybind11/pull/4753>`_
+
+* ``PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF`` was disabled for PyPy in general
+  (not just PyPy Windows).
+  `#4751 <https://github.com/pybind/pybind11/pull/4751>`_
+
+
 Version 2.11.0 (July 14, 2023)
 -----------------------------
 
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 27c426db5b..bf424371e5 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -324,11 +324,8 @@ PYBIND11_WARNING_POP
 #endif
 
 // See description of PR #4246:
-#if !defined(NDEBUG) && !defined(PY_ASSERT_GIL_HELD_INCREF_DECREF)                                \
-    && !(defined(PYPY_VERSION)                                                                    \
-         && defined(_MSC_VER)) /* PyPy Windows: pytest hangs indefinitely at the end of the       \
-                                  process (see PR #4268) */                                       \
-    && !defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+#if !defined(PYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF) && !defined(NDEBUG)                       \
+    && !defined(PYPY_VERSION) && !defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
 #    define PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
 #endif
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index c93e3d3b92..64aad63476 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -303,7 +303,12 @@ class handle : public detail::object_api<handle> {
             stderr,
             "%s is being called while the GIL is either not held or invalid. Please see "
             "https://pybind11.readthedocs.io/en/stable/advanced/"
-            "misc.html#common-sources-of-global-interpreter-lock-errors for debugging advice.\n",
+            "misc.html#common-sources-of-global-interpreter-lock-errors for debugging advice.\n"
+            "If you are convinced there is no bug in your code, you can #define "
+            "PYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF"
+            "to disable this check. In that case you have to ensure this #define is consistently "
+            "used for all translation units linked into a given pybind11 extension, otherwise "
+            "there will be ODR violations.",
             function_name.c_str());
         fflush(stderr);
         if (Py_TYPE(m_ptr)->tp_name != nullptr) {

From 8a099e44b3d5f85b20f05828d919d2332a8de841 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 17 Jul 2023 10:24:25 -0700
Subject: [PATCH 623/638] Fix version number mishap: actually update 0 to 1
 (#4756)

---
 include/pybind11/detail/common.h | 4 ++--
 pybind11/_version.py             | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index bf424371e5..31a54c773a 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,11 +11,11 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 11
-#define PYBIND11_VERSION_PATCH 0
+#define PYBIND11_VERSION_PATCH 1
 
 // Similar to Python's convention: https://docs.python.org/3/c-api/apiabiversion.html
 // Additional convention: 0xD = dev
-#define PYBIND11_VERSION_HEX 0x020B0000
+#define PYBIND11_VERSION_HEX 0x020B0100
 
 // Define some generic pybind11 helper macros for warning management.
 //
diff --git a/pybind11/_version.py b/pybind11/_version.py
index 1c310e0c95..9280fa054e 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.11.0"
+__version__ = "2.11.1"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

From 11284cc442c92b565512ebf47a3c15083c0474ba Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 18:21:41 -0400
Subject: [PATCH 624/638] Remove `./tmp` shim file to restore worktree

---
 tmp | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 delete mode 100644 tmp

diff --git a/tmp b/tmp
deleted file mode 100644
index e69de29bb2..0000000000

From f342c361670a6803823f81d69cedf1c7b1ce0b99 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 13:47:33 -0400
Subject: [PATCH 625/638] import clang tidy setup

---
 .clang-format           | 19 +++++++++++++++++++
 .clang-tidy             |  8 +++++++-
 .pre-commit-config.yaml | 10 +++-------
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/.clang-format b/.clang-format
index 8e0fd8b014..b477a16037 100644
--- a/.clang-format
+++ b/.clang-format
@@ -3,17 +3,36 @@
 # clang-format --style=llvm --dump-config
 BasedOnStyle: LLVM
 AccessModifierOffset: -4
+AllowShortLambdasOnASingleLine: true
 AlwaysBreakTemplateDeclarations: Yes
 BinPackArguments: false
 BinPackParameters: false
 BreakBeforeBinaryOperators: All
 BreakConstructorInitializers: BeforeColon
 ColumnLimit: 99
+CommentPragmas: 'NOLINT:.*|^ IWYU pragma:'
+IncludeBlocks: Regroup
 IndentCaseLabels: true
 IndentPPDirectives: AfterHash
 IndentWidth: 4
 Language: Cpp
 SpaceAfterCStyleCast: true
 Standard: Cpp11
+StatementMacros: ['PyObject_HEAD']
 TabWidth: 4
+IncludeCategories:
+  - Regex:           '<pybind11/.*'
+    Priority:        -1
+  - Regex:           'pybind11.h"$'
+    Priority:        1
+  - Regex:           '^".*/?detail/'
+    Priority:        1
+    SortPriority:    2
+  - Regex:           '^"'
+    Priority:        1
+    SortPriority:    3
+  - Regex:           '<[[:alnum:]._]+>'
+    Priority:        4
+  - Regex:           '.*'
+    Priority:        5
 ...
diff --git a/.clang-tidy b/.clang-tidy
index d853a703ce..d01ca352cc 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -2,9 +2,12 @@ FormatStyle: file
 
 Checks: '
 *bugprone*,
+clang-analyzer-optin.performance.Padding,
+clang-analyzer-optin.cplusplus.VirtualCall,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-prefer-member-initializer,
+cppcoreguidelines-pro-type-static-cast-downcast,
 cppcoreguidelines-slicing,
-clang-analyzer-optin.cplusplus.VirtualCall,
 google-explicit-constructor,
 llvm-namespace-comment,
 misc-misplaced-const,
@@ -31,14 +34,17 @@ modernize-use-override,
 modernize-use-using,
 *performance*,
 readability-avoid-const-params-in-decls,
+readability-braces-around-statements,
 readability-const-return-type,
 readability-container-size-empty,
 readability-delete-null-pointer,
 readability-else-after-return,
 readability-implicit-bool-conversion,
+readability-inconsistent-declaration-parameter-name,
 readability-make-member-function-const,
 readability-misplaced-array-index,
 readability-non-const-parameter,
+readability-qualified-auto,
 readability-redundant-function-ptr-dereference,
 readability-redundant-smartptr-get,
 readability-redundant-string-cstr,
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2014cb2b42..c31cab71c7 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -141,11 +141,7 @@ repos:
     entry: PyBind|Numpy|Cmake|CCache|PyTest
     exclude: .pre-commit-config.yaml
 
-- repo: local
+- repo: https://github.com/pre-commit/mirrors-clang-format
+  rev: "v13.0.0"
   hooks:
-  - id: check-style
-    name: Classic check-style
-    language: system
-    types:
-    - c++
-    entry: ./tools/check-style.sh
+  - id: clang-format

From 7f05a75703f57e4465f0a640a810db5ce775059f Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 17:12:17 -0400
Subject: [PATCH 626/638] run re-format

---
 include/pybind11/attr.h                    |  207 +--
 include/pybind11/buffer_info.h             |  104 +-
 include/pybind11/cast.h                    |  823 +++++++-----
 include/pybind11/chrono.h                  |  115 +-
 include/pybind11/complex.h                 |   23 +-
 include/pybind11/detail/class.h            |   66 +-
 include/pybind11/detail/common.h           |  945 ++++++++------
 include/pybind11/detail/descr.h            |   81 +-
 include/pybind11/detail/init.h             |  238 ++--
 include/pybind11/detail/internals.h        |  113 +-
 include/pybind11/detail/type_caster_base.h |  397 +++---
 include/pybind11/detail/typeid.h           |    9 +-
 include/pybind11/eigen.h                   |  486 ++++---
 include/pybind11/embed.h                   |   34 +-
 include/pybind11/eval.h                    |   87 +-
 include/pybind11/functional.h              |   13 +-
 include/pybind11/gil.h                     |   30 +-
 include/pybind11/iostream.h                |   41 +-
 include/pybind11/numpy.h                   | 1039 ++++++++-------
 include/pybind11/operators.h               |  253 ++--
 include/pybind11/options.h                 |   42 +-
 include/pybind11/pybind11.h                | 1370 +++++++++++---------
 include/pybind11/pytypes.h                 |  987 ++++++++------
 include/pybind11/stl.h                     |  139 +-
 include/pybind11/stl/filesystem.h          |   46 +-
 include/pybind11/stl_bind.h                |  465 +++----
 tests/constructor_stats.h                  |  124 +-
 tests/cross_module_gil_utils.cpp           |   37 +-
 tests/local_bindings.h                     |   41 +-
 tests/object.h                             |   61 +-
 tests/pybind11_cross_module_tests.cpp      |   86 +-
 tests/pybind11_tests.cpp                   |   20 +-
 tests/pybind11_tests.h                     |   29 +-
 tests/test_async.cpp                       |    5 +-
 tests/test_buffers.cpp                     |   67 +-
 tests/test_builtin_casters.cpp             |  302 +++--
 tests/test_call_policies.cpp               |   43 +-
 tests/test_callbacks.cpp                   |   60 +-
 tests/test_chrono.cpp                      |   33 +-
 tests/test_class.cpp                       |  276 ++--
 tests/test_constants_and_functions.cpp     |   67 +-
 tests/test_copy_move.cpp                   |  163 ++-
 tests/test_custom_type_casters.cpp         |  100 +-
 tests/test_docstring_options.cpp           |   55 +-
 tests/test_eigen.cpp                       |  285 ++--
 tests/test_embed/catch.cpp                 |    8 +-
 tests/test_embed/external_module.cpp       |    9 +-
 tests/test_embed/test_interpreter.cpp      |   59 +-
 tests/test_enum.cpp                        |   83 +-
 tests/test_eval.cpp                        |   28 +-
 tests/test_exceptions.cpp                  |   95 +-
 tests/test_exceptions.h                    |    1 +
 tests/test_factory_constructors.cpp        |   83 +-
 tests/test_gil_scoped.cpp                  |   44 +-
 tests/test_iostream.cpp                    |   30 +-
 tests/test_kwargs_and_defaults.cpp         |  241 ++--
 tests/test_local_bindings.cpp              |   38 +-
 tests/test_methods_and_attributes.cpp      |  194 +--
 tests/test_modules.cpp                     |   66 +-
 tests/test_multiple_inheritance.cpp        |  144 +-
 tests/test_numpy_array.cpp                 |  249 ++--
 tests/test_numpy_dtypes.cpp                |  240 ++--
 tests/test_numpy_vectorize.cpp             |   32 +-
 tests/test_opaque_types.cpp                |   15 +-
 tests/test_operator_overloading.cpp        |  176 ++-
 tests/test_ownership_transfer.cpp          |  223 ++--
 tests/test_pickling.cpp                    |    6 +-
 tests/test_pytypes.cpp                     |  167 ++-
 tests/test_sequences_and_iterators.cpp     |  225 ++--
 tests/test_smart_ptr.cpp                   |  205 ++-
 tests/test_stl.cpp                         |  236 ++--
 tests/test_stl_binders.cpp                 |   54 +-
 tests/test_tagbased_polymorphic.cpp        |   85 +-
 tests/test_thread.cpp                      |   10 +-
 tests/test_virtual_functions.cpp           |  278 ++--
 75 files changed, 7617 insertions(+), 5714 deletions(-)

diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index bf9fb3479b..6fea1051c9 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -20,54 +20,62 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 /// @{
 
 /// Annotation for methods
-struct is_method { handle class_;
+struct is_method {
+    handle class_;
     explicit is_method(const handle &c) : class_(c) {}
 };
 
 /// Annotation for operators
-struct is_operator { };
+struct is_operator {};
 
 /// Annotation for classes that cannot be subclassed
-struct is_final { };
+struct is_final {};
 
 /// Annotation for parent scope
-struct scope { handle value;
+struct scope {
+    handle value;
     explicit scope(const handle &s) : value(s) {}
 };
 
 /// Annotation for documentation
-struct doc { const char *value;
+struct doc {
+    const char *value;
     explicit doc(const char *value) : value(value) {}
 };
 
 /// Annotation for function names
-struct name { const char *value;
+struct name {
+    const char *value;
     explicit name(const char *value) : value(value) {}
 };
 
 /// Annotation indicating that a function is an overload associated with a given "sibling"
-struct sibling { handle value;
+struct sibling {
+    handle value;
     explicit sibling(const handle &value) : value(value.ptr()) {}
 };
 
 /// Annotation indicating that a class derives from another given type
-template <typename T> struct base {
+template <typename T>
+struct base {
 
-    PYBIND11_DEPRECATED("base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
-    base() { } // NOLINT(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
+    PYBIND11_DEPRECATED(
+        "base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
+    base() {} // NOLINT(modernize-use-equals-default): breaks MSVC 2015 when adding an attribute
 };
 
 /// Keep patient alive while nurse lives
-template <size_t Nurse, size_t Patient> struct keep_alive { };
+template <size_t Nurse, size_t Patient>
+struct keep_alive {};
 
 /// Annotation indicating that a class is involved in a multiple inheritance relationship
-struct multiple_inheritance { };
+struct multiple_inheritance {};
 
 /// Annotation which enables dynamic attributes, i.e. adds `__dict__` to a class
-struct dynamic_attr { };
+struct dynamic_attr {};
 
 /// Annotation which enables the buffer protocol for a type
-struct buffer_protocol { };
+struct buffer_protocol {};
 
 /// Annotation which requests that a special metaclass is created for a type
 struct metaclass {
@@ -78,7 +86,7 @@ struct metaclass {
     metaclass() {}
 
     /// Override pybind11's default metaclass
-    explicit metaclass(handle value) : value(value) { }
+    explicit metaclass(handle value) : value(value) {}
 };
 
 /// Specifies a custom callback with signature `void (PyHeapTypeObject*)` that
@@ -99,15 +107,16 @@ struct custom_type_setup {
 };
 
 /// Annotation that marks a class as local to the module:
-struct module_local { const bool value;
+struct module_local {
+    const bool value;
     constexpr explicit module_local(bool v = true) : value(v) {}
 };
 
 /// Annotation to mark enums as an arithmetic type
-struct arithmetic { };
+struct arithmetic {};
 
 /// Mark a function for addition at the beginning of the existing overload chain instead of the end
-struct prepend { };
+struct prepend {};
 
 /** \rst
     A call policy which places one or more guard variables (``Ts...``) around the function call.
@@ -127,9 +136,13 @@ struct prepend { };
             return foo(args...); // forwarded arguments
         });
  \endrst */
-template <typename... Ts> struct call_guard;
+template <typename... Ts>
+struct call_guard;
 
-template <> struct call_guard<> { using type = detail::void_type; };
+template <>
+struct call_guard<> {
+    using type = detail::void_type;
+};
 
 template <typename T>
 struct call_guard<T> {
@@ -154,7 +167,8 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 enum op_id : int;
 enum op_type : int;
 struct undefined_t;
-template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t> struct op_;
+template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t>
+struct op_;
 void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret);
 
 /// Internal data structure which holds metadata about a keyword argument
@@ -166,15 +180,16 @@ struct argument_record {
     bool none : 1;     ///< True if None is allowed when loading
 
     argument_record(const char *name, const char *descr, handle value, bool convert, bool none)
-        : name(name), descr(descr), value(value), convert(convert), none(none) { }
+        : name(name), descr(descr), value(value), convert(convert), none(none) {}
 };
 
-/// Internal data structure which holds metadata about a bound function (signature, overloads, etc.)
+/// Internal data structure which holds metadata about a bound function (signature, overloads,
+/// etc.)
 struct function_record {
     function_record()
         : is_constructor(false), is_new_style_constructor(false), is_stateless(false),
-          is_operator(false), is_method(false), has_args(false),
-          has_kwargs(false), prepend(false) { }
+          is_operator(false), is_method(false), has_args(false), has_kwargs(false),
+          prepend(false) {}
 
     /// Function name
     char *name = nullptr; /* why no C++ strings? They generate heavier code.. */
@@ -189,13 +204,13 @@ struct function_record {
     std::vector<argument_record> args;
 
     /// Pointer to lambda function which converts arguments and performs the actual call
-    handle (*impl) (function_call &) = nullptr;
+    handle (*impl)(function_call &) = nullptr;
 
     /// Storage for the wrapped function pointer and captured data, if any
-    void *data[3] = { };
+    void *data[3] = {};
 
     /// Pointer to custom destructor for 'data' (if needed)
-    void (*free_data) (function_record *ptr) = nullptr;
+    void (*free_data)(function_record *ptr) = nullptr;
 
     /// Return value policy associated with this function
     return_value_policy policy = return_value_policy::automatic;
@@ -251,7 +266,7 @@ struct function_record {
 struct type_record {
     PYBIND11_NOINLINE type_record()
         : multiple_inheritance(false), dynamic_attr(false), buffer_protocol(false),
-          default_holder(true), module_local(false), is_final(false) { }
+          default_holder(true), module_local(false), is_final(false) {}
 
     /// Handle to the parent scope
     handle scope;
@@ -313,22 +328,22 @@ struct type_record {
     /// Is the class inheritable from python classes?
     bool is_final : 1;
 
-    PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *)) {
+    PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *) ) {
         auto *base_info = detail::get_type_info(base, false);
         if (!base_info) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
-            pybind11_fail("generic_type: type \"" + std::string(name) +
-                          "\" referenced unknown base type \"" + tname + "\"");
+            pybind11_fail("generic_type: type \"" + std::string(name)
+                          + "\" referenced unknown base type \"" + tname + "\"");
         }
 
         if (default_holder != base_info->default_holder) {
             std::string tname(base.name());
             detail::clean_type_id(tname);
-            pybind11_fail("generic_type: type \"" + std::string(name) + "\" " +
-                    (default_holder ? "does not have" : "has") +
-                    " a non-default holder type while its base \"" + tname + "\" " +
-                    (base_info->default_holder ? "does not" : "does"));
+            pybind11_fail("generic_type: type \"" + std::string(name) + "\" "
+                          + (default_holder ? "does not have" : "has")
+                          + " a non-default holder type while its base \"" + tname + "\" "
+                          + (base_info->default_holder ? "does not" : "does"));
         }
 
         bases.append((PyObject *) base_info->type);
@@ -343,14 +358,13 @@ struct type_record {
     }
 };
 
-inline function_call::function_call(const function_record &f, handle p) :
-        func(f), parent(p) {
+inline function_call::function_call(const function_record &f, handle p) : func(f), parent(p) {
     args.reserve(f.nargs);
     args_convert.reserve(f.nargs);
 }
 
 /// Tag for a new-style `__init__` defined in `detail/init.h`
-struct is_new_style_constructor { };
+struct is_new_style_constructor {};
 
 /**
  * Partial template specializations to process custom attributes provided to
@@ -358,60 +372,79 @@ struct is_new_style_constructor { };
  * fields in the type_record and function_record data structures or executed at
  * runtime to deal with custom call policies (e.g. keep_alive).
  */
-template <typename T, typename SFINAE = void> struct process_attribute;
+template <typename T, typename SFINAE = void>
+struct process_attribute;
 
-template <typename T> struct process_attribute_default {
+template <typename T>
+struct process_attribute_default {
     /// Default implementation: do nothing
-    static void init(const T &, function_record *) { }
-    static void init(const T &, type_record *) { }
-    static void precall(function_call &) { }
-    static void postcall(function_call &, handle) { }
+    static void init(const T &, function_record *) {}
+    static void init(const T &, type_record *) {}
+    static void precall(function_call &) {}
+    static void postcall(function_call &, handle) {}
 };
 
 /// Process an attribute specifying the function's name
-template <> struct process_attribute<name> : process_attribute_default<name> {
+template <>
+struct process_attribute<name> : process_attribute_default<name> {
     static void init(const name &n, function_record *r) { r->name = const_cast<char *>(n.value); }
 };
 
 /// Process an attribute specifying the function's docstring
-template <> struct process_attribute<doc> : process_attribute_default<doc> {
+template <>
+struct process_attribute<doc> : process_attribute_default<doc> {
     static void init(const doc &n, function_record *r) { r->doc = const_cast<char *>(n.value); }
 };
 
 /// Process an attribute specifying the function's docstring (provided as a C-style string)
-template <> struct process_attribute<const char *> : process_attribute_default<const char *> {
+template <>
+struct process_attribute<const char *> : process_attribute_default<const char *> {
     static void init(const char *d, function_record *r) { r->doc = const_cast<char *>(d); }
     static void init(const char *d, type_record *r) { r->doc = const_cast<char *>(d); }
 };
-template <> struct process_attribute<char *> : process_attribute<const char *> { };
+template <>
+struct process_attribute<char *> : process_attribute<const char *> {};
 
 /// Process an attribute indicating the function's return value policy
-template <> struct process_attribute<return_value_policy> : process_attribute_default<return_value_policy> {
+template <>
+struct process_attribute<return_value_policy> : process_attribute_default<return_value_policy> {
     static void init(const return_value_policy &p, function_record *r) { r->policy = p; }
 };
 
-/// Process an attribute which indicates that this is an overloaded function associated with a given sibling
-template <> struct process_attribute<sibling> : process_attribute_default<sibling> {
+/// Process an attribute which indicates that this is an overloaded function associated with a
+/// given sibling
+template <>
+struct process_attribute<sibling> : process_attribute_default<sibling> {
     static void init(const sibling &s, function_record *r) { r->sibling = s.value; }
 };
 
 /// Process an attribute which indicates that this function is a method
-template <> struct process_attribute<is_method> : process_attribute_default<is_method> {
-    static void init(const is_method &s, function_record *r) { r->is_method = true; r->scope = s.class_; }
+template <>
+struct process_attribute<is_method> : process_attribute_default<is_method> {
+    static void init(const is_method &s, function_record *r) {
+        r->is_method = true;
+        r->scope = s.class_;
+    }
 };
 
 /// Process an attribute which indicates the parent scope of a method
-template <> struct process_attribute<scope> : process_attribute_default<scope> {
+template <>
+struct process_attribute<scope> : process_attribute_default<scope> {
     static void init(const scope &s, function_record *r) { r->scope = s.value; }
 };
 
 /// Process an attribute which indicates that this function is an operator
-template <> struct process_attribute<is_operator> : process_attribute_default<is_operator> {
+template <>
+struct process_attribute<is_operator> : process_attribute_default<is_operator> {
     static void init(const is_operator &, function_record *r) { r->is_operator = true; }
 };
 
-template <> struct process_attribute<is_new_style_constructor> : process_attribute_default<is_new_style_constructor> {
-    static void init(const is_new_style_constructor &, function_record *r) { r->is_new_style_constructor = true; }
+template <>
+struct process_attribute<is_new_style_constructor>
+    : process_attribute_default<is_new_style_constructor> {
+    static void init(const is_new_style_constructor &, function_record *r) {
+        r->is_new_style_constructor = true;
+    }
 };
 
 inline void check_kw_only_arg(const arg &a, function_record *r) {
@@ -428,7 +461,8 @@ inline void append_self_arg_if_needed(function_record *r) {
 }
 
 /// Process a keyword argument attribute (*without* a default value)
-template <> struct process_attribute<arg> : process_attribute_default<arg> {
+template <>
+struct process_attribute<arg> : process_attribute_default<arg> {
     static void init(const arg &a, function_record *r) {
         append_self_arg_if_needed(r);
         r->args.emplace_back(a.name, nullptr, handle(), !a.flag_noconvert, a.flag_none);
@@ -438,7 +472,8 @@ template <> struct process_attribute<arg> : process_attribute_default<arg> {
 };
 
 /// Process a keyword argument attribute (*with* a default value)
-template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
+template <>
+struct process_attribute<arg_v> : process_attribute_default<arg_v> {
     static void init(const arg_v &a, function_record *r) {
         if (r->is_method && r->args.empty()) {
             r->args.emplace_back(
@@ -454,15 +489,16 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
             descr += a.type + "'";
             if (r->is_method) {
                 if (r->name) {
-                    descr += " in method '" + (std::string) str(r->scope) + "." + (std::string) r->name + "'";
+                    descr += " in method '" + (std::string) str(r->scope) + "."
+                             + (std::string) r->name + "'";
                 } else {
                     descr += " in method of '" + (std::string) str(r->scope) + "'";
                 }
             } else if (r->name) {
                 descr += " in function '" + (std::string) r->name + "'";
             }
-            pybind11_fail("arg(): could not convert default argument "
-                          + descr + " into a Python object (type not registered yet?)");
+            pybind11_fail("arg(): could not convert default argument " + descr
+                          + " into a Python object (type not registered yet?)");
 #else
             pybind11_fail("arg(): could not convert default argument "
                           "into a Python object (type not registered yet?). "
@@ -476,7 +512,8 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 };
 
 /// Process a keyword-only-arguments-follow pseudo argument
-template <> struct process_attribute<kw_only> : process_attribute_default<kw_only> {
+template <>
+struct process_attribute<kw_only> : process_attribute_default<kw_only> {
     static void init(const kw_only &, function_record *r) {
         append_self_arg_if_needed(r);
         if (r->has_args && r->nargs_pos != static_cast<std::uint16_t>(r->args.size())) {
@@ -488,20 +525,23 @@ template <> struct process_attribute<kw_only> : process_attribute_default<kw_onl
 };
 
 /// Process a positional-only-argument maker
-template <> struct process_attribute<pos_only> : process_attribute_default<pos_only> {
+template <>
+struct process_attribute<pos_only> : process_attribute_default<pos_only> {
     static void init(const pos_only &, function_record *r) {
         append_self_arg_if_needed(r);
         r->nargs_pos_only = static_cast<std::uint16_t>(r->args.size());
         if (r->nargs_pos_only > r->nargs_pos) {
             pybind11_fail("pos_only(): cannot follow a py::args() argument");
         }
-            // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
+        // It also can't follow a kw_only, but a static_assert in pybind11.h checks that
     }
 };
 
-/// Process a parent class attribute.  Single inheritance only (class_ itself already guarantees that)
+/// Process a parent class attribute.  Single inheritance only (class_ itself already guarantees
+/// that)
 template <typename T>
-struct process_attribute<T, enable_if_t<is_pyobject<T>::value>> : process_attribute_default<handle> {
+struct process_attribute<T, enable_if_t<is_pyobject<T>::value>>
+    : process_attribute_default<handle> {
     static void init(const handle &h, type_record *r) { r->bases.append(h); }
 };
 
@@ -514,7 +554,9 @@ struct process_attribute<base<T>> : process_attribute_default<base<T>> {
 /// Process a multiple inheritance attribute
 template <>
 struct process_attribute<multiple_inheritance> : process_attribute_default<multiple_inheritance> {
-    static void init(const multiple_inheritance &, type_record *r) { r->multiple_inheritance = true; }
+    static void init(const multiple_inheritance &, type_record *r) {
+        r->multiple_inheritance = true;
+    }
 };
 
 template <>
@@ -560,34 +602,41 @@ template <>
 struct process_attribute<arithmetic> : process_attribute_default<arithmetic> {};
 
 template <typename... Ts>
-struct process_attribute<call_guard<Ts...>> : process_attribute_default<call_guard<Ts...>> { };
+struct process_attribute<call_guard<Ts...>> : process_attribute_default<call_guard<Ts...>> {};
 
 /**
  * Process a keep_alive call policy -- invokes keep_alive_impl during the
  * pre-call handler if both Nurse, Patient != 0 and use the post-call handler
  * otherwise
  */
-template <size_t Nurse, size_t Patient> struct process_attribute<keep_alive<Nurse, Patient>> : public process_attribute_default<keep_alive<Nurse, Patient>> {
+template <size_t Nurse, size_t Patient>
+struct process_attribute<keep_alive<Nurse, Patient>>
+    : public process_attribute_default<keep_alive<Nurse, Patient>> {
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
-    static void precall(function_call &call) { keep_alive_impl(Nurse, Patient, call, handle()); }
+    static void precall(function_call &call) {
+        keep_alive_impl(Nurse, Patient, call, handle());
+    }
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
-    static void postcall(function_call &, handle) { }
+    static void postcall(function_call &, handle) {}
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
-    static void precall(function_call &) { }
+    static void precall(function_call &) {}
     template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
-    static void postcall(function_call &call, handle ret) { keep_alive_impl(Nurse, Patient, call, ret); }
+    static void postcall(function_call &call, handle ret) {
+        keep_alive_impl(Nurse, Patient, call, ret);
+    }
 };
 
 /// Recursively iterate over variadic template arguments
-template <typename... Args> struct process_attributes {
-    static void init(const Args&... args, function_record *r) {
+template <typename... Args>
+struct process_attributes {
+    static void init(const Args &...args, function_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
         (void) expander{
             0, ((void) process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
     }
-    static void init(const Args&... args, type_record *r) {
+    static void init(const Args &...args, type_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
@@ -619,7 +668,7 @@ using extract_guard_t = typename exactly_one_t<is_call_guard, call_guard<>, Extr
 /// Check the number of named arguments at compile time
 template <typename... Extra,
           size_t named = constexpr_sum(std::is_base_of<arg, Extra>::value...),
-          size_t self  = constexpr_sum(std::is_same<is_method, Extra>::value...)>
+          size_t self = constexpr_sum(std::is_same<is_method, Extra>::value...)>
 constexpr bool expected_num_args(size_t nargs, bool has_args, bool has_kwargs) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(nargs, has_args, has_kwargs);
     return named == 0 || (self + named + size_t(has_args) + size_t(has_kwargs)) == nargs;
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 9f1d047801..06120d5563 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -44,8 +44,8 @@ struct buffer_info {
     void *ptr = nullptr;          // Pointer to the underlying storage
     ssize_t itemsize = 0;         // Size of individual items in bytes
     ssize_t size = 0;             // Total number of entries
-    std::string format; // For homogeneous buffers, this should be set to
-                        // format_descriptor<T>::format()
+    std::string format;           // For homogeneous buffers, this should be set to
+                                  // format_descriptor<T>::format()
     ssize_t ndim = 0;             // Number of dimensions
     std::vector<ssize_t> shape;   // Shape of the tensor (1 entry per dimension)
     std::vector<ssize_t> strides; // Number of bytes between adjacent entries
@@ -54,10 +54,15 @@ struct buffer_info {
 
     buffer_info() = default;
 
-    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
-                detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
-    : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
-      shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
+    buffer_info(void *ptr,
+                ssize_t itemsize,
+                const std::string &format,
+                ssize_t ndim,
+                detail::any_container<ssize_t> shape_in,
+                detail::any_container<ssize_t> strides_in,
+                bool readonly = false)
+        : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
+          shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
         if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size()) {
             pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
         }
@@ -67,29 +72,48 @@ struct buffer_info {
     }
 
     template <typename T>
-    buffer_info(T *ptr, detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
-    : buffer_info(private_ctr_tag(), ptr, sizeof(T), format_descriptor<T>::format(), static_cast<ssize_t>(shape_in->size()), std::move(shape_in), std::move(strides_in), readonly) { }
-
-    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t size, bool readonly=false)
-    : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}, readonly) { }
+    buffer_info(T *ptr,
+                detail::any_container<ssize_t> shape_in,
+                detail::any_container<ssize_t> strides_in,
+                bool readonly = false)
+        : buffer_info(private_ctr_tag(),
+                      ptr,
+                      sizeof(T),
+                      format_descriptor<T>::format(),
+                      static_cast<ssize_t>(shape_in->size()),
+                      std::move(shape_in),
+                      std::move(strides_in),
+                      readonly) {}
+
+    buffer_info(void *ptr,
+                ssize_t itemsize,
+                const std::string &format,
+                ssize_t size,
+                bool readonly = false)
+        : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}, readonly) {}
 
     template <typename T>
-    buffer_info(T *ptr, ssize_t size, bool readonly=false)
-    : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size, readonly) { }
+    buffer_info(T *ptr, ssize_t size, bool readonly = false)
+        : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size, readonly) {}
 
     template <typename T>
-    buffer_info(const T *ptr, ssize_t size, bool readonly=true)
-    : buffer_info(const_cast<T*>(ptr), sizeof(T), format_descriptor<T>::format(), size, readonly) { }
+    buffer_info(const T *ptr, ssize_t size, bool readonly = true)
+        : buffer_info(
+            const_cast<T *>(ptr), sizeof(T), format_descriptor<T>::format(), size, readonly) {}
 
     explicit buffer_info(Py_buffer *view, bool ownview = true)
-    : buffer_info(view->buf, view->itemsize, view->format, view->ndim,
+        : buffer_info(
+            view->buf,
+            view->itemsize,
+            view->format,
+            view->ndim,
             {view->shape, view->shape + view->ndim},
             /* Though buffer::request() requests PyBUF_STRIDES, ctypes objects
              * ignore this flag and return a view with NULL strides.
              * When strides are NULL, build them manually.  */
             view->strides
-            ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
-            : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
+                ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
+                : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
             (view->readonly != 0)) {
         // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         this->m_view = view;
@@ -98,7 +122,7 @@ struct buffer_info {
     }
 
     buffer_info(const buffer_info &) = delete;
-    buffer_info& operator=(const buffer_info &) = delete;
+    buffer_info &operator=(const buffer_info &) = delete;
 
     buffer_info(buffer_info &&other) noexcept { (*this) = std::move(other); }
 
@@ -117,17 +141,28 @@ struct buffer_info {
     }
 
     ~buffer_info() {
-        if (m_view && ownview) { PyBuffer_Release(m_view); delete m_view; }
+        if (m_view && ownview) {
+            PyBuffer_Release(m_view);
+            delete m_view;
+        }
     }
 
     Py_buffer *view() const { return m_view; }
     Py_buffer *&view() { return m_view; }
-private:
-    struct private_ctr_tag { };
 
-    buffer_info(private_ctr_tag, void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
-                detail::any_container<ssize_t> &&shape_in, detail::any_container<ssize_t> &&strides_in, bool readonly)
-    : buffer_info(ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) { }
+private:
+    struct private_ctr_tag {};
+
+    buffer_info(private_ctr_tag,
+                void *ptr,
+                ssize_t itemsize,
+                const std::string &format,
+                ssize_t ndim,
+                detail::any_container<ssize_t> &&shape_in,
+                detail::any_container<ssize_t> &&strides_in,
+                bool readonly)
+        : buffer_info(
+            ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) {}
 
     Py_buffer *m_view = nullptr;
     bool ownview = false;
@@ -135,17 +170,22 @@ struct buffer_info {
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T, typename SFINAE = void> struct compare_buffer_info {
-    static bool compare(const buffer_info& b) {
+template <typename T, typename SFINAE = void>
+struct compare_buffer_info {
+    static bool compare(const buffer_info &b) {
         return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
     }
 };
 
-template <typename T> struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
-    static bool compare(const buffer_info& b) {
-        return (size_t) b.itemsize == sizeof(T) && (b.format == format_descriptor<T>::value ||
-            ((sizeof(T) == sizeof(long)) && b.format == (std::is_unsigned<T>::value ? "L" : "l")) ||
-            ((sizeof(T) == sizeof(size_t)) && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
+template <typename T>
+struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
+    static bool compare(const buffer_info &b) {
+        return (size_t) b.itemsize == sizeof(T)
+               && (b.format == format_descriptor<T>::value
+                   || ((sizeof(T) == sizeof(long))
+                       && b.format == (std::is_unsigned<T>::value ? "L" : "l"))
+                   || ((sizeof(T) == sizeof(size_t))
+                       && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
     }
 };
 
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 71c2175418..cbdd98e94c 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -10,11 +10,12 @@
 
 #pragma once
 
-#include "pytypes.h"
 #include "detail/common.h"
 #include "detail/descr.h"
 #include "detail/type_caster_base.h"
 #include "detail/typeid.h"
+#include "pytypes.h"
+
 #include <array>
 #include <cstring>
 #include <functional>
@@ -30,35 +31,42 @@
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename type, typename SFINAE = void> class type_caster : public type_caster_base<type> { };
-template <typename type> using make_caster = type_caster<intrinsic_t<type>>;
+template <typename type, typename SFINAE = void>
+class type_caster : public type_caster_base<type> {};
+template <typename type>
+using make_caster = type_caster<intrinsic_t<type>>;
 
 // Shortcut for calling a caster's `cast_op_type` cast operator for casting a type_caster to a T
-template <typename T> typename make_caster<T>::template cast_op_type<T> cast_op(make_caster<T> &caster) {
+template <typename T>
+typename make_caster<T>::template cast_op_type<T> cast_op(make_caster<T> &caster) {
     return caster.operator typename make_caster<T>::template cast_op_type<T>();
 }
-template <typename T> typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>
+template <typename T>
+typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>
 cast_op(make_caster<T> &&caster) {
-    return std::move(caster).operator
-        typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>();
+    return std::move(caster).operator typename make_caster<T>::
+        template cast_op_type<typename std::add_rvalue_reference<T>::type>();
 }
 
-template <typename type> class type_caster<std::reference_wrapper<type>> {
+template <typename type>
+class type_caster<std::reference_wrapper<type>> {
 private:
     using caster_t = make_caster<type>;
     caster_t subcaster;
-    using reference_t = type&;
-    using subcaster_cast_op_type =
-        typename caster_t::template cast_op_type<reference_t>;
-
-    static_assert(std::is_same<typename std::remove_const<type>::type &, subcaster_cast_op_type>::value ||
-                  std::is_same<reference_t, subcaster_cast_op_type>::value,
-                  "std::reference_wrapper<T> caster requires T to have a caster with an "
-                  "`operator T &()` or `operator const T &()`");
+    using reference_t = type &;
+    using subcaster_cast_op_type = typename caster_t::template cast_op_type<reference_t>;
+
+    static_assert(
+        std::is_same<typename std::remove_const<type>::type &, subcaster_cast_op_type>::value
+            || std::is_same<reference_t, subcaster_cast_op_type>::value,
+        "std::reference_wrapper<T> caster requires T to have a caster with an "
+        "`operator T &()` or `operator const T &()`");
+
 public:
     bool load(handle src, bool convert) { return subcaster.load(src, convert); }
     static constexpr auto name = caster_t::name;
-    static handle cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
+    static handle
+    cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
         // It is definitely wrong to take ownership of this pointer, so mask that rvp
         if (policy == return_value_policy::take_ownership
             || policy == return_value_policy::automatic) {
@@ -66,7 +74,8 @@ template <typename type> class type_caster<std::reference_wrapper<type>> {
         }
         return caster_t::cast(&src.get(), policy, parent);
     }
-    template <typename T> using cast_op_type = std::reference_wrapper<type>;
+    template <typename T>
+    using cast_op_type = std::reference_wrapper<type>;
     explicit operator std::reference_wrapper<type>() { return cast_op<type &>(subcaster); }
 };
 
@@ -93,24 +102,25 @@ public:
     template <typename T_>                                                                        \
     using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
 
-template <typename CharT> using is_std_char_type = any_of<
-    std::is_same<CharT, char>, /* std::string */
+template <typename CharT>
+using is_std_char_type = any_of<std::is_same<CharT, char>, /* std::string */
 #if defined(PYBIND11_HAS_U8STRING)
-    std::is_same<CharT, char8_t>, /* std::u8string */
+                                std::is_same<CharT, char8_t>, /* std::u8string */
 #endif
-    std::is_same<CharT, char16_t>, /* std::u16string */
-    std::is_same<CharT, char32_t>, /* std::u32string */
-    std::is_same<CharT, wchar_t> /* std::wstring */
->;
-
+                                std::is_same<CharT, char16_t>, /* std::u16string */
+                                std::is_same<CharT, char32_t>, /* std::u32string */
+                                std::is_same<CharT, wchar_t>   /* std::wstring */
+                                >;
 
 template <typename T>
 struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_type<T>::value>> {
     using _py_type_0 = conditional_t<sizeof(T) <= sizeof(long), long, long long>;
-    using _py_type_1 = conditional_t<std::is_signed<T>::value, _py_type_0, typename std::make_unsigned<_py_type_0>::type>;
+    using _py_type_1 = conditional_t<std::is_signed<T>::value,
+                                     _py_type_0,
+                                     typename std::make_unsigned<_py_type_0>::type>;
     using py_type = conditional_t<std::is_floating_point<T>::value, double, _py_type_1>;
-public:
 
+public:
     bool load(handle src, bool convert) {
         py_type py_value;
 
@@ -140,14 +150,13 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
             // PyPy: 7.3.7's 3.8 does not implement PyLong_*'s __index__ calls.
 #if PY_VERSION_HEX < 0x03080000 || defined(PYPY_VERSION)
             object index;
-            if (!PYBIND11_LONG_CHECK(src.ptr())) {  // So: index_check(src.ptr())
+            if (!PYBIND11_LONG_CHECK(src.ptr())) { // So: index_check(src.ptr())
                 index = reinterpret_steal<object>(PyNumber_Index(src.ptr()));
                 if (!index) {
                     PyErr_Clear();
                     if (!convert)
                         return false;
-                }
-                else {
+                } else {
                     src_or_index = index;
                 }
             }
@@ -156,8 +165,8 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
                 py_value = as_unsigned<py_type>(src_or_index.ptr());
             } else { // signed integer:
                 py_value = sizeof(T) <= sizeof(long)
-                    ? (py_type) PyLong_AsLong(src_or_index.ptr())
-                    : (py_type) PYBIND11_LONG_AS_LONGLONG(src_or_index.ptr());
+                               ? (py_type) PyLong_AsLong(src_or_index.ptr())
+                               : (py_type) PYBIND11_LONG_AS_LONGLONG(src_or_index.ptr());
             }
         }
 
@@ -166,12 +175,14 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
 
         // Check to see if the conversion is valid (integers should match exactly)
         // Signed/unsigned checks happen elsewhere
-        if (py_err || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T) && py_value != (py_type) (T) py_value)) {
+        if (py_err
+            || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T)
+                && py_value != (py_type) (T) py_value)) {
             PyErr_Clear();
             if (py_err && convert && (PyNumber_Check(src.ptr()) != 0)) {
                 auto tmp = reinterpret_steal<object>(std::is_floating_point<T>::value
-                                                     ? PyNumber_Float(src.ptr())
-                                                     : PyNumber_Long(src.ptr()));
+                                                         ? PyNumber_Float(src.ptr())
+                                                         : PyNumber_Long(src.ptr()));
                 PyErr_Clear();
                 return load(tmp, false);
             }
@@ -182,32 +193,40 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
         return true;
     }
 
-    template<typename U = T>
+    template <typename U = T>
     static typename std::enable_if<std::is_floating_point<U>::value, handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PyFloat_FromDouble((double) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) <= sizeof(long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value
+                                       && (sizeof(U) <= sizeof(long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PYBIND11_LONG_FROM_SIGNED((long) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) <= sizeof(unsigned long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value
+                                       && (sizeof(U) <= sizeof(unsigned long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PYBIND11_LONG_FROM_UNSIGNED((unsigned long) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) > sizeof(long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value
+                                       && (sizeof(U) > sizeof(long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PyLong_FromLongLong((long long) src);
     }
 
-    template<typename U = T>
-    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) > sizeof(unsigned long)), handle>::type
+    template <typename U = T>
+    static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value
+                                       && (sizeof(U) > sizeof(unsigned long)),
+                                   handle>::type
     cast(U src, return_value_policy /* policy */, handle /* parent */) {
         return PyLong_FromUnsignedLongLong((unsigned long long) src);
     }
@@ -215,7 +234,8 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
     PYBIND11_TYPE_CASTER(T, const_name<std::is_integral<T>::value>("int", "float"));
 };
 
-template<typename T> struct void_caster {
+template <typename T>
+struct void_caster {
 public:
     bool load(handle src, bool) {
         if (src && src.is_none()) {
@@ -229,9 +249,11 @@ template<typename T> struct void_caster {
     PYBIND11_TYPE_CASTER(T, const_name("None"));
 };
 
-template <> class type_caster<void_type> : public void_caster<void_type> {};
+template <>
+class type_caster<void_type> : public void_caster<void_type> {};
 
-template <> class type_caster<void> : public type_caster<void_type> {
+template <>
+class type_caster<void> : public type_caster<void_type> {
 public:
     using type_caster<void_type>::cast;
 
@@ -268,16 +290,20 @@ template <> class type_caster<void> : public type_caster<void_type> {
         return none().inc_ref();
     }
 
-    template <typename T> using cast_op_type = void*&;
+    template <typename T>
+    using cast_op_type = void *&;
     explicit operator void *&() { return value; }
     static constexpr auto name = const_name("capsule");
+
 private:
     void *value = nullptr;
 };
 
-template <> class type_caster<std::nullptr_t> : public void_caster<std::nullptr_t> { };
+template <>
+class type_caster<std::nullptr_t> : public void_caster<std::nullptr_t> {};
 
-template <> class type_caster<bool> {
+template <>
+class type_caster<bool> {
 public:
     bool load(handle src, bool convert) {
         if (!src) {
@@ -296,14 +322,14 @@ template <> class type_caster<bool> {
 
             Py_ssize_t res = -1;
             if (src.is_none()) {
-                res = 0;  // None is implicitly converted to False
+                res = 0; // None is implicitly converted to False
             }
-            #if defined(PYPY_VERSION)
+#if defined(PYPY_VERSION)
             // On PyPy, check that "__bool__" (or "__nonzero__" on Python 2.7) attr exists
             else if (hasattr(src, PYBIND11_BOOL_ATTR)) {
                 res = PyObject_IsTrue(src.ptr());
             }
-            #else
+#else
             // Alternate approach for CPython: this does the same as the above, but optimized
             // using the CPython API so as to avoid an unneeded attribute lookup.
             else if (auto *tp_as_number = src.ptr()->ob_type->tp_as_number) {
@@ -311,7 +337,7 @@ template <> class type_caster<bool> {
                     res = (*PYBIND11_NB_BOOL(tp_as_number))(src.ptr());
                 }
             }
-            #endif
+#endif
             if (res == 0 || res == 1) {
                 value = (res != 0);
                 return true;
@@ -327,20 +353,25 @@ template <> class type_caster<bool> {
 };
 
 // Helper class for UTF-{8,16,32} C++ stl strings:
-template <typename StringType, bool IsView = false> struct string_caster {
+template <typename StringType, bool IsView = false>
+struct string_caster {
     using CharT = typename StringType::value_type;
 
     // Simplify life by being able to assume standard char sizes (the standard only guarantees
     // minimums, but Python requires exact sizes)
-    static_assert(!std::is_same<CharT, char>::value || sizeof(CharT) == 1, "Unsupported char size != 1");
+    static_assert(!std::is_same<CharT, char>::value || sizeof(CharT) == 1,
+                  "Unsupported char size != 1");
 #if defined(PYBIND11_HAS_U8STRING)
-    static_assert(!std::is_same<CharT, char8_t>::value || sizeof(CharT) == 1, "Unsupported char8_t size != 1");
+    static_assert(!std::is_same<CharT, char8_t>::value || sizeof(CharT) == 1,
+                  "Unsupported char8_t size != 1");
 #endif
-    static_assert(!std::is_same<CharT, char16_t>::value || sizeof(CharT) == 2, "Unsupported char16_t size != 2");
-    static_assert(!std::is_same<CharT, char32_t>::value || sizeof(CharT) == 4, "Unsupported char32_t size != 4");
+    static_assert(!std::is_same<CharT, char16_t>::value || sizeof(CharT) == 2,
+                  "Unsupported char16_t size != 2");
+    static_assert(!std::is_same<CharT, char32_t>::value || sizeof(CharT) == 4,
+                  "Unsupported char32_t size != 4");
     // wchar_t can be either 16 bits (Windows) or 32 (everywhere else)
     static_assert(!std::is_same<CharT, wchar_t>::value || sizeof(CharT) == 2 || sizeof(CharT) == 4,
-            "Unsupported wchar_t size != 2/4");
+                  "Unsupported wchar_t size != 2/4");
     static constexpr size_t UTF_N = 8 * sizeof(CharT);
 
     bool load(handle src, bool) {
@@ -364,7 +395,10 @@ template <typename StringType, bool IsView = false> struct string_caster {
                 return false;
 
             temp = reinterpret_steal<object>(PyUnicode_FromObject(load_src.ptr()));
-            if (!temp) { PyErr_Clear(); return false; }
+            if (!temp) {
+                PyErr_Clear();
+                return false;
+            }
             load_src = temp;
 #endif
         }
@@ -385,11 +419,19 @@ template <typename StringType, bool IsView = false> struct string_caster {
         }
 #endif
 
-        auto utfNbytes = reinterpret_steal<object>(PyUnicode_AsEncodedString(
-            load_src.ptr(), UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr));
-        if (!utfNbytes) { PyErr_Clear(); return false; }
+        auto utfNbytes
+            = reinterpret_steal<object>(PyUnicode_AsEncodedString(load_src.ptr(),
+                                                                  UTF_N == 8    ? "utf-8"
+                                                                  : UTF_N == 16 ? "utf-16"
+                                                                                : "utf-32",
+                                                                  nullptr));
+        if (!utfNbytes) {
+            PyErr_Clear();
+            return false;
+        }
 
-        const auto *buffer = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
+        const auto *buffer
+            = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
         size_t length = (size_t) PYBIND11_BYTES_SIZE(utfNbytes.ptr()) / sizeof(CharT);
         // Skip BOM for UTF-16/32
         if (PYBIND11_SILENCE_MSVC_C4127(UTF_N > 8)) {
@@ -406,7 +448,8 @@ template <typename StringType, bool IsView = false> struct string_caster {
         return true;
     }
 
-    static handle cast(const StringType &src, return_value_policy /* policy */, handle /* parent */) {
+    static handle
+    cast(const StringType &src, return_value_policy /* policy */, handle /* parent */) {
         const char *buffer = reinterpret_cast<const char *>(src.data());
         auto nbytes = ssize_t(src.size() * sizeof(CharT));
         handle s = decode_utfN(buffer, nbytes);
@@ -421,14 +464,19 @@ template <typename StringType, bool IsView = false> struct string_caster {
 private:
     static handle decode_utfN(const char *buffer, ssize_t nbytes) {
 #if !defined(PYPY_VERSION)
-        return
-            UTF_N == 8  ? PyUnicode_DecodeUTF8(buffer, nbytes, nullptr) :
-            UTF_N == 16 ? PyUnicode_DecodeUTF16(buffer, nbytes, nullptr, nullptr) :
-                          PyUnicode_DecodeUTF32(buffer, nbytes, nullptr, nullptr);
+        return UTF_N == 8    ? PyUnicode_DecodeUTF8(buffer, nbytes, nullptr)
+               : UTF_N == 16 ? PyUnicode_DecodeUTF16(buffer, nbytes, nullptr, nullptr)
+                             : PyUnicode_DecodeUTF32(buffer, nbytes, nullptr, nullptr);
 #else
-        // PyPy segfaults when on PyUnicode_DecodeUTF16 (and possibly on PyUnicode_DecodeUTF32 as well),
-        // so bypass the whole thing by just passing the encoding as a string value, which works properly:
-        return PyUnicode_Decode(buffer, nbytes, UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr);
+        // PyPy segfaults when on PyUnicode_DecodeUTF16 (and possibly on PyUnicode_DecodeUTF32 as
+        // well), so bypass the whole thing by just passing the encoding as a string value, which
+        // works properly:
+        return PyUnicode_Decode(buffer,
+                                nbytes,
+                                UTF_N == 8    ? "utf-8"
+                                : UTF_N == 16 ? "utf-16"
+                                              : "utf-32",
+                                nullptr);
 #endif
     }
 
@@ -451,27 +499,33 @@ template <typename StringType, bool IsView = false> struct string_caster {
     }
 
     template <typename C = CharT>
-    bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) { return false; }
+    bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) {
+        return false;
+    }
 };
 
 template <typename CharT, class Traits, class Allocator>
-struct type_caster<std::basic_string<CharT, Traits, Allocator>, enable_if_t<is_std_char_type<CharT>::value>>
+struct type_caster<std::basic_string<CharT, Traits, Allocator>,
+                   enable_if_t<is_std_char_type<CharT>::value>>
     : string_caster<std::basic_string<CharT, Traits, Allocator>> {};
 
 #ifdef PYBIND11_HAS_STRING_VIEW
 template <typename CharT, class Traits>
-struct type_caster<std::basic_string_view<CharT, Traits>, enable_if_t<is_std_char_type<CharT>::value>>
+struct type_caster<std::basic_string_view<CharT, Traits>,
+                   enable_if_t<is_std_char_type<CharT>::value>>
     : string_caster<std::basic_string_view<CharT, Traits>, true> {};
 #endif
 
 // Type caster for C-style strings.  We basically use a std::string type caster, but also add the
 // ability to use None as a nullptr char* (which the string caster doesn't allow).
-template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
+template <typename CharT>
+struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
     using StringType = std::basic_string<CharT>;
     using StringCaster = type_caster<StringType>;
     StringCaster str_caster;
     bool none = false;
     CharT one_char = 0;
+
 public:
     bool load(handle src, bool convert) {
         if (!src) {
@@ -521,10 +575,10 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
         }
 
         // If we're in UTF-8 mode, we have two possible failures: one for a unicode character that
-        // is too high, and one for multiple unicode characters (caught later), so we need to figure
-        // out how long the first encoded character is in bytes to distinguish between these two
-        // errors.  We also allow want to allow unicode characters U+0080 through U+00FF, as those
-        // can fit into a single char value.
+        // is too high, and one for multiple unicode characters (caught later), so we need to
+        // figure out how long the first encoded character is in bytes to distinguish between these
+        // two errors.  We also allow want to allow unicode characters U+0080 through U+00FF, as
+        // those can fit into a single char value.
         if (PYBIND11_SILENCE_MSVC_C4127(StringCaster::UTF_N == 8) && str_len > 1 && str_len <= 4) {
             auto v0 = static_cast<unsigned char>(value[0]);
             // low bits only: 0-127
@@ -539,7 +593,8 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
             if (char0_bytes == str_len) {
                 // If we have a 128-255 value, we can decode it into a single char:
                 if (char0_bytes == 2 && (v0 & 0xFC) == 0xC0) { // 0x110000xx 0x10xxxxxx
-                    one_char = static_cast<CharT>(((v0 & 3) << 6) + (static_cast<unsigned char>(value[1]) & 0x3F));
+                    one_char = static_cast<CharT>(((v0 & 3) << 6)
+                                                  + (static_cast<unsigned char>(value[1]) & 0x3F));
                     return one_char;
                 }
                 // Otherwise we have a single character, but it's > U+00FF
@@ -566,16 +621,18 @@ template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type
     }
 
     static constexpr auto name = const_name(PYBIND11_STRING_NAME);
-    template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
+    template <typename _T>
+    using cast_op_type = pybind11::detail::cast_op_type<_T>;
 };
 
 // Base implementation for std::tuple and std::pair
-template <template<typename...> class Tuple, typename... Ts> class tuple_caster {
+template <template <typename...> class Tuple, typename... Ts>
+class tuple_caster {
     using type = Tuple<Ts...>;
     static constexpr auto size = sizeof...(Ts);
     using indices = make_index_sequence<size>;
-public:
 
+public:
     bool load(handle src, bool convert) {
         if (!isinstance<sequence>(src)) {
             return false;
@@ -606,18 +663,24 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
         return cast(*src, policy, parent);
     }
 
-    static constexpr auto name = const_name("Tuple[") + concat(make_caster<Ts>::name...) + const_name("]");
+    static constexpr auto name
+        = const_name("Tuple[") + concat(make_caster<Ts>::name...) + const_name("]");
 
-    template <typename T> using cast_op_type = type;
+    template <typename T>
+    using cast_op_type = type;
 
     explicit operator type() & { return implicit_cast(indices{}); }
     explicit operator type() && { return std::move(*this).implicit_cast(indices{}); }
 
 protected:
     template <size_t... Is>
-    type implicit_cast(index_sequence<Is...>) & { return type(cast_op<Ts>(std::get<Is>(subcasters))...); }
+    type implicit_cast(index_sequence<Is...>) & {
+        return type(cast_op<Ts>(std::get<Is>(subcasters))...);
+    }
     template <size_t... Is>
-    type implicit_cast(index_sequence<Is...>) && { return type(cast_op<Ts>(std::move(std::get<Is>(subcasters)))...); }
+    type implicit_cast(index_sequence<Is...>) && {
+        return type(cast_op<Ts>(std::move(std::get<Is>(subcasters)))...);
+    }
 
     static constexpr bool load_impl(const sequence &, bool, index_sequence<>) { return true; }
 
@@ -639,12 +702,12 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
 
     /* Implementation: Convert a C++ tuple into a Python tuple */
     template <typename T, size_t... Is>
-    static handle cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
+    static handle
+    cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(src, policy, parent);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(policy, parent);
-        std::array<object, size> entries{{
-            reinterpret_steal<object>(make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...
-        }};
+        std::array<object, size> entries{{reinterpret_steal<object>(
+            make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...}};
         for (const auto &entry : entries) {
             if (!entry) {
                 return handle();
@@ -661,11 +724,11 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
     Tuple<make_caster<Ts>...> subcasters;
 };
 
-template <typename T1, typename T2> class type_caster<std::pair<T1, T2>>
-    : public tuple_caster<std::pair, T1, T2> {};
+template <typename T1, typename T2>
+class type_caster<std::pair<T1, T2>> : public tuple_caster<std::pair, T1, T2> {};
 
-template <typename... Ts> class type_caster<std::tuple<Ts...>>
-    : public tuple_caster<std::tuple, Ts...> {};
+template <typename... Ts>
+class type_caster<std::tuple<Ts...>> : public tuple_caster<std::tuple, Ts...> {};
 
 /// Helper class which abstracts away certain actions. Users can provide specializations for
 /// custom holders, but it's only necessary if the type has a non-standard interface.
@@ -674,12 +737,11 @@ struct holder_helper {
     static auto get(const T &p) -> decltype(p.get()) { return p.get(); }
 };
 
-inline const detail::type_info* get_lowest_type(handle src, bool do_throw = true) {
-    auto* py_type = (PyTypeObject*)src.get_type().ptr();
+inline const detail::type_info *get_lowest_type(handle src, bool do_throw = true) {
+    auto *py_type = (PyTypeObject *) src.get_type().ptr();
     return detail::get_type_info(py_type, do_throw);
 }
 
-
 /// Type caster for holder types like std::shared_ptr, etc.
 /// The SFINAE hook is provided to help work around the current lack of support
 /// for smart-pointer interoperability. Please consider it an implementation
@@ -690,7 +752,7 @@ struct copyable_holder_caster : public type_caster_base<type> {
 public:
     using base = type_caster_base<type>;
     static_assert(std::is_base_of<base, type_caster<type>>::value,
-            "Holder classes are only supported for custom types");
+                  "Holder classes are only supported for custom types");
     using base::base;
     using base::cast;
     using base::typeinfo;
@@ -703,12 +765,12 @@ struct copyable_holder_caster : public type_caster_base<type> {
         return base::template load_impl<copyable_holder_caster<type, holder_type>>(src, convert);
     }
 
-    explicit operator type*() { return this->value; }
+    explicit operator type *() { return this->value; }
     // static_cast works around compiler error with MSVC 17 and CUDA 10.2
     // see issue #2180
-    explicit operator type&() { return *(static_cast<type *>(this->value)); }
-    explicit operator holder_type*() { return std::addressof(holder); }
-    explicit operator holder_type&() { return holder; }
+    explicit operator type &() { return *(static_cast<type *>(this->value)); }
+    explicit operator holder_type *() { return std::addressof(holder); }
+    explicit operator holder_type &() { return holder; }
 
     // Risk increasing the `shared_ptr` ref count temporarily to maintain writeable
     // semantics without too much `const_cast<>` ooginess.
@@ -722,7 +784,7 @@ struct copyable_holder_caster : public type_caster_base<type> {
         return type_caster_base<type>::cast_holder(ptr, holder_erased(std::addressof(src)));
     }
 
-  // TODO(eric.cousineau): Define cast_op_type???
+    // TODO(eric.cousineau): Define cast_op_type???
 
 protected:
     friend class type_caster_generic;
@@ -734,7 +796,7 @@ struct copyable_holder_caster : public type_caster_base<type> {
 
     bool load_value(value_and_holder &&v_h, LoadType load_type) {
         // TODO(eric.cousineau): Restore `do_relelase_to_cpp` logic?
-        (void)load_type;
+        (void) load_type;
 
         if (v_h.holder_constructed()) {
             value = v_h.value_ptr();
@@ -748,13 +810,16 @@ struct copyable_holder_caster : public type_caster_base<type> {
                          "of type '"
                          + type_id<holder_type>() + "''");
 #endif
-
     }
 
-    template <typename T = holder_type, detail::enable_if_t<!std::is_constructible<T, const T &, type*>::value, int> = 0>
-    bool try_implicit_casts(handle, bool) { return false; }
+    template <typename T = holder_type,
+              detail::enable_if_t<!std::is_constructible<T, const T &, type *>::value, int> = 0>
+    bool try_implicit_casts(handle, bool) {
+        return false;
+    }
 
-    template <typename T = holder_type, detail::enable_if_t<std::is_constructible<T, const T &, type*>::value, int> = 0>
+    template <typename T = holder_type,
+              detail::enable_if_t<std::is_constructible<T, const T &, type *>::value, int> = 0>
     bool try_implicit_casts(handle src, bool convert) {
         for (auto &cast : typeinfo->implicit_casts) {
             copyable_holder_caster sub_caster(*cast.first);
@@ -769,23 +834,23 @@ struct copyable_holder_caster : public type_caster_base<type> {
 
     static bool try_direct_conversions(handle) { return false; }
 
-
     holder_type holder;
-    constexpr static detail::HolderTypeId holder_type_id = detail::get_holder_type_id<holder_type>::value;
+    constexpr static detail::HolderTypeId holder_type_id
+        = detail::get_holder_type_id<holder_type>::value;
 };
 
 /// Specialize for the common std::shared_ptr, so users don't need to
 template <typename T>
-class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::shared_ptr<T>> { };
+class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::shared_ptr<T>> {};
 
 /// Type caster for holder types like std::unique_ptr.
 /// Please consider the SFINAE hook an implementation detail, as explained
 /// in the comment for the copyable_holder_caster.
 template <typename type, typename holder_type, typename SFINAE = void>
 struct move_only_holder_caster : type_caster_base<type> {
-        using base = type_caster_base<type>;
+    using base = type_caster_base<type>;
     static_assert(std::is_base_of<base, type_caster<type>>::value,
-            "Holder classes are only supported for custom types");
+                  "Holder classes are only supported for custom types");
     using base::base;
     using base::cast;
     using base::typeinfo;
@@ -795,20 +860,19 @@ struct move_only_holder_caster : type_caster_base<type> {
     // destructor; otherwise, the compiler will incorrectly use the copy
     // constructor.
     move_only_holder_caster() = default;
-    move_only_holder_caster(move_only_holder_caster&&) = default;
-    move_only_holder_caster(const move_only_holder_caster&) = delete;
+    move_only_holder_caster(move_only_holder_caster &&) = default;
+    move_only_holder_caster(const move_only_holder_caster &) = delete;
     ~move_only_holder_caster() {
         if (holder) {
             // If the argument was loaded into C++, but not transferred out,
             // then this was most likely part of a failed overload in
             // `argument_loader`. Transfer ownership back to Python.
-            move_only_holder_caster::cast(
-                std::move(holder), return_value_policy{}, handle{});
+            move_only_holder_caster::cast(std::move(holder), return_value_policy{}, handle{});
         }
     }
 
     static_assert(std::is_base_of<type_caster_base<type>, type_caster<type>>::value,
-            "Holder classes are only supported for custom types");
+                  "Holder classes are only supported for custom types");
 
     static handle cast(holder_type &&src, return_value_policy, handle) {
         // Move `src` so that `holder_helper<>::get()` can call `release` if need be.
@@ -818,17 +882,17 @@ struct move_only_holder_caster : type_caster_base<type> {
         return type_caster_base<type>::cast_holder(ptr, holder_erased(std::addressof(src)));
     }
 
-  // Disable these?
-//  explicit operator type*() { return this->value; }
-//  explicit operator type&() { return *(this->value); }
+    // Disable these?
+    //  explicit operator type*() { return this->value; }
+    //  explicit operator type&() { return *(this->value); }
 
-//  explicit operator holder_type*() { return &holder; }
+    //  explicit operator holder_type*() { return &holder; }
 
-  // Force rvalue.
-  template <typename T>
-  using cast_op_type = holder_type&&;
+    // Force rvalue.
+    template <typename T>
+    using cast_op_type = holder_type &&;
 
-  explicit operator holder_type&&() { return std::move(holder); }
+    explicit operator holder_type &&() { return std::move(holder); }
 
     bool load(handle src, bool convert) {
         return base::template load_impl<move_only_holder_caster>(src, convert);
@@ -854,35 +918,36 @@ struct move_only_holder_caster : type_caster_base<type> {
         //   `wrapper<Child>`.
         //   Anything deriving from `Child` does not derive from `PyBase`, so we should
         //   NOT try to release using `PyBase`s mechanism.
-        //   Additionally, if `Child` does not have a wrapper (for whatever reason) and is extended,
-        //   then we still can NOT use `PyBase` since it's not part of the hierachy.
-        handle src = (PyObject*)v_h.inst;
+        //   Additionally, if `Child` does not have a wrapper (for whatever reason) and is
+        //   extended, then we still can NOT use `PyBase` since it's not part of the hierachy.
+        handle src = (PyObject *) v_h.inst;
         object obj = reinterpret_borrow<object>(src);
         // Try to get the lowest-hierarchy level of the type.
         // This requires that we are single-inheritance at most.
-        const detail::type_info* lowest_type = nullptr;
+        const detail::type_info *lowest_type = nullptr;
         switch (load_type) {
             case LoadType::PureCpp: {
                 // We already have the lowest type.
                 lowest_type = typeinfo;
                 break;
             }
-            // If the base type is explicitly mentioned, then we can rely on `DerivedCppSinglePySingle` being used.
+            // If the base type is explicitly mentioned, then we can rely on
+            // `DerivedCppSinglePySingle` being used.
             case LoadType::DerivedCppSinglePySingle:
-                // However, if it is not, it may be that we have a C++ type inheriting from another C++ type without the inheritance being registered.
-                // In this case, we delegate by effectively downcasting in Python by finding the lowest-level type.
+                // However, if it is not, it may be that we have a C++ type inheriting from another
+                // C++ type without the inheritance being registered. In this case, we delegate by
+                // effectively downcasting in Python by finding the lowest-level type.
                 // @note No `break` here on purpose!
             case LoadType::ConversionNeeded: {
-                    // Try to get the lowest-hierarchy (closets to child class) of the type.
+                // Try to get the lowest-hierarchy (closets to child class) of the type.
                 // The usage of `get_type_info` implicitly requires single inheritance.
-                auto* py_type = (PyTypeObject*)obj.get_type().ptr();
+                auto *py_type = (PyTypeObject *) obj.get_type().ptr();
                 lowest_type = detail::get_type_info(py_type);
                 break;
             }
             case LoadType::DerivedCppMulti: {
-                throw std::runtime_error(
-                    "pybind11 does not support avoiding slicing with "
-                    "multiple inheritance");
+                throw std::runtime_error("pybind11 does not support avoiding slicing with "
+                                         "multiple inheritance");
             }
             default: {
                 throw std::runtime_error("Unsupported load type");
@@ -890,7 +955,7 @@ struct move_only_holder_caster : type_caster_base<type> {
         }
         if (!lowest_type)
             throw std::runtime_error("No valid lowest type. Internal error?");
-        auto& release_info = lowest_type->release_info;
+        auto &release_info = lowest_type->release_info;
         if (!release_info.release_to_cpp)
             throw std::runtime_error("No release mechanism in lowest type?");
         release_info.release_to_cpp(v_h.inst, &holder, std::move(obj));
@@ -902,47 +967,87 @@ struct move_only_holder_caster : type_caster_base<type> {
 
 template <typename type, typename deleter>
 class type_caster<std::unique_ptr<type, deleter>>
-    : public move_only_holder_caster<type, std::unique_ptr<type, deleter>> { };
+    : public move_only_holder_caster<type, std::unique_ptr<type, deleter>> {};
 
 template <typename type, typename holder_type>
 using type_caster_holder = conditional_t<is_copy_constructible<holder_type>::value,
                                          copyable_holder_caster<type, holder_type>,
                                          move_only_holder_caster<type, holder_type>>;
 
-template <typename T, bool Value = false> struct always_construct_holder { static constexpr bool value = Value; };
+template <typename T, bool Value = false>
+struct always_construct_holder {
+    static constexpr bool value = Value;
+};
 
 /// Create a specialization for custom holder types (silently ignores std::shared_ptr)
-#define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type, ...) \
-    namespace pybind11 { namespace detail { \
-    template <typename type> \
-    struct always_construct_holder<holder_type> : always_construct_holder<void, ##__VA_ARGS__>  { }; \
-    template <typename type> \
-    class type_caster<holder_type, enable_if_t<!is_shared_ptr<holder_type>::value>> \
-        : public type_caster_holder<type, holder_type> { }; \
-    }}
+#define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type, ...)                                      \
+    namespace pybind11 {                                                                          \
+    namespace detail {                                                                            \
+    template <typename type>                                                                      \
+    struct always_construct_holder<holder_type> : always_construct_holder<void, ##__VA_ARGS__> {  \
+    };                                                                                            \
+    template <typename type>                                                                      \
+    class type_caster<holder_type, enable_if_t<!is_shared_ptr<holder_type>::value>>               \
+        : public type_caster_holder<type, holder_type> {};                                        \
+    }                                                                                             \
+    }
 
 // PYBIND11_DECLARE_HOLDER_TYPE holder types:
-template <typename base, typename holder> struct is_holder_type :
-    std::is_base_of<detail::type_caster_holder<base, holder>, detail::type_caster<holder>> {};
+template <typename base, typename holder>
+struct is_holder_type
+    : std::is_base_of<detail::type_caster_holder<base, holder>, detail::type_caster<holder>> {};
 // Specialization for always-supported unique_ptr holders:
-template <typename base, typename deleter> struct is_holder_type<base, std::unique_ptr<base, deleter>> :
-    std::true_type {};
-
-template <typename T> struct handle_type_name { static constexpr auto name = const_name<T>(); };
-template <> struct handle_type_name<bool_> { static constexpr auto name = const_name("bool"); };
-template <> struct handle_type_name<bytes> { static constexpr auto name = const_name(PYBIND11_BYTES_NAME); };
-template <> struct handle_type_name<int_> { static constexpr auto name = const_name("int"); };
-template <> struct handle_type_name<iterable> { static constexpr auto name = const_name("Iterable"); };
-template <> struct handle_type_name<iterator> { static constexpr auto name = const_name("Iterator"); };
-template <> struct handle_type_name<float_> { static constexpr auto name = const_name("float"); };
-template <> struct handle_type_name<none> { static constexpr auto name = const_name("None"); };
-template <> struct handle_type_name<args> { static constexpr auto name = const_name("*args"); };
-template <> struct handle_type_name<kwargs> { static constexpr auto name = const_name("**kwargs"); };
+template <typename base, typename deleter>
+struct is_holder_type<base, std::unique_ptr<base, deleter>> : std::true_type {};
+
+template <typename T>
+struct handle_type_name {
+    static constexpr auto name = const_name<T>();
+};
+template <>
+struct handle_type_name<bool_> {
+    static constexpr auto name = const_name("bool");
+};
+template <>
+struct handle_type_name<bytes> {
+    static constexpr auto name = const_name(PYBIND11_BYTES_NAME);
+};
+template <>
+struct handle_type_name<int_> {
+    static constexpr auto name = const_name("int");
+};
+template <>
+struct handle_type_name<iterable> {
+    static constexpr auto name = const_name("Iterable");
+};
+template <>
+struct handle_type_name<iterator> {
+    static constexpr auto name = const_name("Iterator");
+};
+template <>
+struct handle_type_name<float_> {
+    static constexpr auto name = const_name("float");
+};
+template <>
+struct handle_type_name<none> {
+    static constexpr auto name = const_name("None");
+};
+template <>
+struct handle_type_name<args> {
+    static constexpr auto name = const_name("*args");
+};
+template <>
+struct handle_type_name<kwargs> {
+    static constexpr auto name = const_name("**kwargs");
+};
 
 template <typename type>
 struct pyobject_caster {
     template <typename T = type, enable_if_t<std::is_same<T, handle>::value, int> = 0>
-    bool load(handle src, bool /* convert */) { value = src; return static_cast<bool>(value); }
+    bool load(handle src, bool /* convert */) {
+        value = src;
+        return static_cast<bool>(value);
+    }
 
     template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) {
@@ -952,7 +1057,8 @@ struct pyobject_caster {
         // un-cluttered later after Python 2 support is dropped.
         if (PYBIND11_SILENCE_MSVC_C4127(std::is_same<T, str>::value) && isinstance<bytes>(src)) {
             PyObject *str_from_bytes = PyUnicode_FromEncodedObject(src.ptr(), "utf-8", nullptr);
-            if (!str_from_bytes) throw error_already_set();
+            if (!str_from_bytes)
+                throw error_already_set();
             value = reinterpret_steal<type>(str_from_bytes);
             return true;
         }
@@ -971,7 +1077,7 @@ struct pyobject_caster {
 };
 
 template <typename T>
-class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caster<T> { };
+class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caster<T> {};
 
 // Our conditions for enabling moving are quite restrictive:
 // At compile time:
@@ -982,69 +1088,81 @@ class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caste
 // - if the type is non-copy-constructible, the object must be the sole owner of the type (i.e. it
 //   must have ref_count() == 1)h
 // If any of the above are not satisfied, we fall back to copying.
-template <typename T> using move_is_plain_type = satisfies_none_of<T,
-    std::is_void, std::is_pointer, std::is_reference, std::is_const
->;
-template <typename T, typename SFINAE = void> struct move_common : std::false_type {};
-template <typename T> struct move_common<T, enable_if_t<all_of<
-    move_is_plain_type<T>,
-    std::is_move_constructible<T>,
-    std::is_same<
-        intrinsic_t<typename make_caster<T>::template cast_op_type<T&>>,
-        T>
->::value>> : std::true_type {};
-template <typename T, typename SFINAE = void> struct move_always : std::false_type {};
-template <typename T> struct move_always<T, enable_if_t<all_of<
-    move_common<T>,
-    negation<is_copy_constructible<T>>
->::value>> : std::true_type {};
-template <typename T, typename SFINAE = void> struct move_if_unreferenced : std::false_type {};
-template <typename T> struct move_if_unreferenced<T, enable_if_t<all_of<
-    move_common<T>,
-    is_copy_constructible<T>
->::value>> : std::true_type {};
-template <typename T> using move_never = negation<move_common<T>>;
+template <typename T>
+using move_is_plain_type
+    = satisfies_none_of<T, std::is_void, std::is_pointer, std::is_reference, std::is_const>;
+template <typename T, typename SFINAE = void>
+struct move_common : std::false_type {};
+template <typename T>
+struct move_common<
+    T,
+    enable_if_t<all_of<
+        move_is_plain_type<T>,
+        std::is_move_constructible<T>,
+        std::is_same<intrinsic_t<typename make_caster<T>::template cast_op_type<T &>>, T>>::value>>
+    : std::true_type {};
+template <typename T, typename SFINAE = void>
+struct move_always : std::false_type {};
+template <typename T>
+struct move_always<T,
+                   enable_if_t<all_of<move_common<T>, negation<is_copy_constructible<T>>>::value>>
+    : std::true_type {};
+template <typename T, typename SFINAE = void>
+struct move_if_unreferenced : std::false_type {};
+template <typename T>
+struct move_if_unreferenced<T,
+                            enable_if_t<all_of<move_common<T>, is_copy_constructible<T>>::value>>
+    : std::true_type {};
+template <typename T>
+using move_never = negation<move_common<T>>;
 
 // Detect whether returning a `type` from a cast on type's type_caster is going to result in a
 // reference or pointer to a local variable of the type_caster.  Basically, only
 // non-reference/pointer `type`s and reference/pointers from a type_caster_generic are safe;
 // everything else returns a reference/pointer to a local variable.
-template <typename type> using cast_is_temporary_value_reference = bool_constant<
-    (std::is_reference<type>::value || std::is_pointer<type>::value) &&
-    !std::is_base_of<type_caster_generic, make_caster<type>>::value &&
-    !std::is_same<intrinsic_t<type>, void>::value
->;
+template <typename type>
+using cast_is_temporary_value_reference
+    = bool_constant<(std::is_reference<type>::value || std::is_pointer<type>::value)
+                    && !std::is_base_of<type_caster_generic, make_caster<type>>::value
+                    && !std::is_same<intrinsic_t<type>, void>::value>;
 
 // When a value returned from a C++ function is being cast back to Python, we almost always want to
 // force `policy = move`, regardless of the return value policy the function/method was declared
 // with.
-template <typename Return, typename SFINAE = void> struct return_value_policy_override {
+template <typename Return, typename SFINAE = void>
+struct return_value_policy_override {
     static return_value_policy policy(return_value_policy p) { return p; }
 };
 
-template <typename Return> struct return_value_policy_override<Return,
-        detail::enable_if_t<std::is_base_of<type_caster_generic, make_caster<Return>>::value, void>> {
+template <typename Return>
+struct return_value_policy_override<
+    Return,
+    detail::enable_if_t<std::is_base_of<type_caster_generic, make_caster<Return>>::value, void>> {
     static return_value_policy policy(return_value_policy p) {
-        return !std::is_lvalue_reference<Return>::value &&
-               !std::is_pointer<Return>::value
-                   ? return_value_policy::move : p;
+        return !std::is_lvalue_reference<Return>::value && !std::is_pointer<Return>::value
+                   ? return_value_policy::move
+                   : p;
     }
 };
 
 // Basic python -> C++ casting; throws if casting fails
-template <typename T, typename SFINAE> type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
+template <typename T, typename SFINAE>
+type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
     if (!conv.load(handle, true)) {
 #if defined(NDEBUG)
-        throw cast_error("Unable to cast Python instance to C++ type (compile in debug mode for details)");
+        throw cast_error(
+            "Unable to cast Python instance to C++ type (compile in debug mode for details)");
 #else
-        throw cast_error("Unable to cast Python instance of type " +
-            (std::string) str(type::handle_of(handle)) + " to C++ type '" + type_id<T>() + "'");
+        throw cast_error("Unable to cast Python instance of type "
+                         + (std::string) str(type::handle_of(handle)) + " to C++ type '"
+                         + type_id<T>() + "'");
 #endif
     }
     return conv;
 }
 // Wrapper around the above that also constructs and returns a type_caster
-template <typename T> make_caster<T> load_type(const handle &handle) {
+template <typename T>
+make_caster<T> load_type(const handle &handle) {
     make_caster<T> conv;
     load_type(conv, handle);
     return conv;
@@ -1057,54 +1175,68 @@ template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> =
 T cast(const handle &handle) {
     using namespace detail;
     static_assert(!cast_is_temporary_value_reference<T>::value,
-            "Unable to cast type to reference: value is local to type caster");
+                  "Unable to cast type to reference: value is local to type caster");
     return cast_op<T>(load_type<T>(handle));
 }
 
 // pytype -> pytype (calls converting constructor)
 template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
-T cast(const handle &handle) { return T(reinterpret_borrow<object>(handle)); }
+T cast(const handle &handle) {
+    return T(reinterpret_borrow<object>(handle));
+}
 
 // C++ type -> py::object
 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
-object cast(T &&value, return_value_policy policy = return_value_policy::automatic_reference,
+object cast(T &&value,
+            return_value_policy policy = return_value_policy::automatic_reference,
             handle parent = handle()) {
     using no_ref_T = typename std::remove_reference<T>::type;
     if (policy == return_value_policy::automatic) {
-        policy = std::is_pointer<no_ref_T>::value ? return_value_policy::take_ownership :
-                 std::is_lvalue_reference<T>::value ? return_value_policy::copy : return_value_policy::move;
+        policy = std::is_pointer<no_ref_T>::value     ? return_value_policy::take_ownership
+                 : std::is_lvalue_reference<T>::value ? return_value_policy::copy
+                                                      : return_value_policy::move;
     } else if (policy == return_value_policy::automatic_reference) {
         policy = std::is_pointer<no_ref_T>::value     ? return_value_policy::reference
                  : std::is_lvalue_reference<T>::value ? return_value_policy::copy
                                                       : return_value_policy::move;
     }
-    return reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
+    return reinterpret_steal<object>(
+        detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
 }
 
-template <typename T> T handle::cast() const { return pybind11::cast<T>(*this); }
-template <> inline void handle::cast() const { return; }
+template <typename T>
+T handle::cast() const {
+    return pybind11::cast<T>(*this);
+}
+template <>
+inline void handle::cast() const {
+    return;
+}
 
 template <typename T>
 detail::enable_if_t<
-        // TODO(eric.cousineau): Figure out how to prevent perfect-forwarding more elegantly.
-        std::is_rvalue_reference<T&&>::value && !detail::is_pyobject<detail::intrinsic_t<T>>::value, object>
-    move(T&& value) {
+    // TODO(eric.cousineau): Figure out how to prevent perfect-forwarding more elegantly.
+    std::is_rvalue_reference<T &&>::value && !detail::is_pyobject<detail::intrinsic_t<T>>::value,
+    object>
+move(T &&value) {
     // TODO(eric.cousineau): Add policies, parent, etc.
     // It'd be nice to supply a parent, but for now, just leave it as-is.
     handle no_parent;
-    return reinterpret_steal<object>(
-        detail::make_caster<T>::cast(std::move(value), return_value_policy::take_ownership, no_parent));
+    return reinterpret_steal<object>(detail::make_caster<T>::cast(
+        std::move(value), return_value_policy::take_ownership, no_parent));
 }
 
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1) {
 #if defined(NDEBUG)
-        throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
+        throw cast_error(
+            "Unable to cast Python instance to C++ rvalue: instance has multiple references"
             " (compile in debug mode for details)");
 #else
-        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj)) +
-                " instance to C++ " + type_id<T>() + " instance: instance has multiple references");
+        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj))
+                         + " instance to C++ " + type_id<T>()
+                         + " instance: instance has multiple references");
 #endif
     }
 
@@ -1118,52 +1250,81 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
 //   object has multiple references, but trying to copy will fail to compile.
 // - If both movable and copyable, check ref count: if 1, move; otherwise copy
 // - Otherwise (not movable), copy.
-template <typename T> detail::enable_if_t<detail::move_always<T>::value, T> cast(object &&object) {
+template <typename T>
+detail::enable_if_t<detail::move_always<T>::value, T> cast(object &&object) {
     return move<T>(std::move(object));
 }
-template <typename T> detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
+template <typename T>
+detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
     if (object.ref_count() > 1) {
         return cast<T>(object);
     }
     return move<T>(std::move(object));
 }
-template <typename T> detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
+template <typename T>
+detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
     return cast<T>(object);
 }
 
-template <typename T> T object::cast() const & { return pybind11::cast<T>(*this); }
-template <typename T> T object::cast() && { return pybind11::cast<T>(std::move(*this)); }
-template <> inline void object::cast() const & { return; }
-template <> inline void object::cast() && { return; }
+template <typename T>
+T object::cast() const & {
+    return pybind11::cast<T>(*this);
+}
+template <typename T>
+T object::cast() && {
+    return pybind11::cast<T>(std::move(*this));
+}
+template <>
+inline void object::cast() const & {
+    return;
+}
+template <>
+inline void object::cast() && {
+    return;
+}
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Declared in pytypes.h:
 template <typename T, enable_if_t<!is_pyobject<T>::value, int>>
-object object_or_cast(T &&o) { return pybind11::cast(std::forward<T>(o)); }
+object object_or_cast(T &&o) {
+    return pybind11::cast(std::forward<T>(o));
+}
 
 // Placeholder type for the unneeded (and dead code) static variable in the
 // PYBIND11_OVERRIDE_OVERRIDE macro
 struct override_unused {};
-template <typename ret_type> using override_caster_t = conditional_t<
-    cast_is_temporary_value_reference<ret_type>::value, make_caster<ret_type>, override_unused>;
+template <typename ret_type>
+using override_caster_t = conditional_t<cast_is_temporary_value_reference<ret_type>::value,
+                                        make_caster<ret_type>,
+                                        override_unused>;
 
 // Trampoline use: for reference/pointer types to value-converted values, we do a value cast, then
 // store the result in the given variable.  For other types, this is a no-op.
-template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&o, make_caster<T> &caster) {
+template <typename T>
+enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&o,
+                                                                     make_caster<T> &caster) {
     return cast_op<T>(load_type(caster, o));
 }
-template <typename T> enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&, override_unused &) {
-    pybind11_fail("Internal error: cast_ref fallback invoked"); }
-
-// Trampoline use: Having a pybind11::cast with an invalid reference type is going to static_assert, even
-// though if it's in dead code, so we provide a "trampoline" to pybind11::cast that only does anything in
-// cases where pybind11::cast is valid.
-template <typename T> enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&o) {
-    return pybind11::cast<T>(std::move(o)); }
-template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&) {
-    pybind11_fail("Internal error: cast_safe fallback invoked"); }
-template <> inline void cast_safe<void>(object &&) {}
+template <typename T>
+enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&,
+                                                                      override_unused &) {
+    pybind11_fail("Internal error: cast_ref fallback invoked");
+}
+
+// Trampoline use: Having a pybind11::cast with an invalid reference type is going to
+// static_assert, even though if it's in dead code, so we provide a "trampoline" to pybind11::cast
+// that only does anything in cases where pybind11::cast is valid.
+template <typename T>
+enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&o) {
+    return pybind11::cast<T>(std::move(o));
+}
+template <typename T>
+enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&) {
+    pybind11_fail("Internal error: cast_safe fallback invoked");
+}
+template <>
+inline void cast_safe<void>(object &&) {}
 
 PYBIND11_NAMESPACE_END(detail)
 
@@ -1183,21 +1344,21 @@ inline cast_error cast_error_unable_to_convert_call_arg(const std::string &name,
 #endif
 
 template <return_value_policy policy = return_value_policy::automatic_reference>
-tuple make_tuple() { return tuple(0); }
+tuple make_tuple() {
+    return tuple(0);
+}
 
-template <return_value_policy policy = return_value_policy::automatic_reference,
-          typename... Args> tuple make_tuple(Args&&... args_) {
+template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+tuple make_tuple(Args &&...args_) {
     constexpr size_t size = sizeof...(Args);
-    std::array<object, size> args {
-        { reinterpret_steal<object>(detail::make_caster<Args>::cast(
-            std::forward<Args>(args_), policy, nullptr))... }
-    };
+    std::array<object, size> args{{reinterpret_steal<object>(
+        detail::make_caster<Args>::cast(std::forward<Args>(args_), policy, nullptr))...}};
     for (size_t i = 0; i < args.size(); i++) {
         if (!args[i]) {
 #if defined(NDEBUG)
             throw cast_error_unable_to_convert_call_arg();
 #else
-            std::array<std::string, size> argtypes { {type_id<Args>()...} };
+            std::array<std::string, size> argtypes{{type_id<Args>()...}};
             throw cast_error_unable_to_convert_call_arg(std::to_string(i), argtypes[i]);
 #endif
         }
@@ -1213,18 +1374,28 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
 /// \ingroup annotations
 /// Annotation for arguments
 struct arg {
-    /// Constructs an argument with the name of the argument; if null or omitted, this is a positional argument.
-    constexpr explicit arg(const char *name = nullptr) : name(name), flag_noconvert(false), flag_none(true) { }
+    /// Constructs an argument with the name of the argument; if null or omitted, this is a
+    /// positional argument.
+    constexpr explicit arg(const char *name = nullptr)
+        : name(name), flag_noconvert(false), flag_none(true) {}
     /// Assign a value to this argument
-    template <typename T> arg_v operator=(T &&value) const;
+    template <typename T>
+    arg_v operator=(T &&value) const;
     /// Indicate that the type should not be converted in the type caster
-    arg &noconvert(bool flag = true) { flag_noconvert = flag; return *this; }
+    arg &noconvert(bool flag = true) {
+        flag_noconvert = flag;
+        return *this;
+    }
     /// Indicates that the argument should/shouldn't allow None (e.g. for nullable pointer args)
-    arg &none(bool flag = true) { flag_none = flag; return *this; }
+    arg &none(bool flag = true) {
+        flag_none = flag;
+        return *this;
+    }
 
-    const char *name; ///< If non-null, this is a named kwargs argument
-    bool flag_noconvert : 1; ///< If set, do not allow conversion (requires a supporting type caster!)
-    bool flag_none : 1; ///< If set (the default), allow None to be passed to this argument
+    const char *name;        ///< If non-null, this is a named kwargs argument
+    bool flag_noconvert : 1; ///< If set, do not allow conversion (requires a supporting type
+                             ///< caster!)
+    bool flag_none : 1;      ///< If set (the default), allow None to be passed to this argument
 };
 
 /// \ingroup annotations
@@ -1233,13 +1404,12 @@ struct arg_v : arg {
 private:
     template <typename T>
     arg_v(arg &&base, T &&x, const char *descr = nullptr)
-        : arg(base),
-          value(reinterpret_steal<object>(
-              detail::make_caster<T>::cast(x, return_value_policy::automatic, {})
-          )),
+        : arg(base), value(reinterpret_steal<object>(
+                         detail::make_caster<T>::cast(x, return_value_policy::automatic, {}))),
           descr(descr)
 #if !defined(NDEBUG)
-        , type(type_id<T>())
+          ,
+          type(type_id<T>())
 #endif
     {
         // Workaround! See:
@@ -1254,18 +1424,24 @@ struct arg_v : arg {
     /// Direct construction with name, default, and description
     template <typename T>
     arg_v(const char *name, T &&x, const char *descr = nullptr)
-        : arg_v(arg(name), std::forward<T>(x), descr) { }
+        : arg_v(arg(name), std::forward<T>(x), descr) {}
 
     /// Called internally when invoking `py::arg("a") = value`
     template <typename T>
     arg_v(const arg &base, T &&x, const char *descr = nullptr)
-        : arg_v(arg(base), std::forward<T>(x), descr) { }
+        : arg_v(arg(base), std::forward<T>(x), descr) {}
 
     /// Same as `arg::noconvert()`, but returns *this as arg_v&, not arg&
-    arg_v &noconvert(bool flag = true) { arg::noconvert(flag); return *this; }
+    arg_v &noconvert(bool flag = true) {
+        arg::noconvert(flag);
+        return *this;
+    }
 
     /// Same as `arg::nonone()`, but returns *this as arg_v&, not arg&
-    arg_v &none(bool flag = true) { arg::none(flag); return *this; }
+    arg_v &none(bool flag = true) {
+        arg::none(flag);
+        return *this;
+    }
 
     /// The default value
     object value;
@@ -1278,13 +1454,13 @@ struct arg_v : arg {
 };
 
 /// \ingroup annotations
-/// Annotation indicating that all following arguments are keyword-only; the is the equivalent of an
-/// unnamed '*' argument (in Python 3)
+/// Annotation indicating that all following arguments are keyword-only; the is the equivalent of
+/// an unnamed '*' argument (in Python 3)
 struct kw_only {};
 
 /// \ingroup annotations
-/// Annotation indicating that all previous arguments are positional-only; the is the equivalent of an
-/// unnamed '/' argument (in Python 3.8)
+/// Annotation indicating that all previous arguments are positional-only; the is the equivalent of
+/// an unnamed '/' argument (in Python 3.8)
 struct pos_only {};
 
 template <typename T>
@@ -1293,7 +1469,8 @@ arg_v arg::operator=(T &&value) const {
 }
 
 /// Alias for backward compatibility -- to be removed in version 2.0
-template <typename /*unused*/> using arg_t = arg_v;
+template <typename /*unused*/>
+using arg_t = arg_v;
 
 inline namespace literals {
 /** \rst
@@ -1304,8 +1481,10 @@ constexpr arg operator"" _a(const char *name, size_t) { return arg(name); }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T> using is_kw_only = std::is_same<intrinsic_t<T>, kw_only>;
-template <typename T> using is_pos_only = std::is_same<intrinsic_t<T>, pos_only>;
+template <typename T>
+using is_kw_only = std::is_same<intrinsic_t<T>, kw_only>;
+template <typename T>
+using is_pos_only = std::is_same<intrinsic_t<T>, pos_only>;
 
 // forward declaration (definition in attr.h)
 struct function_record;
@@ -1334,18 +1513,20 @@ struct function_call {
     handle init_self;
 };
 
-
 /// Helper class which loads arguments for C++ functions called from Python
 template <typename... Args>
 class argument_loader {
     using indices = make_index_sequence<sizeof...(Args)>;
 
-    template <typename Arg> using argument_is_args   = std::is_same<intrinsic_t<Arg>, args>;
-    template <typename Arg> using argument_is_kwargs = std::is_same<intrinsic_t<Arg>, kwargs>;
+    template <typename Arg>
+    using argument_is_args = std::is_same<intrinsic_t<Arg>, args>;
+    template <typename Arg>
+    using argument_is_kwargs = std::is_same<intrinsic_t<Arg>, kwargs>;
     // Get kwargs argument position, or -1 if not present:
     static constexpr auto kwargs_pos = constexpr_last<argument_is_kwargs, Args...>();
 
-    static_assert(kwargs_pos == -1 || kwargs_pos == (int) sizeof...(Args) - 1, "py::kwargs is only permitted as the last argument of a function");
+    static_assert(kwargs_pos == -1 || kwargs_pos == (int) sizeof...(Args) - 1,
+                  "py::kwargs is only permitted as the last argument of a function");
 
 public:
     static constexpr bool has_kwargs = kwargs_pos != -1;
@@ -1353,28 +1534,28 @@ class argument_loader {
     // py::args argument position; -1 if not present.
     static constexpr int args_pos = constexpr_last<argument_is_args, Args...>();
 
-    static_assert(args_pos == -1 || args_pos == constexpr_first<argument_is_args, Args...>(), "py::args cannot be specified more than once");
+    static_assert(args_pos == -1 || args_pos == constexpr_first<argument_is_args, Args...>(),
+                  "py::args cannot be specified more than once");
 
     static constexpr auto arg_names = concat(type_descr(make_caster<Args>::name)...);
 
-    bool load_args(function_call &call) {
-        return load_impl_sequence(call, indices{});
-    }
+    bool load_args(function_call &call) { return load_impl_sequence(call, indices{}); }
 
     template <typename Return, typename Guard, typename Func>
     // NOLINTNEXTLINE(readability-const-return-type)
     enable_if_t<!std::is_void<Return>::value, Return> call(Func &&f) && {
-        return std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
+        return std::move(*this).template call_impl<remove_cv_t<Return>>(
+            std::forward<Func>(f), indices{}, Guard{});
     }
 
     template <typename Return, typename Guard, typename Func>
     enable_if_t<std::is_void<Return>::value, void_type> call(Func &&f) && {
-        std::move(*this).template call_impl<remove_cv_t<Return>>(std::forward<Func>(f), indices{}, Guard{});
+        std::move(*this).template call_impl<remove_cv_t<Return>>(
+            std::forward<Func>(f), indices{}, Guard{});
         return void_type();
     }
 
 private:
-
     static bool load_impl_sequence(function_call &, index_sequence<>) { return true; }
 
     template <size_t... Is>
@@ -1408,7 +1589,7 @@ class simple_collector {
 public:
     template <typename... Ts>
     explicit simple_collector(Ts &&...values)
-        : m_args(pybind11::make_tuple<policy>(std::forward<Ts>(values)...)) { }
+        : m_args(pybind11::make_tuple<policy>(std::forward<Ts>(values)...)) {}
 
     const tuple &args() const & { return m_args; }
     dict kwargs() const { return {}; }
@@ -1461,13 +1642,14 @@ class unpacking_collector {
 private:
     template <typename T>
     void process(list &args_list, T &&x) {
-        auto o = reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
+        auto o = reinterpret_steal<object>(
+            detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
         if (!o) {
 #if defined(NDEBUG)
             throw cast_error_unable_to_convert_call_arg();
 #else
-            throw cast_error_unable_to_convert_call_arg(
-                std::to_string(args_list.size()), type_id<T>());
+            throw cast_error_unable_to_convert_call_arg(std::to_string(args_list.size()),
+                                                        type_id<T>());
 #endif
         }
         args_list.append(o);
@@ -1479,7 +1661,7 @@ class unpacking_collector {
         }
     }
 
-    void process(list &/*args_list*/, arg_v a) {
+    void process(list & /*args_list*/, arg_v a) {
         if (!a.name) {
 #if defined(NDEBUG)
             nameless_argument_error();
@@ -1504,7 +1686,7 @@ class unpacking_collector {
         m_kwargs[a.name] = a.value;
     }
 
-    void process(list &/*args_list*/, detail::kwargs_proxy kp) {
+    void process(list & /*args_list*/, detail::kwargs_proxy kp) {
         if (!kp) {
             return;
         }
@@ -1526,8 +1708,9 @@ class unpacking_collector {
                          "(compile in debug mode for details)");
     }
     [[noreturn]] static void nameless_argument_error(const std::string &type) {
-        throw type_error("Got kwargs without a name of type '" + type + "'; only named "
-                         "arguments may be passed via py::arg() to a python function call. ");
+        throw type_error("Got kwargs without a name of type '" + type
+                         + "'; only named "
+                           "arguments may be passed via py::arg() to a python function call. ");
     }
     [[noreturn]] static void multiple_values_error() {
         throw type_error("Got multiple values for keyword argument "
@@ -1548,29 +1731,30 @@ class unpacking_collector {
 // fails to compile enable_if_t<!all_of<is_positional<Args>...>::value>
 // (tested with ICC 2021.1 Beta 20200827).
 template <typename... Args>
-constexpr bool args_are_all_positional()
-{
-  return all_of<is_positional<Args>...>::value;
+constexpr bool args_are_all_positional() {
+    return all_of<is_positional<Args>...>::value;
 }
 
 /// Collect only positional arguments for a Python function call
-template <return_value_policy policy, typename... Args,
+template <return_value_policy policy,
+          typename... Args,
           typename = enable_if_t<args_are_all_positional<Args...>()>>
 simple_collector<policy> collect_arguments(Args &&...args) {
     return simple_collector<policy>(std::forward<Args>(args)...);
 }
 
 /// Collect all arguments, including keywords and unpacking (only instantiated when needed)
-template <return_value_policy policy, typename... Args,
+template <return_value_policy policy,
+          typename... Args,
           typename = enable_if_t<!args_are_all_positional<Args...>()>>
 unpacking_collector<policy> collect_arguments(Args &&...args) {
     // Following argument order rules for generalized unpacking according to PEP 448
-    static_assert(
-        constexpr_last<is_positional, Args...>() < constexpr_first<is_keyword_or_ds, Args...>()
-        && constexpr_last<is_s_unpacking, Args...>() < constexpr_first<is_ds_unpacking, Args...>(),
-        "Invalid function call: positional args must precede keywords and ** unpacking; "
-        "* unpacking must precede ** unpacking"
-    );
+    static_assert(constexpr_last<is_positional, Args...>()
+                          < constexpr_first<is_keyword_or_ds, Args...>()
+                      && constexpr_last<is_s_unpacking, Args...>()
+                             < constexpr_first<is_ds_unpacking, Args...>(),
+                  "Invalid function call: positional args must precede keywords and ** unpacking; "
+                  "* unpacking must precede ** unpacking");
     return unpacking_collector<policy>(std::forward<Args>(args)...);
 }
 
@@ -1593,22 +1777,21 @@ object object_api<Derived>::call(Args &&...args) const {
 
 PYBIND11_NAMESPACE_END(detail)
 
-
-template<typename T>
+template <typename T>
 handle type::handle_of() {
-   static_assert(
-      std::is_base_of<detail::type_caster_generic, detail::make_caster<T>>::value,
-      "py::type::of<T> only supports the case where T is a registered C++ types."
-    );
+    static_assert(std::is_base_of<detail::type_caster_generic, detail::make_caster<T>>::value,
+                  "py::type::of<T> only supports the case where T is a registered C++ types.");
 
     return detail::get_type_handle(typeid(T), true);
 }
 
-
-#define PYBIND11_MAKE_OPAQUE(...) \
-    namespace pybind11 { namespace detail { \
-        template<> class type_caster<__VA_ARGS__> : public type_caster_base<__VA_ARGS__> { }; \
-    }}
+#define PYBIND11_MAKE_OPAQUE(...)                                                                 \
+    namespace pybind11 {                                                                          \
+    namespace detail {                                                                            \
+    template <>                                                                                   \
+    class type_caster<__VA_ARGS__> : public type_caster_base<__VA_ARGS__> {};                     \
+    }                                                                                             \
+    }
 
 /// Lets you pass a type containing a `,` through a macro parameter without needing a separate
 /// typedef, e.g.:
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index cfa635a011..ad5e97b024 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -15,25 +15,25 @@
 #include <chrono>
 #include <cmath>
 #include <ctime>
-#include <mutex>
-
 #include <datetime.h>
+#include <mutex>
 
 // Backport the PyDateTime_DELTA functions from Python3.3 if required
 #ifndef PyDateTime_DELTA_GET_DAYS
-#define PyDateTime_DELTA_GET_DAYS(o)         (((PyDateTime_Delta*)o)->days)
+#    define PyDateTime_DELTA_GET_DAYS(o) (((PyDateTime_Delta *) o)->days)
 #endif
 #ifndef PyDateTime_DELTA_GET_SECONDS
-#define PyDateTime_DELTA_GET_SECONDS(o)      (((PyDateTime_Delta*)o)->seconds)
+#    define PyDateTime_DELTA_GET_SECONDS(o) (((PyDateTime_Delta *) o)->seconds)
 #endif
 #ifndef PyDateTime_DELTA_GET_MICROSECONDS
-#define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta*)o)->microseconds)
+#    define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta *) o)->microseconds)
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename type> class duration_caster {
+template <typename type>
+class duration_caster {
 public:
     using rep = typename type::rep;
     using period = typename type::period;
@@ -45,7 +45,9 @@ template <typename type> class duration_caster {
         using namespace std::chrono;
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
         if (!src) {
             return false;
@@ -53,26 +55,30 @@ template <typename type> class duration_caster {
         // If invoked with datetime.delta object
         if (PyDelta_Check(src.ptr())) {
             value = type(duration_cast<duration<rep, period>>(
-                  days(PyDateTime_DELTA_GET_DAYS(src.ptr()))
+                days(PyDateTime_DELTA_GET_DAYS(src.ptr()))
                 + seconds(PyDateTime_DELTA_GET_SECONDS(src.ptr()))
                 + microseconds(PyDateTime_DELTA_GET_MICROSECONDS(src.ptr()))));
             return true;
         }
         // If invoked with a float we assume it is seconds and convert
         if (PyFloat_Check(src.ptr())) {
-            value = type(duration_cast<duration<rep, period>>(duration<double>(PyFloat_AsDouble(src.ptr()))));
+            value = type(duration_cast<duration<rep, period>>(
+                duration<double>(PyFloat_AsDouble(src.ptr()))));
             return true;
         }
         return false;
     }
 
     // If this is a duration just return it back
-    static const std::chrono::duration<rep, period>& get_duration(const std::chrono::duration<rep, period> &src) {
+    static const std::chrono::duration<rep, period> &
+    get_duration(const std::chrono::duration<rep, period> &src) {
         return src;
     }
 
     // If this is a time_point get the time_since_epoch
-    template <typename Clock> static std::chrono::duration<rep, period> get_duration(const std::chrono::time_point<Clock, std::chrono::duration<rep, period>> &src) {
+    template <typename Clock>
+    static std::chrono::duration<rep, period>
+    get_duration(const std::chrono::time_point<Clock, std::chrono::duration<rep, period>> &src) {
         return src.time_since_epoch();
     }
 
@@ -84,9 +90,12 @@ template <typename type> class duration_caster {
         auto d = get_duration(src);
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
-        // Declare these special duration types so the conversions happen with the correct primitive types (int)
+        // Declare these special duration types so the conversions happen with the correct
+        // primitive types (int)
         using dd_t = duration<int, std::ratio<86400>>;
         using ss_t = duration<int, std::ratio<1>>;
         using us_t = duration<int, std::micro>;
@@ -118,14 +127,17 @@ inline std::tm *localtime_thread_safe(const std::time_t *time, std::tm *buf) {
 }
 
 // This is for casting times on the system clock into datetime.datetime instances
-template <typename Duration> class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
+template <typename Duration>
+class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
 public:
     using type = std::chrono::time_point<std::chrono::system_clock, Duration>;
     bool load(handle src, bool) {
         using namespace std::chrono;
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
         if (!src) {
             return false;
@@ -135,32 +147,32 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         microseconds msecs;
 
         if (PyDateTime_Check(src.ptr())) {
-            cal.tm_sec   = PyDateTime_DATE_GET_SECOND(src.ptr());
-            cal.tm_min   = PyDateTime_DATE_GET_MINUTE(src.ptr());
-            cal.tm_hour  = PyDateTime_DATE_GET_HOUR(src.ptr());
-            cal.tm_mday  = PyDateTime_GET_DAY(src.ptr());
-            cal.tm_mon   = PyDateTime_GET_MONTH(src.ptr()) - 1;
-            cal.tm_year  = PyDateTime_GET_YEAR(src.ptr()) - 1900;
+            cal.tm_sec = PyDateTime_DATE_GET_SECOND(src.ptr());
+            cal.tm_min = PyDateTime_DATE_GET_MINUTE(src.ptr());
+            cal.tm_hour = PyDateTime_DATE_GET_HOUR(src.ptr());
+            cal.tm_mday = PyDateTime_GET_DAY(src.ptr());
+            cal.tm_mon = PyDateTime_GET_MONTH(src.ptr()) - 1;
+            cal.tm_year = PyDateTime_GET_YEAR(src.ptr()) - 1900;
             cal.tm_isdst = -1;
-            msecs        = microseconds(PyDateTime_DATE_GET_MICROSECOND(src.ptr()));
+            msecs = microseconds(PyDateTime_DATE_GET_MICROSECOND(src.ptr()));
         } else if (PyDate_Check(src.ptr())) {
-            cal.tm_sec   = 0;
-            cal.tm_min   = 0;
-            cal.tm_hour  = 0;
-            cal.tm_mday  = PyDateTime_GET_DAY(src.ptr());
-            cal.tm_mon   = PyDateTime_GET_MONTH(src.ptr()) - 1;
-            cal.tm_year  = PyDateTime_GET_YEAR(src.ptr()) - 1900;
+            cal.tm_sec = 0;
+            cal.tm_min = 0;
+            cal.tm_hour = 0;
+            cal.tm_mday = PyDateTime_GET_DAY(src.ptr());
+            cal.tm_mon = PyDateTime_GET_MONTH(src.ptr()) - 1;
+            cal.tm_year = PyDateTime_GET_YEAR(src.ptr()) - 1900;
             cal.tm_isdst = -1;
-            msecs        = microseconds(0);
+            msecs = microseconds(0);
         } else if (PyTime_Check(src.ptr())) {
-            cal.tm_sec   = PyDateTime_TIME_GET_SECOND(src.ptr());
-            cal.tm_min   = PyDateTime_TIME_GET_MINUTE(src.ptr());
-            cal.tm_hour  = PyDateTime_TIME_GET_HOUR(src.ptr());
-            cal.tm_mday  = 1;   // This date (day, month, year) = (1, 0, 70)
-            cal.tm_mon   = 0;   // represents 1-Jan-1970, which is the first
-            cal.tm_year  = 70;  // earliest available date for Python's datetime
+            cal.tm_sec = PyDateTime_TIME_GET_SECOND(src.ptr());
+            cal.tm_min = PyDateTime_TIME_GET_MINUTE(src.ptr());
+            cal.tm_hour = PyDateTime_TIME_GET_HOUR(src.ptr());
+            cal.tm_mday = 1;  // This date (day, month, year) = (1, 0, 70)
+            cal.tm_mon = 0;   // represents 1-Jan-1970, which is the first
+            cal.tm_year = 70; // earliest available date for Python's datetime
             cal.tm_isdst = -1;
-            msecs        = microseconds(PyDateTime_TIME_GET_MICROSECOND(src.ptr()));
+            msecs = microseconds(PyDateTime_TIME_GET_MICROSECOND(src.ptr()));
         } else {
             return false;
         }
@@ -169,14 +181,18 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         return true;
     }
 
-    static handle cast(const std::chrono::time_point<std::chrono::system_clock, Duration> &src, return_value_policy /* policy */, handle /* parent */) {
+    static handle cast(const std::chrono::time_point<std::chrono::system_clock, Duration> &src,
+                       return_value_policy /* policy */,
+                       handle /* parent */) {
         using namespace std::chrono;
 
         // Lazy initialise the PyDateTime import
-        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+        if (!PyDateTimeAPI) {
+            PyDateTime_IMPORT;
+        }
 
-        // Get out microseconds, and make sure they are positive, to avoid bug in eastern hemisphere time zones
-        // (cfr. https://github.com/pybind/pybind11/issues/2417)
+        // Get out microseconds, and make sure they are positive, to avoid bug in eastern
+        // hemisphere time zones (cfr. https://github.com/pybind/pybind11/issues/2417)
         using us_t = duration<int, std::micro>;
         auto us = duration_cast<us_t>(src.time_since_epoch() % seconds(1));
         if (us.count() < 0) {
@@ -184,9 +200,10 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         }
 
         // Subtract microseconds BEFORE `system_clock::to_time_t`, because:
-        // > If std::time_t has lower precision, it is implementation-defined whether the value is rounded or truncated.
-        // (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
-        std::time_t tt = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
+        // > If std::time_t has lower precision, it is implementation-defined whether the value is
+        // rounded or truncated. (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
+        std::time_t tt
+            = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
 
         std::tm localtime;
         std::tm *localtime_ptr = localtime_thread_safe(&tt, &localtime);
@@ -207,13 +224,13 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
 // Other clocks that are not the system clock are not measured as datetime.datetime objects
 // since they are not measured on calendar time. So instead we just make them timedeltas
 // Or if they have passed us a time as a float we convert that
-template <typename Clock, typename Duration> class type_caster<std::chrono::time_point<Clock, Duration>>
-: public duration_caster<std::chrono::time_point<Clock, Duration>> {
-};
+template <typename Clock, typename Duration>
+class type_caster<std::chrono::time_point<Clock, Duration>>
+    : public duration_caster<std::chrono::time_point<Clock, Duration>> {};
 
-template <typename Rep, typename Period> class type_caster<std::chrono::duration<Rep, Period>>
-: public duration_caster<std::chrono::duration<Rep, Period>> {
-};
+template <typename Rep, typename Period>
+class type_caster<std::chrono::duration<Rep, Period>>
+    : public duration_caster<std::chrono::duration<Rep, Period>> {};
 
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/complex.h b/include/pybind11/complex.h
index 72c87359bc..8a831c12ce 100644
--- a/include/pybind11/complex.h
+++ b/include/pybind11/complex.h
@@ -10,36 +10,42 @@
 #pragma once
 
 #include "pybind11.h"
+
 #include <complex>
 
 /// glibc defines I as a macro which breaks things, e.g., boost template names
 #ifdef I
-#  undef I
+#    undef I
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
-template <typename T> struct format_descriptor<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
+template <typename T>
+struct format_descriptor<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr const char c = format_descriptor<T>::c;
-    static constexpr const char value[3] = { 'Z', c, '\0' };
+    static constexpr const char value[3] = {'Z', c, '\0'};
     static std::string format() { return std::string(value); }
 };
 
 #ifndef PYBIND11_CPP17
 
-template <typename T> constexpr const char format_descriptor<
-    std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>>::value[3];
+template <typename T>
+constexpr const char
+    format_descriptor<std::complex<T>,
+                      detail::enable_if_t<std::is_floating_point<T>::value>>::value[3];
 
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <typename T> struct is_fmt_numeric<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
+template <typename T>
+struct is_fmt_numeric<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr bool value = true;
     static constexpr int index = is_fmt_numeric<T>::index + 3;
 };
 
-template <typename T> class type_caster<std::complex<T>> {
+template <typename T>
+class type_caster<std::complex<T>> {
 public:
     bool load(handle src, bool convert) {
         if (!src) {
@@ -57,7 +63,8 @@ template <typename T> class type_caster<std::complex<T>> {
         return true;
     }
 
-    static handle cast(const std::complex<T> &src, return_value_policy /* policy */, handle /* parent */) {
+    static handle
+    cast(const std::complex<T> &src, return_value_policy /* policy */, handle /* parent */) {
         return PyComplex_FromDoubles((double) src.real(), (double) src.imag());
     }
 
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 9d6c08be0b..14f8a7a7e4 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -16,12 +16,13 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if PY_VERSION_HEX >= 0x03030000 && !defined(PYPY_VERSION)
-#  define PYBIND11_BUILTIN_QUALNAME
-#  define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
+#    define PYBIND11_BUILTIN_QUALNAME
+#    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
 #else
 // In pre-3.3 Python, we still set __qualname__ so that we can produce reliable function type
 // signatures; in 3.3+ this macro expands to nothing:
-#  define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj) setattr((PyObject *) obj, "__qualname__", nameobj)
+#    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)                                             \
+        setattr((PyObject *) obj, "__qualname__", nameobj)
 #endif
 
 inline std::string get_fully_qualified_tp_name(PyTypeObject *type) {
@@ -71,9 +72,9 @@ inline PyTypeObject *make_static_property_type() {
     }
 
     heap_type->ht_name = name_obj.inc_ref().ptr();
-#ifdef PYBIND11_BUILTIN_QUALNAME
+#    ifdef PYBIND11_BUILTIN_QUALNAME
     heap_type->ht_qualname = name_obj.inc_ref().ptr();
-#endif
+#    endif
 
     auto *type = &heap_type->ht_type;
     type->tp_name = name;
@@ -107,8 +108,10 @@ inline PyTypeObject *make_static_property_type() {
             def __set__(self, obj, value):
                 cls = obj if isinstance(obj, type) else type(obj)
                 property.__set__(self, cls, value)
-        )", Py_file_input, d.ptr(), d.ptr()
-    );
+        )",
+                                    Py_file_input,
+                                    d.ptr(),
+                                    d.ptr());
     if (result == nullptr)
         throw error_already_set();
     Py_DECREF(result);
@@ -121,7 +124,7 @@ inline PyTypeObject *make_static_property_type() {
     By default, Python replaces the `static_property` itself, but for wrapped C++ types
     we need to call `static_property.__set__()` in order to propagate the new value to
     the underlying C++ data structure. */
-extern "C" inline int pybind11_meta_setattro(PyObject* obj, PyObject* name, PyObject* value) {
+extern "C" inline int pybind11_meta_setattro(PyObject *obj, PyObject *name, PyObject *value) {
     // Use `_PyType_Lookup()` instead of `PyObject_GetAttr()` in order to get the raw
     // descriptor (`property`) instead of calling `tp_descr_get` (`property.__get__()`).
     PyObject *descr = _PyType_Lookup((PyTypeObject *) obj, name);
@@ -190,7 +193,8 @@ extern "C" inline PyObject *pybind11_meta_call(PyObject *type, PyObject *args, P
     // Ensure that the base __init__ function(s) were called
     for (const auto &vh : values_and_holders(instance)) {
         if (!vh.holder_constructed()) {
-            PyErr_Format(PyExc_TypeError, "%.200s.__init__() must be called when overriding __init__",
+            PyErr_Format(PyExc_TypeError,
+                         "%.200s.__init__() must be called when overriding __init__",
                          get_fully_qualified_tp_name(vh.type->type).c_str());
             Py_DECREF(self);
             return nullptr;
@@ -209,9 +213,8 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
     // 1) be found in internals.registered_types_py
     // 2) have exactly one associated `detail::type_info`
     auto found_type = internals.registered_types_py.find(type);
-    if (found_type != internals.registered_types_py.end() &&
-        found_type->second.size() == 1 &&
-        found_type->second[0]->type == type) {
+    if (found_type != internals.registered_types_py.end() && found_type->second.size() == 1
+        && found_type->second[0]->type == type) {
 
         auto *tinfo = found_type->second[0];
         auto tindex = std::type_index(*tinfo->cpptype);
@@ -226,7 +229,7 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
 
         // Actually just `std::erase_if`, but that's only available in C++20
         auto &cache = internals.inactive_override_cache;
-        for (auto it = cache.begin(), last = cache.end(); it != last; ) {
+        for (auto it = cache.begin(), last = cache.end(); it != last;) {
             if (it->first == (PyObject *) tinfo->type) {
                 it = cache.erase(it);
             } else {
@@ -243,7 +246,7 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
 /** This metaclass is assigned by default to all pybind11 types and is required in order
     for static properties to function correctly. Users may override this using `py::metaclass`.
     Return value: New reference. */
-inline PyTypeObject* make_default_metaclass() {
+inline PyTypeObject *make_default_metaclass() {
     constexpr auto *name = "pybind11_type";
     auto name_obj = reinterpret_steal<object>(PYBIND11_FROM_STRING(name));
 
@@ -287,9 +290,12 @@ inline PyTypeObject* make_default_metaclass() {
 
 /// For multiple inheritance types we need to recursively register/deregister base pointers for any
 /// base classes with pointers that are difference from the instance value pointer so that we can
-/// correctly recognize an offset base class pointer. This calls a function with any offset base ptrs.
-inline void traverse_offset_bases(void *valueptr, const detail::type_info *tinfo, instance *self,
-        bool (*f)(void * /*parentptr*/, instance * /*self*/)) {
+/// correctly recognize an offset base class pointer. This calls a function with any offset base
+/// ptrs.
+inline void traverse_offset_bases(void *valueptr,
+                                  const detail::type_info *tinfo,
+                                  instance *self,
+                                  bool (*f)(void * /*parentptr*/, instance * /*self*/)) {
     for (handle h : reinterpret_borrow<tuple>(tinfo->type->tp_bases)) {
         if (auto *parent_tinfo = get_type_info((PyTypeObject *) h.ptr())) {
             for (auto &c : parent_tinfo->implicit_casts) {
@@ -337,13 +343,13 @@ inline bool deregister_instance(instance *self, void *valptr, const type_info *t
     return ret;
 }
 
-/// Instance creation function for all pybind11 types. It allocates the internal instance layout for
-/// holding C++ objects and holders.  Allocation is done lazily (the first time the instance is cast
-/// to a reference or pointer), and initialization is done by an `__init__` function.
+/// Instance creation function for all pybind11 types. It allocates the internal instance layout
+/// for holding C++ objects and holders.  Allocation is done lazily (the first time the instance is
+/// cast to a reference or pointer), and initialization is done by an `__init__` function.
 inline PyObject *make_new_instance(PyTypeObject *type) {
 #if defined(PYPY_VERSION)
-    // PyPy gets tp_basicsize wrong (issue 2482) under multiple inheritance when the first inherited
-    // object is a plain Python type (i.e. not derived from an extension type).  Fix it.
+    // PyPy gets tp_basicsize wrong (issue 2482) under multiple inheritance when the first
+    // inherited object is a plain Python type (i.e. not derived from an extension type).  Fix it.
     ssize_t instance_size = static_cast<ssize_t>(sizeof(instance));
     if (type->tp_basicsize < instance_size) {
         type->tp_basicsize = instance_size;
@@ -517,7 +523,8 @@ extern "C" inline PyObject *pybind11_get_dict(PyObject *self, void *) {
 /// dynamic_attr: Support for `instance.__dict__ = dict()`.
 extern "C" inline int pybind11_set_dict(PyObject *self, PyObject *new_dict, void *) {
     if (!PyDict_Check(new_dict)) {
-        PyErr_Format(PyExc_TypeError, "__dict__ must be set to a dictionary, not a '%.200s'",
+        PyErr_Format(PyExc_TypeError,
+                     "__dict__ must be set to a dictionary, not a '%.200s'",
                      get_fully_qualified_tp_name(Py_TYPE(new_dict)).c_str());
         return -1;
     }
@@ -546,15 +553,14 @@ extern "C" inline int pybind11_clear(PyObject *self) {
 inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
     auto *type = &heap_type->ht_type;
     type->tp_flags |= Py_TPFLAGS_HAVE_GC;
-    type->tp_dictoffset = type->tp_basicsize; // place dict at the end
-    type->tp_basicsize += (ssize_t)sizeof(PyObject *); // and allocate enough space for it
+    type->tp_dictoffset = type->tp_basicsize;           // place dict at the end
+    type->tp_basicsize += (ssize_t) sizeof(PyObject *); // and allocate enough space for it
     type->tp_traverse = pybind11_traverse;
     type->tp_clear = pybind11_clear;
 
     static PyGetSetDef getset[] = {
-        {const_cast<char*>("__dict__"), pybind11_get_dict, pybind11_set_dict, nullptr, nullptr},
-        {nullptr, nullptr, nullptr, nullptr, nullptr}
-    };
+        {const_cast<char *>("__dict__"), pybind11_get_dict, pybind11_set_dict, nullptr, nullptr},
+        {nullptr, nullptr, nullptr, nullptr, nullptr}};
     type->tp_getset = getset;
 }
 
@@ -623,7 +629,7 @@ inline void enable_buffer_protocol(PyHeapTypeObject *heap_type) {
 
 /** Create a brand new Python type according to the `type_record` specification.
     Return value: New reference. */
-inline PyObject* make_new_python_type(const type_record &rec) {
+inline PyObject *make_new_python_type(const type_record &rec) {
     auto name = reinterpret_steal<object>(PYBIND11_FROM_STRING(rec.name));
 
     auto qualname = name;
@@ -684,7 +690,7 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     auto *type = &heap_type->ht_type;
     type->tp_name = full_name;
     type->tp_doc = tp_doc;
-    type->tp_base = type_incref((PyTypeObject *)base);
+    type->tp_base = type_incref((PyTypeObject *) base);
     type->tp_basicsize = static_cast<ssize_t>(sizeof(instance));
     if (!bases.empty()) {
         type->tp_bases = bases.release().ptr();
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index df9a88a718..8dfd23ff63 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -21,89 +21,90 @@
 #define PYBIND11_NAMESPACE_END(name) }
 
 // Robust support for some features and loading modules compiled against different pybind versions
-// requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute on
-// the main `pybind11` namespace.
+// requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute
+// on the main `pybind11` namespace.
 #if !defined(PYBIND11_NAMESPACE)
-#  ifdef __GNUG__
-#    define PYBIND11_NAMESPACE pybind11 __attribute__((visibility("hidden")))
-#  else
-#    define PYBIND11_NAMESPACE pybind11
-#  endif
+#    ifdef __GNUG__
+#        define PYBIND11_NAMESPACE pybind11 __attribute__((visibility("hidden")))
+#    else
+#        define PYBIND11_NAMESPACE pybind11
+#    endif
 #endif
 
 #if !(defined(_MSC_VER) && __cplusplus == 199711L)
-#  if __cplusplus >= 201402L
-#    define PYBIND11_CPP14
-#    if __cplusplus >= 201703L
-#      define PYBIND11_CPP17
-#      if __cplusplus >= 202002L
-#        define PYBIND11_CPP20
-#      endif
+#    if __cplusplus >= 201402L
+#        define PYBIND11_CPP14
+#        if __cplusplus >= 201703L
+#            define PYBIND11_CPP17
+#            if __cplusplus >= 202002L
+#                define PYBIND11_CPP20
+#            endif
+#        endif
 #    endif
-#  endif
 #elif defined(_MSC_VER) && __cplusplus == 199711L
 // MSVC sets _MSVC_LANG rather than __cplusplus (supposedly until the standard is fully
 // implemented). Unless you use the /Zc:__cplusplus flag on Visual Studio 2017 15.7 Preview 3
 // or newer.
-#  if _MSVC_LANG >= 201402L
-#    define PYBIND11_CPP14
-#    if _MSVC_LANG > 201402L && _MSC_VER >= 1910
-#      define PYBIND11_CPP17
-#      if _MSVC_LANG >= 202002L
-#        define PYBIND11_CPP20
-#      endif
+#    if _MSVC_LANG >= 201402L
+#        define PYBIND11_CPP14
+#        if _MSVC_LANG > 201402L && _MSC_VER >= 1910
+#            define PYBIND11_CPP17
+#            if _MSVC_LANG >= 202002L
+#                define PYBIND11_CPP20
+#            endif
+#        endif
 #    endif
-#  endif
 #endif
 
 // Compiler version assertions
 #if defined(__INTEL_COMPILER)
-#  if __INTEL_COMPILER < 1800
-#    error pybind11 requires Intel C++ compiler v18 or newer
-#  elif __INTEL_COMPILER < 1900 && defined(PYBIND11_CPP14)
-#    error pybind11 supports only C++11 with Intel C++ compiler v18. Use v19 or newer for C++14.
-#  endif
+#    if __INTEL_COMPILER < 1800
+#        error pybind11 requires Intel C++ compiler v18 or newer
+#    elif __INTEL_COMPILER < 1900 && defined(PYBIND11_CPP14)
+#        error pybind11 supports only C++11 with Intel C++ compiler v18. Use v19 or newer for C++14.
+#    endif
 /* The following pragma cannot be pop'ed:
    https://community.intel.com/t5/Intel-C-Compiler/Inline-and-no-inline-warning/td-p/1216764 */
-#  pragma warning disable 2196 // warning #2196: routine is both "inline" and "noinline"
+#    pragma warning disable 2196 // warning #2196: routine is both "inline" and "noinline"
 #elif defined(__clang__) && !defined(__apple_build_version__)
-#  if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
-#    error pybind11 requires clang 3.3 or newer
-#  endif
+#    if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
+#        error pybind11 requires clang 3.3 or newer
+#    endif
 #elif defined(__clang__)
 // Apple changes clang version macros to its Xcode version; the first Xcode release based on
 // (upstream) clang 3.3 was Xcode 5:
-#  if __clang_major__ < 5
-#    error pybind11 requires Xcode/clang 5.0 or newer
-#  endif
+#    if __clang_major__ < 5
+#        error pybind11 requires Xcode/clang 5.0 or newer
+#    endif
 #elif defined(__GNUG__)
-#  if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8)
-#    error pybind11 requires gcc 4.8 or newer
-#  endif
+#    if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8)
+#        error pybind11 requires gcc 4.8 or newer
+#    endif
 #elif defined(_MSC_VER)
 // Pybind hits various compiler bugs in 2015u2 and earlier, and also makes use of some stl features
 // (e.g. std::negation) added in 2015u3:
-#  if _MSC_FULL_VER < 190024210
-#    error pybind11 requires MSVC 2015 update 3 or newer
-#  endif
+#    if _MSC_FULL_VER < 190024210
+#        error pybind11 requires MSVC 2015 update 3 or newer
+#    endif
 #endif
 
 #if !defined(PYBIND11_EXPORT)
-#  if defined(WIN32) || defined(_WIN32)
-#    define PYBIND11_EXPORT __declspec(dllexport)
-#  else
-#    define PYBIND11_EXPORT __attribute__ ((visibility("default")))
-#  endif
+#    if defined(WIN32) || defined(_WIN32)
+#        define PYBIND11_EXPORT __declspec(dllexport)
+#    else
+#        define PYBIND11_EXPORT __attribute__((visibility("default")))
+#    endif
 #endif
 
 #if !defined(PYBIND11_EXPORT_EXCEPTION)
-#  ifdef __MINGW32__
+#    ifdef __MINGW32__
 // workaround for:
-// error: 'dllexport' implies default visibility, but xxx has already been declared with a different visibility
-#    define PYBIND11_EXPORT_EXCEPTION
-#  else
-#    define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
-#  endif
+// error: 'dllexport' implies default visibility, but xxx has already been declared with a
+// different visibility
+#        define PYBIND11_EXPORT_EXCEPTION
+#    else
+#        define PYBIND11_EXPORT_EXCEPTION PYBIND11_EXPORT
+#    endif
 #endif
 
 // For CUDA, GCC7, GCC8:
@@ -112,104 +113,103 @@
 // However, the measured shared-library size saving when using noinline are only
 // 1.7% for CUDA, -0.2% for GCC7, and 0.0% for GCC8 (using -DCMAKE_BUILD_TYPE=MinSizeRel,
 // the default under pybind11/tests).
-#if !defined(PYBIND11_NOINLINE_FORCED) && \
-    (defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8)))
-#  define PYBIND11_NOINLINE_DISABLED
+#if !defined(PYBIND11_NOINLINE_FORCED)                                                            \
+    && (defined(__CUDACC__) || (defined(__GNUC__) && (__GNUC__ == 7 || __GNUC__ == 8)))
+#    define PYBIND11_NOINLINE_DISABLED
 #endif
 
 // The PYBIND11_NOINLINE macro is for function DEFINITIONS.
 // In contrast, FORWARD DECLARATIONS should never use this macro:
 // https://stackoverflow.com/questions/9317473/forward-declaration-of-inline-functions
 #if defined(PYBIND11_NOINLINE_DISABLED) // Option for maximum portability and experimentation.
-#  define PYBIND11_NOINLINE inline
+#    define PYBIND11_NOINLINE inline
 #elif defined(_MSC_VER)
-#  define PYBIND11_NOINLINE __declspec(noinline) inline
+#    define PYBIND11_NOINLINE __declspec(noinline) inline
 #else
-#  define PYBIND11_NOINLINE __attribute__ ((noinline)) inline
+#    define PYBIND11_NOINLINE __attribute__((noinline)) inline
 #endif
 
 #if defined(__MINGW32__)
 // For unknown reasons all PYBIND11_DEPRECATED member trigger a warning when declared
 // whether it is used or not
-#  define PYBIND11_DEPRECATED(reason)
+#    define PYBIND11_DEPRECATED(reason)
 #elif defined(PYBIND11_CPP14)
-#  define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
+#    define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
 #else
-#  define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
+#    define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
 #endif
 
 #if defined(PYBIND11_CPP17)
-#  define PYBIND11_MAYBE_UNUSED [[maybe_unused]]
+#    define PYBIND11_MAYBE_UNUSED [[maybe_unused]]
 #elif defined(_MSC_VER) && !defined(__clang__)
-#  define PYBIND11_MAYBE_UNUSED
+#    define PYBIND11_MAYBE_UNUSED
 #else
-#  define PYBIND11_MAYBE_UNUSED __attribute__ ((__unused__))
+#    define PYBIND11_MAYBE_UNUSED __attribute__((__unused__))
 #endif
 
 /* Don't let Python.h #define (v)snprintf as macro because they are implemented
    properly in Visual Studio since 2015. */
 #if defined(_MSC_VER) && _MSC_VER >= 1900
-#  define HAVE_SNPRINTF 1
+#    define HAVE_SNPRINTF 1
 #endif
 
 /// Include Python header, disable linking to pythonX_d.lib on Windows in debug mode
 #if defined(_MSC_VER)
-#  pragma warning(push)
+#    pragma warning(push)
 // C4505: 'PySlice_GetIndicesEx': unreferenced local function has been removed (PyPy only)
-#  pragma warning(disable: 4505)
-#  if defined(_DEBUG) && !defined(Py_DEBUG)
+#    pragma warning(disable : 4505)
+#    if defined(_DEBUG) && !defined(Py_DEBUG)
 // Workaround for a VS 2022 issue.
 // NOTE: This workaround knowingly violates the Python.h include order requirement:
 // https://docs.python.org/3/c-api/intro.html#include-files
 // See https://github.com/pybind/pybind11/pull/3497 for full context.
-#    include <yvals.h>
-#    if _MSVC_STL_VERSION >= 143
-#      include <crtdefs.h>
+#        include <yvals.h>
+#        if _MSVC_STL_VERSION >= 143
+#            include <crtdefs.h>
+#        endif
+#        define PYBIND11_DEBUG_MARKER
+#        undef _DEBUG
 #    endif
-#    define PYBIND11_DEBUG_MARKER
-#    undef _DEBUG
-#  endif
 #endif
 
 // https://en.cppreference.com/w/c/chrono/localtime
 #if defined(__STDC_LIB_EXT1__) && !defined(__STDC_WANT_LIB_EXT1__)
-#  define __STDC_WANT_LIB_EXT1__
+#    define __STDC_WANT_LIB_EXT1__
 #endif
 
 #ifdef __has_include
 // std::optional (but including it in c++14 mode isn't allowed)
-#  if defined(PYBIND11_CPP17) && __has_include(<optional>)
-#    define PYBIND11_HAS_OPTIONAL 1
-#  endif
+#    if defined(PYBIND11_CPP17) && __has_include(<optional>)
+#        define PYBIND11_HAS_OPTIONAL 1
+#    endif
 // std::experimental::optional (but not allowed in c++11 mode)
-#  if defined(PYBIND11_CPP14) && (__has_include(<experimental/optional>) && \
+#    if defined(PYBIND11_CPP14) && (__has_include(<experimental/optional>) && \
                                  !__has_include(<optional>))
-#    define PYBIND11_HAS_EXP_OPTIONAL 1
-#  endif
+#        define PYBIND11_HAS_EXP_OPTIONAL 1
+#    endif
 // std::variant
-#  if defined(PYBIND11_CPP17) && __has_include(<variant>)
-#    define PYBIND11_HAS_VARIANT 1
-#  endif
+#    if defined(PYBIND11_CPP17) && __has_include(<variant>)
+#        define PYBIND11_HAS_VARIANT 1
+#    endif
 #elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
-#  define PYBIND11_HAS_OPTIONAL 1
-#  define PYBIND11_HAS_VARIANT 1
+#    define PYBIND11_HAS_OPTIONAL 1
+#    define PYBIND11_HAS_VARIANT 1
 #endif
 
 #if defined(PYBIND11_CPP17)
-#  if defined(__has_include)
-#    if __has_include(<string_view>)
-#      define PYBIND11_HAS_STRING_VIEW
+#    if defined(__has_include)
+#        if __has_include(<string_view>)
+#            define PYBIND11_HAS_STRING_VIEW
+#        endif
+#    elif defined(_MSC_VER)
+#        define PYBIND11_HAS_STRING_VIEW
 #    endif
-#  elif defined(_MSC_VER)
-#    define PYBIND11_HAS_STRING_VIEW
-#  endif
 #endif
 
 #if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
-#  define PYBIND11_HAS_U8STRING
+#    define PYBIND11_HAS_U8STRING
 #endif
 
-
 #include <Python.h>
 #include <frameobject.h>
 #include <pythread.h>
@@ -218,43 +218,43 @@
    tends to weak havok in C++ codebases that expect these to work
    like regular functions (potentially with several overloads) */
 #if defined(isalnum)
-#  undef isalnum
-#  undef isalpha
-#  undef islower
-#  undef isspace
-#  undef isupper
-#  undef tolower
-#  undef toupper
+#    undef isalnum
+#    undef isalpha
+#    undef islower
+#    undef isspace
+#    undef isupper
+#    undef tolower
+#    undef toupper
 #endif
 
 #if defined(copysign)
-#  undef copysign
+#    undef copysign
 #endif
 
 #if defined(_MSC_VER)
-#  if defined(PYBIND11_DEBUG_MARKER)
-#    define _DEBUG
-#    undef PYBIND11_DEBUG_MARKER
-#  endif
-#  pragma warning(pop)
+#    if defined(PYBIND11_DEBUG_MARKER)
+#        define _DEBUG
+#        undef PYBIND11_DEBUG_MARKER
+#    endif
+#    pragma warning(pop)
 #endif
 
 #include <cstddef>
 #include <cstring>
-#include <forward_list>
-#include <vector>
-#include <string>
-#include <stdexcept>
 #include <exception>
-#include <unordered_set>
-#include <unordered_map>
+#include <forward_list>
 #include <memory>
-#include <typeindex>
+#include <stdexcept>
+#include <string>
 #include <type_traits>
+#include <typeindex>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
 #if defined(__has_include)
-#  if __has_include(<version>)
-#    include <version>
-#  endif
+#    if __has_include(<version>)
+#        include <version>
+#    endif
 #endif
 
 // #define PYBIND11_STR_LEGACY_PERMISSIVE
@@ -271,70 +271,71 @@
 //               behavior.
 
 #if PY_MAJOR_VERSION >= 3 /// Compatibility macros for various Python versions
-#define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
-#define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
-#define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
-#define PYBIND11_BYTES_CHECK PyBytes_Check
-#define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
-#define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
-#define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
-#define PYBIND11_BYTES_AS_STRING PyBytes_AsString
-#define PYBIND11_BYTES_SIZE PyBytes_Size
-#define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
-#define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
-#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
-#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
-#define PYBIND11_BYTES_NAME "bytes"
-#define PYBIND11_STRING_NAME "str"
-#define PYBIND11_SLICE_OBJECT PyObject
-#define PYBIND11_FROM_STRING PyUnicode_FromString
-#define PYBIND11_STR_TYPE ::pybind11::str
-#define PYBIND11_BOOL_ATTR "__bool__"
-#define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
-#define PYBIND11_BUILTINS_MODULE "builtins"
+#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
+#    define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
+#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
+#    define PYBIND11_BYTES_CHECK PyBytes_Check
+#    define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
+#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
+#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
+#    define PYBIND11_BYTES_AS_STRING PyBytes_AsString
+#    define PYBIND11_BYTES_SIZE PyBytes_Size
+#    define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
+#    define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
+#    define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
+#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
+#    define PYBIND11_BYTES_NAME "bytes"
+#    define PYBIND11_STRING_NAME "str"
+#    define PYBIND11_SLICE_OBJECT PyObject
+#    define PYBIND11_FROM_STRING PyUnicode_FromString
+#    define PYBIND11_STR_TYPE ::pybind11::str
+#    define PYBIND11_BOOL_ATTR "__bool__"
+#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
+#    define PYBIND11_BUILTINS_MODULE "builtins"
 // Providing a separate declaration to make Clang's -Wmissing-prototypes happy.
 // See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#define PYBIND11_PLUGIN_IMPL(name) \
-    extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name(); \
-    extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
+#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
+        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();               \
+        extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
 
 #else
-#define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
-#define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
-#define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
-#define PYBIND11_BYTES_CHECK PyString_Check
-#define PYBIND11_BYTES_FROM_STRING PyString_FromString
-#define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
-#define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
-#define PYBIND11_BYTES_AS_STRING PyString_AsString
-#define PYBIND11_BYTES_SIZE PyString_Size
-#define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
-#define PYBIND11_LONG_AS_LONGLONG(o) (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
-#define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
-#define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
-#define PYBIND11_BYTES_NAME "str"
-#define PYBIND11_STRING_NAME "unicode"
-#define PYBIND11_SLICE_OBJECT PySliceObject
-#define PYBIND11_FROM_STRING PyString_FromString
-#define PYBIND11_STR_TYPE ::pybind11::bytes
-#define PYBIND11_BOOL_ATTR "__nonzero__"
-#define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
-#define PYBIND11_BUILTINS_MODULE "__builtin__"
+#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
+#    define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
+#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
+#    define PYBIND11_BYTES_CHECK PyString_Check
+#    define PYBIND11_BYTES_FROM_STRING PyString_FromString
+#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
+#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
+#    define PYBIND11_BYTES_AS_STRING PyString_AsString
+#    define PYBIND11_BYTES_SIZE PyString_Size
+#    define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
+#    define PYBIND11_LONG_AS_LONGLONG(o)                                                          \
+        (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
+#    define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
+#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
+#    define PYBIND11_BYTES_NAME "str"
+#    define PYBIND11_STRING_NAME "unicode"
+#    define PYBIND11_SLICE_OBJECT PySliceObject
+#    define PYBIND11_FROM_STRING PyString_FromString
+#    define PYBIND11_STR_TYPE ::pybind11::bytes
+#    define PYBIND11_BOOL_ATTR "__nonzero__"
+#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
+#    define PYBIND11_BUILTINS_MODULE "__builtin__"
 // Providing a separate PyInit decl to make Clang's -Wmissing-prototypes happy.
 // See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#define PYBIND11_PLUGIN_IMPL(name) \
-    static PyObject *pybind11_init_wrapper();                           \
-    extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT void init##name(); \
-    extern "C" PYBIND11_EXPORT void init##name() {                      \
-        (void)pybind11_init_wrapper();                                  \
-    }                                                                   \
-    PyObject *pybind11_init_wrapper()
+#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
+        static PyObject *pybind11_init_wrapper();                                                 \
+        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT void init##name();                       \
+        extern "C" PYBIND11_EXPORT void init##name() { (void) pybind11_init_wrapper(); }          \
+        PyObject *pybind11_init_wrapper()
 #endif
 
 #if PY_VERSION_HEX >= 0x03050000 && PY_VERSION_HEX < 0x03050200
 extern "C" {
-    struct _Py_atomic_address { void *value; };
-    PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
+struct _Py_atomic_address {
+    void *value;
+};
+PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
 }
 #endif
 
@@ -342,46 +343,48 @@ extern "C" {
 #define PYBIND11_STRINGIFY(x) #x
 #define PYBIND11_TOSTRING(x) PYBIND11_STRINGIFY(x)
 #define PYBIND11_CONCAT(first, second) first##second
-#define PYBIND11_ENSURE_INTERNALS_READY \
-    pybind11::detail::get_internals();
-
-#define PYBIND11_CHECK_PYTHON_VERSION \
-    {                                                                          \
-        const char *compiled_ver = PYBIND11_TOSTRING(PY_MAJOR_VERSION)         \
-            "." PYBIND11_TOSTRING(PY_MINOR_VERSION);                           \
-        const char *runtime_ver = Py_GetVersion();                             \
-        size_t len = std::strlen(compiled_ver);                                \
-        if (std::strncmp(runtime_ver, compiled_ver, len) != 0                  \
-                || (runtime_ver[len] >= '0' && runtime_ver[len] <= '9')) {     \
-            PyErr_Format(PyExc_ImportError,                                    \
-                "Python version mismatch: module was compiled for Python %s, " \
-                "but the interpreter version is incompatible: %s.",            \
-                compiled_ver, runtime_ver);                                    \
-            return nullptr;                                                    \
-        }                                                                      \
+#define PYBIND11_ENSURE_INTERNALS_READY pybind11::detail::get_internals();
+
+#define PYBIND11_CHECK_PYTHON_VERSION                                                             \
+    {                                                                                             \
+        const char *compiled_ver                                                                  \
+            = PYBIND11_TOSTRING(PY_MAJOR_VERSION) "." PYBIND11_TOSTRING(PY_MINOR_VERSION);        \
+        const char *runtime_ver = Py_GetVersion();                                                \
+        size_t len = std::strlen(compiled_ver);                                                   \
+        if (std::strncmp(runtime_ver, compiled_ver, len) != 0                                     \
+            || (runtime_ver[len] >= '0' && runtime_ver[len] <= '9')) {                            \
+            PyErr_Format(PyExc_ImportError,                                                       \
+                         "Python version mismatch: module was compiled for Python %s, "           \
+                         "but the interpreter version is incompatible: %s.",                      \
+                         compiled_ver,                                                            \
+                         runtime_ver);                                                            \
+            return nullptr;                                                                       \
+        }                                                                                         \
     }
 
 #if PY_VERSION_HEX >= 0x03030000
 
-#define PYBIND11_CATCH_INIT_EXCEPTIONS \
-        catch (pybind11::error_already_set &e) {                                 \
-            pybind11::raise_from(e, PyExc_ImportError, "initialization failed"); \
-            return nullptr;                                                      \
-        } catch (const std::exception &e) {                                      \
-            PyErr_SetString(PyExc_ImportError, e.what());                        \
-            return nullptr;                                                      \
-        }                                                                        \
+#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
+        catch (pybind11::error_already_set & e) {                                                 \
+            pybind11::raise_from(e, PyExc_ImportError, "initialization failed");                  \
+            return nullptr;                                                                       \
+        }                                                                                         \
+        catch (const std::exception &e) {                                                         \
+            PyErr_SetString(PyExc_ImportError, e.what());                                         \
+            return nullptr;                                                                       \
+        }
 
 #else
 
-#define PYBIND11_CATCH_INIT_EXCEPTIONS \
-        catch (pybind11::error_already_set &e) {                               \
-            PyErr_SetString(PyExc_ImportError, e.what());                      \
-            return nullptr;                                                    \
-        } catch (const std::exception &e) {                                    \
-            PyErr_SetString(PyExc_ImportError, e.what());                      \
-            return nullptr;                                                    \
-        }                                                                      \
+#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
+        catch (pybind11::error_already_set & e) {                                                 \
+            PyErr_SetString(PyExc_ImportError, e.what());                                         \
+            return nullptr;                                                                       \
+        }                                                                                         \
+        catch (const std::exception &e) {                                                         \
+            PyErr_SetString(PyExc_ImportError, e.what());                                         \
+            return nullptr;                                                                       \
+        }
 
 #endif
 
@@ -400,16 +403,17 @@ extern "C" {
             return m.ptr();
         }
 \endrst */
-#define PYBIND11_PLUGIN(name)                                                  \
-    PYBIND11_DEPRECATED("PYBIND11_PLUGIN is deprecated, use PYBIND11_MODULE")  \
-    static PyObject *pybind11_init();                                          \
-    PYBIND11_PLUGIN_IMPL(name) {                                               \
-        PYBIND11_CHECK_PYTHON_VERSION                                          \
-        PYBIND11_ENSURE_INTERNALS_READY                                        \
-        try {                                                                  \
-            return pybind11_init();                                            \
-        } PYBIND11_CATCH_INIT_EXCEPTIONS                                       \
-    }                                                                          \
+#define PYBIND11_PLUGIN(name)                                                                     \
+    PYBIND11_DEPRECATED("PYBIND11_PLUGIN is deprecated, use PYBIND11_MODULE")                     \
+    static PyObject *pybind11_init();                                                             \
+    PYBIND11_PLUGIN_IMPL(name) {                                                                  \
+        PYBIND11_CHECK_PYTHON_VERSION                                                             \
+        PYBIND11_ENSURE_INTERNALS_READY                                                           \
+        try {                                                                                     \
+            return pybind11_init();                                                               \
+        }                                                                                         \
+        PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
+    }                                                                                             \
     PyObject *pybind11_init()
 
 /** \rst
@@ -454,7 +458,7 @@ extern "C" {
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 using ssize_t = Py_ssize_t;
-using size_t  = std::size_t;
+using size_t = std::size_t;
 
 template <typename IntType>
 inline ssize_t ssize_t_cast(const IntType &val) {
@@ -518,10 +522,14 @@ class object;
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-inline static constexpr int log2(size_t n, int k = 0) { return (n <= 1) ? k : log2(n >> 1, k + 1); }
+inline static constexpr int log2(size_t n, int k = 0) {
+    return (n <= 1) ? k : log2(n >> 1, k + 1);
+}
 
 // Returns the size as a multiple of sizeof(void *), rounded up.
-inline static constexpr size_t size_in_ptrs(size_t s) { return 1 + ((s - 1) >> log2(sizeof(void *))); }
+inline static constexpr size_t size_in_ptrs(size_t s) {
+    return 1 + ((s - 1) >> log2(sizeof(void *)));
+}
 
 /**
  * The space to allocate for simple layout instance holders (see below) in multiple of the size of
@@ -531,7 +539,7 @@ inline static constexpr size_t size_in_ptrs(size_t s) { return 1 + ((s - 1) >> l
  */
 constexpr size_t instance_simple_holder_in_ptrs() {
     static_assert(sizeof(std::shared_ptr<int>) >= sizeof(std::unique_ptr<int>),
-            "pybind assumes std::shared_ptrs are at least as big as std::unique_ptrs");
+                  "pybind assumes std::shared_ptrs are at least as big as std::unique_ptrs");
     return size_in_ptrs(sizeof(std::shared_ptr<int>));
 }
 
@@ -555,61 +563,56 @@ struct get_holder_type_id<std::unique_ptr<T, Deleter>, void> {
 };
 
 class holder_erased {
- public:
+public:
     holder_erased() = default;
-    holder_erased(const holder_erased&) = default;
-    holder_erased& operator=(const holder_erased&) = default;
+    holder_erased(const holder_erased &) = default;
+    holder_erased &operator=(const holder_erased &) = default;
 
     template <typename holder_type>
-    holder_erased(const holder_type* holder)
-        : ptr_(const_cast<holder_type*>(holder)),
-          type_id_(get_holder_type_id<holder_type>::value),
-          is_const_(true) {}
+    holder_erased(const holder_type *holder)
+        : ptr_(const_cast<holder_type *>(holder)),
+          type_id_(get_holder_type_id<holder_type>::value), is_const_(true) {}
 
     template <typename holder_type>
-    holder_erased(holder_type* holder)
-        : holder_erased(static_cast<const holder_type*>(holder)) {
-          is_const_ = false;
+    holder_erased(holder_type *holder) : holder_erased(static_cast<const holder_type *>(holder)) {
+        is_const_ = false;
     }
 
-    holder_erased(const void* ptr, HolderTypeId type_id)
-        : ptr_(const_cast<void*>(ptr)),
-          type_id_(type_id),
-          is_const_(true) {}
+    holder_erased(const void *ptr, HolderTypeId type_id)
+        : ptr_(const_cast<void *>(ptr)), type_id_(type_id), is_const_(true) {}
 
-    holder_erased(void* ptr, HolderTypeId type_id)
-          : ptr_(ptr),
-            type_id_(type_id),
-            is_const_(false) {}
+    holder_erased(void *ptr, HolderTypeId type_id)
+        : ptr_(ptr), type_id_(type_id), is_const_(false) {}
 
     holder_erased(std::nullptr_t) {}
 
-    void* ptr() const { return ptr_; }
+    void *ptr() const { return ptr_; }
     HolderTypeId type_id() const { return type_id_; }
 
     template <typename holder_type>
-    holder_type& mutable_cast() const {
+    holder_type &mutable_cast() const {
         if (is_const_)
             throw std::runtime_error("Trying to mutate const reference?");
         return do_cast<holder_type>();
     }
 
     template <typename holder_type>
-    const holder_type& cast() const {
+    const holder_type &cast() const {
         return do_cast<holder_type>();
     }
 
     operator bool() const { return ptr_; }
- private:
+
+private:
     template <typename holder_type>
-    holder_type& do_cast() const {
+    holder_type &do_cast() const {
         if (type_id_ != get_holder_type_id<holder_type>::value) {
             throw std::runtime_error("Mismatch on holder type.");
         }
-        return *reinterpret_cast<holder_type*>(ptr_);
+        return *reinterpret_cast<holder_type *>(ptr_);
     }
 
-    void* ptr_{};
+    void *ptr_{};
     HolderTypeId type_id_{HolderTypeId::Unknown};
     bool is_const_{true};
 };
@@ -638,21 +641,21 @@ struct instance {
     /**
      * An instance has two possible value/holder layouts.
      *
-     * Simple layout (when this flag is true), means the `simple_value_holder` is set with a pointer
-     * and the holder object governing that pointer, i.e. [val1*][holder].  This layout is applied
-     * whenever there is no python-side multiple inheritance of bound C++ types *and* the type's
-     * holder will fit in the default space (which is large enough to hold either a std::unique_ptr
-     * or std::shared_ptr).
+     * Simple layout (when this flag is true), means the `simple_value_holder` is set with a
+     * pointer and the holder object governing that pointer, i.e. [val1*][holder].  This layout is
+     * applied whenever there is no python-side multiple inheritance of bound C++ types *and* the
+     * type's holder will fit in the default space (which is large enough to hold either a
+     * std::unique_ptr or std::shared_ptr).
      *
-     * Non-simple layout applies when using custom holders that require more space than `shared_ptr`
-     * (which is typically the size of two pointers), or when multiple inheritance is used on the
-     * python side.  Non-simple layout allocates the required amount of memory to have multiple
-     * bound C++ classes as parents.  Under this layout, `nonsimple.values_and_holders` is set to a
-     * pointer to allocated space of the required space to hold a sequence of value pointers and
-     * holders followed `status`, a set of bit flags (1 byte each), i.e.
-     * [val1*][holder1][val2*][holder2]...[bb...]  where each [block] is rounded up to a multiple of
-     * `sizeof(void *)`.  `nonsimple.status` is, for convenience, a pointer to the
-     * beginning of the [bb...] block (but not independently allocated).
+     * Non-simple layout applies when using custom holders that require more space than
+     * `shared_ptr` (which is typically the size of two pointers), or when multiple inheritance is
+     * used on the python side.  Non-simple layout allocates the required amount of memory to have
+     * multiple bound C++ classes as parents.  Under this layout, `nonsimple.values_and_holders` is
+     * set to a pointer to allocated space of the required space to hold a sequence of value
+     * pointers and holders followed `status`, a set of bit flags (1 byte each), i.e.
+     * [val1*][holder1][val2*][holder2]...[bb...]  where each [block] is rounded up to a multiple
+     * of `sizeof(void *)`.  `nonsimple.status` is, for convenience, a pointer to the beginning of
+     * the [bb...] block (but not independently allocated).
      *
      * Status bits indicate whether the associated holder is constructed (&
      * status_holder_constructed) and whether the value pointer is registered (&
@@ -666,27 +669,28 @@ struct instance {
     /// If true, get_internals().patients has an entry for this object
     bool has_patients : 1;
 
-    typedef void (*release_to_cpp_t)(instance* inst, holder_erased external_holder, object&& obj);
+    typedef void (*release_to_cpp_t)(instance *inst, holder_erased external_holder, object &&obj);
     using reclaim_from_cpp_t = object (*)(instance *, holder_erased);
 
     struct type_release_info_t {
-      // Release an instance to C++ for pure C++ instances or Python-derived classes.
-      release_to_cpp_t release_to_cpp = nullptr;
+        // Release an instance to C++ for pure C++ instances or Python-derived classes.
+        release_to_cpp_t release_to_cpp = nullptr;
 
-      // For classes wrapped in `wrapper<>`. See `move_only_holder_caster` for more info.
-      // Pure / direct C++ objects do not need any fancy releasing mechanisms. They are simply
-      // unwrapped and passed back.
-      bool can_derive_from_wrapper = false;
+        // For classes wrapped in `wrapper<>`. See `move_only_holder_caster` for more info.
+        // Pure / direct C++ objects do not need any fancy releasing mechanisms. They are simply
+        // unwrapped and passed back.
+        bool can_derive_from_wrapper = false;
 
-      // The holder that is contained by this class.
-      HolderTypeId holder_type_id = HolderTypeId::Unknown;
+        // The holder that is contained by this class.
+        HolderTypeId holder_type_id = HolderTypeId::Unknown;
     };
     /// If the instance is a Python-derived type that is owned in C++, then this method
     /// will permit the instance to be reclaimed back by Python.
     // TODO(eric.cousineau): This may not be necessary. See note in `type_caster_generic::cast`.
     reclaim_from_cpp_t reclaim_from_cpp = nullptr;
 
-    /// Initializes all of the above type/values/holders data (but not the instance values themselves)
+    /// Initializes all of the above type/values/holders data (but not the instance values
+    /// themselves)
     void allocate_layout();
 
     /// Destroys/deallocates all of the above
@@ -695,26 +699,32 @@ struct instance {
     /// Returns the value_and_holder wrapper for the given type (or the first, if `find_type`
     /// omitted).  Returns a default-constructed (with `.inst = nullptr`) object on failure if
     /// `throw_if_missing` is false.
-    value_and_holder get_value_and_holder(const type_info *find_type = nullptr, bool throw_if_missing = true);
+    value_and_holder get_value_and_holder(const type_info *find_type = nullptr,
+                                          bool throw_if_missing = true);
 
     /// Bit values for the non-simple status flags
-    static constexpr uint8_t status_holder_constructed  = 1;
+    static constexpr uint8_t status_holder_constructed = 1;
     static constexpr uint8_t status_instance_registered = 2;
 };
 
-static_assert(std::is_standard_layout<instance>::value, "Internal error: `pybind11::detail::instance` is not standard layout!");
+static_assert(std::is_standard_layout<instance>::value,
+              "Internal error: `pybind11::detail::instance` is not standard layout!");
 
 /// from __cpp_future__ import (convenient aliases from C++14/17)
 #if defined(PYBIND11_CPP14) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
-using std::enable_if_t;
 using std::conditional_t;
+using std::enable_if_t;
 using std::remove_cv_t;
 using std::remove_reference_t;
 #else
-template <bool B, typename T = void> using enable_if_t = typename std::enable_if<B, T>::type;
-template <bool B, typename T, typename F> using conditional_t = typename std::conditional<B, T, F>::type;
-template <typename T> using remove_cv_t = typename std::remove_cv<T>::type;
-template <typename T> using remove_reference_t = typename std::remove_reference<T>::type;
+template <bool B, typename T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+template <bool B, typename T, typename F>
+using conditional_t = typename std::conditional<B, T, F>::type;
+template <typename T>
+using remove_cv_t = typename std::remove_cv<T>::type;
+template <typename T>
+using remove_reference_t = typename std::remove_reference<T>::type;
 #endif
 
 #if defined(PYBIND11_CPP20)
@@ -734,114 +744,189 @@ using remove_cvref_t = typename remove_cvref<T>::type;
 using std::index_sequence;
 using std::make_index_sequence;
 #else
-template<size_t ...> struct index_sequence  { };
-template<size_t N, size_t ...S> struct make_index_sequence_impl : make_index_sequence_impl <N - 1, N - 1, S...> { };
-template<size_t ...S> struct make_index_sequence_impl <0, S...> { using type = index_sequence<S...>; };
-template<size_t N> using make_index_sequence = typename make_index_sequence_impl<N>::type;
+template <size_t...>
+struct index_sequence {};
+template <size_t N, size_t... S>
+struct make_index_sequence_impl : make_index_sequence_impl<N - 1, N - 1, S...> {};
+template <size_t... S>
+struct make_index_sequence_impl<0, S...> {
+    using type = index_sequence<S...>;
+};
+template <size_t N>
+using make_index_sequence = typename make_index_sequence_impl<N>::type;
 #endif
 
 /// Make an index sequence of the indices of true arguments
-template <typename ISeq, size_t, bool...> struct select_indices_impl { using type = ISeq; };
-template <size_t... IPrev, size_t I, bool B, bool... Bs> struct select_indices_impl<index_sequence<IPrev...>, I, B, Bs...>
-    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>, I + 1, Bs...> {};
-template <bool... Bs> using select_indices = typename select_indices_impl<index_sequence<>, 0, Bs...>::type;
+template <typename ISeq, size_t, bool...>
+struct select_indices_impl {
+    using type = ISeq;
+};
+template <size_t... IPrev, size_t I, bool B, bool... Bs>
+struct select_indices_impl<index_sequence<IPrev...>, I, B, Bs...>
+    : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>,
+                          I + 1,
+                          Bs...> {};
+template <bool... Bs>
+using select_indices = typename select_indices_impl<index_sequence<>, 0, Bs...>::type;
 
 /// Backports of std::bool_constant and std::negation to accommodate older compilers
-template <bool B> using bool_constant = std::integral_constant<bool, B>;
-template <typename T> struct negation : bool_constant<!T::value> { };
+template <bool B>
+using bool_constant = std::integral_constant<bool, B>;
+template <typename T>
+struct negation : bool_constant<!T::value> {};
 
 // PGI/Intel cannot detect operator delete with the "compatible" void_t impl, so
 // using the new one (C++14 defect, so generally works on newer compilers, even
 // if not in C++17 mode)
 #if defined(__PGIC__) || defined(__INTEL_COMPILER)
-template<typename... > using void_t = void;
+template <typename...>
+using void_t = void;
 #else
-template <typename...> struct void_t_impl { using type = void; };
-template <typename... Ts> using void_t = typename void_t_impl<Ts...>::type;
+template <typename...>
+struct void_t_impl {
+    using type = void;
+};
+template <typename... Ts>
+using void_t = typename void_t_impl<Ts...>::type;
 #endif
 
-
 /// Compile-time all/any/none of that check the boolean value of all template types
 #if defined(__cpp_fold_expressions) && !(defined(_MSC_VER) && (_MSC_VER < 1916))
-template <class... Ts> using all_of = bool_constant<(Ts::value && ...)>;
-template <class... Ts> using any_of = bool_constant<(Ts::value || ...)>;
+template <class... Ts>
+using all_of = bool_constant<(Ts::value && ...)>;
+template <class... Ts>
+using any_of = bool_constant<(Ts::value || ...)>;
 #elif !defined(_MSC_VER)
-template <bool...> struct bools {};
-template <class... Ts> using all_of = std::is_same<
-    bools<Ts::value..., true>,
-    bools<true, Ts::value...>>;
-template <class... Ts> using any_of = negation<all_of<negation<Ts>...>>;
+template <bool...>
+struct bools {};
+template <class... Ts>
+using all_of = std::is_same<bools<Ts::value..., true>, bools<true, Ts::value...>>;
+template <class... Ts>
+using any_of = negation<all_of<negation<Ts>...>>;
 #else
 // MSVC has trouble with the above, but supports std::conjunction, which we can use instead (albeit
 // at a slight loss of compilation efficiency).
-template <class... Ts> using all_of = std::conjunction<Ts...>;
-template <class... Ts> using any_of = std::disjunction<Ts...>;
+template <class... Ts>
+using all_of = std::conjunction<Ts...>;
+template <class... Ts>
+using any_of = std::disjunction<Ts...>;
 #endif
-template <class... Ts> using none_of = negation<any_of<Ts...>>;
+template <class... Ts>
+using none_of = negation<any_of<Ts...>>;
 
-template <class T, template<class> class... Predicates> using satisfies_all_of = all_of<Predicates<T>...>;
-template <class T, template<class> class... Predicates> using satisfies_any_of = any_of<Predicates<T>...>;
-template <class T, template<class> class... Predicates> using satisfies_none_of = none_of<Predicates<T>...>;
+template <class T, template <class> class... Predicates>
+using satisfies_all_of = all_of<Predicates<T>...>;
+template <class T, template <class> class... Predicates>
+using satisfies_any_of = any_of<Predicates<T>...>;
+template <class T, template <class> class... Predicates>
+using satisfies_none_of = none_of<Predicates<T>...>;
 
 /// Strip the class from a method type
-template <typename T> struct remove_class { };
-template <typename C, typename R, typename... A> struct remove_class<R (C::*)(A...)> { using type = R (A...); };
-template <typename C, typename R, typename... A> struct remove_class<R (C::*)(A...) const> { using type = R (A...); };
+template <typename T>
+struct remove_class {};
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...)> {
+    using type = R(A...);
+};
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...) const> {
+    using type = R(A...);
+};
 
 /// Helper template to strip away type modifiers
-template <typename T> struct intrinsic_type                       { using type = T; };
-template <typename T> struct intrinsic_type<const T>              { using type = typename intrinsic_type<T>::type; };
-template <typename T> struct intrinsic_type<T*>                   { using type = typename intrinsic_type<T>::type; };
-template <typename T> struct intrinsic_type<T&>                   { using type = typename intrinsic_type<T>::type; };
-template <typename T> struct intrinsic_type<T&&>                  { using type = typename intrinsic_type<T>::type; };
-template <typename T, size_t N> struct intrinsic_type<const T[N]> { using type = typename intrinsic_type<T>::type; };
-template <typename T, size_t N> struct intrinsic_type<T[N]>       { using type = typename intrinsic_type<T>::type; };
-template <typename T> using intrinsic_t = typename intrinsic_type<T>::type;
+template <typename T>
+struct intrinsic_type {
+    using type = T;
+};
+template <typename T>
+struct intrinsic_type<const T> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+struct intrinsic_type<T *> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+struct intrinsic_type<T &> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+struct intrinsic_type<T &&> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T, size_t N>
+struct intrinsic_type<const T[N]> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T, size_t N>
+struct intrinsic_type<T[N]> {
+    using type = typename intrinsic_type<T>::type;
+};
+template <typename T>
+using intrinsic_t = typename intrinsic_type<T>::type;
 
 /// Helper type to replace 'void' in some expressions
-struct void_type { };
+struct void_type {};
 
 /// Helper template which holds a list of types
-template <typename...> struct type_list { };
+template <typename...>
+struct type_list {};
 
 /// Compile-time integer sum
 #ifdef __cpp_fold_expressions
-template <typename... Ts> constexpr size_t constexpr_sum(Ts... ns) { return (0 + ... + size_t{ns}); }
+template <typename... Ts>
+constexpr size_t constexpr_sum(Ts... ns) {
+    return (0 + ... + size_t{ns});
+}
 #else
 constexpr size_t constexpr_sum() { return 0; }
 template <typename T, typename... Ts>
-constexpr size_t constexpr_sum(T n, Ts... ns) { return size_t{n} + constexpr_sum(ns...); }
+constexpr size_t constexpr_sum(T n, Ts... ns) {
+    return size_t{n} + constexpr_sum(ns...);
+}
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(constexpr_impl)
 /// Implementation details for constexpr functions
 constexpr int first(int i) { return i; }
 template <typename T, typename... Ts>
-constexpr int first(int i, T v, Ts... vs) { return v ? i : first(i + 1, vs...); }
+constexpr int first(int i, T v, Ts... vs) {
+    return v ? i : first(i + 1, vs...);
+}
 
 constexpr int last(int /*i*/, int result) { return result; }
 template <typename T, typename... Ts>
-constexpr int last(int i, int result, T v, Ts... vs) { return last(i + 1, v ? i : result, vs...); }
+constexpr int last(int i, int result, T v, Ts... vs) {
+    return last(i + 1, v ? i : result, vs...);
+}
 PYBIND11_NAMESPACE_END(constexpr_impl)
 
 /// Return the index of the first type in Ts which satisfies Predicate<T>.
 /// Returns sizeof...(Ts) if none match.
-template <template<typename> class Predicate, typename... Ts>
-constexpr int constexpr_first() { return constexpr_impl::first(0, Predicate<Ts>::value...); }
+template <template <typename> class Predicate, typename... Ts>
+constexpr int constexpr_first() {
+    return constexpr_impl::first(0, Predicate<Ts>::value...);
+}
 
 /// Return the index of the last type in Ts which satisfies Predicate<T>, or -1 if none match.
-template <template<typename> class Predicate, typename... Ts>
-constexpr int constexpr_last() { return constexpr_impl::last(0, -1, Predicate<Ts>::value...); }
+template <template <typename> class Predicate, typename... Ts>
+constexpr int constexpr_last() {
+    return constexpr_impl::last(0, -1, Predicate<Ts>::value...);
+}
 
 /// Return the Nth element from the parameter pack
 template <size_t N, typename T, typename... Ts>
-struct pack_element { using type = typename pack_element<N - 1, Ts...>::type; };
+struct pack_element {
+    using type = typename pack_element<N - 1, Ts...>::type;
+};
 template <typename T, typename... Ts>
-struct pack_element<0, T, Ts...> { using type = T; };
+struct pack_element<0, T, Ts...> {
+    using type = T;
+};
 
 /// Return the one and only type which matches the predicate, or Default if none match.
 /// If more than one type matches the predicate, fail at compile-time.
-template <template<typename> class Predicate, typename Default, typename... Ts>
+template <template <typename> class Predicate, typename Default, typename... Ts>
 struct exactly_one {
     static constexpr auto found = constexpr_sum(Predicate<Ts>::value...);
     static_assert(found <= 1, "Found more than one type matching the predicate");
@@ -849,62 +934,81 @@ struct exactly_one {
     static constexpr auto index = found ? constexpr_first<Predicate, Ts...>() : 0;
     using type = conditional_t<found, typename pack_element<index, Ts...>::type, Default>;
 };
-template <template<typename> class P, typename Default>
-struct exactly_one<P, Default> { using type = Default; };
+template <template <typename> class P, typename Default>
+struct exactly_one<P, Default> {
+    using type = Default;
+};
 
-template <template<typename> class Predicate, typename Default, typename... Ts>
+template <template <typename> class Predicate, typename Default, typename... Ts>
 using exactly_one_t = typename exactly_one<Predicate, Default, Ts...>::type;
 
 /// Defer the evaluation of type T until types Us are instantiated
-template <typename T, typename... /*Us*/> struct deferred_type { using type = T; };
-template <typename T, typename... Us> using deferred_t = typename deferred_type<T, Us...>::type;
+template <typename T, typename... /*Us*/>
+struct deferred_type {
+    using type = T;
+};
+template <typename T, typename... Us>
+using deferred_t = typename deferred_type<T, Us...>::type;
 
 /// Like is_base_of, but requires a strict base (i.e. `is_strict_base_of<T, T>::value == false`,
 /// unlike `std::is_base_of`)
-template <typename Base, typename Derived> using is_strict_base_of = bool_constant<
-    std::is_base_of<Base, Derived>::value && !std::is_same<Base, Derived>::value>;
-
-/// Like is_base_of, but also requires that the base type is accessible (i.e. that a Derived pointer
-/// can be converted to a Base pointer)
-/// For unions, `is_base_of<T, T>::value` is False, so we need to check `is_same` as well.
-template <typename Base, typename Derived> using is_accessible_base_of = bool_constant<
-    (std::is_same<Base, Derived>::value || std::is_base_of<Base, Derived>::value) && std::is_convertible<Derived *, Base *>::value>;
-
-template <template<typename...> class Base>
+template <typename Base, typename Derived>
+using is_strict_base_of
+    = bool_constant<std::is_base_of<Base, Derived>::value && !std::is_same<Base, Derived>::value>;
+
+/// Like is_base_of, but also requires that the base type is accessible (i.e. that a Derived
+/// pointer can be converted to a Base pointer) For unions, `is_base_of<T, T>::value` is False, so
+/// we need to check `is_same` as well.
+template <typename Base, typename Derived>
+using is_accessible_base_of
+    = bool_constant<(std::is_same<Base, Derived>::value || std::is_base_of<Base, Derived>::value)
+                    && std::is_convertible<Derived *, Base *>::value>;
+
+template <template <typename...> class Base>
 struct is_template_base_of_impl {
-    template <typename... Us> static std::true_type check(Base<Us...> *);
+    template <typename... Us>
+    static std::true_type check(Base<Us...> *);
     static std::false_type check(...);
 };
 
 /// Check if a template is the base of a type. For example:
 /// `is_template_base_of<Base, T>` is true if `struct T : Base<U> {}` where U can be anything
-template <template<typename...> class Base, typename T>
+template <template <typename...> class Base, typename T>
 #if !defined(_MSC_VER)
-using is_template_base_of = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T>*)nullptr));
+using is_template_base_of
+    = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr));
 #else // MSVC2015 has trouble with decltype in template aliases
-struct is_template_base_of : decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T>*)nullptr)) { };
+struct is_template_base_of
+    : decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T> *) nullptr)) {
+};
 #endif
 
 /// Check if T is an instantiation of the template `Class`. For example:
 /// `is_instantiation<shared_ptr, T>` is true if `T == shared_ptr<U>` where U can be anything.
-template <template<typename...> class Class, typename T>
-struct is_instantiation : std::false_type { };
-template <template<typename...> class Class, typename... Us>
-struct is_instantiation<Class, Class<Us...>> : std::true_type { };
+template <template <typename...> class Class, typename T>
+struct is_instantiation : std::false_type {};
+template <template <typename...> class Class, typename... Us>
+struct is_instantiation<Class, Class<Us...>> : std::true_type {};
 
 /// Check if T is std::shared_ptr<U> where U can be anything
-template <typename T> using is_shared_ptr = is_instantiation<std::shared_ptr, T>;
+template <typename T>
+using is_shared_ptr = is_instantiation<std::shared_ptr, T>;
 
 /// Check if T looks like an input iterator
-template <typename T, typename = void> struct is_input_iterator : std::false_type {};
+template <typename T, typename = void>
+struct is_input_iterator : std::false_type {};
 template <typename T>
-struct is_input_iterator<T, void_t<decltype(*std::declval<T &>()), decltype(++std::declval<T &>())>>
+struct is_input_iterator<T,
+                         void_t<decltype(*std::declval<T &>()), decltype(++std::declval<T &>())>>
     : std::true_type {};
 
-template <typename T> using is_function_pointer = bool_constant<
-    std::is_pointer<T>::value && std::is_function<typename std::remove_pointer<T>::type>::value>;
+template <typename T>
+using is_function_pointer
+    = bool_constant<std::is_pointer<T>::value
+                    && std::is_function<typename std::remove_pointer<T>::type>::value>;
 
-template <typename F> struct strip_function_object {
+template <typename F>
+struct strip_function_object {
     // If you are encountering an
     // 'error: name followed by "::" must be a class or namespace name'
     // with the Intel compiler and a noexcept function here,
@@ -917,34 +1021,35 @@ template <typename Function, typename F = remove_reference_t<Function>>
 using function_signature_t = conditional_t<
     std::is_function<F>::value,
     F,
-    typename conditional_t<
-        std::is_pointer<F>::value || std::is_member_pointer<F>::value,
-        std::remove_pointer<F>,
-        strip_function_object<F>
-    >::type
->;
+    typename conditional_t<std::is_pointer<F>::value || std::is_member_pointer<F>::value,
+                           std::remove_pointer<F>,
+                           strip_function_object<F>>::type>;
 
 /// Returns true if the type looks like a lambda: that is, isn't a function, pointer or member
 /// pointer.  Note that this can catch all sorts of other things, too; this is intended to be used
 /// in a place where passing a lambda makes sense.
-template <typename T> using is_lambda = satisfies_none_of<remove_reference_t<T>,
-        std::is_function, std::is_pointer, std::is_member_pointer>;
+template <typename T>
+using is_lambda = satisfies_none_of<remove_reference_t<T>,
+                                    std::is_function,
+                                    std::is_pointer,
+                                    std::is_member_pointer>;
 
 // [workaround(intel)] Internal error on fold expression
 /// Apply a function over each element of a parameter pack
 #if defined(__cpp_fold_expressions) && !defined(__INTEL_COMPILER)
 // Intel compiler produces an internal error on this fold expression (tested with ICC 19.0.2)
-#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
+#    define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
 #else
 using expand_side_effects = bool[];
-#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (void)pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
+#    define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN)                                                 \
+        (void) pybind11::detail::expand_side_effects { ((PATTERN), void(), false)..., false }
 #endif
 
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4275)
+#    pragma warning(push)
+#    pragma warning(disable : 4275)
 //     warning C4275: An exported class was derived from a class that wasn't exported.
 //     Can be ignored when derived from a STL class.
 #endif
@@ -956,14 +1061,15 @@ class PYBIND11_EXPORT_EXCEPTION builtin_exception : public std::runtime_error {
     virtual void set_error() const = 0;
 };
 #if defined(_MSC_VER)
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
-#define PYBIND11_RUNTIME_EXCEPTION(name, type) \
-    class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception { public: \
-        using builtin_exception::builtin_exception; \
-        name() : name("") { } \
-        void set_error() const override { PyErr_SetString(type, what()); } \
+#define PYBIND11_RUNTIME_EXCEPTION(name, type)                                                    \
+    class PYBIND11_EXPORT_EXCEPTION name : public builtin_exception {                             \
+    public:                                                                                       \
+        using builtin_exception::builtin_exception;                                               \
+        name() : name("") {}                                                                      \
+        void set_error() const override { PyErr_SetString(type, what()); }                        \
     };
 
 PYBIND11_RUNTIME_EXCEPTION(stop_iteration, PyExc_StopIteration)
@@ -979,10 +1085,15 @@ PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybin
                                                            /// casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
 
-[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
-[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const std::string &reason) { throw std::runtime_error(reason); }
+[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const char *reason) {
+    throw std::runtime_error(reason);
+}
+[[noreturn]] PYBIND11_NOINLINE void pybind11_fail(const std::string &reason) {
+    throw std::runtime_error(reason);
+}
 
-template <typename T, typename SFINAE = void> struct format_descriptor { };
+template <typename T, typename SFINAE = void>
+struct format_descriptor {};
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 // Returns the index of the given type in the type char array below, and in the list in numpy.h
@@ -990,25 +1101,38 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // complex float,double,long double.  Note that the long double types only participate when long
 // double is actually longer than double (it isn't under MSVC).
 // NB: not only the string below but also complex.h and numpy.h rely on this order.
-template <typename T, typename SFINAE = void> struct is_fmt_numeric { static constexpr bool value = false; };
-template <typename T> struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
+template <typename T, typename SFINAE = void>
+struct is_fmt_numeric {
+    static constexpr bool value = false;
+};
+template <typename T>
+struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
     static constexpr bool value = true;
-    static constexpr int index = std::is_same<T, bool>::value ? 0 : 1 + (
-        std::is_integral<T>::value ? detail::log2(sizeof(T))*2 + std::is_unsigned<T>::value : 8 + (
-        std::is_same<T, double>::value ? 1 : std::is_same<T, long double>::value ? 2 : 0));
+    static constexpr int index
+        = std::is_same<T, bool>::value
+              ? 0
+              : 1
+                    + (std::is_integral<T>::value
+                           ? detail::log2(sizeof(T)) * 2 + std::is_unsigned<T>::value
+                           : 8
+                                 + (std::is_same<T, double>::value        ? 1
+                                    : std::is_same<T, long double>::value ? 2
+                                                                          : 0));
 };
 PYBIND11_NAMESPACE_END(detail)
 
-template <typename T> struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
+template <typename T>
+struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
     static constexpr const char c = "?bBhHiIqQfdg"[detail::is_fmt_numeric<T>::index];
-    static constexpr const char value[2] = { c, '\0' };
+    static constexpr const char value[2] = {c, '\0'};
     static std::string format() { return std::string(1, c); }
 };
 
 #if !defined(PYBIND11_CPP17)
 
-template <typename T> constexpr const char format_descriptor<
-    T, detail::enable_if_t<std::is_arithmetic<T>::value>>::value[2];
+template <typename T>
+constexpr const char
+    format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>>::value[2];
 
 #endif
 
@@ -1020,7 +1144,10 @@ struct error_scope {
 };
 
 /// Dummy destructor wrapper that can be used to expose classes with a private destructor
-struct nodelete { template <typename T> void operator()(T*) { } };
+struct nodelete {
+    template <typename T>
+    void operator()(T *) {}
+};
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename... Args>
@@ -1029,22 +1156,27 @@ struct overload_cast_impl {
     constexpr overload_cast_impl() {}
 
     template <typename Return>
-    constexpr auto operator()(Return (*pf)(Args...)) const noexcept
-                              -> decltype(pf) { return pf; }
+    constexpr auto operator()(Return (*pf)(Args...)) const noexcept -> decltype(pf) {
+        return pf;
+    }
 
     template <typename Return, typename Class>
     constexpr auto operator()(Return (Class::*pmf)(Args...), std::false_type = {}) const noexcept
-                              -> decltype(pmf) { return pmf; }
+        -> decltype(pmf) {
+        return pmf;
+    }
 
     template <typename Return, typename Class>
     constexpr auto operator()(Return (Class::*pmf)(Args...) const, std::true_type) const noexcept
-                              -> decltype(pmf) { return pmf; }
+        -> decltype(pmf) {
+        return pmf;
+    }
 };
 PYBIND11_NAMESPACE_END(detail)
 
 // overload_cast requires variable templates: C++14
 #if defined(PYBIND11_CPP14)
-#define PYBIND11_OVERLOAD_CAST 1
+#    define PYBIND11_OVERLOAD_CAST 1
 /// Syntax sugar for resolving overloaded function pointers:
 ///  - regular: static_cast<Return (Class::*)(Arg0, Arg1, Arg2)>(&Class::func)
 ///  - sweet:   overload_cast<Arg0, Arg1, Arg2>(&Class::func)
@@ -1059,7 +1191,8 @@ static constexpr detail::overload_cast_impl<Args...> overload_cast = {};
 static constexpr auto const_ = std::true_type{};
 
 #if !defined(PYBIND11_CPP14) // no overload_cast: providing something that static_assert-fails:
-template <typename... Args> struct overload_cast {
+template <typename... Args>
+struct overload_cast {
     static_assert(detail::deferred_t<std::false_type, Args...>::value,
                   "pybind11::overload_cast<...> requires compiling in C++14 mode");
 };
@@ -1073,27 +1206,31 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename T>
 class any_container {
     std::vector<T> v;
+
 public:
     any_container() = default;
 
     // Can construct from a pair of iterators
     template <typename It, typename = enable_if_t<is_input_iterator<It>::value>>
-    any_container(It first, It last) : v(first, last) { }
+    any_container(It first, It last) : v(first, last) {}
 
     // Implicit conversion constructor from any arbitrary container type
     // with values convertible to T
-    template <typename Container, typename = enable_if_t<std::is_convertible<decltype(*std::begin(std::declval<const Container &>())), T>::value>>
+    template <typename Container,
+              typename = enable_if_t<
+                  std::is_convertible<decltype(*std::begin(std::declval<const Container &>())),
+                                      T>::value>>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    any_container(const Container &c) : any_container(std::begin(c), std::end(c)) { }
+    any_container(const Container &c) : any_container(std::begin(c), std::end(c)) {}
 
     // initializer_list's aren't deducible, so don't get matched by the above template;
     // we need this to explicitly allow implicit conversion from one:
     template <typename TIn, typename = enable_if_t<std::is_convertible<TIn, T>::value>>
-    any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) { }
+    any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) {}
 
     // Avoid copying if given an rvalue vector of the correct type.
     // NOLINTNEXTLINE(google-explicit-constructor)
-    any_container(std::vector<T> &&v) : v(std::move(v)) { }
+    any_container(std::vector<T> &&v) : v(std::move(v)) {}
 
     // Moves the vector out of an rvalue any_container
     // NOLINTNEXTLINE(google-explicit-constructor)
@@ -1109,10 +1246,11 @@ class any_container {
 };
 
 // Forward-declaration; see detail/class.h
-std::string get_fully_qualified_tp_name(PyTypeObject*);
+std::string get_fully_qualified_tp_name(PyTypeObject *);
 
 template <typename T>
-inline static std::shared_ptr<T> try_get_shared_from_this(std::enable_shared_from_this<T> *holder_value_ptr) {
+inline static std::shared_ptr<T>
+try_get_shared_from_this(std::enable_shared_from_this<T> *holder_value_ptr) {
 // Pre C++17, this code path exploits undefined behavior, but is known to work on many platforms.
 // Use at your own risk!
 // See also https://en.cppreference.com/w/cpp/memory/enable_shared_from_this, and in particular
@@ -1122,8 +1260,7 @@ inline static std::shared_ptr<T> try_get_shared_from_this(std::enable_shared_fro
 #else
     try {
         return holder_value_ptr->shared_from_this();
-    }
-    catch (const std::bad_weak_ptr &) {
+    } catch (const std::bad_weak_ptr &) {
         return nullptr;
     }
 #endif
@@ -1134,7 +1271,9 @@ template <typename... Args>
 #if defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER < 1920 // MSVC 2017
 constexpr
 #endif
-inline void silence_unused_warnings(Args &&...) {}
+    inline void
+    silence_unused_warnings(Args &&...) {
+}
 
 // MSVC warning C4100: Unreferenced formal parameter
 #if defined(_MSC_VER) && _MSC_VER <= 1916
@@ -1146,7 +1285,7 @@ inline void silence_unused_warnings(Args &&...) {}
 
 // GCC -Wunused-but-set-parameter  All GCC versions (as of July 2021).
 #if defined(__GNUG__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)                   \
+#    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)                       \
         detail::silence_unused_warnings(__VA_ARGS__)
 #else
 #    define PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(...)
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 0f93e06b21..e7a5e2c145 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -15,9 +15,9 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if !defined(_MSC_VER)
-#  define PYBIND11_DESCR_CONSTEXPR static constexpr
+#    define PYBIND11_DESCR_CONSTEXPR static constexpr
 #else
-#  define PYBIND11_DESCR_CONSTEXPR const
+#    define PYBIND11_DESCR_CONSTEXPR const
 #endif
 
 /* Concatenate type signatures at compile time */
@@ -27,14 +27,14 @@ struct descr {
 
     constexpr descr() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
-    constexpr descr(char const (&s)[N+1]) : descr(s, make_index_sequence<N>()) { }
+    constexpr descr(char const (&s)[N + 1]) : descr(s, make_index_sequence<N>()) {}
 
     template <size_t... Is>
-    constexpr descr(char const (&s)[N+1], index_sequence<Is...>) : text{s[Is]..., '\0'} { }
+    constexpr descr(char const (&s)[N + 1], index_sequence<Is...>) : text{s[Is]..., '\0'} {}
 
     template <typename... Chars>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} { }
+    constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} {}
 
     static constexpr std::array<const std::type_info *, sizeof...(Ts) + 1> types() {
         return {{&typeid(Ts)..., nullptr}};
@@ -42,81 +42,106 @@ struct descr {
 };
 
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2, size_t... Is1, size_t... Is2>
-constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b,
-                                                   index_sequence<Is1...>, index_sequence<Is2...>) {
+constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a,
+                                                   const descr<N2, Ts2...> &b,
+                                                   index_sequence<Is1...>,
+                                                   index_sequence<Is2...>) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(b);
     return {a.text[Is1]..., b.text[Is2]...};
 }
 
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2>
-constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b) {
+constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a,
+                                                   const descr<N2, Ts2...> &b) {
     return plus_impl(a, b, make_index_sequence<N1>(), make_index_sequence<N2>());
 }
 
 template <size_t N>
-constexpr descr<N - 1> const_name(char const(&text)[N]) { return descr<N - 1>(text); }
-constexpr descr<0> const_name(char const(&)[1]) { return {}; }
+constexpr descr<N - 1> const_name(char const (&text)[N]) {
+    return descr<N - 1>(text);
+}
+constexpr descr<0> const_name(char const (&)[1]) { return {}; }
 
-template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
-template <size_t...Digits> struct int_to_str<0, Digits...> {
+template <size_t Rem, size_t... Digits>
+struct int_to_str : int_to_str<Rem / 10, Rem % 10, Digits...> {};
+template <size_t... Digits>
+struct int_to_str<0, Digits...> {
     // WARNING: This only works with C++17 or higher.
     static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...);
 };
 
 // Ternary description (like std::conditional)
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> const_name(char const(&text1)[N1], char const(&)[N2]) {
+constexpr enable_if_t<B, descr<N1 - 1>> const_name(char const (&text1)[N1], char const (&)[N2]) {
     return const_name(text1);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> const_name(char const(&)[N1], char const(&text2)[N2]) {
+constexpr enable_if_t<!B, descr<N2 - 1>> const_name(char const (&)[N1], char const (&text2)[N2]) {
     return const_name(text2);
 }
 
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<B, T1> const_name(const T1 &d, const T2 &) { return d; }
+constexpr enable_if_t<B, T1> const_name(const T1 &d, const T2 &) {
+    return d;
+}
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<!B, T2> const_name(const T1 &, const T2 &d) { return d; }
+constexpr enable_if_t<!B, T2> const_name(const T1 &, const T2 &d) {
+    return d;
+}
 
 template <size_t Size>
 auto constexpr const_name() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
     return int_to_str<Size / 10, Size % 10>::digits;
 }
 
-template <typename Type> constexpr descr<1, Type> const_name() { return {'%'}; }
+template <typename Type>
+constexpr descr<1, Type> const_name() {
+    return {'%'};
+}
 
 // If "_" is defined as a macro, py::detail::_ cannot be provided.
 // It is therefore best to use py::detail::const_name universally.
 // This block is for backward compatibility only.
 // (The const_name code is repeated to avoid introducing a "_" #define ourselves.)
 #ifndef _
-#define PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
+#    define PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
 template <size_t N>
-constexpr descr<N-1> _(char const(&text)[N]) { return const_name<N>(text); }
+constexpr descr<N - 1> _(char const (&text)[N]) {
+    return const_name<N>(text);
+}
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> _(char const(&text1)[N1], char const(&text2)[N2]) {
-    return const_name<B,N1,N2>(text1, text2);
+constexpr enable_if_t<B, descr<N1 - 1>> _(char const (&text1)[N1], char const (&text2)[N2]) {
+    return const_name<B, N1, N2>(text1, text2);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> _(char const(&text1)[N1], char const(&text2)[N2]) {
-    return const_name<B,N1,N2>(text1, text2);
+constexpr enable_if_t<!B, descr<N2 - 1>> _(char const (&text1)[N1], char const (&text2)[N2]) {
+    return const_name<B, N1, N2>(text1, text2);
 }
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<B, T1> _(const T1 &d1, const T2 &d2) { return const_name<B,T1,T2>(d1, d2); }
+constexpr enable_if_t<B, T1> _(const T1 &d1, const T2 &d2) {
+    return const_name<B, T1, T2>(d1, d2);
+}
 template <bool B, typename T1, typename T2>
-constexpr enable_if_t<!B, T2> _(const T1 &d1, const T2 &d2) { return const_name<B,T1,T2>(d1, d2); }
+constexpr enable_if_t<!B, T2> _(const T1 &d1, const T2 &d2) {
+    return const_name<B, T1, T2>(d1, d2);
+}
 
 template <size_t Size>
 auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
     return const_name<Size>();
 }
-template <typename Type> constexpr descr<1, Type> _() { return const_name<Type>(); }
-#endif  // #ifndef _
+template <typename Type>
+constexpr descr<1, Type> _() {
+    return const_name<Type>();
+}
+#endif // #ifndef _
 
 constexpr descr<0> concat() { return {}; }
 
 template <size_t N, typename... Ts>
-constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) { return descr; }
+constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) {
+    return descr;
+}
 
 template <size_t N, typename... Ts, typename... Args>
 constexpr auto concat(const descr<N, Ts...> &d, const Args &...args)
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index ba408d76cc..e1e665a69b 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -22,7 +22,8 @@ class type_caster<value_and_holder> {
         return true;
     }
 
-    template <typename> using cast_op_type = value_and_holder &;
+    template <typename>
+    using cast_op_type = value_and_holder &;
     explicit operator value_and_holder &() { return *value; }
     static constexpr auto name = const_name<value_and_holder>();
 
@@ -39,11 +40,15 @@ inline void no_nullptr(void *ptr) {
 }
 
 // Implementing functions for all forms of py::init<...> and py::init(...)
-template <typename Class> using Cpp = typename Class::type;
-template <typename Class> using Alias = typename Class::type_alias;
-template <typename Class> using Holder = typename Class::holder_type;
+template <typename Class>
+using Cpp = typename Class::type;
+template <typename Class>
+using Alias = typename Class::type_alias;
+template <typename Class>
+using Holder = typename Class::holder_type;
 
-template <typename Class> using is_alias_constructible = std::is_constructible<Alias<Class>, Cpp<Class> &&>;
+template <typename Class>
+using is_alias_constructible = std::is_constructible<Alias<Class>, Cpp<Class> &&>;
 
 // Takes a Cpp pointer and returns true if it actually is a polymorphic Alias instance.
 template <typename Class, enable_if_t<Class::has_alias, int> = 0>
@@ -52,17 +57,27 @@ bool is_alias(Cpp<Class> *ptr) {
 }
 // Failing fallback version of the above for a no-alias class (always returns false)
 template <typename /*Class*/>
-constexpr bool is_alias(void *) { return false; }
+constexpr bool is_alias(void *) {
+    return false;
+}
 
 // Constructs and returns a new object; if the given arguments don't map to a constructor, we fall
 // back to brace aggregate initiailization so that for aggregate initialization can be used with
 // py::init, e.g.  `py::init<int, int>` to initialize a `struct T { int a; int b; }`.  For
 // non-aggregate types, we need to use an ordinary T(...) constructor (invoking as `T{...}` usually
 // works, but will not do the expected thing when `T` has an `initializer_list<T>` constructor).
-template <typename Class, typename... Args, detail::enable_if_t<std::is_constructible<Class, Args...>::value, int> = 0>
-inline Class *construct_or_initialize(Args &&...args) { return new Class(std::forward<Args>(args)...); }
-template <typename Class, typename... Args, detail::enable_if_t<!std::is_constructible<Class, Args...>::value, int> = 0>
-inline Class *construct_or_initialize(Args &&...args) { return new Class{std::forward<Args>(args)...}; }
+template <typename Class,
+          typename... Args,
+          detail::enable_if_t<std::is_constructible<Class, Args...>::value, int> = 0>
+inline Class *construct_or_initialize(Args &&...args) {
+    return new Class(std::forward<Args>(args)...);
+}
+template <typename Class,
+          typename... Args,
+          detail::enable_if_t<!std::is_constructible<Class, Args...>::value, int> = 0>
+inline Class *construct_or_initialize(Args &&...args) {
+    return new Class{std::forward<Args>(args)...};
+}
 
 // Attempts to constructs an alias using a `Alias(Cpp &&)` constructor.  This allows types with
 // an alias to provide only a single Cpp factory function as long as the Alias can be
@@ -71,12 +86,14 @@ inline Class *construct_or_initialize(Args &&...args) { return new Class{std::fo
 // inherit all the base class constructors.
 template <typename Class>
 void construct_alias_from_cpp(std::true_type /*is_alias_constructible*/,
-                              value_and_holder &v_h, Cpp<Class> &&base) {
+                              value_and_holder &v_h,
+                              Cpp<Class> &&base) {
     v_h.value_ptr() = new Alias<Class>(std::move(base));
 }
 template <typename Class>
 [[noreturn]] void construct_alias_from_cpp(std::false_type /*!is_alias_constructible*/,
-                                           value_and_holder &, Cpp<Class> &&) {
+                                           value_and_holder &,
+                                           Cpp<Class> &&) {
     throw type_error("pybind11::init(): unable to convert returned instance to required "
                      "alias class: no `Alias<Class>(Class &&)` constructor available");
 }
@@ -86,8 +103,8 @@ template <typename Class>
 template <typename Class>
 void construct(...) {
     static_assert(!std::is_same<Class, Class>::value /* always false */,
-            "pybind11::init(): init function must return a compatible pointer, "
-            "holder, or value");
+                  "pybind11::init(): init function must return a compatible pointer, "
+                  "holder, or value");
 }
 
 // Pointer return v1: the factory function returns a class pointer for a registered class.
@@ -108,7 +125,7 @@ void construct(value_and_holder &v_h, Cpp<Class> *ptr, bool need_alias) {
         // the holder and destruction happens when we leave the C++ scope, and the holder
         // class gets to handle the destruction however it likes.
         v_h.value_ptr() = ptr;
-        v_h.set_instance_registered(true); // To prevent init_instance from registering it
+        v_h.set_instance_registered(true);          // To prevent init_instance from registering it
         v_h.type->init_instance(v_h.inst, nullptr); // Set up the holder
         Holder<Class> temp_holder(std::move(v_h.holder<Holder<Class>>())); // Steal the holder
         v_h.type->dealloc(v_h); // Destroys the moved-out holder remains, resets value ptr to null
@@ -131,7 +148,8 @@ void construct(value_and_holder &v_h, Alias<Class> *alias_ptr, bool) {
 
 // Holder return: copy its pointer, and move or copy the returned holder into the new instance's
 // holder.  This also handles types like std::shared_ptr<T> and std::unique_ptr<T> where T is a
-// derived type (through those holder's implicit conversion from derived class holder constructors).
+// derived type (through those holder's implicit conversion from derived class holder
+// constructors).
 template <typename Class>
 void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
@@ -155,7 +173,7 @@ template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
-        "pybind11::init() return-by-value factory function requires a movable class");
+                  "pybind11::init() return-by-value factory function requires a movable class");
     if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias) {
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
     } else {
@@ -168,7 +186,8 @@ void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
 // cases where Alias initialization is always desired.
 template <typename Class>
 void construct(value_and_holder &v_h, Alias<Class> &&result, bool) {
-    static_assert(std::is_move_constructible<Alias<Class>>::value,
+    static_assert(
+        std::is_move_constructible<Alias<Class>>::value,
         "pybind11::init() return-by-alias-value factory function requires a movable alias class");
     v_h.value_ptr() = new Alias<Class>(std::move(result));
 }
@@ -177,16 +196,21 @@ void construct(value_and_holder &v_h, Alias<Class> &&result, bool) {
 template <typename... Args>
 struct constructor {
     template <typename Class, typename... Extra, enable_if_t<!Class::has_alias, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+    static void execute(Class &cl, const Extra &...extra) {
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 
-    template <typename Class, typename... Extra,
-              enable_if_t<Class::has_alias &&
-                          std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
+    template <typename Class,
+              typename... Extra,
+              enable_if_t<Class::has_alias && std::is_constructible<Cpp<Class>, Args...>::value,
+                          int> = 0>
+    static void execute(Class &cl, const Extra &...extra) {
         cl.def(
             "__init__",
             [](value_and_holder &v_h, Args... args) {
@@ -202,30 +226,46 @@ struct constructor {
             extra...);
     }
 
-    template <typename Class, typename... Extra,
-              enable_if_t<Class::has_alias &&
-                          !std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+    template <typename Class,
+              typename... Extra,
+              enable_if_t<Class::has_alias && !std::is_constructible<Cpp<Class>, Args...>::value,
+                          int> = 0>
+    static void execute(Class &cl, const Extra &...extra) {
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                v_h.value_ptr()
+                    = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
 // Implementing class for py::init_alias<...>()
-template <typename... Args> struct alias_constructor {
-    template <typename Class, typename... Extra,
-              enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value, int> = 0>
-    static void execute(Class &cl, const Extra&... extra) {
-        cl.def("__init__", [](value_and_holder &v_h, Args... args) {
-            v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
-        }, is_new_style_constructor(), extra...);
+template <typename... Args>
+struct alias_constructor {
+    template <typename Class,
+              typename... Extra,
+              enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value,
+                          int> = 0>
+    static void execute(Class &cl, const Extra &...extra) {
+        cl.def(
+            "__init__",
+            [](value_and_holder &v_h, Args... args) {
+                v_h.value_ptr()
+                    = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
 // Implementation class for py::init(Func) and py::init(Func, AliasFunc)
-template <typename CFunc, typename AFunc = void_type (*)(),
-          typename = function_signature_t<CFunc>, typename = function_signature_t<AFunc>>
+template <typename CFunc,
+          typename AFunc = void_type (*)(),
+          typename = function_signature_t<CFunc>,
+          typename = function_signature_t<AFunc>>
 struct factory;
 
 // Specialization for py::init(Func)
@@ -243,22 +283,32 @@ struct factory<Func, void_type (*)(), Return(Args...)> {
     // instance, or the alias needs to be constructible from a `Class &&` argument.
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) && {
-        #if defined(PYBIND11_CPP14)
-        cl.def("__init__", [func = std::move(class_factory)]
-        #else
+#if defined(PYBIND11_CPP14)
+        cl.def(
+            "__init__",
+            [func = std::move(class_factory)]
+#else
         auto &func = class_factory;
-        cl.def("__init__", [func]
-        #endif
-        (value_and_holder &v_h, Args... args) {
-            construct<Class>(v_h, func(std::forward<Args>(args)...),
-                             Py_TYPE(v_h.inst) != v_h.type->type);
-        }, is_new_style_constructor(), extra...);
+        cl.def(
+            "__init__",
+            [func]
+#endif
+            (value_and_holder &v_h, Args... args) {
+                construct<Class>(
+                    v_h, func(std::forward<Args>(args)...), Py_TYPE(v_h.inst) != v_h.type->type);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
 // Specialization for py::init(Func, AliasFunc)
-template <typename CFunc, typename AFunc,
-          typename CReturn, typename... CArgs, typename AReturn, typename... AArgs>
+template <typename CFunc,
+          typename AFunc,
+          typename CReturn,
+          typename... CArgs,
+          typename AReturn,
+          typename... AArgs>
 struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
     static_assert(sizeof...(CArgs) == sizeof...(AArgs),
                   "pybind11::init(class_factory, alias_factory): class and alias factories "
@@ -271,30 +321,37 @@ struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
     remove_reference_t<AFunc> alias_factory;
 
     factory(CFunc &&c, AFunc &&a)
-        : class_factory(std::forward<CFunc>(c)), alias_factory(std::forward<AFunc>(a)) { }
+        : class_factory(std::forward<CFunc>(c)), alias_factory(std::forward<AFunc>(a)) {}
 
     // The class factory is called when the `self` type passed to `__init__` is the direct
     // class (i.e. not inherited), the alias factory when `self` is a Python-side subtype.
     template <typename Class, typename... Extra>
-    void execute(Class &cl, const Extra&... extra) && {
-        static_assert(Class::has_alias, "The two-argument version of `py::init()` can "
-                                        "only be used if the class has an alias");
-        #if defined(PYBIND11_CPP14)
-        cl.def("__init__", [class_func = std::move(class_factory), alias_func = std::move(alias_factory)]
-        #else
+    void execute(Class &cl, const Extra &...extra) && {
+        static_assert(Class::has_alias,
+                      "The two-argument version of `py::init()` can "
+                      "only be used if the class has an alias");
+#if defined(PYBIND11_CPP14)
+        cl.def(
+            "__init__",
+            [class_func = std::move(class_factory), alias_func = std::move(alias_factory)]
+#else
         auto &class_func = class_factory;
         auto &alias_func = alias_factory;
-        cl.def("__init__", [class_func, alias_func]
-        #endif
-        (value_and_holder &v_h, CArgs... args) {
-            if (Py_TYPE(v_h.inst) == v_h.type->type) {
-                // If the instance type equals the registered type we don't have inheritance, so
-                // don't need the alias and can construct using the class function:
-                construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
-            } else {
-                construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
-            }
-        }, is_new_style_constructor(), extra...);
+        cl.def(
+            "__init__",
+            [class_func, alias_func]
+#endif
+            (value_and_holder &v_h, CArgs... args) {
+                if (Py_TYPE(v_h.inst) == v_h.type->type) {
+                    // If the instance type equals the registered type we don't have inheritance,
+                    // so don't need the alias and can construct using the class function:
+                    construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
+                } else {
+                    construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
+                }
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
@@ -305,7 +362,9 @@ void setstate(value_and_holder &v_h, T &&result, bool need_alias) {
 }
 
 /// Set both the C++ and Python states
-template <typename Class, typename T, typename O,
+template <typename Class,
+          typename T,
+          typename O,
           enable_if_t<std::is_convertible<O, handle>::value, int> = 0>
 void setstate(value_and_holder &v_h, std::pair<T, O> &&result, bool need_alias) {
     construct<Class>(v_h, std::move(result.first), need_alias);
@@ -319,12 +378,18 @@ void setstate(value_and_holder &v_h, std::pair<T, O> &&result, bool need_alias)
 }
 
 /// Implementation for py::pickle(GetState, SetState)
-template <typename Get, typename Set,
-          typename = function_signature_t<Get>, typename = function_signature_t<Set>>
+template <typename Get,
+          typename Set,
+          typename = function_signature_t<Get>,
+          typename = function_signature_t<Set>>
 struct pickle_factory;
 
-template <typename Get, typename Set,
-          typename RetState, typename Self, typename NewInstance, typename ArgState>
+template <typename Get,
+          typename Set,
+          typename RetState,
+          typename Self,
+          typename NewInstance,
+          typename ArgState>
 struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
     static_assert(std::is_same<intrinsic_t<RetState>, intrinsic_t<ArgState>>::value,
                   "The type returned by `__getstate__` must be the same "
@@ -333,23 +398,28 @@ struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
     remove_reference_t<Get> get;
     remove_reference_t<Set> set;
 
-    pickle_factory(Get get, Set set)
-        : get(std::forward<Get>(get)), set(std::forward<Set>(set)) { }
+    pickle_factory(Get get, Set set) : get(std::forward<Get>(get)), set(std::forward<Set>(set)) {}
 
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) && {
         cl.def("__getstate__", std::move(get));
 
 #if defined(PYBIND11_CPP14)
-        cl.def("__setstate__", [func = std::move(set)]
+        cl.def(
+            "__setstate__",
+            [func = std::move(set)]
 #else
         auto &func = set;
-        cl.def("__setstate__", [func]
+        cl.def(
+            "__setstate__",
+            [func]
 #endif
-        (value_and_holder &v_h, ArgState state) {
-            setstate<Class>(v_h, func(std::forward<ArgState>(state)),
-                            Py_TYPE(v_h.inst) != v_h.type->type);
-        }, is_new_style_constructor(), extra...);
+            (value_and_holder &v_h, ArgState state) {
+                setstate<Class>(
+                    v_h, func(std::forward<ArgState>(state)), Py_TYPE(v_h.inst) != v_h.type->type);
+            },
+            is_new_style_constructor(),
+            extra...);
     }
 };
 
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index bf72cb30f3..a3816a74a0 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "../pytypes.h"
+
 #include <exception>
 
 /// Tracks the `internals` and `type_info` ABI version independent of the main library version.
@@ -136,7 +137,7 @@ template <typename value_type>
 using type_map = std::unordered_map<std::type_index, value_type, type_hash, type_equal_to>;
 
 struct override_hash {
-    inline size_t operator()(const std::pair<const PyObject *, std::string>& v) const {
+    inline size_t operator()(const std::pair<const PyObject *, std::string> &v) const {
         size_t value = std::hash<const void *>()(v.first);
         value ^= std::hash<std::string>()(v.second);
         return value;
@@ -151,8 +152,9 @@ struct internals {
     type_map<type_info *> registered_types_cpp;
     // PyTypeObject* -> base type_info(s)
     std::unordered_map<PyTypeObject *, std::vector<type_info *>> registered_types_py;
-    std::unordered_multimap<const void *, instance*> registered_instances; // void * -> instance*
-    std::unordered_set<std::pair<const PyObject *, std::string>, override_hash> inactive_override_cache;
+    std::unordered_multimap<const void *, instance *> registered_instances; // void * -> instance*
+    std::unordered_set<std::pair<const PyObject *, std::string>, override_hash>
+        inactive_override_cache;
     type_map<std::vector<bool (*)(PyObject *, void *&)>> direct_conversions;
     std::unordered_map<const PyObject *, std::vector<PyObject *>> patients;
     std::forward_list<ExceptionTranslator> registered_exception_translators;
@@ -198,8 +200,8 @@ struct type_info {
     void *(*operator_new)(size_t);
     void (*init_instance)(instance *, holder_erased);
     void (*dealloc)(value_and_holder &v_h);
-    std::vector<PyObject *(*)(PyObject *, PyTypeObject *)> implicit_conversions;
-    std::vector<std::pair<const std::type_info *, void *(*)(void *)>> implicit_casts;
+    std::vector<PyObject *(*) (PyObject *, PyTypeObject *)> implicit_conversions;
+    std::vector<std::pair<const std::type_info *, void *(*) (void *)>> implicit_casts;
     std::vector<bool (*)(PyObject *, void *&)> *direct_conversions;
     buffer_info *(*get_buffer)(PyObject *, void *) = nullptr;
     void *get_buffer_data = nullptr;
@@ -221,67 +223,71 @@ struct type_info {
 
 /// On MSVC, debug and release builds are not ABI-compatible!
 #if defined(_MSC_VER) && defined(_DEBUG)
-#  define PYBIND11_BUILD_TYPE "_debug"
+#    define PYBIND11_BUILD_TYPE "_debug"
 #else
-#  define PYBIND11_BUILD_TYPE ""
+#    define PYBIND11_BUILD_TYPE ""
 #endif
 
 /// Let's assume that different compilers are ABI-incompatible.
 /// A user can manually set this string if they know their
 /// compiler is compatible.
 #ifndef PYBIND11_COMPILER_TYPE
-#  if defined(_MSC_VER)
-#    define PYBIND11_COMPILER_TYPE "_msvc"
-#  elif defined(__INTEL_COMPILER)
-#    define PYBIND11_COMPILER_TYPE "_icc"
-#  elif defined(__clang__)
-#    define PYBIND11_COMPILER_TYPE "_clang"
-#  elif defined(__PGI)
-#    define PYBIND11_COMPILER_TYPE "_pgi"
-#  elif defined(__MINGW32__)
-#    define PYBIND11_COMPILER_TYPE "_mingw"
-#  elif defined(__CYGWIN__)
-#    define PYBIND11_COMPILER_TYPE "_gcc_cygwin"
-#  elif defined(__GNUC__)
-#    define PYBIND11_COMPILER_TYPE "_gcc"
-#  else
-#    define PYBIND11_COMPILER_TYPE "_unknown"
-#  endif
+#    if defined(_MSC_VER)
+#        define PYBIND11_COMPILER_TYPE "_msvc"
+#    elif defined(__INTEL_COMPILER)
+#        define PYBIND11_COMPILER_TYPE "_icc"
+#    elif defined(__clang__)
+#        define PYBIND11_COMPILER_TYPE "_clang"
+#    elif defined(__PGI)
+#        define PYBIND11_COMPILER_TYPE "_pgi"
+#    elif defined(__MINGW32__)
+#        define PYBIND11_COMPILER_TYPE "_mingw"
+#    elif defined(__CYGWIN__)
+#        define PYBIND11_COMPILER_TYPE "_gcc_cygwin"
+#    elif defined(__GNUC__)
+#        define PYBIND11_COMPILER_TYPE "_gcc"
+#    else
+#        define PYBIND11_COMPILER_TYPE "_unknown"
+#    endif
 #endif
 
 /// Also standard libs
 #ifndef PYBIND11_STDLIB
-#  if defined(_LIBCPP_VERSION)
-#    define PYBIND11_STDLIB "_libcpp"
-#  elif defined(__GLIBCXX__) || defined(__GLIBCPP__)
-#    define PYBIND11_STDLIB "_libstdcpp"
-#  else
-#    define PYBIND11_STDLIB ""
-#  endif
+#    if defined(_LIBCPP_VERSION)
+#        define PYBIND11_STDLIB "_libcpp"
+#    elif defined(__GLIBCXX__) || defined(__GLIBCPP__)
+#        define PYBIND11_STDLIB "_libstdcpp"
+#    else
+#        define PYBIND11_STDLIB ""
+#    endif
 #endif
 
 /// On Linux/OSX, changes in __GXX_ABI_VERSION__ indicate ABI incompatibility.
 #ifndef PYBIND11_BUILD_ABI
-#  if defined(__GXX_ABI_VERSION)
-#    define PYBIND11_BUILD_ABI "_cxxabi" PYBIND11_TOSTRING(__GXX_ABI_VERSION)
-#  else
-#    define PYBIND11_BUILD_ABI ""
-#  endif
+#    if defined(__GXX_ABI_VERSION)
+#        define PYBIND11_BUILD_ABI "_cxxabi" PYBIND11_TOSTRING(__GXX_ABI_VERSION)
+#    else
+#        define PYBIND11_BUILD_ABI ""
+#    endif
 #endif
 
 #ifndef PYBIND11_INTERNALS_KIND
-#  if defined(WITH_THREAD)
-#    define PYBIND11_INTERNALS_KIND ""
-#  else
-#    define PYBIND11_INTERNALS_KIND "_without_thread"
-#  endif
+#    if defined(WITH_THREAD)
+#        define PYBIND11_INTERNALS_KIND ""
+#    else
+#        define PYBIND11_INTERNALS_KIND "_without_thread"
+#    endif
 #endif
 
-#define PYBIND11_INTERNALS_ID "__pybind11_internals_v" \
-    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI PYBIND11_BUILD_TYPE "__"
+#define PYBIND11_INTERNALS_ID                                                                     \
+    "__pybind11_internals_v" PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION)                        \
+        PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI         \
+            PYBIND11_BUILD_TYPE "__"
 
-#define PYBIND11_MODULE_LOCAL_ID "__pybind11_module_local_v" \
-    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI PYBIND11_BUILD_TYPE "__"
+#define PYBIND11_MODULE_LOCAL_ID                                                                  \
+    "__pybind11_module_local_v" PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION)                     \
+        PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI         \
+            PYBIND11_BUILD_TYPE "__"
 
 /// Each module locally stores a pointer to the `internals` data. The data
 /// itself is shared among modules with the same `PYBIND11_INTERNALS_ID`.
@@ -398,8 +404,12 @@ inline void translate_local_exception(std::exception_ptr p) {
         if (p) {
             std::rethrow_exception(p);
         }
-    } catch (error_already_set &e)       { e.restore();   return;
-    } catch (const builtin_exception &e) { e.set_error(); return;
+    } catch (error_already_set &e) {
+        e.restore();
+        return;
+    } catch (const builtin_exception &e) {
+        e.set_error();
+        return;
     }
 }
 #endif
@@ -414,7 +424,7 @@ PYBIND11_NOINLINE internals &get_internals() {
     // Ensure that the GIL is held since we will need to make Python calls.
     // Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
     struct gil_scoped_acquire_local {
-        gil_scoped_acquire_local() : state (PyGILState_Ensure()) {}
+        gil_scoped_acquire_local() : state(PyGILState_Ensure()) {}
         ~gil_scoped_acquire_local() { PyGILState_Release(state); }
         const PyGILState_STATE state;
     } gil;
@@ -514,11 +524,10 @@ struct local_internals {
 
 /// Works like `get_internals`, but for things which are locally registered.
 inline local_internals &get_local_internals() {
-  static local_internals locals;
-  return locals;
+    static local_internals locals;
+    return locals;
 }
 
-
 /// Constructs a std::string with the given arguments, stores it in `internals`, and returns its
 /// `c_str()`.  Such strings objects have a long storage duration -- the internal strings are only
 /// cleared when the program exits or after interpreter shutdown (when embedding), and so are
@@ -550,7 +559,7 @@ PYBIND11_NOINLINE void *set_shared_data(const std::string &name, void *data) {
 /// Returns a typed reference to a shared data entry (by using `get_shared_data()`) if
 /// such entry exists. Otherwise, a new object of default-constructible type `T` is
 /// added to the shared data under the given name and a reference to it is returned.
-template<typename T>
+template <typename T>
 T &get_or_create_shared_data(const std::string &name) {
     auto &internals = detail::get_internals();
     auto it = internals.shared_data.find(name);
diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h
index cabce4dd4f..5e29c146d4 100644
--- a/include/pybind11/detail/type_caster_base.h
+++ b/include/pybind11/detail/type_caster_base.h
@@ -14,6 +14,7 @@
 #include "descr.h"
 #include "internals.h"
 #include "typeid.h"
+
 #include <cstdint>
 #include <iterator>
 #include <new>
@@ -32,7 +33,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// Adding a patient will keep it alive up until the enclosing function returns.
 class loader_life_support {
 private:
-    loader_life_support* parent = nullptr;
+    loader_life_support *parent = nullptr;
     std::unordered_set<PyObject *> keep_alive;
 
 #if defined(WITH_THREAD)
@@ -98,7 +99,8 @@ class loader_life_support {
 // Gets the cache entry for the given type, creating it if necessary.  The return value is the pair
 // returned by emplace, i.e. an iterator for the entry and a bool set to `true` if the entry was
 // just created.
-inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type);
+inline std::pair<decltype(internals::registered_types_py)::iterator, bool>
+all_type_info_get_cache(PyTypeObject *type);
 
 // Populates a just-created cache entry.
 PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_info *> &bases) {
@@ -119,23 +121,25 @@ PYBIND11_NOINLINE void all_type_info_populate(PyTypeObject *t, std::vector<type_
         auto it = type_dict.find(type);
         if (it != type_dict.end()) {
             // We found a cache entry for it, so it's either pybind-registered or has pre-computed
-            // pybind bases, but we have to make sure we haven't already seen the type(s) before: we
-            // want to follow Python/virtual C++ rules that there should only be one instance of a
-            // common base.
+            // pybind bases, but we have to make sure we haven't already seen the type(s) before:
+            // we want to follow Python/virtual C++ rules that there should only be one instance of
+            // a common base.
             for (auto *tinfo : it->second) {
                 // NB: Could use a second set here, rather than doing a linear search, but since
                 // having a large number of immediate pybind11-registered types seems fairly
                 // unlikely, that probably isn't worthwhile.
                 bool found = false;
                 for (auto *known : bases) {
-                    if (known == tinfo) { found = true; break; }
+                    if (known == tinfo) {
+                        found = true;
+                        break;
+                    }
                 }
                 if (!found) {
                     bases.push_back(tinfo);
                 }
             }
-        }
-        else if (type->tp_bases) {
+        } else if (type->tp_bases) {
             // It's some python type, so keep follow its bases classes to look for one or more
             // registered types
             if (i + 1 == check.size()) {
@@ -177,7 +181,7 @@ inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type)
  * ancestors are pybind11-registered.  Throws an exception if there are multiple bases--use
  * `all_type_info` instead if you want to support multiple bases.
  */
-PYBIND11_NOINLINE detail::type_info* get_type_info(PyTypeObject *type, bool do_throw = true) {
+PYBIND11_NOINLINE detail::type_info *get_type_info(PyTypeObject *type, bool do_throw = true) {
     const auto &bases = all_type_info(type);
     if (bases.empty()) {
         return nullptr;
@@ -185,7 +189,7 @@ PYBIND11_NOINLINE detail::type_info* get_type_info(PyTypeObject *type, bool do_t
     if (bases.size() > 1) {
         if (do_throw) {
             pybind11_fail(
-            "pybind11::detail::get_type_info: type has multiple pybind11-registered bases");
+                "pybind11::detail::get_type_info: type has multiple pybind11-registered bases");
         } else {
             return nullptr;
         }
@@ -211,9 +215,10 @@ inline detail::type_info *get_global_type_info(const std::type_index &tp) {
     return nullptr;
 }
 
-/// Return the type info for a given C++ type; on lookup failure can either throw or return nullptr.
+/// Return the type info for a given C++ type; on lookup failure can either throw or return
+/// nullptr.
 PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
-                                                          bool throw_if_missing = false) {
+                                                   bool throw_if_missing = false) {
     if (auto *ltype = get_local_type_info(tp)) {
         return ltype;
     }
@@ -224,7 +229,8 @@ PYBIND11_NOINLINE detail::type_info *get_type_info(const std::type_index &tp,
     if (throw_if_missing) {
         std::string tname = tp.name();
         detail::clean_type_id(tname);
-        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname + "\"");
+        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname
+                      + "\"");
     }
     return nullptr;
 }
@@ -235,17 +241,19 @@ PYBIND11_NOINLINE handle get_type_handle(const std::type_info &tp, bool throw_if
 }
 
 // Searches the inheritance graph for a registered Python instance, using all_type_info().
-PYBIND11_NOINLINE handle find_registered_python_instance(
-        void *src, const detail::type_info *tinfo,
-        bool should_take_ownership, holder_erased existing_holder) {
+PYBIND11_NOINLINE handle find_registered_python_instance(void *src,
+                                                         const detail::type_info *tinfo,
+                                                         bool should_take_ownership,
+                                                         holder_erased existing_holder) {
     // We only come across `!existing_holder` if we are coming from `cast` and not `cast_holder`.
-    const bool is_bare_ptr = !existing_holder.ptr() && existing_holder.type_id() == HolderTypeId::Unknown;
+    const bool is_bare_ptr
+        = !existing_holder.ptr() && existing_holder.type_id() == HolderTypeId::Unknown;
 
     auto it_instances = get_internals().registered_instances.equal_range(src);
     for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
         for (auto *instance_type : detail::all_type_info(Py_TYPE(it_i->second))) {
             if (instance_type && same_type(*instance_type->cpptype, *tinfo->cpptype)) {
-                instance* const inst = it_i->second;
+                instance *const inst = it_i->second;
 
                 bool try_to_reclaim = false;
                 if (!is_bare_ptr) {
@@ -256,7 +264,8 @@ PYBIND11_NOINLINE handle find_registered_python_instance(
                         }
                         case detail::HolderTypeId::SharedPtr: {
                             if (should_take_ownership) {
-                                // Only try to reclaim the object if (a) it is not owned and (b) has no holder.
+                                // Only try to reclaim the object if (a) it is not owned and (b)
+                                // has no holder.
                                 if (!inst->simple_holder_constructed) {
                                     if (inst->owned)
                                         throw std::runtime_error("Internal error?");
@@ -272,26 +281,30 @@ PYBIND11_NOINLINE handle find_registered_python_instance(
                     }
                 }
                 if (try_to_reclaim) {
-                    // If this object has already been registered, but we wish to take ownership of it,
-                    // then use the `has_cpp_release` mechanisms to reclaim ownership.
-                    // @note This should be the sole occurrence of this registered object when releasing back.
+                    // If this object has already been registered, but we wish to take ownership of
+                    // it, then use the `has_cpp_release` mechanisms to reclaim ownership.
+                    // @note This should be the sole occurrence of this registered object when
+                    // releasing back.
                     // @note This code path should not be invoked for pure C++
 
-                    // TODO(eric.cousineau): This may be still be desirable if this is a raw pointer...
-                    // Need to think of a desirable workflow - and if there is possible interop.
+                    // TODO(eric.cousineau): This may be still be desirable if this is a raw
+                    // pointer... Need to think of a desirable workflow - and if there is possible
+                    // interop.
                     if (!existing_holder) {
                         throw std::runtime_error("Internal error: Should have non-null holder.");
                     }
-                    // TODO(eric.cousineau): This field may not be necessary if the lowest-level type is valid.
-                    // See `move_only_holder_caster::load_value`.
+                    // TODO(eric.cousineau): This field may not be necessary if the lowest-level
+                    // type is valid. See `move_only_holder_caster::load_value`.
                     if (!inst->reclaim_from_cpp) {
-                        throw std::runtime_error("Instance is registered but does not have a registered reclaim method. Internal error?");
+                        throw std::runtime_error("Instance is registered but does not have a "
+                                                 "registered reclaim method. Internal error?");
                     }
                     return inst->reclaim_from_cpp(inst, existing_holder).release();
                 } else {
                     // TODO(eric.cousineau): Should really check that ownership is consistent.
-                    // e.g. if we say to take ownership of a pointer that is passed, does not have a holder...
-                    // In the end, pybind11 would let ownership slip, and leak memory, possibly violating RAII (if someone is using that...)
+                    // e.g. if we say to take ownership of a pointer that is passed, does not have
+                    // a holder... In the end, pybind11 would let ownership slip, and leak memory,
+                    // possibly violating RAII (if someone is using that...)
                     return handle((PyObject *) it_i->second).inc_ref();
                 }
             }
@@ -307,10 +320,10 @@ struct value_and_holder {
     void **vh = nullptr;
 
     // Main constructor for a found value/holder:
-    value_and_holder(instance *i, const detail::type_info *type, size_t vpos, size_t index) :
-        inst{i}, index{index}, type{type},
-        vh{inst->simple_layout ? inst->simple_value_holder : &inst->nonsimple.values_and_holders[vpos]}
-    {}
+    value_and_holder(instance *i, const detail::type_info *type, size_t vpos, size_t index)
+        : inst{i}, index{index}, type{type}, vh{inst->simple_layout
+                                                    ? inst->simple_value_holder
+                                                    : &inst->nonsimple.values_and_holders[vpos]} {}
 
     // Default constructor (used to signal a value-and-holder not found by get_value_and_holder())
     value_and_holder() = default;
@@ -318,16 +331,18 @@ struct value_and_holder {
     // Used for past-the-end iterator
     explicit value_and_holder(size_t index) : index{index} {}
 
-    template <typename V = void> V *&value_ptr() const {
+    template <typename V = void>
+    V *&value_ptr() const {
         return reinterpret_cast<V *&>(vh[0]);
     }
     // True if this `value_and_holder` has a non-null value pointer
     explicit operator bool() const { return value_ptr() != nullptr; }
 
-    template <typename H> H &holder() const {
+    template <typename H>
+    H &holder() const {
         return reinterpret_cast<H &>(vh[1]);
     }
-    void* holder_ptr() const { return &vh[1]; }
+    void *holder_ptr() const { return &vh[1]; }
     bool holder_constructed() const {
         return inst->simple_layout
                    ? inst->simple_holder_constructed
@@ -345,8 +360,8 @@ struct value_and_holder {
     }
     bool instance_registered() const {
         return inst->simple_layout
-            ? inst->simple_instance_registered
-            : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
+                   ? inst->simple_instance_registered
+                   : ((inst->nonsimple.status[index] & instance::status_instance_registered) != 0);
     }
     // NOLINTNEXTLINE(readability-make-member-function-const)
     void set_instance_registered(bool v = true) {
@@ -379,11 +394,10 @@ struct values_and_holders {
         friend struct values_and_holders;
         iterator(instance *inst, const type_vec *tinfo)
             : inst{inst}, types{tinfo},
-            curr(inst /* instance */,
-                 types->empty() ? nullptr : (*types)[0] /* type info */,
-                 0, /* vpos: (non-simple types only): the first vptr comes first */
-                 0 /* index */)
-        {}
+              curr(inst /* instance */,
+                   types->empty() ? nullptr : (*types)[0] /* type info */,
+                   0, /* vpos: (non-simple types only): the first vptr comes first */
+                   0 /* index */) {}
         // Past-the-end iterator:
         explicit iterator(size_t end) : curr(end) {}
 
@@ -426,7 +440,9 @@ struct values_and_holders {
  * The returned object should be short-lived: in particular, it must not outlive the called-upon
  * instance.
  */
-PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/, bool throw_if_missing /*= true in common.h*/) {
+PYBIND11_NOINLINE value_and_holder
+instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/,
+                               bool throw_if_missing /*= true in common.h*/) {
     // Optimize common case:
     if (!find_type || Py_TYPE(this) == find_type->type) {
         return value_and_holder(this, find_type, 0, 0);
@@ -444,12 +460,13 @@ PYBIND11_NOINLINE value_and_holder instance::get_value_and_holder(const type_inf
 
 #if defined(NDEBUG)
     pybind11_fail("pybind11::detail::instance::get_value_and_holder: "
-            "type is not a pybind11 base of the given instance "
-            "(compile in debug mode for type details)");
+                  "type is not a pybind11 base of the given instance "
+                  "(compile in debug mode for type details)");
 #else
-    pybind11_fail("pybind11::detail::instance::get_value_and_holder: `" +
-            get_fully_qualified_tp_name(find_type->type) + "' is not a pybind11 base of the given `" +
-            get_fully_qualified_tp_name(Py_TYPE(this)) + "' instance");
+    pybind11_fail("pybind11::detail::instance::get_value_and_holder: `"
+                  + get_fully_qualified_tp_name(find_type->type)
+                  + "' is not a pybind11 base of the given `"
+                  + get_fully_qualified_tp_name(Py_TYPE(this)) + "' instance");
 #endif
 }
 
@@ -463,23 +480,22 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
             "instance allocation failed: new instance has no pybind11-registered base types");
     }
 
-    simple_layout =
-        n_types == 1 && tinfo.front()->holder_size_in_ptrs <= instance_simple_holder_in_ptrs();
+    simple_layout
+        = n_types == 1 && tinfo.front()->holder_size_in_ptrs <= instance_simple_holder_in_ptrs();
 
     // Simple path: no python-side multiple inheritance, and a small-enough holder
     if (simple_layout) {
         simple_value_holder[0] = nullptr;
         simple_holder_constructed = false;
         simple_instance_registered = false;
-    }
-    else { // multiple base types or a too-large holder
+    } else { // multiple base types or a too-large holder
         // Allocate space to hold: [v1*][h1][v2*][h2]...[bb...] where [vN*] is a value pointer,
         // [hN] is the (uninitialized) holder instance for value N, and [bb...] is a set of bool
         // values that tracks whether each associated holder has been initialized.  Each [block] is
         // padded, if necessary, to an integer multiple of sizeof(void *).
         size_t space = 0;
         for (auto *t : tinfo) {
-            space += 1; // value pointer
+            space += 1;                      // value pointer
             space += t->holder_size_in_ptrs; // holder instance
         }
         size_t flags_at = space;
@@ -498,10 +514,12 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
         }
 #else
         nonsimple.values_and_holders = (void **) PyMem_New(void *, space);
-        if (!nonsimple.values_and_holders) throw std::bad_alloc();
+        if (!nonsimple.values_and_holders)
+            throw std::bad_alloc();
         std::memset(nonsimple.values_and_holders, 0, space * sizeof(void *));
 #endif
-        nonsimple.status = reinterpret_cast<std::uint8_t *>(&nonsimple.values_and_holders[flags_at]);
+        nonsimple.status
+            = reinterpret_cast<std::uint8_t *>(&nonsimple.values_and_holders[flags_at]);
     }
     owned = true;
 }
@@ -559,24 +577,23 @@ PYBIND11_NOINLINE std::string error_string() {
         Py_XINCREF(frame);
         errorString += "\n\nAt:\n";
         while (frame) {
-#if PY_VERSION_HEX >= 0x030900B1
+#    if PY_VERSION_HEX >= 0x030900B1
             PyCodeObject *f_code = PyFrame_GetCode(frame);
-#else
+#    else
             PyCodeObject *f_code = frame->f_code;
             Py_INCREF(f_code);
-#endif
+#    endif
             int lineno = PyFrame_GetLineNumber(frame);
-            errorString +=
-                "  " + handle(f_code->co_filename).cast<std::string>() +
-                "(" + std::to_string(lineno) + "): " +
-                handle(f_code->co_name).cast<std::string>() + "\n";
+            errorString += "  " + handle(f_code->co_filename).cast<std::string>() + "("
+                           + std::to_string(lineno)
+                           + "): " + handle(f_code->co_name).cast<std::string>() + "\n";
             Py_DECREF(f_code);
-#if PY_VERSION_HEX >= 0x030900B1
+#    if PY_VERSION_HEX >= 0x030900B1
             auto *b_frame = PyFrame_GetBack(frame);
-#else
+#    else
             auto *b_frame = frame->f_back;
             Py_XINCREF(b_frame);
-#endif
+#    endif
             Py_DECREF(frame);
             frame = b_frame;
         }
@@ -586,7 +603,7 @@ PYBIND11_NOINLINE std::string error_string() {
     return errorString;
 }
 
-PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_info *type ) {
+PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_info *type) {
     auto &instances = get_internals().registered_instances;
     auto range = instances.equal_range(ptr);
     for (auto it = range.first; it != range.second; ++it) {
@@ -605,9 +622,9 @@ inline PyThreadState *get_thread_state_unchecked() {
 #elif PY_VERSION_HEX < 0x03000000
     return _PyThreadState_Current;
 #elif PY_VERSION_HEX < 0x03050000
-    return (PyThreadState*) _Py_atomic_load_relaxed(&_PyThreadState_Current);
+    return (PyThreadState *) _Py_atomic_load_relaxed(&_PyThreadState_Current);
 #elif PY_VERSION_HEX < 0x03050200
-    return (PyThreadState*) _PyThreadState_Current.value;
+    return (PyThreadState *) _PyThreadState_Current.value;
 #else
     return _PyThreadState_UncheckedGet();
 #endif
@@ -618,20 +635,21 @@ void keep_alive_impl(handle nurse, handle patient);
 inline PyObject *make_new_instance(PyTypeObject *type);
 
 enum class LoadType {
-  PureCpp,
-  DerivedCppSinglePySingle,
-  DerivedCppSinglePyMulti,
-  DerivedCppMulti,
-  /// Polymorphic casting or copy-based casting may be necessary.
-  ConversionNeeded,
+    PureCpp,
+    DerivedCppSinglePySingle,
+    DerivedCppSinglePyMulti,
+    DerivedCppMulti,
+    /// Polymorphic casting or copy-based casting may be necessary.
+    ConversionNeeded,
 };
 
-typedef type_info* base_ptr_t;
+typedef type_info *base_ptr_t;
 using bases_t = const std::vector<base_ptr_t>;
 
-inline LoadType determine_load_type(handle src, const type_info* typeinfo,
-                             const bases_t** out_bases = nullptr,
-                             base_ptr_t* out_base = nullptr) {
+inline LoadType determine_load_type(handle src,
+                                    const type_info *typeinfo,
+                                    const bases_t **out_bases = nullptr,
+                                    base_ptr_t *out_base = nullptr) {
     // Null out inputs.
     if (out_bases)
         *out_bases = nullptr;
@@ -649,9 +667,9 @@ inline LoadType determine_load_type(handle src, const type_info* typeinfo,
     }
     // Case 2: We have a derived class
     else if (PyType_IsSubtype(srctype, typeinfo->type)) {
-        const bases_t& bases = all_type_info(srctype);
+        const bases_t &bases = all_type_info(srctype);
         if (out_bases)
-            *out_bases = &bases;  // Copy to output for caching.
+            *out_bases = &bases; // Copy to output for caching.
         const bool no_cpp_mi = typeinfo->simple_type;
         // Case 2a: the python type is a Python-inherited derived class that inherits from just
         // one simple (no MI) pybind11 class, or is an exact match, so the C++ instance is of
@@ -659,8 +677,8 @@ inline LoadType determine_load_type(handle src, const type_info* typeinfo,
         // (This is essentially the same as case 2b, but because not using multiple inheritance
         // is extremely common, we handle it specially to avoid the loop iterator and type
         // pointer lookup overhead)
-        // TODO(eric.cousineau): This seems to also capture C++-registered classes as well, not just Python-derived
-        // classes.
+        // TODO(eric.cousineau): This seems to also capture C++-registered classes as well, not
+        // just Python-derived classes.
         if (bases.size() == 1 && (no_cpp_mi || bases.front()->type == typeinfo->type)) {
             return LoadType::DerivedCppSinglePySingle;
         }
@@ -668,14 +686,15 @@ inline LoadType determine_load_type(handle src, const type_info* typeinfo,
         // we can find an exact match (or, for a simple C++ type, an inherited match); if so, we
         // can safely reinterpret_cast to the relevant pointer.
         else if (bases.size() > 1) {
-           for (auto base : bases) {
-               if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type) : base->type == typeinfo->type) {
-                   if (out_base) {
-                       *out_base = base;
-                   }
-                   return LoadType::DerivedCppSinglePyMulti;
-               }
-           }
+            for (auto base : bases) {
+                if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type)
+                              : base->type == typeinfo->type) {
+                    if (out_base) {
+                        *out_base = base;
+                    }
+                    return LoadType::DerivedCppSinglePyMulti;
+                }
+            }
         }
         // Case 2c: C++ multiple inheritance is involved and we couldn't find an exact type match
         // in the registered bases, above, so try implicit casting (needed for proper C++ casting
@@ -694,11 +713,11 @@ class type_caster_generic {
     explicit type_caster_generic(const type_info *typeinfo)
         : typeinfo(typeinfo), cpptype(typeinfo ? typeinfo->cpptype : nullptr) {}
 
-    bool load(handle src, bool convert) {
-        return load_impl<type_caster_generic>(src, convert);
-    }
+    bool load(handle src, bool convert) { return load_impl<type_caster_generic>(src, convert); }
 
-    PYBIND11_NOINLINE static handle cast(const void *_src, return_value_policy policy, handle parent,
+    PYBIND11_NOINLINE static handle cast(const void *_src,
+                                         return_value_policy policy,
+                                         handle parent,
                                          const detail::type_info *tinfo,
                                          void *(*copy_constructor)(const void *),
                                          void *(*move_constructor)(const void *),
@@ -712,9 +731,11 @@ class type_caster_generic {
             return none().release();
         }
 
-        const bool should_take_ownership = policy == return_value_policy::automatic || policy == return_value_policy::take_ownership;
+        const bool should_take_ownership = policy == return_value_policy::automatic
+                                           || policy == return_value_policy::take_ownership;
 
-        if (handle registered_inst = find_registered_python_instance(src, tinfo, should_take_ownership, existing_holder)) {
+        if (handle registered_inst = find_registered_python_instance(
+                src, tinfo, should_take_ownership, existing_holder)) {
             return registered_inst;
         }
 
@@ -746,8 +767,8 @@ class type_caster_generic {
 #else
                     std::string type_name(tinfo->cpptype->name());
                     detail::clean_type_id(type_name);
-                    throw cast_error("return_value_policy = copy, but type " +
-                                     type_name + " is non-copyable!");
+                    throw cast_error("return_value_policy = copy, but type " + type_name
+                                     + " is non-copyable!");
 #endif
                 }
                 wrapper->owned = true;
@@ -766,8 +787,8 @@ class type_caster_generic {
 #else
                     std::string type_name(tinfo->cpptype->name());
                     detail::clean_type_id(type_name);
-                    throw cast_error("return_value_policy = move, but type " +
-                                     type_name + " is neither movable nor copyable!");
+                    throw cast_error("return_value_policy = move, but type " + type_name
+                                     + " is neither movable nor copyable!");
 #endif
                 }
                 wrapper->owned = true;
@@ -798,16 +819,15 @@ class type_caster_generic {
             if (type->operator_new) {
                 vptr = type->operator_new(type->type_size);
             } else {
-                #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
-                    if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
-                        vptr = ::operator new(type->type_size,
-                                              std::align_val_t(type->type_align));
-                    } else {
-                        vptr = ::operator new(type->type_size);
-                    }
-                #else
+#if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
+                if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
+                    vptr = ::operator new(type->type_size, std::align_val_t(type->type_align));
+                } else {
                     vptr = ::operator new(type->type_size);
-                #endif
+                }
+#else
+                vptr = ::operator new(type->type_size);
+#endif
             }
         }
         value = vptr;
@@ -850,7 +870,8 @@ class type_caster_generic {
         }
 
         type_info *foreign_typeinfo = reinterpret_borrow<capsule>(getattr(pytype, local_key));
-        // Only consider this foreign loader if actually foreign and is a loader of the correct cpp type
+        // Only consider this foreign loader if actually foreign and is a loader of the correct cpp
+        // type
         if (foreign_typeinfo->module_local_load == &local_load
             || (cpptype && !same_type(*cpptype, *foreign_typeinfo->cpptype))) {
             return false;
@@ -878,7 +899,7 @@ class type_caster_generic {
         auto &this_ = static_cast<ThisT &>(*this);
         this_.check_holder_compat();
 
-        const bases_t* bases = nullptr;
+        const bases_t *bases = nullptr;
         base_ptr_t base_py_multi = nullptr;
         LoadType load_type = determine_load_type(src, typeinfo, &bases, &base_py_multi);
         switch (load_type) {
@@ -893,8 +914,9 @@ class type_caster_generic {
                 return true;
             }
             case LoadType::DerivedCppSinglePyMulti: {
-                this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base_py_multi),
-                                 load_type);
+                this_.load_value(
+                    reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base_py_multi),
+                    load_type);
                 return true;
             }
             case LoadType::DerivedCppMulti: {
@@ -931,28 +953,29 @@ class type_caster_generic {
 
         // Global typeinfo has precedence over foreign module_local
         if (try_load_foreign_module_local(src)) {
-           return true;
+            return true;
         }
 
         // Custom converters didn't take None, now we convert None to nullptr.
         if (src.is_none()) {
-           // Defer accepting None to other overloads (if we aren't in convert mode):
-           if (!convert) {
-               return false;
-           }
-           value = nullptr;
-           return true;
+            // Defer accepting None to other overloads (if we aren't in convert mode):
+            if (!convert) {
+                return false;
+            }
+            value = nullptr;
+            return true;
         }
 
         return false;
     }
 
-
     // Called to do type lookup and wrap the pointer and type in a pair when a dynamic_cast
     // isn't needed or can't be used.  If the type is unknown, sets the error and returns a pair
     // with .second = nullptr.  (p.first = nullptr is not an error: it becomes None).
-    PYBIND11_NOINLINE static std::pair<const void *, const type_info *> src_and_type(
-            const void *src, const std::type_info &cast_type, const std::type_info *rtti_type = nullptr) {
+    PYBIND11_NOINLINE static std::pair<const void *, const type_info *>
+    src_and_type(const void *src,
+                 const std::type_info &cast_type,
+                 const std::type_info *rtti_type = nullptr) {
         if (auto *tpi = get_type_info(cast_type)) {
             return {src, const_cast<const type_info *>(tpi)};
         }
@@ -978,10 +1001,9 @@ class type_caster_generic {
  * `movable_cast_op_type` instead.
  */
 template <typename T>
-using cast_op_type =
-    conditional_t<std::is_pointer<remove_reference_t<T>>::value,
-        typename std::add_pointer<intrinsic_t<T>>::type,
-        typename std::add_lvalue_reference<intrinsic_t<T>>::type>;
+using cast_op_type = conditional_t<std::is_pointer<remove_reference_t<T>>::value,
+                                   typename std::add_pointer<intrinsic_t<T>>::type,
+                                   typename std::add_lvalue_reference<intrinsic_t<T>>::type>;
 
 /**
  * Determine suitable casting operator for a type caster with a movable value.  Such a type caster
@@ -991,40 +1013,50 @@ using cast_op_type =
  * These operator are automatically provided when using the PYBIND11_TYPE_CASTER macro.
  */
 template <typename T>
-using movable_cast_op_type =
-    conditional_t<std::is_pointer<typename std::remove_reference<T>::type>::value,
-        typename std::add_pointer<intrinsic_t<T>>::type,
-    conditional_t<std::is_rvalue_reference<T>::value,
-        typename std::add_rvalue_reference<intrinsic_t<T>>::type,
-        typename std::add_lvalue_reference<intrinsic_t<T>>::type>>;
+using movable_cast_op_type
+    = conditional_t<std::is_pointer<typename std::remove_reference<T>::type>::value,
+                    typename std::add_pointer<intrinsic_t<T>>::type,
+                    conditional_t<std::is_rvalue_reference<T>::value,
+                                  typename std::add_rvalue_reference<intrinsic_t<T>>::type,
+                                  typename std::add_lvalue_reference<intrinsic_t<T>>::type>>;
 
 // std::is_copy_constructible isn't quite enough: it lets std::vector<T> (and similar) through when
 // T is non-copyable, but code containing such a copy constructor fails to actually compile.
-template <typename T, typename SFINAE = void> struct is_copy_constructible : std::is_copy_constructible<T> {};
+template <typename T, typename SFINAE = void>
+struct is_copy_constructible : std::is_copy_constructible<T> {};
 
 // Specialization for types that appear to be copy constructible but also look like stl containers
 // (we specifically check for: has `value_type` and `reference` with `reference = value_type&`): if
 // so, copy constructability depends on whether the value_type is copy constructible.
-template <typename Container> struct is_copy_constructible<Container, enable_if_t<all_of<
-        std::is_copy_constructible<Container>,
-        std::is_same<typename Container::value_type &, typename Container::reference>,
-        // Avoid infinite recursion
-        negation<std::is_same<Container, typename Container::value_type>>
-    >::value>> : is_copy_constructible<typename Container::value_type> {};
+template <typename Container>
+struct is_copy_constructible<
+    Container,
+    enable_if_t<
+        all_of<std::is_copy_constructible<Container>,
+               std::is_same<typename Container::value_type &, typename Container::reference>,
+               // Avoid infinite recursion
+               negation<std::is_same<Container, typename Container::value_type>>>::value>>
+    : is_copy_constructible<typename Container::value_type> {};
 
 // Likewise for std::pair
-// (after C++17 it is mandatory that the copy constructor not exist when the two types aren't themselves
-// copy constructible, but this can not be relied upon when T1 or T2 are themselves containers).
-template <typename T1, typename T2> struct is_copy_constructible<std::pair<T1, T2>>
+// (after C++17 it is mandatory that the copy constructor not exist when the two types aren't
+// themselves copy constructible, but this can not be relied upon when T1 or T2 are themselves
+// containers).
+template <typename T1, typename T2>
+struct is_copy_constructible<std::pair<T1, T2>>
     : all_of<is_copy_constructible<T1>, is_copy_constructible<T2>> {};
 
 // The same problems arise with std::is_copy_assignable, so we use the same workaround.
-template <typename T, typename SFINAE = void> struct is_copy_assignable : std::is_copy_assignable<T> {};
-template <typename Container> struct is_copy_assignable<Container, enable_if_t<all_of<
-        std::is_copy_assignable<Container>,
-        std::is_same<typename Container::value_type &, typename Container::reference>
-    >::value>> : is_copy_assignable<typename Container::value_type> {};
-template <typename T1, typename T2> struct is_copy_assignable<std::pair<T1, T2>>
+template <typename T, typename SFINAE = void>
+struct is_copy_assignable : std::is_copy_assignable<T> {};
+template <typename Container>
+struct is_copy_assignable<Container,
+                          enable_if_t<all_of<std::is_copy_assignable<Container>,
+                                             std::is_same<typename Container::value_type &,
+                                                          typename Container::reference>>::value>>
+    : is_copy_assignable<typename Container::value_type> {};
+template <typename T1, typename T2>
+struct is_copy_assignable<std::pair<T1, T2>>
     : all_of<is_copy_assignable<T1>, is_copy_assignable<T2>> {};
 
 PYBIND11_NAMESPACE_END(detail)
@@ -1051,16 +1083,14 @@ PYBIND11_NAMESPACE_END(detail)
 // std::enable_if. User provided specializations will always have higher priority than
 // the default implementation and specialization provided in polymorphic_type_hook_base.
 template <typename itype, typename SFINAE = void>
-struct polymorphic_type_hook_base
-{
-    static const void *get(const itype *src, const std::type_info*&) { return src; }
+struct polymorphic_type_hook_base {
+    static const void *get(const itype *src, const std::type_info *&) { return src; }
 };
 template <typename itype>
-struct polymorphic_type_hook_base<itype, detail::enable_if_t<std::is_polymorphic<itype>::value>>
-{
-    static const void *get(const itype *src, const std::type_info*& type) {
+struct polymorphic_type_hook_base<itype, detail::enable_if_t<std::is_polymorphic<itype>::value>> {
+    static const void *get(const itype *src, const std::type_info *&type) {
         type = src ? &typeid(*src) : nullptr;
-        return dynamic_cast<const void*>(src);
+        return dynamic_cast<const void *>(src);
     }
 };
 template <typename itype, typename SFINAE = void>
@@ -1069,14 +1099,15 @@ struct polymorphic_type_hook : public polymorphic_type_hook_base<itype> {};
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Generic type caster for objects stored on the heap
-template <typename type> class type_caster_base : public type_caster_generic {
+template <typename type>
+class type_caster_base : public type_caster_generic {
     using itype = intrinsic_t<type>;
 
 public:
     static constexpr auto name = const_name<type>();
 
-    type_caster_base() : type_caster_base(typeid(type)) { }
-    explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
+    type_caster_base() : type_caster_base(typeid(type)) {}
+    explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) {}
 
     static handle cast(const itype &src, return_value_policy policy, handle parent) {
         if (policy == return_value_policy::automatic
@@ -1110,16 +1141,19 @@ template <typename type> class type_caster_base : public type_caster_generic {
                 return {vsrc, tpi};
             }
         }
-        // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer, so
-        // don't do a cast
+        // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer,
+        // so don't do a cast
         return type_caster_generic::src_and_type(src, cast_type, instance_type);
     }
 
     static handle cast(const itype *src, return_value_policy policy, handle parent) {
         auto st = src_and_type(src);
-        return type_caster_generic::cast(
-            st.first, policy, parent, st.second,
-            make_copy_constructor(src), make_move_constructor(src));
+        return type_caster_generic::cast(st.first,
+                                         policy,
+                                         parent,
+                                         st.second,
+                                         make_copy_constructor(src),
+                                         make_move_constructor(src));
     }
 
     static handle cast_holder(const itype *src, holder_erased holder) {
@@ -1127,17 +1161,22 @@ template <typename type> class type_caster_base : public type_caster_generic {
         if (!holder) {
             throw std::runtime_error("Internal error: Should not have null holder");
         }
-        return type_caster_generic::cast(
-            st.first, return_value_policy::take_ownership, {}, st.second,
-            nullptr, nullptr, holder);
+        return type_caster_generic::cast(st.first,
+                                         return_value_policy::take_ownership,
+                                         {},
+                                         st.second,
+                                         nullptr,
+                                         nullptr,
+                                         holder);
     }
 
-    template <typename T> using cast_op_type = detail::cast_op_type<T>;
+    template <typename T>
+    using cast_op_type = detail::cast_op_type<T>;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator itype*() { return (type *) value; }
+    operator itype *() { return (type *) value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator itype&() {
+    operator itype &() {
         if (!value) {
             throw reference_cast_error();
         }
@@ -1145,20 +1184,20 @@ template <typename type> class type_caster_base : public type_caster_generic {
     }
 
 protected:
-    using Constructor = void *(*)(const void *);
+    using Constructor = void *(*) (const void *);
 
     /* Only enabled when the types are {copy,move}-constructible *and* when the type
-       does not have a private operator new implementation. A comma operator is used in the decltype
-       argument to apply SFINAE to the public copy/move constructors.*/
+       does not have a private operator new implementation. A comma operator is used in the
+       decltype argument to apply SFINAE to the public copy/move constructors.*/
     template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
-    static auto make_copy_constructor(const T *) -> decltype(new T(std::declval<const T>()), Constructor{}) {
-        return [](const void *arg) -> void * {
-            return new T(*reinterpret_cast<const T *>(arg));
-        };
+    static auto make_copy_constructor(const T *)
+        -> decltype(new T(std::declval<const T>()), Constructor{}) {
+        return [](const void *arg) -> void * { return new T(*reinterpret_cast<const T *>(arg)); };
     }
 
     template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
-    static auto make_move_constructor(const T *) -> decltype(new T(std::declval<T&&>()), Constructor{}) {
+    static auto make_move_constructor(const T *)
+        -> decltype(new T(std::declval<T &&>()), Constructor{}) {
         return [](const void *arg) -> void * {
             return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
         };
diff --git a/include/pybind11/detail/typeid.h b/include/pybind11/detail/typeid.h
index 53c166bebc..8d99fc0286 100644
--- a/include/pybind11/detail/typeid.h
+++ b/include/pybind11/detail/typeid.h
@@ -13,7 +13,7 @@
 #include <cstdlib>
 
 #if defined(__GNUG__)
-#include <cxxabi.h>
+#    include <cxxabi.h>
 #endif
 
 #include "common.h"
@@ -34,8 +34,8 @@ inline void erase_all(std::string &string, const std::string &search) {
 PYBIND11_NOINLINE void clean_type_id(std::string &name) {
 #if defined(__GNUG__)
     int status = 0;
-    std::unique_ptr<char, void (*)(void *)> res {
-        abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status), std::free };
+    std::unique_ptr<char, void (*)(void *)> res{
+        abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status), std::free};
     if (status == 0) {
         name = res.get();
     }
@@ -49,7 +49,8 @@ PYBIND11_NOINLINE void clean_type_id(std::string &name) {
 PYBIND11_NAMESPACE_END(detail)
 
 /// Return a string representation of a C++ type
-template <typename T> static std::string type_id() {
+template <typename T>
+static std::string type_id() {
     std::string name(typeid(T).name());
     detail::clean_type_id(name);
     return name;
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index 275c9898bd..8009338716 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -23,79 +23,90 @@
 // 2. we definitely want to ignore any MSVC warnings originating from Eigen code,
 // it is probably best to keep this around indefinitely.
 #if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4127) // C4127: conditional expression is constant
+#    pragma warning(push)
+#    pragma warning(disable : 4127) // C4127: conditional expression is constant
 #endif
 
 #include <Eigen/Core>
 #include <Eigen/SparseCore>
 
 #if defined(_MSC_VER)
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
 // Eigen prior to 3.2.7 doesn't have proper move constructors--but worse, some classes get implicit
 // move constructors that break things.  We could detect this an explicitly copy, but an extra copy
 // of matrices seems highly undesirable.
-static_assert(EIGEN_VERSION_AT_LEAST(3,2,7), "Eigen support in pybind11 requires Eigen >= 3.2.7");
+static_assert(EIGEN_VERSION_AT_LEAST(3, 2, 7),
+              "Eigen support in pybind11 requires Eigen >= 3.2.7");
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 // Provide a convenience alias for easier pass-by-ref usage with fully dynamic strides:
 using EigenDStride = Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic>;
-template <typename MatrixType> using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
-template <typename MatrixType> using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
+template <typename MatrixType>
+using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
+template <typename MatrixType>
+using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-#if EIGEN_VERSION_AT_LEAST(3,3,0)
+#if EIGEN_VERSION_AT_LEAST(3, 3, 0)
 using EigenIndex = Eigen::Index;
-template<typename Scalar, int Flags, typename StorageIndex>
+template <typename Scalar, int Flags, typename StorageIndex>
 using EigenMapSparseMatrix = Eigen::Map<Eigen::SparseMatrix<Scalar, Flags, StorageIndex>>;
 #else
 using EigenIndex = EIGEN_DEFAULT_DENSE_INDEX_TYPE;
-template<typename Scalar, int Flags, typename StorageIndex>
+template <typename Scalar, int Flags, typename StorageIndex>
 using EigenMapSparseMatrix = Eigen::MappedSparseMatrix<Scalar, Flags, StorageIndex>;
 #endif
 
 // Matches Eigen::Map, Eigen::Ref, blocks, etc:
-template <typename T> using is_eigen_dense_map = all_of<is_template_base_of<Eigen::DenseBase, T>, std::is_base_of<Eigen::MapBase<T, Eigen::ReadOnlyAccessors>, T>>;
-template <typename T> using is_eigen_mutable_map = std::is_base_of<Eigen::MapBase<T, Eigen::WriteAccessors>, T>;
-template <typename T> using is_eigen_dense_plain = all_of<negation<is_eigen_dense_map<T>>, is_template_base_of<Eigen::PlainObjectBase, T>>;
-template <typename T> using is_eigen_sparse = is_template_base_of<Eigen::SparseMatrixBase, T>;
+template <typename T>
+using is_eigen_dense_map = all_of<is_template_base_of<Eigen::DenseBase, T>,
+                                  std::is_base_of<Eigen::MapBase<T, Eigen::ReadOnlyAccessors>, T>>;
+template <typename T>
+using is_eigen_mutable_map = std::is_base_of<Eigen::MapBase<T, Eigen::WriteAccessors>, T>;
+template <typename T>
+using is_eigen_dense_plain
+    = all_of<negation<is_eigen_dense_map<T>>, is_template_base_of<Eigen::PlainObjectBase, T>>;
+template <typename T>
+using is_eigen_sparse = is_template_base_of<Eigen::SparseMatrixBase, T>;
 // Test for objects inheriting from EigenBase<Derived> that aren't captured by the above.  This
 // basically covers anything that can be assigned to a dense matrix but that don't have a typical
 // matrix data layout that can be copied from their .data().  For example, DiagonalMatrix and
 // SelfAdjointView fall into this category.
-template <typename T> using is_eigen_other = all_of<
-    is_template_base_of<Eigen::EigenBase, T>,
-    negation<any_of<is_eigen_dense_map<T>, is_eigen_dense_plain<T>, is_eigen_sparse<T>>>
->;
+template <typename T>
+using is_eigen_other
+    = all_of<is_template_base_of<Eigen::EigenBase, T>,
+             negation<any_of<is_eigen_dense_map<T>, is_eigen_dense_plain<T>, is_eigen_sparse<T>>>>;
 
 // Captures numpy/eigen conformability status (returned by EigenProps::conformable()):
-template <bool EigenRowMajor> struct EigenConformable {
+template <bool EigenRowMajor>
+struct EigenConformable {
     bool conformable = false;
     EigenIndex rows = 0, cols = 0;
-    EigenDStride stride{0, 0};      // Only valid if negativestrides is false!
-    bool negativestrides = false;   // If true, do not use stride!
+    EigenDStride stride{0, 0};    // Only valid if negativestrides is false!
+    bool negativestrides = false; // If true, do not use stride!
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     EigenConformable(bool fits = false) : conformable{fits} {}
     // Matrix type:
-    EigenConformable(EigenIndex r, EigenIndex c,
-            EigenIndex rstride, EigenIndex cstride) :
-        conformable{true}, rows{r}, cols{c},
-        //TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity. http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
-        stride{EigenRowMajor ? (rstride > 0 ? rstride : 0) : (cstride > 0 ? cstride : 0) /* outer stride */,
-               EigenRowMajor ? (cstride > 0 ? cstride : 0) : (rstride > 0 ? rstride : 0) /* inner stride */ },
-        negativestrides{rstride < 0 || cstride < 0} {
-
-    }
+    EigenConformable(EigenIndex r, EigenIndex c, EigenIndex rstride, EigenIndex cstride)
+        : conformable{true}, rows{r}, cols{c},
+          // TODO: when Eigen bug #747 is fixed, remove the tests for non-negativity.
+          // http://eigen.tuxfamily.org/bz/show_bug.cgi?id=747
+          stride{EigenRowMajor ? (rstride > 0 ? rstride : 0)
+                               : (cstride > 0 ? cstride : 0) /* outer stride */,
+                 EigenRowMajor ? (cstride > 0 ? cstride : 0)
+                               : (rstride > 0 ? rstride : 0) /* inner stride */},
+          negativestrides{rstride < 0 || cstride < 0} {}
     // Vector type:
     EigenConformable(EigenIndex r, EigenIndex c, EigenIndex stride)
-        : EigenConformable(r, c, r == 1 ? c*stride : stride, c == 1 ? r : r*stride) {}
+        : EigenConformable(r, c, r == 1 ? c * stride : stride, c == 1 ? r : r * stride) {}
 
-    template <typename props> bool stride_compatible() const {
+    template <typename props>
+    bool stride_compatible() const {
         // To have compatible strides, we need (on both dimensions) one of fully dynamic strides,
         // matching strides, or a dimension size of 1 (in which case the stride value is
         // irrelevant). Alternatively, if any dimension size is 0, the strides are not relevant
@@ -115,39 +126,52 @@ template <bool EigenRowMajor> struct EigenConformable {
     operator bool() const { return conformable; }
 };
 
-template <typename Type> struct eigen_extract_stride { using type = Type; };
+template <typename Type>
+struct eigen_extract_stride {
+    using type = Type;
+};
 template <typename PlainObjectType, int MapOptions, typename StrideType>
-struct eigen_extract_stride<Eigen::Map<PlainObjectType, MapOptions, StrideType>> { using type = StrideType; };
+struct eigen_extract_stride<Eigen::Map<PlainObjectType, MapOptions, StrideType>> {
+    using type = StrideType;
+};
 template <typename PlainObjectType, int Options, typename StrideType>
-struct eigen_extract_stride<Eigen::Ref<PlainObjectType, Options, StrideType>> { using type = StrideType; };
+struct eigen_extract_stride<Eigen::Ref<PlainObjectType, Options, StrideType>> {
+    using type = StrideType;
+};
 
 template <typename Scalar>
-using is_pyobject_dtype = std::is_base_of<npy_format_descriptor_object, npy_format_descriptor<Scalar>>;
+using is_pyobject_dtype
+    = std::is_base_of<npy_format_descriptor_object, npy_format_descriptor<Scalar>>;
 
 // Helper struct for extracting information from an Eigen type
-template <typename Type_> struct EigenProps {
+template <typename Type_>
+struct EigenProps {
     using Type = Type_;
     using Scalar = typename Type::Scalar;
     using StrideType = typename eigen_extract_stride<Type>::type;
-    static constexpr EigenIndex
-        rows = Type::RowsAtCompileTime,
-        cols = Type::ColsAtCompileTime,
-        size = Type::SizeAtCompileTime;
-    static constexpr bool
-        row_major = Type::IsRowMajor,
-        vector = Type::IsVectorAtCompileTime, // At least one dimension has fixed size 1
-        fixed_rows = rows != Eigen::Dynamic,
-        fixed_cols = cols != Eigen::Dynamic,
-        fixed = size != Eigen::Dynamic, // Fully-fixed size
-        dynamic = !fixed_rows && !fixed_cols; // Fully-dynamic size
-
-    template <EigenIndex i, EigenIndex ifzero> using if_zero = std::integral_constant<EigenIndex, i == 0 ? ifzero : i>;
-    static constexpr EigenIndex inner_stride = if_zero<StrideType::InnerStrideAtCompileTime, 1>::value,
-                                outer_stride = if_zero<StrideType::OuterStrideAtCompileTime,
-                                                       vector ? size : row_major ? cols : rows>::value;
-    static constexpr bool dynamic_stride = inner_stride == Eigen::Dynamic && outer_stride == Eigen::Dynamic;
-    static constexpr bool requires_row_major = !dynamic_stride && !vector && (row_major ? inner_stride : outer_stride) == 1;
-    static constexpr bool requires_col_major = !dynamic_stride && !vector && (row_major ? outer_stride : inner_stride) == 1;
+    static constexpr EigenIndex rows = Type::RowsAtCompileTime, cols = Type::ColsAtCompileTime,
+                                size = Type::SizeAtCompileTime;
+    static constexpr bool row_major = Type::IsRowMajor,
+                          vector
+                          = Type::IsVectorAtCompileTime, // At least one dimension has fixed size 1
+        fixed_rows = rows != Eigen::Dynamic, fixed_cols = cols != Eigen::Dynamic,
+                          fixed = size != Eigen::Dynamic, // Fully-fixed size
+        dynamic = !fixed_rows && !fixed_cols;             // Fully-dynamic size
+
+    template <EigenIndex i, EigenIndex ifzero>
+    using if_zero = std::integral_constant<EigenIndex, i == 0 ? ifzero : i>;
+    static constexpr EigenIndex inner_stride
+        = if_zero<StrideType::InnerStrideAtCompileTime, 1>::value,
+        outer_stride = if_zero < StrideType::OuterStrideAtCompileTime,
+        vector      ? size
+        : row_major ? cols
+                    : rows > ::value;
+    static constexpr bool dynamic_stride
+        = inner_stride == Eigen::Dynamic && outer_stride == Eigen::Dynamic;
+    static constexpr bool requires_row_major
+        = !dynamic_stride && !vector && (row_major ? inner_stride : outer_stride) == 1;
+    static constexpr bool requires_col_major
+        = !dynamic_stride && !vector && (row_major ? outer_stride : inner_stride) == 1;
 
     // Takes an input array and determines whether we can make it fit into the Eigen type.  If
     // the array is a vector, we attempt to fit it into either an Eigen 1xN or Nx1 vector
@@ -159,16 +183,14 @@ template <typename Type_> struct EigenProps {
         }
 
         constexpr bool is_pyobject = is_pyobject_dtype<Scalar>::value;
-        ssize_t scalar_size = (is_pyobject ? static_cast<ssize_t>(sizeof(PyObject*)) :
-                               static_cast<ssize_t>(sizeof(Scalar)));
+        ssize_t scalar_size = (is_pyobject ? static_cast<ssize_t>(sizeof(PyObject *))
+                                           : static_cast<ssize_t>(sizeof(Scalar)));
 
         if (dims == 2) { // Matrix type: require exact match (or dynamic)
 
-            EigenIndex
-                np_rows = a.shape(0),
-                np_cols = a.shape(1),
-                np_rstride = a.strides(0) / scalar_size,
-                np_cstride = a.strides(1) / scalar_size;
+            EigenIndex np_rows = a.shape(0), np_cols = a.shape(1),
+                       np_rstride = a.strides(0) / scalar_size,
+                       np_cstride = a.strides(1) / scalar_size;
             if ((PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && np_rows != rows)
                 || (PYBIND11_SILENCE_MSVC_C4127(fixed_cols) && np_cols != cols)) {
                 return false;
@@ -177,10 +199,9 @@ template <typename Type_> struct EigenProps {
             return {np_rows, np_cols, np_rstride, np_cstride};
         }
 
-        // Otherwise we're storing an n-vector.  Only one of the strides will be used, but whichever
-        // is used, we want the (single) numpy stride value.
-        const EigenIndex n = a.shape(0),
-              stride = a.strides(0) / scalar_size;
+        // Otherwise we're storing an n-vector.  Only one of the strides will be used, but
+        // whichever is used, we want the (single) numpy stride value.
+        const EigenIndex n = a.shape(0), stride = a.strides(0) / scalar_size;
 
         if (vector) { // Eigen type is a compile-time vector
             if (PYBIND11_SILENCE_MSVC_C4127(fixed) && size != n) {
@@ -203,88 +224,88 @@ template <typename Type_> struct EigenProps {
         if (PYBIND11_SILENCE_MSVC_C4127(fixed_rows) && rows != n) {
             return false;
         }
-            return {n, 1, stride};
+        return {n, 1, stride};
     }
 
-    static constexpr bool show_writeable = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
+    static constexpr bool show_writeable
+        = is_eigen_dense_map<Type>::value && is_eigen_mutable_map<Type>::value;
     static constexpr bool show_order = is_eigen_dense_map<Type>::value;
     static constexpr bool show_c_contiguous = show_order && requires_row_major;
-    static constexpr bool show_f_contiguous = !show_c_contiguous && show_order && requires_col_major;
-
-    static constexpr auto descriptor =
-        const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name +
-        const_name("[")  + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) +
-        const_name(", ") + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) +
-        const_name("]") +
-        // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to be
-        // satisfied: writeable=True (for a mutable reference), and, depending on the map's stride
-        // options, possibly f_contiguous or c_contiguous.  We include them in the descriptor output
-        // to provide some hint as to why a TypeError is occurring (otherwise it can be confusing to
-        // see that a function accepts a 'numpy.ndarray[float64[3,2]]' and an error message that you
-        // *gave* a numpy.ndarray of the right type and dimensions.
-        const_name<show_writeable>(", flags.writeable", "") +
-        const_name<show_c_contiguous>(", flags.c_contiguous", "") +
-        const_name<show_f_contiguous>(", flags.f_contiguous", "") +
-        const_name("]");
+    static constexpr bool show_f_contiguous
+        = !show_c_contiguous && show_order && requires_col_major;
+
+    static constexpr auto descriptor
+        = const_name("numpy.ndarray[") + npy_format_descriptor<Scalar>::name + const_name("[")
+          + const_name<fixed_rows>(const_name<(size_t) rows>(), const_name("m")) + const_name(", ")
+          + const_name<fixed_cols>(const_name<(size_t) cols>(), const_name("n")) + const_name("]")
+          +
+          // For a reference type (e.g. Ref<MatrixXd>) we have other constraints that might need to
+          // be satisfied: writeable=True (for a mutable reference), and, depending on the map's
+          // stride options, possibly f_contiguous or c_contiguous.  We include them in the
+          // descriptor output to provide some hint as to why a TypeError is occurring (otherwise
+          // it can be confusing to see that a function accepts a 'numpy.ndarray[float64[3,2]]' and
+          // an error message that you *gave* a numpy.ndarray of the right type and dimensions.
+          const_name<show_writeable>(", flags.writeable", "")
+          + const_name<show_c_contiguous>(", flags.c_contiguous", "")
+          + const_name<show_f_contiguous>(", flags.f_contiguous", "") + const_name("]");
 };
 
 // Casts an Eigen type to numpy array.  If given a base, the numpy array references the src data,
 // otherwise it'll make a copy.  writeable lets you turn off the writeable flag for the array.
-template <typename props> handle eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
+template <typename props>
+handle
+eigen_array_cast(typename props::Type const &src, handle base = handle(), bool writeable = true) {
     constexpr ssize_t elem_size = sizeof(typename props::Scalar);
     array a;
     using Scalar = typename props::Type::Scalar;
-    bool is_pyobject = static_cast<pybind11::detail::npy_api::constants>(npy_format_descriptor<Scalar>::value) == npy_api::NPY_OBJECT_;
+    bool is_pyobject
+        = static_cast<pybind11::detail::npy_api::constants>(npy_format_descriptor<Scalar>::value)
+          == npy_api::NPY_OBJECT_;
 
     if (!is_pyobject) {
         if (props::vector) {
-            a = array({ src.size() }, { elem_size * src.innerStride() }, src.data(), base);
+            a = array({src.size()}, {elem_size * src.innerStride()}, src.data(), base);
         } else {
             a = array({src.rows(), src.cols()},
-                  {elem_size * src.rowStride(), elem_size * src.colStride()},
+                      {elem_size * src.rowStride(), elem_size * src.colStride()},
                       src.data(),
-                  base);
+                      base);
         }
-    }
-    else {
+    } else {
         if (base) {
             // Should be disabled by upstream calls to this method.
             // TODO(eric.cousineau): Write tests to ensure that this is not
             // reachable.
-            throw cast_error(
-                "dtype=object does not permit array referencing. "
-                "(NOTE: this generally not be reachable, as upstream APIs "
-                "should fail before this.");
+            throw cast_error("dtype=object does not permit array referencing. "
+                             "(NOTE: this generally not be reachable, as upstream APIs "
+                             "should fail before this.");
         }
         handle empty_base{};
         auto policy = return_value_policy::copy;
         if (props::vector) {
-            a = array(
-                npy_format_descriptor<Scalar>::dtype(),
-                { (size_t) src.size() },
-                nullptr,
-                empty_base
-            );
+            a = array(npy_format_descriptor<Scalar>::dtype(),
+                      {(size_t) src.size()},
+                      nullptr,
+                      empty_base);
             constexpr bool is_row = props::fixed_rows && props::rows == 1;
             for (ssize_t i = 0; i < src.size(); ++i) {
                 const Scalar src_val = is_row ? src(0, i) : src(i, 0);
-                auto value_ = reinterpret_steal<object>(make_caster<Scalar>::cast(src_val, policy, empty_base));
+                auto value_ = reinterpret_steal<object>(
+                    make_caster<Scalar>::cast(src_val, policy, empty_base));
                 if (!value_) {
                     return handle();
                 }
                 a.attr("itemset")(i, value_);
             }
-        }
-        else {
-            a = array(
-                npy_format_descriptor<Scalar>::dtype(),
-                {(size_t) src.rows(), (size_t) src.cols()},
-                nullptr,
-                empty_base
-            );
+        } else {
+            a = array(npy_format_descriptor<Scalar>::dtype(),
+                      {(size_t) src.rows(), (size_t) src.cols()},
+                      nullptr,
+                      empty_base);
             for (ssize_t i = 0; i < src.rows(); ++i) {
                 for (ssize_t j = 0; j < src.cols(); ++j) {
-                    auto value_ = reinterpret_steal<object>(make_caster<Scalar>::cast(src(i, j), policy, empty_base));
+                    auto value_ = reinterpret_steal<object>(
+                        make_caster<Scalar>::cast(src(i, j), policy, empty_base));
                     if (!value_) {
                         return handle();
                     }
@@ -312,10 +333,10 @@ handle eigen_ref_array(Type &src, handle parent = none()) {
     return eigen_array_cast<props>(src, parent, !std::is_const<Type>::value);
 }
 
-// Takes a pointer to some dense, plain Eigen type, builds a capsule around it, then returns a numpy
-// array that references the encapsulated data with a python-side reference to the capsule to tie
-// its destruction to that of any dependent python objects.  Const-ness is determined by whether or
-// not the Type of the pointer given is const.
+// Takes a pointer to some dense, plain Eigen type, builds a capsule around it, then returns a
+// numpy array that references the encapsulated data with a python-side reference to the capsule to
+// tie its destruction to that of any dependent python objects.  Const-ness is determined by
+// whether or not the Type of the pointer given is const.
 template <typename props, typename Type, typename = enable_if_t<is_eigen_dense_plain<Type>::value>>
 handle eigen_encapsulate(Type *src) {
     capsule base(src, [](void *o) { delete static_cast<Type *>(o); });
@@ -324,7 +345,7 @@ handle eigen_encapsulate(Type *src) {
 
 // Type caster for regular, dense matrix types (e.g. MatrixXd), but not maps/refs/etc. of dense
 // types.
-template<typename Type>
+template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     using Scalar = typename Type::Scalar;
     using props = EigenProps<Type>;
@@ -364,10 +385,8 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
             } else if (ref.ndim() == 1) {
                 buf = buf.squeeze();
             }
-            result =
-                detail::npy_api::get().PyArray_CopyInto_(ref.ptr(), buf.ptr());
-        }
-        else {
+            result = detail::npy_api::get().PyArray_CopyInto_(ref.ptr(), buf.ptr());
+        } else {
             if (dims == 1) {
                 if (Type::RowsAtCompileTime == Eigen::Dynamic) {
                     value.resize(buf.shape(0), 1);
@@ -376,24 +395,26 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
                 }
 
                 for (ssize_t i = 0; i < buf.shape(0); ++i) {
-                    make_caster <Scalar> conv_val;
+                    make_caster<Scalar> conv_val;
                     if (!conv_val.load(buf.attr("item")(i).cast<pybind11::object>(), convert)) {
                         return false;
                     }
                     value(i) = cast_op<Scalar>(conv_val);
                 }
             } else {
-                if (Type::RowsAtCompileTime == Eigen::Dynamic || Type::ColsAtCompileTime == Eigen::Dynamic) {
+                if (Type::RowsAtCompileTime == Eigen::Dynamic
+                    || Type::ColsAtCompileTime == Eigen::Dynamic) {
                     value.resize(buf.shape(0), buf.shape(1));
                 }
                 for (ssize_t i = 0; i < buf.shape(0); ++i) {
                     for (ssize_t j = 0; j < buf.shape(1); ++j) {
                         // p is the const void pointer to the item
                         make_caster<Scalar> conv_val;
-                        if (!conv_val.load(buf.attr("item")(i,j).cast<pybind11::object>(), convert)) {
+                        if (!conv_val.load(buf.attr("item")(i, j).cast<pybind11::object>(),
+                                           convert)) {
                             return false;
                         }
-                        value(i,j) = cast_op<Scalar>(conv_val);
+                        value(i, j) = cast_op<Scalar>(conv_val);
                     }
                 }
             }
@@ -408,7 +429,6 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     }
 
 private:
-
     // Cast implementation
     template <typename CType>
     static handle cast_impl(CType *src, return_value_policy policy, handle parent) {
@@ -431,7 +451,8 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
                     throw cast_error("unhandled return_value_policy: should not happen!");
             };
         } else {
-            // For arrays of `dtype=object`, referencing is invalid, so we should squash that as soon as possible.
+            // For arrays of `dtype=object`, referencing is invalid, so we should squash that as
+            // soon as possible.
             switch (policy) {
                 case return_value_policy::automatic:
                 case return_value_policy::move:
@@ -441,7 +462,8 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
                 case return_value_policy::take_ownership:
                 case return_value_policy::reference:
                 case return_value_policy::reference_internal:
-                    throw cast_error("dtype=object arrays must be copied, and cannot be referenced");
+                    throw cast_error(
+                        "dtype=object arrays must be copied, and cannot be referenced");
                 default:
                     throw cast_error("unhandled return_value_policy: should not happen!");
             };
@@ -449,7 +471,6 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     }
 
 public:
-
     // Normal returned non-reference, non-const value:
     static handle cast(Type &&src, return_value_policy /* policy */, handle parent) {
         return cast_impl(&src, return_value_policy::move, parent);
@@ -486,42 +507,45 @@ struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     static constexpr auto name = props::descriptor;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type*() { return &value; }
+    operator Type *() { return &value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type&() { return value; }
+    operator Type &() { return value; }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type&&() && { return std::move(value); }
-    template <typename T> using cast_op_type = movable_cast_op_type<T>;
+    operator Type &&() && { return std::move(value); }
+    template <typename T>
+    using cast_op_type = movable_cast_op_type<T>;
 
 private:
     Type value;
 };
 
 // Base class for casting reference/map/block/etc. objects back to python.
-template <typename MapType> struct eigen_map_caster {
+template <typename MapType>
+struct eigen_map_caster {
 private:
     using props = EigenProps<MapType>;
     using Scalar = typename props::Scalar;
 
 public:
-
     // Directly referencing a ref/map's data is a bit dangerous (whatever the map/ref points to has
-    // to stay around), but we'll allow it under the assumption that you know what you're doing (and
-    // have an appropriate keep_alive in place).  We return a numpy array pointing directly at the
-    // ref's data (The numpy array ends up read-only if the ref was to a const matrix type.) Note
-    // that this means you need to ensure you don't destroy the object in some other way (e.g. with
-    // an appropriate keep_alive, or with a reference to a statically allocated matrix).
+    // to stay around), but we'll allow it under the assumption that you know what you're doing
+    // (and have an appropriate keep_alive in place).  We return a numpy array pointing directly at
+    // the ref's data (The numpy array ends up read-only if the ref was to a const matrix type.)
+    // Note that this means you need to ensure you don't destroy the object in some other way (e.g.
+    // with an appropriate keep_alive, or with a reference to a statically allocated matrix).
     static handle cast(const MapType &src, return_value_policy policy, handle parent) {
         if (!is_pyobject_dtype<Scalar>::value) {
             switch (policy) {
                 case return_value_policy::copy:
                     return eigen_array_cast<props>(src);
                 case return_value_policy::reference_internal:
-                    return eigen_array_cast<props>(src, parent, is_eigen_mutable_map<MapType>::value);
+                    return eigen_array_cast<props>(
+                        src, parent, is_eigen_mutable_map<MapType>::value);
                 case return_value_policy::reference:
                 case return_value_policy::automatic:
                 case return_value_policy::automatic_reference:
-                    return eigen_array_cast<props>(src, none(), is_eigen_mutable_map<MapType>::value);
+                    return eigen_array_cast<props>(
+                        src, none(), is_eigen_mutable_map<MapType>::value);
                 default:
                     // move, take_ownership don't make any sense for a ref/map:
                     pybind11_fail("Invalid return_value_policy for Eigen Map/Ref/Block type");
@@ -534,7 +558,8 @@ template <typename MapType> struct eigen_map_caster {
                 case return_value_policy::reference:
                 case return_value_policy::automatic:
                 case return_value_policy::automatic_reference:
-                    throw cast_error("dtype=object arrays must be copied, and cannot be referenced");
+                    throw cast_error(
+                        "dtype=object arrays must be copied, and cannot be referenced");
                 default:
                     // move, take_ownership don't make any sense for a ref/map:
                     pybind11_fail("Invalid return_value_policy for Eigen Map/Ref/Block type");
@@ -549,51 +574,59 @@ template <typename MapType> struct eigen_map_caster {
     // you end up here if you try anyway.
     bool load(handle, bool) = delete;
     operator MapType() = delete;
-    template <typename> using cast_op_type = MapType;
+    template <typename>
+    using cast_op_type = MapType;
 };
 
 // We can return any map-like object (but can only load Refs, specialized next):
-template <typename Type> struct type_caster<Type, enable_if_t<is_eigen_dense_map<Type>::value>>
-    : eigen_map_caster<Type> {};
+template <typename Type>
+struct type_caster<Type, enable_if_t<is_eigen_dense_map<Type>::value>> : eigen_map_caster<Type> {};
 
 // Loader for Ref<...> arguments.  See the documentation for info on how to make this work without
 // copying (it requires some extra effort in many cases).
 template <typename PlainObjectType, typename StrideType>
 struct type_caster<
     Eigen::Ref<PlainObjectType, 0, StrideType>,
-    enable_if_t<is_eigen_dense_map<Eigen::Ref<PlainObjectType, 0, StrideType>>::value>
-> : public eigen_map_caster<Eigen::Ref<PlainObjectType, 0, StrideType>> {
+    enable_if_t<is_eigen_dense_map<Eigen::Ref<PlainObjectType, 0, StrideType>>::value>>
+    : public eigen_map_caster<Eigen::Ref<PlainObjectType, 0, StrideType>> {
 private:
     using Type = Eigen::Ref<PlainObjectType, 0, StrideType>;
     using props = EigenProps<Type>;
     using Scalar = typename props::Scalar;
     using MapType = Eigen::Map<PlainObjectType, 0, StrideType>;
-    using Array = array_t<Scalar, array::forcecast |
-                ((props::row_major ? props::inner_stride : props::outer_stride) == 1 ? array::c_style :
-                 (props::row_major ? props::outer_stride : props::inner_stride) == 1 ? array::f_style : 0)>;
+    using Array
+        = array_t<Scalar,
+                  array::forcecast
+                      | ((props::row_major ? props::inner_stride : props::outer_stride) == 1
+                             ? array::c_style
+                         : (props::row_major ? props::outer_stride : props::inner_stride) == 1
+                             ? array::f_style
+                             : 0)>;
     static constexpr bool need_writeable = is_eigen_mutable_map<Type>::value;
     // Delay construction (these have no default constructor)
     std::unique_ptr<MapType> map;
     std::unique_ptr<Type> ref;
     // Our array.  When possible, this is just a numpy array pointing to the source data, but
-    // sometimes we can't avoid copying (e.g. input is not a numpy array at all, has an incompatible
-    // layout, or is an array of a type that needs to be converted).  Using a numpy temporary
-    // (rather than an Eigen temporary) saves an extra copy when we need both type conversion and
-    // storage order conversion.  (Note that we refuse to use this temporary copy when loading an
-    // argument for a Ref<M> with M non-const, i.e. a read-write reference).
+    // sometimes we can't avoid copying (e.g. input is not a numpy array at all, has an
+    // incompatible layout, or is an array of a type that needs to be converted).  Using a numpy
+    // temporary (rather than an Eigen temporary) saves an extra copy when we need both type
+    // conversion and storage order conversion.  (Note that we refuse to use this temporary copy
+    // when loading an argument for a Ref<M> with M non-const, i.e. a read-write reference).
     Array copy_or_ref;
     typename std::remove_cv<PlainObjectType>::type val;
+
 public:
     bool load(handle src, bool convert) {
-        // First check whether what we have is already an array of the right type.  If not, we can't
-        // avoid a copy (because the copy is also going to do type conversion).
+        // First check whether what we have is already an array of the right type.  If not, we
+        // can't avoid a copy (because the copy is also going to do type conversion).
         bool need_copy = !isinstance<Array>(src);
 
         EigenConformable<props::row_major> fits;
         constexpr bool is_pyobject = is_pyobject_dtype<Scalar>::value;
         // TODO(eric.cousineau): Make this compile-time once Drake does not use this in any code
         // for scalar types.
-        //static_assert(!(is_pyobject && need_writeable), "dtype=object cannot provide writeable references");
+        // static_assert(!(is_pyobject && need_writeable), "dtype=object cannot provide writeable
+        // references");
         if (is_pyobject && need_writeable) {
             throw cast_error("dtype=object cannot provide writeable references");
         }
@@ -615,8 +648,7 @@ struct type_caster<
                 } else {
                     copy_or_ref = std::move(aref);
                 }
-            }
-            else {
+            } else {
                 need_copy = true;
             }
         }
@@ -644,28 +676,30 @@ struct type_caster<
             } else {
                 auto dims = copy.ndim();
                 if (dims == 1) {
-                    if (Type::RowsAtCompileTime == Eigen::Dynamic || Type::ColsAtCompileTime == Eigen::Dynamic) {
+                    if (Type::RowsAtCompileTime == Eigen::Dynamic
+                        || Type::ColsAtCompileTime == Eigen::Dynamic) {
                         val.resize(copy.shape(0), 1);
                     }
                     for (ssize_t i = 0; i < copy.shape(0); ++i) {
-                        make_caster <Scalar> conv_val;
+                        make_caster<Scalar> conv_val;
                         if (!conv_val.load(copy.attr("item")(i).template cast<pybind11::object>(),
                                            convert)) {
                             return false;
                         }
                         val(i) = cast_op<Scalar>(conv_val);
-
                     }
                 } else {
-                    if (Type::RowsAtCompileTime == Eigen::Dynamic || Type::ColsAtCompileTime == Eigen::Dynamic) {
+                    if (Type::RowsAtCompileTime == Eigen::Dynamic
+                        || Type::ColsAtCompileTime == Eigen::Dynamic) {
                         val.resize(copy.shape(0), copy.shape(1));
                     }
                     for (ssize_t i = 0; i < copy.shape(0); ++i) {
                         for (ssize_t j = 0; j < copy.shape(1); ++j) {
                             // p is the const void pointer to the item
-                            make_caster <Scalar> conv_val;
-                            if (!conv_val.load(copy.attr("item")(i, j).template cast<pybind11::object>(),
-                                               convert)) {
+                            make_caster<Scalar> conv_val;
+                            if (!conv_val.load(
+                                    copy.attr("item")(i, j).template cast<pybind11::object>(),
+                                    convert)) {
                                 return false;
                             }
                             val(i, j) = cast_op<Scalar>(conv_val);
@@ -678,54 +712,76 @@ struct type_caster<
         }
 
         ref.reset();
-        map.reset(new MapType(data(copy_or_ref), fits.rows, fits.cols, make_stride(fits.stride.outer(), fits.stride.inner())));
+        map.reset(new MapType(data(copy_or_ref),
+                              fits.rows,
+                              fits.cols,
+                              make_stride(fits.stride.outer(), fits.stride.inner())));
         ref.reset(new Type(*map));
 
         return true;
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type*() { return ref.get(); }
+    operator Type *() { return ref.get(); }
     // NOLINTNEXTLINE(google-explicit-constructor)
-    operator Type&() { return *ref; }
-    template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
+    operator Type &() { return *ref; }
+    template <typename _T>
+    using cast_op_type = pybind11::detail::cast_op_type<_T>;
 
 private:
     template <typename T = Type, enable_if_t<is_eigen_mutable_map<T>::value, int> = 0>
-    Scalar *data(Array &a) { return a.mutable_data(); }
+    Scalar *data(Array &a) {
+        return a.mutable_data();
+    }
 
     template <typename T = Type, enable_if_t<!is_eigen_mutable_map<T>::value, int> = 0>
-    const Scalar *data(Array &a) { return a.data(); }
+    const Scalar *data(Array &a) {
+        return a.data();
+    }
 
     // Attempt to figure out a constructor of `Stride` that will work.
     // If both strides are fixed, use a default constructor:
-    template <typename S> using stride_ctor_default = bool_constant<
-        S::InnerStrideAtCompileTime != Eigen::Dynamic && S::OuterStrideAtCompileTime != Eigen::Dynamic &&
-        std::is_default_constructible<S>::value>;
+    template <typename S>
+    using stride_ctor_default = bool_constant<S::InnerStrideAtCompileTime != Eigen::Dynamic
+                                              && S::OuterStrideAtCompileTime != Eigen::Dynamic
+                                              && std::is_default_constructible<S>::value>;
     // Otherwise, if there is a two-index constructor, assume it is (outer,inner) like
     // Eigen::Stride, and use it:
-    template <typename S> using stride_ctor_dual = bool_constant<
-        !stride_ctor_default<S>::value && std::is_constructible<S, EigenIndex, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_dual
+        = bool_constant<!stride_ctor_default<S>::value
+                        && std::is_constructible<S, EigenIndex, EigenIndex>::value>;
     // Otherwise, if there is a one-index constructor, and just one of the strides is dynamic, use
     // it (passing whichever stride is dynamic).
-    template <typename S> using stride_ctor_outer = bool_constant<
-        !any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value &&
-        S::OuterStrideAtCompileTime == Eigen::Dynamic && S::InnerStrideAtCompileTime != Eigen::Dynamic &&
-        std::is_constructible<S, EigenIndex>::value>;
-    template <typename S> using stride_ctor_inner = bool_constant<
-        !any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value &&
-        S::InnerStrideAtCompileTime == Eigen::Dynamic && S::OuterStrideAtCompileTime != Eigen::Dynamic &&
-        std::is_constructible<S, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_outer
+        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
+                        && S::OuterStrideAtCompileTime == Eigen::Dynamic
+                        && S::InnerStrideAtCompileTime != Eigen::Dynamic
+                        && std::is_constructible<S, EigenIndex>::value>;
+    template <typename S>
+    using stride_ctor_inner
+        = bool_constant<!any_of<stride_ctor_default<S>, stride_ctor_dual<S>>::value
+                        && S::InnerStrideAtCompileTime == Eigen::Dynamic
+                        && S::OuterStrideAtCompileTime != Eigen::Dynamic
+                        && std::is_constructible<S, EigenIndex>::value>;
 
     template <typename S = StrideType, enable_if_t<stride_ctor_default<S>::value, int> = 0>
-    static S make_stride(EigenIndex, EigenIndex) { return S(); }
+    static S make_stride(EigenIndex, EigenIndex) {
+        return S();
+    }
     template <typename S = StrideType, enable_if_t<stride_ctor_dual<S>::value, int> = 0>
-    static S make_stride(EigenIndex outer, EigenIndex inner) { return S(outer, inner); }
+    static S make_stride(EigenIndex outer, EigenIndex inner) {
+        return S(outer, inner);
+    }
     template <typename S = StrideType, enable_if_t<stride_ctor_outer<S>::value, int> = 0>
-    static S make_stride(EigenIndex outer, EigenIndex) { return S(outer); }
+    static S make_stride(EigenIndex outer, EigenIndex) {
+        return S(outer);
+    }
     template <typename S = StrideType, enable_if_t<stride_ctor_inner<S>::value, int> = 0>
-    static S make_stride(EigenIndex, EigenIndex inner) { return S(inner); }
-
+    static S make_stride(EigenIndex, EigenIndex inner) {
+        return S(inner);
+    }
 };
 
 // type_caster for special matrix types (e.g. DiagonalMatrix), which are EigenBase, but not
@@ -735,14 +791,18 @@ struct type_caster<
 template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
 protected:
-    using Matrix = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
+    using Matrix
+        = Eigen::Matrix<typename Type::Scalar, Type::RowsAtCompileTime, Type::ColsAtCompileTime>;
     using props = EigenProps<Matrix>;
+
 public:
     static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
         handle h = eigen_encapsulate<props>(new Matrix(src));
         return h;
     }
-    static handle cast(const Type *src, return_value_policy policy, handle parent) { return cast(*src, policy, parent); }
+    static handle cast(const Type *src, return_value_policy policy, handle parent) {
+        return cast(*src, policy, parent);
+    }
 
     static constexpr auto name = props::descriptor;
 
@@ -751,10 +811,11 @@ struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
     // you end up here if you try anyway.
     bool load(handle, bool) = delete;
     operator Type() = delete;
-    template <typename> using cast_op_type = Type;
+    template <typename>
+    using cast_op_type = Type;
 };
 
-template<typename Type>
+template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
     using Scalar = typename Type::Scalar;
     using StorageIndex = remove_reference_t<decltype(*std::declval<Type>().outerIndexPtr())>;
@@ -775,8 +836,7 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
             // when scipy is not available, instead of raising an import error.
             return false;
         }
-        object matrix_type = sparse_module.attr(
-            rowMajor ? "csr_matrix" : "csc_matrix");
+        object matrix_type = sparse_module.attr(rowMajor ? "csr_matrix" : "csc_matrix");
 
         if (!type::handle_of(obj).is(matrix_type)) {
             try {
@@ -797,32 +857,36 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         }
 
         value = EigenMapSparseMatrix<Scalar,
-                                     Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
-                                     StorageIndex>(
-            shape[0].cast<Index>(), shape[1].cast<Index>(), nnz,
-            outerIndices.mutable_data(), innerIndices.mutable_data(), values.mutable_data());
+                                     Type::Flags &(Eigen::RowMajor | Eigen::ColMajor),
+                                     StorageIndex>(shape[0].cast<Index>(),
+                                                   shape[1].cast<Index>(),
+                                                   nnz,
+                                                   outerIndices.mutable_data(),
+                                                   innerIndices.mutable_data(),
+                                                   values.mutable_data());
 
         return true;
     }
 
     static handle cast(const Type &src, return_value_policy /* policy */, handle /* parent */) {
-        const_cast<Type&>(src).makeCompressed();
+        const_cast<Type &>(src).makeCompressed();
 
-        object matrix_type = module_::import("scipy.sparse").attr(
-            rowMajor ? "csr_matrix" : "csc_matrix");
+        object matrix_type
+            = module_::import("scipy.sparse").attr(rowMajor ? "csr_matrix" : "csc_matrix");
 
         array data(src.nonZeros(), src.valuePtr());
         array outerIndices((rowMajor ? src.rows() : src.cols()) + 1, src.outerIndexPtr());
         array innerIndices(src.nonZeros(), src.innerIndexPtr());
 
-        return matrix_type(
-            std::make_tuple(data, innerIndices, outerIndices),
-            std::make_pair(src.rows(), src.cols())
-        ).release();
+        return matrix_type(std::make_tuple(data, innerIndices, outerIndices),
+                           std::make_pair(src.rows(), src.cols()))
+            .release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[", "scipy.sparse.csc_matrix[")
-            + npy_format_descriptor<Scalar>::name + const_name("]"));
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name<(Type::IsRowMajor) != 0>("scipy.sparse.csr_matrix[",
+                                                             "scipy.sparse.csc_matrix[")
+                             + npy_format_descriptor<Scalar>::name + const_name("]"));
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 0c3f778136..84e4422212 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -16,21 +16,17 @@
 #include <vector>
 
 #if defined(PYPY_VERSION)
-#  error Embedding the interpreter is not supported with PyPy
+#    error Embedding the interpreter is not supported with PyPy
 #endif
 
 #if PY_MAJOR_VERSION >= 3
-#  define PYBIND11_EMBEDDED_MODULE_IMPL(name)            \
-      extern "C" PyObject *pybind11_init_impl_##name();  \
-      extern "C" PyObject *pybind11_init_impl_##name() { \
-          return pybind11_init_wrapper_##name();         \
-      }
+#    define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                   \
+        extern "C" PyObject *pybind11_init_impl_##name();                                         \
+        extern "C" PyObject *pybind11_init_impl_##name() { return pybind11_init_wrapper_##name(); }
 #else
-#  define PYBIND11_EMBEDDED_MODULE_IMPL(name)            \
-      extern "C" void pybind11_init_impl_##name();       \
-      extern "C" void pybind11_init_impl_##name() {      \
-          pybind11_init_wrapper_##name();                \
-      }
+#    define PYBIND11_EMBEDDED_MODULE_IMPL(name)                                                   \
+        extern "C" void pybind11_init_impl_##name();                                              \
+        extern "C" void pybind11_init_impl_##name() { pybind11_init_wrapper_##name(); }
 #endif
 
 /** \rst
@@ -72,7 +68,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
 struct embedded_module {
 #if PY_MAJOR_VERSION >= 3
-    using init_t = PyObject *(*)();
+    using init_t = PyObject *(*) ();
 #else
     using init_t = void (*)();
 #endif
@@ -106,10 +102,10 @@ inline wchar_t *widen_chars(const char *safe_arg) {
     wchar_t *widened_arg = nullptr;
 
 // warning C4996: 'mbstowcs': This function or variable may be unsafe.
-#if defined(_MSC_VER)
-#pragma warning(push)
-#pragma warning(disable:4996)
-#endif
+#    if defined(_MSC_VER)
+#        pragma warning(push)
+#        pragma warning(disable : 4996)
+#    endif
 
 #    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
     size_t count = std::strlen(safe_arg);
@@ -121,9 +117,9 @@ inline wchar_t *widen_chars(const char *safe_arg) {
         std::mbstowcs(widened_arg, safe_arg, count + 1);
     }
 
-#if defined(_MSC_VER)
-#pragma warning(pop)
-#endif
+#    if defined(_MSC_VER)
+#        pragma warning(pop)
+#    endif
 
 #endif
     return widened_arg;
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 8009fbde58..731dedd4b1 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -11,24 +11,24 @@
 
 #pragma once
 
-#include <utility>
-
 #include "pybind11.h"
 
+#include <utility>
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline void ensure_builtins_in_globals(object &global) {
-    #if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
-        // Running exec and eval on Python 2 and 3 adds `builtins` module under
-        // `__builtins__` key to globals if not yet present.
-        // Python 3.8 made PyRun_String behave similarly. Let's also do that for
-        // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
-        if (!global.contains("__builtins__"))
-            global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
-    #else
-        (void) global;
-    #endif
+#if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
+    // Running exec and eval on Python 2 and 3 adds `builtins` module under
+    // `__builtins__` key to globals if not yet present.
+    // Python 3.8 made PyRun_String behave similarly. Let's also do that for
+    // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
+    if (!global.contains("__builtins__"))
+        global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
+#else
+    (void) global;
+#endif
 }
 
 PYBIND11_NAMESPACE_END(detail)
@@ -58,10 +58,17 @@ object eval(const str &expr, object global = globals(), object local = object())
 
     int start = 0;
     switch (mode) {
-        case eval_expr:             start = Py_eval_input;   break;
-        case eval_single_statement: start = Py_single_input; break;
-        case eval_statements:       start = Py_file_input;   break;
-        default: pybind11_fail("invalid evaluation mode");
+        case eval_expr:
+            start = Py_eval_input;
+            break;
+        case eval_single_statement:
+            start = Py_single_input;
+            break;
+        case eval_statements:
+            start = Py_file_input;
+            break;
+        default:
+            pybind11_fail("invalid evaluation mode");
     }
 
     PyObject *result = PyRun_String(buffer.c_str(), start, global.ptr(), local.ptr());
@@ -74,8 +81,7 @@ object eval(const str &expr, object global = globals(), object local = object())
 template <eval_mode mode = eval_expr, size_t N>
 object eval(const char (&s)[N], object global = globals(), object local = object()) {
     /* Support raw string literals by removing common leading whitespace */
-    auto expr = (s[0] == '\n') ? str(module_::import("textwrap").attr("dedent")(s))
-                               : str(s);
+    auto expr = (s[0] == '\n') ? str(module_::import("textwrap").attr("dedent")(s)) : str(s);
     return eval<mode>(expr, global, local);
 }
 
@@ -112,28 +118,34 @@ object eval_file(str fname, object global = globals(), object local = object())
 
     int start = 0;
     switch (mode) {
-        case eval_expr:             start = Py_eval_input;   break;
-        case eval_single_statement: start = Py_single_input; break;
-        case eval_statements:       start = Py_file_input;   break;
-        default: pybind11_fail("invalid evaluation mode");
+        case eval_expr:
+            start = Py_eval_input;
+            break;
+        case eval_single_statement:
+            start = Py_single_input;
+            break;
+        case eval_statements:
+            start = Py_file_input;
+            break;
+        default:
+            pybind11_fail("invalid evaluation mode");
     }
 
     int closeFile = 1;
     std::string fname_str = (std::string) fname;
-#if PY_VERSION_HEX >= 0x03040000
+#    if PY_VERSION_HEX >= 0x03040000
     FILE *f = _Py_fopen_obj(fname.ptr(), "r");
-#elif PY_VERSION_HEX >= 0x03000000
+#    elif PY_VERSION_HEX >= 0x03000000
     FILE *f = _Py_fopen(fname.ptr(), "r");
-#else
+#    else
     /* No unicode support in open() :( */
-    auto fobj = reinterpret_steal<object>(PyFile_FromString(
-        const_cast<char *>(fname_str.c_str()),
-        const_cast<char*>("r")));
+    auto fobj = reinterpret_steal<object>(
+        PyFile_FromString(const_cast<char *>(fname_str.c_str()), const_cast<char *>("r")));
     FILE *f = nullptr;
     if (fobj)
         f = PyFile_AsFile(fobj.ptr());
     closeFile = 0;
-#endif
+#    endif
     if (!f) {
         PyErr_Clear();
         pybind11_fail("File \"" + fname_str + "\" could not be opened!");
@@ -142,20 +154,19 @@ object eval_file(str fname, object global = globals(), object local = object())
     // In Python2, this should be encoded by getfilesystemencoding.
     // We don't boher setting it since Python2 is past EOL anyway.
     // See PR#3233
-#if PY_VERSION_HEX >= 0x03000000
+#    if PY_VERSION_HEX >= 0x03000000
     if (!global.contains("__file__")) {
         global["__file__"] = std::move(fname);
     }
-#endif
+#    endif
 
-#if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
-    PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(),
-                                  local.ptr());
+#    if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
+    PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(), local.ptr());
     (void) closeFile;
-#else
-    PyObject *result = PyRun_FileEx(f, fname_str.c_str(), start, global.ptr(),
-                                    local.ptr(), closeFile);
-#endif
+#    else
+    PyObject *result
+        = PyRun_FileEx(f, fname_str.c_str(), start, global.ptr(), local.ptr(), closeFile);
+#    endif
 
     if (!result) {
         throw error_already_set();
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index 95a1a02af7..69cfed5476 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "pybind11.h"
+
 #include <functional>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -19,7 +20,7 @@ template <typename Return, typename... Args>
 struct type_caster<std::function<Return(Args...)>> {
     using type = std::function<Return(Args...)>;
     using retval_type = conditional_t<std::is_same<Return, void>::value, void_type, Return>;
-    using function_type = Return (*) (Args...);
+    using function_type = Return (*)(Args...);
 
 public:
     bool load(handle src, bool convert) {
@@ -76,7 +77,9 @@ struct type_caster<std::function<Return(Args...)>> {
             // This triggers a syntax error under very special conditions (very weird indeed).
             explicit
 #endif
-            func_handle(function &&f_) noexcept : f(std::move(f_)) {}
+                func_handle(function &&f_) noexcept
+                : f(std::move(f_)) {
+            }
             func_handle(const func_handle &f_) { operator=(f_); }
             func_handle &operator=(const func_handle &f_) {
                 gil_scoped_acquire acq;
@@ -118,8 +121,10 @@ struct type_caster<std::function<Return(Args...)>> {
         return cpp_function(std::forward<Func>(f_), policy).release();
     }
 
-    PYBIND11_TYPE_CASTER(type, const_name("Callable[[") + concat(make_caster<Args>::name...) + const_name("], ")
-                               + make_caster<retval_type>::name + const_name("]"));
+    PYBIND11_TYPE_CASTER(type,
+                         const_name("Callable[[") + concat(make_caster<Args>::name...)
+                             + const_name("], ") + make_caster<retval_type>::name
+                             + const_name("]"));
 };
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/gil.h b/include/pybind11/gil.h
index 345177f84f..446f4620b2 100644
--- a/include/pybind11/gil.h
+++ b/include/pybind11/gil.h
@@ -14,7 +14,6 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
-
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 // forward declarations
@@ -22,7 +21,6 @@ PyThreadState *get_thread_state_unchecked();
 
 PYBIND11_NAMESPACE_END(detail)
 
-
 #if defined(WITH_THREAD) && !defined(PYPY_VERSION)
 
 /* The functions below essentially reproduce the PyGILState_* API using a RAII
@@ -64,11 +62,11 @@ class gil_scoped_acquire {
 
         if (!tstate) {
             tstate = PyThreadState_New(internals.istate);
-            #if !defined(NDEBUG)
+#    if !defined(NDEBUG)
             if (!tstate) {
                 pybind11_fail("scoped_acquire: could not create thread state!");
             }
-#endif
+#    endif
             tstate->gilstate_counter = 0;
             PYBIND11_TLS_REPLACE_VALUE(internals.tstate, tstate);
         } else {
@@ -82,26 +80,24 @@ class gil_scoped_acquire {
         inc_ref();
     }
 
-    void inc_ref() {
-        ++tstate->gilstate_counter;
-    }
+    void inc_ref() { ++tstate->gilstate_counter; }
 
     PYBIND11_NOINLINE void dec_ref() {
         --tstate->gilstate_counter;
-        #if !defined(NDEBUG)
+#    if !defined(NDEBUG)
         if (detail::get_thread_state_unchecked() != tstate) {
             pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
         }
         if (tstate->gilstate_counter < 0) {
             pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
         }
-#endif
+#    endif
         if (tstate->gilstate_counter == 0) {
-            #if !defined(NDEBUG)
+#    if !defined(NDEBUG)
             if (!release) {
                 pybind11_fail("scoped_acquire::dec_ref(): internal error!");
             }
-#endif
+#    endif
             PyThreadState_Clear(tstate);
             if (active) {
                 PyThreadState_DeleteCurrent();
@@ -116,9 +112,7 @@ class gil_scoped_acquire {
     /// could be shutting down when this is called, as thread deletion is not
     /// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
     /// protect subsequent code.
-    PYBIND11_NOINLINE void disarm() {
-        active = false;
-    }
+    PYBIND11_NOINLINE void disarm() { active = false; }
 
     PYBIND11_NOINLINE ~gil_scoped_acquire() {
         dec_ref();
@@ -126,6 +120,7 @@ class gil_scoped_acquire {
             PyEval_SaveThread();
         }
     }
+
 private:
     PyThreadState *tstate = nullptr;
     bool release = true;
@@ -154,9 +149,7 @@ class gil_scoped_release {
     /// could be shutting down when this is called, as thread deletion is not
     /// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
     /// protect subsequent code.
-    PYBIND11_NOINLINE void disarm() {
-        active = false;
-    }
+    PYBIND11_NOINLINE void disarm() { active = false; }
 
     ~gil_scoped_release() {
         if (!tstate) {
@@ -173,6 +166,7 @@ class gil_scoped_release {
             PYBIND11_TLS_REPLACE_VALUE(key, tstate);
         }
     }
+
 private:
     PyThreadState *tstate;
     bool disassoc;
@@ -181,6 +175,7 @@ class gil_scoped_release {
 #elif defined(PYPY_VERSION)
 class gil_scoped_acquire {
     PyGILState_STATE state;
+
 public:
     gil_scoped_acquire() { state = PyGILState_Ensure(); }
     ~gil_scoped_acquire() { PyGILState_Release(state); }
@@ -189,6 +184,7 @@ class gil_scoped_acquire {
 
 class gil_scoped_release {
     PyThreadState *state;
+
 public:
     gil_scoped_release() { state = PyEval_SaveThread(); }
     ~gil_scoped_release() { PyEval_RestoreThread(state); }
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index d6cf223726..12e1f19f0c 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -58,31 +58,23 @@ class pythonbuf : public std::streambuf {
     size_t utf8_remainder() const {
         const auto rbase = std::reverse_iterator<char *>(pbase());
         const auto rpptr = std::reverse_iterator<char *>(pptr());
-        auto is_ascii = [](char c) {
-            return (static_cast<unsigned char>(c) & 0x80) == 0x00;
-        };
-        auto is_leading = [](char c) {
-            return (static_cast<unsigned char>(c) & 0xC0) == 0xC0;
-        };
-        auto is_leading_2b = [](char c) {
-            return static_cast<unsigned char>(c) <= 0xDF;
-        };
-        auto is_leading_3b = [](char c) {
-            return static_cast<unsigned char>(c) <= 0xEF;
-        };
+        auto is_ascii = [](char c) { return (static_cast<unsigned char>(c) & 0x80) == 0x00; };
+        auto is_leading = [](char c) { return (static_cast<unsigned char>(c) & 0xC0) == 0xC0; };
+        auto is_leading_2b = [](char c) { return static_cast<unsigned char>(c) <= 0xDF; };
+        auto is_leading_3b = [](char c) { return static_cast<unsigned char>(c) <= 0xEF; };
         // If the last character is ASCII, there are no incomplete code points
         if (is_ascii(*rpptr)) {
             return 0;
         }
         // Otherwise, work back from the end of the buffer and find the first
         // UTF-8 leading byte
-        const auto rpend   = rbase - rpptr >= 3 ? rpptr + 3 : rbase;
+        const auto rpend = rbase - rpptr >= 3 ? rpptr + 3 : rbase;
         const auto leading = std::find_if(rpptr, rpend, is_leading);
         if (leading == rbase) {
             return 0;
         }
-        const auto dist    = static_cast<size_t>(leading - rpptr);
-        size_t remainder   = 0;
+        const auto dist = static_cast<size_t>(leading - rpptr);
+        size_t remainder = 0;
 
         if (dist == 0) {
             remainder = 1; // 1-byte code point is impossible
@@ -103,7 +95,7 @@ class pythonbuf : public std::streambuf {
         if (pbase() != pptr()) { // If buffer is not empty
             gil_scoped_acquire tmp;
             // This subtraction cannot be negative, so dropping the sign.
-            auto size        = static_cast<size_t>(pptr() - pbase());
+            auto size = static_cast<size_t>(pptr() - pbase());
             size_t remainder = utf8_remainder();
 
             if (size > remainder) {
@@ -122,9 +114,7 @@ class pythonbuf : public std::streambuf {
         return 0;
     }
 
-    int sync() override {
-        return _sync();
-    }
+    int sync() override { return _sync(); }
 
 public:
     explicit pythonbuf(const object &pyostream, size_t buffer_size = 1024)
@@ -133,17 +123,14 @@ class pythonbuf : public std::streambuf {
         setp(d_buffer.get(), d_buffer.get() + buf_size - 1);
     }
 
-    pythonbuf(pythonbuf&&) = default;
+    pythonbuf(pythonbuf &&) = default;
 
     /// Sync before destroy
-    ~pythonbuf() override {
-        _sync();
-    }
+    ~pythonbuf() override { _sync(); }
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
-
 /** \rst
     This a move-only guard that redirects output.
 
@@ -183,9 +170,7 @@ class scoped_ostream_redirect {
         old = costream.rdbuf(&buffer);
     }
 
-    ~scoped_ostream_redirect() {
-        costream.rdbuf(old);
-    }
+    ~scoped_ostream_redirect() { costream.rdbuf(old); }
 
     scoped_ostream_redirect(const scoped_ostream_redirect &) = delete;
     scoped_ostream_redirect(scoped_ostream_redirect &&other) = default;
@@ -193,7 +178,6 @@ class scoped_ostream_redirect {
     scoped_ostream_redirect &operator=(scoped_ostream_redirect &&) = delete;
 };
 
-
 /** \rst
     Like `scoped_ostream_redirect`, but redirects cerr by default. This class
     is provided primary to make ``py::call_guard`` easier to make.
@@ -213,7 +197,6 @@ class scoped_estream_redirect : public scoped_ostream_redirect {
         : scoped_ostream_redirect(costream, pyostream) {}
 };
 
-
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Class to redirect output as a context manager. C++ backend.
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index a003834e96..9d6240f94b 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -11,19 +11,20 @@
 
 #include "pybind11.h"
 #include "complex.h"
-#include <numeric>
+
 #include <algorithm>
 #include <array>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
+#include <functional>
+#include <numeric>
 #include <sstream>
 #include <string>
-#include <functional>
 #include <type_traits>
+#include <typeindex>
 #include <utility>
 #include <vector>
-#include <typeindex>
 
 /* This will be true on all flat address space platforms and allows us to reduce the
    whole npy_intp / ssize_t / Py_intptr_t business down to just ssize_t for all size
@@ -39,9 +40,13 @@ class array; // Forward declaration
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-template <> struct handle_type_name<array> { static constexpr auto name = const_name("numpy.ndarray"); };
+template <>
+struct handle_type_name<array> {
+    static constexpr auto name = const_name("numpy.ndarray");
+};
 
-template <typename type, typename SFINAE = void> struct npy_format_descriptor;
+template <typename type, typename SFINAE = void>
+struct npy_format_descriptor;
 
 struct PyArrayDescr_Proxy {
     PyObject_HEAD
@@ -70,22 +75,21 @@ struct PyArray_Proxy {
 };
 
 struct PyVoidScalarObject_Proxy {
-    PyObject_VAR_HEAD
-    char *obval;
+    PyObject_VAR_HEAD char *obval;
     PyArrayDescr_Proxy *descr;
     int flags;
     PyObject *base;
 };
 
 struct numpy_type_info {
-    PyObject* dtype_ptr;
+    PyObject *dtype_ptr;
     std::string format_str;
 };
 
 struct numpy_internals {
     std::unordered_map<std::type_index, numpy_type_info> registered_dtypes;
 
-    numpy_type_info *get_type_info(const std::type_info& tinfo, bool throw_if_missing = true) {
+    numpy_type_info *get_type_info(const std::type_info &tinfo, bool throw_if_missing = true) {
         auto it = registered_dtypes.find(std::type_index(tinfo));
         if (it != registered_dtypes.end()) {
             return &(it->second);
@@ -96,28 +100,34 @@ struct numpy_internals {
         return nullptr;
     }
 
-    template<typename T> numpy_type_info *get_type_info(bool throw_if_missing = true) {
+    template <typename T>
+    numpy_type_info *get_type_info(bool throw_if_missing = true) {
         return get_type_info(typeid(typename std::remove_cv<T>::type), throw_if_missing);
     }
 };
 
-PYBIND11_NOINLINE void load_numpy_internals(numpy_internals* &ptr) {
+PYBIND11_NOINLINE void load_numpy_internals(numpy_internals *&ptr) {
     ptr = &get_or_create_shared_data<numpy_internals>("_numpy_internals");
 }
 
-inline numpy_internals& get_numpy_internals() {
-    static numpy_internals* ptr = nullptr;
+inline numpy_internals &get_numpy_internals() {
+    static numpy_internals *ptr = nullptr;
     if (!ptr) {
         load_numpy_internals(ptr);
     }
     return *ptr;
 }
 
-template <typename T> struct same_size {
-    template <typename U> using as = bool_constant<sizeof(T) == sizeof(U)>;
+template <typename T>
+struct same_size {
+    template <typename U>
+    using as = bool_constant<sizeof(T) == sizeof(U)>;
 };
 
-template <typename Concrete> constexpr int platform_lookup() { return -1; }
+template <typename Concrete>
+constexpr int platform_lookup() {
+    return -1;
+}
 
 // Lookup a type according to its size, and return a value corresponding to the NumPy typenum.
 template <typename Concrete, typename T, typename... Ts, typename... Ints>
@@ -135,15 +145,26 @@ struct npy_api {
         NPY_ARRAY_ALIGNED_ = 0x0100,
         NPY_ARRAY_WRITEABLE_ = 0x0400,
         NPY_BOOL_ = 0,
-        NPY_BYTE_, NPY_UBYTE_,
-        NPY_SHORT_, NPY_USHORT_,
-        NPY_INT_, NPY_UINT_,
-        NPY_LONG_, NPY_ULONG_,
-        NPY_LONGLONG_, NPY_ULONGLONG_,
-        NPY_FLOAT_, NPY_DOUBLE_, NPY_LONGDOUBLE_,
-        NPY_CFLOAT_, NPY_CDOUBLE_, NPY_CLONGDOUBLE_,
+        NPY_BYTE_,
+        NPY_UBYTE_,
+        NPY_SHORT_,
+        NPY_USHORT_,
+        NPY_INT_,
+        NPY_UINT_,
+        NPY_LONG_,
+        NPY_ULONG_,
+        NPY_LONGLONG_,
+        NPY_ULONGLONG_,
+        NPY_FLOAT_,
+        NPY_DOUBLE_,
+        NPY_LONGDOUBLE_,
+        NPY_CFLOAT_,
+        NPY_CDOUBLE_,
+        NPY_CLONGDOUBLE_,
         NPY_OBJECT_ = 17,
-        NPY_STRING_, NPY_UNICODE_, NPY_VOID_,
+        NPY_STRING_,
+        NPY_UNICODE_,
+        NPY_VOID_,
         // Platform-dependent normalization
         NPY_INT8_ = NPY_BYTE_,
         NPY_UINT8_ = NPY_UBYTE_,
@@ -152,13 +173,14 @@ struct npy_api {
         // `npy_common.h` defines the integer aliases. In order, it checks:
         // NPY_BITSOF_LONG, NPY_BITSOF_LONGLONG, NPY_BITSOF_INT, NPY_BITSOF_SHORT, NPY_BITSOF_CHAR
         // and assigns the alias to the first matching size, so we should check in this order.
-        NPY_INT32_ = platform_lookup<std::int32_t, long, int, short>(
-            NPY_LONG_, NPY_INT_, NPY_SHORT_),
+        NPY_INT32_
+        = platform_lookup<std::int32_t, long, int, short>(NPY_LONG_, NPY_INT_, NPY_SHORT_),
         NPY_UINT32_ = platform_lookup<std::uint32_t, unsigned long, unsigned int, unsigned short>(
             NPY_ULONG_, NPY_UINT_, NPY_USHORT_),
-        NPY_INT64_ = platform_lookup<std::int64_t, long, long long, int>(
-            NPY_LONG_, NPY_LONGLONG_, NPY_INT_),
-        NPY_UINT64_ = platform_lookup<std::uint64_t, unsigned long, unsigned long long, unsigned int>(
+        NPY_INT64_
+        = platform_lookup<std::int64_t, long, long long, int>(NPY_LONG_, NPY_LONGLONG_, NPY_INT_),
+        NPY_UINT64_
+        = platform_lookup<std::uint64_t, unsigned long, unsigned long long, unsigned int>(
             NPY_ULONG_, NPY_ULONGLONG_, NPY_UINT_),
     };
 
@@ -167,7 +189,7 @@ struct npy_api {
         int len;
     };
 
-    static npy_api& get() {
+    static npy_api &get() {
         static npy_api api = lookup();
         return api;
     }
@@ -181,9 +203,14 @@ struct npy_api {
 
     unsigned int (*PyArray_GetNDArrayCFeatureVersion_)();
     PyObject *(*PyArray_DescrFromType_)(int);
-    PyObject *(*PyArray_NewFromDescr_)
-        (PyTypeObject *, PyObject *, int, Py_intptr_t const *,
-         Py_intptr_t const *, void *, int, PyObject *);
+    PyObject *(*PyArray_NewFromDescr_)(PyTypeObject *,
+                                       PyObject *,
+                                       int,
+                                       Py_intptr_t const *,
+                                       Py_intptr_t const *,
+                                       void *,
+                                       int,
+                                       PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     PyObject *(*PyArray_DescrNewFromType_)(int);
     int (*PyArray_CopyInto_)(PyObject *, PyObject *);
@@ -192,17 +219,23 @@ struct npy_api {
     PyTypeObject *PyVoidArrType_Type_;
     PyTypeObject *PyArrayDescr_Type_;
     PyObject *(*PyArray_DescrFromScalar_)(PyObject *);
-    PyObject *(*PyArray_FromAny_) (PyObject *, PyObject *, int, int, int, PyObject *);
-    int (*PyArray_DescrConverter_) (PyObject *, PyObject **);
-    bool (*PyArray_EquivTypes_) (PyObject *, PyObject *);
-    int (*PyArray_GetArrayParamsFromObject_)(PyObject *, PyObject *, unsigned char, PyObject **, int *,
-                                             Py_intptr_t *, PyObject **, PyObject *);
+    PyObject *(*PyArray_FromAny_)(PyObject *, PyObject *, int, int, int, PyObject *);
+    int (*PyArray_DescrConverter_)(PyObject *, PyObject **);
+    bool (*PyArray_EquivTypes_)(PyObject *, PyObject *);
+    int (*PyArray_GetArrayParamsFromObject_)(PyObject *,
+                                             PyObject *,
+                                             unsigned char,
+                                             PyObject **,
+                                             int *,
+                                             Py_intptr_t *,
+                                             PyObject **,
+                                             PyObject *);
     PyObject *(*PyArray_Squeeze_)(PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
-    PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
-    PyObject* (*PyArray_Newshape_)(PyObject*, PyArray_Dims*, int);
-    PyObject* (*PyArray_View_)(PyObject*, PyObject*, PyObject*);
+    PyObject *(*PyArray_Resize_)(PyObject *, PyArray_Dims *, int, int);
+    PyObject *(*PyArray_Newshape_)(PyObject *, PyArray_Dims *, int);
+    PyObject *(*PyArray_View_)(PyObject *, PyObject *, PyObject *);
 
 private:
     enum functions {
@@ -265,86 +298,103 @@ struct npy_api {
     }
 };
 
-inline PyArray_Proxy* array_proxy(void* ptr) {
-    return reinterpret_cast<PyArray_Proxy*>(ptr);
-}
+inline PyArray_Proxy *array_proxy(void *ptr) { return reinterpret_cast<PyArray_Proxy *>(ptr); }
 
-inline const PyArray_Proxy* array_proxy(const void* ptr) {
-    return reinterpret_cast<const PyArray_Proxy*>(ptr);
+inline const PyArray_Proxy *array_proxy(const void *ptr) {
+    return reinterpret_cast<const PyArray_Proxy *>(ptr);
 }
 
-inline PyArrayDescr_Proxy* array_descriptor_proxy(PyObject* ptr) {
-   return reinterpret_cast<PyArrayDescr_Proxy*>(ptr);
+inline PyArrayDescr_Proxy *array_descriptor_proxy(PyObject *ptr) {
+    return reinterpret_cast<PyArrayDescr_Proxy *>(ptr);
 }
 
-inline const PyArrayDescr_Proxy* array_descriptor_proxy(const PyObject* ptr) {
-   return reinterpret_cast<const PyArrayDescr_Proxy*>(ptr);
+inline const PyArrayDescr_Proxy *array_descriptor_proxy(const PyObject *ptr) {
+    return reinterpret_cast<const PyArrayDescr_Proxy *>(ptr);
 }
 
-inline bool check_flags(const void* ptr, int flag) {
+inline bool check_flags(const void *ptr, int flag) {
     return (flag == (array_proxy(ptr)->flags & flag));
 }
 
-template <typename T> struct is_std_array : std::false_type { };
-template <typename T, size_t N> struct is_std_array<std::array<T, N>> : std::true_type { };
-template <typename T> struct is_complex : std::false_type { };
-template <typename T> struct is_complex<std::complex<T>> : std::true_type { };
+template <typename T>
+struct is_std_array : std::false_type {};
+template <typename T, size_t N>
+struct is_std_array<std::array<T, N>> : std::true_type {};
+template <typename T>
+struct is_complex : std::false_type {};
+template <typename T>
+struct is_complex<std::complex<T>> : std::true_type {};
 
-template <typename T> struct array_info_scalar {
+template <typename T>
+struct array_info_scalar {
     using type = T;
     static constexpr bool is_array = false;
     static constexpr bool is_empty = false;
     static constexpr auto extents = const_name("");
-    static void append_extents(list& /* shape */) { }
+    static void append_extents(list & /* shape */) {}
 };
 // Computes underlying type and a comma-separated list of extents for array
 // types (any mix of std::array and built-in arrays). An array of char is
 // treated as scalar because it gets special handling.
-template <typename T> struct array_info : array_info_scalar<T> { };
-template <typename T, size_t N> struct array_info<std::array<T, N>> {
+template <typename T>
+struct array_info : array_info_scalar<T> {};
+template <typename T, size_t N>
+struct array_info<std::array<T, N>> {
     using type = typename array_info<T>::type;
     static constexpr bool is_array = true;
     static constexpr bool is_empty = (N == 0) || array_info<T>::is_empty;
     static constexpr size_t extent = N;
 
     // appends the extents to shape
-    static void append_extents(list& shape) {
+    static void append_extents(list &shape) {
         shape.append(N);
         array_info<T>::append_extents(shape);
     }
 
     static constexpr auto extents = const_name<array_info<T>::is_array>(
-        concat(const_name<N>(), array_info<T>::extents), const_name<N>()
-    );
+        concat(const_name<N>(), array_info<T>::extents), const_name<N>());
 };
 // For numpy we have special handling for arrays of characters, so we don't include
 // the size in the array extents.
-template <size_t N> struct array_info<char[N]> : array_info_scalar<char[N]> { };
-template <size_t N> struct array_info<std::array<char, N>> : array_info_scalar<std::array<char, N>> { };
-template <typename T, size_t N> struct array_info<T[N]> : array_info<std::array<T, N>> { };
-template <typename T> using remove_all_extents_t = typename array_info<T>::type;
-
-template <typename T> using is_pod_struct = all_of<
-    std::is_standard_layout<T>,     // since we're accessing directly in memory
-                                    // we need a standard layout type
-#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623 || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
-    // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after 5)
-    // don't implement is_trivially_copyable, so approximate it
-    std::is_trivially_destructible<T>,
-    satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
+template <size_t N>
+struct array_info<char[N]> : array_info_scalar<char[N]> {};
+template <size_t N>
+struct array_info<std::array<char, N>> : array_info_scalar<std::array<char, N>> {};
+template <typename T, size_t N>
+struct array_info<T[N]> : array_info<std::array<T, N>> {};
+template <typename T>
+using remove_all_extents_t = typename array_info<T>::type;
+
+template <typename T>
+using is_pod_struct
+    = all_of<std::is_standard_layout<T>, // since we're accessing directly in memory
+                                         // we need a standard layout type
+#if defined(__GLIBCXX__)                                                                          \
+    && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623              \
+        || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
+             // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after
+             // 5) don't implement is_trivially_copyable, so approximate it
+             std::is_trivially_destructible<T>,
+             satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
 #else
-    std::is_trivially_copyable<T>,
+             std::is_trivially_copyable<T>,
 #endif
-    satisfies_none_of<T, std::is_reference, std::is_array, is_std_array, std::is_arithmetic, is_complex, std::is_enum>
->;
+             satisfies_none_of<T,
+                               std::is_reference,
+                               std::is_array,
+                               is_std_array,
+                               std::is_arithmetic,
+                               is_complex,
+                               std::is_enum>>;
 
 // Replacement for std::is_pod (deprecated in C++20)
-template <typename T> using is_pod = all_of<
-    std::is_standard_layout<T>,
-    std::is_trivial<T>
->;
+template <typename T>
+using is_pod = all_of<std::is_standard_layout<T>, std::is_trivial<T>>;
 
-template <ssize_t Dim = 0, typename Strides> ssize_t byte_offset_unsafe(const Strides &) { return 0; }
+template <ssize_t Dim = 0, typename Strides>
+ssize_t byte_offset_unsafe(const Strides &) {
+    return 0;
+}
 template <ssize_t Dim = 0, typename Strides, typename... Ix>
 ssize_t byte_offset_unsafe(const Strides &strides, ssize_t i, Ix... index) {
     return i * strides[Dim] + byte_offset_unsafe<Dim + 1>(strides, index...);
@@ -352,7 +402,7 @@ ssize_t byte_offset_unsafe(const Strides &strides, ssize_t i, Ix... index) {
 
 /**
  * Proxy class providing unsafe, unchecked const access to array data.  This is constructed through
- * the `unchecked<T, N>()` method of `array` or the `unchecked<N>()` method of `array_t<T>`.  `Dims`
+ * the `unchecked<T, N>()` method of `array` or the `unchecked<N>()` method of `array_t<T>`. `Dims`
  * will be -1 for dimensions determined at runtime.
  */
 template <typename T, ssize_t Dims>
@@ -362,15 +412,17 @@ class unchecked_reference {
     const unsigned char *data_;
     // Storing the shape & strides in local variables (i.e. these arrays) allows the compiler to
     // make large performance gains on big, nested loops, but requires compile-time dimensions
-    conditional_t<Dynamic, const ssize_t *, std::array<ssize_t, (size_t) Dims>>
-            shape_, strides_;
+    conditional_t<Dynamic, const ssize_t *, std::array<ssize_t, (size_t) Dims>> shape_, strides_;
     const ssize_t dims_;
 
     friend class pybind11::array;
     // Constructor for compile-time dimensions:
     template <bool Dyn = Dynamic>
-    unchecked_reference(const void *data, const ssize_t *shape, const ssize_t *strides, enable_if_t<!Dyn, ssize_t>)
-    : data_{reinterpret_cast<const unsigned char *>(data)}, dims_{Dims} {
+    unchecked_reference(const void *data,
+                        const ssize_t *shape,
+                        const ssize_t *strides,
+                        enable_if_t<!Dyn, ssize_t>)
+        : data_{reinterpret_cast<const unsigned char *>(data)}, dims_{Dims} {
         for (size_t i = 0; i < (size_t) dims_; i++) {
             shape_[i] = shape[i];
             strides_[i] = strides[i];
@@ -378,8 +430,12 @@ class unchecked_reference {
     }
     // Constructor for runtime dimensions:
     template <bool Dyn = Dynamic>
-    unchecked_reference(const void *data, const ssize_t *shape, const ssize_t *strides, enable_if_t<Dyn, ssize_t> dims)
-    : data_{reinterpret_cast<const unsigned char *>(data)}, shape_{shape}, strides_{strides}, dims_{dims} {}
+    unchecked_reference(const void *data,
+                        const ssize_t *shape,
+                        const ssize_t *strides,
+                        enable_if_t<Dyn, ssize_t> dims)
+        : data_{reinterpret_cast<const unsigned char *>(data)}, shape_{shape}, strides_{strides},
+          dims_{dims} {}
 
 public:
     /**
@@ -387,20 +443,27 @@ class unchecked_reference {
      * number of dimensions, this requires the correct number of arguments; for run-time
      * dimensionality, this is not checked (and so is up to the caller to use safely).
      */
-    template <typename... Ix> const T &operator()(Ix... index) const {
+    template <typename... Ix>
+    const T &operator()(Ix... index) const {
         static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
-                "Invalid number of indices for unchecked array reference");
-        return *reinterpret_cast<const T *>(data_ + byte_offset_unsafe(strides_, ssize_t(index)...));
+                      "Invalid number of indices for unchecked array reference");
+        return *reinterpret_cast<const T *>(data_
+                                            + byte_offset_unsafe(strides_, ssize_t(index)...));
     }
     /**
      * Unchecked const reference access to data; this operator only participates if the reference
      * is to a 1-dimensional array.  When present, this is exactly equivalent to `obj(index)`.
      */
     template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
-    const T &operator[](ssize_t index) const { return operator()(index); }
+    const T &operator[](ssize_t index) const {
+        return operator()(index);
+    }
 
     /// Pointer access to the data at the given indices.
-    template <typename... Ix> const T *data(Ix... ix) const { return &operator()(ssize_t(ix)...); }
+    template <typename... Ix>
+    const T *data(Ix... ix) const {
+        return &operator()(ssize_t(ix)...);
+    }
 
     /// Returns the item size, i.e. sizeof(T)
     constexpr static ssize_t itemsize() { return sizeof(T); }
@@ -411,21 +474,22 @@ class unchecked_reference {
     /// Returns the number of dimensions of the array
     ssize_t ndim() const { return dims_; }
 
-    /// Returns the total number of elements in the referenced array, i.e. the product of the shapes
+    /// Returns the total number of elements in the referenced array, i.e. the product of the
+    /// shapes
     template <bool Dyn = Dynamic>
     enable_if_t<!Dyn, ssize_t> size() const {
-        return std::accumulate(shape_.begin(), shape_.end(), (ssize_t) 1, std::multiplies<ssize_t>());
+        return std::accumulate(
+            shape_.begin(), shape_.end(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
     template <bool Dyn = Dynamic>
     enable_if_t<Dyn, ssize_t> size() const {
         return std::accumulate(shape_, shape_ + ndim(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
 
-    /// Returns the total number of bytes used by the referenced data.  Note that the actual span in
-    /// memory may be larger if the referenced array has non-contiguous strides (e.g. for a slice).
-    ssize_t nbytes() const {
-        return size() * itemsize();
-    }
+    /// Returns the total number of bytes used by the referenced data.  Note that the actual span
+    /// in memory may be larger if the referenced array has non-contiguous strides (e.g. for a
+    /// slice).
+    ssize_t nbytes() const { return size() * itemsize(); }
 };
 
 template <typename T, ssize_t Dims>
@@ -434,15 +498,17 @@ class unchecked_mutable_reference : public unchecked_reference<T, Dims> {
     using ConstBase = unchecked_reference<T, Dims>;
     using ConstBase::ConstBase;
     using ConstBase::Dynamic;
+
 public:
     // Bring in const-qualified versions from base class
     using ConstBase::operator();
     using ConstBase::operator[];
 
     /// Mutable, unchecked access to data at the given indices.
-    template <typename... Ix> T& operator()(Ix... index) {
+    template <typename... Ix>
+    T &operator()(Ix... index) {
         static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
-                "Invalid number of indices for unchecked array reference");
+                      "Invalid number of indices for unchecked array reference");
         return const_cast<T &>(ConstBase::operator()(index...));
     }
     /**
@@ -451,18 +517,25 @@ class unchecked_mutable_reference : public unchecked_reference<T, Dims> {
      * exactly equivalent to `obj(index)`.
      */
     template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
-    T &operator[](ssize_t index) { return operator()(index); }
+    T &operator[](ssize_t index) {
+        return operator()(index);
+    }
 
     /// Mutable pointer access to the data at the given indices.
-    template <typename... Ix> T *mutable_data(Ix... ix) { return &operator()(ssize_t(ix)...); }
+    template <typename... Ix>
+    T *mutable_data(Ix... ix) {
+        return &operator()(ssize_t(ix)...);
+    }
 };
 
 template <typename T, ssize_t Dim>
 struct type_caster<unchecked_reference<T, Dim>> {
-    static_assert(Dim == 0 && Dim > 0 /* always fail */, "unchecked array proxy object is not castable");
+    static_assert(Dim == 0 && Dim > 0 /* always fail */,
+                  "unchecked array proxy object is not castable");
 };
 template <typename T, ssize_t Dim>
-struct type_caster<unchecked_mutable_reference<T, Dim>> : type_caster<unchecked_reference<T, Dim>> {};
+struct type_caster<unchecked_mutable_reference<T, Dim>>
+    : type_caster<unchecked_reference<T, Dim>> {};
 
 PYBIND11_NAMESPACE_END(detail)
 
@@ -503,25 +576,20 @@ class dtype : public object {
     }
 
     /// Return dtype associated with a C++ type.
-    template <typename T> static dtype of() {
+    template <typename T>
+    static dtype of() {
         return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::dtype();
     }
 
     /// Size of the data type in bytes.
-    ssize_t itemsize() const {
-        return detail::array_descriptor_proxy(m_ptr)->elsize;
-    }
+    ssize_t itemsize() const { return detail::array_descriptor_proxy(m_ptr)->elsize; }
 
     /// Returns true for structured data types.
-    bool has_fields() const {
-        return detail::array_descriptor_proxy(m_ptr)->names != nullptr;
-    }
+    bool has_fields() const { return detail::array_descriptor_proxy(m_ptr)->names != nullptr; }
 
     /// Single-character code for dtype's kind.
     /// For example, floating point types are 'f' and integral types are 'i'.
-    char kind() const {
-        return detail::array_descriptor_proxy(m_ptr)->kind;
-    }
+    char kind() const { return detail::array_descriptor_proxy(m_ptr)->kind; }
 
     /// Single-character for dtype's type.
     /// For example, ``float`` is 'f', ``double`` 'd', ``int`` 'i', and ``long`` 'l'.
@@ -535,7 +603,10 @@ class dtype : public object {
 private:
     static object _dtype_from_pep3118() {
         static PyObject *obj = module_::import("numpy.core._internal")
-            .attr("_dtype_from_pep3118").cast<object>().release().ptr();
+                                   .attr("_dtype_from_pep3118")
+                                   .cast<object>()
+                                   .release()
+                                   .ptr();
         return reinterpret_borrow<object>(obj);
     }
 
@@ -546,7 +617,11 @@ class dtype : public object {
             return *this;
         }
 
-        struct field_descr { PYBIND11_STR_TYPE name; object format; pybind11::int_ offset; };
+        struct field_descr {
+            PYBIND11_STR_TYPE name;
+            object format;
+            pybind11::int_ offset;
+        };
         std::vector<field_descr> field_descriptors;
 
         for (auto field : attr("fields").attr("items")()) {
@@ -557,16 +632,18 @@ class dtype : public object {
             if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
             }
-            field_descriptors.push_back({(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
+            field_descriptors.push_back(
+                {(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
         }
 
-        std::sort(field_descriptors.begin(), field_descriptors.end(),
-                  [](const field_descr& a, const field_descr& b) {
+        std::sort(field_descriptors.begin(),
+                  field_descriptors.end(),
+                  [](const field_descr &a, const field_descr &b) {
                       return a.offset.cast<int>() < b.offset.cast<int>();
                   });
 
         list names, formats, offsets;
-        for (auto& descr : field_descriptors) {
+        for (auto &descr : field_descriptors) {
             names.append(descr.name);
             formats.append(descr.format);
             offsets.append(descr.offset);
@@ -591,8 +668,11 @@ class array : public buffer {
     using StridesContainer = detail::any_container<ssize_t>;
 
     // Constructs an array taking shape/strides from arbitrary container types
-    array(const pybind11::dtype &dt, ShapeContainer shape, StridesContainer strides,
-          const void *ptr = nullptr, handle base = handle()) {
+    array(const pybind11::dtype &dt,
+          ShapeContainer shape,
+          StridesContainer strides,
+          const void *ptr = nullptr,
+          handle base = handle()) {
 
         if (strides->empty()) {
             *strides = detail::c_strides(*shape, dt.itemsize());
@@ -608,7 +688,8 @@ class array : public buffer {
         if (base && ptr) {
             if (isinstance<array>(base)) {
                 /* Copy flags from base (except ownership bit) */
-                flags = reinterpret_borrow<array>(base).flags() & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
+                flags = reinterpret_borrow<array>(base).flags()
+                        & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
             } else {
                 /* Writable by default, easy to downgrade later on if needed */
                 flags = detail::npy_api::NPY_ARRAY_WRITEABLE_;
@@ -617,11 +698,15 @@ class array : public buffer {
 
         auto &api = detail::npy_api::get();
         auto tmp = reinterpret_steal<object>(api.PyArray_NewFromDescr_(
-            api.PyArray_Type_, descr.release().ptr(), (int) ndim,
+            api.PyArray_Type_,
+            descr.release().ptr(),
+            (int) ndim,
             // Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
-            reinterpret_cast<Py_intptr_t*>(shape->data()),
-            reinterpret_cast<Py_intptr_t*>(strides->data()),
-            const_cast<void *>(ptr), flags, nullptr));
+            reinterpret_cast<Py_intptr_t *>(shape->data()),
+            reinterpret_cast<Py_intptr_t *>(strides->data()),
+            const_cast<void *>(ptr),
+            flags,
+            nullptr));
         if (!tmp) {
             throw error_already_set();
         }
@@ -629,32 +714,39 @@ class array : public buffer {
             if (base) {
                 api.PyArray_SetBaseObject_(tmp.ptr(), base.inc_ref().ptr());
             } else {
-                tmp = reinterpret_steal<object>(api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */));
+                tmp = reinterpret_steal<object>(
+                    api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */));
             }
         }
         m_ptr = tmp.release().ptr();
     }
 
-    array(const pybind11::dtype &dt, ShapeContainer shape, const void *ptr = nullptr, handle base = handle())
-        : array(dt, std::move(shape), {}, ptr, base) { }
+    array(const pybind11::dtype &dt,
+          ShapeContainer shape,
+          const void *ptr = nullptr,
+          handle base = handle())
+        : array(dt, std::move(shape), {}, ptr, base) {}
 
-    template <typename T, typename = detail::enable_if_t<std::is_integral<T>::value && !std::is_same<bool, T>::value>>
+    template <typename T,
+              typename
+              = detail::enable_if_t<std::is_integral<T>::value && !std::is_same<bool, T>::value>>
     array(const pybind11::dtype &dt, T count, const void *ptr = nullptr, handle base = handle())
-        : array(dt, {{count}}, ptr, base) { }
+        : array(dt, {{count}}, ptr, base) {}
 
     template <typename T>
     array(ShapeContainer shape, StridesContainer strides, const T *ptr, handle base = handle())
-        : array(pybind11::dtype::of<T>(), std::move(shape), std::move(strides), ptr, base) { }
+        : array(pybind11::dtype::of<T>(), std::move(shape), std::move(strides), ptr, base) {}
 
     template <typename T>
     array(ShapeContainer shape, const T *ptr, handle base = handle())
-        : array(std::move(shape), {}, ptr, base) { }
+        : array(std::move(shape), {}, ptr, base) {}
 
     template <typename T>
-    explicit array(ssize_t count, const T *ptr, handle base = handle()) : array({count}, {}, ptr, base) { }
+    explicit array(ssize_t count, const T *ptr, handle base = handle())
+        : array({count}, {}, ptr, base) {}
 
     explicit array(const buffer_info &info, handle base = handle())
-    : array(pybind11::dtype(info), info.shape, info.strides, info.ptr, base) { }
+        : array(pybind11::dtype(info), info.shape, info.strides, info.ptr, base) {}
 
     /// Array descriptor (dtype)
     pybind11::dtype dtype() const {
@@ -672,24 +764,16 @@ class array : public buffer {
     }
 
     /// Total number of bytes
-    ssize_t nbytes() const {
-        return size() * itemsize();
-    }
+    ssize_t nbytes() const { return size() * itemsize(); }
 
     /// Number of dimensions
-    ssize_t ndim() const {
-        return detail::array_proxy(m_ptr)->nd;
-    }
+    ssize_t ndim() const { return detail::array_proxy(m_ptr)->nd; }
 
     /// Base object
-    object base() const {
-        return reinterpret_borrow<object>(detail::array_proxy(m_ptr)->base);
-    }
+    object base() const { return reinterpret_borrow<object>(detail::array_proxy(m_ptr)->base); }
 
     /// Dimensions of the array
-    const ssize_t* shape() const {
-        return detail::array_proxy(m_ptr)->dimensions;
-    }
+    const ssize_t *shape() const { return detail::array_proxy(m_ptr)->dimensions; }
 
     /// Dimension along a given axis
     ssize_t shape(ssize_t dim) const {
@@ -700,9 +784,7 @@ class array : public buffer {
     }
 
     /// Strides of the array
-    const ssize_t* strides() const {
-        return detail::array_proxy(m_ptr)->strides;
-    }
+    const ssize_t *strides() const { return detail::array_proxy(m_ptr)->strides; }
 
     /// Stride along a given axis
     ssize_t strides(ssize_t dim) const {
@@ -713,9 +795,7 @@ class array : public buffer {
     }
 
     /// Return the NumPy array flags
-    int flags() const {
-        return detail::array_proxy(m_ptr)->flags;
-    }
+    int flags() const { return detail::array_proxy(m_ptr)->flags; }
 
     /// If set, the array is writeable (otherwise the buffer is read-only)
     bool writeable() const {
@@ -729,21 +809,24 @@ class array : public buffer {
 
     /// Pointer to the contained data. If index is not provided, points to the
     /// beginning of the buffer. May throw if the index would lead to out of bounds access.
-    template<typename... Ix> const void* data(Ix... index) const {
+    template <typename... Ix>
+    const void *data(Ix... index) const {
         return static_cast<const void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
     }
 
     /// Mutable pointer to the contained data. If index is not provided, points to the
     /// beginning of the buffer. May throw if the index would lead to out of bounds access.
     /// May throw if the array is not writeable.
-    template<typename... Ix> void* mutable_data(Ix... index) {
+    template <typename... Ix>
+    void *mutable_data(Ix... index) {
         check_writeable();
         return static_cast<void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
     }
 
     /// Byte offset from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
-    template<typename... Ix> ssize_t offset_at(Ix... index) const {
+    template <typename... Ix>
+    ssize_t offset_at(Ix... index) const {
         if ((ssize_t) sizeof...(index) > ndim()) {
             fail_dim_check(sizeof...(index), "too many indices for an array");
         }
@@ -754,7 +837,8 @@ class array : public buffer {
 
     /// Item count from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
-    template<typename... Ix> ssize_t index_at(Ix... index) const {
+    template <typename... Ix>
+    ssize_t index_at(Ix... index) const {
         return offset_at(index...) / itemsize();
     }
 
@@ -764,23 +848,26 @@ class array : public buffer {
      * care: the array must not be destroyed or reshaped for the duration of the returned object,
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
-    template <typename T, ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
+    template <typename T, ssize_t Dims = -1>
+    detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
         if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
         }
-        return detail::unchecked_mutable_reference<T, Dims>(mutable_data(), shape(), strides(), ndim());
+        return detail::unchecked_mutable_reference<T, Dims>(
+            mutable_data(), shape(), strides(), ndim());
     }
 
     /**
      * Returns a proxy object that provides const access to the array's data without bounds or
      * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
-     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed or
-     * reshaped for the duration of the returned object, and the caller must take care not to access
-     * invalid dimensions or dimension indices.
+     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed
+     * or reshaped for the duration of the returned object, and the caller must take care not to
+     * access invalid dimensions or dimension indices.
      */
-    template <typename T, ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
+    template <typename T, ssize_t Dims = -1>
+    detail::unchecked_reference<T, Dims> unchecked() const & {
         if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
@@ -791,7 +878,7 @@ class array : public buffer {
 
     /// Return a new view with all of the dimensions of length 1 removed
     array squeeze() {
-        auto& api = detail::npy_api::get();
+        auto &api = detail::npy_api::get();
         return reinterpret_steal<array>(api.PyArray_Squeeze_(m_ptr));
     }
 
@@ -799,19 +886,19 @@ class array : public buffer {
     /// If refcheck is true and more that one reference exist to this array
     /// then resize will succeed only if it makes a reshape, i.e. original size doesn't change
     void resize(ShapeContainer new_shape, bool refcheck = true) {
-        detail::npy_api::PyArray_Dims d = {
-            // Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
-            reinterpret_cast<Py_intptr_t*>(new_shape->data()),
-            int(new_shape->size())
-        };
+        detail::npy_api::PyArray_Dims d
+            = {// Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
+               reinterpret_cast<Py_intptr_t *>(new_shape->data()),
+               int(new_shape->size())};
         // try to resize, set ordering param to -1 cause it's not used anyway
         auto new_array = reinterpret_steal<object>(
-            detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1)
-        );
+            detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1));
         if (!new_array) {
             throw error_already_set();
         }
-        if (isinstance<array>(new_array)) { *this = std::move(new_array); }
+        if (isinstance<array>(new_array)) {
+            *this = std::move(new_array);
+        }
     }
 
     /// Optional `order` parameter omitted, to be added as needed.
@@ -852,14 +939,16 @@ class array : public buffer {
     }
 
 protected:
-    template<typename, typename> friend struct detail::npy_format_descriptor;
+    template <typename, typename>
+    friend struct detail::npy_format_descriptor;
 
-    void fail_dim_check(ssize_t dim, const std::string& msg) const {
-        throw index_error(msg + ": " + std::to_string(dim) +
-                          " (ndim = " + std::to_string(ndim()) + ")");
+    void fail_dim_check(ssize_t dim, const std::string &msg) const {
+        throw index_error(msg + ": " + std::to_string(dim) + " (ndim = " + std::to_string(ndim())
+                          + ")");
     }
 
-    template<typename... Ix> ssize_t byte_offset(Ix... index) const {
+    template <typename... Ix>
+    ssize_t byte_offset(Ix... index) const {
         check_dimensions(index...);
         return detail::byte_offset_unsafe(strides(), ssize_t(index)...);
     }
@@ -870,17 +959,19 @@ class array : public buffer {
         }
     }
 
-    template<typename... Ix> void check_dimensions(Ix... index) const {
+    template <typename... Ix>
+    void check_dimensions(Ix... index) const {
         check_dimensions_impl(ssize_t(0), shape(), ssize_t(index)...);
     }
 
-    void check_dimensions_impl(ssize_t, const ssize_t*) const { }
+    void check_dimensions_impl(ssize_t, const ssize_t *) const {}
 
-    template<typename... Ix> void check_dimensions_impl(ssize_t axis, const ssize_t* shape, ssize_t i, Ix... index) const {
+    template <typename... Ix>
+    void check_dimensions_impl(ssize_t axis, const ssize_t *shape, ssize_t i, Ix... index) const {
         if (i >= *shape) {
-            throw index_error(std::string("index ") + std::to_string(i) +
-                              " is out of bounds for axis " + std::to_string(axis) +
-                              " with size " + std::to_string(*shape));
+            throw index_error(std::string("index ") + std::to_string(i)
+                              + " is out of bounds for axis " + std::to_string(axis)
+                              + " with size " + std::to_string(*shape));
         }
         check_dimensions_impl(axis + 1, shape + 1, index...);
     }
@@ -896,20 +987,26 @@ class array : public buffer {
     }
 };
 
-template <typename T, int ExtraFlags = array::forcecast> class array_t : public array {
+template <typename T, int ExtraFlags = array::forcecast>
+class array_t : public array {
 private:
     struct private_ctor {};
     // Delegating constructor needed when both moving and accessing in the same constructor
-    array_t(private_ctor, ShapeContainer &&shape, StridesContainer &&strides, const T *ptr, handle base)
+    array_t(private_ctor,
+            ShapeContainer &&shape,
+            StridesContainer &&strides,
+            const T *ptr,
+            handle base)
         : array(std::move(shape), std::move(strides), ptr, base) {}
+
 public:
     static_assert(!detail::array_info<T>::is_array, "Array types cannot be used with array_t");
 
     using value_type = T;
 
     array_t() : array(0, static_cast<const T *>(nullptr)) {}
-    array_t(handle h, borrowed_t) : array(h, borrowed_t{}) { }
-    array_t(handle h, stolen_t) : array(h, stolen_t{}) { }
+    array_t(handle h, borrowed_t) : array(h, borrowed_t{}) {}
+    array_t(handle h, stolen_t) : array(h, stolen_t{}) {}
 
     PYBIND11_DEPRECATED("Use array_t<T>::ensure() instead")
     array_t(handle h, bool is_borrowed) : array(raw_array_t(h.ptr()), stolen_t{}) {
@@ -928,10 +1025,13 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
         }
     }
 
-    explicit array_t(const buffer_info& info, handle base = handle()) : array(info, base) { }
+    explicit array_t(const buffer_info &info, handle base = handle()) : array(info, base) {}
 
-    array_t(ShapeContainer shape, StridesContainer strides, const T *ptr = nullptr, handle base = handle())
-        : array(std::move(shape), std::move(strides), ptr, base) { }
+    array_t(ShapeContainer shape,
+            StridesContainer strides,
+            const T *ptr = nullptr,
+            handle base = handle())
+        : array(std::move(shape), std::move(strides), ptr, base) {}
 
     explicit array_t(ShapeContainer shape, const T *ptr = nullptr, handle base = handle())
         : array_t(private_ctor{},
@@ -942,38 +1042,43 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
                   base) {}
 
     explicit array_t(ssize_t count, const T *ptr = nullptr, handle base = handle())
-        : array({count}, {}, ptr, base) { }
+        : array({count}, {}, ptr, base) {}
 
-    constexpr ssize_t itemsize() const {
-        return sizeof(T);
-    }
+    constexpr ssize_t itemsize() const { return sizeof(T); }
 
-    template<typename... Ix> ssize_t index_at(Ix... index) const {
+    template <typename... Ix>
+    ssize_t index_at(Ix... index) const {
         return offset_at(index...) / itemsize();
     }
 
-    template<typename... Ix> const T* data(Ix... index) const {
-        return static_cast<const T*>(array::data(index...));
+    template <typename... Ix>
+    const T *data(Ix... index) const {
+        return static_cast<const T *>(array::data(index...));
     }
 
-    template<typename... Ix> T* mutable_data(Ix... index) {
-        return static_cast<T*>(array::mutable_data(index...));
+    template <typename... Ix>
+    T *mutable_data(Ix... index) {
+        return static_cast<T *>(array::mutable_data(index...));
     }
 
     // Reference to element at a given index
-    template<typename... Ix> const T& at(Ix... index) const {
+    template <typename... Ix>
+    const T &at(Ix... index) const {
         if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
         }
-        return *(static_cast<const T*>(array::data()) + byte_offset(ssize_t(index)...) / itemsize());
+        return *(static_cast<const T *>(array::data())
+                 + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     // Mutable reference to element at a given index
-    template<typename... Ix> T& mutable_at(Ix... index) {
+    template <typename... Ix>
+    T &mutable_at(Ix... index) {
         if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
         }
-        return *(static_cast<T*>(array::mutable_data()) + byte_offset(ssize_t(index)...) / itemsize());
+        return *(static_cast<T *>(array::mutable_data())
+                 + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     /**
@@ -982,7 +1087,8 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
      * care: the array must not be destroyed or reshaped for the duration of the returned object,
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
-    template <ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
+    template <ssize_t Dims = -1>
+    detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
         return array::mutable_unchecked<T, Dims>();
     }
 
@@ -993,7 +1099,8 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
      * for the duration of the returned object, and the caller must take care not to access invalid
      * dimensions or dimension indices.
      */
-    template <ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
+    template <ssize_t Dims = -1>
+    detail::unchecked_reference<T, Dims> unchecked() const & {
         return array::unchecked<T, Dims>();
     }
 
@@ -1010,7 +1117,8 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
     static bool check_(handle h) {
         const auto &api = detail::npy_api::get();
         return api.PyArray_Check_(h.ptr())
-               && api.PyArray_EquivTypes_(detail::array_proxy(h.ptr())->descr, dtype::of<T>().ptr())
+               && api.PyArray_EquivTypes_(detail::array_proxy(h.ptr())->descr,
+                                          dtype::of<T>().ptr())
                && detail::check_flags(h.ptr(), ExtraFlags & (array::c_style | array::f_style));
     }
 
@@ -1021,9 +1129,13 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
             PyErr_SetString(PyExc_ValueError, "cannot create a pybind11::array_t from a nullptr");
             return nullptr;
         }
-        return detail::npy_api::get().PyArray_FromAny_(
-            ptr, dtype::of<T>().release().ptr(), 0, 0,
-            detail::npy_api::NPY_ARRAY_ENSUREARRAY_ | ExtraFlags, nullptr);
+        return detail::npy_api::get().PyArray_FromAny_(ptr,
+                                                       dtype::of<T>().release().ptr(),
+                                                       0,
+                                                       0,
+                                                       detail::npy_api::NPY_ARRAY_ENSUREARRAY_
+                                                           | ExtraFlags,
+                                                       nullptr);
     }
 };
 
@@ -1034,10 +1146,12 @@ struct format_descriptor<T, detail::enable_if_t<detail::is_pod_struct<T>::value>
     }
 };
 
-template <size_t N> struct format_descriptor<char[N]> {
+template <size_t N>
+struct format_descriptor<char[N]> {
     static std::string format() { return std::to_string(N) + "s"; }
 };
-template <size_t N> struct format_descriptor<std::array<char, N>> {
+template <size_t N>
+struct format_descriptor<std::array<char, N>> {
     static std::string format() { return std::to_string(N) + "s"; }
 };
 
@@ -1079,7 +1193,7 @@ struct pyobject_caster<array_t<T, ExtraFlags>> {
 
 template <typename T>
 struct compare_buffer_info<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
-    static bool compare(const buffer_info& b) {
+    static bool compare(const buffer_info &b) {
         return npy_api::get().PyArray_EquivTypes_(dtype::of<T>().ptr(), dtype(b).ptr());
     }
 };
@@ -1090,42 +1204,54 @@ struct npy_format_descriptor_name;
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_integral<T>::value>> {
     static constexpr auto name = const_name<std::is_same<T, bool>::value>(
-        const_name("bool"), const_name<std::is_signed<T>::value>("numpy.int", "numpy.uint") + const_name<sizeof(T)*8>()
-    );
+        const_name("bool"),
+        const_name<std::is_signed<T>::value>("numpy.int", "numpy.uint")
+            + const_name<sizeof(T) * 8>());
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::value>> {
-    static constexpr auto name = const_name<std::is_same<T, float>::value
-                                   || std::is_same<T, const float>::value
-                                   || std::is_same<T, double>::value
-                                   || std::is_same<T, const double>::value>(
-        const_name("numpy.float") + const_name<sizeof(T)*8>(), const_name("numpy.longdouble")
-    );
+    static constexpr auto name = const_name < std::is_same<T, float>::value
+                                 || std::is_same<T, const float>::value
+                                 || std::is_same<T, double>::value
+                                 || std::is_same<T, const double>::value
+                                        > (const_name("numpy.float") + const_name<sizeof(T) * 8>(),
+                                           const_name("numpy.longdouble"));
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<is_complex<T>::value>> {
-    static constexpr auto name = const_name<std::is_same<typename T::value_type, float>::value
-                                   || std::is_same<typename T::value_type, const float>::value
-                                   || std::is_same<typename T::value_type, double>::value
-                                   || std::is_same<typename T::value_type, const double>::value>(
-        const_name("numpy.complex") + const_name<sizeof(typename T::value_type)*16>(), const_name("numpy.longcomplex")
-    );
+    static constexpr auto name = const_name < std::is_same<typename T::value_type, float>::value
+                                 || std::is_same<typename T::value_type, const float>::value
+                                 || std::is_same<typename T::value_type, double>::value
+                                 || std::is_same<typename T::value_type, const double>::value
+                                        > (const_name("numpy.complex")
+                                               + const_name<sizeof(typename T::value_type) * 16>(),
+                                           const_name("numpy.longcomplex"));
 };
 
 template <typename T>
-struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmetic, is_complex>::value>>
+struct npy_format_descriptor<
+    T,
+    enable_if_t<satisfies_any_of<T, std::is_arithmetic, is_complex>::value>>
     : npy_format_descriptor_name<T> {
 private:
     // NB: the order here must match the one in common.h
-    constexpr static const int values[15] = {
-        npy_api::NPY_BOOL_,
-        npy_api::NPY_BYTE_,   npy_api::NPY_UBYTE_,   npy_api::NPY_INT16_,    npy_api::NPY_UINT16_,
-        npy_api::NPY_INT32_,  npy_api::NPY_UINT32_,  npy_api::NPY_INT64_,    npy_api::NPY_UINT64_,
-        npy_api::NPY_FLOAT_,  npy_api::NPY_DOUBLE_,  npy_api::NPY_LONGDOUBLE_,
-        npy_api::NPY_CFLOAT_, npy_api::NPY_CDOUBLE_, npy_api::NPY_CLONGDOUBLE_
-    };
+    constexpr static const int values[15] = {npy_api::NPY_BOOL_,
+                                             npy_api::NPY_BYTE_,
+                                             npy_api::NPY_UBYTE_,
+                                             npy_api::NPY_INT16_,
+                                             npy_api::NPY_UINT16_,
+                                             npy_api::NPY_INT32_,
+                                             npy_api::NPY_UINT32_,
+                                             npy_api::NPY_INT64_,
+                                             npy_api::NPY_UINT64_,
+                                             npy_api::NPY_FLOAT_,
+                                             npy_api::NPY_DOUBLE_,
+                                             npy_api::NPY_LONGDOUBLE_,
+                                             npy_api::NPY_CFLOAT_,
+                                             npy_api::NPY_CDOUBLE_,
+                                             npy_api::NPY_CLONGDOUBLE_};
 
 public:
     static constexpr int value = values[detail::is_fmt_numeric<T>::index];
@@ -1138,20 +1264,31 @@ struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmet
     }
 };
 
-#define PYBIND11_DECL_CHAR_FMT \
-    static constexpr auto name = const_name("S") + const_name<N>(); \
-    static pybind11::dtype dtype() { return pybind11::dtype(std::string("S") + std::to_string(N)); }
-template <size_t N> struct npy_format_descriptor<char[N]> { PYBIND11_DECL_CHAR_FMT };
-template <size_t N> struct npy_format_descriptor<std::array<char, N>> { PYBIND11_DECL_CHAR_FMT };
+#define PYBIND11_DECL_CHAR_FMT                                                                    \
+    static constexpr auto name = const_name("S") + const_name<N>();                               \
+    static pybind11::dtype dtype() {                                                              \
+        return pybind11::dtype(std::string("S") + std::to_string(N));                             \
+    }
+template <size_t N>
+struct npy_format_descriptor<char[N]> {
+    PYBIND11_DECL_CHAR_FMT
+};
+template <size_t N>
+struct npy_format_descriptor<std::array<char, N>> {
+    PYBIND11_DECL_CHAR_FMT
+};
 #undef PYBIND11_DECL_CHAR_FMT
 
-template<typename T> struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
+template <typename T>
+struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
 private:
     using base_descr = npy_format_descriptor<typename array_info<T>::type>;
+
 public:
     static_assert(!array_info<T>::is_empty, "Zero-sized arrays are not supported");
 
-    static constexpr auto name = const_name("(") + array_info<T>::extents + const_name(")") + base_descr::name;
+    static constexpr auto name
+        = const_name("(") + array_info<T>::extents + const_name(")") + base_descr::name;
     static pybind11::dtype dtype() {
         list shape;
         array_info<T>::append_extents(shape);
@@ -1159,9 +1296,11 @@ template<typename T> struct npy_format_descriptor<T, enable_if_t<array_info<T>::
     }
 };
 
-template<typename T> struct npy_format_descriptor<T, enable_if_t<std::is_enum<T>::value>> {
+template <typename T>
+struct npy_format_descriptor<T, enable_if_t<std::is_enum<T>::value>> {
 private:
     using base_descr = npy_format_descriptor<typename std::underlying_type<T>::type>;
+
 public:
     static constexpr auto name = base_descr::name;
     static pybind11::dtype dtype() { return base_descr::dtype(); }
@@ -1175,12 +1314,12 @@ struct field_descriptor {
     dtype descr;
 };
 
-PYBIND11_NOINLINE void register_structured_dtype(
-    any_container<field_descriptor> fields,
-    const std::type_info& tinfo, ssize_t itemsize,
-    bool (*direct_converter)(PyObject *, void *&)) {
+PYBIND11_NOINLINE void register_structured_dtype(any_container<field_descriptor> fields,
+                                                 const std::type_info &tinfo,
+                                                 ssize_t itemsize,
+                                                 bool (*direct_converter)(PyObject *, void *&)) {
 
-    auto& numpy_internals = get_numpy_internals();
+    auto &numpy_internals = get_numpy_internals();
     if (numpy_internals.get_type_info(tinfo, false)) {
         pybind11_fail("NumPy: dtype is already registered");
     }
@@ -1188,11 +1327,13 @@ PYBIND11_NOINLINE void register_structured_dtype(
     // Use ordered fields because order matters as of NumPy 1.14:
     // https://docs.scipy.org/doc/numpy/release.html#multiple-field-indexing-assignment-of-structured-arrays
     std::vector<field_descriptor> ordered_fields(std::move(fields));
-    std::sort(ordered_fields.begin(), ordered_fields.end(),
+    std::sort(
+        ordered_fields.begin(),
+        ordered_fields.end(),
         [](const field_descriptor &a, const field_descriptor &b) { return a.offset < b.offset; });
 
     list names, formats, offsets;
-    for (auto& field : ordered_fields) {
+    for (auto &field : ordered_fields) {
         if (!field.descr) {
             pybind11_fail(std::string("NumPy: unsupported field dtype: `") + field.name + "` @ "
                           + tinfo.name());
@@ -1221,7 +1362,7 @@ PYBIND11_NOINLINE void register_structured_dtype(
     // overriding the endianness. Putting the ^ in front of individual fields
     // isn't guaranteed to work due to https://github.com/numpy/numpy/issues/9049
     oss << "^T{";
-    for (auto& field : ordered_fields) {
+    for (auto &field : ordered_fields) {
         if (field.offset > offset) {
             oss << (field.offset - offset) << 'x';
         }
@@ -1235,25 +1376,25 @@ PYBIND11_NOINLINE void register_structured_dtype(
     auto format_str = oss.str();
 
     // Sanity check: verify that NumPy properly parses our buffer format string
-    auto& api = npy_api::get();
-    auto arr =  array(buffer_info(nullptr, itemsize, format_str, 1));
+    auto &api = npy_api::get();
+    auto arr = array(buffer_info(nullptr, itemsize, format_str, 1));
     if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr())) {
         pybind11_fail("NumPy: invalid buffer descriptor!");
     }
 
     auto tindex = std::type_index(tinfo);
-    numpy_internals.registered_dtypes[tindex] = { dtype_ptr, format_str };
+    numpy_internals.registered_dtypes[tindex] = {dtype_ptr, format_str};
     get_internals().direct_conversions[tindex].push_back(direct_converter);
 }
 
-template <typename T, typename SFINAE> struct npy_format_descriptor {
-    static_assert(is_pod_struct<T>::value, "Attempt to use a non-POD or unimplemented POD type as a numpy dtype");
+template <typename T, typename SFINAE>
+struct npy_format_descriptor {
+    static_assert(is_pod_struct<T>::value,
+                  "Attempt to use a non-POD or unimplemented POD type as a numpy dtype");
 
     static constexpr auto name = make_caster<T>::name;
 
-    static pybind11::dtype dtype() {
-        return reinterpret_borrow<pybind11::dtype>(dtype_ptr());
-    }
+    static pybind11::dtype dtype() { return reinterpret_borrow<pybind11::dtype>(dtype_ptr()); }
 
     static std::string format() {
         static auto format_str = get_numpy_internals().get_type_info<T>(true)->format_str;
@@ -1261,18 +1402,20 @@ template <typename T, typename SFINAE> struct npy_format_descriptor {
     }
 
     static void register_dtype(any_container<field_descriptor> fields) {
-        register_structured_dtype(std::move(fields), typeid(typename std::remove_cv<T>::type),
-                                  sizeof(T), &direct_converter);
+        register_structured_dtype(std::move(fields),
+                                  typeid(typename std::remove_cv<T>::type),
+                                  sizeof(T),
+                                  &direct_converter);
     }
 
 private:
-    static PyObject* dtype_ptr() {
-        static PyObject* ptr = get_numpy_internals().get_type_info<T>(true)->dtype_ptr;
+    static PyObject *dtype_ptr() {
+        static PyObject *ptr = get_numpy_internals().get_type_info<T>(true)->dtype_ptr;
         return ptr;
     }
 
-    static bool direct_converter(PyObject *obj, void*& value) {
-        auto& api = npy_api::get();
+    static bool direct_converter(PyObject *obj, void *&value) {
+        auto &api = npy_api::get();
         if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_)) {
             return false;
         }
@@ -1287,78 +1430,80 @@ template <typename T, typename SFINAE> struct npy_format_descriptor {
 };
 
 #ifdef __CLION_IDE__ // replace heavy macro with dummy code for the IDE (doesn't affect code)
-# define PYBIND11_NUMPY_DTYPE(Type, ...) ((void)0)
-# define PYBIND11_NUMPY_DTYPE_EX(Type, ...) ((void)0)
+#    define PYBIND11_NUMPY_DTYPE(Type, ...) ((void) 0)
+#    define PYBIND11_NUMPY_DTYPE_EX(Type, ...) ((void) 0)
 #else
 
-#define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
-    ::pybind11::detail::field_descriptor {                                                    \
-        Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
-        ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),           \
-        ::pybind11::detail::npy_format_descriptor<decltype(std::declval<T>().Field)>::dtype() \
-    }
+#    define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
+        ::pybind11::detail::field_descriptor {                                                    \
+            Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
+                ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),       \
+                ::pybind11::detail::npy_format_descriptor<                                        \
+                    decltype(std::declval<T>().Field)>::dtype()                                   \
+        }
 
 // Extract name, offset and format descriptor for a struct field
-#define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
+#    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #    Field)
 
 // The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
 // (C) William Swanson, Paul Fultz
-#define PYBIND11_EVAL0(...) __VA_ARGS__
-#define PYBIND11_EVAL1(...) PYBIND11_EVAL0 (PYBIND11_EVAL0 (PYBIND11_EVAL0 (__VA_ARGS__)))
-#define PYBIND11_EVAL2(...) PYBIND11_EVAL1 (PYBIND11_EVAL1 (PYBIND11_EVAL1 (__VA_ARGS__)))
-#define PYBIND11_EVAL3(...) PYBIND11_EVAL2 (PYBIND11_EVAL2 (PYBIND11_EVAL2 (__VA_ARGS__)))
-#define PYBIND11_EVAL4(...) PYBIND11_EVAL3 (PYBIND11_EVAL3 (PYBIND11_EVAL3 (__VA_ARGS__)))
-#define PYBIND11_EVAL(...)  PYBIND11_EVAL4 (PYBIND11_EVAL4 (PYBIND11_EVAL4 (__VA_ARGS__)))
-#define PYBIND11_MAP_END(...)
-#define PYBIND11_MAP_OUT
-#define PYBIND11_MAP_COMMA ,
-#define PYBIND11_MAP_GET_END() 0, PYBIND11_MAP_END
-#define PYBIND11_MAP_NEXT0(test, next, ...) next PYBIND11_MAP_OUT
-#define PYBIND11_MAP_NEXT1(test, next) PYBIND11_MAP_NEXT0 (test, next, 0)
-#define PYBIND11_MAP_NEXT(test, next)  PYBIND11_MAP_NEXT1 (PYBIND11_MAP_GET_END test, next)
-#if defined(_MSC_VER) && !defined(__clang__) // MSVC is not as eager to expand macros, hence this workaround
-#define PYBIND11_MAP_LIST_NEXT1(test, next) \
-    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
-#else
-#define PYBIND11_MAP_LIST_NEXT1(test, next) \
-    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
-#endif
-#define PYBIND11_MAP_LIST_NEXT(test, next) \
-    PYBIND11_MAP_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
-#define PYBIND11_MAP_LIST0(f, t, x, peek, ...) \
-    f(t, x) PYBIND11_MAP_LIST_NEXT (peek, PYBIND11_MAP_LIST1) (f, t, peek, __VA_ARGS__)
-#define PYBIND11_MAP_LIST1(f, t, x, peek, ...) \
-    f(t, x) PYBIND11_MAP_LIST_NEXT (peek, PYBIND11_MAP_LIST0) (f, t, peek, __VA_ARGS__)
+#    define PYBIND11_EVAL0(...) __VA_ARGS__
+#    define PYBIND11_EVAL1(...) PYBIND11_EVAL0(PYBIND11_EVAL0(PYBIND11_EVAL0(__VA_ARGS__)))
+#    define PYBIND11_EVAL2(...) PYBIND11_EVAL1(PYBIND11_EVAL1(PYBIND11_EVAL1(__VA_ARGS__)))
+#    define PYBIND11_EVAL3(...) PYBIND11_EVAL2(PYBIND11_EVAL2(PYBIND11_EVAL2(__VA_ARGS__)))
+#    define PYBIND11_EVAL4(...) PYBIND11_EVAL3(PYBIND11_EVAL3(PYBIND11_EVAL3(__VA_ARGS__)))
+#    define PYBIND11_EVAL(...) PYBIND11_EVAL4(PYBIND11_EVAL4(PYBIND11_EVAL4(__VA_ARGS__)))
+#    define PYBIND11_MAP_END(...)
+#    define PYBIND11_MAP_OUT
+#    define PYBIND11_MAP_COMMA ,
+#    define PYBIND11_MAP_GET_END() 0, PYBIND11_MAP_END
+#    define PYBIND11_MAP_NEXT0(test, next, ...) next PYBIND11_MAP_OUT
+#    define PYBIND11_MAP_NEXT1(test, next) PYBIND11_MAP_NEXT0(test, next, 0)
+#    define PYBIND11_MAP_NEXT(test, next) PYBIND11_MAP_NEXT1(PYBIND11_MAP_GET_END test, next)
+#    if defined(_MSC_VER)                                                                         \
+        && !defined(__clang__) // MSVC is not as eager to expand macros, hence this workaround
+#        define PYBIND11_MAP_LIST_NEXT1(test, next)                                               \
+            PYBIND11_EVAL0(PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0))
+#    else
+#        define PYBIND11_MAP_LIST_NEXT1(test, next)                                               \
+            PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0)
+#    endif
+#    define PYBIND11_MAP_LIST_NEXT(test, next)                                                    \
+        PYBIND11_MAP_LIST_NEXT1(PYBIND11_MAP_GET_END test, next)
+#    define PYBIND11_MAP_LIST0(f, t, x, peek, ...)                                                \
+        f(t, x) PYBIND11_MAP_LIST_NEXT(peek, PYBIND11_MAP_LIST1)(f, t, peek, __VA_ARGS__)
+#    define PYBIND11_MAP_LIST1(f, t, x, peek, ...)                                                \
+        f(t, x) PYBIND11_MAP_LIST_NEXT(peek, PYBIND11_MAP_LIST0)(f, t, peek, __VA_ARGS__)
 // PYBIND11_MAP_LIST(f, t, a1, a2, ...) expands to f(t, a1), f(t, a2), ...
-#define PYBIND11_MAP_LIST(f, t, ...) \
-    PYBIND11_EVAL (PYBIND11_MAP_LIST1 (f, t, __VA_ARGS__, (), 0))
-
-#define PYBIND11_NUMPY_DTYPE(Type, ...) \
-    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
-        (::std::vector<::pybind11::detail::field_descriptor> \
-         {PYBIND11_MAP_LIST (PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
-
-#if defined(_MSC_VER) && !defined(__clang__)
-#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
-    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
-#else
-#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
-    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
-#endif
-#define PYBIND11_MAP2_LIST_NEXT(test, next) \
-    PYBIND11_MAP2_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
-#define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...) \
-    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST1) (f, t, peek, __VA_ARGS__)
-#define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...) \
-    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST0) (f, t, peek, __VA_ARGS__)
+#    define PYBIND11_MAP_LIST(f, t, ...)                                                          \
+        PYBIND11_EVAL(PYBIND11_MAP_LIST1(f, t, __VA_ARGS__, (), 0))
+
+#    define PYBIND11_NUMPY_DTYPE(Type, ...)                                                       \
+        ::pybind11::detail::npy_format_descriptor<Type>::register_dtype(                          \
+            ::std::vector<::pybind11::detail::field_descriptor>{                                  \
+                PYBIND11_MAP_LIST(PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
+
+#    if defined(_MSC_VER) && !defined(__clang__)
+#        define PYBIND11_MAP2_LIST_NEXT1(test, next)                                              \
+            PYBIND11_EVAL0(PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0))
+#    else
+#        define PYBIND11_MAP2_LIST_NEXT1(test, next)                                              \
+            PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0)
+#    endif
+#    define PYBIND11_MAP2_LIST_NEXT(test, next)                                                   \
+        PYBIND11_MAP2_LIST_NEXT1(PYBIND11_MAP_GET_END test, next)
+#    define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...)                                          \
+        f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT(peek, PYBIND11_MAP2_LIST1)(f, t, peek, __VA_ARGS__)
+#    define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...)                                          \
+        f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT(peek, PYBIND11_MAP2_LIST0)(f, t, peek, __VA_ARGS__)
 // PYBIND11_MAP2_LIST(f, t, a1, a2, ...) expands to f(t, a1, a2), f(t, a3, a4), ...
-#define PYBIND11_MAP2_LIST(f, t, ...) \
-    PYBIND11_EVAL (PYBIND11_MAP2_LIST1 (f, t, __VA_ARGS__, (), 0))
+#    define PYBIND11_MAP2_LIST(f, t, ...)                                                         \
+        PYBIND11_EVAL(PYBIND11_MAP2_LIST1(f, t, __VA_ARGS__, (), 0))
 
-#define PYBIND11_NUMPY_DTYPE_EX(Type, ...) \
-    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
-        (::std::vector<::pybind11::detail::field_descriptor> \
-         {PYBIND11_MAP2_LIST (PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
+#    define PYBIND11_NUMPY_DTYPE_EX(Type, ...)                                                    \
+        ::pybind11::detail::npy_format_descriptor<Type>::register_dtype(                          \
+            ::std::vector<::pybind11::detail::field_descriptor>{                                  \
+                PYBIND11_MAP2_LIST(PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
 
 struct npy_format_descriptor_object {
 public:
@@ -1372,11 +1517,13 @@ struct npy_format_descriptor_object {
     static constexpr auto name = _("object");
 };
 
-#define PYBIND11_NUMPY_OBJECT_DTYPE(Type) \
-    namespace pybind11 { namespace detail { \
-        template <> struct npy_format_descriptor<Type> : \
-            public npy_format_descriptor_object {}; \
-    }}
+#    define PYBIND11_NUMPY_OBJECT_DTYPE(Type)                                                     \
+        namespace pybind11 {                                                                      \
+        namespace detail {                                                                        \
+        template <>                                                                               \
+        struct npy_format_descriptor<Type> : public npy_format_descriptor_object {};              \
+        }                                                                                         \
+        }
 
 #endif // __CLION_IDE__
 
@@ -1388,8 +1535,8 @@ class common_iterator {
 
     common_iterator() : m_strides() {}
 
-    common_iterator(void* ptr, const container_type& strides, const container_type& shape)
-        : p_ptr(reinterpret_cast<char*>(ptr)), m_strides(strides.size()) {
+    common_iterator(void *ptr, const container_type &strides, const container_type &shape)
+        : p_ptr(reinterpret_cast<char *>(ptr)), m_strides(strides.size()) {
         m_strides.back() = static_cast<value_type>(strides.back());
         for (size_type i = m_strides.size() - 1; i != 0; --i) {
             size_type j = i - 1;
@@ -1398,27 +1545,22 @@ class common_iterator {
         }
     }
 
-    void increment(size_type dim) {
-        p_ptr += m_strides[dim];
-    }
+    void increment(size_type dim) { p_ptr += m_strides[dim]; }
 
-    void* data() const {
-        return p_ptr;
-    }
+    void *data() const { return p_ptr; }
 
 private:
     char *p_ptr{0};
     container_type m_strides;
 };
 
-template <size_t N> class multi_array_iterator {
+template <size_t N>
+class multi_array_iterator {
 public:
     using container_type = std::vector<ssize_t>;
 
-    multi_array_iterator(const std::array<buffer_info, N> &buffers,
-                         const container_type &shape)
-        : m_shape(shape.size()), m_index(shape.size(), 0),
-          m_common_iterator() {
+    multi_array_iterator(const std::array<buffer_info, N> &buffers, const container_type &shape)
+        : m_shape(shape.size()), m_index(shape.size(), 0), m_common_iterator() {
 
         // Manual copy to avoid conversion warning if using std::copy
         for (size_t i = 0; i < shape.size(); ++i) {
@@ -1431,7 +1573,7 @@ template <size_t N> class multi_array_iterator {
         }
     }
 
-    multi_array_iterator& operator++() {
+    multi_array_iterator &operator++() {
         for (size_t j = m_index.size(); j != 0; --j) {
             size_t i = j - 1;
             if (++m_index[i] != m_shape[i]) {
@@ -1443,12 +1585,12 @@ template <size_t N> class multi_array_iterator {
         return *this;
     }
 
-    template <size_t K, class T = void> T* data() const {
-        return reinterpret_cast<T*>(m_common_iterator[K].data());
+    template <size_t K, class T = void>
+    T *data() const {
+        return reinterpret_cast<T *>(m_common_iterator[K].data());
     }
 
 private:
-
     using common_iter = common_iterator;
 
     void init_common_iterator(const buffer_info &buffer,
@@ -1490,29 +1632,33 @@ template <size_t N> class multi_array_iterator {
 
 enum class broadcast_trivial { non_trivial, c_trivial, f_trivial };
 
-// Populates the shape and number of dimensions for the set of buffers.  Returns a broadcast_trivial
-// enum value indicating whether the broadcast is "trivial"--that is, has each buffer being either a
-// singleton or a full-size, C-contiguous (`c_trivial`) or Fortran-contiguous (`f_trivial`) storage
-// buffer; returns `non_trivial` otherwise.
+// Populates the shape and number of dimensions for the set of buffers.  Returns a
+// broadcast_trivial enum value indicating whether the broadcast is "trivial"--that is, has each
+// buffer being either a singleton or a full-size, C-contiguous (`c_trivial`) or Fortran-contiguous
+// (`f_trivial`) storage buffer; returns `non_trivial` otherwise.
 template <size_t N>
-broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &ndim, std::vector<ssize_t> &shape) {
-    ndim = std::accumulate(buffers.begin(), buffers.end(), ssize_t(0), [](ssize_t res, const buffer_info &buf) {
-        return std::max(res, buf.ndim);
-    });
+broadcast_trivial
+broadcast(const std::array<buffer_info, N> &buffers, ssize_t &ndim, std::vector<ssize_t> &shape) {
+    ndim = std::accumulate(
+        buffers.begin(), buffers.end(), ssize_t(0), [](ssize_t res, const buffer_info &buf) {
+            return std::max(res, buf.ndim);
+        });
 
     shape.clear();
     shape.resize((size_t) ndim, 1);
 
-    // Figure out the output size, and make sure all input arrays conform (i.e. are either size 1 or
-    // the full size).
+    // Figure out the output size, and make sure all input arrays conform (i.e. are either size 1
+    // or the full size).
     for (size_t i = 0; i < N; ++i) {
         auto res_iter = shape.rbegin();
         auto end = buffers[i].shape.rend();
-        for (auto shape_iter = buffers[i].shape.rbegin(); shape_iter != end; ++shape_iter, ++res_iter) {
+        for (auto shape_iter = buffers[i].shape.rbegin(); shape_iter != end;
+             ++shape_iter, ++res_iter) {
             const auto &dim_size_in = *shape_iter;
             auto &dim_size_out = *res_iter;
 
-            // Each input dimension can either be 1 or `n`, but `n` values must match across buffers
+            // Each input dimension can either be 1 or `n`, but `n` values must match across
+            // buffers
             if (dim_size_out == 1) {
                 dim_size_out = dim_size_in;
             } else if (dim_size_in != 1 && dim_size_in != dim_size_out) {
@@ -1542,8 +1688,10 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
         if (trivial_broadcast_c) {
             ssize_t expect_stride = buffers[i].itemsize;
             auto end = buffers[i].shape.crend();
-            for (auto shape_iter = buffers[i].shape.crbegin(), stride_iter = buffers[i].strides.crbegin();
-                    trivial_broadcast_c && shape_iter != end; ++shape_iter, ++stride_iter) {
+            for (auto shape_iter = buffers[i].shape.crbegin(),
+                      stride_iter = buffers[i].strides.crbegin();
+                 trivial_broadcast_c && shape_iter != end;
+                 ++shape_iter, ++stride_iter) {
                 if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
                 } else {
@@ -1556,8 +1704,10 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
         if (trivial_broadcast_f) {
             ssize_t expect_stride = buffers[i].itemsize;
             auto end = buffers[i].shape.cend();
-            for (auto shape_iter = buffers[i].shape.cbegin(), stride_iter = buffers[i].strides.cbegin();
-                    trivial_broadcast_f && shape_iter != end; ++shape_iter, ++stride_iter) {
+            for (auto shape_iter = buffers[i].shape.cbegin(),
+                      stride_iter = buffers[i].strides.cbegin();
+                 trivial_broadcast_f && shape_iter != end;
+                 ++shape_iter, ++stride_iter) {
                 if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
                 } else {
@@ -1567,28 +1717,31 @@ broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &
         }
     }
 
-    return
-        trivial_broadcast_c ? broadcast_trivial::c_trivial :
-        trivial_broadcast_f ? broadcast_trivial::f_trivial :
-        broadcast_trivial::non_trivial;
+    return trivial_broadcast_c   ? broadcast_trivial::c_trivial
+           : trivial_broadcast_f ? broadcast_trivial::f_trivial
+                                 : broadcast_trivial::non_trivial;
 }
 
 template <typename T>
 struct vectorize_arg {
-    static_assert(!std::is_rvalue_reference<T>::value, "Functions with rvalue reference arguments cannot be vectorized");
+    static_assert(!std::is_rvalue_reference<T>::value,
+                  "Functions with rvalue reference arguments cannot be vectorized");
     // The wrapped function gets called with this type:
     using call_type = remove_reference_t<T>;
     // Is this a vectorized argument?
-    static constexpr bool vectorize =
-        satisfies_any_of<call_type, std::is_arithmetic, is_complex, is_pod>::value &&
-        satisfies_none_of<call_type, std::is_pointer, std::is_array, is_std_array, std::is_enum>::value &&
-        (!std::is_reference<T>::value ||
-         (std::is_lvalue_reference<T>::value && std::is_const<call_type>::value));
+    static constexpr bool vectorize
+        = satisfies_any_of<call_type, std::is_arithmetic, is_complex, is_pod>::value
+          && satisfies_none_of<call_type,
+                               std::is_pointer,
+                               std::is_array,
+                               is_std_array,
+                               std::is_enum>::value
+          && (!std::is_reference<T>::value
+              || (std::is_lvalue_reference<T>::value && std::is_const<call_type>::value));
     // Accept this type: an array for vectorized types, otherwise the type as-is:
     using type = conditional_t<vectorize, array_t<remove_cv_t<call_type>, array::forcecast>, T>;
 };
 
-
 // py::vectorize when a return type is present
 template <typename Func, typename Return, typename... Args>
 struct vectorize_returned_array {
@@ -1601,17 +1754,11 @@ struct vectorize_returned_array {
         return array_t<Return>(shape);
     }
 
-    static Return *mutable_data(Type &array) {
-        return array.mutable_data();
-    }
+    static Return *mutable_data(Type &array) { return array.mutable_data(); }
 
-    static Return call(Func &f, Args &... args) {
-        return f(args...);
-    }
+    static Return call(Func &f, Args &...args) { return f(args...); }
 
-    static void call(Return *out, size_t i, Func &f, Args &... args) {
-        out[i] = f(args...);
-    }
+    static void call(Return *out, size_t i, Func &f, Args &...args) { out[i] = f(args...); }
 };
 
 // py::vectorize when a return type is not present
@@ -1619,25 +1766,18 @@ template <typename Func, typename... Args>
 struct vectorize_returned_array<Func, void, Args...> {
     using Type = none;
 
-    static Type create(broadcast_trivial, const std::vector<ssize_t> &) {
-        return none();
-    }
+    static Type create(broadcast_trivial, const std::vector<ssize_t> &) { return none(); }
 
-    static void *mutable_data(Type &) {
-        return nullptr;
-    }
+    static void *mutable_data(Type &) { return nullptr; }
 
-    static detail::void_type call(Func &f, Args &... args) {
+    static detail::void_type call(Func &f, Args &...args) {
         f(args...);
         return {};
     }
 
-    static void call(void *, size_t, Func &f, Args &... args) {
-        f(args...);
-    }
+    static void call(void *, size_t, Func &f, Args &...args) { f(args...); }
 };
 
-
 template <typename Func, typename Return, typename... Args>
 struct vectorize_helper {
 
@@ -1650,8 +1790,9 @@ struct vectorize_helper {
 
     static constexpr size_t N = sizeof...(Args);
     static constexpr size_t NVectorized = constexpr_sum(vectorize_arg<Args>::vectorize...);
-    static_assert(NVectorized >= 1,
-            "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
+    static_assert(
+        NVectorized >= 1,
+        "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
 
 public:
     template <typename T,
@@ -1670,10 +1811,11 @@ struct vectorize_helper {
 private:
     remove_reference_t<Func> f;
 
-    // Internal compiler error in MSVC 19.16.27025.1 (Visual Studio 2017 15.9.4), when compiling with "/permissive-" flag
-    // when arg_call_types is manually inlined.
+    // Internal compiler error in MSVC 19.16.27025.1 (Visual Studio 2017 15.9.4), when compiling
+    // with "/permissive-" flag when arg_call_types is manually inlined.
     using arg_call_types = std::tuple<typename vectorize_arg<Args>::call_type...>;
-    template <size_t Index> using param_n_t = typename std::tuple_element<Index, arg_call_types>::type;
+    template <size_t Index>
+    using param_n_t = typename std::tuple_element<Index, arg_call_types>::type;
 
     using returned_array = vectorize_returned_array<Func, Return, Args...>;
 
@@ -1684,17 +1826,20 @@ struct vectorize_helper {
     //     - BIndex is a incremental sequence (beginning at 0) of the same size as VIndex, so that
     //       we can store vectorized buffer_infos in an array (argument VIndex has its buffer at
     //       index BIndex in the array).
-    template <size_t... Index, size_t... VIndex, size_t... BIndex> object run(
-            typename vectorize_arg<Args>::type &...args,
-            index_sequence<Index...> i_seq, index_sequence<VIndex...> vi_seq, index_sequence<BIndex...> bi_seq) {
+    template <size_t... Index, size_t... VIndex, size_t... BIndex>
+    object run(typename vectorize_arg<Args>::type &...args,
+               index_sequence<Index...> i_seq,
+               index_sequence<VIndex...> vi_seq,
+               index_sequence<BIndex...> bi_seq) {
 
         // Pointers to values the function was called with; the vectorized ones set here will start
         // out as array_t<T> pointers, but they will be changed them to T pointers before we make
         // call the wrapped function.  Non-vectorized pointers are left as-is.
-        std::array<void *, N> params{{ &args... }};
+        std::array<void *, N> params{{&args...}};
 
         // The array of `buffer_info`s of vectorized arguments:
-        std::array<buffer_info, NVectorized> buffers{{ reinterpret_cast<array *>(params[VIndex])->request()... }};
+        std::array<buffer_info, NVectorized> buffers{
+            {reinterpret_cast<array *>(params[VIndex])->request()...}};
 
         /* Determine dimensions parameters of output array */
         ssize_t nd = 0;
@@ -1702,13 +1847,15 @@ struct vectorize_helper {
         auto trivial = broadcast(buffers, nd, shape);
         auto ndim = (size_t) nd;
 
-        size_t size = std::accumulate(shape.begin(), shape.end(), (size_t) 1, std::multiplies<size_t>());
+        size_t size
+            = std::accumulate(shape.begin(), shape.end(), (size_t) 1, std::multiplies<size_t>());
 
         // If all arguments are 0-dimension arrays (i.e. single values) return a plain value (i.e.
         // not wrapped in an array).
         if (size == 1 && ndim == 0) {
             PYBIND11_EXPAND_SIDE_EFFECTS(params[VIndex] = buffers[BIndex].ptr);
-            return cast(returned_array::call(f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...));
+            return cast(
+                returned_array::call(f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...));
         }
 
         auto result = returned_array::create(trivial, shape);
@@ -1733,20 +1880,21 @@ struct vectorize_helper {
                        std::array<void *, N> &params,
                        Return *out,
                        size_t size,
-                       index_sequence<Index...>, index_sequence<VIndex...>, index_sequence<BIndex...>) {
+                       index_sequence<Index...>,
+                       index_sequence<VIndex...>,
+                       index_sequence<BIndex...>) {
 
         // Initialize an array of mutable byte references and sizes with references set to the
         // appropriate pointer in `params`; as we iterate, we'll increment each pointer by its size
         // (except for singletons, which get an increment of 0).
-        std::array<std::pair<unsigned char *&, const size_t>, NVectorized> vecparams{{
-            std::pair<unsigned char *&, const size_t>(
-                    reinterpret_cast<unsigned char *&>(params[VIndex] = buffers[BIndex].ptr),
-                    buffers[BIndex].size == 1 ? 0 : sizeof(param_n_t<VIndex>)
-            )...
-        }};
+        std::array<std::pair<unsigned char *&, const size_t>, NVectorized> vecparams{
+            {std::pair<unsigned char *&, const size_t>(
+                reinterpret_cast<unsigned char *&>(params[VIndex] = buffers[BIndex].ptr),
+                buffers[BIndex].size == 1 ? 0 : sizeof(param_n_t<VIndex>))...}};
 
         for (size_t i = 0; i < size; ++i) {
-            returned_array::call(out, i, f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...);
+            returned_array::call(
+                out, i, f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...);
             for (auto &x : vecparams) {
                 x.first += x.second;
             }
@@ -1759,55 +1907,70 @@ struct vectorize_helper {
                          Return *out,
                          size_t size,
                          const std::vector<ssize_t> &output_shape,
-                         index_sequence<Index...>, index_sequence<VIndex...>, index_sequence<BIndex...>) {
+                         index_sequence<Index...>,
+                         index_sequence<VIndex...>,
+                         index_sequence<BIndex...>) {
 
         multi_array_iterator<NVectorized> input_iter(buffers, output_shape);
 
         for (size_t i = 0; i < size; ++i, ++input_iter) {
-            PYBIND11_EXPAND_SIDE_EFFECTS((
-                params[VIndex] = input_iter.template data<BIndex>()
-            ));
-            returned_array::call(out, i, f, *reinterpret_cast<param_n_t<Index> *>(std::get<Index>(params))...);
+            PYBIND11_EXPAND_SIDE_EFFECTS((params[VIndex] = input_iter.template data<BIndex>()));
+            returned_array::call(
+                out, i, f, *reinterpret_cast<param_n_t<Index> *>(std::get<Index>(params))...);
         }
     }
 };
 
 template <typename Func, typename Return, typename... Args>
-vectorize_helper<Func, Return, Args...>
-vectorize_extractor(const Func &f, Return (*) (Args ...)) {
+vectorize_helper<Func, Return, Args...> vectorize_extractor(const Func &f, Return (*)(Args...)) {
     return detail::vectorize_helper<Func, Return, Args...>(f);
 }
 
-template <typename T, int Flags> struct handle_type_name<array_t<T, Flags>> {
-    static constexpr auto name = const_name("numpy.ndarray[") + npy_format_descriptor<T>::name + const_name("]");
+template <typename T, int Flags>
+struct handle_type_name<array_t<T, Flags>> {
+    static constexpr auto name
+        = const_name("numpy.ndarray[") + npy_format_descriptor<T>::name + const_name("]");
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
 // Vanilla pointer vectorizer:
 template <typename Return, typename... Args>
-detail::vectorize_helper<Return (*)(Args...), Return, Args...>
-vectorize(Return (*f) (Args ...)) {
+detail::vectorize_helper<Return (*)(Args...), Return, Args...> vectorize(Return (*f)(Args...)) {
     return detail::vectorize_helper<Return (*)(Args...), Return, Args...>(f);
 }
 
 // lambda vectorizer:
 template <typename Func, detail::enable_if_t<detail::is_lambda<Func>::value, int> = 0>
-auto vectorize(Func &&f) -> decltype(
-        detail::vectorize_extractor(std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr)) {
-    return detail::vectorize_extractor(std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr);
+auto vectorize(Func &&f)
+    -> decltype(detail::vectorize_extractor(std::forward<Func>(f),
+                                            (detail::function_signature_t<Func> *) nullptr)) {
+    return detail::vectorize_extractor(std::forward<Func>(f),
+                                       (detail::function_signature_t<Func> *) nullptr);
 }
 
 // Vectorize a class method (non-const):
-template <typename Return, typename Class, typename... Args,
-          typename Helper = detail::vectorize_helper<decltype(std::mem_fn(std::declval<Return (Class::*)(Args...)>())), Return, Class *, Args...>>
+template <typename Return,
+          typename Class,
+          typename... Args,
+          typename Helper = detail::vectorize_helper<
+              decltype(std::mem_fn(std::declval<Return (Class::*)(Args...)>())),
+              Return,
+              Class *,
+              Args...>>
 Helper vectorize(Return (Class::*f)(Args...)) {
     return Helper(std::mem_fn(f));
 }
 
 // Vectorize a class method (const):
-template <typename Return, typename Class, typename... Args,
-          typename Helper = detail::vectorize_helper<decltype(std::mem_fn(std::declval<Return (Class::*)(Args...) const>())), Return, const Class *, Args...>>
+template <typename Return,
+          typename Class,
+          typename... Args,
+          typename Helper = detail::vectorize_helper<
+              decltype(std::mem_fn(std::declval<Return (Class::*)(Args...) const>())),
+              Return,
+              const Class *,
+              Args...>>
 Helper vectorize(Return (Class::*f)(Args...) const) {
     return Helper(std::mem_fn(f));
 }
diff --git a/include/pybind11/operators.h b/include/pybind11/operators.h
index 2a61531589..7865d35e10 100644
--- a/include/pybind11/operators.h
+++ b/include/pybind11/operators.h
@@ -16,12 +16,50 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Enumeration with all supported operator types
 enum op_id : int {
-    op_add, op_sub, op_mul, op_div, op_mod, op_divmod, op_pow, op_lshift,
-    op_rshift, op_and, op_xor, op_or, op_neg, op_pos, op_abs, op_invert,
-    op_int, op_long, op_float, op_str, op_cmp, op_gt, op_ge, op_lt, op_le,
-    op_eq, op_ne, op_iadd, op_isub, op_imul, op_idiv, op_imod, op_ilshift,
-    op_irshift, op_iand, op_ixor, op_ior, op_complex, op_bool, op_nonzero,
-    op_repr, op_truediv, op_itruediv, op_hash
+    op_add,
+    op_sub,
+    op_mul,
+    op_div,
+    op_mod,
+    op_divmod,
+    op_pow,
+    op_lshift,
+    op_rshift,
+    op_and,
+    op_xor,
+    op_or,
+    op_neg,
+    op_pos,
+    op_abs,
+    op_invert,
+    op_int,
+    op_long,
+    op_float,
+    op_str,
+    op_cmp,
+    op_gt,
+    op_ge,
+    op_lt,
+    op_le,
+    op_eq,
+    op_ne,
+    op_iadd,
+    op_isub,
+    op_imul,
+    op_idiv,
+    op_imod,
+    op_ilshift,
+    op_irshift,
+    op_iand,
+    op_ixor,
+    op_ior,
+    op_complex,
+    op_bool,
+    op_nonzero,
+    op_repr,
+    op_truediv,
+    op_itruediv,
+    op_hash
 };
 
 enum op_type : int {
@@ -30,126 +68,145 @@ enum op_type : int {
     op_u  /* unary operator */
 };
 
-struct self_t { };
+struct self_t {};
 static const self_t self = self_t();
 
 /// Type for an unused type slot
-struct undefined_t { };
+struct undefined_t {};
 
 /// Don't warn about an unused variable
 inline self_t __self() { return self; }
 
 /// base template of operator implementations
-template <op_id, op_type, typename B, typename L, typename R> struct op_impl { };
+template <op_id, op_type, typename B, typename L, typename R>
+struct op_impl {};
 
 /// Operator implementation generator
-template <op_id id, op_type ot, typename L, typename R> struct op_ {
-    template <typename Class, typename... Extra> void execute(Class &cl, const Extra&... extra) const {
+template <op_id id, op_type ot, typename L, typename R>
+struct op_ {
+    template <typename Class, typename... Extra>
+    void execute(Class &cl, const Extra &...extra) const {
         using Base = typename Class::type;
         using L_type = conditional_t<std::is_same<L, self_t>::value, Base, L>;
         using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute, is_operator(), extra...);
-        #if PY_MAJOR_VERSION < 3
-        if (PYBIND11_SILENCE_MSVC_C4127(id == op_truediv) ||
-            PYBIND11_SILENCE_MSVC_C4127(id == op_itruediv))
-            cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
-                    &op::execute, is_operator(), extra...);
-        #endif
+#if PY_MAJOR_VERSION < 3
+        if (PYBIND11_SILENCE_MSVC_C4127(id == op_truediv)
+            || PYBIND11_SILENCE_MSVC_C4127(id == op_itruediv))
+            cl.def(id == op_itruediv ? "__idiv__"
+                   : ot == op_l      ? "__div__"
+                                     : "__rdiv__",
+                   &op::execute,
+                   is_operator(),
+                   extra...);
+#endif
     }
-    template <typename Class, typename... Extra> void execute_cast(Class &cl, const Extra&... extra) const {
+    template <typename Class, typename... Extra>
+    void execute_cast(Class &cl, const Extra &...extra) const {
         using Base = typename Class::type;
         using L_type = conditional_t<std::is_same<L, self_t>::value, Base, L>;
         using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
         using op = op_impl<id, ot, Base, L_type, R_type>;
         cl.def(op::name(), &op::execute_cast, is_operator(), extra...);
-        #if PY_MAJOR_VERSION < 3
+#if PY_MAJOR_VERSION < 3
         if (id == op_truediv || id == op_itruediv)
-            cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
-                    &op::execute, is_operator(), extra...);
-        #endif
+            cl.def(id == op_itruediv ? "__idiv__"
+                   : ot == op_l      ? "__div__"
+                                     : "__rdiv__",
+                   &op::execute,
+                   is_operator(),
+                   extra...);
+#endif
     }
 };
 
-#define PYBIND11_BINARY_OPERATOR(id, rid, op, expr)                                    \
-template <typename B, typename L, typename R> struct op_impl<op_##id, op_l, B, L, R> { \
-    static char const* name() { return "__" #id "__"; }                                \
-    static auto execute(const L &l, const R &r) -> decltype(expr) { return (expr); }   \
-    static B execute_cast(const L &l, const R &r) { return B(expr); }                  \
-};                                                                                     \
-template <typename B, typename L, typename R> struct op_impl<op_##id, op_r, B, L, R> { \
-    static char const* name() { return "__" #rid "__"; }                               \
-    static auto execute(const R &r, const L &l) -> decltype(expr) { return (expr); }   \
-    static B execute_cast(const R &r, const L &l) { return B(expr); }                  \
-};                                                                                     \
-inline op_<op_##id, op_l, self_t, self_t> op(const self_t &, const self_t &) {         \
-    return op_<op_##id, op_l, self_t, self_t>();                                       \
-}                                                                                      \
-template <typename T> op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {    \
-    return op_<op_##id, op_l, self_t, T>();                                            \
-}                                                                                      \
-template <typename T> op_<op_##id, op_r, T, self_t> op(const T &, const self_t &) {    \
-    return op_<op_##id, op_r, T, self_t>();                                            \
-}
-
-#define PYBIND11_INPLACE_OPERATOR(id, op, expr)                                        \
-template <typename B, typename L, typename R> struct op_impl<op_##id, op_l, B, L, R> { \
-    static char const* name() { return "__" #id "__"; }                                \
-    static auto execute(L &l, const R &r) -> decltype(expr) { return expr; }           \
-    static B execute_cast(L &l, const R &r) { return B(expr); }                        \
-};                                                                                     \
-template <typename T> op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {    \
-    return op_<op_##id, op_l, self_t, T>();                                            \
-}
-
-#define PYBIND11_UNARY_OPERATOR(id, op, expr)                                          \
-template <typename B, typename L> struct op_impl<op_##id, op_u, B, L, undefined_t> {   \
-    static char const* name() { return "__" #id "__"; }                                \
-    static auto execute(const L &l) -> decltype(expr) { return expr; }                 \
-    static B execute_cast(const L &l) { return B(expr); }                              \
-};                                                                                     \
-inline op_<op_##id, op_u, self_t, undefined_t> op(const self_t &) {                    \
-    return op_<op_##id, op_u, self_t, undefined_t>();                                  \
-}
-
-PYBIND11_BINARY_OPERATOR(sub,       rsub,         operator-,    l - r)
-PYBIND11_BINARY_OPERATOR(add,       radd,         operator+,    l + r)
-PYBIND11_BINARY_OPERATOR(mul,       rmul,         operator*,    l * r)
-PYBIND11_BINARY_OPERATOR(truediv,   rtruediv,     operator/,    l / r)
-PYBIND11_BINARY_OPERATOR(mod,       rmod,         operator%,    l % r)
-PYBIND11_BINARY_OPERATOR(lshift,    rlshift,      operator<<,   l << r)
-PYBIND11_BINARY_OPERATOR(rshift,    rrshift,      operator>>,   l >> r)
-PYBIND11_BINARY_OPERATOR(and,       rand,         operator&,    l & r)
-PYBIND11_BINARY_OPERATOR(xor,       rxor,         operator^,    l ^ r)
-PYBIND11_BINARY_OPERATOR(eq,        eq,           operator==,   l == r)
-PYBIND11_BINARY_OPERATOR(ne,        ne,           operator!=,   l != r)
-PYBIND11_BINARY_OPERATOR(or,        ror,          operator|,    l | r)
-PYBIND11_BINARY_OPERATOR(gt,        lt,           operator>,    l > r)
-PYBIND11_BINARY_OPERATOR(ge,        le,           operator>=,   l >= r)
-PYBIND11_BINARY_OPERATOR(lt,        gt,           operator<,    l < r)
-PYBIND11_BINARY_OPERATOR(le,        ge,           operator<=,   l <= r)
-//PYBIND11_BINARY_OPERATOR(pow,       rpow,         pow,          std::pow(l,  r))
-PYBIND11_INPLACE_OPERATOR(iadd,     operator+=,   l += r)
-PYBIND11_INPLACE_OPERATOR(isub,     operator-=,   l -= r)
-PYBIND11_INPLACE_OPERATOR(imul,     operator*=,   l *= r)
-PYBIND11_INPLACE_OPERATOR(itruediv, operator/=,   l /= r)
-PYBIND11_INPLACE_OPERATOR(imod,     operator%=,   l %= r)
-PYBIND11_INPLACE_OPERATOR(ilshift,  operator<<=,  l <<= r)
-PYBIND11_INPLACE_OPERATOR(irshift,  operator>>=,  l >>= r)
-PYBIND11_INPLACE_OPERATOR(iand,     operator&=,   l &= r)
-PYBIND11_INPLACE_OPERATOR(ixor,     operator^=,   l ^= r)
-PYBIND11_INPLACE_OPERATOR(ior,      operator|=,   l |= r)
-PYBIND11_UNARY_OPERATOR(neg,        operator-,    -l)
-PYBIND11_UNARY_OPERATOR(pos,        operator+,    +l)
+#define PYBIND11_BINARY_OPERATOR(id, rid, op, expr)                                               \
+    template <typename B, typename L, typename R>                                                 \
+    struct op_impl<op_##id, op_l, B, L, R> {                                                      \
+        static char const *name() { return "__" #id "__"; }                                       \
+        static auto execute(const L &l, const R &r) -> decltype(expr) { return (expr); }          \
+        static B execute_cast(const L &l, const R &r) { return B(expr); }                         \
+    };                                                                                            \
+    template <typename B, typename L, typename R>                                                 \
+    struct op_impl<op_##id, op_r, B, L, R> {                                                      \
+        static char const *name() { return "__" #rid "__"; }                                      \
+        static auto execute(const R &r, const L &l) -> decltype(expr) { return (expr); }          \
+        static B execute_cast(const R &r, const L &l) { return B(expr); }                         \
+    };                                                                                            \
+    inline op_<op_##id, op_l, self_t, self_t> op(const self_t &, const self_t &) {                \
+        return op_<op_##id, op_l, self_t, self_t>();                                              \
+    }                                                                                             \
+    template <typename T>                                                                         \
+    op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {                                 \
+        return op_<op_##id, op_l, self_t, T>();                                                   \
+    }                                                                                             \
+    template <typename T>                                                                         \
+    op_<op_##id, op_r, T, self_t> op(const T &, const self_t &) {                                 \
+        return op_<op_##id, op_r, T, self_t>();                                                   \
+    }
+
+#define PYBIND11_INPLACE_OPERATOR(id, op, expr)                                                   \
+    template <typename B, typename L, typename R>                                                 \
+    struct op_impl<op_##id, op_l, B, L, R> {                                                      \
+        static char const *name() { return "__" #id "__"; }                                       \
+        static auto execute(L &l, const R &r) -> decltype(expr) { return expr; }                  \
+        static B execute_cast(L &l, const R &r) { return B(expr); }                               \
+    };                                                                                            \
+    template <typename T>                                                                         \
+    op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {                                 \
+        return op_<op_##id, op_l, self_t, T>();                                                   \
+    }
+
+#define PYBIND11_UNARY_OPERATOR(id, op, expr)                                                     \
+    template <typename B, typename L>                                                             \
+    struct op_impl<op_##id, op_u, B, L, undefined_t> {                                            \
+        static char const *name() { return "__" #id "__"; }                                       \
+        static auto execute(const L &l) -> decltype(expr) { return expr; }                        \
+        static B execute_cast(const L &l) { return B(expr); }                                     \
+    };                                                                                            \
+    inline op_<op_##id, op_u, self_t, undefined_t> op(const self_t &) {                           \
+        return op_<op_##id, op_u, self_t, undefined_t>();                                         \
+    }
+
+PYBIND11_BINARY_OPERATOR(sub, rsub, operator-, l - r)
+PYBIND11_BINARY_OPERATOR(add, radd, operator+, l + r)
+PYBIND11_BINARY_OPERATOR(mul, rmul, operator*, l *r)
+PYBIND11_BINARY_OPERATOR(truediv, rtruediv, operator/, l / r)
+PYBIND11_BINARY_OPERATOR(mod, rmod, operator%, l % r)
+PYBIND11_BINARY_OPERATOR(lshift, rlshift, operator<<, l << r)
+PYBIND11_BINARY_OPERATOR(rshift, rrshift, operator>>, l >> r)
+PYBIND11_BINARY_OPERATOR(and, rand, operator&, l &r)
+PYBIND11_BINARY_OPERATOR(xor, rxor, operator^, l ^ r)
+PYBIND11_BINARY_OPERATOR(eq, eq, operator==, l == r)
+PYBIND11_BINARY_OPERATOR(ne, ne, operator!=, l != r)
+PYBIND11_BINARY_OPERATOR(or, ror, operator|, l | r)
+PYBIND11_BINARY_OPERATOR(gt, lt, operator>, l > r)
+PYBIND11_BINARY_OPERATOR(ge, le, operator>=, l >= r)
+PYBIND11_BINARY_OPERATOR(lt, gt, operator<, l < r)
+PYBIND11_BINARY_OPERATOR(le, ge, operator<=, l <= r)
+// PYBIND11_BINARY_OPERATOR(pow,       rpow,         pow,          std::pow(l,  r))
+PYBIND11_INPLACE_OPERATOR(iadd, operator+=, l += r)
+PYBIND11_INPLACE_OPERATOR(isub, operator-=, l -= r)
+PYBIND11_INPLACE_OPERATOR(imul, operator*=, l *= r)
+PYBIND11_INPLACE_OPERATOR(itruediv, operator/=, l /= r)
+PYBIND11_INPLACE_OPERATOR(imod, operator%=, l %= r)
+PYBIND11_INPLACE_OPERATOR(ilshift, operator<<=, l <<= r)
+PYBIND11_INPLACE_OPERATOR(irshift, operator>>=, l >>= r)
+PYBIND11_INPLACE_OPERATOR(iand, operator&=, l &= r)
+PYBIND11_INPLACE_OPERATOR(ixor, operator^=, l ^= r)
+PYBIND11_INPLACE_OPERATOR(ior, operator|=, l |= r)
+PYBIND11_UNARY_OPERATOR(neg, operator-, -l)
+PYBIND11_UNARY_OPERATOR(pos, operator+, +l)
 // WARNING: This usage of `abs` should only be done for existing STL overloads.
 // Adding overloads directly in to the `std::` namespace is advised against:
 // https://en.cppreference.com/w/cpp/language/extending_std
-PYBIND11_UNARY_OPERATOR(abs,        abs,          std::abs(l))
-PYBIND11_UNARY_OPERATOR(hash,       hash,         std::hash<L>()(l))
-PYBIND11_UNARY_OPERATOR(invert,     operator~,    (~l))
-PYBIND11_UNARY_OPERATOR(bool,       operator!,    !!l)
-PYBIND11_UNARY_OPERATOR(int,        int_,         (int) l)
-PYBIND11_UNARY_OPERATOR(float,      float_,       (double) l)
+PYBIND11_UNARY_OPERATOR(abs, abs, std::abs(l))
+PYBIND11_UNARY_OPERATOR(hash, hash, std::hash<L>()(l))
+PYBIND11_UNARY_OPERATOR(invert, operator~, (~l))
+PYBIND11_UNARY_OPERATOR(bool, operator!, !!l)
+PYBIND11_UNARY_OPERATOR(int, int_, (int) l)
+PYBIND11_UNARY_OPERATOR(float, float_, (double) l)
 
 #undef PYBIND11_BINARY_OPERATOR
 #undef PYBIND11_INPLACE_OPERATOR
diff --git a/include/pybind11/options.h b/include/pybind11/options.h
index 810e5e0104..1e493bdcc4 100644
--- a/include/pybind11/options.h
+++ b/include/pybind11/options.h
@@ -15,44 +15,54 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 class options {
 public:
-
     // Default RAII constructor, which leaves settings as they currently are.
     options() : previous_state(global_state()) {}
 
     // Class is non-copyable.
-    options(const options&) = delete;
-    options& operator=(const options&) = delete;
+    options(const options &) = delete;
+    options &operator=(const options &) = delete;
 
     // Destructor, which restores settings that were in effect before.
-    ~options() {
-        global_state() = previous_state;
-    }
+    ~options() { global_state() = previous_state; }
 
     // Setter methods (affect the global state):
 
-    options& disable_user_defined_docstrings() & { global_state().show_user_defined_docstrings = false; return *this; }
+    options &disable_user_defined_docstrings() & {
+        global_state().show_user_defined_docstrings = false;
+        return *this;
+    }
 
-    options& enable_user_defined_docstrings() & { global_state().show_user_defined_docstrings = true; return *this; }
+    options &enable_user_defined_docstrings() & {
+        global_state().show_user_defined_docstrings = true;
+        return *this;
+    }
 
-    options& disable_function_signatures() & { global_state().show_function_signatures = false; return *this; }
+    options &disable_function_signatures() & {
+        global_state().show_function_signatures = false;
+        return *this;
+    }
 
-    options& enable_function_signatures() & { global_state().show_function_signatures = true; return *this; }
+    options &enable_function_signatures() & {
+        global_state().show_function_signatures = true;
+        return *this;
+    }
 
     // Getter methods (return the global state):
 
-    static bool show_user_defined_docstrings() { return global_state().show_user_defined_docstrings; }
+    static bool show_user_defined_docstrings() {
+        return global_state().show_user_defined_docstrings;
+    }
 
     static bool show_function_signatures() { return global_state().show_function_signatures; }
 
     // This type is not meant to be allocated on the heap.
-    void* operator new(size_t) = delete;
+    void *operator new(size_t) = delete;
 
 private:
-
     struct state {
-        bool show_user_defined_docstrings = true;  //< Include user-supplied texts in docstrings.
-        bool show_function_signatures = true;      //< Include auto-generated function signatures
-                                                   //  in docstrings.
+        bool show_user_defined_docstrings = true; //< Include user-supplied texts in docstrings.
+        bool show_function_signatures = true;     //< Include auto-generated function signatures
+                                                  //  in docstrings.
     };
 
     static state &global_state() {
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 586636d981..4471db97f7 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -10,30 +10,29 @@
 
 #pragma once
 
+#include "detail/class.h"
+#include "detail/init.h"
 #include "attr.h"
 #include "gil.h"
 #include "options.h"
-#include "detail/class.h"
-#include "detail/init.h"
 
 #include <cstdlib>
+#include <cstring>
 #include <memory>
 #include <new>
-#include <vector>
 #include <string>
 #include <utility>
-
-#include <cstring>
+#include <vector>
 
 #if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
-#  define PYBIND11_STD_LAUNDER std::launder
-#  define PYBIND11_HAS_STD_LAUNDER 1
+#    define PYBIND11_STD_LAUNDER std::launder
+#    define PYBIND11_HAS_STD_LAUNDER 1
 #else
-#  define PYBIND11_STD_LAUNDER
-#  define PYBIND11_HAS_STD_LAUNDER 0
+#    define PYBIND11_STD_LAUNDER
+#    define PYBIND11_HAS_STD_LAUNDER 0
 #endif
 #if defined(__GNUG__) && !defined(__clang__)
-#  include <cxxabi.h>
+#    include <cxxabi.h>
 #endif
 
 /* https://stackoverflow.com/questions/46798456/handling-gccs-noexcept-type-warning
@@ -56,7 +55,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // Return true if one of the translators completed without raising an exception
 // itself. Return of false indicates that if there are other translators
 // available, they should be tried.
-inline bool apply_exception_translators(std::forward_list<ExceptionTranslator>& translators) {
+inline bool apply_exception_translators(std::forward_list<ExceptionTranslator> &translators) {
     auto last_exception = std::current_exception();
 
     for (auto &translator : translators) {
@@ -80,37 +79,40 @@ PYBIND11_NAMESPACE_END(detail)
 
 // TODO(eric.cousineau): Move into detail namespace.
 template <typename... Args>
-void unused(Args&&...) {}
+void unused(Args &&...) {}
 
 /// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object
 class cpp_function : public function {
 public:
     cpp_function() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(std::nullptr_t) { }
+    cpp_function(std::nullptr_t) {}
 
     /// Construct a cpp_function from a vanilla function pointer
     template <typename Return, typename... Args, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (*f)(Args...), const Extra&... extra) {
+    cpp_function(Return (*f)(Args...), const Extra &...extra) {
         initialize(f, f, extra...);
     }
 
     /// Construct a cpp_function from a lambda function (possibly with internal state)
-    template <typename Func, typename... Extra,
+    template <typename Func,
+              typename... Extra,
               typename = detail::enable_if_t<detail::is_lambda<Func>::value>>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Func &&f, const Extra&... extra) {
-        initialize(std::forward<Func>(f),
-                   (detail::function_signature_t<Func> *) nullptr, extra...);
+    cpp_function(Func &&f, const Extra &...extra) {
+        initialize(
+            std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr, extra...);
     }
 
     /// Construct a cpp_function from a class method (non-const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...), const Extra&... extra) {
-        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*) (Class *, Arg...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...), const Extra &...extra) {
+        initialize(
+            [f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+            (Return(*)(Class *, Arg...)) nullptr,
+            extra...);
     }
 
     /// Construct a cpp_function from a class method (non-const, lvalue ref-qualifier)
@@ -118,17 +120,21 @@ class cpp_function : public function {
     /// but with an added `&`.
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...)&, const Extra&... extra) {
-        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*) (Class *, Arg...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...) &, const Extra &...extra) {
+        initialize(
+            [f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+            (Return(*)(Class *, Arg...)) nullptr,
+            extra...);
     }
 
     /// Construct a cpp_function from a class method (const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...) const, const Extra&... extra) {
-        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*)(const Class *, Arg ...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...) const, const Extra &...extra) {
+        initialize([f](const Class *c,
+                       Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+                   (Return(*)(const Class *, Arg...)) nullptr,
+                   extra...);
     }
 
     /// Construct a cpp_function from a class method (const, lvalue ref-qualifier)
@@ -136,9 +142,11 @@ class cpp_function : public function {
     /// but with an added `&`.
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    cpp_function(Return (Class::*f)(Arg...) const&, const Extra&... extra) {
-        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
-                   (Return (*)(const Class *, Arg ...)) nullptr, extra...);
+    cpp_function(Return (Class::*f)(Arg...) const &, const Extra &...extra) {
+        initialize([f](const Class *c,
+                       Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
+                   (Return(*)(const Class *, Arg...)) nullptr,
+                   extra...);
     }
 
     /// Return the function name
@@ -148,9 +156,10 @@ class cpp_function : public function {
     struct InitializingFunctionRecordDeleter {
         // `destruct(function_record, false)`: `initialize_generic` copies strings and
         // takes care of cleaning up in case of exceptions. So pass `false` to `free_strings`.
-        void operator()(detail::function_record * rec) { destruct(rec, false); }
+        void operator()(detail::function_record *rec) { destruct(rec, false); }
     };
-    using unique_function_record = std::unique_ptr<detail::function_record, InitializingFunctionRecordDeleter>;
+    using unique_function_record
+        = std::unique_ptr<detail::function_record, InitializingFunctionRecordDeleter>;
 
     /// Space optimization: don't inline this frequently instantiated fragment
     PYBIND11_NOINLINE unique_function_record make_function_record() {
@@ -159,11 +168,14 @@ class cpp_function : public function {
 
     /// Special internal constructor for functors, lambda functions, etc.
     template <typename Func, typename Return, typename... Args, typename... Extra>
-    void initialize(Func &&f, Return (*)(Args...), const Extra&... extra) {
+    void initialize(Func &&f, Return (*)(Args...), const Extra &...extra) {
         using namespace detail;
-        struct capture { remove_reference_t<Func> f; };
+        struct capture {
+            remove_reference_t<Func> f;
+        };
 
-        /* Store the function including any extra state it might have (e.g. a lambda capture object) */
+        /* Store the function including any extra state it might have (e.g. a lambda capture
+         * object) */
         // The unique_ptr makes sure nothing is leaked in case of an exception.
         auto unique_rec = make_function_record();
         auto *rec = unique_rec.get();
@@ -174,16 +186,16 @@ class cpp_function : public function {
                enough space to use the placement new operator. However, the
                'if' statement above ensures that this is the case. */
 #if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wplacement-new"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wplacement-new"
 #endif
-            new ((capture *) &rec->data) capture { std::forward<Func>(f) };
+            new ((capture *) &rec->data) capture{std::forward<Func>(f)};
 #if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
 #if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wstrict-aliasing"
 #endif
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
@@ -195,21 +207,22 @@ class cpp_function : public function {
                 };
             }
 #if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
         } else {
-            rec->data[0] = new capture { std::forward<Func>(f) };
+            rec->data[0] = new capture{std::forward<Func>(f)};
             rec->free_data = [](function_record *r) { delete ((capture *) r->data[0]); };
         }
 
         /* Type casters for the function arguments and return value */
         using cast_in = argument_loader<Args...>;
-        using cast_out = make_caster<
-            conditional_t<std::is_void<Return>::value, void_type, Return>
-        >;
+        using cast_out
+            = make_caster<conditional_t<std::is_void<Return>::value, void_type, Return>>;
 
-        static_assert(expected_num_args<Extra...>(sizeof...(Args), cast_in::args_pos >= 0, cast_in::has_kwargs),
-                      "The number of argument annotations does not match the number of function arguments");
+        static_assert(
+            expected_num_args<Extra...>(
+                sizeof...(Args), cast_in::args_pos >= 0, cast_in::has_kwargs),
+            "The number of argument annotations does not match the number of function arguments");
 
         /* Dispatch code which converts function arguments and performs the actual function call */
         rec->impl = [](function_call &call) -> handle {
@@ -229,14 +242,17 @@ class cpp_function : public function {
             auto *cap = const_cast<capture *>(reinterpret_cast<const capture *>(data));
 
             /* Override policy for rvalues -- usually to enforce rvp::move on an rvalue */
-            return_value_policy policy = return_value_policy_override<Return>::policy(call.func.policy);
+            return_value_policy policy
+                = return_value_policy_override<Return>::policy(call.func.policy);
 
             /* Function scope guard -- defaults to the compile-to-nothing `void_type` */
             using Guard = extract_guard_t<Extra...>;
 
             /* Perform the function call */
-            handle result = cast_out::cast(
-                std::move(args_converter).template call<Return, Guard>(cap->f), policy, call.parent);
+            handle result
+                = cast_out::cast(std::move(args_converter).template call<Return, Guard>(cap->f),
+                                 policy,
+                                 call.parent);
 
             /* Invoke call policy post-call hook */
             process_attributes<Extra...>::postcall(call, result);
@@ -245,9 +261,9 @@ class cpp_function : public function {
         };
 
         rec->nargs_pos = cast_in::args_pos >= 0
-            ? static_cast<std::uint16_t>(cast_in::args_pos)
-            : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if
-                                                     // we have a kw_only
+                             ? static_cast<std::uint16_t>(cast_in::args_pos)
+                             : sizeof...(Args) - cast_in::has_kwargs; // Will get reduced more if
+                                                                      // we have a kw_only
         rec->has_args = cast_in::args_pos >= 0;
         rec->has_kwargs = cast_in::has_kwargs;
 
@@ -258,19 +274,26 @@ class cpp_function : public function {
             constexpr bool has_kw_only_args = any_of<std::is_same<kw_only, Extra>...>::value,
                            has_pos_only_args = any_of<std::is_same<pos_only, Extra>...>::value,
                            has_arg_annotations = any_of<is_keyword<Extra>...>::value;
-            static_assert(has_arg_annotations || !has_kw_only_args, "py::kw_only requires the use of argument annotations");
-            static_assert(has_arg_annotations || !has_pos_only_args, "py::pos_only requires the use of argument annotations (for docstrings and aligning the annotations to the argument)");
-
-            static_assert(constexpr_sum(is_kw_only<Extra>::value...) <= 1, "py::kw_only may be specified only once");
-            static_assert(constexpr_sum(is_pos_only<Extra>::value...) <= 1, "py::pos_only may be specified only once");
+            static_assert(has_arg_annotations || !has_kw_only_args,
+                          "py::kw_only requires the use of argument annotations");
+            static_assert(has_arg_annotations || !has_pos_only_args,
+                          "py::pos_only requires the use of argument annotations (for docstrings "
+                          "and aligning the annotations to the argument)");
+
+            static_assert(constexpr_sum(is_kw_only<Extra>::value...) <= 1,
+                          "py::kw_only may be specified only once");
+            static_assert(constexpr_sum(is_pos_only<Extra>::value...) <= 1,
+                          "py::pos_only may be specified only once");
             constexpr auto kw_only_pos = constexpr_first<is_kw_only, Extra...>();
             constexpr auto pos_only_pos = constexpr_first<is_pos_only, Extra...>();
-            static_assert(!(has_kw_only_args && has_pos_only_args) || pos_only_pos < kw_only_pos, "py::pos_only must come before py::kw_only");
+            static_assert(!(has_kw_only_args && has_pos_only_args) || pos_only_pos < kw_only_pos,
+                          "py::pos_only must come before py::kw_only");
         }
 
         /* Generate a readable signature describing the function's arguments and return
            value types */
-        static constexpr auto signature = const_name("(") + cast_in::arg_names + const_name(") -> ") + cast_out::name;
+        static constexpr auto signature
+            = const_name("(") + cast_in::arg_names + const_name(") -> ") + cast_out::name;
         PYBIND11_DESCR_CONSTEXPR auto types = decltype(signature)::types();
 
         /* Register the function with Python from generic (non-templated) code */
@@ -279,17 +302,18 @@ class cpp_function : public function {
 
         /* Stash some additional information used by an important optimization in 'functional.h' */
         using FunctionType = Return (*)(Args...);
-        constexpr bool is_function_ptr =
-            std::is_convertible<Func, FunctionType>::value &&
-            sizeof(capture) == sizeof(void *);
+        constexpr bool is_function_ptr
+            = std::is_convertible<Func, FunctionType>::value && sizeof(capture) == sizeof(void *);
         if (is_function_ptr) {
             rec->is_stateless = true;
-            rec->data[1] = const_cast<void *>(reinterpret_cast<const void *>(&typeid(FunctionType)));
+            rec->data[1]
+                = const_cast<void *>(reinterpret_cast<const void *>(&typeid(FunctionType)));
         }
     }
 
-    // Utility class that keeps track of all duplicated strings, and cleans them up in its destructor,
-    // unless they are released. Basically a RAII-solution to deal with exceptions along the way.
+    // Utility class that keeps track of all duplicated strings, and cleans them up in its
+    // destructor, unless they are released. Basically a RAII-solution to deal with exceptions
+    // along the way.
     class strdup_guard {
     public:
         ~strdup_guard() {
@@ -302,26 +326,29 @@ class cpp_function : public function {
             strings.push_back(t);
             return t;
         }
-        void release() {
-            strings.clear();
-        }
+        void release() { strings.clear(); }
+
     private:
         std::vector<char *> strings;
     };
 
     /// Register a function call with Python (generic non-templated code goes here)
-    void initialize_generic(unique_function_record &&unique_rec, const char *text,
-                            const std::type_info *const *types, size_t args) {
+    void initialize_generic(unique_function_record &&unique_rec,
+                            const char *text,
+                            const std::type_info *const *types,
+                            size_t args) {
         // Do NOT receive `unique_rec` by value. If this function fails to move out the unique_ptr,
-        // we do not want this to destuct the pointer. `initialize` (the caller) still relies on the
-        // pointee being alive after this call. Only move out if a `capsule` is going to keep it alive.
+        // we do not want this to destuct the pointer. `initialize` (the caller) still relies on
+        // the pointee being alive after this call. Only move out if a `capsule` is going to keep
+        // it alive.
         auto *rec = unique_rec.get();
 
         // Keep track of strdup'ed strings, and clean them up as long as the function's capsule
         // has not taken ownership yet (when `unique_rec.release()` is called).
-        // Note: This cannot easily be fixed by a `unique_ptr` with custom deleter, because the strings
-        // are only referenced before strdup'ing. So only *after* the following block could `destruct`
-        // safely be called, but even then, `repr` could still throw in the middle of copying all strings.
+        // Note: This cannot easily be fixed by a `unique_ptr` with custom deleter, because the
+        // strings are only referenced before strdup'ing. So only *after* the following block could
+        // `destruct` safely be called, but even then, `repr` could still throw in the middle of
+        // copying all strings.
         strdup_guard guarded_strdup;
 
         /* Create copies of all referenced C-style strings */
@@ -329,7 +356,7 @@ class cpp_function : public function {
         if (rec->doc) {
             rec->doc = guarded_strdup(rec->doc);
         }
-        for (auto &a: rec->args) {
+        for (auto &a : rec->args) {
             if (a.name) {
                 a.name = guarded_strdup(a.name);
             }
@@ -345,15 +372,19 @@ class cpp_function : public function {
 
 #if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
         if (rec->is_constructor && !rec->is_new_style_constructor) {
-            const auto class_name = detail::get_fully_qualified_tp_name((PyTypeObject *) rec->scope.ptr());
+            const auto class_name
+                = detail::get_fully_qualified_tp_name((PyTypeObject *) rec->scope.ptr());
             const auto func_name = std::string(rec->name);
-            PyErr_WarnEx(
-                PyExc_FutureWarning,
-                ("pybind11-bound class '" + class_name + "' is using an old-style "
-                 "placement-new '" + func_name + "' which has been deprecated. See "
-                 "the upgrade guide in pybind11's docs. This message is only visible "
-                 "when compiled in debug mode.").c_str(), 0
-            );
+            PyErr_WarnEx(PyExc_FutureWarning,
+                         ("pybind11-bound class '" + class_name
+                          + "' is using an old-style "
+                            "placement-new '"
+                          + func_name
+                          + "' which has been deprecated. See "
+                            "the upgrade guide in pybind11's docs. This message is only visible "
+                            "when compiled in debug mode.")
+                             .c_str(),
+                         0);
         }
 #endif
 
@@ -404,16 +435,14 @@ class cpp_function : public function {
                 }
                 if (auto *tinfo = detail::get_type_info(*t)) {
                     handle th((PyObject *) tinfo->type);
-                    signature +=
-                        th.attr("__module__").cast<std::string>() + "." +
-                        // Python 3.3+, but we backport it to earlier versions
-                        th.attr("__qualname__").cast<std::string>();
+                    signature += th.attr("__module__").cast<std::string>() + "." +
+                                 // Python 3.3+, but we backport it to earlier versions
+                                 th.attr("__qualname__").cast<std::string>();
                 } else if (rec->is_new_style_constructor && arg_index == 0) {
                     // A new-style `__init__` takes `self` as `value_and_holder`.
                     // Rewrite it to the proper class type.
-                    signature +=
-                        rec->scope.attr("__module__").cast<std::string>() + "." +
-                        rec->scope.attr("__qualname__").cast<std::string>();
+                    signature += rec->scope.attr("__module__").cast<std::string>() + "."
+                                 + rec->scope.attr("__qualname__").cast<std::string>();
                 } else {
                     std::string tname(t->name());
                     detail::clean_type_id(tname);
@@ -449,7 +478,8 @@ class cpp_function : public function {
         if (rec->sibling) {
             if (PyCFunction_Check(rec->sibling.ptr())) {
                 auto *self = PyCFunction_GET_SELF(rec->sibling.ptr());
-                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self) : capsule(self);
+                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self)
+                                                                : capsule(self);
                 chain = (detail::function_record *) rec_capsule;
                 /* Never append a method to an overload chain of a parent class;
                    instead, hide the parent's overloads in this case */
@@ -474,9 +504,8 @@ class cpp_function : public function {
                 = reinterpret_cast<PyCFunction>(reinterpret_cast<void (*)()>(dispatcher));
             rec->def->ml_flags = METH_VARARGS | METH_KEYWORDS;
 
-            capsule rec_capsule(unique_rec.release(), [](void *ptr) {
-                destruct((detail::function_record *) ptr);
-            });
+            capsule rec_capsule(unique_rec.release(),
+                                [](void *ptr) { destruct((detail::function_record *) ptr); });
             guarded_strdup.release();
 
             object scope_module;
@@ -501,12 +530,12 @@ class cpp_function : public function {
                     "overloading a method with both static and instance methods is not supported; "
 #if defined(NDEBUG)
                     "compile in debug mode for more details"
-                    #else
+#else
                     "error while attempting to bind "
                     + std::string(rec->is_method ? "instance" : "static") + " method "
                     + std::string(pybind11::str(rec->scope.attr("__name__"))) + "."
                     + std::string(rec->name) + signature
-                    #endif
+#endif
                 );
             }
 
@@ -516,7 +545,8 @@ class cpp_function : public function {
                 // chain.
                 chain_start = rec;
                 rec->next = chain;
-                auto rec_capsule = reinterpret_borrow<capsule>(((PyCFunctionObject *) m_ptr)->m_self);
+                auto rec_capsule
+                    = reinterpret_borrow<capsule>(((PyCFunctionObject *) m_ptr)->m_self);
                 rec_capsule.set_pointer(unique_rec.release());
                 guarded_strdup.release();
             } else {
@@ -555,8 +585,8 @@ class cpp_function : public function {
                 signatures += "\n";
             }
             if (it->doc && it->doc[0] != '\0' && options::show_user_defined_docstrings()) {
-                // If we're appending another docstring, and aren't printing function signatures, we
-                // need to append a newline first:
+                // If we're appending another docstring, and aren't printing function signatures,
+                // we need to append a newline first:
                 if (!options::show_function_signatures()) {
                     if (first_user_def) {
                         first_user_def = false;
@@ -593,11 +623,11 @@ class cpp_function : public function {
 
     /// When a cpp_function is GCed, release any memory allocated by pybind11
     static void destruct(detail::function_record *rec, bool free_strings = true) {
-        // If on Python 3.9, check the interpreter "MICRO" (patch) version.
-        // If this is running on 3.9.0, we have to work around a bug.
-        #if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
-            static bool is_zero = Py_GetVersion()[4] == '0';
-        #endif
+// If on Python 3.9, check the interpreter "MICRO" (patch) version.
+// If this is running on 3.9.0, we have to work around a bug.
+#if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
+        static bool is_zero = Py_GetVersion()[4] == '0';
+#endif
 
         while (rec) {
             detail::function_record *next = rec->next;
@@ -611,7 +641,7 @@ class cpp_function : public function {
                 std::free((char *) rec->name);
                 std::free((char *) rec->doc);
                 std::free((char *) rec->signature);
-                for (auto &arg: rec->args) {
+                for (auto &arg : rec->args) {
                     std::free(const_cast<char *>(arg.name));
                     std::free(const_cast<char *>(arg.descr));
                 }
@@ -621,23 +651,22 @@ class cpp_function : public function {
             }
             if (rec->def) {
                 std::free(const_cast<char *>(rec->def->ml_doc));
-                // Python 3.9.0 decref's these in the wrong order; rec->def
-                // If loaded on 3.9.0, let these leak (use Python 3.9.1 at runtime to fix)
-                // See https://github.com/python/cpython/pull/22670
-                #if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
+// Python 3.9.0 decref's these in the wrong order; rec->def
+// If loaded on 3.9.0, let these leak (use Python 3.9.1 at runtime to fix)
+// See https://github.com/python/cpython/pull/22670
+#if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
                 if (!is_zero) {
                     delete rec->def;
                 }
 #else
-                    delete rec->def;
-                #endif
+                delete rec->def;
+#endif
             }
             delete rec;
             rec = next;
         }
     }
 
-
     /// Main dispatch logic for calls to functions bound using pybind11
     static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) {
         using namespace detail;
@@ -655,8 +684,11 @@ class cpp_function : public function {
 
         auto self_value_and_holder = value_and_holder();
         if (overloads->is_constructor) {
-            if (!parent || !PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
-                PyErr_SetString(PyExc_TypeError, "__init__(self, ...) called with invalid or missing `self` argument");
+            if (!parent
+                || !PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
+                PyErr_SetString(
+                    PyExc_TypeError,
+                    "__init__(self, ...) called with invalid or missing `self` argument");
                 return nullptr;
             }
 
@@ -687,23 +719,23 @@ class cpp_function : public function {
                    1. Copy all positional arguments we were given, also checking to make sure that
                       named positional arguments weren't *also* specified via kwarg.
                    2. If we weren't given enough, try to make up the omitted ones by checking
-                      whether they were provided by a kwarg matching the `py::arg("name")` name.  If
+                      whether they were provided by a kwarg matching the `py::arg("name")` name. If
                       so, use it (and remove it from kwargs); if not, see if the function binding
                       provided a default that we can use.
-                   3. Ensure that either all keyword arguments were "consumed", or that the function
-                      takes a kwargs argument to accept unconsumed kwargs.
+                   3. Ensure that either all keyword arguments were "consumed", or that the
+                   function takes a kwargs argument to accept unconsumed kwargs.
                    4. Any positional arguments still left get put into a tuple (for args), and any
                       leftover kwargs get put into a dict.
                    5. Pack everything into a vector; if we have py::args or py::kwargs, they are an
                       extra tuple or dict at the end of the positional arguments.
                    6. Call the function call dispatcher (function_record::impl)
 
-                   If one of these fail, move on to the next overload and keep trying until we get a
-                   result other than PYBIND11_TRY_NEXT_OVERLOAD.
+                   If one of these fail, move on to the next overload and keep trying until we get
+                   a result other than PYBIND11_TRY_NEXT_OVERLOAD.
                  */
 
                 const function_record &func = *it;
-                size_t num_args = func.nargs;    // Number of positional arguments that we need
+                size_t num_args = func.nargs; // Number of positional arguments that we need
                 if (func.has_args) {
                     --num_args; // (but don't count py::args
                 }
@@ -744,8 +776,10 @@ class cpp_function : public function {
                 // 1. Copy any position arguments given.
                 bool bad_arg = false;
                 for (; args_copied < args_to_copy; ++args_copied) {
-                    const argument_record *arg_rec = args_copied < func.args.size() ? &func.args[args_copied] : nullptr;
-                    if (kwargs_in && arg_rec && arg_rec->name && dict_getitemstring(kwargs_in, arg_rec->name)) {
+                    const argument_record *arg_rec
+                        = args_copied < func.args.size() ? &func.args[args_copied] : nullptr;
+                    if (kwargs_in && arg_rec && arg_rec->name
+                        && dict_getitemstring(kwargs_in, arg_rec->name)) {
                         bad_arg = true;
                         break;
                     }
@@ -821,7 +855,8 @@ class cpp_function : public function {
                         }
 
                         if (value) {
-                            // If we're at the py::args index then first insert a stub for it to be replaced later
+                            // If we're at the py::args index then first insert a stub for it to be
+                            // replaced later
                             if (func.has_args && call.args.size() == func.nargs_pos) {
                                 call.args.push_back(none());
                             }
@@ -879,11 +914,12 @@ class cpp_function : public function {
                     call.kwargs_ref = std::move(kwargs);
                 }
 
-                // 5. Put everything in a vector.  Not technically step 5, we've been building it
-                // in `call.args` all along.
-                #if !defined(NDEBUG)
+// 5. Put everything in a vector.  Not technically step 5, we've been building it
+// in `call.args` all along.
+#if !defined(NDEBUG)
                 if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs) {
-                    pybind11_fail("Internal error: function call dispatcher inserted wrong number of arguments!");
+                    pybind11_fail("Internal error: function call dispatcher inserted wrong number "
+                                  "of arguments!");
                 }
 #endif
 
@@ -925,7 +961,8 @@ class cpp_function : public function {
             }
 
             if (overloaded && !second_pass.empty() && result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) {
-                // The no-conversion pass finished without success, try again with conversion allowed
+                // The no-conversion pass finished without success, try again with conversion
+                // allowed
                 for (auto &call : second_pass) {
                     try {
                         loader_life_support guard{};
@@ -948,7 +985,7 @@ class cpp_function : public function {
             e.restore();
             return nullptr;
 #ifdef __GLIBCXX__
-        } catch ( abi::__forced_unwind& ) {
+        } catch (abi::__forced_unwind &) {
             throw;
 #endif
         } catch (...) {
@@ -968,7 +1005,8 @@ class cpp_function : public function {
                 - delegate translation to the next translator by throwing a new type of exception.
              */
 
-            auto &local_exception_translators = get_local_internals().registered_exception_translators;
+            auto &local_exception_translators
+                = get_local_internals().registered_exception_translators;
             if (detail::apply_exception_translators(local_exception_translators)) {
                 return nullptr;
             }
@@ -977,7 +1015,8 @@ class cpp_function : public function {
                 return nullptr;
             }
 
-            PyErr_SetString(PyExc_SystemError, "Exception escaped from default exception translator!");
+            PyErr_SetString(PyExc_SystemError,
+                            "Exception escaped from default exception translator!");
             return nullptr;
         }
 
@@ -996,17 +1035,18 @@ class cpp_function : public function {
                 return handle(Py_NotImplemented).inc_ref().ptr();
             }
 
-            std::string msg = std::string(overloads->name) + "(): incompatible " +
-                std::string(overloads->is_constructor ? "constructor" : "function") +
-                " arguments. The following argument types are supported:\n";
+            std::string msg = std::string(overloads->name) + "(): incompatible "
+                              + std::string(overloads->is_constructor ? "constructor" : "function")
+                              + " arguments. The following argument types are supported:\n";
 
             int ctr = 0;
             for (const function_record *it2 = overloads; it2 != nullptr; it2 = it2->next) {
-                msg += "    "+ std::to_string(++ctr) + ". ";
+                msg += "    " + std::to_string(++ctr) + ". ";
 
                 bool wrote_sig = false;
                 if (overloads->is_constructor) {
-                    // For a constructor, rewrite `(self: Object, arg0, ...) -> NoneType` as `Object(arg0, ...)`
+                    // For a constructor, rewrite `(self: Object, arg0, ...) -> NoneType` as
+                    // `Object(arg0, ...)`
                     std::string sig = it2->signature;
                     size_t start = sig.find('(') + 7; // skip "(self: "
                     if (start < sig.size()) {
@@ -1042,7 +1082,7 @@ class cpp_function : public function {
                 }
                 try {
                     msg += pybind11::repr(args_[ti]);
-                } catch (const error_already_set&) {
+                } catch (const error_already_set &) {
                     msg += "<repr raised Error>";
                 }
             }
@@ -1063,7 +1103,7 @@ class cpp_function : public function {
                         msg += pybind11::str("{}=").format(kwarg.first);
                         try {
                             msg += pybind11::repr(kwarg.second);
-                        } catch (const error_already_set&) {
+                        } catch (const error_already_set &) {
                             msg += "<repr raised Error>";
                         }
                     }
@@ -1105,7 +1145,6 @@ class cpp_function : public function {
     }
 };
 
-
 /// Wrapper for Python extension modules
 class module_ : public object {
 public:
@@ -1127,11 +1166,15 @@ class module_ : public object {
         details on the ``Extra&& ... extra`` argument, see section :ref:`extras`.
     \endrst */
     template <typename Func, typename... Extra>
-    module_ &def(const char *name_, Func &&f, const Extra& ... extra) {
-        cpp_function func(std::forward<Func>(f), name(name_), scope(*this),
-                          sibling(getattr(*this, name_, none())), extra...);
+    module_ &def(const char *name_, Func &&f, const Extra &...extra) {
+        cpp_function func(std::forward<Func>(f),
+                          name(name_),
+                          scope(*this),
+                          sibling(getattr(*this, name_, none())),
+                          extra...);
         // NB: allow overwriting here because cpp_function sets up a chain with the intention of
-        // overwriting (and has already checked internally that it isn't overwriting non-functions).
+        // overwriting (and has already checked internally that it isn't overwriting
+        // non-functions).
         add_object(name_, func, true /* overwrite */);
         return *this;
     }
@@ -1147,8 +1190,8 @@ class module_ : public object {
             py::module_ m3 = m2.def_submodule("subsub", "A submodule of 'example.sub'");
     \endrst */
     module_ def_submodule(const char *name, const char *doc = nullptr) {
-        std::string full_name = std::string(PyModule_GetName(m_ptr))
-            + std::string(".") + std::string(name);
+        std::string full_name
+            = std::string(PyModule_GetName(m_ptr)) + std::string(".") + std::string(name);
         auto result = reinterpret_borrow<module_>(PyImport_AddModule(full_name.c_str()));
         if (doc && options::show_user_defined_docstrings()) {
             result.attr("__doc__") = pybind11::str(doc);
@@ -1208,22 +1251,22 @@ class module_ : public object {
 #if PY_MAJOR_VERSION >= 3
         // module_def is PyModuleDef
         // Placement new (not an allocation).
-        def = new (def) PyModuleDef {
-            /* m_base */     PyModuleDef_HEAD_INIT,
-            /* m_name */     name,
-            /* m_doc */      options::show_user_defined_docstrings() ? doc : nullptr,
-            /* m_size */     -1,
-            /* m_methods */  nullptr,
-            /* m_slots */    nullptr,
-            /* m_traverse */ nullptr,
-            /* m_clear */    nullptr,
-            /* m_free */     nullptr
-        };
+        def = new (def)
+            PyModuleDef{/* m_base */ PyModuleDef_HEAD_INIT,
+                        /* m_name */ name,
+                        /* m_doc */ options::show_user_defined_docstrings() ? doc : nullptr,
+                        /* m_size */ -1,
+                        /* m_methods */ nullptr,
+                        /* m_slots */ nullptr,
+                        /* m_traverse */ nullptr,
+                        /* m_clear */ nullptr,
+                        /* m_free */ nullptr};
         auto *m = PyModule_Create(def);
 #else
         // Ignore module_def *def; only necessary for Python 3
         (void) def;
-        auto m = Py_InitModule3(name, nullptr, options::show_user_defined_docstrings() ? doc : nullptr);
+        auto m = Py_InitModule3(
+            name, nullptr, options::show_user_defined_docstrings() ? doc : nullptr);
 #endif
         if (m == nullptr) {
             if (PyErr_Occurred()) {
@@ -1231,7 +1274,8 @@ class module_ : public object {
             }
             pybind11_fail("Internal error in module_::create_extension_module()");
         }
-        // TODO: Should be reinterpret_steal for Python 3, but Python also steals it again when returned from PyInit_...
+        // TODO: Should be reinterpret_steal for Python 3, but Python also steals it again when
+        // returned from PyInit_...
         //       For Python 2, reinterpret_borrow is correct.
         return reinterpret_borrow<module_>(m);
     }
@@ -1251,10 +1295,10 @@ inline dict globals() {
 }
 
 #if PY_VERSION_HEX >= 0x03030000
-template <typename... Args,
-          typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
-PYBIND11_DEPRECATED("make_simple_namespace should be replaced with py::module_::import(\"types\").attr(\"SimpleNamespace\") ")
-object make_simple_namespace(Args&&... args_) {
+template <typename... Args, typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
+PYBIND11_DEPRECATED("make_simple_namespace should be replaced with "
+                    "py::module_::import(\"types\").attr(\"SimpleNamespace\") ")
+object make_simple_namespace(Args &&...args_) {
     return module_::import("types").attr("SimpleNamespace")(std::forward<Args>(args_)...);
 }
 #endif
@@ -1305,13 +1349,12 @@ class generic_type : public object {
         } else {
             internals.registered_types_cpp[tindex] = tinfo;
         }
-        internals.registered_types_py[(PyTypeObject *) m_ptr] = { tinfo };
+        internals.registered_types_py[(PyTypeObject *) m_ptr] = {tinfo};
 
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {
             mark_parents_nonsimple(tinfo->type);
             tinfo->simple_ancestors = false;
-        }
-        else if (rec.bases.size() == 1) {
+        } else if (rec.bases.size() == 1) {
             auto *parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
             assert(parent_tinfo != nullptr);
             bool parent_simple_ancestors = parent_tinfo->simple_ancestors;
@@ -1339,10 +1382,9 @@ class generic_type : public object {
         }
     }
 
-    void install_buffer_funcs(
-            buffer_info *(*get_buffer)(PyObject *, void *),
-            void *get_buffer_data) {
-        auto *type = (PyHeapTypeObject*) m_ptr;
+    void install_buffer_funcs(buffer_info *(*get_buffer)(PyObject *, void *),
+                              void *get_buffer_data) {
+        auto *type = (PyHeapTypeObject *) m_ptr;
         auto *tinfo = detail::get_type_info(&type->ht_type);
 
         if (!type->ht_type.tp_as_buffer) {
@@ -1358,58 +1400,76 @@ class generic_type : public object {
 
     // rec_func must be set for either fget or fset.
     void def_property_static_impl(const char *name,
-                                  handle fget, handle fset,
+                                  handle fget,
+                                  handle fset,
                                   detail::function_record *rec_func) {
         const auto is_static = (rec_func != nullptr) && !(rec_func->is_method && rec_func->scope);
         const auto has_doc = (rec_func != nullptr) && (rec_func->doc != nullptr)
                              && pybind11::options::show_user_defined_docstrings();
-        auto property = handle((PyObject *) (is_static ? get_internals().static_property_type
-                                                       : &PyProperty_Type));
+        auto property = handle(
+            (PyObject *) (is_static ? get_internals().static_property_type : &PyProperty_Type));
         attr(name) = property(fget.ptr() ? fget : none(),
                               fset.ptr() ? fset : none(),
-                              /*deleter*/none(),
+                              /*deleter*/ none(),
                               pybind11::str(has_doc ? rec_func->doc : ""));
     }
 };
 
 /// Set the pointer to operator new if it exists. The cast is needed because it can be overloaded.
-template <typename T, typename = void_t<decltype(static_cast<void *(*)(size_t)>(T::operator new))>>
-void set_operator_new(type_record *r) { r->operator_new = &T::operator new; }
-
-template <typename> void set_operator_new(...) { }
+template <typename T,
+          typename = void_t<decltype(static_cast<void *(*) (size_t)>(T::operator new))>>
+void set_operator_new(type_record *r) {
+    r->operator_new = &T::operator new;
+}
 
-template <typename T, typename SFINAE = void> struct has_operator_delete : std::false_type { };
-template <typename T> struct has_operator_delete<T, void_t<decltype(static_cast<void (*)(void *)>(T::operator delete))>>
-    : std::true_type { };
-template <typename T, typename SFINAE = void> struct has_operator_delete_size : std::false_type { };
-template <typename T> struct has_operator_delete_size<T, void_t<decltype(static_cast<void (*)(void *, size_t)>(T::operator delete))>>
-    : std::true_type { };
+template <typename>
+void set_operator_new(...) {}
+
+template <typename T, typename SFINAE = void>
+struct has_operator_delete : std::false_type {};
+template <typename T>
+struct has_operator_delete<T, void_t<decltype(static_cast<void (*)(void *)>(T::operator delete))>>
+    : std::true_type {};
+template <typename T, typename SFINAE = void>
+struct has_operator_delete_size : std::false_type {};
+template <typename T>
+struct has_operator_delete_size<
+    T,
+    void_t<decltype(static_cast<void (*)(void *, size_t)>(T::operator delete))>> : std::true_type {
+};
 /// Call class-specific delete if it exists or global otherwise. Can also be an overload set.
 template <typename T, enable_if_t<has_operator_delete<T>::value, int> = 0>
-void call_operator_delete(T *p, size_t, size_t) { T::operator delete(p); }
-template <typename T, enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
-void call_operator_delete(T *p, size_t s, size_t) { T::operator delete(p, s); }
+void call_operator_delete(T *p, size_t, size_t) {
+    T::operator delete(p);
+}
+template <
+    typename T,
+    enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
+void call_operator_delete(T *p, size_t s, size_t) {
+    T::operator delete(p, s);
+}
 
 inline void call_operator_delete(void *p, size_t s, size_t a) {
-    (void)s; (void)a;
-    #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
-        if (a > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
-            #ifdef __cpp_sized_deallocation
-                ::operator delete(p, s, std::align_val_t(a));
-            #else
-                ::operator delete(p, std::align_val_t(a));
-            #endif
-            return;
-        }
-    #endif
-    #ifdef __cpp_sized_deallocation
-        ::operator delete(p, s);
-    #else
-        ::operator delete(p);
-    #endif
+    (void) s;
+    (void) a;
+#if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
+    if (a > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
+#    ifdef __cpp_sized_deallocation
+        ::operator delete(p, s, std::align_val_t(a));
+#    else
+        ::operator delete(p, std::align_val_t(a));
+#    endif
+        return;
+    }
+#endif
+#ifdef __cpp_sized_deallocation
+    ::operator delete(p, s);
+#else
+    ::operator delete(p);
+#endif
 }
 
-inline void add_class_method(object& cls, const char *name_, const cpp_function &cf) {
+inline void add_class_method(object &cls, const char *name_, const cpp_function &cf) {
     cls.attr(cf.name()) = cf;
     if (std::strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
         cls.attr("__hash__") = none();
@@ -1421,18 +1481,22 @@ PYBIND11_NAMESPACE_END(detail)
 /// Given a pointer to a member function, cast it to its `Derived` version.
 /// Forward everything else unchanged.
 template <typename /*Derived*/, typename F>
-auto method_adaptor(F &&f) -> decltype(std::forward<F>(f)) { return std::forward<F>(f); }
+auto method_adaptor(F &&f) -> decltype(std::forward<F>(f)) {
+    return std::forward<F>(f);
+}
 
 template <typename Derived, typename Return, typename Class, typename... Args>
 auto method_adaptor(Return (Class::*pmf)(Args...)) -> Return (Derived::*)(Args...) {
-    static_assert(detail::is_accessible_base_of<Class, Derived>::value,
+    static_assert(
+        detail::is_accessible_base_of<Class, Derived>::value,
         "Cannot bind an inaccessible base class method; use a lambda definition instead");
     return pmf;
 }
 
 template <typename Derived, typename Return, typename Class, typename... Args>
 auto method_adaptor(Return (Class::*pmf)(Args...) const) -> Return (Derived::*)(Args...) const {
-    static_assert(detail::is_accessible_base_of<Class, Derived>::value,
+    static_assert(
+        detail::is_accessible_base_of<Class, Derived>::value,
         "Cannot bind an inaccessible base class method; use a lambda definition instead");
     return pmf;
 }
@@ -1442,20 +1506,19 @@ namespace detail {
 template <template <typename...> class Tpl>
 struct is_base_template_of_impl {
     // Use pointers for robustness.
-    template <typename ... Base>
-    static std::true_type check(const Tpl<Base...>*);
-    static std::false_type check(void*);
+    template <typename... Base>
+    static std::true_type check(const Tpl<Base...> *);
+    static std::false_type check(void *);
 };
 
 template <template <typename...> class Tpl, typename Derived>
-using is_base_template_of =
-    decltype(is_base_template_of_impl<Tpl>::check(
-        std::declval<Derived*>()));
+using is_base_template_of
+    = decltype(is_base_template_of_impl<Tpl>::check(std::declval<Derived *>()));
 
 template <typename type, typename alias, bool compatible>
 struct wrapper_interface_impl {
-    static void use_cpp_lifetime(type* cppobj, object&& obj, detail::HolderTypeId holder_type_id) {
-        auto* tr = dynamic_cast<alias*>(cppobj);
+    static void use_cpp_lifetime(type *cppobj, object &&obj, detail::HolderTypeId holder_type_id) {
+        auto *tr = dynamic_cast<alias *>(cppobj);
         if (tr == nullptr) {
             // This has been invoked at too high of a level; should use a
             // downcast class's `release_to_cpp` mechanism (if it supports it).
@@ -1469,8 +1532,8 @@ struct wrapper_interface_impl {
         tr->use_cpp_lifetime(std::move(obj), holder_type_id);
     }
 
-    static object release_cpp_lifetime(type* cppobj) {
-        auto* tr = dynamic_cast<alias*>(cppobj);
+    static object release_cpp_lifetime(type *cppobj) {
+        auto *tr = dynamic_cast<alias *>(cppobj);
         if (tr == nullptr) {
             // This shouldn't happen here...
             throw std::runtime_error("Internal error?");
@@ -1482,14 +1545,12 @@ struct wrapper_interface_impl {
 
 template <typename type, typename alias>
 struct wrapper_interface_impl<type, alias, false> {
-    static void use_cpp_lifetime(type*, object&&, detail::HolderTypeId) {
+    static void use_cpp_lifetime(type *, object &&, detail::HolderTypeId) {
         // This should be captured by runtime flag.
         // TODO(eric.cousineau): Runtime flag may not be necessary.
         throw std::runtime_error("Internal error?");
     }
-    static object release_cpp_lifetime(type*) {
-        throw std::runtime_error("Internal error?");
-    }
+    static object release_cpp_lifetime(type *) { throw std::runtime_error("Internal error?"); }
 };
 
 template <detail::HolderTypeId holder_type_id = detail::HolderTypeId::Unknown>
@@ -1500,17 +1561,18 @@ struct holder_check_impl {
         return true;
     }
     template <typename holder_type>
-    static bool allow_null_external_holder(const holder_type&) {
+    static bool allow_null_external_holder(const holder_type &) {
         return false;
     }
     template <typename holder_type>
-    static bool attempt_holder_transfer(holder_type& holder, detail::holder_erased external_holder_raw) {
+    static bool attempt_holder_transfer(holder_type &holder,
+                                        detail::holder_erased external_holder_raw) {
         // Only called when holder types are different.
         unused(holder, external_holder_raw);
         throw std::runtime_error("Unable to transfer between holders of different types");
     }
     template <typename holder_type>
-    static bool accept_holder(detail::holder_erased external_holder_raw, holder_type& holder) {
+    static bool accept_holder(detail::holder_erased external_holder_raw, holder_type &holder) {
         // Only called when holder types are different.
         unused(holder, external_holder_raw);
         throw std::runtime_error("Unable to transfer between holders of different types");
@@ -1518,11 +1580,12 @@ struct holder_check_impl {
 };
 
 template <>
-struct holder_check_impl<detail::HolderTypeId::SharedPtr> : public holder_check_impl<detail::HolderTypeId::Unknown> {
+struct holder_check_impl<detail::HolderTypeId::SharedPtr>
+    : public holder_check_impl<detail::HolderTypeId::Unknown> {
     template <typename holder_type>
-    static bool check_destruct(detail::instance* inst, detail::holder_erased holder_raw) {
-        const auto& h = holder_raw.cast<holder_type>();
-        handle src((PyObject*)inst);
+    static bool check_destruct(detail::instance *inst, detail::holder_erased holder_raw) {
+        const auto &h = holder_raw.cast<holder_type>();
+        handle src((PyObject *) inst);
         const detail::type_info *lowest_type = get_lowest_type(src, false);
         if (!lowest_type)
             // We have multiple inheritance, skip.
@@ -1532,13 +1595,14 @@ struct holder_check_impl<detail::HolderTypeId::SharedPtr> : public holder_check_
         if (load_type == detail::LoadType::DerivedCppSinglePySingle) {
             if (h.use_count() > 1) {
                 // Increase reference count
-                const auto& release_info = lowest_type->release_info;
+                const auto &release_info = lowest_type->release_info;
                 if (release_info.can_derive_from_wrapper) {
                     // Increase reference count
                     object obj = reinterpret_borrow<object>(src);
                     // Release to C++.
-                    holder_type* null_holder = nullptr;
-                    release_info.release_to_cpp(inst, detail::holder_erased(null_holder), std::move(obj));
+                    holder_type *null_holder = nullptr;
+                    release_info.release_to_cpp(
+                        inst, detail::holder_erased(null_holder), std::move(obj));
                     return false;
                 }
             }
@@ -1547,22 +1611,23 @@ struct holder_check_impl<detail::HolderTypeId::SharedPtr> : public holder_check_
     }
 
     template <typename holder_type>
-    static bool allow_null_external_holder(const holder_type& holder) {
+    static bool allow_null_external_holder(const holder_type &holder) {
         // Called by `release_to_cpp`.
         if (holder.use_count() == 1)
             // TODO(eric.cousineau): This may not hold true if we pass temporaries???
             // Or if we've copied a `holder` in copyable_holder_caster...
-            throw std::runtime_error("Internal error: Should have non-null shared_ptr<> external_holder if use_count() == 1");
+            throw std::runtime_error("Internal error: Should have non-null shared_ptr<> "
+                                     "external_holder if use_count() == 1");
         else
             return true;
     }
 
     template <typename holder_type>
-    static bool accept_holder(detail::holder_erased external_holder_raw, holder_type& holder) {
+    static bool accept_holder(detail::holder_erased external_holder_raw, holder_type &holder) {
         // Only accept shared_ptr from `external_holder_raw`.
         if (external_holder_raw.type_id() == detail::HolderTypeId::UniquePtr) {
             using T = typename holder_type::element_type;
-            auto& external_holder = external_holder_raw.mutable_cast<std::unique_ptr<T>>();
+            auto &external_holder = external_holder_raw.mutable_cast<std::unique_ptr<T>>();
             // Transfer to internal.
             holder = std::move(external_holder);
             return true;
@@ -1572,63 +1637,67 @@ struct holder_check_impl<detail::HolderTypeId::SharedPtr> : public holder_check_
     }
 };
 
-
 template <>
-struct holder_check_impl<detail::HolderTypeId::UniquePtr> : public holder_check_impl<detail::HolderTypeId::Unknown> {
-      template <typename holder_type>
-      static bool attempt_holder_transfer(holder_type& holder, detail::holder_erased external_holder_raw) {
-          // Only accept shared_ptr from `external_holder_raw`.
-          if (external_holder_raw.type_id() == detail::HolderTypeId::SharedPtr) {
-              using T = typename holder_type::element_type;
-              auto& external_holder = external_holder_raw.mutable_cast<std::shared_ptr<T>>();
-              // Transfer to external.
-              external_holder = std::move(holder);
-              return true;
-          } else {
-              return false;
-          }
-      }
+struct holder_check_impl<detail::HolderTypeId::UniquePtr>
+    : public holder_check_impl<detail::HolderTypeId::Unknown> {
+    template <typename holder_type>
+    static bool attempt_holder_transfer(holder_type &holder,
+                                        detail::holder_erased external_holder_raw) {
+        // Only accept shared_ptr from `external_holder_raw`.
+        if (external_holder_raw.type_id() == detail::HolderTypeId::SharedPtr) {
+            using T = typename holder_type::element_type;
+            auto &external_holder = external_holder_raw.mutable_cast<std::shared_ptr<T>>();
+            // Transfer to external.
+            external_holder = std::move(holder);
+            return true;
+        } else {
+            return false;
+        }
+    }
 };
 
-}  // namespace detail
+} // namespace detail
 
 template <typename type_, typename... options>
 class class_ : public detail::generic_type {
-    template <typename T> using is_holder = detail::is_holder_type<type_, T>;
-    template <typename T> using is_subtype = detail::is_strict_base_of<type_, T>;
-    template <typename T> using is_base = detail::is_strict_base_of<T, type_>;
+    template <typename T>
+    using is_holder = detail::is_holder_type<type_, T>;
+    template <typename T>
+    using is_subtype = detail::is_strict_base_of<type_, T>;
+    template <typename T>
+    using is_base = detail::is_strict_base_of<T, type_>;
     // struct instead of using here to help MSVC:
-    template <typename T> struct is_valid_class_option :
-        detail::any_of<is_holder<T>, is_subtype<T>, is_base<T>> {};
+    template <typename T>
+    struct is_valid_class_option : detail::any_of<is_holder<T>, is_subtype<T>, is_base<T>> {};
 
 public:
     using type = type_;
     using type_alias = detail::exactly_one_t<is_subtype, void, options...>;
     constexpr static bool has_alias = !std::is_void<type_alias>::value;
-    constexpr static bool has_wrapper =
-        detail::is_base_template_of<wrapper, type_alias>::value;
+    constexpr static bool has_wrapper = detail::is_base_template_of<wrapper, type_alias>::value;
     using holder_type = detail::exactly_one_t<is_holder, std::unique_ptr<type>, options...>;
-    constexpr static detail::HolderTypeId holder_type_id = detail::get_holder_type_id<holder_type>::value;
+    constexpr static detail::HolderTypeId holder_type_id
+        = detail::get_holder_type_id<holder_type>::value;
 
     static_assert(detail::all_of<is_valid_class_option<options>...>::value,
-            "Unknown/invalid class_ template parameters provided");
+                  "Unknown/invalid class_ template parameters provided");
 
     static_assert(!has_alias || std::is_polymorphic<type>::value,
-            "Cannot use an alias class with a non-polymorphic type");
+                  "Cannot use an alias class with a non-polymorphic type");
 
     PYBIND11_OBJECT(class_, generic_type, PyType_Check)
 
     template <typename... Extra>
-    class_(handle scope, const char *name, const Extra &... extra) {
+    class_(handle scope, const char *name, const Extra &...extra) {
         using namespace detail;
 
         // MI can only be specified via class_ template options, not constructor parameters
         static_assert(
             none_of<is_pyobject<Extra>...>::value || // no base class arguments, or:
-            (   constexpr_sum(is_pyobject<Extra>::value...) == 1 && // Exactly one base
-                constexpr_sum(is_base<options>::value...)   == 0 && // no template option bases
-                // no multiple_inheritance attr
-                none_of<std::is_same<multiple_inheritance, Extra>...>::value),
+                (constexpr_sum(is_pyobject<Extra>::value...) == 1 && // Exactly one base
+                 constexpr_sum(is_base<options>::value...) == 0 &&   // no template option bases
+                 // no multiple_inheritance attr
+                 none_of<std::is_same<multiple_inheritance, Extra>...>::value),
             "Error: multiple inheritance bases must be specified via class_ template options");
 
         type_record record;
@@ -1636,14 +1705,15 @@ class class_ : public detail::generic_type {
         record.name = name;
         record.type = &typeid(type);
         record.type_size = sizeof(conditional_t<has_alias, type_alias, type>);
-        record.type_align = alignof(conditional_t<has_alias, type_alias, type>&);
+        record.type_align = alignof(conditional_t<has_alias, type_alias, type> &);
         record.holder_size = sizeof(holder_type);
         record.init_instance = init_instance;
         record.dealloc = dealloc;
         record.default_holder = detail::is_instantiation<std::unique_ptr, holder_type>::value;
 
-        // TODO(eric.cousineau): Determine if it is possible to permit releasing without a wrapper...
-        auto& release_info = record.release_info;
+        // TODO(eric.cousineau): Determine if it is possible to permit releasing without a
+        // wrapper...
+        auto &release_info = record.release_info;
         release_info.can_derive_from_wrapper = has_wrapper;
         release_info.release_to_cpp = release_to_cpp;
         release_info.holder_type_id = holder_type_id;
@@ -1659,12 +1729,14 @@ class class_ : public detail::generic_type {
         generic_type::initialize(record);
 
         if (has_alias) {
-            auto &instances = record.module_local ? get_local_internals().registered_types_cpp : get_internals().registered_types_cpp;
-            instances[std::type_index(typeid(type_alias))] = instances[std::type_index(typeid(type))];
+            auto &instances = record.module_local ? get_local_internals().registered_types_cpp
+                                                  : get_internals().registered_types_cpp;
+            instances[std::type_index(typeid(type_alias))]
+                = instances[std::type_index(typeid(type))];
         }
     }
 
-    static detail::type_info* get_type_info() {
+    static detail::type_info *get_type_info() {
         std::type_index id(typeid(type));
         return detail::get_type_info(id);
     }
@@ -1672,7 +1744,7 @@ class class_ : public detail::generic_type {
     using wrapper_interface = detail::wrapper_interface_impl<type, type_alias, has_wrapper>;
     using holder_check = detail::holder_check_impl<holder_type_id>;
 
-    static bool allow_destruct(detail::instance* inst, detail::holder_erased holder) {
+    static bool allow_destruct(detail::instance *inst, detail::holder_erased holder) {
         // TODO(eric.cousineau): There should not be a case where shared_ptr<> lives in
         // C++ and Python, with it being owned by C++. Check this.
         return holder_check::template check_destruct<holder_type>(inst, holder);
@@ -1688,7 +1760,7 @@ class class_ : public detail::generic_type {
             // not yet supported for this fork's ownership transfer setup).
             return;
         }
-        auto& release_info = lowest_type->release_info;
+        auto &release_info = lowest_type->release_info;
         // The references are as follows:
         //   1. When Python calls __del__ via tp_del (default slot)
         //   2. When Python gets the instance-bound __del__ method.
@@ -1718,12 +1790,15 @@ class class_ : public detail::generic_type {
         }
     }
 
-    static void release_to_cpp(detail::instance* inst, detail::holder_erased external_holder_raw, object&& obj) {
+    static void release_to_cpp(detail::instance *inst,
+                               detail::holder_erased external_holder_raw,
+                               object &&obj) {
         using detail::LoadType;
         auto v_h = inst->get_value_and_holder();
-        auto* tinfo = get_type_info();
+        auto *tinfo = get_type_info();
         if (!inst->owned || !v_h.holder_constructed()) {
-            throw std::runtime_error("C++ object must be owned by pybind11 when attempting to release to C++");
+            throw std::runtime_error(
+                "C++ object must be owned by pybind11 when attempting to release to C++");
         }
         LoadType load_type = determine_load_type(obj, tinfo);
         switch (load_type) {
@@ -1735,23 +1810,23 @@ class class_ : public detail::generic_type {
                 // wrapper-wrapper alias, we do not need to worry about not being in the correct
                 // hierarchy, since we will simply release from it.
 
-                // TODO(eric.cousineau): Presently, there is no support for a consistent use of weak references.
-                // If a PureCpp object is released from Python, then all weak references are invalidated,
-                // even if it comes back...
-                // Ideally, this could check if there are weak references. But to whom should the lifetime be extended?
+                // TODO(eric.cousineau): Presently, there is no support for a consistent use of
+                // weak references. If a PureCpp object is released from Python, then all weak
+                // references are invalidated, even if it comes back... Ideally, this could check
+                // if there are weak references. But to whom should the lifetime be extended?
                 // Perhaps the first weak reference that is available?
                 break;
             }
             case LoadType::DerivedCppSinglePySingle: {
                 if (!tinfo->release_info.can_derive_from_wrapper) {
-                    // This could be relaxed if there is an optional `release` mechanism for holders.
-                    // However, there is still slicing.
+                    // This could be relaxed if there is an optional `release` mechanism for
+                    // holders. However, there is still slicing.
                     throw std::runtime_error(
                         "Python-extended C++ class does not inherit from pybind11::wrapper<>, "
                         "and the instance will be sliced. Either avoid this situation, or "
                         "the type extends pybind11::wrapper<>.");
                 }
-                auto* cppobj = reinterpret_cast<type*>(v_h.value_ptr());
+                auto *cppobj = reinterpret_cast<type *>(v_h.value_ptr());
                 wrapper_interface::use_cpp_lifetime(cppobj, std::move(obj), holder_type_id);
                 break;
             }
@@ -1779,19 +1854,22 @@ class class_ : public detail::generic_type {
         holder.~holder_type();
         v_h.set_holder_constructed(false);
         inst->owned = false;
-        // Register this type's reclamation procedure, since it's wrapper may have the contained object.
+        // Register this type's reclamation procedure, since it's wrapper may have the contained
+        // object.
         inst->reclaim_from_cpp = reclaim_from_cpp;
     }
 
-    static object reclaim_from_cpp(detail::instance* inst, detail::holder_erased external_holder_raw) {
+    static object reclaim_from_cpp(detail::instance *inst,
+                                   detail::holder_erased external_holder_raw) {
         using detail::LoadType;
         auto v_h = inst->get_value_and_holder();
-        auto* tinfo = get_type_info();
+        auto *tinfo = get_type_info();
         // TODO(eric.cousineau): Should relax this to not require a holder be constructed,
         // only that the holder itself be default (unique_ptr<>).
         if (inst->owned) {
             throw std::runtime_error(
-                "reclaim_from_cpp: Python object already owned! Did you forget to explicitly use a "
+                "reclaim_from_cpp: Python object already owned! Did you forget to explicitly use "
+                "a "
                 "py::return_value_policy (e.g. reference or reference internal) when passing back "
                 "non-owned pointers of the C++ object?");
         }
@@ -1802,7 +1880,7 @@ class class_ : public detail::generic_type {
             throw std::runtime_error("reclaim_from_cpp: No external holder - internal error?");
         }
         // Is this valid?
-        handle h(reinterpret_cast<PyObject*>(inst));
+        handle h(reinterpret_cast<PyObject *>(inst));
         LoadType load_type = determine_load_type(h, tinfo);
         {
             // TODO(eric.cousineau): Consider releasing a raw pointer, to make it easier for
@@ -1823,7 +1901,7 @@ class class_ : public detail::generic_type {
                 break;
             }
             case LoadType::DerivedCppSinglePySingle: {
-                auto* cppobj = reinterpret_cast<type*>(v_h.value_ptr());
+                auto *cppobj = reinterpret_cast<type *>(v_h.value_ptr());
                 obj = wrapper_interface::release_cpp_lifetime(cppobj);
                 break;
             }
@@ -1843,54 +1921,60 @@ class class_ : public detail::generic_type {
     }
 
     template <typename Base, detail::enable_if_t<!is_base<Base>::value, int> = 0>
-    static void add_base(detail::type_record &) { }
+    static void add_base(detail::type_record &) {}
 
     template <typename Func, typename... Extra>
-    class_ &def(const char *name_, Func&& f, const Extra&... extra) {
-        cpp_function cf(method_adaptor<type>(std::forward<Func>(f)), name(name_), is_method(*this),
-                        sibling(getattr(*this, name_, none())), extra...);
+    class_ &def(const char *name_, Func &&f, const Extra &...extra) {
+        cpp_function cf(method_adaptor<type>(std::forward<Func>(f)),
+                        name(name_),
+                        is_method(*this),
+                        sibling(getattr(*this, name_, none())),
+                        extra...);
         add_class_method(*this, name_, cf);
         return *this;
     }
 
-    template <typename Func, typename... Extra> class_ &
-    def_static(const char *name_, Func &&f, const Extra&... extra) {
+    template <typename Func, typename... Extra>
+    class_ &def_static(const char *name_, Func &&f, const Extra &...extra) {
         static_assert(!std::is_member_function_pointer<Func>::value,
-                "def_static(...) called with a non-static member function pointer");
-        cpp_function cf(std::forward<Func>(f), name(name_), scope(*this),
-                        sibling(getattr(*this, name_, none())), extra...);
+                      "def_static(...) called with a non-static member function pointer");
+        cpp_function cf(std::forward<Func>(f),
+                        name(name_),
+                        scope(*this),
+                        sibling(getattr(*this, name_, none())),
+                        extra...);
         attr(cf.name()) = staticmethod(cf);
         return *this;
     }
 
     template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
-    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra&... extra) {
+    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
         op.execute(*this, extra...);
         return *this;
     }
 
     template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
-    class_ & def_cast(const detail::op_<id, ot, L, R> &op, const Extra&... extra) {
+    class_ &def_cast(const detail::op_<id, ot, L, R> &op, const Extra &...extra) {
         op.execute_cast(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
-    class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra&... extra) {
+    class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra &...extra) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(init);
         init.execute(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
-    class_ &def(const detail::initimpl::alias_constructor<Args...> &init, const Extra&... extra) {
+    class_ &def(const detail::initimpl::alias_constructor<Args...> &init, const Extra &...extra) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(init);
         init.execute(*this, extra...);
         return *this;
     }
 
     template <typename... Args, typename... Extra>
-    class_ &def(detail::initimpl::factory<Args...> &&init, const Extra&... extra) {
+    class_ &def(detail::initimpl::factory<Args...> &&init, const Extra &...extra) {
         std::move(init).execute(*this, extra...);
         return *this;
     }
@@ -1902,52 +1986,59 @@ class class_ : public detail::generic_type {
     }
 
     template <typename Func>
-    class_& def_buffer(Func &&func) {
-        struct capture { Func func; };
-        auto *ptr = new capture { std::forward<Func>(func) };
-        install_buffer_funcs([](PyObject *obj, void *ptr) -> buffer_info* {
-            detail::make_caster<type> caster;
-            if (!caster.load(obj, false)) {
-                return nullptr;
-            }
-            return new buffer_info(((capture *) ptr)->func(caster));
-        }, ptr);
+    class_ &def_buffer(Func &&func) {
+        struct capture {
+            Func func;
+        };
+        auto *ptr = new capture{std::forward<Func>(func)};
+        install_buffer_funcs(
+            [](PyObject *obj, void *ptr) -> buffer_info * {
+                detail::make_caster<type> caster;
+                if (!caster.load(obj, false)) {
+                    return nullptr;
+                }
+                return new buffer_info(((capture *) ptr)->func(caster));
+            },
+            ptr);
         weakref(m_ptr, cpp_function([ptr](handle wr) {
-            delete ptr;
-            wr.dec_ref();
-        })).release();
+                    delete ptr;
+                    wr.dec_ref();
+                }))
+            .release();
         return *this;
     }
 
     template <typename Return, typename Class, typename... Args>
     class_ &def_buffer(Return (Class::*func)(Args...)) {
-        return def_buffer([func] (type &obj) { return (obj.*func)(); });
+        return def_buffer([func](type &obj) { return (obj.*func)(); });
     }
 
     template <typename Return, typename Class, typename... Args>
     class_ &def_buffer(Return (Class::*func)(Args...) const) {
-        return def_buffer([func] (const type &obj) { return (obj.*func)(); });
+        return def_buffer([func](const type &obj) { return (obj.*func)(); });
     }
 
     template <typename C, typename D, typename... Extra>
-    class_ &def_readwrite(const char *name, D C::*pm, const Extra&... extra) {
-        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value, "def_readwrite() requires a class member (or base class member)");
-        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this)),
-                     fset([pm](type &c, const D &value) { c.*pm = value; }, is_method(*this));
+    class_ &def_readwrite(const char *name, D C::*pm, const Extra &...extra) {
+        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value,
+                      "def_readwrite() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D & { return c.*pm; }, is_method(*this)),
+            fset([pm](type &c, const D &value) { c.*pm = value; }, is_method(*this));
         def_property(name, fget, fset, return_value_policy::reference_internal, extra...);
         return *this;
     }
 
     template <typename C, typename D, typename... Extra>
-    class_ &def_readonly(const char *name, const D C::*pm, const Extra& ...extra) {
-        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value, "def_readonly() requires a class member (or base class member)");
-        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this));
+    class_ &def_readonly(const char *name, const D C::*pm, const Extra &...extra) {
+        static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value,
+                      "def_readonly() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D & { return c.*pm; }, is_method(*this));
         def_property_readonly(name, fget, return_value_policy::reference_internal, extra...);
         return *this;
     }
 
     template <typename D, typename... Extra>
-    class_ &def_readwrite_static(const char *name, D *pm, const Extra& ...extra) {
+    class_ &def_readwrite_static(const char *name, D *pm, const Extra &...extra) {
         cpp_function fget([pm](const object &) -> const D & { return *pm; }, scope(*this)),
             fset([pm](const object &, const D &value) { *pm = value; }, scope(*this));
         def_property_static(name, fget, fset, return_value_policy::reference, extra...);
@@ -1955,7 +2046,7 @@ class class_ : public detail::generic_type {
     }
 
     template <typename D, typename... Extra>
-    class_ &def_readonly_static(const char *name, const D *pm, const Extra& ...extra) {
+    class_ &def_readonly_static(const char *name, const D *pm, const Extra &...extra) {
         cpp_function fget([pm](const object &) -> const D & { return *pm; }, scope(*this));
         def_property_readonly_static(name, fget, return_value_policy::reference, extra...);
         return *this;
@@ -1963,66 +2054,91 @@ class class_ : public detail::generic_type {
 
     /// Uses return_value_policy::reference_internal by default
     template <typename Getter, typename... Extra>
-    class_ &def_property_readonly(const char *name, const Getter &fget, const Extra& ...extra) {
-        return def_property_readonly(name, cpp_function(method_adaptor<type>(fget)),
-                                     return_value_policy::reference_internal, extra...);
+    class_ &def_property_readonly(const char *name, const Getter &fget, const Extra &...extra) {
+        return def_property_readonly(name,
+                                     cpp_function(method_adaptor<type>(fget)),
+                                     return_value_policy::reference_internal,
+                                     extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property_readonly(const char *name, const cpp_function &fget, const Extra& ...extra) {
+    class_ &
+    def_property_readonly(const char *name, const cpp_function &fget, const Extra &...extra) {
         return def_property(name, fget, nullptr, extra...);
     }
 
     /// Uses return_value_policy::reference by default
     template <typename Getter, typename... Extra>
-    class_ &def_property_readonly_static(const char *name, const Getter &fget, const Extra& ...extra) {
-        return def_property_readonly_static(name, cpp_function(fget), return_value_policy::reference, extra...);
+    class_ &
+    def_property_readonly_static(const char *name, const Getter &fget, const Extra &...extra) {
+        return def_property_readonly_static(
+            name, cpp_function(fget), return_value_policy::reference, extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property_readonly_static(const char *name, const cpp_function &fget, const Extra& ...extra) {
+    class_ &def_property_readonly_static(const char *name,
+                                         const cpp_function &fget,
+                                         const Extra &...extra) {
         return def_property_static(name, fget, nullptr, extra...);
     }
 
     /// Uses return_value_policy::reference_internal by default
     template <typename Getter, typename Setter, typename... Extra>
-    class_ &def_property(const char *name, const Getter &fget, const Setter &fset, const Extra& ...extra) {
+    class_ &
+    def_property(const char *name, const Getter &fget, const Setter &fset, const Extra &...extra) {
         return def_property(name, fget, cpp_function(method_adaptor<type>(fset)), extra...);
     }
     template <typename Getter, typename... Extra>
-    class_ &def_property(const char *name, const Getter &fget, const cpp_function &fset, const Extra& ...extra) {
-        return def_property(name, cpp_function(method_adaptor<type>(fget)), fset,
-                            return_value_policy::reference_internal, extra...);
+    class_ &def_property(const char *name,
+                         const Getter &fget,
+                         const cpp_function &fset,
+                         const Extra &...extra) {
+        return def_property(name,
+                            cpp_function(method_adaptor<type>(fget)),
+                            fset,
+                            return_value_policy::reference_internal,
+                            extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
+    class_ &def_property(const char *name,
+                         const cpp_function &fget,
+                         const cpp_function &fset,
+                         const Extra &...extra) {
         return def_property_static(name, fget, fset, is_method(*this), extra...);
     }
 
     /// Uses return_value_policy::reference by default
     template <typename Getter, typename... Extra>
-    class_ &def_property_static(const char *name, const Getter &fget, const cpp_function &fset, const Extra& ...extra) {
-        return def_property_static(name, cpp_function(fget), fset, return_value_policy::reference, extra...);
+    class_ &def_property_static(const char *name,
+                                const Getter &fget,
+                                const cpp_function &fset,
+                                const Extra &...extra) {
+        return def_property_static(
+            name, cpp_function(fget), fset, return_value_policy::reference, extra...);
     }
 
     /// Uses cpp_function's return_value_policy by default
     template <typename... Extra>
-    class_ &def_property_static(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
-        static_assert( 0 == detail::constexpr_sum(std::is_base_of<arg, Extra>::value...),
+    class_ &def_property_static(const char *name,
+                                const cpp_function &fget,
+                                const cpp_function &fset,
+                                const Extra &...extra) {
+        static_assert(0 == detail::constexpr_sum(std::is_base_of<arg, Extra>::value...),
                       "Argument annotations are not allowed for properties");
         auto rec_fget = get_function_record(fget), rec_fset = get_function_record(fset);
         auto *rec_active = rec_fget;
         if (rec_fget) {
-           char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific documentation string */
-           detail::process_attributes<Extra...>::init(extra..., rec_fget);
-           if (rec_fget->doc && rec_fget->doc != doc_prev) {
-              std::free(doc_prev);
-              rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
-           }
+            char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific
+                                               documentation string */
+            detail::process_attributes<Extra...>::init(extra..., rec_fget);
+            if (rec_fget->doc && rec_fget->doc != doc_prev) {
+                std::free(doc_prev);
+                rec_fget->doc = PYBIND11_COMPAT_STRDUP(rec_fget->doc);
+            }
         }
         if (rec_fset) {
             char *doc_prev = rec_fset->doc;
@@ -2042,11 +2158,13 @@ class class_ : public detail::generic_type {
 private:
     /// Initialize holder object, variant 1: object derives from enable_shared_from_this
     template <typename T>
-    static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
-            const holder_type * /* unused */, const std::enable_shared_from_this<T> * /* dummy */) {
+    static void init_holder(detail::instance *inst,
+                            detail::value_and_holder &v_h,
+                            const holder_type * /* unused */,
+                            const std::enable_shared_from_this<T> * /* dummy */) {
 
         auto sh = std::dynamic_pointer_cast<typename holder_type::element_type>(
-                detail::try_get_shared_from_this(v_h.value_ptr<type>()));
+            detail::try_get_shared_from_this(v_h.value_ptr<type>()));
         if (sh) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(std::move(sh));
             v_h.set_holder_constructed();
@@ -2059,18 +2177,25 @@ class class_ : public detail::generic_type {
     }
 
     static void init_holder_from_existing(const detail::value_and_holder &v_h,
-            const holder_type *holder_ptr, std::true_type /*is_copy_constructible*/) {
-        new (std::addressof(v_h.holder<holder_type>())) holder_type(*reinterpret_cast<const holder_type *>(holder_ptr));
+                                          const holder_type *holder_ptr,
+                                          std::true_type /*is_copy_constructible*/) {
+        new (std::addressof(v_h.holder<holder_type>()))
+            holder_type(*reinterpret_cast<const holder_type *>(holder_ptr));
     }
 
     static void init_holder_from_existing(const detail::value_and_holder &v_h,
-            const holder_type *holder_ptr, std::false_type /*is_copy_constructible*/) {
-        new (std::addressof(v_h.holder<holder_type>())) holder_type(std::move(*const_cast<holder_type *>(holder_ptr)));
-    }
-
-    /// Initialize holder object, variant 2: try to construct from existing holder object, if possible
-    static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
-            const holder_type *holder_ptr, const void * /* dummy -- not enable_shared_from_this<T>) */) {
+                                          const holder_type *holder_ptr,
+                                          std::false_type /*is_copy_constructible*/) {
+        new (std::addressof(v_h.holder<holder_type>()))
+            holder_type(std::move(*const_cast<holder_type *>(holder_ptr)));
+    }
+
+    /// Initialize holder object, variant 2: try to construct from existing holder object, if
+    /// possible
+    static void init_holder(detail::instance *inst,
+                            detail::value_and_holder &v_h,
+                            const holder_type *holder_ptr,
+                            const void * /* dummy -- not enable_shared_from_this<T>) */) {
         if (holder_ptr) {
             init_holder_from_existing(v_h, holder_ptr, std::is_copy_constructible<holder_type>());
             v_h.set_holder_constructed();
@@ -2080,7 +2205,8 @@ class class_ : public detail::generic_type {
     }
 
     /// Initialize a holder object simply (to be converted).
-    static void init_holder_simple(detail::instance *inst, detail::value_and_holder &v_h, type* value) {
+    static void
+    init_holder_simple(detail::instance *inst, detail::value_and_holder &v_h, type *value) {
         if (inst->owned || detail::always_construct_holder<holder_type>::value) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(value);
             v_h.set_holder_constructed();
@@ -2088,13 +2214,13 @@ class class_ : public detail::generic_type {
     }
 
     /// Performs instance initialization including constructing a holder and registering the known
-    /// instance.  Should be called as soon as the `type` value_ptr is set for an instance.  Takes an
-    /// optional pointer to an existing holder to use; if not specified and the instance is
+    /// instance.  Should be called as soon as the `type` value_ptr is set for an instance.  Takes
+    /// an optional pointer to an existing holder to use; if not specified and the instance is
     /// `.owned`, a new holder will be constructed to manage the value pointer.
     static void init_instance(detail::instance *inst, detail::holder_erased holder_ptr) {
         using namespace detail;
         auto v_h = inst->get_value_and_holder(detail::get_type_info(typeid(type)));
-        type* value_ptr = v_h.value_ptr<type>();
+        type *value_ptr = v_h.value_ptr<type>();
         if (!v_h.instance_registered()) {
             register_instance(inst, value_ptr, v_h.type);
             v_h.set_instance_registered();
@@ -2109,16 +2235,16 @@ class class_ : public detail::generic_type {
             if (!v_h.holder_constructed()) {
                 throw std::runtime_error("Bad edge case");
             }
-            auto& holder = v_h.holder<holder_type>();
+            auto &holder = v_h.holder<holder_type>();
             holder_check::accept_holder(holder_ptr, holder);
         }
 
         // TODO(eric.cousineau): Inject override of __del__ for intercepting C++ stuff
-        handle self((PyObject*)inst);
+        handle self((PyObject *) inst);
         handle h_type = self.get_type();
 
         // Use hacky Python-style inheritance check.
-        auto *py_type = (PyTypeObject*)h_type.ptr();
+        auto *py_type = (PyTypeObject *) h_type.ptr();
         bool is_py_derived = py_type->tp_dealloc != detail::pybind11_object_dealloc;
 
         bool can_add_del = true;
@@ -2148,9 +2274,9 @@ class class_ : public detail::generic_type {
             if (!hasattr(h_type, orig_field.c_str())) {
                 // NOTE: This is NOT tied to this particular type.
                 auto del_new = [orig_field](handle h_self) {
-                  // TODO(eric.cousineau): Make this global, not tied to this type.
-                  object del_orig = getattr(h_self.get_type(), orig_field.c_str());
-                  del_wrapped(h_self, del_orig);
+                    // TODO(eric.cousineau): Make this global, not tied to this type.
+                    object del_orig = getattr(h_self.get_type(), orig_field.c_str());
+                    del_wrapped(h_self, del_orig);
                 };
                 // Replace with an Python-instance-unbound function.
                 object new_dtor_py = cpp_function(del_new, is_method(h_type));
@@ -2172,35 +2298,42 @@ class class_ : public detail::generic_type {
         if (v_h.holder_constructed()) {
             v_h.holder<holder_type>().~holder_type();
             v_h.set_holder_constructed(false);
-        }
-        else {
-            detail::call_operator_delete(v_h.value_ptr<type>(),
-                v_h.type->type_size,
-                v_h.type->type_align
-            );
+        } else {
+            detail::call_operator_delete(
+                v_h.value_ptr<type>(), v_h.type->type_size, v_h.type->type_align);
         }
         v_h.value_ptr() = nullptr;
     }
 
     static detail::function_record *get_function_record(handle h) {
         h = detail::get_function(h);
-        return h ? (detail::function_record *) reinterpret_borrow<capsule>(PyCFunction_GET_SELF(h.ptr()))
+        return h ? (detail::function_record *) reinterpret_borrow<capsule>(
+                   PyCFunction_GET_SELF(h.ptr()))
                  : nullptr;
     }
 };
 
 /// Binds an existing constructor taking arguments Args...
-template <typename... Args> detail::initimpl::constructor<Args...> init() { return {}; }
+template <typename... Args>
+detail::initimpl::constructor<Args...> init() {
+    return {};
+}
 /// Like `init<Args...>()`, but the instance is always constructed through the alias class (even
 /// when not inheriting on the Python side).
-template <typename... Args> detail::initimpl::alias_constructor<Args...> init_alias() { return {}; }
+template <typename... Args>
+detail::initimpl::alias_constructor<Args...> init_alias() {
+    return {};
+}
 
 /// Binds a factory function as a constructor
 template <typename Func, typename Ret = detail::initimpl::factory<Func>>
-Ret init(Func &&f) { return {std::forward<Func>(f)}; }
+Ret init(Func &&f) {
+    return {std::forward<Func>(f)};
+}
 
-/// Dual-argument factory function: the first function is called when no alias is needed, the second
-/// when an alias is needed (i.e. due to python-side inheritance).  Arguments must be identical.
+/// Dual-argument factory function: the first function is called when no alias is needed, the
+/// second when an alias is needed (i.e. due to python-side inheritance).  Arguments must be
+/// identical.
 template <typename CFunc, typename AFunc, typename Ret = detail::initimpl::factory<CFunc, AFunc>>
 Ret init(CFunc &&c, AFunc &&a) {
     return {std::forward<CFunc>(c), std::forward<AFunc>(a)};
@@ -2226,7 +2359,7 @@ inline str enum_name(handle arg) {
 }
 
 struct enum_base {
-    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) { }
+    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) {}
 
     PYBIND11_NOINLINE void init(bool is_arithmetic, bool is_convertible) {
         m_base.attr("__entries") = dict();
@@ -2248,38 +2381,47 @@ struct enum_base {
             [](handle arg) -> str {
                 object type_name = type::handle_of(arg).attr("__name__");
                 return pybind11::str("{}.{}").format(type_name, enum_name(arg));
-            }, name("name"), is_method(m_base)
-        );
+            },
+            name("name"),
+            is_method(m_base));
 
-        m_base.attr("__doc__") = static_property(cpp_function(
-            [](handle arg) -> std::string {
-                std::string docstring;
-                dict entries = arg.attr("__entries");
-                if (((PyTypeObject *) arg.ptr())->tp_doc) {
-                    docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
-                }
-                docstring += "Members:";
-                for (auto kv : entries) {
-                    auto key = std::string(pybind11::str(kv.first));
-                    auto comment = kv.second[int_(1)];
-                    docstring += "\n\n  " + key;
-                    if (!comment.is_none()) {
-                        docstring += " : " + (std::string) pybind11::str(comment);
+        m_base.attr("__doc__") = static_property(
+            cpp_function(
+                [](handle arg) -> std::string {
+                    std::string docstring;
+                    dict entries = arg.attr("__entries");
+                    if (((PyTypeObject *) arg.ptr())->tp_doc) {
+                        docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
                     }
-                }
-                return docstring;
-            }, name("__doc__")
-        ), none(), none(), "");
+                    docstring += "Members:";
+                    for (auto kv : entries) {
+                        auto key = std::string(pybind11::str(kv.first));
+                        auto comment = kv.second[int_(1)];
+                        docstring += "\n\n  " + key;
+                        if (!comment.is_none()) {
+                            docstring += " : " + (std::string) pybind11::str(comment);
+                        }
+                    }
+                    return docstring;
+                },
+                name("__doc__")),
+            none(),
+            none(),
+            "");
 
         m_base.attr("__members__") = static_property(cpp_function(
-            [](handle arg) -> dict {
-                dict entries = arg.attr("__entries"), m;
-                for (auto kv : entries) {
-                    m[kv.first] = kv.second[int_(0)];
-                }
-                return m;
-            }, name("__members__")), none(), none(), ""
-        );
+                                                         [](handle arg) -> dict {
+                                                             dict entries = arg.attr("__entries"),
+                                                                  m;
+                                                             for (auto kv : entries) {
+                                                                 m[kv.first] = kv.second[int_(0)];
+                                                             }
+                                                             return m;
+                                                         },
+                                                         name("__members__")),
+                                                     none(),
+                                                     none(),
+                                                     "");
 
 #define PYBIND11_ENUM_OP_STRICT(op, expr, strict_behavior)                                        \
     m_base.attr(op) = cpp_function(                                                               \
@@ -2313,42 +2455,42 @@ struct enum_base {
         arg("other"))
 
         if (is_convertible) {
-            PYBIND11_ENUM_OP_CONV_LHS("__eq__", !b.is_none() &&  a.equal(b));
-            PYBIND11_ENUM_OP_CONV_LHS("__ne__",  b.is_none() || !a.equal(b));
+            PYBIND11_ENUM_OP_CONV_LHS("__eq__", !b.is_none() && a.equal(b));
+            PYBIND11_ENUM_OP_CONV_LHS("__ne__", b.is_none() || !a.equal(b));
 
             if (is_arithmetic) {
-                PYBIND11_ENUM_OP_CONV("__lt__",   a <  b);
-                PYBIND11_ENUM_OP_CONV("__gt__",   a >  b);
-                PYBIND11_ENUM_OP_CONV("__le__",   a <= b);
-                PYBIND11_ENUM_OP_CONV("__ge__",   a >= b);
-                PYBIND11_ENUM_OP_CONV("__and__",  a &  b);
-                PYBIND11_ENUM_OP_CONV("__rand__", a &  b);
-                PYBIND11_ENUM_OP_CONV("__or__",   a |  b);
-                PYBIND11_ENUM_OP_CONV("__ror__",  a |  b);
-                PYBIND11_ENUM_OP_CONV("__xor__",  a ^  b);
-                PYBIND11_ENUM_OP_CONV("__rxor__", a ^  b);
+                PYBIND11_ENUM_OP_CONV("__lt__", a < b);
+                PYBIND11_ENUM_OP_CONV("__gt__", a > b);
+                PYBIND11_ENUM_OP_CONV("__le__", a <= b);
+                PYBIND11_ENUM_OP_CONV("__ge__", a >= b);
+                PYBIND11_ENUM_OP_CONV("__and__", a & b);
+                PYBIND11_ENUM_OP_CONV("__rand__", a & b);
+                PYBIND11_ENUM_OP_CONV("__or__", a | b);
+                PYBIND11_ENUM_OP_CONV("__ror__", a | b);
+                PYBIND11_ENUM_OP_CONV("__xor__", a ^ b);
+                PYBIND11_ENUM_OP_CONV("__rxor__", a ^ b);
                 m_base.attr("__invert__")
                     = cpp_function([](const object &arg) { return ~(int_(arg)); },
                                    name("__invert__"),
                                    is_method(m_base));
             }
         } else {
-            PYBIND11_ENUM_OP_STRICT("__eq__",  int_(a).equal(int_(b)), return false);
+            PYBIND11_ENUM_OP_STRICT("__eq__", int_(a).equal(int_(b)), return false);
             PYBIND11_ENUM_OP_STRICT("__ne__", !int_(a).equal(int_(b)), return true);
 
             if (is_arithmetic) {
-                #define PYBIND11_THROW throw type_error("Expected an enumeration of matching type!");
-                PYBIND11_ENUM_OP_STRICT("__lt__", int_(a) <  int_(b), PYBIND11_THROW);
-                PYBIND11_ENUM_OP_STRICT("__gt__", int_(a) >  int_(b), PYBIND11_THROW);
+#define PYBIND11_THROW throw type_error("Expected an enumeration of matching type!");
+                PYBIND11_ENUM_OP_STRICT("__lt__", int_(a) < int_(b), PYBIND11_THROW);
+                PYBIND11_ENUM_OP_STRICT("__gt__", int_(a) > int_(b), PYBIND11_THROW);
                 PYBIND11_ENUM_OP_STRICT("__le__", int_(a) <= int_(b), PYBIND11_THROW);
                 PYBIND11_ENUM_OP_STRICT("__ge__", int_(a) >= int_(b), PYBIND11_THROW);
-                #undef PYBIND11_THROW
+#undef PYBIND11_THROW
             }
         }
 
-        #undef PYBIND11_ENUM_OP_CONV_LHS
-        #undef PYBIND11_ENUM_OP_CONV
-        #undef PYBIND11_ENUM_OP_STRICT
+#undef PYBIND11_ENUM_OP_CONV_LHS
+#undef PYBIND11_ENUM_OP_CONV
+#undef PYBIND11_ENUM_OP_STRICT
 
         m_base.attr("__getstate__") = cpp_function(
             [](const object &arg) { return int_(arg); }, name("__getstate__"), is_method(m_base));
@@ -2357,12 +2499,13 @@ struct enum_base {
             [](const object &arg) { return int_(arg); }, name("__hash__"), is_method(m_base));
     }
 
-    PYBIND11_NOINLINE void value(char const* name_, object value, const char *doc = nullptr) {
+    PYBIND11_NOINLINE void value(char const *name_, object value, const char *doc = nullptr) {
         dict entries = m_base.attr("__entries");
         str name(name_);
         if (entries.contains(name)) {
             std::string type_name = (std::string) str(m_base.attr("__name__"));
-            throw value_error(type_name + ": element \"" + std::string(name_) + "\" already exists!");
+            throw value_error(type_name + ": element \"" + std::string(name_)
+                              + "\" already exists!");
         }
 
         entries[name] = std::make_pair(value, doc);
@@ -2380,38 +2523,66 @@ struct enum_base {
     handle m_parent;
 };
 
-template <bool is_signed, size_t length> struct equivalent_integer {};
-template <> struct equivalent_integer<true,  1> { using type = int8_t;   };
-template <> struct equivalent_integer<false, 1> { using type = uint8_t;  };
-template <> struct equivalent_integer<true,  2> { using type = int16_t;  };
-template <> struct equivalent_integer<false, 2> { using type = uint16_t; };
-template <> struct equivalent_integer<true,  4> { using type = int32_t;  };
-template <> struct equivalent_integer<false, 4> { using type = uint32_t; };
-template <> struct equivalent_integer<true,  8> { using type = int64_t;  };
-template <> struct equivalent_integer<false, 8> { using type = uint64_t; };
+template <bool is_signed, size_t length>
+struct equivalent_integer {};
+template <>
+struct equivalent_integer<true, 1> {
+    using type = int8_t;
+};
+template <>
+struct equivalent_integer<false, 1> {
+    using type = uint8_t;
+};
+template <>
+struct equivalent_integer<true, 2> {
+    using type = int16_t;
+};
+template <>
+struct equivalent_integer<false, 2> {
+    using type = uint16_t;
+};
+template <>
+struct equivalent_integer<true, 4> {
+    using type = int32_t;
+};
+template <>
+struct equivalent_integer<false, 4> {
+    using type = uint32_t;
+};
+template <>
+struct equivalent_integer<true, 8> {
+    using type = int64_t;
+};
+template <>
+struct equivalent_integer<false, 8> {
+    using type = uint64_t;
+};
 
 template <typename IntLike>
-using equivalent_integer_t = typename equivalent_integer<std::is_signed<IntLike>::value, sizeof(IntLike)>::type;
+using equivalent_integer_t =
+    typename equivalent_integer<std::is_signed<IntLike>::value, sizeof(IntLike)>::type;
 
 PYBIND11_NAMESPACE_END(detail)
 
 /// Binds C++ enumerations and enumeration classes to Python
-template <typename Type> class enum_ : public class_<Type> {
+template <typename Type>
+class enum_ : public class_<Type> {
 public:
     using Base = class_<Type>;
-    using Base::def;
     using Base::attr;
+    using Base::def;
     using Base::def_property_readonly;
     using Base::def_property_readonly_static;
     using Underlying = typename std::underlying_type<Type>::type;
     // Scalar is the integer representation of underlying type
-    using Scalar = detail::conditional_t<detail::any_of<
-        detail::is_std_char_type<Underlying>, std::is_same<Underlying, bool>
-    >::value, detail::equivalent_integer_t<Underlying>, Underlying>;
+    using Scalar = detail::conditional_t<detail::any_of<detail::is_std_char_type<Underlying>,
+                                                        std::is_same<Underlying, bool>>::value,
+                                         detail::equivalent_integer_t<Underlying>,
+                                         Underlying>;
 
     template <typename... Extra>
-    enum_(const handle &scope, const char *name, const Extra&... extra)
-      : class_<Type>(scope, name, extra...), m_base(*this, scope) {
+    enum_(const handle &scope, const char *name, const Extra &...extra)
+        : class_<Type>(scope, name, extra...), m_base(*this, scope) {
         constexpr bool is_arithmetic = detail::any_of<std::is_same<arithmetic, Extra>...>::value;
         constexpr bool is_convertible = std::is_convertible<Type, Underlying>::value;
         m_base.init(is_arithmetic, is_convertible);
@@ -2420,25 +2591,28 @@ template <typename Type> class enum_ : public class_<Type> {
         def_property_readonly("value", [](Type value) { return (Scalar) value; });
         def("__int__", [](Type value) { return (Scalar) value; });
         def("__index__", [](Type value) { return (Scalar) value; });
-        #if PY_MAJOR_VERSION < 3
-            def("__long__", [](Type value) { return (Scalar) value; });
-        #endif
+#if PY_MAJOR_VERSION < 3
+        def("__long__", [](Type value) { return (Scalar) value; });
+#endif
         attr("__setstate__") = cpp_function(
             [](detail::value_and_holder &v_h, Scalar arg) {
-                detail::initimpl::setstate<Base>(v_h, static_cast<Type>(arg),
-                        Py_TYPE(v_h.inst) != v_h.type->type); },
+                detail::initimpl::setstate<Base>(
+                    v_h, static_cast<Type>(arg), Py_TYPE(v_h.inst) != v_h.type->type);
+            },
             detail::is_new_style_constructor(),
-            pybind11::name("__setstate__"), is_method(*this), arg("state"));
+            pybind11::name("__setstate__"),
+            is_method(*this),
+            arg("state"));
     }
 
     /// Export enumeration entries into the parent scope
-    enum_& export_values() {
+    enum_ &export_values() {
         m_base.export_values();
         return *this;
     }
 
     /// Add an enumeration entry
-    enum_& value(char const* name, Type value, const char *doc = nullptr) {
+    enum_ &value(char const *name, Type value, const char *doc = nullptr) {
         m_base.value(name, pybind11::cast(value, return_value_policy::copy), doc);
         return *this;
     }
@@ -2449,7 +2623,6 @@ template <typename Type> class enum_ : public class_<Type> {
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-
 PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
     if (!nurse || !patient) {
         pybind11_fail("Could not activate keep_alive!");
@@ -2464,13 +2637,14 @@ PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
         /* It's a pybind-registered type, so we can store the patient in the
          * internal list. */
         add_patient(nurse.ptr(), patient.ptr());
-    }
-    else {
+    } else {
         /* Fall back to clever approach based on weak references taken from
          * Boost.Python. This is not used for pybind-registered types because
          * the objects can be destroyed out-of-order in a GC pass. */
-        cpp_function disable_lifesupport(
-            [patient](handle weakref) { patient.dec_ref(); weakref.dec_ref(); });
+        cpp_function disable_lifesupport([patient](handle weakref) {
+            patient.dec_ref();
+            weakref.dec_ref();
+        });
 
         weakref wr(nurse, disable_lifesupport);
 
@@ -2479,7 +2653,8 @@ PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
     }
 }
 
-PYBIND11_NOINLINE void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
+PYBIND11_NOINLINE void
+keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
     auto get_arg = [&](size_t n) {
         if (n == 0) {
             return ret;
@@ -2496,31 +2671,34 @@ PYBIND11_NOINLINE void keep_alive_impl(size_t Nurse, size_t Patient, function_ca
     keep_alive_impl(get_arg(Nurse), get_arg(Patient));
 }
 
-inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type) {
-    auto res = get_internals().registered_types_py
+inline std::pair<decltype(internals::registered_types_py)::iterator, bool>
+all_type_info_get_cache(PyTypeObject *type) {
+    auto res = get_internals()
+                   .registered_types_py
 #ifdef __cpp_lib_unordered_map_try_emplace
-        .try_emplace(type);
+                   .try_emplace(type);
 #else
-        .emplace(type, std::vector<detail::type_info *>());
+                   .emplace(type, std::vector<detail::type_info *>());
 #endif
     if (res.second) {
         // New cache entry created; set up a weak reference to automatically remove it if the type
         // gets destroyed:
         weakref((PyObject *) type, cpp_function([type](handle wr) {
-            get_internals().registered_types_py.erase(type);
+                    get_internals().registered_types_py.erase(type);
 
-            // TODO consolidate the erasure code in pybind11_meta_dealloc() in class.h
-            auto &cache = get_internals().inactive_override_cache;
-            for (auto it = cache.begin(), last = cache.end(); it != last; ) {
-                if (it->first == reinterpret_cast<PyObject *>(type)) {
-                    it = cache.erase(it);
-                } else {
-                    ++it;
-                }
-            }
+                    // TODO consolidate the erasure code in pybind11_meta_dealloc() in class.h
+                    auto &cache = get_internals().inactive_override_cache;
+                    for (auto it = cache.begin(), last = cache.end(); it != last;) {
+                        if (it->first == reinterpret_cast<PyObject *>(type)) {
+                            it = cache.erase(it);
+                        } else {
+                            ++it;
+                        }
+                    }
 
-            wr.dec_ref();
-        })).release();
+                    wr.dec_ref();
+                }))
+            .release();
     }
 
     return res;
@@ -2529,7 +2707,12 @@ inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_t
 /* There are a large number of apparently unused template arguments because
  * each combination requires a separate py::class_ registration.
  */
-template <typename Access, return_value_policy Policy, typename Iterator, typename Sentinel, typename ValueType, typename... Extra>
+template <typename Access,
+          return_value_policy Policy,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType,
+          typename... Extra>
 struct iterator_state {
     Iterator it;
     Sentinel end;
@@ -2544,12 +2727,10 @@ template <typename Iterator, typename SFINAE = decltype(*std::declval<Iterator &
 struct iterator_access {
     using result_type = decltype(*std::declval<Iterator &>());
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
-    result_type operator()(Iterator &it) const {
-        return *it;
-    }
+    result_type operator()(Iterator &it) const { return *it; }
 };
 
-template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).first) >
+template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).first)>
 class iterator_key_access {
 private:
     using pair_type = decltype(*std::declval<Iterator &>());
@@ -2564,14 +2745,11 @@ class iterator_key_access {
      * (it's not used in the first branch because going via decltype and back
      * through declval does not perfectly preserve references).
      */
-    using result_type = conditional_t<
-        std::is_reference<decltype(*std::declval<Iterator &>())>::value,
-        decltype(((*std::declval<Iterator &>()).first)),
-        decltype(std::declval<pair_type>().first)
-    >;
-    result_type operator()(Iterator &it) const {
-        return (*it).first;
-    }
+    using result_type
+        = conditional_t<std::is_reference<decltype(*std::declval<Iterator &>())>::value,
+                        decltype(((*std::declval<Iterator &>()).first)),
+                        decltype(std::declval<pair_type>().first)>;
+    result_type operator()(Iterator &it) const { return (*it).first; }
 };
 
 template <typename Iterator, typename SFINAE = decltype((*std::declval<Iterator &>()).second)>
@@ -2580,14 +2758,11 @@ class iterator_value_access {
     using pair_type = decltype(*std::declval<Iterator &>());
 
 public:
-    using result_type = conditional_t<
-        std::is_reference<decltype(*std::declval<Iterator &>())>::value,
-        decltype(((*std::declval<Iterator &>()).second)),
-        decltype(std::declval<pair_type>().second)
-    >;
-    result_type operator()(Iterator &it) const {
-        return (*it).second;
-    }
+    using result_type
+        = conditional_t<std::is_reference<decltype(*std::declval<Iterator &>())>::value,
+                        decltype(((*std::declval<Iterator &>()).second)),
+                        decltype(std::declval<pair_type>().second)>;
+    result_type operator()(Iterator &it) const { return (*it).second; }
 };
 
 template <typename Access,
@@ -2596,7 +2771,7 @@ template <typename Access,
           typename Sentinel,
           typename ValueType,
           typename... Extra>
-iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&... extra) {
+iterator make_iterator_impl(Iterator first, Sentinel last, Extra &&...extra) {
     using state = detail::iterator_state<Access, Policy, Iterator, Sentinel, ValueType, Extra...>;
     // TODO: state captures only the types of Extra, not the values
 
@@ -2633,14 +2808,13 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename Sentinel,
           typename ValueType = typename detail::iterator_access<Iterator>::result_type,
           typename... Extra>
-iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_access<Iterator>,
-        Policy,
-        Iterator,
-        Sentinel,
-        ValueType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+iterator make_iterator(Iterator first, Sentinel last, Extra &&...extra) {
+    return detail::make_iterator_impl<detail::iterator_access<Iterator>,
+                                      Policy,
+                                      Iterator,
+                                      Sentinel,
+                                      ValueType,
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the keys (`.first`) of a iterator over pairs from a
@@ -2651,13 +2825,12 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename KeyType = typename detail::iterator_key_access<Iterator>::result_type,
           typename... Extra>
 iterator make_key_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_key_access<Iterator>,
-        Policy,
-        Iterator,
-        Sentinel,
-        KeyType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+    return detail::make_iterator_impl<detail::iterator_key_access<Iterator>,
+                                      Policy,
+                                      Iterator,
+                                      Sentinel,
+                                      KeyType,
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes a python iterator over the values (`.second`) of a iterator over pairs from a
@@ -2668,36 +2841,43 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
           typename ValueType = typename detail::iterator_value_access<Iterator>::result_type,
           typename... Extra>
 iterator make_value_iterator(Iterator first, Sentinel last, Extra &&...extra) {
-    return detail::make_iterator_impl<
-        detail::iterator_value_access<Iterator>,
-        Policy, Iterator,
-        Sentinel,
-        ValueType,
-        Extra...>(first, last, std::forward<Extra>(extra)...);
+    return detail::make_iterator_impl<detail::iterator_value_access<Iterator>,
+                                      Policy,
+                                      Iterator,
+                                      Sentinel,
+                                      ValueType,
+                                      Extra...>(first, last, std::forward<Extra>(extra)...);
 }
 
 /// Makes an iterator over values of an stl container or other container supporting
 /// `std::begin()`/`std::end()`
 template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_iterator(Type &value, Extra&&... extra) {
+          typename Type,
+          typename... Extra>
+iterator make_iterator(Type &value, Extra &&...extra) {
     return make_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
 /// Makes an iterator over the keys (`.first`) of a stl map-like container supporting
 /// `std::begin()`/`std::end()`
 template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_key_iterator(Type &value, Extra&&... extra) {
+          typename Type,
+          typename... Extra>
+iterator make_key_iterator(Type &value, Extra &&...extra) {
     return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
 /// Makes an iterator over the values (`.second`) of a stl map-like container supporting
 /// `std::begin()`/`std::end()`
 template <return_value_policy Policy = return_value_policy::reference_internal,
-          typename Type, typename... Extra> iterator make_value_iterator(Type &value, Extra&&... extra) {
+          typename Type,
+          typename... Extra>
+iterator make_value_iterator(Type &value, Extra &&...extra) {
     return make_value_iterator<Policy>(std::begin(value), std::end(value), extra...);
 }
 
-template <typename InputType, typename OutputType> void implicitly_convertible() {
+template <typename InputType, typename OutputType>
+void implicitly_convertible() {
     struct set_flag {
         bool &flag;
         explicit set_flag(bool &flag_) : flag(flag_) { flag_ = true; }
@@ -2728,19 +2908,17 @@ template <typename InputType, typename OutputType> void implicitly_convertible()
     }
 }
 
-
 inline void register_exception_translator(ExceptionTranslator &&translator) {
     detail::get_internals().registered_exception_translators.push_front(
         std::forward<ExceptionTranslator>(translator));
 }
 
-
 /**
-  * Add a new module-local exception translator. Locally registered functions
-  * will be tried before any globally registered exception translators, which
-  * will only be invoked if the module-local handlers do not deal with
-  * the exception.
-  */
+ * Add a new module-local exception translator. Locally registered functions
+ * will be tried before any globally registered exception translators, which
+ * will only be invoked if the module-local handlers do not deal with
+ * the exception.
+ */
 inline void register_local_exception_translator(ExceptionTranslator &&translator) {
     detail::get_local_internals().registered_exception_translators.push_front(
         std::forward<ExceptionTranslator>(translator));
@@ -2758,8 +2936,8 @@ class exception : public object {
 public:
     exception() = default;
     exception(handle scope, const char *name, handle base = PyExc_Exception) {
-        std::string full_name = scope.attr("__name__").cast<std::string>() +
-                                std::string(".") + name;
+        std::string full_name
+            = scope.attr("__name__").cast<std::string>() + std::string(".") + name;
         m_ptr = PyErr_NewException(const_cast<char *>(full_name.c_str()), base.ptr(), NULL);
         if (hasattr(scope, "__dict__") && scope.attr("__dict__").contains(name)) {
             pybind11_fail("Error during initialization: multiple incompatible "
@@ -2770,9 +2948,7 @@ class exception : public object {
     }
 
     // Sets the current python exception to this exception object with the given message
-    void operator()(const char *message) {
-        PyErr_SetString(m_ptr, message);
-    }
+    void operator()(const char *message) { PyErr_SetString(m_ptr, message); }
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -2780,21 +2956,22 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // register_exception approach below.  (It would be simpler to have the static local variable
 // directly in register_exception, but that makes clang <3.5 segfault - issue #1349).
 template <typename CppException>
-exception<CppException> &get_exception_object() { static exception<CppException> ex; return ex; }
+exception<CppException> &get_exception_object() {
+    static exception<CppException> ex;
+    return ex;
+}
 
 // Helper function for register_exception and register_local_exception
 template <typename CppException>
-exception<CppException> &register_exception_impl(handle scope,
-                                                const char *name,
-                                                handle base,
-                                                bool isLocal) {
+exception<CppException> &
+register_exception_impl(handle scope, const char *name, handle base, bool isLocal) {
     auto &ex = detail::get_exception_object<CppException>();
     if (!ex) {
         ex = exception<CppException>(scope, name, base);
     }
 
-    auto register_func = isLocal ? &register_local_exception_translator
-                                 : &register_exception_translator;
+    auto register_func
+        = isLocal ? &register_local_exception_translator : &register_exception_translator;
 
     register_func([](std::exception_ptr p) {
         if (!p) {
@@ -2818,9 +2995,8 @@ PYBIND11_NAMESPACE_END(detail)
  * exception object and translator directly.
  */
 template <typename CppException>
-exception<CppException> &register_exception(handle scope,
-                                            const char *name,
-                                            handle base = PyExc_Exception) {
+exception<CppException> &
+register_exception(handle scope, const char *name, handle base = PyExc_Exception) {
     return detail::register_exception_impl<CppException>(scope, name, base, false /* isLocal */);
 }
 
@@ -2833,9 +3009,8 @@ exception<CppException> &register_exception(handle scope,
  * exception object and translator directly.
  */
 template <typename CppException>
-exception<CppException> &register_local_exception(handle scope,
-                                                  const char *name,
-                                                  handle base = PyExc_Exception) {
+exception<CppException> &
+register_local_exception(handle scope, const char *name, handle base = PyExc_Exception) {
     return detail::register_exception_impl<CppException>(scope, name, base, true /* isLocal */);
 }
 
@@ -2890,7 +3065,8 @@ error_already_set::~error_already_set() {
 }
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-inline function get_type_override(const void *this_ptr, const type_info *this_type, const char *name)  {
+inline function
+get_type_override(const void *this_ptr, const type_info *this_type, const char *name) {
     handle self = get_object_handle(this_ptr, this_type);
     if (!self) {
         return function();
@@ -2914,13 +3090,13 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
     /* Don't call dispatch code if invoked from overridden function.
        Unfortunately this doesn't work on PyPy. */
 #if !defined(PYPY_VERSION)
-#if PY_VERSION_HEX >= 0x03090000
+#    if PY_VERSION_HEX >= 0x03090000
     PyFrameObject *frame = PyThreadState_GetFrame(PyThreadState_Get());
     if (frame != nullptr) {
         PyCodeObject *f_code = PyFrame_GetCode(frame);
         // f_code is guaranteed to not be NULL
         if ((std::string) str(f_code->co_name) == name && f_code->co_argcount > 0) {
-            PyObject* locals = PyEval_GetLocals();
+            PyObject *locals = PyEval_GetLocals();
             if (locals != nullptr) {
                 PyObject *co_varnames = PyObject_GetAttrString((PyObject *) f_code, "co_varnames");
                 PyObject *self_arg = PyTuple_GET_ITEM(co_varnames, 0);
@@ -2936,35 +3112,39 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
         Py_DECREF(f_code);
         Py_DECREF(frame);
     }
-#else
+#    else
     PyFrameObject *frame = PyThreadState_Get()->frame;
     if (frame != nullptr && (std::string) str(frame->f_code->co_name) == name
         && frame->f_code->co_argcount > 0) {
         PyFrame_FastToLocals(frame);
-        PyObject *self_caller = dict_getitem(
-            frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
+        PyObject *self_caller
+            = dict_getitem(frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
         if (self_caller == self.ptr()) {
             return function();
         }
     }
-#endif
+#    endif
 
 #else
     /* PyPy currently doesn't provide a detailed cpyext emulation of
        frame objects, so we have to emulate this using Python. This
        is going to be slow..*/
-    dict d; d["self"] = self; d["name"] = pybind11::str(name);
-    PyObject *result = PyRun_String(
-        "import inspect\n"
-        "frame = inspect.currentframe()\n"
-        "if frame is not None:\n"
-        "    frame = frame.f_back\n"
-        "    if frame is not None and str(frame.f_code.co_name) == name and "
-        "frame.f_code.co_argcount > 0:\n"
-        "        self_caller = frame.f_locals[frame.f_code.co_varnames[0]]\n"
-        "        if self_caller == self:\n"
-        "            self = None\n",
-        Py_file_input, d.ptr(), d.ptr());
+    dict d;
+    d["self"] = self;
+    d["name"] = pybind11::str(name);
+    PyObject *result
+        = PyRun_String("import inspect\n"
+                       "frame = inspect.currentframe()\n"
+                       "if frame is not None:\n"
+                       "    frame = frame.f_back\n"
+                       "    if frame is not None and str(frame.f_code.co_name) == name and "
+                       "frame.f_code.co_argcount > 0:\n"
+                       "        self_caller = frame.f_locals[frame.f_code.co_varnames[0]]\n"
+                       "        if self_caller == self:\n"
+                       "            self = None\n",
+                       Py_file_input,
+                       d.ptr(),
+                       d.ptr());
     if (result == nullptr)
         throw error_already_set();
     if (d["self"].is_none())
@@ -2985,7 +3165,8 @@ PYBIND11_NAMESPACE_END(detail)
   :name: The name of the overridden Python method to retrieve.
   :return: The Python method by this name from the object or an empty function wrapper.
  \endrst */
-template <class T> function get_override(const T *this_ptr, const char *name) {
+template <class T>
+function get_override(const T *this_ptr, const char *name) {
     auto *tinfo = detail::get_type_info(typeid(T));
     return tinfo ? detail::get_type_override(this_ptr, tinfo, name) : function();
 }
@@ -3023,20 +3204,21 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
         );
       }
 \endrst */
-#define PYBIND11_OVERRIDE_NAME(ret_type, cname, name, fn, ...) \
-    do { \
+#define PYBIND11_OVERRIDE_NAME(ret_type, cname, name, fn, ...)                                    \
+    do {                                                                                          \
         PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
-        return cname::fn(__VA_ARGS__); \
+        return cname::fn(__VA_ARGS__);                                                            \
     } while (false)
 
 /** \rst
     Macro for pure virtual functions, this function is identical to
     :c:macro:`PYBIND11_OVERRIDE_NAME`, except that it throws if no override can be found.
 \endrst */
-#define PYBIND11_OVERRIDE_PURE_NAME(ret_type, cname, name, fn, ...) \
-    do { \
+#define PYBIND11_OVERRIDE_PURE_NAME(ret_type, cname, name, fn, ...)                               \
+    do {                                                                                          \
         PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
-        pybind11::pybind11_fail("Tried to call pure virtual function \"" PYBIND11_STRINGIFY(cname) "::" name "\""); \
+        pybind11::pybind11_fail(                                                                  \
+            "Tried to call pure virtual function \"" PYBIND11_STRINGIFY(cname) "::" name "\"");   \
     } while (false)
 
 /** \rst
@@ -3064,21 +3246,22 @@ template <class T> function get_override(const T *this_ptr, const char *name) {
           }
       };
 \endrst */
-#define PYBIND11_OVERRIDE(ret_type, cname, fn, ...) \
+#define PYBIND11_OVERRIDE(ret_type, cname, fn, ...)                                               \
     PYBIND11_OVERRIDE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
 
 /** \rst
     Macro for pure virtual functions, this function is identical to :c:macro:`PYBIND11_OVERRIDE`,
     except that it throws if no override can be found.
 \endrst */
-#define PYBIND11_OVERRIDE_PURE(ret_type, cname, fn, ...) \
-    PYBIND11_OVERRIDE_PURE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
-
+#define PYBIND11_OVERRIDE_PURE(ret_type, cname, fn, ...)                                          \
+    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
+        PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
 
 // Deprecated versions
 
 PYBIND11_DEPRECATED("get_type_overload has been deprecated")
-inline function get_type_overload(const void *this_ptr, const detail::type_info *this_type, const char *name) {
+inline function
+get_type_overload(const void *this_ptr, const detail::type_info *this_type, const char *name) {
     return detail::get_type_override(this_ptr, this_type, name);
 }
 
@@ -3087,15 +3270,16 @@ inline function get_overload(const T *this_ptr, const char *name) {
     return get_override(this_ptr, name);
 }
 
-#define PYBIND11_OVERLOAD_INT(ret_type, cname, name, ...) \
+#define PYBIND11_OVERLOAD_INT(ret_type, cname, name, ...)                                         \
     PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__)
-#define PYBIND11_OVERLOAD_NAME(ret_type, cname, name, fn, ...) \
+#define PYBIND11_OVERLOAD_NAME(ret_type, cname, name, fn, ...)                                    \
     PYBIND11_OVERRIDE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, fn, __VA_ARGS__)
-#define PYBIND11_OVERLOAD_PURE_NAME(ret_type, cname, name, fn, ...) \
-    PYBIND11_OVERRIDE_PURE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, fn, __VA_ARGS__);
-#define PYBIND11_OVERLOAD(ret_type, cname, fn, ...) \
+#define PYBIND11_OVERLOAD_PURE_NAME(ret_type, cname, name, fn, ...)                               \
+    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
+        PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, fn, __VA_ARGS__);
+#define PYBIND11_OVERLOAD(ret_type, cname, fn, ...)                                               \
     PYBIND11_OVERRIDE(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), fn, __VA_ARGS__)
-#define PYBIND11_OVERLOAD_PURE(ret_type, cname, fn, ...) \
+#define PYBIND11_OVERLOAD_PURE(ret_type, cname, fn, ...)                                          \
     PYBIND11_OVERRIDE_PURE(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), fn, __VA_ARGS__);
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 4931b75512..204030a9aa 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -11,39 +11,44 @@
 
 #include "detail/common.h"
 #include "buffer_info.h"
+
 #include <iostream>
-#include <utility>
 #include <type_traits>
+#include <utility>
 
 #if defined(PYBIND11_HAS_OPTIONAL)
-#  include <optional>
+#    include <optional>
 #endif
 
 #ifdef PYBIND11_HAS_STRING_VIEW
-#  include <string_view>
+#    include <string_view>
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /* A few forward declarations */
-class handle; class object;
-class str; class iterator;
+class handle;
+class object;
+class str;
+class iterator;
 class type;
-struct arg; struct arg_v;
+struct arg;
+struct arg_v;
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 class args_proxy;
 bool isinstance_generic(handle obj, const std::type_info &tp);
 
 // Accessor forward declarations
-template <typename Policy> class accessor;
+template <typename Policy>
+class accessor;
 namespace accessor_policies {
-    struct obj_attr;
-    struct str_attr;
-    struct generic_item;
-    struct sequence_item;
-    struct list_item;
-    struct tuple_item;
+struct obj_attr;
+struct str_attr;
+struct generic_item;
+struct sequence_item;
+struct list_item;
+struct tuple_item;
 } // namespace accessor_policies
 using obj_attr_accessor = accessor<accessor_policies::obj_attr>;
 using str_attr_accessor = accessor<accessor_policies::str_attr>;
@@ -53,8 +58,9 @@ using list_accessor = accessor<accessor_policies::list_item>;
 using tuple_accessor = accessor<accessor_policies::tuple_item>;
 
 /// Tag and check to identify a class which implements the Python object API
-class pyobject_tag { };
-template <typename T> using is_pyobject = std::is_base_of<pyobject_tag, remove_reference_t<T>>;
+class pyobject_tag {};
+template <typename T>
+using is_pyobject = std::is_base_of<pyobject_tag, remove_reference_t<T>>;
 
 /** \rst
     A mixin class which adds common functions to `handle`, `object` and various accessors.
@@ -102,7 +108,8 @@ class object_api : public pyobject_tag {
     args_proxy operator*() const;
 
     /// Check if the given item is contained within this object, i.e. ``item in obj``.
-    template <typename T> bool contains(T &&item) const;
+    template <typename T>
+    bool contains(T &&item) const;
 
     /** \rst
         Assuming the Python object is a function or implements the ``__call__``
@@ -114,22 +121,24 @@ class object_api : public pyobject_tag {
         function will throw a `cast_error` exception. When the Python function
         call fails, a `error_already_set` exception is thrown.
     \endrst */
-    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    template <return_value_policy policy = return_value_policy::automatic_reference,
+              typename... Args>
     object operator()(Args &&...args) const;
-    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    template <return_value_policy policy = return_value_policy::automatic_reference,
+              typename... Args>
     PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
-        object call(Args&&... args) const;
+    object call(Args &&...args) const;
 
     /// Equivalent to ``obj is other`` in Python.
-    bool is(object_api const& other) const { return derived().ptr() == other.derived().ptr(); }
+    bool is(object_api const &other) const { return derived().ptr() == other.derived().ptr(); }
     /// Equivalent to ``obj is None`` in Python.
     bool is_none() const { return derived().ptr() == Py_None; }
     /// Equivalent to obj == other in Python
-    bool equal(object_api const &other) const      { return rich_compare(other, Py_EQ); }
-    bool not_equal(object_api const &other) const  { return rich_compare(other, Py_NE); }
-    bool operator<(object_api const &other) const  { return rich_compare(other, Py_LT); }
+    bool equal(object_api const &other) const { return rich_compare(other, Py_EQ); }
+    bool not_equal(object_api const &other) const { return rich_compare(other, Py_NE); }
+    bool operator<(object_api const &other) const { return rich_compare(other, Py_LT); }
     bool operator<=(object_api const &other) const { return rich_compare(other, Py_LE); }
-    bool operator>(object_api const &other) const  { return rich_compare(other, Py_GT); }
+    bool operator>(object_api const &other) const { return rich_compare(other, Py_GT); }
     bool operator>=(object_api const &other) const { return rich_compare(other, Py_GE); }
 
     object operator-() const;
@@ -189,7 +198,7 @@ class handle : public detail::object_api<handle> {
     handle() = default;
     /// Creates a ``handle`` from the given raw Python object pointer
     // NOLINTNEXTLINE(google-explicit-constructor)
-    handle(PyObject *ptr) : m_ptr(ptr) { } // Allow implicit conversion from PyObject*
+    handle(PyObject *ptr) : m_ptr(ptr) {} // Allow implicit conversion from PyObject*
 
     /// Return the underlying ``PyObject *`` pointer
     PyObject *ptr() const { return m_ptr; }
@@ -200,20 +209,27 @@ class handle : public detail::object_api<handle> {
         preferable to use the `object` class which derives from `handle` and calls
         this function automatically. Returns a reference to itself.
     \endrst */
-    const handle& inc_ref() const & { Py_XINCREF(m_ptr); return *this; }
+    const handle &inc_ref() const & {
+        Py_XINCREF(m_ptr);
+        return *this;
+    }
 
     /** \rst
         Manually decrease the reference count of the Python object. Usually, it is
         preferable to use the `object` class which derives from `handle` and calls
         this function automatically. Returns a reference to itself.
     \endrst */
-    const handle& dec_ref() const & { Py_XDECREF(m_ptr); return *this; }
+    const handle &dec_ref() const & {
+        Py_XDECREF(m_ptr);
+        return *this;
+    }
 
     /** \rst
         Attempt to cast the Python object into the given C++ type. A `cast_error`
         will be throw upon failure.
     \endrst */
-    template <typename T> T cast() const;
+    template <typename T>
+    T cast() const;
     /// Return ``true`` when the `handle` wraps a valid Python object
     explicit operator bool() const { return m_ptr != nullptr; }
     /** \rst
@@ -226,6 +242,7 @@ class handle : public detail::object_api<handle> {
     bool operator!=(const handle &h) const { return m_ptr != h.m_ptr; }
     PYBIND11_DEPRECATED("Use handle::operator bool() instead")
     bool check() const { return m_ptr != nullptr; }
+
 protected:
     PyObject *m_ptr = nullptr;
 };
@@ -252,7 +269,10 @@ class object : public handle {
     /// Copy constructor; always increases the reference count
     object(const object &o) : handle(o) { inc_ref(); }
     /// Move constructor; steals the object from ``other`` and preserves its reference count
-    object(object &&other) noexcept { m_ptr = other.m_ptr; other.m_ptr = nullptr; }
+    object(object &&other) noexcept {
+        m_ptr = other.m_ptr;
+        other.m_ptr = nullptr;
+    }
     /// Destructor; automatically calls `handle::dec_ref()`
     ~object() { dec_ref(); }
 
@@ -262,12 +282,12 @@ class object : public handle {
         Python object.
     \endrst */
     handle release() {
-      PyObject *tmp = m_ptr;
-      m_ptr = nullptr;
-      return handle(tmp);
+        PyObject *tmp = m_ptr;
+        m_ptr = nullptr;
+        return handle(tmp);
     }
 
-    object& operator=(const object &other) {
+    object &operator=(const object &other) {
         other.inc_ref();
         // Use temporary variable to ensure `*this` remains valid while
         // `Py_XDECREF` executes, in case `*this` is accessible from Python.
@@ -277,7 +297,7 @@ class object : public handle {
         return *this;
     }
 
-    object& operator=(object &&other) noexcept {
+    object &operator=(object &&other) noexcept {
         if (this != &other) {
             handle temp(m_ptr);
             m_ptr = other.m_ptr;
@@ -288,24 +308,28 @@ class object : public handle {
     }
 
     // Calling cast() on an object lvalue just copies (via handle::cast)
-    template <typename T> T cast() const &;
+    template <typename T>
+    T cast() const &;
     // Calling on an object rvalue does a move, if needed and/or possible
-    template <typename T> T cast() &&;
+    template <typename T>
+    T cast() &&;
 
 protected:
     // Tags for choosing constructors from raw PyObject *
-    struct borrowed_t { };
-    struct stolen_t { };
+    struct borrowed_t {};
+    struct stolen_t {};
 
     /// @cond BROKEN
-    template <typename T> friend T reinterpret_borrow(handle);
-    template <typename T> friend T reinterpret_steal(handle);
+    template <typename T>
+    friend T reinterpret_borrow(handle);
+    template <typename T>
+    friend T reinterpret_steal(handle);
     /// @endcond
 
 public:
     // Only accessible from derived classes and the reinterpret_* functions
     object(handle h, borrowed_t) : handle(h) { inc_ref(); }
-    object(handle h, stolen_t) : handle(h) { }
+    object(handle h, stolen_t) : handle(h) {}
 };
 
 /** \rst
@@ -321,7 +345,10 @@ class object : public handle {
         // or
         py::tuple t = reinterpret_borrow<py::tuple>(p); // <-- `p` must be already be a `tuple`
 \endrst */
-template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrowed_t{}}; }
+template <typename T>
+T reinterpret_borrow(handle h) {
+    return {h, object::borrowed_t{}};
+}
 
 /** \rst
     Like `reinterpret_borrow`, but steals the reference.
@@ -331,15 +358,18 @@ template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrow
         PyObject *p = PyObject_Str(obj);
         py::str s = reinterpret_steal<py::str>(p); // <-- `p` must be already be a `str`
 \endrst */
-template <typename T> T reinterpret_steal(handle h) { return {h, object::stolen_t{}}; }
+template <typename T>
+T reinterpret_steal(handle h) {
+    return {h, object::stolen_t{}};
+}
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 std::string error_string();
 PYBIND11_NAMESPACE_END(detail)
 
 #if defined(_MSC_VER)
-#  pragma warning(push)
-#  pragma warning(disable: 4275 4251)
+#    pragma warning(push)
+#    pragma warning(disable : 4275 4251)
 //     warning C4275: An exported class was derived from a class that wasn't exported.
 //     Can be ignored when derived from a STL class.
 #endif
@@ -363,19 +393,22 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
     /// Give the currently-held error back to Python, if any.  If there is currently a Python error
     /// already set it is cleared first.  After this call, the current object no longer stores the
     /// error variables (but the `.what()` string is still available).
-    void restore() { PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr()); }
+    void restore() {
+        PyErr_Restore(m_type.release().ptr(), m_value.release().ptr(), m_trace.release().ptr());
+    }
 
-    /// If it is impossible to raise the currently-held error, such as in a destructor, we can write
-    /// it out using Python's unraisable hook (`sys.unraisablehook`). The error context should be
-    /// some object whose `repr()` helps identify the location of the error. Python already knows the
-    /// type and value of the error, so there is no need to repeat that. After this call, the current
-    /// object no longer stores the error variables, and neither does Python.
+    /// If it is impossible to raise the currently-held error, such as in a destructor, we can
+    /// write it out using Python's unraisable hook (`sys.unraisablehook`). The error context
+    /// should be some object whose `repr()` helps identify the location of the error. Python
+    /// already knows the type and value of the error, so there is no need to repeat that. After
+    /// this call, the current object no longer stores the error variables, and neither does
+    /// Python.
     void discard_as_unraisable(object err_context) {
         restore();
         PyErr_WriteUnraisable(err_context.ptr());
     }
-    /// An alternate version of `discard_as_unraisable()`, where a string provides information on the
-    /// location of the error. For example, `__func__` could be helpful.
+    /// An alternate version of `discard_as_unraisable()`, where a string provides information on
+    /// the location of the error. For example, `__func__` could be helpful.
     void discard_as_unraisable(const char *err_context) {
         discard_as_unraisable(reinterpret_steal<object>(PYBIND11_FROM_STRING(err_context)));
     }
@@ -391,15 +424,15 @@ class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::runtime_error {
         return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
     }
 
-    const object& type() const { return m_type; }
-    const object& value() const { return m_value; }
-    const object& trace() const { return m_trace; }
+    const object &type() const { return m_type; }
+    const object &value() const { return m_value; }
+    const object &trace() const { return m_trace; }
 
 private:
     object m_type, m_value, m_trace;
 };
 #if defined(_MSC_VER)
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
 #if PY_VERSION_HEX >= 0x03030000
@@ -436,7 +469,7 @@ inline void raise_from(PyObject *type, const char *message) {
 /// from the error contained in error_already_set to indicate that the chosen error was
 /// caused by the original error. After this function is called error_already_set will
 /// no longer contain an error.
-inline void raise_from(error_already_set& err, PyObject *type, const char *message) {
+inline void raise_from(error_already_set &err, PyObject *type, const char *message) {
     err.restore();
     raise_from(type, message);
 }
@@ -454,13 +487,21 @@ inline void raise_from(error_already_set& err, PyObject *type, const char *messa
     `object` or a class which was exposed to Python as ``py::class_<T>``.
 \endrst */
 template <typename T, detail::enable_if_t<std::is_base_of<object, T>::value, int> = 0>
-bool isinstance(handle obj) { return T::check_(obj); }
+bool isinstance(handle obj) {
+    return T::check_(obj);
+}
 
 template <typename T, detail::enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
-bool isinstance(handle obj) { return detail::isinstance_generic(obj, typeid(T)); }
+bool isinstance(handle obj) {
+    return detail::isinstance_generic(obj, typeid(T));
+}
 
-template <> inline bool isinstance<handle>(handle) = delete;
-template <> inline bool isinstance<object>(handle obj) { return obj.ptr() != nullptr; }
+template <>
+inline bool isinstance<handle>(handle) = delete;
+template <>
+inline bool isinstance<object>(handle obj) {
+    return obj.ptr() != nullptr;
+}
 
 /// \ingroup python_builtins
 /// Return true if ``obj`` is an instance of the ``type``.
@@ -483,22 +524,30 @@ inline bool hasattr(handle obj, const char *name) {
 }
 
 inline void delattr(handle obj, handle name) {
-    if (PyObject_DelAttr(obj.ptr(), name.ptr()) != 0) { throw error_already_set(); }
+    if (PyObject_DelAttr(obj.ptr(), name.ptr()) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline void delattr(handle obj, const char *name) {
-    if (PyObject_DelAttrString(obj.ptr(), name) != 0) { throw error_already_set(); }
+    if (PyObject_DelAttrString(obj.ptr(), name) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline object getattr(handle obj, handle name) {
     PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr());
-    if (!result) { throw error_already_set(); }
+    if (!result) {
+        throw error_already_set();
+    }
     return reinterpret_steal<object>(result);
 }
 
 inline object getattr(handle obj, const char *name) {
     PyObject *result = PyObject_GetAttrString(obj.ptr(), name);
-    if (!result) { throw error_already_set(); }
+    if (!result) {
+        throw error_already_set();
+    }
     return reinterpret_steal<object>(result);
 }
 
@@ -519,16 +568,22 @@ inline object getattr(handle obj, const char *name, handle default_) {
 }
 
 inline void setattr(handle obj, handle name, handle value) {
-    if (PyObject_SetAttr(obj.ptr(), name.ptr(), value.ptr()) != 0) { throw error_already_set(); }
+    if (PyObject_SetAttr(obj.ptr(), name.ptr(), value.ptr()) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline void setattr(handle obj, const char *name, handle value) {
-    if (PyObject_SetAttrString(obj.ptr(), name, value.ptr()) != 0) { throw error_already_set(); }
+    if (PyObject_SetAttrString(obj.ptr(), name, value.ptr()) != 0) {
+        throw error_already_set();
+    }
 }
 
 inline ssize_t hash(handle obj) {
     auto h = PyObject_Hash(obj.ptr());
-    if (h == -1) { throw error_already_set(); }
+    if (h == -1) {
+        throw error_already_set();
+    }
     return h;
 }
 
@@ -553,8 +608,7 @@ inline handle get_function(handle value) {
 // aren't swallowed (see #2862)
 
 // copied from cpython _PyDict_GetItemStringWithError
-inline PyObject * dict_getitemstring(PyObject *v, const char *key)
-{
+inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
 #if PY_MAJOR_VERSION >= 3
     PyObject *kv = nullptr, *rv = nullptr;
     kv = PyUnicode_FromString(key);
@@ -573,8 +627,7 @@ inline PyObject * dict_getitemstring(PyObject *v, const char *key)
 #endif
 }
 
-inline PyObject * dict_getitem(PyObject *v, PyObject *key)
-{
+inline PyObject *dict_getitem(PyObject *v, PyObject *key) {
 #if PY_MAJOR_VERSION >= 3
     PyObject *rv = PyDict_GetItemWithError(v, key);
     if (rv == NULL && PyErr_Occurred()) {
@@ -586,11 +639,13 @@ inline PyObject * dict_getitem(PyObject *v, PyObject *key)
 #endif
 }
 
-// Helper aliases/functions to support implicit casting of values given to python accessors/methods.
-// When given a pyobject, this simply returns the pyobject as-is; for other C++ type, the value goes
-// through pybind11::cast(obj) to convert it to an `object`.
+// Helper aliases/functions to support implicit casting of values given to python
+// accessors/methods. When given a pyobject, this simply returns the pyobject as-is; for other C++
+// type, the value goes through pybind11::cast(obj) to convert it to an `object`.
 template <typename T, enable_if_t<is_pyobject<T>::value, int> = 0>
-auto object_or_cast(T &&o) -> decltype(std::forward<T>(o)) { return std::forward<T>(o); }
+auto object_or_cast(T &&o) -> decltype(std::forward<T>(o)) {
+    return std::forward<T>(o);
+}
 // The following casting version is implemented in cast.h:
 template <typename T, enable_if_t<!is_pyobject<T>::value, int> = 0>
 object object_or_cast(T &&o);
@@ -598,50 +653,61 @@ object object_or_cast(T &&o);
 inline handle object_or_cast(PyObject *ptr) { return ptr; }
 
 #if defined(_MSC_VER) && _MSC_VER < 1920
-#  pragma warning(push)
-#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
+#    pragma warning(push)
+#    pragma warning(disable : 4522) // warning C4522: multiple assignment operators specified
 #endif
 template <typename Policy>
 class accessor : public object_api<accessor<Policy>> {
     using key_type = typename Policy::key_type;
 
 public:
-    accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) { }
+    accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) {}
     accessor(const accessor &) = default;
     accessor(accessor &&) noexcept = default;
 
-    // accessor overload required to override default assignment operator (templates are not allowed
-    // to replace default compiler-generated assignments).
+    // accessor overload required to override default assignment operator (templates are not
+    // allowed to replace default compiler-generated assignments).
     void operator=(const accessor &a) && { std::move(*this).operator=(handle(a)); }
     void operator=(const accessor &a) & { operator=(handle(a)); }
 
-    template <typename T> void operator=(T &&value) && {
+    template <typename T>
+    void operator=(T &&value) && {
         Policy::set(obj, key, object_or_cast(std::forward<T>(value)));
     }
-    template <typename T> void operator=(T &&value) & {
+    template <typename T>
+    void operator=(T &&value) & {
         get_cache() = reinterpret_borrow<object>(object_or_cast(std::forward<T>(value)));
     }
 
     template <typename T = Policy>
-    PYBIND11_DEPRECATED("Use of obj.attr(...) as bool is deprecated in favor of pybind11::hasattr(obj, ...)")
-    explicit operator enable_if_t<std::is_same<T, accessor_policies::str_attr>::value ||
-            std::is_same<T, accessor_policies::obj_attr>::value, bool>() const {
+    PYBIND11_DEPRECATED(
+        "Use of obj.attr(...) as bool is deprecated in favor of pybind11::hasattr(obj, ...)")
+    explicit
+    operator enable_if_t<std::is_same<T, accessor_policies::str_attr>::value
+                             || std::is_same<T, accessor_policies::obj_attr>::value,
+                         bool>() const {
         return hasattr(obj, key);
     }
     template <typename T = Policy>
     PYBIND11_DEPRECATED("Use of obj[key] as bool is deprecated in favor of obj.contains(key)")
-    explicit operator enable_if_t<std::is_same<T, accessor_policies::generic_item>::value, bool>() const {
+    explicit
+    operator enable_if_t<std::is_same<T, accessor_policies::generic_item>::value, bool>() const {
         return obj.contains(key);
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator object() const { return get_cache(); }
     PyObject *ptr() const { return get_cache().ptr(); }
-    template <typename T> T cast() const { return get_cache().template cast<T>(); }
+    template <typename T>
+    T cast() const {
+        return get_cache().template cast<T>();
+    }
 
 private:
     object &get_cache() const {
-        if (!cache) { cache = Policy::get(obj, key); }
+        if (!cache) {
+            cache = Policy::get(obj, key);
+        }
         return cache;
     }
 
@@ -651,7 +717,7 @@ class accessor : public object_api<accessor<Policy>> {
     mutable object cache;
 };
 #if defined(_MSC_VER) && _MSC_VER < 1920
-#  pragma warning(pop)
+#    pragma warning(pop)
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(accessor_policies)
@@ -672,12 +738,16 @@ struct generic_item {
 
     static object get(handle obj, handle key) {
         PyObject *result = PyObject_GetItem(obj.ptr(), key.ptr());
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_steal<object>(result);
     }
 
     static void set(handle obj, handle key, handle val) {
-        if (PyObject_SetItem(obj.ptr(), key.ptr(), val.ptr()) != 0) { throw error_already_set(); }
+        if (PyObject_SetItem(obj.ptr(), key.ptr(), val.ptr()) != 0) {
+            throw error_already_set();
+        }
     }
 };
 
@@ -687,7 +757,9 @@ struct sequence_item {
     template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     static object get(handle obj, const IdxType &index) {
         PyObject *result = PySequence_GetItem(obj.ptr(), ssize_t_cast(index));
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_steal<object>(result);
     }
 
@@ -706,7 +778,9 @@ struct list_item {
     template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     static object get(handle obj, const IdxType &index) {
         PyObject *result = PyList_GetItem(obj.ptr(), ssize_t_cast(index));
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_borrow<object>(result);
     }
 
@@ -725,7 +799,9 @@ struct tuple_item {
     template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
     static object get(handle obj, const IdxType &index) {
         PyObject *result = PyTuple_GetItem(obj.ptr(), ssize_t_cast(index));
-        if (!result) { throw error_already_set(); }
+        if (!result) {
+            throw error_already_set();
+        }
         return reinterpret_borrow<object>(result);
     }
 
@@ -752,7 +828,7 @@ class generic_iterator : public Policy {
     using pointer = typename Policy::pointer;
 
     generic_iterator() = default;
-    generic_iterator(handle seq, ssize_t index) : Policy(seq, index) { }
+    generic_iterator(handle seq, ssize_t index) : Policy(seq, index) {}
 
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator*() const { return Policy::dereference(); }
@@ -760,22 +836,48 @@ class generic_iterator : public Policy {
     reference operator[](difference_type n) const { return *(*this + n); }
     pointer operator->() const { return **this; }
 
-    It &operator++() { Policy::increment(); return *this; }
-    It operator++(int) { auto copy = *this; Policy::increment(); return copy; }
-    It &operator--() { Policy::decrement(); return *this; }
-    It operator--(int) { auto copy = *this; Policy::decrement(); return copy; }
-    It &operator+=(difference_type n) { Policy::advance(n); return *this; }
-    It &operator-=(difference_type n) { Policy::advance(-n); return *this; }
+    It &operator++() {
+        Policy::increment();
+        return *this;
+    }
+    It operator++(int) {
+        auto copy = *this;
+        Policy::increment();
+        return copy;
+    }
+    It &operator--() {
+        Policy::decrement();
+        return *this;
+    }
+    It operator--(int) {
+        auto copy = *this;
+        Policy::decrement();
+        return copy;
+    }
+    It &operator+=(difference_type n) {
+        Policy::advance(n);
+        return *this;
+    }
+    It &operator-=(difference_type n) {
+        Policy::advance(-n);
+        return *this;
+    }
 
-    friend It operator+(const It &a, difference_type n) { auto copy = a; return copy += n; }
+    friend It operator+(const It &a, difference_type n) {
+        auto copy = a;
+        return copy += n;
+    }
     friend It operator+(difference_type n, const It &b) { return b + n; }
-    friend It operator-(const It &a, difference_type n) { auto copy = a; return copy -= n; }
+    friend It operator-(const It &a, difference_type n) {
+        auto copy = a;
+        return copy -= n;
+    }
     friend difference_type operator-(const It &a, const It &b) { return a.distance_to(b); }
 
     friend bool operator==(const It &a, const It &b) { return a.equal(b); }
     friend bool operator!=(const It &a, const It &b) { return !(a == b); }
-    friend bool operator< (const It &a, const It &b) { return b - a > 0; }
-    friend bool operator> (const It &a, const It &b) { return b < a; }
+    friend bool operator<(const It &a, const It &b) { return b - a > 0; }
+    friend bool operator>(const It &a, const It &b) { return b < a; }
     friend bool operator>=(const It &a, const It &b) { return !(a < b); }
     friend bool operator<=(const It &a, const It &b) { return !(a > b); }
 };
@@ -787,7 +889,7 @@ struct arrow_proxy {
     T value;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    arrow_proxy(T &&value) noexcept : value(std::move(value)) { }
+    arrow_proxy(T &&value) noexcept : value(std::move(value)) {}
     T *operator->() const { return &value; }
 };
 
@@ -799,7 +901,7 @@ class sequence_fast_readonly {
     using reference = const handle; // PR #3263
     using pointer = arrow_proxy<const handle>;
 
-    sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) { }
+    sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) {}
 
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference dereference() const { return *ptr; }
@@ -821,7 +923,7 @@ class sequence_slow_readwrite {
     using reference = sequence_accessor;
     using pointer = arrow_proxy<const sequence_accessor>;
 
-    sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) { }
+    sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) {}
 
     reference dereference() const { return {obj, static_cast<size_t>(index)}; }
     void increment() { ++index; }
@@ -887,33 +989,38 @@ inline bool PyNone_Check(PyObject *o) { return o == Py_None; }
 inline bool PyEllipsis_Check(PyObject *o) { return o == Py_Ellipsis; }
 
 #ifdef PYBIND11_STR_LEGACY_PERMISSIVE
-inline bool PyUnicode_Check_Permissive(PyObject *o) { return PyUnicode_Check(o) || PYBIND11_BYTES_CHECK(o); }
-#define PYBIND11_STR_CHECK_FUN detail::PyUnicode_Check_Permissive
+inline bool PyUnicode_Check_Permissive(PyObject *o) {
+    return PyUnicode_Check(o) || PYBIND11_BYTES_CHECK(o);
+}
+#    define PYBIND11_STR_CHECK_FUN detail::PyUnicode_Check_Permissive
 #else
-#define PYBIND11_STR_CHECK_FUN PyUnicode_Check
+#    define PYBIND11_STR_CHECK_FUN PyUnicode_Check
 #endif
 
 inline bool PyStaticMethod_Check(PyObject *o) { return o->ob_type == &PyStaticMethod_Type; }
 
 class kwargs_proxy : public handle {
 public:
-    explicit kwargs_proxy(handle h) : handle(h) { }
+    explicit kwargs_proxy(handle h) : handle(h) {}
 };
 
 class args_proxy : public handle {
 public:
-    explicit args_proxy(handle h) : handle(h) { }
+    explicit args_proxy(handle h) : handle(h) {}
     kwargs_proxy operator*() const { return kwargs_proxy(*this); }
 };
 
 /// Python argument categories (using PEP 448 terms)
-template <typename T> using is_keyword = std::is_base_of<arg, T>;
-template <typename T> using is_s_unpacking = std::is_same<args_proxy, T>; // * unpacking
-template <typename T> using is_ds_unpacking = std::is_same<kwargs_proxy, T>; // ** unpacking
-template <typename T> using is_positional = satisfies_none_of<T,
-    is_keyword, is_s_unpacking, is_ds_unpacking
->;
-template <typename T> using is_keyword_or_ds = satisfies_any_of<T, is_keyword, is_ds_unpacking>;
+template <typename T>
+using is_keyword = std::is_base_of<arg, T>;
+template <typename T>
+using is_s_unpacking = std::is_same<args_proxy, T>; // * unpacking
+template <typename T>
+using is_ds_unpacking = std::is_same<kwargs_proxy, T>; // ** unpacking
+template <typename T>
+using is_positional = satisfies_none_of<T, is_keyword, is_s_unpacking, is_ds_unpacking>;
+template <typename T>
+using is_keyword_or_ds = satisfies_any_of<T, is_keyword, is_ds_unpacking>;
 
 // Call argument collector forward declarations
 template <return_value_policy policy = return_value_policy::automatic_reference>
@@ -927,53 +1034,60 @@ PYBIND11_NAMESPACE_END(detail)
 //       inheriting ctors: `using Parent::Parent`. It's not an option right now because
 //       the `using` statement triggers the parent deprecation warning even if the ctor
 //       isn't even used.
-#define PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
-    public: \
-        PYBIND11_DEPRECATED("Use reinterpret_borrow<"#Name">() or reinterpret_steal<"#Name">()") \
-        Name(handle h, bool is_borrowed) : Parent(is_borrowed ? Parent(h, borrowed_t{}) : Parent(h, stolen_t{})) { } \
-        Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) { } \
-        Name(handle h, stolen_t) : Parent(h, stolen_t{}) { } \
-        PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead") \
-        bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); } \
-        static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); } \
-        template <typename Policy_> \
-        /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-        Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }
-
-#define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun) \
-    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
-    /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(const object &o) \
-    : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
-    { if (!m_ptr) throw error_already_set(); } \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(object &&o) \
-    : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
-    { if (!m_ptr) throw error_already_set(); }
-
-#define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun) \
-    PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun) \
-    Name() : Parent() { }
-
-#define PYBIND11_OBJECT_CHECK_FAILED(Name, o_ptr) \
-    ::pybind11::type_error("Object of type '" + \
-                           ::pybind11::detail::get_fully_qualified_tp_name(Py_TYPE(o_ptr)) + \
-                           "' is not an instance of '" #Name "'")
-
-#define PYBIND11_OBJECT(Name, Parent, CheckFun) \
-    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
-    /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(const object &o) : Parent(o) \
-    { if (m_ptr && !check_(m_ptr)) throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr); } \
-    /* NOLINTNEXTLINE(google-explicit-constructor) */ \
-    Name(object &&o) : Parent(std::move(o)) \
-    { if (m_ptr && !check_(m_ptr)) throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr); }
-
-#define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun) \
-    PYBIND11_OBJECT(Name, Parent, CheckFun) \
-    Name() : Parent() { }
+#define PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                            \
+public:                                                                                           \
+    PYBIND11_DEPRECATED("Use reinterpret_borrow<" #Name ">() or reinterpret_steal<" #Name ">()")  \
+    Name(handle h, bool is_borrowed)                                                              \
+        : Parent(is_borrowed ? Parent(h, borrowed_t{}) : Parent(h, stolen_t{})) {}                \
+    Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) {}                                       \
+    Name(handle h, stolen_t) : Parent(h, stolen_t{}) {}                                           \
+    PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead")                       \
+    bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); }                     \
+    static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); }              \
+    template <typename Policy_> /* NOLINTNEXTLINE(google-explicit-constructor) */                 \
+    Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) {}
+
+#define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                   \
+    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                                \
+    /* This is deliberately not 'explicit' to allow implicit conversion from object: */           \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(const object &o)                                                                         \
+        : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) {               \
+        if (!m_ptr)                                                                               \
+            throw error_already_set();                                                            \
+    }                                                                                             \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(object &&o) : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) {  \
+        if (!m_ptr)                                                                               \
+            throw error_already_set();                                                            \
+    }
+
+#define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun)                           \
+    PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                       \
+    Name() : Parent() {}
+
+#define PYBIND11_OBJECT_CHECK_FAILED(Name, o_ptr)                                                 \
+    ::pybind11::type_error("Object of type '"                                                     \
+                           + ::pybind11::detail::get_fully_qualified_tp_name(Py_TYPE(o_ptr))      \
+                           + "' is not an instance of '" #Name "'")
+
+#define PYBIND11_OBJECT(Name, Parent, CheckFun)                                                   \
+    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                                \
+    /* This is deliberately not 'explicit' to allow implicit conversion from object: */           \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(const object &o) : Parent(o) {                                                           \
+        if (m_ptr && !check_(m_ptr))                                                              \
+            throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr);                                      \
+    }                                                                                             \
+    /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
+    Name(object &&o) : Parent(std::move(o)) {                                                     \
+        if (m_ptr && !check_(m_ptr))                                                              \
+            throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr);                                      \
+    }
+
+#define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun)                                           \
+    PYBIND11_OBJECT(Name, Parent, CheckFun)                                                       \
+    Name() : Parent() {}
 
 /// \addtogroup pytypes
 /// @{
@@ -996,7 +1110,7 @@ class iterator : public object {
 
     PYBIND11_OBJECT_DEFAULT(iterator, object, PyIter_Check)
 
-    iterator& operator++() {
+    iterator &operator++() {
         advance();
         return *this;
     }
@@ -1010,13 +1124,16 @@ class iterator : public object {
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference operator*() const {
         if (m_ptr && !value.ptr()) {
-            auto& self = const_cast<iterator &>(*this);
+            auto &self = const_cast<iterator &>(*this);
             self.advance();
         }
         return value;
     }
 
-    pointer operator->() const { operator*(); return &value; }
+    pointer operator->() const {
+        operator*();
+        return &value;
+    }
 
     /** \rst
          The value which marks the end of the iteration. ``it == iterator::sentinel()``
@@ -1039,21 +1156,21 @@ class iterator : public object {
 private:
     void advance() {
         value = reinterpret_steal<object>(PyIter_Next(m_ptr));
-        if (PyErr_Occurred()) { throw error_already_set(); }
+        if (PyErr_Occurred()) {
+            throw error_already_set();
+        }
     }
 
 private:
     object value = {};
 };
 
-
-
 class type : public object {
 public:
     PYBIND11_OBJECT(type, object, PyType_Check)
 
     /// Return a type handle from a handle or an object
-    static handle handle_of(handle h) { return handle((PyObject*) Py_TYPE(h.ptr())); }
+    static handle handle_of(handle h) { return handle((PyObject *) Py_TYPE(h.ptr())); }
 
     /// Return a type object from a handle or an object
     static type of(handle h) { return type(type::handle_of(h), borrowed_t{}); }
@@ -1062,14 +1179,16 @@ class type : public object {
     /// Convert C++ type to handle if previously registered. Does not convert
     /// standard types, like int, float. etc. yet.
     /// See https://github.com/pybind/pybind11/issues/2486
-    template<typename T>
+    template <typename T>
     static handle handle_of();
 
     /// Convert C++ type to type if previously registered. Does not convert
     /// standard types, like int, float. etc. yet.
     /// See https://github.com/pybind/pybind11/issues/2486
-    template<typename T>
-    static type of() {return type(type::handle_of<T>(), borrowed_t{}); }
+    template <typename T>
+    static type of() {
+        return type(type::handle_of<T>(), borrowed_t{});
+    }
 };
 
 class iterable : public object {
@@ -1091,29 +1210,29 @@ class str : public object {
         }
     }
 
-    // 'explicit' is explicitly omitted from the following constructors to allow implicit conversion to py::str from C++ string-like objects
+    // 'explicit' is explicitly omitted from the following constructors to allow implicit
+    // conversion to py::str from C++ string-like objects
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(const char *c = "")
-        : object(PyUnicode_FromString(c), stolen_t{}) {
+    str(const char *c = "") : object(PyUnicode_FromString(c), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate string object!");
         }
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(const std::string &s) : str(s.data(), s.size()) { }
+    str(const std::string &s) : str(s.data(), s.size()) {}
 
 #ifdef PYBIND11_HAS_STRING_VIEW
     // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
     template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(T s) : str(s.data(), s.size()) { }
+    str(T s) : str(s.data(), s.size()) {}
 
-# ifdef PYBIND11_HAS_U8STRING
+#    ifdef PYBIND11_HAS_U8STRING
     // reinterpret_cast here is safe (C++20 guarantees char8_t has the same size/alignment as char)
     // NOLINTNEXTLINE(google-explicit-constructor)
-    str(std::u8string_view s) : str(reinterpret_cast<const char*>(s.data()), s.size()) { }
-# endif
+    str(std::u8string_view s) : str(reinterpret_cast<const char *>(s.data()), s.size()) {}
+#    endif
 
 #endif
 
@@ -1156,9 +1275,11 @@ class str : public object {
     static PyObject *raw_str(PyObject *op) {
         PyObject *str_value = PyObject_Str(op);
 #if PY_MAJOR_VERSION < 3
-        if (!str_value) throw error_already_set();
+        if (!str_value)
+            throw error_already_set();
         PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
-        Py_XDECREF(str_value); str_value = unicode;
+        Py_XDECREF(str_value);
+        str_value = unicode;
 #endif
         return str_value;
     }
@@ -1180,8 +1301,7 @@ class bytes : public object {
 
     // Allow implicit conversion:
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bytes(const char *c = "")
-        : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
+    bytes(const char *c = "") : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate bytes object!");
         }
@@ -1197,7 +1317,7 @@ class bytes : public object {
 
     // Allow implicit conversion:
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bytes(const std::string &s) : bytes(s.data(), s.size()) { }
+    bytes(const std::string &s) : bytes(s.data(), s.size()) {}
 
     explicit bytes(const pybind11::str &s);
 
@@ -1215,7 +1335,7 @@ class bytes : public object {
     // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
     template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bytes(T s) : bytes(s.data(), s.size()) { }
+    bytes(T s) : bytes(s.data(), s.size()) {}
 
     // Obtain a string view that views the current `bytes` buffer value.  Note that this is only
     // valid so long as the `bytes` instance remains alive and so generally should not outlive the
@@ -1230,7 +1350,6 @@ class bytes : public object {
         return {buffer, static_cast<size_t>(length)};
     }
 #endif
-
 };
 // Note: breathe >= 4.17.0 will fail to build docs if the below two constructors
 // are included in the doxygen group; close here and reopen after as a workaround
@@ -1256,7 +1375,7 @@ inline bytes::bytes(const pybind11::str &s) {
     m_ptr = obj.release().ptr();
 }
 
-inline str::str(const bytes& b) {
+inline str::str(const bytes &b) {
     char *buffer = nullptr;
     ssize_t length = 0;
     if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length)) {
@@ -1283,10 +1402,9 @@ class bytearray : public object {
         }
     }
 
-    bytearray()
-        : bytearray("", 0) {}
+    bytearray() : bytearray("", 0) {}
 
-    explicit bytearray(const std::string &s) : bytearray(s.data(), s.size()) { }
+    explicit bytearray(const std::string &s) : bytearray(s.data(), s.size()) {}
 
     size_t size() const { return static_cast<size_t>(PyByteArray_Size(m_ptr)); }
 
@@ -1305,22 +1423,22 @@ class bytearray : public object {
 class none : public object {
 public:
     PYBIND11_OBJECT(none, object, detail::PyNone_Check)
-    none() : object(Py_None, borrowed_t{}) { }
+    none() : object(Py_None, borrowed_t{}) {}
 };
 
 class ellipsis : public object {
 public:
     PYBIND11_OBJECT(ellipsis, object, detail::PyEllipsis_Check)
-    ellipsis() : object(Py_Ellipsis, borrowed_t{}) { }
+    ellipsis() : object(Py_Ellipsis, borrowed_t{}) {}
 };
 
 class bool_ : public object {
 public:
     PYBIND11_OBJECT_CVT(bool_, object, PyBool_Check, raw_bool)
-    bool_() : object(Py_False, borrowed_t{}) { }
+    bool_() : object(Py_False, borrowed_t{}) {}
     // Allow implicit conversion from and to `bool`:
     // NOLINTNEXTLINE(google-explicit-constructor)
-    bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) { }
+    bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) {}
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator bool() const { return (m_ptr != nullptr) && PyLong_AsLong(m_ptr) != 0; }
 
@@ -1358,10 +1476,9 @@ PYBIND11_NAMESPACE_END(detail)
 class int_ : public object {
 public:
     PYBIND11_OBJECT_CVT(int_, object, PYBIND11_LONG_CHECK, PyNumber_Long)
-    int_() : object(PyLong_FromLong(0), stolen_t{}) { }
+    int_() : object(PyLong_FromLong(0), stolen_t{}) {}
     // Allow implicit conversion from C++ integral types:
-    template <typename T,
-              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     int_(T value) {
         if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
@@ -1382,15 +1499,12 @@ class int_ : public object {
         }
     }
 
-    template <typename T,
-              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     operator T() const {
-        return std::is_unsigned<T>::value
-            ? detail::as_unsigned<T>(m_ptr)
-            : sizeof(T) <= sizeof(long)
-              ? (T) PyLong_AsLong(m_ptr)
-              : (T) PYBIND11_LONG_AS_LONGLONG(m_ptr);
+        return std::is_unsigned<T>::value  ? detail::as_unsigned<T>(m_ptr)
+               : sizeof(T) <= sizeof(long) ? (T) PyLong_AsLong(m_ptr)
+                                           : (T) PYBIND11_LONG_AS_LONGLONG(m_ptr);
     }
 };
 
@@ -1427,9 +1541,7 @@ class weakref : public object {
     }
 
 private:
-    static PyObject *raw_weakref(PyObject *o) {
-        return PyWeakref_NewRef(o, nullptr);
-    }
+    static PyObject *raw_weakref(PyObject *o) { return PyWeakref_NewRef(o, nullptr); }
 };
 
 class slice : public object {
@@ -1450,19 +1562,21 @@ class slice : public object {
         : slice(int_(start_), int_(stop_), int_(step_)) {}
 #endif
 
-    bool compute(size_t length, size_t *start, size_t *stop, size_t *step,
-                 size_t *slicelength) const {
+    bool
+    compute(size_t length, size_t *start, size_t *stop, size_t *step, size_t *slicelength) const {
         return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
-                                    (ssize_t) length, (ssize_t *) start,
-                                    (ssize_t *) stop, (ssize_t *) step,
-                                    (ssize_t *) slicelength) == 0;
+                                    (ssize_t) length,
+                                    (ssize_t *) start,
+                                    (ssize_t *) stop,
+                                    (ssize_t *) step,
+                                    (ssize_t *) slicelength)
+               == 0;
     }
-    bool compute(ssize_t length, ssize_t *start, ssize_t *stop, ssize_t *step,
-      ssize_t *slicelength) const {
-      return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
-          length, start,
-          stop, step,
-          slicelength) == 0;
+    bool compute(
+        ssize_t length, ssize_t *start, ssize_t *stop, ssize_t *step, ssize_t *slicelength) const {
+        return PySlice_GetIndicesEx(
+                   (PYBIND11_SLICE_OBJECT *) m_ptr, length, start, stop, step, slicelength)
+               == 0;
     }
 
 private:
@@ -1476,9 +1590,12 @@ class capsule : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(capsule, object, PyCapsule_CheckExact)
     PYBIND11_DEPRECATED("Use reinterpret_borrow<capsule>() or reinterpret_steal<capsule>()")
-    capsule(PyObject *ptr, bool is_borrowed) : object(is_borrowed ? object(ptr, borrowed_t{}) : object(ptr, stolen_t{})) { }
+    capsule(PyObject *ptr, bool is_borrowed)
+        : object(is_borrowed ? object(ptr, borrowed_t{}) : object(ptr, stolen_t{})) {}
 
-    explicit capsule(const void *value, const char *name = nullptr, void (*destructor)(PyObject *) = nullptr)
+    explicit capsule(const void *value,
+                     const char *name = nullptr,
+                     void (*destructor)(PyObject *) = nullptr)
         : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
@@ -1487,7 +1604,7 @@ class capsule : public object {
 
     PYBIND11_DEPRECATED("Please pass a destructor that takes a void pointer as input")
     capsule(const void *value, void (*destruct)(PyObject *))
-        : object(PyCapsule_New(const_cast<void*>(value), nullptr, destruct), stolen_t{}) {
+        : object(PyCapsule_New(const_cast<void *>(value), nullptr, destruct), stolen_t{}) {
         if (!m_ptr) {
             pybind11_fail("Could not allocate capsule object!");
         }
@@ -1526,8 +1643,8 @@ class capsule : public object {
     }
 
     /// Get the pointer the capsule holds.
-    template<typename T = void>
-    T* get_pointer() const {
+    template <typename T = void>
+    T *get_pointer() const {
         const auto *name = this->name();
         T *result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
         if (!result) {
@@ -1571,9 +1688,8 @@ class tuple : public object {
 // fails to compile enable_if_t<all_of<is_keyword_or_ds<Args>...>::value> part below
 // (tested with ICC 2021.1 Beta 20200827).
 template <typename... Args>
-constexpr bool args_are_all_keyword_or_ds()
-{
-  return detail::all_of<detail::is_keyword_or_ds<Args>...>::value;
+constexpr bool args_are_all_keyword_or_ds() {
+    return detail::all_of<detail::is_keyword_or_ds<Args>...>::value;
 }
 
 class dict : public object {
@@ -1586,16 +1702,18 @@ class dict : public object {
     }
     template <typename... Args,
               typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>,
-              // MSVC workaround: it can't compile an out-of-line definition, so defer the collector
+              // MSVC workaround: it can't compile an out-of-line definition, so defer the
+              // collector
               typename collector = detail::deferred_t<detail::unpacking_collector<>, Args...>>
-    explicit dict(Args &&...args) : dict(collector(std::forward<Args>(args)...).kwargs()) { }
+    explicit dict(Args &&...args) : dict(collector(std::forward<Args>(args)...).kwargs()) {}
 
     size_t size() const { return (size_t) PyDict_Size(m_ptr); }
     bool empty() const { return size() == 0; }
     detail::dict_iterator begin() const { return {*this, 0}; }
     detail::dict_iterator end() const { return {}; }
     void clear() /* py-non-const */ { PyDict_Clear(ptr()); }
-    template <typename T> bool contains(T &&key) const {
+    template <typename T>
+    bool contains(T &&key) const {
         return PyDict_Contains(m_ptr, detail::object_or_cast(std::forward<T>(key)).ptr()) == 1;
     }
 
@@ -1643,7 +1761,8 @@ class list : public object {
     detail::item_accessor operator[](handle h) const { return object::operator[](h); }
     detail::list_iterator begin() const { return {*this, 0}; }
     detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
-    template <typename T> void append(T &&val) /* py-non-const */ {
+    template <typename T>
+    void append(T &&val) /* py-non-const */ {
         PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
     }
     template <typename IdxType,
@@ -1655,8 +1774,12 @@ class list : public object {
     }
 };
 
-class args : public tuple { PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check) };
-class kwargs : public dict { PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)  };
+class args : public tuple {
+    PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check)
+};
+class kwargs : public dict {
+    PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)
+};
 
 class set : public object {
 public:
@@ -1668,11 +1791,13 @@ class set : public object {
     }
     size_t size() const { return (size_t) PySet_Size(m_ptr); }
     bool empty() const { return size() == 0; }
-    template <typename T> bool add(T &&val) /* py-non-const */ {
+    template <typename T>
+    bool add(T &&val) /* py-non-const */ {
         return PySet_Add(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 0;
     }
     void clear() /* py-non-const */ { PySet_Clear(m_ptr); }
-    template <typename T> bool contains(T &&val) const {
+    template <typename T>
+    bool contains(T &&val) const {
         return PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 1;
     }
 };
@@ -1726,14 +1851,13 @@ class memoryview : public object {
         For creating a ``memoryview`` from objects that support buffer protocol,
         use ``memoryview(const object& obj)`` instead of this constructor.
      \endrst */
-    explicit memoryview(const buffer_info& info) {
+    explicit memoryview(const buffer_info &info) {
         if (!info.view()) {
             pybind11_fail("Prohibited to create memoryview without Py_buffer");
         }
         // Note: PyMemoryView_FromBuffer never increments obj reference.
-        m_ptr = (info.view()->obj) ?
-            PyMemoryView_FromObject(info.view()->obj) :
-            PyMemoryView_FromBuffer(info.view());
+        m_ptr = (info.view()->obj) ? PyMemoryView_FromObject(info.view()->obj)
+                                   : PyMemoryView_FromBuffer(info.view());
         if (!m_ptr) {
             pybind11_fail("Unable to create memoryview from buffer descriptor");
         }
@@ -1763,34 +1887,40 @@ class memoryview : public object {
         :param readonly: Flag to indicate if the underlying storage may be
             written to.
      \endrst */
-    static memoryview from_buffer(
-        void *ptr, ssize_t itemsize, const char *format,
-        detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides, bool readonly = false);
-
-    static memoryview from_buffer(
-        const void *ptr, ssize_t itemsize, const char *format,
-        detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides) {
+    static memoryview from_buffer(void *ptr,
+                                  ssize_t itemsize,
+                                  const char *format,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides,
+                                  bool readonly = false);
+
+    static memoryview from_buffer(const void *ptr,
+                                  ssize_t itemsize,
+                                  const char *format,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides) {
         return memoryview::from_buffer(
             const_cast<void *>(ptr), itemsize, format, std::move(shape), std::move(strides), true);
     }
 
-    template<typename T>
-    static memoryview from_buffer(
-        T *ptr, detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides, bool readonly = false) {
-        return memoryview::from_buffer(
-            reinterpret_cast<void*>(ptr), sizeof(T),
-            format_descriptor<T>::value, shape, strides, readonly);
+    template <typename T>
+    static memoryview from_buffer(T *ptr,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides,
+                                  bool readonly = false) {
+        return memoryview::from_buffer(reinterpret_cast<void *>(ptr),
+                                       sizeof(T),
+                                       format_descriptor<T>::value,
+                                       shape,
+                                       strides,
+                                       readonly);
     }
 
-    template<typename T>
-    static memoryview from_buffer(
-        const T *ptr, detail::any_container<ssize_t> shape,
-        detail::any_container<ssize_t> strides) {
-        return memoryview::from_buffer(
-            const_cast<T*>(ptr), shape, strides, true);
+    template <typename T>
+    static memoryview from_buffer(const T *ptr,
+                                  detail::any_container<ssize_t> shape,
+                                  detail::any_container<ssize_t> strides) {
+        return memoryview::from_buffer(const_cast<T *>(ptr), shape, strides, true);
     }
 
 #if PY_MAJOR_VERSION >= 3
@@ -1809,9 +1939,8 @@ class memoryview : public object {
            https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromMemory
      \endrst */
     static memoryview from_memory(void *mem, ssize_t size, bool readonly = false) {
-        PyObject* ptr = PyMemoryView_FromMemory(
-            reinterpret_cast<char*>(mem), size,
-            (readonly) ? PyBUF_READ : PyBUF_WRITE);
+        PyObject *ptr = PyMemoryView_FromMemory(
+            reinterpret_cast<char *>(mem), size, (readonly) ? PyBUF_READ : PyBUF_WRITE);
         if (!ptr) {
             pybind11_fail("Could not allocate memoryview object!");
         }
@@ -1819,23 +1948,25 @@ class memoryview : public object {
     }
 
     static memoryview from_memory(const void *mem, ssize_t size) {
-        return memoryview::from_memory(const_cast<void*>(mem), size, true);
+        return memoryview::from_memory(const_cast<void *>(mem), size, true);
     }
 
-#ifdef PYBIND11_HAS_STRING_VIEW
+#    ifdef PYBIND11_HAS_STRING_VIEW
     static memoryview from_memory(std::string_view mem) {
-        return from_memory(const_cast<char*>(mem.data()), static_cast<ssize_t>(mem.size()), true);
+        return from_memory(const_cast<char *>(mem.data()), static_cast<ssize_t>(mem.size()), true);
     }
-#endif
+#    endif
 
 #endif
 };
 
 /// @cond DUPLICATE
-inline memoryview memoryview::from_buffer(
-    void *ptr, ssize_t itemsize, const char* format,
-    detail::any_container<ssize_t> shape,
-    detail::any_container<ssize_t> strides, bool readonly) {
+inline memoryview memoryview::from_buffer(void *ptr,
+                                          ssize_t itemsize,
+                                          const char *format,
+                                          detail::any_container<ssize_t> shape,
+                                          detail::any_container<ssize_t> strides,
+                                          bool readonly) {
     size_t ndim = shape->size();
     if (ndim != strides->size()) {
         pybind11_fail("memoryview: shape length doesn't match strides length");
@@ -1850,13 +1981,13 @@ inline memoryview memoryview::from_buffer(
     view.len = size * itemsize;
     view.readonly = static_cast<int>(readonly);
     view.itemsize = itemsize;
-    view.format = const_cast<char*>(format);
+    view.format = const_cast<char *>(format);
     view.ndim = static_cast<int>(ndim);
     view.shape = shape->data();
     view.strides = strides->data();
     view.suboffsets = nullptr;
     view.internal = nullptr;
-    PyObject* obj = PyMemoryView_FromBuffer(&view);
+    PyObject *obj = PyMemoryView_FromBuffer(&view);
     if (!obj) {
         throw error_already_set();
     }
@@ -1901,15 +2032,19 @@ inline str repr(handle h) {
     }
 #if PY_MAJOR_VERSION < 3
     PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
-    Py_XDECREF(str_value); str_value = unicode;
-    if (!str_value) throw error_already_set();
+    Py_XDECREF(str_value);
+    str_value = unicode;
+    if (!str_value)
+        throw error_already_set();
 #endif
     return reinterpret_steal<str>(str_value);
 }
 
 inline iterator iter(handle obj) {
     PyObject *result = PyObject_GetIter(obj.ptr());
-    if (!result) { throw error_already_set(); }
+    if (!result) {
+        throw error_already_set();
+    }
     return reinterpret_steal<iterator>(result);
 }
 /// @} python_builtins
@@ -1921,128 +2056,150 @@ inline iterator iter(handle obj) {
 /// @note Do NOT use the methods in this class.
 template <typename Base>
 class wrapper : public Base {
- public:
-  using Base::Base;
-
-  virtual ~wrapper() {  // NOLINT(modernize-use-override)
-      delete_py_if_in_cpp();
-  }
-
-  // To be used by the holder casters, by means of `wrapper_interface<>`.
-  // TODO(eric.cousineau): Make this private to ensure contract?
-  void use_cpp_lifetime(object&& patient, detail::HolderTypeId holder_type_id) {
-      if (lives_in_cpp()) {
-          throw std::runtime_error("Instance already lives in C++");
-      }
-      holder_type_id_ = holder_type_id;
-      patient_ = std::move(patient);
-      // @note It would be nice to put `resurrect_python3` here, but this is called by
-      // `PyObject_CallFinalizer`, which will end up reversing its effect anyways.
-  }
-
-  /// To be used by `move_only_holder_caster`.
-  object release_cpp_lifetime() {
-      if (!lives_in_cpp()) {
-          throw std::runtime_error("Instance does not live in C++");
-      }
-      resurrect_python3();
-      // Remove existing reference.
-      object tmp = std::move(patient_);
-      assert(!patient_);
-      return tmp;
-  }
-
- protected:
+public:
+    using Base::Base;
+
+    virtual ~wrapper() { // NOLINT(modernize-use-override)
+        delete_py_if_in_cpp();
+    }
+
+    // To be used by the holder casters, by means of `wrapper_interface<>`.
+    // TODO(eric.cousineau): Make this private to ensure contract?
+    void use_cpp_lifetime(object &&patient, detail::HolderTypeId holder_type_id) {
+        if (lives_in_cpp()) {
+            throw std::runtime_error("Instance already lives in C++");
+        }
+        holder_type_id_ = holder_type_id;
+        patient_ = std::move(patient);
+        // @note It would be nice to put `resurrect_python3` here, but this is called by
+        // `PyObject_CallFinalizer`, which will end up reversing its effect anyways.
+    }
+
+    /// To be used by `move_only_holder_caster`.
+    object release_cpp_lifetime() {
+        if (!lives_in_cpp()) {
+            throw std::runtime_error("Instance does not live in C++");
+        }
+        resurrect_python3();
+        // Remove existing reference.
+        object tmp = std::move(patient_);
+        assert(!patient_);
+        return tmp;
+    }
+
+protected:
     // TODO(eric.cousineau): Verify this with an example workflow.
-  void delete_py_if_in_cpp() {
-      if (lives_in_cpp()) {
-          // Ensure that we still are the unique one, such that the Python classes
-          // destructor will be called.
+    void delete_py_if_in_cpp() {
+        if (lives_in_cpp()) {
+            // Ensure that we still are the unique one, such that the Python classes
+            // destructor will be called.
 #ifdef PYBIND11_WARN_DANGLING_UNIQUE_PYREF
-          if (holder_type_id_ == detail::HolderTypeId::UniquePtr) {
-              if (patient_.ref_count() != 1) {
-                  // TODO(eric.cousineau): Add Python class name
-                  std::string class_name = patient_.get_type().str();
-                  std::cerr
-                      << "WARNING(pybind11): When destroying Python subclass (" << class_name << "), "
-                      << "of a pybind11 class using a unique_ptr holder in C++, "
-                      << "ref_count == " << patient_.ref_count() << " != 1, which may cause undefined behavior." << std::endl
-                      << "  Please consider reviewing your code to trim existing references, or use a move-compatible container." << std::endl;
-              }
-          }
-#endif  // PYBIND11_WARN_DANGLING_UNIQUE_HOLDER
-          // Release object.
-          release_cpp_lifetime();
-      }
-  }
-
-  // Handle PEP 442, implemented in Python3, where resurrection more than once
-  // is a bit more dicey.
-  inline void resurrect_python3() {
-#if PY_VERSION_HEX >= 0x03080000
-    // Leak it as a means to stay alive for now.
-    // See: https://bugs.python.org/issue40240
-    if (_PyGC_FINALIZED(patient_.ptr())) {
-        if (leaked_) {
-          throw std::runtime_error("__del__ called twice in Python 3.8+?");
+            if (holder_type_id_ == detail::HolderTypeId::UniquePtr) {
+                if (patient_.ref_count() != 1) {
+                    // TODO(eric.cousineau): Add Python class name
+                    std::string class_name = patient_.get_type().str();
+                    std::cerr << "WARNING(pybind11): When destroying Python subclass ("
+                              << class_name << "), "
+                              << "of a pybind11 class using a unique_ptr holder in C++, "
+                              << "ref_count == " << patient_.ref_count()
+                              << " != 1, which may cause undefined behavior." << std::endl
+                              << "  Please consider reviewing your code to trim existing "
+                                 "references, or use a move-compatible container."
+                              << std::endl;
+                }
+            }
+#endif // PYBIND11_WARN_DANGLING_UNIQUE_HOLDER
+       // Release object.
+            release_cpp_lifetime();
         }
-        leaked_ = true;
-        patient_.inc_ref();
     }
+
+    // Handle PEP 442, implemented in Python3, where resurrection more than once
+    // is a bit more dicey.
+    inline void resurrect_python3() {
+#if PY_VERSION_HEX >= 0x03080000
+        // Leak it as a means to stay alive for now.
+        // See: https://bugs.python.org/issue40240
+        if (_PyGC_FINALIZED(patient_.ptr())) {
+            if (leaked_) {
+                throw std::runtime_error("__del__ called twice in Python 3.8+?");
+            }
+            leaked_ = true;
+            patient_.inc_ref();
+        }
 #elif PY_VERSION_HEX >= 0x03000000
-    // Reverse single-finalization constraint in Python3.
-    // This was a really dirty workaround:
-    // See: https://bugs.python.org/issue32377
-    if (_PyGC_FINALIZED(patient_.ptr())) {
-        _PyGC_SET_FINALIZED(patient_.ptr(), 0);
-    }
-#endif  // PY_VERSION_HEX >= 0x03080000
-  }
-
- private:
-  inline bool lives_in_cpp() const {
-      // NOTE: This is *false* if, for whatever reason, the wrapper class is
-      // constructed in C++... Meh. Not gonna worry about that situation.
-      return static_cast<bool>(patient_);
-  }
-
-  object patient_;
-  detail::HolderTypeId holder_type_id_{detail::HolderTypeId::Unknown};
+        // Reverse single-finalization constraint in Python3.
+        // This was a really dirty workaround:
+        // See: https://bugs.python.org/issue32377
+        if (_PyGC_FINALIZED(patient_.ptr())) {
+            _PyGC_SET_FINALIZED(patient_.ptr(), 0);
+        }
+#endif // PY_VERSION_HEX >= 0x03080000
+    }
+
+private:
+    inline bool lives_in_cpp() const {
+        // NOTE: This is *false* if, for whatever reason, the wrapper class is
+        // constructed in C++... Meh. Not gonna worry about that situation.
+        return static_cast<bool>(patient_);
+    }
+
+    object patient_;
+    detail::HolderTypeId holder_type_id_{detail::HolderTypeId::Unknown};
 #if PY_VERSION_HEX >= 0x03080000
-  bool leaked_{false};
-#endif  // PY_VERSION_HEX >= 0x03080000
+    bool leaked_{false};
+#endif // PY_VERSION_HEX >= 0x03080000
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
-template <typename D> iterator object_api<D>::begin() const { return iter(derived()); }
-template <typename D> iterator object_api<D>::end() const { return iterator::sentinel(); }
-template <typename D> item_accessor object_api<D>::operator[](handle key) const {
+template <typename D>
+iterator object_api<D>::begin() const {
+    return iter(derived());
+}
+template <typename D>
+iterator object_api<D>::end() const {
+    return iterator::sentinel();
+}
+template <typename D>
+item_accessor object_api<D>::operator[](handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
 }
-template <typename D> item_accessor object_api<D>::operator[](const char *key) const {
+template <typename D>
+item_accessor object_api<D>::operator[](const char *key) const {
     return {derived(), pybind11::str(key)};
 }
-template <typename D> obj_attr_accessor object_api<D>::attr(handle key) const {
+template <typename D>
+obj_attr_accessor object_api<D>::attr(handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
 }
-template <typename D> str_attr_accessor object_api<D>::attr(const char *key) const {
+template <typename D>
+str_attr_accessor object_api<D>::attr(const char *key) const {
     return {derived(), key};
 }
-template <typename D> args_proxy object_api<D>::operator*() const {
+template <typename D>
+args_proxy object_api<D>::operator*() const {
     return args_proxy(derived().ptr());
 }
-template <typename D> template <typename T> bool object_api<D>::contains(T &&item) const {
+template <typename D>
+template <typename T>
+bool object_api<D>::contains(T &&item) const {
     return attr("__contains__")(std::forward<T>(item)).template cast<bool>();
 }
 
 template <typename D>
-pybind11::str object_api<D>::str() const { return pybind11::str(derived()); }
+pybind11::str object_api<D>::str() const {
+    return pybind11::str(derived());
+}
 
 template <typename D>
-str_attr_accessor object_api<D>::doc() const { return attr("__doc__"); }
+str_attr_accessor object_api<D>::doc() const {
+    return attr("__doc__");
+}
 
 template <typename D>
-handle object_api<D>::get_type() const { return type::handle_of(derived()); }
+handle object_api<D>::get_type() const {
+    return type::handle_of(derived());
+}
 
 template <typename D>
 bool object_api<D>::rich_compare(object_api const &other, int value) const {
@@ -2053,43 +2210,43 @@ bool object_api<D>::rich_compare(object_api const &other, int value) const {
     return rv == 1;
 }
 
-#define PYBIND11_MATH_OPERATOR_UNARY(op, fn)                                   \
-    template <typename D> object object_api<D>::op() const {                   \
-        object result = reinterpret_steal<object>(fn(derived().ptr()));        \
-        if (!result.ptr())                                                     \
-            throw error_already_set();                                         \
-        return result;                                                         \
-    }
-
-#define PYBIND11_MATH_OPERATOR_BINARY(op, fn)                                  \
-    template <typename D>                                                      \
-    object object_api<D>::op(object_api const &other) const {                  \
-        object result = reinterpret_steal<object>(                             \
-            fn(derived().ptr(), other.derived().ptr()));                       \
-        if (!result.ptr())                                                     \
-            throw error_already_set();                                         \
-        return result;                                                         \
-    }
-
-PYBIND11_MATH_OPERATOR_UNARY (operator~,   PyNumber_Invert)
-PYBIND11_MATH_OPERATOR_UNARY (operator-,   PyNumber_Negative)
-PYBIND11_MATH_OPERATOR_BINARY(operator+,   PyNumber_Add)
-PYBIND11_MATH_OPERATOR_BINARY(operator+=,  PyNumber_InPlaceAdd)
-PYBIND11_MATH_OPERATOR_BINARY(operator-,   PyNumber_Subtract)
-PYBIND11_MATH_OPERATOR_BINARY(operator-=,  PyNumber_InPlaceSubtract)
-PYBIND11_MATH_OPERATOR_BINARY(operator*,   PyNumber_Multiply)
-PYBIND11_MATH_OPERATOR_BINARY(operator*=,  PyNumber_InPlaceMultiply)
-PYBIND11_MATH_OPERATOR_BINARY(operator/,   PyNumber_TrueDivide)
-PYBIND11_MATH_OPERATOR_BINARY(operator/=,  PyNumber_InPlaceTrueDivide)
-PYBIND11_MATH_OPERATOR_BINARY(operator|,   PyNumber_Or)
-PYBIND11_MATH_OPERATOR_BINARY(operator|=,  PyNumber_InPlaceOr)
-PYBIND11_MATH_OPERATOR_BINARY(operator&,   PyNumber_And)
-PYBIND11_MATH_OPERATOR_BINARY(operator&=,  PyNumber_InPlaceAnd)
-PYBIND11_MATH_OPERATOR_BINARY(operator^,   PyNumber_Xor)
-PYBIND11_MATH_OPERATOR_BINARY(operator^=,  PyNumber_InPlaceXor)
-PYBIND11_MATH_OPERATOR_BINARY(operator<<,  PyNumber_Lshift)
+#define PYBIND11_MATH_OPERATOR_UNARY(op, fn)                                                      \
+    template <typename D>                                                                         \
+    object object_api<D>::op() const {                                                            \
+        object result = reinterpret_steal<object>(fn(derived().ptr()));                           \
+        if (!result.ptr())                                                                        \
+            throw error_already_set();                                                            \
+        return result;                                                                            \
+    }
+
+#define PYBIND11_MATH_OPERATOR_BINARY(op, fn)                                                     \
+    template <typename D>                                                                         \
+    object object_api<D>::op(object_api const &other) const {                                     \
+        object result = reinterpret_steal<object>(fn(derived().ptr(), other.derived().ptr()));    \
+        if (!result.ptr())                                                                        \
+            throw error_already_set();                                                            \
+        return result;                                                                            \
+    }
+
+PYBIND11_MATH_OPERATOR_UNARY(operator~, PyNumber_Invert)
+PYBIND11_MATH_OPERATOR_UNARY(operator-, PyNumber_Negative)
+PYBIND11_MATH_OPERATOR_BINARY(operator+, PyNumber_Add)
+PYBIND11_MATH_OPERATOR_BINARY(operator+=, PyNumber_InPlaceAdd)
+PYBIND11_MATH_OPERATOR_BINARY(operator-, PyNumber_Subtract)
+PYBIND11_MATH_OPERATOR_BINARY(operator-=, PyNumber_InPlaceSubtract)
+PYBIND11_MATH_OPERATOR_BINARY(operator*, PyNumber_Multiply)
+PYBIND11_MATH_OPERATOR_BINARY(operator*=, PyNumber_InPlaceMultiply)
+PYBIND11_MATH_OPERATOR_BINARY(operator/, PyNumber_TrueDivide)
+PYBIND11_MATH_OPERATOR_BINARY(operator/=, PyNumber_InPlaceTrueDivide)
+PYBIND11_MATH_OPERATOR_BINARY(operator|, PyNumber_Or)
+PYBIND11_MATH_OPERATOR_BINARY(operator|=, PyNumber_InPlaceOr)
+PYBIND11_MATH_OPERATOR_BINARY(operator&, PyNumber_And)
+PYBIND11_MATH_OPERATOR_BINARY(operator&=, PyNumber_InPlaceAnd)
+PYBIND11_MATH_OPERATOR_BINARY(operator^, PyNumber_Xor)
+PYBIND11_MATH_OPERATOR_BINARY(operator^=, PyNumber_InPlaceXor)
+PYBIND11_MATH_OPERATOR_BINARY(operator<<, PyNumber_Lshift)
 PYBIND11_MATH_OPERATOR_BINARY(operator<<=, PyNumber_InPlaceLshift)
-PYBIND11_MATH_OPERATOR_BINARY(operator>>,  PyNumber_Rshift)
+PYBIND11_MATH_OPERATOR_BINARY(operator>>, PyNumber_Rshift)
 PYBIND11_MATH_OPERATOR_BINARY(operator>>=, PyNumber_InPlaceRshift)
 
 #undef PYBIND11_MATH_OPERATOR_UNARY
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index fb1eea67bf..b661296887 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -9,26 +9,27 @@
 
 #pragma once
 
-#include "detail/common.h"
 #include "pybind11.h"
-#include <set>
-#include <unordered_set>
-#include <map>
-#include <unordered_map>
+#include "detail/common.h"
+
+#include <deque>
 #include <iostream>
 #include <list>
-#include <deque>
+#include <map>
+#include <set>
+#include <unordered_map>
+#include <unordered_set>
 #include <valarray>
 
 // See `detail/common.h` for implementation of these guards.
 #if defined(PYBIND11_HAS_OPTIONAL)
-#  include <optional>
+#    include <optional>
 #elif defined(PYBIND11_HAS_EXP_OPTIONAL)
-#  include <experimental/optional>
+#    include <experimental/optional>
 #endif
 
 #if defined(PYBIND11_HAS_VARIANT)
-#  include <variant>
+#    include <variant>
 #endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
@@ -37,8 +38,9 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 /// Extracts an const lvalue reference or rvalue reference for U based on the type of T (e.g. for
 /// forwarding a container element).  Typically used indirect via forwarded_type(), below.
 template <typename T, typename U>
-using forwarded_type = conditional_t<
-    std::is_lvalue_reference<T>::value, remove_reference_t<U> &, remove_reference_t<U> &&>;
+using forwarded_type = conditional_t<std::is_lvalue_reference<T>::value,
+                                     remove_reference_t<U> &,
+                                     remove_reference_t<U> &&>;
 
 /// Forwards a value U as rvalue or lvalue according to whether T is rvalue or lvalue; typically
 /// used for forwarding a container's elements.
@@ -47,7 +49,8 @@ forwarded_type<T, U> forward_like(U &&u) {
     return std::forward<detail::forwarded_type<T, U>>(std::forward<U>(u));
 }
 
-template <typename Type, typename Key> struct set_caster {
+template <typename Type, typename Key>
+struct set_caster {
     using type = Type;
     using key_conv = make_caster<Key>;
 
@@ -74,7 +77,8 @@ template <typename Type, typename Key> struct set_caster {
         }
         pybind11::set s;
         for (auto &&value : src) {
-            auto value_ = reinterpret_steal<object>(key_conv::cast(forward_like<T>(value), policy, parent));
+            auto value_ = reinterpret_steal<object>(
+                key_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_ || !s.add(value_)) {
                 return handle();
             }
@@ -85,8 +89,9 @@ template <typename Type, typename Key> struct set_caster {
     PYBIND11_TYPE_CASTER(type, const_name("Set[") + key_conv::name + const_name("]"));
 };
 
-template <typename Type, typename Key, typename Value> struct map_caster {
-    using key_conv   = make_caster<Key>;
+template <typename Type, typename Key, typename Value>
+struct map_caster {
+    using key_conv = make_caster<Key>;
     using value_conv = make_caster<Value>;
 
     bool load(handle src, bool convert) {
@@ -116,8 +121,10 @@ template <typename Type, typename Key, typename Value> struct map_caster {
             policy_value = return_value_policy_override<Value>::policy(policy_value);
         }
         for (auto &&kv : src) {
-            auto key = reinterpret_steal<object>(key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
-            auto value = reinterpret_steal<object>(value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
+            auto key = reinterpret_steal<object>(
+                key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
+            auto value = reinterpret_steal<object>(
+                value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
             if (!key || !value) {
                 return handle();
             }
@@ -126,10 +133,13 @@ template <typename Type, typename Key, typename Value> struct map_caster {
         return d.release();
     }
 
-    PYBIND11_TYPE_CASTER(Type, const_name("Dict[") + key_conv::name + const_name(", ") + value_conv::name + const_name("]"));
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name("Dict[") + key_conv::name + const_name(", ") + value_conv::name
+                             + const_name("]"));
 };
 
-template <typename Type, typename Value> struct list_caster {
+template <typename Type, typename Value>
+struct list_caster {
     using value_conv = make_caster<Value>;
 
     bool load(handle src, bool convert) {
@@ -151,7 +161,7 @@ template <typename Type, typename Value> struct list_caster {
 
 private:
     template <
-        typename T                                                                          = Type,
+        typename T = Type,
         enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
     void reserve_maybe(const sequence &s, Type *) {
         value.reserve(s.size());
@@ -167,7 +177,8 @@ template <typename Type, typename Value> struct list_caster {
         list l(src.size());
         ssize_t index = 0;
         for (auto &&value : src) {
-            auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
+            auto value_ = reinterpret_steal<object>(
+                value_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_) {
                 return handle();
             }
@@ -179,16 +190,17 @@ template <typename Type, typename Value> struct list_caster {
     PYBIND11_TYPE_CASTER(Type, const_name("List[") + value_conv::name + const_name("]"));
 };
 
-template <typename Type, typename Alloc> struct type_caster<std::vector<Type, Alloc>>
- : list_caster<std::vector<Type, Alloc>, Type> { };
+template <typename Type, typename Alloc>
+struct type_caster<std::vector<Type, Alloc>> : list_caster<std::vector<Type, Alloc>, Type> {};
 
-template <typename Type, typename Alloc> struct type_caster<std::deque<Type, Alloc>>
- : list_caster<std::deque<Type, Alloc>, Type> { };
+template <typename Type, typename Alloc>
+struct type_caster<std::deque<Type, Alloc>> : list_caster<std::deque<Type, Alloc>, Type> {};
 
-template <typename Type, typename Alloc> struct type_caster<std::list<Type, Alloc>>
- : list_caster<std::list<Type, Alloc>, Type> { };
+template <typename Type, typename Alloc>
+struct type_caster<std::list<Type, Alloc>> : list_caster<std::list<Type, Alloc>, Type> {};
 
-template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> struct array_caster {
+template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0>
+struct array_caster {
     using value_conv = make_caster<Value>;
 
 private:
@@ -229,7 +241,8 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
         list l(src.size());
         ssize_t index = 0;
         for (auto &&value : src) {
-            auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
+            auto value_ = reinterpret_steal<object>(
+                value_conv::cast(forward_like<T>(value), policy, parent));
             if (!value_) {
                 return handle();
             }
@@ -238,29 +251,40 @@ template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> s
         return l.release();
     }
 
-    PYBIND11_TYPE_CASTER(ArrayType, const_name("List[") + value_conv::name + const_name<Resizable>(const_name(""), const_name("[") + const_name<Size>() + const_name("]")) + const_name("]"));
+    PYBIND11_TYPE_CASTER(ArrayType,
+                         const_name("List[") + value_conv::name
+                             + const_name<Resizable>(const_name(""),
+                                                     const_name("[") + const_name<Size>()
+                                                         + const_name("]"))
+                             + const_name("]"));
 };
 
-template <typename Type, size_t Size> struct type_caster<std::array<Type, Size>>
- : array_caster<std::array<Type, Size>, Type, false, Size> { };
+template <typename Type, size_t Size>
+struct type_caster<std::array<Type, Size>>
+    : array_caster<std::array<Type, Size>, Type, false, Size> {};
 
-template <typename Type> struct type_caster<std::valarray<Type>>
- : array_caster<std::valarray<Type>, Type, true> { };
+template <typename Type>
+struct type_caster<std::valarray<Type>> : array_caster<std::valarray<Type>, Type, true> {};
 
-template <typename Key, typename Compare, typename Alloc> struct type_caster<std::set<Key, Compare, Alloc>>
-  : set_caster<std::set<Key, Compare, Alloc>, Key> { };
+template <typename Key, typename Compare, typename Alloc>
+struct type_caster<std::set<Key, Compare, Alloc>>
+    : set_caster<std::set<Key, Compare, Alloc>, Key> {};
 
-template <typename Key, typename Hash, typename Equal, typename Alloc> struct type_caster<std::unordered_set<Key, Hash, Equal, Alloc>>
-  : set_caster<std::unordered_set<Key, Hash, Equal, Alloc>, Key> { };
+template <typename Key, typename Hash, typename Equal, typename Alloc>
+struct type_caster<std::unordered_set<Key, Hash, Equal, Alloc>>
+    : set_caster<std::unordered_set<Key, Hash, Equal, Alloc>, Key> {};
 
-template <typename Key, typename Value, typename Compare, typename Alloc> struct type_caster<std::map<Key, Value, Compare, Alloc>>
-  : map_caster<std::map<Key, Value, Compare, Alloc>, Key, Value> { };
+template <typename Key, typename Value, typename Compare, typename Alloc>
+struct type_caster<std::map<Key, Value, Compare, Alloc>>
+    : map_caster<std::map<Key, Value, Compare, Alloc>, Key, Value> {};
 
-template <typename Key, typename Value, typename Hash, typename Equal, typename Alloc> struct type_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>>
-  : map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> { };
+template <typename Key, typename Value, typename Hash, typename Equal, typename Alloc>
+struct type_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>>
+    : map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> {};
 
 // This type caster is intended to be used for std::optional and std::experimental::optional
-template<typename Type, typename Value = typename Type::value_type> struct optional_caster {
+template <typename Type, typename Value = typename Type::value_type>
+struct optional_caster {
     using value_conv = make_caster<Value>;
 
     template <typename T>
@@ -279,7 +303,7 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
             return false;
         }
         if (src.is_none()) {
-            return true;  // default-constructed value is already empty
+            return true; // default-constructed value is already empty
         }
         value_conv inner_caster;
         if (!inner_caster.load(src, convert)) {
@@ -294,18 +318,20 @@ template<typename Type, typename Value = typename Type::value_type> struct optio
 };
 
 #if defined(PYBIND11_HAS_OPTIONAL)
-template<typename T> struct type_caster<std::optional<T>>
-    : public optional_caster<std::optional<T>> {};
+template <typename T>
+struct type_caster<std::optional<T>> : public optional_caster<std::optional<T>> {};
 
-template<> struct type_caster<std::nullopt_t>
-    : public void_caster<std::nullopt_t> {};
+template <>
+struct type_caster<std::nullopt_t> : public void_caster<std::nullopt_t> {};
 #endif
 
 #if defined(PYBIND11_HAS_EXP_OPTIONAL)
-template<typename T> struct type_caster<std::experimental::optional<T>>
+template <typename T>
+struct type_caster<std::experimental::optional<T>>
     : public optional_caster<std::experimental::optional<T>> {};
 
-template<> struct type_caster<std::experimental::nullopt_t>
+template <>
+struct type_caster<std::experimental::nullopt_t>
     : public void_caster<std::experimental::nullopt_t> {};
 #endif
 
@@ -326,7 +352,7 @@ struct variant_caster_visitor {
 /// `namespace::variant` types which provide a `namespace::visit()` function are handled here
 /// automatically using argument-dependent lookup. Users can provide specializations for other
 /// variant-like classes, e.g. `boost::variant` and `boost::apply_visitor`.
-template <template<typename...> class Variant>
+template <template <typename...> class Variant>
 struct visit_helper {
     template <typename... Args>
     static auto call(Args &&...args) -> decltype(visit(std::forward<Args>(args)...)) {
@@ -335,9 +361,10 @@ struct visit_helper {
 };
 
 /// Generic variant caster
-template <typename Variant> struct variant_caster;
+template <typename Variant>
+struct variant_caster;
 
-template <template<typename...> class V, typename... Ts>
+template <template <typename...> class V, typename... Ts>
 struct variant_caster<V<Ts...>> {
     static_assert(sizeof...(Ts) > 0, "Variant must consist of at least one alternative.");
 
@@ -371,12 +398,14 @@ struct variant_caster<V<Ts...>> {
     }
 
     using Type = V<Ts...>;
-    PYBIND11_TYPE_CASTER(Type, const_name("Union[") + detail::concat(make_caster<Ts>::name...) + const_name("]"));
+    PYBIND11_TYPE_CASTER(Type,
+                         const_name("Union[") + detail::concat(make_caster<Ts>::name...)
+                             + const_name("]"));
 };
 
 #if defined(PYBIND11_HAS_VARIANT)
 template <typename... Ts>
-struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> { };
+struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> {};
 #endif
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/stl/filesystem.h b/include/pybind11/stl/filesystem.h
index 59ac38b9ba..747992f51c 100644
--- a/include/pybind11/stl/filesystem.h
+++ b/include/pybind11/stl/filesystem.h
@@ -4,21 +4,20 @@
 
 #pragma once
 
-#include "../cast.h"
 #include "../pybind11.h"
-#include "../pytypes.h"
-
 #include "../detail/common.h"
 #include "../detail/descr.h"
+#include "../cast.h"
+#include "../pytypes.h"
 
 #include <string>
 
 #ifdef __has_include
-#  if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
+#    if defined(PYBIND11_CPP17) && __has_include(<filesystem>) && \
       PY_VERSION_HEX >= 0x03060000
-#    include <filesystem>
-#    define PYBIND11_HAS_FILESYSTEM 1
-#  endif
+#        include <filesystem>
+#        define PYBIND11_HAS_FILESYSTEM 1
+#    endif
 #endif
 
 #if !defined(PYBIND11_HAS_FILESYSTEM) && !defined(PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL)
@@ -30,28 +29,29 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if defined(PYBIND11_HAS_FILESYSTEM)
-template<typename T> struct path_caster {
+template <typename T>
+struct path_caster {
 
 private:
-    static PyObject* unicode_from_fs_native(const std::string& w) {
-#if !defined(PYPY_VERSION)
+    static PyObject *unicode_from_fs_native(const std::string &w) {
+#    if !defined(PYPY_VERSION)
         return PyUnicode_DecodeFSDefaultAndSize(w.c_str(), ssize_t(w.size()));
-#else
+#    else
         // PyPy mistakenly declares the first parameter as non-const.
-        return PyUnicode_DecodeFSDefaultAndSize(
-            const_cast<char*>(w.c_str()), ssize_t(w.size()));
-#endif
+        return PyUnicode_DecodeFSDefaultAndSize(const_cast<char *>(w.c_str()), ssize_t(w.size()));
+#    endif
     }
 
-    static PyObject* unicode_from_fs_native(const std::wstring& w) {
+    static PyObject *unicode_from_fs_native(const std::wstring &w) {
         return PyUnicode_FromWideChar(w.c_str(), ssize_t(w.size()));
     }
 
 public:
-    static handle cast(const T& path, return_value_policy, handle) {
+    static handle cast(const T &path, return_value_policy, handle) {
         if (auto py_str = unicode_from_fs_native(path.native())) {
-            return module_::import("pathlib").attr("Path")(reinterpret_steal<object>(py_str))
-                   .release();
+            return module_::import("pathlib")
+                .attr("Path")(reinterpret_steal<object>(py_str))
+                .release();
         }
         return nullptr;
     }
@@ -60,12 +60,12 @@ template<typename T> struct path_caster {
         // PyUnicode_FSConverter and PyUnicode_FSDecoder normally take care of
         // calling PyOS_FSPath themselves, but that's broken on PyPy (PyPy
         // issue #3168) so we do it ourselves instead.
-        PyObject* buf = PyOS_FSPath(handle.ptr());
+        PyObject *buf = PyOS_FSPath(handle.ptr());
         if (!buf) {
             PyErr_Clear();
             return false;
         }
-        PyObject* native = nullptr;
+        PyObject *native = nullptr;
         if constexpr (std::is_same_v<typename T::value_type, char>) {
             if (PyUnicode_FSConverter(buf, &native) != 0) {
                 if (auto *c_str = PyBytes_AsString(native)) {
@@ -78,7 +78,7 @@ template<typename T> struct path_caster {
             if (PyUnicode_FSDecoder(buf, &native) != 0) {
                 if (auto *c_str = PyUnicode_AsWideCharString(native, nullptr)) {
                     // AsWideCharString returns a new string that must be free'd.
-                    value = c_str;  // Copies the string.
+                    value = c_str; // Copies the string.
                     PyMem_Free(c_str);
                 }
             }
@@ -95,8 +95,8 @@ template<typename T> struct path_caster {
     PYBIND11_TYPE_CASTER(T, const_name("os.PathLike"));
 };
 
-template<> struct type_caster<std::filesystem::path>
-    : public path_caster<std::filesystem::path> {};
+template <>
+struct type_caster<std::filesystem::path> : public path_caster<std::filesystem::path> {};
 #endif // PYBIND11_HAS_FILESYSTEM
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index 2f997d6b03..3a3e54dd48 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -19,74 +19,87 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 /* SFINAE helper class used by 'is_comparable */
-template <typename T>  struct container_traits {
-    template <typename T2> static std::true_type test_comparable(decltype(std::declval<const T2 &>() == std::declval<const T2 &>())*);
-    template <typename T2> static std::false_type test_comparable(...);
-    template <typename T2> static std::true_type test_value(typename T2::value_type *);
-    template <typename T2> static std::false_type test_value(...);
-    template <typename T2> static std::true_type test_pair(typename T2::first_type *, typename T2::second_type *);
-    template <typename T2> static std::false_type test_pair(...);
-
-    static constexpr const bool is_comparable = std::is_same<std::true_type, decltype(test_comparable<T>(nullptr))>::value;
-    static constexpr const bool is_pair = std::is_same<std::true_type, decltype(test_pair<T>(nullptr, nullptr))>::value;
-    static constexpr const bool is_vector = std::is_same<std::true_type, decltype(test_value<T>(nullptr))>::value;
+template <typename T>
+struct container_traits {
+    template <typename T2>
+    static std::true_type
+    test_comparable(decltype(std::declval<const T2 &>() == std::declval<const T2 &>()) *);
+    template <typename T2>
+    static std::false_type test_comparable(...);
+    template <typename T2>
+    static std::true_type test_value(typename T2::value_type *);
+    template <typename T2>
+    static std::false_type test_value(...);
+    template <typename T2>
+    static std::true_type test_pair(typename T2::first_type *, typename T2::second_type *);
+    template <typename T2>
+    static std::false_type test_pair(...);
+
+    static constexpr const bool is_comparable
+        = std::is_same<std::true_type, decltype(test_comparable<T>(nullptr))>::value;
+    static constexpr const bool is_pair
+        = std::is_same<std::true_type, decltype(test_pair<T>(nullptr, nullptr))>::value;
+    static constexpr const bool is_vector
+        = std::is_same<std::true_type, decltype(test_value<T>(nullptr))>::value;
     static constexpr const bool is_element = !is_pair && !is_vector;
 };
 
 /* Default: is_comparable -> std::false_type */
 template <typename T, typename SFINAE = void>
-struct is_comparable : std::false_type { };
+struct is_comparable : std::false_type {};
 
 /* For non-map data structures, check whether operator== can be instantiated */
 template <typename T>
 struct is_comparable<
-    T, enable_if_t<container_traits<T>::is_element &&
-                   container_traits<T>::is_comparable>>
-    : std::true_type { };
+    T,
+    enable_if_t<container_traits<T>::is_element && container_traits<T>::is_comparable>>
+    : std::true_type {};
 
 /* For a vector/map data structure, recursively check the value type
    (which is std::pair for maps) */
 template <typename T>
 struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
-    static constexpr const bool value =
-        is_comparable<typename T::value_type>::value;
+    static constexpr const bool value = is_comparable<typename T::value_type>::value;
 };
 
 /* For pairs, recursively check the two data types */
 template <typename T>
 struct is_comparable<T, enable_if_t<container_traits<T>::is_pair>> {
-    static constexpr const bool value =
-        is_comparable<typename T::first_type>::value &&
-        is_comparable<typename T::second_type>::value;
+    static constexpr const bool value = is_comparable<typename T::first_type>::value
+                                        && is_comparable<typename T::second_type>::value;
 };
 
 /* Fallback functions */
-template <typename, typename, typename... Args> void vector_if_copy_constructible(const Args &...) { }
-template <typename, typename, typename... Args> void vector_if_equal_operator(const Args &...) { }
-template <typename, typename, typename... Args> void vector_if_insertion_operator(const Args &...) { }
-template <typename, typename, typename... Args> void vector_modifiers(const Args &...) { }
+template <typename, typename, typename... Args>
+void vector_if_copy_constructible(const Args &...) {}
+template <typename, typename, typename... Args>
+void vector_if_equal_operator(const Args &...) {}
+template <typename, typename, typename... Args>
+void vector_if_insertion_operator(const Args &...) {}
+template <typename, typename, typename... Args>
+void vector_modifiers(const Args &...) {}
 
-template<typename Vector, typename Class_>
+template <typename Vector, typename Class_>
 void vector_if_copy_constructible(enable_if_t<is_copy_constructible<Vector>::value, Class_> &cl) {
     cl.def(init<const Vector &>(), "Copy constructor");
 }
 
-template<typename Vector, typename Class_>
+template <typename Vector, typename Class_>
 void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_> &cl) {
     using T = typename Vector::value_type;
 
     cl.def(self == self);
     cl.def(self != self);
 
-    cl.def("count",
-        [](const Vector &v, const T &x) {
-            return std::count(v.begin(), v.end(), x);
-        },
+    cl.def(
+        "count",
+        [](const Vector &v, const T &x) { return std::count(v.begin(), v.end(), x); },
         arg("x"),
-        "Return the number of times ``x`` appears in the list"
-    );
+        "Return the number of times ``x`` appears in the list");
 
-    cl.def("remove", [](Vector &v, const T &x) {
+    cl.def(
+        "remove",
+        [](Vector &v, const T &x) {
             auto p = std::find(v.begin(), v.end(), x);
             if (p != v.end()) {
                 v.erase(p);
@@ -96,23 +109,21 @@ void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_>
         },
         arg("x"),
         "Remove the first item from the list whose value is x. "
-        "It is an error if there is no such item."
-    );
+        "It is an error if there is no such item.");
 
-    cl.def("__contains__",
-        [](const Vector &v, const T &x) {
-            return std::find(v.begin(), v.end(), x) != v.end();
-        },
+    cl.def(
+        "__contains__",
+        [](const Vector &v, const T &x) { return std::find(v.begin(), v.end(), x) != v.end(); },
         arg("x"),
-        "Return true the container contains ``x``"
-    );
+        "Return true the container contains ``x``");
 }
 
 // Vector modifiers -- requires a copyable vector_type:
-// (Technically, some of these (pop and __delitem__) don't actually require copyability, but it seems
-// silly to allow deletion but not insertion, so include them here too.)
+// (Technically, some of these (pop and __delitem__) don't actually require copyability, but it
+// seems silly to allow deletion but not insertion, so include them here too.)
 template <typename Vector, typename Class_>
-void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_type>::value, Class_> &cl) {
+void vector_modifiers(
+    enable_if_t<is_copy_constructible<typename Vector::value_type>::value, Class_> &cl) {
     using T = typename Vector::value_type;
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
@@ -127,10 +138,11 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         return i;
     };
 
-    cl.def("append",
-           [](Vector &v, const T &value) { v.push_back(value); },
-           arg("x"),
-           "Add an item to the end of the list");
+    cl.def(
+        "append",
+        [](Vector &v, const T &value) { v.push_back(value); },
+        arg("x"),
+        "Add an item to the end of the list");
 
     cl.def(init([](const iterable &it) {
         auto v = std::unique_ptr<Vector>(new Vector());
@@ -141,20 +153,14 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         return v.release();
     }));
 
-    cl.def("clear",
-        [](Vector &v) {
-            v.clear();
-        },
-        "Clear the contents"
-    );
+    cl.def(
+        "clear", [](Vector &v) { v.clear(); }, "Clear the contents");
 
-    cl.def("extend",
-       [](Vector &v, const Vector &src) {
-           v.insert(v.end(), src.begin(), src.end());
-       },
-       arg("L"),
-       "Extend the list by appending all the items in the given list"
-    );
+    cl.def(
+        "extend",
+        [](Vector &v, const Vector &src) { v.insert(v.end(), src.begin(), src.end()); },
+        arg("L"),
+        "Extend the list by appending all the items in the given list");
 
     cl.def(
         "extend",
@@ -179,7 +185,8 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         arg("L"),
         "Extend the list by appending all the items in the given list");
 
-    cl.def("insert",
+    cl.def(
+        "insert",
         [](Vector &v, DiffType i, const T &x) {
             // Can't use wrap_i; i == v.size() is OK
             if (i < 0) {
@@ -190,9 +197,9 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             }
             v.insert(v.begin() + i, x);
         },
-        arg("i") , arg("x"),
-        "Insert an item at a given position."
-    );
+        arg("i"),
+        arg("x"),
+        "Insert an item at a given position.");
 
     cl.def(
         "pop",
@@ -206,7 +213,8 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
         },
         "Remove and return the last item");
 
-    cl.def("pop",
+    cl.def(
+        "pop",
         [wrap_i](Vector &v, DiffType i) {
             i = wrap_i(i, v.size());
             T t = std::move(v[(SizeType) i]);
@@ -214,15 +222,12 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             return t;
         },
         arg("i"),
-        "Remove and return the item at index ``i``"
-    );
+        "Remove and return the item at index ``i``");
 
-    cl.def("__setitem__",
-        [wrap_i](Vector &v, DiffType i, const T &t) {
-            i = wrap_i(i, v.size());
-            v[(SizeType)i] = t;
-        }
-    );
+    cl.def("__setitem__", [wrap_i](Vector &v, DiffType i, const T &t) {
+        i = wrap_i(i, v.size());
+        v[(SizeType) i] = t;
+    });
 
     /// Slicing protocol
     cl.def(
@@ -237,7 +242,7 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
             auto *seq = new Vector();
             seq->reserve((size_t) slicelength);
 
-            for (size_t i=0; i<slicelength; ++i) {
+            for (size_t i = 0; i < slicelength; ++i) {
                 seq->push_back(v[start]);
                 start += step;
             }
@@ -259,20 +264,20 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
                     "Left and right hand size of slice assignment have different sizes!");
             }
 
-            for (size_t i=0; i<slicelength; ++i) {
+            for (size_t i = 0; i < slicelength; ++i) {
                 v[start] = value[i];
                 start += step;
             }
         },
         "Assign list elements using a slice object");
 
-    cl.def("__delitem__",
+    cl.def(
+        "__delitem__",
         [wrap_i](Vector &v, DiffType i) {
             i = wrap_i(i, v.size());
             v.erase(v.begin() + i);
         },
-        "Delete the list elements at index ``i``"
-    );
+        "Delete the list elements at index ``i``");
 
     cl.def(
         "__delitem__",
@@ -297,8 +302,10 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
 
 // If the type has an operator[] that doesn't return a reference (most notably std::vector<bool>),
 // we have to access by copying; otherwise we return by reference.
-template <typename Vector> using vector_needs_copy = negation<
-    std::is_same<decltype(std::declval<Vector>()[typename Vector::size_type()]), typename Vector::value_type &>>;
+template <typename Vector>
+using vector_needs_copy
+    = negation<std::is_same<decltype(std::declval<Vector>()[typename Vector::size_type()]),
+                            typename Vector::value_type &>>;
 
 // The usual case: access and iterate by reference
 template <typename Vector, typename Class_>
@@ -306,7 +313,7 @@ void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl)
     using T = typename Vector::value_type;
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
-    using ItType   = typename Vector::iterator;
+    using ItType = typename Vector::iterator;
 
     auto wrap_i = [](DiffType i, SizeType n) {
         if (i < 0) {
@@ -318,21 +325,22 @@ void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl)
         return i;
     };
 
-    cl.def("__getitem__",
+    cl.def(
+        "__getitem__",
         [wrap_i](Vector &v, DiffType i) -> T & {
             i = wrap_i(i, v.size());
-            return v[(SizeType)i];
+            return v[(SizeType) i];
         },
         return_value_policy::reference_internal // ref + keepalive
     );
 
-    cl.def("__iter__",
-           [](Vector &v) {
-               return make_iterator<
-                   return_value_policy::reference_internal, ItType, ItType, T&>(
-                   v.begin(), v.end());
-           },
-           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    cl.def(
+        "__iter__",
+        [](Vector &v) {
+            return make_iterator<return_value_policy::reference_internal, ItType, ItType, T &>(
+                v.begin(), v.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
     );
 }
 
@@ -342,7 +350,7 @@ void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl)
     using T = typename Vector::value_type;
     using SizeType = typename Vector::size_type;
     using DiffType = typename Vector::difference_type;
-    using ItType   = typename Vector::iterator;
+    using ItType = typename Vector::iterator;
     cl.def("__getitem__", [](const Vector &v, DiffType i) -> T {
         if (i < 0 && (i += v.size()) < 0) {
             throw index_error();
@@ -353,25 +361,27 @@ void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl)
         return v[(SizeType) i];
     });
 
-    cl.def("__iter__",
-           [](Vector &v) {
-               return make_iterator<
-                   return_value_policy::copy, ItType, ItType, T>(
-                   v.begin(), v.end());
-           },
-           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    cl.def(
+        "__iter__",
+        [](Vector &v) {
+            return make_iterator<return_value_policy::copy, ItType, ItType, T>(v.begin(), v.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
     );
 }
 
-template <typename Vector, typename Class_> auto vector_if_insertion_operator(Class_ &cl, std::string const &name)
-    -> decltype(std::declval<std::ostream&>() << std::declval<typename Vector::value_type>(), void()) {
+template <typename Vector, typename Class_>
+auto vector_if_insertion_operator(Class_ &cl, std::string const &name)
+    -> decltype(std::declval<std::ostream &>() << std::declval<typename Vector::value_type>(),
+                void()) {
     using size_type = typename Vector::size_type;
 
-    cl.def("__repr__",
-           [name](Vector &v) {
+    cl.def(
+        "__repr__",
+        [name](Vector &v) {
             std::ostringstream s;
             s << name << '[';
-            for (size_type i=0; i < v.size(); ++i) {
+            for (size_type i = 0; i < v.size(); ++i) {
                 s << v[i];
                 if (i != v.size() - 1) {
                     s << ", ";
@@ -380,8 +390,7 @@ template <typename Vector, typename Class_> auto vector_if_insertion_operator(Cl
             s << ']';
             return s.str();
         },
-        "Return the canonical string representation of this list."
-    );
+        "Return the canonical string representation of this list.");
 }
 
 // Provide the buffer interface for vectors if we have data() and we have a format for it
@@ -390,7 +399,11 @@ template <typename Vector, typename Class_> auto vector_if_insertion_operator(Cl
 template <typename Vector, typename = void>
 struct vector_has_data_and_format : std::false_type {};
 template <typename Vector>
-struct vector_has_data_and_format<Vector, enable_if_t<std::is_same<decltype(format_descriptor<typename Vector::value_type>::format(), std::declval<Vector>().data()), typename Vector::value_type*>::value>> : std::true_type {};
+struct vector_has_data_and_format<
+    Vector,
+    enable_if_t<std::is_same<decltype(format_descriptor<typename Vector::value_type>::format(),
+                                      std::declval<Vector>().data()),
+                             typename Vector::value_type *>::value>> : std::true_type {};
 
 // [workaround(intel)] Separate function required here
 // Workaround as the Intel compiler does not compile the enable_if_t part below
@@ -405,17 +418,23 @@ constexpr bool args_any_are_buffer() {
 
 // Add the buffer interface to a vector
 template <typename Vector, typename Class_, typename... Args>
-void vector_buffer_impl(Class_& cl, std::true_type) {
+void vector_buffer_impl(Class_ &cl, std::true_type) {
     using T = typename Vector::value_type;
 
-    static_assert(vector_has_data_and_format<Vector>::value, "There is not an appropriate format descriptor for this vector");
+    static_assert(vector_has_data_and_format<Vector>::value,
+                  "There is not an appropriate format descriptor for this vector");
 
     // numpy.h declares this for arbitrary types, but it may raise an exception and crash hard
     // at runtime if PYBIND11_NUMPY_DTYPE hasn't been called, so check here
     format_descriptor<T>::format();
 
-    cl.def_buffer([](Vector& v) -> buffer_info {
-        return buffer_info(v.data(), static_cast<ssize_t>(sizeof(T)), format_descriptor<T>::format(), 1, {v.size()}, {sizeof(T)});
+    cl.def_buffer([](Vector &v) -> buffer_info {
+        return buffer_info(v.data(),
+                           static_cast<ssize_t>(sizeof(T)),
+                           format_descriptor<T>::format(),
+                           1,
+                           {v.size()},
+                           {sizeof(T)});
     });
 
     cl.def(init([](const buffer &buf) {
@@ -429,7 +448,7 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
                              + " C++: " + format_descriptor<T>::format() + ")");
         }
 
-        T *p = static_cast<T*>(info.ptr);
+        T *p = static_cast<T *>(info.ptr);
         ssize_t step = info.strides[0] / static_cast<ssize_t>(sizeof(T));
         T *end = p + info.shape[0] * step;
         if (step == 1) {
@@ -441,18 +460,18 @@ void vector_buffer_impl(Class_& cl, std::true_type) {
             vec.push_back(*p);
         }
         return vec;
-
     }));
 
     return;
 }
 
 template <typename Vector, typename Class_, typename... Args>
-void vector_buffer_impl(Class_&, std::false_type) {}
+void vector_buffer_impl(Class_ &, std::false_type) {}
 
 template <typename Vector, typename Class_, typename... Args>
-void vector_buffer(Class_& cl) {
-    vector_buffer_impl<Vector, Class_, Args...>(cl, detail::any_of<std::is_same<Args, buffer_protocol>...>{});
+void vector_buffer(Class_ &cl) {
+    vector_buffer_impl<Vector, Class_, Args...>(
+        cl, detail::any_of<std::is_same<Args, buffer_protocol>...>{});
 }
 
 PYBIND11_NAMESPACE_END(detail)
@@ -461,7 +480,7 @@ PYBIND11_NAMESPACE_END(detail)
 // std::vector
 //
 template <typename Vector, typename holder_type = std::unique_ptr<Vector>, typename... Args>
-class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, Args&&... args) {
+class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, Args &&...args) {
     using Class_ = class_<Vector, holder_type>;
 
     // If the value_type is unregistered (e.g. a converting type) or is itself registered
@@ -492,18 +511,13 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
     // Accessor and iterator; return by value if copyable, otherwise we return by ref + keep-alive
     detail::vector_accessor<Vector, Class_>(cl);
 
-    cl.def("__bool__",
-        [](const Vector &v) -> bool {
-            return !v.empty();
-        },
-        "Check whether the list is nonempty"
-    );
+    cl.def(
+        "__bool__",
+        [](const Vector &v) -> bool { return !v.empty(); },
+        "Check whether the list is nonempty");
 
     cl.def("__len__", &Vector::size);
 
-
-
-
 #if 0
     // C++ style functions deprecated, leaving it here as an example
     cl.def(init<size_type>());
@@ -547,8 +561,6 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
     return cl;
 }
 
-
-
 //
 // std::map, std::unordered_map
 //
@@ -556,55 +568,58 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 /* Fallback functions */
-template <typename, typename, typename... Args> void map_if_insertion_operator(const Args &...) { }
-template <typename, typename, typename... Args> void map_assignment(const Args &...) { }
+template <typename, typename, typename... Args>
+void map_if_insertion_operator(const Args &...) {}
+template <typename, typename, typename... Args>
+void map_assignment(const Args &...) {}
 
 // Map assignment when copy-assignable: just copy the value
 template <typename Map, typename Class_>
-void map_assignment(enable_if_t<is_copy_assignable<typename Map::mapped_type>::value, Class_> &cl) {
+void map_assignment(
+    enable_if_t<is_copy_assignable<typename Map::mapped_type>::value, Class_> &cl) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
 
-    cl.def("__setitem__",
-           [](Map &m, const KeyType &k, const MappedType &v) {
-               auto it = m.find(k);
-               if (it != m.end()) {
-                   it->second = v;
-               } else {
-                   m.emplace(k, v);
-               }
-           }
-    );
+    cl.def("__setitem__", [](Map &m, const KeyType &k, const MappedType &v) {
+        auto it = m.find(k);
+        if (it != m.end()) {
+            it->second = v;
+        } else {
+            m.emplace(k, v);
+        }
+    });
 }
 
-// Not copy-assignable, but still copy-constructible: we can update the value by erasing and reinserting
-template<typename Map, typename Class_>
-void map_assignment(enable_if_t<
-        !is_copy_assignable<typename Map::mapped_type>::value &&
-        is_copy_constructible<typename Map::mapped_type>::value,
-        Class_> &cl) {
+// Not copy-assignable, but still copy-constructible: we can update the value by erasing and
+// reinserting
+template <typename Map, typename Class_>
+void map_assignment(enable_if_t<!is_copy_assignable<typename Map::mapped_type>::value
+                                    && is_copy_constructible<typename Map::mapped_type>::value,
+                                Class_> &cl) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
 
-    cl.def("__setitem__",
-           [](Map &m, const KeyType &k, const MappedType &v) {
-               // We can't use m[k] = v; because value type might not be default constructable
-               auto r = m.emplace(k, v);
-               if (!r.second) {
-                   // value type is not copy assignable so the only way to insert it is to erase it first...
-                   m.erase(r.first);
-                   m.emplace(k, v);
-               }
-           }
-    );
+    cl.def("__setitem__", [](Map &m, const KeyType &k, const MappedType &v) {
+        // We can't use m[k] = v; because value type might not be default constructable
+        auto r = m.emplace(k, v);
+        if (!r.second) {
+            // value type is not copy assignable so the only way to insert it is to erase it
+            // first...
+            m.erase(r.first);
+            m.emplace(k, v);
+        }
+    });
 }
 
+template <typename Map, typename Class_>
+auto map_if_insertion_operator(Class_ &cl, std::string const &name)
+    -> decltype(std::declval<std::ostream &>() << std::declval<typename Map::key_type>()
+                                               << std::declval<typename Map::mapped_type>(),
+                void()) {
 
-template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &cl, std::string const &name)
--> decltype(std::declval<std::ostream&>() << std::declval<typename Map::key_type>() << std::declval<typename Map::mapped_type>(), void()) {
-
-    cl.def("__repr__",
-           [name](Map &m) {
+    cl.def(
+        "__repr__",
+        [name](Map &m) {
             std::ostringstream s;
             s << name << '{';
             bool f = false;
@@ -618,32 +633,28 @@ template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &
             s << '}';
             return s.str();
         },
-        "Return the canonical string representation of this map."
-    );
+        "Return the canonical string representation of this map.");
 }
 
-template<typename Map>
-struct keys_view
-{
+template <typename Map>
+struct keys_view {
     Map &map;
 };
 
-template<typename Map>
-struct values_view
-{
+template <typename Map>
+struct values_view {
     Map &map;
 };
 
-template<typename Map>
-struct items_view
-{
+template <typename Map>
+struct items_view {
     Map &map;
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
 template <typename Map, typename holder_type = std::unique_ptr<Map>, typename... Args>
-class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&... args) {
+class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&...args) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
     using KeysView = detail::keys_view<Map>;
@@ -674,101 +685,97 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     // Register stream insertion operator (if possible)
     detail::map_if_insertion_operator<Map, Class_>(cl, name);
 
-    cl.def("__bool__",
+    cl.def(
+        "__bool__",
         [](const Map &m) -> bool { return !m.empty(); },
-        "Check whether the map is nonempty"
-    );
+        "Check whether the map is nonempty");
 
-    cl.def("__iter__",
-           [](Map &m) { return make_key_iterator(m.begin(), m.end()); },
-           keep_alive<0, 1>() /* Essential: keep map alive while iterator exists */
+    cl.def(
+        "__iter__",
+        [](Map &m) { return make_key_iterator(m.begin(), m.end()); },
+        keep_alive<0, 1>() /* Essential: keep map alive while iterator exists */
     );
 
-    cl.def("keys",
-           [](Map &m) { return KeysView{m}; },
-           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    cl.def(
+        "keys",
+        [](Map &m) { return KeysView{m}; },
+        keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
-    cl.def("values",
-           [](Map &m) { return ValuesView{m}; },
-           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    cl.def(
+        "values",
+        [](Map &m) { return ValuesView{m}; },
+        keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
-    cl.def("items",
-           [](Map &m) { return ItemsView{m}; },
-           keep_alive<0, 1>() /* Essential: keep map alive while view exists */
+    cl.def(
+        "items",
+        [](Map &m) { return ItemsView{m}; },
+        keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
-    cl.def("__getitem__",
+    cl.def(
+        "__getitem__",
         [](Map &m, const KeyType &k) -> MappedType & {
             auto it = m.find(k);
             if (it == m.end()) {
                 throw key_error();
             }
-           return it->second;
+            return it->second;
         },
         return_value_policy::reference_internal // ref + keepalive
     );
 
-    cl.def("__contains__",
-        [](Map &m, const KeyType &k) -> bool {
-            auto it = m.find(k);
-            if (it == m.end()) {
-                return false;
-            }
-           return true;
+    cl.def("__contains__", [](Map &m, const KeyType &k) -> bool {
+        auto it = m.find(k);
+        if (it == m.end()) {
+            return false;
         }
-    );
+        return true;
+    });
     // Fallback for when the object is not of the key type
     cl.def("__contains__", [](Map &, const object &) -> bool { return false; });
 
     // Assignment provided only if the type is copyable
     detail::map_assignment<Map, Class_>(cl);
 
-    cl.def("__delitem__",
-           [](Map &m, const KeyType &k) {
-               auto it = m.find(k);
-               if (it == m.end()) {
-                   throw key_error();
-               }
-               m.erase(it);
-           }
-    );
+    cl.def("__delitem__", [](Map &m, const KeyType &k) {
+        auto it = m.find(k);
+        if (it == m.end()) {
+            throw key_error();
+        }
+        m.erase(it);
+    });
 
     cl.def("__len__", &Map::size);
 
     keys_view.def("__len__", [](KeysView &view) { return view.map.size(); });
-    keys_view.def("__iter__",
-        [](KeysView &view) {
-            return make_key_iterator(view.map.begin(), view.map.end());
-        },
+    keys_view.def(
+        "__iter__",
+        [](KeysView &view) { return make_key_iterator(view.map.begin(), view.map.end()); },
         keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
     );
-    keys_view.def("__contains__",
-        [](KeysView &view, const KeyType &k) -> bool {
-            auto it = view.map.find(k);
-            if (it == view.map.end()) {
-                return false;
-            }
-            return true;
+    keys_view.def("__contains__", [](KeysView &view, const KeyType &k) -> bool {
+        auto it = view.map.find(k);
+        if (it == view.map.end()) {
+            return false;
         }
-    );
+        return true;
+    });
     // Fallback for when the object is not of the key type
     keys_view.def("__contains__", [](KeysView &, const object &) -> bool { return false; });
 
     values_view.def("__len__", [](ValuesView &view) { return view.map.size(); });
-    values_view.def("__iter__",
-        [](ValuesView &view) {
-            return make_value_iterator(view.map.begin(), view.map.end());
-        },
+    values_view.def(
+        "__iter__",
+        [](ValuesView &view) { return make_value_iterator(view.map.begin(), view.map.end()); },
         keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
     );
 
     items_view.def("__len__", [](ItemsView &view) { return view.map.size(); });
-    items_view.def("__iter__",
-        [](ItemsView &view) {
-            return make_iterator(view.map.begin(), view.map.end());
-        },
+    items_view.def(
+        "__iter__",
+        [](ItemsView &view) { return make_iterator(view.map.begin(), view.map.end()); },
         keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
     );
 
diff --git a/tests/constructor_stats.h b/tests/constructor_stats.h
index ccb623e1c3..a3835c21e6 100644
--- a/tests/constructor_stats.h
+++ b/tests/constructor_stats.h
@@ -56,7 +56,8 @@ from the ConstructorStats instance `.values()` method.
 In some cases, when you need to track instances of a C++ class not registered with pybind11, you
 need to add a function returning the ConstructorStats for the C++ class; this can be done with:
 
-    m.def("get_special_cstats", &ConstructorStats::get<SpecialClass>, py::return_value_policy::reference)
+    m.def("get_special_cstats", &ConstructorStats::get<SpecialClass>,
+py::return_value_policy::reference)
 
 Finally, you can suppress the output messages, but keep the constructor tracking (for
 inspection/testing in python) by using the functions with `print_` replaced with `track_` (e.g.
@@ -65,17 +66,18 @@ inspection/testing in python) by using the functions with `print_` replaced with
 */
 
 #include "pybind11_tests.h"
-#include <unordered_map>
+
 #include <list>
-#include <typeindex>
 #include <sstream>
+#include <typeindex>
+#include <unordered_map>
 
 class ConstructorStats {
 protected:
-    std::unordered_map<void*, int> _instances; // Need a map rather than set because members can
-                                               // shared address with parents
-    std::list<std::string> _values; // Used to track values
-                                    // (e.g. of value constructors)
+    std::unordered_map<void *, int> _instances; // Need a map rather than set because members can
+                                                // shared address with parents
+    std::list<std::string> _values;             // Used to track values
+                                                // (e.g. of value constructors)
 public:
     int default_constructions = 0;
     int copy_constructions = 0;
@@ -98,9 +100,7 @@ class ConstructorStats {
         default_constructions++;
     }
 
-    void created(void *inst) {
-        ++_instances[inst];
-    }
+    void created(void *inst) { ++_instances[inst]; }
 
     void destroyed(void *inst) {
         if (--_instances[inst] < 0) {
@@ -114,11 +114,12 @@ class ConstructorStats {
         // Force garbage collection to ensure any pending destructors are invoked:
 #if defined(PYPY_VERSION)
         PyObject *globals = PyEval_GetGlobals();
-        PyObject *result = PyRun_String(
-            "import gc\n"
-            "for i in range(2):"
-            "    gc.collect()\n",
-            Py_file_input, globals, globals);
+        PyObject *result = PyRun_String("import gc\n"
+                                        "for i in range(2):"
+                                        "    gc.collect()\n",
+                                        Py_file_input,
+                                        globals,
+                                        globals);
         if (result == nullptr)
             throw py::error_already_set();
         Py_DECREF(result);
@@ -140,7 +141,8 @@ class ConstructorStats {
 
     void value() {} // Recursion terminator
     // Takes one or more values, converts them to strings, then stores them.
-    template <typename T, typename... Tmore> void value(const T &v, Tmore &&...args) {
+    template <typename T, typename... Tmore>
+    void value(const T &v, Tmore &&...args) {
         std::ostringstream oss;
         oss << v;
         _values.push_back(oss.str());
@@ -158,13 +160,14 @@ class ConstructorStats {
     }
 
     // Gets constructor stats from a C++ type index
-    static ConstructorStats& get(std::type_index type) {
+    static ConstructorStats &get(std::type_index type) {
         static std::unordered_map<std::type_index, ConstructorStats> all_cstats;
         return all_cstats[type];
     }
 
     // Gets constructor stats from a C++ type
-    template <typename T> static ConstructorStats& get() {
+    template <typename T>
+    static ConstructorStats &get() {
 #if defined(PYPY_VERSION)
         gc();
 #endif
@@ -172,11 +175,12 @@ class ConstructorStats {
     }
 
     // Gets constructor stats from a Python class
-    static ConstructorStats& get(py::object class_) {
+    static ConstructorStats &get(py::object class_) {
         auto &internals = py::detail::get_internals();
         const std::type_index *t1 = nullptr, *t2 = nullptr;
         try {
-            auto *type_info = internals.registered_types_py.at((PyTypeObject *) class_.ptr()).at(0);
+            auto *type_info
+                = internals.registered_types_py.at((PyTypeObject *) class_.ptr()).at(0);
             for (auto &p : internals.registered_types_cpp) {
                 if (p.second == type_info) {
                     if (t1) {
@@ -186,18 +190,20 @@ class ConstructorStats {
                     t1 = &p.first;
                 }
             }
+        } catch (const std::out_of_range &) {
         }
-        catch (const std::out_of_range&) {}
         if (!t1) {
             throw std::runtime_error("Unknown class passed to ConstructorStats::get()");
         }
         auto &cs1 = get(*t1);
-        // If we have both a t1 and t2 match, one is probably the trampoline class; return whichever
-        // has more constructions (typically one or the other will be 0)
+        // If we have both a t1 and t2 match, one is probably the trampoline class; return
+        // whichever has more constructions (typically one or the other will be 0)
         if (t2) {
             auto &cs2 = get(*t2);
-            int cs1_total = cs1.default_constructions + cs1.copy_constructions + cs1.move_constructions + (int) cs1._values.size();
-            int cs2_total = cs2.default_constructions + cs2.copy_constructions + cs2.move_constructions + (int) cs2._values.size();
+            int cs1_total = cs1.default_constructions + cs1.copy_constructions
+                            + cs1.move_constructions + (int) cs1._values.size();
+            int cs2_total = cs2.default_constructions + cs2.copy_constructions
+                            + cs2.move_constructions + (int) cs2._values.size();
             if (cs2_total > cs1_total) {
                 return cs2;
             }
@@ -209,78 +215,108 @@ class ConstructorStats {
 // To track construction/destruction, you need to call these methods from the various
 // constructors/operators.  The ones that take extra values record the given values in the
 // constructor stats values for later inspection.
-template <class T> void track_copy_created(T *inst) { ConstructorStats::get<T>().copy_created(inst); }
-template <class T> void track_move_created(T *inst) { ConstructorStats::get<T>().move_created(inst); }
-template <class T, typename... Values> void track_copy_assigned(T *, Values &&...values) {
+template <class T>
+void track_copy_created(T *inst) {
+    ConstructorStats::get<T>().copy_created(inst);
+}
+template <class T>
+void track_move_created(T *inst) {
+    ConstructorStats::get<T>().move_created(inst);
+}
+template <class T, typename... Values>
+void track_copy_assigned(T *, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.copy_assignments++;
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_move_assigned(T *, Values &&...values) {
+template <class T, typename... Values>
+void track_move_assigned(T *, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.move_assignments++;
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_default_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void track_default_created(T *inst, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.default_created(inst);
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void track_created(T *inst, Values &&...values) {
     auto &cst = ConstructorStats::get<T>();
     cst.created(inst);
     cst.value(std::forward<Values>(values)...);
 }
-template <class T, typename... Values> void track_destroyed(T *inst) {
+template <class T, typename... Values>
+void track_destroyed(T *inst) {
     ConstructorStats::get<T>().destroyed(inst);
 }
-template <class T, typename... Values> void track_values(T *, Values &&...values) {
+template <class T, typename... Values>
+void track_values(T *, Values &&...values) {
     ConstructorStats::get<T>().value(std::forward<Values>(values)...);
 }
 
 /// Don't cast pointers to Python, print them as strings
 inline const char *format_ptrs(const char *p) { return p; }
 template <typename T>
-py::str format_ptrs(T *p) { return "{:#x}"_s.format(reinterpret_cast<std::uintptr_t>(p)); }
+py::str format_ptrs(T *p) {
+    return "{:#x}"_s.format(reinterpret_cast<std::uintptr_t>(p));
+}
 template <typename T>
-auto format_ptrs(T &&x) -> decltype(std::forward<T>(x)) { return std::forward<T>(x); }
+auto format_ptrs(T &&x) -> decltype(std::forward<T>(x)) {
+    return std::forward<T>(x);
+}
 
 template <class T, typename... Output>
 void print_constr_details(T *inst, const std::string &action, Output &&...output) {
-    py::print("###", py::type_id<T>(), "@", format_ptrs(inst), action,
+    py::print("###",
+              py::type_id<T>(),
+              "@",
+              format_ptrs(inst),
+              action,
               format_ptrs(std::forward<Output>(output))...);
 }
 
 // Verbose versions of the above:
-template <class T, typename... Values> void print_copy_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
+template <class T, typename... Values>
+void print_copy_created(T *inst,
+                        Values &&...values) { // NB: this prints, but doesn't store, given values
     print_constr_details(inst, "created via copy constructor", values...);
     track_copy_created(inst);
 }
-template <class T, typename... Values> void print_move_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
+template <class T, typename... Values>
+void print_move_created(T *inst,
+                        Values &&...values) { // NB: this prints, but doesn't store, given values
     print_constr_details(inst, "created via move constructor", values...);
     track_move_created(inst);
 }
-template <class T, typename... Values> void print_copy_assigned(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_copy_assigned(T *inst, Values &&...values) {
     print_constr_details(inst, "assigned via copy assignment", values...);
     track_copy_assigned(inst, values...);
 }
-template <class T, typename... Values> void print_move_assigned(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_move_assigned(T *inst, Values &&...values) {
     print_constr_details(inst, "assigned via move assignment", values...);
     track_move_assigned(inst, values...);
 }
-template <class T, typename... Values> void print_default_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_default_created(T *inst, Values &&...values) {
     print_constr_details(inst, "created via default constructor", values...);
     track_default_created(inst, values...);
 }
-template <class T, typename... Values> void print_created(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_created(T *inst, Values &&...values) {
     print_constr_details(inst, "created", values...);
     track_created(inst, values...);
 }
-template <class T, typename... Values> void print_destroyed(T *inst, Values &&...values) { // Prints but doesn't store given values
+template <class T, typename... Values>
+void print_destroyed(T *inst, Values &&...values) { // Prints but doesn't store given values
     print_constr_details(inst, "destroyed", values...);
     track_destroyed(inst);
 }
-template <class T, typename... Values> void print_values(T *inst, Values &&...values) {
+template <class T, typename... Values>
+void print_values(T *inst, Values &&...values) {
     print_constr_details(inst, ":", values...);
     track_values(inst, values...);
 }
diff --git a/tests/cross_module_gil_utils.cpp b/tests/cross_module_gil_utils.cpp
index 07db9f6e48..f3aca1561a 100644
--- a/tests/cross_module_gil_utils.cpp
+++ b/tests/cross_module_gil_utils.cpp
@@ -7,6 +7,7 @@
     BSD-style license that can be found in the LICENSE file.
 */
 #include <pybind11/pybind11.h>
+
 #include <cstdint>
 
 // This file mimics a DSO that makes pybind11 calls but does not define a
@@ -25,34 +26,25 @@ void gil_acquire() { py::gil_scoped_acquire gil; }
 constexpr char kModuleName[] = "cross_module_gil_utils";
 
 #if PY_MAJOR_VERSION >= 3
-struct PyModuleDef moduledef = {
-    PyModuleDef_HEAD_INIT,
-    kModuleName,
-    NULL,
-    0,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL
-};
+struct PyModuleDef moduledef
+    = {PyModuleDef_HEAD_INIT, kModuleName, NULL, 0, NULL, NULL, NULL, NULL, NULL};
 #else
-PyMethodDef module_methods[] = {
-    {NULL, NULL, 0, NULL}
-};
+PyMethodDef module_methods[] = {{NULL, NULL, 0, NULL}};
 #endif
 
-}  // namespace
+} // namespace
 
 extern "C" PYBIND11_EXPORT
 #if PY_MAJOR_VERSION >= 3
-PyObject* PyInit_cross_module_gil_utils()
+    PyObject *
+    PyInit_cross_module_gil_utils()
 #else
-void initcross_module_gil_utils()
+    void
+    initcross_module_gil_utils()
 #endif
 {
 
-    PyObject* m =
+    PyObject *m =
 #if PY_MAJOR_VERSION >= 3
         PyModule_Create(&moduledef);
 #else
@@ -60,11 +52,10 @@ void initcross_module_gil_utils()
 #endif
 
     if (m != NULL) {
-        static_assert(
-            sizeof(&gil_acquire) == sizeof(void*),
-            "Function pointer must have the same size as void*");
-        PyModule_AddObject(m, "gil_acquire_funcaddr",
-                           PyLong_FromVoidPtr(reinterpret_cast<void*>(&gil_acquire)));
+        static_assert(sizeof(&gil_acquire) == sizeof(void *),
+                      "Function pointer must have the same size as void*");
+        PyModule_AddObject(
+            m, "gil_acquire_funcaddr", PyLong_FromVoidPtr(reinterpret_cast<void *>(&gil_acquire)));
     }
 
 #if PY_MAJOR_VERSION >= 3
diff --git a/tests/local_bindings.h b/tests/local_bindings.h
index 4c936c19a5..01d2785353 100644
--- a/tests/local_bindings.h
+++ b/tests/local_bindings.h
@@ -1,12 +1,13 @@
 #pragma once
-#include <utility>
-
 #include "pybind11_tests.h"
 
+#include <utility>
+
 /// Simple class used to test py::local:
-template <int> class LocalBase {
+template <int>
+class LocalBase {
 public:
-    explicit LocalBase(int i) : i(i) { }
+    explicit LocalBase(int i) : i(i) {}
     int i = -1;
 };
 
@@ -35,12 +36,12 @@ using NonLocalVec2 = std::vector<NonLocal2>;
 using NonLocalMap = std::unordered_map<std::string, NonLocalType>;
 using NonLocalMap2 = std::unordered_map<std::string, uint8_t>;
 
-
 // Exception that will be caught via the module local translator.
 class LocalException : public std::exception {
 public:
-    explicit LocalException(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit LocalException(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -48,8 +49,9 @@ class LocalException : public std::exception {
 // Exception that will be registered with register_local_exception_translator
 class LocalSimpleException : public std::exception {
 public:
-    explicit LocalSimpleException(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit LocalSimpleException(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -58,17 +60,16 @@ PYBIND11_MAKE_OPAQUE(LocalVec);
 PYBIND11_MAKE_OPAQUE(LocalVec2);
 PYBIND11_MAKE_OPAQUE(LocalMap);
 PYBIND11_MAKE_OPAQUE(NonLocalVec);
-//PYBIND11_MAKE_OPAQUE(NonLocalVec2); // same type as LocalVec2
+// PYBIND11_MAKE_OPAQUE(NonLocalVec2); // same type as LocalVec2
 PYBIND11_MAKE_OPAQUE(NonLocalMap);
 PYBIND11_MAKE_OPAQUE(NonLocalMap2);
 
-
 // Simple bindings (used with the above):
 template <typename T, int Adjust = 0, typename... Args>
-py::class_<T> bind_local(Args && ...args) {
-    return py::class_<T>(std::forward<Args>(args)...)
-        .def(py::init<int>())
-        .def("get", [](T &i) { return i.i + Adjust; });
+py::class_<T> bind_local(Args &&...args) {
+    return py::class_<T>(std::forward<Args>(args)...).def(py::init<int>()).def("get", [](T &i) {
+        return i.i + Adjust;
+    });
 };
 
 // Simulate a foreign library base class (to match the example in the docs):
@@ -81,5 +82,11 @@ class Pet {
 };
 } // namespace pets
 
-struct MixGL { int i; explicit MixGL(int i) : i{i} {} };
-struct MixGL2 { int i; explicit MixGL2(int i) : i{i} {} };
+struct MixGL {
+    int i;
+    explicit MixGL(int i) : i{i} {}
+};
+struct MixGL2 {
+    int i;
+    explicit MixGL2(int i) : i{i} {}
+};
diff --git a/tests/object.h b/tests/object.h
index 6365457c34..564dd4a7a5 100644
--- a/tests/object.h
+++ b/tests/object.h
@@ -1,8 +1,9 @@
 #if !defined(__OBJECT_H)
-#define __OBJECT_H
+#    define __OBJECT_H
 
-#include <atomic>
-#include "constructor_stats.h"
+#    include "constructor_stats.h"
+
+#    include <atomic>
 
 /// Reference counted object base class
 class Object {
@@ -35,13 +36,15 @@ class Object {
     }
 
     virtual std::string toString() const = 0;
+
 protected:
     /** \brief Virtual protected deconstructor.
      * (Will only be called by \ref ref)
      */
     virtual ~Object() { print_destroyed(this); }
+
 private:
-    mutable std::atomic<int> m_refCount { 0 };
+    mutable std::atomic<int> m_refCount{0};
 };
 
 // Tag class used to track constructions of ref objects.  When we track constructors, below, we
@@ -60,10 +63,14 @@ class ref_tag {};
  *
  * \ingroup libcore
  */
-template <typename T> class ref {
+template <typename T>
+class ref {
 public:
     /// Create a nullptr reference
-    ref() : m_ptr(nullptr) { print_default_created(this); track_default_created((ref_tag*) this); }
+    ref() : m_ptr(nullptr) {
+        print_default_created(this);
+        track_default_created((ref_tag *) this);
+    }
 
     /// Construct a reference from a pointer
     explicit ref(T *ptr) : m_ptr(ptr) {
@@ -71,8 +78,8 @@ template <typename T> class ref {
             ((Object *) m_ptr)->incRef();
         }
 
-        print_created(this, "from pointer", m_ptr); track_created((ref_tag*) this, "from pointer");
-
+        print_created(this, "from pointer", m_ptr);
+        track_created((ref_tag *) this, "from pointer");
     }
 
     /// Copy constructor
@@ -81,14 +88,16 @@ template <typename T> class ref {
             ((Object *) m_ptr)->incRef();
         }
 
-        print_copy_created(this, "with pointer", m_ptr); track_copy_created((ref_tag*) this);
+        print_copy_created(this, "with pointer", m_ptr);
+        track_copy_created((ref_tag *) this);
     }
 
     /// Move constructor
     ref(ref &&r) noexcept : m_ptr(r.m_ptr) {
         r.m_ptr = nullptr;
 
-        print_move_created(this, "with pointer", m_ptr); track_move_created((ref_tag*) this);
+        print_move_created(this, "with pointer", m_ptr);
+        track_move_created((ref_tag *) this);
     }
 
     /// Destroy this reference
@@ -97,12 +106,14 @@ template <typename T> class ref {
             ((Object *) m_ptr)->decRef();
         }
 
-        print_destroyed(this); track_destroyed((ref_tag*) this);
+        print_destroyed(this);
+        track_destroyed((ref_tag *) this);
     }
 
     /// Move another reference into the current one
     ref &operator=(ref &&r) noexcept {
-        print_move_assigned(this, "pointer", r.m_ptr); track_move_assigned((ref_tag*) this);
+        print_move_assigned(this, "pointer", r.m_ptr);
+        track_move_assigned((ref_tag *) this);
 
         if (*this == r) {
             return *this;
@@ -116,7 +127,7 @@ template <typename T> class ref {
     }
 
     /// Overwrite this reference with another reference
-    ref& operator=(const ref& r) {
+    ref &operator=(const ref &r) {
         if (this == &r) {
             return *this;
         }
@@ -137,8 +148,9 @@ template <typename T> class ref {
     }
 
     /// Overwrite this reference with a pointer to another object
-    ref& operator=(T *ptr) {
-        print_values(this, "assigned pointer"); track_values((ref_tag*) this, "assigned pointer");
+    ref &operator=(T *ptr) {
+        print_values(this, "assigned pointer");
+        track_values((ref_tag *) this, "assigned pointer");
 
         if (m_ptr == ptr) {
             return *this;
@@ -160,31 +172,32 @@ template <typename T> class ref {
     bool operator!=(const ref &r) const { return m_ptr != r.m_ptr; }
 
     /// Compare this reference with a pointer
-    bool operator==(const T* ptr) const { return m_ptr == ptr; }
+    bool operator==(const T *ptr) const { return m_ptr == ptr; }
 
     /// Compare this reference with a pointer
-    bool operator!=(const T* ptr) const { return m_ptr != ptr; }
+    bool operator!=(const T *ptr) const { return m_ptr != ptr; }
 
     /// Access the object referenced by this reference
-    T* operator->() { return m_ptr; }
+    T *operator->() { return m_ptr; }
 
     /// Access the object referenced by this reference
-    const T* operator->() const { return m_ptr; }
+    const T *operator->() const { return m_ptr; }
 
     /// Return a C++ reference to the referenced object
-    T& operator*() { return *m_ptr; }
+    T &operator*() { return *m_ptr; }
 
     /// Return a const C++ reference to the referenced object
-    const T& operator*() const { return *m_ptr; }
+    const T &operator*() const { return *m_ptr; }
 
     /// Return a pointer to the referenced object
-    explicit operator T* () { return m_ptr; }
+    explicit operator T *() { return m_ptr; }
 
     /// Return a const pointer to the referenced object
-    T* get_ptr() { return m_ptr; }
+    T *get_ptr() { return m_ptr; }
 
     /// Return a pointer to the referenced object
-    const T* get_ptr() const { return m_ptr; }
+    const T *get_ptr() const { return m_ptr; }
+
 private:
     T *m_ptr;
 };
diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp
index 82228a440a..9379f3f259 100644
--- a/tests/pybind11_cross_module_tests.cpp
+++ b/tests/pybind11_cross_module_tests.cpp
@@ -7,12 +7,12 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
+#include <pybind11/stl_bind.h>
+
 #include "local_bindings.h"
+#include "pybind11_tests.h"
 #include "test_exceptions.h"
 
-#include <pybind11/stl_bind.h>
-
 #include <numeric>
 #include <utility>
 
@@ -30,39 +30,45 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
 
     // test_exceptions.py
     py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException");
-    m.def("raise_runtime_error", []() { PyErr_SetString(PyExc_RuntimeError, "My runtime error"); throw py::error_already_set(); });
-    m.def("raise_value_error", []() { PyErr_SetString(PyExc_ValueError, "My value error"); throw py::error_already_set(); });
+    m.def("raise_runtime_error", []() {
+        PyErr_SetString(PyExc_RuntimeError, "My runtime error");
+        throw py::error_already_set();
+    });
+    m.def("raise_value_error", []() {
+        PyErr_SetString(PyExc_ValueError, "My value error");
+        throw py::error_already_set();
+    });
     m.def("throw_pybind_value_error", []() { throw py::value_error("pybind11 value error"); });
     m.def("throw_pybind_type_error", []() { throw py::type_error("pybind11 type error"); });
     m.def("throw_stop_iteration", []() { throw py::stop_iteration(); });
     m.def("throw_local_error", []() { throw LocalException("just local"); });
     m.def("throw_local_simple_error", []() { throw LocalSimpleException("external mod"); });
     py::register_exception_translator([](std::exception_ptr p) {
-      try {
-          if (p) {
-              std::rethrow_exception(p);
-          }
-      } catch (const shared_exception &e) {
-          PyErr_SetString(PyExc_KeyError, e.what());
-      }
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const shared_exception &e) {
+            PyErr_SetString(PyExc_KeyError, e.what());
+        }
     });
 
     // translate the local exception into a key error but only in this module
     py::register_local_exception_translator([](std::exception_ptr p) {
-      try {
-          if (p) {
-            std::rethrow_exception(p);
-          }
-      } catch (const LocalException &e) {
-        PyErr_SetString(PyExc_KeyError, e.what());
-      }
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const LocalException &e) {
+            PyErr_SetString(PyExc_KeyError, e.what());
+        }
     });
 
     // test_local_bindings.py
     // Local to both:
-    bind_local<LocalType, 1>(m, "LocalType", py::module_local())
-        .def("get2", [](LocalType &t) { return t.i + 2; })
-        ;
+    bind_local<LocalType, 1>(m, "LocalType", py::module_local()).def("get2", [](LocalType &t) {
+        return t.i + 2;
+    });
 
     // Can only be called with our python type:
     m.def("local_value", [](LocalType &l) { return l.i; });
@@ -70,9 +76,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_nonlocal_failure
     // This registration will fail (global registration when LocalFail is already registered
     // globally in the main test module):
-    m.def("register_nonlocal", [m]() {
-        bind_local<NonLocalType, 0>(m, "NonLocalType");
-    });
+    m.def("register_nonlocal", [m]() { bind_local<NonLocalType, 0>(m, "NonLocalType"); });
 
     // test_stl_bind_local
     // stl_bind.h binders defaults to py::module_local if the types are local or converting:
@@ -82,27 +86,21 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_stl_bind_global
     // and global if the type (or one of the types, for the map) is global (so these will fail,
     // assuming pybind11_tests is already loaded):
-    m.def("register_nonlocal_vec", [m]() {
-        py::bind_vector<NonLocalVec>(m, "NonLocalVec");
-    });
-    m.def("register_nonlocal_map", [m]() {
-        py::bind_map<NonLocalMap>(m, "NonLocalMap");
-    });
+    m.def("register_nonlocal_vec", [m]() { py::bind_vector<NonLocalVec>(m, "NonLocalVec"); });
+    m.def("register_nonlocal_map", [m]() { py::bind_map<NonLocalMap>(m, "NonLocalMap"); });
     // The default can, however, be overridden to global using `py::module_local()` or
     // `py::module_local(false)`.
     // Explicitly made local:
     py::bind_vector<NonLocalVec2>(m, "NonLocalVec2", py::module_local());
     // Explicitly made global (and so will fail to bind):
-    m.def("register_nonlocal_map2", [m]() {
-        py::bind_map<NonLocalMap2>(m, "NonLocalMap2", py::module_local(false));
-    });
+    m.def("register_nonlocal_map2",
+          [m]() { py::bind_map<NonLocalMap2>(m, "NonLocalMap2", py::module_local(false)); });
 
     // test_mixed_local_global
     // We try this both with the global type registered first and vice versa (the order shouldn't
     // matter).
-    m.def("register_mixed_global_local", [m]() {
-        bind_local<MixedGlobalLocal, 200>(m, "MixedGlobalLocal", py::module_local());
-    });
+    m.def("register_mixed_global_local",
+          [m]() { bind_local<MixedGlobalLocal, 200>(m, "MixedGlobalLocal", py::module_local()); });
     m.def("register_mixed_local_global", [m]() {
         bind_local<MixedLocalGlobal, 2000>(m, "MixedLocalGlobal", py::module_local(false));
     });
@@ -110,14 +108,14 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); });
 
     // test_internal_locals_differ
-    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
+    m.def("local_cpp_types_addr",
+          []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
 
     // test_stl_caster_vs_stl_bind
     py::bind_vector<std::vector<int>>(m, "VectorInt");
 
-    m.def("load_vector_via_binding", [](std::vector<int> &v) {
-        return std::accumulate(v.begin(), v.end(), 0);
-    });
+    m.def("load_vector_via_binding",
+          [](std::vector<int> &v) { return std::accumulate(v.begin(), v.end(), 0); });
 
     // test_cross_module_calls
     m.def("return_self", [](LocalVec *v) { return v; });
@@ -127,11 +125,9 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     public:
         explicit Dog(std::string name) : Pet(std::move(name)) {}
     };
-    py::class_<pets::Pet>(m, "Pet", py::module_local())
-        .def("name", &pets::Pet::name);
+    py::class_<pets::Pet>(m, "Pet", py::module_local()).def("name", &pets::Pet::name);
     // Binding for local extending class:
-    py::class_<Dog, pets::Pet>(m, "Dog")
-        .def(py::init<std::string>());
+    py::class_<Dog, pets::Pet>(m, "Dog").def(py::init<std::string>());
     m.def("pet_name", [](pets::Pet &p) { return p.name(); });
 
     py::class_<MixGL>(m, "MixGL", py::module_local()).def(py::init<int>());
diff --git a/tests/pybind11_tests.cpp b/tests/pybind11_tests.cpp
index ec4581efd2..d9b88fcc24 100644
--- a/tests/pybind11_tests.cpp
+++ b/tests/pybind11_tests.cpp
@@ -8,6 +8,7 @@
 */
 
 #include "pybind11_tests.h"
+
 #include "constructor_stats.h"
 
 #include <functional>
@@ -31,9 +32,7 @@ std::list<std::function<void(py::module_ &)>> &initializers() {
     return inits;
 }
 
-test_initializer::test_initializer(Initializer init) {
-    initializers().emplace_back(init);
-}
+test_initializer::test_initializer(Initializer init) { initializers().emplace_back(init); }
 
 test_initializer::test_initializer(const char *submodule_name, Initializer init) {
     initializers().emplace_back([=](py::module_ &parent) {
@@ -51,15 +50,16 @@ void bind_ConstructorStats(py::module_ &m) {
         .def_readwrite("move_assignments", &ConstructorStats::move_assignments)
         .def_readwrite("copy_constructions", &ConstructorStats::copy_constructions)
         .def_readwrite("move_constructions", &ConstructorStats::move_constructions)
-        .def_static("get", (ConstructorStats &(*)(py::object)) &ConstructorStats::get, py::return_value_policy::reference_internal)
+        .def_static("get",
+                    (ConstructorStats & (*) (py::object)) & ConstructorStats::get,
+                    py::return_value_policy::reference_internal)
 
-        // Not exactly ConstructorStats, but related: expose the internal pybind number of registered instances
-        // to allow instance cleanup checks (invokes a GC first)
+        // Not exactly ConstructorStats, but related: expose the internal pybind number of
+        // registered instances to allow instance cleanup checks (invokes a GC first)
         .def_static("detail_reg_inst", []() {
             ConstructorStats::gc();
             return py::detail::get_internals().registered_instances.size();
-        })
-        ;
+        });
 }
 
 PYBIND11_MODULE(pybind11_tests, m) {
@@ -79,12 +79,12 @@ PYBIND11_MODULE(pybind11_tests, m) {
         .def("get_value", &UserType::value, "Get value using a method")
         .def("set_value", &UserType::set, "Set value using a method")
         .def_property("value", &UserType::value, &UserType::set, "Get/set value using a property")
-        .def("__repr__", [](const UserType& u) { return "UserType({})"_s.format(u.value()); });
+        .def("__repr__", [](const UserType &u) { return "UserType({})"_s.format(u.value()); });
 
     py::class_<IncType, UserType>(m, "IncType")
         .def(py::init<>())
         .def(py::init<int>())
-        .def("__repr__", [](const IncType& u) { return "IncType({})"_s.format(u.value()); });
+        .def("__repr__", [](const IncType &u) { return "IncType({})"_s.format(u.value()); });
 
     for (const auto &initializer : initializers()) {
         initializer(m);
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index f6e1a6523b..283801a1b7 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -1,11 +1,12 @@
 #pragma once
 
-#include <pybind11/pybind11.h>
 #include <pybind11/eval.h>
+#include <pybind11/pybind11.h>
 
 #if defined(_MSC_VER) && _MSC_VER < 1910
 // We get some really long type names here which causes MSVC 2015 to emit warnings
-#    pragma warning(disable : 4503) // NOLINT: warning C4503: decorated name length exceeded, name was truncated
+#    pragma warning(                                                                              \
+        disable : 4503) // NOLINT: warning C4503: decorated name length exceeded, name was truncated
 #endif
 
 namespace py = pybind11;
@@ -25,13 +26,13 @@ class test_initializer {
     void test_submodule_##name(py::module_ &(variable))
 
 /// Dummy type which is not exported anywhere -- something to trigger a conversion error
-struct UnregisteredType { };
+struct UnregisteredType {};
 
 /// A user-defined type which is exported and can be used by any test
 class UserType {
 public:
     UserType() = default;
-    explicit UserType(int i) : i(i) { }
+    explicit UserType(int i) : i(i) {}
 
     int value() const { return i; }
     void set(int set) { i = set; }
@@ -45,7 +46,7 @@ class IncType : public UserType {
 public:
     using UserType::UserType;
     IncType() = default;
-    IncType(const IncType &other) : IncType(other.value() + 1) { }
+    IncType(const IncType &other) : IncType(other.value() + 1) {}
     IncType(IncType &&) = delete;
     IncType &operator=(const IncType &) = delete;
     IncType &operator=(IncType &&) = delete;
@@ -57,16 +58,21 @@ union IntFloat {
     float f;
 };
 
-/// Custom cast-only type that casts to a string "rvalue" or "lvalue" depending on the cast context.
-/// Used to test recursive casters (e.g. std::tuple, stl containers).
+/// Custom cast-only type that casts to a string "rvalue" or "lvalue" depending on the cast
+/// context. Used to test recursive casters (e.g. std::tuple, stl containers).
 struct RValueCaster {};
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
-template<> class type_caster<RValueCaster> {
+template <>
+class type_caster<RValueCaster> {
 public:
     PYBIND11_TYPE_CASTER(RValueCaster, const_name("RValueCaster"));
-    static handle cast(RValueCaster &&, return_value_policy, handle) { return py::str("rvalue").release(); }
-    static handle cast(const RValueCaster &, return_value_policy, handle) { return py::str("lvalue").release(); }
+    static handle cast(RValueCaster &&, return_value_policy, handle) {
+        return py::str("rvalue").release();
+    }
+    static handle cast(const RValueCaster &, return_value_policy, handle) {
+        return py::str("lvalue").release();
+    }
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
@@ -80,5 +86,6 @@ void ignoreOldStyleInitWarnings(F &&body) {
     with warnings.catch_warnings():
         warnings.filterwarnings("ignore", message=message, category=FutureWarning)
         body()
-    )", py::dict(py::arg("body") = py::cpp_function(body)));
+    )",
+             py::dict(py::arg("body") = py::cpp_function(body)));
 }
diff --git a/tests/test_async.cpp b/tests/test_async.cpp
index e6e01d72c9..a5d7224657 100644
--- a/tests/test_async.cpp
+++ b/tests/test_async.cpp
@@ -11,12 +11,11 @@
 
 TEST_SUBMODULE(async_module, m) {
     struct DoesNotSupportAsync {};
-    py::class_<DoesNotSupportAsync>(m, "DoesNotSupportAsync")
-        .def(py::init<>());
+    py::class_<DoesNotSupportAsync>(m, "DoesNotSupportAsync").def(py::init<>());
     struct SupportsAsync {};
     py::class_<SupportsAsync>(m, "SupportsAsync")
         .def(py::init<>())
-        .def("__await__", [](const SupportsAsync& self) -> py::object {
+        .def("__await__", [](const SupportsAsync &self) -> py::object {
             static_cast<void>(self);
             py::object loop = py::module_::import("asyncio.events").attr("get_event_loop")();
             py::object f = loop.attr("create_future")();
diff --git a/tests/test_buffers.cpp b/tests/test_buffers.cpp
index 3a4d304676..6b6e8cba7f 100644
--- a/tests/test_buffers.cpp
+++ b/tests/test_buffers.cpp
@@ -7,10 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 TEST_SUBMODULE(buffers, m) {
     // test_from_python / test_to_python:
     class Matrix {
@@ -23,7 +24,8 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         Matrix(const Matrix &s) : m_rows(s.m_rows), m_cols(s.m_cols) {
-            print_copy_created(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            print_copy_created(this,
+                               std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[(size_t) (m_rows * m_cols)];
             memcpy(m_data, s.m_data, sizeof(float) * (size_t) (m_rows * m_cols));
@@ -37,7 +39,8 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         ~Matrix() {
-            print_destroyed(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            print_destroyed(this,
+                            std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             delete[] m_data;
         }
 
@@ -56,27 +59,33 @@ TEST_SUBMODULE(buffers, m) {
         }
 
         Matrix &operator=(Matrix &&s) noexcept {
-            print_move_assigned(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
+            print_move_assigned(this,
+                                std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
             if (&s != this) {
                 delete[] m_data;
-                m_rows = s.m_rows; m_cols = s.m_cols; m_data = s.m_data;
-                s.m_rows = 0; s.m_cols = 0; s.m_data = nullptr;
+                m_rows = s.m_rows;
+                m_cols = s.m_cols;
+                m_data = s.m_data;
+                s.m_rows = 0;
+                s.m_cols = 0;
+                s.m_data = nullptr;
             }
             return *this;
         }
 
         float operator()(py::ssize_t i, py::ssize_t j) const {
-            return m_data[(size_t) (i*m_cols + j)];
+            return m_data[(size_t) (i * m_cols + j)];
         }
 
         float &operator()(py::ssize_t i, py::ssize_t j) {
-            return m_data[(size_t) (i*m_cols + j)];
+            return m_data[(size_t) (i * m_cols + j)];
         }
 
         float *data() { return m_data; }
 
         py::ssize_t rows() const { return m_rows; }
         py::ssize_t cols() const { return m_cols; }
+
     private:
         py::ssize_t m_rows;
         py::ssize_t m_cols;
@@ -117,11 +126,10 @@ TEST_SUBMODULE(buffers, m) {
         /// Provide buffer access
         .def_buffer([](Matrix &m) -> py::buffer_info {
             return py::buffer_info(
-                m.data(),                               /* Pointer to buffer */
-                { m.rows(), m.cols() },                 /* Buffer dimensions */
-                { sizeof(float) * size_t(m.cols()),     /* Strides (in bytes) for each index */
-                  sizeof(float) }
-            );
+                m.data(),                          /* Pointer to buffer */
+                {m.rows(), m.cols()},              /* Buffer dimensions */
+                {sizeof(float) * size_t(m.cols()), /* Strides (in bytes) for each index */
+                 sizeof(float)});
         });
 
     // test_inherited_protocol
@@ -130,9 +138,7 @@ TEST_SUBMODULE(buffers, m) {
         explicit SquareMatrix(py::ssize_t n) : Matrix(n, n) {}
     };
     // Derived classes inherit the buffer protocol and the buffer access function
-    py::class_<SquareMatrix, Matrix>(m, "SquareMatrix")
-        .def(py::init<py::ssize_t>());
-
+    py::class_<SquareMatrix, Matrix>(m, "SquareMatrix").def(py::init<py::ssize_t>());
 
     // test_pointer_to_member_fn
     // Tests that passing a pointer to member to the base class works in
@@ -141,8 +147,8 @@ TEST_SUBMODULE(buffers, m) {
         int32_t value = 0;
 
         py::buffer_info get_buffer_info() {
-            return py::buffer_info(&value, sizeof(value),
-                                   py::format_descriptor<int32_t>::format(), 1);
+            return py::buffer_info(
+                &value, sizeof(value), py::format_descriptor<int32_t>::format(), 1);
         }
     };
     py::class_<Buffer>(m, "Buffer", py::buffer_protocol())
@@ -150,7 +156,6 @@ TEST_SUBMODULE(buffers, m) {
         .def_readwrite("value", &Buffer::value)
         .def_buffer(&Buffer::get_buffer_info);
 
-
     class ConstBuffer {
         std::unique_ptr<int32_t> value;
 
@@ -159,8 +164,8 @@ TEST_SUBMODULE(buffers, m) {
         void set_value(int32_t v) { *value = v; }
 
         py::buffer_info get_buffer_info() const {
-            return py::buffer_info(value.get(), sizeof(*value),
-                                   py::format_descriptor<int32_t>::format(), 1);
+            return py::buffer_info(
+                value.get(), sizeof(*value), py::format_descriptor<int32_t>::format(), 1);
         }
 
         ConstBuffer() : value(new int32_t{0}) {}
@@ -170,7 +175,7 @@ TEST_SUBMODULE(buffers, m) {
         .def_property("value", &ConstBuffer::get_value, &ConstBuffer::set_value)
         .def_buffer(&ConstBuffer::get_buffer_info);
 
-    struct DerivedBuffer : public Buffer { };
+    struct DerivedBuffer : public Buffer {};
     py::class_<DerivedBuffer>(m, "DerivedBuffer", py::buffer_protocol())
         .def(py::init<>())
         .def_readwrite("value", (int32_t DerivedBuffer::*) &DerivedBuffer::value)
@@ -180,9 +185,7 @@ TEST_SUBMODULE(buffers, m) {
         const uint8_t value = 0;
         explicit BufferReadOnly(uint8_t value) : value(value) {}
 
-        py::buffer_info get_buffer_info() {
-            return py::buffer_info(&value, 1);
-        }
+        py::buffer_info get_buffer_info() { return py::buffer_info(&value, 1); }
     };
     py::class_<BufferReadOnly>(m, "BufferReadOnly", py::buffer_protocol())
         .def(py::init<uint8_t>())
@@ -192,9 +195,7 @@ TEST_SUBMODULE(buffers, m) {
         uint8_t value = 0;
         bool readonly = false;
 
-        py::buffer_info get_buffer_info() {
-            return py::buffer_info(&value, 1, readonly);
-        }
+        py::buffer_info get_buffer_info() { return py::buffer_info(&value, 1, readonly); }
     };
     py::class_<BufferReadOnlySelect>(m, "BufferReadOnlySelect", py::buffer_protocol())
         .def(py::init<>())
@@ -213,9 +214,11 @@ TEST_SUBMODULE(buffers, m) {
         .def_readonly("strides", &py::buffer_info::strides)
         .def_readonly("readonly", &py::buffer_info::readonly)
         .def("__repr__", [](py::handle self) {
-             return py::str("itemsize={0.itemsize!r}, size={0.size!r}, format={0.format!r}, ndim={0.ndim!r}, shape={0.shape!r}, strides={0.strides!r}, readonly={0.readonly!r}").format(self);
-        })
-        ;
+            return py::str("itemsize={0.itemsize!r}, size={0.size!r}, format={0.format!r}, "
+                           "ndim={0.ndim!r}, shape={0.shape!r}, strides={0.strides!r}, "
+                           "readonly={0.readonly!r}")
+                .format(self);
+        });
 
     m.def("get_buffer_info", [](const py::buffer &buffer) { return buffer.request(); });
 }
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index dda9aa8db2..048b1c2141 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -7,64 +7,67 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/complex.h>
 
+#include "pybind11_tests.h"
+
 struct ConstRefCasted {
-  int tag;
+    int tag;
 };
 
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <>
 class type_caster<ConstRefCasted> {
- public:
-  static constexpr auto name = const_name<ConstRefCasted>();
-
-  // Input is unimportant, a new value will always be constructed based on the
-  // cast operator.
-  bool load(handle, bool) { return true; }
-
-  explicit operator ConstRefCasted &&() {
-      value = {1};
-      // NOLINTNEXTLINE(performance-move-const-arg)
-      return std::move(value);
-  }
-  explicit operator ConstRefCasted &() {
-      value = {2};
-      return value;
-  }
-  explicit operator ConstRefCasted *() {
-      value = {3};
-      return &value;
-  }
-
-  explicit operator const ConstRefCasted &() {
-      value = {4};
-      return value;
-  }
-  explicit operator const ConstRefCasted *() {
-      value = {5};
-      return &value;
-  }
-
-  // custom cast_op to explicitly propagate types to the conversion operators.
-  template <typename T_>
-  using cast_op_type =
-      /// const
-      conditional_t<
-          std::is_same<remove_reference_t<T_>, const ConstRefCasted*>::value, const ConstRefCasted*,
-      conditional_t<
-          std::is_same<T_, const ConstRefCasted&>::value, const ConstRefCasted&,
-      /// non-const
-      conditional_t<
-          std::is_same<remove_reference_t<T_>, ConstRefCasted*>::value, ConstRefCasted*,
-      conditional_t<
-          std::is_same<T_, ConstRefCasted&>::value, ConstRefCasted&,
-          /* else */ConstRefCasted&&>>>>;
-
- private:
-  ConstRefCasted value = {0};
+public:
+    static constexpr auto name = const_name<ConstRefCasted>();
+
+    // Input is unimportant, a new value will always be constructed based on the
+    // cast operator.
+    bool load(handle, bool) { return true; }
+
+    explicit operator ConstRefCasted &&() {
+        value = {1};
+        // NOLINTNEXTLINE(performance-move-const-arg)
+        return std::move(value);
+    }
+    explicit operator ConstRefCasted &() {
+        value = {2};
+        return value;
+    }
+    explicit operator ConstRefCasted *() {
+        value = {3};
+        return &value;
+    }
+
+    explicit operator const ConstRefCasted &() {
+        value = {4};
+        return value;
+    }
+    explicit operator const ConstRefCasted *() {
+        value = {5};
+        return &value;
+    }
+
+    // custom cast_op to explicitly propagate types to the conversion operators.
+    template <typename T_>
+    using cast_op_type =
+        /// const
+        conditional_t<
+            std::is_same<remove_reference_t<T_>, const ConstRefCasted *>::value,
+            const ConstRefCasted *,
+            conditional_t<
+                std::is_same<T_, const ConstRefCasted &>::value,
+                const ConstRefCasted &,
+                /// non-const
+                conditional_t<std::is_same<remove_reference_t<T_>, ConstRefCasted *>::value,
+                              ConstRefCasted *,
+                              conditional_t<std::is_same<T_, ConstRefCasted &>::value,
+                                            ConstRefCasted &,
+                                            /* else */ ConstRefCasted &&>>>>;
+
+private:
+    ConstRefCasted value = {0};
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
@@ -74,25 +77,43 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("string_roundtrip", [](const char *s) { return s; });
 
     // test_unicode_conversion
-    // Some test characters in utf16 and utf32 encodings.  The last one (the 𝐀) contains a null byte
-    char32_t a32 = 0x61 /*a*/, z32 = 0x7a /*z*/, ib32 = 0x203d /*‽*/, cake32 = 0x1f382 /*🎂*/,              mathbfA32 = 0x1d400 /*𝐀*/;
-    char16_t b16 = 0x62 /*b*/, z16 = 0x7a,       ib16 = 0x203d,       cake16_1 = 0xd83c, cake16_2 = 0xdf82, mathbfA16_1 = 0xd835, mathbfA16_2 = 0xdc00;
+    // Some test characters in utf16 and utf32 encodings.  The last one (the 𝐀) contains a null
+    // byte
+    char32_t a32 = 0x61 /*a*/, z32 = 0x7a /*z*/, ib32 = 0x203d /*‽*/, cake32 = 0x1f382 /*🎂*/,
+             mathbfA32 = 0x1d400 /*𝐀*/;
+    char16_t b16 = 0x62 /*b*/, z16 = 0x7a, ib16 = 0x203d, cake16_1 = 0xd83c, cake16_2 = 0xdf82,
+             mathbfA16_1 = 0xd835, mathbfA16_2 = 0xdc00;
     std::wstring wstr;
-    wstr.push_back(0x61); // a
+    wstr.push_back(0x61);   // a
     wstr.push_back(0x2e18); // ⸘
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) { wstr.push_back(mathbfA16_1); wstr.push_back(mathbfA16_2); } // 𝐀, utf16
-    else { wstr.push_back((wchar_t) mathbfA32); } // 𝐀, utf32
+    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+        wstr.push_back(mathbfA16_1);
+        wstr.push_back(mathbfA16_2);
+    } // 𝐀, utf16
+    else {
+        wstr.push_back((wchar_t) mathbfA32);
+    }                     // 𝐀, utf32
     wstr.push_back(0x7a); // z
 
-    m.def("good_utf8_string", []() { return std::string((const char*)u8"Say utf8\u203d \U0001f382 \U0001d400"); }); // Say utf8‽ 🎂 𝐀
-    m.def("good_utf16_string", [=]() { return std::u16string({ b16, ib16, cake16_1, cake16_2, mathbfA16_1, mathbfA16_2, z16 }); }); // b‽🎂𝐀z
-    m.def("good_utf32_string", [=]() { return std::u32string({ a32, mathbfA32, cake32, ib32, z32 }); }); // a𝐀🎂‽z
+    m.def("good_utf8_string", []() {
+        return std::string((const char *) u8"Say utf8\u203d \U0001f382 \U0001d400");
+    }); // Say utf8‽ 🎂 𝐀
+    m.def("good_utf16_string", [=]() {
+        return std::u16string({b16, ib16, cake16_1, cake16_2, mathbfA16_1, mathbfA16_2, z16});
+    }); // b‽🎂𝐀z
+    m.def("good_utf32_string", [=]() {
+        return std::u32string({a32, mathbfA32, cake32, ib32, z32});
+    });                                                 // a𝐀🎂‽z
     m.def("good_wchar_string", [=]() { return wstr; }); // a‽𝐀z
-    m.def("bad_utf8_string", []()  { return std::string("abc\xd0" "def"); });
-    m.def("bad_utf16_string", [=]() { return std::u16string({ b16, char16_t(0xd800), z16 }); });
+    m.def("bad_utf8_string", []() {
+        return std::string("abc\xd0"
+                           "def");
+    });
+    m.def("bad_utf16_string", [=]() { return std::u16string({b16, char16_t(0xd800), z16}); });
 #if PY_MAJOR_VERSION >= 3
-    // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger UnicodeDecodeError
-    m.def("bad_utf32_string", [=]() { return std::u32string({ a32, char32_t(0xd800), z32 }); });
+    // Under Python 2.7, invalid unicode UTF-32 characters don't appear to trigger
+    // UnicodeDecodeError
+    m.def("bad_utf32_string", [=]() { return std::u32string({a32, char32_t(0xd800), z32}); });
     if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
         m.def("bad_wchar_string", [=]() {
             return std::wstring({wchar_t(0x61), wchar_t(0xd800)});
@@ -120,8 +141,13 @@ TEST_SUBMODULE(builtin_casters, m) {
 
 #ifdef PYBIND11_HAS_U8STRING
     m.attr("has_u8string") = true;
-    m.def("good_utf8_u8string", []() { return std::u8string(u8"Say utf8\u203d \U0001f382 \U0001d400"); }); // Say utf8‽ 🎂 𝐀
-    m.def("bad_utf8_u8string", []()  { return std::u8string((const char8_t*)"abc\xd0" "def"); });
+    m.def("good_utf8_u8string", []() {
+        return std::u8string(u8"Say utf8\u203d \U0001f382 \U0001d400");
+    }); // Say utf8‽ 🎂 𝐀
+    m.def("bad_utf8_u8string", []() {
+        return std::u8string((const char8_t *) "abc\xd0"
+                                               "def");
+    });
 
     m.def("u8_char8_Z", []() -> char8_t { return u8'Z'; });
 
@@ -133,46 +159,63 @@ TEST_SUBMODULE(builtin_casters, m) {
     // test_string_view
 #ifdef PYBIND11_HAS_STRING_VIEW
     m.attr("has_string_view") = true;
-    m.def("string_view_print",   [](std::string_view s)    { py::print(s, s.size()); });
+    m.def("string_view_print", [](std::string_view s) { py::print(s, s.size()); });
     m.def("string_view16_print", [](std::u16string_view s) { py::print(s, s.size()); });
     m.def("string_view32_print", [](std::u32string_view s) { py::print(s, s.size()); });
-    m.def("string_view_chars",   [](std::string_view s)    { py::list l;
+    m.def("string_view_chars", [](std::string_view s) {
+        py::list l;
         for (auto c : s) {
             l.append((std::uint8_t) c);
         }
-        return l; });
-    m.def("string_view16_chars", [](std::u16string_view s) { py::list l;
+        return l;
+    });
+    m.def("string_view16_chars", [](std::u16string_view s) {
+        py::list l;
         for (auto c : s) {
             l.append((int) c);
         }
-        return l; });
-    m.def("string_view32_chars", [](std::u32string_view s) { py::list l;
+        return l;
+    });
+    m.def("string_view32_chars", [](std::u32string_view s) {
+        py::list l;
         for (auto c : s) {
             l.append((int) c);
         }
-        return l; });
-    m.def("string_view_return",   []() { return std::string_view((const char*)u8"utf8 secret \U0001f382"); });
-    m.def("string_view16_return", []() { return std::u16string_view(u"utf16 secret \U0001f382"); });
-    m.def("string_view32_return", []() { return std::u32string_view(U"utf32 secret \U0001f382"); });
+        return l;
+    });
+    m.def("string_view_return",
+          []() { return std::string_view((const char *) u8"utf8 secret \U0001f382"); });
+    m.def("string_view16_return",
+          []() { return std::u16string_view(u"utf16 secret \U0001f382"); });
+    m.def("string_view32_return",
+          []() { return std::u32string_view(U"utf32 secret \U0001f382"); });
 
     // The inner lambdas here are to also test implicit conversion
     using namespace std::literals;
-    m.def("string_view_bytes", []() { return [](py::bytes b) { return b; }("abc \x80\x80 def"sv); });
-    m.def("string_view_str",   []() { return [](py::str s) { return s; }("abc \342\200\275 def"sv); });
-    m.def("string_view_from_bytes", [](const py::bytes &b) { return [](std::string_view s) { return s; }(b); });
-#if PY_MAJOR_VERSION >= 3
+    m.def("string_view_bytes",
+          []() { return [](py::bytes b) { return b; }("abc \x80\x80 def"sv); });
+    m.def("string_view_str",
+          []() { return [](py::str s) { return s; }("abc \342\200\275 def"sv); });
+    m.def("string_view_from_bytes",
+          [](const py::bytes &b) { return [](std::string_view s) { return s; }(b); });
+#    if PY_MAJOR_VERSION >= 3
     m.def("string_view_memoryview", []() {
         static constexpr auto val = "Have some \360\237\216\202"sv;
         return py::memoryview::from_memory(val);
     });
-#endif
+#    endif
 
-#   ifdef PYBIND11_HAS_U8STRING
-    m.def("string_view8_print",  [](std::u8string_view s) { py::print(s, s.size()); });
-    m.def("string_view8_chars",  [](std::u8string_view s) { py::list l; for (auto c : s) l.append((std::uint8_t) c); return l; });
+#    ifdef PYBIND11_HAS_U8STRING
+    m.def("string_view8_print", [](std::u8string_view s) { py::print(s, s.size()); });
+    m.def("string_view8_chars", [](std::u8string_view s) {
+        py::list l;
+        for (auto c : s)
+            l.append((std::uint8_t) c);
+        return l;
+    });
     m.def("string_view8_return", []() { return std::u8string_view(u8"utf8 secret \U0001f382"); });
-    m.def("string_view8_str",    []() { return py::str{std::u8string_view{u8"abc ‽ def"}}; });
-#   endif
+    m.def("string_view8_str", []() { return py::str{std::u8string_view{u8"abc ‽ def"}}; });
+#    endif
 
     struct TypeWithBothOperatorStringAndStringView {
         // NOLINTNEXTLINE(google-explicit-constructor)
@@ -194,7 +237,8 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_int_convert
     m.def("int_passthrough", [](int arg) { return arg; });
-    m.def("int_passthrough_noconvert", [](int arg) { return arg; }, py::arg{}.noconvert());
+    m.def(
+        "int_passthrough_noconvert", [](int arg) { return arg; }, py::arg{}.noconvert());
 
     // test_tuple
     m.def(
@@ -203,19 +247,27 @@ TEST_SUBMODULE(builtin_casters, m) {
             return std::make_pair(input.second, input.first);
         },
         "Return a pair in reversed order");
-    m.def("tuple_passthrough", [](std::tuple<bool, std::string, int> input) {
-        return std::make_tuple(std::get<2>(input), std::get<1>(input), std::get<0>(input));
-    }, "Return a triple in reversed order");
+    m.def(
+        "tuple_passthrough",
+        [](std::tuple<bool, std::string, int> input) {
+            return std::make_tuple(std::get<2>(input), std::get<1>(input), std::get<0>(input));
+        },
+        "Return a triple in reversed order");
     m.def("empty_tuple", []() { return std::tuple<>(); });
     static std::pair<RValueCaster, RValueCaster> lvpair;
     static std::tuple<RValueCaster, RValueCaster, RValueCaster> lvtuple;
-    static std::pair<RValueCaster, std::tuple<RValueCaster, std::pair<RValueCaster, RValueCaster>>> lvnested;
+    static std::pair<RValueCaster, std::tuple<RValueCaster, std::pair<RValueCaster, RValueCaster>>>
+        lvnested;
     m.def("rvalue_pair", []() { return std::make_pair(RValueCaster{}, RValueCaster{}); });
     m.def("lvalue_pair", []() -> const decltype(lvpair) & { return lvpair; });
-    m.def("rvalue_tuple", []() { return std::make_tuple(RValueCaster{}, RValueCaster{}, RValueCaster{}); });
+    m.def("rvalue_tuple",
+          []() { return std::make_tuple(RValueCaster{}, RValueCaster{}, RValueCaster{}); });
     m.def("lvalue_tuple", []() -> const decltype(lvtuple) & { return lvtuple; });
     m.def("rvalue_nested", []() {
-        return std::make_pair(RValueCaster{}, std::make_tuple(RValueCaster{}, std::make_pair(RValueCaster{}, RValueCaster{}))); });
+        return std::make_pair(
+            RValueCaster{},
+            std::make_tuple(RValueCaster{}, std::make_pair(RValueCaster{}, RValueCaster{})));
+    });
     m.def("lvalue_nested", []() -> const decltype(lvnested) & { return lvnested; });
 
     static std::pair<int, std::string> int_string_pair{2, "items"};
@@ -223,11 +275,11 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_builtins_cast_return_none
     m.def("return_none_string", []() -> std::string * { return nullptr; });
-    m.def("return_none_char",   []() -> const char *  { return nullptr; });
-    m.def("return_none_bool",   []() -> bool *        { return nullptr; });
-    m.def("return_none_int",    []() -> int *         { return nullptr; });
-    m.def("return_none_float",  []() -> float *       { return nullptr; });
-    m.def("return_none_pair",   []() -> std::pair<int,int> * { return nullptr; });
+    m.def("return_none_char", []() -> const char * { return nullptr; });
+    m.def("return_none_bool", []() -> bool * { return nullptr; });
+    m.def("return_none_int", []() -> int * { return nullptr; });
+    m.def("return_none_float", []() -> float * { return nullptr; });
+    m.def("return_none_pair", []() -> std::pair<int, int> * { return nullptr; });
 
     // test_none_deferred
     m.def("defer_none_cstring", [](char *) { return false; });
@@ -245,7 +297,8 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_bool_caster
     m.def("bool_passthrough", [](bool arg) { return arg; });
-    m.def("bool_passthrough_noconvert", [](bool arg) { return arg; }, py::arg{}.noconvert());
+    m.def(
+        "bool_passthrough_noconvert", [](bool arg) { return arg; }, py::arg{}.noconvert());
 
     // TODO: This should be disabled and fixed in future Intel compilers
 #if !defined(__INTEL_COMPILER)
@@ -253,13 +306,15 @@ TEST_SUBMODULE(builtin_casters, m) {
     // When compiled with the Intel compiler, this results in segmentation faults when importing
     // the module. Tested with icc (ICC) 2021.1 Beta 20200827, this should be tested again when
     // a newer version of icc is available.
-    m.def("bool_passthrough_noconvert2", [](bool arg) { return arg; }, py::arg().noconvert());
+    m.def(
+        "bool_passthrough_noconvert2", [](bool arg) { return arg; }, py::arg().noconvert());
 #endif
 
     // test_reference_wrapper
     m.def("refwrap_builtin", [](std::reference_wrapper<int> p) { return 10 * p.get(); });
     m.def("refwrap_usertype", [](std::reference_wrapper<UserType> p) { return p.get().value(); });
-    m.def("refwrap_usertype_const", [](std::reference_wrapper<const UserType> p) { return p.get().value(); });
+    m.def("refwrap_usertype_const",
+          [](std::reference_wrapper<const UserType> p) { return p.get().value(); });
 
     m.def("refwrap_lvalue", []() -> std::reference_wrapper<UserType> {
         static UserType x(1);
@@ -272,17 +327,20 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // Not currently supported (std::pair caster has return-by-value cast operator);
     // triggers static_assert failure.
-    //m.def("refwrap_pair", [](std::reference_wrapper<std::pair<int, int>>) { });
+    // m.def("refwrap_pair", [](std::reference_wrapper<std::pair<int, int>>) { });
 
-    m.def("refwrap_list", [](bool copy) {
-        static IncType x1(1), x2(2);
-        py::list l;
-        for (const auto &f : {std::ref(x1), std::ref(x2)}) {
-            l.append(py::cast(f, copy ? py::return_value_policy::copy
-                                      : py::return_value_policy::reference));
-        }
-        return l;
-    }, "copy"_a);
+    m.def(
+        "refwrap_list",
+        [](bool copy) {
+            static IncType x1(1), x2(2);
+            py::list l;
+            for (const auto &f : {std::ref(x1), std::ref(x2)}) {
+                l.append(py::cast(
+                    f, copy ? py::return_value_policy::copy : py::return_value_policy::reference));
+            }
+            return l;
+        },
+        "copy"_a);
 
     m.def("refwrap_iiw", [](const IncType &w) { return w.value(); });
     m.def("refwrap_call_iiw", [](IncType &w, const py::function &f) {
@@ -299,12 +357,13 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // test_complex
     m.def("complex_cast", [](float x) { return "{}"_s.format(x); });
-    m.def("complex_cast", [](std::complex<float> x) { return "({}, {})"_s.format(x.real(), x.imag()); });
+    m.def("complex_cast",
+          [](std::complex<float> x) { return "({}, {})"_s.format(x.real(), x.imag()); });
 
     // test int vs. long (Python 2)
-    m.def("int_cast", []() {return (int) 42;});
-    m.def("long_cast", []() {return (long) 42;});
-    m.def("longlong_cast", []() {return  ULLONG_MAX;});
+    m.def("int_cast", []() { return (int) 42; });
+    m.def("long_cast", []() { return (long) 42; });
+    m.def("longlong_cast", []() { return ULLONG_MAX; });
 
     /// test void* cast operator
     m.def("test_void_caster", []() -> bool {
@@ -315,20 +374,21 @@ TEST_SUBMODULE(builtin_casters, m) {
 
     // Tests const/non-const propagation in cast_op.
     m.def("takes", [](ConstRefCasted x) { return x.tag; });
-    m.def("takes_move", [](ConstRefCasted&& x) { return x.tag; });
-    m.def("takes_ptr", [](ConstRefCasted* x) { return x->tag; });
-    m.def("takes_ref", [](ConstRefCasted& x) { return x.tag; });
+    m.def("takes_move", [](ConstRefCasted &&x) { return x.tag; });
+    m.def("takes_ptr", [](ConstRefCasted *x) { return x->tag; });
+    m.def("takes_ref", [](ConstRefCasted &x) { return x.tag; });
     m.def("takes_ref_wrap", [](std::reference_wrapper<ConstRefCasted> x) { return x.get().tag; });
-    m.def("takes_const_ptr", [](const ConstRefCasted* x) { return x->tag; });
-    m.def("takes_const_ref", [](const ConstRefCasted& x) { return x.tag; });
-    m.def("takes_const_ref_wrap", [](std::reference_wrapper<const ConstRefCasted> x) { return x.get().tag; });
+    m.def("takes_const_ptr", [](const ConstRefCasted *x) { return x->tag; });
+    m.def("takes_const_ref", [](const ConstRefCasted &x) { return x.tag; });
+    m.def("takes_const_ref_wrap",
+          [](std::reference_wrapper<const ConstRefCasted> x) { return x.get().tag; });
 
     // For Drake issue: https://github.com/RobotLocomotion/drake/issues/9398
     m.def("test_pointer_caster", []() -> bool {
         UserType a;
         UserType *a_ptr = &a;
-        py::object o = py::cast(&a); // Rvalue
+        py::object o = py::cast(&a);     // Rvalue
         py::object o1 = py::cast(a_ptr); // Non-rvalue
-        return (py::cast<UserType*>(o) == a_ptr && py::cast<UserType*>(o1) == a_ptr);
+        return (py::cast<UserType *>(o) == a_ptr && py::cast<UserType *>(o1) == a_ptr);
     });
 }
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index 8136bf4f8e..d177008cfe 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -40,18 +40,17 @@ TEST_SUBMODULE(call_policies, m) {
         Child(Child &&) = default;
         ~Child() { py::print("Releasing child."); }
     };
-    py::class_<Child>(m, "Child")
-        .def(py::init<>());
+    py::class_<Child>(m, "Child").def(py::init<>());
 
     class Parent {
     public:
         Parent() { py::print("Allocating parent."); }
-        Parent(const Parent& parent) = default;
+        Parent(const Parent &parent) = default;
         ~Parent() { py::print("Releasing parent."); }
-        void addChild(Child *) { }
+        void addChild(Child *) {}
         Child *returnChild() { return new Child(); }
         Child *returnNullChild() { return nullptr; }
-        static Child *staticFunction(Parent*) { return new Child(); }
+        static Child *staticFunction(Parent *) { return new Child(); }
     };
     py::class_<Parent>(m, "Parent")
         .def(py::init<>())
@@ -62,11 +61,12 @@ TEST_SUBMODULE(call_policies, m) {
         .def("returnChildKeepAlive", &Parent::returnChild, py::keep_alive<1, 0>())
         .def("returnNullChildKeepAliveChild", &Parent::returnNullChild, py::keep_alive<1, 0>())
         .def("returnNullChildKeepAliveParent", &Parent::returnNullChild, py::keep_alive<0, 1>())
-        .def_static(
-            "staticFunction", &Parent::staticFunction, py::keep_alive<1, 0>());
+        .def_static("staticFunction", &Parent::staticFunction, py::keep_alive<1, 0>());
 
-    m.def("free_function", [](Parent*, Child*) {}, py::keep_alive<1, 2>());
-    m.def("invalid_arg_index", []{}, py::keep_alive<0, 1>());
+    m.def(
+        "free_function", [](Parent *, Child *) {}, py::keep_alive<1, 2>());
+    m.def(
+        "invalid_arg_index", [] {}, py::keep_alive<0, 1>());
 
 #if !defined(PYPY_VERSION)
     // test_alive_gc
@@ -74,21 +74,28 @@ TEST_SUBMODULE(call_policies, m) {
     public:
         using Parent::Parent;
     };
-    py::class_<ParentGC, Parent>(m, "ParentGC", py::dynamic_attr())
-        .def(py::init<>());
+    py::class_<ParentGC, Parent>(m, "ParentGC", py::dynamic_attr()).def(py::init<>());
 #endif
 
     // test_call_guard
     m.def("unguarded_call", &CustomGuard::report_status);
     m.def("guarded_call", &CustomGuard::report_status, py::call_guard<CustomGuard>());
 
-    m.def("multiple_guards_correct_order", []() {
-        return CustomGuard::report_status() + std::string(" & ") + DependentGuard::report_status();
-    }, py::call_guard<CustomGuard, DependentGuard>());
-
-    m.def("multiple_guards_wrong_order", []() {
-        return DependentGuard::report_status() + std::string(" & ") + CustomGuard::report_status();
-    }, py::call_guard<DependentGuard, CustomGuard>());
+    m.def(
+        "multiple_guards_correct_order",
+        []() {
+            return CustomGuard::report_status() + std::string(" & ")
+                   + DependentGuard::report_status();
+        },
+        py::call_guard<CustomGuard, DependentGuard>());
+
+    m.def(
+        "multiple_guards_wrong_order",
+        []() {
+            return DependentGuard::report_status() + std::string(" & ")
+                   + CustomGuard::report_status();
+        },
+        py::call_guard<DependentGuard, CustomGuard>());
 
 #if defined(WITH_THREAD) && !defined(PYPY_VERSION)
     // `py::call_guard<py::gil_scoped_release>()` should work in PyPy as well,
diff --git a/tests/test_callbacks.cpp b/tests/test_callbacks.cpp
index 55f9c86148..92b8053de4 100644
--- a/tests/test_callbacks.cpp
+++ b/tests/test_callbacks.cpp
@@ -7,11 +7,12 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/functional.h>
-#include <thread>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
+#include <thread>
 
 int dummy_function(int i) { return i + 1; }
 
@@ -20,11 +21,12 @@ TEST_SUBMODULE(callbacks, m) {
     m.def("test_callback1", [](const py::object &func) { return func(); });
     m.def("test_callback2", [](const py::object &func) { return func("Hello", 'x', true, 5); });
     m.def("test_callback3", [](const std::function<int(int)> &func) {
-        return "func(43) = " + std::to_string(func(43)); });
-    m.def("test_callback4", []() -> std::function<int(int)> { return [](int i) { return i+1; }; });
-    m.def("test_callback5", []() {
-        return py::cpp_function([](int i) { return i+1; }, py::arg("number"));
+        return "func(43) = " + std::to_string(func(43));
     });
+    m.def("test_callback4",
+          []() -> std::function<int(int)> { return [](int i) { return i + 1; }; });
+    m.def("test_callback5",
+          []() { return py::cpp_function([](int i) { return i + 1; }, py::arg("number")); });
 
     // test_keyword_args_and_generalized_unpacking
     m.def("test_tuple_unpacking", [](const py::function &f) {
@@ -34,9 +36,9 @@ TEST_SUBMODULE(callbacks, m) {
     });
 
     m.def("test_dict_unpacking", [](const py::function &f) {
-        auto d1 = py::dict("key"_a="value", "a"_a=1);
+        auto d1 = py::dict("key"_a = "value", "a"_a = 1);
         auto d2 = py::dict();
-        auto d3 = py::dict("b"_a=2);
+        auto d3 = py::dict("b"_a = 2);
         return f("positional", 1, **d1, **d2, **d3);
     });
 
@@ -44,32 +46,40 @@ TEST_SUBMODULE(callbacks, m) {
 
     m.def("test_unpacking_and_keywords1", [](const py::function &f) {
         auto args = py::make_tuple(2);
-        auto kwargs = py::dict("d"_a=4);
-        return f(1, *args, "c"_a=3, **kwargs);
+        auto kwargs = py::dict("d"_a = 4);
+        return f(1, *args, "c"_a = 3, **kwargs);
     });
 
     m.def("test_unpacking_and_keywords2", [](const py::function &f) {
-        auto kwargs1 = py::dict("a"_a=1);
-        auto kwargs2 = py::dict("c"_a=3, "d"_a=4);
-        return f("positional", *py::make_tuple(1), 2, *py::make_tuple(3, 4), 5,
-                 "key"_a="value", **kwargs1, "b"_a=2, **kwargs2, "e"_a=5);
+        auto kwargs1 = py::dict("a"_a = 1);
+        auto kwargs2 = py::dict("c"_a = 3, "d"_a = 4);
+        return f("positional",
+                 *py::make_tuple(1),
+                 2,
+                 *py::make_tuple(3, 4),
+                 5,
+                 "key"_a = "value",
+                 **kwargs1,
+                 "b"_a = 2,
+                 **kwargs2,
+                 "e"_a = 5);
     });
 
     m.def("test_unpacking_error1", [](const py::function &f) {
-        auto kwargs = py::dict("x"_a=3);
-        return f("x"_a=1, "y"_a=2, **kwargs); // duplicate ** after keyword
+        auto kwargs = py::dict("x"_a = 3);
+        return f("x"_a = 1, "y"_a = 2, **kwargs); // duplicate ** after keyword
     });
 
     m.def("test_unpacking_error2", [](const py::function &f) {
-        auto kwargs = py::dict("x"_a=3);
-        return f(**kwargs, "x"_a=1); // duplicate keyword after **
+        auto kwargs = py::dict("x"_a = 3);
+        return f(**kwargs, "x"_a = 1); // duplicate keyword after **
     });
 
     m.def("test_arg_conversion_error1",
           [](const py::function &f) { f(234, UnregisteredType(), "kw"_a = 567); });
 
     m.def("test_arg_conversion_error2", [](const py::function &f) {
-        f(234, "expected_name"_a=UnregisteredType(), "kw"_a=567);
+        f(234, "expected_name"_a = UnregisteredType(), "kw"_a = 567);
     });
 
     // test_lambda_closure_cleanup
@@ -158,7 +168,6 @@ TEST_SUBMODULE(callbacks, m) {
             return "matches dummy_function: eval(1) = " + std::to_string(r);
         }
         return "argument does NOT match dummy_function. This should never happen!";
-
     });
 
     class AbstractBase {
@@ -190,7 +199,7 @@ TEST_SUBMODULE(callbacks, m) {
     // test_movable_object
     m.def("callback_with_movable", [](const std::function<void(MovableObject &)> &f) {
         auto x = MovableObject();
-        f(x); // lvalue reference shouldn't move out object
+        f(x);           // lvalue reference shouldn't move out object
         return x.valid; // must still return `true`
     });
 
@@ -202,9 +211,10 @@ TEST_SUBMODULE(callbacks, m) {
 
     // This checks that builtin functions can be passed as callbacks
     // rather than throwing RuntimeError due to trying to extract as capsule
-    m.def("test_sum_builtin", [](const std::function<double(py::iterable)> &sum_builtin, const py::iterable &i) {
-      return sum_builtin(i);
-    });
+    m.def("test_sum_builtin",
+          [](const std::function<double(py::iterable)> &sum_builtin, const py::iterable &i) {
+              return sum_builtin(i);
+          });
 
     // test async Python callbacks
     using callback_f = std::function<void(int)>;
diff --git a/tests/test_chrono.cpp b/tests/test_chrono.cpp
index 6537050803..8be0ffd183 100644
--- a/tests/test_chrono.cpp
+++ b/tests/test_chrono.cpp
@@ -8,21 +8,20 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/chrono.h>
+
+#include "pybind11_tests.h"
+
 #include <chrono>
 
 struct different_resolutions {
-    using time_point_h = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::hours>;
-    using time_point_m = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::minutes>;
-    using time_point_s = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::seconds>;
-    using time_point_ms = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::milliseconds>;
-    using time_point_us = std::chrono::time_point<
-        std::chrono::system_clock, std::chrono::microseconds>;
+    using time_point_h = std::chrono::time_point<std::chrono::system_clock, std::chrono::hours>;
+    using time_point_m = std::chrono::time_point<std::chrono::system_clock, std::chrono::minutes>;
+    using time_point_s = std::chrono::time_point<std::chrono::system_clock, std::chrono::seconds>;
+    using time_point_ms
+        = std::chrono::time_point<std::chrono::system_clock, std::chrono::milliseconds>;
+    using time_point_us
+        = std::chrono::time_point<std::chrono::system_clock, std::chrono::microseconds>;
     time_point_h timestamp_h;
     time_point_m timestamp_m;
     time_point_s timestamp_s;
@@ -65,12 +64,11 @@ TEST_SUBMODULE(chrono, m) {
     // Roundtrip a duration in microseconds from a float argument
     m.def("test_chrono7", [](std::chrono::microseconds t) { return t; });
     // Float durations (issue #719)
-    m.def("test_chrono_float_diff", [](std::chrono::duration<float> a, std::chrono::duration<float> b) {
-        return a - b; });
+    m.def("test_chrono_float_diff",
+          [](std::chrono::duration<float> a, std::chrono::duration<float> b) { return a - b; });
 
-    m.def("test_nano_timepoint", [](timestamp start, timespan delta) -> timestamp {
-        return start + delta;
-    });
+    m.def("test_nano_timepoint",
+          [](timestamp start, timespan delta) -> timestamp { return start + delta; });
 
     // Test different resolutions
     py::class_<different_resolutions>(m, "different_resolutions")
@@ -79,6 +77,5 @@ TEST_SUBMODULE(chrono, m) {
         .def_readwrite("timestamp_m", &different_resolutions::timestamp_m)
         .def_readwrite("timestamp_s", &different_resolutions::timestamp_s)
         .def_readwrite("timestamp_ms", &different_resolutions::timestamp_ms)
-        .def_readwrite("timestamp_us", &different_resolutions::timestamp_us)
-        ;
+        .def_readwrite("timestamp_us", &different_resolutions::timestamp_us);
 }
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index f42f74cc4c..eba41da98b 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -11,18 +11,19 @@
 // Intel compiler requires a separate header file to support aligned new operators
 // and does not set the __cpp_aligned_new feature macro.
 // This header needs to be included before pybind11.
-#include <aligned_new>
+#    include <aligned_new>
 #endif
 
-#include "pybind11_tests.h"
+#include <pybind11/stl.h>
+
 #include "constructor_stats.h"
 #include "local_bindings.h"
-#include <pybind11/stl.h>
+#include "pybind11_tests.h"
 
 #include <utility>
 
 #if defined(_MSC_VER)
-#  pragma warning(disable: 4324)
+#    pragma warning(disable : 4324)
 //     warning C4324: structure was padded due to alignment specifier
 #endif
 
@@ -75,6 +76,7 @@ TEST_SUBMODULE(class_, m) {
             : m_name(name), m_species(species) {}
         std::string name() const { return m_name; }
         std::string species() const { return m_species; }
+
     private:
         std::string m_name;
         std::string m_species;
@@ -101,27 +103,24 @@ TEST_SUBMODULE(class_, m) {
     };
 
     py::class_<Pet> pet_class(m, "Pet");
-    pet_class
-        .def(py::init<std::string, std::string>())
+    pet_class.def(py::init<std::string, std::string>())
         .def("name", &Pet::name)
         .def("species", &Pet::species);
 
     /* One way of declaring a subclass relationship: reference parent's class_ object */
-    py::class_<Dog>(m, "Dog", pet_class)
-        .def(py::init<std::string>());
+    py::class_<Dog>(m, "Dog", pet_class).def(py::init<std::string>());
 
     /* Another way of declaring a subclass relationship: reference parent's C++ type */
-    py::class_<Rabbit, Pet>(m, "Rabbit")
-        .def(py::init<std::string>());
+    py::class_<Rabbit, Pet>(m, "Rabbit").def(py::init<std::string>());
 
     /* And another: list parent in class template arguments */
-    py::class_<Hamster, Pet>(m, "Hamster")
-        .def(py::init<std::string>());
+    py::class_<Hamster, Pet>(m, "Hamster").def(py::init<std::string>());
 
     /* Constructors are not inherited by default */
     py::class_<Chimera, Pet>(m, "Chimera");
 
-    m.def("pet_name_species", [](const Pet &pet) { return pet.name() + " is a " + pet.species(); });
+    m.def("pet_name_species",
+          [](const Pet &pet) { return pet.name() + " is a " + pet.species(); });
     m.def("dog_bark", [](const Dog &dog) { return dog.bark(); });
 
     // test_automatic_upcasting
@@ -131,15 +130,15 @@ TEST_SUBMODULE(class_, m) {
         BaseClass(BaseClass &&) = default;
         virtual ~BaseClass() = default;
     };
-    struct DerivedClass1 : BaseClass { };
-    struct DerivedClass2 : BaseClass { };
+    struct DerivedClass1 : BaseClass {};
+    struct DerivedClass2 : BaseClass {};
 
     py::class_<BaseClass>(m, "BaseClass").def(py::init<>());
     py::class_<DerivedClass1>(m, "DerivedClass1").def(py::init<>());
     py::class_<DerivedClass2>(m, "DerivedClass2").def(py::init<>());
 
-    m.def("return_class_1", []() -> BaseClass* { return new DerivedClass1(); });
-    m.def("return_class_2", []() -> BaseClass* { return new DerivedClass2(); });
+    m.def("return_class_1", []() -> BaseClass * { return new DerivedClass1(); });
+    m.def("return_class_2", []() -> BaseClass * { return new DerivedClass2(); });
     m.def("return_class_n", [](int n) -> BaseClass * {
         if (n == 1) {
             return new DerivedClass1();
@@ -149,19 +148,17 @@ TEST_SUBMODULE(class_, m) {
         }
         return new BaseClass();
     });
-    m.def("return_none", []() -> BaseClass* { return nullptr; });
+    m.def("return_none", []() -> BaseClass * { return nullptr; });
 
     // test_isinstance
     m.def("check_instances", [](const py::list &l) {
-        return py::make_tuple(
-            py::isinstance<py::tuple>(l[0]),
-            py::isinstance<py::dict>(l[1]),
-            py::isinstance<Pet>(l[2]),
-            py::isinstance<Pet>(l[3]),
-            py::isinstance<Dog>(l[4]),
-            py::isinstance<Rabbit>(l[5]),
-            py::isinstance<UnregisteredType>(l[6])
-        );
+        return py::make_tuple(py::isinstance<py::tuple>(l[0]),
+                              py::isinstance<py::dict>(l[1]),
+                              py::isinstance<Pet>(l[2]),
+                              py::isinstance<Pet>(l[3]),
+                              py::isinstance<Dog>(l[4]),
+                              py::isinstance<Rabbit>(l[5]),
+                              py::isinstance<UnregisteredType>(l[6]));
     });
 
     struct Invalid {};
@@ -180,18 +177,16 @@ TEST_SUBMODULE(class_, m) {
 
     m.def("get_type_of", [](py::object ob) { return py::type::of(std::move(ob)); });
 
-    m.def("get_type_classic", [](py::handle h) {
-        return h.get_type();
-    });
+    m.def("get_type_classic", [](py::handle h) { return h.get_type(); });
 
     m.def("as_type", [](const py::object &ob) { return py::type(ob); });
 
     // test_mismatched_holder
-    struct MismatchBase1 { };
-    struct MismatchDerived1 : MismatchBase1 { };
+    struct MismatchBase1 {};
+    struct MismatchDerived1 : MismatchBase1 {};
 
-    struct MismatchBase2 { };
-    struct MismatchDerived2 : MismatchBase2 { };
+    struct MismatchBase2 {};
+    struct MismatchDerived2 : MismatchBase2 {};
 
     m.def("mismatched_holder_1", []() {
         auto mod = py::module_::import("__main__");
@@ -201,16 +196,14 @@ TEST_SUBMODULE(class_, m) {
     m.def("mismatched_holder_2", []() {
         auto mod = py::module_::import("__main__");
         py::class_<MismatchBase2>(mod, "MismatchBase2");
-        py::class_<MismatchDerived2, std::shared_ptr<MismatchDerived2>,
-                   MismatchBase2>(mod, "MismatchDerived2");
+        py::class_<MismatchDerived2, std::shared_ptr<MismatchDerived2>, MismatchBase2>(
+            mod, "MismatchDerived2");
     });
 
     // test_override_static
     // #511: problem with inheritance + overwritten def_static
     struct MyBase {
-        static std::unique_ptr<MyBase> make() {
-            return std::unique_ptr<MyBase>(new MyBase());
-        }
+        static std::unique_ptr<MyBase> make() { return std::unique_ptr<MyBase>(new MyBase()); }
     };
 
     struct MyDerived : MyBase {
@@ -219,8 +212,7 @@ TEST_SUBMODULE(class_, m) {
         }
     };
 
-    py::class_<MyBase>(m, "MyBase")
-        .def_static("make", &MyBase::make);
+    py::class_<MyBase>(m, "MyBase").def_static("make", &MyBase::make);
 
     py::class_<MyDerived, MyBase>(m, "MyDerived")
         .def_static("make", &MyDerived::make)
@@ -233,8 +225,7 @@ TEST_SUBMODULE(class_, m) {
         explicit ConvertibleFromUserType(UserType u) : i(u.value()) {}
     };
 
-    py::class_<ConvertibleFromUserType>(m, "AcceptsUserType")
-        .def(py::init<UserType>());
+    py::class_<ConvertibleFromUserType>(m, "AcceptsUserType").def(py::init<UserType>());
     py::implicitly_convertible<UserType, ConvertibleFromUserType>();
 
     m.def("implicitly_convert_argument", [](const ConvertibleFromUserType &r) { return r.i; });
@@ -257,31 +248,60 @@ TEST_SUBMODULE(class_, m) {
         };
 
         auto *def = new PyMethodDef{"f", f, METH_VARARGS, nullptr};
-        py::capsule def_capsule(def, [](void *ptr) { delete reinterpret_cast<PyMethodDef *>(ptr); });
-        return py::reinterpret_steal<py::object>(PyCFunction_NewEx(def, def_capsule.ptr(), m.ptr()));
+        py::capsule def_capsule(def,
+                                [](void *ptr) { delete reinterpret_cast<PyMethodDef *>(ptr); });
+        return py::reinterpret_steal<py::object>(
+            PyCFunction_NewEx(def, def_capsule.ptr(), m.ptr()));
     }());
 
     // test_operator_new_delete
     struct HasOpNewDel {
         std::uint64_t i;
-        static void *operator new(size_t s) { py::print("A new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("A placement-new", s); return ptr; }
-        static void operator delete(void *p) { py::print("A delete"); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("A new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("A placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p) {
+            py::print("A delete");
+            return ::operator delete(p);
+        }
     };
     struct HasOpNewDelSize {
         std::uint32_t i;
-        static void *operator new(size_t s) { py::print("B new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("B placement-new", s); return ptr; }
-        static void operator delete(void *p, size_t s) { py::print("B delete", s); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("B new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("B placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p, size_t s) {
+            py::print("B delete", s);
+            return ::operator delete(p);
+        }
     };
     struct AliasedHasOpNewDelSize {
         std::uint64_t i;
-        static void *operator new(size_t s) { py::print("C new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("C placement-new", s); return ptr; }
-        static void operator delete(void *p, size_t s) { py::print("C delete", s); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("C new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("C placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p, size_t s) {
+            py::print("C delete", s);
+            return ::operator delete(p);
+        }
         virtual ~AliasedHasOpNewDelSize() = default;
         AliasedHasOpNewDelSize() = default;
-        AliasedHasOpNewDelSize(const AliasedHasOpNewDelSize&) = delete;
+        AliasedHasOpNewDelSize(const AliasedHasOpNewDelSize &) = delete;
     };
     struct PyAliasedHasOpNewDelSize : AliasedHasOpNewDelSize {
         PyAliasedHasOpNewDelSize() = default;
@@ -290,15 +310,28 @@ TEST_SUBMODULE(class_, m) {
     };
     struct HasOpNewDelBoth {
         std::uint32_t i[8];
-        static void *operator new(size_t s) { py::print("D new", s); return ::operator new(s); }
-        static void *operator new(size_t s, void *ptr) { py::print("D placement-new", s); return ptr; }
-        static void operator delete(void *p) { py::print("D delete"); return ::operator delete(p); }
-        static void operator delete(void *p, size_t s) { py::print("D wrong delete", s); return ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("D new", s);
+            return ::operator new(s);
+        }
+        static void *operator new(size_t s, void *ptr) {
+            py::print("D placement-new", s);
+            return ptr;
+        }
+        static void operator delete(void *p) {
+            py::print("D delete");
+            return ::operator delete(p);
+        }
+        static void operator delete(void *p, size_t s) {
+            py::print("D wrong delete", s);
+            return ::operator delete(p);
+        }
     };
     py::class_<HasOpNewDel>(m, "HasOpNewDel").def(py::init<>());
     py::class_<HasOpNewDelSize>(m, "HasOpNewDelSize").def(py::init<>());
     py::class_<HasOpNewDelBoth>(m, "HasOpNewDelBoth").def(py::init<>());
-    py::class_<AliasedHasOpNewDelSize, PyAliasedHasOpNewDelSize> aliased(m, "AliasedHasOpNewDelSize");
+    py::class_<AliasedHasOpNewDelSize, PyAliasedHasOpNewDelSize> aliased(m,
+                                                                         "AliasedHasOpNewDelSize");
     aliased.def(py::init<>());
     aliased.attr("size_noalias") = py::int_(sizeof(AliasedHasOpNewDelSize));
     aliased.attr("size_alias") = py::int_(sizeof(PyAliasedHasOpNewDelSize));
@@ -352,7 +385,7 @@ TEST_SUBMODULE(class_, m) {
         // [workaround(intel)] = default does not work here
         // Removing or defaulting this destructor results in linking errors with the Intel compiler
         // (in Debug builds only, tested with icpc (ICC) 2021.1 Beta 20200827)
-        ~PublicistB() override {};  // NOLINT(modernize-use-equals-default)
+        ~PublicistB() override{}; // NOLINT(modernize-use-equals-default)
         using ProtectedB::foo;
     };
 
@@ -402,8 +435,8 @@ TEST_SUBMODULE(class_, m) {
     py::class_<Nested>(base, "Nested")
         .def(py::init<>())
         .def("fn", [](Nested &, int, NestBase &, Nested &) {})
-        .def("fa", [](Nested &, int, NestBase &, Nested &) {},
-                "a"_a, "b"_a, "c"_a);
+        .def(
+            "fa", [](Nested &, int, NestBase &, Nested &) {}, "a"_a, "b"_a, "c"_a);
     base.def("g", [](NestBase &, Nested &) {});
     base.def("h", []() { return NestBase(); });
 
@@ -413,21 +446,21 @@ TEST_SUBMODULE(class_, m) {
     // generate a useful error message
 
     struct NotRegistered {};
-    struct StringWrapper { std::string str; };
+    struct StringWrapper {
+        std::string str;
+    };
     m.def("test_error_after_conversions", [](int) {});
     m.def("test_error_after_conversions",
           [](const StringWrapper &) -> NotRegistered { return {}; });
     py::class_<StringWrapper>(m, "StringWrapper").def(py::init<std::string>());
     py::implicitly_convertible<std::string, StringWrapper>();
 
-    #if defined(PYBIND11_CPP17)
-        struct alignas(1024) Aligned {
-            std::uintptr_t ptr() const { return (uintptr_t) this; }
-        };
-        py::class_<Aligned>(m, "Aligned")
-            .def(py::init<>())
-            .def("ptr", &Aligned::ptr);
-    #endif
+#if defined(PYBIND11_CPP17)
+    struct alignas(1024) Aligned {
+        std::uintptr_t ptr() const { return (uintptr_t) this; }
+    };
+    py::class_<Aligned>(m, "Aligned").def(py::init<>()).def("ptr", &Aligned::ptr);
+#endif
 
     // test_final
     struct IsFinal final {};
@@ -440,9 +473,7 @@ TEST_SUBMODULE(class_, m) {
     // test_exception_rvalue_abort
     struct PyPrintDestructor {
         PyPrintDestructor() = default;
-        ~PyPrintDestructor() {
-            py::print("Print from destructor");
-        }
+        ~PyPrintDestructor() { py::print("Print from destructor"); }
         void throw_something() { throw std::runtime_error("error"); }
     };
     py::class_<PyPrintDestructor>(m, "PyPrintDestructor")
@@ -456,8 +487,7 @@ TEST_SUBMODULE(class_, m) {
         .def(py::init([]() { return &samePointer; }));
 
     struct Empty {};
-    py::class_<Empty>(m, "Empty")
-        .def(py::init<>());
+    py::class_<Empty>(m, "Empty").def(py::init<>());
 
     // test_base_and_derived_nested_scope
     struct BaseWithNested {
@@ -500,10 +530,10 @@ TEST_SUBMODULE(class_, m) {
 
     // Test #1922 (drake#11424).
     class ExampleVirt2 {
-        public:
-            virtual ~ExampleVirt2() = default;
-            virtual std::string get_name() const { return "ExampleVirt2"; }
-        };
+    public:
+        virtual ~ExampleVirt2() = default;
+        virtual std::string get_name() const { return "ExampleVirt2"; }
+    };
     class PyExampleVirt2 : public ExampleVirt2 {
     public:
         std::string get_name() const override {
@@ -513,16 +543,18 @@ TEST_SUBMODULE(class_, m) {
     py::class_<ExampleVirt2, PyExampleVirt2>(m, "ExampleVirt2")
         .def(py::init())
         .def("get_name", &ExampleVirt2::get_name);
-    m.def("example_virt2_get_name",
-        [](const ExampleVirt2& obj) { return obj.get_name(); });
+    m.def("example_virt2_get_name", [](const ExampleVirt2 &obj) { return obj.get_name(); });
 }
 
-template <int N> class BreaksBase { public:
+template <int N>
+class BreaksBase {
+public:
     virtual ~BreaksBase() = default;
     BreaksBase() = default;
-    BreaksBase(const BreaksBase&) = delete;
+    BreaksBase(const BreaksBase &) = delete;
 };
-template <int N> class BreaksTramp : public BreaksBase<N> {};
+template <int N>
+class BreaksTramp : public BreaksBase<N> {};
 // These should all compile just fine:
 using DoesntBreak1 = py::class_<BreaksBase<1>, std::unique_ptr<BreaksBase<1>>, BreaksTramp<1>>;
 using DoesntBreak2 = py::class_<BreaksBase<2>, BreaksTramp<2>, std::unique_ptr<BreaksBase<2>>>;
@@ -532,45 +564,83 @@ using DoesntBreak5 = py::class_<BreaksBase<5>>;
 using DoesntBreak6 = py::class_<BreaksBase<6>, std::shared_ptr<BreaksBase<6>>, BreaksTramp<6>>;
 using DoesntBreak7 = py::class_<BreaksBase<7>, BreaksTramp<7>, std::shared_ptr<BreaksBase<7>>>;
 using DoesntBreak8 = py::class_<BreaksBase<8>, std::shared_ptr<BreaksBase<8>>>;
-#define CHECK_BASE(N) static_assert(std::is_same<typename DoesntBreak##N::type, BreaksBase<(N)>>::value, \
-        "DoesntBreak" #N " has wrong type!")
-CHECK_BASE(1); CHECK_BASE(2); CHECK_BASE(3); CHECK_BASE(4); CHECK_BASE(5); CHECK_BASE(6); CHECK_BASE(7); CHECK_BASE(8);
-#define CHECK_ALIAS(N) static_assert(DoesntBreak##N::has_alias && std::is_same<typename DoesntBreak##N::type_alias, BreaksTramp<(N)>>::value, \
+#define CHECK_BASE(N)                                                                             \
+    static_assert(std::is_same<typename DoesntBreak##N::type, BreaksBase<(N)>>::value,            \
+                  "DoesntBreak" #N " has wrong type!")
+CHECK_BASE(1);
+CHECK_BASE(2);
+CHECK_BASE(3);
+CHECK_BASE(4);
+CHECK_BASE(5);
+CHECK_BASE(6);
+CHECK_BASE(7);
+CHECK_BASE(8);
+#define CHECK_ALIAS(N)                                                                            \
+    static_assert(                                                                                \
+        DoesntBreak##N::has_alias                                                                 \
+            && std::is_same<typename DoesntBreak##N::type_alias, BreaksTramp<(N)>>::value,        \
         "DoesntBreak" #N " has wrong type_alias!")
-#define CHECK_NOALIAS(N) static_assert(!DoesntBreak##N::has_alias && std::is_void<typename DoesntBreak##N::type_alias>::value, \
-        "DoesntBreak" #N " has type alias, but shouldn't!")
-CHECK_ALIAS(1); CHECK_ALIAS(2); CHECK_NOALIAS(3); CHECK_ALIAS(4); CHECK_NOALIAS(5); CHECK_ALIAS(6); CHECK_ALIAS(7); CHECK_NOALIAS(8);
-#define CHECK_HOLDER(N, TYPE) static_assert(std::is_same<typename DoesntBreak##N::holder_type, std::TYPE##_ptr<BreaksBase<(N)>>>::value, \
-        "DoesntBreak" #N " has wrong holder_type!")
-CHECK_HOLDER(1, unique); CHECK_HOLDER(2, unique); CHECK_HOLDER(3, unique); CHECK_HOLDER(4, unique); CHECK_HOLDER(5, unique);
-CHECK_HOLDER(6, shared); CHECK_HOLDER(7, shared); CHECK_HOLDER(8, shared);
+#define CHECK_NOALIAS(N)                                                                          \
+    static_assert(!DoesntBreak##N::has_alias                                                      \
+                      && std::is_void<typename DoesntBreak##N::type_alias>::value,                \
+                  "DoesntBreak" #N " has type alias, but shouldn't!")
+CHECK_ALIAS(1);
+CHECK_ALIAS(2);
+CHECK_NOALIAS(3);
+CHECK_ALIAS(4);
+CHECK_NOALIAS(5);
+CHECK_ALIAS(6);
+CHECK_ALIAS(7);
+CHECK_NOALIAS(8);
+#define CHECK_HOLDER(N, TYPE)                                                                     \
+    static_assert(std::is_same<typename DoesntBreak##N::holder_type,                              \
+                               std::TYPE##_ptr<BreaksBase<(N)>>>::value,                          \
+                  "DoesntBreak" #N " has wrong holder_type!")
+CHECK_HOLDER(1, unique);
+CHECK_HOLDER(2, unique);
+CHECK_HOLDER(3, unique);
+CHECK_HOLDER(4, unique);
+CHECK_HOLDER(5, unique);
+CHECK_HOLDER(6, shared);
+CHECK_HOLDER(7, shared);
+CHECK_HOLDER(8, shared);
 
 // There's no nice way to test that these fail because they fail to compile; leave them here,
 // though, so that they can be manually tested by uncommenting them (and seeing that compilation
 // failures occurs).
 
 // We have to actually look into the type: the typedef alone isn't enough to instantiate the type:
-#define CHECK_BROKEN(N) static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-(N)>>::value, \
-        "Breaks1 has wrong type!");
+#define CHECK_BROKEN(N)                                                                           \
+    static_assert(std::is_same<typename Breaks##N::type, BreaksBase<-(N)>>::value,                \
+                  "Breaks1 has wrong type!");
 
 #ifdef PYBIND11_NEVER_DEFINED_EVER
 // Two holder classes:
-typedef py::class_<BreaksBase<-1>, std::unique_ptr<BreaksBase<-1>>, std::unique_ptr<BreaksBase<-1>>> Breaks1;
+typedef py::
+    class_<BreaksBase<-1>, std::unique_ptr<BreaksBase<-1>>, std::unique_ptr<BreaksBase<-1>>>
+        Breaks1;
 CHECK_BROKEN(1);
 // Two aliases:
 typedef py::class_<BreaksBase<-2>, BreaksTramp<-2>, BreaksTramp<-2>> Breaks2;
 CHECK_BROKEN(2);
 // Holder + 2 aliases
-typedef py::class_<BreaksBase<-3>, std::unique_ptr<BreaksBase<-3>>, BreaksTramp<-3>, BreaksTramp<-3>> Breaks3;
+typedef py::
+    class_<BreaksBase<-3>, std::unique_ptr<BreaksBase<-3>>, BreaksTramp<-3>, BreaksTramp<-3>>
+        Breaks3;
 CHECK_BROKEN(3);
 // Alias + 2 holders
-typedef py::class_<BreaksBase<-4>, std::unique_ptr<BreaksBase<-4>>, BreaksTramp<-4>, std::shared_ptr<BreaksBase<-4>>> Breaks4;
+typedef py::class_<BreaksBase<-4>,
+                   std::unique_ptr<BreaksBase<-4>>,
+                   BreaksTramp<-4>,
+                   std::shared_ptr<BreaksBase<-4>>>
+    Breaks4;
 CHECK_BROKEN(4);
 // Invalid option (not a subclass or holder)
 typedef py::class_<BreaksBase<-5>, BreaksTramp<-4>> Breaks5;
 CHECK_BROKEN(5);
 // Invalid option: multiple inheritance not supported:
-template <> struct BreaksBase<-8> : BreaksBase<-6>, BreaksBase<-7> {};
+template <>
+struct BreaksBase<-8> : BreaksBase<-6>, BreaksBase<-7> {};
 typedef py::class_<BreaksBase<-8>, BreaksBase<-6>, BreaksBase<-7>> Breaks8;
 CHECK_BROKEN(8);
 #endif
diff --git a/tests/test_constants_and_functions.cpp b/tests/test_constants_and_functions.cpp
index c0554503fa..7a6dae1a10 100644
--- a/tests/test_constants_and_functions.cpp
+++ b/tests/test_constants_and_functions.cpp
@@ -12,20 +12,14 @@
 
 enum MyEnum { EFirstEntry = 1, ESecondEntry };
 
-std::string test_function1() {
-    return "test_function()";
-}
+std::string test_function1() { return "test_function()"; }
 
-std::string test_function2(MyEnum k) {
-    return "test_function(enum=" + std::to_string(k) + ")";
-}
+std::string test_function2(MyEnum k) { return "test_function(enum=" + std::to_string(k) + ")"; }
 
-std::string test_function3(int i) {
-    return "test_function(" + std::to_string(i) + ")";
-}
+std::string test_function3(int i) { return "test_function(" + std::to_string(i) + ")"; }
 
-py::str test_function4()           { return "test_function()"; }
-py::str test_function4(char *)     { return "test_function(char *)"; }
+py::str test_function4() { return "test_function()"; }
+py::str test_function4(char *) { return "test_function(char *)"; }
 py::str test_function4(int, float) { return "test_function(int, float)"; }
 py::str test_function4(float, int) { return "test_function(float, int)"; }
 
@@ -44,50 +38,50 @@ std::string print_bytes(const py::bytes &bytes) {
     return ret;
 }
 
-// Test that we properly handle C++17 exception specifiers (which are part of the function signature
-// in C++17).  These should all still work before C++17, but don't affect the function signature.
+// Test that we properly handle C++17 exception specifiers (which are part of the function
+// signature in C++17).  These should all still work before C++17, but don't affect the function
+// signature.
 namespace test_exc_sp {
 // [workaround(intel)] Unable to use noexcept instead of noexcept(true)
 // Make the f1 test basically the same as the f2 test in C++17 mode for the Intel compiler as
 // it fails to compile with a plain noexcept (tested with icc (ICC) 2021.1 Beta 20200827).
 #if defined(__INTEL_COMPILER) && defined(PYBIND11_CPP17)
-int f1(int x) noexcept(true) { return x+1; }
+int f1(int x) noexcept(true) { return x + 1; }
 #else
-int f1(int x) noexcept { return x+1; }
+int f1(int x) noexcept { return x + 1; }
 #endif
-int f2(int x) noexcept(true) { return x+2; }
-int f3(int x) noexcept(false) { return x+3; }
+int f2(int x) noexcept(true) { return x + 2; }
+int f3(int x) noexcept(false) { return x + 3; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wdeprecated"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
 // NOLINTNEXTLINE(modernize-use-noexcept)
-int f4(int x) throw() { return x+4; } // Deprecated equivalent to noexcept(true)
+int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
 struct C {
-    int m1(int x) noexcept { return x-1; }
-    int m2(int x) const noexcept { return x-2; }
-    int m3(int x) noexcept(true) { return x-3; }
-    int m4(int x) const noexcept(true) { return x-4; }
-    int m5(int x) noexcept(false) { return x-5; }
-    int m6(int x) const noexcept(false) { return x-6; }
+    int m1(int x) noexcept { return x - 1; }
+    int m2(int x) const noexcept { return x - 2; }
+    int m3(int x) noexcept(true) { return x - 3; }
+    int m4(int x) const noexcept(true) { return x - 4; }
+    int m5(int x) noexcept(false) { return x - 5; }
+    int m6(int x) const noexcept(false) { return x - 6; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wdeprecated"
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wdeprecated"
 #endif
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m7(int x) throw() { return x - 7; }
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m8(int x) const throw() { return x - 8; }
 #if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#  pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
 };
 } // namespace test_exc_sp
 
-
 TEST_SUBMODULE(constants_and_functions, m) {
     // test_constants
     m.attr("some_constant") = py::int_(14);
@@ -129,8 +123,7 @@ TEST_SUBMODULE(constants_and_functions, m) {
         .def("m5", &C::m5)
         .def("m6", &C::m6)
         .def("m7", &C::m7)
-        .def("m8", &C::m8)
-        ;
+        .def("m8", &C::m8);
     m.def("f1", f1);
     m.def("f2", f2);
 #if defined(__INTEL_COMPILER)
@@ -150,8 +143,12 @@ TEST_SUBMODULE(constants_and_functions, m) {
         uint64_t zeros[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
     };
     m.def("register_large_capture_with_invalid_arguments", [](py::module_ m) {
-        LargeCapture capture;  // VS 2015's MSVC is acting up if we create the array here
-        m.def("should_raise", [capture](int) { return capture.zeros[9] + 33; }, py::kw_only(), py::arg());
+        LargeCapture capture; // VS 2015's MSVC is acting up if we create the array here
+        m.def(
+            "should_raise",
+            [capture](int) { return capture.zeros[9] + 33; },
+            py::kw_only(),
+            py::arg());
     });
     m.def("register_with_raising_repr", [](py::module_ m, const py::object &default_value) {
         m.def(
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 007b96c5b3..6e1bdd8568 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -8,30 +8,33 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 template <typename derived>
 struct empty {
-    static const derived& get_one() { return instance_; }
+    static const derived &get_one() { return instance_; }
     static derived instance_;
 };
 
 struct lacking_copy_ctor : public empty<lacking_copy_ctor> {
     lacking_copy_ctor() = default;
-    lacking_copy_ctor(const lacking_copy_ctor& other) = delete;
+    lacking_copy_ctor(const lacking_copy_ctor &other) = delete;
 };
 
-template <> lacking_copy_ctor empty<lacking_copy_ctor>::instance_ = {};
+template <>
+lacking_copy_ctor empty<lacking_copy_ctor>::instance_ = {};
 
 struct lacking_move_ctor : public empty<lacking_move_ctor> {
     lacking_move_ctor() = default;
-    lacking_move_ctor(const lacking_move_ctor& other) = delete;
-    lacking_move_ctor(lacking_move_ctor&& other) = delete;
+    lacking_move_ctor(const lacking_move_ctor &other) = delete;
+    lacking_move_ctor(lacking_move_ctor &&other) = delete;
 };
 
-template <> lacking_move_ctor empty<lacking_move_ctor>::instance_ = {};
+template <>
+lacking_move_ctor empty<lacking_move_ctor>::instance_ = {};
 
 /* Custom type caster move/copy test classes */
 class MoveOnlyInt {
@@ -71,7 +74,11 @@ class MoveOrCopyInt {
         // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         value = c.value;
     }
-    MoveOrCopyInt &operator=(const MoveOrCopyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
+    MoveOrCopyInt &operator=(const MoveOrCopyInt &c) {
+        print_copy_assigned(this, c.value);
+        value = c.value;
+        return *this;
+    }
     ~MoveOrCopyInt() { print_destroyed(this); }
 
     int value;
@@ -85,32 +92,55 @@ class CopyOnlyInt {
         // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
         value = c.value;
     }
-    CopyOnlyInt &operator=(const CopyOnlyInt &c) { print_copy_assigned(this, c.value); value = c.value; return *this; }
+    CopyOnlyInt &operator=(const CopyOnlyInt &c) {
+        print_copy_assigned(this, c.value);
+        value = c.value;
+        return *this;
+    }
     ~CopyOnlyInt() { print_destroyed(this); }
 
     int value;
 };
 PYBIND11_NAMESPACE_BEGIN(pybind11)
 PYBIND11_NAMESPACE_BEGIN(detail)
-template <> struct type_caster<MoveOnlyInt> {
+template <>
+struct type_caster<MoveOnlyInt> {
     PYBIND11_TYPE_CASTER(MoveOnlyInt, const_name("MoveOnlyInt"));
-    bool load(handle src, bool) { value = MoveOnlyInt(src.cast<int>()); return true; }
-    static handle cast(const MoveOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
+    bool load(handle src, bool) {
+        value = MoveOnlyInt(src.cast<int>());
+        return true;
+    }
+    static handle cast(const MoveOnlyInt &m, return_value_policy r, handle p) {
+        return pybind11::cast(m.value, r, p);
+    }
 };
 
-template <> struct type_caster<MoveOrCopyInt> {
+template <>
+struct type_caster<MoveOrCopyInt> {
     PYBIND11_TYPE_CASTER(MoveOrCopyInt, const_name("MoveOrCopyInt"));
-    bool load(handle src, bool) { value = MoveOrCopyInt(src.cast<int>()); return true; }
-    static handle cast(const MoveOrCopyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
+    bool load(handle src, bool) {
+        value = MoveOrCopyInt(src.cast<int>());
+        return true;
+    }
+    static handle cast(const MoveOrCopyInt &m, return_value_policy r, handle p) {
+        return pybind11::cast(m.value, r, p);
+    }
 };
 
-template <> struct type_caster<CopyOnlyInt> {
+template <>
+struct type_caster<CopyOnlyInt> {
 protected:
     CopyOnlyInt value;
+
 public:
     static constexpr auto name = const_name("CopyOnlyInt");
-    bool load(handle src, bool) { value = CopyOnlyInt(src.cast<int>()); return true; }
-    static handle cast(const CopyOnlyInt &m, return_value_policy r, handle p) { return pybind11::cast(m.value, r, p); }
+    bool load(handle src, bool) {
+        value = CopyOnlyInt(src.cast<int>());
+        return true;
+    }
+    static handle cast(const CopyOnlyInt &m, return_value_policy r, handle p) {
+        return pybind11::cast(m.value, r, p);
+    }
     static handle cast(const CopyOnlyInt *src, return_value_policy policy, handle parent) {
         if (!src) {
             return none().release();
@@ -119,7 +149,8 @@ template <> struct type_caster<CopyOnlyInt> {
     }
     explicit operator CopyOnlyInt *() { return &value; }
     explicit operator CopyOnlyInt &() { return value; }
-    template <typename T> using cast_op_type = pybind11::detail::cast_op_type<T>;
+    template <typename T>
+    using cast_op_type = pybind11::detail::cast_op_type<T>;
 };
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
@@ -127,23 +158,21 @@ PYBIND11_NAMESPACE_END(pybind11)
 TEST_SUBMODULE(copy_move_policies, m) {
     // test_lacking_copy_ctor
     py::class_<lacking_copy_ctor>(m, "lacking_copy_ctor")
-        .def_static("get_one", &lacking_copy_ctor::get_one,
-                    py::return_value_policy::copy);
+        .def_static("get_one", &lacking_copy_ctor::get_one, py::return_value_policy::copy);
     // test_lacking_move_ctor
     py::class_<lacking_move_ctor>(m, "lacking_move_ctor")
-        .def_static("get_one", &lacking_move_ctor::get_one,
-                    py::return_value_policy::move);
+        .def_static("get_one", &lacking_move_ctor::get_one, py::return_value_policy::move);
 
     // test_move_and_copy_casts
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("move_and_copy_casts", [](const py::object &o) {
         int r = 0;
         r += py::cast<MoveOrCopyInt>(o).value; /* moves */
-        r += py::cast<MoveOnlyInt>(o).value; /* moves */
-        r += py::cast<CopyOnlyInt>(o).value; /* copies */
-        auto m1(py::cast<MoveOrCopyInt>(o)); /* moves */
-        auto m2(py::cast<MoveOnlyInt>(o)); /* moves */
-        auto m3(py::cast<CopyOnlyInt>(o)); /* copies */
+        r += py::cast<MoveOnlyInt>(o).value;   /* moves */
+        r += py::cast<CopyOnlyInt>(o).value;   /* copies */
+        auto m1(py::cast<MoveOrCopyInt>(o));   /* moves */
+        auto m2(py::cast<MoveOnlyInt>(o));     /* moves */
+        auto m3(py::cast<CopyOnlyInt>(o));     /* copies */
         r += m1.value + m2.value + m3.value;
 
         return r;
@@ -157,28 +186,34 @@ TEST_SUBMODULE(copy_move_policies, m) {
     // Changing this breaks the existing test: needs careful review.
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("copy_only", [](CopyOnlyInt m) { return m.value; });
-    m.def("move_pair", [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) {
-        return p.first.value + p.second.value;
-    });
+    m.def("move_pair",
+          [](std::pair<MoveOnlyInt, MoveOrCopyInt> p) { return p.first.value + p.second.value; });
     m.def("move_tuple", [](std::tuple<MoveOnlyInt, MoveOrCopyInt, MoveOnlyInt> t) {
         return std::get<0>(t).value + std::get<1>(t).value + std::get<2>(t).value;
     });
     m.def("copy_tuple", [](std::tuple<CopyOnlyInt, CopyOnlyInt> t) {
         return std::get<0>(t).value + std::get<1>(t).value;
     });
-    m.def("move_copy_nested", [](std::pair<MoveOnlyInt, std::pair<std::tuple<MoveOrCopyInt, CopyOnlyInt, std::tuple<MoveOnlyInt>>, MoveOrCopyInt>> x) {
-        return x.first.value + std::get<0>(x.second.first).value + std::get<1>(x.second.first).value +
-            std::get<0>(std::get<2>(x.second.first)).value + x.second.second.value;
-    });
+    m.def("move_copy_nested",
+          [](std::pair<MoveOnlyInt,
+                       std::pair<std::tuple<MoveOrCopyInt, CopyOnlyInt, std::tuple<MoveOnlyInt>>,
+                                 MoveOrCopyInt>> x) {
+              return x.first.value + std::get<0>(x.second.first).value
+                     + std::get<1>(x.second.first).value
+                     + std::get<0>(std::get<2>(x.second.first)).value + x.second.second.value;
+          });
     m.def("move_and_copy_cstats", []() {
         ConstructorStats::gc();
         // Reset counts to 0 so that previous tests don't affect later ones:
         auto &mc = ConstructorStats::get<MoveOrCopyInt>();
-        mc.move_assignments = mc.move_constructions = mc.copy_assignments = mc.copy_constructions = 0;
+        mc.move_assignments = mc.move_constructions = mc.copy_assignments = mc.copy_constructions
+            = 0;
         auto &mo = ConstructorStats::get<MoveOnlyInt>();
-        mo.move_assignments = mo.move_constructions = mo.copy_assignments = mo.copy_constructions = 0;
+        mo.move_assignments = mo.move_constructions = mo.copy_assignments = mo.copy_constructions
+            = 0;
         auto &co = ConstructorStats::get<CopyOnlyInt>();
-        co.move_assignments = co.move_constructions = co.copy_assignments = co.copy_constructions = 0;
+        co.move_assignments = co.move_constructions = co.copy_assignments = co.copy_constructions
+            = 0;
         py::dict d;
         d["MoveOrCopyInt"] = py::cast(mc, py::return_value_policy::reference);
         d["MoveOnlyInt"] = py::cast(mo, py::return_value_policy::reference);
@@ -188,18 +223,13 @@ TEST_SUBMODULE(copy_move_policies, m) {
 #ifdef PYBIND11_HAS_OPTIONAL
     // test_move_and_copy_load_optional
     m.attr("has_optional") = true;
-    m.def("move_optional", [](std::optional<MoveOnlyInt> o) {
-        return o->value;
-    });
-    m.def("move_or_copy_optional", [](std::optional<MoveOrCopyInt> o) {
-        return o->value;
-    });
-    m.def("copy_optional", [](std::optional<CopyOnlyInt> o) {
-        return o->value;
-    });
-    m.def("move_optional_tuple", [](std::optional<std::tuple<MoveOrCopyInt, MoveOnlyInt, CopyOnlyInt>> x) {
-        return std::get<0>(*x).value + std::get<1>(*x).value + std::get<2>(*x).value;
-    });
+    m.def("move_optional", [](std::optional<MoveOnlyInt> o) { return o->value; });
+    m.def("move_or_copy_optional", [](std::optional<MoveOrCopyInt> o) { return o->value; });
+    m.def("copy_optional", [](std::optional<CopyOnlyInt> o) { return o->value; });
+    m.def("move_optional_tuple",
+          [](std::optional<std::tuple<MoveOrCopyInt, MoveOnlyInt, CopyOnlyInt>> x) {
+              return std::get<0>(*x).value + std::get<1>(*x).value + std::get<2>(*x).value;
+          });
 #else
     m.attr("has_optional") = false;
 #endif
@@ -210,6 +240,7 @@ TEST_SUBMODULE(copy_move_policies, m) {
     // added later.
     struct PrivateOpNew {
         int value = 1;
+
     private:
         void *operator new(size_t bytes) {
             void *ptr = std::malloc(bytes);
@@ -221,10 +252,13 @@ TEST_SUBMODULE(copy_move_policies, m) {
     };
     py::class_<PrivateOpNew>(m, "PrivateOpNew").def_readonly("value", &PrivateOpNew::value);
     m.def("private_op_new_value", []() { return PrivateOpNew(); });
-    m.def("private_op_new_reference", []() -> const PrivateOpNew & {
-        static PrivateOpNew x{};
-        return x;
-    }, py::return_value_policy::reference);
+    m.def(
+        "private_op_new_reference",
+        []() -> const PrivateOpNew & {
+            static PrivateOpNew x{};
+            return x;
+        },
+        py::return_value_policy::reference);
 
     // test_move_fallback
     // #389: rvp::move should fall-through to copy on non-movable objects
@@ -234,16 +268,25 @@ TEST_SUBMODULE(copy_move_policies, m) {
         MoveIssue1(const MoveIssue1 &c) = default;
         MoveIssue1(MoveIssue1 &&) = delete;
     };
-    py::class_<MoveIssue1>(m, "MoveIssue1").def(py::init<int>()).def_readwrite("value", &MoveIssue1::v);
+    py::class_<MoveIssue1>(m, "MoveIssue1")
+        .def(py::init<int>())
+        .def_readwrite("value", &MoveIssue1::v);
 
     struct MoveIssue2 {
         int v;
         explicit MoveIssue2(int v) : v{v} {}
         MoveIssue2(MoveIssue2 &&) = default;
     };
-    py::class_<MoveIssue2>(m, "MoveIssue2").def(py::init<int>()).def_readwrite("value", &MoveIssue2::v);
+    py::class_<MoveIssue2>(m, "MoveIssue2")
+        .def(py::init<int>())
+        .def_readwrite("value", &MoveIssue2::v);
 
-    // #2742: Don't expect ownership of raw pointer to `new`ed object to be transferred with `py::return_value_policy::move`
-    m.def("get_moveissue1", [](int i) { return std::unique_ptr<MoveIssue1>(new MoveIssue1(i)); }, py::return_value_policy::move);
-    m.def("get_moveissue2", [](int i) { return MoveIssue2(i); }, py::return_value_policy::move);
+    // #2742: Don't expect ownership of raw pointer to `new`ed object to be transferred with
+    // `py::return_value_policy::move`
+    m.def(
+        "get_moveissue1",
+        [](int i) { return std::unique_ptr<MoveIssue1>(new MoveIssue1(i)); },
+        py::return_value_policy::move);
+    m.def(
+        "get_moveissue2", [](int i) { return MoveIssue2(i); }, py::return_value_policy::move);
 }
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
index 48613ee5a1..1d6341582c 100644
--- a/tests/test_custom_type_casters.cpp
+++ b/tests/test_custom_type_casters.cpp
@@ -7,16 +7,23 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
-
+#include "pybind11_tests.h"
 
 // py::arg/py::arg_v testing: these arguments just record their argument when invoked
-class ArgInspector1 { public: std::string arg = "(default arg inspector 1)"; };
-class ArgInspector2 { public: std::string arg = "(default arg inspector 2)"; };
-class ArgAlwaysConverts { };
-namespace pybind11 { namespace detail {
-template <> struct type_caster<ArgInspector1> {
+class ArgInspector1 {
+public:
+    std::string arg = "(default arg inspector 1)";
+};
+class ArgInspector2 {
+public:
+    std::string arg = "(default arg inspector 2)";
+};
+class ArgAlwaysConverts {};
+namespace pybind11 {
+namespace detail {
+template <>
+struct type_caster<ArgInspector1> {
 public:
     // Classic
 #ifdef PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
@@ -26,9 +33,10 @@ template <> struct type_caster<ArgInspector1> {
 #endif
 
     bool load(handle src, bool convert) {
-        value.arg = "loading ArgInspector1 argument " +
-            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
-            "Argument value = " + (std::string) str(src);
+        value.arg = "loading ArgInspector1 argument " + std::string(convert ? "WITH" : "WITHOUT")
+                    + " conversion allowed.  "
+                      "Argument value = "
+                    + (std::string) str(src);
         return true;
     }
 
@@ -36,14 +44,16 @@ template <> struct type_caster<ArgInspector1> {
         return str(src.arg).release();
     }
 };
-template <> struct type_caster<ArgInspector2> {
+template <>
+struct type_caster<ArgInspector2> {
 public:
     PYBIND11_TYPE_CASTER(ArgInspector2, const_name("ArgInspector2"));
 
     bool load(handle src, bool convert) {
-        value.arg = "loading ArgInspector2 argument " +
-            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
-            "Argument value = " + (std::string) str(src);
+        value.arg = "loading ArgInspector2 argument " + std::string(convert ? "WITH" : "WITHOUT")
+                    + " conversion allowed.  "
+                      "Argument value = "
+                    + (std::string) str(src);
         return true;
     }
 
@@ -51,13 +61,12 @@ template <> struct type_caster<ArgInspector2> {
         return str(src.arg).release();
     }
 };
-template <> struct type_caster<ArgAlwaysConverts> {
+template <>
+struct type_caster<ArgAlwaysConverts> {
 public:
     PYBIND11_TYPE_CASTER(ArgAlwaysConverts, const_name("ArgAlwaysConverts"));
 
-    bool load(handle, bool convert) {
-        return convert;
-    }
+    bool load(handle, bool convert) { return convert; }
 
     static handle cast(const ArgAlwaysConverts &, return_value_policy, handle) {
         return py::none().release();
@@ -73,14 +82,19 @@ class DestructionTester {
     ~DestructionTester() { print_destroyed(this); }
     DestructionTester(const DestructionTester &) { print_copy_created(this); }
     DestructionTester(DestructionTester &&) noexcept { print_move_created(this); }
-    DestructionTester &operator=(const DestructionTester &) { print_copy_assigned(this); return *this; }
+    DestructionTester &operator=(const DestructionTester &) {
+        print_copy_assigned(this);
+        return *this;
+    }
     DestructionTester &operator=(DestructionTester &&) noexcept {
         print_move_assigned(this);
         return *this;
     }
 };
-namespace pybind11 { namespace detail {
-template <> struct type_caster<DestructionTester> {
+namespace pybind11 {
+namespace detail {
+template <>
+struct type_caster<DestructionTester> {
     PYBIND11_TYPE_CASTER(DestructionTester, const_name("DestructionTester"));
     bool load(handle, bool) { return true; }
 
@@ -115,9 +129,14 @@ TEST_SUBMODULE(custom_type_casters, m) {
     py::class_<ArgInspector>(m, "ArgInspector")
         .def(py::init<>())
         .def("f", &ArgInspector::f, py::arg(), py::arg() = ArgAlwaysConverts())
-        .def("g", &ArgInspector::g, "a"_a.noconvert(), "b"_a, "c"_a.noconvert()=13, "d"_a=ArgInspector2(), py::arg() = ArgAlwaysConverts())
-        .def_static("h", &ArgInspector::h, py::arg{}.noconvert(), py::arg() = ArgAlwaysConverts())
-        ;
+        .def("g",
+             &ArgInspector::g,
+             "a"_a.noconvert(),
+             "b"_a,
+             "c"_a.noconvert() = 13,
+             "d"_a = ArgInspector2(),
+             py::arg() = ArgAlwaysConverts())
+        .def_static("h", &ArgInspector::h, py::arg{}.noconvert(), py::arg() = ArgAlwaysConverts());
     m.def(
         "arg_inspect_func",
         [](const ArgInspector2 &a, const ArgInspector1 &b, ArgAlwaysConverts) {
@@ -127,20 +146,33 @@ TEST_SUBMODULE(custom_type_casters, m) {
         py::arg_v(nullptr, ArgInspector1()).noconvert(true),
         py::arg() = ArgAlwaysConverts());
 
-    m.def("floats_preferred", [](double f) { return 0.5 * f; }, "f"_a);
-    m.def("floats_only", [](double f) { return 0.5 * f; }, "f"_a.noconvert());
-    m.def("ints_preferred", [](int i) { return i / 2; }, "i"_a);
-    m.def("ints_only", [](int i) { return i / 2; }, "i"_a.noconvert());
+    m.def(
+        "floats_preferred", [](double f) { return 0.5 * f; }, "f"_a);
+    m.def(
+        "floats_only", [](double f) { return 0.5 * f; }, "f"_a.noconvert());
+    m.def(
+        "ints_preferred", [](int i) { return i / 2; }, "i"_a);
+    m.def(
+        "ints_only", [](int i) { return i / 2; }, "i"_a.noconvert());
 
     // test_custom_caster_destruction
     // Test that `take_ownership` works on types with a custom type caster when given a pointer
 
     // default policy: don't take ownership:
-    m.def("custom_caster_no_destroy", []() { static auto *dt = new DestructionTester(); return dt; });
+    m.def("custom_caster_no_destroy", []() {
+        static auto *dt = new DestructionTester();
+        return dt;
+    });
 
-    m.def("custom_caster_destroy", []() { return new DestructionTester(); },
-            py::return_value_policy::take_ownership); // Takes ownership: destroy when finished
-    m.def("custom_caster_destroy_const", []() -> const DestructionTester * { return new DestructionTester(); },
-            py::return_value_policy::take_ownership); // Likewise (const doesn't inhibit destruction)
-    m.def("destruction_tester_cstats", &ConstructorStats::get<DestructionTester>, py::return_value_policy::reference);
+    m.def(
+        "custom_caster_destroy",
+        []() { return new DestructionTester(); },
+        py::return_value_policy::take_ownership); // Takes ownership: destroy when finished
+    m.def(
+        "custom_caster_destroy_const",
+        []() -> const DestructionTester * { return new DestructionTester(); },
+        py::return_value_policy::take_ownership); // Likewise (const doesn't inhibit destruction)
+    m.def("destruction_tester_cstats",
+          &ConstructorStats::get<DestructionTester>,
+          py::return_value_policy::reference);
 }
diff --git a/tests/test_docstring_options.cpp b/tests/test_docstring_options.cpp
index 8a97af55fc..4d44f4e20d 100644
--- a/tests/test_docstring_options.cpp
+++ b/tests/test_docstring_options.cpp
@@ -15,35 +15,52 @@ TEST_SUBMODULE(docstring_options, m) {
         py::options options;
         options.disable_function_signatures();
 
-        m.def("test_function1", [](int, int) {}, py::arg("a"), py::arg("b"));
-        m.def("test_function2", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
-
-        m.def("test_overloaded1", [](int) {}, py::arg("i"), "Overload docstring");
-        m.def("test_overloaded1", [](double) {}, py::arg("d"));
-
-        m.def("test_overloaded2", [](int) {}, py::arg("i"), "overload docstring 1");
-        m.def("test_overloaded2", [](double) {}, py::arg("d"), "overload docstring 2");
-
-        m.def("test_overloaded3", [](int) {}, py::arg("i"));
-        m.def("test_overloaded3", [](double) {}, py::arg("d"), "Overload docstr");
+        m.def(
+            "test_function1", [](int, int) {}, py::arg("a"), py::arg("b"));
+        m.def(
+            "test_function2", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+
+        m.def(
+            "test_overloaded1", [](int) {}, py::arg("i"), "Overload docstring");
+        m.def(
+            "test_overloaded1", [](double) {}, py::arg("d"));
+
+        m.def(
+            "test_overloaded2", [](int) {}, py::arg("i"), "overload docstring 1");
+        m.def(
+            "test_overloaded2", [](double) {}, py::arg("d"), "overload docstring 2");
+
+        m.def(
+            "test_overloaded3", [](int) {}, py::arg("i"));
+        m.def(
+            "test_overloaded3", [](double) {}, py::arg("d"), "Overload docstr");
 
         options.enable_function_signatures();
 
-        m.def("test_function3", [](int, int) {}, py::arg("a"), py::arg("b"));
-        m.def("test_function4", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+        m.def(
+            "test_function3", [](int, int) {}, py::arg("a"), py::arg("b"));
+        m.def(
+            "test_function4", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
 
         options.disable_function_signatures().disable_user_defined_docstrings();
 
-        m.def("test_function5", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+        m.def(
+            "test_function5", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
 
         {
             py::options nested_options;
             nested_options.enable_user_defined_docstrings();
-            m.def("test_function6", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+            m.def(
+                "test_function6",
+                [](int, int) {},
+                py::arg("a"),
+                py::arg("b"),
+                "A custom docstring");
         }
     }
 
-    m.def("test_function7", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+    m.def(
+        "test_function7", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
 
     {
         py::options options;
@@ -63,7 +80,9 @@ TEST_SUBMODULE(docstring_options, m) {
             int getValue() const { return value; }
         };
         py::class_<DocstringTestFoo>(m, "DocstringTestFoo", "This is a class docstring")
-            .def_property("value_prop", &DocstringTestFoo::getValue, &DocstringTestFoo::setValue, "This is a property docstring")
-        ;
+            .def_property("value_prop",
+                          &DocstringTestFoo::getValue,
+                          &DocstringTestFoo::setValue,
+                          "This is a property docstring");
     }
 }
diff --git a/tests/test_eigen.cpp b/tests/test_eigen.cpp
index 77eb4a3a47..51bf36eb79 100644
--- a/tests/test_eigen.cpp
+++ b/tests/test_eigen.cpp
@@ -7,21 +7,23 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/eigen.h>
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #if defined(_MSC_VER)
-#if _MSC_VER < 1910  // VS 2015's MSVC
-#  pragma warning(disable: 4127) // C4127: conditional expression is constant
-#endif
-#  pragma warning(disable: 4996) // C4996: std::unary_negation is deprecated
+#    if _MSC_VER < 1910                 // VS 2015's MSVC
+#        pragma warning(disable : 4127) // C4127: conditional expression is constant
+#    endif
+#    pragma warning(disable : 4996) // C4996: std::unary_negation is deprecated
 #endif
 
+#include "Eigen/src/Core/util/DisableStupidWarnings.h"
+
 #include <Eigen/Cholesky>
 #include <unsupported/Eigen/AutoDiff>
-#include "Eigen/src/Core/util/DisableStupidWarnings.h"
 
 using MatrixXdR = Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
 typedef Eigen::AutoDiffScalar<Eigen::VectorXd> ADScalar;
@@ -37,7 +39,8 @@ PYBIND11_NUMPY_OBJECT_DTYPE(ADScalar);
 
 // Sets/resets a testing reference matrix to have values of 10*r + c, where r and c are the
 // (1-based) row/column number.
-template <typename M> void reset_ref(M &x) {
+template <typename M>
+void reset_ref(M &x) {
     for (int i = 0; i < x.rows(); i++) {
         for (int j = 0; j < x.cols(); j++) {
             x(i, j) = 11 + 10 * i + j;
@@ -69,22 +72,22 @@ void reset_refs() {
     reset_ref(get_rm());
 }
 
-VectorXADScalar& get_cm_adscalar() {
+VectorXADScalar &get_cm_adscalar() {
     static VectorXADScalar value(1);
     return value;
 };
-VectorXADScalarR& get_rm_adscalar() {
+VectorXADScalarR &get_rm_adscalar() {
     static VectorXADScalarR value(1);
     return value;
 };
 
-
 // Returns element 2,1 from a matrix (used to test copy/nocopy)
 double get_elem(const Eigen::Ref<const Eigen::MatrixXd> &m) { return m(2, 1); };
 
 // Returns a matrix with 10*r + 100*c added to each matrix element (to help test that the matrix
 // reference is referencing rows/columns correctly).
-template <typename MatrixArgType> Eigen::MatrixXd adjust_matrix(MatrixArgType m) {
+template <typename MatrixArgType>
+Eigen::MatrixXd adjust_matrix(MatrixArgType m) {
     Eigen::MatrixXd ret(m);
     for (int c = 0; c < m.cols(); c++) {
         for (int r = 0; r < m.rows(); r++) {
@@ -107,7 +110,8 @@ TEST_SUBMODULE(eigen, m) {
     using FixedMatrixR = Eigen::Matrix<float, 5, 6, Eigen::RowMajor>;
     using FixedMatrixC = Eigen::Matrix<float, 5, 6>;
     using DenseMatrixR = Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
-    using DenseADScalarMatrixR = Eigen::Matrix<ADScalar, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
+    using DenseADScalarMatrixR
+        = Eigen::Matrix<ADScalar, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
     using DenseMatrixC = Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic>;
     using DenseADScalarMatrixC = Eigen::Matrix<ADScalar, Eigen::Dynamic, Eigen::Dynamic>;
     using FourRowMatrixC = Eigen::Matrix<float, 4, Eigen::Dynamic>;
@@ -119,35 +123,43 @@ TEST_SUBMODULE(eigen, m) {
 
     // various tests
     m.def("double_col", [](const Eigen::VectorXf &x) -> Eigen::VectorXf { return 2.0f * x; });
-    m.def("double_adscalar_col", [](const VectorXADScalar &x) -> VectorXADScalar { return 2.0f * x; });
-    m.def("double_adscalar_col5", [](const Vector5ADScalar &x) -> Vector5ADScalar { return 2.0f * x; });
-    m.def("double_row", [](const Eigen::RowVectorXf &x) -> Eigen::RowVectorXf { return 2.0f * x; });
-    m.def("double_adscalar_row", [](const VectorXADScalarR &x) -> VectorXADScalarR { return 2.0f * x; });
-    m.def("double_adscalar_row6", [](const Vector6ADScalarR &x) -> Vector6ADScalarR { return 2.0f * x; });
-    m.def("double_complex", [](const Eigen::VectorXcf &x) -> Eigen::VectorXcf { return 2.0f * x; });
+    m.def("double_adscalar_col",
+          [](const VectorXADScalar &x) -> VectorXADScalar { return 2.0f * x; });
+    m.def("double_adscalar_col5",
+          [](const Vector5ADScalar &x) -> Vector5ADScalar { return 2.0f * x; });
+    m.def("double_row",
+          [](const Eigen::RowVectorXf &x) -> Eigen::RowVectorXf { return 2.0f * x; });
+    m.def("double_adscalar_row",
+          [](const VectorXADScalarR &x) -> VectorXADScalarR { return 2.0f * x; });
+    m.def("double_adscalar_row6",
+          [](const Vector6ADScalarR &x) -> Vector6ADScalarR { return 2.0f * x; });
+    m.def("double_complex",
+          [](const Eigen::VectorXcf &x) -> Eigen::VectorXcf { return 2.0f * x; });
     m.def("double_threec", [](py::EigenDRef<Eigen::Vector3f> x) { x *= 2; });
     m.def("double_threer", [](py::EigenDRef<Eigen::RowVector3f> x) { x *= 2; });
     m.def("double_mat_cm", [](const Eigen::MatrixXf &x) -> Eigen::MatrixXf { return 2.0f * x; });
     m.def("double_mat_rm", [](const DenseMatrixR &x) -> DenseMatrixR { return 2.0f * x; });
 
-
     // test_eigen_ref_to_python
     // Different ways of passing via Eigen::Ref; the first and second are the Eigen-recommended
     m.def("cholesky1",
           [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
-    m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
-    m.def("cholesky3", [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
+    m.def("cholesky2", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd {
+        return x.llt().matrixL();
+    });
+    m.def("cholesky3",
+          [](const Eigen::Ref<MatrixXdR> &x) -> Eigen::MatrixXd { return x.llt().matrixL(); });
     m.def("cholesky4", [](const Eigen::Ref<const MatrixXdR> &x) -> Eigen::MatrixXd {
         return x.llt().matrixL();
     });
 
     // test_eigen_ref_mutators
-    // Mutators: these add some value to the given element using Eigen, but Eigen should be mapping into
-    // the numpy array data and so the result should show up there.  There are three versions: one that
-    // works on a contiguous-row matrix (numpy's default), one for a contiguous-column matrix, and one
-    // for any matrix.
-    auto add_rm = [](Eigen::Ref<MatrixXdR> x, int r, int c, double v) { x(r,c) += v; };
-    auto add_cm = [](Eigen::Ref<Eigen::MatrixXd> x, int r, int c, double v) { x(r,c) += v; };
+    // Mutators: these add some value to the given element using Eigen, but Eigen should be mapping
+    // into the numpy array data and so the result should show up there.  There are three versions:
+    // one that works on a contiguous-row matrix (numpy's default), one for a contiguous-column
+    // matrix, and one for any matrix.
+    auto add_rm = [](Eigen::Ref<MatrixXdR> x, int r, int c, double v) { x(r, c) += v; };
+    auto add_cm = [](Eigen::Ref<Eigen::MatrixXd> x, int r, int c, double v) { x(r, c) += v; };
 
     // Mutators (Eigen maps into numpy variables):
     m.def("add_rm", add_rm); // Only takes row-contiguous
@@ -160,94 +172,132 @@ TEST_SUBMODULE(eigen, m) {
     m.def("add2", add_cm);
     m.def("add2", add_rm);
     // This one accepts a matrix of any stride:
-    m.def("add_any", [](py::EigenDRef<Eigen::MatrixXd> x, int r, int c, double v) { x(r,c) += v; });
+    m.def("add_any",
+          [](py::EigenDRef<Eigen::MatrixXd> x, int r, int c, double v) { x(r, c) += v; });
 
     // Return mutable references (numpy maps into eigen variables)
     m.def("get_cm_ref", []() { return Eigen::Ref<Eigen::MatrixXd>(get_cm()); });
     m.def("get_rm_ref", []() { return Eigen::Ref<MatrixXdR>(get_rm()); });
-    m.def("get_cm_ref_adscalar", []() {
-        return py::EigenDRef<VectorXADScalar>(get_cm_adscalar());
-    });
-    m.def("get_rm_ref_adscalar", []() {
-        return py::EigenDRef<VectorXADScalarR>(get_rm_adscalar());
-    });
+    m.def("get_cm_ref_adscalar",
+          []() { return py::EigenDRef<VectorXADScalar>(get_cm_adscalar()); });
+    m.def("get_rm_ref_adscalar",
+          []() { return py::EigenDRef<VectorXADScalarR>(get_rm_adscalar()); });
     // The same references, but non-mutable (numpy maps into eigen variables, but is !writeable)
     m.def("get_cm_const_ref", []() { return Eigen::Ref<const Eigen::MatrixXd>(get_cm()); });
     m.def("get_rm_const_ref", []() { return Eigen::Ref<const MatrixXdR>(get_rm()); });
-    m.def("get_cm_const_ref_adscalar", []() { return Eigen::Ref<const VectorXADScalar>(get_cm_adscalar()); });
-    m.def("get_rm_const_ref_adscalar", []() { return Eigen::Ref<const VectorXADScalarR>(get_rm_adscalar()); });
+    m.def("get_cm_const_ref_adscalar",
+          []() { return Eigen::Ref<const VectorXADScalar>(get_cm_adscalar()); });
+    m.def("get_rm_const_ref_adscalar",
+          []() { return Eigen::Ref<const VectorXADScalarR>(get_rm_adscalar()); });
 
     m.def("reset_refs", reset_refs); // Restores get_{cm,rm}_ref to original values
 
     // Increments and returns ref to (same) matrix
-    m.def("incr_matrix", [](Eigen::Ref<Eigen::MatrixXd> m, double v) {
-        m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
-        return m;
-    }, py::return_value_policy::reference);
+    m.def(
+        "incr_matrix",
+        [](Eigen::Ref<Eigen::MatrixXd> m, double v) {
+            m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
+            return m;
+        },
+        py::return_value_policy::reference);
 
     // Increments ADScalar Matrix, returns a copy.
-    m.def("incr_adscalar_matrix", [](const Eigen::Ref<const DenseADScalarMatrixC>& m, double v) {
-      DenseADScalarMatrixC out = m;
-      out.array() += v;
-      return out;
+    m.def("incr_adscalar_matrix", [](const Eigen::Ref<const DenseADScalarMatrixC> &m, double v) {
+        DenseADScalarMatrixC out = m;
+        out.array() += v;
+        return out;
     });
 
     // Same, but accepts a matrix of any strides
-    m.def("incr_matrix_any", [](py::EigenDRef<Eigen::MatrixXd> m, double v) {
-        m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
-        return m;
-    }, py::return_value_policy::reference);
+    m.def(
+        "incr_matrix_any",
+        [](py::EigenDRef<Eigen::MatrixXd> m, double v) {
+            m += Eigen::MatrixXd::Constant(m.rows(), m.cols(), v);
+            return m;
+        },
+        py::return_value_policy::reference);
 
     // Returns an eigen slice of even rows
-    m.def("even_rows", [](py::EigenDRef<Eigen::MatrixXd> m) {
-        return py::EigenDMap<Eigen::MatrixXd>(
-                m.data(), (m.rows() + 1) / 2, m.cols(),
+    m.def(
+        "even_rows",
+        [](py::EigenDRef<Eigen::MatrixXd> m) {
+            return py::EigenDMap<Eigen::MatrixXd>(
+                m.data(),
+                (m.rows() + 1) / 2,
+                m.cols(),
                 py::EigenDStride(m.outerStride(), 2 * m.innerStride()));
-    }, py::return_value_policy::reference);
+        },
+        py::return_value_policy::reference);
 
     // Returns an eigen slice of even columns
-    m.def("even_cols", [](py::EigenDRef<Eigen::MatrixXd> m) {
-        return py::EigenDMap<Eigen::MatrixXd>(
-                m.data(), m.rows(), (m.cols() + 1) / 2,
+    m.def(
+        "even_cols",
+        [](py::EigenDRef<Eigen::MatrixXd> m) {
+            return py::EigenDMap<Eigen::MatrixXd>(
+                m.data(),
+                m.rows(),
+                (m.cols() + 1) / 2,
                 py::EigenDStride(2 * m.outerStride(), m.innerStride()));
-    }, py::return_value_policy::reference);
+        },
+        py::return_value_policy::reference);
 
     // Returns diagonals: a vector-like object with an inner stride != 1
     m.def("diagonal", [](const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.diagonal(); });
-    m.def("diagonal_1", [](const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.diagonal<1>(); });
-    m.def("diagonal_n", [](const Eigen::Ref<const Eigen::MatrixXd> &x, int index) { return x.diagonal(index); });
+    m.def("diagonal_1",
+          [](const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.diagonal<1>(); });
+    m.def("diagonal_n",
+          [](const Eigen::Ref<const Eigen::MatrixXd> &x, int index) { return x.diagonal(index); });
 
     // Return a block of a matrix (gives non-standard strides)
-    m.def("block", [](const Eigen::Ref<const Eigen::MatrixXd> &x, int start_row, int start_col, int block_rows, int block_cols) {
-        return x.block(start_row, start_col, block_rows, block_cols);
-    });
+    m.def("block",
+          [](const Eigen::Ref<const Eigen::MatrixXd> &x,
+             int start_row,
+             int start_col,
+             int block_rows,
+             int block_cols) { return x.block(start_row, start_col, block_rows, block_cols); });
 
     // test_eigen_return_references, test_eigen_keepalive
     // return value referencing/copying tests:
     class ReturnTester {
         Eigen::MatrixXd mat = create();
         DenseADScalarMatrixR ad_mat = create_ADScalar_mat();
+
     public:
         ReturnTester() { print_created(this); }
         ~ReturnTester() { print_destroyed(this); }
-        static Eigen::MatrixXd create() {  return Eigen::MatrixXd::Ones(10, 10); }
-        static DenseADScalarMatrixR create_ADScalar_mat() { DenseADScalarMatrixR ad_mat(2, 2);
-            ad_mat << 1, 2, 3, 7; return ad_mat; }
+        static Eigen::MatrixXd create() { return Eigen::MatrixXd::Ones(10, 10); }
+        static DenseADScalarMatrixR create_ADScalar_mat() {
+            DenseADScalarMatrixR ad_mat(2, 2);
+            ad_mat << 1, 2, 3, 7;
+            return ad_mat;
+        }
         // NOLINTNEXTLINE(readability-const-return-type)
         static const Eigen::MatrixXd createConst() { return Eigen::MatrixXd::Ones(10, 10); }
         Eigen::MatrixXd &get() { return mat; }
-        DenseADScalarMatrixR& get_ADScalarMat() {return ad_mat;}
+        DenseADScalarMatrixR &get_ADScalarMat() { return ad_mat; }
         Eigen::MatrixXd *getPtr() { return &mat; }
         const Eigen::MatrixXd &view() { return mat; }
         const Eigen::MatrixXd *viewPtr() { return &mat; }
         Eigen::Ref<Eigen::MatrixXd> ref() { return mat; }
         Eigen::Ref<const Eigen::MatrixXd> refConst() { return mat; }
-        Eigen::Block<Eigen::MatrixXd> block(int r, int c, int nrow, int ncol) { return mat.block(r, c, nrow, ncol); }
-        Eigen::Block<const Eigen::MatrixXd> blockConst(int r, int c, int nrow, int ncol) const { return mat.block(r, c, nrow, ncol); }
-        py::EigenDMap<Eigen::Matrix2d> corners() { return py::EigenDMap<Eigen::Matrix2d>(mat.data(),
-                    py::EigenDStride(mat.outerStride() * (mat.outerSize()-1), mat.innerStride() * (mat.innerSize()-1))); }
-        py::EigenDMap<const Eigen::Matrix2d> cornersConst() const { return py::EigenDMap<const Eigen::Matrix2d>(mat.data(),
-                    py::EigenDStride(mat.outerStride() * (mat.outerSize()-1), mat.innerStride() * (mat.innerSize()-1))); }
+        Eigen::Block<Eigen::MatrixXd> block(int r, int c, int nrow, int ncol) {
+            return mat.block(r, c, nrow, ncol);
+        }
+        Eigen::Block<const Eigen::MatrixXd> blockConst(int r, int c, int nrow, int ncol) const {
+            return mat.block(r, c, nrow, ncol);
+        }
+        py::EigenDMap<Eigen::Matrix2d> corners() {
+            return py::EigenDMap<Eigen::Matrix2d>(
+                mat.data(),
+                py::EigenDStride(mat.outerStride() * (mat.outerSize() - 1),
+                                 mat.innerStride() * (mat.innerSize() - 1)));
+        }
+        py::EigenDMap<const Eigen::Matrix2d> cornersConst() const {
+            return py::EigenDMap<const Eigen::Matrix2d>(
+                mat.data(),
+                py::EigenDStride(mat.outerStride() * (mat.outerSize() - 1),
+                                 mat.innerStride() * (mat.innerSize() - 1)));
+        }
     };
     using rvp = py::return_value_policy;
     py::class_<ReturnTester>(m, "ReturnTester")
@@ -259,9 +309,9 @@ TEST_SUBMODULE(eigen, m) {
         .def("get_ptr", &ReturnTester::getPtr, rvp::reference_internal)
         .def("view", &ReturnTester::view, rvp::reference_internal)
         .def("view_ptr", &ReturnTester::view, rvp::reference_internal)
-        .def("copy_get", &ReturnTester::get)   // Default rvp: copy
-        .def("copy_view", &ReturnTester::view) //         "
-        .def("ref", &ReturnTester::ref) // Default for Ref is to reference
+        .def("copy_get", &ReturnTester::get)       // Default rvp: copy
+        .def("copy_view", &ReturnTester::view)     //         "
+        .def("ref", &ReturnTester::ref)            // Default for Ref is to reference
         .def("ref_const", &ReturnTester::refConst) // Likewise, but const
         .def("ref_safe", &ReturnTester::ref, rvp::reference_internal)
         .def("ref_const_safe", &ReturnTester::refConst, rvp::reference_internal)
@@ -272,31 +322,25 @@ TEST_SUBMODULE(eigen, m) {
         .def("block_const", &ReturnTester::blockConst, rvp::reference_internal)
         .def("copy_block", &ReturnTester::block, rvp::copy)
         .def("corners", &ReturnTester::corners, rvp::reference_internal)
-        .def("corners_const", &ReturnTester::cornersConst, rvp::reference_internal)
-        ;
+        .def("corners_const", &ReturnTester::cornersConst, rvp::reference_internal);
 
     py::class_<ADScalar>(m, "AutoDiffXd")
         .def("__init__",
-             [](ADScalar & self,
-                double value,
-                const Eigen::VectorXd& derivatives) {
-               new (&self) ADScalar(value, derivatives);
+             [](ADScalar &self, double value, const Eigen::VectorXd &derivatives) {
+                 new (&self) ADScalar(value, derivatives);
              })
-        .def("value", [](const ADScalar & self) {
-          return self.value();
-        })
-        .def("__repr__", [](const ADScalar& self) {
-          return py::str("<ADScalar {} deriv={}>").format(self.value(), self.derivatives());
-        })
-        ;
+        .def("value", [](const ADScalar &self) { return self.value(); })
+        .def("__repr__", [](const ADScalar &self) {
+            return py::str("<ADScalar {} deriv={}>").format(self.value(), self.derivatives());
+        });
 
     m.def("equal_to", [](double a, double b) { return a == b; });
     // AutDiff's operator== only compares the value; we should compare the full scalar.
-    m.def("equal_to", [](const ADScalar& a, const ADScalar& b) {
-      auto& a_d = a.derivatives();
-      auto& b_d = b.derivatives();
-      return a.value() == b.value() && a_d.size() == b_d.size() &&
-          (a_d.array() == b_d.array()).all();
+    m.def("equal_to", [](const ADScalar &a, const ADScalar &b) {
+        auto &a_d = a.derivatives();
+        auto &b_d = b.derivatives();
+        return a.value() == b.value() && a_d.size() == b_d.size()
+               && (a_d.array() == b_d.array()).all();
     });
 
     // test_special_matrix_objects
@@ -310,21 +354,16 @@ TEST_SUBMODULE(eigen, m) {
     });
 
     // Returns a SelfAdjointView referencing the lower triangle of m
-    m.def("symmetric_lower", [](const Eigen::MatrixXi &m) {
-            return m.selfadjointView<Eigen::Lower>();
-    });
+    m.def("symmetric_lower",
+          [](const Eigen::MatrixXi &m) { return m.selfadjointView<Eigen::Lower>(); });
     // Returns a SelfAdjointView referencing the lower triangle of m
-    m.def("symmetric_upper", [](const Eigen::MatrixXi &m) {
-            return m.selfadjointView<Eigen::Upper>();
-    });
+    m.def("symmetric_upper",
+          [](const Eigen::MatrixXi &m) { return m.selfadjointView<Eigen::Upper>(); });
 
     // Test matrix for various functions below.
     Eigen::MatrixXf mat(5, 6);
-    mat << 0,  3,  0,  0,  0, 11,
-           22, 0,  0,  0, 17, 11,
-           7,  5,  0,  1,  0, 11,
-           0,  0,  0,  0,  0, 11,
-           0,  0, 14,  0,  8, 11;
+    mat << 0, 3, 0, 0, 0, 11, 22, 0, 0, 0, 17, 11, 7, 5, 0, 1, 0, 11, 0, 0, 0, 0, 0, 11, 0, 0, 14,
+        0, 8, 11;
 
     // test_fixed, and various other tests
     m.def("fixed_r", [mat]() -> FixedMatrixR { return FixedMatrixR(mat); });
@@ -349,7 +388,8 @@ TEST_SUBMODULE(eigen, m) {
         // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
         return Eigen::SparseView<Eigen::MatrixXf>(mat);
     });
-    m.def("sparse_c", [mat]() -> SparseMatrixC { return Eigen::SparseView<Eigen::MatrixXf>(mat); });
+    m.def("sparse_c",
+          [mat]() -> SparseMatrixC { return Eigen::SparseView<Eigen::MatrixXf>(mat); });
     m.def("sparse_copy_r", [](const SparseMatrixR &m) -> SparseMatrixR { return m; });
     m.def("sparse_copy_c", [](const SparseMatrixC &m) -> SparseMatrixC { return m; });
     // test_partially_fixed
@@ -363,7 +403,8 @@ TEST_SUBMODULE(eigen, m) {
     m.def("cpp_copy", [](py::handle m) { return m.cast<Eigen::MatrixXd>()(1, 0); });
     m.def("cpp_ref_c", [](py::handle m) { return m.cast<Eigen::Ref<Eigen::MatrixXd>>()(1, 0); });
     m.def("cpp_ref_r", [](py::handle m) { return m.cast<Eigen::Ref<MatrixXdR>>()(1, 0); });
-    m.def("cpp_ref_any", [](py::handle m) { return m.cast<py::EigenDRef<Eigen::MatrixXd>>()(1, 0); });
+    m.def("cpp_ref_any",
+          [](py::handle m) { return m.cast<py::EigenDRef<Eigen::MatrixXd>>()(1, 0); });
 
     // [workaround(intel)] ICC 20/21 breaks with py::arg().stuff, using py::arg{}.stuff works.
 
@@ -377,17 +418,25 @@ TEST_SUBMODULE(eigen, m) {
         [](const Eigen::Ref<const Eigen::MatrixXd> &m) -> double { return get_elem(m); },
         py::arg{}.noconvert());
     // Also test a row-major-only no-copy const ref:
-    m.def("get_elem_rm_nocopy", [](Eigen::Ref<const Eigen::Matrix<long, -1, -1, Eigen::RowMajor>> &m) -> long { return m(2, 1); },
-            py::arg{}.noconvert());
+    m.def(
+        "get_elem_rm_nocopy",
+        [](Eigen::Ref<const Eigen::Matrix<long, -1, -1, Eigen::RowMajor>> &m) -> long {
+            return m(2, 1);
+        },
+        py::arg{}.noconvert());
 
     // test_issue738_issue2038
     // Issue #738: 1xN or Nx1 2D matrices were neither accepted nor properly copied with an
     // incompatible stride value on the length-1 dimension--but that should be allowed (without
     // requiring a copy!) because the stride value can be safely ignored on a size-1 dimension.
-    // Issue #2039: 0xN (col-major) or Nx0 (row-major) matrices were not accepted properly, due to a similar
-    // situation.
-    m.def("iss738_f1", &adjust_matrix<const Eigen::Ref<const Eigen::MatrixXd> &>, py::arg().noconvert());
-    m.def("iss738_f2", &adjust_matrix<const Eigen::Ref<const Eigen::Matrix<double, -1, -1, Eigen::RowMajor>> &>, py::arg().noconvert());
+    // Issue #2039: 0xN (col-major) or Nx0 (row-major) matrices were not accepted properly, due to
+    // a similar situation.
+    m.def("iss738_f1",
+          &adjust_matrix<const Eigen::Ref<const Eigen::MatrixXd> &>,
+          py::arg().noconvert());
+    m.def("iss738_f2",
+          &adjust_matrix<const Eigen::Ref<const Eigen::Matrix<double, -1, -1, Eigen::RowMajor>> &>,
+          py::arg().noconvert());
 
     // test_issue1105
     // Issue #1105: when converting from a numpy two-dimensional (Nx1) or (1xN) value into a dense
@@ -400,13 +449,11 @@ TEST_SUBMODULE(eigen, m) {
     m.def("iss1105_row_obj", [](VectorXADScalarR) { return true; });
 
     // Test the shape of a matrix via `type_caster`s.
-    m.def("cpp_matrix_shape", [](const MatrixX<double>& A) {
-        return py::make_tuple(A.rows(), A.cols());
-    });
-    m.def("cpp_matrix_shape", [](const MatrixX<ADScalar>& A) {
-        return py::make_tuple(A.rows(), A.cols());
-    });
-    m.def("cpp_matrix_shape_ref", [](const Eigen::Ref<const MatrixX<ADScalar>>& A) {
+    m.def("cpp_matrix_shape",
+          [](const MatrixX<double> &A) { return py::make_tuple(A.rows(), A.cols()); });
+    m.def("cpp_matrix_shape",
+          [](const MatrixX<ADScalar> &A) { return py::make_tuple(A.rows(), A.cols()); });
+    m.def("cpp_matrix_shape_ref", [](const Eigen::Ref<const MatrixX<ADScalar>> &A) {
         return py::make_tuple(A.rows(), A.cols());
     });
 
diff --git a/tests/test_embed/catch.cpp b/tests/test_embed/catch.cpp
index 67a8d51432..96d2e3f92a 100644
--- a/tests/test_embed/catch.cpp
+++ b/tests/test_embed/catch.cpp
@@ -4,14 +4,14 @@
 #include <pybind11/embed.h>
 
 #ifdef _MSC_VER
-// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to catch
-// 2.0.1; this should be fixed in the next catch release after 2.0.1).
-#  pragma warning(disable: 4996)
+// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
+// catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
+#    pragma warning(disable : 4996)
 #endif
 
 // Catch uses _ internally, which breaks gettext style defines
 #ifdef _
-#undef _
+#    undef _
 #endif
 
 #define CATCH_CONFIG_RUNNER
diff --git a/tests/test_embed/external_module.cpp b/tests/test_embed/external_module.cpp
index 4909522993..5c482fe061 100644
--- a/tests/test_embed/external_module.cpp
+++ b/tests/test_embed/external_module.cpp
@@ -13,11 +13,8 @@ PYBIND11_MODULE(external_module, m) {
         int v;
     };
 
-    py::class_<A>(m, "A")
-        .def(py::init<int>())
-        .def_readwrite("value", &A::v);
+    py::class_<A>(m, "A").def(py::init<int>()).def_readwrite("value", &A::v);
 
-    m.def("internals_at", []() {
-        return reinterpret_cast<uintptr_t>(&py::detail::get_internals());
-    });
+    m.def("internals_at",
+          []() { return reinterpret_cast<uintptr_t>(&py::detail::get_internals()); });
 }
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 601a19092f..5782bda618 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -1,13 +1,12 @@
 #include <pybind11/embed.h>
 
 #ifdef _MSC_VER
-// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to catch
-// 2.0.1; this should be fixed in the next catch release after 2.0.1).
-#  pragma warning(disable: 4996)
+// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
+// catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
+#    pragma warning(disable : 4996)
 #endif
 
 #include <catch.hpp>
-
 #include <cstdlib>
 #include <fstream>
 #include <functional>
@@ -62,14 +61,14 @@ PYBIND11_EMBEDDED_MODULE(widget_module, m) {
 }
 
 PYBIND11_EMBEDDED_MODULE(trampoline_module, m) {
-    py::class_<test_override_cache_helper, test_override_cache_helper_trampoline, std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
+    py::class_<test_override_cache_helper,
+               test_override_cache_helper_trampoline,
+               std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
         .def(py::init_alias<>())
         .def("func", &test_override_cache_helper::func);
 }
 
-PYBIND11_EMBEDDED_MODULE(throw_exception, ) {
-    throw std::runtime_error("C++ Error");
-}
+PYBIND11_EMBEDDED_MODULE(throw_exception, ) { throw std::runtime_error("C++ Error"); }
 
 PYBIND11_EMBEDDED_MODULE(throw_error_already_set, ) {
     auto d = py::dict();
@@ -80,11 +79,13 @@ TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
     auto module_ = py::module_::import("test_interpreter");
     REQUIRE(py::hasattr(module_, "DerivedWidget"));
 
-    auto locals = py::dict("hello"_a="Hello, World!", "x"_a=5, **module_.attr("__dict__"));
+    auto locals = py::dict("hello"_a = "Hello, World!", "x"_a = 5, **module_.attr("__dict__"));
     py::exec(R"(
         widget = DerivedWidget("{} - {}".format(hello, x))
         message = widget.the_message
-    )", py::globals(), locals);
+    )",
+             py::globals(),
+             locals);
     REQUIRE(locals["message"].cast<std::string>() == "Hello, World! - 5");
 
     auto py_widget = module_.attr("DerivedWidget")("The question");
@@ -124,20 +125,21 @@ TEST_CASE("Override cache") {
 
 TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
-    REQUIRE_THROWS_WITH(py::module_::import("throw_exception"),
-                        "ImportError: C++ Error");
+    REQUIRE_THROWS_WITH(py::module_::import("throw_exception"), "ImportError: C++ Error");
 #if PY_VERSION_HEX >= 0x03030000
     REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                         Catch::Contains("ImportError: initialization failed"));
 
-    auto locals = py::dict("is_keyerror"_a=false, "message"_a="not set");
+    auto locals = py::dict("is_keyerror"_a = false, "message"_a = "not set");
     py::exec(R"(
         try:
             import throw_error_already_set
         except ImportError as e:
             is_keyerror = type(e.__cause__) == KeyError
             message = str(e.__cause__)
-    )", py::globals(), locals);
+    )",
+             py::globals(),
+             locals);
     REQUIRE(locals["is_keyerror"].cast<bool>() == true);
     REQUIRE(locals["message"].cast<std::string>() == "'missing'");
 #else
@@ -179,11 +181,12 @@ TEST_CASE("Restart the interpreter") {
     REQUIRE(py::module_::import("widget_module").attr("add")(1, 2).cast<int>() == 3);
     REQUIRE(has_pybind11_internals_builtin());
     REQUIRE(has_pybind11_internals_static());
-    REQUIRE(py::module_::import("external_module").attr("A")(123).attr("value").cast<int>() == 123);
+    REQUIRE(py::module_::import("external_module").attr("A")(123).attr("value").cast<int>()
+            == 123);
 
     // local and foreign module internals should point to the same internals:
-    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp()) ==
-            py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
+    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp())
+            == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
 
     // Restart the interpreter.
     py::finalize_interpreter();
@@ -198,16 +201,19 @@ TEST_CASE("Restart the interpreter") {
     pybind11::detail::get_internals();
     REQUIRE(has_pybind11_internals_builtin());
     REQUIRE(has_pybind11_internals_static());
-    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp()) ==
-            py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
+    REQUIRE(reinterpret_cast<uintptr_t>(*py::detail::get_internals_pp())
+            == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
 
     // Make sure that an interpreter with no get_internals() created until finalize still gets the
     // internals destroyed
     py::finalize_interpreter();
     py::initialize_interpreter();
     bool ran = false;
-    py::module_::import("__main__").attr("internals_destroy_test") =
-        py::capsule(&ran, [](void *ran) { py::detail::get_internals(); *static_cast<bool *>(ran) = true; });
+    py::module_::import("__main__").attr("internals_destroy_test")
+        = py::capsule(&ran, [](void *ran) {
+              py::detail::get_internals();
+              *static_cast<bool *>(ran) = true;
+          });
     REQUIRE_FALSE(has_pybind11_internals_builtin());
     REQUIRE_FALSE(has_pybind11_internals_static());
     REQUIRE_FALSE(ran);
@@ -281,7 +287,7 @@ TEST_CASE("Threads") {
     REQUIRE_FALSE(has_pybind11_internals_static());
 
     constexpr auto num_threads = 10;
-    auto locals = py::dict("count"_a=0);
+    auto locals = py::dict("count"_a = 0);
 
     {
         py::gil_scoped_release gil_release{};
@@ -322,9 +328,8 @@ TEST_CASE("Reload module from file") {
     bool dont_write_bytecode = sys.attr("dont_write_bytecode").cast<bool>();
     sys.attr("dont_write_bytecode") = true;
     // Reset the value at scope exit
-    scope_exit reset_dont_write_bytecode([&]() {
-        sys.attr("dont_write_bytecode") = dont_write_bytecode;
-    });
+    scope_exit reset_dont_write_bytecode(
+        [&]() { sys.attr("dont_write_bytecode") = dont_write_bytecode; });
 
     std::string module_name = "test_module_reload";
     std::string module_file = module_name + ".py";
@@ -335,9 +340,7 @@ TEST_CASE("Reload module from file") {
     test_module << "    return 1\n";
     test_module.close();
     // Delete the file at scope exit
-    scope_exit delete_module_file([&]() {
-        std::remove(module_file.c_str());
-    });
+    scope_exit delete_module_file([&]() { std::remove(module_file.c_str()); });
 
     // Import the module from file
     auto module_ = py::module_::import(module_name.c_str());
diff --git a/tests/test_enum.cpp b/tests/test_enum.cpp
index 40c48d412a..2597b275ef 100644
--- a/tests/test_enum.cpp
+++ b/tests/test_enum.cpp
@@ -11,11 +11,7 @@
 
 TEST_SUBMODULE(enums, m) {
     // test_unscoped_enum
-    enum UnscopedEnum {
-        EOne = 1,
-        ETwo,
-        EThree
-    };
+    enum UnscopedEnum { EOne = 1, ETwo, EThree };
     py::enum_<UnscopedEnum>(m, "UnscopedEnum", py::arithmetic(), "An unscoped enumeration")
         .value("EOne", EOne, "Docstring for EOne")
         .value("ETwo", ETwo, "Docstring for ETwo")
@@ -23,10 +19,7 @@ TEST_SUBMODULE(enums, m) {
         .export_values();
 
     // test_scoped_enum
-    enum class ScopedEnum {
-        Two = 2,
-        Three
-    };
+    enum class ScopedEnum { Two = 2, Three };
     py::enum_<ScopedEnum>(m, "ScopedEnum", py::arithmetic())
         .value("Two", ScopedEnum::Two)
         .value("Three", ScopedEnum::Three);
@@ -36,11 +29,7 @@ TEST_SUBMODULE(enums, m) {
     });
 
     // test_binary_operators
-    enum Flags {
-        Read = 4,
-        Write = 2,
-        Execute = 1
-    };
+    enum Flags { Read = 4, Write = 2, Execute = 1 };
     py::enum_<Flags>(m, "Flags", py::arithmetic())
         .value("Read", Flags::Read)
         .value("Write", Flags::Write)
@@ -50,14 +39,9 @@ TEST_SUBMODULE(enums, m) {
     // test_implicit_conversion
     class ClassWithUnscopedEnum {
     public:
-        enum EMode {
-            EFirstMode = 1,
-            ESecondMode
-        };
-
-        static EMode test_function(EMode mode) {
-            return mode;
-        }
+        enum EMode { EFirstMode = 1, ESecondMode };
+
+        static EMode test_function(EMode mode) { return mode; }
     };
     py::class_<ClassWithUnscopedEnum> exenum_class(m, "ClassWithUnscopedEnum");
     exenum_class.def_static("test_function", &ClassWithUnscopedEnum::test_function);
@@ -67,19 +51,17 @@ TEST_SUBMODULE(enums, m) {
         .export_values();
 
     // test_enum_to_int
-    m.def("test_enum_to_int", [](int) { });
-    m.def("test_enum_to_uint", [](uint32_t) { });
-    m.def("test_enum_to_long_long", [](long long) { });
+    m.def("test_enum_to_int", [](int) {});
+    m.def("test_enum_to_uint", [](uint32_t) {});
+    m.def("test_enum_to_long_long", [](long long) {});
 
     // test_duplicate_enum_name
-    enum SimpleEnum
-    {
-        ONE, TWO, THREE
-    };
+    enum SimpleEnum { ONE, TWO, THREE };
 
     m.def("register_bad_enum", [m]() {
         py::enum_<SimpleEnum>(m, "SimpleEnum")
-            .value("ONE", SimpleEnum::ONE)          //NOTE: all value function calls are called with the same first parameter value
+            .value("ONE", SimpleEnum::ONE) // NOTE: all value function calls are called with the
+                                           // same first parameter value
             .value("ONE", SimpleEnum::TWO)
             .value("ONE", SimpleEnum::THREE)
             .export_values();
@@ -90,33 +72,36 @@ TEST_SUBMODULE(enums, m) {
     enum class ScopedShortEnum : short {};
     enum class ScopedLongEnum : long {};
     enum UnscopedUInt64Enum : std::uint64_t {};
-    static_assert(py::detail::all_of<
-        std::is_same<py::enum_<UnscopedUCharEnum>::Scalar, unsigned char>,
-        std::is_same<py::enum_<ScopedShortEnum>::Scalar, short>,
-        std::is_same<py::enum_<ScopedLongEnum>::Scalar, long>,
-        std::is_same<py::enum_<UnscopedUInt64Enum>::Scalar, std::uint64_t>
-    >::value, "Error during the deduction of enum's scalar type with normal integer underlying");
+    static_assert(
+        py::detail::all_of<
+            std::is_same<py::enum_<UnscopedUCharEnum>::Scalar, unsigned char>,
+            std::is_same<py::enum_<ScopedShortEnum>::Scalar, short>,
+            std::is_same<py::enum_<ScopedLongEnum>::Scalar, long>,
+            std::is_same<py::enum_<UnscopedUInt64Enum>::Scalar, std::uint64_t>>::value,
+        "Error during the deduction of enum's scalar type with normal integer underlying");
 
     // test_enum_scalar_with_char_underlying
-    enum class ScopedCharEnum   : char     { Zero, Positive };
-    enum class ScopedWCharEnum  : wchar_t  { Zero, Positive };
+    enum class ScopedCharEnum : char { Zero, Positive };
+    enum class ScopedWCharEnum : wchar_t { Zero, Positive };
     enum class ScopedChar32Enum : char32_t { Zero, Positive };
     enum class ScopedChar16Enum : char16_t { Zero, Positive };
 
     // test the scalar of char type enums according to chapter 'Character types'
     // from https://en.cppreference.com/w/cpp/language/types
-    static_assert(py::detail::any_of<
-        std::is_same<py::enum_<ScopedCharEnum>::Scalar, signed char>, // e.g. gcc on x86
-        std::is_same<py::enum_<ScopedCharEnum>::Scalar, unsigned char>  // e.g. arm linux
-    >::value, "char should be cast to either signed char or unsigned char");
     static_assert(
-        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 2 ||
-        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 4
-    , "wchar_t should be either 16 bits (Windows) or 32 (everywhere else)");
-    static_assert(py::detail::all_of<
-        std::is_same<py::enum_<ScopedChar32Enum>::Scalar, std::uint_least32_t>,
-        std::is_same<py::enum_<ScopedChar16Enum>::Scalar, std::uint_least16_t>
-    >::value, "char32_t, char16_t (and char8_t)'s size, signedness, and alignment is determined");
+        py::detail::any_of<
+            std::is_same<py::enum_<ScopedCharEnum>::Scalar, signed char>,  // e.g. gcc on x86
+            std::is_same<py::enum_<ScopedCharEnum>::Scalar, unsigned char> // e.g. arm linux
+            >::value,
+        "char should be cast to either signed char or unsigned char");
+    static_assert(sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 2
+                      || sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 4,
+                  "wchar_t should be either 16 bits (Windows) or 32 (everywhere else)");
+    static_assert(
+        py::detail::all_of<
+            std::is_same<py::enum_<ScopedChar32Enum>::Scalar, std::uint_least32_t>,
+            std::is_same<py::enum_<ScopedChar16Enum>::Scalar, std::uint_least16_t>>::value,
+        "char32_t, char16_t (and char8_t)'s size, signedness, and alignment is determined");
 #if defined(PYBIND11_HAS_U8STRING)
     enum class ScopedChar8Enum : char8_t { Zero, Positive };
     static_assert(std::is_same<py::enum_<ScopedChar8Enum>::Scalar, unsigned char>::value);
diff --git a/tests/test_eval.cpp b/tests/test_eval.cpp
index e40dde70ec..cd2903f0ab 100644
--- a/tests/test_eval.cpp
+++ b/tests/test_eval.cpp
@@ -7,10 +7,10 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-
 #include <pybind11/eval.h>
 
 #include "pybind11_tests.h"
+
 #include <utility>
 
 TEST_SUBMODULE(eval_, m) {
@@ -20,16 +20,13 @@ TEST_SUBMODULE(eval_, m) {
 
     m.def("test_eval_statements", [global]() {
         auto local = py::dict();
-        local["call_test"] = py::cpp_function([&]() -> int {
-            return 42;
-        });
+        local["call_test"] = py::cpp_function([&]() -> int { return 42; });
 
         // Regular string literal
-        py::exec(
-            "message = 'Hello World!'\n"
-            "x = call_test()",
-            global, local
-        );
+        py::exec("message = 'Hello World!'\n"
+                 "x = call_test()",
+                 global,
+                 local);
 
         // Multi-line raw string literal
         py::exec(R"(
@@ -37,8 +34,9 @@ TEST_SUBMODULE(eval_, m) {
                 print(message)
             else:
                 raise RuntimeError
-            )", global, local
-        );
+            )",
+                 global,
+                 local);
         auto x = local["x"].cast<int>();
 
         return x == 42;
@@ -53,9 +51,7 @@ TEST_SUBMODULE(eval_, m) {
 
     m.def("test_eval_single_statement", []() {
         auto local = py::dict();
-        local["call_test"] = py::cpp_function([&]() -> int {
-            return 42;
-        });
+        local["call_test"] = py::cpp_function([&]() -> int { return 42; });
 
         auto result = py::eval<py::eval_single_statement>("x = call_test()", py::dict(), local);
         auto x = local["x"].cast<int>();
@@ -114,7 +110,9 @@ TEST_SUBMODULE(eval_, m) {
 
             def func_local():
                 return local_value
-            )", global, local);
+            )",
+                 global,
+                 local);
         return std::make_pair(global, local);
     });
 }
diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp
index ab7dfbf691..f6f93611a2 100644
--- a/tests/test_exceptions.cpp
+++ b/tests/test_exceptions.cpp
@@ -9,8 +9,8 @@
 #include "test_exceptions.h"
 
 #include "local_bindings.h"
-
 #include "pybind11_tests.h"
+
 #include <exception>
 #include <stdexcept>
 #include <utility>
@@ -18,8 +18,9 @@
 // A type that should be raised as an exception in Python
 class MyException : public std::exception {
 public:
-    explicit MyException(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -27,8 +28,9 @@ class MyException : public std::exception {
 // A type that should be translated to a standard Python exception
 class MyException2 : public std::exception {
 public:
-    explicit MyException2(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException2(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
@@ -36,13 +38,13 @@ class MyException2 : public std::exception {
 // A type that is not derived from std::exception (and is thus unknown)
 class MyException3 {
 public:
-    explicit MyException3(const char * m) : message{m} {}
-    virtual const char * what() const noexcept {return message.c_str();}
+    explicit MyException3(const char *m) : message{m} {}
+    virtual const char *what() const noexcept { return message.c_str(); }
     // Rule of 5 BEGIN: to preempt compiler warnings.
-    MyException3(const MyException3&) = default;
-    MyException3(MyException3&&) = default;
-    MyException3& operator=(const MyException3&) = default;
-    MyException3& operator=(MyException3&&) = default;
+    MyException3(const MyException3 &) = default;
+    MyException3(MyException3 &&) = default;
+    MyException3 &operator=(const MyException3 &) = default;
+    MyException3 &operator=(MyException3 &&) = default;
     virtual ~MyException3() = default;
     // Rule of 5 END.
 private:
@@ -53,13 +55,13 @@ class MyException3 {
 // and delegated to its exception translator
 class MyException4 : public std::exception {
 public:
-    explicit MyException4(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException4(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
 
-
 // Like the above, but declared via the helper function
 class MyException5 : public std::logic_error {
 public:
@@ -71,17 +73,16 @@ class MyException5_1 : public MyException5 {
     using MyException5::MyException5;
 };
 
-
 // Exception that will be caught via the module local translator.
 class MyException6 : public std::exception {
 public:
-    explicit MyException6(const char * m) : message{m} {}
-    const char * what() const noexcept override {return message.c_str();}
+    explicit MyException6(const char *m) : message{m} {}
+    const char *what() const noexcept override { return message.c_str(); }
+
 private:
     std::string message = "";
 };
 
-
 struct PythonCallInDestructor {
     explicit PythonCallInDestructor(const py::dict &d) : d(d) {}
     ~PythonCallInDestructor() { d["good"] = true; }
@@ -89,8 +90,6 @@ struct PythonCallInDestructor {
     py::dict d;
 };
 
-
-
 struct PythonAlreadySetInDestructor {
     explicit PythonAlreadySetInDestructor(const py::str &s) : s(s) {}
     ~PythonAlreadySetInDestructor() {
@@ -98,8 +97,7 @@ struct PythonAlreadySetInDestructor {
         try {
             // Assign to a py::object to force read access of nonexistent dict entry
             py::object o = foo["bar"];
-        }
-        catch (py::error_already_set& ex) {
+        } catch (py::error_already_set &ex) {
             ex.discard_as_unraisable(s);
         }
     }
@@ -108,9 +106,8 @@ struct PythonAlreadySetInDestructor {
 };
 
 TEST_SUBMODULE(exceptions, m) {
-    m.def("throw_std_exception", []() {
-        throw std::runtime_error("This exception was intentionally thrown.");
-    });
+    m.def("throw_std_exception",
+          []() { throw std::runtime_error("This exception was intentionally thrown."); });
 
     // make a new custom exception and use it as a translation target
     static py::exception<MyException> ex(m, "MyException");
@@ -157,26 +154,30 @@ TEST_SUBMODULE(exceptions, m) {
     // A slightly more complicated one that declares MyException5_1 as a subclass of MyException5
     py::register_exception<MyException5_1>(m, "MyException5_1", ex5.ptr());
 
-    //py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException")
+    // py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException")
 
     py::register_local_exception_translator([](std::exception_ptr p) {
-      try {
-          if (p) {
-            std::rethrow_exception(p);
-          }
-      } catch (const MyException6 &e) {
-        PyErr_SetString(PyExc_RuntimeError, e.what());
-      }
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const MyException6 &e) {
+            PyErr_SetString(PyExc_RuntimeError, e.what());
+        }
     });
 
     m.def("throws1", []() { throw MyException("this error should go to a custom type"); });
-    m.def("throws2", []() { throw MyException2("this error should go to a standard Python exception"); });
+    m.def("throws2",
+          []() { throw MyException2("this error should go to a standard Python exception"); });
     m.def("throws3", []() { throw MyException3("this error cannot be translated"); });
     m.def("throws4", []() { throw MyException4("this error is rethrown"); });
-    m.def("throws5", []() { throw MyException5("this is a helper-defined translated exception"); });
+    m.def("throws5",
+          []() { throw MyException5("this is a helper-defined translated exception"); });
     m.def("throws5_1", []() { throw MyException5_1("MyException5 subclass"); });
     m.def("throws6", []() { throw MyException6("MyException6 only handled in this module"); });
-    m.def("throws_logic_error", []() { throw std::logic_error("this error should fall through to the standard handler"); });
+    m.def("throws_logic_error", []() {
+        throw std::logic_error("this error should fall through to the standard handler");
+    });
     m.def("throws_overflow_error", []() { throw std::overflow_error(""); });
     m.def("throws_local_error", []() { throw LocalException("never caught"); });
     m.def("throws_local_simple_error", []() { throw LocalSimpleException("this mod"); });
@@ -185,8 +186,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             // Assign to a py::object to force read access of nonexistent dict entry
             py::object o = foo["bar"];
-        }
-        catch (py::error_already_set& ex) {
+        } catch (py::error_already_set &ex) {
             if (!ex.matches(PyExc_KeyError)) {
                 throw;
             }
@@ -199,8 +199,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             // Assign to a py::object to force read access of nonexistent dict entry
             py::object o = foo["bar"];
-        }
-        catch (py::error_already_set &ex) {
+        } catch (py::error_already_set &ex) {
             if (!ex.matches(PyExc_Exception)) {
                 throw;
             }
@@ -212,8 +211,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             // On Python >= 3.6, this raises a ModuleNotFoundError, a subclass of ImportError
             py::module_::import("nonexistent");
-        }
-        catch (py::error_already_set &ex) {
+        } catch (py::error_already_set &ex) {
             if (!ex.matches(PyExc_ImportError)) {
                 throw;
             }
@@ -228,10 +226,9 @@ TEST_SUBMODULE(exceptions, m) {
         }
         try {
             throw py::error_already_set();
-        } catch (const std::runtime_error& e) {
-            if ((err && e.what() != std::string("ValueError: foo")) ||
-                (!err && e.what() != std::string("Unknown internal error occurred")))
-            {
+        } catch (const std::runtime_error &e) {
+            if ((err && e.what() != std::string("ValueError: foo"))
+                || (!err && e.what() != std::string("Unknown internal error occurred"))) {
                 PyErr_Clear();
                 throw std::runtime_error("error message mismatch");
             }
@@ -249,7 +246,7 @@ TEST_SUBMODULE(exceptions, m) {
             PythonCallInDestructor set_dict_in_destructor(d);
             PyErr_SetString(PyExc_ValueError, "foo");
             throw py::error_already_set();
-        } catch (const py::error_already_set&) {
+        } catch (const py::error_already_set &) {
             retval = true;
         }
         return retval;
@@ -275,7 +272,7 @@ TEST_SUBMODULE(exceptions, m) {
           });
 
     // Test repr that cannot be displayed
-    m.def("simple_bool_passthrough", [](bool x) {return x;});
+    m.def("simple_bool_passthrough", [](bool x) { return x; });
 
     m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
 
@@ -291,7 +288,7 @@ TEST_SUBMODULE(exceptions, m) {
         try {
             PyErr_SetString(PyExc_ValueError, "inner");
             throw py::error_already_set();
-        } catch (py::error_already_set& e) {
+        } catch (py::error_already_set &e) {
             py::raise_from(e, PyExc_ValueError, "outer");
             throw py::error_already_set();
         }
diff --git a/tests/test_exceptions.h b/tests/test_exceptions.h
index 9d428312eb..03684b89fa 100644
--- a/tests/test_exceptions.h
+++ b/tests/test_exceptions.h
@@ -1,5 +1,6 @@
 #pragma once
 #include "pybind11_tests.h"
+
 #include <stdexcept>
 
 // shared exceptions for cross_module_tests
diff --git a/tests/test_factory_constructors.cpp b/tests/test_factory_constructors.cpp
index 455c75d536..81e32f5abe 100644
--- a/tests/test_factory_constructors.cpp
+++ b/tests/test_factory_constructors.cpp
@@ -10,6 +10,7 @@
 
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
+
 #include <cmath>
 #include <new>
 #include <utility>
@@ -87,6 +88,7 @@ class TestFactory6 {
 protected:
     int value;
     bool alias = false;
+
 public:
     explicit TestFactory6(int i) : value{i} { print_created(this, i); }
     TestFactory6(TestFactory6 &&f) noexcept {
@@ -133,6 +135,7 @@ class TestFactory7 {
 protected:
     int value;
     bool alias = false;
+
 public:
     explicit TestFactory7(int i) : value{i} { print_created(this, i); }
     TestFactory7(TestFactory7 &&f) noexcept {
@@ -166,14 +169,15 @@ class PyTF7 : public TestFactory7 {
     int get() override { PYBIND11_OVERRIDE(int, TestFactory7, get, /*no args*/); }
 };
 
-
 class TestFactoryHelper {
 public:
     // Non-movable, non-copyable type:
     // Return via pointer:
     static TestFactory1 *construct1() { return new TestFactory1(); }
     // Holder:
-    static std::unique_ptr<TestFactory1> construct1(int a) { return std::unique_ptr<TestFactory1>(new TestFactory1(a)); }
+    static std::unique_ptr<TestFactory1> construct1(int a) {
+        return std::unique_ptr<TestFactory1>(new TestFactory1(a));
+    }
     // pointer again
     static TestFactory1 *construct1_string(std::string a) {
         return new TestFactory1(std::move(a));
@@ -183,7 +187,9 @@ class TestFactoryHelper {
     // pointer:
     static TestFactory2 *construct2() { return new TestFactory2(); }
     // holder:
-    static std::unique_ptr<TestFactory2> construct2(int a) { return std::unique_ptr<TestFactory2>(new TestFactory2(a)); }
+    static std::unique_ptr<TestFactory2> construct2(int a) {
+        return std::unique_ptr<TestFactory2>(new TestFactory2(a));
+    }
     // by value moving:
     static TestFactory2 construct2(std::string a) { return TestFactory2(std::move(a)); }
 
@@ -191,16 +197,18 @@ class TestFactoryHelper {
     // pointer:
     static TestFactory3 *construct3() { return new TestFactory3(); }
     // holder:
-    static std::shared_ptr<TestFactory3> construct3(int a) { return std::shared_ptr<TestFactory3>(new TestFactory3(a)); }
+    static std::shared_ptr<TestFactory3> construct3(int a) {
+        return std::shared_ptr<TestFactory3>(new TestFactory3(a));
+    }
 };
 
 TEST_SUBMODULE(factory_constructors, m) {
 
     // Define various trivial types to allow simpler overload resolution:
     py::module_ m_tag = m.def_submodule("tag");
-#define MAKE_TAG_TYPE(Name) \
-    struct Name##_tag {}; \
-    py::class_<Name##_tag>(m_tag, #Name "_tag").def(py::init<>()); \
+#define MAKE_TAG_TYPE(Name)                                                                       \
+    struct Name##_tag {};                                                                         \
+    py::class_<Name##_tag>(m_tag, #Name "_tag").def(py::init<>());                                \
     m_tag.attr(#Name) = py::cast(Name##_tag{})
     MAKE_TAG_TYPE(pointer);
     MAKE_TAG_TYPE(unique_ptr);
@@ -223,9 +231,9 @@ TEST_SUBMODULE(factory_constructors, m) {
         .def(py::init([](unique_ptr_tag, int v) { return TestFactoryHelper::construct1(v); }))
         .def(py::init(&TestFactoryHelper::construct1_string)) // raw function pointer
         .def(py::init([](pointer_tag) { return TestFactoryHelper::construct1(); }))
-        .def(py::init([](py::handle, int v, py::handle) { return TestFactoryHelper::construct1(v); }))
-        .def_readwrite("value", &TestFactory1::value)
-        ;
+        .def(py::init(
+            [](py::handle, int v, py::handle) { return TestFactoryHelper::construct1(v); }))
+        .def_readwrite("value", &TestFactory1::value);
     py::class_<TestFactory2>(m, "TestFactory2")
         .def(py::init([](pointer_tag, int v) { return TestFactoryHelper::construct2(v); }))
         .def(py::init([](unique_ptr_tag, std::string v) {
@@ -236,7 +244,10 @@ TEST_SUBMODULE(factory_constructors, m) {
 
     // Stateful & reused:
     int c = 1;
-    auto c4a = [c](pointer_tag, TF4_tag, int a) { (void) c; return new TestFactory4(a);};
+    auto c4a = [c](pointer_tag, TF4_tag, int a) {
+        (void) c;
+        return new TestFactory4(a);
+    };
 
     // test_init_factory_basic, test_init_factory_casting
     py::class_<TestFactory3, std::shared_ptr<TestFactory3>> pyTestFactory3(m, "TestFactory3");
@@ -253,16 +264,17 @@ TEST_SUBMODULE(factory_constructors, m) {
         .def(py::init(c4a)) // derived ptr
         .def(py::init([](pointer_tag, TF5_tag, int a) { return new TestFactory5(a); }))
         // derived shared ptr:
-        .def(py::init([](shared_ptr_tag, TF4_tag, int a) { return std::make_shared<TestFactory4>(a); }))
-        .def(py::init([](shared_ptr_tag, TF5_tag, int a) { return std::make_shared<TestFactory5>(a); }))
+        .def(py::init(
+            [](shared_ptr_tag, TF4_tag, int a) { return std::make_shared<TestFactory4>(a); }))
+        .def(py::init(
+            [](shared_ptr_tag, TF5_tag, int a) { return std::make_shared<TestFactory5>(a); }))
 
         // Returns nullptr:
         .def(py::init([](null_ptr_tag) { return (TestFactory3 *) nullptr; }))
         .def(py::init([](null_unique_ptr_tag) { return std::unique_ptr<TestFactory3>(); }))
         .def(py::init([](null_shared_ptr_tag) { return std::shared_ptr<TestFactory3>(); }))
 
-        .def_readwrite("value", &TestFactory3::value)
-        ;
+        .def_readwrite("value", &TestFactory3::value);
 
     // test_init_factory_casting
     py::class_<TestFactory4, TestFactory3, std::shared_ptr<TestFactory4>>(m, "TestFactory4")
@@ -346,9 +358,7 @@ TEST_SUBMODULE(factory_constructors, m) {
     py::class_<NoPlacementNew>(m, "NoPlacementNew")
         .def(py::init<int>())
         .def(py::init([]() { return new NoPlacementNew(100); }))
-        .def_readwrite("i", &NoPlacementNew::i)
-        ;
-
+        .def_readwrite("i", &NoPlacementNew::i);
 
     // test_reallocations
     // Class that has verbose operator_new/operator_delete calls
@@ -358,23 +368,36 @@ TEST_SUBMODULE(factory_constructors, m) {
         explicit NoisyAlloc(double d) { py::print(py::str("NoisyAlloc(double {})").format(d)); }
         ~NoisyAlloc() { py::print("~NoisyAlloc()"); }
 
-        static void *operator new(size_t s) { py::print("noisy new"); return ::operator new(s); }
-        static void *operator new(size_t, void *p) { py::print("noisy placement new"); return p; }
-        static void operator delete(void *p, size_t) { py::print("noisy delete"); ::operator delete(p); }
+        static void *operator new(size_t s) {
+            py::print("noisy new");
+            return ::operator new(s);
+        }
+        static void *operator new(size_t, void *p) {
+            py::print("noisy placement new");
+            return p;
+        }
+        static void operator delete(void *p, size_t) {
+            py::print("noisy delete");
+            ::operator delete(p);
+        }
         static void operator delete(void *, void *) { py::print("noisy placement delete"); }
 #if defined(_MSC_VER) && _MSC_VER < 1910
         // MSVC 2015 bug: the above "noisy delete" isn't invoked (fixed in MSVC 2017)
-        static void operator delete(void *p) { py::print("noisy delete"); ::operator delete(p); }
+        static void operator delete(void *p) {
+            py::print("noisy delete");
+            ::operator delete(p);
+        }
 #endif
     };
 
-
     py::class_<NoisyAlloc> pyNoisyAlloc(m, "NoisyAlloc");
-        // Since these overloads have the same number of arguments, the dispatcher will try each of
-        // them until the arguments convert.  Thus we can get a pre-allocation here when passing a
-        // single non-integer:
+    // Since these overloads have the same number of arguments, the dispatcher will try each of
+    // them until the arguments convert.  Thus we can get a pre-allocation here when passing a
+    // single non-integer:
     ignoreOldStyleInitWarnings([&pyNoisyAlloc]() {
-        pyNoisyAlloc.def("__init__", [](NoisyAlloc *a, int i) { new (a) NoisyAlloc(i); }); // Regular constructor, runs first, requires preallocation
+        pyNoisyAlloc.def("__init__", [](NoisyAlloc *a, int i) {
+            new (a) NoisyAlloc(i);
+        }); // Regular constructor, runs first, requires preallocation
     });
 
     pyNoisyAlloc.def(py::init([](double d) { return new NoisyAlloc(d); }));
@@ -385,7 +408,8 @@ TEST_SUBMODULE(factory_constructors, m) {
     pyNoisyAlloc.def(py::init([](double d, int) { return NoisyAlloc(d); }));
     // Old-style placement new init; requires preallocation
     ignoreOldStyleInitWarnings([&pyNoisyAlloc]() {
-        pyNoisyAlloc.def("__init__", [](NoisyAlloc &a, double d, double) { new (&a) NoisyAlloc(d); });
+        pyNoisyAlloc.def("__init__",
+                         [](NoisyAlloc &a, double d, double) { new (&a) NoisyAlloc(d); });
     });
     // Requires deallocation of previous overload preallocated value:
     pyNoisyAlloc.def(py::init([](int i, double) { return new NoisyAlloc(i); }));
@@ -395,7 +419,8 @@ TEST_SUBMODULE(factory_constructors, m) {
             "__init__", [](NoisyAlloc &a, int i, const std::string &) { new (&a) NoisyAlloc(i); });
     });
 
-    // static_assert testing (the following def's should all fail with appropriate compilation errors):
+    // static_assert testing (the following def's should all fail with appropriate compilation
+    // errors):
 #if 0
     struct BadF1Base {};
     struct BadF1 : BadF1Base {};
diff --git a/tests/test_gil_scoped.cpp b/tests/test_gil_scoped.cpp
index b261085c88..97efdc1616 100644
--- a/tests/test_gil_scoped.cpp
+++ b/tests/test_gil_scoped.cpp
@@ -7,43 +7,41 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/functional.h>
 
+#include "pybind11_tests.h"
 
-class VirtClass  {
+class VirtClass {
 public:
     virtual ~VirtClass() = default;
     VirtClass() = default;
-    VirtClass(const VirtClass&) = delete;
+    VirtClass(const VirtClass &) = delete;
     virtual void virtual_func() {}
     virtual void pure_virtual_func() = 0;
 };
 
 class PyVirtClass : public VirtClass {
-    void virtual_func() override {
-        PYBIND11_OVERRIDE(void, VirtClass, virtual_func,);
-    }
+    void virtual_func() override { PYBIND11_OVERRIDE(void, VirtClass, virtual_func, ); }
     void pure_virtual_func() override {
-        PYBIND11_OVERRIDE_PURE(void, VirtClass, pure_virtual_func,);
+        PYBIND11_OVERRIDE_PURE(void, VirtClass, pure_virtual_func, );
     }
 };
 
 TEST_SUBMODULE(gil_scoped, m) {
-  py::class_<VirtClass, PyVirtClass>(m, "VirtClass")
-      .def(py::init<>())
-      .def("virtual_func", &VirtClass::virtual_func)
-      .def("pure_virtual_func", &VirtClass::pure_virtual_func);
-
-  m.def("test_callback_py_obj", [](py::object &func) { func(); });
-  m.def("test_callback_std_func", [](const std::function<void()> &func) { func(); });
-  m.def("test_callback_virtual_func", [](VirtClass &virt) { virt.virtual_func(); });
-  m.def("test_callback_pure_virtual_func", [](VirtClass &virt) { virt.pure_virtual_func(); });
-  m.def("test_cross_module_gil", []() {
-      auto cm = py::module_::import("cross_module_gil_utils");
-      auto gil_acquire
-          = reinterpret_cast<void (*)()>(PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
-      py::gil_scoped_release gil_release;
-      gil_acquire();
-  });
+    py::class_<VirtClass, PyVirtClass>(m, "VirtClass")
+        .def(py::init<>())
+        .def("virtual_func", &VirtClass::virtual_func)
+        .def("pure_virtual_func", &VirtClass::pure_virtual_func);
+
+    m.def("test_callback_py_obj", [](py::object &func) { func(); });
+    m.def("test_callback_std_func", [](const std::function<void()> &func) { func(); });
+    m.def("test_callback_virtual_func", [](VirtClass &virt) { virt.virtual_func(); });
+    m.def("test_callback_pure_virtual_func", [](VirtClass &virt) { virt.pure_virtual_func(); });
+    m.def("test_cross_module_gil", []() {
+        auto cm = py::module_::import("cross_module_gil_utils");
+        auto gil_acquire = reinterpret_cast<void (*)()>(
+            PyLong_AsVoidPtr(cm.attr("gil_acquire_funcaddr").ptr()));
+        py::gil_scoped_release gil_release;
+        gil_acquire();
+    });
 }
diff --git a/tests/test_iostream.cpp b/tests/test_iostream.cpp
index ef54b0a1c5..dd0e19e0bd 100644
--- a/tests/test_iostream.cpp
+++ b/tests/test_iostream.cpp
@@ -7,12 +7,14 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#if defined(_MSC_VER) && _MSC_VER < 1910  // VS 2015's MSVC
-#  pragma warning(disable: 4702) // unreachable code in system header (xatomic.h(382))
+#if defined(_MSC_VER) && _MSC_VER < 1910 // VS 2015's MSVC
+#    pragma warning(disable : 4702)      // unreachable code in system header (xatomic.h(382))
 #endif
 
 #include <pybind11/iostream.h>
+
 #include "pybind11_tests.h"
+
 #include <atomic>
 #include <iostream>
 #include <mutex>
@@ -51,13 +53,12 @@ struct TestThread {
                     std::cout << "x" << std::flush;
                 }
                 std::this_thread::sleep_for(std::chrono::microseconds(50));
-            } };
+            }
+        };
         t_ = new std::thread(std::move(thread_f));
     }
 
-    ~TestThread() {
-        delete t_;
-    }
+    ~TestThread() { delete t_; }
 
     void stop() { stop_ = true; }
 
@@ -75,7 +76,6 @@ struct TestThread {
     std::atomic<bool> stop_;
 };
 
-
 TEST_SUBMODULE(iostream, m) {
 
     add_ostream_redirect(m);
@@ -92,9 +92,11 @@ TEST_SUBMODULE(iostream, m) {
         std::cout << msg << std::flush;
     });
 
-    m.def("guard_output", &noisy_function,
-            py::call_guard<py::scoped_ostream_redirect>(),
-            py::arg("msg"), py::arg("flush")=true);
+    m.def("guard_output",
+          &noisy_function,
+          py::call_guard<py::scoped_ostream_redirect>(),
+          py::arg("msg"),
+          py::arg("flush") = true);
 
     m.def("captured_err", [](const std::string &msg) {
         py::scoped_ostream_redirect redir(std::cerr, py::module_::import("sys").attr("stderr"));
@@ -103,9 +105,11 @@ TEST_SUBMODULE(iostream, m) {
 
     m.def("noisy_function", &noisy_function, py::arg("msg"), py::arg("flush") = true);
 
-    m.def("dual_guard", &noisy_funct_dual,
-            py::call_guard<py::scoped_ostream_redirect, py::scoped_estream_redirect>(),
-            py::arg("msg"), py::arg("emsg"));
+    m.def("dual_guard",
+          &noisy_funct_dual,
+          py::call_guard<py::scoped_ostream_redirect, py::scoped_estream_redirect>(),
+          py::arg("msg"),
+          py::arg("emsg"));
 
     m.def("raw_output", [](const std::string &msg) { std::cout << msg << std::flush; });
 
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index d09630a8cd..7418afefb4 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -7,39 +7,43 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #include <utility>
 
 TEST_SUBMODULE(kwargs_and_defaults, m) {
-    auto kw_func = [](int x, int y) { return "x=" + std::to_string(x) + ", y=" + std::to_string(y); };
+    auto kw_func
+        = [](int x, int y) { return "x=" + std::to_string(x) + ", y=" + std::to_string(y); };
 
     // test_named_arguments
     m.def("kw_func0", kw_func);
     m.def("kw_func1", kw_func, py::arg("x"), py::arg("y"));
     m.def("kw_func2", kw_func, py::arg("x") = 100, py::arg("y") = 200);
-    m.def("kw_func3", [](const char *) { }, py::arg("data") = std::string("Hello world!"));
+    m.def(
+        "kw_func3", [](const char *) {}, py::arg("data") = std::string("Hello world!"));
 
     /* A fancier default argument */
     std::vector<int> list{{13, 17}};
-    m.def("kw_func4", [](const std::vector<int> &entries) {
-        std::string ret = "{";
-        for (int i : entries) {
-            ret += std::to_string(i) + " ";
-        }
-        ret.back() = '}';
-        return ret;
-    }, py::arg("myList") = list);
+    m.def(
+        "kw_func4",
+        [](const std::vector<int> &entries) {
+            std::string ret = "{";
+            for (int i : entries) {
+                ret += std::to_string(i) + " ";
+            }
+            ret.back() = '}';
+            return ret;
+        },
+        py::arg("myList") = list);
 
-    m.def("kw_func_udl", kw_func, "x"_a, "y"_a=300);
-    m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a=0);
+    m.def("kw_func_udl", kw_func, "x"_a, "y"_a = 300);
+    m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a = 0);
 
     // test_args_and_kwargs
-    m.def("args_function", [](py::args args) -> py::tuple {
-        return std::move(args);
-    });
+    m.def("args_function", [](py::args args) -> py::tuple { return std::move(args); });
     m.def("args_kwargs_function", [](const py::args &args, const py::kwargs &kwargs) {
         return py::make_tuple(args, kwargs);
     });
@@ -54,35 +58,60 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     };
     m.def("mixed_plus_args_kwargs", mixed_plus_both);
 
-    m.def("mixed_plus_args_kwargs_defaults", mixed_plus_both,
-            py::arg("i") = 1, py::arg("j") = 3.14159);
-
-    m.def("args_kwonly",
-            [](int i, double j, const py::args &args, int z) { return py::make_tuple(i, j, args, z); },
-            "i"_a, "j"_a, "z"_a);
-    m.def("args_kwonly_kwargs",
-            [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
-                return py::make_tuple(i, j, args, z, kwargs); },
-            "i"_a, "j"_a, py::kw_only{}, "z"_a);
-    m.def("args_kwonly_kwargs_defaults",
-            [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
-                return py::make_tuple(i, j, args, z, kwargs); },
-            "i"_a = 1, "j"_a = 3.14159, "z"_a = 42);
-    m.def("args_kwonly_full_monty",
-            [](int h, int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
-                return py::make_tuple(h, i, j, args, z, kwargs); },
-            py::arg() = 1, py::arg() = 2, py::pos_only{}, "j"_a = 3.14159, "z"_a = 42);
-
-
-    // test_args_refcount
-    // PyPy needs a garbage collection to get the reference count values to match CPython's behaviour
-    #ifdef PYPY_VERSION
-    #define GC_IF_NEEDED ConstructorStats::gc()
-    #else
-    #define GC_IF_NEEDED
-    #endif
-    m.def("arg_refcount_h", [](py::handle h) { GC_IF_NEEDED; return h.ref_count(); });
-    m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) { GC_IF_NEEDED; return h.ref_count(); });
+    m.def("mixed_plus_args_kwargs_defaults",
+          mixed_plus_both,
+          py::arg("i") = 1,
+          py::arg("j") = 3.14159);
+
+    m.def(
+        "args_kwonly",
+        [](int i, double j, const py::args &args, int z) { return py::make_tuple(i, j, args, z); },
+        "i"_a,
+        "j"_a,
+        "z"_a);
+    m.def(
+        "args_kwonly_kwargs",
+        [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+            return py::make_tuple(i, j, args, z, kwargs);
+        },
+        "i"_a,
+        "j"_a,
+        py::kw_only{},
+        "z"_a);
+    m.def(
+        "args_kwonly_kwargs_defaults",
+        [](int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+            return py::make_tuple(i, j, args, z, kwargs);
+        },
+        "i"_a = 1,
+        "j"_a = 3.14159,
+        "z"_a = 42);
+    m.def(
+        "args_kwonly_full_monty",
+        [](int h, int i, double j, const py::args &args, int z, const py::kwargs &kwargs) {
+            return py::make_tuple(h, i, j, args, z, kwargs);
+        },
+        py::arg() = 1,
+        py::arg() = 2,
+        py::pos_only{},
+        "j"_a = 3.14159,
+        "z"_a = 42);
+
+// test_args_refcount
+// PyPy needs a garbage collection to get the reference count values to match CPython's behaviour
+#ifdef PYPY_VERSION
+#    define GC_IF_NEEDED ConstructorStats::gc()
+#else
+#    define GC_IF_NEEDED
+#endif
+    m.def("arg_refcount_h", [](py::handle h) {
+        GC_IF_NEEDED;
+        return h.ref_count();
+    });
+    m.def("arg_refcount_h", [](py::handle h, py::handle, py::handle) {
+        GC_IF_NEEDED;
+        return h.ref_count();
+    });
     m.def("arg_refcount_o", [](const py::object &o) {
         GC_IF_NEEDED;
         return o.ref_count();
@@ -109,23 +138,42 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
 
     // pybind11 won't allow these to be bound: args and kwargs, if present, must be at the end.
     // Uncomment these to test that the static_assert is indeed working:
-//    m.def("bad_args1", [](py::args, int) {});
-//    m.def("bad_args2", [](py::kwargs, int) {});
-//    m.def("bad_args3", [](py::kwargs, py::args) {});
-//    m.def("bad_args4", [](py::args, int, py::kwargs) {});
-//    m.def("bad_args5", [](py::args, py::kwargs, int) {});
-//    m.def("bad_args6", [](py::args, py::args) {});
-//    m.def("bad_args7", [](py::kwargs, py::kwargs) {});
+    //    m.def("bad_args1", [](py::args, int) {});
+    //    m.def("bad_args2", [](py::kwargs, int) {});
+    //    m.def("bad_args3", [](py::kwargs, py::args) {});
+    //    m.def("bad_args4", [](py::args, int, py::kwargs) {});
+    //    m.def("bad_args5", [](py::args, py::kwargs, int) {});
+    //    m.def("bad_args6", [](py::args, py::args) {});
+    //    m.def("bad_args7", [](py::kwargs, py::kwargs) {});
 
     // test_keyword_only_args
-    m.def("kw_only_all", [](int i, int j) { return py::make_tuple(i, j); },
-            py::kw_only(), py::arg("i"), py::arg("j"));
-    m.def("kw_only_some", [](int i, int j, int k) { return py::make_tuple(i, j, k); },
-            py::arg(), py::kw_only(), py::arg("j"), py::arg("k"));
-    m.def("kw_only_with_defaults", [](int i, int j, int k, int z) { return py::make_tuple(i, j, k, z); },
-            py::arg() = 3, "j"_a = 4, py::kw_only(), "k"_a = 5, "z"_a);
-    m.def("kw_only_mixed", [](int i, int j) { return py::make_tuple(i, j); },
-            "i"_a, py::kw_only(), "j"_a);
+    m.def(
+        "kw_only_all",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        py::kw_only(),
+        py::arg("i"),
+        py::arg("j"));
+    m.def(
+        "kw_only_some",
+        [](int i, int j, int k) { return py::make_tuple(i, j, k); },
+        py::arg(),
+        py::kw_only(),
+        py::arg("j"),
+        py::arg("k"));
+    m.def(
+        "kw_only_with_defaults",
+        [](int i, int j, int k, int z) { return py::make_tuple(i, j, k, z); },
+        py::arg() = 3,
+        "j"_a = 4,
+        py::kw_only(),
+        "k"_a = 5,
+        "z"_a);
+    m.def(
+        "kw_only_mixed",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        "i"_a,
+        py::kw_only(),
+        "j"_a);
     m.def(
         "kw_only_plus_more",
         [](int i, int j, int k, const py::kwargs &kwargs) {
@@ -137,31 +185,57 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
         py::arg("k") /* kw-only */);
 
     m.def("register_invalid_kw_only", [](py::module_ m) {
-        m.def("bad_kw_only", [](int i, int j) { return py::make_tuple(i, j); },
-                py::kw_only(), py::arg() /* invalid unnamed argument */, "j"_a);
+        m.def(
+            "bad_kw_only",
+            [](int i, int j) { return py::make_tuple(i, j); },
+            py::kw_only(),
+            py::arg() /* invalid unnamed argument */,
+            "j"_a);
     });
 
     // test_positional_only_args
-    m.def("pos_only_all", [](int i, int j) { return py::make_tuple(i, j); },
-            py::arg("i"), py::arg("j"), py::pos_only());
-    m.def("pos_only_mix", [](int i, int j) { return py::make_tuple(i, j); },
-            py::arg("i"), py::pos_only(), py::arg("j"));
-    m.def("pos_kw_only_mix", [](int i, int j, int k) { return py::make_tuple(i, j, k); },
-            py::arg("i"), py::pos_only(), py::arg("j"), py::kw_only(), py::arg("k"));
-    m.def("pos_only_def_mix", [](int i, int j, int k) { return py::make_tuple(i, j, k); },
-            py::arg("i"), py::arg("j") = 2, py::pos_only(), py::arg("k") = 3);
-
+    m.def(
+        "pos_only_all",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        py::arg("i"),
+        py::arg("j"),
+        py::pos_only());
+    m.def(
+        "pos_only_mix",
+        [](int i, int j) { return py::make_tuple(i, j); },
+        py::arg("i"),
+        py::pos_only(),
+        py::arg("j"));
+    m.def(
+        "pos_kw_only_mix",
+        [](int i, int j, int k) { return py::make_tuple(i, j, k); },
+        py::arg("i"),
+        py::pos_only(),
+        py::arg("j"),
+        py::kw_only(),
+        py::arg("k"));
+    m.def(
+        "pos_only_def_mix",
+        [](int i, int j, int k) { return py::make_tuple(i, j, k); },
+        py::arg("i"),
+        py::arg("j") = 2,
+        py::pos_only(),
+        py::arg("k") = 3);
 
     // These should fail to compile:
 #ifdef PYBIND11_NEVER_DEFINED_EVER
     // argument annotations are required when using kw_only
-    m.def("bad_kw_only1", [](int) {}, py::kw_only());
+    m.def(
+        "bad_kw_only1", [](int) {}, py::kw_only());
     // can't specify both `py::kw_only` and a `py::args` argument
-    m.def("bad_kw_only2", [](int i, py::args) {}, py::kw_only(), "i"_a);
+    m.def(
+        "bad_kw_only2", [](int i, py::args) {}, py::kw_only(), "i"_a);
 #endif
 
     // test_function_signatures (along with most of the above)
-    struct KWClass { void foo(int, float) {} };
+    struct KWClass {
+        void foo(int, float) {}
+    };
     py::class_<KWClass>(m, "KWClass")
         .def("foo0", &KWClass::foo)
         .def("foo1", &KWClass::foo, "x"_a, "y"_a);
@@ -182,11 +256,18 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
         .def(py::init([](int) { return first_arg_kw_only(); }),
              py::kw_only(), // This being before any args was broken
              py::arg("i") = 0)
-        .def("method", [](first_arg_kw_only&, int, int) {},
-             py::kw_only(), // and likewise here
-             py::arg("i") = 1, py::arg("j") = 2)
+        .def(
+            "method",
+            [](first_arg_kw_only &, int, int) {},
+            py::kw_only(), // and likewise here
+            py::arg("i") = 1,
+            py::arg("j") = 2)
         // Closely related: pos_only marker didn't show up properly when it was before any other
         // arguments (although that is fairly useless in practice).
-        .def("pos_only", [](first_arg_kw_only&, int, int) {},
-                py::pos_only{}, py::arg("i"), py::arg("j"));
+        .def(
+            "pos_only",
+            [](first_arg_kw_only &, int, int) {},
+            py::pos_only{},
+            py::arg("i"),
+            py::arg("j"));
 }
diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp
index 0fb3ecc19f..1373677447 100644
--- a/tests/test_local_bindings.cpp
+++ b/tests/test_local_bindings.cpp
@@ -8,12 +8,12 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "local_bindings.h"
-
 #include <pybind11/stl.h>
 #include <pybind11/stl_bind.h>
 
+#include "local_bindings.h"
+#include "pybind11_tests.h"
+
 #include <numeric>
 #include <utility>
 
@@ -24,9 +24,9 @@ TEST_SUBMODULE(local_bindings, m) {
 
     // test_local_bindings
     // Register a class with py::module_local:
-    bind_local<LocalType, -1>(m, "LocalType", py::module_local())
-        .def("get3", [](LocalType &t) { return t.i + 3; })
-        ;
+    bind_local<LocalType, -1>(m, "LocalType", py::module_local()).def("get3", [](LocalType &t) {
+        return t.i + 3;
+    });
 
     m.def("local_value", [](LocalType &l) { return l.i; });
 
@@ -35,14 +35,14 @@ TEST_SUBMODULE(local_bindings, m) {
     // one, in pybind11_cross_module_tests.cpp, is designed to fail):
     bind_local<NonLocalType, 0>(m, "NonLocalType")
         .def(py::init<int>())
-        .def("get", [](LocalType &i) { return i.i; })
-        ;
+        .def("get", [](LocalType &i) { return i.i; });
 
     // test_duplicate_local
-    // py::module_local declarations should be visible across compilation units that get linked together;
-    // this tries to register a duplicate local.  It depends on a definition in test_class.cpp and
-    // should raise a runtime error from the duplicate definition attempt.  If test_class isn't
-    // available it *also* throws a runtime error (with "test_class not enabled" as value).
+    // py::module_local declarations should be visible across compilation units that get linked
+    // together; this tries to register a duplicate local.  It depends on a definition in
+    // test_class.cpp and should raise a runtime error from the duplicate definition attempt.  If
+    // test_class isn't available it *also* throws a runtime error (with "test_class not enabled"
+    // as value).
     m.def("register_local_external", [m]() {
         auto main = py::module_::import("pybind11_tests");
         if (py::hasattr(main, "class_")) {
@@ -79,12 +79,12 @@ TEST_SUBMODULE(local_bindings, m) {
     m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); });
 
     // test_internal_locals_differ
-    m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
+    m.def("local_cpp_types_addr",
+          []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; });
 
     // test_stl_caster_vs_stl_bind
-    m.def("load_vector_via_caster", [](std::vector<int> v) {
-        return std::accumulate(v.begin(), v.end(), 0);
-    });
+    m.def("load_vector_via_caster",
+          [](std::vector<int> v) { return std::accumulate(v.begin(), v.end(), 0); });
 
     // test_cross_module_calls
     m.def("return_self", [](LocalVec *v) { return v; });
@@ -94,11 +94,9 @@ TEST_SUBMODULE(local_bindings, m) {
     public:
         explicit Cat(std::string name) : Pet(std::move(name)) {}
     };
-    py::class_<pets::Pet>(m, "Pet", py::module_local())
-        .def("get_name", &pets::Pet::name);
+    py::class_<pets::Pet>(m, "Pet", py::module_local()).def("get_name", &pets::Pet::name);
     // Binding for local extending class:
-    py::class_<Cat, pets::Pet>(m, "Cat")
-        .def(py::init<std::string>());
+    py::class_<Cat, pets::Pet>(m, "Cat").def(py::init<std::string>());
     m.def("pet_name", [](pets::Pet &p) { return p.name(); });
 
     py::class_<MixGL>(m, "MixGL").def(py::init<int>());
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 9e55452dec..10515e26f9 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -8,8 +8,8 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 
 #if !defined(PYBIND11_OVERLOAD_CAST)
 template <typename... Args>
@@ -27,7 +27,10 @@ class ExampleMandA {
 
     std::string toString() const { return "ExampleMandA[value=" + std::to_string(value) + "]"; }
 
-    void operator=(const ExampleMandA &e) { print_copy_assigned(this); value = e.value; }
+    void operator=(const ExampleMandA &e) {
+        print_copy_assigned(this);
+        value = e.value;
+    }
     void operator=(ExampleMandA &&e) noexcept {
         print_move_assigned(this);
         value = e.value;
@@ -40,37 +43,37 @@ class ExampleMandA {
     void add4(ExampleMandA *other) { value += other->value; }       // passing by pointer
     void add5(const ExampleMandA *other) { value += other->value; } // passing by const pointer
 
-    void add6(int other) { value += other; }                        // passing by value
-    void add7(int &other) { value += other; }                       // passing by reference
-    void add8(const int &other) { value += other; }                 // passing by const reference
+    void add6(int other) { value += other; }        // passing by value
+    void add7(int &other) { value += other; }       // passing by reference
+    void add8(const int &other) { value += other; } // passing by const reference
     // NOLINTNEXTLINE(readability-non-const-parameter) Deliberately non-const for testing
-    void add9(int *other) { value += *other; }                      // passing by pointer
-    void add10(const int *other) { value += *other; }               // passing by const pointer
-
-    void consume_str(std::string&&) {}
-
-    ExampleMandA self1() { return *this; }                          // return by value
-    ExampleMandA &self2() { return *this; }                         // return by reference
-    const ExampleMandA &self3() const { return *this; }             // return by const reference
-    ExampleMandA *self4() { return this; }                          // return by pointer
-    const ExampleMandA *self5() const { return this; }              // return by const pointer
-
-    int internal1() const { return value; }                         // return by value
-    int &internal2() { return value; }                              // return by reference
-    const int &internal3() const { return value; }                  // return by const reference
-    int *internal4() { return &value; }                             // return by pointer
-    const int *internal5() { return &value; }                       // return by const pointer
-
-    py::str overloaded()             { return "()"; }
-    py::str overloaded(int)          { return "(int)"; }
-    py::str overloaded(int, float)   { return "(int, float)"; }
-    py::str overloaded(float, int)   { return "(float, int)"; }
-    py::str overloaded(int, int)     { return "(int, int)"; }
+    void add9(int *other) { value += *other; }        // passing by pointer
+    void add10(const int *other) { value += *other; } // passing by const pointer
+
+    void consume_str(std::string &&) {}
+
+    ExampleMandA self1() { return *this; }              // return by value
+    ExampleMandA &self2() { return *this; }             // return by reference
+    const ExampleMandA &self3() const { return *this; } // return by const reference
+    ExampleMandA *self4() { return this; }              // return by pointer
+    const ExampleMandA *self5() const { return this; }  // return by const pointer
+
+    int internal1() const { return value; }        // return by value
+    int &internal2() { return value; }             // return by reference
+    const int &internal3() const { return value; } // return by const reference
+    int *internal4() { return &value; }            // return by pointer
+    const int *internal5() { return &value; }      // return by const pointer
+
+    py::str overloaded() { return "()"; }
+    py::str overloaded(int) { return "(int)"; }
+    py::str overloaded(int, float) { return "(int, float)"; }
+    py::str overloaded(float, int) { return "(float, int)"; }
+    py::str overloaded(int, int) { return "(int, int)"; }
     py::str overloaded(float, float) { return "(float, float)"; }
-    py::str overloaded(int)          const { return "(int) const"; }
-    py::str overloaded(int, float)   const { return "(int, float) const"; }
-    py::str overloaded(float, int)   const { return "(float, int) const"; }
-    py::str overloaded(int, int)     const { return "(int, int) const"; }
+    py::str overloaded(int) const { return "(int) const"; }
+    py::str overloaded(int, float) const { return "(int, float) const"; }
+    py::str overloaded(float, int) const { return "(float, int) const"; }
+    py::str overloaded(int, int) const { return "(int, int) const"; }
     py::str overloaded(float, float) const { return "(float, float) const"; }
 
     static py::str overloaded(float) { return "static float"; }
@@ -112,7 +115,10 @@ UserType TestPropRVP::sv1(1);
 UserType TestPropRVP::sv2(1);
 
 // Test None-allowed py::arg argument policy
-class NoneTester { public: int answer = 42; };
+class NoneTester {
+public:
+    int answer = 42;
+};
 int none1(const NoneTester &obj) { return obj.answer; }
 int none2(NoneTester *obj) { return obj ? obj->answer : -1; }
 int none3(std::shared_ptr<NoneTester> &obj) { return obj ? obj->answer : -1; }
@@ -134,11 +140,15 @@ struct StrIssue {
     explicit StrIssue(int i) : val{i} {}
 };
 
-// Issues #854, #910: incompatible function args when member function/pointer is in unregistered base class
+// Issues #854, #910: incompatible function args when member function/pointer is in unregistered
+// base class
 class UnregisteredBase {
 public:
     void do_nothing() const {}
-    void increase_value() { rw_value++; ro_value += 0.25; }
+    void increase_value() {
+        rw_value++;
+        ro_value += 0.25;
+    }
     void set_int(int v) { rw_value = v; }
     int get_int() const { return rw_value; }
     double get_double() const { return ro_value; }
@@ -161,10 +171,10 @@ struct RefQualified {
 
 // Test rvalue ref param
 struct RValueRefParam {
-    std::size_t func1(std::string&& s) { return s.size(); }
-    std::size_t func2(std::string&& s) const { return s.size(); }
-    std::size_t func3(std::string&& s) & { return s.size(); }
-    std::size_t func4(std::string&& s) const & { return s.size(); }
+    std::size_t func1(std::string &&s) { return s.size(); }
+    std::size_t func2(std::string &&s) const { return s.size(); }
+    std::size_t func3(std::string &&s) & { return s.size(); }
+    std::size_t func4(std::string &&s) const & { return s.size(); }
 };
 
 TEST_SUBMODULE(methods_and_attributes, m) {
@@ -172,8 +182,8 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     py::class_<ExampleMandA> emna(m, "ExampleMandA");
     emna.def(py::init<>())
         .def(py::init<int>())
-        .def(py::init<std::string&&>())
-        .def(py::init<const ExampleMandA&>())
+        .def(py::init<std::string &&>())
+        .def(py::init<const ExampleMandA &>())
         .def("add1", &ExampleMandA::add1)
         .def("add2", &ExampleMandA::add2)
         .def("add3", &ExampleMandA::add3)
@@ -198,16 +208,20 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 #if defined(PYBIND11_OVERLOAD_CAST)
         .def("overloaded", py::overload_cast<>(&ExampleMandA::overloaded))
         .def("overloaded", py::overload_cast<int>(&ExampleMandA::overloaded))
-        .def("overloaded", py::overload_cast<int,   float>(&ExampleMandA::overloaded))
-        .def("overloaded", py::overload_cast<float,   int>(&ExampleMandA::overloaded))
-        .def("overloaded", py::overload_cast<int,     int>(&ExampleMandA::overloaded))
+        .def("overloaded", py::overload_cast<int, float>(&ExampleMandA::overloaded))
+        .def("overloaded", py::overload_cast<float, int>(&ExampleMandA::overloaded))
+        .def("overloaded", py::overload_cast<int, int>(&ExampleMandA::overloaded))
         .def("overloaded", py::overload_cast<float, float>(&ExampleMandA::overloaded))
         .def("overloaded_float", py::overload_cast<float, float>(&ExampleMandA::overloaded))
-        .def("overloaded_const", py::overload_cast<int         >(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<int,   float>(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<float,   int>(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<int,     int>(&ExampleMandA::overloaded, py::const_))
-        .def("overloaded_const", py::overload_cast<float, float>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const", py::overload_cast<int>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<int, float>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<float, int>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<int, int>(&ExampleMandA::overloaded, py::const_))
+        .def("overloaded_const",
+             py::overload_cast<float, float>(&ExampleMandA::overloaded, py::const_))
 #else
         // Use both the traditional static_cast method and the C++11 compatible overload_cast_
         .def("overloaded", overload_cast_<>()(&ExampleMandA::overloaded))
@@ -225,16 +239,29 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 #endif
         // test_no_mixed_overloads
         // Raise error if trying to mix static/non-static overloads on the same name:
-        .def_static("add_mixed_overloads1", []() {
-            auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(py::module_::import("pybind11_tests.methods_and_attributes").attr("ExampleMandA"));
-            emna.def       ("overload_mixed1", static_cast<py::str (ExampleMandA::*)(int, int)>(&ExampleMandA::overloaded))
-                .def_static("overload_mixed1", static_cast<py::str (              *)(float   )>(&ExampleMandA::overloaded));
-        })
-        .def_static("add_mixed_overloads2", []() {
-            auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(py::module_::import("pybind11_tests.methods_and_attributes").attr("ExampleMandA"));
-            emna.def_static("overload_mixed2", static_cast<py::str (              *)(float   )>(&ExampleMandA::overloaded))
-                .def       ("overload_mixed2", static_cast<py::str (ExampleMandA::*)(int, int)>(&ExampleMandA::overloaded));
-        })
+        .def_static("add_mixed_overloads1",
+                    []() {
+                        auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(
+                            py::module_::import("pybind11_tests.methods_and_attributes")
+                                .attr("ExampleMandA"));
+                        emna.def("overload_mixed1",
+                                 static_cast<py::str (ExampleMandA::*)(int, int)>(
+                                     &ExampleMandA::overloaded))
+                            .def_static(
+                                "overload_mixed1",
+                                static_cast<py::str (*)(float)>(&ExampleMandA::overloaded));
+                    })
+        .def_static("add_mixed_overloads2",
+                    []() {
+                        auto emna = py::reinterpret_borrow<py::class_<ExampleMandA>>(
+                            py::module_::import("pybind11_tests.methods_and_attributes")
+                                .attr("ExampleMandA"));
+                        emna.def_static("overload_mixed2",
+                                        static_cast<py::str (*)(float)>(&ExampleMandA::overloaded))
+                            .def("overload_mixed2",
+                                 static_cast<py::str (ExampleMandA::*)(int, int)>(
+                                     &ExampleMandA::overloaded));
+                    })
         .def("__str__", &ExampleMandA::toString)
         .def_readwrite("value", &ExampleMandA::value);
 
@@ -307,7 +334,7 @@ TEST_SUBMODULE(methods_and_attributes, m) {
                                       [](const py::object &) { return UserType(1); });
 
     // test_metaclass_override
-    struct MetaclassOverride { };
+    struct MetaclassOverride {};
     py::class_<MetaclassOverride>(m, "MetaclassOverride", py::metaclass((PyObject *) &PyType_Type))
         .def_property_readonly_static("readonly", [](const py::object &) { return 1; });
 
@@ -315,22 +342,21 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     m.def("overload_order", [](const std::string &) { return 1; });
     m.def("overload_order", [](const std::string &) { return 2; });
     m.def("overload_order", [](int) { return 3; });
-    m.def("overload_order", [](int) { return 4; }, py::prepend{});
+    m.def(
+        "overload_order", [](int) { return 4; }, py::prepend{});
 
 #if !defined(PYPY_VERSION)
     // test_dynamic_attributes
     class DynamicClass {
     public:
         DynamicClass() { print_default_created(this); }
-        DynamicClass(const DynamicClass&) = delete;
+        DynamicClass(const DynamicClass &) = delete;
         ~DynamicClass() { print_destroyed(this); }
     };
-    py::class_<DynamicClass>(m, "DynamicClass", py::dynamic_attr())
-        .def(py::init());
+    py::class_<DynamicClass>(m, "DynamicClass", py::dynamic_attr()).def(py::init());
 
-    class CppDerivedDynamicClass : public DynamicClass { };
-    py::class_<CppDerivedDynamicClass, DynamicClass>(m, "CppDerivedDynamicClass")
-        .def(py::init());
+    class CppDerivedDynamicClass : public DynamicClass {};
+    py::class_<CppDerivedDynamicClass, DynamicClass>(m, "CppDerivedDynamicClass").def(py::init());
 #endif
 
     // test_bad_arg_default
@@ -340,20 +366,27 @@ TEST_SUBMODULE(methods_and_attributes, m) {
 #else
     m.attr("debug_enabled") = false;
 #endif
-    m.def("bad_arg_def_named", []{
+    m.def("bad_arg_def_named", [] {
         auto m = py::module_::import("pybind11_tests");
-        m.def("should_fail", [](int, UnregisteredType) {}, py::arg(), py::arg("a") = UnregisteredType());
+        m.def(
+            "should_fail",
+            [](int, UnregisteredType) {},
+            py::arg(),
+            py::arg("a") = UnregisteredType());
     });
-    m.def("bad_arg_def_unnamed", []{
+    m.def("bad_arg_def_unnamed", [] {
         auto m = py::module_::import("pybind11_tests");
-        m.def("should_fail", [](int, UnregisteredType) {}, py::arg(), py::arg() = UnregisteredType());
+        m.def(
+            "should_fail",
+            [](int, UnregisteredType) {},
+            py::arg(),
+            py::arg() = UnregisteredType());
     });
 
     // [workaround(intel)] ICC 20/21 breaks with py::arg().stuff, using py::arg{}.stuff works.
 
     // test_accepts_none
-    py::class_<NoneTester, std::shared_ptr<NoneTester>>(m, "NoneTester")
-        .def(py::init<>());
+    py::class_<NoneTester, std::shared_ptr<NoneTester>>(m, "NoneTester").def(py::init<>());
     m.def("no_none1", &none1, py::arg{}.none(false));
     m.def("no_none2", &none2, py::arg{}.none(false));
     m.def("no_none3", &none3, py::arg{}.none(false));
@@ -371,21 +404,19 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     // test_casts_none
     // Issue #2778: implicit casting from None to object (not pointer)
     py::class_<NoneCastTester>(m, "NoneCastTester")
-          .def(py::init<>())
-          .def(py::init<int>())
-          .def(py::init([](py::none const&) { return NoneCastTester{}; }));
+        .def(py::init<>())
+        .def(py::init<int>())
+        .def(py::init([](py::none const &) { return NoneCastTester{}; }));
     py::implicitly_convertible<py::none, NoneCastTester>();
-    m.def("ok_obj_or_none", [](NoneCastTester const& foo) { return foo.answer; });
-
+    m.def("ok_obj_or_none", [](NoneCastTester const &foo) { return foo.answer; });
 
     // test_str_issue
     // Issue #283: __str__ called on uninitialized instance when constructor arguments invalid
     py::class_<StrIssue>(m, "StrIssue")
         .def(py::init<int>())
         .def(py::init<>())
-        .def("__str__", [](const StrIssue &si) {
-            return "StrIssue[" + std::to_string(si.val) + "]"; }
-        );
+        .def("__str__",
+             [](const StrIssue &si) { return "StrIssue[" + std::to_string(si.val) + "]"; });
 
     // test_unregistered_base_implementations
     //
@@ -408,7 +439,8 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         // This one is in the registered class:
         .def("sum", &RegisteredDerived::sum);
 
-    using Adapted = decltype(py::method_adaptor<RegisteredDerived>(&RegisteredDerived::do_nothing));
+    using Adapted
+        = decltype(py::method_adaptor<RegisteredDerived>(&RegisteredDerived::do_nothing));
     static_assert(std::is_same<Adapted, void (RegisteredDerived::*)() const>::value, "");
 
     // test_methods_and_attributes
diff --git a/tests/test_modules.cpp b/tests/test_modules.cpp
index ba80a64c9a..8aa2a4bdbd 100644
--- a/tests/test_modules.cpp
+++ b/tests/test_modules.cpp
@@ -8,8 +8,8 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 
 TEST_SUBMODULE(modules, m) {
     // test_nested_modules
@@ -22,23 +22,30 @@ TEST_SUBMODULE(modules, m) {
     public:
         explicit A(int v) : v(v) { print_created(this, v); }
         ~A() { print_destroyed(this); }
-        A(const A&) { print_copy_created(this); }
-        A& operator=(const A &copy) { print_copy_assigned(this); v = copy.v; return *this; }
+        A(const A &) { print_copy_created(this); }
+        A &operator=(const A &copy) {
+            print_copy_assigned(this);
+            v = copy.v;
+            return *this;
+        }
         std::string toString() const { return "A[" + std::to_string(v) + "]"; }
 
     private:
         int v;
     };
-    py::class_<A>(m_sub, "A")
-        .def(py::init<int>())
-        .def("__repr__", &A::toString);
+    py::class_<A>(m_sub, "A").def(py::init<int>()).def("__repr__", &A::toString);
 
     class B {
     public:
         B() { print_default_created(this); }
         ~B() { print_destroyed(this); }
-        B(const B&) { print_copy_created(this); }
-        B& operator=(const B &copy) { print_copy_assigned(this); a1 = copy.a1; a2 = copy.a2; return *this; }
+        B(const B &) { print_copy_created(this); }
+        B &operator=(const B &copy) {
+            print_copy_assigned(this);
+            a1 = copy.a1;
+            a2 = copy.a2;
+            return *this;
+        }
         A &get_a1() { return a1; }
         A &get_a2() { return a2; }
 
@@ -47,10 +54,16 @@ TEST_SUBMODULE(modules, m) {
     };
     py::class_<B>(m_sub, "B")
         .def(py::init<>())
-        .def("get_a1", &B::get_a1, "Return the internal A 1", py::return_value_policy::reference_internal)
-        .def("get_a2", &B::get_a2, "Return the internal A 2", py::return_value_policy::reference_internal)
-        .def_readwrite("a1", &B::a1)  // def_readonly uses an internal
-                                      // reference return policy by default
+        .def("get_a1",
+             &B::get_a1,
+             "Return the internal A 1",
+             py::return_value_policy::reference_internal)
+        .def("get_a2",
+             &B::get_a2,
+             "Return the internal A 2",
+             py::return_value_policy::reference_internal)
+        .def_readwrite("a1", &B::a1) // def_readonly uses an internal
+                                     // reference return policy by default
         .def_readwrite("a2", &B::a2);
 
     // This is intentionally "py::module" to verify it still can be used in place of "py::module_"
@@ -59,13 +72,14 @@ TEST_SUBMODULE(modules, m) {
     // test_duplicate_registration
     // Registering two things with the same name
     m.def("duplicate_registration", []() {
-        class Dupe1 { };
-        class Dupe2 { };
-        class Dupe3 { };
-        class DupeException { };
+        class Dupe1 {};
+        class Dupe2 {};
+        class Dupe3 {};
+        class DupeException {};
 
         // Go ahead and leak, until we have a non-leaking py::module_ constructor
-        auto dm = py::module_::create_extension_module("dummy", nullptr, new py::module_::module_def);
+        auto dm
+            = py::module_::create_extension_module("dummy", nullptr, new py::module_::module_def);
         auto failures = py::list();
 
         py::class_<Dupe1>(dm, "Dupe1");
@@ -76,27 +90,33 @@ TEST_SUBMODULE(modules, m) {
         try {
             py::class_<Dupe1>(dm, "Dupe1");
             failures.append("Dupe1 class");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             dm.def("Dupe1", []() { return Dupe1(); });
             failures.append("Dupe1 function");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             py::class_<Dupe3>(dm, "dupe1_factory");
             failures.append("dupe1_factory");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             py::exception<Dupe3>(dm, "Dupe2");
             failures.append("Dupe2");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             dm.def("DupeException", []() { return 30; });
             failures.append("DupeException1");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
         try {
             py::class_<DupeException>(dm, "DupeException");
             failures.append("DupeException2");
-        } catch (std::runtime_error &) {}
+        } catch (std::runtime_error &) {
+        }
 
         return failures;
     });
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index 17229b3b17..eb83b9e2fc 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -8,14 +8,15 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include "constructor_stats.h"
+#include "pybind11_tests.h"
 
 namespace {
 
 // Many bases for testing that multiple inheritance from many classes (i.e. requiring extra
 // space for holder constructed flags) works.
-template <int N> struct BaseN {
+template <int N>
+struct BaseN {
     explicit BaseN(int i) : i(i) {}
     int i;
 };
@@ -48,17 +49,17 @@ int VanillaStaticMix2::static_value = 12;
 template <typename T, typename Ptr = std::unique_ptr<T>>
 class Container {
 public:
-    Container(Ptr ptr)
-        : ptr_(std::move(ptr)) {}
-    T* get() const { return ptr_.get(); }
+    Container(Ptr ptr) : ptr_(std::move(ptr)) {}
+    T *get() const { return ptr_.get(); }
     Ptr release() { return std::move(ptr_); }
 
-    static void def(py::module &m, const std::string& name) {
+    static void def(py::module &m, const std::string &name) {
         py::class_<Container>(m, name.c_str())
             .def(py::init<Ptr>())
             .def("get", &Container::get)
             .def("release", &Container::release);
     }
+
 private:
     Ptr ptr_;
 };
@@ -75,13 +76,23 @@ struct Base2a {
     int i;
 };
 struct Base12a : Base1a, Base2a {
-    Base12a(int i, int j) : Base1a(i), Base2a(j) { }
+    Base12a(int i, int j) : Base1a(i), Base2a(j) {}
 };
 
 // test_mi_unaligned_base
 // test_mi_base_return
-struct I801B1 { int a = 1; I801B1() = default; I801B1(const I801B1 &) = default; virtual ~I801B1() = default; };
-struct I801B2 { int b = 2; I801B2() = default; I801B2(const I801B2 &) = default; virtual ~I801B2() = default; };
+struct I801B1 {
+    int a = 1;
+    I801B1() = default;
+    I801B1(const I801B1 &) = default;
+    virtual ~I801B1() = default;
+};
+struct I801B2 {
+    int b = 2;
+    I801B2() = default;
+    I801B2(const I801B2 &) = default;
+    virtual ~I801B2() = default;
+};
 struct I801C : I801B1, I801B2 {};
 struct I801D : I801C {}; // Indirect MI
 
@@ -100,8 +111,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         int i;
     };
     py::class_<Base1> b1(m, "Base1");
-    b1.def(py::init<int>())
-      .def("foo", &Base1::foo);
+    b1.def(py::init<int>()).def("foo", &Base1::foo);
 
     struct Base2 {
         explicit Base2(int i) : i(i) {}
@@ -109,20 +119,17 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         int i;
     };
     py::class_<Base2> b2(m, "Base2");
-    b2.def(py::init<int>())
-      .def("bar", &Base2::bar);
-
+    b2.def(py::init<int>()).def("bar", &Base2::bar);
 
     // test_multiple_inheritance_cpp
     struct Base12 : Base1, Base2 {
-        Base12(int i, int j) : Base1(i), Base2(j) { }
+        Base12(int i, int j) : Base1(i), Base2(j) {}
     };
     struct MIType : Base12 {
-        MIType(int i, int j) : Base12(i, j) { }
+        MIType(int i, int j) : Base12(i, j) {}
     };
     py::class_<Base12, Base1, Base2>(m, "Base12");
-    py::class_<MIType, Base12>(m, "MIType")
-        .def(py::init<int, int>());
+    py::class_<MIType, Base12>(m, "MIType").def(py::init<int, int>());
 
     Container<Base1>::def(m, "ContainerBase1");
 
@@ -131,21 +138,32 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     py::class_<BaseN<(N)>>(m, "BaseN" #N).def(py::init<int>()).def("f" #N, [](BaseN<N> &b) {      \
         return b.i + (N);                                                                         \
     })
-    PYBIND11_BASEN( 1); PYBIND11_BASEN( 2); PYBIND11_BASEN( 3); PYBIND11_BASEN( 4);
-    PYBIND11_BASEN( 5); PYBIND11_BASEN( 6); PYBIND11_BASEN( 7); PYBIND11_BASEN( 8);
-    PYBIND11_BASEN( 9); PYBIND11_BASEN(10); PYBIND11_BASEN(11); PYBIND11_BASEN(12);
-    PYBIND11_BASEN(13); PYBIND11_BASEN(14); PYBIND11_BASEN(15); PYBIND11_BASEN(16);
+    PYBIND11_BASEN(1);
+    PYBIND11_BASEN(2);
+    PYBIND11_BASEN(3);
+    PYBIND11_BASEN(4);
+    PYBIND11_BASEN(5);
+    PYBIND11_BASEN(6);
+    PYBIND11_BASEN(7);
+    PYBIND11_BASEN(8);
+    PYBIND11_BASEN(9);
+    PYBIND11_BASEN(10);
+    PYBIND11_BASEN(11);
+    PYBIND11_BASEN(12);
+    PYBIND11_BASEN(13);
+    PYBIND11_BASEN(14);
+    PYBIND11_BASEN(15);
+    PYBIND11_BASEN(16);
     PYBIND11_BASEN(17);
 
     // Uncommenting this should result in a compile time failure (MI can only be specified via
-    // template parameters because pybind has to know the types involved; see discussion in #742 for
-    // details).
-//    struct Base12v2 : Base1, Base2 {
-//        Base12v2(int i, int j) : Base1(i), Base2(j) { }
-//    };
-//    py::class_<Base12v2>(m, "Base12v2", b1, b2)
-//        .def(py::init<int, int>());
-
+    // template parameters because pybind has to know the types involved; see discussion in #742
+    // for details).
+    //    struct Base12v2 : Base1, Base2 {
+    //        Base12v2(int i, int j) : Base1(i), Base2(j) { }
+    //    };
+    //    py::class_<Base12v2>(m, "Base12v2", b1, b2)
+    //        .def(py::init<int, int>());
 
     // test_multiple_inheritance_virtbase
     // Test the case where not all base classes are specified, and where pybind11 requires the
@@ -158,8 +176,8 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def(py::init<int>())
         .def("bar", &Base2a::bar);
 
-    py::class_<Base12a, /* Base1 missing */ Base2a,
-               std::shared_ptr<Base12a>>(m, "Base12a", py::multiple_inheritance())
+    py::class_<Base12a, /* Base1 missing */ Base2a, std::shared_ptr<Base12a>>(
+        m, "Base12a", py::multiple_inheritance())
         .def(py::init<int, int>());
 
     Container<Base2a, std::shared_ptr<Base2a>>::def(m, "ContainerBase2a");
@@ -171,11 +189,18 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_mi_base_return
     // Issue #801: invalid casting to derived type with MI bases
     // Unregistered classes:
-    struct I801B3 { int c = 3; virtual ~I801B3() = default; };
+    struct I801B3 {
+        int c = 3;
+        virtual ~I801B3() = default;
+    };
     struct I801E : I801B3, I801D {};
 
-    py::class_<I801B1, std::shared_ptr<I801B1>>(m, "I801B1").def(py::init<>()).def_readonly("a", &I801B1::a);
-    py::class_<I801B2, std::shared_ptr<I801B2>>(m, "I801B2").def(py::init<>()).def_readonly("b", &I801B2::b);
+    py::class_<I801B1, std::shared_ptr<I801B1>>(m, "I801B1")
+        .def(py::init<>())
+        .def_readonly("a", &I801B1::a);
+    py::class_<I801B2, std::shared_ptr<I801B2>>(m, "I801B2")
+        .def(py::init<>())
+        .def_readonly("b", &I801B2::b);
     py::class_<I801C, I801B1, I801B2, std::shared_ptr<I801C>>(m, "I801C").def(py::init<>());
     py::class_<I801D, I801C, std::shared_ptr<I801D>>(m, "I801D").def(py::init<>());
 
@@ -200,11 +225,8 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     m.def("i801e_c", []() -> I801C * { return new I801E(); });
     m.def("i801e_b2", []() -> I801B2 * { return new I801E(); });
 
-
     // test_mi_static_properties
-    py::class_<Vanilla>(m, "Vanilla")
-        .def(py::init<>())
-        .def("vanilla", &Vanilla::vanilla);
+    py::class_<Vanilla>(m, "Vanilla").def(py::init<>()).def("vanilla", &Vanilla::vanilla);
 
     py::class_<WithStatic1>(m, "WithStatic1")
         .def(py::init<>())
@@ -216,22 +238,19 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def_static("static_func2", &WithStatic2::static_func2)
         .def_readwrite_static("static_value2", &WithStatic2::static_value2);
 
-    py::class_<VanillaStaticMix1, Vanilla, WithStatic1, WithStatic2>(
-        m, "VanillaStaticMix1")
+    py::class_<VanillaStaticMix1, Vanilla, WithStatic1, WithStatic2>(m, "VanillaStaticMix1")
         .def(py::init<>())
         .def_static("static_func", &VanillaStaticMix1::static_func)
         .def_readwrite_static("static_value", &VanillaStaticMix1::static_value);
 
-    py::class_<VanillaStaticMix2, WithStatic1, Vanilla, WithStatic2>(
-        m, "VanillaStaticMix2")
+    py::class_<VanillaStaticMix2, WithStatic1, Vanilla, WithStatic2>(m, "VanillaStaticMix2")
         .def(py::init<>())
         .def_static("static_func", &VanillaStaticMix2::static_func)
         .def_readwrite_static("static_value", &VanillaStaticMix2::static_value);
 
-
-    struct WithDict { };
-    struct VanillaDictMix1 : Vanilla, WithDict { };
-    struct VanillaDictMix2 : WithDict, Vanilla { };
+    struct WithDict {};
+    struct VanillaDictMix1 : Vanilla, WithDict {};
+    struct VanillaDictMix2 : WithDict, Vanilla {};
     py::class_<WithDict>(m, "WithDict", py::dynamic_attr()).def(py::init<>());
     py::class_<VanillaDictMix1, Vanilla, WithDict>(m, "VanillaDictMix1").def(py::init<>());
     py::class_<VanillaDictMix2, WithDict, Vanilla>(m, "VanillaDictMix2").def(py::init<>());
@@ -239,18 +258,25 @@ TEST_SUBMODULE(multiple_inheritance, m) {
     // test_diamond_inheritance
     // Issue #959: segfault when constructing diamond inheritance instance
     // All of these have int members so that there will be various unequal pointers involved.
-    struct B { int b; B() = default; B(const B&) = default; virtual ~B() = default; };
-    struct C0 : public virtual B { int c0; };
-    struct C1 : public virtual B { int c1; };
-    struct D : public C0, public C1 { int d; };
-    py::class_<B>(m, "B")
-        .def("b", [](B *self) { return self; });
-    py::class_<C0, B>(m, "C0")
-        .def("c0", [](C0 *self) { return self; });
-    py::class_<C1, B>(m, "C1")
-        .def("c1", [](C1 *self) { return self; });
-    py::class_<D, C0, C1>(m, "D")
-        .def(py::init<>());
+    struct B {
+        int b;
+        B() = default;
+        B(const B &) = default;
+        virtual ~B() = default;
+    };
+    struct C0 : public virtual B {
+        int c0;
+    };
+    struct C1 : public virtual B {
+        int c1;
+    };
+    struct D : public C0, public C1 {
+        int d;
+    };
+    py::class_<B>(m, "B").def("b", [](B *self) { return self; });
+    py::class_<C0, B>(m, "C0").def("c0", [](C0 *self) { return self; });
+    py::class_<C1, B>(m, "C1").def("c1", [](C1 *self) { return self; });
+    py::class_<D, C0, C1>(m, "D").def(py::init<>());
 
     // test_pr3635_diamond_*
     // - functions are get_{base}_{var}, return {var}
diff --git a/tests/test_numpy_array.cpp b/tests/test_numpy_array.cpp
index 17fc4de2ec..8bc77a33fa 100644
--- a/tests/test_numpy_array.cpp
+++ b/tests/test_numpy_array.cpp
@@ -7,11 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-
 #include <pybind11/numpy.h>
 #include <pybind11/stl.h>
 
+#include "pybind11_tests.h"
+
 #include <cstdint>
 #include <utility>
 
@@ -22,7 +22,7 @@ struct DtypeCheck {
 };
 
 template <typename T>
-DtypeCheck get_dtype_check(const char* name) {
+DtypeCheck get_dtype_check(const char *name) {
     py::module_ np = py::module_::import("numpy");
     DtypeCheck check{};
     check.numpy = np.attr("dtype")(np.attr(name));
@@ -31,17 +31,15 @@ DtypeCheck get_dtype_check(const char* name) {
 }
 
 std::vector<DtypeCheck> get_concrete_dtype_checks() {
-    return {
-        // Normalization
-        get_dtype_check<std::int8_t>("int8"),
-        get_dtype_check<std::uint8_t>("uint8"),
-        get_dtype_check<std::int16_t>("int16"),
-        get_dtype_check<std::uint16_t>("uint16"),
-        get_dtype_check<std::int32_t>("int32"),
-        get_dtype_check<std::uint32_t>("uint32"),
-        get_dtype_check<std::int64_t>("int64"),
-        get_dtype_check<std::uint64_t>("uint64")
-    };
+    return {// Normalization
+            get_dtype_check<std::int8_t>("int8"),
+            get_dtype_check<std::uint8_t>("uint8"),
+            get_dtype_check<std::int16_t>("int16"),
+            get_dtype_check<std::uint16_t>("uint16"),
+            get_dtype_check<std::int32_t>("int32"),
+            get_dtype_check<std::uint32_t>("uint32"),
+            get_dtype_check<std::int64_t>("int64"),
+            get_dtype_check<std::uint64_t>("uint64")};
 }
 
 struct DtypeSizeCheck {
@@ -80,15 +78,18 @@ using arr = py::array;
 using arr_t = py::array_t<uint16_t, 0>;
 static_assert(std::is_same<arr_t::value_type, uint16_t>::value, "");
 
-template<typename... Ix> arr data(const arr& a, Ix... index) {
+template <typename... Ix>
+arr data(const arr &a, Ix... index) {
     return arr(a.nbytes() - a.offset_at(index...), (const uint8_t *) a.data(index...));
 }
 
-template<typename... Ix> arr data_t(const arr_t& a, Ix... index) {
+template <typename... Ix>
+arr data_t(const arr_t &a, Ix... index) {
     return arr(a.size() - a.index_at(index...), a.data(index...));
 }
 
-template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
+template <typename... Ix>
+arr &mutate_data(arr &a, Ix... index) {
     auto *ptr = (uint8_t *) a.mutable_data(index...);
     for (py::ssize_t i = 0; i < a.nbytes() - a.offset_at(index...); i++) {
         ptr[i] = (uint8_t) (ptr[i] * 2);
@@ -96,7 +97,8 @@ template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
     return a;
 }
 
-template<typename... Ix> arr_t& mutate_data_t(arr_t& a, Ix... index) {
+template <typename... Ix>
+arr_t &mutate_data_t(arr_t &a, Ix... index) {
     auto ptr = a.mutable_data(index...);
     for (py::ssize_t i = 0; i < a.size() - a.index_at(index...); i++) {
         ptr[i]++;
@@ -104,20 +106,40 @@ template<typename... Ix> arr_t& mutate_data_t(arr_t& a, Ix... index) {
     return a;
 }
 
-template<typename... Ix> py::ssize_t index_at(const arr& a, Ix... idx) { return a.index_at(idx...); }
-template<typename... Ix> py::ssize_t index_at_t(const arr_t& a, Ix... idx) { return a.index_at(idx...); }
-template<typename... Ix> py::ssize_t offset_at(const arr& a, Ix... idx) { return a.offset_at(idx...); }
-template<typename... Ix> py::ssize_t offset_at_t(const arr_t& a, Ix... idx) { return a.offset_at(idx...); }
-template<typename... Ix> py::ssize_t at_t(const arr_t& a, Ix... idx) { return a.at(idx...); }
-template<typename... Ix> arr_t& mutate_at_t(arr_t& a, Ix... idx) { a.mutable_at(idx...)++; return a; }
-
-#define def_index_fn(name, type) \
-    sm.def(#name, [](type a) { return name(a); }); \
-    sm.def(#name, [](type a, int i) { return name(a, i); }); \
-    sm.def(#name, [](type a, int i, int j) { return name(a, i, j); }); \
+template <typename... Ix>
+py::ssize_t index_at(const arr &a, Ix... idx) {
+    return a.index_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t index_at_t(const arr_t &a, Ix... idx) {
+    return a.index_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t offset_at(const arr &a, Ix... idx) {
+    return a.offset_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t offset_at_t(const arr_t &a, Ix... idx) {
+    return a.offset_at(idx...);
+}
+template <typename... Ix>
+py::ssize_t at_t(const arr_t &a, Ix... idx) {
+    return a.at(idx...);
+}
+template <typename... Ix>
+arr_t &mutate_at_t(arr_t &a, Ix... idx) {
+    a.mutable_at(idx...)++;
+    return a;
+}
+
+#define def_index_fn(name, type)                                                                  \
+    sm.def(#name, [](type a) { return name(a); });                                                \
+    sm.def(#name, [](type a, int i) { return name(a, i); });                                      \
+    sm.def(#name, [](type a, int i, int j) { return name(a, i, j); });                            \
     sm.def(#name, [](type a, int i, int j, int k) { return name(a, i, j, k); });
 
-template <typename T, typename T2> py::handle auxiliaries(T &&r, T2 &&r2) {
+template <typename T, typename T2>
+py::handle auxiliaries(T &&r, T2 &&r2) {
     if (r.ndim() != 2) {
         throw std::domain_error("error: ndim != 2");
     }
@@ -138,16 +160,18 @@ template <typename T, typename T2> py::handle auxiliaries(T &&r, T2 &&r2) {
 static int data_i = 42;
 
 TEST_SUBMODULE(numpy_array, sm) {
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // test_dtypes
     py::class_<DtypeCheck>(sm, "DtypeCheck")
         .def_readonly("numpy", &DtypeCheck::numpy)
         .def_readonly("pybind11", &DtypeCheck::pybind11)
-        .def("__repr__", [](const DtypeCheck& self) {
-            return py::str("<DtypeCheck numpy={} pybind11={}>").format(
-                self.numpy, self.pybind11);
+        .def("__repr__", [](const DtypeCheck &self) {
+            return py::str("<DtypeCheck numpy={} pybind11={}>").format(self.numpy, self.pybind11);
         });
     sm.def("get_concrete_dtype_checks", &get_concrete_dtype_checks);
 
@@ -155,41 +179,41 @@ TEST_SUBMODULE(numpy_array, sm) {
         .def_readonly("name", &DtypeSizeCheck::name)
         .def_readonly("size_cpp", &DtypeSizeCheck::size_cpp)
         .def_readonly("size_numpy", &DtypeSizeCheck::size_numpy)
-        .def("__repr__", [](const DtypeSizeCheck& self) {
-            return py::str("<DtypeSizeCheck name='{}' size_cpp={} size_numpy={} dtype={}>").format(
-                self.name, self.size_cpp, self.size_numpy, self.dtype);
+        .def("__repr__", [](const DtypeSizeCheck &self) {
+            return py::str("<DtypeSizeCheck name='{}' size_cpp={} size_numpy={} dtype={}>")
+                .format(self.name, self.size_cpp, self.size_numpy, self.dtype);
         });
     sm.def("get_platform_dtype_size_checks", &get_platform_dtype_size_checks);
 
     // test_array_attributes
-    sm.def("ndim", [](const arr& a) { return a.ndim(); });
-    sm.def("shape", [](const arr& a) { return arr(a.ndim(), a.shape()); });
-    sm.def("shape", [](const arr& a, py::ssize_t dim) { return a.shape(dim); });
-    sm.def("strides", [](const arr& a) { return arr(a.ndim(), a.strides()); });
-    sm.def("strides", [](const arr& a, py::ssize_t dim) { return a.strides(dim); });
-    sm.def("writeable", [](const arr& a) { return a.writeable(); });
-    sm.def("size", [](const arr& a) { return a.size(); });
-    sm.def("itemsize", [](const arr& a) { return a.itemsize(); });
-    sm.def("nbytes", [](const arr& a) { return a.nbytes(); });
-    sm.def("owndata", [](const arr& a) { return a.owndata(); });
+    sm.def("ndim", [](const arr &a) { return a.ndim(); });
+    sm.def("shape", [](const arr &a) { return arr(a.ndim(), a.shape()); });
+    sm.def("shape", [](const arr &a, py::ssize_t dim) { return a.shape(dim); });
+    sm.def("strides", [](const arr &a) { return arr(a.ndim(), a.strides()); });
+    sm.def("strides", [](const arr &a, py::ssize_t dim) { return a.strides(dim); });
+    sm.def("writeable", [](const arr &a) { return a.writeable(); });
+    sm.def("size", [](const arr &a) { return a.size(); });
+    sm.def("itemsize", [](const arr &a) { return a.itemsize(); });
+    sm.def("nbytes", [](const arr &a) { return a.nbytes(); });
+    sm.def("owndata", [](const arr &a) { return a.owndata(); });
 
     // test_index_offset
-    def_index_fn(index_at, const arr&);
-    def_index_fn(index_at_t, const arr_t&);
-    def_index_fn(offset_at, const arr&);
-    def_index_fn(offset_at_t, const arr_t&);
+    def_index_fn(index_at, const arr &);
+    def_index_fn(index_at_t, const arr_t &);
+    def_index_fn(offset_at, const arr &);
+    def_index_fn(offset_at_t, const arr_t &);
     // test_data
-    def_index_fn(data, const arr&);
-    def_index_fn(data_t, const arr_t&);
+    def_index_fn(data, const arr &);
+    def_index_fn(data_t, const arr_t &);
     // test_mutate_data, test_mutate_readonly
-    def_index_fn(mutate_data, arr&);
-    def_index_fn(mutate_data_t, arr_t&);
-    def_index_fn(at_t, const arr_t&);
-    def_index_fn(mutate_at_t, arr_t&);
+    def_index_fn(mutate_data, arr &);
+    def_index_fn(mutate_data_t, arr_t &);
+    def_index_fn(at_t, const arr_t &);
+    def_index_fn(mutate_at_t, arr_t &);
 
     // test_make_c_f_array
-    sm.def("make_f_array", [] { return py::array_t<float>({ 2, 2 }, { 4, 8 }); });
-    sm.def("make_c_array", [] { return py::array_t<float>({ 2, 2 }, { 8, 4 }); });
+    sm.def("make_f_array", [] { return py::array_t<float>({2, 2}, {4, 8}); });
+    sm.def("make_c_array", [] { return py::array_t<float>({2, 2}, {8, 4}); });
 
     // test_empty_shaped_array
     sm.def("make_empty_shaped_array", [] { return py::array(py::dtype("f"), {}, {}); });
@@ -198,18 +222,16 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_wrap
     sm.def("wrap", [](const py::array &a) {
-        return py::array(
-            a.dtype(),
-            {a.shape(), a.shape() + a.ndim()},
-            {a.strides(), a.strides() + a.ndim()},
-            a.data(),
-            a
-        );
+        return py::array(a.dtype(),
+                         {a.shape(), a.shape() + a.ndim()},
+                         {a.strides(), a.strides() + a.ndim()},
+                         a.data(),
+                         a);
     });
 
     // test_numpy_view
     struct ArrayClass {
-        int data[2] = { 1, 2 };
+        int data[2] = {1, 2};
         ArrayClass() { py::print("ArrayClass()"); }
         ~ArrayClass() { py::print("~ArrayClass()"); }
     };
@@ -217,13 +239,12 @@ TEST_SUBMODULE(numpy_array, sm) {
         .def(py::init<>())
         .def("numpy_view", [](py::object &obj) {
             py::print("ArrayClass::numpy_view()");
-            auto &a = obj.cast<ArrayClass&>();
+            auto &a = obj.cast<ArrayClass &>();
             return py::array_t<int>({2}, {4}, a.data, obj);
-        }
-    );
+        });
 
     // test_cast_numpy_int64_to_uint64
-    sm.def("function_taking_uint64", [](uint64_t) { });
+    sm.def("function_taking_uint64", [](uint64_t) {});
 
     // test_isinstance
     sm.def("isinstance_untyped", [](py::object yes, py::object no) {
@@ -236,18 +257,14 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_constructors
     sm.def("default_constructors", []() {
-        return py::dict(
-            "array"_a=py::array(),
-            "array_t<int32>"_a=py::array_t<std::int32_t>(),
-            "array_t<double>"_a=py::array_t<double>()
-        );
+        return py::dict("array"_a = py::array(),
+                        "array_t<int32>"_a = py::array_t<std::int32_t>(),
+                        "array_t<double>"_a = py::array_t<double>());
     });
     sm.def("converting_constructors", [](const py::object &o) {
-        return py::dict(
-            "array"_a=py::array(o),
-            "array_t<int32>"_a=py::array_t<std::int32_t>(o),
-            "array_t<double>"_a=py::array_t<double>(o)
-        );
+        return py::dict("array"_a = py::array(o),
+                        "array_t<int32>"_a = py::array_t<std::int32_t>(o),
+                        "array_t<double>"_a = py::array_t<double>(o));
     });
 
     // test_overload_resolution
@@ -294,17 +311,21 @@ TEST_SUBMODULE(numpy_array, sm) {
     sm.def("issue685", [](const py::object &) { return "other"; });
 
     // test_array_unchecked_fixed_dims
-    sm.def("proxy_add2", [](py::array_t<double> a, double v) {
-        auto r = a.mutable_unchecked<2>();
-        for (py::ssize_t i = 0; i < r.shape(0); i++) {
-            for (py::ssize_t j = 0; j < r.shape(1); j++) {
-                r(i, j) += v;
+    sm.def(
+        "proxy_add2",
+        [](py::array_t<double> a, double v) {
+            auto r = a.mutable_unchecked<2>();
+            for (py::ssize_t i = 0; i < r.shape(0); i++) {
+                for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                    r(i, j) += v;
+                }
             }
-        }
-    }, py::arg{}.noconvert(), py::arg());
+        },
+        py::arg{}.noconvert(),
+        py::arg());
 
     sm.def("proxy_init3", [](double start) {
-        py::array_t<double, py::array::c_style> a({ 3, 3, 3 });
+        py::array_t<double, py::array::c_style> a({3, 3, 3});
         auto r = a.mutable_unchecked<3>();
         for (py::ssize_t i = 0; i < r.shape(0); i++) {
             for (py::ssize_t j = 0; j < r.shape(1); j++) {
@@ -316,7 +337,7 @@ TEST_SUBMODULE(numpy_array, sm) {
         return a;
     });
     sm.def("proxy_init3F", [](double start) {
-        py::array_t<double, py::array::f_style> a({ 3, 3, 3 });
+        py::array_t<double, py::array::f_style> a({3, 3, 3});
         auto r = a.mutable_unchecked<3>();
         for (py::ssize_t k = 0; k < r.shape(2); k++) {
             for (py::ssize_t j = 0; j < r.shape(1); j++) {
@@ -356,19 +377,23 @@ TEST_SUBMODULE(numpy_array, sm) {
 
     // test_array_unchecked_dyn_dims
     // Same as the above, but without a compile-time dimensions specification:
-    sm.def("proxy_add2_dyn", [](py::array_t<double> a, double v) {
-        auto r = a.mutable_unchecked();
-        if (r.ndim() != 2) {
-            throw std::domain_error("error: ndim != 2");
-        }
-        for (py::ssize_t i = 0; i < r.shape(0); i++) {
-            for (py::ssize_t j = 0; j < r.shape(1); j++) {
-                r(i, j) += v;
+    sm.def(
+        "proxy_add2_dyn",
+        [](py::array_t<double> a, double v) {
+            auto r = a.mutable_unchecked();
+            if (r.ndim() != 2) {
+                throw std::domain_error("error: ndim != 2");
             }
-        }
-    }, py::arg{}.noconvert(), py::arg());
+            for (py::ssize_t i = 0; i < r.shape(0); i++) {
+                for (py::ssize_t j = 0; j < r.shape(1); j++) {
+                    r(i, j) += v;
+                }
+            }
+        },
+        py::arg{}.noconvert(),
+        py::arg());
     sm.def("proxy_init3_dyn", [](double start) {
-        py::array_t<double, py::array::c_style> a({ 3, 3, 3 });
+        py::array_t<double, py::array::c_style> a({3, 3, 3});
         auto r = a.mutable_unchecked();
         if (r.ndim() != 3) {
             throw std::domain_error("error: ndim != 3");
@@ -386,29 +411,31 @@ TEST_SUBMODULE(numpy_array, sm) {
         return auxiliaries(a.unchecked(), a.mutable_unchecked());
     });
 
-    sm.def("array_auxiliaries2", [](py::array_t<double> a) {
-        return auxiliaries(a, a);
-    });
+    sm.def("array_auxiliaries2", [](py::array_t<double> a) { return auxiliaries(a, a); });
 
     // test_array_failures
-    // Issue #785: Uninformative "Unknown internal error" exception when constructing array from empty object:
+    // Issue #785: Uninformative "Unknown internal error" exception when constructing array from
+    // empty object:
     sm.def("array_fail_test", []() { return py::array(py::object()); });
     sm.def("array_t_fail_test", []() { return py::array_t<double>(py::object()); });
     // Make sure the error from numpy is being passed through:
-    sm.def("array_fail_test_negative_size", []() { int c = 0; return py::array(-1, &c); });
+    sm.def("array_fail_test_negative_size", []() {
+        int c = 0;
+        return py::array(-1, &c);
+    });
 
     // test_initializer_list
     // Issue (unnumbered; reported in #788): regression: initializer lists can be ambiguous
     sm.def("array_initializer_list1", []() { return py::array_t<float>(1); });
     // { 1 } also works for the above, but clang warns about it
-    sm.def("array_initializer_list2", []() { return py::array_t<float>({ 1, 2 }); });
-    sm.def("array_initializer_list3", []() { return py::array_t<float>({ 1, 2, 3 }); });
-    sm.def("array_initializer_list4", []() { return py::array_t<float>({ 1, 2, 3, 4 }); });
+    sm.def("array_initializer_list2", []() { return py::array_t<float>({1, 2}); });
+    sm.def("array_initializer_list3", []() { return py::array_t<float>({1, 2, 3}); });
+    sm.def("array_initializer_list4", []() { return py::array_t<float>({1, 2, 3, 4}); });
 
     // test_array_resize
     // reshape array to 2D without changing size
     sm.def("array_reshape2", [](py::array_t<double> a) {
-        const auto dim_sz = (py::ssize_t)std::sqrt(a.size());
+        const auto dim_sz = (py::ssize_t) std::sqrt(a.size());
         if (dim_sz * dim_sz != a.size()) {
             throw std::domain_error(
                 "array_reshape2: input array total size is not a squared integer");
diff --git a/tests/test_numpy_dtypes.cpp b/tests/test_numpy_dtypes.cpp
index a6566c5c65..dd5b123dc4 100644
--- a/tests/test_numpy_dtypes.cpp
+++ b/tests/test_numpy_dtypes.cpp
@@ -7,13 +7,14 @@
   BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/numpy.h>
 
+#include "pybind11_tests.h"
+
 #ifdef __GNUC__
-#define PYBIND11_PACKED(cls) cls __attribute__((__packed__))
+#    define PYBIND11_PACKED(cls) cls __attribute__((__packed__))
 #else
-#define PYBIND11_PACKED(cls) __pragma(pack(push, 1)) cls __pragma(pack(pop))
+#    define PYBIND11_PACKED(cls) __pragma(pack(push, 1)) cls __pragma(pack(pop))
 #endif
 
 namespace py = pybind11;
@@ -25,7 +26,7 @@ struct SimpleStruct {
     long double ldbl_;
 };
 
-std::ostream& operator<<(std::ostream& os, const SimpleStruct& v) {
+std::ostream &operator<<(std::ostream &os, const SimpleStruct &v) {
     return os << "s:" << v.bool_ << "," << v.uint_ << "," << v.float_ << "," << v.ldbl_;
 }
 
@@ -43,7 +44,7 @@ PYBIND11_PACKED(struct PackedStruct {
     long double ldbl_;
 });
 
-std::ostream& operator<<(std::ostream& os, const PackedStruct& v) {
+std::ostream &operator<<(std::ostream &os, const PackedStruct &v) {
     return os << "p:" << v.bool_ << "," << v.uint_ << "," << v.float_ << "," << v.ldbl_;
 }
 
@@ -52,7 +53,7 @@ PYBIND11_PACKED(struct NestedStruct {
     PackedStruct b;
 });
 
-std::ostream& operator<<(std::ostream& os, const NestedStruct& v) {
+std::ostream &operator<<(std::ostream &os, const NestedStruct &v) {
     return os << "n:a=" << v.a << ";b=" << v.b;
 }
 
@@ -70,7 +71,7 @@ struct PartialNestedStruct {
     uint64_t dummy2;
 };
 
-struct UnboundStruct { };
+struct UnboundStruct {};
 
 struct StringStruct {
     char a[3];
@@ -82,7 +83,7 @@ struct ComplexStruct {
     std::complex<double> cdbl;
 };
 
-std::ostream& operator<<(std::ostream& os, const ComplexStruct& v) {
+std::ostream &operator<<(std::ostream &os, const ComplexStruct &v) {
     return os << "c:" << v.cflt << "," << v.cdbl;
 }
 
@@ -106,7 +107,7 @@ PYBIND11_PACKED(struct EnumStruct {
     E2 e2;
 });
 
-std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
+std::ostream &operator<<(std::ostream &os, const StringStruct &v) {
     os << "a='";
     for (size_t i = 0; i < 3 && (v.a[i] != 0); i++) {
         os << v.a[i];
@@ -118,7 +119,7 @@ std::ostream& operator<<(std::ostream& os, const StringStruct& v) {
     return os << "'";
 }
 
-std::ostream& operator<<(std::ostream& os, const ArrayStruct& v) {
+std::ostream &operator<<(std::ostream &os, const ArrayStruct &v) {
     os << "a={";
     for (int i = 0; i < 3; i++) {
         if (i > 0) {
@@ -142,15 +143,14 @@ std::ostream& operator<<(std::ostream& os, const ArrayStruct& v) {
     return os << '}';
 }
 
-std::ostream& operator<<(std::ostream& os, const EnumStruct& v) {
+std::ostream &operator<<(std::ostream &os, const EnumStruct &v) {
     return os << "e1=" << (v.e1 == E1::A ? "A" : "B") << ",e2=" << (v.e2 == E2::X ? "X" : "Y");
 }
 
 template <typename T>
 py::array mkarray_via_buffer(size_t n) {
-    return py::array(py::buffer_info(nullptr, sizeof(T),
-                                     py::format_descriptor<T>::format(),
-                                     1, { n }, { sizeof(T) }));
+    return py::array(py::buffer_info(
+        nullptr, sizeof(T), py::format_descriptor<T>::format(), 1, {n}, {sizeof(T)}));
 }
 
 #define SET_TEST_VALS(s, i)                                                                       \
@@ -188,9 +188,9 @@ py::list print_recarray(py::array_t<S, 0> arr) {
 py::array_t<int32_t, 0> test_array_ctors(int i) {
     using arr_t = py::array_t<int32_t, 0>;
 
-    std::vector<int32_t> data { 1, 2, 3, 4, 5, 6 };
-    std::vector<py::ssize_t> shape { 3, 2 };
-    std::vector<py::ssize_t> strides { 8, 4 };
+    std::vector<int32_t> data{1, 2, 3, 4, 5, 6};
+    std::vector<py::ssize_t> shape{3, 2};
+    std::vector<py::ssize_t> strides{8, 4};
 
     auto *ptr = data.data();
     auto *vptr = (void *) ptr;
@@ -210,36 +210,62 @@ py::array_t<int32_t, 0> test_array_ctors(int i) {
     };
 
     switch (i) {
-    // shape: (3, 2)
-    case 10: return arr_t(shape, strides, ptr);
-    case 11: return py::array(shape, strides, ptr);
-    case 12: return py::array(dtype, shape, strides, vptr);
-    case 13: return arr_t(shape, ptr);
-    case 14: return py::array(shape, ptr);
-    case 15: return py::array(dtype, shape, vptr);
-    case 16: return arr_t(buf_ndim2);
-    case 17: return py::array(buf_ndim2);
-    // shape: (3, 2) - post-fill
-    case 20: return fill(arr_t(shape, strides));
-    case 21: return py::array(shape, strides, ptr); // can't have nullptr due to templated ctor
-    case 22: return fill(py::array(dtype, shape, strides));
-    case 23: return fill(arr_t(shape));
-    case 24: return py::array(shape, ptr); // can't have nullptr due to templated ctor
-    case 25: return fill(py::array(dtype, shape));
-    case 26: return fill(arr_t(buf_ndim2_null));
-    case 27: return fill(py::array(buf_ndim2_null));
-    // shape: (6, )
-    case 30: return arr_t(6, ptr);
-    case 31: return py::array(6, ptr);
-    case 32: return py::array(dtype, 6, vptr);
-    case 33: return arr_t(buf_ndim1);
-    case 34: return py::array(buf_ndim1);
-    // shape: (6, )
-    case 40: return fill(arr_t(6));
-    case 41: return py::array(6, ptr);  // can't have nullptr due to templated ctor
-    case 42: return fill(py::array(dtype, 6));
-    case 43: return fill(arr_t(buf_ndim1_null));
-    case 44: return fill(py::array(buf_ndim1_null));
+        // shape: (3, 2)
+        case 10:
+            return arr_t(shape, strides, ptr);
+        case 11:
+            return py::array(shape, strides, ptr);
+        case 12:
+            return py::array(dtype, shape, strides, vptr);
+        case 13:
+            return arr_t(shape, ptr);
+        case 14:
+            return py::array(shape, ptr);
+        case 15:
+            return py::array(dtype, shape, vptr);
+        case 16:
+            return arr_t(buf_ndim2);
+        case 17:
+            return py::array(buf_ndim2);
+        // shape: (3, 2) - post-fill
+        case 20:
+            return fill(arr_t(shape, strides));
+        case 21:
+            return py::array(shape, strides, ptr); // can't have nullptr due to templated ctor
+        case 22:
+            return fill(py::array(dtype, shape, strides));
+        case 23:
+            return fill(arr_t(shape));
+        case 24:
+            return py::array(shape, ptr); // can't have nullptr due to templated ctor
+        case 25:
+            return fill(py::array(dtype, shape));
+        case 26:
+            return fill(arr_t(buf_ndim2_null));
+        case 27:
+            return fill(py::array(buf_ndim2_null));
+        // shape: (6, )
+        case 30:
+            return arr_t(6, ptr);
+        case 31:
+            return py::array(6, ptr);
+        case 32:
+            return py::array(dtype, 6, vptr);
+        case 33:
+            return arr_t(buf_ndim1);
+        case 34:
+            return py::array(buf_ndim1);
+        // shape: (6, )
+        case 40:
+            return fill(arr_t(6));
+        case 41:
+            return py::array(6, ptr); // can't have nullptr due to templated ctor
+        case 42:
+            return fill(py::array(dtype, 6));
+        case 43:
+            return fill(arr_t(buf_ndim1_null));
+        case 44:
+            return fill(py::array(buf_ndim1_null));
     }
     return arr_t();
 }
@@ -251,9 +277,15 @@ py::list test_dtype_ctors() {
     list.append(py::dtype::from_args(py::str("bool")));
     py::list names, offsets, formats;
     py::dict dict;
-    names.append(py::str("a")); names.append(py::str("b")); dict["names"] = names;
-    offsets.append(py::int_(1)); offsets.append(py::int_(10)); dict["offsets"] = offsets;
-    formats.append(py::dtype("int32")); formats.append(py::dtype("float64")); dict["formats"] = formats;
+    names.append(py::str("a"));
+    names.append(py::str("b"));
+    dict["names"] = names;
+    offsets.append(py::int_(1));
+    offsets.append(py::int_(10));
+    dict["offsets"] = offsets;
+    formats.append(py::dtype("int32"));
+    formats.append(py::dtype("float64"));
+    dict["formats"] = formats;
     dict["itemsize"] = py::int_(20);
     list.append(py::dtype::from_args(dict));
     list.append(py::dtype(names, formats, offsets, 20));
@@ -266,8 +298,11 @@ struct A {};
 struct B {};
 
 TEST_SUBMODULE(numpy_dtypes, m) {
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // typeinfo may be registered before the dtype descriptor for scalar casts to work...
     py::class_<SimpleStruct>(m, "SimpleStruct")
@@ -285,11 +320,10 @@ TEST_SUBMODULE(numpy_dtypes, m) {
             if (py::len(tup) != 4) {
                 throw py::cast_error("Invalid size");
             }
-            return SimpleStruct{
-                tup[0].cast<bool>(),
-                tup[1].cast<uint32_t>(),
-                tup[2].cast<float>(),
-                tup[3].cast<long double>()};
+            return SimpleStruct{tup[0].cast<bool>(),
+                                tup[1].cast<uint32_t>(),
+                                tup[2].cast<float>(),
+                                tup[3].cast<long double>()};
         });
 
     PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_);
@@ -311,18 +345,18 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 #ifdef PYBIND11_NEVER_DEFINED_EVER
     // If enabled, this should produce a static_assert failure telling the user that the struct
     // is not a POD type
-    struct NotPOD { std::string v; NotPOD() : v("hi") {}; };
+    struct NotPOD {
+        std::string v;
+        NotPOD() : v("hi"){};
+    };
     PYBIND11_NUMPY_DTYPE(NotPOD, v);
 #endif
 
     // Check that dtypes can be registered programmatically, both from
     // initializer lists of field descriptors and from other containers.
-    py::detail::npy_format_descriptor<A>::register_dtype(
-        {}
-    );
+    py::detail::npy_format_descriptor<A>::register_dtype({});
     py::detail::npy_format_descriptor<B>::register_dtype(
-        std::vector<py::detail::field_descriptor>{}
-    );
+        std::vector<py::detail::field_descriptor>{});
 
     // test_recarray, test_scalar_conversion
     m.def("create_rec_simple", &create_recarray<SimpleStruct>);
@@ -355,17 +389,15 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("get_format_unbound", []() { return py::format_descriptor<UnboundStruct>::format(); });
     m.def("print_format_descriptors", []() {
         py::list l;
-        for (const auto &fmt : {
-            py::format_descriptor<SimpleStruct>::format(),
-            py::format_descriptor<PackedStruct>::format(),
-            py::format_descriptor<NestedStruct>::format(),
-            py::format_descriptor<PartialStruct>::format(),
-            py::format_descriptor<PartialNestedStruct>::format(),
-            py::format_descriptor<StringStruct>::format(),
-            py::format_descriptor<ArrayStruct>::format(),
-            py::format_descriptor<EnumStruct>::format(),
-            py::format_descriptor<ComplexStruct>::format()
-        }) {
+        for (const auto &fmt : {py::format_descriptor<SimpleStruct>::format(),
+                                py::format_descriptor<PackedStruct>::format(),
+                                py::format_descriptor<NestedStruct>::format(),
+                                py::format_descriptor<PartialStruct>::format(),
+                                py::format_descriptor<PartialNestedStruct>::format(),
+                                py::format_descriptor<StringStruct>::format(),
+                                py::format_descriptor<ArrayStruct>::format(),
+                                py::format_descriptor<EnumStruct>::format(),
+                                py::format_descriptor<ComplexStruct>::format()}) {
             l.append(py::cast(fmt));
         }
         return l;
@@ -373,12 +405,9 @@ TEST_SUBMODULE(numpy_dtypes, m) {
 
     // test_dtype
     std::vector<const char *> dtype_names{
-        "byte", "short", "intc", "int_", "longlong",
-        "ubyte", "ushort", "uintc", "uint", "ulonglong",
-        "half", "single", "double", "longdouble",
-        "csingle", "cdouble", "clongdouble",
-        "bool_", "datetime64", "timedelta64", "object_"
-    };
+        "byte",    "short",   "intc",        "int_",  "longlong",   "ubyte",       "ushort",
+        "uintc",   "uint",    "ulonglong",   "half",  "single",     "double",      "longdouble",
+        "csingle", "cdouble", "clongdouble", "bool_", "datetime64", "timedelta64", "object_"};
 
     m.def("print_dtypes", []() {
         py::list l;
@@ -415,9 +444,12 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         py::list list;
         auto dt1 = py::dtype::of<int32_t>();
         auto dt2 = py::dtype::of<SimpleStruct>();
-        list.append(dt1); list.append(dt2);
-        list.append(py::bool_(dt1.has_fields())); list.append(py::bool_(dt2.has_fields()));
-        list.append(py::int_(dt1.itemsize())); list.append(py::int_(dt2.itemsize()));
+        list.append(dt1);
+        list.append(dt2);
+        list.append(py::bool_(dt1.has_fields()));
+        list.append(py::bool_(dt2.has_fields()));
+        list.append(py::int_(dt1.itemsize()));
+        list.append(py::int_(dt2.itemsize()));
         return list;
     });
     struct TrailingPaddingStruct {
@@ -436,14 +468,20 @@ TEST_SUBMODULE(numpy_dtypes, m) {
             for (py::ssize_t i = 0; i < req.size * req.itemsize; i++) {
                 static_cast<char *>(req.ptr)[i] = 0;
             }
-            ptr[1].a[0] = 'a'; ptr[1].b[0] = 'a';
-            ptr[2].a[0] = 'a'; ptr[2].b[0] = 'a';
-            ptr[3].a[0] = 'a'; ptr[3].b[0] = 'a';
-
-            ptr[2].a[1] = 'b'; ptr[2].b[1] = 'b';
-            ptr[3].a[1] = 'b'; ptr[3].b[1] = 'b';
-
-            ptr[3].a[2] = 'c'; ptr[3].b[2] = 'c';
+            ptr[1].a[0] = 'a';
+            ptr[1].b[0] = 'a';
+            ptr[2].a[0] = 'a';
+            ptr[2].b[0] = 'a';
+            ptr[3].a[0] = 'a';
+            ptr[3].b[0] = 'a';
+
+            ptr[2].a[1] = 'b';
+            ptr[2].b[1] = 'b';
+            ptr[3].a[1] = 'b';
+            ptr[3].b[1] = 'b';
+
+            ptr[3].a[2] = 'c';
+            ptr[3].b[2] = 'c';
         }
         return arr;
     });
@@ -513,14 +551,19 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     PYBIND11_NUMPY_DTYPE(CompareStruct, x, y, z);
     m.def("compare_buffer_info", []() {
         py::list list;
-        list.append(py::bool_(py::detail::compare_buffer_info<float>::compare(py::buffer_info(nullptr, sizeof(float), "f", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<unsigned>::compare(py::buffer_info(nullptr, sizeof(int), "I", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(py::buffer_info(nullptr, sizeof(long), "l", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(py::buffer_info(nullptr, sizeof(long), sizeof(long) == sizeof(int) ? "i" : "q", 1))));
-        list.append(py::bool_(py::detail::compare_buffer_info<CompareStruct>::compare(py::buffer_info(nullptr, sizeof(CompareStruct), "T{?:x:3xI:y:f:z:}", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<float>::compare(
+            py::buffer_info(nullptr, sizeof(float), "f", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<unsigned>::compare(
+            py::buffer_info(nullptr, sizeof(int), "I", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(
+            py::buffer_info(nullptr, sizeof(long), "l", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<long>::compare(
+            py::buffer_info(nullptr, sizeof(long), sizeof(long) == sizeof(int) ? "i" : "q", 1))));
+        list.append(py::bool_(py::detail::compare_buffer_info<CompareStruct>::compare(
+            py::buffer_info(nullptr, sizeof(CompareStruct), "T{?:x:3xI:y:f:z:}", 1))));
         return list;
     });
-    m.def("buffer_to_dtype", [](py::buffer& buf) { return py::dtype(buf.request()); });
+    m.def("buffer_to_dtype", [](py::buffer &buf) { return py::dtype(buf.request()); });
 
     // test_scalar_conversion
     auto f_simple = [](SimpleStruct s) { return s.uint_ * 10; };
@@ -534,7 +577,8 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("f_simple_pass_thru_vectorized", py::vectorize(f_simple_pass_thru));
 
     // test_register_dtype
-    m.def("register_dtype", []() { PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_); });
+    m.def("register_dtype",
+          []() { PYBIND11_NUMPY_DTYPE(SimpleStruct, bool_, uint_, float_, ldbl_); });
 
     // test_str_leak
     m.def("dtype_wrapper", [](py::object d) { return py::dtype::from_args(std::move(d)); });
diff --git a/tests/test_numpy_vectorize.cpp b/tests/test_numpy_vectorize.cpp
index eb5281fb1d..eab08ec0a6 100644
--- a/tests/test_numpy_vectorize.cpp
+++ b/tests/test_numpy_vectorize.cpp
@@ -8,38 +8,43 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/numpy.h>
 
+#include "pybind11_tests.h"
+
 #include <utility>
 
 double my_func(int x, float y, double z) {
     py::print("my_func(x:int={}, y:float={:.0f}, z:float={:.0f})"_s.format(x, y, z));
-    return (float) x*y*z;
+    return (float) x * y * z;
 }
 
 TEST_SUBMODULE(numpy_vectorize, m) {
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // test_vectorize, test_docs, test_array_collapse
     // Vectorize all arguments of a function (though non-vector arguments are also allowed)
     m.def("vectorized_func", py::vectorize(my_func));
 
-    // Vectorize a lambda function with a capture object (e.g. to exclude some arguments from the vectorization)
+    // Vectorize a lambda function with a capture object (e.g. to exclude some arguments from the
+    // vectorization)
     m.def("vectorized_func2", [](py::array_t<int> x, py::array_t<float> y, float z) {
         return py::vectorize([z](int x, float y) { return my_func(x, y, z); })(std::move(x),
                                                                                std::move(y));
     });
 
     // Vectorize a complex-valued function
-    m.def("vectorized_func3", py::vectorize(
-        [](std::complex<double> c) { return c * std::complex<double>(2.f); }
-    ));
+    m.def("vectorized_func3",
+          py::vectorize([](std::complex<double> c) { return c * std::complex<double>(2.f); }));
 
     // test_type_selection
     // NumPy function which only accepts specific data types
-    // A lot of these no lints could be replaced with const refs, and probably should at some point.
+    // A lot of these no lints could be replaced with const refs, and probably should at some
+    // point.
     m.def("selective_func",
           [](const py::array_t<int, py::array::c_style> &) { return "Int branch taken."; });
     m.def("selective_func",
@@ -49,8 +54,8 @@ TEST_SUBMODULE(numpy_vectorize, m) {
     });
 
     // test_passthrough_arguments
-    // Passthrough test: references and non-pod types should be automatically passed through (in the
-    // function definition below, only `b`, `d`, and `g` are vectorized):
+    // Passthrough test: references and non-pod types should be automatically passed through (in
+    // the function definition below, only `b`, `d`, and `g` are vectorized):
     struct NonPODClass {
         explicit NonPODClass(int v) : value{v} {}
         int value;
@@ -76,8 +81,7 @@ TEST_SUBMODULE(numpy_vectorize, m) {
         int value = 0;
     };
     py::class_<VectorizeTestClass> vtc(m, "VectorizeTestClass");
-    vtc .def(py::init<int>())
-        .def_readwrite("value", &VectorizeTestClass::value);
+    vtc.def(py::init<int>()).def_readwrite("value", &VectorizeTestClass::value);
 
     // Automatic vectorizing of methods
     vtc.def("method", py::vectorize(&VectorizeTestClass::method));
@@ -99,5 +103,5 @@ TEST_SUBMODULE(numpy_vectorize, m) {
               return py::detail::broadcast(buffers, ndim, shape);
           });
 
-    m.def("add_to", py::vectorize([](NonPODClass& x, int a) { x.value += a; }));
+    m.def("add_to", py::vectorize([](NonPODClass &x, int a) { x.value += a; }));
 }
diff --git a/tests/test_opaque_types.cpp b/tests/test_opaque_types.cpp
index 2da2457474..0386dba03d 100644
--- a/tests/test_opaque_types.cpp
+++ b/tests/test_opaque_types.cpp
@@ -7,8 +7,10 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/stl.h>
+
+#include "pybind11_tests.h"
+
 #include <vector>
 
 // IMPORTANT: Disable internal pybind11 translation mechanisms for STL data structures
@@ -26,12 +28,13 @@ TEST_SUBMODULE(opaque_types, m) {
         .def(py::init<>())
         .def("pop_back", &StringList::pop_back)
         /* There are multiple versions of push_back(), etc. Select the right ones. */
-        .def("push_back", (void (StringList::*)(const std::string &)) &StringList::push_back)
-        .def("back", (std::string &(StringList::*)()) &StringList::back)
+        .def("push_back", (void(StringList::*)(const std::string &)) & StringList::push_back)
+        .def("back", (std::string & (StringList::*) ()) & StringList::back)
         .def("__len__", [](const StringList &v) { return v.size(); })
-        .def("__iter__", [](StringList &v) {
-           return py::make_iterator(v.begin(), v.end());
-        }, py::keep_alive<0, 1>());
+        .def(
+            "__iter__",
+            [](StringList &v) { return py::make_iterator(v.begin(), v.end()); },
+            py::keep_alive<0, 1>());
 
     class ClassWithSTLVecProperty {
     public:
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index ffa059d5b5..a4b895a897 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -7,11 +7,13 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/operators.h>
+#include <pybind11/stl.h>
+
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
+
 #include <functional>
-#include <pybind11/operators.h>
-#include <pybind11/stl.h>
 
 class Vector2 {
 public:
@@ -21,17 +23,24 @@ class Vector2 {
         print_move_created(this);
         v.x = v.y = 0;
     }
-    Vector2 &operator=(const Vector2 &v) { x = v.x; y = v.y; print_copy_assigned(this); return *this; }
+    Vector2 &operator=(const Vector2 &v) {
+        x = v.x;
+        y = v.y;
+        print_copy_assigned(this);
+        return *this;
+    }
     Vector2 &operator=(Vector2 &&v) noexcept {
-        x   = v.x;
-        y   = v.y;
+        x = v.x;
+        y = v.y;
         v.x = v.y = 0;
         print_move_assigned(this);
         return *this;
     }
     ~Vector2() { print_destroyed(this); }
 
-    std::string toString() const { return "[" + std::to_string(x) + ", " + std::to_string(y) + "]"; }
+    std::string toString() const {
+        return "[" + std::to_string(x) + ", " + std::to_string(y) + "]";
+    }
 
     Vector2 operator-() const { return Vector2(-x, -y); }
     Vector2 operator+(const Vector2 &v) const { return Vector2(x + v.x, y + v.y); }
@@ -42,30 +51,51 @@ class Vector2 {
     Vector2 operator/(float value) const { return Vector2(x / value, y / value); }
     Vector2 operator*(const Vector2 &v) const { return Vector2(x * v.x, y * v.y); }
     Vector2 operator/(const Vector2 &v) const { return Vector2(x / v.x, y / v.y); }
-    Vector2& operator+=(const Vector2 &v) { x += v.x; y += v.y; return *this; }
-    Vector2& operator-=(const Vector2 &v) { x -= v.x; y -= v.y; return *this; }
-    Vector2& operator*=(float v) { x *= v; y *= v; return *this; }
-    Vector2& operator/=(float v) { x /= v; y /= v; return *this; }
-    Vector2& operator*=(const Vector2 &v) { x *= v.x; y *= v.y; return *this; }
-    Vector2& operator/=(const Vector2 &v) { x /= v.x; y /= v.y; return *this; }
+    Vector2 &operator+=(const Vector2 &v) {
+        x += v.x;
+        y += v.y;
+        return *this;
+    }
+    Vector2 &operator-=(const Vector2 &v) {
+        x -= v.x;
+        y -= v.y;
+        return *this;
+    }
+    Vector2 &operator*=(float v) {
+        x *= v;
+        y *= v;
+        return *this;
+    }
+    Vector2 &operator/=(float v) {
+        x /= v;
+        y /= v;
+        return *this;
+    }
+    Vector2 &operator*=(const Vector2 &v) {
+        x *= v.x;
+        y *= v.y;
+        return *this;
+    }
+    Vector2 &operator/=(const Vector2 &v) {
+        x /= v.x;
+        y /= v.y;
+        return *this;
+    }
 
     friend Vector2 operator+(float f, const Vector2 &v) { return Vector2(f + v.x, f + v.y); }
     friend Vector2 operator-(float f, const Vector2 &v) { return Vector2(f - v.x, f - v.y); }
     friend Vector2 operator*(float f, const Vector2 &v) { return Vector2(f * v.x, f * v.y); }
     friend Vector2 operator/(float f, const Vector2 &v) { return Vector2(f / v.x, f / v.y); }
 
-    bool operator==(const Vector2 &v) const {
-        return x == v.x && y == v.y;
-    }
-    bool operator!=(const Vector2 &v) const {
-        return x != v.x || y != v.y;
-    }
+    bool operator==(const Vector2 &v) const { return x == v.x && y == v.y; }
+    bool operator!=(const Vector2 &v) const { return x != v.x || y != v.y; }
+
 private:
     float x, y;
 };
 
-class C1 { };
-class C2 { };
+class C1 {};
+class C2 {};
 
 int operator+(const C1 &, const C1 &) { return 11; }
 int operator+(const C2 &, const C2 &) { return 22; }
@@ -84,43 +114,41 @@ bool operator==(const HashMe &lhs, const HashMe &rhs) { return lhs.member == rhs
 // namespace instead, per this recommendation:
 // https://en.cppreference.com/w/cpp/language/extending_std#Adding_template_specializations
 namespace std {
-    template<>
-    struct hash<Vector2> {
-        // Not a good hash function, but easy to test
-        size_t operator()(const Vector2 &) { return 4; }
-    };
+template <>
+struct hash<Vector2> {
+    // Not a good hash function, but easy to test
+    size_t operator()(const Vector2 &) { return 4; }
+};
 
-    // HashMe has a hash function in C++ but no `__hash__` for Python.
-    template <>
-    struct hash<HashMe> {
-        std::size_t operator()(const HashMe &selector) const {
-            return std::hash<std::string>()(selector.member);
-        }
-    };
+// HashMe has a hash function in C++ but no `__hash__` for Python.
+template <>
+struct hash<HashMe> {
+    std::size_t operator()(const HashMe &selector) const {
+        return std::hash<std::string>()(selector.member);
+    }
+};
 } // namespace std
 
 // Not a good abs function, but easy to test.
-std::string abs(const Vector2&) {
-    return "abs(Vector2)";
-}
+std::string abs(const Vector2 &) { return "abs(Vector2)"; }
 
 // MSVC & Intel warns about unknown pragmas, and warnings are errors.
 #if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-  #pragma GCC diagnostic push
-  // clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
-  // `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
-  // Here, we suppress the warning using `#pragma diagnostic`.
-  // Taken from: https://github.com/RobotLocomotion/drake/commit/aaf84b46
-  // TODO(eric): This could be resolved using a function / functor (e.g. `py::self()`).
-  #if defined(__APPLE__) && defined(__clang__)
-    #if (__clang_major__ >= 10)
-      #pragma GCC diagnostic ignored "-Wself-assign-overloaded"
-    #endif
-  #elif defined(__clang__)
-    #if (__clang_major__ >= 7)
-      #pragma GCC diagnostic ignored "-Wself-assign-overloaded"
-    #endif
-  #endif
+#    pragma GCC diagnostic push
+// clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
+// `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
+// Here, we suppress the warning using `#pragma diagnostic`.
+// Taken from: https://github.com/RobotLocomotion/drake/commit/aaf84b46
+// TODO(eric): This could be resolved using a function / functor (e.g. `py::self()`).
+#    if defined(__APPLE__) && defined(__clang__)
+#        if (__clang_major__ >= 10)
+#            pragma GCC diagnostic ignored "-Wself-assign-overloaded"
+#        endif
+#    elif defined(__clang__)
+#        if (__clang_major__ >= 7)
+#            pragma GCC diagnostic ignored "-Wself-assign-overloaded"
+#        endif
+#    endif
 #endif
 
 TEST_SUBMODULE(operators, m) {
@@ -154,46 +182,52 @@ TEST_SUBMODULE(operators, m) {
         .def(py::hash(py::self))
         // N.B. See warning about usage of `py::detail::abs(py::self)` in
         // `operators.h`.
-        .def("__abs__", [](const Vector2& v) { return abs(v); })
-        ;
+        .def("__abs__", [](const Vector2 &v) { return abs(v); });
 
     m.attr("Vector") = m.attr("Vector2");
 
     // test_operators_notimplemented
     // #393: need to return NotSupported to ensure correct arithmetic operator behavior
-    py::class_<C1>(m, "C1")
-        .def(py::init<>())
-        .def(py::self + py::self);
+    py::class_<C1>(m, "C1").def(py::init<>()).def(py::self + py::self);
 
     py::class_<C2>(m, "C2")
         .def(py::init<>())
         .def(py::self + py::self)
-        .def("__add__", [](const C2& c2, const C1& c1) { return c2 + c1; })
-        .def("__radd__", [](const C2& c2, const C1& c1) { return c1 + c2; });
+        .def("__add__", [](const C2 &c2, const C1 &c1) { return c2 + c1; })
+        .def("__radd__", [](const C2 &c2, const C1 &c1) { return c1 + c2; });
 
     // test_nested
     // #328: first member in a class can't be used in operators
-    struct NestABase { int value = -2; };
+    struct NestABase {
+        int value = -2;
+    };
     py::class_<NestABase>(m, "NestABase")
         .def(py::init<>())
         .def_readwrite("value", &NestABase::value);
 
     struct NestA : NestABase {
         int value = 3;
-        NestA& operator+=(int i) { value += i; return *this; }
+        NestA &operator+=(int i) {
+            value += i;
+            return *this;
+        }
     };
     py::class_<NestA>(m, "NestA")
         .def(py::init<>())
         .def(py::self += int())
-        .def("as_base", [](NestA &a) -> NestABase& {
-            return (NestABase&) a;
-        }, py::return_value_policy::reference_internal);
+        .def(
+            "as_base",
+            [](NestA &a) -> NestABase & { return (NestABase &) a; },
+            py::return_value_policy::reference_internal);
     m.def("get_NestA", [](const NestA &a) { return a.value; });
 
     struct NestB {
         NestA a;
         int value = 4;
-        NestB& operator-=(int i) { value -= i; return *this; }
+        NestB &operator-=(int i) {
+            value -= i;
+            return *this;
+        }
     };
     py::class_<NestB>(m, "NestB")
         .def(py::init<>())
@@ -204,7 +238,10 @@ TEST_SUBMODULE(operators, m) {
     struct NestC {
         NestB b;
         int value = 5;
-        NestC& operator*=(int i) { value *= i; return *this; }
+        NestC &operator*=(int i) {
+            value *= i;
+            return *this;
+        }
     };
     py::class_<NestC>(m, "NestC")
         .def(py::init<>())
@@ -212,16 +249,15 @@ TEST_SUBMODULE(operators, m) {
         .def_readwrite("b", &NestC::b);
     m.def("get_NestC", [](const NestC &c) { return c.value; });
 
-
     // test_overriding_eq_reset_hash
     // #2191 Overriding __eq__ should set __hash__ to None
     struct Comparable {
         int value;
-        bool operator==(const Comparable& rhs) const {return value == rhs.value;}
+        bool operator==(const Comparable &rhs) const { return value == rhs.value; }
     };
 
     struct Hashable : Comparable {
-        explicit Hashable(int value): Comparable{value}{};
+        explicit Hashable(int value) : Comparable{value} {};
         size_t hash() const { return static_cast<size_t>(value); }
     };
 
@@ -229,9 +265,7 @@ TEST_SUBMODULE(operators, m) {
         using Hashable::Hashable;
     };
 
-    py::class_<Comparable>(m, "Comparable")
-        .def(py::init<int>())
-        .def(py::self == py::self);
+    py::class_<Comparable>(m, "Comparable").def(py::init<int>()).def(py::self == py::self);
 
     py::class_<Hashable>(m, "Hashable")
         .def(py::init<int>())
@@ -250,5 +284,5 @@ TEST_SUBMODULE(operators, m) {
     m.def("get_unhashable_HashMe_set", []() { return std::unordered_set<HashMe>{{"one"}}; });
 }
 #if !defined(_MSC_VER) && !defined(__INTEL_COMPILER)
-  #pragma GCC diagnostic pop
+#    pragma GCC diagnostic pop
 #endif
diff --git a/tests/test_ownership_transfer.cpp b/tests/test_ownership_transfer.cpp
index 49724e04eb..113e02a88d 100644
--- a/tests/test_ownership_transfer.cpp
+++ b/tests/test_ownership_transfer.cpp
@@ -8,90 +8,82 @@
 */
 
 #if defined(_MSC_VER) && _MSC_VER < 1910
-#  pragma warning(disable: 4702) // unreachable code in system header
+#    pragma warning(disable : 4702) // unreachable code in system header
 #endif
 
-#include <memory>
-#include "pybind11_tests.h"
 #include "object.h"
+#include "pybind11_tests.h"
+
+#include <memory>
 
 enum Label : int {
-  BaseBadLabel,
-  ChildBadLabel,
-  BaseLabel,
-  ChildLabel,
-
-  BaseBadUniqueLabel,
-  ChildBadUniqueLabel,
-  BaseUniqueLabel,
-  ChildUniqueLabel,
+    BaseBadLabel,
+    ChildBadLabel,
+    BaseLabel,
+    ChildLabel,
+
+    BaseBadUniqueLabel,
+    ChildBadUniqueLabel,
+    BaseUniqueLabel,
+    ChildUniqueLabel,
 };
 
 // For attaching instances of `ConstructorStats`.
 template <int label>
 class Stats {};
 
-
 template <int label>
 class DefineBase {
- public:
-  DefineBase(int value)
-      : value_(value) {
-    track_created(this, value);
-  }
-  // clang does not like having an implicit copy constructor when the
-  // class is virtual (and rightly so).
-  DefineBase(const DefineBase&) = delete;
-  virtual ~DefineBase() {
-    track_destroyed(this);
-  }
-  virtual int value() const { return value_; }
- private:
-  int value_{};
+public:
+    DefineBase(int value) : value_(value) { track_created(this, value); }
+    // clang does not like having an implicit copy constructor when the
+    // class is virtual (and rightly so).
+    DefineBase(const DefineBase &) = delete;
+    virtual ~DefineBase() { track_destroyed(this); }
+    virtual int value() const { return value_; }
+
+private:
+    int value_{};
 };
 
 template <int label>
 class DefineBaseContainer {
- public:
-  using T = DefineBase<label>;
-  DefineBaseContainer(std::shared_ptr<T> obj)
-      : obj_(obj) {}
-  std::shared_ptr<T> get() const { return obj_; }
-  std::shared_ptr<T> release() { return std::move(obj_); }
- private:
-  std::shared_ptr<T> obj_;
+public:
+    using T = DefineBase<label>;
+    DefineBaseContainer(std::shared_ptr<T> obj) : obj_(obj) {}
+    std::shared_ptr<T> get() const { return obj_; }
+    std::shared_ptr<T> release() { return std::move(obj_); }
+
+private:
+    std::shared_ptr<T> obj_;
 };
 
 template <int label>
 class DefineBaseUniqueContainer {
- public:
-  using T = DefineBase<label>;
-  DefineBaseUniqueContainer(std::unique_ptr<T> obj)
-      : obj_(std::move(obj)) {}
-  T* get() const { return obj_.get(); }
-  std::unique_ptr<T> release() { return std::move(obj_); }
- private:
-  std::unique_ptr<T> obj_;
+public:
+    using T = DefineBase<label>;
+    DefineBaseUniqueContainer(std::unique_ptr<T> obj) : obj_(std::move(obj)) {}
+    T *get() const { return obj_.get(); }
+    std::unique_ptr<T> release() { return std::move(obj_); }
+
+private:
+    std::unique_ptr<T> obj_;
 };
 
 template <int label>
 class DefinePyBase : public DefineBase<label> {
- public:
-  using BaseT = DefineBase<label>;
-  using BaseT::BaseT;
-  int value() const override {
-    PYBIND11_OVERLOAD(int, BaseT, value);
-  }
+public:
+    using BaseT = DefineBase<label>;
+    using BaseT::BaseT;
+    int value() const override { PYBIND11_OVERLOAD(int, BaseT, value); }
 };
 
 template <int label>
 class DefinePyBaseWrapped : public py::wrapper<DefineBase<label>> {
- public:
-  using BaseT = py::wrapper<DefineBase<label>>;
-  using BaseT::BaseT;
-  int value() const override {
-    PYBIND11_OVERLOAD(int, BaseT, value);
-  }
+public:
+    using BaseT = py::wrapper<DefineBase<label>>;
+    using BaseT::BaseT;
+    int value() const override { PYBIND11_OVERLOAD(int, BaseT, value); }
 };
 
 // BaseBad - No wrapper alias.
@@ -118,24 +110,21 @@ using BaseUniqueContainer = DefineBaseUniqueContainer<BaseUniqueLabel>;
 using ChildUniqueStats = Stats<ChildUniqueLabel>;
 
 class PyInstanceStats {
- public:
-  PyInstanceStats(ConstructorStats& cstats, py::handle h)
-    : cstats_(cstats),
-      h_(h) {}
-  void track_created() {
-    cstats_.created(h_.ptr());
-    cstats_.value(py::str(h_).cast<std::string>());
-  }
-  void track_destroyed() {
-    cstats_.destroyed(h_.ptr());
-  }
- private:
-  ConstructorStats& cstats_;
-  py::handle h_;
+public:
+    PyInstanceStats(ConstructorStats &cstats, py::handle h) : cstats_(cstats), h_(h) {}
+    void track_created() {
+        cstats_.created(h_.ptr());
+        cstats_.value(py::str(h_).cast<std::string>());
+    }
+    void track_destroyed() { cstats_.destroyed(h_.ptr()); }
+
+private:
+    ConstructorStats &cstats_;
+    py::handle h_;
 };
 
-PyInstanceStats get_instance_cstats(ConstructorStats& cstats, py::handle h) {
-  return PyInstanceStats(cstats, h);
+PyInstanceStats get_instance_cstats(ConstructorStats &cstats, py::handle h) {
+    return PyInstanceStats(cstats, h);
 }
 
 template <typename C, typename... Args>
@@ -145,51 +134,49 @@ template <typename... Args>
 using class_unique_ = py::class_<Args...>;
 
 TEST_SUBMODULE(ownership_transfer, m) {
-  // No alias - will not have lifetime extended.
-  class_shared_<BaseBad>(m, "BaseBad")
-      .def(py::init<int>())
-      .def("value", &BaseBad::value);
-  class_shared_<BaseBadContainer>(m, "BaseBadContainer")
-      .def(py::init<std::shared_ptr<BaseBad>>())
-      .def("get", &BaseBadContainer::get)
-      .def("release", &BaseBadContainer::release);
-  class_shared_<ChildBadStats>(m, "ChildBadStats");
-
-  // Has alias - will have lifetime extended.
-  class_shared_<Base, py::wrapper<PyBase>>(m, "Base")
-      .def(py::init<int>())
-      // Factory method for alias.
-      .def(py::init([]() { return new py::wrapper<PyBase>(10); }))
-      .def("value", &Base::value);
-  class_shared_<BaseContainer>(m, "BaseContainer")
-      .def(py::init<std::shared_ptr<Base>>())
-      .def("get", &BaseContainer::get)
-      .def("release", &BaseContainer::release);
-  class_shared_<ChildStats>(m, "ChildStats");
-
-  class_unique_<BaseBadUnique>(m, "BaseBadUnique")
-      .def(py::init<int>())
-      .def("value", &BaseBadUnique::value);
-  class_unique_<BaseBadUniqueContainer>(m, "BaseBadUniqueContainer")
-      .def(py::init<std::unique_ptr<BaseBadUnique>>())
-      .def("get", &BaseBadUniqueContainer::get)
-      .def("release", &BaseBadUniqueContainer::release);
-  class_unique_<ChildBadUniqueStats>(m, "ChildBadUniqueStats");
-
-  class_unique_<BaseUnique, PyBaseUnique>(m, "BaseUnique")
-      .def(py::init<int>())
-      // Factory method.
-      .def(py::init([]() { return new PyBaseUnique(10); }))
-      .def("value", &BaseUnique::value);
-  class_unique_<BaseUniqueContainer>(m, "BaseUniqueContainer")
-      .def(py::init<std::unique_ptr<BaseUnique>>())
-      .def("get", &BaseUniqueContainer::get)
-      .def("release", &BaseUniqueContainer::release);
-  class_unique_<ChildUniqueStats>(m, "ChildUniqueStats");
-
-  class_shared_<PyInstanceStats>(m, "InstanceStats")
-      .def(py::init<ConstructorStats&, py::handle>())
-      .def("track_created", &PyInstanceStats::track_created)
-      .def("track_destroyed", &PyInstanceStats::track_destroyed);
-  m.def("get_instance_cstats", &get_instance_cstats);
+    // No alias - will not have lifetime extended.
+    class_shared_<BaseBad>(m, "BaseBad").def(py::init<int>()).def("value", &BaseBad::value);
+    class_shared_<BaseBadContainer>(m, "BaseBadContainer")
+        .def(py::init<std::shared_ptr<BaseBad>>())
+        .def("get", &BaseBadContainer::get)
+        .def("release", &BaseBadContainer::release);
+    class_shared_<ChildBadStats>(m, "ChildBadStats");
+
+    // Has alias - will have lifetime extended.
+    class_shared_<Base, py::wrapper<PyBase>>(m, "Base")
+        .def(py::init<int>())
+        // Factory method for alias.
+        .def(py::init([]() { return new py::wrapper<PyBase>(10); }))
+        .def("value", &Base::value);
+    class_shared_<BaseContainer>(m, "BaseContainer")
+        .def(py::init<std::shared_ptr<Base>>())
+        .def("get", &BaseContainer::get)
+        .def("release", &BaseContainer::release);
+    class_shared_<ChildStats>(m, "ChildStats");
+
+    class_unique_<BaseBadUnique>(m, "BaseBadUnique")
+        .def(py::init<int>())
+        .def("value", &BaseBadUnique::value);
+    class_unique_<BaseBadUniqueContainer>(m, "BaseBadUniqueContainer")
+        .def(py::init<std::unique_ptr<BaseBadUnique>>())
+        .def("get", &BaseBadUniqueContainer::get)
+        .def("release", &BaseBadUniqueContainer::release);
+    class_unique_<ChildBadUniqueStats>(m, "ChildBadUniqueStats");
+
+    class_unique_<BaseUnique, PyBaseUnique>(m, "BaseUnique")
+        .def(py::init<int>())
+        // Factory method.
+        .def(py::init([]() { return new PyBaseUnique(10); }))
+        .def("value", &BaseUnique::value);
+    class_unique_<BaseUniqueContainer>(m, "BaseUniqueContainer")
+        .def(py::init<std::unique_ptr<BaseUnique>>())
+        .def("get", &BaseUniqueContainer::get)
+        .def("release", &BaseUniqueContainer::release);
+    class_unique_<ChildUniqueStats>(m, "ChildUniqueStats");
+
+    class_shared_<PyInstanceStats>(m, "InstanceStats")
+        .def(py::init<ConstructorStats &, py::handle>())
+        .def("track_created", &PyInstanceStats::track_created)
+        .def("track_destroyed", &PyInstanceStats::track_destroyed);
+    m.def("get_instance_cstats", &get_instance_cstats);
 }
diff --git a/tests/test_pickling.cpp b/tests/test_pickling.cpp
index efe0463df0..bf1ee4671c 100644
--- a/tests/test_pickling.cpp
+++ b/tests/test_pickling.cpp
@@ -20,11 +20,11 @@
 namespace exercise_trampoline {
 
 struct SimpleBase {
-    int num               = 0;
+    int num = 0;
     virtual ~SimpleBase() = default;
 
     // For compatibility with old clang versions:
-    SimpleBase()                   = default;
+    SimpleBase() = default;
     SimpleBase(const SimpleBase &) = default;
 };
 
@@ -50,7 +50,7 @@ void wrap(py::module m) {
                 }
                 auto cpp_state = std::unique_ptr<SimpleBase>(new SimpleBaseTrampoline);
                 cpp_state->num = t[0].cast<int>();
-                auto py_state  = t[1].cast<py::dict>();
+                auto py_state = t[1].cast<py::dict>();
                 return std::make_pair(std::move(cpp_state), py_state);
             }));
 
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 196a54c41f..9364cccf69 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -7,22 +7,21 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include <utility>
-
 #include "pybind11_tests.h"
 
+#include <utility>
 
 TEST_SUBMODULE(pytypes, m) {
     // test_bool
-    m.def("get_bool", []{return py::bool_(false);});
+    m.def("get_bool", [] { return py::bool_(false); });
     // test_int
-    m.def("get_int", []{return py::int_(0);});
+    m.def("get_int", [] { return py::int_(0); });
     // test_iterator
-    m.def("get_iterator", []{return py::iterator();});
+    m.def("get_iterator", [] { return py::iterator(); });
     // test_iterable
-    m.def("get_iterable", []{return py::iterable();});
+    m.def("get_iterable", [] { return py::iterable(); });
     // test_float
-    m.def("get_float", []{return py::float_(0.0f);});
+    m.def("get_float", [] { return py::float_(0.0f); });
     // test_list
     m.def("list_no_args", []() { return py::list{}; });
     m.def("list_ssize_t", []() { return py::list{(py::ssize_t) 0}; });
@@ -45,7 +44,7 @@ TEST_SUBMODULE(pytypes, m) {
         }
     });
     // test_none
-    m.def("get_none", []{return py::none();});
+    m.def("get_none", [] { return py::none(); });
     m.def("print_none", [](const py::none &none) { py::print("none: {}"_s.format(none)); });
 
     // test_set
@@ -66,15 +65,15 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("set_contains", [](const py::set &set, const char *key) { return set.contains(key); });
 
     // test_dict
-    m.def("get_dict", []() { return py::dict("key"_a="value"); });
+    m.def("get_dict", []() { return py::dict("key"_a = "value"); });
     m.def("print_dict", [](const py::dict &dict) {
         for (auto item : dict) {
             py::print("key: {}, value={}"_s.format(item.first, item.second));
         }
     });
     m.def("dict_keyword_constructor", []() {
-        auto d1 = py::dict("x"_a=1, "y"_a=2);
-        auto d2 = py::dict("z"_a=3, **d1);
+        auto d1 = py::dict("x"_a = 1, "y"_a = 2);
+        auto d2 = py::dict("z"_a = 3, **d1);
         return d2;
     });
     m.def("dict_contains",
@@ -91,7 +90,8 @@ TEST_SUBMODULE(pytypes, m) {
 #if PY_VERSION_HEX >= 0x03030000
     // test_simple_namespace
     m.def("get_simple_namespace", []() {
-        auto ns = py::module_::import("types").attr("SimpleNamespace")("attr"_a=42, "x"_a="foo", "wrong"_a=1);
+        auto ns = py::module_::import("types").attr("SimpleNamespace")(
+            "attr"_a = 42, "x"_a = "foo", "wrong"_a = 1);
         py::delattr(ns, "wrong");
         py::setattr(ns, "right", py::int_(2));
         return ns;
@@ -103,16 +103,15 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("str_from_char_size_t", []() { return py::str{"blue", (py::size_t) 4}; });
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });
-    m.def("str_from_object", [](const py::object& obj) { return py::str(obj); });
-    m.def("repr_from_object", [](const py::object& obj) { return py::repr(obj); });
+    m.def("str_from_object", [](const py::object &obj) { return py::str(obj); });
+    m.def("repr_from_object", [](const py::object &obj) { return py::repr(obj); });
     m.def("str_from_handle", [](py::handle h) { return py::str(h); });
-    m.def("str_from_string_from_str", [](const py::str& obj) {
-        return py::str(static_cast<std::string>(obj));
-    });
+    m.def("str_from_string_from_str",
+          [](const py::str &obj) { return py::str(static_cast<std::string>(obj)); });
 
     m.def("str_format", []() {
         auto s1 = "{} + {} = {}"_s.format(1, 2, 3);
-        auto s2 = "{a} + {b} = {c}"_s.format("a"_a=1, "b"_a=2, "c"_a=3);
+        auto s2 = "{a} + {b} = {c}"_s.format("a"_a = 1, "b"_a = 2, "c"_a = 3);
         return py::make_tuple(s1, s2);
     });
 
@@ -131,9 +130,7 @@ TEST_SUBMODULE(pytypes, m) {
     // test_capsule
     m.def("return_capsule_with_destructor", []() {
         py::print("creating capsule");
-        return py::capsule([]() {
-            py::print("destructing capsule");
-        });
+        return py::capsule([]() { py::print("destructing capsule"); });
     });
 
     m.def("return_capsule_with_destructor_2", []() {
@@ -148,23 +145,23 @@ TEST_SUBMODULE(pytypes, m) {
             if (ptr) {
                 const auto *name = PyCapsule_GetName(ptr);
                 py::print("destructing capsule ({}, '{}')"_s.format(
-                    (size_t) PyCapsule_GetPointer(ptr, name), name
-                ));
+                    (size_t) PyCapsule_GetPointer(ptr, name), name));
             }
         });
 
         capsule.set_pointer((void *) 1234);
 
         // Using get_pointer<T>()
-        void* contents1 = static_cast<void*>(capsule);
-        void* contents2 = capsule.get_pointer();
-        void* contents3 = capsule.get_pointer<void>();
+        void *contents1 = static_cast<void *>(capsule);
+        void *contents2 = capsule.get_pointer();
+        void *contents3 = capsule.get_pointer<void>();
 
         auto result1 = reinterpret_cast<size_t>(contents1);
         auto result2 = reinterpret_cast<size_t>(contents2);
         auto result3 = reinterpret_cast<size_t>(contents3);
 
-        py::print("created capsule ({}, '{}')"_s.format(result1 & result2 & result3, capsule.name()));
+        py::print(
+            "created capsule ({}, '{}')"_s.format(result1 & result2 & result3, capsule.name()));
         return capsule;
     });
 
@@ -244,51 +241,45 @@ TEST_SUBMODULE(pytypes, m) {
 
     // test_constructors
     m.def("default_constructors", []() {
-        return py::dict(
-            "bytes"_a=py::bytes(),
-            "bytearray"_a=py::bytearray(),
-            "str"_a=py::str(),
-            "bool"_a=py::bool_(),
-            "int"_a=py::int_(),
-            "float"_a=py::float_(),
-            "tuple"_a=py::tuple(),
-            "list"_a=py::list(),
-            "dict"_a=py::dict(),
-            "set"_a=py::set()
-        );
+        return py::dict("bytes"_a = py::bytes(),
+                        "bytearray"_a = py::bytearray(),
+                        "str"_a = py::str(),
+                        "bool"_a = py::bool_(),
+                        "int"_a = py::int_(),
+                        "float"_a = py::float_(),
+                        "tuple"_a = py::tuple(),
+                        "list"_a = py::list(),
+                        "dict"_a = py::dict(),
+                        "set"_a = py::set());
     });
 
     m.def("converting_constructors", [](const py::dict &d) {
-        return py::dict(
-            "bytes"_a=py::bytes(d["bytes"]),
-            "bytearray"_a=py::bytearray(d["bytearray"]),
-            "str"_a=py::str(d["str"]),
-            "bool"_a=py::bool_(d["bool"]),
-            "int"_a=py::int_(d["int"]),
-            "float"_a=py::float_(d["float"]),
-            "tuple"_a=py::tuple(d["tuple"]),
-            "list"_a=py::list(d["list"]),
-            "dict"_a=py::dict(d["dict"]),
-            "set"_a=py::set(d["set"]),
-            "memoryview"_a=py::memoryview(d["memoryview"])
-        );
+        return py::dict("bytes"_a = py::bytes(d["bytes"]),
+                        "bytearray"_a = py::bytearray(d["bytearray"]),
+                        "str"_a = py::str(d["str"]),
+                        "bool"_a = py::bool_(d["bool"]),
+                        "int"_a = py::int_(d["int"]),
+                        "float"_a = py::float_(d["float"]),
+                        "tuple"_a = py::tuple(d["tuple"]),
+                        "list"_a = py::list(d["list"]),
+                        "dict"_a = py::dict(d["dict"]),
+                        "set"_a = py::set(d["set"]),
+                        "memoryview"_a = py::memoryview(d["memoryview"]));
     });
 
     m.def("cast_functions", [](const py::dict &d) {
         // When converting between Python types, obj.cast<T>() should be the same as T(obj)
-        return py::dict(
-            "bytes"_a=d["bytes"].cast<py::bytes>(),
-            "bytearray"_a=d["bytearray"].cast<py::bytearray>(),
-            "str"_a=d["str"].cast<py::str>(),
-            "bool"_a=d["bool"].cast<py::bool_>(),
-            "int"_a=d["int"].cast<py::int_>(),
-            "float"_a=d["float"].cast<py::float_>(),
-            "tuple"_a=d["tuple"].cast<py::tuple>(),
-            "list"_a=d["list"].cast<py::list>(),
-            "dict"_a=d["dict"].cast<py::dict>(),
-            "set"_a=d["set"].cast<py::set>(),
-            "memoryview"_a=d["memoryview"].cast<py::memoryview>()
-        );
+        return py::dict("bytes"_a = d["bytes"].cast<py::bytes>(),
+                        "bytearray"_a = d["bytearray"].cast<py::bytearray>(),
+                        "str"_a = d["str"].cast<py::str>(),
+                        "bool"_a = d["bool"].cast<py::bool_>(),
+                        "int"_a = d["int"].cast<py::int_>(),
+                        "float"_a = d["float"].cast<py::float_>(),
+                        "tuple"_a = d["tuple"].cast<py::tuple>(),
+                        "list"_a = d["list"].cast<py::list>(),
+                        "dict"_a = d["dict"].cast<py::dict>(),
+                        "set"_a = d["set"].cast<py::set>(),
+                        "memoryview"_a = d["memoryview"].cast<py::memoryview>());
     });
 
     m.def("convert_to_pybind11_str", [](const py::object &o) { return py::str(o); });
@@ -341,10 +332,7 @@ TEST_SUBMODULE(pytypes, m) {
         l.append(py::cast(12));
         l.append(py::int_(15));
 
-        return py::dict(
-            "d"_a=d,
-            "l"_a=l
-        );
+        return py::dict("d"_a = d, "l"_a = l);
     });
 
     // test_print
@@ -352,16 +340,17 @@ TEST_SUBMODULE(pytypes, m) {
         py::print("Hello, World!");
         py::print(1, 2.0, "three", true, std::string("-- multiple args"));
         auto args = py::make_tuple("and", "a", "custom", "separator");
-        py::print("*args", *args, "sep"_a="-");
-        py::print("no new line here", "end"_a=" -- ");
+        py::print("*args", *args, "sep"_a = "-");
+        py::print("no new line here", "end"_a = " -- ");
         py::print("next print");
 
         auto py_stderr = py::module_::import("sys").attr("stderr");
-        py::print("this goes to stderr", "file"_a=py_stderr);
+        py::print("this goes to stderr", "file"_a = py_stderr);
 
-        py::print("flush", "flush"_a=true);
+        py::print("flush", "flush"_a = true);
 
-        py::print("{a} + {b} = {c}"_s.format("a"_a="py::print", "b"_a="str.format", "c"_a="this"));
+        py::print(
+            "{a} + {b} = {c}"_s.format("a"_a = "py::print", "b"_a = "str.format", "c"_a = "this"));
     });
 
     m.def("print_failure", []() { py::print(42, UnregisteredType()); });
@@ -406,8 +395,8 @@ TEST_SUBMODULE(pytypes, m) {
           [](const py::buffer &b) { return py::memoryview(b.request()); });
 
     m.def("test_memoryview_from_buffer", [](bool is_unsigned) {
-        static const int16_t si16[] = { 3, 1, 4, 1, 5 };
-        static const uint16_t ui16[] = { 2, 7, 1, 8 };
+        static const int16_t si16[] = {3, 1, 4, 1, 5};
+        static const uint16_t ui16[] = {2, 7, 1, 8};
         if (is_unsigned) {
             return py::memoryview::from_buffer(ui16, {4}, {sizeof(uint16_t)});
         }
@@ -415,32 +404,29 @@ TEST_SUBMODULE(pytypes, m) {
     });
 
     m.def("test_memoryview_from_buffer_nativeformat", []() {
-        static const char* format = "@i";
-        static const int32_t arr[] = { 4, 7, 5 };
-        return py::memoryview::from_buffer(
-            arr, sizeof(int32_t), format, { 3 }, { sizeof(int32_t) });
+        static const char *format = "@i";
+        static const int32_t arr[] = {4, 7, 5};
+        return py::memoryview::from_buffer(arr, sizeof(int32_t), format, {3}, {sizeof(int32_t)});
     });
 
     m.def("test_memoryview_from_buffer_empty_shape", []() {
-        static const char* buf = "";
-        return py::memoryview::from_buffer(buf, 1, "B", { }, { });
+        static const char *buf = "";
+        return py::memoryview::from_buffer(buf, 1, "B", {}, {});
     });
 
     m.def("test_memoryview_from_buffer_invalid_strides", []() {
-        static const char* buf = "\x02\x03\x04";
-        return py::memoryview::from_buffer(buf, 1, "B", { 3 }, { });
+        static const char *buf = "\x02\x03\x04";
+        return py::memoryview::from_buffer(buf, 1, "B", {3}, {});
     });
 
     m.def("test_memoryview_from_buffer_nullptr", []() {
-        return py::memoryview::from_buffer(
-            static_cast<void*>(nullptr), 1, "B", { }, { });
+        return py::memoryview::from_buffer(static_cast<void *>(nullptr), 1, "B", {}, {});
     });
 
 #if PY_MAJOR_VERSION >= 3
     m.def("test_memoryview_from_memory", []() {
-        const char* buf = "\xff\xe1\xab\x37";
-        return py::memoryview::from_memory(
-            buf, static_cast<py::ssize_t>(strlen(buf)));
+        const char *buf = "\xff\xe1\xab\x37";
+        return py::memoryview::from_memory(buf, static_cast<py::ssize_t>(strlen(buf)));
     });
 #endif
 
@@ -461,8 +447,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("pass_to_std_string", [](const std::string &s) { return s.size(); });
 
     // test_weakref
-    m.def("weakref_from_handle",
-          [](py::handle h) { return py::weakref(h); });
+    m.def("weakref_from_handle", [](py::handle h) { return py::weakref(h); });
     m.def("weakref_from_handle_and_function",
           [](py::handle h, py::function f) { return py::weakref(h, std::move(f)); });
     m.def("weakref_from_object", [](const py::object &o) { return py::weakref(o); });
diff --git a/tests/test_sequences_and_iterators.cpp b/tests/test_sequences_and_iterators.cpp
index 5d4275f36d..addbfe9bb4 100644
--- a/tests/test_sequences_and_iterators.cpp
+++ b/tests/test_sequences_and_iterators.cpp
@@ -8,44 +8,52 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/operators.h>
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #include <algorithm>
 #include <utility>
 #include <vector>
 
 #ifdef PYBIND11_HAS_OPTIONAL
-#include <optional>
-#endif  // PYBIND11_HAS_OPTIONAL
-
+#    include <optional>
+#endif // PYBIND11_HAS_OPTIONAL
 
-template<typename T>
+template <typename T>
 class NonZeroIterator {
-    const T* ptr_;
+    const T *ptr_;
+
 public:
     explicit NonZeroIterator(const T *ptr) : ptr_(ptr) {}
-    const T& operator*() const { return *ptr_; }
-    NonZeroIterator& operator++() { ++ptr_; return *this; }
+    const T &operator*() const { return *ptr_; }
+    NonZeroIterator &operator++() {
+        ++ptr_;
+        return *this;
+    }
 };
 
 class NonZeroSentinel {};
 
-template<typename A, typename B>
-bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentinel&) {
+template <typename A, typename B>
+bool operator==(const NonZeroIterator<std::pair<A, B>> &it, const NonZeroSentinel &) {
     return !(*it).first || !(*it).second;
 }
 
 /* Iterator where dereferencing returns prvalues instead of references. */
-template<typename T>
+template <typename T>
 class NonRefIterator {
-    const T* ptr_;
+    const T *ptr_;
+
 public:
     explicit NonRefIterator(const T *ptr) : ptr_(ptr) {}
     T operator*() const { return T(*ptr_); }
-    NonRefIterator& operator++() { ++ptr_; return *this; }
+    NonRefIterator &operator++() {
+        ++ptr_;
+        return *this;
+    }
     bool operator==(const NonRefIterator &other) const { return ptr_ == other.ptr_; }
 };
 
@@ -54,17 +62,18 @@ class NonCopyableInt {
     explicit NonCopyableInt(int value) : value_(value) {}
     NonCopyableInt(const NonCopyableInt &) = delete;
     NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
-        other.value_ = -1;  // detect when an unwanted move occurs
+        other.value_ = -1; // detect when an unwanted move occurs
     }
     NonCopyableInt &operator=(const NonCopyableInt &) = delete;
     NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
         value_ = other.value_;
-        other.value_ = -1;  // detect when an unwanted move occurs
+        other.value_ = -1; // detect when an unwanted move occurs
         return *this;
     }
     int get() const { return value_; }
     void set(int value) { value_ = value; }
     ~NonCopyableInt() = default;
+
 private:
     int value_;
 };
@@ -81,7 +90,9 @@ py::list test_random_access_iterator(PythonType x) {
     auto checks = py::list();
     auto assert_equal = [&checks](py::handle a, py::handle b) {
         auto result = PyObject_RichCompareBool(a.ptr(), b.ptr(), Py_EQ);
-        if (result == -1) { throw py::error_already_set(); }
+        if (result == -1) {
+            throw py::error_already_set();
+        }
         checks.append(result != 0);
     };
 
@@ -116,7 +127,7 @@ py::list test_random_access_iterator(PythonType x) {
 
 TEST_SUBMODULE(sequences_and_iterators, m) {
     // test_sliceable
-    class Sliceable{
+    class Sliceable {
     public:
         explicit Sliceable(int n) : size(n) {}
         int start, stop, step;
@@ -130,18 +141,20 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
                 throw py::error_already_set();
             }
             int istart = static_cast<int>(start);
-            int istop  = static_cast<int>(stop);
-            int istep  = static_cast<int>(step);
+            int istop = static_cast<int>(stop);
+            int istep = static_cast<int>(step);
             return std::make_tuple(istart, istop, istep);
         });
 
     m.def("make_forward_slice_size_t", []() { return py::slice(0, -1, 1); });
-    m.def("make_reversed_slice_object", []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
+    m.def("make_reversed_slice_object",
+          []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
 #ifdef PYBIND11_HAS_OPTIONAL
     m.attr("has_optional") = true;
-    m.def("make_reversed_slice_size_t_optional_verbose", []() { return py::slice(std::nullopt, std::nullopt, -1); });
-    // Warning: The following spelling may still compile if optional<> is not present and give wrong answers.
-    // Please use with caution.
+    m.def("make_reversed_slice_size_t_optional_verbose",
+          []() { return py::slice(std::nullopt, std::nullopt, -1); });
+    // Warning: The following spelling may still compile if optional<> is not present and give
+    // wrong answers. Please use with caution.
     m.def("make_reversed_slice_size_t_optional", []() { return py::slice({}, {}, -1); });
 #else
     m.attr("has_optional") = false;
@@ -166,7 +179,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             print_copy_created(this);
             // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
             m_data = new float[m_size];
-            memcpy(m_data, s.m_data, sizeof(float)*m_size);
+            memcpy(m_data, s.m_data, sizeof(float) * m_size);
         }
         Sequence(Sequence &&s) noexcept : m_size(s.m_size), m_data(s.m_data) {
             print_move_created(this);
@@ -174,14 +187,17 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             s.m_data = nullptr;
         }
 
-        ~Sequence() { print_destroyed(this); delete[] m_data; }
+        ~Sequence() {
+            print_destroyed(this);
+            delete[] m_data;
+        }
 
         Sequence &operator=(const Sequence &s) {
             if (&s != this) {
                 delete[] m_data;
                 m_size = s.m_size;
                 m_data = new float[m_size];
-                memcpy(m_data, s.m_data, sizeof(float)*m_size);
+                memcpy(m_data, s.m_data, sizeof(float) * m_size);
             }
             print_copy_assigned(this);
             return *this;
@@ -235,7 +251,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         size_t size() const { return m_size; }
 
         const float *begin() const { return m_data; }
-        const float *end() const { return m_data+m_size; }
+        const float *end() const { return m_data + m_size; }
 
     private:
         size_t m_size;
@@ -303,8 +319,8 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         ;
 
     // test_map_iterator
-    // Interface of a map-like object that isn't (directly) an unordered_map, but provides some basic
-    // map-like functionality.
+    // Interface of a map-like object that isn't (directly) an unordered_map, but provides some
+    // basic map-like functionality.
     class StringMap {
     public:
         StringMap() = default;
@@ -314,8 +330,10 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         void set(const std::string &key, std::string val) { map[key] = std::move(val); }
         std::string get(const std::string &key) const { return map.at(key); }
         size_t size() const { return map.size(); }
+
     private:
         std::unordered_map<std::string, std::string> map;
+
     public:
         decltype(map.cbegin()) begin() const { return map.cbegin(); }
         decltype(map.cend()) end() const { return map.cend(); }
@@ -350,90 +368,115 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     class IntPairs {
     public:
         explicit IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
-        const std::pair<int, int>* begin() const { return data_.data(); }
+        const std::pair<int, int> *begin() const { return data_.data(); }
         // .end() only required for py::make_iterator(self) overload
-        const std::pair<int, int>* end() const { return data_.data() + data_.size(); }
+        const std::pair<int, int> *end() const { return data_.data() + data_.size(); }
+
     private:
         std::vector<std::pair<int, int>> data_;
     };
     py::class_<IntPairs>(m, "IntPairs")
         .def(py::init<std::vector<std::pair<int, int>>>())
-        .def("nonzero", [](const IntPairs& s) {
-            return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
-        .def("nonzero_keys", [](const IntPairs& s) {
-            return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
-        .def("nonzero_values", [](const IntPairs& s) {
-            return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
-        }, py::keep_alive<0, 1>())
+        .def(
+            "nonzero",
+            [](const IntPairs &s) {
+                return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()),
+                                         NonZeroSentinel());
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonzero_keys",
+            [](const IntPairs &s) {
+                return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()),
+                                             NonZeroSentinel());
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonzero_values",
+            [](const IntPairs &s) {
+                return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()),
+                                               NonZeroSentinel());
+            },
+            py::keep_alive<0, 1>())
 
         // test iterator that returns values instead of references
-        .def("nonref", [](const IntPairs& s) {
-             return py::make_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
-                                      NonRefIterator<std::pair<int, int>>(s.end()));
-        }, py::keep_alive<0, 1>())
-        .def("nonref_keys", [](const IntPairs& s) {
-             return py::make_key_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
-                                          NonRefIterator<std::pair<int, int>>(s.end()));
-        }, py::keep_alive<0, 1>())
-        .def("nonref_values", [](const IntPairs& s) {
-             return py::make_value_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
-                                            NonRefIterator<std::pair<int, int>>(s.end()));
-        }, py::keep_alive<0, 1>())
+        .def(
+            "nonref",
+            [](const IntPairs &s) {
+                return py::make_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                         NonRefIterator<std::pair<int, int>>(s.end()));
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonref_keys",
+            [](const IntPairs &s) {
+                return py::make_key_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                             NonRefIterator<std::pair<int, int>>(s.end()));
+            },
+            py::keep_alive<0, 1>())
+        .def(
+            "nonref_values",
+            [](const IntPairs &s) {
+                return py::make_value_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
+                                               NonRefIterator<std::pair<int, int>>(s.end()));
+            },
+            py::keep_alive<0, 1>())
 
         // test single-argument make_iterator
-        .def("simple_iterator", [](IntPairs& self) {
-            return py::make_iterator(self);
-        }, py::keep_alive<0, 1>())
-        .def("simple_keys", [](IntPairs& self) {
-            return py::make_key_iterator(self);
-        }, py::keep_alive<0, 1>())
-        .def("simple_values", [](IntPairs& self) {
-            return py::make_value_iterator(self);
-        }, py::keep_alive<0, 1>())
+        .def(
+            "simple_iterator",
+            [](IntPairs &self) { return py::make_iterator(self); },
+            py::keep_alive<0, 1>())
+        .def(
+            "simple_keys",
+            [](IntPairs &self) { return py::make_key_iterator(self); },
+            py::keep_alive<0, 1>())
+        .def(
+            "simple_values",
+            [](IntPairs &self) { return py::make_value_iterator(self); },
+            py::keep_alive<0, 1>())
 
         // Test iterator with an Extra (doesn't do anything useful, so not used
         // at runtime, but tests need to be able to compile with the correct
         // overload. See PR #3293.
-        .def("_make_iterator_extras", [](IntPairs& self) {
-            return py::make_iterator(self, py::call_guard<int>());
-        }, py::keep_alive<0, 1>())
-        .def("_make_key_extras", [](IntPairs& self) {
-            return py::make_key_iterator(self, py::call_guard<int>());
-        }, py::keep_alive<0, 1>())
-        .def("_make_value_extras", [](IntPairs& self) {
-            return py::make_value_iterator(self, py::call_guard<int>());
-        }, py::keep_alive<0, 1>())
-        ;
+        .def(
+            "_make_iterator_extras",
+            [](IntPairs &self) { return py::make_iterator(self, py::call_guard<int>()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "_make_key_extras",
+            [](IntPairs &self) { return py::make_key_iterator(self, py::call_guard<int>()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "_make_value_extras",
+            [](IntPairs &self) { return py::make_value_iterator(self, py::call_guard<int>()); },
+            py::keep_alive<0, 1>());
 
     // test_iterater_referencing
     py::class_<NonCopyableInt>(m, "NonCopyableInt")
         .def(py::init<int>())
         .def("set", &NonCopyableInt::set)
-        .def("__int__", &NonCopyableInt::get)
-        ;
+        .def("__int__", &NonCopyableInt::get);
     py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
         .def(py::init<>())
-        .def("append", [](std::vector<NonCopyableInt> &vec, int value) {
-            vec.emplace_back(value);
-        })
+        .def("append",
+             [](std::vector<NonCopyableInt> &vec, int value) { vec.emplace_back(value); })
         .def("__iter__", [](std::vector<NonCopyableInt> &vec) {
             return py::make_iterator(vec.begin(), vec.end());
-        })
-        ;
+        });
     py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
         .def(py::init<>())
-        .def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
-            vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
-        })
-        .def("keys", [](std::vector<NonCopyableIntPair> &vec) {
-            return py::make_key_iterator(vec.begin(), vec.end());
-        })
+        .def("append",
+             [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
+                 vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
+             })
+        .def("keys",
+             [](std::vector<NonCopyableIntPair> &vec) {
+                 return py::make_key_iterator(vec.begin(), vec.end());
+             })
         .def("values", [](std::vector<NonCopyableIntPair> &vec) {
             return py::make_value_iterator(vec.begin(), vec.end());
-        })
-        ;
+        });
 
 #if 0
     // Obsolete: special data structure for exposing custom iterator types to python
@@ -511,7 +554,9 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
 
     // test_iterator_rvp
     // #388: Can't make iterators via make_iterator() with different r/v policies
-    static std::vector<int> list = { 1, 2, 3 };
-    m.def("make_iterator_1", []() { return py::make_iterator<py::return_value_policy::copy>(list); });
-    m.def("make_iterator_2", []() { return py::make_iterator<py::return_value_policy::automatic>(list); });
+    static std::vector<int> list = {1, 2, 3};
+    m.def("make_iterator_1",
+          []() { return py::make_iterator<py::return_value_policy::copy>(list); });
+    m.def("make_iterator_2",
+          []() { return py::make_iterator<py::return_value_policy::automatic>(list); });
 }
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 8cb4b4a8f0..73d3bad6d1 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -8,21 +8,23 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#if defined(_MSC_VER) && _MSC_VER < 1910  // VS 2015's MSVC
-#  pragma warning(disable: 4702) // unreachable code in system header (xatomic.h(382))
+#if defined(_MSC_VER) && _MSC_VER < 1910 // VS 2015's MSVC
+#    pragma warning(disable : 4702)      // unreachable code in system header (xatomic.h(382))
 #endif
 
-#include "pybind11_tests.h"
 #include "object.h"
+#include "pybind11_tests.h"
 
 namespace {
 
 // This is just a wrapper around unique_ptr, but with extra fields to deliberately bloat up the
-// holder size to trigger the non-simple-layout internal instance layout for single inheritance with
-// large holder type:
-template <typename T> class huge_unique_ptr {
+// holder size to trigger the non-simple-layout internal instance layout for single inheritance
+// with large holder type:
+template <typename T>
+class huge_unique_ptr {
     std::unique_ptr<T> ptr;
     uint64_t padding[10];
+
 public:
     explicit huge_unique_ptr(T *p) : ptr(p) {}
     T *get() { return ptr.get(); }
@@ -32,10 +34,11 @@ template <typename T> class huge_unique_ptr {
 template <typename T>
 class custom_unique_ptr {
     std::unique_ptr<T> impl;
+
 public:
     explicit custom_unique_ptr(T *p) : impl(p) {}
-    T* get() const { return impl.get(); }
-    T* release_ptr() { return impl.release(); }
+    T *get() const { return impl.get(); }
+    T *release_ptr() { return impl.release(); }
 };
 
 // Simple custom holder that works like shared_ptr and has operator& overload
@@ -44,11 +47,12 @@ class custom_unique_ptr {
 template <typename T>
 class shared_ptr_with_addressof_operator {
     std::shared_ptr<T> impl;
+
 public:
-    shared_ptr_with_addressof_operator( ) = default;
+    shared_ptr_with_addressof_operator() = default;
     explicit shared_ptr_with_addressof_operator(T *p) : impl(p) {}
-    T* get() const { return impl.get(); }
-    T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
+    T *get() const { return impl.get(); }
+    T **operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
 };
 
 // Simple custom holder that works like unique_ptr and has operator& overload
@@ -57,12 +61,13 @@ class shared_ptr_with_addressof_operator {
 template <typename T>
 class unique_ptr_with_addressof_operator {
     std::unique_ptr<T> impl;
+
 public:
     unique_ptr_with_addressof_operator() = default;
     explicit unique_ptr_with_addressof_operator(T *p) : impl(p) {}
-    T* get() const { return impl.get(); }
-    T* release_ptr() { return impl.release(); }
-    T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
+    T *get() const { return impl.get(); }
+    T *release_ptr() { return impl.release(); }
+    T **operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
 };
 
 // Custom object with builtin reference counting (see 'object.h' for the implementation)
@@ -70,8 +75,10 @@ class MyObject1 : public Object {
 public:
     explicit MyObject1(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const override { return "MyObject1[" + std::to_string(value) + "]"; }
+
 protected:
     ~MyObject1() override { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -83,6 +90,7 @@ class MyObject2 {
     explicit MyObject2(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject2[" + std::to_string(value) + "]"; }
     virtual ~MyObject2() { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -94,6 +102,7 @@ class MyObject3 : public std::enable_shared_from_this<MyObject3> {
     explicit MyObject3(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject3[" + std::to_string(value) + "]"; }
     virtual ~MyObject3() { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -117,6 +126,7 @@ class MyObject4 {
             delete o;
         }
     }
+
 private:
     ~MyObject4() {
         myobject4_instances.erase(this);
@@ -144,6 +154,7 @@ class MyObject4a {
             delete o;
         }
     }
+
 protected:
     virtual ~MyObject4a() {
         myobject4a_instances.erase(this);
@@ -232,14 +243,14 @@ struct TypeForMoveOnlyHolderWithAddressOf {
 };
 
 // test_smart_ptr_from_default
-struct HeldByDefaultHolder { };
+struct HeldByDefaultHolder {};
 
 // test_shared_ptr_gc
 // #187: issue involving std::shared_ptr<> return value policy & garbage collection
 struct ElementBase {
     virtual ~ElementBase() = default; /* Force creation of virtual table */
     ElementBase() = default;
-    ElementBase(const ElementBase&) = delete;
+    ElementBase(const ElementBase &) = delete;
 };
 
 struct ElementA : ElementBase {
@@ -259,11 +270,12 @@ struct ElementList {
 // It is always possible to construct a ref<T> from an Object* pointer without
 // possible inconsistencies, hence the 'true' argument at the end.
 // Make pybind11 aware of the non-standard getter member function
-namespace pybind11 { namespace detail {
-    template <typename T>
-    struct holder_helper<ref<T>> {
-        static const T *get(const ref<T> &p) { return p.get_ptr(); }
-    };
+namespace pybind11 {
+namespace detail {
+template <typename T>
+struct holder_helper<ref<T>> {
+    static const T *get(const ref<T> &p) { return p.get_ptr(); }
+};
 } // namespace detail
 } // namespace pybind11
 
@@ -287,8 +299,7 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::class_<Object, ref<Object>> obj(m, "Object");
     obj.def("getRefCount", &Object::getRefCount);
 
-    py::class_<MyObject1, ref<MyObject1>>(m, "MyObject1", obj)
-        .def(py::init<int>());
+    py::class_<MyObject1, ref<MyObject1>>(m, "MyObject1", obj).def(py::init<int>());
     py::implicitly_convertible<py::int_, MyObject1>();
 
     m.def("make_object_1", []() -> Object * { return new MyObject1(1); });
@@ -307,25 +318,27 @@ TEST_SUBMODULE(smart_ptr, m) {
     // Expose constructor stats for the ref type
     m.def("cstats_ref", &ConstructorStats::get<ref_tag>);
 
-    py::class_<MyObject2, std::shared_ptr<MyObject2>>(m, "MyObject2")
-        .def(py::init<int>());
+    py::class_<MyObject2, std::shared_ptr<MyObject2>>(m, "MyObject2").def(py::init<int>());
     m.def("make_myobject2_1", []() { return new MyObject2(6); });
     m.def("make_myobject2_2", []() { return std::make_shared<MyObject2>(7); });
     m.def("print_myobject2_1", [](const MyObject2 *obj) { py::print(obj->toString()); });
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("print_myobject2_2", [](std::shared_ptr<MyObject2> obj) { py::print(obj->toString()); });
-    m.def("print_myobject2_3", [](const std::shared_ptr<MyObject2> &obj) { py::print(obj->toString()); });
-    m.def("print_myobject2_4", [](const std::shared_ptr<MyObject2> *obj) { py::print((*obj)->toString()); });
+    m.def("print_myobject2_3",
+          [](const std::shared_ptr<MyObject2> &obj) { py::print(obj->toString()); });
+    m.def("print_myobject2_4",
+          [](const std::shared_ptr<MyObject2> *obj) { py::print((*obj)->toString()); });
 
-    py::class_<MyObject3, std::shared_ptr<MyObject3>>(m, "MyObject3")
-        .def(py::init<int>());
+    py::class_<MyObject3, std::shared_ptr<MyObject3>>(m, "MyObject3").def(py::init<int>());
     m.def("make_myobject3_1", []() { return new MyObject3(8); });
     m.def("make_myobject3_2", []() { return std::make_shared<MyObject3>(9); });
     m.def("print_myobject3_1", [](const MyObject3 *obj) { py::print(obj->toString()); });
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("print_myobject3_2", [](std::shared_ptr<MyObject3> obj) { py::print(obj->toString()); });
-    m.def("print_myobject3_3", [](const std::shared_ptr<MyObject3> &obj) { py::print(obj->toString()); });
-    m.def("print_myobject3_4", [](const std::shared_ptr<MyObject3> *obj) { py::print((*obj)->toString()); });
+    m.def("print_myobject3_3",
+          [](const std::shared_ptr<MyObject3> &obj) { py::print(obj->toString()); });
+    m.def("print_myobject3_4",
+          [](const std::shared_ptr<MyObject3> *obj) { py::print((*obj)->toString()); });
 
     // test_smart_ptr_refcounting
     m.def("test_object1_refcounting", []() {
@@ -421,11 +434,18 @@ TEST_SUBMODULE(smart_ptr, m) {
              [](const HolderWithAddressOf *obj) { py::print((*obj).get()->toString()); });
 
     // test_move_only_holder_with_addressof_operator
-    using MoveOnlyHolderWithAddressOf = unique_ptr_with_addressof_operator<TypeForMoveOnlyHolderWithAddressOf>;
-    py::class_<TypeForMoveOnlyHolderWithAddressOf, MoveOnlyHolderWithAddressOf>(m, "TypeForMoveOnlyHolderWithAddressOf")
-        .def_static("make", []() { return MoveOnlyHolderWithAddressOf(new TypeForMoveOnlyHolderWithAddressOf(0)); })
+    using MoveOnlyHolderWithAddressOf
+        = unique_ptr_with_addressof_operator<TypeForMoveOnlyHolderWithAddressOf>;
+    py::class_<TypeForMoveOnlyHolderWithAddressOf, MoveOnlyHolderWithAddressOf>(
+        m, "TypeForMoveOnlyHolderWithAddressOf")
+        .def_static("make",
+                    []() {
+                        return MoveOnlyHolderWithAddressOf(
+                            new TypeForMoveOnlyHolderWithAddressOf(0));
+                    })
         .def_readwrite("value", &TypeForMoveOnlyHolderWithAddressOf::value)
-        .def("print_object", [](const TypeForMoveOnlyHolderWithAddressOf *obj) { py::print(obj->toString()); });
+        .def("print_object",
+             [](const TypeForMoveOnlyHolderWithAddressOf *obj) { py::print(obj->toString()); });
 
     // test_smart_ptr_from_default
     py::class_<HeldByDefaultHolder, std::unique_ptr<HeldByDefaultHolder>>(m, "HeldByDefaultHolder")
@@ -455,17 +475,13 @@ TEST_SUBMODULE(smart_ptr, m) {
     class UniquePtrHeld {
     public:
         UniquePtrHeld() = delete;
-        UniquePtrHeld(const UniquePtrHeld&) = delete;
-        UniquePtrHeld(UniquePtrHeld&&) = delete;
+        UniquePtrHeld(const UniquePtrHeld &) = delete;
+        UniquePtrHeld(UniquePtrHeld &&) = delete;
 
-        UniquePtrHeld(int value)
-            : value_(value) {
-            print_created(this, value);
-        }
-        ~UniquePtrHeld() {
-            print_destroyed(this);
-        }
+        UniquePtrHeld(int value) : value_(value) { print_created(this, value); }
+        ~UniquePtrHeld() { print_destroyed(this); }
         int value() const { return value_; }
+
     private:
         int value_{};
     };
@@ -474,92 +490,69 @@ TEST_SUBMODULE(smart_ptr, m) {
         .def("value", &UniquePtrHeld::value);
 
     class UniquePtrOther {};
-    py::class_<UniquePtrOther>(m, "UniquePtrOther")
-        .def(py::init<>());
+    py::class_<UniquePtrOther>(m, "UniquePtrOther").def(py::init<>());
 
-    m.def("unique_ptr_pass_through",
-        [](std::unique_ptr<UniquePtrHeld> obj) {
-            return obj;
-        });
-    m.def("unique_ptr_terminal",
-        [](std::unique_ptr<UniquePtrHeld> obj) {
-            obj.reset();
-            return nullptr;
-        });
+    m.def("unique_ptr_pass_through", [](std::unique_ptr<UniquePtrHeld> obj) { return obj; });
+    m.def("unique_ptr_terminal", [](std::unique_ptr<UniquePtrHeld> obj) {
+        obj.reset();
+        return nullptr;
+    });
 
     // Check traits in a concise manner.
-    static_assert(
-        py::detail::move_common<std::unique_ptr<UniquePtrHeld>>::value,
-        "This must be true.");
+    static_assert(py::detail::move_common<std::unique_ptr<UniquePtrHeld>>::value,
+                  "This must be true.");
 
     // Guarantee API works as expected.
-    m.def("unique_ptr_pass_through_cast_from_py",
-        [](py::object obj_py) {
-            auto obj =
-                py::cast<std::unique_ptr<UniquePtrHeld>>(std::move(obj_py));
-            return obj;
-        });
-    m.def("unique_ptr_pass_through_move_from_py",
-        [](py::object obj_py) {
-            return py::move<std::unique_ptr<UniquePtrHeld>>(std::move(obj_py));
-        });
+    m.def("unique_ptr_pass_through_cast_from_py", [](py::object obj_py) {
+        auto obj = py::cast<std::unique_ptr<UniquePtrHeld>>(std::move(obj_py));
+        return obj;
+    });
+    m.def("unique_ptr_pass_through_move_from_py", [](py::object obj_py) {
+        return py::move<std::unique_ptr<UniquePtrHeld>>(std::move(obj_py));
+    });
 
     m.def("unique_ptr_pass_through_move_to_py",
-        [](std::unique_ptr<UniquePtrHeld> obj) {
-            return py::move(std::move(obj));
-        });
+          [](std::unique_ptr<UniquePtrHeld> obj) { return py::move(std::move(obj)); });
 
     m.def("unique_ptr_pass_through_cast_to_py",
-        [](std::unique_ptr<UniquePtrHeld> obj) {
-            return py::cast(std::move(obj));
-        });
+          [](std::unique_ptr<UniquePtrHeld> obj) { return py::cast(std::move(obj)); });
 
     class FirstT {};
-    py::class_<FirstT>(m, "FirstT")
-        .def(py::init());
+    py::class_<FirstT>(m, "FirstT").def(py::init());
     class SecondT {};
-    py::class_<SecondT>(m, "SecondT")
-        .def(py::init());
-
-    m.def("unique_ptr_overload",
-        [](std::unique_ptr<UniquePtrHeld> obj, FirstT) {
-            py::dict out;
-            out["obj"] = py::cast(std::move(obj));
-            out["overload"] = 1;
-            return out;
-        });
-    m.def("unique_ptr_overload",
-        [](std::unique_ptr<UniquePtrHeld> obj, SecondT) {
-            py::dict out;
-            out["obj"] = py::cast(std::move(obj));
-            out["overload"] = 2;
-            return out;
-        });
+    py::class_<SecondT>(m, "SecondT").def(py::init());
+
+    m.def("unique_ptr_overload", [](std::unique_ptr<UniquePtrHeld> obj, FirstT) {
+        py::dict out;
+        out["obj"] = py::cast(std::move(obj));
+        out["overload"] = 1;
+        return out;
+    });
+    m.def("unique_ptr_overload", [](std::unique_ptr<UniquePtrHeld> obj, SecondT) {
+        py::dict out;
+        out["obj"] = py::cast(std::move(obj));
+        out["overload"] = 2;
+        return out;
+    });
 
     // Ensure class is non-empty, so it's easier to detect double-free
     // corruption. (If empty, this may be harder to see easily.)
-    struct SharedPtrHeld { int value = 10; };
+    struct SharedPtrHeld {
+        int value = 10;
+    };
     py::class_<SharedPtrHeld, std::shared_ptr<SharedPtrHeld>>(m, "SharedPtrHeld")
         .def(py::init<>());
     m.def("shared_ptr_held_in_unique_ptr",
-        []() {
-            return std::unique_ptr<SharedPtrHeld>(new SharedPtrHeld());
-        });
+          []() { return std::unique_ptr<SharedPtrHeld>(new SharedPtrHeld()); });
     m.def("shared_ptr_held_func",
-        [](std::shared_ptr<SharedPtrHeld> obj) {
-            return obj != nullptr && obj->value == 10;
-        });
+          [](std::shared_ptr<SharedPtrHeld> obj) { return obj != nullptr && obj->value == 10; });
 
     // Test passing ownership of registered, but unowned, C++ instances back to
     // Python. This happens when a raw pointer is passed first, and then
     // ownership is transfered.
     struct UniquePtrHeldContainer {
-        UniquePtrHeldContainer() {
-            value_.reset(new UniquePtrHeld(10));
-        }
-        UniquePtrHeld* get() const {
-            return value_.get();
-        }
+        UniquePtrHeldContainer() { value_.reset(new UniquePtrHeld(10)); }
+        UniquePtrHeld *get() const { return value_.get(); }
         using Ptr = std::unique_ptr<UniquePtrHeld>;
         Ptr reset(Ptr to) {
             Ptr from = std::move(value_);
diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 77fc9b99b7..44a6eb2e3e 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -7,39 +7,43 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/stl.h>
 
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #ifndef PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
-#define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
+#    define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
 #endif
 #include <pybind11/stl/filesystem.h>
 
-#include <vector>
 #include <string>
+#include <vector>
 
 #if defined(PYBIND11_TEST_BOOST)
-#include <boost/optional.hpp>
+#    include <boost/optional.hpp>
 
-namespace pybind11 { namespace detail {
+namespace pybind11 {
+namespace detail {
 template <typename T>
 struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
 
 template <>
 struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
-}} // namespace pybind11::detail
+} // namespace detail
+} // namespace pybind11
 #endif
 
 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
 #if defined(PYBIND11_HAS_VARIANT)
 using std::variant;
 #elif defined(PYBIND11_TEST_BOOST) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
-#  include <boost/variant.hpp>
-#  define PYBIND11_HAS_VARIANT 1
+#    include <boost/variant.hpp>
+#    define PYBIND11_HAS_VARIANT 1
 using boost::variant;
 
-namespace pybind11 { namespace detail {
+namespace pybind11 {
+namespace detail {
 template <typename... Ts>
 struct type_caster<boost::variant<Ts...>> : variant_caster<boost::variant<Ts...>> {};
 
@@ -50,7 +54,8 @@ struct visit_helper<boost::variant> {
         return boost::apply_visitor(args...);
     }
 };
-}} // namespace pybind11::detail
+} // namespace detail
+} // namespace pybind11
 #endif
 
 PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
@@ -63,26 +68,23 @@ struct TplCtorClass {
 };
 
 namespace std {
-    template <>
-    struct hash<TplCtorClass> { size_t operator()(const TplCtorClass &) const { return 0; } };
+template <>
+struct hash<TplCtorClass> {
+    size_t operator()(const TplCtorClass &) const { return 0; }
+};
 } // namespace std
 
-
 template <template <typename> class OptionalImpl, typename T>
-struct OptionalHolder
-{
+struct OptionalHolder {
     // NOLINTNEXTLINE(modernize-use-equals-default): breaks GCC 4.8
-    OptionalHolder() {};
-    bool member_initialized() const {
-        return member && member->initialized;
-    }
+    OptionalHolder(){};
+    bool member_initialized() const { return member && member->initialized; }
     OptionalImpl<T> member = T{};
 };
 
-
 enum class EnumType {
-  kSet = 42,
-  kUnset = 85,
+    kSet = 42,
+    kUnset = 85,
 };
 
 // This is used to test that return-by-ref and return-by-copy policies are
@@ -102,7 +104,7 @@ class OptionalProperties {
         value = EnumType::kUnset;
     }
 
-    OptionalEnumValue& access_by_ref() { return value; }
+    OptionalEnumValue &access_by_ref() { return value; }
     OptionalEnumValue access_by_copy() { return value; }
 
 private:
@@ -122,62 +124,56 @@ class ReferenceSensitiveOptional {
 
     ReferenceSensitiveOptional() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
-    ReferenceSensitiveOptional(const T& value) : storage{value} {}
+    ReferenceSensitiveOptional(const T &value) : storage{value} {}
     // NOLINTNEXTLINE(google-explicit-constructor)
-    ReferenceSensitiveOptional(T&& value) : storage{std::move(value)} {}
-    ReferenceSensitiveOptional& operator=(const T& value) {
+    ReferenceSensitiveOptional(T &&value) : storage{std::move(value)} {}
+    ReferenceSensitiveOptional &operator=(const T &value) {
         storage = {value};
         return *this;
     }
-    ReferenceSensitiveOptional& operator=(T&& value) {
+    ReferenceSensitiveOptional &operator=(T &&value) {
         storage = {std::move(value)};
         return *this;
     }
 
     template <typename... Args>
-    T& emplace(Args&&... args) {
+    T &emplace(Args &&...args) {
         storage.clear();
         storage.emplace_back(std::forward<Args>(args)...);
         return storage.back();
     }
 
-    const T& value() const noexcept {
+    const T &value() const noexcept {
         assert(!storage.empty());
         return storage[0];
     }
 
-    const T& operator*() const noexcept {
-        return value();
-    }
+    const T &operator*() const noexcept { return value(); }
 
-    const T* operator->() const noexcept {
-        return &value();
-    }
+    const T *operator->() const noexcept { return &value(); }
 
-    explicit operator bool() const noexcept {
-        return !storage.empty();
-    }
+    explicit operator bool() const noexcept { return !storage.empty(); }
 
 private:
     std::vector<T> storage;
 };
 
-namespace pybind11 { namespace detail {
+namespace pybind11 {
+namespace detail {
 template <typename T>
-struct type_caster<ReferenceSensitiveOptional<T>> : optional_caster<ReferenceSensitiveOptional<T>> {};
+struct type_caster<ReferenceSensitiveOptional<T>>
+    : optional_caster<ReferenceSensitiveOptional<T>> {};
 } // namespace detail
 } // namespace pybind11
 
-
 TEST_SUBMODULE(stl, m) {
     // test_vector
     m.def("cast_vector", []() { return std::vector<int>{1}; });
     m.def("load_vector", [](const std::vector<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });
     // `std::vector<bool>` is special because it returns proxy objects instead of references
     m.def("cast_bool_vector", []() { return std::vector<bool>{true, false}; });
-    m.def("load_bool_vector", [](const std::vector<bool> &v) {
-        return v.at(0) == true && v.at(1) == false;
-    });
+    m.def("load_bool_vector",
+          [](const std::vector<bool> &v) { return v.at(0) == true && v.at(1) == false; });
     // Unnumbered regression (caused by #936): pointers to stl containers aren't castable
     static std::vector<RValueCaster> lvv{2};
     m.def("cast_ptr_vector", []() { return &lvv; });
@@ -187,12 +183,12 @@ TEST_SUBMODULE(stl, m) {
     m.def("load_deque", [](const std::deque<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });
 
     // test_array
-    m.def("cast_array", []() { return std::array<int, 2> {{1 , 2}}; });
+    m.def("cast_array", []() { return std::array<int, 2>{{1, 2}}; });
     m.def("load_array", [](const std::array<int, 2> &a) { return a[0] == 1 && a[1] == 2; });
 
     // test_valarray
     m.def("cast_valarray", []() { return std::valarray<int>{1, 4, 9}; });
-    m.def("load_valarray", [](const std::valarray<int>& v) {
+    m.def("load_valarray", [](const std::valarray<int> &v) {
         return v.size() == 3 && v[0] == 1 && v[1] == 4 && v[2] == 9;
     });
 
@@ -214,10 +210,12 @@ TEST_SUBMODULE(stl, m) {
     // NB: map and set keys are `const`, so while we technically do move them (as `const Type &&`),
     // casters don't typically do anything with that, which means they fall to the `const Type &`
     // caster.
-    m.def("cast_rv_map", []() { return std::unordered_map<std::string, RValueCaster>{{"a", RValueCaster{}}}; });
+    m.def("cast_rv_map", []() {
+        return std::unordered_map<std::string, RValueCaster>{{"a", RValueCaster{}}};
+    });
     m.def("cast_rv_nested", []() {
         std::vector<std::array<std::list<std::unordered_map<std::string, RValueCaster>>, 2>> v;
-        v.emplace_back(); // add an array
+        v.emplace_back();           // add an array
         v.back()[0].emplace_back(); // add a map to the array
         v.back()[0].back().emplace("b", RValueCaster{});
         v.back()[0].back().emplace("c", RValueCaster{});
@@ -226,13 +224,15 @@ TEST_SUBMODULE(stl, m) {
         return v;
     });
     static std::array<RValueCaster, 2> lva;
-    static std::unordered_map<std::string, RValueCaster> lvm{{"a", RValueCaster{}}, {"b", RValueCaster{}}};
-    static std::unordered_map<std::string, std::vector<std::list<std::array<RValueCaster, 2>>>> lvn;
-    lvn["a"].emplace_back(); // add a list
+    static std::unordered_map<std::string, RValueCaster> lvm{{"a", RValueCaster{}},
+                                                             {"b", RValueCaster{}}};
+    static std::unordered_map<std::string, std::vector<std::list<std::array<RValueCaster, 2>>>>
+        lvn;
+    lvn["a"].emplace_back();        // add a list
     lvn["a"].back().emplace_back(); // add an array
-    lvn["a"].emplace_back(); // another list
+    lvn["a"].emplace_back();        // another list
     lvn["a"].back().emplace_back(); // add an array
-    lvn["b"].emplace_back(); // add a list
+    lvn["b"].emplace_back();        // add a list
     lvn["b"].back().emplace_back(); // add an array
     lvn["b"].back().emplace_back(); // add another array
     m.def("cast_lv_vector", []() -> const decltype(lvv) & { return lvv; });
@@ -253,7 +253,9 @@ TEST_SUBMODULE(stl, m) {
 
     // test_move_out_container
     struct MoveOutContainer {
-        struct Value { int value; };
+        struct Value {
+            int value;
+        };
         std::list<Value> move_list() const { return {{0}, {1}, {2}}; }
     };
     py::class_<MoveOutContainer::Value>(m, "MoveOutContainerValue")
@@ -266,7 +268,7 @@ TEST_SUBMODULE(stl, m) {
     struct NoAssign {
         int value;
 
-        explicit NoAssign(int value = 0) : value(value) { }
+        explicit NoAssign(int value = 0) : value(value) {}
         NoAssign(const NoAssign &) = default;
         NoAssign(NoAssign &&) = default;
 
@@ -277,13 +279,10 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def(py::init<int>());
 
-
-    struct MoveOutDetector
-    {
+    struct MoveOutDetector {
         MoveOutDetector() = default;
-        MoveOutDetector(const MoveOutDetector&) = default;
-        MoveOutDetector(MoveOutDetector&& other) noexcept
-         : initialized(other.initialized) {
+        MoveOutDetector(const MoveOutDetector &) = default;
+        MoveOutDetector(MoveOutDetector &&other) noexcept : initialized(other.initialized) {
             // steal underlying resource
             other.initialized = false;
         }
@@ -293,23 +292,22 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def_readonly("initialized", &MoveOutDetector::initialized);
 
-
 #ifdef PYBIND11_HAS_OPTIONAL
     // test_optional
     m.attr("has_optional") = true;
 
     using opt_int = std::optional<int>;
     using opt_no_assign = std::optional<NoAssign>;
-    m.def("double_or_zero", [](const opt_int& x) -> int {
-        return x.value_or(0) * 2;
-    });
+    m.def("double_or_zero", [](const opt_int &x) -> int { return x.value_or(0) * 2; });
     m.def("half_or_none", [](int x) -> opt_int { return x != 0 ? opt_int(x / 2) : opt_int(); });
-    m.def("test_nullopt", [](opt_int x) {
-        return x.value_or(42);
-    }, py::arg_v("x", std::nullopt, "None"));
-    m.def("test_no_assign", [](const opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", std::nullopt, "None"));
+    m.def(
+        "test_nullopt",
+        [](opt_int x) { return x.value_or(42); },
+        py::arg_v("x", std::nullopt, "None"));
+    m.def(
+        "test_no_assign",
+        [](const opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", std::nullopt, "None"));
 
     m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
     m.def("nodefer_none_optional", [](const py::none &) { return false; });
@@ -333,18 +331,17 @@ TEST_SUBMODULE(stl, m) {
 
     using exp_opt_int = std::experimental::optional<int>;
     using exp_opt_no_assign = std::experimental::optional<NoAssign>;
-    m.def("double_or_zero_exp", [](const exp_opt_int& x) -> int {
-        return x.value_or(0) * 2;
-    });
-    m.def("half_or_none_exp", [](int x) -> exp_opt_int {
-        return x ? exp_opt_int(x / 2) : exp_opt_int();
-    });
-    m.def("test_nullopt_exp", [](exp_opt_int x) {
-        return x.value_or(42);
-    }, py::arg_v("x", std::experimental::nullopt, "None"));
-    m.def("test_no_assign_exp", [](const exp_opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", std::experimental::nullopt, "None"));
+    m.def("double_or_zero_exp", [](const exp_opt_int &x) -> int { return x.value_or(0) * 2; });
+    m.def("half_or_none_exp",
+          [](int x) -> exp_opt_int { return x ? exp_opt_int(x / 2) : exp_opt_int(); });
+    m.def(
+        "test_nullopt_exp",
+        [](exp_opt_int x) { return x.value_or(42); },
+        py::arg_v("x", std::experimental::nullopt, "None"));
+    m.def(
+        "test_no_assign_exp",
+        [](const exp_opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", std::experimental::nullopt, "None"));
 
     using opt_exp_holder = OptionalHolder<std::experimental::optional, MoveOutDetector>;
     py::class_<opt_exp_holder>(m, "OptionalExpHolder", "Class with optional member")
@@ -365,18 +362,17 @@ TEST_SUBMODULE(stl, m) {
 
     using boost_opt_int = boost::optional<int>;
     using boost_opt_no_assign = boost::optional<NoAssign>;
-    m.def("double_or_zero_boost", [](const boost_opt_int& x) -> int {
-        return x.value_or(0) * 2;
-    });
-    m.def("half_or_none_boost", [](int x) -> boost_opt_int {
-        return x != 0 ? boost_opt_int(x / 2) : boost_opt_int();
-    });
-    m.def("test_nullopt_boost", [](boost_opt_int x) {
-        return x.value_or(42);
-    }, py::arg_v("x", boost::none, "None"));
-    m.def("test_no_assign_boost", [](const boost_opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", boost::none, "None"));
+    m.def("double_or_zero_boost", [](const boost_opt_int &x) -> int { return x.value_or(0) * 2; });
+    m.def("half_or_none_boost",
+          [](int x) -> boost_opt_int { return x != 0 ? boost_opt_int(x / 2) : boost_opt_int(); });
+    m.def(
+        "test_nullopt_boost",
+        [](boost_opt_int x) { return x.value_or(42); },
+        py::arg_v("x", boost::none, "None"));
+    m.def(
+        "test_no_assign_boost",
+        [](const boost_opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", boost::none, "None"));
 
     using opt_boost_holder = OptionalHolder<boost::optional, MoveOutDetector>;
     py::class_<opt_boost_holder>(m, "OptionalBoostHolder", "Class with optional member")
@@ -394,9 +390,8 @@ TEST_SUBMODULE(stl, m) {
     // test_refsensitive_optional
     using refsensitive_opt_int = ReferenceSensitiveOptional<int>;
     using refsensitive_opt_no_assign = ReferenceSensitiveOptional<NoAssign>;
-    m.def("double_or_zero_refsensitive", [](const refsensitive_opt_int& x) -> int {
-        return (x ? x.value() : 0) * 2;
-    });
+    m.def("double_or_zero_refsensitive",
+          [](const refsensitive_opt_int &x) -> int { return (x ? x.value() : 0) * 2; });
     m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
         return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
     });
@@ -405,12 +400,14 @@ TEST_SUBMODULE(stl, m) {
         // NOLINTNEXTLINE(performance-unnecessary-value-param)
         [](refsensitive_opt_int x) { return x ? x.value() : 42; },
         py::arg_v("x", refsensitive_opt_int(), "None"));
-    m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
-        return x ? x->value : 42;
-    }, py::arg_v("x", refsensitive_opt_no_assign(), "None"));
+    m.def(
+        "test_no_assign_refsensitive",
+        [](const refsensitive_opt_no_assign &x) { return x ? x->value : 42; },
+        py::arg_v("x", refsensitive_opt_no_assign(), "None"));
 
     using opt_refsensitive_holder = OptionalHolder<ReferenceSensitiveOptional, MoveOutDetector>;
-    py::class_<opt_refsensitive_holder>(m, "OptionalRefSensitiveHolder", "Class with optional member")
+    py::class_<opt_refsensitive_holder>(
+        m, "OptionalRefSensitiveHolder", "Class with optional member")
         .def(py::init<>())
         .def_readonly("member", &opt_refsensitive_holder::member)
         .def("member_initialized", &opt_refsensitive_holder::member_initialized);
@@ -424,7 +421,7 @@ TEST_SUBMODULE(stl, m) {
 #ifdef PYBIND11_HAS_FILESYSTEM
     // test_fs_path
     m.attr("has_filesystem") = true;
-    m.def("parent_path", [](const std::filesystem::path& p) { return p.parent_path(); });
+    m.def("parent_path", [](const std::filesystem::path &p) { return p.parent_path(); });
 #endif
 
 #ifdef PYBIND11_HAS_VARIANT
@@ -472,13 +469,13 @@ TEST_SUBMODULE(stl, m) {
     // #171: Can't return STL structures containing reference wrapper
     m.def("return_vec_of_reference_wrapper", [](std::reference_wrapper<UserType> p4) {
         static UserType p1{1}, p2{2}, p3{3};
-        return std::vector<std::reference_wrapper<UserType>> {
-            std::ref(p1), std::ref(p2), std::ref(p3), p4
-        };
+        return std::vector<std::reference_wrapper<UserType>>{
+            std::ref(p1), std::ref(p2), std::ref(p3), p4};
     });
 
     // test_stl_pass_by_pointer
-    m.def("stl_pass_by_pointer", [](std::vector<int>* v) { return *v; }, "v"_a=nullptr);
+    m.def(
+        "stl_pass_by_pointer", [](std::vector<int> *v) { return *v; }, "v"_a = nullptr);
 
     // #1258: pybind11/stl.h converts string to vector<string>
     m.def("func_with_string_or_vector_string_arg_overload",
@@ -496,19 +493,24 @@ TEST_SUBMODULE(stl, m) {
     py::class_<Placeholder>(m, "Placeholder");
 
     /// test_stl_vector_ownership
-    m.def("test_stl_ownership",
-          []() {
-              std::vector<Placeholder *> result;
-              result.push_back(new Placeholder());
-              return result;
-          },
-          py::return_value_policy::take_ownership);
+    m.def(
+        "test_stl_ownership",
+        []() {
+            std::vector<Placeholder *> result;
+            result.push_back(new Placeholder());
+            return result;
+        },
+        py::return_value_policy::take_ownership);
 
     m.def("array_cast_sequence", [](std::array<int, 3> x) { return x; });
 
     /// test_issue_1561
-    struct Issue1561Inner { std::string data; };
-    struct Issue1561Outer { std::vector<Issue1561Inner> list; };
+    struct Issue1561Inner {
+        std::string data;
+    };
+    struct Issue1561Outer {
+        std::vector<Issue1561Inner> list;
+    };
 
     py::class_<Issue1561Inner>(m, "Issue1561Inner")
         .def(py::init<std::string>())
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index bf534aec8d..ca9630bd19 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -7,12 +7,13 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/numpy.h>
+#include <pybind11/stl_bind.h>
+
 #include "pybind11_tests.h"
 
-#include <pybind11/stl_bind.h>
-#include <pybind11/numpy.h>
-#include <map>
 #include <deque>
+#include <map>
 #include <unordered_map>
 
 class El {
@@ -23,7 +24,7 @@ class El {
     int a;
 };
 
-std::ostream & operator<<(std::ostream &s, El const&v) {
+std::ostream &operator<<(std::ostream &s, El const &v) {
     s << "El{" << v.a << '}';
     return s;
 }
@@ -40,7 +41,8 @@ class E_nc {
     int value;
 };
 
-template <class Container> Container *one_to_n(int n) {
+template <class Container>
+Container *one_to_n(int n) {
     auto *v = new Container();
     for (int i = 1; i <= n; i++) {
         v->emplace_back(i);
@@ -48,7 +50,8 @@ template <class Container> Container *one_to_n(int n) {
     return v;
 }
 
-template <class Map> Map *times_ten(int n) {
+template <class Map>
+Map *times_ten(int n) {
     auto *m = new Map();
     for (int i = 1; i <= n; i++) {
         m->emplace(int(i), E_nc(10 * i));
@@ -56,7 +59,8 @@ template <class Map> Map *times_ten(int n) {
     return m;
 }
 
-template <class NestMap> NestMap *times_hundred(int n) {
+template <class NestMap>
+NestMap *times_hundred(int n) {
     auto *m = new NestMap();
     for (int i = 1; i <= n; i++) {
         for (int j = 1; j <= n; j++) {
@@ -71,8 +75,7 @@ TEST_SUBMODULE(stl_binders, m) {
     py::bind_vector<std::vector<unsigned int>>(m, "VectorInt", py::buffer_protocol());
 
     // test_vector_custom
-    py::class_<El>(m, "El")
-        .def(py::init<int>());
+    py::class_<El>(m, "El").def(py::init<int>());
     py::bind_vector<std::vector<El>>(m, "VectorEl");
     py::bind_vector<std::vector<std::vector<El>>>(m, "VectorVectorEl");
 
@@ -82,11 +85,10 @@ TEST_SUBMODULE(stl_binders, m) {
 
     // test_map_string_double_const
     py::bind_map<std::map<std::string, double const>>(m, "MapStringDoubleConst");
-    py::bind_map<std::unordered_map<std::string, double const>>(m, "UnorderedMapStringDoubleConst");
+    py::bind_map<std::unordered_map<std::string, double const>>(m,
+                                                                "UnorderedMapStringDoubleConst");
 
-    py::class_<E_nc>(m, "ENC")
-        .def(py::init<int>())
-        .def_readwrite("value", &E_nc::value);
+    py::class_<E_nc>(m, "ENC").def(py::init<int>()).def_readwrite("value", &E_nc::value);
 
     // test_noncopyable_containers
     py::bind_vector<std::vector<E_nc>>(m, "VectorENC");
@@ -116,17 +118,31 @@ TEST_SUBMODULE(stl_binders, m) {
     // test_vector_buffer
     py::bind_vector<std::vector<unsigned char>>(m, "VectorUChar", py::buffer_protocol());
     // no dtype declared for this version:
-    struct VUndeclStruct { bool w; uint32_t x; double y; bool z; };
-    m.def("create_undeclstruct", [m] () mutable {
-        py::bind_vector<std::vector<VUndeclStruct>>(m, "VectorUndeclStruct", py::buffer_protocol());
+    struct VUndeclStruct {
+        bool w;
+        uint32_t x;
+        double y;
+        bool z;
+    };
+    m.def("create_undeclstruct", [m]() mutable {
+        py::bind_vector<std::vector<VUndeclStruct>>(
+            m, "VectorUndeclStruct", py::buffer_protocol());
     });
 
     // The rest depends on numpy:
-    try { py::module_::import("numpy"); }
-    catch (...) { return; }
+    try {
+        py::module_::import("numpy");
+    } catch (...) {
+        return;
+    }
 
     // test_vector_buffer_numpy
-    struct VStruct { bool w; uint32_t x; double y; bool z; };
+    struct VStruct {
+        bool w;
+        uint32_t x;
+        double y;
+        bool z;
+    };
     PYBIND11_NUMPY_DTYPE(VStruct, w, x, y, z);
     py::class_<VStruct>(m, "VStruct").def_readwrite("x", &VStruct::x);
     py::bind_vector<std::vector<VStruct>>(m, "VectorStruct", py::buffer_protocol());
diff --git a/tests/test_tagbased_polymorphic.cpp b/tests/test_tagbased_polymorphic.cpp
index d54d1fd325..2807e86ba3 100644
--- a/tests/test_tagbased_polymorphic.cpp
+++ b/tests/test_tagbased_polymorphic.cpp
@@ -7,11 +7,11 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
 #include <pybind11/stl.h>
 
-struct Animal
-{
+#include "pybind11_tests.h"
+
+struct Animal {
     // Make this type also a "standard" polymorphic type, to confirm that
     // specializing polymorphic_type_hook using enable_if_t still works
     // (https://github.com/pybind/pybind11/pull/2016/).
@@ -20,57 +20,54 @@ struct Animal
     // Enum for tag-based polymorphism.
     enum class Kind {
         Unknown = 0,
-        Dog = 100, Labrador, Chihuahua, LastDog = 199,
-        Cat = 200, Panther, LastCat = 299
+        Dog = 100,
+        Labrador,
+        Chihuahua,
+        LastDog = 199,
+        Cat = 200,
+        Panther,
+        LastCat = 299
     };
-    static const std::type_info* type_of_kind(Kind kind);
+    static const std::type_info *type_of_kind(Kind kind);
     static std::string name_of_kind(Kind kind);
 
     const Kind kind;
     const std::string name;
 
-  protected:
-    Animal(const std::string& _name, Kind _kind)
-        : kind(_kind), name(_name)
-    {}
+protected:
+    Animal(const std::string &_name, Kind _kind) : kind(_kind), name(_name) {}
 };
 
-struct Dog : Animal
-{
+struct Dog : Animal {
     explicit Dog(const std::string &_name, Kind _kind = Kind::Dog) : Animal(_name, _kind) {}
     std::string bark() const { return name_of_kind(kind) + " " + name + " goes " + sound; }
     std::string sound = "WOOF!";
 };
 
-struct Labrador : Dog
-{
+struct Labrador : Dog {
     explicit Labrador(const std::string &_name, int _excitement = 9001)
         : Dog(_name, Kind::Labrador), excitement(_excitement) {}
     int excitement;
 };
 
-struct Chihuahua : Dog
-{
+struct Chihuahua : Dog {
     explicit Chihuahua(const std::string &_name) : Dog(_name, Kind::Chihuahua) {
         sound = "iyiyiyiyiyi";
     }
     std::string bark() const { return Dog::bark() + " and runs in circles"; }
 };
 
-struct Cat : Animal
-{
+struct Cat : Animal {
     explicit Cat(const std::string &_name, Kind _kind = Kind::Cat) : Animal(_name, _kind) {}
     std::string purr() const { return "mrowr"; }
 };
 
-struct Panther : Cat
-{
+struct Panther : Cat {
     explicit Panther(const std::string &_name) : Cat(_name, Kind::Panther) {}
     std::string purr() const { return "mrrrRRRRRR"; }
 };
 
-std::vector<std::unique_ptr<Animal>> create_zoo()
-{
+std::vector<std::unique_ptr<Animal>> create_zoo() {
     std::vector<std::unique_ptr<Animal>> ret;
     ret.emplace_back(new Labrador("Fido", 15000));
 
@@ -85,19 +82,24 @@ std::vector<std::unique_ptr<Animal>> create_zoo()
     return ret;
 }
 
-const std::type_info* Animal::type_of_kind(Kind kind)
-{
+const std::type_info *Animal::type_of_kind(Kind kind) {
     switch (kind) {
         case Kind::Unknown:
-        case Kind::Dog: break;
+        case Kind::Dog:
+            break;
 
-        case Kind::Labrador: return &typeid(Labrador);
-        case Kind::Chihuahua: return &typeid(Chihuahua);
+        case Kind::Labrador:
+            return &typeid(Labrador);
+        case Kind::Chihuahua:
+            return &typeid(Chihuahua);
 
         case Kind::LastDog:
-        case Kind::Cat: break;
-        case Kind::Panther: return &typeid(Panther);
-        case Kind::LastCat: break;
+        case Kind::Cat:
+            break;
+        case Kind::Panther:
+            return &typeid(Panther);
+        case Kind::LastCat:
+            break;
     }
 
     if (kind >= Kind::Dog && kind <= Kind::LastDog) {
@@ -109,25 +111,24 @@ const std::type_info* Animal::type_of_kind(Kind kind)
     return nullptr;
 }
 
-std::string Animal::name_of_kind(Kind kind)
-{
+std::string Animal::name_of_kind(Kind kind) {
     std::string raw_name = type_of_kind(kind)->name();
     py::detail::clean_type_id(raw_name);
     return raw_name;
 }
 
 namespace pybind11 {
-    template <typename itype>
-    struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_base_of<Animal, itype>::value>>
-    {
-        static const void *get(const itype *src, const std::type_info*& type)
-        { type = src ? Animal::type_of_kind(src->kind) : nullptr; return src; }
-    };
+template <typename itype>
+struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_base_of<Animal, itype>::value>> {
+    static const void *get(const itype *src, const std::type_info *&type) {
+        type = src ? Animal::type_of_kind(src->kind) : nullptr;
+        return src;
+    }
+};
 } // namespace pybind11
 
 TEST_SUBMODULE(tagbased_polymorphic, m) {
-    py::class_<Animal>(m, "Animal")
-        .def_readonly("name", &Animal::name);
+    py::class_<Animal>(m, "Animal").def_readonly("name", &Animal::name);
     py::class_<Dog, Animal>(m, "Dog")
         .def(py::init<std::string>())
         .def_readwrite("sound", &Dog::sound)
@@ -138,9 +139,7 @@ TEST_SUBMODULE(tagbased_polymorphic, m) {
     py::class_<Chihuahua, Dog>(m, "Chihuahua")
         .def(py::init<std::string>())
         .def("bark", &Chihuahua::bark);
-    py::class_<Cat, Animal>(m, "Cat")
-        .def(py::init<std::string>())
-        .def("purr", &Cat::purr);
+    py::class_<Cat, Animal>(m, "Cat").def(py::init<std::string>()).def("purr", &Cat::purr);
     py::class_<Panther, Cat>(m, "Panther")
         .def(py::init<std::string>())
         .def("purr", &Panther::purr);
diff --git a/tests/test_thread.cpp b/tests/test_thread.cpp
index 19d91768b3..1536503b6b 100644
--- a/tests/test_thread.cpp
+++ b/tests/test_thread.cpp
@@ -10,20 +10,20 @@
 #include <pybind11/cast.h>
 #include <pybind11/pybind11.h>
 
+#include "pybind11_tests.h"
+
 #include <chrono>
 #include <thread>
 
-#include "pybind11_tests.h"
-
 namespace py = pybind11;
 
 namespace {
 
 struct IntStruct {
-    explicit IntStruct(int v) : value(v) {};
+    explicit IntStruct(int v) : value(v){};
     ~IntStruct() { value = -value; }
-    IntStruct(const IntStruct&) = default;
-    IntStruct& operator=(const IntStruct&) = default;
+    IntStruct(const IntStruct &) = default;
+    IntStruct &operator=(const IntStruct &) = default;
 
     int value;
 };
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index 1e47b367d2..0ca83386d5 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -7,13 +7,15 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
-#include "pybind11_tests.h"
-#include "constructor_stats.h"
 #include <pybind11/functional.h>
+
+#include "constructor_stats.h"
+#include "pybind11_tests.h"
+
 #include <thread>
 
 /* This is an example class that we'll want to be able to extend from Python */
-class ExampleVirt  {
+class ExampleVirt {
 public:
     explicit ExampleVirt(int state) : state(state) { print_created(this, state); }
     ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
@@ -25,7 +27,8 @@ class ExampleVirt  {
 
     virtual int run(int value) {
         py::print("Original implementation of "
-                  "ExampleVirt::run(state={}, value={}, str1={}, str2={})"_s.format(state, value, get_string1(), *get_string2()));
+                  "ExampleVirt::run(state={}, value={}, str1={}, str2={})"_s.format(
+                      state, value, get_string1(), *get_string2()));
         return state + value;
     }
 
@@ -33,8 +36,8 @@ class ExampleVirt  {
     virtual void pure_virtual() = 0;
 
     // Returning a reference/pointer to a type converted from python (numbers, strings, etc.) is a
-    // bit trickier, because the actual int& or std::string& or whatever only exists temporarily, so
-    // we have to handle it specially in the trampoline class (see below).
+    // bit trickier, because the actual int& or std::string& or whatever only exists temporarily,
+    // so we have to handle it specially in the trampoline class (see below).
     virtual const std::string &get_string1() { return str1; }
     virtual const std::string *get_string2() { return &str2; }
 
@@ -50,59 +53,53 @@ class PyExampleVirt : public ExampleVirt {
 
     int run(int value) override {
         /* Generate wrapping code that enables native function overloading */
-        PYBIND11_OVERRIDE(
-            int,         /* Return type */
-            ExampleVirt, /* Parent class */
-            run,         /* Name of function */
-            value        /* Argument(s) */
+        PYBIND11_OVERRIDE(int,         /* Return type */
+                          ExampleVirt, /* Parent class */
+                          run,         /* Name of function */
+                          value        /* Argument(s) */
         );
     }
 
     bool run_bool() override {
-        PYBIND11_OVERRIDE_PURE(
-            bool,         /* Return type */
-            ExampleVirt,  /* Parent class */
-            run_bool,     /* Name of function */
-                          /* This function has no arguments. The trailing comma
-                             in the previous line is needed for some compilers */
+        PYBIND11_OVERRIDE_PURE(bool,        /* Return type */
+                               ExampleVirt, /* Parent class */
+                               run_bool,    /* Name of function */
+                                            /* This function has no arguments. The trailing comma
+                                               in the previous line is needed for some compilers */
         );
     }
 
     void pure_virtual() override {
-        PYBIND11_OVERRIDE_PURE(
-            void,         /* Return type */
-            ExampleVirt,  /* Parent class */
-            pure_virtual, /* Name of function */
-                          /* This function has no arguments. The trailing comma
-                             in the previous line is needed for some compilers */
+        PYBIND11_OVERRIDE_PURE(void,         /* Return type */
+                               ExampleVirt,  /* Parent class */
+                               pure_virtual, /* Name of function */
+                                             /* This function has no arguments. The trailing comma
+                                                in the previous line is needed for some compilers */
         );
     }
 
     // We can return reference types for compatibility with C++ virtual interfaces that do so, but
     // note they have some significant limitations (see the documentation).
     const std::string &get_string1() override {
-        PYBIND11_OVERRIDE(
-            const std::string &, /* Return type */
-            ExampleVirt,         /* Parent class */
-            get_string1,         /* Name of function */
-                                 /* (no arguments) */
+        PYBIND11_OVERRIDE(const std::string &, /* Return type */
+                          ExampleVirt,         /* Parent class */
+                          get_string1,         /* Name of function */
+                                               /* (no arguments) */
         );
     }
 
     const std::string *get_string2() override {
-        PYBIND11_OVERRIDE(
-            const std::string *, /* Return type */
-            ExampleVirt,         /* Parent class */
-            get_string2,         /* Name of function */
-                                 /* (no arguments) */
+        PYBIND11_OVERRIDE(const std::string *, /* Return type */
+                          ExampleVirt,         /* Parent class */
+                          get_string2,         /* Name of function */
+                                               /* (no arguments) */
         );
     }
-
 };
 
 class NonCopyable {
 public:
-    NonCopyable(int a, int b) : value{new int(a*b)} { print_created(this, a, b); }
+    NonCopyable(int a, int b) : value{new int(a * b)} { print_created(this, a, b); }
     NonCopyable(NonCopyable &&o) noexcept : value{std::move(o.value)} { print_move_created(this); }
     NonCopyable(const NonCopyable &) = delete;
     NonCopyable() = delete;
@@ -124,11 +121,12 @@ class NonCopyable {
 // when it is not referenced elsewhere, but copied if it is still referenced.
 class Movable {
 public:
-    Movable(int a, int b) : value{a+b} { print_created(this, a, b); }
+    Movable(int a, int b) : value{a + b} { print_created(this, a, b); }
     Movable(const Movable &m) : value{m.value} { print_copy_created(this); }
     Movable(Movable &&m) noexcept : value{m.value} { print_move_created(this); }
     std::string get_value() const { return std::to_string(value); }
     ~Movable() { print_destroyed(this); }
+
 private:
     int value;
 };
@@ -137,7 +135,7 @@ class NCVirt {
 public:
     virtual ~NCVirt() = default;
     NCVirt() = default;
-    NCVirt(const NCVirt&) = delete;
+    NCVirt(const NCVirt &) = delete;
     virtual NonCopyable get_noncopyable(int a, int b) { return NonCopyable(a, b); }
     virtual Movable get_movable(int a, int b) = 0;
 
@@ -160,7 +158,7 @@ struct Base {
     virtual std::string dispatch() const { return {}; };
     virtual ~Base() = default;
     Base() = default;
-    Base(const Base&) = delete;
+    Base(const Base &) = delete;
 };
 
 struct DispatchIssue : Base {
@@ -173,33 +171,33 @@ struct DispatchIssue : Base {
 // objects and send the result to the visitor functor
 struct AdderBase {
     struct Data {};
-    using DataVisitor = std::function<void (const Data&)>;
+    using DataVisitor = std::function<void(const Data &)>;
 
-    virtual void operator()(const Data& first, const Data& second, const DataVisitor& visitor) const = 0;
+    virtual void
+    operator()(const Data &first, const Data &second, const DataVisitor &visitor) const = 0;
     virtual ~AdderBase() = default;
     AdderBase() = default;
-    AdderBase(const AdderBase&) = delete;
+    AdderBase(const AdderBase &) = delete;
 };
 
 struct Adder : AdderBase {
-    void operator()(const Data& first, const Data& second, const DataVisitor& visitor) const override {
-        PYBIND11_OVERRIDE_PURE_NAME(void, AdderBase, "__call__", operator(), first, second, visitor);
+    void
+    operator()(const Data &first, const Data &second, const DataVisitor &visitor) const override {
+        PYBIND11_OVERRIDE_PURE_NAME(
+            void, AdderBase, "__call__", operator(), first, second, visitor);
     }
 };
 
-
 static void test_gil() {
     {
         py::gil_scoped_acquire lock;
         py::print("1st lock acquired");
-
     }
 
     {
         py::gil_scoped_acquire lock;
         py::print("2nd lock acquired");
     }
-
 }
 
 static void test_gil_from_thread() {
@@ -225,12 +223,12 @@ class test_override_cache_helper_trampoline : public test_override_cache_helper
     int func() override { PYBIND11_OVERRIDE(int, test_override_cache_helper, func); }
 };
 
-inline int test_override_cache(std::shared_ptr<test_override_cache_helper> const &instance) { return instance->func(); }
-
-
+inline int test_override_cache(std::shared_ptr<test_override_cache_helper> const &instance) {
+    return instance->func();
+}
 
-// Forward declaration (so that we can put the main tests here; the inherited virtual approaches are
-// rather long).
+// Forward declaration (so that we can put the main tests here; the inherited virtual approaches
+// are rather long).
 void initialize_inherited_virtuals(py::module_ &m);
 
 TEST_SUBMODULE(virtual_functions, m) {
@@ -242,11 +240,9 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def("run_bool", &ExampleVirt::run_bool)
         .def("pure_virtual", &ExampleVirt::pure_virtual);
 
-    py::class_<NonCopyable>(m, "NonCopyable")
-        .def(py::init<int, int>());
+    py::class_<NonCopyable>(m, "NonCopyable").def(py::init<int, int>());
 
-    py::class_<Movable>(m, "Movable")
-        .def(py::init<int, int>());
+    py::class_<Movable>(m, "Movable").def(py::init<int, int>());
 
     // test_move_support
 #if !defined(__INTEL_COMPILER) && !defined(__CUDACC__) && !defined(__PGIC__)
@@ -259,7 +255,7 @@ TEST_SUBMODULE(virtual_functions, m) {
 #endif
 
     m.def("runExampleVirt", [](ExampleVirt *ex, int value) { return ex->run(value); });
-    m.def("runExampleVirtBool", [](ExampleVirt* ex) { return ex->run_bool(); });
+    m.def("runExampleVirtBool", [](ExampleVirt *ex) { return ex->run_bool(); });
     m.def("runExampleVirtVirtual", [](ExampleVirt *ex) { ex->pure_virtual(); });
 
     m.def("cstats_debug", &ConstructorStats::get<ExampleVirt>);
@@ -270,27 +266,25 @@ TEST_SUBMODULE(virtual_functions, m) {
     // that were not extended on the Python side
     struct A {
         A() = default;
-        A(const A&) = delete;
+        A(const A &) = delete;
         virtual ~A() = default;
         virtual void f() { py::print("A.f()"); }
     };
 
     struct PyA : A {
         PyA() { py::print("PyA.PyA()"); }
-        PyA(const PyA&) = delete;
+        PyA(const PyA &) = delete;
         ~PyA() override { py::print("PyA.~PyA()"); }
 
         void f() override {
             py::print("PyA.f()");
-            // This convolution just gives a `void`, but tests that PYBIND11_TYPE() works to protect
-            // a type containing a ,
+            // This convolution just gives a `void`, but tests that PYBIND11_TYPE() works to
+            // protect a type containing a ,
             PYBIND11_OVERRIDE(PYBIND11_TYPE(typename std::enable_if<true, void>::type), A, f);
         }
     };
 
-    py::class_<A, PyA>(m, "A")
-        .def(py::init<>())
-        .def("f", &A::f);
+    py::class_<A, PyA>(m, "A").def(py::init<>()).def("f", &A::f);
 
     m.def("call_f", [](A *a) { a->f(); });
 
@@ -298,14 +292,14 @@ TEST_SUBMODULE(virtual_functions, m) {
     // ... unless we explicitly request it, as in this example:
     struct A2 {
         A2() = default;
-        A2(const A2&) = delete;
+        A2(const A2 &) = delete;
         virtual ~A2() = default;
         virtual void f() { py::print("A2.f()"); }
     };
 
     struct PyA2 : A2 {
         PyA2() { py::print("PyA2.PyA2()"); }
-        PyA2(const PyA2&) = delete;
+        PyA2(const PyA2 &) = delete;
         ~PyA2() override { py::print("PyA2.~PyA2()"); }
         void f() override {
             py::print("PyA2.f()");
@@ -326,7 +320,7 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def(py::init<>())
         .def("dispatch", &Base::dispatch);
 
-    m.def("dispatch_issue_go", [](const Base * b) { return b->dispatch(); });
+    m.def("dispatch_issue_go", [](const Base *b) { return b->dispatch(); });
 
     // test_recursive_dispatch_issue
     // #3357: Recursive dispatch fails to find python function override
@@ -334,31 +328,39 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def(pybind11::init<>())
         .def("__call__", &AdderBase::operator());
 
-    pybind11::class_<AdderBase::Data>(m, "Data")
-        .def(pybind11::init<>());
-
-    m.def("add2", [](const AdderBase::Data& first, const AdderBase::Data& second,
-                     const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
-        adder(first, second, visitor);
-    });
-
-    m.def("add3", [](const AdderBase::Data& first, const AdderBase::Data& second, const AdderBase::Data& third,
-                     const AdderBase& adder, const AdderBase::DataVisitor& visitor) {
-        adder(first, second, [&] (const AdderBase::Data& first_plus_second) {
-            adder(first_plus_second, third, visitor); // NOLINT(readability-suspicious-call-argument)
-        });
-    });
+    pybind11::class_<AdderBase::Data>(m, "Data").def(pybind11::init<>());
+
+    m.def("add2",
+          [](const AdderBase::Data &first,
+             const AdderBase::Data &second,
+             const AdderBase &adder,
+             const AdderBase::DataVisitor &visitor) { adder(first, second, visitor); });
+
+    m.def("add3",
+          [](const AdderBase::Data &first,
+             const AdderBase::Data &second,
+             const AdderBase::Data &third,
+             const AdderBase &adder,
+             const AdderBase::DataVisitor &visitor) {
+              adder(first, second, [&](const AdderBase::Data &first_plus_second) {
+                  adder(first_plus_second,
+                        third,
+                        visitor); // NOLINT(readability-suspicious-call-argument)
+              });
+          });
 
     // test_override_ref
     // #392/397: overriding reference-returning functions
     class OverrideTest {
     public:
-        struct A { std::string value = "hi"; };
+        struct A {
+            std::string value = "hi";
+        };
         std::string v;
         A a;
         explicit OverrideTest(const std::string &v) : v{v} {}
         OverrideTest() = default;
-        OverrideTest(const OverrideTest&) = delete;
+        OverrideTest(const OverrideTest &) = delete;
         virtual std::string str_value() { return v; }
         virtual std::string &str_ref() { return v; }
         virtual A A_value() { return a; }
@@ -369,17 +371,22 @@ TEST_SUBMODULE(virtual_functions, m) {
     class PyOverrideTest : public OverrideTest {
     public:
         using OverrideTest::OverrideTest;
-        std::string str_value() override { PYBIND11_OVERRIDE(std::string, OverrideTest, str_value); }
+        std::string str_value() override {
+            PYBIND11_OVERRIDE(std::string, OverrideTest, str_value);
+        }
         // Not allowed (enabling the below should hit a static_assert failure): we can't get a
         // reference to a python numeric value, since we only copy values in the numeric type
         // caster:
 #ifdef PYBIND11_NEVER_DEFINED_EVER
-        std::string &str_ref() override { PYBIND11_OVERRIDE(std::string &, OverrideTest, str_ref); }
+        std::string &str_ref() override {
+            PYBIND11_OVERRIDE(std::string &, OverrideTest, str_ref);
+        }
 #endif
         // But we can work around it like this:
     private:
         std::string _tmp;
         std::string str_ref_helper() { PYBIND11_OVERRIDE(std::string, OverrideTest, str_ref); }
+
     public:
         std::string &str_ref() override { return _tmp = str_ref_helper(); }
 
@@ -398,14 +405,15 @@ TEST_SUBMODULE(virtual_functions, m) {
         .def("A_value", &OverrideTest::A_value)
         .def("A_ref", &OverrideTest::A_ref);
 
-    py::class_<test_override_cache_helper, test_override_cache_helper_trampoline, std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
+    py::class_<test_override_cache_helper,
+               test_override_cache_helper_trampoline,
+               std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
         .def(py::init_alias<>())
         .def("func", &test_override_cache_helper::func);
 
     m.def("test_override_cache", test_override_cache);
 }
 
-
 // Inheriting virtual methods.  We do two versions here: the repeat-everything version and the
 // templated trampoline versions mentioned in docs/advanced.rst.
 //
@@ -414,83 +422,96 @@ TEST_SUBMODULE(virtual_functions, m) {
 // properly (pybind11, sensibly, doesn't allow us to bind the same C++ class to
 // multiple python classes).
 class A_Repeat {
-#define A_METHODS \
-public: \
-    virtual int unlucky_number() = 0; \
-    virtual std::string say_something(unsigned times) { \
-        std::string s = ""; \
-        for (unsigned i = 0; i < times; ++i) \
-            s += "hi"; \
-        return s; \
-    } \
-    std::string say_everything() { \
-        return say_something(1) + " " + std::to_string(unlucky_number()); \
+#define A_METHODS                                                                                 \
+public:                                                                                           \
+    virtual int unlucky_number() = 0;                                                             \
+    virtual std::string say_something(unsigned times) {                                           \
+        std::string s = "";                                                                       \
+        for (unsigned i = 0; i < times; ++i)                                                      \
+            s += "hi";                                                                            \
+        return s;                                                                                 \
+    }                                                                                             \
+    std::string say_everything() {                                                                \
+        return say_something(1) + " " + std::to_string(unlucky_number());                         \
     }
-A_METHODS
+    A_METHODS
     A_Repeat() = default;
-    A_Repeat(const A_Repeat&) = delete;
+    A_Repeat(const A_Repeat &) = delete;
     virtual ~A_Repeat() = default;
 };
 class B_Repeat : public A_Repeat {
-#define B_METHODS \
-public: \
-    int unlucky_number() override { return 13; } \
-    std::string say_something(unsigned times) override { \
-        return "B says hi " + std::to_string(times) + " times"; \
-    } \
+#define B_METHODS                                                                                 \
+public:                                                                                           \
+    int unlucky_number() override { return 13; }                                                  \
+    std::string say_something(unsigned times) override {                                          \
+        return "B says hi " + std::to_string(times) + " times";                                   \
+    }                                                                                             \
     virtual double lucky_number() { return 7.0; }
-B_METHODS
+    B_METHODS
 };
 class C_Repeat : public B_Repeat {
-#define C_METHODS \
-public: \
-    int unlucky_number() override { return 4444; } \
+#define C_METHODS                                                                                 \
+public:                                                                                           \
+    int unlucky_number() override { return 4444; }                                                \
     double lucky_number() override { return 888; }
-C_METHODS
+    C_METHODS
 };
 class D_Repeat : public C_Repeat {
 #define D_METHODS // Nothing overridden.
-D_METHODS
+    D_METHODS
 };
 
 // Base classes for templated inheritance trampolines.  Identical to the repeat-everything version:
 class A_Tpl {
     A_METHODS;
     A_Tpl() = default;
-    A_Tpl(const A_Tpl&) = delete;
+    A_Tpl(const A_Tpl &) = delete;
     virtual ~A_Tpl() = default;
 };
-class B_Tpl : public A_Tpl { B_METHODS };
-class C_Tpl : public B_Tpl { C_METHODS };
-class D_Tpl : public C_Tpl { D_METHODS };
-
+class B_Tpl : public A_Tpl {
+    B_METHODS
+};
+class C_Tpl : public B_Tpl {
+    C_METHODS
+};
+class D_Tpl : public C_Tpl {
+    D_METHODS
+};
 
 // Inheritance approach 1: each trampoline gets every virtual method (11 in total)
 class PyA_Repeat : public A_Repeat {
 public:
     using A_Repeat::A_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE_PURE(int, A_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, A_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, A_Repeat, say_something, times);
+    }
 };
 class PyB_Repeat : public B_Repeat {
 public:
     using B_Repeat::B_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE(int, B_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, B_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, B_Repeat, say_something, times);
+    }
     double lucky_number() override { PYBIND11_OVERRIDE(double, B_Repeat, lucky_number, ); }
 };
 class PyC_Repeat : public C_Repeat {
 public:
     using C_Repeat::C_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE(int, C_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, C_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, C_Repeat, say_something, times);
+    }
     double lucky_number() override { PYBIND11_OVERRIDE(double, C_Repeat, lucky_number, ); }
 };
 class PyD_Repeat : public D_Repeat {
 public:
     using D_Repeat::D_Repeat;
     int unlucky_number() override { PYBIND11_OVERRIDE(int, D_Repeat, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, D_Repeat, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, D_Repeat, say_something, times);
+    }
     double lucky_number() override { PYBIND11_OVERRIDE(double, D_Repeat, lucky_number, ); }
 };
 
@@ -513,7 +534,9 @@ class PyA_Tpl : public Base {
 public:
     using Base::Base; // Inherit constructors
     int unlucky_number() override { PYBIND11_OVERRIDE_PURE(int, Base, unlucky_number, ); }
-    std::string say_something(unsigned times) override { PYBIND11_OVERRIDE(std::string, Base, say_something, times); }
+    std::string say_something(unsigned times) override {
+        PYBIND11_OVERRIDE(std::string, Base, say_something, times);
+    }
 };
 template <class Base = B_Tpl>
 class PyB_Tpl : public PyA_Tpl<Base> {
@@ -548,10 +571,8 @@ void initialize_inherited_virtuals(py::module_ &m) {
     py::class_<B_Repeat, A_Repeat, PyB_Repeat>(m, "B_Repeat")
         .def(py::init<>())
         .def("lucky_number", &B_Repeat::lucky_number);
-    py::class_<C_Repeat, B_Repeat, PyC_Repeat>(m, "C_Repeat")
-        .def(py::init<>());
-    py::class_<D_Repeat, C_Repeat, PyD_Repeat>(m, "D_Repeat")
-        .def(py::init<>());
+    py::class_<C_Repeat, B_Repeat, PyC_Repeat>(m, "C_Repeat").def(py::init<>());
+    py::class_<D_Repeat, C_Repeat, PyD_Repeat>(m, "D_Repeat").def(py::init<>());
 
     // test_
     // Method 2: Templated trampolines
@@ -563,11 +584,8 @@ void initialize_inherited_virtuals(py::module_ &m) {
     py::class_<B_Tpl, A_Tpl, PyB_Tpl<>>(m, "B_Tpl")
         .def(py::init<>())
         .def("lucky_number", &B_Tpl::lucky_number);
-    py::class_<C_Tpl, B_Tpl, PyB_Tpl<C_Tpl>>(m, "C_Tpl")
-        .def(py::init<>());
-    py::class_<D_Tpl, C_Tpl, PyB_Tpl<D_Tpl>>(m, "D_Tpl")
-        .def(py::init<>());
-
+    py::class_<C_Tpl, B_Tpl, PyB_Tpl<C_Tpl>>(m, "C_Tpl").def(py::init<>());
+    py::class_<D_Tpl, C_Tpl, PyB_Tpl<D_Tpl>>(m, "D_Tpl").def(py::init<>());
 
     // Fix issue #1454 (crash when acquiring/releasing GIL on another thread in Python 2.7)
     m.def("test_gil", &test_gil);

From 91e209bbfc75472bd65508df3e6b66fd51105b50 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 17:27:35 -0400
Subject: [PATCH 627/638] re-run pre-commit

---
 include/pybind11/cast.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index f96a87ac22..15c38d0e06 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1204,8 +1204,14 @@ object cast(T &&value,
         detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
 }
 
-template <typename T> T handle::cast() const { return pybind11::cast<T>(*this); }
-template <> inline void handle::cast() const { return; }
+template <typename T>
+T handle::cast() const {
+    return pybind11::cast<T>(*this);
+}
+template <>
+inline void handle::cast() const {
+    return;
+}
 
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
@@ -1222,7 +1228,7 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     }
 
     // Move into a temporary and return that, because the reference may be a local value of `conv`
-    T ret = std::move(detail::load_type<T>(obj).operator T&());
+    T ret = std::move(detail::load_type<T>(obj).operator T &());
     return ret;
 }
 

From 111af7ca061ce8c297a0dbcad40c956486aaceb9 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 17:44:05 -0400
Subject: [PATCH 628/638] huh, missed carrying this one over - oops!

---
 include/pybind11/cast.h     | 15 ++++++++++++++-
 include/pybind11/pybind11.h |  2 +-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 8eff767c91..c5dbda9ed3 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1205,6 +1205,19 @@ inline void handle::cast() const {
     return;
 }
 
+template <typename T>
+detail::enable_if_t<
+    // TODO(eric.cousineau): Figure out how to prevent perfect-forwarding more elegantly.
+    std::is_rvalue_reference<T &&>::value && !detail::is_pyobject<detail::intrinsic_t<T>>::value,
+    object>
+move(T &&value) {
+    // TODO(eric.cousineau): Add policies, parent, etc.
+    // It'd be nice to supply a parent, but for now, just leave it as-is.
+    handle no_parent;
+    return reinterpret_steal<object>(detail::make_caster<T>::cast(
+        std::move(value), return_value_policy::take_ownership, no_parent));
+}
+
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1) {
@@ -1220,7 +1233,7 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     }
 
     // Move into a temporary and return that, because the reference may be a local value of `conv`
-    T ret = std::move(detail::load_type<T>(obj).operator T &());
+    T ret = std::move(detail::cast_op<T>(detail::load_type<T>(obj)));
     return ret;
 }
 
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 6288c479ae..2ad636d6b1 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2189,7 +2189,7 @@ class class_ : public detail::generic_type {
     static void
     init_holder_simple(detail::instance *inst, detail::value_and_holder &v_h, type *value) {
         if (PYBIND11_SILENCE_MSVC_C4127(detail::always_construct_holder<holder_type>::value)
-                   || inst->owned) {
+            || inst->owned) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(value);
             v_h.set_holder_constructed();
         }

From 6b3378e0bf9e62dde79106ff972d1eb9ead1dda7 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 17:53:40 -0400
Subject: [PATCH 629/638] partial revert to proper form of 8adef2c

---
 include/pybind11/detail/class.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index 39cfcba513..42720f844d 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -162,12 +162,6 @@ extern "C" inline int pybind11_meta_setattro(PyObject *obj, PyObject *name, PyOb
  * to do a special case bypass for PyInstanceMethod_Types.
  */
 extern "C" inline PyObject *pybind11_meta_getattro(PyObject *obj, PyObject *name) {
-    // Workaround! See:
-    // https://github.com/RobotLocomotion/drake/issues/14740
-    // https://github.com/pybind/pybind11/pull/2685
-    if (PyErr_Occurred()) {
-        PyErr_Clear();
-    }
     PyObject *descr = _PyType_Lookup((PyTypeObject *) obj, name);
     if (descr && PyInstanceMethod_Check(descr)) {
         Py_INCREF(descr);

From 9ad3610cf7a608502fe860dd5f7db1128796be7b Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 18:39:56 -0400
Subject: [PATCH 630/638] Restore files lost in replay

---
 pybind11/_version.pyi      |  6 ++++
 pybind11/setup_helpers.pyi | 63 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 pybind11/_version.pyi
 create mode 100644 pybind11/setup_helpers.pyi

diff --git a/pybind11/_version.pyi b/pybind11/_version.pyi
new file mode 100644
index 0000000000..d45e5dc907
--- /dev/null
+++ b/pybind11/_version.pyi
@@ -0,0 +1,6 @@
+from typing import Tuple, Union
+
+def _to_int(s: str) -> Union[int, str]: ...
+
+__version__: str
+version_info: Tuple[Union[int, str], ...]
diff --git a/pybind11/setup_helpers.pyi b/pybind11/setup_helpers.pyi
new file mode 100644
index 0000000000..074744eb82
--- /dev/null
+++ b/pybind11/setup_helpers.pyi
@@ -0,0 +1,63 @@
+# IMPORTANT: Should stay in sync with setup_helpers.py (mostly checked by CI /
+# pre-commit).
+
+import contextlib
+import distutils.ccompiler
+from distutils.command.build_ext import build_ext as _build_ext  # type: ignore
+from distutils.extension import Extension as _Extension
+from types import TracebackType
+from typing import Any, Callable, Dict, Iterator, List, Optional, Type, TypeVar, Union
+
+WIN: bool
+PY2: bool
+MACOS: bool
+STD_TMPL: str
+
+class Pybind11Extension(_Extension):
+    def _add_cflags(self, *flags: str) -> None: ...
+    def _add_lflags(self, *flags: str) -> None: ...
+    def __init__(
+        self, *args: Any, cxx_std: int = 0, language: str = "c++", **kwargs: Any
+    ) -> None: ...
+    @property
+    def cxx_std(self) -> int: ...
+    @cxx_std.setter
+    def cxx_std(self, level: int) -> None: ...
+
+@contextlib.contextmanager
+def tmp_chdir() -> Iterator[str]: ...
+def has_flag(compiler: distutils.ccompiler.CCompiler, flag: str) -> bool: ...
+def auto_cpp_level(compiler: distutils.ccompiler.CCompiler) -> Union[int, str]: ...
+
+class build_ext(_build_ext):  # type: ignore
+    def build_extensions(self) -> None: ...
+
+def intree_extensions(
+    paths: Iterator[str], package_dir: Optional[Dict[str, str]] = None
+) -> List[Pybind11Extension]: ...
+def no_recompile(obj: str, src: str) -> bool: ...
+def naive_recompile(obj: str, src: str) -> bool: ...
+
+T = TypeVar("T", bound="ParallelCompile")
+
+class ParallelCompile:
+    envvar: Optional[str]
+    default: int
+    max: int
+    needs_recompile: Callable[[str, str], bool]
+    def __init__(
+        self,
+        envvar: Optional[str] = None,
+        default: int = 0,
+        max: int = 0,
+        needs_recompile: Callable[[str, str], bool] = no_recompile,
+    ) -> None: ...
+    def function(self) -> Any: ...
+    def install(self: T) -> T: ...
+    def __enter__(self: T) -> T: ...
+    def __exit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_value: Optional[BaseException],
+        traceback: Optional[TracebackType],
+    ) -> None: ...

From cc9fb570ecc853103e721b3158d7ba3d9ed82dc3 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 18:44:51 -0400
Subject: [PATCH 631/638] configure: Disable windows and cmake 3.4 testing

---
 .github/workflows/configure.yml | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index ca36d5ddb3..4157062c98 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -14,22 +14,22 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        runs-on: [ubuntu-latest, macos-latest, windows-latest]
+        runs-on: [ubuntu-latest, macos-latest] #, windows-latest]
         arch: [x64]
         cmake: ["3.23"]
 
         include:
-        - runs-on: ubuntu-latest
-          arch: x64
-          cmake: 3.4
+        # - runs-on: ubuntu-latest
+        #   arch: x64
+        #   cmake: 3.4
 
         - runs-on: macos-latest
           arch: x64
           cmake: 3.7
 
-        - runs-on: windows-2019
-          arch: x64 # x86 compilers seem to be missing on 2019 image
-          cmake: 3.18
+        # - runs-on: windows-2019
+        #   arch: x64 # x86 compilers seem to be missing on 2019 image
+        #   cmake: 3.18
 
     name: 🐍 3.7 • CMake ${{ matrix.cmake }} • ${{ matrix.runs-on }}
     runs-on: ${{ matrix.runs-on }}

From e61bb561a67037ca2ddcb1386f44a6014c8091e4 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 18:49:49 -0400
Subject: [PATCH 632/638] fix ci syntax err

---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6a491ea743..26967e52fe 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -593,7 +593,7 @@ jobs:
   #       container:
   #         - "centos:7"  # GCC 4.8
   #         - "almalinux:8"
-          - "almalinux:9"
+  #         - "almalinux:9"
 
   #   name: "🐍 3 • ${{ matrix.container }} • x64"
   #   container: "${{ matrix.container }}"
@@ -800,7 +800,7 @@ jobs:
   #     uses: actions/setup-python@v4
   #     with:
   #       python-version: ${{ matrix.python }}
-        architecture: x86
+  #       architecture: x86
 
   #   - name: Update CMake
   #     uses: jwlawson/actions-setup-cmake@v1.12

From 432c941ea7b1db6bc93276de2d1b99faa04e66ad Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 19:33:53 -0400
Subject: [PATCH 633/638] Prep fork for effective rename

---
 include/pybind11/{eigen.h => eigen/matrix.h} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename include/pybind11/{eigen.h => eigen/matrix.h} (100%)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen/matrix.h
similarity index 100%
rename from include/pybind11/eigen.h
rename to include/pybind11/eigen/matrix.h

From 44b38a5152aafa1e2466aae5800db24a65723220 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 19:47:21 -0400
Subject: [PATCH 634/638] oops forgot to keep this

---
 include/pybind11/eigen.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 include/pybind11/eigen.h

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
new file mode 100644
index 0000000000..273b9c9308
--- /dev/null
+++ b/include/pybind11/eigen.h
@@ -0,0 +1,12 @@
+/*
+    pybind11/eigen.h: Transparent conversion for dense and sparse Eigen matrices
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "eigen/matrix.h"

From 8edb23712a393e5632956c892f50c850930f4ae4 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 19:49:52 -0400
Subject: [PATCH 635/638] fix latent err

---
 include/pybind11/pybind11.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ee05d235d8..14d0ae7462 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -2206,8 +2206,7 @@ class class_ : public detail::generic_type {
     /// Initialize a holder object simply (to be converted).
     static void
     init_holder_simple(detail::instance *inst, detail::value_and_holder &v_h, type *value) {
-        if (PYBIND11_SILENCE_MSVC_C4127(detail::always_construct_holder<holder_type>::value)
-            || inst->owned) {
+        if (detail::always_construct_holder<holder_type>::value|| inst->owned) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(value);
             v_h.set_holder_constructed();
         }

From f35d257aec3a0bf4286cb88e6bfea4fb7fb6d852 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Thu, 12 Oct 2023 19:52:30 -0400
Subject: [PATCH 636/638] fix ci syntax err

---
 .github/workflows/ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3463c87229..348335aa96 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -406,7 +406,7 @@ jobs:
 
   # # Testing on CentOS 7 + PGI compilers, which seems to require more workarounds
   # centos-nvhpc7:
-    if: ${{ false }}  # JOB DISABLED (NEEDS WORK): https://github.com/pybind/pybind11/issues/4690
+  #   if: ${{ false }}  # JOB DISABLED (NEEDS WORK): https://github.com/pybind/pybind11/issues/4690
   #   runs-on: ubuntu-latest
   #   name: "🐍 3 • CentOS7 / PGI 22.9 • x64"
   #   container: centos:7
@@ -778,8 +778,8 @@ jobs:
   #           args: -DCMAKE_CXX_STANDARD=20
   #         - python: 3.8
   #           args: -DCMAKE_CXX_STANDARD=17
-          - python: 3.7
-            args: -DCMAKE_CXX_STANDARD=14
+  #         - python: 3.7
+  #           args: -DCMAKE_CXX_STANDARD=14
 
 
   #   name: "🐍 ${{ matrix.python }} • MSVC 2019 • x86 ${{ matrix.args }}"

From 22186cc26110250265995473da616548753cd3a4 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Tue, 17 Oct 2023 13:36:01 -0400
Subject: [PATCH 637/638] only check ref_count for temporary values

---
 include/pybind11/cast.h         | 20 +++++++++++---------
 tests/test_smart_ptr.cpp        | 11 +++++++++++
 tests/test_smart_ptr.py         | 13 +++++++++++++
 tests/test_virtual_functions.py |  5 ++++-
 4 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index ab14b44f3b..baae9abb35 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1258,18 +1258,20 @@ move(T &&value) {
 }
 
 template <typename T>
-detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
-    if (obj.ref_count() > 1) {
+detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {\
+    if constexpr (detail::cast_is_temporary_value_reference<T>::value) {
+        if (obj.ref_count() > 1) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
-        throw cast_error(
-            "Unable to cast Python " + str(type::handle_of(obj)).cast<std::string>()
-            + " instance to C++ rvalue: instance has multiple references"
-              " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
+            throw cast_error(
+                "Unable to cast Python " + str(type::handle_of(obj)).cast<std::string>()
+                + " instance to C++ rvalue: instance has multiple references"
+                    " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
-        throw cast_error("Unable to move from Python "
-                         + str(type::handle_of(obj)).cast<std::string>() + " instance to C++ "
-                         + type_id<T>() + " instance: instance has multiple references");
+            throw cast_error("Unable to move from Python "
+                             + str(type::handle_of(obj)).cast<std::string>() + " instance to C++ "
+                             + type_id<T>() + " instance: instance has multiple references");
 #endif
+        }
     }
 
     // Move into a temporary and return that, because the reference may be a local value of `conv`
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 2b78a1332f..095b43e709 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -10,6 +10,7 @@
 
 #include "object.h"
 #include "pybind11_tests.h"
+#include "pybind11/functional.h"
 
 namespace {
 
@@ -531,6 +532,16 @@ TEST_SUBMODULE(smart_ptr, m) {
         return out;
     });
 
+    using Callback = std::function<std::unique_ptr<UniquePtrHeld>()>;
+    m.def("unique_ptr_callback",
+        [](const Callback& callback) {
+            auto obj = callback();
+            if (obj->value() != 10) {
+                throw std::runtime_error("obj.value() must be 10");
+            }
+            return callback();
+        });
+
     // Ensure class is non-empty, so it's easier to detect double-free
     // corruption. (If empty, this may be harder to see easily.)
     struct SharedPtrHeld {
diff --git a/tests/test_smart_ptr.py b/tests/test_smart_ptr.py
index c6b1d80530..80ecbbc0fc 100644
--- a/tests/test_smart_ptr.py
+++ b/tests/test_smart_ptr.py
@@ -378,3 +378,16 @@ def check_reset(obj_new):
 
     check_reset(obj_new=m.UniquePtrHeld(10))
     check_reset(obj_new=None)
+
+
+def test_unique_ptr_self_reference():
+    obj = None
+
+    def make_unique_ptr_held():
+        nonlocal obj
+        # This simulates a self-reference for a derived type.
+        obj = m.UniquePtrHeld(10)
+        return obj
+
+    out = m.unique_ptr_callback(make_unique_ptr_held)
+    assert obj is out
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index c17af7df58..5a04ae9170 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -215,7 +215,10 @@ def get_movable(self, a, b):
     ncv2 = NCVirtExt2()
     assert ncv2.print_movable(7, 7) == "14"
     # Don't check the exception message here because it differs under debug/non-debug mode
-    with pytest.raises(RuntimeError):
+
+    # N.B. Drake fork allows this behavior.
+    if True:
+    # with pytest.raises(RuntimeError):
         ncv2.print_nc(9, 9)
 
     nc_stats = ConstructorStats.get(m.NonCopyable)

From d280f26c38efc54e5e681e1c9367667e4cd8630d Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Tue, 17 Oct 2023 14:31:01 -0400
Subject: [PATCH 638/638] fixup! no if constexpr please

---
 include/pybind11/cast.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index baae9abb35..57b94b64eb 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1259,7 +1259,7 @@ move(T &&value) {
 
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {\
-    if constexpr (detail::cast_is_temporary_value_reference<T>::value) {
+    if (detail::cast_is_temporary_value_reference<T>::value) {
         if (obj.ref_count() > 1) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
             throw cast_error(